Q — ^^:: — m Fishery Bulletin ■^'virES o* '^ JUN 1 1 1979 A Woods Hole, Vol. 77, No. 1 / JanuaryTSTS RICHARDSON, SALLY L., and WAYNE A, LAROCHE. Development and occur- rence of larvae and juveniles of the rockfishes Se6astes crameri,Sebastes pinniger, and Sebastes helvomaculatus (family Scorpaenidae) off Oregon 1 LEATHERWOOD, STEPHEN. Aerial survey of the bottlenosed dolphin, Tursiops truncatus, and the West Indian manatee, Trichechus manatus, in the Indian and Banana Rivers, Florida 47 MORGAN, STEVEN G., and ANTHONY J. PROVENZANO, JR. Development of pelagic larvae and postlarva of Squilla empusa (Crustacea, Stomatopoda), with an assessment of larval characters within the Squillidae 61 COHEN, DANIEL M., and JOSEPH L. RUSSO. Variation in the fourbeard rockling, Enchelyopus cimbrius, a North Atlantic gadid fish, with comments on the genera of rocklings 91 SUMIDA, B. Y., E. H. AHLSTROM, and H. G. MOSER. Early development of seven flatfishes of the eastern North Pacific with heavily pigmented larvae (Pisces, Pleuronectiformes) 105 GREENBLATT, PAUL R. Associations of tuna with flotsam in the eastern tropical Pacific 147 HAYNES, EVAN. Description of larvae of the northern shrimp, Panda/as borealis, reared in situ in Kachemak Bay, Alaska 157 TRICAS, TIMOTHY C. Relationships of the blue shark, Prionace glauca, and its prey species near Santa Catalina Island, California 175 OMORI, MAKOTO, and DAVID GLUCK. Life history and vertical migration of the pelagic shrimp Sergestes similis off the southern California coast 183 NEVES, RICHARD J., and LINDA DEPRES. The oceanic migration of American shad, Alosa sapidissima, along the Atlantic coast 199 KENDALL, ARTHUR W., JR., and LIONEL A. WALFORD. Sources and distribu- tion of bluefish, Pomatomus saltatrix, larvae and juveniles off the east coast of the United States 213 WAHLE, ROY J., REINO O. KOSKI, and ROBERT Z. SMITH. Contribution of 1960-63 brood hatchery-reared sockeye salmon, Oncorhynchus nerka, to the Co- lumbia River commercial fishery 229 MEYER, THOMAS L., RICHARD A. COOPER, and RICHARD W. LANGTON. Relative abundance, behavior, and food habits of the American sand lance, Ammo- dytes americanus, from the Gulf of Maine 243 (Continued on next page) 0 Rpaf.tlp Washincrt.nn U.S. DEPARTMENT OF COMMERCE Juanita M. Kreps, Secretary NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION Richard A. Frank, Administrator Terry L. Leitzell, Assistant Administrator for Fisheries NATIONAL MARINE FISHERIES SERVICE Fishery Bulletin The Fishery Bulletin carries original research reports and technical notes on investigations in fishery science, engineering, and economics. The Bulletin of the United States Fish Conunission was begun in 1881; it became the Bulletin of the Bureau of Fisheries in 1904 and the Fishery Bulletin of the Fish and Wildlife Service in 1941. Separates were issued as documents through volume 46; the last document was No. 1103. Beginning with volume 47 in 1931 and continuing through volume 62 in 1963, each separate appeared as a numbered bulletin. A new system began in 1963 with volume 63 in which papers are bound together in a single issue of the bulletin instead of being issued individually. Beginning with volume 70. number 1. January 1972, the Fishery Bulletin became a periodical, issued quarterly In this form, it is available by subscription ftxjm the Superintendent of Documents, U.S. Government Printing Office, Washington, DC 20402. It is also available free in limited numbers to libraries, research institutions. State and Federal agencies, and in exchange for other scientific publications. EDITOR Dr. Jay C. Quast Scientific Editor, Fishery Bulletin Northwest and Ala.ska Fisheries Center Auke Bay Laboratory National Marine Fisheries Service, NOAA P.O. Bo.\ 155. Auke Bay. AK 99821 Editorial Committee Dr Klhert H Ahlstrom Dr. Merton C. Ingham National Marine Fisheries Service National Marine Fisheries Service Dr. Bruce B. Collette Dr. Reuben Lasker National Marine F'isheries Service National Marine Fisheries Service Dr. Edward D. Houde Dr. Jerome J. Pella University of Miami National Marine Fisheries Service Dr. Sally L. Richardson Gulf Coast Research Laboratory Kiyoshi G. Fukano, Managing Editor The Fishery Bulletin (USPS 090-870) is published quarterly by Scientific Publications Office. National Manne Fistieries Service. NOAA. Room 450. 1107 NE 45tti Street, Seattle, WA 98105 Controlled circulation paid to Finance Department. USPS. Wastiington, DC 20260, Afthougti tfie contents tiave been copyrighted and may be repfinled entirely, reference to source is appreciated. The Secretary of Commerce has determined that the publication of this penodical is necessary in the transaction of the public business required by law of this Department Use of funds for printing of this periodical has been approved by the Director of the Office of f\i1anagement and Budget through 31 March 1982. Fishery Bulletin CONTENTS Vol. 77, No. 1 January 1979 RICHARDSON, SALLY L., and WAYNE A. LAROCHE. Development and occur- rence of larvae and juveniles of the rockfishes Se6as (O >.2 F . n O CD S "^ O (o ■Q CD E -5 £ E - ___ c at "> ^ o "> ™ o Q) CD i: -ill C 0) ?r *= O E w CD 0) X -; 2 S aleulianus S alutus S atrovirens S aunculatus S aurora S babcocki S borealis S brevispinis S carnatus S caunnus S chlorostictus S chrysomelas S ciliatus S constellatus S cortezi S cramen S dalli S diploproa S elongatus S emphaeus S ensfter S entomelas S eos S exsul S flavidus S gilli S goodei S helvomacuiatus S hopktnsi S lord am S lentiginosus S levis S macdonaldi S maliger S melanops S melanostomu . S miniatus S. mystinus S nebulosus S nigrocmctus S notius S ovalis S paucispinis S peduncularis S philtipsi S pinniger S polyspinis S pronger S rasfrelliger S reedi S rosaceus S rosenblatti S rubernmus S rubnvinctus S rufi nanus S rufus S saxicola S semicinctus S serranoides S sernceps S simulator S sinensis S spinorbis S umbrosus S variegatus S. vanspinis S wilsoni S zacentrus S new sp (Lea and Fitch) (P-1 L- L' L- P- P* 'Described as S rubnvinctus. but northern occurrence indicates it must be S babcocki ^Described as S rhodochloris ^These descriptions ot S rubnvinctus must be S babcocki due to the northern occurrence of specimens. RICHARDSON and LAROCHE DEVELOPMENT AND OCCURRENCE OF ROCKFISHES Longest dorsal fin spine = distance from base to = distance from base to = distance from base to tip Longest dorsal fin ray = tip. Longest anal fin spine tip. All body lengths given refer to standard length unless noted otherwise. Developmental Terminology Terminology for development of Sebastes spp. used in this paper is as follows: Preflexion larva = prior to notochord flexion. Flexion larva = undergoing notochord flexion from time urostyle begins to slant upward until urostyle is in final upturned position and caudal fin is formed. Postflexion larva = from completion of noto- chord flexion (urostyle may still extend beyond the base of the caudal fin) to onset of transformation of 13th dorsal spine and 3d anal spine from soft ray to spine, and to the associated onset of development of juvenile pigment pattern (usually addition of pigment to the dorsum). Transforming larva = from onset to completion of transformation of 13th dorsal spine and 3d anal spine from soft ray to fully developed spine. Also from the onset of development of juvenile pigment pattern to development of distinctive juvenile pigmentation, often in the form of melanistic sad- dles over the dorsum. Pelagic juvenile = from completion of formation of 13th dorsal and 3d anal spine (and thus attain- ment of adult complement of actual fin spines and rays) and development of juvenile pigmentation until no longer captured pelagically. Benthic juvenile = from time of first capture on bottom and usual associated decrease in intensity of melanistic pigmentation to attainment of sex- ual maturitv. Spination (Figure 1, Table 2) Difficulties arise in naming all the spines found in the head region of larvae and juveniles of Sebastes because not all are found in adults. Further complications arise because the names traditionally used for a number of the head spines do not reflect the bone from which the spine origi- nates. For these reasons we include a composite diagram of spines which may occur during the larval and juvenile periods. The terminology is a combination and modification of that used by Phil- lips (1957), Chen ( 1971), Moser (1972), and Moser and Ahlstrom (1978). Most names used in this paper are the same as those used for adult rockfishes to avoid confusion, even though the bones from which the spines originate are not in- dicated by the name. Exceptions are as follows. The two spines found on the opercular margin are here called the subopercular and the interopercu- lar according to the bones from which they origi- nate. The superior posttemporal (supracleithral of adults), inferior posttemporal (not found in adults), and supracleithral (cleithral of adults) are so-called because of their origin. This is done to avoid confusion with a spine present on the poste- rior margin of the cleithrum, which is here called the cleithral spine. Use of the term infraorbital INFERIOR INFRAORBITAL SERIES. 1ST SUPERIOR INFRAORBITAL SERIES, 1ST SUPERIOR INFRAORBITAL SERIES, 2ND INFERIOR INFRAORBITAL SERIES. 2ND --' INFERIOR INFRAORBITAL SERIES, 3RD -'" SUPERIOR INFRAORBITAL SERIES, 3RD SUPERIOR INFRAORBITAL SERIES, 4 TH ANTERIOR PREOPERCULAR SERIES, I ST- 3RD POSTERIOR PREOPERCULAR SERIES, IST-5TH INTEROPERCULAR SUBOPERCULAR INFERIOR OPERCULAR SUPERIOR OPERCULAR NASAL PREOCULAR SUPRAOCULAR F'jST'XULAR Ip' TrMPANIC PTEROTIC PARIETAL NUCHAL r.FERIOR POSTTEMPORAL -yjPERIOR POSTTEMPORAL SUPRACLEITHRAL Figure l . — Composite diagram of spines present in the head region of larval and juvenile Sebastes species including names used in this paper. Refer to Table 2 for correspondmg names used for adults and bones from which spines originate. FISHERY BULLETIN VOL .NO 1 Table 2. — Names of head region spines of larval and juvenile Sebastes spp. used in this paper with corresponding names used for adults and bones from which the spines originate. Spines listed in the first column are shown in Figure 1 clockwise beginning with the nasal. Bone from which Name used in this paper Name used in adults^ spine(s) originates^ Nasal Nasal Nasal Preocular Preocular Prefrontal Supraocular Supraocular Frontal Postocular Postocular Frontal Coronal Coronal Frontal Tympanic Tympanic Frontal Rerotic Pterotic Pterotic Panetal Panetal Parietal Nuchal Nuchal Parietal Interior postlemporal — Postlemporal Superior postlemporal Supracleithral Postlemporal Supracleithral Cleithral Supracleithrum Cleithral — Cleithnjm Superior opercular Opercular Opercle Inferior opercular Opercular Opercle Subopercuiar Gill cover spine Subopercle Interopercuiar Gill cover spine Interopercle Posterior preopercular senes. lst-5th Preopercular Preopercle Antenor preopercular series. 1sl-3d — Preopercle Superior infraorbital senes, 4th — Infraorbilal 3 (2d suborbital) Superior infraorbital senes — Infraorbital 2 fist suborbital) Inferior infraorbital series, 3d — Infraorbital l (preorbital) Inferior infraorbital series, 2d Lachrymal projection (suborbital spine) Infraorbital 1 (preorbital) Superior infraorbital series, 2d — Infraorbital 1 (preorbital) Superior infraorbital series. 1st — Infraorbital 1 (preorbital) Inferior infraorbital series, isl Lachrymal projection (suborbial spine) Infraorbital 1 (preorbital) 'After Phillips (1957) and Chen (1971) ■'Afler Malsubara (1943) and Weitzman (1962) follows Weitzman (1962 Poss.* as recommendeii by SEBASTES CRAMERl (JORDAN) (Figures 2, 3, 4) Literature. — Pigment patterns of preextrusion larvae of S. crameri were described by Westrheim et al.," including one figure, and Westrheim (19751. Preextrusion larvae (mean total length = 5.7 mm) have a rowof 10 to 23 melanophores(45'7f of 60 larvae had <16 melanophores) along the ventral body midline which stops short of the anus by four myomeres. Melanophore(s) are also usu- ally present on the ventral finfold in the hypural region. The gut is pigmented. No pigment occurs on the head, nape, or dorsal body midline, how- ever. Westrheim ( 1975) reported that S. crameri larvae, along with several other species, reared for several days develop pigment spots on the head, nape, and or lower jaw. *S. G. Poss, Ph.D. Candidate, Department of Zoolog>', Univer- sity of Michigan, Ann Arbor, Ml 48109. pers. commun. .Julv 1977. 'Westrheim, S. J., W. R. Harling, and D. Davenport. 1968, Preliminary report on the maturity, spawning season and larval identification of rockfishes i.Sebastotles ) collected off British Columbia in 1967. Fish. Res. Board Can., Manuscr Rep. 9.51.23 p. Identification (Table 3, Appendix Tables 2-6l. — Eighty-one specimens of S. crameri, ranging from 8.0 to 130.5 mm, were identified. Juveniles were identified using the following combination of characters recorded from specimens in our collec- tions: Gill rakers = 30-34 Lateral line pores = 43-50 Pectoral fin rays = 18-20, usually 19 Anal fin soft rays = 7 Dorsal fin soft rays = 13-15 Supraocular spine = present Interorbital space = flat to convex. No other species on our list of potential species agrees with all these characters. In addition, the characteristic pigment banding of adults was ob- vious on larger juveniles. Larvae and juveniles were relatively abundant in our collections and adults are known to be abundant in terms of biomass in trawl catches off the Oregon coast (Demory et al. 1976; Niska 1976). The develop- mental series was linked together primarily on the basis of pigmentation and also body shape and time of occurrence. Identification of most of the smaller specimens was further substantiated by meristics, particularly the constancy in nurn lor of anal and pectoral fin rays (Table 3). RICHARDSON and LAROCHE DEVELOPMENT AND OCCURRENCE OF ROCKFISHES 9.0 mm 12.6 mm 14.7 mm FICI RE 2.— Planktonic larvae (9.0, 12.6, 14.7 mml of Si>6as/(?,s crameri. FISHERY Bl'LLETIN VOL 77. NO '). •'' 19.0 mm 3.<^ , ^'¥i^>:J^. '^-/ r %-':^«^< 5c^- t-' ^^-"f^ ;i^(' 22.7 mm 31.8 mm FICL'RK 3.— Transforming specimen 1 19.0 mmi and pelagic juveniles (22.7, 31.8 mmi t,{ Sebastes cr, RICHARDSON and LAROCHE DEVELOPMENT AND OCCURRENCE OF ROCKFISHES V> 'X>\ 56.9 mm ..r^'^^^s^^s^s 78.8 mm Figure 4. — Pelagic juvenile (56.9 mm) and benthic juvenile (78.8 mm) oC Sebastes crameri. Distinguishing Features. — Characters useful to distinguish the smallest i(ientified larvae (8.0 mm) are the heavily pigmented pectoral and pel- vic fins, the presence of a heavy nape pigment patch from which some melanophores extend down and over the gut externally on the body wall, the absence of dorsal midline pigment other than at the nape, the presence of ventral midline pig- ment as =11 distinct melanophores of which the anterior ones are embedded and only the posteri- ormost ones remain on the ventral body surface, and pigment at the tip of the lower jaw. The pres- ence of pigment on the first dorsal fin in larvae as small as 11 mm is also a useful character. Meris- tics, presence of a supraocular spine, flat to convex shape of the interorbital space, heavily pigmented FISHERY BULLETIN: VOL. 77. NO. 1 Table 3. — Meristics from larvae and juveniles ofSebastes crameri off Oregon, based on unstained specimens. Specimens above dashed line are undergoing notochord flexion. All specimens had 8 superior and 7 inferior principal caudal fin rays and 7 branchiostcgal rays on each side. Standard length (mm) Dorsal fin spines and rays Anal fin spines and rays Pectoral fin rays Pelvic f spines and Left n rays Right 3111 rakers first arch) Lateral line pores Diagonal scale Left Right Left Right Lett Right rows B.O (') (') — 19 (') (') _ 8.0 (') (') 19 19 i') P) — — — — — 9.0 III + IM3-14 P.7 19 19 M') l.C) _ 9.0 P. 14 P.7 19 19 I.C) 1,0 _ — — — 9.3 P. 14 P.7 19 19 l.C) 1,0 - — — — — 10,6 VI + IM3 P,7 19 19 1.5 1,5 S 10.6 VlllfP.14 ll',7 19 19 1,5 1.5 _ _ _ — — 10.7 IX + I'.13 IP, 7 — 19 1,5 1.5 — 12.2 X + 11.14 IIP,7 19 19 1,5 1.5 _ 19+ 8=27 _ — _ 12.6 XUIM3 IIP.7 19 19 1,5 1.5 — = 19+ 8=27 _ _ _ 12.8 Xl»|i.l4 IIP.7 19 19 1,5 1.5 — — — _ 13.6 XIIIM3 IIP.7 19 19 1,5 1.5 _ -18+ 8=26 — — _ 13.8 XIIIM4 IIP,7 19 20 1.5 1.5 _ -20+ 8=28 — _ _ 14.4 XIIP.14 IIP,7 19 19 1,5 1.5 — -20+ 8=28 _ — _ 14.7 XIIP.14 IIP.7 20 19 1,5 1.5 _ 21+ 9 = 30 _ _ _ 15.4 XIIP.14 IIP.7 18 18 1,5 1.5 — — _ _ _ '16.0 XIIP.14 IIP.7 19 19 1,5 1.5 — 21+ 8=29 _ _ _ '16.3 XIIP,14 IIP.7 19 19 1,5 1.5 — 22+ 8=30 — _ _ '17.3 XIIIM3 IIP.7 19 19 1.5 1.5 — 21+ 9=30 _ _ _ '17.4 XIIIJ.13 IIP.7 19 19 1,5 1.5 _ 22+ 9=31 _ — — '18.2 Xlll^,14 IIP.7 19 19 1.5 1.5 _ 20+ 9=29 _ _ _ '18.4 XIIP,13 IIP,7 20 19 1,5 1,5 — 22+ 9=31 — — — '18.6 XIIIM4 IIP.7 20 20 1,5 1.5 _ 22+ 8=30 _ _ _ '19.0 XIII-M4 IIP.7 19 20 1,5 1.5 _ 22+10 = 32 _ — — '20.0 XIIP.14 IIP,7 19 19 1.5 1,5 21^ 9- = 30 22+ 9=31 _ _ _ '20.3 XIIIJ.14 IIP.7 19 19 1,5 1,5 22 + 9 = =31 22+ 9 = 31 — — — *21.0 XIIP.14 IIP,7 19 19 1.5 1.5 22 + 9- =31 21+ 9=30 _ _ _ 522.7 XIII.13 III.7 20 20 1.5 1.5 22 + 9 =31 22+ 9 = 31 _ 523.5 XIII. 13 111,7 19 19 1.5 1.5 23 + 9 =32 22+10=32 _ =24.2 XIII.14 111,7 19 19 1.5 1.5 23 + 9 = 32 22+ 9=31 _ — — 525.6 XIII.15 III.7 19 20 1.5 1.5 22 + 9 = 31 23+ 9=32 _ _ _ 528.6 XIII.14 111,7 19 19 1.5 1.5 22 + 9 =31 23 + 10 = 33 — =30.0 XIII.13 III.7 19 19 1.5 1.5 22 + 9 =31 23+ 9=32 •48 -47 _ 531.8 Xlil.l3 111,7 19 19 1.5 1.5 23 + 10 = =33 22+10=32 46 _ _ 535.7 XIII.14 III.7 19 19 1.5 1.5 23- 9 = 32 23+ 9 = 32 45 -43 — 538.2 XIII.14 111,7 19 19 1.5 1.5 23 + 10 =33 23+ 9=32 — — _ 556.9 XIII.14 III.7 19 19 1,5 1.5 22 + 9 =31 22+ 9 = 31 45 46 _ 546.8 XIII.13 III.7 19 19 1,5 1.5 24 + 9 =33 23+ 9=32 -48 — — 549.2 XIII.14 111,7 19 19 1.5 1.5 23 + 10 =33 24 + 10=34 ^43 =46 _ 558.9 XIII.14 III.7 19 19 1.5 1.5 22+ 9 =31 22+ 9=31 45 45 — 563.0 XIII.14 III.7 19 19 1.5 1.5 23 + 9 =32 23+ 9=32 45 46 _ 563.2 XIII.13 III.7 19 19 1.5 1.5 22 + 9 = =31 23+ 9=32 JO 46 _ 565.0 XIII.14 111.7 19 20 1.5 1.5 24 + 9 = 33 24+ 9=33 49 50 _ 567.6 XIII.14 111,7 19 19 1.5 1.5 22 + 10 = 32 23 + 10=33 47 48 — 578.8 XIII, 14 III.7 19 19 1,5 1,5 22- 9- -31 22- 9-31 48 44 _ '86.1 XIII.13 111,7 19 18 1.5 1,5 23 + 9 =32 23+ 9=32 46 46 _ 591.8 Xlll,14 III.7 19 19 1.5 1,5 22 + 10 = 32 23-10=33 47 49 -53 594.4 XIII.14 III.7 19 19 1.5 1,5 22 + 8 =30 22- 9=31 49 47 -59 594.7 XIII.14 111,7 19 20 15 1,5 23 + 10 =33 23- 9=32 45 45 — 596.2 XIII.13 III.7 19 18 1.5 1,5 22 + 9 =31 22+ 9=31 47 45 •55 5105 6 XIII.13 111,7 19 19 1.5 1.5 22 + 9 = -31 22+ 9 31 47 47 -51 5125.7 XIII.14 111,7 19 19 1.5 1.5 23- 9 = -32 23+10-33 45 44 -59 5130.5 XIII.13 111,7 20 2" 1.5 l.."^ 23 + 10 = =33 23+ 9=32 46 47 -60 forming ^Nol formed ^Posteriormost dorsal or anal spine appears as a soft ray ^Transforming. ^Pelagic juvenile 5Ben1nic juvenile pectoral and pelvic fins, and pigment banding pat- tern on the body serve to distinguish juveniles. General Development. — The smallest specimens (8.0-9.0 mm) of S. craryieri in the series are under- fi^o'.ig the final stages of notochord flexion, which i.'^ completed by the time larvae are 10 mm. Trans- formation from postflexion larvae to pelagic juveniles is rather gradual beginning when larvae are about 16 mm. It is charactorized by addition ot pigment beneath the second d^rs.'l fin along witli initiation of structural change of ihe "prespines" in the dorsal and anal fins. Tr.msformation is complete in 22 mm specimens and the juvenile pigment pattern is obvious. Transition from pelagic to bentbic habitat probably occurs when fish are 40 to 60 riim. The largest 1 elagif uvenile. captured in a neuston net. was 56.9 mm and the 1' RICHARDSON and LAROCHE DEVELOPMENT AND OCCURRENCE OF ROCKFISHES smallest juvenile taken in a bottom trawl was 46.8 mm. Morphology (Tables 4, 5). — Measurements of var- ious body parts were made on 53 selected speci- mens of S. crameri, ranging from 8.0 to 130.5 mm long, to examine developmental morphology. Rel- ative body depth at the pectoral fin base and at the anus increases somewhat, 32 to 34% SL and 24 to 28'7f SL, respectively, during development from flexion larvae to benthic juveniles. A more marked change occurs in snout to anus distance which increases from 54 to 65'7f SL. The distance from the snout to the pelvic fin base increases slightly. Head length decreases somewhat during de- velopment from 39 to 369c SL, while major de- creases occur in eye diameter (40-33% HL), upper jaw length (56-41% HL), and interorbital distance (36-23% HL). Snout length first increases slightly and then decreases with respect to head length. The length of the angle gill raker increases from 9 to 16% HL. Fin Development (Tables 3, 4, 5). — Pectoral fins are formed in 8 mm larvae of S. crameri and the adult complement of 18 to 20 (usually 19) fin rays (or ray elements) are countable in 9 mm speci- mens. The fins become more elongate with de- velopment, increasing from 17% SL in flexion lar- vae to a maximum of 32% SL in pelagic juveniles. Depth of the pectoral fin base decreases from 13 to 10% SL. Pelvic fin buds are present on 8 mm lai'vae and the forming spines and rays (1,5) can be counted in 9 mm larvae although they are not fully developed until the larvae reach about 10 mm. Length of the pelvic fins increased from 7 to 21% SL during the larval and juvenile periods. Length of the pelvic spine, which is less than the longest ray, increases from 5%' SL in flexion larvae to 19% during trans- formation, and then decreases to an average of 13% in benthic juveniles. In 8.0 mm larvae the adult complement of 8 -i- 7 principal caudal rays can be counted although notochord flexion does not appear to be complete until larvae are >9.3 mm. Counts of superior and inferior secondary caudal rays made on one stained juvenile, 38.2 mm, were 12 and 13, respec- tively. Bases of some dorsal and anal fin rays and spines are visible on 8 mm larvae. Development of the second dorsal and anal soft rays occurs simul- taneously with the central rays forming first and the posteriormost rays last. Developing soft ray elements are visible and adult complements can be counted on 9 mm larvae although rays do not appear fully formed until larvae are >10 mm. Dorsal spines begin to form slightly after initia- tion of soft ray formation at =9 mm. The third, fourth, and fifth dorsal spines develop first. The 12th spine is not formed until larvae are >13 mm long. The second anal spine is formed at 10.6 mm and the first is formed by 12 mm. The transition of dorsal and anal fin "prespines" to spines is com- plete at around 22 mm. The longest dorsal spine increases from 22 to 45% HL during the pelvic phase, and decreases to 37% in benthic juveniles. The longestdorsal ray increases from 26 to 41-43% HL during development. The longest anal spine increases from 16 to 37 or 38% HL. Spination (Tables 4, 6). — Spines visible on the left side of the head of an 8.0 mm larva of S. crameri consist of the parietal; the second, third, and fourth preopercular spines of the posterior series; the first, second, and third preopercular spines of the anterior series; the postocular; and the pterot- ic. Another more developed 8.0 mm specimen has a developing nuchal spine bump; the inferior post- temporal; the first spine of the inferior infraorbital series, and the first spine on the superior infraor- bital series. The parietal spine is relatively short, averaging 6.5 to 6.6% HL in larvae and decreasing to 3.0% HL in pelagic juveniles. The nuchal spine in- creases in length from 1% HL in flexion larvae to 4% in postflexion and transforming specimens then decreases to 3% in pelagic juveniles. Parietal and nuchal spines begin to fuse near their bases at 10.7 mm, gradually fusing towards the tips until in specimens >38 mm the parietal tip is no longer visible. In benthic juveniles the nuchal and parietal spines are fused and their relative lengths are =2% HL; however, increased pigment and musculature allowed measurement only from tip to body junction. The parietal spine and ridge are not serrated in larvae <9 mm. Serrations first appear at the center of the parietal ridge at 9 mm and persist until =39 mm. The posterior series of preopercular spines are among the most prominent in the larvae. The first through fifth spines of the series are present in larvae >10 mm. The third spine of the series is the largest, averaging 17 or 18% HL in larvae and then decreasing to 7% HL in benthic juveniles. Spines in the posterior preopercular series never 11 FISHERY BULLETIN: VOL. 77. NO. 1 Table 4.— Body proportions of larvae and juventies of Sebastes cramen.S. pinniger. andS. helvomaculatus . Values given are percent standard length iSL) or head length (HLl including mean, standard deviation, and range in parentheses. (Number of specimens measured may be derived from Tables 5, 8. and 11.) Item Sebastes cramerl Sebastes pinniger Sebastes helvomaculatus Body depth at pectoral tin baseiSL: Flexion Postflexion Transforming Pelagic Juvenile Benthic Juvenile Body depth at anusiSL: Flexion Postflexion Transforming Pelagic Juvenile Benlhic Juvenile Snouf fo anus length SL: Flexion Postflexion Transforming Pelagic Juvenile Bentfiic Juvenile Snout to pelvic fin ongin:SL Flexion Postflexion Transforming Pelagic Juvenile Benthic Juvenile Head lenglh'SL Flexion Postflexion Transforming Pelagic Juvenile Benthic Juvenile Eye diameterlHL: Flexion Postflexion Transforming Pelagic Juvenile Benthic Juvenile Upper law length HL Flexion Postflexion Transforming Pelagic Juvenile Benthic Juvenile Snout lengthHL Flexion Postflexion Transforming Pelagic Juvenile Benthic Juvenile Interorbital distance HL- Flexion Postflexion Transforming Pelagic Juvenile Benthic Juvenile 4r7g/e gill raker length HL Flexion Postflexion Transforming Pelagic Juvenile Benthic Juvenile Longest dorsal spine length^ HL Flexion Postflexion Transforming Pelagic Juvenile Benthic Juvenile Longest dorsal ray length^ HL. Flexion Postflexion Transforming Pelagic Juvenile Benthic Juvenile Longest anal spine length^ HL: Flexion Postflexion Transforming 31.8±2.05(29.0-33.8) 31. 7 ±1,26(30 3- 34 9) 32.4±1 74(29 5-35 6) 32.7±1 89(30,3-37.4) 34.4±1,96( 30.1-36.5) 23.6^0 67(22 6-24 4) 24 9±1 19(22 6-26 5) 26.7±1 34(24 7-29 4) 26.8 ±1 15(26 2-29.2) 27.7±1 56(25 1-30 7) 54.0±1 28(52 5-559) 60.5±325(55 1-65 1) 61 .a±3 26(54 3-65 0) 61 .6 ±2 63(57 9-64 3) 65.0:!: 1.81(61. 5- 68 7) 37.6±1 56(35.0-38.9) 40 8±2 02(38 1-44 3) 39 8±3 49(34 1-46.5) 38.9±3 23(34.0-44 5) 40.5 ±1.86(37.3-43.1) 39.0±1 55(37 5-41 1) 38.9 ±1 90(36 8-43 4) 36 6 ±2 43(32 8-38 7) 35.8±1 82(32 3-38 3) 36.4 ±2 75(31 8-39 9) 40.2±1 82(37 8-42 9) 38.2± 1.87(33 9-40 0) 36 9±2 47(33 3-42 1) 30 4 ±2 60(26 6-35 0) 31 .6±2 05(28 9-35 6) 46.5±4.35(40.5-50.0) 43 6±2 45(40 0-46 3) 438±5 55(34 2-50 9) 41 3±4 06(33 9-47 5) 41 2±2 44(37 8-45 6) 29.1 ±1 38(27 0-30 7) 30 0±1 65(26 1-31 7) 31 2±2 69(27 0-35 6) 28 2±2 97(24 6-32 1) 26.3±2.43(22 4-31 2) 35.6 ±1.95(32 4-37 1) 33.0±1 94(29 3-36 0) 31 2±339(259-368) 25 9±2 48(23 0-30 0) 21.6±2 18(18 0-26.8) 8.6±0.00(8.6) 11 4±1 77(8 6-14 4) 13 1 ±1 13(11 1-15 1) 139±082(13 3-15 1) 158tl 06(13 7-174) 21 6±2. 26(19 4-24 1) 34.3±7 13(26 2-45 1) 44 7± 1.55(42 0-46 2) 36.9 ±4 32(31 7-44 3) 26.2±6.96(14 6-33 3) 41.4±232(39 3-43 9) 42.0±2 97(38 1-46 7) 43 1*4 74(37 6-48.1) 15 6±3.16(9 6-18.5) 28.1 ±3 46(23.0-32 0) 40.3±0.92(39.7-41 0) 38 1 ±2 51(33 7-42 0) 35 9±1 36(33 3-38 3) 33.0 ±1.88(29.8-37 0) 34.9±2 15(32 7-37.0) 27 6 ±0 92(26 9-28 2) 285-1 92(24 7-30 6) 27 6»1 63(24 8-30 9) 26.0±1. 11(239-28.0) 29 8±3 68(27 3-34 0) 58 8±1 63(57 7-60 0) 59 6 ±3 42(51 7-62 6) 606 • 1 84(58 1-63 1) 61 4. '3 50(56 0-67 4) 64 2±3 27(60.6-67 0) 41 1 ±3 61(38 5-43 6) 40 7±3 03(34 7-44 9) 41 9*2 74(38 7-46 2) 39 9±3 83(32 9-45-5) 42.7±2.86(41.0-460) 43 0 ±0.92(42.3-43 6) 42 4 • 2 58(38 2-47 7) 40 5±1 39(38 0-42 6) 37 5±2 52(33.3-42 1) 366±0 51(360-37 0) 37 3 1 27(36.4-38 2) 39 3 1 89(37 5-41 3) 37 5 1 35(34 2-38 7) 34 2 2 77(30 8-42 3) 26 8 -3 22(24 0-30 3) 47 8 -0 99(47 1-46 5) 46 1 3 73(41 2-524) 42 1 ►3.64(35.6-47.0) 41 3- 3 14(34.6-47 4) 44 9 ±2 15(42 7-47 0) 26 9 ►0 28(26 7-27 1) 28 7 -3 45(23.8-34 8) 30 2 ±3 31(25 8-36 5) 27 3 *3 68(21 7-32 5) 28 8 ±0 72(28 0-29 4) 37 3 •127(36 4-38 2) 342 ±2 26(30 4-38 2) 30 0 ± 1 82(26 3-32 3) 24 4 •3 31(19 5-30 8) 198 •137(183-210) 106 ±1 42(8.3-123) 130 •0 72(11 5-14 5) 14 1 ±1 21(11 7-16 5) 149 ±1 10(138-160) 20 1 ±6 05(13 0-28 6) 32 4 •5 49(23 6-40 6) 38 0±3 79(33.1-46 2) 35 6±4 74(32 0-41 0) 31 5 ±4 26(23.8-38 0) 38 5± 3 60(30 8-42 9) 41 6 ±3 46(35 4-48 7) 42 6±3 83(40 0-47 0) 18 7 ±2 52(14 6-21 3) 28 5 ±5.65(20.0-38 6) 33 3 ±1.44(32.5-35.0) 33 4 ±0 46(33 0-33 9) 32 6±1 79(30 6-35 8) 31 2 ±1.58(28 4-32 9) 33 4 ±1.63(32-3-34.6) 20 7±0.61(20.0-21 2) 24 5 ±2.56(21 6-26 3) 24 7±1 22(23.1-26.9) 23 2±1 24(21 2-25.0) 25 4 ±2 33(23 7-27 0) 56 1 ±1.28(55 0-57 5) 59 1 ±0 50(58 6-59 6) 61 7±1 86(59 2-64 5) 62 8 ±2 46(59 8-66 0) 638*1 06(630-645) 40 5±1 27(39 0-41 2) 40 9±0 45(40 4-41 3) 42 8=3 13(38 0-47 3) 42 8±3 16(39 3-48 2) 40 0 ±0 92(39.4-40.7) 41.4±1.27(40 0-42.5) 42.0±2 03(40 4-44.3) 40 8±1 92(36 4-43 0) 40 1±1 48(37 5-41 9) 37 6 ±0 57(37 2-38 0) 38 8±1 63(29 4-31 2) 36 3±0.36(35 9-36 6) 35 5 ±2 38(32 0-38 8) 33 6 : 1 76(30 8-36 9) 31 6±5 30(27 8-35 3) 45 0 ±3.29(4 1.2-46.9) 44 0±3 00(41 0-47 0) 45 7 ±4 23(39 7-53 1) 45 1 ±2 63(40 2-47 6) 52 1 ±0 78(51 5-52.6) 32 3±2 20(30 0-34 4) 330±1 18(31 7-34 1) 32 4±3 72(25 0-37 9) 31 7 ±2.49(26 7-34 1) 26 7±0.42(26.4-27 0) 30 6±1 04(29 4-31 2) 31 4 ±0 55(30 8-31 8) 27 0±2 89(23 3-30 6) 21 5±3 83(13 3-25 6) 146±247(129-164) 134±095(12.3-14 1) 15 1±1 46(12 9-180) 14 2±1 90(12 7-15 7) 10 6±0 50(10 3-1 10) 19 0±0 64(18 6-19 5) 29 2±6 08(22 4-37 5) 30 9±2 93(28 0-35 7) 37 0 ±4.88(33 6-40 5) 22 8±7 39(1 5 9-30 6) 26 4 ±5 14(20 5-29 5) 36 1 ±3 08(32 5-41 7) 35 1 ±2 53(32 0-38 1) 42 8 ±3 89(40 0-45 5) 160±1 91(146-173) 27 3 ±4 46(22.4-36 1) 12 RICHARDSON and LAROCHE, DEVELOPMENT AND OCCURRENCE OF ROCKHSHES Table 4.— Continued. Item Sebastes cramen Sebastes pinniger Sebastes helvomaculatus Pelagic Juvenile Benthic Juvenile Pectoral fin length SL Flexion Postflexion Transforming Pelagic Juvenile Benthic Juvenile Pectoral tin base depth SL Flexion Postflexion Transforming Pelagic Juvenile Benthic Juvenile Pelvic fin length 'SL: Flexion Postflexion Transforming Pelagic Juvenile Benthic Juvenile Pelvic spine length SL Flexion Postflexion Transforming Pelagic Juvenile Benthic Juvenile Parietal spine lengthHL Flexion Postflexion Transforming Pelagic Juvenile Benthic Juvenile Nuchal spine length HL Flexion Postflexion Transforming Pelagic Juvenile Benlhic Juvenile Preopercular spine lengthiHL Flexion Postflexion Transforming Pelagic Juvenile Benthic Juvenile 37 8-4 36(31,2-43 5) 36 5*4 34(30 6-44 31 17 1 ±1 52(150-189) 21 1 12 26(17 0-23 5) 27 1^1,54(24 7-29 5) 32 1-1 73(30 2-35 3) 29 5±3 61(25 0-38 9) 126-1 27(108-138) 11 IrO 39(10 4-11 8) 104±061(95-11 7) 96i051(85-102) 10,2:0 53(8 8-10 9) 7,3:1 81(52-98) 15,3:1 46(12,3-16,9) 20 6:1 01(18.3-22 1) 20 9:0 60(20 1-21 9) 20 7 '0 97(18 5-22 2) 4 7:1 42(3 4-6 2) 11 4:2 20(6 8-14 6) 18 8:1,65(14,5-20 1) 19 0:1 35(16.2-20,7) 13 9:1 34(12,3-17 1) 65:1 01(54-7 4) 6 6:1 06(5 2-8 5) 6 0:1 24(3 7-7 4) 2 9:0 98(1 8-4 2) 1 1 :0 00(1 1) 4 1 :0 73(3 4-5 8) 44:088(3 1-6 0) 3 2:1 03(2 0-5 0) 1 7:0 64(0 7-2 8) 176 13 84(120-205) 170:1 09(15 5-185) 183:1 53(160-19,7) 12 0:2 85(8 6-16 2) 72:2 72(3 Ml 4) 37 4:4 07(30 8-44 0) 34 5:2 50(32 0-37 0) 25 0:2 69(23 1-26 9) 24 7:2 64(20 2-28 5) 27 0:2 42(22 7-31 5) 26 2:1 36(24 0-28 5) 243:1 21(22 9-25 0) 148:092(14 1-154) 12 6:083(11 4-13 6) 107:0 69(9 7-11 5) 9 1:0 64(8 2-10 1) 8 9:0.23(8 6-9 0) 13 8:2 19(12 3-15 4) 172:4 12(10 0-22 8) 22 7:1 59(20,8-25 3) 21 7:1,29(19,4-23 7) 21 3:2,08(19.0-23 0) 5 1:0 00(5 1) 12 1:299(82-150) 19.5:1 38(17 6-21 7) 17 9:2 10(14 5-22 1) 125:0 50(120-130) 24 4:0 35(24,2-24 4) 19 5:7 17(8 8-23 5) 10 2:3 07(3 9-12 9) 7 1:2.66(5.4-10 2) 4 4:1 63(2 5-6 9) 4 8:1 57(2 3-7 2) 3 1:0 96(1 9-5 4) 1 4:0 64(1 0-2 1) 34 4:2 83(32 4-36 4) 31 8:4 86(25 0-39 0) 23 6:2 09(21 2-29 1) 12 8:3 96(9 1-22 2) 4 8:1 39(4 0-6 4) 32 4:5 70(26 8-38 1) 48 8:4 67(45 5-52 1) 23 6:2 11(21 2-25 0) 24 4-0 57(23 9-25 0) 26 0 : 1 45(24 3-28 3) 26 6:0 28(26 1-26 9) 27 0:0 85(26 4-27 6) 12 5:0 00(12 5) 11 5:084(11 0-125) 9 9:0 64(9 0-10 8) 90:033(82-9 1) 9 3:0 71(8 8-9 8) 135:1 32(125-150) 155:070(148-162) 193*1 62(167-21 6) 192- 1 36(173-21 4) 22 7 1 0 99(22 0-23 4) 8 3:0 15(8 2-8.5) 12 3:2 26(10 2-14 7) 176:1 02(158-19 1) 164-1 99(135-189) 14 9-0 71(14 4-154) 27 4:4 19(22 9-31 2) 185:224(159-20 0) 126:239(90-163) 56-331(1 1-9 5) 3 1 :000(3 1) 1 8:0 85(1 2-2 4) 4 3:1 51(2 6-5 0) 4 6:0 78(3 0-4 9) 3 5:1 13(1 7-5 2) 27 4:4 19(22 9-31 2) 31 2 '064(308-31 7) 20 2-3 58(16 2-26 5) 11 8 16 29(2 5-15 9) 1 6:1 34(0 6-2 51 'Usually third or fourth in larvae -Usually midfin ^The second spine. fifth or sixth in juveniles develop strong serrations. Spines in the anterior preopercular series are much shorter than those in the posterior series. The second or middle spine is present only in larvae prior to completion of notochord flexion. <10 mm. Its appearance as a spine changes to a small bump which then fuses with the ridges connecting it to the third preoper- cular spine of the posterior series- The first and third anterior spines are present on larvae through pelagic juveniles of =23 mm and then are no longer visible- The superior and inferior opercular spines and the interopercular spine appear by the time the larvae reach 12 mm, although percursor bumps may be seen as early as 9 mm. These spines persist into the juvenile stage. The subopercular spine is present in juveniles >78 mm. Around the eye, the ridge anterior to the post- ocular spine becomes serrated at 10.6 mm. These serrations disappear at the time of supraocular spine formation, >21 mm. The preocular spme begins to appear in transforming specimens >16 mm and is strongly formed by the time fish are 20 mm. Beneath the eye the second spine of the in- ferior infraorbital series forms in larvae >10 mm. The fourth spine of the superior infraorbital series develops under the posterior third of the eye on larvae >13.6 mm and it persists through the juvenile stage as do the two inferior infraorbital spines. The second and third superior and third inferior infraorbital spines never develop. Tiny serrations appear along a ridge between the first and fourth superior infraorbital spines in speci- mens 14.4 to 38.2 mm. The first spine of the superior infraorbital series disappears in speci- mens >50 mm. The nasal spine develops m larvae of =10 mm and persists in juveniles. 13 FISHERY BULLETIN: VOL. 77. NO I T.'\BLE 5. — Measurements (millimeters I of larvae and juveniles o(Sebasles cramen from waters off Oregon. Specimens above dashed line are undergoing notochord flexion. 55 |f en ■a'St .c O 0) 0) S ctsz S E 2$ ^ £ c (5 _ c 9? £ _ -D Q. 01 h > 01 is Q- c Sue •^ > en ra "* — Q. c a. UO, l«s 25 mm. This spine forms at the anterior edge of a foramen of the cephalic lateral line system. The pterotic spine is present in flexion larvae and disappears in juveniles >50 mm. The supracleithral spine develops in larvae of ~11 mm and the superior posttemporal spine can be seen on specimens >18 mm. These latter three spines per- sist in juveniles, however, the inferior posttem- poral becomes reduced in larger juveniles. A cleithral spine develops dorsal to the pectoral fin base immediately posterior to the opercular mar- gin on juveniles >30 mm. 14 RICHARDSON and LAROCHE: DEVELOPMENT AND OCCURRENCE OF ROCKFISHES Scale Formation. — Lateral line pores are visible on transforming specimens >18.2 mm. Develop- ing scales are first visible on unstained specimens =20 mm on the posterodorsal region of the head and anterodorsal region of the trunk above the gut cavity. Scale development proceeds posteriorly with the body being covered by 29 mm. Pigmentation. — Melanistic pigment on 8.0 mm specimens of S. crameri (similar to the 9 mm specimen illustrated) is present on the head over the brain. Melanophores line the inside tip of the lower jaw and may also be present along the an- teroventral margin of the maxillary. In the ab- dominal region interna! melanophores are dense- ly concentrated on the dorsal surface of the gut and more sparsely distributed laterally and ventrally. Additional external melanophores are present on the body wall over the gut cavity. A heavy con- centration of external melanophores and some in- TABLE 6. — Development of spines in the head region o^ Schastcs crameri larvae andjuveniles. Specimens above dashed line are undergoing notochord flexion. + denotes spine present and - denotes spine absent. Standard length (mm) Parietal Nuctial Preopercular (anterior series) Preopercular (posterior series) Opercular 5tti Supenor Interior cular Inter- Sub- oper- oper- Pre- Supra- Post- cular cular ocular ocular ocular 80 + - + 80 + + + 90 -f + + 90 + - + 93 + + - 106 + + + 106 4- -f -f 122 + -t- + 126 + + + 128 + + + 136 + + + 138 + + + 14 4 + + + 14 7 + + + 154 + -1- + -'16 0 -*- + + M63 + + + ^173 + + -t- '174 + -f + '182 + + + '184 + + + '18 6 + + + '19.0 -f- + -t- '20-0 + -1- + '203 + + + '21.0 -f + ■t- '227 + + + =23-5 + + V) '24-2 + + '25-6 + + - '28.6 + + - '30-0 -t- + - '31.8 + + - '357 -*- + - '382 -*- -f - '56 9 + + - M6.8 + + - ■•49.2 + + - '58 9 + -(- - "63.0 + + _ -63 2 + + - "65 0 + + _ "67 6 + + - "788 + + _ "86.1 + + - "91 8 + + - "94.4 + + - "947 + + - "96.2 + + _ "1056 + -f - "125 7 ^^ + 5 _ "1305 -i-5 + S - (') V) 'Bump indicates beginning of spine formation. ^Transtorming ^Pelagic )uvenile ^Benthic juvenile ^Parietal and nuchal spines fused ^Spine IS bifid 15 FISHERY BULLETIN: VOL, 77. NO 1 Table 6. —Continued. Infraorbitals Nasal length (mm) Interior Superior Posttemporal <-„p„. 1st 2d 3d 1st 2d 3d 4tfi Coronal Tympanic Pterotic Superior Interior cleithral Cleilhral 8.0 80 90 90 93 106 106 122 126 128 136 138 144 147 154 '160 '163 '17,3 '174 '182 '18 4 '186 '19.0 '20.0 '20,3 '2' 0 J22 7 J23,5 >242 325.6 ^28.6 '30.0 '31 8 '35.7 '382 '56 9 "46.8 M9 2 ■■58 9 '630 ■•632 -65 0 "67.6 '78 8 "86 1 "91 8 "944 "94 7 "96 2 "105 6 "125.7 "130.5 {') + + + + + + + + + + + + + + + + + + + + + + (') + + + + + + + ternal pigment is present in the nape region al- though the dorsal midline is pigmentless. A few large stellate melanophores extend laterally from the nape to the gut cavity. A series of 10 or 11 distinct melanophores is visible along the ventral midline of the tail, the anterior five of which are embedded in musculature dorsal to the developing anal fin. A few small melanophores may be pres- ent on the notochord tip. The pectoral fins are distinctively and heavily pigmented. A dense con- centration of melanophores occurs on the proximal surface of the fin base but the distal surface is unpigmented. Elongate melanophores line the inner and outer surfaces of the fin blades creating a striated appearance. The developing pelvic fins are also pigmented. As larvae develop, pigment increases on the head over the brain. Melanophores persist along the tip of the lower jaw and the anteroventral margin of the maxillary. Several melanophores develop around the bases of the posttemporal and supracleithral spines in larvae >10.5 mm and on the dorsal part of the operculum anterior to the opercular spines in larvae >13.5 mm. Pigmentation within the gut cavity remains in- tense through larval development and external melanophores remain scattered on the body wall over the gut. In larvae -10.5 mm, as dorsal fin 16 RICHARDSON and LAROCHE: DEVELOPMENT AND OCCURRENCE OF ROCKFISHES spines develop, melanophores are added to the nape patch along the dorsal midline and posteri- orly along the dorsolateral body surface. The large stellate melanophores extending from the nape patch to the gut disappear by 12 mm. A few exter- nal melanophores appear along the anterior mar- gin of the middle of the cleithrum beneath the gill cover in 12 or 13 mm larvae. In the tail region the ventral midline melano- phores gradually become embedded, anterior ones first, and are obscured by overlying musculature by the time larvae are 13 mm long. A melanophore is sometimes present near the tip of the notochord. The pigmentation of the paired fins increases m intensity throughout the larval period, although the di.stal base of the pectoral fin remains unpig- mented. As the pelvic fins develop, melanophores line the rays giving a striated appearance similar to that of the pectoral fins. Melanophores appear on the anterior portion of the spinous dorsal fin by the time larvae are 11 mm long, and the anterior two-thirds of the fin remains rather heavily pigmented throughout larval development. The soft dorsal and anal fins remain unpigmented. One to several internal, vertically elongate melanophores appear at the base of the caudal fin posterior to the hypural elements on most larvae >9 mm long, but the fin base is never completely lined with pigment. During the transformation period, 16 to 21 mm, pelagic juvenile pigmentation begins to develop. On the head, pigment increases around the post- temporal spines and joins with the nape pigment. Internal and external melanophores are added on the dorsal part of the opercle forming a patch which expands ventrally on specimens >19 mm. Scattered melanophores appear along the dorsal surface of the snout and the anterior portion of the upper lip (internal and external) on specimens >18.5 mm long. Pigment increases around the orbit, lining the dorsal, posterior, and ventral margin of the orbit by 19 mm. In the abdominal region, an increase in musculature over the gut cavity obscures the internal gut pigment although scattered external melanophores persist. The nape patch extends anteriorly joining the head pigment, laterally toward the body midline, and posteriorly to the 12th dorsal spine. Two saddles of intensified melanistic pigment begin to develop beneath the first dorsal fin late in the transforma- tion period. An anterior saddle joins the head pig- ment and another saddle located midfin expands ventrolaterally. Melanophores are added dorsally and ventrally along the anterior margin of the cleithrum beneath the gill cover, eventually ap- pearing as a line of pigment. In the tail region, melanophores appear beneath the middle of the second dorsal fin in 16 mm specimens. They ex- pand anteriorly to join the pigment beneath the spinous dorsal, posteriorly over the caudal pedun- cle, and laterally towards the body midline ap- pearing as a saddle by 20 mm. Some melanophores at the base of the second dorsal fin become concen- trated along muscles surrounding the dorsal pterygiophores giving the appearance of vertical lines of pigment by 20 mm. An additional melanophore may appear at the point of articula- tion of each dorsal soft ray 4 through 10 beginning on 18 mm specimens. Pigment is added internally and externally along the lateral midline of the caudal peduncle. On the first dorsal fin pigmenta- tion increases extending posteriorly to the 1 1th or 12th dorsal spine. In pelagic juveniles >22 mm long, small melanophores appear over the surface of the head. Melanophores almost entirely ring the orbit by 31 mm. Pigment increases on the snout and upper and lower jaws. The two pigment saddles beneath the first dorsal fin become more pronounced and extend moi-e ventrolaterally. A third saddle forms beneath the first dorsal fin posterior to the first two in specimens about 22 to 25 mm long. In the tail region, the saddle beneath the second dorsal fin extends to the lateral midline by 24 mm and even- tually reaches the ventral body margin in a 57 mm specimen. The number of melanophores increases on the caudal peduncle until dorsal and lateral pigment are joined forming a fifth pigment saddle in juveniles about 25 mm long. This fifth saddle eventually extends to the ventral body margin as does the saddle beneath the spinous dorsal fin. An increase in the number of melanophores occurs along the lateral midline of the caudal peduncle giving the appearance of a distinguishable, but not heavy, line of pigment. Small melanophores are added between saddles 3 and 4 and 4 and 5, along the myosepta first. The pectoral and pelvic fins remain heavily pigmented, although the amount of pigment on the base of the rayed portion of the pectoral fin decreases. Pigmentation on the spinous dorsal fin decreases in intensity between spines III and V, and between spines VIII and IX, corresponding to areas between the first, second, and third pigment saddles on the body. On speci- mens >38 mm long, pigment on the dorsal fin 17 FISHERY BULLETIN VOL 77. NO. 1 above the third saddle darkens into a distinct black blotch. Melanophores are added to the basal half of the second dorsal fin above the fourth sad- dle, appearing continuous with it on specimens ■29 mm long. Melanophores are also added to the basal half of the anal fin eventually extending from the second anal spine to the posteriormost anal fin ray on all specimens >38 mm. Specimens >36 mm have a melanophore at the point of ar- ticulation of each soft anal fin ray, although these melanophores soon become obscured by muscula- ture and scales. Three to seven small external melanophores are added near the bases of the caudal fin rays forming an indistinct line. Benthic juveniles >60 mm long retain essen- tially the same melanistic pigment pattern as pelagic juveniles except the intensity decreases resulting in a somewhat faded appearance. Addi- tional light scatterings of melanophores appear in the lower jaw and gular region, second dorsal and anal fins, and body in general. Two bars of pigment radiate ventrally from the posteroventral margin of the eye. The basic banding pattern and black blotch at the base of the dorsal fin remain evident in the largest juvenile, 130 mm, examined. This is the same banding pattern apparent in adults, however, the black blotch on the spinous dorsal fin disappears. In life (Moser**) a juvenile (122 mm) is reddish- brown dorsally, with white on the belly and five brownish bars on the bodv. The first four bars "H. G, Moser. Fishery Biologist (Research i. Southwest Fisheries Center. National Marine Fisheries ,Service, NOAA. P.O. Box 271, La Jolla, CA 92038, pers. commun. 1977. extend ventrally to slightly below the lateral line and dorsally onto the dorsal fins as diffuse dark areas. The head is reddish-brown and pale below eye level, with three brownish transverse bars: one at the anterior level of the orbit, one at the posterior level of the orbit, and one between and posterior to the parietal ridges. A large spot is on the opercle dorsally, and the axillary region has a dusky blotch. Except for the dark bars, the first and second dorsal fins are dusky at the base, grad- ing to pale orange or yellowish with Vermillion or deep red at the margin. The basal half of the anal and pelvic fins is whitish and the distal half grades from reddish to dark orange-red at the tips. The outer pelvic ray has a milky white lateral margin. The pectorals and caudal fins are pale orange, the pectorals with dark orange-red tips and the caudal with a faint dusky band on its posterior half Occurrence (Figures .5, 6 1. — Sebastes crameri ranges from Santa Catalina Island off southern California to the Bering Sea (Miller and Lea 1972). Off Oregon, Washington, and British Co- lumbia it is primarily an outer shelf/upper slope species generally occuring in depths of 150 to 300 m (Snytko and Fadeev 1974). Distinct population clumps have been found off the Oregon coast be- tween lat. 44°30' and 45°20' N (Snytko and Fadeev 1974). Most of our collections containing young S. crameri were taken along a transect off Newport (lat. 44°39.1' N) off the central Oregon coast. The smallest larvae and the greatest numbers of lar- vae and pelagicjuveniles were taken at stations 83 and 93 km offshore (water depths 700-1,300 m). The nearest inshore station on this transect at L- • r •r L ^» h Pelagic Juveniles 1 . . ■ ■-■ ^1 ^i ^1 'i V*™""" *'. ; ^*\ Lil* r H : A„^ Benthic Juveniles / -:.. : - "i - \ ^1 V~-— ,.| FlOURE 5. — Number of specimens and location of capture oflarvae and juveniles ofSehnstes crameri ofTOregon ( 1961-75) described in this paper. 18 RICHARDSON and LAROCHE: DEVELOPMENT AND OCCURRENCE OF ROCKFISHES MAR 40 60 eO 100 Stondofd Length (mm) 20 140 Figure 6. — Seasonal occurrence of larvae and juveniles of Sebastes cramen off Oregon. Data from 1961 to 1975 combined. Dashed line separates pelagic and benthic stages. which a larva (15.7 mm) was taken was 28 km (depth 95 m). The farthest offshore occurrence on this transect was a 26 mm pelagicjuvenile 194 km offshore. Benthic juveniles were generally taken nearer to shore than larvae or pelagic juveniles at depths of 55 to 200 m. Most pelagic specimens came from Isaacs-Kidd midwater trawls towed obliquely through the water column. Four speci- mens, 17.7, 24.0, 38.2, and 56.9 mm, were collected in a neuston net in June, 56 to 65 km off Newport. Spawning times reported for S. crameri are November through March off California (Phillips 1964) and primarily February off Oregon, Washington, and British Columbia (Westrheim 1975; Westrheim et al. see footnote 7). However, mature females with ovaries containing embryos have been collected in February, March, ,'\pril. and June (Westrheim et al.,^ see footnote 7; Mar- ling et al.'"). Pelagic specimens in our collections were taken primarily in April, May, and June although two postflexion larvae were taken in August. Larvae under 10 mm were only taken in April and May. No specimens were taken Sep- tember through February. Because of a lack of information on larval growth, parturition time 'Westrheim. S. J.. W R. Harling, D, Davenport, and M. S, Smith. 1968. Preliminary report on maturity, spawning sea- son, and larval identification of rockfishes iSeicstorfcsl collected off British Columbia in 1968- Fish, Res. Board Can.. Manuscr Rep. 1005, 28 p, '"Harlmg.W. R.. M.S. Smith, and N, A, Webb. 1971. Pre- liminary report on maturity, spawning season, and larval iden- tification of rockfishes iScorpaenidae) collected during 1970. Fish. Res. Board Can. Manuscr. Rep. 1137, 26 p. cannot be inferred. The wide range of lengths of pelagic specimens, 8 to .30 mm in April, 9 to 36 mm in May, 18 to 57 mm in July, indicates spawning may be variable and protracted. Benthic juveniles were taken March through July. In trawl surveys off Oregon, adults ranked sec- ond in biomass only to S. diploproa of all rockfishes collected over the continental slope and fifth or sixth on the continental shelf (Demory et al. 1976). Snytko and Fadeev ( 1974) reported it to be one of the most abundant trawl-caught rockfish species over the slope together with S. alutus, S. saxicola, and S. diploproa. This species was one of the three major contributors to the 1963-71 Ore- gon landings of the Pacific ocean perch fishery exceeding ,S. alutiis in 1971 (Niska 1976). Al- though little can be said about the actual abun- dance of larvae and juveniles off Oregon because of the various kinds of samples examined and irregu- lar nature of the sampling effort, they were one of the more common kinds relative to the other species of Sebastes in the samples. SEBASTES PINNIGER (GILL) (Figures 7, 8, 9) Literature. — Pigmentation of preextrusion larvae of S. pinniger was listed in tabular form by Wes- trheim (1975). Newborn to 2-wk-old larvae were described by Waldron (1968) and the older larva was redrawn by Moseretal. (1977). Mean length of larvae at hatching is 3.6 mm SL. Newborn lar- vae have an irregular double row of pigment (usu- ally <16 melanophores) along the ventral midline between the 18th and 22d myomere and some pigment above the yolk sac near the anus. After 2 wk additional melanophores are present at the tip of the lower jaw, on the ventral part of the yolk sac, on the pectoral fins, along the dorsal midline in an irregular double row between the 19th and 21st myomeres, and in the hypural region. The ventral midline melanophores may extend as far forward as the 14th myomere. Identification (Table 7, Appendix Tables 2-6).— A total of 269 specimens of S. pinniger, 7.9 to 181 mm long, were identified. Juveniles were iden- tified using the following combination of charac- ters compiled from specimens in our collections: Gill rakers = 40-45, left arch; 38-46, right arch Lateral line pores = 40-45 Pectoral fin rays = 16-18, usually 17 19 FISHERY BULLETIN VOL 77. NO 1 8.9 mm 9.8 mm I4.lmm Figure 7.— Planktonic larvae (8.9. 9.B mm.l and transforming specimen (14.1 mm) of Sebastes pinniger. 20 RICHARDSON and LAROCHE: DEVELOPMENT AND OCCURRENCE OF ROCKFISHES 16.2 mm 20.0 mm 29.4 mm Figure 8. — Transforming specimen 1 16.2 mmi and pelagic juveniles i20.0, 29.4 mm) of Sebastes pinniger. 21 FISHERY BULLETIN VOL, 77. NO 1 40 0 mm 59.4 mm Figure 9. — Pelagic juvenile (40.0 mm) and benthic juvenile (59.4 mm) of Sehastes pinniger. Anal fin soft rays = 7 Dorsal fin soft rays = 13-15, usually 14 or 15 Supraocular spine = present Interorbital space = flat to convex. Large juveniles ( >26 mm SL) have the black blotch at the base of the posterior half of the spi- nous dorsal fin characteristic of adults. Other Sebastes juveniles which have a black blotch, e.g.. S. nu'lanops, S. //ac/f/w.s, S. cranieri, do not agree with the characters given above. Of the Sebastes species occurring off Oregon, S. pinmger has the best fit to all these characters. Sebastes rmniatus and S. emphaeus also agree with many of the counts. However, juvenile S. iiiiniatus and S. em- phaeus lack a black blotch at the posterior base of the spinous dorsal fin. Sebastes mtniatus usually has 18 rather than 17 pectoral rays, and S. em- phaeus lacks supraocular spines. The larvae and juveniles in the series in question were among the most abundant in our collections. Adult S. pin- niger are known to be abundant in trawlable areas offshore whereas S. miniatus are not commonly taken (Demory et al. 1976; Niska 1976). Sebastes emphaeus, although not previously reported from Oregon, is well represented in our samp'es. Fig- ment pattern, general body shape, time of occur- rence, and constancy in number of anal fin soft rays and pectoral rays helped link the dev iop- mental series together. 22 RICHARDSON and LAROCHE: DEVELOPMENT AND OCCURRENCE OF ROCKFISHES Table?. — Meristics from larvae and juveniles of Se6as/espmni^<>r off Oregon, based on unstained specimens. Specimens above dashed line are undergoing notochord flexion. All specimens had 8 superior and 7 inferior principal caudal fin rays and 7 branch iostegal rays on each side. standard length (mm) Dorsal fin spines and rays Anal fin spines and rays Pectoral fin rays Pelvic fin spines and rays Left Rigtit Gill rakers (first arcti) Lateral line pores Diagonal scale Left Riglit Left Rigtit Left Right rows 78 78 CI — f7 17 — M') IV) — — — — — 88 Vllltl=.14 III5.7 8.9 IX^IMS IIIJ.7 93 XIIP,14 IIP.7 98 XIIP,14 IIP.7 107 XIII3.14 IIP,7 107 XIIIMS ll|5,7 109 XIIIM5 IIP,7 123 XIIP.15 IIIJ.7 12 3 XIIIM4 1IP.7 ■■128 XIII3.15 IIIJ.7 M30 XIIP,14 IIP.7 '14 1 Xll|5,14 IIP. 7 "142 XIIP.U lll'.7 ■■152 XIIIM5 lll'.7 "160 XIIIM4 IIP.7 "160 XIIIM4 III5.7 "162 Xll|5,15 IIP7 "168 Xll|5.t4 IIIJ.7 "178 XIII5.15 IIP.7 "18 4 XIM5.14 IIP.7 M86 XIII, 16 III.7 ^■189 XIII.IS III.7 M94 XIII.IS 111,7 5195 XIII.14 111,7 520 0 XIII.14 III.7 520 8 Xlll,14 111,7 522 4 XIII.14 III.7 523 4 XIII.14 111,7 526 4 Xlll,14 IM.7 526 4 XIII.14 III.7 526 6 XIII.IS III.7 528 6 XIII.14 III.7 528 8 XIII.15 III.7 529 4 XIII.14 III. 7 530 4 XIII.13 III.7 530 9 Xlll,14 111,7 534 1 XIII.14 III.7 538 0 XIII.14 III.7 538 7 XIII.IS 111,7 5392 XIII.14 '11.7 5400 XIII.14 l'l,7 541 0 XIII.14 .117 542 4 XIII.IS 111,7 5594 XIII.14 111,7 5117 7 Xlll,14 111,7 5181 XIII.IS III.7 17 17 18 17 17 17 17 17 17 17 17 17 17 17 17 18 17 18 17 17 17 17 17 17 17 17 17 17 17 1- 16 17 17 17 17 17 1; 17 17 17 17 17 17 17 17 17 17 17 17 17 17 17 17 17 17 17 17 18 17 17 18 17 17 17 17 17 17 17 17 ■7 17 17 17 I.S IS 1.5 I.S 1,5 1,5 IS 1.5 I.S 1.5 I.S 1,5 1.5 15 1,5 1,5 1,5 I.S I.S 1.5 IS 1.5 1,5 1.5 1.5 I.S 1.5 1,5 1.5 1 ; i.f I.S 1.5 1,5 1.5 1.5 1.5 15 l.i 1.5 1.5 I.S 1,5 1.5 1,5 1,5 1,5 — — — IS — — — 1.5 _ _ — 1.5 — — — I.S — — — 1,5 — — — 1,5 — — — 1,5 — — — I.S — — — I.S -~ — — 1.5 — _ — 1.5 — 27- 12 or 13 = 39 or 40 — 1,5 — — — 1,5 — — — 1,5 — 28+13=41 — 1,5 — — — 1,5 — 27 + 13=40 — 1.5 — _ — I.S — 27 + 12 = 39 — I.S — — — 1,5 27-14=41 28-14=42 — 1.5 29-13=42 28-13=41 _ 1,5 27*13=40 26' 12-38 — 1,5 27-13=40 27-12 39 — 1,5 27-14=41 28-13-41 44 1,5 28-13=41 28-13=41 — I.S 28-13 = 41 29-13=42 _ IS 29*13=42 28-14=42 -44 1.5 29+15=44 29 + 14 = 43 -43 I.S 28- 14=^42 2d -13=41 — 1,5 28-13 = 41 29 + 14=43 — IS 28-13=41 29*14 = 43 »42 IS 29-13 = 42 28-13 41 — 1.5 28- 13 = 41 28 + 14=42 -44 1.5 28-13 = 41 28 + 13 41 «44 1.5 31 ■ 14 = 45 31 + 15-46 — 1,5 29-14=43 29 + 14=43 .44 l,S 28*14 = 42 29 + 14=43 — 1,5 27-13 = 40 29+i:.=42 =42 1,5 29-14=43 29+1 4 43 =41 1.5 28 + 14=42 29 + 13=42 40 1,5 30-14=44 30-1- 44 — I.S 29-14 = 43 29-14 = 43 1,5 29-14=43 29-14 = 43 :.,_ l,S 29-14 = 43 29- 13-42 45 1.5 30-14=44 28-14=42 43 =44 =40 x44 «42 «44 =41 43 40 43 44 43 =51 =50 'Forming ^Not formed ^Postenormost dorsal or anal spine appears as a soft ray "Transforming 5Pelagic luvemle 5Benthic juvenile Distinguishing Features. — Characters useful in distinguishing the smallest larvae (7.8 mm) of S. pintager identified from our collections are the presence of remnants of both dorsal and ventral midline melanophores the anterior of which are nternal, the lightly pigmented pectoral fins, melanophores at the tip of the lower jaw and on the anteroventral margin of the maxillary, the pres- ence of one or two large external stellate melano- phores on the (i- sum just posterior to the parietal spines, the relatively deep body (40'7f SL), long parietal spines (24'^f HL), and long pectoral fins (25% SL). Later stage larvae are characterized by their relative lack of pigment on the trunk except over the gut, together with the relatively deep body and long parietal and third posterior preopercu- lar spines. Meristics, presence of the supraocular spine, flat to convex shape of the interorbital space, and dark blotch at the base of the spinous dorsal serve to distinguish the juveniles. 23 FISHERY Bl'M-ETIN VOL 77. NO. 1 General Development. — The smallest larvae of S. pinniger identified, 7.8 mm, are in the final stage of notochord flexion. By the time larvae are 8.8 mm long, fle.xion is complete. Transformation to pelagic juvenile begins in larvae -12.5 mm long with the initiation of spine formation in the dorsal and anal fin "prespines" and the appearance of a patch of melanophores on the dorsum immediately posterior to the second dorsal fin. Transformation of the "prespines" to spines is complete in speci- mens > 18.6 mm and some pigment has been added beneath the first dorsal fin marking the beginning of pelagic juvenile pigmentation. The dorsal pig- mentation becomes more pronounced during the pelagic juvenile period which lasts until ~40 to 50 mm. The largest pelagic juvenile taken was 42.4 mm and the smallest benthic juvenile was 59.4 mm. Morphology (Tables 4, 8). — Forty-eight specimens of S. pinniger. 7.8 to 181.0 mm long, were mea- sured for developmental morphology. Larvae ap- pear quite deep bodied, but body depth at the pec- toral fin ba.se decreases considerably during the pelagic period from 40 to 33'r SL. In comparison, body depth at the anus/SL changes relatively lit- tle, decreasing slightly then increasing. Snout to anus length increases from 59 to 64'^( SL while snout to pelvic fin distance increases to a lesser degree. Head length decreases from 43 to 37*^^ SL during development as more marked changes occur in eye diameter, decreasing from 37-39 to 27'r HL, and interorbital distance, decreasing from 37 to 20Cf HL. Upper jaw length/HL first decreases and then increases while snout length/HL increases then decreases. The length of the angle gill raker in- creases with respect to head length from 1 1 to 14 or 15'7f. Larvae and young juveniles up to 24 mm have a prominent symphyseal knob directed anteroven- trally. It becomes less obvious with development and is barely noticeable by the time juveniles are 29 mm long. Fin Development (Tables 4, 7, 8). — Pectoral fins are present and the adult complement of 16 to 18 (usually 17) rays can be counted in 7.8 mm larvae of S. pinniger. although the ventral rays are not fully formed until >8 mm. The pectoral fins are relatively long in flexion and postflexion larvae averaging 2.5''( SL and they maintain this approx- imate proportion through development. Depth of 24 the pectoral fin base decreases from 15 to 9'/f SL. Developing pelvic fins are visible on 7.8 mm larvae and the adult complement of I, 5 is count- able in postflexion larvae of 8.8 mm. The pelvic fins are rather long, averaging 14'^f SL in flexion larvae and increasing to a maximum of 23'^f SL in transforming specimens. Length of the pelvic spine, always less than the fin itself, increases from 5^'<- SL in flexion larvae to 2Cf( in transform- ing specimens then decreases to 1.3''f in benthic juveniles. The adult complement of principal caudal rays can be counted in 7.8 mm larvae, before the com- pletion of notochord flexion at 8.8 mm. Counts of secondary caudal rays were 11 superior and 12 inferior rays on each of two stained juveniles, 29.5 and 33.4 mm. Bases of some of the dorsal and anal fin ray and spine elements are visible on the 7.8 mm larvae. The adult complement of ray and spine elements is present in postflexion larvae >9 mm and the rays and spines (with "prespines") appear fully formed by 9.3 mm. Transformation of "prespines" to spines is completed by 18.5 mm. The longest dorsal spine increases from 20 to 38'? HL during the pelagic period. The longest dorsal ray increases from 32 to 42 or 439*^ . The longest anal spine in- creases from 19 to 37'7( HL during pelagic de- velopment. Spmation (Tables 4, 9). — Spines present on the left side of the head of the two smallest specimens of S. pinniger, 7.8 mm, include the parietal; the nuchal; the first and third anterior preopercular; the second, third, and fourth posterior preopercu- lar; the postocular, the pterotic, the inferior post- temporal; the first spine of the inferior infraorbital series; and the first spine of the superior infraorbi- tal series. The parietal spine and ridge are heavily and relatively deeply serrated in small larvae and the spine is relatively long, averaging 24'f HL in flex- ion larvae. Its relative length decreases with de- velopment to 20^7^ HL in flexion larvae, 10^ in transforming specimens, and 77c in early pelagic juveniles, <20 mm. The much smaller nuchal spine averages 4 or 57r HL in postflexion and transforming larvae, decreasing to 19f in benthic juveniles. The parietal and nuchal spines fuse to- gether, beginning in pelagic juveniles -20 mm until only the nuchal tip is visible in juveniles >40 mm. Serrations along the parietal ridge can be seen on specimens up to 39 mm. RICHARDSON and LAROCHE: DEVELOPMENT AND OCCURRENCE OF ROCKFISHES Table 8. — Measurements (millimeters) of larvae and juveniles of Sebastes pinmger from waters off Oregon. Specimens above dashed Ime are undergoing notochord flexion. o — t- £ en c li S O) 0) — I O OJ c — CO S (U c E ra »-□ UJ Is £•5 c ra _ n O 0) c m£ Q- C Q. is CL h - 111 3 c o -t 78 98 4.6 3-3 0.88 1,6 12 1 2 32 2 1 21 1 1 0 40 1 2 3.4 0.80 (') 1 2 — (*) (') (') 78 95 45 3.4 0.92 1 6 13 1 3 3 1 22 1 8 1 2 C) 0 96 30 084 C) 1 1 — (^1 (») .......... 88 11 2 55 42 1 0 22 1 5 1 4 37 25 2 1 1 2 0 72 0 88 36 — _ 1 2 _ _ 1 0 8.9 11 1 46 34 0 92 1 4 1 4 1 3 30 22 1 8 1 2 0 88 1 1 34 0 76 016 1 2 — 0 46 1 1 (=) 93 11 5 56 40 1 3 1 9 1 5 1 4 35 26 2 1 1 2 1 2 1 4 38 0 94 0 10 1 4 — 0 52 1 1 {') 98 123 58 4 1 1 2 1 9 1 6 1 5 38 30 2 7 1 2 — 1 7 34 0 96 0 18 1 6 0 34 — 1 3 0 60 107 14 1 66 4 7 1 3 22 1 9 1 6 43 32 27 1 4 — 1 9 48 — — — 054 1 1 1 5 1 0 107 134 63 46 1 6 20 1 9 1 4 39 29 27 1 3 1 6 23 4 7 — — 1 2 0 48 1 0 1 4 0 88 109 128 63 45 1 2 22 1 8 1 5 43 33 — 1 4 1 6 20 44 — — 1 5 0 44 0 92 1 4 0 84 123 155 77 50 1 3 2 1 1 9 1 7 4 4 34 30 1 4 — 24 4 9 0 44 0 18 1 6 0 56 — 1 9 1 0 123 154 76 52 1 6 — 2 1 1 7 48 3 7 35 1 4 — 28 52 — 0 36 1 3 0 64 1 5 1 9 — '128 157 80 52 1 9 2 1 20 1 6 4 5 34 29 1 3 24 27 59 0 66 0 18 1 3 0 70 1 5 1 6 1 3 '130 152 82 55 1 7 2 1 2 1 1 6 4 8 3 5 35 1 5 — 27 59 0 60 0 30 1 6 0 68 1 3 20 1 1 '14 1 17 1 85 59 21 21 22 1 7 49 35 — 1 5 26 30 60 0 68 0 32 1 3 0 68 — — 1 5 '142 168 86 57 1 6 — 22 1 8 5 1 39 — 16 25 30 58 — 0 36 1 3 0 72 1 7 22 1 5 '152 192 9 1 62 1 9 28 23 20 54 4 3 43 1 7 3 1 3 7 62 0 80 0 40 1 5 0 84 1 9 24 1 8 '160 20 0 94 62 1 7 28 24 20 59 4 5 45 1 8 — 38 62 — 0 28 1 4 0 80 24 — 20 '160 208 93 66 1 7 31 25 20 57 4 5 4 5 1 6 — — 62 0 26 0 18 1 4 088 — 24 1 7 '16.2 20 6 102 69 1 9 32 26 20 62 50 5 1 1 8 — 4 1 6 7 — 0 50 1 6 0 90 28 29 — '166 197 10 1 67 2 1 28 2 5 1 9 63 4 7 4 5 1 8 — — 65 — 0 34 1 6 0 88 22 25 — '178 20 8 107 70 22 28 27 20 64 52 48 1 8 36 4 1 76 — — 1 6 090 — 28 — '184 21 8 107 70 1 9 28 25 22 64 5 1 4 4 20 40 4 4 75 0 72 0 16 1 6 0 94 — 30 27 «186 22 9 11 7 76 23 33 26 20 62 4 7 50 1 8 36 42 86 0 70 0 32 — 1 1 26 32 26 «189 23 5 11 7 7 7 24 33 2 7 2 1 64 48 — 1 9 36 4 1 84 — — 1 6 09 — — 24 "194 23 4 11 2 80 19 34 27 22 66 54 52 1 9 4 2 46 76 0 46 0 30 1 7 1 1 — 31 26 "195 24 6 115 82 22 3 5 28 22 67 52 — 20 43 46 66 0 84 0 44 1 4 1 0 30 — 2 7 "20 0 25 4 11 5 74 1 8 34 28 22 74 56 5 7 20 — 46 80 0 40 0 30 — 1 1 — 32 28 "20 8 24 8 126 80 26 3 1 28 21 70 53 59 20 39 42 85 Joined 0 32 1 2 1 2 — — 27 •22 4 26 7 130 84 20 34 30 23 7 7 59 60 22 45 52 80 Joined 0 26 1 4 1 2 — — 32 '234 28 8 13 1 78 2 1 3 7 33 24 80 63 6 1 2 1 4 7 5 1 77 Joined 0 28 — 1 2 36 38 33 "26 4 33 4 15.2 9 1 2 1 4 2 35 26 89 70 73 25 — 60 99 Joined 0 40 1 4 1 5 — 40 40 "26 4 312 173 104 34 40 34 24 89 70 72 24 46 55 120 Joined 0 20 1 2 1 5 — — 32 "26 6 32 0 170 10 6 26 42 34 22 89 7 1 7 1 24 48 6 1 109 Joined 0 40 — 1 4 — — 36 "28 6 38 1 179 107 30 40 35 27 92 73 76 26 — 64 1 1 4 Joined 0 28 1 3 1 5 — 42 4 1 •28 8 36 3 192 106 34 43 3 7 26 96 76 76 26 52 62 13 1 Joined 0 30 1 2 1 5 40 4 1 4 4 "29 4 37 1 179 10 1 26 4 1 37 27 105 80 7 5 28 52 66 107 Joined 0 28 1 2 1 6 44 4 4 4 4 "30 4 38 1 20 5 11 5 3 7 49 3 7 26 10 1 7 5 7 7 25 52 65 134 Joined — 1 2 1 6 44 4 4 4 4 "30 9 38 6 20 8 130 4 1 45 40 27 104 81 86 28 55 72 134 Joined — 1 2 1 6 46 46 — "34 1 42 6 22 7 125 39 53 4 0 27 11 0 83 — 28 5 7 66 155 Joined 0 34 1 5 1 6 4 4 48 48 "38 0 46 6 22 5 138 30 57 4 7 30 11 6 9 1 93 31 — 7 7 14 1 Joined 0 30 1 3 1 9 49 57 53 "387 46 4 23 4 133 33 60 4 5 29 120 98 96 34 66 78 142 Joined 0 46 1 4 2 1 54 — — "39 2 48 8 23 5 139 32 59 4 5 30 11 7 10 1 102 33 57 80 146 Joined 0 30 1 3 1 9 — 6 1 53 "40 0 49 1 23 5 149 36 60 4 7 33 12 5 104 96 36 65 88 155 Joined 0 30 1 4 2 1 53 66 63 "41 0 50 4 25 0 14 7 43 59 46 31 122 98 104 34 63 84 178 Joined 0 30 1 5 2 1 56 66 55 ■42 4 51 7 26 4 154 4 3 5 7 49 30 130 11 0 102 37 64 87 165 Joined 0 40 1 4 2 1 51 63 52 »59 4 71 0 36 0 21 8 64 93 66 40 194 162 136 51 74 11 3 24 4 Joined 0 46 1 4 30 7 4 89 75 '1177 141 8 78 3 43 8 125 195 11 2 86 41 6 33 2 29 4 10 1 148 25 5 48 3 Joined 0 64 1 7 66 138 174 142 »181 224 1172 65 4 18 1 30 6 159 137 67 2 61 5 45 1 163 218 41 2 83 5 Joined 0 70 2 3 106 26 7 30 9 23 9 'Usually third or fourth in larvae, fifth or sixth in juveniles ^Usually midfin ^The second spine *Bump ^Not formed ^Forming 'Transforming "Pelagic juvenile 'Benthic juvenile The posterior series of preopercular spines are prominent in S. pinmger larvae. The heavily ser- rated third spine is relatively long averaging 32 to 34'7( HL in flexion and postflexion larvae. Its relative length then decreses to 5^f in benthic juveniles. All five spines of the series are present in larvae >10 mm. Serrations are visible on the second, third, and fourth spines until =29 mm. The first posterior preopercular spine is some- times bifid in pelagic juveniles. The smaller first and third spines of the anterior preopercular series are also conspicuous on small larvae, but decrease in prominence until they are no longer visible in pelagic juveniles >26 mm. The second anterior preopercular spine never becomes appar- ent. 25 FISHERY BULLETIN: VOL, 77. NO. 1 The superior opercular spine is present on lar- vae by 9 mm and the inferior opercular spine ap- pears later in larvae —12 or 13 mm. Both spines are present on juveniles. An interopercular spine develops on the edge of the gill cover, usually in larvae >10 mm. A subopercular spine was not present on any of the specimens examined. The ridge anterior to the postocular spine is heavily serrated and remains so until preocular spine formation. The preocular appears first as a bump in transforming larvae =16.0 mm long and develops into a spine in pelagic juveniles >19 mm. Development of the supraocular follows a similar pattern appearing at about the same time as the preocular. Beneath the eye the fourth spine of the superior infraorbital series is present in larvae >9 mm and the third spine of this series is present in all larvae >13 mm. The second superior infraorbi- tal spine never forms. All three superior infraorbi- tal spines disappear by 43 mm. The second spine of the inferior infraorbital series is present on speci- mens >10 mm and the two spines in this series persist in juveniles. The third inferior infraorbital spine never develops. The nasal spine develops T.^BLE 9. — Development of spines in the head region of Sebastes pinniger larvae and juveniles. Specimens above dashed line are undergoing notochored flexion. + denotes spine present and - denotes spine absent. 88 8.9 9.3 9.8 10.7 10.7 10.9 12.3 123 M2.8 '13.0 '14 1 '142 '15.2 '160 '160 '16.2 '16.8 '178 '18 4 '186 M8.9 J 19.4 M9.5 =20.0 ■1208 =22.4 123 4 '264 =26.4 =26 6 =28.6 =28.8 =29.4 =30 4 =30.9 =34.1 =38.0 =387 '39.2 =40.0 '41 0 =42.4 «594 *117.7 6181 Standard length Parietal Nuchal Preopercular (anterior series) 1st 2d 3d Preopercular (posterior series) Opercular Superior Inferior Inter- oper- cular Sub- oper- cular Pre- Supra- ocular ocular Post- {mm) 1st 2d 3d 4th 5th ocular 7.8 78 » + + - + + - + - >- -- + ~ ~ " ~ - 4 + + {') 4- 4- i') {') + - + + (') + + i') f 4 {') (') {') (^) n (') + + + + 'Transtorming, -'Bump tndicates beginnrnq of spine formation ^Pelagic luvemle ■'Spine IS bifid ^Parietal and nuchal spines fused ■^Benthic juvenile ^Spine has become rounded, no sharp tip 26 RICHARDSON and LAROCHE: DEVELOPMENT AND OCCURRENCE OF ROCKFISHES Table 9.— Continued. Infraorbitals Nasal Posttemporal Coronal Tympanic Rerotc Superior Interior Standard length (mm) Inferior Supenor Supra- 1st 2d 3d isl 2d 3d 4th cleithral Cleithral 78 78 4- - - - - - — — + - + - - + - + - 8.8 + - 8.9 + - 9.3 + - 9-8 + - 10,7 + + 10.7 + + 10.9 + + 12.3 -f + 12.3 + + M2.8 + + •13.0 + + '14.1 + + M4.2 + + M5.2 + + M6.0 + + M6.0 + + '16.2 + + '16.8 + + '17.8 + + '184 + + 318.6 + + 318-9 + + 319.4 + + 319.5 + + 320.0 + + 320-8 + + 3224 + + 323.4 + + 326.4 + + 326.4 + + 326,6 + + 328.6 + + 328.8 + + 329,4 + + 330-4 + + 330.9 + + 334.1 + + 338.0 + + 338,7 + + 339.2 + + 340.0 + + 341.0 + + 342,4 + + 659.4 + + 61177 + ^ + M81 + ' + 7 {') + + + + + + + + + + + -I- (^1 first as a bump in larvae >9 mm and is present in juveniles. The tympanic spine appears on specimens >35 mm SL. This spine forms at the anterior edge of a foramen of the cephalic lateral line system. The pterotic spine, present in the smallest larvae, dis- appears in benthic juveniles. The supracleithral spine develops posterior to the inferior post- temporal on larvae >9.5 mm and the superior posttemporal spine is present dorsal to these in specimens >14 or 15 mm. This latter spine is occa- sionally bifid. The inferior posttemporal disap- pears in benthic juveniles. Posterior to the opercle the cleithral spine is visible in pelagic juveniles of 19.5 mm and persists in benthic juveniles. Scale Formation . — Lateral line pores are visible on specimens >17 mm. Scale formation has begun on juveniles >23 mm. Pigmentation . — The smallest larvae of S. pinniger examined, 7.8 mm (similar to the 8.9 mm speci- men illustrated), have pigment on the head over the brain. Melanophores line the inner tip of the lower jaw and a few are present along the antero- ventral margin of the maxillary. In the abdominal region, an internal melanistic shield covers the dorsal half of the gut, appearing darkest on the dorsal surface. A few additional melanophores are present along the ventral midline of the gut cav- ity. Two or three lai-ge stellate melanophores are 27 FISHERY BULLETIN: VOL. 77, NO, 1 on the dorsum immediately posterior to the parietal spines. In the tail region several embed- ded melanophores, sometimes fused, are on the dorsal and ventral body midlines near the caudal peduncle. These midline melanophores are pres- ent in the same region as the midline pigment shown on Waldron's (1968) reared 2-wk-old lar- va. The pectoral fin blades are lightly pigmented with elongate melanophores. Melanophores are also present on the inner side of the pectoral fin base but not on the outer side. The pelvic fins also have a light scattering of melanophores. The caudal fin base is unpigmented. During larval development, pigment increases on the head over the brain. Occasionally one or two melanophores are present on the snout. Melano- phores lining the inner tip of the lower jaw and those on the anteroventral margin of the maxil- lary remain throughout the larval period. The melanistic shield over the gut intensifies laterally and melanophoreson the ventral midline disappear. The two to three stellate melanophores on the dorsum posterior to the parietal spines dis- appear by the time larvae are 9 mm long. In the tail region, the dorsal and ventral midline melanophores near the caudal peduncle are no longer visible on larvae >9 mm. The rayed portions of the pectoral and pelvic fins remain lightly pigmented during the larval period but melanophores are no longer present on the inner side of the pectoral fin base in larvae >10 mm. During the transformation period, 12.8 to 18.6 mm, the amount of pigment increases gradually. In the head region, internal pigment is added to the opercle dorsally until a patch of 6 to 10 melanophores is visible on specimens >16 mm. Internal gut pigmentation decreases in intensity due to overgrowth by musculature. A few melano- phores sometimes appear on the nape and beneath spines V to XI of the first doral fin, although not consistently until late in the transformation period in specimens >17 mm. The most prominent addition of pigment occurs dorsally in the tail re- gion just posterior to the soft dorsal fin. Melano- phores are added along the dorsolateral surface of the caudal peduncle. Directly below these melanophores, three or four internal and one to four external melanophores are added along the lateral midline in specimens >15 mm. The amount of pigment on the pectoral and pelvic fins decreases during this period. During the pelagic juvenile period, 18.9 to 42.4 mm, new pigment is added over the dorsal surface of the head, interorbital, snout, premaxillary (specimen >26 mm), and on the lower jaw (speci- men >35 mm). The opercular patch enlarges. Around the eye, melanophores are added first on the posteroventral margin of the orbit in speci- mens 19 to 23 mm, and eventually line the orbit. A radiating bar of melanophores begins to extend from the posteroventral margin of the orbit on specimens >28 mm, extending onto the preopercle on specimens -30 mm. In the abdominal region, melanophores are added dorsolaterally to the nape and beneath spines V to X of the first dorsal fin forming two pigment patches connected by a dor- sal row of melanophores by 23 mm. The nape patch expands forming a saddle ( first in position) extend- ing from the parietal spine to the third dorsal spine and ventrally to the superior posttemporal spine by 28 mm. Two saddles (second and third) develop from the pigment patch beneath the spi- nous dorsal fin, midfin beneath spines IV to VI and posteriorly beneath spines VIII to XI. These two saddles are separated by a relatively unpigmented area on the dorsum. As they extend more ven- trolaterally, they fuse together in two places just above and below the lateral line creating a second, circular, less pigmented area on specimens >39 mm. These two saddles eventually extend to the dorsal portion of the gut cavity by 42 mm. A single external melanophore may occur on the midan- terior margin of the eleithrum beneath the gill cover. In the tail region, the dorsal patch of pig- ment on the caudal peduncle extends to the lateral line forming another saddle by 23 mm which reaches the ventral body margin by 27 mm. Be- neath the second dorsal fin melanophores increase in number and become concentrated along the muscles surrounding the dorsal pterygiophores appearing as vertical lines of pigment by 23 mm. Melanophores also develop at thepoint of articula- tion of all but the anteriormost three or four dorsal soft rays. A melanistic saddle (fourth in position) develops beneath soft dorsal rays 3 to 12 or 13 extending ventrolaterally to the body midline by 34 mm and three-fourths the distance to the ven- tral margin by 42 mm. The pectoral and pelvic fins are no longer pigmented in specimens >21 mm Pigment develops on the first dorsal fin membrane between spines IX and XI in juveniles '26 mm, eventually forming the "black blotch" characteris- tic of larger juveniles and adults. Melanistic bars form on the first dorsal fin between spines I to III 28 RICHARDSON and LAROCHE DEVELOPMENT AND OCl'URRENCE OF ROCKFISHES and V to VIII above the first and second saddles. By 39 mm the outer half of the fin is completely pigmented, while two unpigmented areas remain on the proximal half of the fin between the two pigment bars. Melanophores are added on the sec- ond dorsal fin above the fourth saddle until the proximal one-fourth of the fin between rays 2 and 13 or 14 is pigmented. The base of the caudal fin never becomes outlined with melanophores, but some melanophores develop on the dorsal second- ary caudal rays. Recently preserved pelagic juveniles of S. pin- niger, 32 to 35 mm, are covered with orange chromatophores which are lost during prolonged preservation. They are present on the dorsal part of the head, on the snout, around the orbit, and on the opercle. On the body they are concentrated along the myosepta and lateral midline, with greater numbers on the dorsal half of the body but also e.xtending to the ventral margin. Orange chromatophores are also concentrated on the spi- nous dorsal fin, along the basal one-fourth of the caudal fin, and the anal fin membrane around the anal spines. A general increase in melanistie pigmentation occurs in benthic juveniles >59 mm. On the head, the two pigment bars beneath the orbit remain distinct and extend over the operculum. Pigment increases between the saddles obscuring the pat- tern seen on pelagic juveniles. Melanophores are added to both the inner and outer surfaces of the pectoral fin base and on the basal one-third of the pectoral fin blade. The pelvic fin remains unpig- mented. The addition of melanophores to the spi- nous dorsal fin obscures the pattern seen on pelagic juveniles although the black blotch re- mains intense and distinct. The entire caudal fin is lightly pigmented with more intense pigment oc- curring over the bases of the primary rays and all upper secondary rays. Occurrence (Figures 10, 11). — Adults of S. ptn- ntger occur between Cape Colnett, Baja Califor- nia, and southeast Alaska (lat. 56" N, long. 134° W) (Hart 1973). Off Oregon they are most common on the continental shelf between 100 and 200 m (Snytko and Fadeev 1974). A major population concentration has been found between lat. 44°30' and 45" N off Oregon (Snytko and Fadeev 1974). :Li.-^_ iui £ 0 <^ 10 MAR -H 1 H/—< 1 APR -I 1 w^^ 1 MAY JUN '< II f AUG 40 60 60 100 Standord Length (mm) 120 180 190 Figure ll. — Seasonal occurrence of larvae and juveniles of Sebastes pinniger off Oregon. Data from 1964 to 1975 combined. Dashed line separates pelagic and benthic stages. ■^ .' : 4 1 ^ •• • /." - Larvae Pelagic Juveniles TIj" T r f Benthic Juve uveniles Figure lO. — Number of specimens and location of capture of larvae and juveniles of Sefeasfespjnm^er off Oregon 1 1964-75 1 described in this paper- 29 FISHERY BULLETIN; VOL, 77, NO 1 Larvae, including transforming specimens, of .S. pinnigcr in our collections were captured at a wide range of stations from 13 to 306 km offshore. The largest numbers and smallest larvae (<8.8 mm) were taken at stations 83 to 120 km off Newport beyond the continental shelf break. This may partly be a reflection of increased sampling effort in that area. Pelagic juveniles occurred at a simi- lar wide range of stations, mostly beyond the con- tinental shelf Interestingly, 30 specimens, rang- ing in length from 8.9 to 18.6 mm were captured 306 km off Coos Bay, Oreg., well beyond the conti- nental shelf Perhaps this wide ranging offshore occurrence of larvae and pelagic juveniles is re- lated to their morphology. The larvae are quite stubby and deep bodied with particularly long head spines, features which could contribute to increased flotation and dispersal by currents. Most specimens were captured in oblique midwater trawl and bongo net tows. Three benthic juveniles were taken close to the coast in depths of 30 to 35 m. Reported spawning times for S. pinniger are November to March off California (Phillips 1964i and January to March off Oregon, Washington, and British Columbia (Westrheim 1975). Larvae <10 mm were taken March through June, and larger pelagic specimens were taken March through August. The wide range in lengths, 9 to 25 mm in March, 7 to 38 mm in April, 8 to 34 mm in May, 9 to 43 mm in June, may be indicative of protracted and variable spawning. Benthic juveniles were taken in June and August. Sehastes pinniger is one of the most abundant trawl-caught rockfish species on the continental shelf off Oregon together with S. flavidus and S. entomelas (Snytko and Fadeev 1974). In trawl surveys off Oregon it ranked either first or second only to S. entomelas in biomass over the shelf (Demory et al. 1976). It was one of the major con- tributors to "other rockfish" landings in Oregon during 1963-71 (Niska 1976). Larvae and juveniles were the most numerous in available collections of the three species described in this paper. SEBASTES HELVOMACULATUS AYRES (Figures 12, 13) Literature. — Westrheim etal. (see footnote 9) pre- sented a schematic illustration of a preextrusion larva of S. helvomaeulatus and described the pigment pattern in a tabular form. The latter table was also in Westrheim (1975). Preextrusion lar- vae (mean total length =4.1 mm) have a ventral midline row of usually <16 (83"^* of 120 larvae) melanophores which stop short of the anus usually by as much as four myomeres. Pigment is absent from the dorsal midline, the head, nape, and lower jaw, and is usually not in the hypural region. The illustration shows some melanophores over the hindgut and ventrally beneath the yolk sac. Wes- trheim (1975) added that larvae of S. hel- vomaeulatus, along with 10 other species which had been reared for several days, develop pigment spots on the head, nape, and/or lower jaw. Identification (Table 10, Appendix Tables 2-6). — Twenty-six specimens of S. helvomaeulatus, 7.7 to 183 mm long, were identified. Juveniles were identified using the following combination of characters obtained from specimens examined in this study; Gill rakers = 28-31 Lateral line pores = 35-43 Pectoral fin rays = 15-17, usually 16 Anal fin soft rays = 5-6, usually 6 Dorsal fin soft rays = 12-14, usually 13 Supraocular spine = present Interorbital space = concave. Of the Sebastes species occurring off Oregon, S. helvomaeulatus has the best fit to the above characters. Sebastes aurora and S. elongatus also agi'ee with many of these characters, butS. aurora was eliminated since it has 24 to 28 gill rakers and S. elongatus was eliminated since it does not have a supraocular spine. Larval and juvenile speci- mens of S. elongatus identified from our collec- tions are noticeably more slender than specimens of S. helvomaeulatus and also are pigmented dif- ferently. Pigment pattern, body shape, time of oc- currence, and constancy in number of anal fin soft rays and pectoral fin rays helped link together the developmental series. Distinguishing Features. — Characters useful in distinguishing the smallest larva of S. hel- vomaeulatus identified, 7.7 mm, are the pig- mented fringes of the pectoral and pelvic fins; the general lack of body pigment; melanophores in- side the tip of the lower jaw; narrow interorbital distance (317f HL); long, deeply serrated, parietal spines (27% HL); and relatively long pectoral fins 30 RICHARDSON and LAROCHE; DEVELOPMENT AND OCCURRENCE OF ROCKFISHES 8.0 mm 10.9 mm 13.4 mm FIGURE 12. — Planktonic larvae (8.0, 10,9 mml and transforming specimen (13.4 mm) o( Sebasles helvomaculatus. 31 FISHERY BULLETIN: VOL. 77, NO, 1 <. ^^,,, < 18 4 mm ^/y^A 41 6 mm ■^ Figure 13. — Transforming specimen (18.4 mm) and pelagic juveniles (22.4, 41.6 mm) of Sehastes helvomaculatus . {2A'7c SL). Later stage larvae change very little in larva to pelagic juvenile. Meristics, presence of a appearance from the smallest larva, except for an supraocular spine, the concave shape and narrow increase of dorsolateral internal gut pigment. A width of the interorbital space, the patch of distinctive pigment patch appears on the caudal melanophores on the caudal peduncle, and the peduncleduring the period of transformation from single melanistic pigment saddle extending pos- 32 RICHARDSON and LAROCHE: DEVELOPMENT AND OCCURRENCE OF ROCKFISHES Table 10.— Meristics from larvae and juveniles of Sebastes helvomaculatus off Oregon, based on unstained specimens Specimens above dashed line are undergoing notochord flexion. All specimens had 8 superior and 7 inferior principal caudal fin rays and 7 branch iostegal rays on each side. Standard length (mm) 77 80 80 Dorsal Anal fin fin spines spines and rays and rays Pectoral fin rays Right Pelvic fin spines and rays Left Right Gill rakers (first arch) Lateral line pores Right IIR7 III2.7 16 16 16 16 16 l.(') l.(') I.C) l.(') I.C) I.C) Right Diagonal scale rows 88 — 111^.6 16 99 Xll|2,13 III2.6 16 109 XIIIM3 IIP.6 16 = 120 XIII'.IS 111^6 16 = 120 Xll|2,13 111^.6 16 =134 Xlll',13 lll=,7 16 =134 Xll|2,13 MR 6 16 = 136 XIIP.13 W3 16 = 178 XIII2.12 111^6 16 = 179 Xlll'.12 lll',6 16 = 184 XIIIM3 111^6 16 =184 Xlll',12 111^6 16 = 186 XIIIM3 III.6 16 '198 Xlll,13 III.6 16 '20 3 Xlll,14 111,6 16 ■'21 6 XIII, 13 111,6 16 «22 1 XIII.14 111,6 16 422 2 XIII.13 111,6 16 422 4 Xlll,13 111,6 16 "238 Xlll,12 111,5 16 •41 6 Xlll,13 111,6 16 M364 XIII.13 111,6 16 5183 XIII.14 111,6 17 16 16 16 16 16 16 16 16 16 16 16 16 17 16 16 16 16 16 15 16 16 15 16 1.5 1.5 1.5 1.5 1.5 1,5 1,5 1.5 1.5 1.5 1,5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 — — _ _ 1.5 — — _ _ 1.5 — _ _ 1.5 — _ — _ 1,5 — _ — 1,5 — _ 1.5 — _ — _ 1.5 — 21+9 = 30 _ 1.5 21+9=30 22 + 9 = 31 •42 — 1.5 21+9 = 30 21+9 = 30 _ _ 1.5 21+9 = 30 20+8=28 _ _ 1.5 21+9 = 30 21+9 = 30 42 _ 1.5 19+8-27 19+8=27 — — 1.5 21 +8 = 29 21+8 = 29 .40 _ 1.5 21+9 = 30 20 + 8 = 28 -39 _ 1.5 21+8=29 21+8=29 -39 _ 1.5 20 + 9=29 20+8 = 28 -40 • 40 1 5 20+8=28 20+8=28 -38 -38 1.5 21+9=30 21+9 = 30 =41 -41 1.5 20 + 9 = 29 20 + 9 = 29 -43 -43 1.5 22 + 9=31 22 + 8=30 39 38 1.3 21+9 = 30 21+9=30 35 35 1,5 22 + 9 = 31 22+9=31 40 39 'Not formed •'Posterior dorsal or anal spine appears as a soft ray =Transtormtng •Pelagic juvenile ^Benihic juvenile teriorly from the nape to dorsal spine XI and ven- trally about one-half the distance to the lateral line, all serve to distinguish pelagic juveniles. General Development. — The smallest larva of S. helvomaculatus identified, 7.7 mm, is in the final stage of notochord flexion, which is completed by 8.8 mm. Transformation to pelagic juvenile begins in larvae =12 mm long with the initiation of spine formation in the dorsal and anal fin "prespines" and the appearance of a lateral pigment patch on the caudal peduncle. Transformation of the "pre- spines" to spines is completed in specimens >19 mm at which time some pigment appears beneath the spinous dorsal fin and pigment is added to the dorsal margin of the caudal peduncle pigment patch marking the beginning of pelagic juveniles pigmentation. More pigment is added beneath the first dorsal fin during the pelagic juvenile period although the saddle never becomes pronounced. Additional small external melanophores cover most of the fish by the end of the pelagic juvenile period, which probably lasts until =40-60 mm. The largest pelagic juvenile examined was 41.6 mm and the smallest benthic juvenile was 1.36.4 mm. Morphology (Tables 4, 11). — Twenty-six speci- mens of S. helvomaculatus, 7.7 to 183 mm long, were measured for developmental morphology. Relative body depth/SL changes little at the pec- toral fin base, decreasing slightly then increasing while it generally increases at the anus. Snout to anus distance increases from 56 to 63 or 64% SL and the snout to pelvic fin distance increases somewhat then decreases. Head length increases slightly (41-42*2 ) then decreases (38%) with respect to standard length. Eye diameter decreases (39-32% HL), as do the interorbital distance (31-15% HL) and snout length (32 or 33-27% HL). Upper jaw length in- creases from 44-46 to 52% HL. The length of the angle gill raker first increases (13-15% HL) then decreases ( 1 1% ). Larvae and juveniles <24 mm have a weak symphyseal knob which becomes less obvious with development. Fin Development (Tables 4, 10, 11).— The adult complement of 15 to 18 (usually 16) pectoral fin rays can be counted on the smallest larva, 7.7 mm, of S. helvomaculatus although the ventralmost rays are not fully developed. Pectoral fins are 33 FISHERY BULLETIN: VOL 77. NO 1 Table 1 1. — Measurements (millimeters) of larvae and juveniles of Sehastes helvomaculatus from waters off Oregon Specimens above dashed line are undergomg notochord flexion, E m ? U i n 2 * I .S ^a 2y= -sBfi "£ ).^>™2ca> (OCT £ ti (0 "* — : 3! a? 7 7 95 43 32 1 1 1 5 1 2 1 0 25 1 6 1 9 0 96 0 64 10 30 10 0 10 - (') (?) I') 60 96 4 4 32 0 96 1 5 1 3 1 0 28 1 7 20 1 0 0 68 1 2 33 090 004 090 - (') (') (') 80 9.9 46 34 1 1 1 4 1 3 1 0 26 I 6 1 7 1 0 0 66 10 33 0 78 0 08 0 78 (') (') (') 88 10,9 52 39 1 3 1 4 1 4 1 2 29 1 9 22 1 1 0 40 1 3 36 0 78 0 10 1 2 0 48 {") 0 80 (*) 99 12,3 58 4 1 1 3 16 1 5 1 3 33 26 24 1 1 1 2 1 6 40 0 80 0 22 1 3 0 56 0 88 12 0 60 109 134 65 4 4 1 5 1 8 1 6 1 4 37 28 26 1 2 1 6 1 7 45 0 70 0 22 — 0 62 0 82 1 3 0 76 «120 149 74 49 1 6 24 1 8 1 5 4 1 30 30 1 2 1 9 20 52 0 80 0 24 1 3 0 78 1 1 1 8 1 1 '120 144 7 1 49 1 5 26 1 9 1 5 4 3 3 1 34 1 3 2 1 24 52 0 72 0 24 — 0 88 — 1 9 1 2 '134 16 8 85 54 1 6 2 7 20 1 6 4 1 34 33 13 24 29 60 0 66 0 30 — 0 82 — 1 9 1 4 '134 168 85 56 18 26 20 1 6 4 7 36 36 1 5 24 26 57 0 72 0 26 1 3 0 72 — 1 9 1 3 '136 168 85 58 22 24 20 1 5 4 4 33 33 1 3 22 24 62 — 0 28 1 1 0 80 1 4 1 9 1 4 '17,8 22 1 107 75 2 7 32 24 1 8 57 4 5 45 1 6 34 38 72 1 0 0 32 — 1 1 23 26 23 '179 22 2 112 73 26 29 2 4 1 7 57 42 4 5 1 7 3 1 32 80 0 80 028 1 3 1 1 — 28 22 '18 4 229 11 0 6 7 2 1 30 2 5 1 9 59 43 49 1 8 32 37 70 096 0 36 1 4 1 1 2 1 — 1 9 '184 23 0 110 72 1 8 34 2 7 1 8 57 4 4 52 1 8 34 37 70 0 70 0 34 1 3 1 1 27 30 26 '186 21 1 120 80 2 7 34 26 19 58 43 48 1 8 34 34 88 0 72 0 24 1 3 1 1 — 26 — '198 24 6 120 82 28 33 28 2 1 64 46 52 1 8 3 1 36 82 — 0 36 1 3 1 2 — 26 22 '20 3 25 3 128 84 28 40 28 20 62 4 7 53 1 8 ^ 4 1 90 0 80 0 34 1 3 1 2 — 30 20 '21 6 26 4 130 84 2 5 40 28 20 7 1 52 57 20 — 40 86 — 0 14 — 1 2 — 32 30 '22 1 26 4 142 89 30 4 2 30 1 9 72 53 59 20 34 44 98 0,72 0 26 — 1 4 28 32 27 '22 2 27 7 146 93 30 4 2 30 1 9 67 5 1 59 20 42 4 4 10 7 0,46 0 32 — 1 3 26 3 1 3 1 '22 4 27 7 134 8,4 26 38 3 1 20 72 56 60 20 4 1 48 88 — 0 44 1 1 1 3 30 32 32 '23 8 29 1 157 94 3 1 4 3 2 9 1 9 72 52 64 22 39 43 107 0 40 0 30 — 1 2 28 34 — '41 6 49 8 26 2 165 4 4 70 57 22 11 8 88 70 34 56 72 166 0 18 — 042 2 1 49 6 1 64 '136 4 169 86 0 51 8 140 26 7 183 6 7 44 0 323 37 6 120 197 30 0 53 8 16 — 13 57 174 20 7 270 = 183 219 118 1 68 1 180 35 8 18 9 11 2 633 494 48 4 18,0 28 2 429 74,5 — — 0,32 7,0 276 31,0 310 'Usually third or founh m 'Usually mtdfin ^The second spine *Not formed ^Forming 'Transforming 'Pelagic juvenile 'Bentfiic juvenile larvae. fittfi or sixth in juveniles rather long, averaging 24-269!^ SL during the pelagic period. Depth of the pectoral fin decreases from 12''f in flexion larvae to 97? in benthic juveniles. Pelvic fin spines and developing rays are visible on the 7.7 mm larva. The adult complement of I, 5 is countable on the smallest postflexion larva, 8.8 mm. The relative length of the pelvic fin increases from 14 to 23'7r^ SL with development. The pelvic spine, always shorter than the pelvic fin rays, in- creases from 8% SL in flexion larvae to IS'/r in transforming larvae and then decreases to 15'% in benthic juveniles. The adult complement of 8 + 7 principal caudal fin rays can be counted on the 7.7 mm preflexion larva. Flexion is completed by 8.8 mm. Superior and inferior secondary caudal rays on two stained juveniles 22.4 and 23.8 mm long, were 12 + 12 and 11 + 11, respectively. Bases of dorsal and anal fin spines and rays are visible on the 7.7 mm larva. Rays and spines (in- cluding "prespines"! are fully formed by 9.9 mm and the adult complements can be counted. "Pre- 34 spines" become spines in specimens >19 mm. The longest dorsal spine increases from 19% HL in postflexion larvae to 377f in benthic juveniles. The longest dorsal ray, always longer than the longest dorsal spine, increases from 23 to 43*^7^ HL during development. The longest anal spine increases from 16 to 49^r HL. Spination iTables 4, 12). — Spines on the left side of the head of the smallest S. helvomaculatus (1.1 mm) include the parietal; first and third anterior preopercular spines; second, third, and fourth posterior preopercular spines; postocular; pterotic; inferior posttemporal; and first spine of the superior infraorbital series. The parietal spine and ridge are deeply serrated in larvae and pelagic juveniles, but the serrations are no longer visible by 41.6 mm. The parietal spine is very long in flexion larvae, averaging 27'^ HL. Its length decreases with development to 3% HL in benthic juveniles. The much smaller nuchal spine, which appears by 8 mm, averages 29f HL in flexion larvae and increases to 4 or 5'S in postflex- RICHARDSON and LAROCHE; DEVELOPMENT AND OCCURRENCE OF ROCKFISHES Table 12.- -Development of spines in the head region o(Sebastes helvomaculatus larvae and juveniles. Specimens above dashed line are undergoing notochord flexion. + denotes spine present and - denotes spme absent. Standard length (mm) Panetal Nuchal Preopercular ' (anlenof series) Preopercular (posterior series) Opercular Superior Inferior Inler- oper- cular Sub- oper- cular Pre- ocular Supra- ocular Post- 1st 2d 3d 1st 2d 3d 4lh 5th ocular 7 7 80 8.0 + — + + + — + + - + + — + - + + + + + - - - - - - + 8.8 9.9 10.9 '12.0 '12.0 '13.4 '13.4 '13.6 '17.8 '17.9 '18.4 '18.4 '18.6 =19.8 '20.3 321.6 322.1 322.2 322.4 323.8 341.6 '136-4 '183 + + + + + + + + Table 12.— Continued. Infraorbitals Nasal Coronal Tympanic Plerotic Posttemporal Superior Inferior ^'Cr^:.' Superior Supra- (mm) 1st 2d 3d 1st 2d 3d 4th cleithral Cleithral 77 80 80 - + - - + - - + - - - - - - + - - + - - + - + - + - + - 9.9 10.9 '12.0 '12.0 '13.4 '13.4 '13.6 '17.8 '17.9 '18.4 '18.4 '18.6 319.8 320.3 321.6 322.1 322.2 322.4 323.8 341.6 '136.4 '183 I}) I}) -(') (') 'Transforming ^Bump indicating beginning of spine formation ^Pelagic juvenile 'Benttiic juvenile ion, transforming, and pelagic juvenile stages. The nuchal and parietal spines are fused together by the time juveniles are 42 mm long. The posterior preopercular spine series is prom- inent in S. helvomaculatus larvae. The third spine of the series is weakly serrated in larvae >8 mm up to pelagic juveniles. It is relatively long in larvae averaging 27 to 31'7f HL in flexion and postflexion stages. Its length decreases to 2'7f in benthic juveniles when it is no longer serrated. 35 FISHERY BULLETIN VOL, 77. NO, 1 Very weak serrations appear on the second and fourth posterior preopercular spines of most larger larvae and smaller pelagic juveniles. All five pos- terior preopercular spines are present on speci- mens >8.0 mm. The first and third anterior preopercular spines seen on the smallest larva are no longer visible on specimens >23 mm. The sec- ond anterior preopercular spine never develops. The superior and inferior opercular spines are present on all specimens >8 mm. The interopercu- lar spine is present at 8.8 mm and persists into benthic juveniles. The subopercular spine is pres- ent just above the interopercular spine on the largest benthic juvenile, 183 mm. The supraocular ridge and the anterior margin of the postocular spine are serrated on specimens up to 23.8 mm. The preocular and supraocular spines are first seen as bumps in a 13.4 mm speci- men. Serrations are present on the supraocular spine but disappear along with those on the su- praocular ridge on larger pelagic juveniles. The first superior infraorbital spine is visible up to 23 mm. The second superior infraorbital spine appears on specimens 12 to 23 mm. The fourth superior infraorbital spine is present on larvae >8 mm and the third superior infraorbital spine is present on larvae >13.4 mm. The third and fourth spines both disappear by 23 mm. The first and second spines of the inferior infraorbital series are present on all specimens >8 mm but appear only as blunt projections on benthic juveniles. The third inferior infraorbital spine never develops. The nasal spine appears as a bump by 9 mm and becomes strong and sharp during the larval period. The tympanic spine develops by 41.6 mm and appears as a strong sharp spine on benthic juveniles. The pterotic spine is present on all specimens >41.6 mm. The inferior posttemporal spine is present on all specimens examined but is minute on the two benthic juveniles, 136 and 183 mm, and probably disappears in larger specimens. The supracleithral spine is present on all speci- mens >8.0 mm. The superior posttemporal ap- pears at 13.4 mm and is present on all larger specimens. Posterior to the opercle the cleithral spine appears on all specimens >19 mm. Scale Formation. — Lateral line pores first appear anteriorly and are visible on specimens >17 mm. Scale formation begins on pelagic juveniles >23 mm. Pigmentation. — The smallest larva of S. hel- vomaculatus, 7.7 mm (similar to the 8.0 mm specimen illustrated), has pigment on the head over the brain. Melanophores line the inner tip of the lower jaw. In the abdominal region, an inter- nal melanistic shield is present over the dorsolat- eral surface of the gut. No other pigment is visible on the body. The pectoral and pelvic fins are fringed with expanded and fused melanophores and have a light scattering of more contracted, elongate melanophores on the fin blades. Both inner and outer pectoral fin base surfaces are un- pigmented. During larval development, pigment over the brain becomes obscured. At 13.4 mm pigment in- side the lower jaw disappears. Specimens >17 mm develop two to six internal melanophores dorsally on the opercle. During the transformation period, 12.0 to 18.6 mm, two or three melanophores may appear just posterior to the orbit on specimens >18 mm. In- ternal gut pigment increases ventrolaterally reaching the ventral surface of the gut by 17.9 mm. The anterior margin of the cleithrum is usu- ally unpigmented. A patch of 9 to 10 large stellate melanophores appears laterally on the caudal peduncle at 12.0 mm at the beginning of the trans- formation period. Melanophores are added to this patch until it extends to the dorsal body surface at = 18 mm. Melanophores in this patch often appear expanded and fused. The pectoral and pelvic fins remain fringed with pigment although this may not be obvious if the fins are frayed. The number of melanophores on the fin blades generally de- creases. During the pelagic juvenile period, 19.8 to 41.6 mm. pigment appears over the head surface, snout, and upper lip of specimens "^22 mm. Melanophores are added along the posteroventral margin of the orbit and a patch of melanophores appears just dorsal to the first superior infraor- bital spine. The internal pigment patch on the operculum remains distinguishable. Internal gut pigment becomes increasingly obscured by muscu- lature. A single saddle of melanophores develops on the dorsal surface of the body over the nape and beneath the spinous dorsal fin anterior to dorsal spine XI. The first melanophores generally appear there at the onset of the pelagic juvenile stage, although a few may develop earlier. This saddle extends ventrolaterally from the nape to the vicin- ity of the supracleithral spine and from the spi- nous dorsal fin halfway to the lateral line by 22 36 RICHARDSON and LAROCHE: DEVELOPMENT AND OCCURRENCE OF ROCKFISHES mm. By 41.6 mm small external melanophores cover all but the ventralmost one-fourth of the abdominal region including most of the pectoral fin base and the dorsal one-fourth of the gut re- gion. The dorsal saddle and internal gut pigmen- tation still appear as more darkly pigmented areas. The caudal peduncle patch expands to the dorsal and ventral body margins. Specimens >20 mm have a few melanophores extending an- teriorly from the peduncle patch along the dorsal body margin under the posteriormost dorsal rays. By 41.6 mm the entire tail region of the body is also covered with small external melanophores, although the caudal peduncle patch and dorsal midline melanophores remain visible. Pectoral and pelvic fins lose all pigment by 41.6 mm, except for a patch of small melanophores on the base of the central pectoral rays. The spinous dorsal fin becomes completely covered with small melano- phores by 41.6 mm and small melanophores cover the proximal one-fourth of the soft dorsal fin. Small melanophores extend onto the bases of the caudal fin rays by 41.6 mm. Melanistic pigment is inconspicuous on the benthic juveniles examined. 136 and 183 mm. The caudal peduncle pigment patch is no longer visi- ble. Occurrence (Figures 14, 15). — Sebastes hel- vomaculatus ranges from Coronado Bank, off San Diego, Calif, to Albatross Bank, Gulf of Alaska, and occurs in depths from 133 to 456 m (Chen 1971). It is apparently primarily a deepwater species judging by some of the older common names given to it, "deep-water scacciatale" and "deep-water scratch-tail" (Phillips 1957). The largest numbers and smallest larvae were taken 83 and 120 km off Newport beyond the continental shelf break. Most pelagic juveniles were taken at the same locations as the larvae, probably reflect- ing the increased sampling effort in that area. One benthic juvenile, 136 mm, was taken in an otter trawl at a depth of 370 m (lat. 44°47.9' N, long. 124°40.9' W). A second juvenile, 183 mm, was col- lected after a seismic profiling explosion on Stonewall Bank ( =lat. 44°30' N, long. 124°25' W). JUL I 1 1 ihX- AU6 J. X-L SEP OCT NOV JlL -4- 20 to 60 80 100 120 140 180 190 Standard Length (mm) Figure 15. — Seasonal occurrence of larvae and juveniles of Sebastes helvomaculatus off Oregon, Data from 1961 to 1976 combined. Dashed line separates pelagic and benthic stages. ' ' ' 1^^- , w--^-^- '• )"-" - ■^ - '. '. i .' L^. ■ \ 1 - i Jl' A „, Pelagic Juveniles ]• , , "^r-. FIGURE 14. — Number of specimens and location of capture of larvae and juveniles of Se6as^es helvomaculatus off Oregon (1961-76) described in this paper. 37 FISHERY BULLETIN: VOL, 77, NO, 1 Based on examination of gonads, Westrheim (1975) reported that parturition of S. hel- vomaculatus takes place primarily in June from Oregon to British Columbia. We took small larvae >10 mm only in July and August. Pelagic juveniles were captured in August, September, and November. The two benthic juveniles were taken in July. Adults of S. helvomaculatux are uncommon in Oregon trawl landings iNiska 1976). They ranked 9th and 16th in biomass in trawl surveys on the Oregon continental shelf and 8th on the continen- tal slope together with S. elongatus and S. zacen- triis (Demory et al. 1976). Larvae and juveniles were not common in our collections. COMPARISONS (TABLE 13) Prior to this paper, developmental series of 7 of the 69 northeast Pacific (including the Gulf of Cal- ifornia) species of Sehastes had been described: S. cortezi, S. sp. Gulf Type A, S. jordani, S. levis, S. macdonaldi , S. melanostomus , and S. paucispinis (Moser 1967, 1972; Moser et al. 1977; Moser and Ahlstrom 1978). While pelagic stages of these species exhibit some similarities to the three de- scribed by us, they also differ in a number of characters. The most notable of these are discus- sed here in a comparative sense. Flexion and postlarvae of S. pinniger are quite deep bodied (38-40/f SL) although body depth at the pectoral fin base decreases considerably (33'7f SL) by the pelagic juvenile stage. Larvae and juveniles of S. melanostomus are also deep bodied. Pelagic stages of S. Jordani are comparatively slender (17-24'7< SL). Prior to completion of notochord flexion, S. paucispinis is also relatively slender bodied. Pelagic stages of S. crameri, S. he/vomaculatus. S. levis. and S. macdonaldi are somewhat intermediate in body depth. Snout to TABLE13, — Morphometric comparison of larvae and juveniles of nine species ofSebastes from the northeast Pacific. Values are mean percentages of body proportions related to standard length (SL) or head length SL: Preflexion — — — — — — 4 — — — Flexion 7 _ 14 1 6 6 12 14 14 Postflexion 15 16 17 Transforming _ 21 _ 19 9 21 14 16 35 23 Pelagic juvenile — 21 _ 19 14 24 22 20 25 22 Benthic juvenile _ 21 _ 23 -_ _ _ — _ 21 Parietal spine length HL: Preflexion — — Flexion 6 27 24 Postflexon 2r-22 7 25-34 18 20-23 20 Transforming 6 13 10 Pelagic juvenile — 3 — 6 _ _ _ — _ 7 Benthic juvenile 3 Preopercular spine lengtti HL: Preflexion — — — — — — — — — — Flexion 18 27 34 Postllexion 17 _ 31 _ _ 35 _ 32 Transforming _ 18 — 20 — _ — — — 24 Pelagic juvenile _ 12 _ 12 — _ _ — _ 13 Benthic juvenile - 7 - 2 — — — — — 5 'Values from Ivloser et al, (1977) and Moser and Ahlstrom (1978) 38 RICHARDSON and LAROCHE DEVELOPMENT AND OCCURRENCE OF ROCKFISHES anus distance is markedly shorter in larvae and juveniles oCS.jordaiii (36-53'^< SL) compared with the other species. The pectoral fins in S.jordani remain compara- tively short (7-22% SL) during pelagic develop- ment while those of S. levis attain an exceptional size (to 45'7( SL). Late larval stages of S. pauci- spinis also have outstandingly long pectoral fins (36'"f SL). Fin lengths among the other species are intermediate by comparison and vary to a lesser degree during development. The pelvic fins of S. pauc7spi>!ii' also become extraordinarily long (35'> SL) during the late larval period whereas those of S.jordani remain relatively short. Parietal spine length varies among species with the largest spines appearing in early larvae of S. helvornacu/atus {279i HL) and S. sp. Gulf Type A (25-349f HL). This spine is noticeablely short on S. cramen (3-7% HL) during the entire pelagic phase. The third preopercular spine is outstand- ingly long on early larvae of S. macdonaldi (35% HL) and S. pinniger (34% HL) but is compara- tively short on S. cramen (17% HL) as is the parietal. Pigmentation on the paired fins varies from the unpigmented condition in S.jordani to the heavily pigmented fins of S. macdonaldi and S. crameri. The pectoral fins of S. cortezi are pigmented at the fin base but not the outer margin, while pigment is primarily concentrated on the outer margin of the fins in S. paucispinis, S. levis, and S. helvomacu- latu.s at least during the early pelagic period. Pec- toral fins of S. pinniger, S. melanostomus, and S. sp. Gulf Type A are lightly pigmented. General body pigmentation differs among the species considered. Larvae of S. pinniger have a '•haracteristic lack of body pigment. A patch of uape pigment develops early in S. crameri and S. macdonaldi. appearing more pronounced in the former species. Postflexion larvae of both S. cram- eri and S. macdonaldi develop pigment on the entire spinous dorsal fin. A characteristic black blotch develops on the posterior portion of the first dorsal fin in pelagic juveniles of S. pinniger. Lar- vae of S. melanostomu.'i, S. paucispini.'i, and S. macdonaldi have a characteristically low number of ventral midline melanophores, 4 to 11 (mean 8), 6 to 14 (mean 9), and 6 to 14 (mean 8), respectively. A patch ofpigment forms on the caudal peduncle of S. helvomaculatus , S . paucispinis, S.jordani, and S. cortezi. The form of the patch varies with the species and is most pronounced in S. hel- vomaculatus. One characteristic melanophore ap- pears at the base of the caudal fin in S. cortezi, while melanophores form a line ofpigment at the base of the caudal fin in S.jordani, but not in any of the other species. Pelagic juveniles of S. helvomaculatus develop only one melanistic pigment saddle beneath the spinous dorsal fin. Five distinct saddles form on S. macdonaldi, S. crameri, S. levis, S. paucispinis, and S. pinniger in comparable locations on the body although a more blotchy pattern develops on S. pinniger. On S. melanostomus, three pro- nounced melanistic bars develop on the body. Ap- parently no obvious saddles or bars develop on pelagic juveniles of S. jordani or S. cortezi. These comparisons together with distinguish- ing features of each species given by us, Moser (1972), Moser et al. (1977), and Moser and Ahlstrom (1978), and range of occurrence should aid in identification of all but the smallest larvae. As additional species are described, such compari- sons may also provide insight into relationships within the genus Sebastes. ACKNOWLEDGMENTS We thank H. Geoffrey Moser for helpful advice and for the use of unpublished data on color pat- tern in a livejuvenile of S. crameri. Stuart G. Poss offered useful advice on head spine terminology. During the course of this study the following people provided helpful information on Sebastes spp.: Carl Bond, Jerry Butler, William N. Esch- meyer, Colin Harris, Michael Hosie, Andy Lamb, Bruce M. Leaman, Alex E. Peden. Jay C. Quast, David Stein, Arthur D. Welander, Sigurd J. Wes- trheim, Norman J. Wilimovsky. Range Bayer, Robert A. Behrstock, Carl Bond, Jerry Butler, Colin Harris, Michael Hosie, Robert Lea, Law- rence Moulton. and Alex Peden provided addi- tional specimens of Sebastes to examine. Special thanks are extended to William G. Pearcy for al- lowing us to use his extensive midwater trawl collections from waters off Oregon. Lo-Chai Chen, H. Geoffrey Moser, Stuart G. Poss, and Sigurd J. Westrheim reviewed an earlier draft of the man- uscript. This research was supported by a 1-yr ( 16 June 1976-15 June 1977) contract No. 03-6-208- 35343. LITERATURE CITED AHLSTROM. E. H. 1961. Distribution and relative abundance of rockfish 39 FISHERY BULLETIN; VOL 77. NO 1 {Sebastodes spp.) larvae off California and Baja Califor- nia. Rapp. P-V. Reun, Cons. Int. Explor. Mer 150:169- 176. 1965, Kinds and abundance offi.'shes in the California Cur- rent region based on egg and larval surveys. Calif Coop Oceanic Fish, Invest, Rep. 10:31-52. Bailey, R. M., J. E. Fitch, E. S. Her.ald. E. a. Lachner, C. C. LINDSEV. C. R. ROBINS, AND W. B. SCOTf. 1970, A list of common and scientific names of fishes from the United States and Canada, Am. Fish. Soc. Spec. Publ. 6, 149 p BARSLIKOV, V, V. 1973, A systematic analysis of the group Sebastex waki- yai-S. paradoxus-S. steindachneri. Communication 2 (containing a redescription of .S. wakiyan. J Ichthyol, (Engl, Transl, Vopr. Ikhtiol.l 13:824-833, Chen, L.-C. 1971, Systematics, variation, distribution, and biology of rockfishes of the subgenus Sfhastomus (Pisces, Scor- paenidae,Sefca,s(e.<;). Bull, ScrippsInst,Oceanogr,,Univ, Calif, 18, 115 p. 1975, The rockfishes. genus Sebaxtes (Scorpaenidae), of the Gulf of California, including three new species, with a discussion of their origin. Proc. Calif Acad. Sci. 40:109- 141. DeLacy, A. C, C. R, Hit/., and R. L, Dryfoo.s, 1964. Maturation, gestation, and birth of rockfish iSebas- todes) from Washington and adjacent waters. Wash. Dep. Fish., Fish. Res. Pap. 2(31:51-67. Demory, R. L., M. J. HosiE, N. Ten Eyck, and B. O, FORSBERG. 1976. Marine resource surveys on the continental shelf off Oregon, 1971-74. Oreg. Dep. Fish. Wildl,, Completion Rep.. July 1, 1971 to June 30, 1975, 49 p. EFREMENKO, V. N., AND L. A, LiSOVENKO. 1970, Morphological features of intraovarian and pelagic larvae of some Sebastotles species inhabiting the Gulf of Alaska. In P. A. Moiseev (editor), Soviet fisheries inves- tigations in the northeast Pacific. Part V, p, 267-286, (Transl, Isr, Program Sci, Transl,; available Clearing- house Fed, Sci, Tech, Inf, Springfield, Va,, as TT71- 50127), EIGENMANN, C, H, 1892, The fishes of San Diego. California, Proc, U.S. Natl, Mus, 15:123-178. FOLLETT, W. I., AND D. G. AINLEV. 1976. Fishes collected by pigeon guillemots, Cepphus co- luniba (Pallas), nesting on Southeast Farallon Island, California. Calif Fish Game 62:28-31, Hart, J, L, 1973. Pacific fishes of Canada. Fish, Res. Board Can. Bull, 180, 740 p. Lea, R, N,, and J. E. Fitch. 1972, Sebastes rufinanus, a new scorpaenid fish from Califomian waters, Copeia 1972:423-427, Matsubara, K, 1943. Studies on the scorpaenoid fishes of Japan, Anat- omy, phylogeny and taxonomy 1 and II, Trans, Sigen- kagaku Kenkvusyo, Tokyo, 486 p, MERKEL, T. J. 1957. Food habits of the king salmon, Oncorhynchus tshawytscha i Walbaum), in the vicinity of San Francisco, California, Calif Fish Game 43:249-270, Miller, d. j,, .\nd r, n, lea. 1972. Guide to the coastal marine fishes of California. 40 Calif Dep, Fish Game, Fish Bull 157, 235 p, Morris, R, W, 1956. Early larvae of four species of rockfish, Sebastodes. Calif Fish Game 42:149-153, MO.SER, H, G, 1967, Reproduction and development of Sebastodes paucispinis and comparison with other rockfishes off southern California. Copeia 1967:773-797, 1972, Development and geographic distribution of the rockfish, Sebastes macdonaldi (Eigenmann and Beeson, 1893), family Scorpaenidae, off southern California and Baja California. Fish, Bull,, US, 70:941-958. M(.)SER, H. G., E, H, AHLSTROM, AND E. M, SANDKNOI', 1977, Guide to the identification of scorpionfish larvae (family Scorpaenidae) in the eastern Pacific with com- parative notes on species ofSebafttes and Helicolenus from other oceans. U.S. Dep, Commer., NOAA Tech, Rep, NMFS Circ, 402, 71 p, MOSER, H. G., AND E. H. AHUSTROM. 1978. Larvae and pelagic juveniles of blackgill rockfish, Sebastes melanostomus, taken in midwater trawls off southern California and Baja California. J. Fish. Res. Board Can, 35:981-996, NISKA, E, L, 1976, Species composition of rockfish in catches by Oregon trawlers 1963-71. Oreg. Dep Fish, Wildl, Inf Rep, 76-7, 80 p. PACIFIC Marine Fisheries Commission. 1964-1976. Data series: Bottom or trawl fish section. Pac. Mar. Fish. Comm., Portland, Oreg., p, 1-472, 500-510, Phillips, J. B. 1957 A review of the rockfishes of California (family Scor- paenidae), Calif Dep, Fish Game, Fish Bull 104, 158 p, 1964, Life history studies on ten species of rockfish (genus Sebastodes). Calif. Dep. Fish Game, Fish Bull. 126, 70p Powell, D, E., D, L. Alverson, and R, Livincstone, Jr. 1952, North Pacific albacore tuna exploration — 1950, U.S. Fish Wildl, Serv,, Fish, Leafl, 402, 56 p. i] PRITCHARD, A. L., AND A. L, TESTER, 1944. Food of spring and coho salmon in British Colum- bia. Fish. Res. Board Can Bull 65. 23 p. QUAST, J. C, AND E. L, Hall, 1972. List of fishes of Alaska and adjacent waters with a guide to some of their literature. U.S. Dep. Commer., NOAA Tech. Rep, NMFS SSRF-658, 47 p. Richardson. S. L. 1977, Larval fishes in ocean waters off Yaquina Bay. Ore- gon: abundance, distribution and seasonality January 1971 to August 1972. Oreg, State Univ, Sea Grant Coll, Prog, Publ, ORESU-T-77-003, 73 p. Richardson, S. L.. and W, G, Pearcy, 1977. Coastal and oceanic fish larvae in an area of up- welling off Yaquina Bay. Oregon, Fish, Bull., US 75:125-145, Rosenblatt, R. H., and L.-C. Chen. 1972. The identity o{ Sebastes babcocki and Sebastes rub- rivmclus. Calif Fish Game 58:32-36, SILLIMAN, R, P, 1941. Fluctuations in the diet of the chinook and silver salmons iOncorhynchus tsckawytscha and O. kisutch ) off Washington, as related to the troll catch of salm- on. Copeia 1941:80-87. SNVTKO, V, A,, AND N, S, FADEEV, 1974. Data on distribution of some species of sea perches along the Pacific coast of North America during the sum- RICHARDSON and LAROCHE DEVELOPMENT AND OCCURRENCE OF ROCKFISHES mer - autumn season. Doc. Subm. Canada-USSR Meet, on Fish, in Moscow-Batumi, USSR, November 1974, 14 p. iTransl. 3436, Can. Transl. Ser.l Taylor, W. R. 1967. An enzyme method of clearing and staining small vertebrates. E>roc. US. Natl. Mas. 122(3596), 17 p. VerHOEVEN, L, a. (editori. 1976. 28th annual report of the Pacific Marine Fisheries Commission for the year 1975. Pac. Mar. Fish. Comm., Portland, Oreg., 46 p. Waldron, K. D. 1968. Early larvae of the canary rockfish.Setastorfespm- niger. J. Fish. Res. Board Can. 25:801-803. Wales, J. H. 1952. Life history of the blue rocklish, Sebastodes mys- tinus. Calif. Fish Game 38:485-498, Weitzman,S. H. 1962. The osteology of Brycon meeki. a generalized characid fish, with an osteological definition of the fami- ly. Stanford Ichthyol. Bull. 8(1), 77 p. WESTRHEIM, S. J. 1966. Northern range extensions for three species of rockhsh iSebastesflai'idus.S.pauctspinis andS.ptnniger) in the North Pacific Ocean. J. Fish. Res. Board Can. 23:1469-1471. 1975. Reproduction, maturation, and identification of lar- vae of some Sehastes iScorpaenidae) species in the north- east Pacific Ocean. J, Fish Res. Board Can. 32:2399- 2411. WESTRHEIM, S. J., AND H. TSUYUKI. 1967. Sebastodes reedi, a new scorpaenid fish in the north- east Pacific Ocean. J. Fish. Res. Board Can. 24:1945- 1954 1972. Synonymy of Sebastes caenaematicus with Sebastes borealis, and range extension record. J. Fish. Res. Board Can. 29:606-607. WHITNEY, J. P. 1893. Salmon in salt water Forest Stream 41:120-121. YOUNG, P. H, 1969. The California partyboat fishery 1947-1967. Calif Dep. Fish Game, Fish Bull. 145, 91 p. 41 FISHERY BULLETIN VOL 77. NO 1 APPENDIX Table l. — Ranges of eastern North Pacific species ofSehastes.' This Hst does not include one new species being described by Lea and Fitch (Chen 1975). Asterisk indicates species in the subgenus Sehastomus. o o — 3 ^ Species Southern range limit O 5 Northern range limit S aleutianus S alutus S atrovirens S aunculatus S aurora S babcocki S borealis S brevispmis S camatus 'S caunnus^ S chlorostictus S chrysomelas S ciliatus 'S constellatus S cortezi S cramen S dalli S diploproa S elongaius S emphaeus 'S ensifer S eniomelas 'S eos 'S exsul S fiavidus S gilli S goodei "S helvomaculatus S hopkinsi S lordani "S lentiginosus S lews S macdonaldi S maliger S melanops S melanostomus S mtniatus S mystinus S nebulosus S nigrocinctus 'S notius S ovaJis S paucispinis S pendunculans S phillipsi S pinniger S polyspinis S pronger S rastrelliger S reedi "S rosaceus "S rosenblaW S rubernmus ■ rubnvtnctus '■ rufinanus rufus saxicola semicinctus serranoides sernceps Simulator sinensis ■ spinorbis umbrosus variegatus varispinis ' wilsoni zacentrus Monterey. Calif La Jolla, Caht Pt San Pablo, Ba)a Hipolilo Bay, Baja San Drego, Calif San Diego, Calif Eureka, Calif Santa Barbara I , Calif San Rogue, Baja San Benito I . Baja Cedros I , Baja Natividad I . Baia Dixon Entrance, B C Thetis Bank. Baja Gult ot Calif Santa Catalina 1 . Calif Sebastian Viscaino Bay, Baja San Martin I , Baja Cedros I . Baja Punta Gorda, Calif ^ Ranger Bank, Ba/a Todos Santos Bay. Baja Sebastian Viscamo Bay, Baja Gult of Calif San Diego, Calif Ensenada, Baja Magdalena Bay, Baja Coronado Bank, Calif Guadalupe I . 6a|a Cape Coinetl, Baja Los Coronados I . Baja Ranger Bank. Baja Gulf of Calif Pi Sur, Calif Paradise Cove, Baja Cedros I , Baja San Benilo I , Baja Pt Santo Tomas. Baja San Miguel I , Baja Pt Buchon, Baja Uncle Sam Bank. Baja Cape Coinetl. Baja Pt Blanco, Baia Gulf of Calif Newport. Calil Cape Coinetl, Baja S E Alaska San Diego, Calif Playa Mario Bay. Baja Crecent City, Calif Turtle Bay. Baja Ranger Bank, Baja Ensenada. Baja Cape Colnett, Baja San Clemenli I , Calif Guadalupe I , Baja Sebastian Viscamo Bay, Baja Sebastian Viscamo Bay Baja San Benito I , Baja Cedros I , Baja Guadalupe I . Baja Gulf of Calif Gulf of Calif Pt San Juanico, Baja Queen Charlotte Sd . B C Gull of Calif Cortez Bank, Calif San Diego, Calif Aleutians and Japan Bering Sea and Japan Timber Cove, Sonoma Co , Calif S E Alaska Amphndile Pt , Vancouver I , 8 C Amchilka I , Alaska S E Kamchatka Bering Sea Eureka, Calif Gult of Alaska Copalis Head. Wash Eureka. Caht Benng Sea San Francisco. Calif Gult of Calif Bering Sea San Francisco. Calif Alaska Peninsula Green I , Montague I , Gult of Alaska Kenai Peninsula, Gult ot Alaska San Francisco. Calif Kodiak. Alaska San Francisco. Calit [''Wash) Gult of Calif Kodiak. Alaska Monterey. Calif Cape Scott. Vancouver I . B C Albatross Bank. Gulf of Alaska Farallon 1 . Calif Le Perouse Bank, Vancouver I . B C Santa Catalina I , Calif Usal. Mendicino Co . Calif Pt Sur. Calif Gult of Alaska Amchitka I , Alaska Wash ^Bering Sea) Vancouver I , B C BC (''Bering Sea) S E Alaska S E Alaska Guadalupe I . Baja San Francisco. Calif Kodiak. Alaska Gult ot Calif Monterey Bay. Calif. S E Alaska Eastern Kamchatka Bering Sea Yaquina Bay. Oreg Sitka, Alaska San Francisco, Calif CPuget Sd , Wash ) Avila, Calif CSan Francisco. Calif ) Gulf ot Alaska San Francisco. Calif San Clementi I . Calif Mad River. Calif S E Alaska PI Pinos. Monterey Co . Calif Redding Rock, Del None Co . Calif San Francisco. Calif San Pedro, Calif CPt Conception. Calif ) Gulf of Calft Gulf of Calif Pt Conception, Calif Unimak Pass, Aleutian I Gult of Calif S E Alaska Sanak 1 , Aleutians 'Compiled from Bailey etal ( 1970), Chen (1971). Lea and Filch (1972), Miller and Lea (1972), Ouast and Hall (1972). Rosenblatt and Chen (1972), Barsukov (1973), Hart (1973), and Chen (1975), and original data for S emphaeus No records from ttie Sea of Okhotsk ^Includes S vexiiiaris (Chen 1975. W N Eschmeyer. Senior Curator tor Research, California Academy of Sciences. Golden Gate Park. San Francisco. CA 941 18, pers commun November 1976) ^Based on data obtained dunng this study 42 RICHARDSON and LAROCHE: DEVELOPMENT AND OCCURRENCE OF ROCKFISHES Appendix Table 2. — Chart showing interorbital curvature and presence or absence of the supraocu- lar spine for rockiishes [Sebastes spp.) occurring off Oregon.' x indicates usual condition; o indicates occasional occurrence. Inlerorbital Interorbital Flat-convex Concave Flat-convex Concave Supraocular spine Supraocular spine Species Present Absent Present Absent Supraocular spine Supraocular spine Species Present Absent Present Absent S- aleutianus S. alutus S. aunculatus S. aurora S. babcocki S. borealis S. brevispinis S. caunnus S. chlorosticlus S cramen S. diploproa S. elongatus S. emphaeus S. entomelas S. eos^ S. flavidus S goodei S. helvomaculatus S. lordani S maliger S melanops S melanostomus S miniatus S mystinus S nebulosus S nigrocinctus S paucispinis S pinniger S pronger S rastrelliger S reedi S rosaceus^ S ruberrimus S saxicola S wilsoni S- zacenlrus ' Compiled from Phillips ( 1 957) , Westrheim and Tsuyuki ( 1 967. and original data for S emphaeus ^Species may be rare off Oregon 1972). Chen (1971). Miller and Lea (1972). and Hart (1973). APPENDIX Table 3. — Numbers of dorsal, anal, and pectoral fin soft rays for rockiishes iSebastes spp.) occurring off Oregon.' x indicates usual numbers, o indicates occasional occurence. Species Dorsal fin rays Anal fin rays Pecloral fm rays 11 12 13 14 15 16 17 5 10 11 15 16 17 18 19 20 21 22 S aleutianus S alulus S aunculatus S aurora S babcocki S borealis S brevispinis S caunnus S chlorostictus S cramen S diploproa S elongatus S emphaeus S entomelas S eos^ S tiavidus S goodei S helvomaculatus S lordani S maliger melanops melanostomus miniatus mystinus nebulosus nigrocinctus paucispinis pinniger pronger S rastrelliger S reedi S rosaceus^ S ruberrimus S saxicola S wilsoni S zacentrus 'Compiled from Phillips (1957). Westrheim (1966), Westrheim and Tsuyuki (1967. 1972). Chen (1971). Miller and Lea (1972). and Hart (1973), and onginal data for S emphaeus ^Species may be rare off Oregon 43 FISHERY BULLETIN: VOL 77. NO 1 Appendix Table 4. — Total numbers of gill rakers on first gill arch for rockfishes(Se6as/esspp.) occurring off Oregon.* Species 22 23 24 25 26 27 26 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 S aleutianus x x x x x x S alutus xxxxxxxxx S auriculatus x x x x x x S aurora x x x x x S babcocki x x x x x S borealis x x x x x S brevispinis x x x x S caurmus x x x x x x x S. chlorostictus x x x x x x S crameri x x x x x x S diplopora X X X X X X S elongatus x x x x x x S emphaeus x x x x x x x S entomelas x x x x S eos' X X X X X X S flavidus X X X X X X X S goodei x x x x x x S helvomaculatus x x x x x x S jordani x x x x x x x S. maliger x x x x x S melanops x x x x x x x S rnelariostomus xxxxxxxxx S miniatus xxxxx xxxx S mysf/nus x x x x x x S nebulosus x x x x x x S nigrocinctus xxxxx S paucispmis xxxx S. pinntger x x x x x x S. proriger xxxx xxxx S. rastrelliger xxxx S reed/ x x x x x x x S fosaceus^ x x x x x x S rubemmus x x x x x x S. saxicola xxxxx S wilsoni XX xxxx S zacenfrus x x x x x x x ' Compiled from Phillips ( 1957), Westrhetm and Tsuyuki( 1967. 1972), Chen (1971). Miller and Lea (1972). and Hart (1973), and original data for S empftaeus ^Species may be rare off Oregon. 44 RICHARDSON and LAROCHE DEVELOPMENT AND OCCURRENCE OF ROCKFISHES 3 1 2 O O Q 1 Q. 3 O 5 3 5 3 ra O fD £ tl ro nj -Q -Q ■Q O CO 07 W CO CO t/l C/1 1 5 O.S c o O TD QJ 0) a> o i o t ^ t o c c fe O O 0) cocoi/icocococococo (if bcittlenosed dolphins and West Indian manatees entering or leaving the Indian River during the time of the aerial surveys, indicating direction of travel relative to tidal flow Dale 11977) Bottlenosed dolphins West Indian manatees 10 Aug 1 1 Aug 12 Aug 13 Aug 14 Aug 15 Aug Total 4 adults moving against tide into river through Sebas- tian Inlet 7 adults 2 calves moving with tide trom river into Sebastian Inlet thence against tide back into river 1 adult moving against tide into river through Sebas- tian Inlet 0 0 1 luvenile milling within Sebastian Inlet at slack tide 15 individuals consisting ol 5 moving against tide 9 moving both with and against tide and i milling within inlet 2 adults milling within Fori Pierce Inlet 2 adults moving against tide into nver through Fort Pierce inlet 0 1 adult moving with tide from river to ocean through Sebastian Inlet 1 adult moving with tide from river to ocean through Sebastian Inlet 6 individuals, consisting ol 2 milling withm inlet 2 moving against tide, and 2 moving with tide T\HLK 4 — Summary of West Indian manatee sightings by day during the six 1-day aerial surveys. August 1977. TaHLK 5. — Some estimates of density of bottlenosed dophms, Tursiops sp., in coastal waters of the southeastern United States. Survey Total no ot Number of an mals Calves ol Other possible Date no sightings Total season calves 10 Aug 1 9 13 H7 6%) 1(0 7»„) 11 Aug 2 12 21 2(9 5%l 1(0 7%) 12 Aug 3 8 18 2(11 1%I O(-) 13 Aug 4 1 1 18 1(5 6%) Ot-) 14 Aug 5 11 41 5(12 2°^l O(-) 15 Aug 6 9 40 4(10 0°o| 3(2 O-'o) Total 60 151 15(9 9%) 5(3 3%) Reynolds'i. and were consistent with those re- ported from aerial surveys conducted in Texas using similar methodology (Barham et a!.**! (Table 5). This consistency and the relatively low var- iance estimates are evidence that this was a realistic estimate of the numbers of dolphins in the rivers during the time of the survey. Biittlenosi'd dolphins have been observed to occur as individuals and in groups of over 200 animals i Leathfruiind and Platter''). Mean herd sizes iif hdtlleno.sed dolphins off eastern P^lnrida and in {hv C!ulf of Mexico vary considi'iahiy I'nim one area to another- ('ii'oups apparently decrease 'Odell. D K.. and J, E Reynolds III In press. Distribution and abundance of the bottlenosed dolphin. Tursiitps Iruniiitus. on the west coast of'Florida. Contract Report to the U.S. Marine Mammal Commission. Wash., D.C., 5.5 p. National Technical Information Service. Wash.. DC 'Barham. E, G . J, C. Sweeny. S. Leatherwood. R. K Beggs. and C. L, Barham, 1978, Aerial census of bottlenosed dol- phins tTursifips truiicatiist in a region of the Texas coast. Un- publ- manuscr,. 34 p. Southwest Fisheries Center. National Marine Fisheries Service. NOAA. P.O, Box 271. La Jolla, CA 920.38 "Leatherwood. S,, and M. F, Platter, 1975, Aerial assess- ment of bottlenosed dolphins off Alabama. Mississippi, and Louisiana, hi D, K, Odell, D. B, Siniff. and G, H. Waring ifditorsi. 7\irsiiips tnmcaliis assessment workshop, p, 49-86, Final Report. U,S, Marine Mammal Commission, Contract MM5AC021 Dolphin Dolphins Location Reference per km^ per n mi.^ Mississippi Leatherwood et al 023 057 gull coast (1978) Louisiana Leatherwood et al 0 44 1 08 gulf coast (1978) Florida' Odell and Reynolds 0 23 0 57 West Coast (see footnote 7) Texas Barham et al (see 0 65 1 61 gull coast footnote 8) Florida This paper 0.6B 1 77 Indian River ^Derived trom their Table 10 by computing the product ol mean I (5 43) and mean herd density (0 0497) in size with distance from shore lOdell and Reynolds see footnote 7i; tend in coastal waters to be larger in deeper and in open water areas than in shallou embaymenls. lagoons, and marshlands I LeatheiuDod and Platter see footnote 9; Leath- erwood et al. 1978; Shane and Schmidley'"); and tend to fluctuate in size seasonally with little pat- tern discernible i Shane and Schmidley see foot- note lOi. The mean group size observed during this stt-id\- IS. 21 \sas well within the limits reported by all authors for eastern Florida and gulf coast v\a- ters. This and the lack olcorrelation between herd size and herd densit\' lurther suppoi't the reason- ableness of this population estimate (only if the distribution of herd sizes were normal could the inference technically lie made that the two vari- ables were independent (Figure 4ii. Because the estimation of variance in total numbers of animals assumes that herd size and '".Shane, S, H,, and D, J, Schmidley, In press. Population hiiilogy of .Atlantic bottlenosed dolphins, Tursittpti truncatus, in the .Aransas Pass area of Texas, Contract Report to the U.S. Marine .Mammal Commi.ssion. Wash,, DC. 2.'i8 p. National Technical Inform.itinn .Service. Wash., D.C. 56 LEATHERWOOD AERIAL SURVEY (IF DOLPHINS AND MANATEES herd density are mutually independent, the data by day were examined for correlation. Using Ken- dall's rank correlation coefficient (Conover 1971) at a = 0.05, mean herd size and mean herd density were demonstrated to be uncorrelated within the area surveyed. The dolphin densities per square kilometer were then multiplied by the area surveyed and a factor of 5 (since the survey covered 20' V of the total area) and the 95'^i confidence limits calculated for the estimate. The figures support an estimate of 438±127 dolphins for the Indian and Banana Riv- ers during the time of the survey. As an alternate method for estimating dolphin densities, I took the average density over repli- cates from column 3, Table 2. This procedure re- sults in a density estimate of 0.40 dolphin km- (1.36 dolphins/n.mi.^), a value very close to the estimate obtained using the method described above (0.41 dolphin km-, 1.41 dolphins/n.mi.^), but having a variance twice as large (0.1837 vs. 0.0941. Because of the higher variance, it can be argued that the first method used, because it takes into account both average herd size and average herd density, is preferable in this case. The numbers of dolphins entering or leaving the river at Sebastian (4 groups totaling 15 animals) and Fort Pierce Inlets (none sighted) were negligi- ble and were judged as insignificant to the total population size. Two of those groups were entering the river against an outgoing tide, one moved from the river into the inlet on an ebbing tide, then turned around and reentered the river, and one was milling within the inlet (Table 3). The surprisingly low estimate does, of course, raise an important question. Is the population of bottlenosed dolphins in the river complex always this small (and only appears larger because of periodic concentrations of animals in limited areas) or is it augmented seasonally by influxes of animals from other areas migrating into,the rivers in response to the movement of fishes? Caldwell ( 1955) and others have suggested lim- ited home ranges for bottlenosed dolphins. Wells et al.," Irvine et al.,'- and Shane and Schmidley "Wells. R. S.. A, B. Irvine, and M. D. Scott 1977, Home range characteristics and group composition of the Atlantic bottlenosed dolphin Tur>ii(>ps tnirtcatus on the west coast of Flonda. In Proceedings lAbstr.l of the Second Conference on the Biology of Marine Mammals, San Diego, Calif., 12-15 Dec. 1977, p. l.i '■^Irvine, A. B., M D, Scott, and R. S Wells, 1977, Move- ments and activities of Atlantic bottlenosed dolphins. In Pro- ceedings lAbstr.l of the Second Conference on the Biology of Marine Mammals, San Diego. Calif, 12-15 Dec. 1977. p. 16. (see footnote 10) have all clearly demonstiated limited home ranges for portions of the popula- tions in their study areas; Wells et al. (see footnote 1 1 ) have shown differences in size and locations of home ranges based on age and sex classes, and all these authors have reported some movements ol' animals into and out of their study areas. Caldwell and Caldwell (1972) summarize the views of the fishermen from eastern Florida that there are "river" and "ocean" T. Iriniciiliis popula- tions. Caldwell et al. (1975) presented evidence from the distribution of cases of "Lobos" disease (lobomycosis) in bottlenosed dolphins that indi- cate greatest susceptibility to the disease in riverine-estuarine stocks and suggest isolation of river from ocean stocks. Shane''' reported that the offshore population of bottlenosed dolphins off Texas rarely interacted with the bay population but that the winter popu- lation in the Port Aransas area was at least twice as large as that in summer, because the bay popu- lation was augmented by "large numbers" of dol- phins entering that area for the winter either from the adjacent gulf or from adjacent bay systems. Whether or not a similar influx occurs in the In- dian River is unclear. Additional surveys during the peak seasons of the most important midwinter fisheries (king and Spanish mackerel, bluefish, spots, and pompano) might provide answers. In considering the questions of the dolphins' population size and alleged damage to nets, it should be remembered that bottlenosed dolphins, at least in some areas, are not uniformly distrib- uted but tend to concentrate in areas of high fish productivity (Leatherwood and Platter see foot- note 9) which are often areas of highest human use (Leatherwood 1975). Irvine et al. (see footnote 12), for example, reported that short-term movements of bottlenosed dolphins near Tampa Bay appear to correlate with movements of mullet. Frequent joint use of resources by dolphins and humans make the dolphins highly visible and could result in inflated estimates of their numbers. Even if not augmented seasonally by immigra- tion from other areas, the relatively small dolphin population in Indian and Banana Rivers could be responsible for net damage of the types reported by Cato and Prochaska ( 1976). Feeding by dolphins near seine and gill net fisheries is well known '^Shane. S, H. 1977, Population biology of Twr-'iio/w /ra(i- latus in Texas. In Proceedings (Ab.str.l of the Second Confer- ence on the Biologvof Marine Mammals. San Diego. Calif. 12-15 Dec. 1977. p. .57. ' 57 FISHERY BULLETIN VOL 77, NO 1 ( Leatherwood 1975), and dolphins sometimes be- come entangled as a consequence (Mitchell 1975). An entangled adult dolphin, struggling for escape, is certainly capable of ripping a small-mesh net apart. Further, bottlenosed dolphins have been documented stealing fish from longlines (Iver- son'''). Even so, dolphins may not actually be re- sponsible for all or even the majority of the dam- age in Indian River. Cato and Prochaska (1976) refer to damage to nets by sharks and cite the need for deterrents. D. K. Caldwell'^ reviewed the evi- dence and concluded that the majority of damage to nets in the Indian River was probably caused by sharks and not by dolphins, citing as support numerous reports by fishermen and others work- ing the area of sharks around nets. He also con- cluded, however, that dolphins were stealing fish and damaging gear in the king mackerel fishery in the nearby Atlantic Ocean. During the aerial sur- veys, I observed huge concentrations of sharks on the sand bars at the entrance of St. Lucie Channel. Therefore, the question of what causes the damage to nets is still open and regulation of the dolphin population based on its supposed size and levels of damage to the fisheries would be premature. Irvine et al. (see footnote 12) reported that in spring calves composed as much as 147^ of the bottlenosed dolphin population near Tampa Bay. Shane (see footnote 13) reported that calves con- stituted from 3.65% (February) to 12.92% (May) of the dolphins in the Port Aransas area (x = 7.61); Leatherwood et al. (1978) reported summer figures from 7.7 to 7.9% calves for coastal Ala- bama, Mississippi, and Louisiana. The 8.1-10.1% calves observed during this survey therefore are well within the reported ranges of percentages of calves in local bottlenosed dolphin populations. It has been noted that in areas where tidal flow is negligible, as is the case within these rivers, dolphin movements appear to be related to some factor other than tide (Shane and Schmidley see footnote 10). Shane and Schmidley found that the dolphins in areas of swiftest current moved against tidal flow. The inability to ascertain a relationship between swimming direction of '■•Iverson.R, T. B. 1975. Bottlenosed dolpliins stealing fish from Hawaiian fishermen's lines. Unpubl- manuscr., 12 p. Southwest Fisheries Center Honolulu Laboratory, National Marine Fisheries Service. NOAA, P O. Box .3830, Honolulu, HI 96812. "'D. K. Caldwell. University of Florida, Biocommunication and Marine Mammal Research Facility. Rt. 1, Box 121, St. Au- gustine, FL 32084, pers. commun. September 1977. groups and tidal flow in the river inlets in this study is perhaps related to our small sample size. Manatees Hartman (see footnote 5) and Irvine and Campbell (1978) reported that Florida manatees concentrated near warmwater refugia during winter months but dispersed during the remain- der of the year. The 151 manatees (some no doubt repeats on successive days) sighted during this survey were distributed throughout the nearshore waters of the Indian-Banana River complex, in- cluding several less saline canals, and animals were not concentrated near the St. Lucie power station or other potential warmwater areas where winter concentrations have been reported (Irvine and Campbell 1978). No manatees were observed in the deeper open water of the rivers. All were in shallower coastal waters, marinas, creek mouths, bayous, and canals. The number of calves ob- | served, composing from 9.9 to 13.2% , depending on the correct classification of the intermediate-sized animals observed, falls within the ranges of 9.6% calves (winter) and 13.4% calves (summer) re- ported by Irvine and Campbell (1978). ACKNOWLEDGMENTS I thank the following for help with this project: aircraft from Orlando Flying Service, Orlando, Fla., were flown by Steve Negrich. Glen Young, Sea World of Florida, flew as second observer. Both men were very competent and patient with the arduous flight schedule. Ed Asper,Sea World, Inc., provided observers at the ocean inlets and offered valuable advice on the animals of the river. Leola Hietala and Louise Anello Irwin typed the manu- script. D. K. Caldwell, A. B. Irvine, Mari Schaef- fer, J. Powers, T. J. Quinn, S. Shane, and R. Wells reviewed the manuscript and made useful sugges- tions for its improvement. Fishery Bulletin re- viewers L. L. Eberhardt and J. R. Gilbert were especially thorough in their treatment. LITERATURE CITED Caldwell. D, K 1955. Evidence of home range of an Atlantic bottlenose dolphin J. Mammal. 36:304-305. C.-^LDWELL. D. K., AND M. C. CALDWELL, 1972. The world of the bottlenosed dolphin J B Lippin- cott Co., Phila.. 157 p. 58 LEATHERWOOD AERIAL SURVEY OF DOLPHINS AND MANATEES Caldwell. D. K.. M. C. Caldwell. J. C. Woodard, L. ajello, W. KAPLAN, and H. M. MCCLURE 1975. Lobomycosis as a disease of the Atlantic bottlenosed dolphin ^Tiirsiops truncatus Montagu. 1821), Am J. Trop. Med. Hygiene 24:105-114. CATO. J. C, AND F. J. PROCHASKA 1976. Porpoise attacking hool < f a 79 KiSHKKV BULLETIN' VOL FlGl'RE 11 ^Sqiiilla emptisa. A-B: stages VI and VII respectively, ventral views. Fifth maxilliped (Figure 13Ri with propodus bearing 18 to 40 spinules, carpus with 9 to 20 .spinules. Pereiopods (Figure 14P to 14Ri slender with or without distal segment of e.xopods setose. Pleopods (Figures 22A to 22C; 23A. 23Bi with distal lobe of gill pinnate. Uropod (Figure 26C) with basal segment ol' exopod armed with 6 to 8 spines, apical segment of exopod with 17 to 60 plumose setae. Endopod of uropod with 10 to 38 plumose setae. Inner spine of basal prolongation with blunt spine on outer prox- imal margin. Basal uropod segment with a dorsal spine on distal margin. Telson (Figure 141) with 8 to 10 pairs of inter- mediate denticles, 26 to 34 submedian denticles. P()stlar\a (Iigure 2 0 Measurements (mmi: RL, 0.50 to 0.60: CL, 2.90 to 3.30; TW, 2.55 to 3.10; RVV. 0.65 to 0.75; tL. 1.95 to 2.55: TL, 12.3 to 14.20. Eyes large, extending to middle of second seg- ment of antennular peduncle. Cornea bilobed, set obliquely on stalk. Ocular scales rounded, anterior margin of opthalmic somite evenly rounded. Antennular process produced into blunt spine directed anterolaterally, antennular peduncle slightly shorter than carapace, antennule ( Figure 25Ai with inner flagellum bearing 34 segments, median flagellum with 30 segments, outer flagel- lum with 15 segments and 22 aesthetascs ar- ranged in eight groups of 2 or 3. Antenna (Figure 25Bi with 63 to 75 plumose setae, endopod with 16 segments. Rostral plate wider than long, lateral margins tapering to rounded apex. Median carina present. Anterolateral angle of carapace without spine, almost forming right angle, posterolateral mar- gins broadly rounded, carinae poorly developed, median carina not bifurcate anteriorly or pos- teriorly, intermediate and lateral carinae present, reflected carinae absent. Mandible (Figure 25C) serrate, mandibular palp absent. Maxillule (Figure 25D) with coxal endite bear- ing 26 to 27 strong marginal teeth and 6 to 9 small medial teeth. Basal endite with one spine flanked 80 MORGAN and PROVENZANO, DEVELOPMENT OF SQUILLA EMPUSA LARVAE AND POSTLARVA FIGURE 18. Squilla empusa. A-E: stage VII, first to fifth pleopods re- spectively. by one strong seta. Distal margin of basis with three setae. Endopod present as palp on distal margin of basis, armed with two setae. Maxilla (Figure 25E) four-segmented, two prox- imal segments with endites, second bilobed. Five pairs of maxillipeds (Figure 25F to 25J) each maxilliped with one epipod. First maxilliped (Figure 25F) with distal margin of propodus bear- ing 14 teeth, inner margin with 48 to 50 strong setae arranged in 10 transverse rows, 2 or .3 most distal setae spatulate with strong setules. Second maxilliped (Figure 25Gi with dactylus bearing six teeth, pectinate propodus with three moveable proximal spines, dorsal ridge of carpus undivided. Pereiopods (Figure 26A) with setose endopod and exopod. Last three thoracic somites with unarmed sub- median and intermediate carinae. Lateral process of fifth thoracic somite subacute, sloping pos- teriorly. Lateral processes of next two somites bilobed each with a small anterior lobe and a large broadly rounded posterior lobe. Median ventral keel of eighth somite with rounded apex. Abdomen broad, depressed, Submedian, inter- mediate, lateral, and marginal carinae present. Abdominal spines in submedian carinae of sixth somite, intermediate and lateral carinae of fifth and sixth somites, and marginal carinae of fifth somite, formula: submedian 6; intermediate 5 to 6; lateral, 5 to 6; marginal, 5. Sixth abdominal so- mite with sharp ventral spine anterior to uropod articulation. Pleopods (Figure 26B to 26Fl with gills. Pleopod setation presented in Table 2. Uropod (Figure 26G) with eight graded move- able spines on outer margin of proximal segment of exopod, last extending to middle of apical seg- ment. Apical segment of exopod extending pos- teriorly to apex of intermediate spine. Basal seg- 81 FISHERY BULLETIN: VOL 77. NO 1 Table 2. — Number of setae on margins of pleopods of the post- larva ofSqutlla empusa. Figure 19- — SquiUa empusa. stage VIII. ventral view. merit of uropod with dorsal spine on distal margin. Basal prolongation of uropod with two spines, me- sial longer. Single rounded lobe between spines of prolongation. Mesial margin of basal prolongation sinuate. Telson (Figure 24) as wide as long, median carina with sharp posterior spine, prelateral lobes absent, postanal ventral carina absent, subme- dian teeth with moveable apices, denticle formula: submedian, 8 to 10; intermediate, 7 to 10; lateral, 1. Postlarva white with brown chromatophores on eyes and all appendages except mouthparts. Carapace with few chromatophores. Exposed thoracomeres with chromatophores along pos- terior margin. Pleomeres with chromatophores along intermediate and lateral carinae and pos- terior margin. Telson with chromatophores along curved dorsal striations and posterior spine. Abdominal somite structure 1 2 3 4 5 Protopod Endopod Exopod 12-15 55-60 55-59 12-15 60-71 61-64 12-15 66-72 62-64 12-14 63-72 61-63 8-11 59-67 53-56 DISCUSSION Brooks 11878) and Faxon ( 1882) have produced the only prior publications on the larvae ofSquilla empusa. Brooks partially described the develop- ment by reconstruction, and Faxon held an un- identified last stage through metamorphosis to at- tempt to identify it with the adult. .'Although Brooks* illustrations and descriptions indicate that he probably was working with S. empu.'^a, Faxon's do not. The carapace of Faxon's last stage larvae appears to be too broad, the posterolateral spines are too short, and a spinule is present on the posterior margin of the carapace midway between the dorsal and posterolateral spines. Further- more, in Faxon's illustrations both the last larval stage and postlarva have broad abdomens with the first pleomere being as wide as the sixth, but in .S. empusa, the abdomen is tapered with smaller an- terior pleomeres grading into larger posterior ones. Faxon collected his larva from Newport, R.I., where only four species of stomatopods are known to reside: S. empusa. Nannnsquilla grayi. Hetern- squilla arinata. and Platysquilla cnodis (Manning 1974). Because the telson of Faxon's postlarva bears four intermediate denticles, it can be attrib- uted to the Squillidae, and S. empusa is the only squillid known to inhabit the area; the other three species belong to the Lysiosquillidae. Few larval descriptions have been made on southern species of squillid larvae, and of these none possesses the pair of spines on the posterior margin of the carapace, seen in Faxon's larva, nor does S. em- pusa. If Alikunhi (1952, 1967) was con-ect in his identification of the late larva and postlarva, these spines occur on Cloridopsis scorpio from the In- dian Ocean. The spines may be only a specific character or they may be diagnostic for the genus Cloriflopsis. The only member of that genus in- habiting the waters of the Western Atlantic is C (luhia which ranges from South Carolina to Brazil. Perhaps Faxon collected a larva of C. duhia which drifted north with the Gulf Stream. Until more larval descriptions are worked out for western At- 82 MORGAN and PROVENZANO DEVELOPMENT OF SQUILLA EMPUSA LARVAE AND POSTLARVA FR;URE 20.— Squilla cmpusa. A-E: stage VTII, first to fifth pleopods re- spectively. lantic species of stomatopods, the identity of Fax- on's larva will remain uncertain. To identify larvae of S. empusa the spinules of the carapace and denticles of the telson should be examined. Stages I and II possess four spinules on the lateral margin of the carapace and four inter- mediate denticles. The third to ninth stages are armed with six spinules on the lateral margin of the carapace. There are two anterior and three posterior spinules all ventrally directed, and one median spinule laterally directed. The telsons of stages III to IX have S to 10 mtermediate denti- cles. Except for Provenzano and Manning (1978), who reared Gonadactyius oerstedii from hatching to metamorphosis, experimenters who have at- 83 FISHERY BULLETIN VOL 77. NO 1 Figure 21. — SquiUa empusa. stage IX, ventral view. tempted to hatch and rear larvae either to link them with an adult or to describe the entire larval development have been unsuccessful at rearing larvae past the first pelagic stage because the lar- vae could not be induced to feed (Manning and Provenzano 1963). Pyne ( 1972) was unable to rear Pterygosquilla arinata schizodontia eggs past the first pelagic stage, but did hold stages I to VII larvae taken from the plankton for periods as long as 10 to 16 days wherein the larvae passed through at least one ecdysis. Pyne also found it possible to keep later stage larvae for very much longer periods of up to 165 days during which time they molted as many as six times. Pyne reared his lar- vae in mass culture using 4-in (10.2-cm) finger bowls. Alikunhi ( 1975) reared planktonic larvae of Oratosquilla nepa in aquaria through metamor- phosis until they reached adulthood, bred, and produced eggs. The manner in which all .species of Squillidae develop is similar. All Squillidae hatch as pseudozeae with four pairs of pleopods and develop into the alima form. Some, if not all, pass through two propelagic stages before the first truly planktonic stage. The alima is characterized by a telson with four or more intermediate denticles, the distance between the submedian spines in later stages being not larger than that between the intermediate and submedian spines, the pro- podus of the second maxilliped bearing three basal spines, the antennular somite generally having a median spine, the posterolateral spine of the carapace having a basal accessory spine, the eye- stalks long, and the exopod of the uropod being longer than the endopod (Gurney 1942, 1946). Alikunhi (1952) added that alima larvae possess carapaces armed with a varying number of spinules on the lateral margins, the sixth abdomi- nal somite usually being equipped with a pair of submedian dorsal spines, and in advanced larvae, the posterolateral angles of the abdominal somites ending in acute or subacute spines. Alikunhi (1952) noted that between allied species, the specific differences are often "trivial" but remarkably constant. He determined that some features, such as the size of the final pelagic stage, the shape and spinulation of the carapace, telson, and uropods.and the presence or absence of teeth other than the terminal on the dactylus of the second maxilliped, hardly show any variation within a species. These characters may be used for specific determinations but are presently of little aid in defining generic alliances for three reasons. First, relatively few stomatopods have been as- sociated definitely with the adult of the species. Second, most of these have had described only one larval .stage of the entire development. Only 19 of the Squillidae have been definitely connected with their larval forms. Provenzano and Manning (1978) listed 17 species of identified stomatopod larvae, but O. masnavensis was omitted and S. empusa has now been added to the list. Of the 19 species, only 2. P. arinata schizodentia andS. em- pusa, have been reared in the laboratory through essentially their entire pelagic development. Two additional species have been hatched from eggs obtained from a known adult and the first pelagic stage described, i.e., Chirida vhoprat by Gurney 84 MORGAN and PROVENZANO DEVELOPMENT OF SQUILLA EMPUSA LARVAE AND POSTLARVA •"'11 III r^hMk *!i% FIGURE 22— Squilh empusa. A-C: stage IX, first to third pleopods respectively. Figure 2Z.—SquiUa empusa. A-B: stage IX, fourth to fifth pleopods respectively; C: stage IX, uropod. 85 FISHERY BULLETIN VOL 77. NO 1 FlOURE 24. — Squilla empiisa. postlarva. dorsal view. ( 1946) andS. mu/ilis by Giesbrecht ( 1910), and the remainder have had the last stage described by holding the final pelagic stage until metamor- phosis occurred and the stomatopod could be corre- lated with an adult of the species. Reconstructions of the larval development of three species, .S. man- tis by Giesbrecht ( 1910), O. oratoriu by Komai and Tung (1929), and O. maasavensis by Gohar and Al-Kholy (1957), were attempted by collecting larval stages from the plankton and piecing them together. Metamorphosis from the last larval stage was obtained for O. massavensis, but since the larvae were not reared, the larval histories may not be entirely factual. Thus, because so few larval forms have been identified and because most of these have had only one stage described, it is difficult to discover which characters are shared by all members of a genus and which characters are only specific. Of the nine genera of Squillidae which have had larvae described, four genera have had one or more larval stages of a single species described, four more genera have had two species identified, and one genus has had larvae of eight species described. A determination of generic characters is difficult at best for those genera for which only one or two species have been described, especially since there are no adequately rep- resented genera with which to compare charac- ters. The third reason why specific characters are of little help in generic definition lies in the incom- plete descriptions of the larval stages. Characters noted by one author are frequently omitted by another, so that even for the genus Oratosquilta, represented by larval descriptions of eight species, consistent characters are difficult to recognize. An assessment of larval characters was at- tempted to determine which ones were constant within each genus. Most characters mentioned in the descriptions appeared to vary a gr-eat deal for the species within a genus, or the characters that varied relatively little within a genus were fre- quently found in other species of different genera. Of possible value in defining generic associations is the presence or absence of teeth (other than the terminal ) on the dactylus of the second maxilliped. These teeth occur during the last stage in the genera Anchisquil la , Clorida , Pterygosquilla , and Squilloides, although for each of these genera lar- vae of only one species have been described. The dactylus of P. annata schizodontia is armed with 5 to 8 teeth and the first stage is easily diagnosed by the posterior spines of the carapace which bear 6 to 16 spirally arranged, proximal spinules. The spinules are replaced by three ventral spinules in the remaining stages (Pyne 1972). The dactyl of the second maxilliped is equipped with two free teeth in A. fasciata, three teeth inS. lata, and inC. latreillei is usually armed with one tooth, rarely with two (Alikunhi 1952). Newly hatched larvae of C. choprai were too inadequately described to be compared withC. latreillei (Tweedie 1935; Gurney 19461, but the dactylus of the second maxilliped was observed to be unarmed. This is not surprising since C. latreillei and S. lata develop teeth on the dactylus of the second maxilliped in the later stages and P. armata schizodontia develops its first tooth in the third stage. 86 MORGAN and PROVENZANO DEVELOPMENT OF St^CILLA E.VtPL'SA LARVAE AND POSTLARVA 1 A.R F J 1 1 0mm 1 C-E 1 Figure 25. — Squilla empusa. postlarva. A, antennule; B. antenna; C, mandible; D. maxillule; E, maxilla; F-J, first to fifth maxillipeds respectively. 87 FISHERY BULLETIN VOL 77. NO 1 I, ,^.^f?ffe mm 0mh ilM^. Figure 26. — Sqmlla cmpusa, postlarva. A, first pereipod; B-F. first to fifth pleopods respec- tively; G, uropod. 88 MORGAN and PROVENZANO: DEVELOPMENT OF SQL' ILL A KMPl'SA LARVAE AND POSTLARVA The second maxilliped of the remaining de- scribed larvae is unarmed throughout the larval development. To distinguish these genera, other characters, such as the presence or absence of a spine on the basis of the second maxilliped, must be relied on. The spine is definitely born by seven of the eight species oi OratosquiUa, but was not mentioned for O. massavensis. Other species, Squilla enipusa. P. armata schizodontia , Aliina hyalina, and Meiosquilla lebouri have the spine, while Harpiosqiiilla harpax and A. fasclata definitely do not. The development of epipods on five pairs of maxillipeds in older larvae appears to be a generic character of Squilla as most other genera bear four pairs of epipods. Characters such as rostral length and spinula- tion. carapace and telson shape, size, and spinula- tion, and overall body size and appearance have been too variable within the limited number of species presently described to use them in defining generic associations of the larvae. Deriving characters which apply to the youngest larvae as well as the old will be difficult since far fewer characters are present in the early stage larvae, and the gross appearance of the young larvae is very similar due to the small degree of differentia- tion. Other characters such as antennular seg- mentation, mouthpart morphology, setation, spi- nation of the maxillipeds, or the presence of ocular, antennular, epistomal, or basal uropodal spines may also need to be examined. The setation and spination of the first maxilliped may be of great value in defining alliances of the species as well as in making specific determinations. How- ever, many more complete descriptions of the lar- val developments undergone by the various species must be accomplished before larval characters can be used in establishing generic re- lationships. The postlarva of Squilla empusa exh-ibited the basic features of first stage postlarva as deter- mined for other species by Alikunhi (1967). These include the absence of anterolateral spines on the carapace, the extremely poorly developed carina- tion of the carapace, acutely pointed marginal denticles of the telson, and moveable apices of the submedian spines of the telson. As with the adult, the postlarva possesses the full complement of teeth on the raptorial dactylus, just as Alikunhi 11967) found. Furthermore, the five pairs of epipods found in the adult are also possessed by the postlarva. Other adult characters were de- veloped upon the next molt. The dorsal carinations of the carapace were developed, the lateral proces- ses of the exposed thoracic somites five through eight resembled those of the adult, the marginal denticles of the telson were not as acute, and the submedian spines were fixed. The abdominal spi- nal formula was still not equal to that of the adult. Nevertheless, after the postlarva had undergone its first molt more than enough characters were shared with the adult to make a definite determi- nation of the species. CONCLUSIONS 1. Squilla einpusa undergoes nine pelagic stages before attaining the postlarval stage. 2. The last stage stomatopod larva and post- larva described by Faxon (1882) are not S. t'inpusd. 3. Larvae of .S. cmputia may be identified by the spinules of the carapace and the inter- mediate denticles of the telson. Stages I and II possess four spinules on the lateral margin of the carapace and four intermediate denti- cles. The third to ninth stages are armed with six spinules on the lateral margin of the carapace. There are two anterior and three posterior spinules all ventralh' directed, and one median spinule laterally directed. The telsons of stages III to I.X have 8 to 10 inter- mediate denticles. 4. Rostral length and spinulation. carapace and telson size and spinulation, and overall body size and appearance probably are specific rather than generic characters. 5. The presence or absence of teeth on the dac- tylus of the second maxilliped. the presence or absence of a spine on the basis of the sec- ond maxilliped. and the number of epipods may all be useful characters in determining generic status of larvae belonging to the Squillidae. However, many more complete descriptions of the larval developments un- dergone by the various species are needed before larval characters can be used in estab- lishing generic relationships. ACKNOWLEDGMENTS We are indebted to the National Science Found- ation for its support of this work under grant DEB76-11716 to the Old Dommion University Re- search Foundation. 89 FISHERY BULLETIN VOL 77. NO. 1 LITERATURE CITED Alikl'nhi. k. h. 1952. An account of the stomatopod larvae of the Madras plankton. Rec. Indian Mus. (Calcutta! 49:239-319. 1967. An account of the post-larval development, moult- ing, and growth of the common stomatopods of the Madras coast. In Symposium on Crustacea. Ernakulam, India, 1965, p 824-939. Mar. Biol. Assoc. India, Symp. Ser. 2. 1975. Studies on Indonesian stomatopods 1. Growth, maturity and spawning of Squilla nepa. Bull. Shrimp Cult. Res. Cent. 1(11:27-32. BROOKS. W. K. 1878. The larval stages of Squilla empusa Say. Johns Hopkins Univ., Chesapeake Zool. Lab. Sci. Res. 1878:143-170. Burrows. M. 1969. The mechanics and neural control of the prey cap- ture strike in the mantid shrimps S(//;i //a andHemisquil- la. Z. vgl, Physiol. 62:361-381. DRAGOVICH. A. 1970. The food of skipjack and yellowfin tunas m the At- lantic Ocean. U.S. Fish Wildl. Serv., Fish. Bull. 68:445- 460. F.WON. W. 1882. I. — Crustacea. In A. Agassiz, W. Faxon, and E. L. Mark (compilersl. Selections from embryological mono- graphs. Mem, Mus. Comp. Zool, (Harv. Univ. I 9(li, 14 plates. Fish. C. J. 1925. Seasonal distribution of the plankton of the Woods Hole region. Bull. [U.S.I Bur, Fish. 41:91-179. GIESBRECHT, W. 1910. Stomatopoden. Erster Theil. Fauna Flora Golfes von Neapel, Monogr. 33, 239 p. GOH.'^R. H. A. F., .-XNl) A. A. AL-KHOLY 1957. The larval stages of three stomatopod Crustacea (from the Red Sea). Publ. Mar. Biol. Stn., Al-Ghardaqa (Red Seal 9:85-130. GURNEY. R. 1942. Larvae of decapod Crustacea. Ray Soc. (Lond.i Publ. 129, 306 p. 1946. Notes on stomatopod larvae. Proc. Zool. Soc. Lond. 116(11:133-175. HlLDEBR.-\ND, H. H. 1954. A study of the fauna of the brown shrimp tPcnacux aztecus Ives) grounds in the western Gulf of Mexico. Publ. Inst. Mar. Sci., Univ. Tex. 3:233-366. Vol. 3, Crustacea. Wiley In- Kaestner. a. 1970. Invertebrate zoology, terscience, N.Y., 523 p. KOMAi. T., AND Y. M. Tung. 1929. Notes on the larval stages of Squilla oratoria, with remarks on some other stomatopod larvae found in the Japanese Seas. Annot, Zool. Jpn. 12:187-214. LEBOUR, M. V. 1924 Young anglers in captivity and some of their enemies. A study in a plunger jar. J. Mar. Biol. Assoc. U.K. 13:721-734. MacGinitie, G. E.. and N. MacGinitie. 1968. Natural history of marine animals, 2d ed. McGraw-Hill, NY., 523 p. Manning, R, B, 1969. Stomatopod Crustacea of the western Atlan- tic, Stud. Trop. Oceanogr. (Miami) 8, 380 p. 1974. Marine flora and fauna of the northeastern United States. Crustacea: Stomatopoda. U.S. Dep. Commer., NOAA Tech. Rep. NMFS CIRC-387, 6 p. Manning. R. B., and A. J. Provenzano, Jr. 1963. Studies on development of stomatopod Crustacea I. Early larval stages of Gonodactylus oerstedii Han- sen. Bull. Mar. Sci. Gulf Caribb. 13:467-487. PICCINETTI, C, AND G. P. MANFRIN 1970. Prime osservazioni suH'ahmentazione di Squilla mantis L. Bologna Univ. Inst. Zool. Note 3l 101:251-263. PROVENZANO, A. J., JR . AND R. B. MANNING 1978. Studies on development of stomatopod Crustacea II. The later larval stages oi Gonodactylus oerstedii Hansen reared in the laboratory. Bull. Mar. Sci. 28:297-315. PYNE, R, R. 1972, Larval development and behaviour of the mantis shrimp Squilla armnta Milne Edwards (Crustacea: Stomatopodal. J. R. Soc. N.Z. 2:121-146. Randall, J, E. 1967. Food habitsof reef fishes of the West Indies. Stud. Trop. Oceanogr. (Miami) 5:665-847, RKINT.JES. J. W., AND J, E. KING. 1953. Food of yellowfin tuna in the central Pacific. U.S. Fish Wildl. Serv., Fish. Bull. 54:91-110. SUNIER. A. 1917. The Stomatopoda of the collection "Visscherijsta- tion" at Batavia. Contrib. Faune Indes Neerl. 1(4):62- 75. TWEEDIE. M. W. F. 1935. Two new species of Squilla from Malayan waters. Bull. Raffles Mus. 10:45-52. 90 VARIATION IN THE FOURBEARD ROCKLING, ENCHELYOPUS CIMBRIUS, A NORTH ATLANTIC GADID FISH, WITH COMMENTS ON THE GENERA OF ROCKLINGS Daniel M. Cohen' and Joseph L. Russo^ ABSTRACT Enchelyopus cimbriun, the fourbeard rockling, is a gadid fish living around the rim of the North Atlantic Ocean. It varies geographically in color pattern; anal, dorsal, and pectoral fin ray counts; and vertebral and gill racker counts. There is a lack of overall concordance in patternsof vanation in color and meristics. Morphometric characters do not distinguish populations from different geographical areas, and the fourbeard rockling is considered to be a single species. New distributional records include the Gulf of Mexico, West Greenland, and West Africa. We classify the rockiings as a tribe, Gaidropsanni, of the subfamily Lotinae. Characters previously used to separate rockiings into five genera — skull shape, vomerine tooth patch shape, number and distribution of supratemporal pores, length of first dorsal fin ray, and size of jaw teeth — do not distinguish nominal genera. Number of snout barbels divides rockiings into three groups that we tentatively recognize as genera: Gaidropsarus. the threebeard rockiings, with two snout barbels; Enchelyopus, the fourbeard rockling. with three snout barbels; and Ciliata, the fivebeard rockiings. with four or more snout barbels. Onogadus and Antonogadus are referred to the synonymy of Gaidrop- sarus. The correct generic name for the fourbeard rockling isEnckelyopus Bloch and Schneider 1801 , with Rhinonemus Gill 1863 as a junior synonym. It is not preempted by Enchelyopus Gronovius 1760 in Zoarcidae. which was used in a work that was not consistently binominal. The fourbeard rockling, Enchelyopus cimbritis, is a locally abundant gadid fish found around the margins of the North Atlantic Ocean. Although this fish has been recorded in the literature for more than 200 yr, many aspects of its biology are obscure. Adults are sedentary bottom dwellers taken at depths ranging from about 1 to 650 m [we have been unable to verify depth records to 1,325 m given by Goode and Bean ( 1896) ]. There is some indication that seasonal offshore-onshore move- ments occur (Bigelow and Schroeder 1953; Tyler 1971). The pelagic larval stages are similar in appearance to young hakes ( Urophycis ) and some- times occur in silvery swarms near the surface (Bigelow and Schroeder 1953). Recent collections discussed in this paper show that fourbeard rockiings are more widely distrib- uted than previously was known and that geo- graphical variation is present. One of our objec- tives in this paper is to describe, compare, and 'Systematics Laboratory. National Marine Fisheries Service, National Museum of Natural History, Washington, DC 20560. ^Systematics Laboratory, National Marine Fisheries Service, National Museum of Natural History, Washington, DC; pres- ent address: Department of Biological Sciences, The George Washington University, Washington, DC 20006. Manuscript accepted August 1978 FISHERY BULLETIN VOL 77. NO 1, IHTH evaluate geographical variation of selected characters and to show that a single species is represented throughout the range of the fish. The rockling group of the family Gadidae, which is characterized by several distinctive features, recently was divided into five genera (Wheeler 1969), although most ichthyologists have recog- nized only three (albeit under a variety of names). The second of our objectives is to show that at present there are valid reasons for only three. The fourbeard rockling is currently named En- chelyopus cimbrius by North American ichthyologists and Rinonemus cimbrius by Euro- peans. Our final objective is to show that En- chelyopus is the correct generic name. METHODS All observations were made on museum speci- mens listed in the Appendix. Counts of dorsal and anal fin rays and vertebrae were taken from X-ray photographs. Vertebral counts do not include the terminal ural element. Gill raker counts include all rakers on upper and lower arms of the first arch. Head pores were examined with the aid of a compressed air jet. Measurements and their 91 FISHERY BULLETIN VOL 77. NO 1 statistical analysis are described under Body Proportions. Statistical tests were performed on the IBM :i70-148' computer at The George Washington University, using computer pro- grams written and maintained at the Systematics Laboratory, NMFS, NOAA. and following .statis- tical methods presented by Zar (1974). GEOGRAPHICAL VARIATION The distribution of the fourbeard rockling may be summarized as the coastal waters of the North Atlantic. In the western Atlantic the species oc- curs in: West Greenland (new record); the north- western Gulf of Saint Lawrence and around New- foundland as well (Leim and Scott 1966 and this paper) to Cape Fear (about lat. 34°N) ( Bigelow and Schroeder 1953); the northeast coast of Florida (Bullis and Thompson 1965); off the Florida Keys (new record); and in the northern Gulf of Mexico (new record). In the eastern Atlantic the species occurs: around Iceland (Saemundsson 1949) and the Faroes (Joensen and Taaning 1970); from northern Norway at about lat. 71°N in the Barents Sea and south along the coasts of Scandinavia (Andriyashev 1954); in the western Baltic (rarely to the Gulf of Finland, Svetovidov 1973); th rough - ^Reference to trade names does not imply endorsement by the National Marine Fisheries Service, NOAA. out the Noi'th Sea and around the British Isles to the northern Bay of Biscay (Wheeler 1969; Du Buit 1968); and off Cape Blanc, Mauritania (new record). It is not known from the Mediterranean. Figure 1 shows the approximate localities from which we have studied specimens. More detailed locality data are presented in the Appendix. Sampling Areas We have compared fish from the following geo- graphical areas. Gulf of Mexico. Only 3 localities are represented in our collections. These specimens are among the most darkly pigmented of any we have studied. Southern Atlantic. Specimens taken from the South Carolina coast at about lat. 33°N to about lat. 29^N on the east coast of Florida, which is as far south as specimens have been caught in the western Atlantic outside of the Gulf of Mexico. There is no reason to doubt that this population is continuous with those farther north, and the northern boundary as here given is arbitrarily limited by available study material. Intermediate. Fish caught in the vicinity of Cape Hatteras from about lat. 35°N to the vicinity of Norfolk Canyon at about lat. 37"N are included in Figure l. — Localities for our specimens of Efichelyopus cimbriu^. Some dots represent more than one collection. For detailed data on localities see Appendix. 92 COHEN and RUSSO: VARUTION IN FOURBEARD ROCKLING this area, which we separate because it is geo- graphically between the region to the south. where fishes are mostly dark colored. Northern Atlantic. This region extends along the western Atlantic coast from north of the vicin- ity of Norfolk Canyon to the northern North American limit of E. cimbrius occurrence. Greenland. A single specimen from West Green- land is apparently the only known occurrence of £. cimbrius from Greenland. Iceland. The region around Iceland. Europe. Although E. cimbrius occupies a con- siderable area we have examined only a small sample, mainly from Denmark and Norway. Africa. Two specimens from off the coast of Mauritania ca. lat. 21°N are the most southerly known. Color Enchvlyopus cimbrius from the Gulf of Mexico and Southern Atlantic areas have on the average more of the dorsal fin colored with dark pigment than do fourbeard rocklings from other areas (Ta- ble 1 ). We have attempted to quantify this charac- ter by coding it on a 0-10 scale with 0 representing Table l. — Frequency distributions of degree of dorsal fin pig- mentation in Enchelyopus cimbrius from eight geographical areas. 0 = no dark pigment in dorsal fin; 10 = entire fin darkly pigmented. Degree of pigmenta ion N Area 0 1 2 3 4 5 6 7 8 9 10 X SD Gull ol Mexico 2 1 5 2 4 1 1 2 18 62 2 1 Southefn Atlantic 1 - 2 6 1 6 17 6 6 2 47 67 19 Intermediate 7 6 4 6 2 1 3 1 30 3 6 2 8 Northern Atlantic 29 5 7 3 — 2 46 18 13 Greenland 1 1 5 - Iceland 5 2 2 1 ■* 10 19 11 Europe 1 26 1 1 1 2 32 14 09 Afnca 1 1 2 1 5 — a fin with no dark pigment and 10 representing a fin that is completely dark. Values were subjec- tively assigned by a single observer (Cohen). Fig- ure 2A shows a New England fish that would be coded as 1; Figure 2B shows the color pattern of a fish from the Gulf of Mexico, which would be coded as 6. Note that fish are morphologically inter- mediate and most variable in the Intermediate region'* where the mean is 3.8 and the standard deviation is highest at 2.8. Two other pigment characters were noted; how- ever, neither was quantified. Fish with light fins lacked dark pigment in the groove along the base of the row of filaments between the strong first dorsal ray and the beginning of the normally de- veloped dorsal fin ( Figure 3 A); fish with dark dor- sal fins had varying amounts of dark pigment in this region (Figure 3B). Also, in many Gulf, Southern Atlantic, and Intermediate fish the body was dusky; in most others the body was a rather light straw color. Meristics Frequencies of both anal fin rays and dorsal fin rays show a pattern similar to, though less pro- nounced than, that shown by dorsal fin pigmenta- tion in the western Atlantic (Tables 2, 3), with fish from the Intermediate area being intermediate between fish from the north and the south. Also, for anal fin rays the standard deviation is larger in fish from the Intermediate area than in adjacent samples. These two characters differ from dorsal pigmentation in having the highest mean in the Iceland sample. Frequencies of pectoral fin rays and vertebrae for North American samples from the Inter- mediate area have nearly identical means in both ■'Detailed descriptions of color variation in samples from Nor- folk Canyon and comparisons with specimens from the northeast coast of Florida have been presented by: P, Szarek. 1974 A preliminary study of Norfolk Canyon Enchelyopus cimbrius. Ichthyology Term Paper. Virginia Institute of Marine Science. Table 2. — Frequency distributionsof numbers of anal fin rays in Enchelyopus cimbrius from eight geographical areas. Number of anal fin rays N X Area 36 37 38 39 40 41 42 43 44 45 46 47 48 49 SO Gulf of Mexico 6 4 2 4 16 40 2 1 2 Southern Atlantic 6 1 1 18 8 3 46 40 8 1 1 Intermediate 1 2 5 4 7 2 2 2 — — 1 26 42 8 22 Northern Atlantic 8 8 9 13 9 2 2 1 52 43 5 1 7 Greenland 1 1 43 — Iceland 2 4 3 1 10 453 09 Europe 1 — 1 1 — 2 1 3 6 1 — — — 1 17 426 30 Afnca 1 1 2 44 5 — 93 FISHERY BULLETIN; VOL, 77. NO. 1 FIGURE2.—£nc/n>/yDpu.s(imfcriu.s. A, USNM 213501. standard length 282 mm, offCape Cod, dorsal fin pattern coded as 1 (see text). B, color pattern of a fish from the Gulf of Mexico (USNM 2 1 784.3 1 drawn on the outline of the fish shown in Figure 2 A, dorsal fin pattern coded as 6 (see text). Table 3. — Frequency distributions of numbers of dorsal fin rays in Emhelyapus ctmbnus from eight geographical areas. Number of dorsal fi n rays N X Area 45 46 47 48 49 50 51 52 53 54 55 SO Guit ol Mexico 1 1 11 3 16 47 0 07 Southern Atlantic 1 8 10 12 7 8 1 47 4/9 15 Intermediate 1 3 8 9 5 — 2 1 29 49 9 1 6 Northern Atlantic 1 — - 6 13 8 12 4 4 3 1 52 50 4 1 y Greenland 1 1 51 — Iceland 5 2 3 10 50 8 09 Europe 1 2 3 3 4 3 1 17 49 2 1 7 Africa 2 2 50,0 — of these characters with Northern Atlantic fish, rather than being intermediate (Tables 4, 5); how- ever, for pectoral fin rays, fish from these two areas have lower counts that are in between Gulf and Alantic, and Greenland, Iceland, and Europe samples. Iceland fish average highest of all in dor- sal and anal fin ray counts and in vertebral counts (not including the few specimens from Greenland and Africa). In pectoral counts, however, Iceland and Europe specimens have identical means. In total gill raker counts (Table 6) eastern At- lantic samples have higher means than do western Atlantic samples, with the highest standard de- viation being in the Northern Atlantic samples. Body Proportions Measurements were taken of the following eight body parts and compared for six of them in fish from the six geogi-aphical areas listed below and described previously under sampling areas (Greenland and Africa are not included in the present analysis). Linear regressions were calcu- lated for the following dependent variables, with standard length as the independent variable: 94 COHEN and RUSSO: VARIATION IN FOURBEARD ROCKLING Table 5. — Frequency distributions of numbers of pectoral fin rays in Enchelyopus cimbrius from eight geographical areas. FIGURE 3— Enchelyopus cimbrius. A. USNM 213501, head length 62.8 mm, off Cape Cod, note absence of dark pigment along base of fin with short rays. B, USNM 217843. head length 33.2 mm, Gulf of Mexico, note dark pigment along base of fin with short ravs. Table 4, — Frequency distributions of numbers of vertebrae in Enchelyopus ctmbnus from eight geographical areas. Number of v 'ertebrae N X Area 49 50 5t 52 53 54 55 SD Gulf of Mexico 9 7 16 51 4 05 Soutfiem Atlantic 1 1 18 22 10 52 51 8 09 Intermediate 4 7 12 6 1 30 52 8 1 0 Northern Atlantic 3 14 26 15 1 59 52 9 09 Greenland 1 1 54 — Iceland 4 3 3 10 53 9 09 Europe 2 3 7 3 15 52 7 1,0 Africa 1 1 2 545 — Number of pectoral fin rays Area 15 16 17 18 19 N X SD Gull of Mexico 1 2 9 6 1 19 17.2 0.9 Southern Atlantic 9 21 14 1 45 172 08 Intermediate 2 9 14 4 29 167 08 Northern Atlantic 5 21 21 5 1 53 165 09 Greenland 1 1 17 — Iceland 1 2 2 5 10 17 1 1 1 Europe 1 2 8 4 1 16 17 1 10 Afnca 2 2 16 — Table 6. — Frequency distributions of total numbers of gill rak- ers on first arch in Enchelyopus ctrnhrtus from eight geographi- cal areas. Number of g ill rakers Area 5 6 7 8 9 10 11 12 13 N X SD Gulf of Mexico 5 3 2 — 1 11 90 13 Southern Atlantic 2 9 12 17 4 44 9 3 1,0 Intermediate 1 1 11 6 5 24 9 5 1.0 Northern Atlantic 3 1 1 8 8 12 6 2 41 9 1 18 Greenland 1 1 9 — Iceland 2 5 2 1 10 10.209 Europe 6 4 3 1 1 15 10,1 1.3 Africa 1 — 1 2 10.0 — tic 53 (50.5-297); Iceland 10 (151-327); Europe 27 (93.8-300). Analysis of covariance was used to compare re- gression lines (Tables 7, 8) for six measurements that we have treated as linear based on a coefficient of determination ir^) of 0.73 or higher (Table 8). Two measurements, ventral fin length and barbel length, had coefficients of determina- tion ranging from 0.42 to 0.61 and were not further analyzed. Fishes from all si.x geographical areas demon- strated overall coincidence at the 0.05 level of sig- nificance in two characters, head length and upper jaw length. Hypotheses concerning overall coinci- dence of regressions for the other characters were rejected and hypotheses concerning the equality of slopes and intercepts were simultaneously tested. The hypothesis concerning the equality of slopes was rejected for the Dj-Dj distance versus stan- dard length regression lines. Regression data were snout to first dorsal fin (pre D, distance); first dor- sal fin to the dorsal fin beginning posterior to the row of small filamentous rays (D,-D:i distance); head length; pectoral fin length; upper jaw length; horizontal diameter of eye (orbit length); length of barbel on lower jaw; and ventral fin length. Num- bers of specimens measured and their size ranges (standard length in millimeters) were: Gulf of Mexico 17 (125-228); Southern Atlantic 46 (125- 263); Intermediate 29 1 104-202); Northern Atlan- TABLE 7. — Significance of differences in six morphometric characters in Enchelyopus cimhrius from six geographical re- gions. Independent variable is standard length. Overall Equality Equality Dependent variable N coincidence ol slopes of intercepts Pre Di distance 165 '0 0048 0 5342 "49 ■ 10 * D,-D3 distance 165 '00024 '00111 '0 0012 Head length 182 03004 — — Pectoral fin length 150 '00061 0 0617 '0 0011 Orbit lengh 166 '22 0 ■ 10 ' 0.1839 "2 4 ■ 10 ' Jaw length 166 0 2892 — — 'Rejection of hypothesis of equality at the 0 05 level of significance 'Reiection of hypothesis of equality at the 0 001 level of significance 95 FISHERY BULLETIN: VOL. Table 8. — Y intercepts in millimeters, slopes, coefficients of determination ir^). and N for regression lines calculated on Enchelyopus cimbnus from six geographi- cal areas. Independent variable is standard length. Measurement Geographical PreD, D,-Dj Head Pectoral Upper jaw Orbit area distance distance length fin length length length Gulf of f^lexico: V intercept 2 91 2 21 2 29 0 17 -3 08 0 10 Slope 0 16 0 12 0 18 0 14 0 11 0 04 r' 0 89 0 86 0 93 0 87 0 87 0 79 N 16 16 17 14 17 17 Soutfiern Atlantic: Y intercept Oil ■4 74 0 22 -0 89 -1 83 0 76 Slope 0 17 015 0 20 0 15 0 11 0 04 r' 0 96 0 89 0 94 091 0 89 090 N 43 44 46 43 44 44 intermediate Y intercept ■0,60 -0 74 ■0 71 0 48 ■2 69 -0 06 Slope 0 18 0 12 021 0 14 0 11 005 /■' 0 95 0 86 0 92 0 87 0 92 0 79 W 29 29 29 29 29 28 Northern Atlantic. Y intercept •0,32 0 47 ■0 43 -2 22 ■3 38 1 64 Slope 0 18 0 12 0 21 0 16 0 12 004 1-2 0,97 0 89 0 97 0 92 0 87 0 92 N 51 51 53 38 51 50 Iceland: Y intercept 0,47 3 59 2 09 6 02 ■5 71 2 65 Slope 0,17 0 10 0 20 0 12 0 13 0 03 r' 0 79 0 92 0 99 0 87 0 98 0 98 N 10 10 10 10 9 10 Europe: Y intercept -061 ■4 37 ■0 74 ■2 06 ■4,70 1,29 Slope 0 18 0 16 0 21 0 15 0 12 0 04 I-' 097 0 73 0 91 0,90 0 91 0 94 N 16 16 27 16 16 17 submitted to a Newman-Keuls multiple range test in order to determine which population sample or groups of population samples were different from others. This procedure failed to detect differences between any slopes, a not uncommon occurrence due to the fact that the analysis of covariance is a more powerful test than is the multiple range test. The sample from Iceland had the lowest slope at 0.10, the Northern Atlantic, Gulf of Mexico, and Intermediate samples each had a slope of 0.12, the Southern Atlantic sample had a slope of 0.15, and the sample from Europe had a slope of 0.16. The hypotheses concerning the equality of Y intercepts was rejected at the 0.0.5 level of sig- nificance for all four characters tested. These re- gression data also were submitted to a Newman- Keuls multiple range test in order to determine which population sample or groups of population samples were different from others. Again, this procedure failed to detect significant differences between any Y intercepts. If a more stringent 0.001 level of significance is used, only orbit length tests as being significantly different with respect to overall coincidence. Data for this regression from each of the six samples were submitted to a continuation of analysis of covariance to determine whether differences in the regression lines were attributable to the slopes and/or the Y intercepts. We accept equality of the slopes with a probability of 0.85. However we re- ject the equality of the Y intercepts after calculat- ing a probability of equality of 2.06 x 10"''. Re- gression data were submitted to a Newman-Keuls test, which failed to detect differences between any pairs of intercepts. Inspection of our data shows that rocklings from Iceland appear to have a proportionally larger eye than do other rocklings; however, our sample is small and may be biased by larger fishes; hence we do not draw inferences from this apparent difference. Although differences between samples appar- ently exist, we do not interpret them as represent- ing the kind of discontinuity that indicates dis- tinct species. Their significance is beyond the scope of this paper. Discussion We believe that the fourbeard cockling is best considered as a single species throughout its en- tire range. Differences in pigment pattern, meris- tics, and the relative size of several body parts do exist; however, there are neither trenchant dis- continuities in variation nor is there any overall 96 COHEN and RVSSO VARIATION IN FOL'RBEARD ROCKLING concordance in patterns of variation. Differences between and similarities among samples are summarized in Figure 4 and discussed below for meristics and color pattern. Differences in morph- ometric characters are so slight that we do not further consider them. Gulf of Mexico and Southern Atlantic samples are quite similar, although at this time the two might be semi-isolated from each other. The clockwise loop current system in the Gulf of Mexico provides a possible pathway for the disper- sal of young, pelagic stage rocklings out of the gulf; there is no present avenue for recruitment into the Gulf of Mexico. If the single rockling taken off the Florida Keys represents more than a stray, then perhaps Gulf of Mexico and Southern Atlantic populations are continuous; otherwise, the north Gulf-northeast Florida distribution pattern is similar to that noted first in fishes by Ginsburg (19521. Although E. cimhnus seems rare in the Gulf of Mexico its occurrence at two widely sepa- rated localities, with a collection of 16 individuals from one of them, indicates that the .species is estab- lished there. Although pelagic stages have not yet been taken from the Gulf of Mexico or Southern Atlantic areas, it seems reasonable to assume that they occur there and are available for dispersal in the Gulf Stream system. Rocklings from the Intermediate area are in- deed intermediate between adjacent populations to the north and south in degree of pigmentation and in dorsal and anal ray counts. Furthermore, for two of these characters, color and number of anal fin rays, the standard deviation is larger than in other populations, implying that recruits from different spawning populations are entering the area or that the characters are genetic and variabil- ity is being maintained during spawning in the Intermediate area. For two characters, numbers of vertebrae and pectoral fin rays. Intermediate and Northern Atlantic fish are nearly identical and differ from Southern Atlantic and Iceland sam- ples. These characters must be determined or mediated differently than are color pattern and dorsal and anal fin ray counts. Gill raker count appears to reflect still a third method of character determination as the means are different on the two sides of the Atlantic. Although pelagic early stages have not been taken in the Intermediate area, they may be available for dispersal to the northeast by means of the Gulf Stream and to the southwest in coastal currents that parallel the Gulf Stream. Such dispersal patterns would help to account for the occurrence of dark-colored rock- lings in the north and light-colored ones in the south. Rocklings from the Northern Atlantic area more closely resemble fish from Europe and Ice- land in degree of pigmentation and number of vertebrae than they do their immediate neighbors to the south. Conversely they are closer to other North American samples in numbers of pectoral CHARACTER Gulf S. Atl. GEOGRAPHICAL AREA Intermed . N. Atl. Iceland Europe Color Anal Rays Dorsal Rays Vertebrae Pectoral Rays Gill Rakers 6.2 40.2 47.0 51.4 17.2 6. 7 40.8 47.9 51.! 17.2 3.8 42.8 43.5 49.9 50.4 52.8 52.9 16.7 ■ 16.S 1.9 1.) 42.6 49.2 FIGL'RE 4. — Summary of means of character states for Enchelyopu^ cimbnus from six geographical areas. Heavy lines are drawn around entries that are discussed in the te.xt as separate entries and that illustrate overall lack of convergence m character states. 97 FISHERY BULLETIN; VOL, 77. NO, 1 rays and gill rakers. Spawning is known to occur in the Northern Atlantic area. Eggs have been taken from surface tows in Passamaquoddy Bay, where spawning peaked at bottom temperatures of 9° to 10°C (Battle 1930). In Long Island Sound eggs were found to be most abundant in the upper 12 m (Williams 1968). In reviewing the natural history of E. cirnbriuK in the Gulf of Maine, Bigelow and Schroeder (1953) mentioned the pos- sibility of planktonic existence as long as 3 mo. Given such a time span, the complex hydrographic regime of the area might occasionally distribute early stages to the south inshore of the Gulf Stream or even more rarely might transport them via the Gulf Stream to the eastern Atlantic. Iceland rocklings are usually light colored, as are fish from the Northern Atlantic and Europe areas. For counts of dorsal and anal fin rays, and vertebrae, Iceland fish have the highest means of all (ignoring the two fish from Africa); perhaps these characters are influenced by temperature, as Iceland has the lowest temperatures of any of the six areas. In numbers of pectoral rays, Iceland and European fish are identical and in gill rakers nearly so, and different from counts of North American ones. Adults at least of the Iceland population may be isolated as Kotthaus and Krefft (1967) did not catch E. cinibritis along the Iceland-Faroe ridge. Enchelyopus cinihrius spawns at least around the southwest coast of Ice- land (Einarsson and Williams 1968). The linear range of the fourbeard rocklingalong the coasts of Europe is about as great as along the coasts of North America. We have examined only a small sample, from southern Scandinavia; hence, it is possible that more variation exists than we have recorded. However, we point out that in our sample the color pattern resembles that of Iceland and Northern Atlantic fish, that counts of anal and dorsal fin rays and vertebrae are lower than those in Iceland, and that in numbers of pectoral fin rays and gill rakers Europe and Iceland fish are more like each other than they are like North American populations. Rocklings are known to spawn in European waters [Svetovidov 1 1973) gives several references]. Enchelyopus cimbrius could have reached Europe from the west via the Gulf Stream system; it seems unlikely that east to west disper- sal is possible. We do not know whether the West Greenland specimen of E. cimbrius represents a breeding population or a stray. The two West African examples are so far re- 98 moved from their nearest known neighbors ( Bay of Biscay ) that we forego conjecture as to their origin. THE GENERA OF ROCKLINGS The rocklings are classified in the subfamily Lotinae of the family Gadidae (Svetovidov 1948) and can be distinguished by the nature of the three dorsal fins, which, although scarcely separated from each other, bear quite different kinds of rays (Figure .5). The first dorsal fin consists of a single, unsegmented ray which is not bilaterally divided (we have examined microscopic sections) and is supported by a strong pterygiophore. The ray is thicker than any others in the dorsal fin and in many species is longer as well. In Enchelyopus cimbrius it is soft, being ossified only proximally. Sharply distinguished from the first and third dor- sal fins is a row of small, unsegmented, bilaterally divided filaments which appear fleshy, although they stain with alizarin. These small rays origi- nate on a compressed ridge that rises from a mid- dorsal groove. Although Bogoljubsky (1908) fol- lowed by Svetovidov ( 1948) did not consider these filaments to be true fin rays they should be consi- dered as such, as examination of an alizarin prep- aration and of sections shows that a simple, os- sified, rod-shaped skeletal support is present for each. The third dorsal fin is composed of ordinary, bilaterally divided, segmented rays, each with a well-developed pterygiophore. A second characteristic of the rocklings is the presence on the snout of prominent barbels ithe closest approach to this character among other gadids being a nasal cirrus in Lota ) in addition to the barbel at the tip of the lower jaw. Thus, the rocklings are distinguished by two specialized characters and can be considered as a distinct tribe of Lotinae, the Gaidropsarini [clas- sified as a distinct family by some, for example, de Buen (1934)]. Although rocklings have been treated under as many as 14 different generic names [see Svetovidov (1973) for synonyms], many ichthyologists (for example, Andriyashev 1954; Norman 1966) follow Svetovidov (1948) in recog- nizing three. More recently, however, five genera have been recognized (Wheeler 1969). How many genera should be recognized and why? In his 1948 treatment of the rocklings, Svetovidov provided diagnoses for the three gen- era that he recognized based on barbel number, skull shape, vomerine tooth patch shape, and COHEN and RUSSO VARIATION IN FOURBEARD ROCKLING 'muiidiiiiiiilM'- ■ r// Fl( ;L'RE 5, — Enchelyopus cimhrius. USNM 217900, standard length 135 mm; photograph of an alizarm preparation m glycerin showing the three different kinds of dorsal fin rays and their skeletal supports. number and distribution of supratemporal pores (our Table 9). Unfortunately, he was unable to study all of the species. We have examined six of the nominal Gaidropsarus species that he recog- nized, both species oiCiliata, and, of course, En- vhelyopus (study material of all genera is listed in the Appendix). Number of barbels is the only character that unequivocally divides our material according to Svetovidov's classification. Proper evaluation of the skull-width character will require the examination of osteological prep- arations, which we have not done. We note, how- ever, that although Ciliata inustela has a notably broad skull, that ofC septentrionalis appears to be narrower. Also, although most species oiGaidrop- Hcinis appear to have narrow skulls, that of G. guttatus appears broad. Regarding the size and shape of the vomerine tooth patch, it is highly variable, and although it may serve to distinguish some species it is of doubtful value at the genus level. Table 9. — Summary of diagnostic characters for three rockling genera given by Svetovidov (1948). Characters Genus and no. No. of Skull Supratemporal of species barbels shape Vomer pores Gaidropsarus 3 Narrow Head large. 3 - 1 pair + 1 (13) apex angular median Enchelyopus 4 Narrow Small 3 - 1 pair + 1 (1) median Ciliata 5 or Broad Head small, 2 - 1 pair (2) more anterior a semicircle Number of supratemporal pores also is a vari- able character. Five of the Gaidropsarus species that we have studied show the pattern given for the genus by Svetovidov (1948), one median and one pair of pores ( = 3). However, G. argentatus has two pairs and no median pores ( = 4). In Ciliata, C. mustela has one pair ( = 2), while C . septentrionalis has three pairs ( = 6). As noted above, Wheeler ( 1969) recognized five genera, the three recognized by Svetovidov (1948): Enchelyopus. CUiata. and Gaidropsarus: and also Onogadus de Buen 19.34; and a genus introduced for the first time, Antonogadus. Onogadus was originally proposed for Gaidrop- sarus ensis, one of the threebeard rocklings, be- cause of its elongate first dorsal ray. Wheeler (in Svetovidov 1973) has subsequently assigned to Onogadus, G. argentatus, a species with a far shorter first dorsal fin ray. We have found the length of the first dorsal fin to be highly variable in Enchelyopus. As presently used, this character does not separate genera. (Wheeler^ has informed us that Onogadus may be differentiated on the basis of vertebral counts. Due to insufficient data we have no comment on this character.) As we have mentioned above, G. argentatus differs from G. ensis and resembles Ciliata in lacking a median supratemporal pore. 'A. Wheeler. Department of Zoology. British Museum (Natural History), Cromwell Road, London S.W. 7. England. Pers. Commun. March 1978. 99 FISHERY BULLETIN VOL 77, NO 1 Antonogadus Wheeler 1969 was first introduced in the combination Anionngaclus macrophthal- mus (Giinther), unfortunately, in a key to species rather than a treatment of genera. Subsequently, another threebeard rockling, Gaidropsarus megalokynodon (Kolombatovic 18941, was refer- red to Antonogadus (Wheeler in Svetovidov 1973) in a checklist. There is no way to tell if the original key characters describing dentition, mouth size, and color are diagnostic of the genus Antonogadus or the species A. macropththalnius; however, we assume that they apply to the genus. Color may be discounted as a generic character as it is highly variable among the species of Gakhvpsarus and varies geographically in the single species of En- chelyopus. Regarding mouth size, Wheeler (1969) noted "mouth large, extending well past eye": however, figures of macrophthalnius given by Gunther [1867, pi. 5, fig. B and 1887, pi. 42, fig. D. the latter as Onus carpenteri, a junior synonym of mac!-ophthalmus according to Wheeler in Svetovidov (1973)] show fish with small mouths. The second species referred to Antonogadus. megalokynodon, is figured by Soljan ( 1963) as hav- ing a large and capacious mouth, but he shows the same condition for several other species of threebeard rocklings. So far as we can tell mouth size is not a useful generic character. Carrying on to dentition, Wheeler (1969) noted, "A pair of large, fang-like, teeth (sometimes three or four) in front of the upper jaw." If Antonogadus is recog- nized on the basis of such a character then it would be necessary to place the two species of Ciliata in separate genera, as C. mustela, the type-species of the genus has bands of equal-sized teeth in the upper and lower jaws, while C. septcntrionalis has in addition to these bands a much enlarged outer row of teeth in the upper jaw and an enlarged inner row in the lower jaw. It is by no means clear that number of barbels alone divides the rocklings into natural species assemblages; convergence may have occurred and other groupings based on different characters may produce a phyletically more correct classification. Obviously, thorough study and a careful analysis of characters is required. For the present there seems insufficient information available to do other than recognize on the basis of number of barbels a single genus with three subgenera, or three genera. We follow the latter course as it is the most conservative in terms of the present usage of names. We recommend therefore, that for the present Onogadus be relegated once again to the synonymy of Gaidropsarus where it should be joined by Antonogadus. THE CORRECT GENERIC NAME FOR THE FOURBEARD ROCKLING Although differences at the species level have not evolved in populations of the fourbeard rock- ling on both sides of the North Atlantic, curiously enough geographical isolation seems to have af- fected the evolution of different generic names. Rhinoncinus is used by European ichthyologists (see, fore.xample, Svetovidov 1973); North Ameri- can ichthyologists use Enrhelyopus (see, for example, Leim and Scott 1966). Which is the cor- rect name? Enchelyopus Gronovius 1760 was the first of the two names proposed. Although only a brief color description was given, reference was made to the same author's pre-Linnean Museum Ichthyo- logicum published in 1754, in which work under the names Mustela vivipera and viviparous eelpout is presented a recognizable description of the species presently named Zoanvs viviparus (Linnaeus). This identification is further verified by a Gronovius specimen still extant in the British Museum, which Wheeler ( 1958) has suggested is a type-specimen of Blennius viviparus Linnaeus. Use of Enchelyopus in Zoarcidae, where it is a senior synonym of Zoarces Cuvier 1829 has been accepted by Norman (1966) and noted as being correct by Andriyashev (1973). Some ichthyologists (Gill 1863b;Jordan 1917), however, seem to have overlooked Gronovius ( 1760) and at- tributed the name to Gronovius (1763) in his Zoophylaceum, a work subsequently ruled on by the International Commission on Zoological Nomenclature (Opinion 89) as being unavailable for purposes of zoological nomenclature. The Commission noted in its ruling that combinations used in the Zoophylaceum were "binary" though not "binomial," which interpretation complied with the then current edition of the Rules, and the work was declared unavailable by suspension of the Rules. Although Gronovius (1760) never has been ruled on by the Commission it follows the same system of nomenclature as does Gronovius (1763) and clearly is not binominal. The same is true of Gronovius (1762), which has been rejected (Opin- ion 332). Under the provisions of the present Code (Article 11(c)), names published in Gronovius ( 1 760) are not available as the author did not con- 100 COHEN and RUSSO VARIATION IN FOURBEARD ROCKLING sistently apply the principles of binominal nomenclature. Although Article ll.(c)(i) ("Uni- nominal genus-group names published before 1931 without associated nominal species are ac- cepted as consistent with the prmciples of binomi- nal nomenclature, in the absence of evidence to the contrary.") might serve as a basis for arguing that the names in Gronovius ( 1760) are available, the interests of stability would be served best by considering the work unavailable, as its accep- tance would require not only that Enchelyopiis Gronovius 1760 replace Zoarceg Cuvier 1829, but also that Cyclogaster Gronovius 1760 replace Liparis Scopoli 1777. If Gronovius (1760) is considered as unavailable for purposes of zoological nomenclature then the first valid use of Enchelyapus is by Bloch and Schneider (1801). The type-species was stated by Jordan (1917) as Gadus cimbrius Linnaeus 1766 as first restricted, and Svetovidov (1973) gave the type as Gadus cimbrius Linnaeus 1766 by monotypy. However, neither of these methods of type fixation is correct as Bloch and Schneider referred 12 species to the genus, and although cimbriua is the first one in order, there is no action that could be construed as a type designation. The earliest type designation for Enchelynpus Bloch and Schneider 1801 that we have been able to find is that of Jordan (1917) as Gadus cinibrius Lin- naeus 1766. Rhinonemus Gill (1863a) was proposed for Motella vaudavuta Storer 1848, a junior synonym of Gadus cimbrius Linnaeus (Goode and Bean 1879) and is therefore a junior synonym of En- chelyopus Bloch and Schneider. ACKNOWLEDGMENTS We are grateful to A. Wheeler for information and discussions about rockling taxonomy, P. Szarek for allowing us to read her unpublished manuscript, and S. Johnson for information on zoarcid nomenclature. For reading and comment- ing on all or part of the manuscript we thank A. Cohen. B. Collette, L. Dempster. M. Fahay, and W. I. Follett. G. S. Myers assisted by allowing access to rare literature. For access to study material we thank D. McAllister, National Museums of Canada; R. Jenkins, Cornell University; J. Kaylor, NMFS, NCAA, Gloucester, Mass.; M. Dick, Harvard University; R. Wigley, NMFS, NCAA, Woods Hole, Mass.; C. Wenner and J. Musick, Virginia Institute of Marine Science; G. Jonsson, Marine Research Institute, Reykjavik; J. G. Nielsen. University of Copenhagen; A. Wheeler. British Museum (Natural History); and M. L. Bauchot, Natural History Museum. Paris. For assistance with computer processing we thank K. K. Beach, E. M. Hamilton, and the Office of Technical Assistance at The George Washington University Center for Academic and Administra- tive Computing. Figures 1-4 were prepared by Keiko Hiratsuka Moore. George Clipper took X-ray photographs. Histological sections of the dorsal fin were prepared by Margaret Melville. The manuscript was typed by A. McClain and V. Tucker. LITERATURE CITED ANDRIYASHEV, A. P. 1954. 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Friorikssen and S. L. Tuxen (editors). The zoology of Iceland, 4(72), 150 p. Munksgaard, Copenh. and Reyk. SCOPOLI, J. A. 1777. Introductio ad histonam naturalem. Pragae, 506 p. s6ljan,T. 1963. Fishes of the Adriatic. Revised Engl. ed. NOLIT, Belgr., 428 p. SVETOVIDOV, A. N. 1948. Treskoobraznye. Faune SSSR, Ryby 9(4), 221 p. Akad. Nauk SSSR. (Transl. 1962, Gadiformes, Fauna USSR, Fishes 9(4i, 304 p. U.S. Dep. Commer., Natl. Tech. Inf Serv., Springfield, Va. OTS 63-11071.) 1973. Gadidae. /n J. C. Hureau and Th Monod (editors). Check-list of the fishes of the north-eastern Atlantic and of the Mediterranean, Vol. I, p. 303-320. UNESCO, Paris. TYLER, A. V. 1971 . Periodic and resident components in communities of Atlantic fishes. J. Fish. Res. Board Can. 28:935-946. WHEELER, A. C. 1958. The Gronovius fish collection: a catalogue and his- torical account. Bull. Br. Mus. (Nat. Hist.) Hist. Ser. 1:187-249. 1969. The fishes of the British Isles and North-West Europe. Macmillan, Lond., Melb.. Toronto, 613 p. Williams, G. C. 1968. Bathymetric distribution of planktonic fish eggs in Long Island Sound. Limnol. Oceanogr. 13:382-385. Zar, J. H. 1974. Biostatistical analysis. Prentice Hall Inc., En- glewood Cliffs, N.J., 620 p. 102 COHEN and RUSSO: VARIATION IN FOIIRBEARD ROCKLING APPENDIX The following abbreviations indicate institu- tions or collections: CU, Cornell University; MCZ. Museum of Comparative Zoology, Harvard Uni- versity: MNHN, Museum National d'Histoire Naturelle, Pans: NEFC, Northeast Fisheries Center, Woods Hole, Mass.; NMC, National Museum of Natural Sciences, Ottawa: USNM, Na- tional Museum of Natural History, Washington. D.C.; ZMUC, Zoologisk Museum, Copenhagen. The "Intermediate" region, below, extends from about lat. 35"N to about lat. 37°N in the western Atlantic. Enchelyoptis cimhriin GULF OF MEXICO— USNM 190346 (3 speci- mens),Si/wrSavstn 294, 27°54'N,95°23'W, 79m. USNM 217843 (16), Oregon 3724, 29°04'N, 88°31'W, 403 m. USNM 217939 (1), Oregon .5795, 24'16'N. 82'30'W, 439 m. SOUTHERN ATLANTIC— USNM 217923 (2), Silver Bay 1611, 29°06'N, 80°00'W, 339-384 m. USNM 217924 (2), Silver Bay 223, 29°14'N, 80°05'W, 247 m. USNM 217935 (1), Oregon 5798, 29n4'N, 80°05'W, 357 m. USNM 217933 (5). Ore- gon 5098, 29°17'N, 80°05'W, 379 m. USNM 217931 (1), Silver Bay 4227, 29°20'N, 80°05'W, 348 m. USNM 217949 ( 2 ), Silver Bay 224, 29°29'N, 80°09'W, 329 m. USNM 217937 (1), Combat 475, 29^30 'N, 80°10'W. 293 m. USNM 217934 (3) Ore- gon 5093, 29''31'N, 80'=09'W, 384 m. USNM 217932 ( 1 ), Silver Bay 219, 29°34'N, 80°09'W, 348 m. USNM 217917 (1), Silver Bay 1607, 29°34'N, 80°09'W, 371 m. USNM 217943 (1). Combat 325, 29'35'N, 80°10'W, 366 m. USNM 217936 (1), Combat 314, 29°38'N, 80°11'W, 329 m. USNM 217918 ( 1 ), Oregon 5238, 29°39'N, 80°12'W, 348 m. USNM 217916 (2), Silver Bay 1606, 29°40'N, 80°12'W, 348 m. USNM 217940 (1), Silver Bay 217, 29°41'N, 80°08'W, 348 m. USNM 2~17919 (2), Silver Bay 458, 29°49'N, SO'IO'W, 220 m. USNM 217921 (2), Silver Bay 1552, 29°43'N, 80°12'W, 302 m. USNM 217948 (1), Combat 435, 29°46'N, 80"12'W. 366 m, USNM 217920 (1), Silver Bay 3742, 29"50'N, 80'13'W, 275 m. USNM 217950 (5i, Silver Bay 1604, 29°50 'N, 80°10 'W, 302 m. USNM 217947 (2), Silver Bay 3678, 29''53'N. 80ni'W, 329 m. USNM 217944 (3), Silver Ba\ 3675, 29°55'N, 80'1 1 'W, 329 m. USNM 217922 ( 1 ) Silver Bay 4367, 29°55'N, 80°11'W, 320m. USNM 217945 (1), Oregon il), 5233, 29°54'N, 80°10'W, 348 m. USNM 217925 il). Combat 471, 29°57'N. 80°12'W,329m.USNM217946(3),Pe/(co/! 182-8, 32''09'N, 79°02'W, 275 m. USNM 217938 (1), Combat 300, 32°15'N, 78°51'W, 348 m. USNM 217927 ( 1 ), Combat 289, 33°03 'N, 77°09'W, 366 m. INTERMEDIATE— USNM 45898 (1), A/6o- /ms.s-.35°40'N,74'52'W. USNM 45895-6 (7), A/6o- tross. 36°02'N, 74°48'W. USNM 217941 (1), Ore- gon II 10763, 36°01'N, 74=48'W, 311-567 m. USNM 217951 (1), Oregon II 10664, 36°12'N, 74^47 'W, 249-329 m. USNM 217942 (2), Oregon II 10724, 36°14'N, 74"45'W, 366-421 m. USNM 217929 (2), Columbus helm 73-10-40, 36°33'N, 74°42'W, 296 m. USNM 217928 (3), Columbus Iselin 73-10-47, 36°37'N, 74°42'W, 316 m. USNM 217926 (3), Columbus Iselin 73-10-89, 37°02'N, 74°38'W, 367 m. USNM 217930 (7), Columbus Iselm 73-10-73, 37'05'N, 74''43'W, 194-479 m. NORTHERN ATLANTIC— USNM 28994 (1), Albatross. 38'39'N,73n 1 'W, 238 m. USNM 45969 (1), Albatross, 38°54'N, 72°51'W. USNM 28917 (li, 39°43'N, 7r32'W. USNM 45891 (1), A/6o- //w,s, 39°48'N, 71°49'W. MCZ 37492 ( 1 ), Capt. Bill II 20, 39°57'N, 7r07'W, 412 m. USNM 28843 (1), Fish Haivk, 39°57'N, 70°32'W. USNM 28816 H), 39°N, 7rW. MCZ 38039 (1), Caryn 3-1, 39°59'N, 70'48'W, 381 m. USNM 33352 il ), Fish Hawk, 40°20'N, 70°35'W. USNM 28709 il), 40°24'N, 70°42'W. USNM 35680 (1), 40°21'N, 70°29'W. USNM 28890 (2). 40°28'N, 70°44'W. USNM 126948 (1), Fish Hawk, Long Island Sound, 22 m. USNMuncat.ll),A/6a^roi;,s/V,4ri4'N,71°41'W. USNM 213501 (7), Blesk 68-18, 22-01, 4r52'N, 68°12'W, 198 m. USNM uncat. (1), Blesk 68-18, 24-02, 41°36'N,68''52'W, 138 m. USNM uncat.(l), Blesk 68-18, 28-01, 42°N, 69°39'W, 210 m. USNM 16656 ( 1 ), Woods Hole. Mass. CU 18353 ^'i). Alba- tross HI 27-45, 41"53'N, 69°10'W, 212 m. USNM uncat. (1), Delaware 60-1-11, 4r52'N, 68n4'W, 227 m. CU 18274 ( 1 ). Albatross III 61-1, 4r49'N, 68°14'W, 154 m. USNM 23761 (1), Prov- incetown, Mass. CU 45869 ( 1 ), Albatross IV 63-5- 69, 42'07'N, 67°3rW. NEFC uncat. (3), Albatross III 70-23, 42°10'N, 68°38'W, 183 m. NEFC uncat. (1), Albatross III 101-103, 42°15'N, 67°10'W, 168 m. CU 23620 (3), Albatross III 27-55, 42°41'N, 69°49'W, 256 m. NEFC uncat. (1), Albatross HI 47B-3-2, 42^41 'N, 70"09'W, 84-139 m. USNM 839251 1 ). Mass. Bay. USNM 2 1918 (I ). .Mass. Bay, 103 134 m. USNM 131920 (6), Mass. Bay. USNM 21918-9 (2), Mass. Bay. MCZ 34614 (3), 42°56'N, 70°18'W, 165 m. MCZ 34611 (3), Albatross II. 43°07'N. TOMO'W, 154 m. USNM 37847 (1 i, Ipswich Bay. Ma.ss. MCZ 34612 (9), Alhutmss II, 43°03'N, 76°09'W. USNM 45897 (1), Albatross. 43°34'N, 63°56'W. MCZ 34613 (4), 43°39'N, 68°12'W. 192 m. MCZ 12340 ( 1 ), Eastport, Maine. USNM 39060 (1), Prince Edward Island. USNM 43229 tl), 47°15'N, 53°58'W. NMC 63-151 (li, 51"28'N, 53°52'W. GREENLAND— ZMUC uncat. (1), Adolf Jen- sen 4420, 64°22'N. 52°54'W, 460-540 m. ICELAND— ZMUC 95-96, (2), North coast of Iceland, ca. 66°N, 18°30'W. ZMUC 830-32 (3), Vestman Islands. ZMUC 26-27 (2), 63°46'N. 22°56'W. ZMUC P379 ( 1 ). south of Iceland. USNM 217909 (1), 65°37'N, 2r00'W. 110 m. USNM 217911 (1), 65°41'N, 2r20'W, 137-152 m. EUROPE— USNM 39724 ( 1 ), Denmark. ZMUC 84-85 (2), 90-93 (4), 501, 503-4 (3), P37284-292 (9), P37294-96 (3), P37298 (1), Denmark. ZMUC P37283 (U, Limfjord, Denmark. P37297 1 1). Kal- lundbors Fjord, Denmark. ZMUC 88 1 1 I. 502 1 1 I. Snekkersten. Denmark. ZMUC 86 ill, 98 (li, Oresund, Denmark. ZMUC 22-23 (2), Skagerak, 200 m. ZMUC 25 (1), off Lindesnds. Norway, 220 m. USNM 44514 (li, Drobak, Norway. AFRICA— MNHN 38-110/111 (2i, off Cape Blanc, Mauritania. Ciliata imntcla USNM 130840 (4). Europe. USNM 44510 (1), Norway. USNM 216711 (2), Oresund, Denmark. FISHERY BULLETIN VOL. 77, NO. 1 cm at a septentriona lis ZMUC 371656-7 i2i, Faroe Islands. Ga idropsa riis a rgeu tutu .v MCZ 38353,38387 (2), western North Atlantic. USNM 217907 (1), Iceland. USNM 217912 (1), Iceland. USNM 217910 (1), Spitsbergen. USNM 217908(2). Iceland. Gil /(Jruf) iiirm e n .v is MCZ 37554 111, we.stern North Atlantic. MCZ 27882 1 1 1, western North Atlantic. MCZ 38425 ( 1 1, western North Atlantic. MCZ uncat. I li. western North Atlantic. USNM 217913 1 1 1, western North Atlantic. GaidropSiirns iiiittutin USNM uncat. i2i. ill, (5i, San Miguel Island, Azores. Gaidropscinis tuediterraneiis USNM uncat. ill, Tunisia. Ga idropsa rns t ii /ga ris USNM uncat. ( 1 ), 1 1 1, l3i, Tunsia. Gaidropsanis sp, USNM uncat. l5i, Amsterdam Island. 104 EARLY DEVELOPMENT OF SEVEN FLATFISHES OF THE EASTERN NORTH PACIFIC WITH HEAVILY PIGMENTED LARVAE (PISCES, PLEURONECTIFORMES) B. Y. SuMiDA, E. H. Ahijstrom, and H. G. Moser' ABSTRACT Eggs and larval series are described for six species of flatfishes occurring off California with heavily pigmented larvae. These are the pleuronectids Pleuronichthys coenosus, P decurrens, P. ntteri, P. verticalis. and Hypsopselta guttulata and the bothid. Hippoglossina stomata. A brief description of postflexion larvae of the Gulf of California species. P ocellatus, is also presented. Eggs of Pleuronichthys are unusual among flatfishes in possessing a sculptured chorion composed of a network of polygonal walls, whereas the chonons of Hypsopsetta guttulata and Hippoglossina stomata eggs are smooth and unomamented. Eggs o{ Hypsopsetta guttulata and P. ritteri are unusual among those of pleuronectid flatfishes in possessing an oil globule. A combmation of pigmentation, morphology, and meristics can distinguish the seven species of flatfishes with heavily pigmented larvae. Larvae of two species, H guttulata and P. decurrens, have a distinctive pterotic spine on either side of the head. Sizes at hatching, at fin formation, and at transformation are important considerations to distinguish these species. Meristic counts, particularly of precaudal and caudal groups of vertebrae, are important to relate a larval series to itsjuvenile and adult stages and thus substantiate identification of the series. This report deals primarily with the eggs, larvae, and early juveniles of flatfishes of the genus Pleuronichthys. Descriptions are included for complete series of larvae of four species, P. decur- rens (curlfin turbot),* P. coenosus (C-0 turbot), P. verticalis (hornyhead turbot), and P. ritteri (spot- ted turbot). A brief account of postflexion larvae of the Gulf of California species, P. ocellatus (Gulf turbot), is also given. Larvae of Pleuronichthys are heavily pigmented, even at hatching, as are those of the pleuronectid, Hypsopsetta guttulata (diamond turbot), and the bothid, Hippoglossina stomata (bigmouth sole). To identify heavily pig- mented flatfish larvae obtained in plankton collec- tions from the eastern North Pacific, it is neces- sary to know the larval developmental, series of all of the above species. These species comprise minor incidental catches within California commercial and sport fisheries and are reported as a general 'Southwest Fisheries Center La JoUa Laboratory. National Marine Fisheries Service. NOAA. P.O. Box 271. La Jolla. CA 92038. ^The common name turbot is used for all species of Pleuronichthys. a usage consistent with Fitch ( 1963). Miller and Lea (1972). and Gates and Frey (1974:79). The American Fisheries Society's list of common names (Bailey et al. 1970) designates P. coenosus and P decurrens as soles, but we disagree with giving species within a genus different common general names. Manuscnpt accepted September 1978. FISHERY BUIXETIN VOL. 77, NO. 1, 1979. grouping of "turbots." Species most commonly caught in the fisheries are P. decurrens. P. coenosus, P. verticalis, and Hypsopsetta guttulata (Frey 1971; Bell 1971; Oliphant 1973; Pinkas 1974; McAllister 1975). No specific catch data are available for Hippoglossina stomata, but the species is probably caught incidentally and in- cluded in the "miscellaneous sole" category of catch data. In a review of the genus Pleuronichthys, Fitch (1963) recognized six species including the five listed above and P. cornutus from off Japan and China. In an earlier review of the genus, Starks and Thompson ( 1910) recognized these six species and P. nephelus Starks and Thompson. Norman (1934) concurred with Starks and Thompson in recognizing seven species. Fitch (1963), however, agreed with Hubbs (1928) in finding no grounds for the separation of P. nephelus from P. coenosus after his examination of the type material of P. nephelus. Fitch's review is thorough; he examined more than 5,700 individuals of the genus. We fol- low his classification. The first descriptions of the eggs and early-stage larvae of Pleuronichthys were given by Budd (1940) who dealt with P. coenosus, P. decurrens. and P. verticalis. Orton and Limbaugh (1953) de- scribed the eggs of Hypsopsetta guttulata and P. 105 FISHERY BULLETIN VOL 77. NO. 1 ritteri. Larvae of P. verticalis were illustrated in Ahlstrom and Moser (1975), and Eldridge (1975) described and illustrated larvae of//, guttulata. MATERIALS AND METHODS Eggs, larvae, and somejuveniles were primarily obtained from California Cooperative Oceanic Fisheries Investigations (CalCOFI) collections. These samples were preserved in a consistent manner as described in Kramer etal.( 1972). Addi- tional material was obtained from bay, estuarine, and coastal collections of Occidental College; Southwest Fisheries Center Tiburon Laboratory, National Marine Fisheries Service; California State University at Fullerton; Scripps Institution of Oceanography; Oregon State University; and Humboldt State University. Specimens of P. rit- teri, P. verticalis, and H. guttulata reared at the Southwest Fisheries Center La Jolla Laboratory, National Marine Fisheries Service, were also utilized. Egg and oil globule diameters were measured using an ocular micrometer in a stereomicroscope. For eggs that were not perfectly round, the greatest diameter was recorded. Scanning elec- tronmicrographs were made for four kinds of Pleuroniehthys eggs and for eggs of Sy nodus lucioceps (Synodontidae). The greatest diameter of 10 randomly selected polygonal facets of the chorion of Pleuronichthys and Synodus eggs were measured using an ocular micrometer in a com- pound microscope. To do this the chorion was cut into pieces that were laid flat on a glass slide with a cover slip over them. The number of specimens examined varied by species, depending on their availability and abun- dance, ranging from several hundred larvae of P. verticalis, the most abundant species, to two lar- vae of P. ocel lotus. For most species, the minimum number of specimens studied is indicated in the morphometric tables with usually twice as much material looked at for pigmentation development. A developmental series of larvae through juveniles was assembled for each species. Mea- surements of selected body parts were taken to provide descriptive and comparative morphomet- ric data. Measurements were made on the right side of each pleuronectid specimen, and on the left side of the bothid, Hippoglossina stomata, using an ocular micrometer in a stereomicroscope. Ter- minology used in the morphometric tables is as follows: Body length = In preflexion and flexion stages, horizontal distance from tip of snout to tip of notochord, referred to as notochord length (NL); in postflexion stages, from tip of snout to posterior margin of hypural elements, i.e., standard length (SL). Snout to anus = Horizontal distance from tip of snout through midline of body to vertical through anus. Head length = Horizontal distance from tip of snout through midline of head to margin of cleithrum preceding the pectoral fin base. Snout length = Horizontal distance from tip of snout to anterior margin of pigmented re- gion of eye. Eye width = Horizontal distance through midline of pigmented eye. Eye height = Vertical distance through center of pigmented eye. Body depth at pectoral base = Vertical distance across body at pectoral fin base prior to for- mation of dorsal fin pterygiophores. An as- terisk follows this measurement in the mor- phometric tables when it includes the depth of dorsal fin pterygiophores. Body depth at anus = Vertical distance across body at anus prior to formation of dorsal fin pterygiophores. An asterisk follows this measurement when it includes the depth of the dorsal fin pterygiophores. Caudal peduncle depth = Vertical distance across tail immediately posterior to terminal dor- sal and anal fin rays. Caudal peduncle length = Medial horizontal dis- tance from vertical through terminal dorsal and anal fin rays to posterior margin of hypural elements. Snout to pelvic fin origin = Horizontal distance from tip of snout to vertical through origin of right pelvic fin (left in H. stomata). Larval specimens for each species were not available in sufficient numbers to clear and stain for complete data on meristics and sequence of ossification of bony elements. However, fin ray counts were made and tabulated on unstained specimens. A partial larval series of P. verticalis, our most abundant species, was cleared with KOH and stained with Alizarin Red-S by Hollister's method (1934) to determine the process of axial skeletal development and fin formation. In addi- tion, several larvae of P. coenosus and P. decur- rens were cleared and stained for precaudal and 106 SUMIDA ET AL EARLY DEVELOPMENT OF SEVEN FLATFISHES total vertebral counts which verified identifica- tions and proved that Budd (1940) confused iden- tifications of larvae of these two species. Radio- graphs of transforming larvae, juveniles, and adults of each species provided additional meristic data. We divide the larval period into three stages, preflexion, flexion, and postflexion, based on the flexion of the notochord which occurs during caudal fin formation (Moser and Ahlstrom 1970; Ahlstrom et al. 1976; Moser et al. 1977). In Pleuronichthys and some other flatfishes the initi- ation of caudal fin formation begins while the notochord is still straight, in the late preflexion stage; we designate this phase as "early caudal formation." We found it convenient to divide the flexion stage into three substages, early flexion, midflexion, and late flexion, dependent upon the state of flexion of the notochord. In the early flex- ion stage, the notochord is very slightly flexed upward; in midflexion, it is flexed midway (nearly a 45° angle); and in late flexion, the notochord is approaching a terminal position, except that the caudal rays remain in a slightly oblique position. Transformation from the larval to juvenile stage was marked by eye migration, development of os- sified pectoral fin rays, scales, and the lateral line. MERISTIC COUNTS OF LARVAE Meristic counts overlap among species consid- ered here, and for discrimination of species it is necessary to use a combination of counts (Table 1). Precaudal and caudal vertebral counts, used in conjunction with dorsal and anal fin counts, are of most use in relating larvae to juveniles or adults. Pelvic fin ray counts are six per side in all seven species and branchiostegal ray counts are seven per side. Pectoral fin counts cannot be made on larvae since ossified pectoral rays form at metamorphosis. Gill rakers are not fully formed during the larval period in the species described. DESCRIPTION OF EGGS Pleuronichthys spp. Eggs of three Pleuronichthys species were first described by Budd (1940) who collected them in plankton hauls from Monterey Bay, Calif. Budd noted the hexagonal patterns on the chorions of Pleuronichthys eggs. This type of ornamentation of the egg shell is confined to Pleuronichthys among flatfishes, but similar polygonal sculptur- ing is found on eggs of the families Synodontidae (Sanzo 1915; Mito 1961) and Callionymidae (Holt 1893; Ehrenbaum 1905; Mito 1962) and in a more exaggerated form on eggs of the sternoptychid, Maurolicus muelleri (Sanzo 1931; Mito 1961). and the macrourid, Coelorhynchus coelorhynchus (Sanzo 1933). Eggs of the three species of Pleuronichthys described by Budd were strikingly different in size; his largest, P. coenosus, averaged 1.88 mm in diameter, his intermediate-sized egg, P. decurrens , 1.44 mm, and his smallest, P. ver- ticalis, 1.07 mm. All had homogeneous yolk, and lacked an oil globule. Our work shows that Budd misidentified the two larger eggs and correspond- ing larvae; the one he called P. coenosus is P. decurrens and vice versa. Orton and Limbaugh 1 1953) described an egg with an hexagonal pattern on its chorion that possessed a single oil globule; they tentatively, but correctly, assigned it to P. ritteri. White ( 1977) illustrated a developing egg of P. ritteri from Newport Bay, Calif Information concerning egg diameters, pres- ence or absence of an oil globule, and character of the chorion are given in Table 2 for six of the seven species treated in this paper. Egg diameters do not change noticeably with the duration of preserva- tion, although some shrinkage is known at the initial time of preservation. There is no overlap in egg size for the three species of Pleuronichthys that lack an oil globule. Eggs of P. decurrens range from 1.84 to 2.08 mm; those of P. coenosus, from Table l. — Meristics of the seven species of flatfishes in the eastern North Pacific that have heavily pigmented larvae.' Pectoral Caudal rays (eyed side) Species rays rays Precaudal Caudal Total giK rakers Total Branched Pleuronichthys decurrens 67-81 46-55 10-14 14-15 24-26 38-41 9-12 79-21 12-15(73) P coenosus 66-78 44-56 9-12 12-73 24-26 37-39 11-15 1 8-20{ 1 91 12-15(73) P verticals 66-79 44-51 10-12 13 23-25 36-38 9-11 79-20 12-14(73) P ocellatus 62-74 44-53 10-12 12-13 22-24 34-36 10-14 19 12-15(73) P rinen 62-72 43-52 9-11 72-13 22-24 34-36 12-17 18-79 73-14 Hypsopsetta gunutata 65-75 47-55 11-13 11-72 22-24 34-36 7+^(5-6) 79-20 13 Hippoglossina stomata 63-70 47-55 11-12 IJ 26-28 37-39 15-21 17'2-)8t 11-73 'Menstics compiled in Table 1 are derived in partfrom literature, particularly Fitch (1963). Norman (1934), Townsend (1936). Clothier (1950). and Ginsburg (1952), and m part from our onginal counts Where a range is given and one count is predominant, that count is italicized ^Lower limb count only 107 FISHERY BULLETIN VOL 77, NO, 1 Table 2, — Measurements of eggs of Pleuronichthy^ species, Hypsopsetta guttulata, and HippogLossina stomata, including Synodus lucioceps for comparative data. Oil globule diameters No 0( Egg diameters (mm) (mm) Species o( chorion measured samples Range Mean SD Range Mean SD Pleuronichthys decurrens Sculptured 41 28 1 84-2 08 1,97 0 058 P coenosus (CalCOFI) Sculptured 20 15 1 28-1 56 1 47 0066 — — — P coenosus (King Harbor) Sculptured 287 2 1 20-1 42 1 29 0047 — — — P. verticatis Sculptured 188 19 1 00-1 16 1.09 0040 — — — P rinen Sculptured 82 13 0 94-1 08 1 01 0029 008-0 14 0 10 0 009 Hypsopsetta guttulata Smooth 35 4 0 78-0 89 0,84 0027 0 12-0 14 0 13 0 010 Hippoglossina stomata Smooth 26 9 1 22-1 38 1,29 0,045 0,20-0 26 0 23 0018 Synodus lucioceps Sculptured 168 8 1 20-1 48 1,32 0049 — — — 1.20 to 1.56 mm; and those of P. uerticalis, from 1.00 to 1.16 mm. Although eggs of P. ritteri, rang- ing in diameter from 0.94 to 1.08 mm, fall within the size range of P. verticalis. they can be readily distinguished by the presence of a small oil globule, 0.08-0. 14 mm in diameter. Eggs of P. ocel- latus were unavailable. Differences in mean diameter of P. coenosus eggs were noted by locality, with eggs taken in open waters off the coast having a larger mean diameter and standard deviation (Table 2, Cal- COFI collections) than eggs sampled from the inlet of a small, shallow, manmade harbor near a power plant discharge (Table 2, King Harbor sam- ples). Except that they are often slightly larger in size, early- and middle-stage eggs of P. coenosus are difficult to differentiate from Synodus lucioceps eggs. They can be separated, however, by careful examination of the size and arrangement of polygons on the chorion. The mean of the greatest distance across polygons (sample size = 200 polygons) on P. coenosus eggs is 0.035 mm in contrast to 0.047 mm for S. lucioceps eggs (Table 3). Furthermore, the polygons on P. coenosus eggs are more regular in arrangement than on S. lucioceps eggs (Figure 1). This more uniform compacting of smaller polygons on P. coenosus eggs versus a more random patterning of larger polygons on S. lucioceps eggs is visible under a light microscope, and will separate these eggs. Late-stage eggs are easily distinguished by the heavy pigmentation on the embryo of P. coenosus compared with the sparse pigment on Table 3, — Comparison of polygon size on chorion of eggs of Pleuronichthys and Synodun lucioceps. No ot No of Range ot eggs polygons diameters Mean SD Species measured measured (mm) (mm) (mm) Synodus lucioceps 20 200 0 038-0,053 0,047 0,0033 Pleuronichthys coenosus 20 200 0 029-0 043 0 035 0 0029 P decurrens 2 20 0 038-0 046 0 042 0 0021 P verticalis 2 20 0 037-0 051 0 042 0 0046 P ritteri 2 20 0,028-0032 0,030 0 0011 advanced S. lucioceps embryos, which also have a longer gut. The arrangement of polygons on the chorion of eggs of the other three species of Pleuronichthys from the eastern Pacific is similarly uniform (Fig- ure 2). The polygons are somewhat larger on the chorion of eggs of P. decurrens and P. verticalis than P. coenosus, averaging ca. 0.042 mm in both species (Table 3). Interestingly, Budd ( 1940) gave the identical value, 0.042 mm, for this measure- ment on eggs of these two species. The polygons are smaller on eggs of P. ritteri. averaging 0.030 mm. The eggs of P. cornutus were described by Mito ( 1963) and Takita and Fujita ( 1964). Mito gave the egg diameters as 1.16-1.26 mm, the oil globule as 0.016-0.020 mm. Takita and Fujita gave similar measurements for the hexagonal meshes of 0.018 mm, but gave a smaller egg diameter of 1.03-1.11 mm. Hypsopsetta guttulata Orton and Limbaugh (1953) obtained running ripe eggs of//, guttulata by stripping ripe adults and obtained similar eggs from plankton collec- tions. The eggs were notable in that they con- tained a conspicuous, moderately large oil globule. This was the first record of an oil globule in eggs of flatfishes of the family Pleuronectidae, subfamily Pleuronectinae. The egg capsule was simple, without polygonal sculpturing or other apparent texture; the yolk was homogenous. Orton (1953) gave a fairly detailed description of pigment de- velopment on embryos of//, guttulata. Neither of the above papers contained information on egg size. Eldridge (1975) reported a mean egg diame- ter of 0.80 mm with usually one oil globule of 0.14 mm in mean diameter and numerous other small oil globules in the yolk. Eggs in our samples had a mean diameter of 0.84 mm (range 0.78-0.89 mm) with a single oil globule averaging 0.13 mm in 108 SUMIDA ET AL . EARLY DEVELOPMENT OF SEVEN FLATFISHES FiGL'RE 1. — Scanning electronmicrographs of Pleuronichthys and Synodus lucwceps eggs. A. Entire egg of P. coenosus, 40 v ; B. Single polygon from same egg showing micropyle and texture of chorion surface, 1 ,880 ^■, C. Side view of same egg showing polygons in perspective and micropyle at lower left. 420 « ; D. Face view of same egg, 480 ■ ; E. Side view of .S. /ucioceps egg showing polygons in perspective, 455 ^ ; note delicate nature of polygons; F. Face view of same egg showing irregular nature of polygons and smooth surface of chorion, 490 ■ . 109 FISHERY BULLETIN VOL 77. NO 1 9 ^^sSSi Figure 2. — Scanning electromicrographs of P/ewronfc/j^A_vs eggs. A. Side view of P. decurrens egg. 475 x; B. Face view of same egg, 475x; C. Side viewofP. wrtica/is egg. 410 X; D. Face view ofsame egg. 450 x; E. Side view of P. n«m egg. 460 x; F.Faceviewof same egg, 475 x. 110 SUMIDA ET AL.: EARLY DEVELOPMENT OF SEVEN FLATFISHES diameter (Table 2). There was no evidence of other small oil globules in the yolk, although a few eggs had a damaged oil globule which had separated in two. However, the original oil globule could easily be determined because of surrounding pigment. The oil globule is positioned near the center of the developing embryo in middle-stage eggs. The body of the late-stage embryo is heavily pigmented, similar to the newly hatched larvae. Hippoglossina stomata Eggs of H. stomata have not been previously described. Eggs are round with a slightly pinkish, unornamented shell and a single oil globule. The egg has a mean diameter of 1.29 mm (range 1.22- 1.38 mm) and the oil globule a mean diameter of 0.23 mm (range 0.20-0.26 mm) (Table 2). The oil globule lacks pigment and lies near the tip of the tail of developing embryos in middle-stage eggs. In late-stage eggs the oil globule is in the posterior part of the yolk sac; the embryo is heavily pig- mented over the body except for the posteriormost portion of the tail; pigment patches occur on the finfolds in the same places as in early preflexion stage larvae; pigment is widespread over the yolk surface. DESCRIPTION OF DEVELOPMENTAL STAGES— LARVAL, TRANSFORMING, AND EARLY JUVENILE Pleuronichthys decurreiis Jordan and Gilbert (curlfin turbot) Figures 3, 4 Literature. — A series of egg stages and two preflex- ion larvae of P. decurrens were described and il- lustrated by Budd ( 1940) but incorrectly identified as P. coenosus. His larval illustrations,were based on a recently hatched specimen, 5.54 mm, and an emaciated specimen. 8 days old, of somewhat smaller size. Distinguishing characters. — Larvae of this species are unique in the genus Pleuronichthys in de- veloping a pterotic spine on each side of the head, in having a higher precaudal vertebral number of 14 or 15, and in having the largest larvae during all stages of development. Larval pigmentation is heaviest in this species with the body and finfold entirely pigmented except for the posteriormost region. Because of their relatively large size and dense pigment, P. decurrens larvae cannot be con- fused with Hippoglossina stomata or Hypsopsetta guttulata. Pigmentation. — Newly hatched, preflexion, and early flexion larvae (4.9-9.8 mm NL) are heavily pigmented over the head, trunk, tail, and finfolds with only the pectoral fin and posteriormost tip of the notochord and finfold unpigmented (Figure 3 A, B, C). As the first few caudal rays become evident (ca. 9.7 mm NL), several small, discrete melanophores appear on the pectoral fin base (Figure 3Ci. In late flexion and early postflexion stages during dorsal and anal fin development, the continuous heavy pigment on the finfolds changes to form three to four dorsal and three ventral bands of pigment which extend out from the body margin to part of the rayed fin membrane (Figure 3D). Larvae at this stage have a soft, saccular body with semitransparent and sparsely pigmented areas in the pterygiophore region between the body proper and developing dorsal and anal fins. Larvae >11.2 mm SL have dorsal and anal pterygiophores fully developed; the pterygiophore region is no longer transparent and the specimens become robust (Figure 4). Morphology. — Larvae of P. decurrens are the largest members of the genus at hatching and attain the largest size before transformation. Our smallest specimen is 4.9 mm NL and has yolk remnants (Table 4). The left eye begins to migrate at 10.5 mm SL and has not completed migration in a larva 21.0 mm SL. The smallest available juvenile is 29.4 mm SL. The gut begins as a tube which diminishes in diameter posteriorly and ends with a free terminal section that diverges from the body in a slight posteriad direction. In 5- to 7-mm NL larvae, the gut increases markedly in diameter and the free terminal section becomes vertical to the body axis. At about 8.0 mm NL, the gut begins to coil and its terminal section begins to slant anteriad. Coiling and the anterior displacement of the anus become more marked as development proceeds. This is reflected in the decreasing relative snout-anus length in postflexion larvae and especially in juveniles (Table 5). Relative head length increases during larval development whereas relative snout length de- creases (Table 5). Relative eye width decreases slightly during the three phases of the larval 111 112 SUMIDA ET AL., EARLY DEVELOPMENT OF SEVEN FLATFISHES Figure 3. — Larval stages of Pleuronichthys decurrens: A. 5.9 mm; B. 6.5 mm; C, 9 7 mm; D 10.0 mm. Figure 4. — Transforming specimen of Pleuronichthys decurrens. 14 A mm. T.ABLE 4. — Morphometries, in millimeters, of larvae and a juvenile o( Pleuronichthys decurrens. (Specimens between dashed lines are undergoing notochord flexion.) Snout Body Body Caudal Caudal Snout Body Lett Noto- to Head Snout Eye Eye depth at depth peduncle peduncle to origin Station length eyei chord^ anus length length width height P baseJ at anus^ depth length pelvic fin 5401-90 60 4 9NL Sym Str 24 0 80 0 14 0 30 024 0,54 0,64 — — — 5704-87 50 56 Sym Str 30 1 1 0 20 0 40 0 32 090 0 96 — — — 6501-63 52 60 Sym Str 30 1 1 0 20 0 40 0 36 090 0 74 — — — 5206-70 65 65 Sym Str 32 1 2 0 22 0 42 0 40 0 94 1 1 — — — 6501-60 70 79 Sym Sir 39 1 6 0 30 0 50 0 48 1 3 1 3 — — — 5003-87 35 85 Sym Str 4 1 18 0 32 0 60 0 56 1 7 1 8- — — — 6606-60 65 93 Sym Str 43 20 0 32 0 66 0 62 1 6 18- — — — 6605-80 80 98 Sym Str 43 2 2 0 36 0 68 064 20 2 2- — — — 5706-93 65 78 Sym E II 39 1 9 0 30 064 064 2 3- 23- _ _ 5711-87 55 9 1 Sym Ell 4 7 2 1 0 40 0 70 0 66 2 4- 25- — — — 5401-85 60 100 Sym Midll 44 26 0 44 0 80 0 72 2.8- 3 0- — — 27 6507-87 55 110 Sym L fl 58 32 0 48 0 98 1 0 40- 4 6- — — 33 5009-47 60 102 SL Sym Flexed 53 34 0 60 0 96 0 94 4 5- 4 6- 1 0 060 34 5407-60 70 105 Migr Flexed 55 36 064 1 1 1 1 4 9- 5 4- 1 0 0 64 34 5805-70 80 11 2 Migc Flexed 57 39 0 64 1 3 1 2 5 2- 59- 1 3 0 68 36 7505-90 70 14 5 Migr Flexed 62 52 0 66 1 6 0 96 8 1- 86- 2 1 0 83 46 4903-82 57 154 luligr Flexed 70 5 7 0 67 1 8 1 7 9 0- 9 7- 2 1 1 1 4 7 6609-80 60 170 Migr Flexed 87 64 0 67 1 9 1 5 9 2- 11 4- 29 1 2 60 5308-73 60 192 f^4igr Flexed 7 7 65 091 1 7 1 5 10 0- 11 4- 28 1 2 64 5004-97 32 21 0 Migr Flexed 84 67 0 66 1 7 1 7 11 7- 124- 32 1 4 62 OtI Santa Cruz Island, Calif 29 4 Over Juv 97 90 0 66 33 25 139- 14 5- 36 22 68 'Sym - symmetrical. Migr ■ migrating. ^Str - straight, E fl - early fleKion. Midll - midllexion, L fl ■ late flexion. Juv - juvenile ^Asterisk indicates inclusion of dorsal fin pterygiopfiores in body depth measurement. 113 FISHERY BULLETIN: VOL 77, NO 1 fa ? s a tfi (D O _ g> a "5 a X S^ Q. 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The head is relatively larger in preflexion lar- vae of P. ritteri than in the other species (Table 5). Relative head length increases throughout the larval period, then is moderately reduced at trans- formation. Mean relative snout length increases in P. ritteri larvae undergoing notochord flexion and decreases during subsequent .stages, but in other species ofPleuronichthys it decreases during all major phases of larval development. Relative eye size is largest in preflexion larvae, becomes reduced in later larval stages, and increases at transformation. The early larvae of P. ritteri are the deepest bodied species of Pleuronichthys. Mean relative body depth measured at the base of the pectoral fin is greater during preflexion and flexion stages of the notochord than in any other species. In post- flexion larvae, however, mean relative body depth is markedly less than in P. decurrens and about equal to that in P. coenosu.'i and P. vertieali.s (Table 5). Fm and axial skeleton formation. — Early caudal formation involving thickening in the hypural area of the developing caudal fin occurs on larvae 4.3-5.1 mm NL (Table 15). Caudal rays are forming on larvae as small as 4.5 mm NL, with a simultaneous initiation of flexion of the notochord. Specimens between 4.5 and 5.6 mm NL undergo notochord flexion. Our smallest specimen with a fully flexed notochord is 5.3 mm SL. The full 128 SUMIDA ET AL.. EARLY DEVELOPMENT OF SEVEN FLATFISHES FlClIRE 15.— Reared larval stages oi Pleuronichthys ritleri. A 2.1 mm; B. 3.0 mm; C. 4.2 mm; D. 4.2 mm. dorsal view. 129 FISHERY BULLETIN VOL, 77, NO Figure 16— Lan-al stages of P/eumnichlhys ntleri: A. 5.6 mm; B. 5.5 mm; C. 6.4 mm. 130 SUMIDA ET AL. EARLY DEVELOPMENT OF SEVEN FLATFISHES Figure 17. — Transforming specimen o( Pleurontchthys ntteri, 10.0 mm. Table 14. — Morphometries, m millimeters, of larvae and juveniles oi Pleuronichthys ntteri. (Specimens between dashed lines are undergoing notochord flexion.) Snout Body Body Caudal Caudal Snout Body Left Noto- to Head Snout Eye Eye deptti at deptti peduncle peduncle to to origin station lengthi eye' ctiord' anus lengtti lengtti widtti fieigtit P base> at anus^ deptti lengtti pelvic fin Oft La Jolla, Calit 2 1 NL Sym Sir 1 2 0 50 0 10 024 0.20 0 20 0 38 — — — 30 Sym Str 1 4 0 60 0 12 0 26 0 22 0 42 0 42 — — — 7412-123 36 33 Sym Str 1 6 0 80 0 14 0 28 024 0 78 0 58 — — — Off La Jolla 42 Sym Str 22 1 0 0 18 0 40 0 32 0 96 0 86 — — — 5709-117 26 43 Sym Str 2 1 1 1 020 0 40 0 36 1 2 12- — — — 7207-123 36 4 4 Sym Sir 2 1 1 1 024 0 34 0 32 1 0 09 — — — 6204-120 25 50 Sym Str 22 1 2 0 20 0 38 0 38 1 2 1 r — — — 5708-12025 51 Sym Str 25 14 0 24 046 0,40 1 8- 1 7' — — 1,3 6507-120 35 45 Sym E fl 23 1 4 0 32 0 44 0 42 1 6- 1 6- 1 2 5506-120 40 48 Sym Ell 23 1 4 0 28 0 40 038 1 5- 1 7- — — 14 5510-11726 55 Sym Midll 2 7 1 2 0 34 0 52 0 48 2 0- 1 9- — — 16 7501-120 25 56 Sym Midfl 2 7 1 5 0 26 0 46 0 40 1 8- 1 5- — — 1 4 5112-120 35 5 3SL Sym Flexed 27 1 7 0 30 0 52 0 52 2 2- 2 2- 0 50 0 36 1 4 5802-137 23 60 f^igr Flexed 29 20 0 32 0 60 0 54 2 4- 2 7- 0 66 0 30 1 8 Oft La Jolla 64 fvligr Flexed 26 22 040 064 0 60 2 5- 2 7- 0 76 0 38 20 Sebastian Viscaino Bay, B C 75 A over Flexed 30 26 0 40 0 80 0 64 2 9- 3 0- 1 0 0 48 27 7501-120 22 4 85 A over Flexed 28 27 0 40 0 86 7 3 6- 3 6- 1 1 0 44 23 Off La Jolla 100 Over Flexed 31 31 0 48 1 0 0 80 4 2- 4 2- 1 4 0 60 26 Reared 127 Over Juv 42 38 0 36 1 4 1 0 5 1- 5 4- 1 4 0 76 34 Reared 150 Over Juv 45 42 0 48 1 6 1 2 5 9- 6 1- 1 8 1 0 39 Reared 167 Over Juv 52 4 7 0 48 1 8 1 4 6 2- 6 4- 20 1 1 42 Off San Juanico, B,C 23 0 Over Juv 72 68 0.83 22 9 9 7- 9 7- 26 1,2 58 'Sym - symmetrical, Migr - migrating A over - About over 2Str - straigtit, E fl - early flexion, fvlidtl - midflexion, Juv - juvenile ^Asterisk indicates inclusion of dorsal fin pterygiophores in body deptti measurement caudal count of 19 rays was observed on a 6.0-nim SL postflexion specimen. Dorsal and anal fin bases are forming in the finfold on larvae 4.3 mm NL, and the full comple- ment of rays develops by 6.0 mm SL. Pelvic fin buds are evident during early caudal formation but rays are first observed on a 6.0-mm specimen. Pectoral rays were fully formed on a 10.0-mm 131 FISHERY BULLETIN VOL 77. NO. 1 Table 15. — Meristics of larvae and juveniles o( Pleuronichthys ritteri. (Specimens between dashed lines are undergoing notochord flexion.) Fin rays Size Pectoral station (mm) Stage' Dorsal Anal Caudal Pelvic right/left Off La Jolla. Calif. 2 1 NL Yolk-sac 0 0 0 0 LP' 30 Prell 0 0 0 0 LP= 7412-123 36 33 Prell 0 0 0 0 LP= Ofl La Jolla 42 Prefl 0 0 0 0 LP' 5709-117.26 43 Prefl Forming Forming Forming 0 LP' 7207-23 36 44 Prell Forming Forming Forming 0 LP' 6204-120.25 50 Prefl Forming Forming Forming 0 LP' 5708-120 25 5 1 Prell Forming Forming Forming Bud LP' nghl/left Precaudal Caudal Total Source of count 6507-120 35 45 E fl Forming Forming ca 6 Bud LP' 5506-120 40 48 Efl Forming Forming ca 4 Bud LP' 5510-117 26 55 lulidfl Forming Forming ca 8 Bud LP' 7501-120 25 56 Midfl Forming Forming ca 8 Bud LP' 5112-120 35 5 3SL Postfl ca 60 ca 45 16 Bud LP' 5802-137 23 60 Postfl 72 49 19 6;6 LP' Oil La Jolla 64 Postfl 65 45 19 6/6 LP' Sebastian Visca no Bay, B C 75 Postfl 70 48 19 6/6 LP' 7501-120 22 4 85 Postfl 69 51 19 6/6 LP' Off La Jolla 100 Postfl 68 47 19 6/6 9/9 12 23 35 X-ray Reared 12 7 Juv 69 47 19 6/6 10/11 12 23 35 X-ray Reared 150 Juv 64 44 19 6/6 10/11 12 23 35 X-ray Reared 16 7 Juv 65 44 19 6/6 11/11 12 22 34 X-ray Off San Juanico BC 23 0 Juv 68 49 Damaged 6/6 9/9 12 23 35 X-ray 'Prefl - preflexion, E fl - early flexion, fwlidfl - midflexion, Postfl - postflexion; Juv - juvenile 'LP refers to functional larval pectoral fins wfiicti tiave no ossified rays larva. A radiograph of this specimen showed 12 precaudal and 23 caudal vertebrae, the typical count for this species. Distribution. — This species ranges from Morro Bay. Calif., to Magdalena Bay, Baja California (Fitch 1963; Miller and Lea 1972; Fierstine et al. 1973). Our egg and larval material, which was collected between .southern California and Mag- dalena Bay, Baja California, shows a markedly coastal, inshore distribution for P. ritteri, with a majority of collections made over or near the con- tinental shelf (Figure 18). Hypsopsettii giittnlata Girard (diamond turbot) Figures 19-22 Literature. — Orton and Limbaugh (1953) and Orton (1953) briefly described the eggs of//, gut- tiilala. Eldridge (1975) described and illustrated larvae of this species, and noted the average size of its egg and oil globule. Although the larval series is quite well described in Eldridge (1975) (except for the omission of the pterotic spine on the head), we are including information about distinguish- ing characters, pigmentation, etc. to facilitate identification. Distinguishing characters. — Larvae of H. gut- tulata are distinguishable from species of Pleuronichthys, except for P. ritteri, by their lower total vertebral number, by attaining comparable stages of development at smaller sizes, and by the presence of a pterotic spine on each side of the head in yolk-sac larvae to midflexion larvae. In the genus Pleuronichthys, only P. decurrens develops pterotic spines. (See Distinguishing characters for P. decurrens. ) The only species with which larval H. guttulata may be confused is P. ritteri because of its rela- tively small size and somewhat similar pigment pattern. (See Distinguishing characters for separating larvae of the two species discussed under P. ritteri .) Pigmentation. — Yolk-sac larvae are heavily pig- mented on the head, trunk, and for a short dis- tance on the tail, with the posteriormost 9 or 10 myomeres remaining unpigmented (Figure 19A). Pigment spots are scattered over the ventral and posterior surfaces of the yolk sac and oil globule, and over the terminus of the gut. Preflexion larvae show little change in pigment pattern. One or two melanophores develop on the pectoral fin base. The isthmus has a line of pig- ment spots, and the entire abdominal area is cov- ered with pigment (Figure 19B.). 132 SUMIDA ET AL- EARLY DEVELOPMENT OF SEVEN FLATFISHES 129° 125° 121° 40' 35' 30' 25' 20° /^ T- 1- -r -r / /^ V T" MENDOCINO MAGDflLENA _ 40° 35° 30° 25° 115° 110° 106° Figure 18. — Distribution of eggs and larvae of Pleuronichthys ritteri examined in this study. (Triangles represent eggs, open circles larvae, and closed circles eggs and larvae. t At the initiation of dorsal and anal fin forma- tion, the tail pigment spreads out dorsally and ventrally onto the finfold, resulting in conspicuous dark mounds of pigment opposing each other in the area between the body and the dorsal and anal fin bases (Figure 19C). The tops of the head, nape, and shoulder area are pigmented in contrast to P. ritteri. which has an unpigmented streak dorsally (Figure 19D). Flexion, postflexion, and early transforming specimens maintain the earlier pigment pattern and the only obvious change is a slight posteriad extension of trunk pigment, leav- ing 5 or 6 unpigmented myomeres posteriorly compared with 9 or 10 in earlier stages (Figure 20). The base of the pectoral fin acquires more pigment spots in postflexion larvae, and pigment on the head similarly increases in density (Figure 20B). Preserved small juveniles are brownish-black with numerous small, dark spots scattered over the body and pterygiophores, giving them a mot- tled appearance (Figure 21). Morphology. — Our smallest yolk-sac larva is 2.2 mm NL and has a posteriorly positioned oil globule 0.14 mm in diameter (Figure 19A). The left eye is beginning to migrate in a specimen 4.4 mm SL and is complete in a 7.3-mm SL larva (Table 16). The smallest available juvenile was 11.2 mm SL. A major distinguishing feature of Hypf^opxetta larvae is the presence of a pterotic spine on each side of the head. The spines are present on the smallest yolk-sac larva and are prominent in most preflexion larvae. The spines begin to regress on late preflexion larvae, and are totally regressed in late flexion specimens. In P. deciirrens the spines are well developed throughout the larval period and begin to regress late in the postflexion stage. Although mean relative body depth of H. gut- tiilata larvae increases with development, it is slightly less in postflexion specimens than in any species of Pleuronichthys , except P. ocellatiis (Ta- ble 5). In newly transformed juveniles, however, relative body depth is greater than in any species oi Pleuronichthys. As a juvenile. H. guttulata as- sumes a diamond-shaped body form. Relative body width is useful to separate Hyp- sopsetta larvae from those of P. ritteri. As shown in Figures 15D and 19D, larvae of Hypsopsetta have narrower bodies. Fin formation. — The caudal fin forms on larvae between 4.0 and 5.2 mm NL and is complete on some specimens as small as 4.4 mm (Table 17). The dorsal and anal fins form simultaneously with the 133 FISHERY BULLETIN VOL 77. NO 1 FIGURE 19.— Larva] stages o[ Hypxopseltu guttulata: A. 2.2 mm; B. 2.6 mm; C. 4.6 mm; D. 4.6 mm, dorsal view. 134 SUMIDA ET AL : EARLY DEVELOPMENT OF SEVEN FLATFISHES Figure 20.— Larval stages of Hypsopsetta guttulala: A. 5.9 mm; B. 6.6 mm. caudal and are complete, or nearly so, on all post- flexion specimens (4.4-8.8 mm SL). Pelvic fins are late in forming compared with their developmen- tal pattern in Pieiironichlhyn larvae. Pelvic buds can be observed only after notochord flexion has been completed, and rays are first evident on the 6.6-mm SL specimen. Distribution. — Hypsopsetta guttulata ranges from Cape Mendocino. Calif., to Magdalena Bay, Baja California, with an isolated population in the upper Gulf of California (Norman 1934; Fitch 1963). Egg and larval material examined by us was collected in bays along the coast, or at Cal- COFI stations located over the continental shelf, a pattern of distribution similar to the habitat of P. ritteri (Figure 22). Hippoglossitia stoma ta Eigentnann and Eigenmann (bigmouth sdIc) Figure 23 Literature. — There is no published account of eggs and larvae of this species. However, Leonard ( 197 1 ) described a larval series oiH. oblonga from the western North Atlantic. Earlier, Agassiz and Whitman ( 1885) and Miller and Marak 1 1962) de- scribed the eggs and early-stage larvae of//, ob- longa. Miller and Marak reported the egg size range as 0.91-1.12 mm (average 1.04 mm) with an oil globule diameter ofca. 0.1 7 mm. The larval size at hatching was 2.7-3.2 mm. Distinguishing characters. — Preflexion larvae of H. stomata may be confused with early larvae of P. 135 FISHERY BULLETIN: VOL. 77. NO 1 m^iCfei,. ^^^-:^^ij,n •%.?.:U^<^---^^ •■-.5 '•^^«;i^ ^: .^^ ..*, Figure 21, — Early juvenile o{ Hypsopsetta guttulata. 1.3.2 mm. coenosus and P. uerticalts due to similarities in size and pigmentation of the larvae, and the pres- ence of pigment on the finfold dorsally and ven- trally, posterior to the anus. Characters of H. stomata larvae which distinguish them from preflexionP. coenosus larvae include the presence of a pigment bar through the eye, heavy pigment on both sides of the pectoral fin base and a sprinkl- ing of pigment on the pectoral blade, a more slen- der, elongate body, and a significantly smaller patch of dorsal finfold pigment. The same charac- ters help to distinguish H. storjiata from P. ver- ticalis. except for the finfold pigmentation. Pleuronichthys verticalis has small, triangular- shaped pigment patches whereas H. stomata has a small rounded pigment cluster on the dorsal finfold and a broad patch on the ventral finfold. Larvae of P. verticalis are also smaller than H. stomata at similar developmental stages. Larvae in the flexion stage and larger are read- ily separable from Pleuronichthys by the preoper- cular spines and development of several elongated dorsal rays in the anteriormost part of the dorsal fin. These do not develop on larval Pleuronichthys or Hypsopsetta. L36 Pigmentation. — Yolk-sac larvae (ca. 3.7 mmi are heavily pigmented on the trunk and tail except for the posteriormost part of the tail which is pig- mented with several small spots dorsally and ven- trally (Figure 23A). The upper head and abdomi- nal region have scattered pigment, with a more concentrated bar of pigment on each side of the eye. Both sides of the pectoral fin base are con- spicuously pigmented. Finfold pigment consists of a small, rounded patch at the edge of the dorsal finfold, and a broad patch on the ventral finfold, both situated posterior to the anus near the mid- point between the anus and tip of the tail (Figure 23Ai. Preflexion larvae, 4. 1-7.0 mm NL, undergo little change in pigmentation except to augment pig- ment in areas of the pectoral fin, abdominal re- gion, and top of the head (Figure 23Bi. On larvae forming the dorsal and anal fins, the dorsal finfold pigment spreads to include the area between the fin rudiments and body margin, and the ventral finfold pigment spreads both an- teriorly and posteriorly (Figure 23C). Pigment on the pectoral fin base intensifies and also extends out onto the fin blade. SUMIDA ET AL.; EARLY DEVELOPMENT OF SEVEN FLATFISHES Table 16. — Morphometries, in millimeters, of larvae and juveniles of Hypsopselta guttulata. (Specimens between dashed lines are undergoing notochord flexion. I Snout Body Body Caudal Caudal Snout Body Letl Noto- to Head Snout Eye Eye depth at depth peduncle peduncle to ongin Station length eye' chord' anus length length width height P base^ at anus^ depth length pelvic fin San Diego Bay 2 2 NL Sym Sir 1 1 0 38 0 08 0 17 0 13 0 18 0 28 _ King Harbor, Calif 23 Sym Sir 1 1 0 46 0 12 0 20 017 0 18 0 34 _ 7501-120 25 28 Sym Sir 1 4 068 012 0 26 0 22 0 62 052 _ _ 7501-120 29 33 Sym Sir 1 7 0 82 0 20 0 30 0 24 0 82 0 72 _ San Diego Bay 36 Sym Sit 1 8 084 0 16 0 32 0 28 0 78 066 _ _ _ San Diego Bay 40 Sym Sir 20 0 88 0 20 0 36 030 0 88 084 _ 7412-127 32 6 4 4 Sym Sic 22 0 90 0 20 037 0 32 1 0 092 - - - 7412-127 32 6 46 Sym Ell 23 1 2 0 24 0 38 0 32 1 1 1 0 7501-120.224 49 Sym Efl 24 1 3 0 22 0 40 0 36 1 2 1 1 — _ _ 7501-120.29 51 Sym E fl 25 1 2 0 22 0,40 036 11 1 1 _ _ King Harbor 52 Sym Lfl 24 1 4 0 28 0 44 0.42 12 12 — - - L A Harbor Calif 4 4 SL Migr Flexed 22 1 6 0 30 0 48 0 42 1 8- 1 9- 0 40 0 40 1 4 La Jolla. Calif 48 Migr Flexed 22 1 5 0 30 0 48 0 40 1 6- 1 T 0 40 0 36 1 4 San Diego Bay 54 Migr Flexed 23 18 0 34 0 52 0 40 1 8- 1 9- 0 42 0 42 1 6 7501-120,22.7 59 Sym Flexed 31 1 8 0 32 0 50 046 2 0- 2 2- 0 44 0 48 1 9 7501-120,24 66 Migf Flexed 32 2 1 0 40 0 62 052 2 3- 2 4- 0 50 0 60 20 Reared 73 Over Flexed 29 25 0 40 090 0 70 3 3- 3 5- 0 76 064 2 1 Reared 79 Over Flexed 29 27 0 44 0 92 0 68 3 6- 3 8- 0 86 0 70 2 1 Reared 8,8 Over Flexed 36 30 0 48 1 0 076 4 1- 4 2- 096 068 26 Reared 112 Over Juv 4 2 37 0 50 1 4 1 1 5 7- 6 0- 1 4 1 0 33 Richardson Bay 129 Over Juv 45 43 0 52 1 2 0 92 7 0- 7 0- 1 5 10 36 Calif 132 Over Juv 48 43 0 75 1 3 1 1 6 7- 7 r 1 4 1 0 36 140 Over Juv 50 47 0 75 1 4 1 2 7 5- 77- 1 6 1 2 38 145 Over Juv 52 48 0 72 1 4 1 0 7 7- 7 9- 1 8 0 88 4 1 184 Over Juv 64 58 0 80 1 7 1 4 10 0- 10 5- 2 1 1 4 5 1 'Sym ■ symmetrical, Migr - migrating ^Str - straight; E (I - early flexion, L Tl - late flexion. Juv ■ )uvenile ^Asterisk indicates inclusion of dorsal tin pterygioptiores m body depth measurement Table 17. — Menstics of larvae and juveniles of Hypsopsetta guttulata. (Specimens between dashed lines are undergoing notochord flexion.) Size Fin rays Verlebrap Pectoral station (mm) Stage' Dorsal Anal Caudal Pelvic right/left Precaudal Caudal Total of count 7501-120 25 2 8 NL Prefl 0 0 0 0 LP' 7501-120 29 33 Prefl 0 0 0 0 LP' San Diego Bay 3.6 Prefl 0 0 0 0 LP' San Dieqo Bay 40 Prefl Forming Forming Forming 0 LP' 7412-127 32 6 4 4 Prefl Forming Forming 6 0 LP' 7412-127 32 6 45 Efl Forming Forming 8 0 LP' 7501-120 22 4 49 Ell Forming Forming 6 0 LP' 7501-120 29 51 E II Forming Forming 4 0 LP' King Harbor, Calif 52 L fl ca 50 ca 35 15 0 LP' LA Harbor, Calif 4 4 SL Postfl 67 47 19 Bud LP' Off La Jolla, Calif 48 Postfl 66 49 19 Bud LP' San Diego Bay 54 PosHI 73 45 19 Bud LP' 7501-120 22 7 5.9 Postfl 73 46 19 Bud LP' 7501-120 24 66 PosHI 69 50 19 6 6 LP' Reared 7 3 Postfl . 68 47 19 6,6 11 11 1 1 23 34 X-ray Reared 79 Postfl 67 51 20 6,6 12 12 12 23 35 X-ray Reared 88 Postfl 72 50 19 6;6 13/13 12 23 35 X-ray Reared 112 Juv 73 48 19 4/6 12/12 12 22 34 X-ray Richardson Bay, Calif 129 Juv 66 48 19 5/6 12/11 12 23 35 X-ray 132 Juv 74 53 19 6/6 11/11 12 23 35 X-ray 140 Juv 78 55 19 6/6 11/11 12 23 35 X-ray 14 5 Juv 71 51 19 6/6 12/12 12 23 35 X-ray 184 Juv 68 51 19 6/6 11/12 12 23 35 X-ray 'Prefl - preflexion, E fl - early flexion, L fl - late flexion, Postfl - postflexion, Juv 'LP refers to functional larval pectoral fins which have no ossified rays juvenile Postflexion and early transforming specimens are less heavily pigmented than earlier stage lar- vae, with a noticeable diminution of pigment on the dorsal area of the head and body ( Figure 23D ) . Morphology. — Larvae of H. stomata are closest to P. coenosus in size at hatching, notochord flexion, and transformation (Table 18). A specimen 3.7 mm NL has a moderate amount of yolk remaining. 137 FISHERY BULLETIN: VOL. 77. NO 1 129° 125° 121° 40' 35< 30' 25' 20' 40° MAGDALENA 115° Figure 22. — Distribution of eggs and larvae of Hypsopsetta gut- tulata examined in this study. (Open circles represent larvae, closed circles eggs and larvae.) The right eye is beginning to migrate in a speci- men 9.1 mm SL and transformation is almost complete at 11.7 mm SL. In early preflexion larvae of Hippoglossina, the gut is shaped like that in Pleuronichthys larvae; however, coiling begins at about 4.5 mm NL and the gut assumes a more compact shape than in Pleuronichthys. This is reflected in the relatively shorter snout-anus length. Mean relative snout- anus length remains at about 4CK7c of the body length throughout the larval period, in contrast to Pleuronichthys larvae in which there is a gradual decrease in relative gut length during larval de- velopment (Table 5). In juveniles, however, there is a decrease in snout-anus length to about 33% of body length, a value comparable with that in Pleuronichthys juveniles. The head is similar in size and shape to that in Pleuronichthys. Relative head length increases gradually during larval development. The same is true for relative snout length and is thus opposite to the condition in Pleuronichthys; however, it de- creases somewhat in juveniles. Relative eye width undergoes a moderate diminution during larval development as in Pleuronichthys, but increases moderately in juveniles. Small preopercular spines develop on larvae from ca. 5.5 mm NL, become most conspicuous on flexion stage larvae, and undergo resorption dur- ing transformation from 9.5 mm SL. This spina- tion is distinctive of H. stomata when compared with Pleuronichthys and Hypsopsetta. Larvae oi Hippoglossina have a slender appear- ance compared with .some of the deeper bodied species of Pleuronichthys. Body depth at the anus is comparatively small in preflexion larvae and remains so in flexion and postflexion larvae and early juveniles (Table 5). As in Hypsop.'ietta, the caudal peduncle is longer and more slender than in Pleuronichthys, except for P. ocellatus postflexion larvae. Fin formation. — Larvae of Hippoglossina stomata are comparable with those of P. coenosus with regard to size at which the caudal fin develops. Caudal fin formation occurs between 6.2 and 8.8 mm NL (Table 19). Although about six caudal rays are formed on a 7.0-mm NL specimen with a straight notochord, all other specimens with caudal rays have the notochord flexing. The smallest, fully flexed specimen is 7.1 mm SL. Postflexion specimens <9.0 mm SL lack the full complement of I8V2 caudal rays. The ural bones supporting the caudal rays are made up of two superior and two inferior hypurals; there is no epural. The lack of an epural bone is a specific 138 SUMIDA ET AL.i EARLY DEVELOPMENT OF SEVEN FLATFISHES Figure 23.— Larval stages of Hippog/ossma slomala: A. 3.8 mm; B. 4.8 mm; C. 8.3 mm; D. 8.6 mm. 139 FISHERY BULLETIN: VOL. 77, NO 1 Table 18. — Morphometries, in millimeters, of larvae o( Hippoglossina stomata. (Specimens between dashed lines are undergoing notochord flexion.) Snout Body Body Caudal Caudal Snout Body Lett Noto- to Head Snout Eye Eye depth at depth peduncle peduncle to origin Stalion length eye' chofd' anus length length width height P base^ at anus^ depth length pelvic tin 720M1735 3 7NL Sym Sir 1 4 0,64 0,10 0 28 0,21 0 50 0 40 _ _ _ 7412-103 29 4 1 Sym Sir 1 8 0,72 007 0 24 0 24 0 48 0 36 — — — 7412.88,5.31 4.8 Sym Sir 2 0 10 0 24 0 36 028 0% 068 — — — 5801-117 35 5.2 Sym Sir 22 1 2 0 24 0 48 0 36 1 2 082 — — — 6310-93 28 6.2 Sym Str 22 1 3 026 0 42 036 12 0,92 — — — 6605-123 37 64 Sym Str 22 1 3 0 24 0 44 0 36 1 4' 1 0 — — — 5910-117 30 6.2 Sym Str 28 1 6 0 30 054 0 42 2 1- 1 3 — — — 6706-110 50 70 Sym Sir 28 1 8 0 32 0 50 0 42 21- 1 8- — — — 5708-118 5 35 66 Sym Ell 27 1 7 0 40 054 0 54 21- 1 7- 1.5 5706-127 34 75 Sym Ell 30 20 0 36 0 66 0 70 22- 18- — — 1 8 6912-83 60 83 Sym E (1 32 1 8 0 42 0 60 0 66 24- 20- — — 20 5807-130.30 7.6 Sym Midll 29 1 9 0 38 064 058 2 2- 2 0- — — 1 8 5709-110 30 79 Sym Midfl 29 19 0 42 0 60 052 2 2- 2 0- — _ 17 6706-12337 88 Sym Midtl 34 23 0 44 0 68 060 28- 24- — — 24 5706-12337 76 Sym L (1 3 1 2 1 0 46 0 66 0 64 2 5- 2 3- — — 18 6706-123 36 85 Sym L II 34 23 0 44 0 70 0 66 2 8- 2 6- — — 23 6608-120 30 7 1 SL Sym Flexed 3 1 22 0 46 0 76 0 78 2 6- 2 4- 0 66 062 21 5708-115 35 80 Sym Flexed 33 24 064 0 72 0 68 29- 27- 062 070 20 6706-123 37 90 Sym Flexed 39 27 0 52 0 84 0 84 3 4- 3 0- 070 0 82 27 6410-83 43 94 Sym Flexed 37 27 0 56 0 84 0 84 3 6- 3 8- 0 80 0 84 23 5701-120 35 9 1 Migr Flexed 38 3 1 0 72 1 0 0 96 3 7- 4 r 092 0 68 27 5709-110 33 99 Migr Flexed 40 32 0 80 0 90 086 4 1' 43- 0.90 0 76 26 6706-123 36 105 Migr Flexed 4 1 35 0 80 1 1 0 94 3 8- 3 9' 0 98 0 88 30 5507-130,30 11 7 Migr Flexed 42 37 096 10 088 44- 4 5- 12 0.90 35 Asuncion Bay. 358 Over Juv 124 12,2 23 4,3 — 134- 130- 3.2 2.9 10.5 BC 38 2 Over Juv 122 13,5 27 42 — 14,2- 13.7- 3.8 3.4 11.4 'Sym - symmetrical. Migr - migrating ^Str ■ straight, E tl - early llexion, Midll - midflexion, L tl - late flexion, Juv - luvemle. ^Asterisk indicates inclusion ol dorsal tin pterygiophores in body depth measurement. Table 19. — Menstics of larvae and juveniles oi Hippoglossina stomata. (Specimens between dashed lines are undergoing notochord flexion.) Size Fin rays Vertebrae Pectoral Source Station (mm) Stage' Dorsal Anal Caudal Pelvic righflell Precaudal Caudal Total ol count 7201-117 35 3 7 NL Prell 0 0 0 0 LP^ 7412-103 29 4 1 Prell 0 0 0 0 LP2 7412-88531 4.8 Prell 0 0 0 0 LP^ 5801-11735 5.2 Pretl 0 0 0 0 LP' 6310-93 28 6.2 Pretl 0 0 0 0 LP' 6605-123 37 6.4 Prell Anterior swelling 0 0 0 LP' 5910-117 30 6 2 Prell Forming 0 Forming 0 LP' 6706-110 50 70 Prell Forming Forming ca 6 0 LP' 5708-118 5 35 66 Ell. Forming Forming ca 6 Bud LP' 5706-127 34 75 Efl Forming Forming ca 10 Bud LP' 6912-83 60 83 Ell Ant 4 Forming ca 10 Bud LP' 5807-130 30 7.6 lyiidll ca 15 ca 15 12 Bud LP' 5709-110 30 7.9 Midfl ca 55 ca 45 12 Bud LP' 6706-123 37 8.8 Midtl ca, 62 ca 50 16 Bud LP' 5706-123 36 7.6 Lfl ca 63 ca 45 14 Bud LP' 6706-123 36 8.5 Lll ca, 68 ca 50 14 Bud LP' 6608-120 30 7 1 SL Postll ca 66 ca 51 16 ca, 5/5 LP' 5708-115 35 8.0 Postll 63 50 ca 18 6/6 LP' 6706-123 37 9.0 Postll 68 53 18'i 5,' 5 LP' 6410-83 43 9.4 Postll 68 54 ca 18 6/6 LP' 5701-120 35 9.1 Postll 67 53 18''i 66 LP' 5709-110 33 9.9 Postll 65 50 18',i 6/6 LP' 6706-123 36 10.5 Postll 66 53 18'/i 6/6 LP' 5507-130 30 11.7 Postll 64 50 18'/! 6/6 LP' Asuncion Bay. 35.8 Juv 67 52 18"j 6/6 10,'10 11 27 38 x-ray BC 38 2 Juv 65 50 1 7','i 6/6 10/10 11 27 38 X-ray 'Prell - prellexion. E fl - early flexion Midll - midllexion, L 11 - lale llexion : Postfl, - postllexion Juv - juvenile ^LP refers to functional larval pectoral fins which have no ossified rays. 140 SUMIDA ET AL EARLY DEVELOPMENT OF SEVEN FLATFISHES character in H. stomata because other species of Hippoglossina possess this bone. The dorsal fin of//, stomata develops quite dif- ferently than in Pleuronichthys. An anterior group of about five dorsal rays is the first to form in H. stomata; these become more elongated than the other rays. The anlage of these is evident on a 6.4-mm NL preflexion specimen and four rays are formed on a 9.3-mm NL early flexion larva. A similar pattern of early forming dorsal fin rays is found in the closely related genera Paralichthys (Okiyama 1967; Smith and Fahay 1970; Ahlstrom and Moser 1975) and Pseudorhombus (Devi 1969). Although the anterior dorsal rays form early, the pelvic fins do not develop elongated rays, such as in the bothid genera Syacium (Aboussouan 1968) and Cyclopsetta (Gutherz 1970). The dorsal fin rays differentiate posteriad but most rays form simultaneously and the full complement is de- veloped on a late flexion specimen. The base of the anal fin is evident during early caudal formation, rays are forming on midflexion specimens, and the total number is formed on a late flexion specimen. Pelvic fin buds are evident on early flexion speci- mens, but rays can be distinguished only on post- flexion larvae. Distribution. — This species ranges from Monterey Bay, Calif., to the Gulf of California, including Guadalupe Island (Miller and Lea 1972). Larvae occurred over a wide band of inshore and offshore stations (Figure 24). The southern limit of H. stomata overlaps the northern range of H. tet- rophthalmus which has different fin counts (Ginsburg 1952). To date, larvae of H. tet- rophthalmus are not known. SUMMARY We used a combination of larval morphology, meristics, and pigmentation to distinguish seven known eastern North Pacific species of flatfishes with heavily pigmented larvae. Table 20 sum- marizes many pertinent characters for identifying eggs and larvae of these species. Information is given for three characters of eggs; size, ornamen- tation of the chorion, and presence or absence of an oil globule. In most instances, the size of a newly hatched larva is directly related to the size of the egg from which it hatched, and such is the case with Pleuronichthys. Pleuronichthys decurrens. with the largest egg, has the largest larva, with a suc- 40' 35' 30' 25' 20' 129° "7 125° "7 — r CAPE MENDOCINO ^MONTEREY BAY POINT 'CONCEPTION O rJ SAN DIEGO \ O c* \, ; A J£] \i. O O o Y^ POJNT \ EUGENIA O Ox o oof '^ 0 A } GULF \ o o 0 y .CALIFORNIA •A MAGDALENA.-^'^^ . ( BAT \ ; . ^ 440 40° 35° 30° 25° 115° )06° FiGL'RE 24. — Distribution of eggs and larvae o^ Hippoglossina stomata examined in this study. (Triangles represent eggs, open circles larvae, and closed circles eggs and larvae.) cessive decrease in larval size of the other species corresponding to their smaller sized eggs. This also applies to the yolk-sac larvae of Hypsopsetta guttulata and Hippoglossina stomata. Pleuron- 141 FISHERY BULLETIN VOL 77. NO 1 ichthys decurrens. with the largest yolk-sac larva, is correspondingly large at caudal fin formation (notochord flexion) and at transformation, whereas Hypsopsctta guttiilata. with the smallest egg, is correspondingly smallest at all stages of larval development with the exception of some overlap with larvae of P. ritten. A larval character that is particularly useful in separating preflexion larvae of H. guttulata from those of P. ritten is the presence of a pterotic spine on each side of the head of//, guttulata. The only species of Pleuronichthys with a pterotic spine is P. decurrens. For relating a lai'val series to its juveniles and adults, and thus substantiating identification of the series, meristic counts, particularly of the pre- caudal and caudal groups of vertebrae, are indis- pensible. One can seldom rely on one meristic character alone, but must use a combination of all available counts. The distribution of pigment, which changes with growth, provides good characters for dis- criminating among larvae of the several species. It is particularly useful with preflexion larvae, and for this reason we emphasize pigment for this stage in Table 20. ACKNOWLEDGMENTS We would like to thank the following individu- als for loan of specimens: Gerald McGowen (Occi- dental College), Joseph Copp and Richard Rosenblatt (Scripps Institution of Oceanography), Maxwell Eldridge (National Marine Fisheries Service, Tiburon), Wayne White (California State University, Fullerton), Robert Behrstock (Hum- boldt State University), and Sally Richardson (Oregon State University). We are grateful to Den- nis Gruber (Scripps Institution of Oceanography) and John Butler (National Marine Fisheries Ser- vice, La Jollai for providing reared specimens. .Ap- preciation is also extended to Susan D'Vincent, Elaine Sandknop, and Betsy Stevens (National Marine Fisheries Service. La Jolla) for their assis- tance in gathering material from our collections. Henry Orr ( National Marine Fisheries Service, La Jolla) deserves thanks for some of the illustra- tions. Our special thanks go to George Boehlert and Ellen Flentye (Scripps Institution of Oceanog- raphy) for providing the scanning electronmicro- graphs, and to John Fitch (California Department of Fish and Game), Edward Houde (University of Miami), David Kramer (National Marine Fisheries Service, La Jolla), and Sally Richardson for their critical review of the manuscript. LITERATURE CITED ABOUSSOUAN, A. 1968. Oeufs et larves de Teleosteens de I'Ouest africain VII. Larves de Syacium guineensis (Blkr.l IBothidae], Bull. Inst Fondam. Afr. Noire, Ser. A Sci Nat. 30:1188-1197. AGAS.SIZ. A., AND C. O. WHITMAN. 1885. Studies from the Newport Marine Laboratory. XVI. The development of osseous fi.shes, I , The pelagic stages of young fishes. Mem. Mus. Comp. Zool Harv. Coll. 14. 56 P AHL.STROM. E. H.. AND H. G. MOSEK. 1975. Distributional at'.as of fish larvae in the Cahfomia Current region: Flatfishes, 1955 through 1960. Calif. Coop. Oceanic Fish, Invest. Atlas 23. text vii-xix, 207 distribution charts. AHL.STROM, E. H., J. L, BUTLER, AND B. Y. SUMIDA. 1976. Pelagic stromateoid fishes (Pisces, Perciformes) of the eastern Pacific: Kinds, distributions, and early life histories and observations on five of these from the north- west Atlantic. Bull. Mar. Sci. 26:285-401. AMAOKA, K. 1970. Studies on the larvae and juveniles of the sinistral flounders - I. Taeruopsettn ocellata (Giinther). Jpn. J- Ichthyol. 17:95-104, 1971. Studies on the larvae and juveniles of the sinistral flounders — II. Chascanopsetta lugiibris. Jpn J Ichthyol. 18:25-32. 1972. Studies on the larvae and juveniles of the sinistral flounders— III. Laeops kilaharae. Jpn. J. Ichthyol. 19:154-165, 1973. Studies on the larvae and juveniles of the sinistral flounders — IV. Arnoglossusjaponiciis. Jpn, J. Ichthyol. 20:145-156. B AILEY, R, M. J. E. FITCH, E. S. HERALD, E. A. LACHNER, C. C. LINDSEY, C, R, ROBINS, AND W, B. SCOTT, 1970, A list of common and scientific names of fishes from the United States and Canada. 3d ed. Am. Fish. Soc, Spec. Publ. 6, 150 p. Bell, R. R. 1971. California marine fish landings for 1970 Calif Dep Fish Game, Fish Bull, 154:33-34, Bruun, a, F, 1937. Chat^canopsetta in the Atlantic; a bathypelagic oc- currence of a flat-fish, with remarks on distribution and development of certain other forms. Vidensk. Medd Dan. Naturhist. Foren. Kbh. 101:125-135. BUDD, P. L. 1940. Development of the eggs and early larvae of six California fishes. Calif. Div. Fish Game, Fish Bull. 56. 50 p. Clothier, C. R. 1950. A key to some southern California fi.shes based on vertebral characters. Calif Div. Fish Game, Fish Bull, 79, 83 p, DEVI, C, B, L 1969. Occurrence of larvae of Pseudorhomhus elevatus Ogilby (Heterosomata— Pisces! along the south-west coa.st of India. Proc. Indian Acad. Sci. 70(Sect. Bi: 178-1 86 142 SUMIDA ET AL EARLY DEVELOPMENT OF SEVEN FLATFISHES §■1 Sri. E x: E 8 n E CSJ w o CO £ E o o o o en C\J ^^ O) E OJ r~ C71 o o OJ SI .- o A CD O >, ^ O '- Q. C\J O 3 a.S cn *:■ o >'5- o.? E Qji=>y_j c C3 i» is a> &E E . CD Q. 3J E get: jb'DC-ocotDSE'OcnQ.ccj 3 c i;S CO , ) ii o t o S % r) 4 S E CVJ o o o (N CVJ — (N 4 O) o Q. (N Q. y 0) ° n O E ' o 2 Q. "Cl i- >,S X So I E sag 6 „ = in "> y o >* a> rrsssc Ss€oE= « C C CO O CT3 A -C CJ S ^"SScDC"^ CD£5<"Q.p«,E- 2 ran a ! E c cQ (0 T3 — D C CB - o 0) m — o u) ra o ^ ™ -^ A C ™ i3 c o e E (0 . 1 (D J ^0 13 . . £ d (D 03 ■_! = i: o o c 0) £ ^ £ o -. 2^ ^ S-, "c o in c c o-m ^ a> — ^ TO 0) ^• "J E Q) J= ii o _ i ■D ro o ■D 1 >- l/i 3 ro o o g 8 O o Q. 5 o c 3 (/) c S o "O X o o o ro c ro ^ ro Q- c J3 Q. to ro 2 T3 -D O C O J£ t '^ = '^ raJ: > re s ■ So -2 ills O 0 o cn ^ — ~ Q) C -O "3 "D ■- ra Q) "" f 3 S E S g o o CD CD cn Q, g" S ^iS ? CD ^5 o i" ro D «55S 143 FISHERY BULLETIN VOL. 77, NO. 1 EHRENBAUM, E. 1905. Nordisches Plankton. Zoologischer Teil. Erster Band: Eier und larven von Fischen. 1905 p. 1-216 Lab- ridae through Pleuronectidae, 1909 p. 217-414 Gadidaeto Amphioxidae. Reprinted 1964 A. Asher and Co.. Amster- dam. ELDRIDGE. M. B. 1975. Early larvae of the diamond turbot.Hypsopsetla gut- tulata. Calif. Fish Game 61:26-34. Fierstine, H. L., K. F. Kline, .\nd G. R. G.arman. 1973. Fishes collected in Morro Bay. California between January, 1968 and December, 1970. Calif. Fish Game 59:73-88. Fitch, J. E. 1963. A review of the fishes of the genus Pleuronichthys. Los Ang. Cty. Mus. Contnb. Sci. 76, 33 p. FREV, H. W. leditori. 1971. California's livmg marme resources and their utili- zation. Calif Dep. Fish Game, 148 p Gates, D. E., and h. w. fkey. 1974. Designated common names of certain marme or- ganisms of California. Calif Dep. Fish Game, Fish Bull 161:55-90. GINSBURG, I. 1952. Flounders of the genus Paralichthys and related genera in American waters. U.S. Fish Wildl. Serv., Fish Bull. 52:267-351, GUTHERZ, E. J. 1970. Characteristics of some larval bothid flatfish, and development and distribution of larval spotfin flounder, Cyclopsetta ftmhnata (Bothidael. U.S. Fish Wildl. Serv.. Fish. Bull. 68:261-283. HOLLISTER, G. 1934. Clearing and dyeing fish for bone study. Zoologica iN.Y.) 12:89-101. Holt, E. W. L. 1893. Survey of fishing grounds, west coast of Ireland. 1890-91: on the eggs and larval and post-larval stages of teleosteans. Sci. Trans. R. Dublin Soc, Ser. 2, 5, 121 p. HUBBS. C. L. 1928. A checklist of the marine fishes of Oregon and Washington. J. Pan-Pac. Res Inst. 3(3):9-16. HUBBS, C. L., AND Y. T. CHU. 1934. Asiatic fishes iDiplopnon and Laeops) having a greatly elongated dorsal ray in very large postlar- vae. Occas. Pap. Mus. Zool., Univ. Mich. 299. 7 p. KRAMER, D., M. J. KALIN, E. G. STEVENS, J. R. THRAILKILL. AND J. R. ZWEIFEL. 1972. Collecting and processing data on fish eggs and lar- vae in the California Current region. U.S. Dep. Com- mer., NCAA Tech, Rep. NMFS CIRC. 370. 38 p. Leonard, S. B. 1971. Larvae of the fourspot flounder, Hippoglossina ob- lunga I Pisces: Bothidae), from the Chesapeake Bight, western North Atlantic. Copeia 1971:676-681. Mr.'\LLI.STER, R. 1975. California marine fish landings for 1973. Calif Dep. Fish Game, Fish Bull 163:33 MILLER, D. J.. AND R. N. LEA. 1972. Guide to the coastal marine fishes of California. Calif Dep. Fish Game, Fish Bull. 157, 235 p., 1976 adden- dum, p. 237-249 in reprint edition. Div. Agric. Sci., Univ. Calif, Sale publ. 4065, 249 p. MILLER, D.. AND R. R. MARAK. 1962. Early larval stages of the fourspot flounder, Para- lichthys ohiongus Copeia 1962:454-455 MITO, S. 1961 Pelagic fish eggs from Japanese waters — I. Clu- peina, Chanina, Stomiatina, Myct/)phida, Anguillida, Be- lonida and Syngnathida. [In Jpn., Engl, summ.j Sci. Bull. Fac. Agnc, Kyushu Univ. 18:285-310 1962. Pelagic fish eggs from Japanese waters — V. Cal- lionymina and Ophidiina, [In Jpn., Engl, summ.] Sci. Bull. Fac Agnc. Kyushu Univ 19:377-380. 1963. Pelagic fish eggs from Japanese waters — IX. Echeneida and Pleuronectida Jpn. J. Ichthyol. 11:81- 102. MOSER, H. G., AND E. H. AHLSTROM. 1970. Development of lantemfishes (family Myctophidae) in the California Current Part I. Species with narrow- eyed larvae. Bull. Los Ang. Cty. Mus. Nat. Hist. Sci. 7. 145 p. MOSER. H. G., E. H. AHLSTROM, AND E. M. SANDKNOP. 1977. Guide to the identification of scorpionfish larvae (family Scorpaenidaei in the eastern Pacific with com- j parative notes on species of Sebastes and Heticolenux from I other oceans. U.S. Dep. Commer.. NCAA Tech. Rep. ' NMFSCirc. 402, 71 p. NIELSEN, J. G. 1963. Descnption of two large unmetamorphosed flatfish- larvae (//e^erosomato), Vidensk. Medd, Dan. Naturhist. Foren Kbh. 125:401-406 Norman. J. R. 1934. A systematic monograph of the flatfishes (Hetero- somata). Vol. I: Psettodidae, Bothidae, Pleuronec- tidae. Br. Mus. (Nat. Hist.), Lond., 459 p. Okiyama, M. j 1967 Studies on the early life history of a flounder, I Paralichthys olivaceus (Temminck et Schlegel). 1. De- * scriptions of postlarvae. Bull. Jpn. Sea Reg. Fish. Res. Lab 17:1-12. OLIPHANT, M. S. 1973. California marine fish landings for 1971. Calif. Dep. Fish Game, Fish Bull. 159:32-33. ORTON, G. L. 1953. Development and migration of pigment cells in. some teleost fishes. J. Morphol. 93:69-99. ORTON, G. L., AND C. LIMBAUCH. 1953. Occurrence of an oil globule m eggs of pleuronectid flatfishes. Copeia 1953:114-115. PINKAS. L. 1974. California manne fish landings for 1972. Calif Dep. Fish Game, Fish Bull. 161:32-33. Sanzo. L. 1915. Contributo alia conoscenta dello sviluppo ncgli Scopelini Muller iSuuru.s^r/seus Lowe, C/i/orop/iMa/mus agassuii Bp. ed Aiilopus filamentosus Cuv,). R. Com. Talassogr. Ital Mem. 49, 21 p. 1931. Uova, larvae e stadi giovanih di Teleostei Sottor- dine: Stomiatoidei Fauna Flora Golfo Napoli Monogr. 3842-92 1933 Uova, larvae e »tadi giovanili di Teleostei Famiglia Macruridae Fauna Flora Golfo Napoli Monogr. 38:255-265. SMITH. W G., AND M. P FAHAY. 1970. Descriptionof eggs and larvae of the summer floun- 144 SUMIDA ET AL EARLY DEVELOPMENT OF SEVEN FLATFISHES der. Paraiichthys dentatus. U.S. Fish Wildl Serv,. Res, TOWNSEND, L. D. Rep. 75, 21 p. 1936. Variations in the meristic characters of flounders STARKS, E. C, AND W. F. THOMPSON. from the northeastern Pacific. Rep. Int. Fish. Comm. 11, 1910. A review of the flounders belonging to the genus 24 p Pleuromchthys. Proc, U.S. Natl. Mus. 38:277-287. WHITE, W F, TaKITA, T.. AND S. FUJlT.i^. 1977, Taxonomic composition, abundance, distribution, 1964. Egg development and prolarval stagesoftheturbot, and seasonality offish eggs and larvae in Newport Bay, Pleuromchthys cornutus (Temminck et Schlegeli. [In California, M, A. Thesis, California State Univ., Fuller- Jpn., Engl. summ.I Bull. Jpn. Soc. Sci. Fish. 30:613-618. ton, 107 p. 145 ASSOCIATIONS OF TUNA WITH FLOTSAM IN THE EASTERN TROPICAL PACIFIC Paul R. Greenblatt' ABSTRACT The fishing record for flotsam-associated tuna in the eastern tropical Pacific was examined. The rivers of Central America are probably the major source of flotsam. Correlation analysis ofthe number of sets occurring in an area indicates that unassociated tuna and flotsam-associated tuna are related. The number of sets made on floating objects has increased dramatically since 1971. The percentage of flotsam-associated sets has increased, indicating that flotsam-associated sets are more important to the tuna fishery than in 1963. The catch per set of tuna associated with flotsam has also increased markedly since 1967. Analysis of length-frequency data indicate that, on a single set basis, tuna fork length is more variable in sets associated with flotsam than with unassociated schoolfish sets. Results of the length-frequency analysis support the idea that flotsam aggregates tuna. The catch of the eastern tropical Pacific tuna fishery consists of mostly yellowfin tuna, Thunnus albacares, and skipjack tuna, Katsuwonus pelamis. The catch is frequently categorized by the conditions under which the purse seine set is made. Scott 1 1969) made a major distinction be- tween associated schools and unassociated schools. Associated schools are caught either in "porpoise sets" (sets associated with porpoise) or "floating object sets" (sets associated with logs or other flotsam). Unassociated schools are caught in "night sets" (sets made at night with the aid of bioluminescence) and "schoolfish sets" (schools seen and set upon during the day). Night sets compose a very small proportion of total sets and will not be discussed in this paper. Porpoise sets catch mostly yellowfin tuna. Floating object sets and schoolfish sets catch yellowfin and skipjack tuna, either as pure or mixed species. Little is known about the attraction of tuna to flotsam. Gooding and Magnuson (1967) and Hunter and Mitchell (1968) observed fish gather- ing around flotsam. These authors attracted some tuna to their flotsam, but never large schools. Tuna were a minor portion of the observed fish assemblages. Hunter and Mitchell ( 1968) postula- ted a connection between schooling behavior and the attraction of fish to flotsam. They concluded that flotsam had the function of providing (p. 27) "... a visual stimulus in an optical void." Gooding 'Southwest Fisheries Center La Jolla Laboratory, National Marine Fisheries Service. NOAA, La Jolla. Calif; present ad- dress: Code A-008, Scripps Institution of Oceanographv. Univer- sity of California, La Jolla, CA 92093. Manuscript accepted August 1978 FISHERY BULLETIN VOL. 77, NO, 1. 1979. and Magnuson ( 1 967) concluded that fish gathered around floating objects at sea primarily because the objects provided shelter from predation. It may be possible that the same factors attracting small- er fish also attract large tuna schools. This paper examines historical tuna fishery data on the catches of yellowfin and skipjack tuna associated with floating objects in the eastern tropical Pacific from 1963 to 1975. The objectives ofthe paper are to 1 ) establish the main sources of flotsam, 2) determine if there is a connection be- tween various set types, 3) see if flotsam- associated sets have become more important to the tuna fishery, 4) determine if the catch rate on flotsam-associated sets has changed, and 5) assess whether flotsam does aggregate tuna schools. METHODS Since the catch of tuna associated with flotsam depends on the presence of tuna, flotsam, fisher- men, strength of attraction, and suitable fishing conditions, I examined each factor in light ofthe published literature and available fishery data from the eastern tropical Pacific tuna fishery. The Inter- American Tropical Tuna Commission ( lATTC) collects information from tuna fishermen operating in the eastern tropical Pacific. Informa- tion collected in logbooks includes date and loca- tion of sets, catch of various species, type of set, and environmental conditions. Although these logbooks remain confidential, it is possible to ob- tain summaries of the information for certain time-area strata. During the beginning portion of 147 FISHERY BULLETIN VOL 77, NO. 1 the year, yellowfin tuna fishing is unregulated. After a quota is reached (Table 1), all yellowfin tuna fishing, except for special allowances must be outside the Commission's Yellowfin Regulatory Area (CYRA) (Figure 1). Due to special rules (see Table l. — Yellowfin quota (thousands of short and metric tonsi. closure data, and annual total catch (thousands of short and metric tons) for the Commission's Yellowfin Regulatory Area, taken from Calkins ( 1976).' Metric tons are given in parenth- eses. Quola Closure Annual Year Quota + inaement^ dale total catch 1966 79 3 ( 71 9) Sept 15 91 1 ( 82 6) 1967 84.5 ( 76 6) June 24 89 6 ( 81 3) 1968 106 0( 96 1) June 18 1146 (1039) 1969 120 0 (108 8) Apr 16 1265 (1147) 1970 1200(108 8) Mar 23 1426 (129 3) 1971 140 0(127 0) Apr 9 1139 1103 3) 1972 120 0(108 8) 140 0(127 0) Mar 5 152 5(138 3) 1973 130 0 (117 9) 1600(145 1) Mar 8 177 8 (161 3) 1974 175 0 (158 7) 195 0(176 9) Mar 18 191 3 (173 5) 1975 175 0(158 7) 1950(176 9) Mar 13 1772 (160 7) 1976 175 0(158 7) 1950(176 9) Mar 27 205 5(186 4) The 1976 fishrng year (through August . 33rd meeting of the Inter-American Tropical 'Calkins. T P 1976 30) Background Paper No Tuna Commission ^The Director ot lATTC may increment the established quota, allowing more yellowlm tuna to be caught Figure l. — Eastern tropical Pacific fishing area divided into three nearshore areas lAreas l-3i and one offshore area (Area 4). The heavy line to the west delimits the boundary' for the Com- mission Yellowfin Area (CYRA). The average number of flotsam- associated sets from 1972 to 1975 by 5" squares is shown. Data represent the unregulated fishing period isee text). Inter-American Tropical Tuna Commission 1967-1975), any detailed reporting of regulated data would compromise the confidentiality of the data; hence, only unregulated catch and number of sets within the CYRA summarized by month and 5' square for 1963-75 were made available to me. The total number of unregulated sets during the 13 yr was approximately 161,000 of which 8,190 were associated with flotsam. In addition, the lATTC provided the total number of flotsam- associated sets occurring each year ( Figure 2 ). One sees that the major trends in the number of sets are contained in the block of unregulated data. NOAA's Southwest Fisheries Center (SWFC) periodically sends technicians aboard tuna sein- ers. These technicians record details about set type, catch, environmental conditions, as well as the fork length (centimeters) of tuna sampled from individual sets. Fork lengths of yellowfin and skip- jack tuna wereonly available for a limited number of sets made in 1973-75. The location of fork length measurements are given in Table 2. Single set catch data were collected by SWFC technicians in 1974-76 (unpubl. data^). ^Unpubl. data on file at the Southwest Fisheries Center. Na- tional Marine Fisheries Service, NOAA, P.O. Box 271, La Jolla. CA 92038. 2,000 - 1963 1965 1967 1969 1971 1973 1975 YEAR Figure 2. — Total number of flotsam-associated sets made in the eastern Pacific and number of unregulated flotsam-associated sets made in the CYRA, 1963-75. 148 GREENBLATT ASSOCIATIONS OF TUNA WITH FLOTSAM Table 2. — Spatial distribution of fork length measurement ( centimeters) of yellowfin and skipjack tuna m the Commission's Yellowfin Regulator>- Area. 1973-75. C YRA subareas are shown in Figure 1. (Source of data, SWFC.) CYRA subarea Number of sets where tork lengtti was measured 1 56 2 12 3 14 4 29 Monthly rainfall in Central America was calcu- lated by averaging the stations reporting to the Environmental Data Service (U.S. Department of Commerce 1963-1975). In order to achieve the objectives of this paper, the data obtained from lATTC and SWFC were examined and analyzed in several ways. The main sources of flotsam were inferred by examining the average distribution of flotsam-associated sets and consideration of the average surface circula- tion. Two methods may be used to determine if differ- ent set types are related: correlation of set types occurring in an area and comparison of fork length distributions (length-frequency gi-aphs) stratified by species and set type. Spearman's rank correla- tion coefficient (Siegel 1956) was calculated to ex- pose possible correlations of numbers of sets. Fork length distributions were weighted by the catch in each set. A high positive correlation between set types occuring in an area would indicate a rela- tionship between set types. Similar looking length-frequency distributions would serve as further evidence that set types are related. An increase in the percentage of flotsam- associated sets would be evidence that flotsam- associated sets have become more important to the fishery. The CYRA was subdivided into three nearshore areas and one offshore area (Figure 1). Stratifying the number of flotsam-associated sets by area allows the determination of area effects. Hence, the importance of flotsam to the fishing industry may be determined by the percentage of flotsam-associated sets occurring each year and stratifying the number of flotsam-associated sets by area. Average rainfall was tabulated to determine if any connection existed between river runoff and the number of flotsam-associated sets. Catch rate is an indicator of the importance of flotsam-associated sets to the tuna fishery. Calcu- lation of the average yearly catch per set (includ- ing zero catch sets) for different set types should demonstrate any trends as well as the relative value of making one set type over another. Calkins (1965) examined tuna length distribu- tions from single sets in the eastern tropical Pacific, finding that single unassociated schoolfish sets caught tuna of a relatively uniform size (i.e., small variance in length). If the fish caught in flotsam-associated sets represent aggregations of solitary tuna, portions of schools, or several schools, then one would expect the variance of tuna length to be greater than for unassociated schools. In order to examine if floating objects act as aggregators, length-frequency data were strat- ified by species and set type. Mean length and standard deviation were calculated on a single set basis for each category and compared using Kruskal-Wallis one-way analysis of variance by ranks (Siegel 1956). If flotsam does aggregate tuna, one would expect more of the larger flotsam-associated sets than unassociated sets. Differences in catch distribu- tion were observed by plotting histograms of tons of tuna caught per set stratified by year and set type and by calculating catch per successful set for each year and set type. The single set catch data, collected by SWFC technicians, existed for the 1974-76 period. RESULTS The availability of logs or other flotsam in an area are determined by the source of the flotsam and the currents in the area. Large rivers flow into the Pacific from southern Mexico (lat. 20°N) and continue down the coast of South America (to lat. 20°S). These rivers are capable of releasing many logs into the Pacific during the rainy season. SWFC and lATTC observers reported large densi- ties of logs near the Gulf of Tehuantepec (lat. 16°N, long. 100°W), the Gulf of Nicoya (lat. lO'^N, long. 85°W), and the Gulf of Fonseca (lat. 13°N, long. 87°W). The average yearly number of flotsam- associated sets in 1972-75 were plotted by 5° squares (Figure 1). In general, most flotsam- associated sets occurred in Areas 1 and 2. Most of the offshore flotsam-associated sets (i.e., Area 4) occurred quite close to Areas 1 and 2. Area 3 did not have large numbers of flotsam-associated sets. If the main source of logs and other flotsam is the rivers of Central America, then it is important to examine the major current patterns in the eastern tropical Pacific to determine if the currents can 149 FISHERY BULLETIN: VOL 77, NO 1 explain the observed distribution of flotsam- associated sets. The average currents in the eastern tropical Pacific, as derived from ship's drift data, were de- termined by Wyrtki (1965). From January until May, the California Current is strong. Circulation near Area 3 is to the south. Circulation near Areas 1 and 2 is gyral. From May to July, both the Equatorial Countercurrent and the California Current are relatively stong. During this period, most countercurrent water turns north and flows along the coast of Central America. Area 3 has a northern and southern flow, the northern flow along the coast. Area 1 maintains its gyral flow. From August through December, the Equatorial Countercurrent is well developed. Circulation in Area 3 is to the south. Area 2 maintains its north- western flow along the coast and Area 1 flow main- tains a gyral pattern. If logs disperse mainly from the Gulf of Nicoya, the Gulf of Tehuantepec. and the Gulf of Fonseca, then the gyral circulation in Area 1 would tend to maintain logs and other flotsam in the area for a considerable time. The northwest coastal current in Area 2 could trans- port flotsam through Area 2 and during part of the year into Area 3. Since the North Equatorial and South Equatorial Currents are rather strong, one would not expect floating objects to persist in Area 4 except near the boundaries with Areas 1 and 2. Hence the location of large rivers and the system of currents is reasonably consistent with the geo- graphical distribution of flotsam-associated sets. In order to compare different set types, Spear- man's rank correlation coefficient was calculated. For each 5° square in the C YRA, the total numbers of flotsam-associated sets, porpoise-associated sets, and unassociated schoolfish sets were tabu- lated for each year. These totals were ranked and the ranks were correlated. Only 5° squares where at least 10 sets occurred were used in calculating correlations. When a minimum of 40 sets was used as the criterion for including a 5° square, the corre- lations were qualitatively the same as with the 10 sets criterion. The results (Table 3) show that a significant positive correlation exists between number of sets on unassociated schoolfish and flotsam-associated tuna. Porpoise sets were uncor- rected with other set types. The above results indicate that fish caught as- sociated with flotsam tended to be caught in the same area at the same time as unassociated school fish. Examination of available length-frequency data on a species basis, weighted by the catch in T.^BLE 3. — Spearmans rank correlation between three types of sets by year. Number of sets/5° square. (Source of data: I ATTC . ) Year N Unassociated schoollisri and porpoise- associated Unassociated schoolfish and flotsam^ associated Porpoise and flotsam- associated 1963 29 -0,0008 0 5421" 0 2538 1964 27 0 0375 0 1581 08138-- 1965 25 ■0 1597 0 3498' 0 1318 1966 28 ■01110 03513- 02914 1967 24 ■92379 0 4621- ■0,2255 1968 24 ■0 1951 0 1886 03463- 1969 25 -0 1523 05957-- 02294 1970 27 ■0 0088 03529- ■00173 1971 26 0 0803 0 5819" 0,2398 1972 32 ■0 0200 05277-- ■00558 1973 34 0 0523 0 3086- 0,1796 1974 27 0-0168 04847" 0,0001 1975 33 02444 0,5139" 00526 •Si. "Si gnificant at Ps gnrticant at Ps 0 05 ;0 01 each set (Figure 3), indicated that unassociated schoolfish and flotsam-associated yellowfin and skipjack tuna had very similar length-frequency distributions. The length-frequency information and the correlation analysis support the idea that unassociated tuna and flotsam-associated tuna are related. Flotsam, acting as an attractant, may aggi-egate tuna that would otherwise be caught in unassociated sets. The number of flotsam-associated sets has in- creased dramatically since 1971 (Figure 2). The trend in percentage of flotsam-associated sets (Fig- ure 4) indicates that flotsam-associated sets have increased in importance to the fishery. Stratifying the number of unregulated flotsam-associated sets by area (Figure 5i shows that the trend of more flotsam-associated sets is not an area effect. All areas, except Area 3, have shown a marked in- crease in number of flotsam-associated sets. Area 3 does not show an increase because logs are only deposited in this region during a limited portion of the year. In January-May, the near surface cur- rent in Area 3 is to the south (Wyrtki 1965), cut- ting off the source of logs that wash down the rivers of Central America. Also, good fishing often occurs in Area 3 during the later months of the year, a period not included in my unregulated data. It appears that the increase in flotsam- associated sets in recent years was not caused by discovery of new areas with abundant flotsam but rather by an increase in fishing effort on flotsam in all areas but Area 3. Average rainfall in Central America was tabu- lated (Table 4) to see if there was a correlation between river runoff and the number of flotsam- associated sets. Comparison of number of flotsam-associated sets and rainfall revealed only 150 GKEENBLATT ASSOCIATIONS OF TUNA WITH FLOTSAM SKIPJACK SCHOOLFISH SKIPJACK ASSOCIATED WITH FLOTSAM 30 *0 50 60 'G 80 90 100 ilO l£0 tJO 30 40 50 60 '0 80 9C' lOO mO 20r Figure 3— Length-frequency distribu- tions of yellowfin and skipjack tuna caught in unassociated schoolfish and flotsam-associated sets Data collected 1973-75 in the CYRA (see Table 2). YELLOWFIN SCHOOLFISH I I I I I I 'I FORK LENGTH (cm) YELLOWFIN ASSOCIATED WITH FLOTSAM 20 1- TABLE 4. — Average yearly rainfall (centimeters) in Central America in 1963-75, (Source; U.S. Department of Commerce.) 1963 64 65 66 67 68 69 70 71 72 73 74 75 YEAR Figure 4. — Percentage of total unregulated sets that were as- sociated with flotsam in the CYRA. 1963-75. small similarities, indicating that the supply of suitable flotsam was not greatly influenced by rainfall. Comparing the average catch per set of different set types indicates the relative importance of each set type to the fishery as well as showing trends in the catch rate (Figure 6). All set types had similar catch rates in 1963-66. Porpoise sets and flotsam- associated sets gave much higher catch per set than unassociated sets in 1971-75. One sees that flotsam-associated sets have been the most valu- able set type for the tuna fisherman since 1971. Average yearly Average yearly Year rainfall Year rainfall 1963 139 0 1970 163 8 1964 136,4 1971 145-5 1965 136 9 1972 145-6 1966 158,5 1973 161 4 1967 151,7 1974 172 3 1968 177J 1975 151 0 1969 177 2 Fork length data was stratified by set type and species. The mean length, standard deviation, and sample size were calculated on a single set basis (Table 5). The average standard deviation of fork length of yellowfin and skipjack tuna associated with flotsam was larger than the standard devia- tion found in unassociated sets, though the mean fork length of flotsam-associated sets was smaller. The probability of getting the results shown (Ta- ble 5) by chance was calculated using Kruskal- Wallis one-way analysis of variance (Siegel 1956: 184) (Table 5 1. The greater variability of fork length of flotsam-associated tuna supports the hypothesis that flotsam aggregates tuna. The yellowfin and skipjack tuna catch distribu- tion on flotsam-associated sets was compared with unassociated schoolfish sets. The average catch per successful set was calculated and the data were plotted as histograms of tonnages using an arbitrary interval of 5 tons (Figure 7). The main 151 FISHERY BULLETIN VOL 77. NO, 1 Figure 5— Number of unregulated flotsam-associated sets per month by area. 1963-75. of;^,Ayv.,-,/, ^l\ A A -iOO FLOTSftM ASSOCIATED U-- 265 CPSS = 24 07 {21 63) 1975 UNflSSOCIATEO SCHOOLFISH CPSS = 16 07 (14 5B) I hi n n r 1975 FLOTSAM ASSOCIATED N^20e CPSS = 27 30 124 76) njfrh-rw. 1976 UNASSOCIATED SCHOOLFISH N = 98l CPSS = 21 21 (19 24) 0 25 50 75 >I00 0 \m. _a — q 1 SHORT TONS 1976 FLOTSAM ASSOCtATED N= 550 CPSS = 26 04 (23 621 1 1 1 nhp-ii-n r 25 50 7l> SHORT TONS 153 FISHERY BULLETIN VOL 77. NO. 1 CYRA. Although they had small numbers of sets, the percentage of successful flotsam-associated sets from 1962 to 1966 was 67.6'*. Changes in percentage of successful sets can not adequately explain the increased catch per set. No satisfactory explanation for the increase in catch per flotsam-associated set has been found. Overall increases in abundance or increased skill of the fishermen can not explain the increase. The above factors may account for some of the increase. Technological advances may account for the in- creased catch rate. It is also reasonable to believe that fishermen have learned to catch flotsam- associated tuna more efficiently and the residence time of tuna with flotsam has increased since 1967. Changes in catch per set on flotsam-associated sets may have been due to technological advances such as bigger nets. If technological advances can explain the increased catch per set on flotsam, then either the catch per set on unassociated schoolfish should have also increased or sets as- sociated with flotsam prior to the technological advances must have caught a low proportion of potential catch. Nets have increased in size, perhaps increasing the probability of catching yel- lowfin and skipjack tuna which may aggregate around flotsam. It is possible that bigger nets could account for increased catch/set of flotsam- associated sets without likewise affecting catch/ set on unassociated schoolfish sets. Fishermen often will drift with logs for consid- erable time, waiting for tuna aggregations to reach an optimal size before setting the net. The spread of such behavior throughout the fleet could cause the overall catch per set of flotsam- associated tuna to increase. Adequate data for testing this "increased knowledge" hypothesis was unavailable. The marked changes occurring in flotsam- associated tuna catch in 1963-75 coincided with a large increase of effort and technology in the porpoise-associated fishery (Green et al. 1971). It is hypothesized that the increased effort and technology in the porpoise-associated fishery may have been related to changes in the catch rate of tuna schools associated with flotsam. When purse seiners set on porpoise, there is often an incidental kill of the marine mammals. Due to recent technological advances, the porpoise kill has been reduced, but in earlier years of the porpoise-associated fishery (the mid-1960's) por- poise mortality was higher (Southwest Fisheries Center^'). This incidental kill may have reduced the porpoise population. The porpoise-associated fishery first developed near shore and thus the nearshore porpoise stocks have been affected for a longer time than offshore stocks. One may reason- ably speculate that, on a species basis, nearshore porpoise stocks have been affected more by inci- dental kills than offshore porpoise stocks. The bond between tuna and porpoise is not un- derstood. It is possible that the mechanisms in- volved in the association of tuna with porpoise is similar to those responsible for their association with flotsam. Tuna associated with flotsam are, on the average, smaller than tuna associated with porpoise (Calkins 1965, tables 2 and 9; Sharp''). Knudsen (1977) gave some evidence that tuna caught in areas where porpoise fishing predomi- nates were generally older and larger than in tra- ditional schoolfish areas. Size overlap, however, did occur (Calkins 1965). Assuming that the number of porpoise schools have declined, the probability of tuna encountering porpoise schools has decreased. The probability of tuna aggregated near flotsam encountering porpoise schools has also decreased. Thus, as a result of decreased en- counter rates with porpoise (slower transition from flotsam to porpoise), the size of the aggrega- tions of tuna near flotsam have increased. In conclusion, the most likely sources of flotsam are the large rivers of Central America. Indirect evidence indicates that tuna caught in unas- sociated schoolfish sets are from the same popula- tion as tuna caught associated with flotsam. It appears that the increase of flotsam-associated sets from 1963 to 1975 was due to an increased interest by fishermen and hence an increased fishing effort on floating objects. The observed in- crease in catch per set may have been a biological change rather than a change in fishing technology or skill. ACKNOWLEDGMENTS I would like to express my thanks to John Hunter who provided guidance in several phases of this study. His comments were extremely help- "Southwest Fisheries Center. 1976. Report of the Work- shop on Stock Assessment of Porpoises Involved in the Eastern Tropical Pacific Yellowfin Tuna Fishery. SWFC Adm Rep, LJ-76-29, 54 p. Southwest Fisheries Center. La Jolla, CA 92038. "G. Sharp, Inter-American Tropical Tuna Commission. Southwest Fisheries Center. La Jolla, CA 92038, pers. commun April 1977. 154 GREENBLATT ASSOCIATIONS OF TLINA WITH FLOTSAM ful. Richard McNeely first suggested the possible interaction of porpoise and flotsam-associated tuna. The Inter-American Tropical Tuna Com- mission provided much of the data. William Flerx and Richard Charter provided insight into the op- eration of the fishery. Gary Sharp provided useful information about yellowfin tuna. Rainfall data were obtained from Eric Forsbergh. William Lenarz, Douglas Chapman, and Robin Allen re- viewed the paper and offered constructive com- ments. LITERATURE CITED Bayliff, W. H., and C. J. Orange. 1967. Observations on the purse seine fishery for tropical tunas in the eastern Pacific Ocean. Inter-Am. Trop. Tuna Comm., Intern. Rep. 4, 79 p. Calkins, T. P. 1965. Variation in size of yellowfin tuna iThunnus alba- cares) within individual purse-seine sets. [In Engl, and Span.) Inter-Am, Trop, Tuna Comm., Bull. 10:461-524. GOODING. R. M., AND J. J. MAGNUSON. 1967. Ecological significance of a drifting object to pelagic fishes. Pac. Sci. 21:486-497. Green. R. E., W. F, Perrin, and B, P, Petrich, 1971. The American tuna purse seine fishery. In H. Kristjonsson (editor), Modern fishing gear of the world. Vol. 3. p, 182-194, Fishing News (Books) Ltd.. Lond, GREENBLATT, P, R, 1977. Factors affecting tuna purse seine fishing ef- fort, ICCATRep.Vol. VI(SCRS-1976). No, 1 ■ Tropical spp,. p, 18-31. Hunter, J. R., and C. T. Mitchell, 1968. Association of fishes with flotsam in the offshore waters of Central America. U.S. Fish Wildl, Serv, Fish. Bull. 66:13-29. Inter-American Tropical Tuna Commission. 1967-1976. Annual Report, 1966-1975. Inter-Am. Trop. Tuna Comm., La Jolla, Calif KNunsEN. P. F. 1977. Spawning of yellowfin tuna and the discrimination of subpopulations, [In Engl, and Span.[ Inter-Am, Trop, Tuna Comm,, Bull, 17:117-169. PELLA, J. J., AND C. T. PSAROPULOS. 1975. Measures of tuna abundance from purse-seine oper- ations m the eastern Pacific Ocean, adjusted for fieet-wide evolution of increased fishing power, 1960-1971, [In Engl, and Span.] Inter-Am. Trop. Tuna Comm.. Bull, 16:281- 400, SCOTT, J, M, 1969, Tuna schooling terminology Calif Fish Game 55:136-140, SlEGEL, S. 1956. Nonparametric statistics for the behavioral sciences. McGraw-Hill Book Co,. N,Y , 312 p. U.S. DEPARTME.NT OF COMMERCE. 1963-1975. Monthly climatic data for the world, NOAA, Environ, Data Serv,, vol, 16-28, var, pagination, WYRTKI, K, 1965, Surface currents of the Eastern Tropical Pacific Ocean, [In Engl, and Span] Inter-Am Trop, Tuna Comm., Bull. 9:269-304. 155 DESCRIPTION OF LARVAE OF THE NORTHERN SHRIMP, PANDALUS BOREALIS, REARED IN SITU IN KACHEMAK BAY. ALASKA Evan Haynes' ABSTRACT Northern shrimp. Panda! us borealis. were reared in situ in Kachemak Bay. Alaska, from Stage I (first zoeali through Stage VIII (second juvenile). Each of the six larval stages and first juvenile stage is described and illustrated, and a bnef description is given for the second juvenile stage. Apparently larvae of P borealis in Alaska waters have at least one less stage than larvae of P. borealis in either British Columbia. Greenland, or Japan waters. Of the known larvae of the North Pacific Ocean, larvae of P- borealis are most similar morphologically to larvae of P goniurus but are separable from them by being slightly larger in size and, in zoeal Stages I-III, by bearing more setae on certain appendages, particularly the antennal scale and certain mouth parts. From Stage IV to megalopa, the rostrum of P. borealis has more dorsal teeth, the second pereopods are more developed, and the pleopods are fringed with more setae than for larvae ofP, goniurus -The criterion of the lack of an outer seta on the maxillule for distinguishing zoeae oi Pandalus from certain other Candea is shown to be invalid In 1972 the National Marine Fisheries Service began studies on the early life history of pandalid shrimp in Alaska waters with the initial objective of describing in detail laboratory-reared larvae of each pandalid species previously unverified. Two previous reports have described larvae of Pan- dalus hypsinotus Brandt reared in the laboratory (Haynes 1976) and P. goniurus Stimpson reared in situ in Kachemak Bay, Alaska (Haynes 1978). This report describes and illustrates each of the six larval stages and the first juvenile stage of north- ern shrimp, P. borealis KrOyer, and compares the stages obtained from rearing in situ with descrip- tions of pandalid shrimp larvae given by other authors. A brief description of the second juvenile stage is included. MATERIALS AND METHODS Rearing techniques were identical in all re- spects to those described in an earlier report on P. goniurus (Haynes 1978). Briefly, the technique consists of obtaining Stage I larvae of known parentage in the laboratory, then rearing the lar- vae in flasks submerged at sea. Larvae from plankton were also reared in flasks at sea in an identical manner beginning with Stage I. Larvae reared in flasks were compared with larvae from 'Northwest and Alaska Fisheries Center Auke Bay Laborato- ry. National Marine Fisheries Service, NOAA, P.O. Box 155, Auke Bay. AK 99821. plankton for verification of sequence of stage and larval morphology. Because the paired appendages of the larvae are symmetrical, only one member (the left) is figured. An exception is the mandibles which are drawn in pairs. Orientation of surface of appendages in the figures is given in the figure legends. The figures of the appendages are in part schematic and repre- sent typical setal counts. Variability in setation or segmentation of paired appendages, such as the difference in number of carpal joints between the left and right second pereopods in the megalopa, is mentioned in the text. Carapace length refers to the straight-line distance from posterior margin of orbit to middorsal posterior margin of carapace. Total body length refers to the distance from tip of rostrum to posterior margin of telson, not includ- ing telson spines. Terminology, methods of measuring, techniques of illustration, and nomenclature of gills and appendages follow Haynes (1976). Comparison of larvae from plankton with cast skins from flasks was facili- tated by first clearing the larvae in W7c KOH. For clarity, setules on setae are usually omitted but spinulose setae are snown. STAGE I ZOEA Mean total length of Stage I (Figure lA) 6.7 mm (range 6.5-7.3 mm; 25 specimens). Live specimens characterized by orange color; conspicuous chromatophores throughout cephalothorax re- Manuscript accepted July 1978 FISHERY BULLETIN VOL 77. NO 1.1979 157 FISHERY BULLETIN VOL 77, NO 1 gion, especially in mouth parts; large chromatophore near tip of antennal scale, at base of telson, and at front of eye; smaller but distinct chromatophores on maxillipeds; ventral surface of each abdominal somite tinged orange; faint greenish hue at base of pereopods. Rostrum slen- der, spiniform, without teeth, about one-third length of carapace, projecting horizontally or slightly downward. Carapace with small, some- what angular dorsal prominence at base of ros- trum and smaller, rounded prominence near pos- terior edge. These two prominences occur in all zoeal stages. Pterygostomian spines present but usually hidden by sessile eyes. Three or four mi- 0. 5 mm Left Right 0. 25 mm 158 HAYNES DESCRIPTION OF PA.MDAI.i'S ROREALIS LARVAE nute spinules along ventral margin of carapace immediately posterior to pterygostomian spine I spinules not shown in Figure lA). These spinules usually occur in all zoeal stages but may vary in number from two to five not only between stages but among individuals within a given stage. ANTENNULE (Figure IB).— First antenna, or antennule, consists of simple unsegmented tubu- lar basal portion with heavily plumose seta termi- nally and distal conical projection with four aesthetascs: one long, one short, and two of inter- mediate length. 0.25 mm 0 . 5 mm 0. 5 mm K 0. 5 mm Figure l. — Stage I zoea ofPandalus horealis: A, whole animal, right side; B. antennule, dorsal; C, antenna, ventral; D, mandibles (left and right), posterior; E, maxillule. ventral; F, maxilla, dorsal; G, first maxiUiped, lateral; H, second maxilliped, lateral; 1, third maxilliped, lateral; J, second pereopod, lateral; K, telson, dorsal. 159 FISHERY BULLETIN VOL 77. NO 1 ANTENNA (Figure IC).— Second antenna, or antenna, consists of inner flagellum (endopodite) and outer antennal scale (exopodite). Flagellum unsegmented, slightly shorter than scale, styliform, and tipped by spinulose spine. Antennal scale distally divided into six joints (the two prox- imal joints incomplete) and fringed with 19 heav- ily plumose setae along terminal and inner mar- gins; small seta occurs on outer margin at base of joints and another proximally near outer margin. Protopodite bears spinous seta at base of flagellum but no spine at base of scale. MANDIBLES (Figure ID).— Without palps in this and all succeeding zoeal stages. Incisor pro- cess of left mandible bears four teeth in contrast to triserrate incisor process of right mandible. Left mandible bears movable premolar denticle (lacinia mobilis) whereas right mandible bears two immobile premolar denticles. Truncated molar process of left mandible bears subterminal tooth that occurs throughout all zoeal stages. MAXILLULE (Figure IE).— First maxilla, or maxillule, bears coxal and basial endites and en- dopodite. Coxopodite (proximal lobe) bears stout seta near base, and eight spinulose spines termi- nally. Basipodite (median lobe) bears nine spinulose spines on terminal margin and large setose seta proximally. Endopodite originates from lateral margin of basipodite; bears three terminal and two subterminal setae, three of them sparsely plumose and remaining two spinulose. MAXILLA (Figure IF). — Second maxilla, or maxilla, bears platelike exopodite (scaphog- nathite) with 11 long, evenly spaced plumose setae along outer margin and one slightly longer and thicker seta at the slightly expanded proximal end. Endopodite gives indication of four partly fused segments and bears nine large plumose setae. Coxopodite and basipodite bilobed. Coxopo- dite bears 21 setae, 4 on distal lobe and 17 on proximal lobe. Basipodite bears eight setae on each lobe. Five setae, three on coxopodite (one on distal lobe and two on proximal lobe) and two on distal lobe of basipodite, bear row of little spines along entire length. An additional seta on proxi- mal lobe of coxopodite is especially spinulose. FIRST MAXILLIPED ( Figure IG i.— Most heav- ily setose of natatory appendages. Protopodite fully segmented; bears 7 setae on proximal seg- ment and 18 slightly smaller setae on distal seg- ment, 9 of them spinulose. Endopodite distinctly four-segmented; setation formula 4, 2, 1, 4. Exopo- dite a longer slender ramus segmented at base; bears two terminal and three or four lateral nata- tory setae. Epipodite a single lobe. SECOND MAXILLIPED (Figure IH).- Protopodite bisegmented; distal segment bears 10 sparsely plumose setae, no setae evident on prox- imal segment. Endopodite distinctly five- segmented, fourth segment expanded laterally; setation formula 7, 3, 1, 2, 4. A seta on segments 1 and 5 of endopodite and three setae on protopodite especially spinulose. Exopodite with 2 terminal and 11 or 12 lateral natatory setae. No epipodite. THIRD MAXILLIPED (Figure ID.— Protopodite bisegmented; distal segment bears four setae. Endopodite distinctly five-segmented; nearly as long as exopodite; setation formula 4, .5, 1, 1,2. Exopodite with 2 terminal and 14 lateral natatory setae. No epipodite. PEREOPODS— Poorly developed, directed under body somewhat anteriorly (Figure lA). First three pairs biramous (second pereopod shown in Figure IJ ), last two pairs uniramous and slightly smaller than pairs 1-3. PLEOPODS.— Absent. TELSON (Figure IK).— Not segmented from sixth abdominal somite; slightly emarginate pos- teriorly; bears 1 + 1 densely plumose setae. Fourth pair of setae longest, about one-half width of tel- son. Minute spinules at base of each seta. Larger spinules along terminal margin between bases of four inner pairs and on setae themselves but rarely on seventh pair. Uropods visible and en- closed. No anal spine. STAGE II ZOEA Mean total length of Stage II (Figure 2 A) 7. .5 mm irange 6.7-8.2 mm; 25 specimens). Chromatophore color and pattern essentially identical to Stage I. except chromatophores larger and color more pronounced, especially in mouth parts. Rostrum still without teeth and not curved downward as sometimes in Stage I. Carapace with prominent supraorbital spine and clearly visible antennal and pterygostomian spines. These three 160 HAYNES: DESCEUPTION OF PANDALUS BOREALIS LARVAE spines persist through all remaining zoeal stages Epipodite of first maxilliped slightly larger than in Stage I but still not bilobed; pleurobranchiae present as primordial buds. ANTENNULE (Figure 2B).— Three-segmen- ted; bears large outer and smaller inner flagellum on terminal margin. Flagella not segmented. Inner flagellum conical, bears one long spine ter- minally. Outer flagellum bears two groups of aes- thetascs: one group terminally consisting of eight aesthetascs, two of them larger than remaining six, and a pair of aesthetascs on inner margin. A small budlike projection (not shown in Figure 2Bi 0.25 mm Figure 2. — Stage II zoea ofPandalus borealis A, whole animal right side; B, antennule. ventral; C. antenna, ventral; D, mandibles (left and right), posterior; E. maxillule. ventral: F, maxilla (exopodite and endopodite), dorsal. 161 FISHERY BULLETIN: VOL. 77, NO. 1 0. 5 mm Figure 2. — Stage II zoea ofPandalus borealis: G, first pereopod, lateral; H, second pereopod, lateral; I. third pereopod. lateral; J, fourth pereopod, lateral; K, fifth pereopod, lateral; L, telson, dorsal. originates at base of flagella and bears five simple setae. Proximal segment of antennule usually bears five setae laterally near slightly expanded base, three plumose setae laterally and distally, about nine dorsally curving but smaller plumose setae around distal joint, and large spine project- ing slightly downward from ventral surface. Second segment bears two plumose setae later- ally and about six dorsally curving plumose setae around distal joint. Third segment bears seven plumose setae laterally, about four of them originating ventrally, and three simple setae laterally at base of outer fla- gellum. 162 HAYNES DESCRIPTION OF PANDALUS BOREALIS LARVAP; ANTENNA (Figure 2C).— Flagellum two- segmented, still shorter than scale, styliform, and tipped by two small simple setae and short spine. Antennal scale fringed with 25 or 26 long, thin, plumose setae along terminal and inner margins; still has six joints distally but only the three most distal joints complete. Protopodite bears minute spine at base of scale in addition to conspicuous spine at base of flagellum. MANDIBLES (Figure 2Dl.— More massive than in Stage I. Incisor processes of both mandi- bles bear additional tooth. Both mandibles bear additional denticles and molar processes more de- veloped. Lacinia mobilis of left mandible consists of single spinous denticle. Curved lip of trun- cated end of molar process of right mandible more developed than in Stage I. MAXILLULE (Figure 2E).— Coxopodite bears 12-15 spines and row of fine hairs proximally; spinules on two of the terminal spines of coxopo- dite resemble a row of teeth. Basipodite and en- dopodite essentially unchanged from Stage I, ex- cept basipodite bears two additional spinulose spines. MAXILLA (Figure 2F, exopodite and endopodite). — Exopodite similar in shape to Stage I except more distinctly expanded proximally; bears 17-19 marginal plumose setae in addition to plumose seta at proximal end. Endopodite un- changed from Stage I. Coxopodite bears 3 setae on distal lobe and 17-19 on proximal lobe. Each lobe of basipodite bears additional seta. MAXILLIPEDS.— Essentially identical to Stage I but bear additional setae as follows. On first maxilliped, protopodite bears 8-10 setae on proximal segment and 19-21 on distal segment; endopodite bears 4, rarely 5, setae on proximal segment; exopodite bears 7 or 8 natatory setae rather than 5 or 6 as in Stage I; no change in epipodite. On second maxilliped, protopodite bears seta on proximal segment and 8-10 setae on distal segment; exopodite bears 14 lateral natatory setae in addition to the 2 terminal setae. On third maxil- liped, endopodite bears additional seta terminally on dactylopodite, 2 additional setae on propodite, and additional seta on carpopodite, setation for- mula 5, 7, 3, 1, 2; exopodite bears 16 lateral nata- tory setae in addition to 2 terminal setae. No gill buds on second or third maxillipeds. FIRST PEREOPOD (Figure 2G).— Protopodite bears three setae. Endopodite functionally de- veloped; five-segmented, terminating in simple conical dactylopodite; setation formula 5, 3, 2. 2, 2. Exopodite, longest among pereopods, bears 2 ter- minal and 14 lateral natatory setae. SECOND PEREOPOD (Figure 2H),— Protopodite bears two setae. Endopodite similar to first pereopod except shorter; setation formula 4, 3, 1, 1, 2. Exopodite bears 2 terminal and 13 or 14 lateral natatory setae. THIRD PEREOPOD (Figure 21).— Protopodite bears two setae. Endopodite one-fourth to one- third longer than exopodite; dactylopodite slightly longer than in first two pereopods; setation for- mula 3, 4, 2, 1, 2. Exopodite noticeably shorter than exopodites of first and second pereopods and bears 2 terminal and 9 or 10 lateral natatory setae. FOURTH PEREOPOD (Figure 2J).— Endopodite five-segmented but still poorly de- veloped and directed under body somewhat an- teriorly as in Stage I (Figure 2A); dactylopodite and propodite bear two setae and three setae, re- spectively. No exopodite. FIFTH PEREOPOD (Figure 2K).— Similar to fourth pereopod but shorter and dactylopodite tipped with single seta. No exopodite. PLEOPODS (Figure 2A).— Present as distinct buds. TELSON (Figure 2L).— Similar in shape to Stage I but distinctly jointed from sixth abdominal somite; bears 8 4-8 densely plumose setae. Uropods still enclosed. Anal spine present but mi- nute. STAGE III ZOEA Mean total length of Stage III 9.5 mm (range 9.0-10.0 mm; 10 specimens). From this stage on, zoeae gradually become more orange and color pattern not useful in identifying a given stage. Rostrum (Figure 3A) projects horizontally but curves slightly downward at tip; bears one or two teeth at base. Epipodite of first maxilliped bilobed; pleurobranchiae present as small buds. ANTENNULE (Figure 3B, inner and outer 163 FISHERY BULLETIN: VOL, 77, NO 1 flagella). — Flagella not segmented. Inner flagel- lum about one-half length of outer flagellum, bear- ing stiff seta at base of terminal spine. Outer flagellum bears four long and two shorter aes- thetascs terminally and two groups of three aes- thetascs each proximally. ANTENNA (Figure 3C).— Flagellum eight- segmented, about equal in length to scale, tipped by three short setae and remnant of terminal spine. Antennal scale narrower than in Stage II and fringed with about 30 plumose setae; two complete joints at tip. Spine on protopodite at base of scale considerably larger than in Stage II. MAXILLIPEDS.— Change in form and setation of maxillipeds from Stage III on is slight and con- sists primarily of second maxilliped becoming 0. 5 mm 0. 5 mm 164 HAYNES: DESCRIPTION OF PANDALUS BOREALIS LARVAE curved as in adult and its propodite slightly vi-id- ened, third maxilliped becoming shaped as in adult, and natatory setae on exopodites of second and third maxillipeds increasing in number to usually 20 in Stage V. FIRST PEREOPOD ( Figure 3D ).— Has begun to acquire adult shape, particularly in widened pro- podite and carpopodite segments. SECOND PEREOPOD (Figure 3E i.— Similar to Stage II except distal joint of propodite projects slightly anteriorly. THIRD, FOURTH (Figure 3F), AND FIFTH PEREOPODS.— Endopodites similar; like first pereopod have begun to acquire adult shape, espe- cially in lengthened dactylopodite and widened propodite. Ischiopodite articulates somewhat lat- erally with meropodite. PLEOPODS (Figure 3G, second pleopod).— Bilobed, unsegmented. and without setae. TELSON (Figure 3H).— Endopodite not fully developed; about one-third length of exopodite and bearing several setae along lateral and posterior margms. Uropods free. Anal spine clearly visible. 0. 5 mm Figure 3. — Stage III zoea of Pandal us borealis: A, whole ammal, right side; B. antennule i inner and outer flagella). ventral; C, antenna, ventral; D. first pereopod. lateral. E. second pereopod, lateral; F. fourth pereopod, lateral; G. second abdominal somite and pleopod, right side; H, telson, dorsal. 165 FISHEKY BULLETIN: VOL 77. NO. 1 STAGE IV ZOEA Mean total length of Stage IV 13.0 mm (range 12.6-13.2 mm; 10 specimens). Rostrum (Figure 4A) bears four to eight but usually six teeth dor- sally, no teeth ventrally; tip not bifid. No change in epipodite of first maxiliiped or pleurobranchiae except slight increase in size. Epipodite on second maxiliiped present as small bud. No mastigobran- chiae. ANTENNULE (Figure 4B, inner and outer 0. 5 mm 0. 5 mm 0. 5 mm 0. 5 mm FK;l;ke 4. — Stage IV zoea nf Pandalus bumaUs: A, rostrum, right side; B. antennule (inner and outer flagella), ventral; C. antenna, ventral; D, first pereopod i distal segments only), lateral; E, second pereopod (distal segments only), lateral; F, second abdominal somite and pleopod, nght side; G, telson. dorsal. 166 HAYNES DESCRIPTION OF PA.VD.AZ.C.S BOREALIS LARVAE flagellai. — Flagella two-segmented. Inner flagel- lum nearly as long as outer flagellum. Outer flagellum bears four aesthetascs and two spines terminally and three groups of three aesthetascs each on proximal segment. ANTENNA (Figure 4C ). — Flagellum 15- segmented; 1.5-2 times length of scale, extending past tips of plumose setae fringing antennal scale. Antennal scale without joints at tip. Other than increase in size, changes in antennal scale from Stage IV onward are negligible. FIRST PEREOPOD (Figure 4D).— Distal joint of propodite projected anteriorly and tipped with small spine. SECOND PEREOPOD (Figure 4E).— Distal joint of propodite projected anteriorly to about one-half length of dactylopodite; projection tipped by two spines, one terminal and other subterminal and much shorter. Dactylopodite bears one termi- nal spine and two considerably shorter subtermi- nal spines. PLEOPODS (Figure 4F, second pleopod).— Segmented; length of second pair of pleopods about one-half height of second abdominal somite. Exopodite usually bears one to four small setae terminally and endopodite sometimes bears single seta terminally. Appendices internae not present. TELSON (Figure 4Gi.— Endopodite of uropod about two-thirds length of exopodite and fringed with about 20 setae. Lateral margins of telson nearly parallel but slightly divergent posteriorly and bear two spines each. Posterior margin still slightly emarginate; bears 6 -(- 6 spines, the out- ermost (sixth) pair usually without spinules. STAGE V ZOEA Mean total length of Stage V 16.0 mm (range 15.2-17.1 mm; 10 specimens). Rostrum (Figure 5A) with 9-12 dorsal teeth, bifid tip, and usually 4. but sometimes 5, partially developed ventral teeth. Pleurobranchiae curve somewhat anteriorly and edges minutely lobulate. Mastigobranchiae occur as minute buds on protopodite of third maxilliped and pereopods 1-4. ANTENNULE (Figure 5B, flagella only).— Inner flagellum four-segmented. Outer flagellum four- or five-segmented; bears six groups of three aesthetascs each. Each segment bears at least one seta but number and location of setae somewhat variable. ANTENNA (Figure 5C).— Flagellum 2-3 times length of scale. FIRST PEREOPOD (Figure 5D, distal segments only). — Projection of propodite at least one-half length of dactylopodite; bears two small spines, one terminally and one subterminally. Dactylopo- dite bears small spine subterminally in addition to terminal spine. SECOND PEREOPOD (Figure 5E, distal seg- ments onlyl. — Chela well formed. Terminal spine of propodite shorter and stouter than in Stage IV. Dactylopodite bears five spines, the distal two especially stout. Carpopodite usually at least par- tially segmented. PLEOPODS (Figure 5F, second pleopod).— Second pair of pleopods about equal in length to height of second abdominal somite; outer flagel- lum fringed with 11 or 12 plumose setae, inner flagellum with about 8 setae. Appendices internae usually present on pleopods 2-5; tips sometimes bear a few cincinnuli. TELSON (Figure 5G). — Lateral margins of tel- son essentially parallel and bear two spines each. Posterior margin straight or slightly emarginate, bearing 6 + 6 spines. Uropods similar in shape to adult; no evidence of transverse hinge of exopo- dite. STAGE VI (MEGALOPA) Mean total length of Stage VI 18.5 mm (range 17.4-20.2 mm, 5 specimens). Rostrum (Figure 6A) shaped as in adult; bears 13-15 dorsal teeth in addition to distinct bifid tip, and 6 or 7 distinct ventral teeth. Usually one or two setae between dorsal teeth. Carapace lacks supraorbital spine. Exopodites on maxillipeds and pereopods 1-3 re- duced. Pleurobranchiae and mastigobranchiae shaped as in adult. Inner and outer flagella of antennule eight- to nine-segmented and five- segmented, respectively. Flagellum of antenna about 6 times length of antennal scale. Mandibles still without palps. Chaelae of first and second pereopods shaped as in adult; carpal joints of left 167 FISHERY BULLETIN: VOL 77. NO 1 0. 5 mm Figure 5. — Stage V zoea of Pandal us borealis: A, rostrum, right side; B.antennulelflagellaonlyl, ventral; C, antenna, ventral; D, first pereopod (distal segments only), dorsal; E, second pereopod idistal segments onlyi, dorsal; F. second abdominal somite and pleopod. right side; G. telson, dorsal. and right second pereopods 20-25 and 10-13, re- spectively. Pleopodal setae extend along entire lateral margins of both flagella; tips of appendices internae bear several distinct cineinnuli. Length of second pair of pereopods, excluding setae, 1.5-2 times height of second abdominal segment. Telson (Figure 6B) shows, for first time, shape and spina- 168 tion similar to adult; lateral margins converge posteriorly but widen slightly at junction with posterior margin; typically four spines on each lateral margin but in this stage and Stages VII and VIII one lateral spine often lacking. Posterior margin of telson rounded but not as much as in Stage VII; bears 3 + 3 stout spines and sometimes HAYNES DESCRIPTION OF PA.WDALUS BOREALIS LARVAE u J 0 . 5 mm Figure 6. — Stage VI imegalopal of Pandalus bnrealis: A. ros- trum, right side; B. t«lson. dorsal. remnants of a spine or two from Stage V. Trans- verse hinge of exopodite of uropod complete. STAGES VII AND VIII (JUVENILES) Mean total length of Stage VII (first juvenile) 18.4 mm (range 15.1-21.0 mm; 5 specimens). Usu- ally two setae between most rostral teeth. Carapace without supraorbital spine. Arthro- branchiae on third maxilliped and pereopods 1-4 present as minute buds. Mandibular palp present for first time; three-segmented. Inner and outer flagella of antennule each 11- to 13-segmented. Exopodites on maxillipeds and pereopods 1-3 rem- nant. Third abdominal somite sometimes bears minute spine on middorsal posterior margin. Car- pal joints of left and right second pereopods 28-30 and 14-17, respectively. Lateral margins of telson (Figure 7) typically bear 5 + 5 spines; posterior margin rounded as in adult. Mean total length of Stage VIII (second juvenile) 21.6 mm (range 19.0-23.6 mm; 8 speci- mens). Morphological differences between Stages VII and VIII slight. Most notable features of Stage VIII: at least three or four setae between most rostral spines; complete lack of exopodites on third maxilliped and pereopods 1-3; inner and outer flagella of antennule each 15- to 16-segmented; lateral margins of telson typically bear 6 + 6 spines. COMPARISON OF LARVAL STAGES WITH DESCRIPTIONS BY OTHER AUTHORS The first description of larvae ascribed to Pan- daliis horealiti was given by Sars ( 1900), based on specimens collected from plankton. Berkeley (1931) showed that Sars' larvae could not be P. borealis; almost simultaneously Lebour (1930) showed that they were Caridion gordoni (Bate). Sars' "post-larval" specimen, however, is consid- ered by both Lebour and Berkeley to be correctly identified as P. borealis . As far as can be compared, my Stage VI (megalopa) and Sars' "post-larval" specimen are essentially identical except for the I' n \ L J 0. 5 mm Figure 7.— Stage VII (first juvenilel of Pandalus borealis: tel- son, dorsal. 169 FISHERY BULLETIN; VOL rostral tip, which in my larva is bifid but in Sars' is styliform, and the chela of the first pereopod, which is completely developed in my larva but not in Sars'. Stephensen ( 1912) described zoeal Stages I to V from plankton that he provisionally identified as "P. propinquus (?)" and Stage III zoeae (1916) as "Spirontocaris-\ar\a No. 4." Berkeley (1931) not- ed the close similarity of the "P. propinquus (?)" specimens to zoeae of P. borealis from British Co- lumbia waters. Stephensen (1935) later decided that both "P. propinquus (?)" and "Spirontocaris- larva No. 4" were actually zoeae of P. borealis. He also compared his zoeae with fragments of a specimen identified by Kr0yer as Dymas typus and decided Kr0yer's specimen was a Stage IV zoea of P. borealis. Comparing the description and figures of Stephensen's ( 1912) zoeae and mine in general for each stage, my zoeae are slightly more advanced than Stephensen's. In my Stage I zoeae the anten- nal scale bears 19 plumose setae; the basipodite and coxopodite of the maxillule bear 9 + 1 and 9 spines, respectively; the endopodite of the first maxilliped is segmented; and the exopodites of maxillipeds 1, 2, and 3 bear 6. 14, and 16 natatory setae, respectively. In Stephensen's Stage I zoeae the antennal scale bears only eight or nine plumose setae; the basipodite and coxopodite of the maxillule bear five and six spines, respec- tively; the endopodite of the first maxilliped is not segmented; and the exopodites of maxillipeds 1, 2, and 3 bear 4, 10, and 10 natatory setae, respec- tively. In Stage II, the relative difference in number of setae and spines between my zoeae and Stephensen's remains essentially the same, except in my zoeae the exopodites of pereopods 1, 2, and 3 bear 16, 16, and 12 setae, respectively, whereas in Stephensen's zoeae they each bear 18 setae. In Stage III, the rostrum of my zoeae bears only a single tooth and the antennal flagellum is eight- jointed, but in Stephensen's zoeae the rostrum bears as many as three teeth and the antennal flagellum is notjointed. In Stage IV, the rostrum of my zoeae bears six or seven teeth, the antennal flagellum is 15-segmented, and the telson bears eight pairs of spines whereas in Stephensen's zoeae the rostrum bears only four teeth, the an- tennal flagellum is still unsegmented, and the tel- son bears only seven pairs of spines. In Stage V, the most obvious difference is that the pleopods are segmented in my zoeae but not in Stephen- sen's. In his 1916 report, Stephensen described an ad- ditional larva which he considered the sixth stage oi P. propinquus G. O. Sars; later (1935) he decided it was P. borealis. According to Stephensen, this stage closely resembles his Stage V zoeae, differ- ing primarily in the left second pereopod being con- siderably longer than the right, and, for both sec- ond pereopods, the joint at the distal end of the carpopodite being complete. In my larvae, mor- phological change from Stage V to Stage VI is sufficiently pronounced that I consider the sixth stage to be the megalopa. If Stephensen was cor- rect in assuming his specimen to be a sixth stage zoea, then P. borealis in Greenland waters has at least six zoeal stages compared with only five zoeal stages in Alaska waters. In her classic study of pandalid larvae from British Columbia waters, Berkeley (1931) de- scribed and figured P. borealis Stage I zoeae reared in the laboratory and Stages II-VI collected from plankton. Her larvae follow a pattern of develop- ment similar to my larvae but each stage is less well developed. For instance, she described the antennal flagellum in her Stage I zoeae as tipped by a simple seta whereas in my zoeae it is tipped by a spinulose spine, and she neither figured nor de- scribed the spinous seta which my zoeae bear on the protopodite at the base of the flagellum. Also, the exopodite of the maxilla of her Stage I zoeae bears 8-10 long simple setae and has no trace of a proximal expansion whereas in my zoeae the exopodite of the maxilla bears 11 long plumose setae as well as one longer, thicker seta at the proximal end which is slightly expanded. In Stage II, the outer flagellum of the antennule of Berke- ley's zoeae is figured as bearing only three aes- thetascs distally whereas my zoeae bear eight. The proximal expansion of the exopodite of the maxilla is "just appearing" in Berkeley's Stage II but in mine it is distinctly expanded. Moreover, she de- scribed the telson as being still indistinctly seg- mented from the sixth abdominal somite but in my zoeae it is always distinctly segmented at Stage II. Berkeley's Stage III zoeae are essentially identical to mine as far as can be determined from her de- scription. Her Stage IV zoeae have four small teeth at the base of the rostrum, the pleopods are without joints, and there is no epipodite on the second maxilliped. In my Stage IV zoeae, the ros- trum usually has six teeth, the pleopods are jointed, and an epipodite occurs on the second maxilliped. In Stage V, the rostral tip of Berke- ley's zoeae is still styliform. There is no evidence 170 HAYNES: DESCRIPTION OF PANDALUS BOREALIS LARVAE from either her description or figure of ventral teeth on the rostrum, and the pleopods have not yet developed appendices internae. In my Stage V zoeae the rostral tip always bears at least a pro- tuberance indicative of the bifid tooth, and pleopods 2-5 bear at least partially developed ap- pendices internae. In contrast to my Stage VI, the megalopa, Berkeley's Stage VI is still typically zoeal: there is still no mention of ventral rostral teeth, the carapace still bears a supraorbital spine, the carpopodites of the second pereopods are not segmented, and the telson bears three pairs of lateral spines (not including the sixth terminal pair) and terminal setal pairs 2-4 have begun to degenerate. Berkeley (1931) also mentioned a P. borealis larva she obtained from plankton that, according to her. corresponds to the sixth stage of P. danae Stimpson and is similar to that described by Sars (1900) as the "post-larval" stage of P. borealis. Berkeley's sixth stage and Sars' "post-larval" stage are typically nonzoeal as indicated by the lack of supraorbital spines, segmentation of the carpopodites of the second pereopods, degenera- tion of the pereopodal and third maxilliped exopo- dites, and the typically adult shape and spination of the telson. Because this stage would be at least the seventh stage, it appears that P. borealis in British Columbia waters, as well as Greenland waters (Stephensen 1916), has at least six zoeal stages compared with only five zoeal stages in Alaska waters. The preceding comparisons show that Berke- ley's zoeae were less well developed at each given stage than mine and an additional stage or two was probably necessary for her zoeae to reach the megalopa stage. An apparent contradiction to this delayed development is the lack of segmentation of the antennal scale in the early stages of Berke- ley's zoeae. As shown by Haynes (1976), however, Berkeley was mistaken in this regard and her specimens undoubtedly possessed a segmented scale in the early stages. The only other description of larvae of P. borealis known to me is that of Kurata ( 1964) who, like Berkeley 1 1931 ), obtained Stage I zoeae in the laboratory from known parentage but Stages II-VII from plankton. Kurata's zoeae are essen- tially identical to mine through Stage V, except the rostrum of Kurata's Stage V zoeae is iden- tical to the rostrum of my Stage IV zoeae. Kurata's Stage VI corresponds to my Stage V, but his Stage VII possesses characteristics intermediate be- tween my Stages V and VI. For instance, in Kura- ta's Stage VII the exopodites on pereopods 1-3 and the third maxilliped have not begun to degenerate nor are the carpopodites segmented whereas in my Stage VI (megalopa) the exopodites on pereopods 1-3 and the third maxilliped are reduced and the carpopodites of the left and right second pereopods are segmented. Also, the lateral spination and shape of the telson of Kurata's Stage VII are typi- cal of postzoeae but posteriorly the telson bears 6 + 6 spines, a typically zoeal characteristic. By studying Stage VII individuals just prior to molt- ing, Kurata found that Stage VIII individuals pos- sessed a distinct mandibular palp and degenera- tion of posterior telson spines 2-4. He concluded that Stage VII was the last zoeal stage and Stage VIII the first postzoea, or megalopa. According to Lebour (1930). the lack of an outer seta on the maxillule in zoeae of Pandalus is one criterion for distinguishing this genus from cer- tain other Caridea. Pike and Williamson (1964), however, found the seta consistently present in early stages of British species of Pandalus. Oc- currence of the seta in Stage I zoeae has been reported by Gurney ( 1942) for Pandalus montagui Leach and P. stenolepis Rathbun; by Kurata (1955, 1964) for P. borealis and P. kesslen Czer- niavski; and Modin and Cox ( 1967) for P.jordani Rathbun. I have consistently found the seta in the early stages of P. hypsinotus, P. goniurus, and P. borealis. Lebour's suggestion that the lack of the seta is a distinguishing criterion for zoeae of Pan- dalus should, therefore, be disregarded. In addition to P. borealis. larvae have been de- scribed, at least in part, for nine other species of pandalids from the North Pacific Ocean: P. goniurus, P. jordani, P. platyceros Brandt, P. danae, P. kessleri, P. hypsinotus, P. stenolepis, Pandalopsis dispar Rathbun, and P. coccinata Urita. Of these nine species, larvae of Pandalus stenolepis, P. jordani. and P. goniurus are most like larvae of P. borealis, being characterized by exopodites on pereopods 1-3 rather than only on pereopods 1 and 2 and by poorly developed pereopods in Stage I. Zoeae of P. stenolepis were described by Needier ( 1938). Based on her descrip- tions, zoeae of P. stenolepis are readily distin- guished from zoeae of P. borealis by 1) the shape and spination of the rostrum, which in Stage I P. stenolepis is about as long as the carapace and projects upward rather than downward as in P. borealis, and 2) the fringed posterior edge of the abdominal somites and the serrated margins of 17] FISHERY BULLETIN VOL 77. NO. 1 the carapace, both of which persist to Stage V in P. stenolepis but never occur in P. borealis. Larvae of P. jordani have been described from specimens reared in the laboratory. Compared with development of similar species, Modin and Cox (1967) and Lee (1969) obtained more stages (11-13 and at least 8, respectively) than expected for larvae of P.jordani from plankton. Because of the possibility of these extra stages, only Stage I zoeae of P. borealis and P. jordani can be com- pared. Upon hatching, zoeae of P. borealis are slightly more developed than zoeae of P. jordani. For instance, in Stage I P. jordani, the exopodites of maxillipeds 1,2, and 3 bear 4, 9-11, and 11 or 12 natatory setae, respectively; the left mandible bears no lacinia mobilis; the basipodite of the maxillule bears six spines terminally; and the scaphognathite of the maxilla bears seven to nine setae along its outer margin. In Stage! P. borealis, maxillipeds 1, 2. and 3 bear 5 or 6, 13 or 14, and 16 natatory setae, respectively; the left mandible bears a single lacinia mobilis; the basipodite of the maxillule bears 9 spines terminally; and the scaphognathite of the maxilla bears 12 setae along its outer margin. Beyond Stage I, the most distin- guishing difference between zoeae of P. jordani and P. borealis seems to be the development of the rostral tip which in zoeae of P. jordani remains acuminate but in zoeae of P. borealis becomes bifid in later stages. In an earlier report (Haynes 1978), I described larvae of P. goniurus reared in the same manner as larvae of P. borealis described here. Larvae of both species are morphologically similar, espe- cially in early stages, and often occur together in plankton. To facilitate identification of larvae of these two species, the most readily observable morphological differences are listed by stage in Table 1. Larvae of P. goniurus are characteristi- cally smaller than those of P. borealis and in Table i.- -Morphological characteristics for distinguishing between larvae of Pandalus borealis and P. goniurus reared in situ in Kachemak Bav. Alaska. Stage and characteristic P borealis P goniurus Stage I zoea Mean total length (mm) No of plumose setae tnnging antennal scale No ot spines terminally on basipodite of maxillule No ot plumose setae on scapliognathite (in addition to single proximal seta) No of nalaory setae on exopodites fVlaxillipeds 1, 2, 3, Stage II zoea Mean total length (mm) No of plumose setae fringing antennal scale No of natatory setae on exopodites: Maxillipeds 1. 2. 3. Pereopods 1. 2. 3. Stage III zoea Mean total length (mm) Rostrum Antennal flagellum Antennal scale Stage IV zoea Mean total length (mm) Rostrum Antennal flagellum Propodite of pereopod 2 Pleopods Stage V zoea Mean total length (mm) Rostrum Chela ot pereopod 2 Pleopods Stage VI (megalopa) Mean total length (mm) Rostrum 6 7 (range 6 5-7 3, 25 specimens) 19 5-6. 13-14, 16 7 5 (range 6 7-8 2, 25 Specimens) About 25 7, 16, 18 16, 16, 12 9 5 (range 9 0-100, 10 specimens) 1-2 conspicuous teeth 8- segmented About 30 setae 13 0 (range 12 6-13 2; 10 specimens) 6-7 dorsal teeth About 1'? ■ scale, extending past tips of plumose setae Projected antenorly about '2 length of dactylopodite Segmented, pleopod 2 about '; height ol abdominal somite 16 0 (range 15 2-17 i. 10 specimens) 9-12 dorsal teeth, tip bifid. 4-5 partially developed ventral teeth Fully formed With appendices internae, fringed with plumose setae, pleopod 2 as long or longer than height of abdominal somite 18 5 (range 17 4-20.2, 5 specimens) 13-15 dorsal teeth. 6-7 ventral teeth 4 0 (range 3 7-4 2, 9 10 specimens) 5 9 {range 4 5-5 3. 10 specimens) About 19 6, 12. 14 12, 8. 8 6 2 (range 6 0-6 6, 10 specimens) 1 inconspicuous tooth 3- segmented About 20 setae 7 7 (range 6 8-8 3. 10 specimens) 2 dorsal teeth Longer than scale but not extending past tips ol plumose setae Projected antenorly only slightly Unsegmented, pleopod 2 about ^ a height of abdominal somite 10 3 (range 8 2- 11 .3: 10 specimens) 5-6 dorsal teeth; tip not bifid (but may show slight protuberance), no ventral teeth Not fully formed, propodite extension about ^ 2 length of dactylopodite Without appendices internae; 2-4 simple setae terminally, pleopod 2 about 2 3 height of abdominal somite 138 (range 11 1-15 8, 6 specimens) 8-9 dorsal teeth. 4-5 ventral teeth 172 HAYNES DESCRIPTION OF PAXriALIS RI}RKALIS LAKVAE Stages I-III the number of setae on certain appen- dages, particularly the antennal scale and certain mouthparts, is fewer than for zoeae of P. borealis. From Stage IV to megalopa, the rostrum of P. borealis has more dorsal teeth, the second pereopods are more developed, and the pleopods are fringed with more setae than for larvae of P. goniurus. LITERATURE CITED Berkeley, a. a. 1931. The post-embryonic development of the common pandalids of British Columbia Contnb- Can Biol 6(61:79-163. GURNEY, R. 1942. Larvae of decapod Crustacea. Ray Soc. (Lond.i Publ. 129. 306 p. Haynes, E. 1976. Description of zoeae of coonstripeshrimp. Pantfa/us hypsinotus. reared in the laboratory. Fish Bull.. U.S. 74:323-342. 1978. Description of larvae of the humpy shrimp. Pan- dalus goniurus. reared in situ in Kachemak Bay. Alas- ka. Fish. Bull.. U.S. 76:235-248. KL'RATA. H. 1955. The post-embryonic development of the prawn, Pandalus kesslert. Bull. Hokkaido Reg. Fish. Res. Lab. 12:1-15. 1964. Larvae of decapod Crustacea of Hokkaido. 3. Pan- dalidae. Bull. Hokkaido Reg. Fish. Res. Lab. 28:23-34. (Transl.. Fish Res. Board Can., 1966. Transl. 693.) LEBOL'R. M. V 1930. The larval stages of Canrfion. with a description of a new species, C. steveni. Proc. Zool. Sue. Lend. 1930:181- 194. LEE, Y. J. 1969. Larval development of pink shrimp, Pandalus jor- dant Rathbun. reared in laboratory. M. S. Thesis, Univ. Washington. Seattle. 62 p. MiiDIN, J. C. A.\D K. W Cux. 1967- Post-embryonic development of laboratory-reared ocean shrxYiip. Pandalus jordani Rathbun. Crustaceana 13:197-219. Needler. a. B, 1938, The larval development of fan(fa/H.s .s^eno/epis. J Fi.sh. Res. Board Can. 4:88-95. Pike, R. B.. and D. I. Williamson. 1964. The larvae of some species of Pandalidae (Decapo- da). Crustaceana 6:265-284. S.\RS. G. O. 1900. Account of the postembryonal development of Pan- dalus borealis Kreyerwith remarks on the development of other pandali. and description of the adult Pandalus borealis. Rep. Nonv. Fish. Mar. Invest. 1:1-45. STEPHENSEN, K. 1912. Report on the Malacostraca collected by the "Tjalfe"'-Expedition. under the direction of cand. mag. Ad. S- Jensen, especially at W. Greenland. Vidensk. Medd, Dan. Naturhist. Foren Kbh. 64:57-134. 1916- Zoogeographical investigation of certain fjords in southern Greenland, with special reference to Crustacea. Pycnogonida and Echinodermata including a list of Al- cyonaria and Pisces. Medd. Gronl. 53:230-378. 1935. Crustacea Decapoda, The Godthaab Expedition 1928. Medd. Gronl. 80:1-94. 17.3 RELATIONSHIPS OF THE BLUE SHARK, PRIONACE GLAUCA, AND ITS PREY SPECIES NEAR SANTA CATALINA ISLAND, CALIFORNIA' Timothy C. Tricas^ ABSTRACT Small fishes and cephalopods associated with both pelagic and inshore habitats composed the major prey for the blue shark. Prtnnace glauca. near Santa Catalina Island, Calif. The northern anchovy. Engraulis mnrdax, was the predominant prey for sharks in the immediate study area while at least 13 species of pelagic cephalopods constituted major prey for sharks in more distant oceanic waters. Inshore species taken by sharks included pipei\sh.Syngnatbus californiensis: jack mackerel, Trachurus sym- metricus; and blacksmith. Chrornis punctipinnis. In addition, sharks moved inshore to feed on winter .spawning schools of market squid. Loligo opalesci'ns. Digestive rate studies and telemetric monitoring of activity patterns indicate that sharks forage in waters near the surface from around midnight through dawn. Diel activities of prey species were examined and show that most prey dispersed in the upper water column at night and refuged during the day either by schooling (anchovies and jack mackerel ) or by retreating to deeper waters (pelagic cephalopods*. Field observations of shark feeding behavior indicate that predatory modes vary in response to prey behavior. Thehlue shark. Prionace glauca (Carcharhinidaei (Figure 1), is a pelagic carnivore cosmopolitan in tropical and warm temperate seas. Because of its pelagic habits, the majority of ecological studies on this species have been predicated on data from sharks captured by sport and commercial fisheries. As a result data has been largely qual- itative, and the shark's role as a predator in the epipelagic habitat has remained unclear. The importance of small fish as prey items for blue sharks has been described by Couch (1862), Lo Bianco (1909). Bigelow and Schroeder (1948), Strasburg ( 1958 ). LeBrasseur ( 1 964 ), Bane ( 1968 ), Stevens (1973), and others. These prey generally are schooling species common in productive coast- al waters. Cephalopods were also reported as major prey but little information is available on specific identifications (see Stevens 1973: Clarke and Stevens 1974). Although blue sharks have been observed feed- ing on dead or wounded cetaceans (Bigelow and Schroeder 1948; Cousteau and Cousteau 1970) there is little indication that they habitually prey on live, healthy marine mammals. The occurrence 'Based on a portion of a thesis submitted in partial fulfillment of the requirements for the M.A. degree in the Department of Biology. California State University. Long Beach. Calif Con- tribution no. 27 from the Catalina Marine Science Center, Uni- versity of Southern California. ^Department of Biology, California State University, Long Beach, Calif; present address: Department of Zoology, Univer- sity of Hawaii at Manoa, Honolulu, HI 96822. of mammalian tissue in the diet of blue sharks is rare (Strasburg 1958; Stevens 1973), and such feeding is most likely directed to dead mammals or those in poor health. Air/sea disasters have re- sulted in attacks on humans by blue sharks (see Schultz and Malin 1963; Fitch^) but these cases usually involved injured persons or corpses. Standard tagging programs (Weeks 1974; Casey 1976; Stevens 1976) and telemetric trackings (Sciarrotta and Nelson 1977) have provided some information on large-scale movements of blue sharks but relatively little is known of their orien- tation mechanisms and predatory behavior. Despite the profusion of descriptive reports, there still exists a great need for quantitative data on ecological relationships between the blue shark and its prey species. With these ideas in mind, I undertook this study within a limited geographic area to 1 ) provide a quantitative assessment of the diet of blue sharks near Catalina Island, 2) estab- lish temporal and/or geographical shifts in food habits, and 3) describe behavioral interactions be- tween the blue shark and its prey species. METHODS The study area was located north of the Isthmus, Santa Catalina Island, Calif. (Figure 2). Beds of Manuscript accepted Julv 1978. FISHERY BULLETIN: VOL. 77. NO. 1, 1979. ^J. E. Fitch, California Department of Fish and Game, Opera- tions Research Branch, 350 Golden Shore, Long Beach, CA 90802, pers. commun. May 1976. 175 FISHERY BULLETIN VOL 77. NO 1 FU'.LRK I. — Female blue shark near the ocean surface. FKiL'RE 2.— Study area at Catalina Island, Calif. Hatching indi- cates sampling regions. Sharks feeding among squid schools were observed at x . giant kelp, Macrocystis pynfera, composed the major habitat alongthe island shore. A submarine shelf, averaging 150 m deep, extends approxi- mately 2 km seaward then slopes to depths near 900 m and forms the floor of the San Pedro Basin. "Inshore" sampling stations were located above the shelf within 3 km of the island, and "offshore" stations centered approximately 6 km north of the Isthmus, over deeper basin waters. Sharks were collected monthly between March 1975 and March 1976. Samples were taken during morning and afternoon hours at both inshore and offshore areas with an attempt to maintain a con- sistent area-time sampling schedule. Sharks were attracted to a drifting 7-m work boat by baiting with slashed Pacific mackere\,Sc(>')ihcr japonicus, suspended in a wire basket 5 m beneath the sur- face. Once attracted, sharks were captured by hook and hand line using mackerel or market squid, Lolign npalesvens, as bait. Sharks were landed as quickly as possible to minimize regurgi- tation and then measured, sexed, and inspected for mating scars and general health. Contents of esophagi and stomachs were filtered through 1-mm mesh netting and preserved. Recognizable prey items and their digestive states were re- corded on site. Intestinal tracts were occasionally examined but contributed little information on the diet because of the small pylorus which re- stricted passage of identifiable prey fragments. Except for the market squid, cephalopods in the diet were represented exclusively by beaks. Beaks were paired into sets of upper and lower halves, and identified when possible according to Clarke (19621 andPinkasetal. (1971 1. Specific identifica- tions were verified by comparisons with beaks from collections of local species. Whole volumes of squid were estimated from beak-size/body-weight regressions for the major cephalopod families given by Clarke ( 1962). For calculations, the den- sity of cephalopod flesh was assumed to be 1 g/cm^. A regre.ssion foi- the family Ocythoidae ( not given by Clarke) was generated by plotting beak measure- ments and body weights from local specimens on Clarke's Octopodidae and Argonautidae regres- sions and constructing a parallel relationship curve. Beak-size/body-weight regressions for Vampyroteuthis infernalis were obtained from specimens of local collections. Unidentified cephalopods were omitted from the quantification as they represented only a minor portion of the diet (four small, infrequent species in eight stomachs). In order to approximate normal shark feeding times, digestive rates for captive sharks were de- termined and then compared with field data on the 176 TRICAS: BLUE SHARK AND ITS PREY SPECIES digestive states of anchovies recovered from wild sharks. Three healthy, active sharks were accli- mated for 24 h in large seawater holding tanks (14°-16°C) at Marineland of the Pacific, and then fed marked anchovies and mcU'ket squid. Stomach contents were examined at 6, 12, and 24 h after feeding and the digestion rates recorded. Short-term movements of sharks were moni- tored in the fall and winter seasons by telemetric instrumentation similar to those of Ferrel et al. 1 1974 1 and Nelson (1974). Transmitters were applied externally to free-swimming sharks with stainless-steel darts. Effective transmission range was approximately 2 km under good conditions but depended largely upon ambient noise from waves, wind, and biological sources. Some trans- mitters included a depth sensor for a record of vertical movements. Signals were tracked using a tuneable ultrasonic receiver and a staff-mounted directional hydrophone. These trackings supple- ment the spring through fall trackings of Sciar- rotta and Nelson il977i. The feeding behavior of blue sharks among spawning squid was studied in January 1976. Just before sunset, squid schools were detected near the bottom (30-40 m deep) using a recording Fathome- ter'' and the work boat anchored directly above. A 1,500-W light was then suspended over the water. Squid typically converged beneath the light and formed a large surface school at which sharks usu- ally appeared and began to feed. Orientation and feeding responses of sharks to moving prey were documented during baiting ses- sions at offshore stations. In these tests, a dead anchovy, attached to a light fishing line was cast beyond the bait-attracted sharks and then re- trieved back towards the boat. All field observa- tions of shark and prey activities were made from the boat, using scuba and/or by snorkeling. RESULTS Sharks were captured during all months of the 1-yr study. Of the 81 sharks sampled, 9¥( had recognizable food items in their stomachs. The northern anchovy, Engraulis mordax, was the predominant prey item for sharks in the study area while other small fishes occurred at much lower frequencies (Figure 3). Although sharks fed on a wide variety of cephalopods, an analysis of relative importance (Table 1) showed L. opalescens and squid of the genus Histioteuthis as the most common and sub- stantial cephalopod prey. Monthly analysis re- vealed important shifts between these prey items ivngnalhui ealitarniei rioihurui lymmttrtiu Soualui ocanlhioi Chroma punt.iipinfn\ Cypirluiiti culilornicu Loligo opaltitrnt Chitottulhii, caly Onythoirulhii borrt (Xythoe tuheitulalu Octapoiruihii dtkl (ktopui vp Va/nftyrolfulhii mlr MjMigoltultUi (D/iOi Lv^unutid jmphipiiiJ Rtnilla holhhtn PhyllOipodii lotiry i\g^ (Chluruphvul FIGL'RE 3. — Stomach contents of 81 blue sharks sampled during the year. Occurrence = percent of the 81 individuals containing that prey species. Inset gives a summary by broader food categories. Table l. — Annual relative importance of identified cephalopod prey in the diet of blue sharks near Santa Catalina Island. Calif. Impwrtance was estimated as an index of relative importance (//?/) inaccordwithPinkasetal- 1 1971)://?/ = uV +V)F,whereN (numerical percent) is the percent of individuals of that species among all individual cephalopods recovered; V (volumetric per- cent) is the percent volume represented by that species of all cephalopods recovered. andF (frequency) is the percent of indi- vidual shark stomachs containing that prey species. ■*Reference to trade names does not imply endorsement by the National Marine Fisheries Service. NOAA, Rank Species F N V IRI 1 Loligo opalescens 21 0 706 31 9 2,152 5 2 Hislioteulhis heteropsis 37 0 11 4 104 806 6 3 Histioleulhis sp 23 5 50 3 124 6 4 Chiroteulhis calyx 148 53 1 4 99 2 5 Thysanoteuthid squid 1 2 2 43 3 52 2 6 Onychoteuthis boreali-iaponicus 86 24 36 51 6 7 Vampyroleuthis mfernalis 4 9 8 22 14 7 8 Octopoteuthis deletron 62 1 0 8 11 2 9 Dosidicus gigas 1 2 2 5 1 64 10 Ocythoe luberculata 4 9 8 4 59 11 Mastigoteuthis pyrodes 37 6 3 33 12 Octopus sp 49 1 4 2 78 13 Leachia sp 1 2 2 004 3 177 (Table 2). The high index for L. opalescens in January 1976 reflected the squid's extensive winter spawning assemblages in the study area, and similarly is the reason for its high annual rank (Table 1 ). Histioteuthid squid were probably the most significant cephalopod prey for sharks in more oceanic waters away from inshore spawning aggregations of L. opalescens. The low average number of anchovies and histioteuthid squid per stomach and the relatively small coefficients of dispersion for these two prey indicate that sharks obtained them somewhat regularly over a wide area (Table 3). Conversely, the large coefficient for market squid during its spawning season concurs with observations that this prey was taken from large schools during its spawning runs at inshore areas. Digestive rate tests for healthy, captive sharks were in order with digestive states of prey recov- ered from wild sharks. Anchovies removed from captive sharks at 6 h after feeding were easily identified, and showed only preliminary digestion of fins and margins of the opercula. Likewise, whole squid were easily recognized and had only slight signs of external surface decomposition. At 12 h after feeding, digestion of anchovies was characterized by decomposed abdominal walls, moderate scale loss, and some skin deterioration. Digestion of squid was still negligible. At 24 h, anchovies were well digested with only vertebrae, otoliths, and small sections of muscle present. Squid heads were separated from the body and lenses had detached from the optic cups, but beaks were still implanted within the buccal mass. In general, digestive rates were at least twice as fast for anchovies than for squid. Times of normal feeding activity were estimated by comparing the digestive rate data obtained from captive sharks with recognizable anchovies recovered from wild sharks. Anchovies that were FISHERY BULLETIN: VOL. 77. NO. 1 Table 3. — Dispersion of the three major prey species in blue shark stomachs off Santa Catalina Island, Calif. Means for mar- ket squid were computed for squid spawning season (Mar. 1975, Dec. -Jan. 1976) and nonspawning season (Apr. -Nov. 1975, Feb. 1976). Coefficients of dispersion (ratioof variance to mean) indi- cate grouping of prey among stomachs. A coefficient of 1 de- scribes a random distribution. Larger coefficients describe in- creasingly contagious (clumped) distributions of prey among shark stomachs (Sokal and Rohlf 1969). No. of Mean no. Coellicient sharl183 m) was the formation of small (4-15 m thick), near-surface daytime schools (0-54.9 m deep) that dispersed at night into a thin surface scattering layer (Mais 1974 1. Field observations from the present study indicate a similar behavior for an- chovies near Catalina. In offshore waters during the day, anchovies occurred in large, dense, polarized schools near the surface. In the early evening, schools dispersed horizontally into less dense feeding assemblages with individuals spaced approximately 0.5 m apart. Later at night (0100-0400 h) more dispersed groups and solitary individuals were observed on several occasions, indicating a more complete nocturnal dissolution. In spite of the abundance of this prey no sharks examined near Catalina had stomachs distended with anchovies; usually only one or two had been taken per day. Data from the digestion studies indicate that most predation on anchovies oc- curred in predawn hours which correlates with the increased nocturnal activity of telemetered sharks reported by Sciarrotta and Nelson ( 1977). It seems probable then, that the few anchovies taken by each shark was at least partially due to the noc- turnal dispersion of schools in offshore waters, whereby assemblage densities were reduced and anchovies taken individually. The localized variability of anchovy abundance and schooling behavior that existed between areas and seasons pre.sented different feeding oppor- tunities for sharks. For example, blue sharks cap- tured during the day off Newport Beach, Calif, and in commercial anchovy fishing grounds near Los Angeles Harbor (author unpubl. data) con- tained many more anchovies (approximately 10- 20/individual) than did sharks sampled in the Catalina study area. The two former areas feature nearshore submarine escarpments where the size and concentrations of anchovy schools were among the greatest anywhere in southern California (Mais 1974). The present status of the blue shark-anchovy association may be the aftermath of a previously more complex predator-prey web. Southern California commercial fisheries have severely de- pleted Scomber japonicus and Pacific sardine, Sardinopa sagax, populations (MacCall et al. 1976), both natural prey for blue sharks (author unpubl. data). Although such declines in major forage species may have resulted in increased predation on anchovies, the southern California population is apparently in little danger of over- exploitation by commercial fisheries or pelagic fish predators (Pinkas et al. 1971; Mais 1974; MacCall et al. 1976). Fishes associated with inshore habitats were also taken by sharks. Jack mackerel, Trachurus symmetriciix, are widely distributed throughout the Gulf of Alaska (Miller and Lea 1972), and inhabit both inshore and pelagic habitats (Feder et al. 1974). In southern California waters, adults of this species generally aggregate near the bot- tom or under kelp forests at rocky banks and shal- low coastal areas during daylight and venture into deeper waters at night. Only rarely do jack mack- erel form sizeable surface schools in the open sea (Mais 1974). Similarly, smaller jack mackerel (e.g., near 25 cm TL), common at inshore areas of Catalina, swam along the outer edges of kelp beds during the day in closely spaced schools and some- times aggregated within the kelp forest proper. At night jack mackerel occurred in open waters (away from kelp) often interspersed with Scomber japonicus. Larger pelagic individuals might rep- resent a schooling prey source for blue .sharks in open waters, but stomach content data indicate this was not the case near Catalina. Neave and Hanavan (1960) described concurrent expansion of blue shark and jack mackerel ranges in the Gulf of Alaska during the summer, although no data was presented on possible predator-prey interac- tions. Pipefish were the second most frequent fish prey for sharks in this study and a principal prey for blue sharks off Newport Beach (Bane 1968 1, but because of their small biomass must be regarded as a prey species of minor importance. Free- swimming pipefish were observed at the surface in open water (far from surfgrass or kelp beds) at night, among flotsam kelp during daylight, and during daytime scuba dives in kelp forest and 180 TRICAS BLUE SHARK AND ITS PREY SPECIES snri'grass, Phyllospadix torreyi, habitats along the shore of the island. The occurrence of pipefish at the surface in the San Pedro Channel at night and the fact that sharks containing freshly ingested pipefish were captured 2-5 km from the island imply that this prey was most likely taken in wa- ters away from inshore kelp and surfgrass habitats. Freshly ingested blacksmith, Chroniis punctipinnis, were recovered from a shark cap- tured near Ship Rock at noon. At Catalina, this planktivorous damselfish formed midwater feed- ing aggregations at the outer edges of the kelp forest during the day, and at times ranged sea- ward up to 100 m from the nearest kelp. At dusk, blacksmith retreated to the protection of rocks and crevices (see Quast 1968; Hobson 1976). Blue sharks frequented waters near exposed kelp stands at Ship Rock and have been reported chas- ing and feeding on blacksmith during the day (Sciarrotta and Nelson 1977; Given'^). With the exception of Mastlgotcufhis pyrodes, Vampyrott'uthis infernaliti, and nonspawning Loligo opalescens, all of the cephalopod prey species (or their congeners for which data are available) occur near the surface at night through vertical ascent from greater depths or by normal epipelagic distribution (Roper and Young 1975; Tricas 1977). Mastigoteuthis pyrodes (mesopelag- ic) and V. infernalis (bathypelagic) occasionally migrate to the lower limits of the epipelagic zone at night i Roper and Young 1975). In their study of blue shark movements near Catalina, Sciarrotta and Nelson (1977) described evening-twilight shoreward movements of sharks from late March through early June and suggested the change in movement patterns as a response to seasonal increases of inshore spawn- ing squid and decreases in availability of pelagic fishes offshore. Such movements, however, may not be strictly food related. For example, daily inshore-offshore migrations of sharks (late March through early June) would not be synchronous with the cold-water winter peak (December through February) of inshore squid spawning ac- tivity near the Isthmus. Also, some sharks ob- served during this study fed among spawning squid schools throughout the day and therefore did not exhibit the diel inshore-offshore movement ^R. Given, Catalina Marine Science Center, P.O. Bo.x 398, Avalon, CA 90704. pers. commun. July 1977. pattern. Furthermore, sharks fed upon anchovies m offshore waters throughout the year and there is no indication that the availability of anchovies or jack mackerel to blue sharks significantly changed over the course of this study. Detection of prey by sharks is often dependent on the reception of abnormal or unusual stimuli such as low-frequency vibrations of struggling or fleeing fishes (Nelson and Gruber 1963; Nelson and Johnson 1972). In addition, olfaction plays a well-documented role in location of injured, stressed, or bleeding prey (Tester 1963; Hobson 1963). Ultimately, however, vision (Gilbert 1963) and possibly electroreception (Kalmijn 1971) are the principal senses used immediately prior to at- tack. For blue sharks in a normal nocturnal feed- ing mode, it is probable that search images are formed for a general size rather than for a particu- lar species. Pipefish, for example, were relatively small in biomass, but represented a length charac- teristic of other prey species. Similarly, most cephalopods in the diet fell within the common prey size range (e.g., 5-25 cm TL). Bioluminescent trails of darting anchovies and other small fish and squid were frequently seen while snorkeling at night in offshore waters and likewise would be readily visible to sharks. Also, the majority of cephalopod species taken by sharks possessed photophores. Bioluminescence associated with prey movements and light organs may represent significant predatory cues for sharks at night. ACKNOWLEDGMENTS Thanks to D. R. Nelson for his assistance and to R. Given and R. Zimmer of the Catalina Marine Science Center. F. G. Hochberg, Santa Barbara Museum of Natural History, and L. Pinkas, California Department of Fish and Game, pro- vided helpful suggestions and access to their cephalopod collections. J. Goldsmith, Marineland of the Pacific, provided sharks and facilities for the digestion rate studies. Thanks to C. Shoemaker for her help in the field, J. McKibben for his technical assistance, and H. Izuta Tricas for her help in preparation of the manuscript. E. S. Hobson and J. C. Quast constructively criticized the manuscript. Special thanks to F. Banting and C. Best for their contribution that made this work possible. Finan- cial support was granted by the Office of Naval Research through contract N00014-75-C-0204, under project NR- 104-062, for the program of shark research of which this study is a part. 181 FISHERY BULLETIN VOL 77. NO 1 LITERATURE CITED Bane, G. W. 1968. The great blue shark. Cahf. Curr. 1( ll;3-4. BIGELOW. H. B.. .AND W. C. SCHROEDER. 1948. Sharks. In J. Tee- Van. C. M. Breder, S. F. Hilde- brand, A. E. Parr, and W. C. Schroeder leditorsi. Fishes of the western North Atlantic, Part one, p. 59-546. Mem. Sears Found. Mar. Res., Yale Univ. 1. Casey, J. G. 1976. Migrations and abundance of sharks along the At- lantic coast. In W. Seaman, Jr. 'editorl. Sharks and man — a perspective, p. 13-14. Fla. Sea Grant Program, Rep. 10. Clarke. M. R. 1962. The identification of cephalod "beaks" and the rela- tionship between beak size and total body weight. Bull. Br. Mus. (Nat. Hist.), Zool. 8:419-480. Clarke, M. R., and J. D. Stevens. 1974. Cephalods, blue sharks and migration. J. Mar. Biol. Assoc. U.K. 54:949-957. Couch, J. 1862. A history of the fishes of the British Islands. Vol. 1, p 26-36, 41-44. Groombridge and Sons, Lond. COUSTEAU, J.-Y., AND P. COUSTEAU. 1970. The shark: splendid savage of the sea. Doubleday and Co., Garden City, N.Y., 277 p. Feder, H. M., C. H. Turner, .\nd C. Limbaui-.h. 1974. Obser\'ations on fishes associated with kelp beds in southern California. Calif Dep. Fish Game, Fish Bull. 160, 144 p. Ferrel, D. W., D. R. Nelson, T. C. sciarrotta, e. a. stan DORA, and H. C. Carter. 1974. A multichannel ultrasonic biotelemetry system for monitoring marine animal behavior at sea. ISA (In- strum. Soc. Am.) Trans, 13:120-131. Gilbert, p. W. 1963. The visual apparatus of sharks. In P. W, Gilbert (editor). Sharks and survival, p. 283-326. D. C. Heath and Co., Boston. ■ HOBSON, E. S. 1963. Feeding behavior in three species of .sharks. Pac. Sci. 17:171-194. HoBsoN, E. S., AND J. R. Chess. 1976. Trophic interactions among fishes and zooplankters near shore at Santa Catalina Island, California. Fish. Bull.. U.S. 74:567-598. KALMI.JN, A. J. 1971. The electric sense of sharks and rays. J. Exp. Biol. 55:371-383. LEBRA.SSEUR. R. J. 1964. Stomach contents of blue shark [Prionace glaiica L.) taken in the Gulf of Alaska. J. Fish. Res. Board Can. 21:861-862. Lo Bianco, S. 1909. Notizie biologiche riguardanti specialmente il periodo di maturita sessuale degli animaJi del golfo di Napoh. Mitt. Zool. Stn. Neapel 19:666-667 MACCAI.I., a. D., G. D. STAL:FFER, AND J. -P. TROADEC. 1976 Southern California recreational and commercial marine fisheries. .Mar. Fish. Rev. 38i 1 ):l-32. M,MS, K. F. 1974. Pelagic fish surveys in the California cur- rent. Calif. Dep. Fish Game, Fish Bull. 162, 79 p. MILLER, D. J., AND R. N. LEA. 1972. Guide to the coastal marine fishes of California. Calif. Dep. Fish Game. Fish Bull. 157, 235 p. Neave, F., and M. G. H.-\NAVAN. 1960. Seasonal distribution of some epipelagic fishes in the Gulf of Alaska region. J. Fish. Res. Board Can. 17:221- 233. Nelson. D. R. 1974. Ultrasonic telemetry of shark behavior. Nav. Res. Rev. 27(12):1-21. Nel.son, D. R., and S. H. Gruber. 1963. Sharks: Attraction by low-frequency sounds. Sci- ence (Wash., DC.) 142:975-977. Nelson, D. R., and R. H. Johnson. 1972. Acoustic attraction of Pacific reef sharks: Effect of pulse intermittency and variability. Comp. Biochem. Physiol. 42A:85-96! PINKAS, L., M. S. OLIPHANT. AND I. L. K. IVER.SON. 1971. Food habits of albacore, bluefin tuna, and bonito in California waters. Calif Dep. Fish Game, Fish Bull 152, 105 p. QUAST, J. C. 1968. Observations on the food of the kelp-bed fishes. In W. J. North and C. L. Hubbs (editors). Utilization of kelp- bed resources m southern California, p. 109-142. Calif Dep. Fish Game, Fish Bull. 139. Roper. C. F. E., and R. E. Young. 1975. Vertical distribution of pelagic cephalo- pods. Smithson. Contrib. Zool. 209, 51 p. SCHULTZ, L. P., AND M. H. MALIN. 1963. A li.stofshark attacks for the world, /n P. W. Gil- bert (editor). Sharks and survival, p. 509-567. D. C. Heath and Co., Boston. !• Sciarrotta, T. C, and D. R. Nelson. 1977. Diel behavior of the blue shark, Prionace glauca. near Santa Catalina Island, California. Fish. Bull.. U.S. 75:519-528. SoKAL, R. R., and F. J. ROHl.F. 1969. Biometry. W.H. Freeman and Co., San Franc, 776 P- Stevens, J. D. 1973. Stomach contents of the blue shark {Prionace glauca L.) off south-west England. J. Mar. Biol. As.soc. U.K. 53:357-361. 1976. First results of shark tagging in the .North-east At- lantic, 1972-1975. J. Mar. Biol. Assoc. U.K. 56:929-937, STRASBURG, D. W. 1958. Distribution, abundance, and habits of pelagic .sharks in the central Pacific Ocean. U.S. Fish Wildl, Ser\'., Fish. Bull. 58:33.5-361. TE.STER, A. L. 1963. The role of olfaction in shark predation. Pac. Sci, 17:145-170, TRICAS, T. C. 1977. Food habits, movements, and seasonal abundance of the blue .shark, Prionace glauca (Carcharhinidael, in southern California water. M.S. Thesis. California State Univ., Long Beach. 79 p. vvkkks, a. 1974. Shark! NOAA 4(11,8-13. 182 LIFE HISTORY AND VERTICAL MIGRATION OF THE PELAGIC SHRIMP SERGESTES SIMILIS OFF THE SOUTHERN CALIFORNIA COAST Makoto Omori' and David Gluck^ ABSTRACT Sergestes similis in the southern California eddy was observed with respect to reproduction, daily and ontogenetic vertical migrations, growth, and longevity. The period of highest spawning activity occurs between late December and early April, but small pulses of spawning are occasionally observed in late spring and summer. The release of eggs takes place close to shore above the continental slope, and then the eggs sink to 200 m or deeper. Nauplius larvae ascend and protozoeal and zoeal laivae stay mostly above 100 m. The daily vertical migration becomes evident after the second protozoeal stage. Adults are abundant between 50 and 200 m at night and 2.50 and 600 m in the daytime. The spawning activity of .S. similis becomeshighest during the period when the verticaUhicknessof the optimum temperature zone (10^-15^Cl is the greatest. The authors speculate that the local population off the southern California coast may be joined by the subarctic population. It is possible that multiple spawnings occur from females of the southern California population. The lifespan ofS.sirntlis is 2.0-2.5 years for females and about 1.5 years for males. Sexual maturity is reached at about 1 year in both sexes. Females reproduce in two successive spawning seasons, and males seem to accomplish multiple fertilizations. Growth trends are similar to those reported for S. similis off Oregon. Growth rates are described using growth curves fitted by the von Bertalanffy and logistic equations. Sergestes similis Hansen is the most abt lani. oceanic, pelagic shrimp in the Nonh Pacific Drift, lat. 40°-50°N. This subarctic a- i transitional species occurs mainly in watei. rthfre t mpera- ture ranges between 3° and 13 J. Its di.-; ration extends from Japan to the coast of North America as far south as lat. 27°N (Pearcy and Forss 1969: Omori at al. 1972). In the cooler part 5.0 mm were sorted, counted, and sexed. The carapace length from the tip of the rostrum to the posterior margin of the carapace at the dorsal midline was measured to the nearest 0.5 mm. Change through time in the carapace length- frequency histograms of S. similis was graphi- cally analyzed using probability paper (Harding 1949; Cassie 1954). In order to compare the growth trends of the S. similis population off southern California with trends in other waters, previous data on the size-frequency distribution of S. similisreporie6 by Genthe (1969), Pearcy and Forss (1969), Omori et al. (1972), and Mutoh and Omori ( 1978) were reanalyzed to obtain average or modal carapace lengths" for the populations at ■"Scripps Institution of Oceanography. 1965. Physical and chemical data CalCOFI cruise 6401. 10 January-4 March 1964. SIO Ref. 65-7, 76 p. ^Reference to trade names does not imply endorsement by the National Marine Fisheries Service, NOA-'V. *BL/CL regression of Sergestes similis < >.5.5 mm CL) are as follows: 186 OMORl and GLUCK LIFE HISTORY OF SERGESTES SIMILIS different sampling dates and locations. The von Bertalanffy and logistic equations were used to fit these growth data. RESULTS Daily and Ontogenetic Vertical Migrations of Larvae and Earl)' Postlarvae Coastal upwelling is generally weak in south- ern California during the winter (Bakun 1973). This is consistent with the data on environmental properties at the sampling stations (Figure 2). The thermocline remained at about 75 m at all stations on Line 60 with the mixed layer temperature ranging from 1L5°C inshore to 14.0°C offshore. Salinity was usually <33.30%o in water above 75-m depth. On Line 90, except for the two outer- most stations, the thermocline was at 30-50 m and the temperature within the mixed layer was >13.5°C. Salinity was >33.20%oat all depths. On Line 100 the thermocline was at about 50 m at Stn. 100.35 and 100.60. Temperature within the mixed layer was about 15°C, and salinity was >33.50%o. The position of the oxycline coincided with that of the thermocline at nearly all stations. Generally, the oxygen level at depths below the mixed layer increased going seaward. The main population of S. sirnilis larvae was always between the surface and 100-m levels, and they occurred in greater abundance at stations on the continental slope (Figure 3). The population density was highest at Stn. 90.32 (101 individuals/m^). The larvae did not occur at Stn. 90.120, 90.140, and 100.120. In these southern offshore stations the temperature above 100 m was >16°C. The temperature-salinity curves characterized the water mass as eastern North Pacific Central water, where S. si mil is has never been found. In this water mass, the J'ortmanni type" larvae (the Sergestes corniculum group, see Yaldwyn 1957 and Omori 1974) were commonly distributed. The vertical distributions of larvae and early postlarvae from eight stations where they were abundant shows that the larvae were scattered BL = 3.15 + 2.85 CL for females. BL = 2.55 + 3.11 CL for males (Omori etal. 1972). The regression for juveniles with carapace length 5.5 mm or less BL 3.08 CL. from 20 to 100 m during the daytime (Figures 4, 5). On Line 90, the distribution pattern did not coin- cide well between the stations closest to shore (Stn. 90.28 and 90.32) and the offshore stations (Stn. 90.60 and 90.70). At Stn. 90.60 in the day- time, the larvae were widely distributed through- out the 0-110 m layer, but larvae occurred only between 44 and 88 m at Stn. 90.32 during the day. The greatest population density observed was within the 66-88 m layer at Stn. 90.32 (about 3,500 individuals/1,000 m^). Nighttime larval distribu- tion was between 20 and 90 m at Stn. 90.70, but again, it was below 40 m at the closest inshore station. A similar inshore and offshore as- semblage was observed along Line 100, although the vertical distribution of the larvae was ex- panded more widely. At Stn. 100.35 the larvae were most abundant between 50 and 100 m in the daytime and 0 and 80 m layer at night. On the other hand, at Stn. 100.60 the main population in the daytime occurred between 20 and 120 m, while at night the distribution ranged from the surface to 140 m with considerable numbers in the 0-40 m layer. At both stations, there was a clear daily vertical migration of the main population of zoeal and postlarval stages. With the present sampling method, there was some doubt whether the same population was measured by day and night tows. However, as indicated in Figures 4 and 5, the estimates of abundance beneath 1 m^ of sea surface did not differ appreciably between day and night at the two closest stations on Lines 60 and 90 and be- tween day and night tows at the same station on Line 100. It can be said, at the least, that the avoidance of nets by larvae in the daytime was no greater than at night. When abundance vs. depth is combined and av- eraged for each larval stage at each station, the extent of daily vertical migration becomes clear. The first protozoeal stage shows at least a re- stricted daily vertical migration (Figure 6). The larvae gradually increase their range of vertical distribution with growth while gradually inhabit- ing deeper water. Thus, the main population of early postlarva (40-45 m at night and 70-75 m in the daytime) shows a deeper distribution than ear- lier larval stages. Eggs of S. sirnilis (about 0.3 mm in diameter) were slightly heavier than the density of the ex- perimental water; the difference in sinking rates was not significant at the 59c level between 1 0° and 14"C under laboratory conditions (Table 3). 187 FISHERY BULLETIN VOL 77, NO 1 Temperature (°C) 5 10 15 20 I I I I I I I I I I I I Salinity ( /oo) 33.00 34.00 a. LU 400 Figure 2. — Vertical profiles of temperature, salinity, and oxygen on CalCOFI Lines 60, 90, and 100, January-February 1964, off southern California. 188 OMORI and GLUCK: LIFE HISTORY OF SERGESTES SIMIUS 130° 125° 120° ESTIMATED ABUNDANCE UNDER I m2 OF SEA SURFACE M 60+ no 40° Figure 3. — Distribution and abundance of Sergestes smiths larvae from January to February 1964, Estimated abundance is expressed as number of mdividuals beneath 1 m^ of sea surface m depths between 0 and 100 m. Table 3. — Experimental data on sinking velocity of eggs of Sergestes simihs in water of salinity 33.72%o. Difference in sink- ing rates is not significant at the S'J level. Replicates Sinking velocity (m/h) Temperature ( C) Average SD Range 10 14 9 9 145 044 091-2 19 181 , 0 52 1 04-2 99 Spawning Season The highest spawning of S. similis took place from late December to early April. Protozoea lar- vae occurred most abundantly between January and April at Stn. 90.37 (Figure 7), but were not found in samples collected in November and De- cember. During 1951-54, a number of PZ2 and PZ3 appeared each year between January and July, but the occurrence of PZl was restricted to January- April, except for August 1952 and July 1954. Although one-third of the autumn months were not represented by samples, these months were scattered enough to make the data sig- nificant. Seasonal abundance of zoeal stages dup- licated that of PZl. Early postlarvae were found in plankton from February to early July. Consider- able numbers of PZl and PZ2 (<1.3 mm BL) ap- parently passed through the mesh of the CalCOFI net, as their measured population densities were almost always lower than those measured for PZ3. The optimum temperature range for larval de- velopment is 10'-15°C(Omori 1979), and the high- est temperature at which adult S. similis occur is 13°C. Thus, the best temperature for the larvae is close to the upper temperature limit of the adult's habitat. Furthermore, comparison of the repro- ductive activity of S. similis with physical and 189 FISHERY BULLETIN, VOL 77, NO 1 NO OF INDIVIDUALS / 1000 m^ Figure 4. — Vertical distribution of larvae and postlarvae of Sergestes similis on CalCOFI Lines 60 and 90 off southern California. PZ, protozoeal stages: Z, zoeal stages; PL. postlar- val stages. Estimated total number of larvae beneath 1 m^ of sea surface indicated by n. chemical environmental data indicates that there is a relationship between temperature and spawn- ing season (Figure 7). Spawning activity was highest during the period when the vertical stratum of optimum temperatures for larvae was thickest. It decreased before colder water was brought in by coastal upwelling which was nor- mally most intense from May to August (see Bakun 1973). A seasonal minimum, or cessation, of spawning occurred during the summer and au- tumn when the upper layer was covered by un- favorably warm temperatures (>15°C). Growth Because of the smaller mesh size, the 6-ft I KMT retained a larger proportion of small shrimp than did the 10-ft IKMT (Figure 8). While specimens of 4 mm CL occurred in the smaller net, few < 7 mm were retained in the larger net. Well-defined progressions of size-frequency modes gave indications of average growth rates for certain cohorts, although we sometimes encoun- tered difficulties in interpreting these trends due to inadequate sampling, and possibly to extended spawning of the species. One 1975 cohort (12.0- 14.5 mm CL) and two conspicuous 1976 cohorts (5.0-11.0 mm CL) were seen in females collected in August 1976 (Figure 8A). The former cohort was not found in the following two samplings. The large-sized 1976 cohort (mean modal length, 8.4 mm CL in August) reached 9.9 mm CL in October, 10.5 mm CL in January, and 11.8mmCLin March 1977. Growth of the small-sized cohort was trace- able until April 1977, when the shrimp attained an average carapace length of 10.4 mm. Recruit- ment of postlarvae <6.0 mm CL ( 1977 cohort) was intense in April. The histogram for March showed only a single mode of males, and it isnot possible to Figure 5.— Vertical distribution of lar- vae and postlarvae of Sergestes similis at CalCOFI Stn. 100.35 and 100 60 off southern California. Estimated total number of larvae beneath 1 m^ of sea sur- face indicated by n. 100 NO OF INDIVIDUALS / 1000 m^ 0 0 0 IO(X) \ 10 100 1000 ^ 10 100 ICXXD \ 10 100 1000 J 190 OMORI and GLUCK: LIFE HISTORY OF SERGESTES SIMILIS RELATIVE ABUNDANCE (%) 0 20 40 20 40 20 40 20 40 20 40 20 40 60 J I I FIGLIRE 6. — Vertical distribution of larvae andpostlarvae of Sergestessimilisoff southern California. Abundance vs. depth at all sampling stations was combined and averaged. Horizontal line indicates the depth at which the cumulative catch represented 509c of the total catch. PZ, protozoeal stages; Z. zoeal stages; PL, postlarval stages. say whether this 1976 cohort represents the large-sized group or not. In the 10-ft IKMT sam- plings the most conspicuous female cohort of 10.5-13.0 mm CL in April reached 13.5-15.5 mm CL in October (Figure 8B). The males grew from an average 10.8 to 11.7 mm CL between April and August. In many cases, the size structure of the population showed the presence of only one or two obvious size groups, but in three cases (April 21, June 21, and July 29) the histograms of females indicated three size groups. Development of the smallest cohort of 0 age-group was traceable until August in both females and males, but in October and November, two cohorts of 0 age were appar- ent. Some estimates of growth were attempted using changes in the average or modal lengths in vari- ous months. In order to show the growth trend more definitely, the results of all previous length measurements of S. fiimilis from various waters were reanalyzed and the average or modal lengths for each size group were plotted together with the present data (Figure 9). Except for the points de- rived from the offshore population in the subarctic North Pacific, where the environment is quite dif- ferent from that of southern California, the major- ity of cohorts had average or modal lengths which fell within the growth curves of three year classes fitted by eye. These data indicate the following: 1 ) as expected from spawning season data, in most cases the modal progressions are evident starting in winter or early spring, 2) growth trends of S. siriiilisoff southern California appear similar to the popula- tion off Oregon (Pearcy and Forss 1969), and 3) growth rates do not vary greatly among many different populations, although there is evidence that a few modal groups grew about twice as rapidly as the ordinary one. The ratio of females to males in all collections was 1.3:1 (553:422). Sex ratio in a cohort was not skewed greatly towards females until the modal length of the female population reached about 13 mm CL. At that point, the males of the cohort rapidly disappeared from the collection, account- ing for the observed imbalance in sex ratio (69:2). DISCUSSION Ontogenetic Migration Omori (1979) found experimentally that: 1) ovigerous females of S. similis shed their eggs at night, 2 1 the eggs took 105 h to hatch into nauplii 191 FISHERY BULLETIN VOL. 77, NO. 1 1953 n PZ I I 1 PZ 2,3 n z 1,2 JFMA MJ J A S 0 N D MONTHS FIGUREV.— Isotherms of 10° and 15'C and occurrence of larvaeof Sergestes stmdis at CalCOFI Stn. 90,37. 1951-54, off southern California at 0-140 m. Shadow indicates zones where tempera- tures exceed the average 10°- 15°C range of 1 950-55, No samplmg indicated by ns. PZ, protozoeal stages; Z, zoeal stages. at lO^C, and 3) mortality increased greatly in temperatures beyond 10°-15°C. We do not know the depth where spawning and hatching of S. similis take place in the natural habitat. How- ever, the laboratory observations, coupled with biological information on the other species of sergestids and euphausiids (Omori et al.^), indi- cate that the eggs of S. similis are shed in shallow water at night when ovigerous females rise up- wards. Adult S. similis seldom occur above the 50-m level at night where the temperature is usu- ally >13°Coffsouthern California. Assuming that AUG 19, 1976 UNSEXEDr-, FEMALES oiJr^.,,^n^ .IPJ CO < UJ N X o < tr UJ m 3 10- MALES :^ 10 12 14 6 8 10 12 10- 10- CO < _1 o N CO < LlI 10- 2 cr 3 10- APR 12,1972 FEMALES jzO. JUNE 21,1953 n -fl JULY 29, 1973 -n^ 1^ l^p AUG 24,1954 Ff ^PP^i 22„, OCT 28,1972 '\\ 10- I \ r NOV 8 , 1975 MALES &^ -f=^ ^ -) — t — I — I — r 10 12 ■ 14 16 8 10 12 CARAPACE LENGTH (mm) 'Omori, M., M. Mutch, and M, Kaetsu, 1974, Prediction of Sergia lucens fishery in 1974/75 season. |In Jpn.l Unpubl. manuscr., 5 p., distributed at the annual meeting of the "Sakura-ebi" Fishing Unions. Shizuoka Prefecture. Japan. Figure 8. — Length-frequency histograms of Sergesles simitts collected with a 6-ft IKMT ( Ai and a lO-ft IKMT (B) off southern California. The samples were arranged m monthly order regard- less of the year of .sampling. Lines trace development of sig- nificant cohorts. 192 OMORl and GLUCK LIFE HISTORY OF SERGESTES SIMILIS 0»0^<1^D«*— I ■ — ICSII^OCTLTiUDr-^CJOcn CD X o 6 i ■^£■5 si a £ QD cfi E O (^^) H19N3n 33VdVdV3 ■^ 0) a Im c e c£ to *' t: -a ■Si o § at CO CO o lT T3 t-. ^ u Cd 73 U cd 3 H) o eg a. Cfl CJ w T3 I- -2 1 in cC J-T X S -o E 55 Ol o c c CJ « o (> u ■c s iS CO 0) o X 0^ CJ Wl TJ C o c Oi 3 T3 C o tfl a" C bD ■x) S ffl a> c 01 05 41 o o cd CO C ^ o S ^ o "« -i o -c s "cd 1 "o 'S E oi C/3 d oT o o a. CO £ cd CO CD u. u o 193 FISHERY BULLETIN: VOL 77. NO, I spawning takes place around 50 m and using data on both the sinking velocity of the eggs and the development time of eggs at 10°C, we can estimate that the eggs sink to about 220-m depth before hatching. The ambient temperatures which eggs may encounter during their descent are 7°-13°C. It is probable that some eggs are laid deeper than 50 m. However, like the population off the Oregon coast (Pearcy and Forss 1969), S. similis is seldom distributed over the continental shelf off southern California. Therefore the majority of eggs would not sink to the bottom but remain within the water column. A comparison of vertical distribution patterns at all stations confirms the following hypotheses: 1) the occurrence of larvae is restricted to water <140 m where the temperature range is 9°-16°C, 2) the larvae often appear in the 0-20 m level at night but rarely in the daytime, and 3) the larval distribution is more restricted inshore than offshore to a limited vertical range. The descent of eggs and ascent of naupliar larvae are well documented in the oceanic euphausiid £Mp/ia(/sia superba and Meganyctiphanes norvegica (Mauchline and Fisher 1969). Presumably the nauplii of S. similis rise from 200 m or deeper to layers where the temperature is usually > 10°C. In this manner, the nauplius, which is probably highly vulnerable to predation, develops in the less hazardous layers which are deeper than the following larval stages. Protozoeal and zoeal lar- vae stay mostly in the shallower environment which is relatively rich in food (phytoplanktonand microzooplankton). They perform daily vertical migration starting PZl, and their downward mi- gration at daytime becomes more marked with each stage. This hypothesis is further supported by the positive phototaxis in N3 to PZl larvae and negative phototaxis after PZ2 observed in the laboratory (Omori 1979). According to Omori (1974), the larvae of pelagic shrimps can be classified into several types on the basis of their ontogenetic migration. The first group is composed of the species living in the epipelagic and upper mesopelagic zones. Their larvae perform migration within the euphotic zone. Sergestes similis belongs to this group, hav- ing a similar pattern to that described for Sergia lucens (Omori 1974), but the negatively buoyant eggs of Sergestes similis differ from Sergia lucens eggs which have density similar to seawater. Adult Sergestes similis were abundant inshore off Oregon during the winter, but they tended to shift to an offshore distribution during the sum- mer (Pearcy and Forss 1969). This inverse rela- tionship between nearshore and offshore stations indicates a horizontal ontogenetic migration of this species by active swimming with the help of subsurface currents. The movement by a species to nearshore regions for spawning is a characteris- tic behavior among several sergestid shrimps (Omori 1974). Relationship Between Spawning Season and Environment Larvae of S. similis, in particular PZl, were more abundant inshore than offshore, which indi- cates that the spawning of S. similis is taking place mainly close to shore above the continental slope off southern California (but not as far in- shore as the continental shelf). The assumption by Pearcy and Forss (1969) that S. similis in the Oregon population spawns during most of the year with a seasonal minimum occurring during the summer was partially true in the southern California population as there were small pulses of spawning in summer and autumn. However, the southern California adult population appears to be recruited largely from the local population spawned from late December to early April. One may argue that the decrease of larvae in the study area in summer and autumn was caused merely by the seasonal change off the southern California gyre. It would be interesting to compare our data with samples from stations outside of the northward flowing path of the gyre. However, we do not think that such an extreme absence of lar- vae in summer and autumn is taking place with the year-round spawning of S. similis. At least some larvae should have successfully remained in the study area to yield noticeable recruitment dur- ing those months. Incidentally, females having fully developed ovaries (Omori 1979) were sel- dom found in the IMKT collection from summer and autumn. Genthe (1969) assumed that maximum reproductive activity of S. similis from the Santa Barbara Channel was in summer and autumn, but his assertion that juveniles collected in August of 5.0-6.5 mm CL are 11 or 12 mo old is misleading. Shrimp of this size are more likely to be of the 6-7 mo class. Omori et al. (see footnote 7) studied the relation- ship between environments and reproductive be- havior of another sergestid, Sergia lucens. in Suruga Bay, Japan, and found that the com- 194 OMORI and GLUCK: LIFE HISTORY OF SERGESTES SIMILIS mencement of spawning and the survivorship of larvae are closely related to the ambient tempera- ture rather than the quantity of food available. This study showed that: 1) S. lucens started spawning in June, immediately after the tempera- ture exceeded 18°C at 20-50 m, and the number of larvae increased with increasing vertical thick- ness of the optimum temperature zone for the growth of larvae (18°-25°C), 2) the population size of S. lucens was determined by the abundance of larvae during the first half of the breeding season, June- August, and 3) the abundance of larvae was often related to the fluctuation in vertical width of the optimum temperature zone. During midsum- mer the warming of surface waters above to 25°C and the shoaling of cold water < 18°C restricted the optimum temperature zone, and consequently the mortality of protozoeal larvae increased. As with S. lucens , a rise in temperature may trigger the commencement of spawning of the Sergestes similis population in the northern sub- arctic waters where surface temperature is < 10°C during most of the year. However, this seems not to be the case for the southern California popula- tion where favorable temperatures were available year-round in some stations between 50 and 100 m. Yet, the spawning began abruptly when the temperature around 100-m depth began to rise. Abundance of larvae was greatest during the period when the vertical thickness of the optimum temperature zone was the greatest, and spawning activity almost ceased both when the ambient temperature was lowered by coastal upwelling and when warm surface water subsequently ap- peared. Thus, the spawning season of S. similis is not always positively correlated with the upwell- ing which causes environmental enrichment and subsequent increase of plankton biomass in the southern California eddy. The correlation of spawning to coastal upwelling in Euphausia pa- ct fica , another very abundant species of the California Current zooplankton assemblage, is the most striking difference affecting the spawn- ing seasons of that organism and S. similis . Simi- lar to S. similis, the southern California popula- tion of E. pacifica seems to be adapted for larval development between 12°and 16°C, but its spawn- ing is highest when coastal upwelling is strongest in May-June (Brinton 1976). Although true mechanisms remain unexplained, we theorize that the distinctive spawning season of S. similis in southern California is based mainly on the adaptation of this species to the vertical thickness of optimum temperature. The vertical thickness of the optimum temperature zone was also corre- lated with the abundance and survival of larvae of S. similis. The cumulative depths of the optimum temperature ranges for S. similis from January to March were 220, 318, 311, and 380 m from 1951 to 1954 whereas the average numbers of protozeal larvae occurring from January to April were 129, 218, 224, and 543 individuals/1,000 m^, respec- tively. In 1951, zoeal larvae were found in the lowest numbers when the cumulative depth was the smallest. One possible interpretation of the irregular small pulse of spawning of S. similis in seasons other than winter and early spring is that shrimp which reproduce during these periods are carried from northern offshore waters, i.e., subarctic North Pacific, to the study area. If temperatures of 9°-10°C in the habitat of S. similis really trigger the commencement of spawning, those living in subarctic waters would start spawning later than July in most areas. The yearly mean velocity of the eastward component of the North Pacific Drift is about 3 cm/s at the surface in the areas lat. 45°N west of long. 150°W. On the other hand, a strong south-flowing current, which flows at the velocity of 5-10 cm/s but occasionally >20-30 cm/s is ob- served throughout the year both at the surface and at 200-m depth off the west coast of the United States ( Wyllie 1966; Stidd'*). If part of the popula- tion of S. similis near lat. 47°N, long. 140°W, e.g., where tremendous numbers are eaten by baleen whales (Omori et al. 1972), is carried southeast- ward by the currents, the shrimp can easily reach the southern California coast within 2 yr at a mean speed of 5 cm/s of flow. The spawning occurs in the summer off California due to continuous recruitment of such northern populations. An electrophoretic study of S. similis population may help to answer this question, although, due to di- verse trophic regimes, genetic variability of the southern California population may be too large to distinguish it from the subarctic population (see Valentine and Ayala 1976). Another possible interpretation is that the phenomenon is caused by the adaptation of the local population to mid latitude irregularities in oceanographic and trophic conditions. It has been observed for several penaeids, sergestids, and euphausiids in temperate and tropical regions ^Stidd.C.K. 1974. Ship drift components: means and stan- dard deviations. SIO Ref. 74-33, 57 p. 195 FISHERY BULLETIN VOL. 77, NO. 1 that the ovary may contain ova at different de- velopmental stages and that not all ova are neces- sarily released at once (King 1948; Mauchline 1968; Roger 1973; Omori 1974). We observed that S. simili.s off southern California always retained considerable numbers of immature ova after spawning. Because the volume of a pair of mature ovaries from this shrimp represents about lOT of the body volume, we can estimate from the volume of each egg that one female has at least 1 ,500 but probably closer to 2,000-2,500 eggs. Nevertheless, the number of eggs released by a female in the laboratory was always <1,140 (Omori 1979). Thus, as has been pointed out for Euphausia pa- cifica off southern California (Brinton 1976), it appears possible that under optimal environmen- tal conditions small ova of S. similis may develop later and produce a second spawning. If a female, which produced the first clutch in late December, released the second clutch 3-4 mo later, two modal size-groups might be seen sometimes in the same age-group. It is probable that unfavorable en- vironmental conditions would prevent the spent ovary from maturing again until the following year. Further evidence of this phenomenon is pro- vided by the increase in the number of spent females and the decrease in the number of fully grown ova in ovaries of S. similis off southern California and Oregon during the summer (Genthe 1969; Pearcy and Forss 1969). The length-frequency histograms in October 1972. November 1975. and from August 1976 to March 1977 (Figure 8) indicate either the occurrence of multiple spawnings for S. similis or individuals from farther north being mixed into the southern California population. Growth, Sexual Maturity, and Longevity If S. similis population is composed of 0 age- group shrimp only and all attain sexual maturity after about 1 yi", the size structure of the popula- tion sampled shows the presence of only one or two size groups. However, the obvious occurrence of three size groups of females during certain periods of the year in this study indicates that the females ofS. similis live 2 yr or more. Large females, 13-16 mm CL, carrying developed ovaries are sometimes collected, indicating that S. similis can reproduce at least twice during its lifetime. The absence of male individuals >14 mm CL resulted in a strong imbalance of sex ratio, indicating that the males die out at an age of < 20 mo. Genthe ( 1969 ) showed evidence of sex reversal (protandrous herma- phroditism) from male to female in S. similis. Similar phenomena have been observed in other sergestids of the genus Acetes (Omori 1975). A detailed study is needed to determine the meaning of these findings, although at the present time we believe that the variance may be explained by abnormalities, since the frequency of occurrence is small. The bias in sex ratio favoring females above a certain size indicates the possibility of multiple fertilizations by males. Thus some females of the 2 age-group may mate with males of the 1 age- group. We obtained an average gi'owth trend of S. similis throughout its life by shifting the average or modal lengths of populations off the California and Oregon coasts horizontally in accordance with the month of their sampling. The growth of S. similis >6 mm CL was best fitted by the von Ber- talanffy equation (Figure 10): /, = 14.7(1 - e<"'03™') for females, and /, = 12.0(1 - e-o "MS") for males, where /, is the carapace length in millimeters at t days. Because of the large mesh sizes of the IKMT nets, however, any average or modal length calcu- lated from these samples over considerable size ranges on either side of 7 mm CL is probably greater than the length of the natural population. Therefore, the initial modal length of the 3-mo old population was fit by eye and connected with those growth curves of larval and early postlarval stages at 10° and 14°C which were obtained under laboratory conditions. It took 52 days for S. similis to reach the first postlarval stage at 14°C (Omori 1979). Under these conditions the logistic equa- tion (Figure lOB) seemed to give the better fit to the growth curves: / 14.7 1-e- 12.0 ' J _p-0.01254((-188.4) for females, for males. Growth is very rapid during the postlarval stages. The juveniles at 4-8 mo old grow, at 0.91 mm CL/mo, during the period from April to Au- gust (logistic equation). The biomass of total zoo- plankton, as well as young Calanus and Euphausia , which are considered to be the most important food for juvenile and adult S. similis. 196 OMORl and GLUCK LIFE HISTORY OF SERGESTES SIMILIS I5n Figure lO— Average growth of Sergestes stmtlis off the California and Oregon coasts. Solid lines (A) are growth curves fit by the von Bertalanffy equation and (Bl are those fit by the logistic equation. Dashed lines are growth curve of early developmental stages of 1 0° and 14°C determined in the laboratorj- lOmori 1979). ^,0 X H O LlI O < < FEMALE (B)^^__- o---^ FEMALE /o-:^5^-»-MALE(B) " -• MALE (A) o FEMALE • MALE i^ UNSEXED OR COMBINED -1 — I — \ — I — I — r n — I — I — I — I — i — I — r JFMAMJJASONDJFMAMJJASONDJFMAMJJA MONTHS usually peaks in the April-July period in southern California waters (Mullin and Brooks 1970; Brin- ton 1976). Shrimp which encounter the best feed- ing conditions probably grow rapidly with low mortality rates and form distinctive modal groups such as those traced in Figure 9. The growth rate gradually decreases after 10-mo old. and the females add only 5 mm CL in 20 more months before dying. The difference in growth rates be- tween the sexes becomes apparent after the shrimp attain a length of about 8 mm CL. The males grow slower than the females, but attain sexual maturity '2-I mo earlier than females be- cause the females become mature at 10.5-11.0 mm CL, whereas the males mature at 9.5-10.0 mm CL (see Genthe 1969; Omori 1979). Since five data points for females on the upper right-hand side of Figure 10 are on the asymptote, it is highly speculative whether these shrimps represent that age-group, or possibly an age-group spawned 5-6 mo later; in which case they would be placed on a different curve. It is apparent, however, that the longevity of the females of S. siinilis is more than 2 yr and that they spawn in two successive spawn- ing seasons during their lives. These observations agree well with those of Matthews and Pinnoi (1973) on Sergestes arciticus Kroyer, which is the most closely related species to S. similis ( Judkins 19721, in Kursfjordan, western Norway. ACKNOWLEDGMENTS We acknowledge the helpful reviews by M. M. Mullin and J. G. Morin. Thanks also to the staff and graduate students of the Food Chain Research Group of the Institute of Marine Resources for their assistance in sampling at sea. Omori is in- debted to the Institute of Marine Resources and the Marine Life Reseaixh Group of Scripps In- stitution of Oceanography for the financial sup- port and hosting of his visit. LITERATURE CITED AHLSTROM, E. H. 1948. A record ofpilchard eggs and larvae collected during surveys made in 1939 to 1941. U.S. Fish Wildl. Serv., Spec. Sci. Rep. Fish. 54, 76 p Bakun, a. 1973. Coastal upwelling indices, west coast of North America. 1946-71. U.S. Dep. Commer., NOAA Tech. Rep ^fMFS SSRF-671, 103 p. B.^RHAM. E. G. 1957. The ecology of sonic scattering layers in the Mon- terey Bay area. California. Hopkins Mar. Stn.. Stanford Univ. Tech. Rep. 1. 182 p. 197 FISHERY BULLETIN: VOL. 77. NO. 1 1963. The deep-scattering layer as observed from the bathyscaph "Trieste". Proc. 16th Int. Congr. Zool. 4:298-300. BRINTON, E. 1967. Vertical migration and avoidance capability of euphausiids in the California Current. Limnol. Oceanogr. 12:451-483. 1976. Population biology of Euphausia pacz^ca off south- em California. Fish. Bull.. U.S. 74:733-762. C.'^SSIE. R. M. 1954. Some uses of probability paper in the analysis of size frequency distributions. Aust. J. Mar. Freshwater Res. 5:513-522. DAVIES, I. E., AND E. G. BARHAM. 1969. The Tucker opening-closing micronekton net and its performance in a study of the deep scattenng layer. Mar. Biol. (Berl.l 2:127-131. Fleminger, a. 1964. Distributional atlas of calanoid copepods in the California Current region. Part. 1 Calif Coop. Oceanic Fish. Invest.. Atlas 2. 313 p. GENTHE, H. C, Jr. 1969. The reproductive biology of Sergestes similis (De- capoda, Natantia). Mar. Biol. iBerl.l 2:203-217. Harding, J. P. 1949. The use of probability paper for the graphical analysis of polymodal frequency distnbutions. J. Mar. Biol. Assoc. U.K. 28:141-153. JUDKINS. D. C. 1972. A revision of the decapod crustacean genus Sergestes (Natantia, Penaeideal sensu lain, with emphasis on the systematics and geographical distribution of Neoser- gestes, new genus. Ph.D. Thesis, Univ. California, San Diego, 274 p. JUDKINS, D. C, AND A. FLEMINGER. 1972. Comparison of foregut contents of Sergestes similis obtained from net collections and albacore stomachs. Fish. Bull., U.S. 70:217-223. King, J. E 1948. A study of the reproductive organs of the common marine shrimp, Penaeus setiferus\ Linnaeus). Biol. Bull. (Woods Hole) 94:244-262. M.'^TTHEWS, J. B. L.. AND S. PINNOI. 1973. Ecological studies on the deep-water pelagic com- munity of Korstjorden, western Norway. The species of Pasiphaea and Sergestes (Crustacea Decapoda) recorded in 1968 and 1969. Sarsia 52:123-144. MAUCHLINE, J. 1968. The development of the eggs in the ovaries of euphausiids and estimation of fecundity. Crustaceana (Leidenl 14:155-163. MAUCHLINE, J., AND L. R. FISHER. 1969. The biology of euphausiids. Adv. Mar. Biol. 7,454 p. MULLIN, M. M., AND E. R. BRCOTKS. 1970. The ecology of the plankton off La Jolla, California, in the period April through September, 1967. VII. Produc- tion of the planktonic copepod, Calanus helgolan- dicus. Bull. Scripps Inst. Oceanogr. Univ. Calif. 17:89- 103. Mutoh, M.. and M. OMORI. 1978. Two records of patchy occurrences of the oceanic ^nmp Sergestes similis Hansen off the east coast of Hon- shu, Japan. [InJpn.l J. Oceanogr. Soc. Jpn. 34:36-38. OMORI, M. 1974. The biology of pelagic shrimps in the ocean. Adv. Mar. Biol. 12:233-324. 1975. The systematics, biogeography, and fishery of epipelagic shrimps of the genus Acetes (Crustacea, De- capoda, Sergestidae). Bull Ocean Res. Inst.. Univ. Tokyo 7. 91 p. 1979. Growth, mortality, and feeding of larval and early postlarval stages of the oceanic shrimp, Sergestes sinulis Hansen. Limnol. Oceanogr. 24:273-288. Omori, M., a. Kawamura, and Y. Aizawa. 1972. Sergestes similis Hansen, its distribution and im- portance as food of fin and sei whales in the North Pacific Ocean. In A. Y. Takenouti et al. (editors). Biological oceanography of the northern North Pacific Ocean, p. 373-391. Idemitsu Shoten, Tokyo. Pearcy, W. G., and C. A. FORSS. 1966. Depth distribution of oceanic shrimps (Decapoda; Natantia) off Oregon. J. Fish. Res. Board Can. 23:1135- 1143. 1969. The oceanic shrimp Sergestes simtlisoffihe Oregon coast. Limnol. Oceanogr. 14:755-765. PEREYRA. W. T.. W. G. PEARCY. AND F. E. CARVEY. JR. 1969. Sebastodes flauidus, a shelf rockfish feeding on mesopelagic fauna, with consideration of the ecological implications. J, Fish. Res. Board Can. 26:2211-2215. Roger, C. 1973. Biological investigations of some important species of Euphausiacea iCrustaceal from the equatorial and south tropical Pacific. In R. Fraser (editor). Oceanog- raphy of the South Pacific 1972, p. 449-456. New Zealand National Commission for UNESCO, Wellington. scripp.s institution of oceanography. univer.sity of California. 1963. Oceanic observation of the Pacific. 1951. Univ. Calif. Press, Berkeley and Los Ang., 598 p. 1965a. Oceanic observations of the Pacific: 1952. Univ. Calif Press, Berkeley and Los Ang.. 617 p. 1965b. Oceanic observations of the Pacific: 1953. Univ. Calif. Press, Berkeley and Los Aug., 576 p. Valentine, J. W., and F. J. Ayala. 1976. Genetic variability in krill. Proc. Natl. Acad. Sci. USA 73:658-660. WYLLIE, J. G. 1966. Geostrophic flow of the California Current at the surface and at 200 meters. Calif. Coop. Oceanic Fish. Invest., Atlas 4, 288 p. YALDWYN, J. C. 1957. Deep-water Crustacea of the genus Sergestes (Deca- poda, Natantia) from Cook Strait, New Zealand. Zool. Publ. Victoria Univ. Wellington 22:1-27. 198 THE OCEANIC MIGRATION OF AMERICAN SHAD, ALOSA SAPIDISSIMA, ALONG THE ATLANTIC COAST Richard J. Neves' and Linda Depres^ ABSTRACT The migratory route of American shad. A/osa sapidissima. in the Atlantic Ocean was studied using 14 yr of catch data collected during bottom trawl surveys by the U.S. National Marine Fisheries Service (and its predecessorl and cooperating foreign countries. All shad catches occurred at bottom tempera- tures from 3° to 15°C. with the most frequent catches between 7° and 13°C. Water temperatures between initial and peak entry of shad into home estuaries along the Atlantic coast are within the same thermal regime (3^-15^C). During the summer, ail shad catches occurred north of lat. 40^N in two primary areas; Gulf of Maine and an area south of Nantucket Shoals. Previous studies on food habits and differences in time of capture during National Marine Fisheries Service surveys indicated that shad were vertical migrators, probably following the diel movements of large zooplankters in the water column. Shad were generally absent from the Gulf of Maine by late autumn, and concentrations were found between lat. 39° and 4 1 °N during the winter. Based on previous tagging studies. National Marine Fisheries Service surveys, and coastal temperature data, most prespawning adults enter coastal waters along the Middle Atlantic Bight from lat. 36' to 40°N and then proceed north or south to natal rivers. Coastal surveys for river herring by North Carolina's anadromous fishery research program and commercial shad catches re[)orted to the International Commission for the Northwest Atlantic Fisheries by member nations concur with our proposed bottom temperature (3°-15^^C)-migratory route hypothesis for shad. The American shad, Alosa sapidissima, is an anadromous fish ranging from the St. Johns River, Fla., to the St. Lawrence River, Canada i Walburg and Nichols 1967). Meristic and tagging studies indicate that discrete spawning populations of shad exist in river systems along the Atlantic coast (Mollis 1948; Hill 1959; Nichols 1960. 1966; Carscadden and Leggett 1975a). Juveniles leave freshwater in autumn and generally remain in the ocean for 3-5 yr before returning to their natal rivers to spawn. Spawning runs occur in a south to north temporal progression, beginning as early as December in Florida and as late as June in Canada (Walburg 1960). Virtually all shad south of Cape Hatteras, N.C., die after spawning, whereas the percentage of repeat spawners in rivers north of North Carolina increases with latitude I Leggett 1969; Chittenden 1975). A considerable amount of literature exists on this species because of its commercial and recre- ational importance inshore, but little research has 'Massachusetts Cooperative Fishery Research Unit, Depart- ment of Forestry and Wildlife Management, University of Mas- sachusetts, Amherst, Mass.; present address; Virginia Coopera- tive Fishery Research Unit, Virginia Polytechnic Institute & State University, Blacksburg, VA 24061. " ^Northeast Fisheries Center Woods Hole Laboratory, Na- tional Marine Fisheries Service. NOAA, Woods Hole, MA 02543. Manuscript accepted .August 1978. FISHERY BULLETIN VOL. 77. NO 1.1979 been done on the oceanic phase of its life history. Talbot and Sykes (1958) provided the first evi- dence of an annual oceanic migration based on 19 yr of tagging studies by the U.S. Fish and Wildlife Service. Tag returns indicated that shad from U.S. rivers congregated with those from Canadian riv- ers (Vladykov 1950. 1956) in the Gulf of Maine during summer and autumn and moved south to possibly overwinter off the Middle and South At- lantic States (Talbot and Sykes 1958; Walburg 1960; Walburg and Nichols 1967; Cheek 1968). In the spring, shad moved north or south toward natal rivers to spawn. Temperature monitoring in rivers with major shad runs, and laboratory experiments, have pro- vided convincing evidence that the timing of diad- romous movements corresponds with specific water temperatures (Walburg and Nichols 1967; Chittenden 1969, 1972; Williams and Bruger 1972; Leggett and Whitney 1972; Leggett 1973). Leggett and Whitney (1972) also postulated that the oceanic distribution of shad was temperature- controlled; tag returns plotted on surface isotherm charts fell within the 13°-18°C isotherms. How- ever, all of the tag returns used to establish this "migrational corridor" at sea were collected in- shore during the spring coastal migration toward 199 FISHERY BULLETIN VOL 77. NO 1 home rivers. The correlation between offshore dis- tribution and surface temperatures was therefore based on extrapolation. The U.S. shad fishery is essentially an inshore operation and commercial catch records have lim- ited value in evaluating the distribution of shad at CAPE HATTERAS sea. Previous tagging studies have relied on other commercial fisheries for offshore tag returns, but these fisheries concentrate effort at a time or place where principal species aggregate. Tag returns from shad taken as bycatch may therefore contain a geographical bias and reflect only the distribu- tion of fishing effort. This paper examines offshore collections of shad from 14 yr of bottom trawl sur- veys by United States and foreign research vessels and interprets available literature on the coastal occurrence of shad. An alternative temperature- based hypothesis is presented to explain the offshore migratory cycle of shad. METHODS The U.S. National Marine Fisheries Service (NMFSi and its predecessor have conducted au- tumn bottom trawl surveys since 1963 using the RV Albatross IV and the RV Delaware II. The survey area extends from Nova Scotia to Cape Hatteras, out to 366 m (200 fm) (Figure 1) and is stratified into geographical zones based on depth and area. Coastal sampling stations are outside the 27-m (15-fm) depth contour. Middle Atlantic stations between New Jersey and Cape Hatteras were added during autumn 1967. A stratified ran- dom sampling design is used in the surveys; trawl stations are allocated to strata in proportion to stratum area and randomly assigned within strata (Grosslein 1969). A standard No. 36 Yankee bottom trawl with a 1.25 cm stretched mesh cod end liner is towed at each station for 30 min at an average speed of 3.5 kn. Autumn surveys were conducted 24 h/day during 1963-76, between 3 September and 16 December. Spring bottom trawl surveys have been con- ducted by NMFS since 1968 over the same geo- graphical area (Figure 1). The No. 36 Yankee trawl was used from 1968 to 1972 and a larger No. 41 Yankee trawl from 1973 to 1976. Trawling pro- cedures were the same as during autumn surveys and occurred between 4 March and 16 May. A detailed description of NMFS bottom trawl sur- veys and survey procedures is provided by Flescher-' and Grosslein.'' In addition to U.S. cruises, periodic autumn trawl surveys were conducted cooperatively with Figure L— National Marine Fisheries Service bottom trawl surve.v area between 27 and 366 m. Cape Hatteras. N.C.. to Nova Scotia, western North Atlantic. ^Flescher, D. 1976. Research vessel cruises. 1963-1975 National Marine Fisheries Service Woods Hole, Massachusetts. NMFS, Woods Hole, Mass., Lab. Ref. No. 76-14, 30 p. "Grosslein, M, D, 1969. Groundfish survev methods. NMFS, Woods Hole, Mass., Lab. Ref. No. 69-2, 34 p. 200 NEVES and DESPRES: OCEANIC MIGRATION OF AMERICAN SHAD the U.S.S.R., Poland, and France from 1969 to 1976, mainly between Georges Bank and Cape Hatteras. Spring trawl surveys, intended primar- ily as juvenile herring surveys, have been made since 1973 by vessels from U.S.S.R., Poland. Ger- man Democratic Republic, and Federal Republic of Germany between Nova Scotia and Cape Hat- teras. Most of the foreign surveys followed NMFS sampling procedures, sampled all or selected strata wiihin respective survey areas, but used various types of bottom trawls. All spring and autumn surveys and additional cruises during summer and winter are summarized in Table 1. Survey station and catch data pertinent to this study included: date, location, time, depth, bottom and surface temperatures, and number, length frequencies, and weight of shad caught. We plotted catch locations from all surveys (Ta- ble 1) by 10' rectangles of latitude and longitude on depth contour maps according to month or sea- son. Locations of shad collections during spring (March-May) and autumn (September-November) were plotted by month. Summer (June-August) and winter (December-February) surveys were grouped by season because of less sampling effort and lower catch frequency. Commercial shad catches by month reported to the International Commission for the Northwest Atlantic Fisheries (ICNAF) by member nations from 1970 to 1975 were provided by Hodder'" and used to define major shad catches within each ICNAF division and their correlation with distribution patterns based on survey data. Surface and bottom temperatures (nearest 1°C) were plotted for each trawl tow that collected shad; foreign catches with missing tem- perature data were omitted from this analysis. Additional oceanographic data on temperature ( Walford and Wicklund 1968; Colton and Stoddard 1972; Churgin and Halminski 1974; U.S. Coast Guard Oceanographic Unit^) and oceanic currents (Bumpus and Lauzier 1965; Stommel 1965; Bum- pus 1973) were reviewed for seasonal patterns along the Atlantic coast. RESULTS Bottom trawls at 10,435 stations during the 77 Table l, — Summary of bottom trawl surveys conducted by United States and foreign research vessels between Cape Hat- teras, N.C, and Nova Scotia, 1963-76, =V. M. Hodder. ICNAF Office. Dartmouth. N. S., Canada B2Y 3Y9. pers. commun. July 1977. ■^U.S. Coast Guard Oceanographic Unit. 1970, 1975. Monthly temperature charts. January to December 1970. January to December 1975. available US Coast Guard Oceanographic Unit. Bldg 159-E Navy Yard Annex. Washington, DC 20590 No ol No ol Season Country surveys stations Inclusive dales Spring United Slates 15 2,514 4 Mar -16 May Foreign 10 597 26 Feb -29 May Summer United Stales 4 810 7 July-28 Aug Foreign 6 618 9 Aug -3 Sepi Autumn United Stales 21 3,657 3 Sepi-16 Dec Foreign 18 1.676 3 Sepl-11 Dec Winter United Slates 3 563 16 Jan -8 Apr Totals 77 10,435 surveys collected 4,770 subadult and adult shad at 527 stations throughout the survey area. United States and foreign research vessels accounted for 315 and 212 of the successful collecting stations, respectively. Shad ranged in size from 8 to 50 cm fork length (FL). Surface and bottom tempera- tures were recorded at 448 of these stations and used to plot catch frequency at 1°C intervals. Shad were collected at survey stations with surface temperatures between 2° and 23°C, and frequent catches occurred throughout most of this temper- ature range (Figure 2). Bottom temperatures at successful collecting stations ranged from 3° to 15°C, but primarily between 5° and IS'C (Figure 3). Most stations with bottom temperatures <3°C occurred in the Gulf of Maine during late winter and early spring; stations with bottom tempera- tures >15°C were mainly off the mid-Atlantic coast during late summer and early autumn. This apparent relationship between shad occurrence and bottom temperatures was examined further by comparing the catches of shad with total sam- pling effort at each temperature (Table 2). Bottom temperatures during surveys ranged from 1° to 23°C, but shad were captured only between 3° and 15°C. Shad catches occurred more frequently at li Flcl'RE 2 — Surface temperatures at 448 stations where Ameri- can shad were collected during bottom trawl surveys, 1963-76, Cape Hatteras, N.C, to Nova Scotia. 201 FISHERY BULLETIN: VOL, 77, NO. I 60 r 540 « J30' •s k J 20 a Z 10 J L 5 6 7 8 9 10 11 12 13 14 IS 16 17 Bottom Temperature °C Fu:URE 3. — Bottom temperatures at 448 stations where Ameri- can shad were collected during bottom trawl surveys, 1963-76, Cape Hatteras. N.C.. to Nova Scotia. Table 2. — Total sampling effort, number of shad catches, and percent catch frequency of shad at each bottom temperature during bottom trawl surveys, 1963-76, Cape Hatteras, N.C., to Nova Scotia. Bottom temperature (C) Total no of trawls Trawls witti shad 1 2 3 4 5 6 7 B 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 16 104 270 567 987 964 1,047 997 909 750 741 739 626 333 164 71 56 41 30 29 34 19 5 0 0 7 16 41 40 55 50 45 40 54 48 37 12 3 0 0 0 0 0 0 0 0 0 0 2 59 2 82 4 15 4 15 5,25 502 495 533 7 29 6 50 591 3 60 1 83 0 0 0 0 0 0 0 0 temperatures between 7" and 1.3°C, with the greatest capture frequency at 11°C (Table 2). Ocean depths at stations with shad ranged from 20 to 340 m, but most of these stations (65'7f ) were <100 m deep (Figure 4). Of the 527 successful collecting stations, 269 iBW) occurred at depths between 50 and 100 m. Since trawling effort dur- ing U.S. spring and fall surveys was proportional to the area of each depth interval (Table 3), the number of shad catches within these depth strata was amenable to chi-square analysis. A compari- son between shad catches at each depth interval and catches at all other depths combined indicated 105 125 145 Median Deplhlmt FIi;lirE 4. — Frequency of American shad catches with depth at 527 survey stations. 1963-76. Cape Hatteras, N.C., to Nova Scotia. T.'iBLE 3. — Depth intervals within the survey area and as- sociated shad catches during U.S. bottom trawl surveys. 1967- 76. Cape Hatteras. N.C., to Nova Scotia. Depth interval (m) Survey area Numt^er of trawls with shad km^ % Observed Expected k' 27-55 56-110 111-185 186-366 Totals 47,412 254 55,009 29 5 53,769 28 9 30,181 16,2 186,391 100-0 45 109 53 23 230 58 68 67 37 230 389- 35 10-- 4 13- 6 32- •P--0.05. ••P 0 01, that the greater capture frequency in the 56- 110 m interval was highly significant (P<0.01); shad catches at all other depths were significantly fewer (P<0.05) than expected (Table 3). Spring surveys were conducted mainly in March and April, accounting in part for the more fre- quent collections during these 2 mo (Figure 5). In March, shad were distributed along the Middle Atlantic Bight. Most fish between Long Island, N.Y., and Cape Cod, Mass., were taken in 60-200 m of water, many along the outer continental shelf (Figure 5). Few shad occurred in <60 m of water north of lat. 40°N, whereas most catches south of Long Island were at depths <60 m. During the summer, shad were not captured south of lat. 40'N (Figure 6). Forty-six collections in July and August were made in two general areas: the Gulf of Maine and southeast of Cape Cod, near Nantucket Shoals. Mean depth at these stations was 95 m, but ranged from 35 to 214 m. Catches were distributed along the coastal margin of the Gulf of Maine and the southern half of Georges Bank; most trawling stations in the deeper, central Gulf did not collect shad. October received the greatest trawling effort during autumn surveys. Shad were again distrib- 202 NEVES and DESPRES: OCEANIC MIGRATION OF AMERICAN SHAD Figure 5. — Location of all American shad catches during spring bottom trawl surveys, 1968-76, Cape Hatteras, N C, to Nova Scotia. ^v'- -200 ^., ^ Georges i' ''■*♦*# Bank,'' ■at ■' '*i ,' E : o Spring :8 • March ♦ April • May \ ""^f \CQpe ] /Hatteras •P" -^^ 5. 203 FISHERY BULLETIN: VOL. 77. NO, 1 %-J y.v Seolia J : I ..■■■ ; :. ' .-S v;r :. j/h. I:-' ^t;-^' I \ : ^- .,' Gull of Moine. . ^* ♦ 200 Ik- • Georges ■ » * -fc^ If* • 1^ Sf I'; S:. * Summer • Winter V ' .Cope 'HoMeras FIGI'RE 6 — Location of all American shad catches during sum- mer and winter bottom trawl surveys, 1963-76, Cape Hatteras. N.C., to Nova Scotia. uted along the Gulf of Maine and Georges Bank perimeter, as well as south of Nantucket Shoals (Figure 7). Most of these captures were along the continental shelf at depths of >60 m. Monthly catches indicated a southward movement out of the Gulf of Maine in late autumn, although some shad remained there into November. During lOyr of autumn bottom trawl surveys along the Middle 204 Atlantic States, shad were never collected offshore south of lat. 39°N. The relatively low number of successful trawl- ing stations during the winter may be inadequate to define the southern limit of the wintering area (Figure 6). Winter catches occurred at 22 stations from southern Long Island (lat. 39°N) to the southern edge of Georges Bank (lat. 41''N) and reflected the same general area where shad began congregating in autumn ( Figure 7). Except for two shallow-water stations, winter collections of shad were made at a mean depth of 108 m. DISTRIBUTION OF INTERNATIONAL CATCHES The season for major shad catches in ICNAF divisions (Figure 8) agreed closely with distribu- tion according to bottom trawl surveys. Largest annual catches were reported by the United States in Subarea 6 ( 1,517-2,812 1). United States catches between 1970 and 1976 occurred primarily in Di- vision 6B and ranged from 112 to 1,272 t in March and April. Most of this spring catch was taken by the inshore commercial fishery. The only other catch of comparable size was made in Division 5Ze by the Federal Republic of Germany during Sep- tember 1973 and totaled 302 t. Catches in Subarea 5 occurred mainly in autumn; however, winter catches were reported in Division 5Zw and 6A between New Jersey and Cape Cod. Canadian catches in Subarea 4 were greatest in May, with decreasing catches throughout the summer. DISCUSSION The sampling design of NMFS bottom trawl surveys covers a large area in a relatively short period of time and provides good data on fish dis- tribution and concurrent environmental condi- tions. Even though these surveys were initially designed to sample primarily demersal species, results do reflect major changes in the abundance of pelagic species as well (Schumacher and An- thony'; Anderson*). Bottom trawls used during U.S. surveys are less effective on A/osa spp. than 'Schumacher, A., and V. C. Anthony. 1972. Georges Bank (ICNAF Division 5Z and Subarea 6) herring assessment. Int. Comm. Northwest Atl, Fish. Anna. Meet. 1972. Res. Doc. No. 24, Serial No. 2715. 36 p. "Anderson, E. D. 1973. Assessmentof Atlantic mackerel in ICNAF Subarea 5 and Statistical Area 6. Int. Comm. North- west Atl. Fish. Annu. Meet. 1973. Res. Doc. No. 14. Serial No. 2916, 37 p. NEVES and DEPRES, OCEANIC MIGRATION OF AMERICAN SHAD Figure 7. — Location of all American shad catches during autumn bottom trawl surveys, 1963-76, Cape Hatteras, N.C, to Nova Scotia. r^-; / Nova Scott ]i "x :S"' o o , ,. V ' f 1 ^ O Gulf of Maine ;*V;:-200' ; .* - '.; ,' ■,■ * •.*■*. '■ii -J :L* _ • •' * ♦ ;■ ^ Georges v '■■^. Bank ' : it/* •:• /V " September * October • November '■^\\ ON •O Cape /Hatteras ^ ^1 -^A^-*^, 205 FISHHRV Hl'LI.ETIN V(1L 77. NO 1 TW ^ \ \ i \ ^ ■ -^iv^ .^ \.y 1 :/ M-^\y f 1 \ #r^^ \ M/^^ 0 ^ :-'^"^' Figure 8. — Seasonal distribution of major American shad catches in the International Commission for the Northwest At- lantic Fisheries divisions. 1970-75, Cape Hatteras. N.C., toNova Scotia. foreign midwater trawls or the wing trawl (Hol- land**), but bottom trawl survey data provide the most complete, available records on offshore oc- currence. Based on the data presented, survey-related ob- servations to be discussed, and literature to be reviewed, we propose the following migratory cycle for American shad. Offshore movements are 'Holland. B. F., Jr. 1975 Anadromous fisheries research program, northern coastal area. Section 11. N.C. Proj. AFCS ll-lJob6, 43p limited to areas and depths with near-bottom temperatures between 3° and 15°C. Shad occur most frequently in offshore areas of intermediate depths (appro.ximately 50-100 m). Adults that survive spawning together with subadults mi- grate to the Gulf of Maine or to an area south of Nantucket Shoals and remain there through the summer and early autumn. During this period of active feeding, shad are vertical migrators and follow the diel movements of zooplankton in the water column. Most shad move out of the Gulf of Maine in autumn with declining water tempera- tures and congregate offshore, between southern Long Island and Nantucket shoals (lat. .39"-4rN) during the winter. Adults enter coastal waters in a broad front toward the Middle Atlantic coast, as far south as North Carolina during the winter and spring. Shad populations returning to South At- lantic rivers migrate south adjacent to the coast and within the 15°C isotherm to reach home rivers by winter and early spring. North Atlantic popu- lations proceed north up the coast in the spring with the warming of coastal waters above 3°C. Offshore Distribution The wide range of surface temperatures at sta- tions where shad were caught does not support the e.xtrapolation of the inshore temperatures-shad migration regime proposed by Leggett and Whit- ney (1972) to explain offshore movements. The influence of temperature on fish behavior and physiology is most pronounced during the spawn- ing season (Laevastu and Hela 19701, particularly for anadromous fishes. Tag returns within the 13°-18°C isotherms (Leggett and Whitney 1972) may have reflected inshore physiological changes in prespawning adults, leading to higher optimal temperatures approaching those for spawning. Our results indicate that near-bottom tempera- tures between 3' and 15°C provide a better basis for predicting shad movements in offshore waters. Offshore catches during NMFS surveys re- vealed that shad are not limited to the Gulf of Maine in summer months as reported by Talbot and Sykes ( 1958). Shad were also collected in an area south of Nantucket Shoals during summer and autumn surveys. Although shad from most river systems have been collected in the Gulf of Maine during the summer (Talbot and Sykes 1958), it is not known whether all populations migrate together at sea. Distribution during the spring is widespread and not indicative of a syn- 206 NEVES and DESPRES OCEANIC MIGRATION OF AMERICAN SHAD chronous species migration as suggested by Leggett (1977). Coastal tagging studies during the spring reveal an aggregation of many spawning stocks that often detour into estuaries along the coast (Sykes and Talbot 1958; Talbot and Sykes 1958; Chittenden 1974; Leggett 1977; White et al.'"). However, the length oftime each population has been inshore is unknown. Until stock iden- tification at sea is feasible, the regional composi- tion and extent of offshore mixing cannot be documented. The location of winter collections (lat. 39°-41°N) coincides with two previously published capture records (Talbot and Sykes 1958; Walburg and Nichols 1967), but the extent of overwintering in deep water off the continental shelf is unknown. Shad collections in the northern Gulf of Maine during November and December were made at depths >100 m and do not conform (based on pre- vious studies) with the expected migration south in late autumn. These and other shad captured in deep water near Nova Scotia during March fVla- dykov 1936) are outside the apparent wintering area, south of Nantucket Shoals. The possibility that some shad overwinter or become thermally isolated in deepwater areas off Nova Scotia (Vla- dykov 1936; Hodder 1966) needs further investi- gation. Circulation patterns along the Atlantic coast do not account for the seasonal distribution of shad according to survey data or their coastal migration routes based on tagging studies (Talbot and Sykes 1958; Leggett 1977). Bottom drift toward shore and coastal drift south in the Middle Atlantic Bight during winter (Bumpus 1973) would aid migrants moving south, but seasonal shifts in di- rectional flow along the east coast and their effect on shad movements are liable to subjective in- terpretation. Spawning populations moving north and south concurrently could be helped or hin- dered by circulation patterns in the mid-Atlantic area. We believe that seasonal shifts in isotherms, as influenced by circulation patterns, are of great- er importance in defining the migratory route of shad. tribution in the water column from three separate sources: food habits, diel differences in catchabil- ity, and effectiveness of various trawls in captur- ing shad. Adult shad are zooplankton feeders and consume primarily large copepods, mysids, and euphausiids (Bigelow and Schroeder 1953; Hil- debrand 1963; Leim and Scott 1966). The con- sumption of food organisms such as mysids and zoobenthos indicates that part of a shad's life is spent near the ocean bottom (Leim 1924; Walburg and Nichols 1967). In general, stomach analyses reveal that shad feed at all depths but particularly where concentrations of zooplankton occur. Trawling stations where shad were collected during U.S. surveys ( 24 h/day) were partitioned by capture time (Eastern Standard Time) into day (0600-1800 h) and night ( 1800-0600 h). Chi-square analysis on time of capture revealed that daytime catches occurred significantly more often (P<0.01) than night collections (Table 4). Of the night catches, 25'^f occurred within 1 h of the daytime interval. Shad were apparently closer to the bot- tom during daylight hours and thus more suscep- tible to bottom trawling gear. Further corrobo- ration of this daytime occurrence nearer to the bottom is evidenced by the frequency of shad catches in foreign bottom trawls. During daylight hours in March 1974-76, foreign research vessels used herring trawls to sample 280 stations from Long Island to Georges Bank and recorded shad at 71 (25'/( ) of these stations. Contemporary surveys by the United States in the same area with the No. 41 Yankee trawl sampled 207 daytime stations and collected shad at 22 ( ll'/f ) of them. Maximum headrope distance off the bottom for the U.S. trawl was 5 m. The larger foreign trawls had a higher opening (6 m) which increased their effectiveness on off-bottom species, although extra-trawl factors such as vessel size, speed, and gear rigging cer- tainly contributed to the greater overall fishing power of these trawls (Grosslein 1969, 1971). We deduce from the above observations that shad are vertical migrators like other schooling planktivores such as herring, Cliipea harengus, and mackerel. Scomber scombrus (Blaxter 1975; Vertical Distribution Presently there is little information on the depths preferred by shad at sea. We inferred dis- '»White,R.L.,J. T.Lane, and P.E.Hamer. 1969. Popula- tion and migration study of major anadromous fish, N.J, Div. Fish Game Misc. Rep. No. 3M, 21 p. Table 4, — Chi-square test comparing the number of day and night catches of shad during U.S. bottom trawl surveys. 1963-76, Cape Hatteras, N.C. to Nova Scotia. Time Day (0600-1800 h) Nighl (1800-0600 h) Totals ••p. 001 Observed 217 98 Expected 1575 157 5 207 FISHERY BULLETIN VOL 77. NO 1 Isakov"; Rikhter'^), following the diel movements of zooplankton in the water column. This reliance on zooplankton for food may be an additional fac- tor influencing shad distribution during the year. Zooplankton distribution in the Gulf of Maine dur- ing summer and autumn is closely tied to local and regional hydrography (Redfield 1941; Sherman 1966; Cohen'-''); concentrations generally occur along areas of current convergence and divergence (Zinkevich 1967) and at depths <100 m (Bigelow 1926; Whiteley 1948). During winter, the waters around Georges Bank are nearly devoid of zoo- plankton, whereas sizeable neritic populations occur from Nantucket Shoals to southern Long Island (Clarke 1940; Grice and Hart 1962; Zin- kevich 1967). Sette (1950) concluded that water temperature had a limiting rather than causal influence on the seasonal movements of mackerel, and Redfield (1941) noted a parallelism between mackerel distribution and areas of zooplankton abundance. Similarly, Zinkevich (1967) related herring movements to water temperature and seasonal shifts in zooplankton concentrations. Catches of shad during bottom trawl surveys along Georges Bank, Gulfof Maine perimeter, and south of Nantucket Shoals may therefore be re- lated to zooplankton abundance in these areas, but direct evidence is lacking. Coastal Migration Tagging studies and the location of NMFS and ICNAF catches during the spring indicate that most shad populations move toward the mid- Atlantic coast from offshore waters, between lat. 36° and 40°N in the winter and early spring. The time an4 location of tag returns by the mid- Atlantic shad fishery demonstrate that shad from most populations occur in this region during the spring (Talbot 1954; Talbot and Sykes 1958; Leggett 1977; White et al. see footnote 10). Shad tagged near southern Long Island in early spring were recaptured on spawning runs as far south as North Carolina (Talbot and Sykes 1958). Tagging "Isakov, V. I, 1976. The peculiarities of diurnal vertical migrations of mackerel in the northwestern Atlantic. Int. Comm. Northwest Atl. Fish. Annu. Meet. 1976, Res. Doc. No. lll.Senal No. 3934. 3 p. '^Rikhter, V. A. 1976. Proposal on trawUng surveys for estimation of pelagic fish stocks in ICNAF Subarea 5 and Statis- tical Area 6. Int. Comm, Northwest Atl. Fish, Annu. Meet, 1976, Res, Doc, No, 116. Serial No, 3939, 3 p, ^•*Cohen, E, B, 1975, An overview of the plankton com- munitiesof the Gulf of Maine, Int, Comm, Northwest Atl, Fish, Annu. Meet, 1975, Res. Doc, No, 106, Serial No, 3599, 16 p. of shad in North Atlantic rivers during the spawn- ing period produced recaptures as far south as the North Carolina coast in subsequent years (Talbot 1954; Vladykov 1956; Talbot and Sykes 1958; Leggett 1977). These tag returns provide an ap- proximate geographical range of entry into coastal waters by returning oceanic migrants (lat. 36°- 40°N). Assuming that the 3°and 15"C isotherms define the northern and southern limits respectively of shad movements at sea, prespawning adults re- turning to coastal waters from the ocean would face a thermal barrier south of Cape Hatteras. Offshore bottom temperatures along the South At- lantic coast remain above 17.5°C during the year, whereas bottom temperatures on the continental shelf north of Cape Hatteras and inshore tempera- tures for the South Atlantic coast drop below 15°C by December ( Figure 9). The proximity of the Gulf Stream to North Carolina creates a narrow coastal corridor at Cape Hatteras, providing the only mi- gratory route to southern rivers if shad returning to these home rivers are to remain within their marine temperature regime. Migration toward shore north of Cape Hatteras and then south along the coast appear to be essential prerequisites for successful homing to South Atlantic rivers. In con- trast, shad returning to North Atlantic rivers dur- ing the spring are not obliged to follow a coastal route because offshore temperatures in the Middle Atlantic Bight are well within the shad's range of oceanic occurrence (Figure 9). However, tag re- turns from adults tagged on spawning runs into North Atlantic rivers indicate that many (most?) adults do enter coastal waters in the lower mid- Atlantic region and migi'ate north along the coast to reach home rivers as repeat spawners the fol- lowingspring(Talbot 1954; Leggett 1977). Results of Atlantic coast tagging are consistent with our upper temperature limit ( 15°C) for shad migration at sea; all prespawning, oceanic migrants enter inshore waters as far south as North Carolina. The significance of the Cape Hatteras region to other aspects of northern versus southern shad biology was discussed by White and Chittenden ( 1977). Based on our proposed migratory route, large shad catches in ICNAF Division 6B during the spring would consist of shad entering home rivers and populations moving toward and along the coast. Catches in Chesapeake Bay and the sounds of North Carolina from late November to early December (Hildebrand and Schroeder 1928; Tal- bot and Sykes 1958; Walburg and Nichols 1967) 208 NEVES and DESPRES OCEANIC MIGRATION OF AMERICAN SHAD f- il NOVEMBER DECEMBER Figure 9. — Mean monthly bottom temperatures dunng winter and spring along the eastern U.S. coast. Cape Cod. Mass.. to Florida. (From Walford and Wicklund 1968.) would be shad returning to natal rivers farther south. Inshore temperatures are unstratified along the Atlantic coast during the winter (Parr 1933). Since freshwater discharge generally oc- curs along the surface from estuaries, water tem- peratures would not preclude near-surface move- ments of shad to detect essential olfactory and rheotaxic cues for successful homing (Dodson and Leggett 1974). Estuarine temperatures from initial to peak ar- rival of shad at home rivers along the Atlantic coast are between 3° and 15°C (Talbot 1954; Massmann and Pacheco 1957; Walburg and Nichols 1967; Leggett 1972; Leggett and Whitney 209 FISHERY BULLETIN VOL 77. NO 1 1972; Chittenden 1976; Sholar'^). Within this temperature regime, southern populations begin reaching home estuaries at the higher tempera- tures, while northern populations do so at the lower temperatures. Peak numbers of shad enter the St. Johns River, Fla., in mid-January when water temperatures are at an annual low of 15°C; the peak in juvenile emigration occurs simultane- ously (Leggett and Whitney 1972; Williams and Bruger 1972). Shad first enter the Connecticut River in late March-early April when water tem- peratures are approximately 4°C and peak in abundance at 13°C (Leggett and Whitney 1972). In general, most shad populations north ofCapeHat- teras begin entering rivers at approximately 4°C, and the peak in upstream migration occurs at temperatures between 10° and 15°C (Leggett and Whitney 1972). The lower thermal tolerance of juvenile shad in freshwater was near 2.2°C in a short-term laboratory .*udy (Chittenden 1972) and roughly 3°-4°C in small ^jutdoor ponds (Blair'^). This lower thermal limit agrees closely with the lowest tem- perature at which subadult shad were collected during NMFS offshore surveys (3°C). Chittenden (1972) also reported that juveniles ceased feeding when water temperatures dropped below 4.4°C. However, we collected 17 juvenile and subadult shad (9-32 cm FL) during a NMFS coastal survey in January 1978, at stations with bottom tempera- tures between 2.8° and 4.3°C. All but one stomach were filled with mysids and copepods, indicating active feeding at these temperatures in saltwater. Further evidence to support our bottom temper- ature regime for predicting the coastal movements of shad is provided by North Carolina's anadro- mous fishery research program. Their annual sur- veys on river herring since 1971 show that shad occur off the North Carolina coast from January to April, at bottom temperatures between 6° and 12°C and at depths <26 m (Johnson et al."*). Shad catches decline substantially when water temper- atures exceed 12°C, coinciding with entry into es- tuaries or possibly, northward migration. This '^Sholar, T. M. 1977. Anadromous fisheries research pro- gram. Cape Fear River System, phase 1. N.C. Proj. AFCS 12.6.3 p. '^Blair, A. B. 1977. American shad culture and distribu- tion studies at Harrison Lake National Fish Hatchery. Proc. Workshop American Shad, Amherst, Mass., Dec. 1976, 10 p. ">Johnson. H. B.. B. F. Holland, Jr., and S G Keefe. 1977. Anadromous fisheries research program, north- em coastal area. Section II. N.C. Proj. AFCS 11-2, 41 p. temperature range concurs with offshore bottom temperatures having the most frequent shad catches during NMFS bottom trawl surveys (7°- 13°C). The shallow depths traveled by coastal migrants during the winter and spring would ac- count for their unavailability to offshore sam- pling. Critical data on the oceanic phase of most anad- romous fishes are lacking (Harden-Jones 1968), and our general description of shad movements must await additional research at sea to corrobo- rate or correct the proposed migratory cycle. It would seem energetically wasteful for North At- lantic populations to follow the same shoreward route as do Middle and South Atlantic shad. The return of all populations to this region may have historical significance, since shad are believed to have been most abundant in the mid-Atlantic por- tion of their coastal range (Leim 1924). Variations in life history patterns among populations are generally considered to be adaptive responses (Cole 1954; Murphy 1968; Gadgil and Bossert 1970), and differences in life history characteris- tics among shad populations in rivers ( Carscadden and Leggett 1975b) may also exist at sea. Endocrine-induced differences in the timing of migratory behavior and gonadal maturation may be life history strategies of adaptive significance, considering the species' wide geographical range (21° of latitude). The lengthy period of migration toward the mid-Atlantic coast from offshore by prespawning adults may stem from population- specific responses to photoperiod or temperature cues. Further study on the sensory systems and environmental cues involved in migration is re- quired before a more comprehensive explanation for the migratory cycle of shad is available. ACKNOWLEDGMENTS We are indebted to the Resource Surveys Inves- tigation section and other staff members at NMFS, Woods Hole, for their cooperation in this endeavor. Special thanks go to Ralph Mayo for sharing his computer expertise and to Bill Leggett, Emory Anderson, Jon Gibson, Brad Brown, and an anonymous reviewer for reviewing the manuscript. The Massachusetts and Virginia Cooperative Fishery Research Units provided financial support. We dedicate this paper to R. J. Reed for his contributions to the study of Ameri- can shad biology. 210 NEVES and DEPRES OCEANIC MIGRATION OF AMERICAN SHAD LITERATURE CITED BIGELOW. H. B. 1926. Plankton of the offshore waters of the Gulf of Maine. Bull. U.S. Bur. Fish. 40. 509 p. BIGELOW, H. B., AND W. C. SCHROEDER 1953. Fishes of the Gulf of Maine. U.S. Fish Wildl. Serv., Fish. Bull. 53, 577 p. BLAXTER. J. H. S. 1975. The role of light in the vertical migration of fish - a review. In G. C. Evans, R. Bainbridge. and O. Rackham (editors). 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Bull. 4:101-115. 212 SOURCES AND DISTRIBUTION OF BLUEFISH, POMATOMUS SALTATRIX, LARVAE AND JUVENILES OFF THE EAST COAST OF THE UNITED STATES Arthur W. Kendall. Jr.' and Lionel A. Walford^ ABSTRACT Larval bluefish are found offshore somewhere between Cape Cod, Mass. , and Palm Beach, Fla. , dunng every season of the year. However, there appear to be two main spawning concentrations — one during spring near the western edge of the Gulf Stream in the South Atlantic Bight and the other during summer over the contmental shelf of the Middle Atlantic Bight. Larvae complete development near the surface; juveniles are strongly associated with the surface. Juveniles from the spring spawning remain at sea and are carried northward past Cape Hatteras, N.C., above the edge of the continental shelf As surface shelf water warms, they move shoreward to spend the summer in estuaries of the Middle Atlantic Bight Bluefish spawned in summer remain at sea asjuveniles or enter estuaries briefly in late summer. In fall, as the water cools, the juveniles move southward out of the Middle Atlantic Bight. It is possible that these two spawnings represent different populations. A smaller fall and winter spawning which occurs offshore south of Cape Hatteras may represent a small population resident to the South Atlantic Bight. Bluefish, Pomatomus saltatrix (Linnaeus), occur in most temperate coastal regions of all world oceans (Briggs 1960). Fowler (1944) erroneously reporteii them from the eastern Pacific where they do not occur. The earliest descriptions of eggs and larvae of bluefish by Agassiz and Whitman ( 1885) which have been quoted by other authors, e.g., Padoa (1956) and Salekhova (1959), are errone- ous. Colton and Honey (1963), Deuel et al. ( 1966). and Norcross et al . ( 1 974 ) correctly described them and showed that bluefish spawn pelagic eggs in the open sea and larval development takes place near the surface. Juveniles generally move from the open sea to coastal areas and estuaries. This pattern has been observed off North .'\merica. in the Black Sea. and off South Africa (Irvme 1947; Bigelow and Schroeder 1953; Oben 1957; Smith 1961). Along the Middle Atlantic Bight, i.e., from Cape Cod, Mass., to Cape Hatteras, N.C., bluefish eggs, larvae, and juveniles have been collected during several ichthyoplankton studies (Sette 1943; Lund and Maltezos 1970; Norcross et al. 1974). Al- though restricted in sampling area or time, these 'Northeast Fisheries Center Sandy Hook Laboratory, Na- tional Marine Fisheries Service, NOAA. Highlands, NJ 07732; present address; Northwest and Alaska Fisheries Center, NMFS, NOAA, 2725 Montlake Boulevard East, Seattle. WA 98112. ^New Jersev Marine Sciences Consortium, Fort Hancock, N.J 07732. studies have indicated that spawning and larval development take place offshore from Chesapeake Bay to southern New England in late spring and summer. Juveniles occur in estuaries along the middle Atlantic coast in summer (Clark^). The sources of data for this paper are plankton collections taken by personnel of the National Marine Fisheries Service (NMFS), NOAA, Sandy Hook Laboratory, as part of a study to investigate the importance of estuaries as nursery areas of Atlantic coast fishes. The first part of this study consisted of a survey of ichthyoplankton over the continental shelf an area thought to be the spawn- ing grounds for many species of fishes. From in- formation gained during this study, we hoped to trace the movement of young stages from spawn- ing grounds and thus evaluate the importance of estuaries as nurseries. From the results of this study, several additional short cruises were con- ducted to study further the distribution of larval and juvenile bluefish in certain offshore areas at specific times of the year. In this paper, information from these studies and those of previous workers is presented to help elucidate the times and places of bluefish spawn- M.tnuscript accepted September 197H FISHERY BULLETIN: VOL 77. NO 1. 1979 =Clark, J, R, 1973. Bluefish. In A. L. Pacheco (editor). Proceedings of a workshop on egg, larval, and juvenile stages of fish in Atlantic coast estuaries, p. 250-251. Middle Atl, Coastal Fish. Cent,. Tech. Publ. 1. 213 FISHERY BinXETIN VOL 77, NO 1 ing along the east coast. Evidence to link the MATERIALS AND METHODS offshore occurrences of bluefish larvae to the es- tuarine occurrences of bluefish juveniles also is (Table 1, Figure 1) presented. This early life history information re- lates to what is known of the number and relative An ichthyoplankton study of Atlantic continen- sizes of populations of bluefish along the east tal shelf waters by the Sandy Hook Laboratory coast. began in 1965-66 with a survey from Cape Cod to T.-\BLE 1.— Bluefish collections 1 from RV Dolphin ichthyoplankton surv ■eys and supplemental cruises for young bluefish off the east coast of the United States. Number of Bluefish Number of Standard Continental shelf area Dates stations Gear' collections Number lengths (mm) Cape Cod to Cape Lookout 3-15 Dec 1965 78 35 Gulf V MV\n" 25 Jan.-9 Feb 1966 86 0 Gulf V MWT 1 1 8.7 6-22 Apr, 1966 92 3 Gulf V MWT 12-24 May 1966 92 63 Gulf V MWT 5 25 3 4-9 1 17-29 June 1966 92 Gulf V 59 MWT 2 2 33-37 5-26 Aug 1966 92 Gull V 25 1,621 2 4-13.2 66 MWT 4 8 9-128 13-18 Sept 1966 30 15 Gulf V MWT 2 2 4 0-6 7 28 Sept -20 Oct 1966 92 Gull V 1 2 3 3-4 0 77 MWT 1 17 26-219 9 Nov -4 Dec 1966 92 Gull V 68 MWT 2 2 49-124 New River. N C . to 15-19 Feb 1966 26 Gulf V 1 1 80 Palm Beach, Fla 7-15 May 1967 80 Gulf V 20 563 2 2-116 80 SMN 11 14 18-34 80 2-m ring 22 July-1 Aug 1967 80 80 53 Gull V SMN MWT 19-26 Oct 1967 80 80 77 Gulf V SMN 3-m ring 5 17 3 9-6 9 27 Jan -4 Feb 1968 80 80 Gull V SMN 2 2 5 1-6,0 50 MWT 2 5 63-92 New York Bight 10-16 June 1969 44 46 15 SMN MWT Nighllighl 1 1 1 1 45 1 45,9 15-18 June 1970 44 44 SMN 2-m ring 3 1 3 1 20 8-35 0 31 3 New Jersey to Maryland 14-18 June 1971 32 SMN 5 8 238-33.7 32 Haedrich 5 7 23,6-32 1 12 MWT 3 3 27,3-357 Virginia to North Carolina 27 Apr -5 May 1971 58 SMN 19 163 12 6-31 4 60 Haedrich 27 1.464 3 9-33,5 19 2-m ring 3 10 4 1-11,3 Cape Hatteras. N C. weekly. 1 1 Apr -31 May 1972 36 Haedrich 21 1.472 3 5-25 4 New Jersey to Virginia 29 Oct-1 Nov 1970 35 SMN 3 3 400-482 35 Haedrich 3 4 36,4-34,9 11 2-m ring 1 3 200 Georgia to Florida 29-31 Jan 1971 24 24 24 SMN Haedrich MWT 'MWT = midwater trawl; SMN = surface meter net, see text for further details 214 KENDALL and WALFORD SOIIRCES AND DLSTRIBl'TION OF BLUEFLSH MIDDLE > ATLANTIC BIGHT SOUTH ^ATLANTIC BIGHT PATHS 10 ^^ NUItSUBY FlGl!RE 1. — Major features of surface waters and bluefish larval and juvenile distribution off the U.S. east coast. Cape Lookout, N.C. Over the year, as weather permitted, 92 stations over 14 transects were sampled during 8 cruises. In 1967-68, the study continued, working from Cape Fear, N.C, to Palm Beach, Fla., sampling at 80 stations over 14 tran- sects during each of 4 seasonal cruises. Plankton was sampled with Gulf V samplers (0.52-mm mesh). The30-min step oblique tows were made at 2.1-2.6 m/s. Two nets were towed simultaneously; one from the surface to 15 m, the other from 18 to 33 m where water depths permitted. Details of gear, procedures, and physical, plankton volume, and juvenile fish data have been published (Clark et al. 1969, 1970). The same procedures were followed on two addi- tional cruises in 1966. One of these (D-66-2) sam- pled 26 stations on five transects between Jacksonville, Fla., and Palm Beach in February 1966. The other ( D-66-1 1 ) sampled 30 stations on the four northernmost transects (Cape Cod to New- Jersey) in September 1966. Collections for pelagicjuvenile fishes were made during the cruises in 1965-66 with a scaled-down Cobb midwater trawl (Clark et al. 1969). During the cruises in 1967-68, several nets were towed for juvenile fishes. At each station a surface meter net with 6-mm mesh was towed beside the ship. Sub- surface samplers included the scaled-down Cobb trawl, and a 1-m and a 2-m ring net (Clark et al. 1970). Several offshore cruises from 1969through 1971 were designed mainly to augment the data on oc- currences of bluefish juveniles. A surface meter net and a Haedrich neuston net (Bartlett and Haedrich 1968) were used in paired tows on most of these cruises. Other sampling equipment used at various times included dip nets with nightlights and several types of midwater nets. In spring 1972, a series of eight weekly cruises near Cape Hatteras aboard a chartered sport fishing boat was conducted working from Oregon Inlet, N.C, out into the Gulf Stream. On each cruise, we made two neuston tows with a Haedrich net near Cape Hatteras. One of these was in the green coastal water, the other in the blue Gulf Stream water, and each tow was within 100 m of the interface between the two water masses. Dur- ing the return to Oregon Inlet, some 60 km north of Diamond Shoals Light Tower, several addi- tional tows sampled the full range of surface water temperatures occurring in the area. Weather and water temperature data relative to these cruises were gathered from the U.S. Naval Oceanographic Office and the U.S. National Weather Service. Additional data on bluefish and juveniles and ancillary observations from these collections are available."* ■•Kendall, A. W.. Jr., and L. A. Walford. 1978. Data as- sociated with offshore larval and juvenile bluefish collections at Sandy Hook Laboratory 1965-1972. Unpubl. manuscr,, .5 p. Report No, SHL 78-9. Northeast Fisheries Center Sandy Hook Laboratory, National Marine Fisheries Service. NOAA, High- lands, NJ 07732. 215 FISHERY BULLETIN VOL 77. NO 1 We will generally refer to bluefish <10 mm standard length (SL) as larvae and those >10 mm SL as juveniles. Bluefish hatch at about 3 mm SL and by 10 mm SL the fin ray development is nearly complete and in living specimens the body is dark blue on the back and silvery on the sides, as in the pelagic juvenile stage of goatfish and mullet (Nor- cross et al. 1974). RESULTS H\dr<)graphiL Ffaturc!) iif Middle and South Atlantic Bights Shelf water characterized by salinities of <35%o, is divided into coastal water ( <33.6%o) and shelf edge water i33.6-35.0"'iMii i Wright and Parker 1976). The Gulf Stream, characterized by salinities "-36. 0"/oc) and/or temperatures -IS'C at 100 m or -IS'C at 200 m, flows generally beyond the edge of the continental shelf The water mass between the shelf water and Gulf Stream, called the slope water, is separated from the shelf water by a strong surface feature, except in midsummer, called the slope front. Surface manifestations such as lines of flotsam, differences in water color, and choppiness of the Gulf Stream are seen on moder- ately calm days. The .shelf water is sluggish and influenced by short-term effects of wind, but gen- erally moves south along the shore. The Gulf Stream moves northward or northeastward at ve- locities over 100 cm/s (Sverdrup et al. 1942). Eggs Bluefish eggs, which share features with pelagic eggs of many other species, were not found in any of our collections. Bluefish eggs have a smooth spherical membrane, a diameter of 0.90-1.20 mm averaging 1.00 mm, a pigmented yolk, a single oil globule about 0.2 mm in diameter, and melanophores in rows on the embryo (Deuel et al. 1966). Even though an egg has all of the above features, it can be identified with certainty as being a bluefish egg only if the oil globule is pig- mented and in later development the number of myomeres has become established at 24 to 28. Two studies have reported occurrences of bluefish eggs along the east coast. Marak and Col- ton (1961) listed a few of them from late May to early June 1953 in 12,8°C water south of Cape Cod. These data are suspect because: 1 ) identifica- tion was based on inadequate descriptions by Agassiz and Whitman (1885) and Perlmutter ( 1939); and 2) adult bluefish in spawning condition are not present off southern New England until later in the year when temperatures are consider- ably warmer. In a second study conducted from 1960 to 1962 off Virginia, Norcross et al. (1974) reported bluefish eggs during the period June through August from near shore to the continental slope. Although none occurred in our collections, from the similarity in distribution of bluefish eggs and larvae seen by Norcross et al. ( 1974), it seems that an accurate indication of spawning location can be derived from the capture of small larvae. Larvae .Scasonal-Cjfographic Distribution Although bluefish larvae occurred between Massachusetts and Florida during every season, two major geographically distinct concentrations of larvae were found; one south of Chesapeake Bay near the Gulf Stream in spring, and the other north of Cape Hatteras over the middle of the continental shelf in summer. During spring, bluefish larvae were taken from near Cape Hatteras to Cape Canaveral, Fla. Of the 473 larvae taken at 25 stations during the surveys of May 1966 and 1967, greatest concentrations were between the offings of New River, N.C., and Charleston, S.C., near the edge of the continental shelf (Figure 2). In April and May 1971, we also caught bluefish larvae near Cape Hatteras primarily offshore near the Gulf Stream. From these data, it appeared that bluefish spawned near the edge of the continental shelf in the South At- lantic Bight during spring. Bluefish dominated the neuston catches near Cape Hatteras during the eight weekly cruises in spring of 1972 (Table 2). They occurred on every cruise and in every water type sampled. The var- iability in catches between paired tows during this series was too large to permit precise comparison among the dates or sampling areas. However, the largest catches were made in water just shoreward of the Gulf Stream. Most of the specimens taken in or near the Gulf Stream were between 5 and 12 mm SL, whereas the few taken over the shelf ranged from 11 to 21 mm SL. The numbers of bluefish caught each week gave no indication of relative abundance during spring in this area, partially because weather-influenced 216 KENDALL and WALFORD SOURCES AND DISTRIBUTION OF BLUEFISH BLUEFISH LMVAE * -P CRUISf D -66 -S MAY 12-24, 1966 AA -PP; CRUISE 0-67-4 MAY 7 - 15, 1967 SELECTED SUFACE 1SOTHBMS ( "C 1 surface temperature patterns affected the catch rate. Large catches just shoreward of the Gulf Stream followed periods of northerly winds which caused a compression of surface isotherms in this area. Following southerly winds the isotherms were spread out and catches were low. It thus appears that the catch rate was related to the width of the band of suitable water, and that in turn was related to wind conditions. No bluefish larvae were collected in the Middle Atlantic Bight in January, April, May, and June 1966, but they were abundant and widespread in August when their distribution extended from east- ern Long Island, N.Y., to Virginia and more or less over the breadth of the continental shelf (Figure 3). They were most abundant off New Jersey and Delaware. Most of these larvae were small (mean, 4.0 mm SL) indicating that spawning had occurred not long before this cruise. The relative number of fish <4 mm SL was gi-eatest at the northern end of the survey area and diminished progressively southward to Delaware Bay ( Figure 4 ). This effect could have resulted from growth of the larvae dur- ing our sampling from north to south in this area over a 3-day period. It also might have resulted if bluefish spawning had started in the south and progressed northward. Either or both of these pro- cesses may have been involved. There was an 11-day gap in sampling between Delaware Bay (Transect F) and Maryland (Transect G). This might account for our finding so few, but larger larvae south of Delaware Bay. Bluefish spawning in middle Atlantic waters was almost finished by the end of summer, judging from the paucity of specimens taken during Sep- tember and October (Figure 5). In September, when we sampled only north of middle New Jer- sey, we caught two larvae; and in October, when the sampling area extended over the whole Middle Atlantic Bight, we again caught two. We have no information on the southerly extent of bluefish larvae during September, since there was no sam- pling south of New Jersey then. Four bluefish larvae were taken during winter cruises, one at each of four stations near the edge of the continental shelf. One was taken off North Carolina ( Transect N) and the other three between St. Augustine, Fla., and Palm Beach (Transects Y, KK, and LL). Figure 2.— Distribution of surface temperatures and larval bluefish in May. Transects A-P sampled May 1966; AA-PP sam- pled May 1967. 217 FISHERY BULLETIN: VOL, 77. NO, 1 Table 2. — Bluefish catches in paired neuston nets during eight weekly cruises off Cape Hatteras, N.C., April, May 1972. f 1 Tow 1 Apr, 2 18 Apr, 27 Apr, 4 1 Vlay 2 11 1 May 2 16 1 May 2 23 1 May 2 31 1 May Item 1 2 1 2 2 GuH Stream Surface temperature ('C) Bluetisti catcti rvlean length (mm SL) 22 0 0 ND 0 23,3 7 109 ND 0 22 5 12 89 224 218 100 23,5 8 11 6 ND 0 240 4 98 ND 0 25 1 0 ND 0 ND 0 ND 0 255 0 ND 0 200 m stioreward ot Gull Stream Surface temperature ( C) Bluelish eaten lytean length (mm SL) 160 4 48 ND 0 195 41 111 20 6 14 10 0 13,2 93 55 22 1 771 99 200 3 123 186 2 91 203 4 106 ND 0 226 6 120 ND 0 ND 0 ND 0 20 5 35 59 195 217 163 Intermediate (shelf) water; Surface temperature (°C) Bluefish catch Mean length (mm SL) 12 5 0 NO 0 10,6 0 117 0 ND 0 ND 0 154 0 170 1 21 4 180 17 12,9 16 1 0 194 2 187 ND 0 15 1 0 ND 0 173 0 163 0 Nearshore: Surface temperature ( C) Bluefish catch Mean length (mm SL) 130 0 ND 0 108 0 ND 0 ND 0 ND 0 ND 0 ND 0 160 5 107 ND 0 195 2 188 20,0 0 ND 0 ND 0 190 0 ND 0 Temperature-Salinity Regimes During the survey, bluefish larvae occurred in two distinct temperature-salinity regimes. One regime was characterized by surface temperatures of 18°-26=C and salinities of .30-32%« (Figure 6i. These conditions prevailed from late spring through the summer above the thermocline in coastal waters of the Middle Atlantic Bight. Blue- fish spawning evidently did not begin there until late July or early August, judging from the small number of large larvae taken in August. Thus, spawning of bluefish in the Middle Atlantic Bight seemed to be influenced partly by features of envi- ronment other than temperature and salinity. The other regime was associated with the inner edge of the Gulf Stream and was characterized by surface temperatures of 20°-26°C and salinities of 35-38%(i. As mentioned above, few bluefish larvae occurred in this water during the fall and winter, considerable numbers during the spring, and none during the summer. Sea.S(>nal Surface Temperature Relations Regardless of season or area, nearly all larvae were taken in waters between 17° and 26°C. Lar- vae appeared on the shelf throughout the South Atlantic Bight in spring where the surface water temperatures ranged from 19° to 24.5°C. North of Cape Hatteras where we took no larvae in spring, shelf water was <15°C, but near the edge of the Gulf Stream where we did take larvae, tempera- tures were >15°C. At the stations where bluefish larvae were taken during August, surface tem- peratures ranged from 18.8° to 25.7°C. Surface water covering most of the Middle Atlantic Bight south of eastern Long Island was within this temperature range (Figure 3). However, south of Cape Hatteras no bluefish larvae were taken in July when temperatures were mostly >26°C. Sur- face water temperature had decreased between our September and October cruises. The 20°C sur- face isotherm was off Long Island in September, but had moved south to Virginia by October. The bluefish larvae were taken in 20.3°C water in Sep- tember and 16.4°C water in October. The few bluefish larvae taken near the edge of the conti- nental shelf off Florida in October were in water >25°C. In winter, all occurrences were in water >20°C, which was limited to the outer portion of the continental shelf from North Carolina to Florida at that time. Diel Cycles of Vertical Distribution The number of larvae caught in shallow tows (0-15 m) when compared with deep tows ( 18-33 m) during day and night provided limited informa- tion about diel cycles of vertical distribution. The catch rate was highly dependent on net depth. At the 46 stations where both nets were towed and either caught bluefish larvae, more occurred in the shallow net at 37 stations indicating that the lar- vae were more abundant in the shallow layer i sign test, P<0.001). Nearly all of the catch of the deeper net may have occurred as it passed through the surface layer during setting and retrieving. Figure 3. — Distribution of surface temperatures (left) and lar- val bluefish (right) in July-August. Transects A-P sampled Au- gust 1966; AA-PP sampled July-August 1967. 218 KENDALL and WALFORD SOURCES AND DISTRIBUTION OF BLUEFISH BLUEflSH LABVAE CftUtSE D -66 - rO AUG. 5 - 26, 1966 LAUVAE / STATION • NONE 1 -5 « - » iiilili"-"" ^■1 >200 219 FISHERY BULLETIN VOL 77. NO 1 FRa'KE 4.— Percent of bluefish larvae <4 mm SL captured on transects B-H (Figure 2l in the Middle Atlantic Bight in August 1966. Indeed, later studies (Kendall and Naplin^i have shown that bluefish larvae occur primarily within 6 m of the surface. The distribution of catches was similar during day and night (Table 3). Larval Lengths The length distribution of larvae taken in the shallow tows was not significantly different from that taken in deeper tows (x^P>0.05) (Table 4). This result is to be expected if, as indicated above, the catches in the deeper tows can be accounted for by contamination in the surface layer. Fish taken during the day, however, were generally smaller (2.5-4.5 mm) than those taken at night (5.5 mm and larger) (x''^ f <0.001). This effect could result from net avoidance by larger larvae during day- time. The cruises were too infrequent to estimate larval growth. Juveniles During the survey cruises we tried to collect pelagic juvenile fishes and during later cruises tried to clarify results from the surveys by sam- pling in areas and during seasons in which juveniles had occurred earlier. We took bluefish juveniles in several kinds of midwater and surface nets. It is difficult to compare the catches of these several nets or the catches made in different years; nevertheless, this limited information about ^Kendall, A. W.. Jr., and N. A, Naplin. Diel-vertical distribu- tion of bluefish iPomatomus sattatrix) larvae and that of as- sociated fish eggs and larvae. Manuscr. in prep. Northeast Fisheries Center Sandy Hook Laboratory, National Marine Fisheries Service. NOAA, Highlands, NJ 07732. Figure 5. — Distribution of surface temperatures and larval bluefish in September-October. •lUEFISH LAHVAE A -D: CftUISE D -66 - II A. '?: SEPT. 13 - le, \9U ^^C r. CKUISE D - 66 - 1 2 \^/ SEPT . a - OCT . 20, 1966 y^ -ft. CRUISE D-67-16 ./V _CAPt COO 9 y-^ ^. CAPE MAITfRAs/ ff ■" <===-^ '7 220 KENDALL and WALfORD SOURCES AND DISTRIBUTION OF BLUEFI! ,1 ' 18- 23 36 81 5 1147 256 7 1 18 1 1 3 - 1 22 11 19 2 48; 41 1 3 223; 18 ^193 1 3 14 NUMBER OF TOWS 1 ^ 33 3! SALINITY %■> 1- 1-n S-9 10-19 >19 FIOURE 6. — Clustering of catches of larval bluefish by temper- ature-salinity combination during RV Dolphin surveys, 1965- 68. Numbers of bluefish larvae superimposed on temperature- salinity combinations where they were caught. Table 3.— RW Dolphin 1965-68 ichthyoplankton survey. A com- parison of bluefish larval catches during day and night. Number of tows Larvae/tow Day Nighl \' t 12 6 0 309 2-10 6 7 0.303 1 1-1 00 7 7 0 080 100 3 2 0 078 Tolals 28 24 0 770 (3df.P 0 80) offshore seasonal geographic distribution of bluefish juveniles indicates a complex pattern of movements from offshore spawning areas to coastal and estuarine nursery areas. In summary we found bluefish juveniles, pre- sumably from the spring spawning, at the surface near the slope front from south of Cape Hatteras to off the Middle Atlantic Bight in April to June (Figure 1). We hypothesize that they move north- ward along the slope front, then cross the shelf, enter estuaries of the Middle Atlantic Bight and after spending the summer in the estuaries, re- turn to the sea and move southward along the coast and out of the Middle Atlantic Bight. Some juveniles from the summer spawning in the Mid- dle Atlantic Bight remain in coastal waters while some enter estuaries briefly. They too leave the Middle Atlantic Bight in early fall. The following is our evidence for these conclusions. In May 1967, juvenile bluefish were scattered over the continental shelf in the South Atlantic Bight and north to Cape Hatteras (Figure 7). The largest specimens were from stations near shore. In April and May 1971, we sampled the offshore area intensively around Cape Hatteras to find any trace of young bluefish which could be attributed to larvae and juveniles such as had appeared pre- viously to the south. During this cruise neuston tows took bluefish juveniles near the edge of the continental shelf ( 100-fm (183-m) isobath) (Figure 8a). All of the specimens taken were in water >15°C, which occurred all across the shelf south of Cape Hatteras, but only near the edge of the shelf north of there. In the June 1966 survey, when 59 stations were sampled, bluefish appeared at each of two widely Table 4.— RV Dolphin ichthyoplankton surveys 1966-68. Length distributions of larval bluefish collected in Gulf V samples. Soutti Atlantic Bight IVIiddle Atlantic Bight Shallow tows Deep tows Day Night midpoint (mm SL) D-66-1 Winter D-66-2 D-68-1 Spring Fall Summer All D-66-5 0-67-4 D-67-16 D-66-10 D-66-1 1 D-66-1 2 data 2.5 97 231 301 27 266 62 328 3.5 4 205 8 610 2 739 89 689 139 828 4.5 128 6 515 1 602 49 371 280 651 5.5 1 4 15 1 136 145 12 72 85 157 6.5 1 2 2 21 1 22 5 1 1 16 27 7.5 5 1 1 14 2 7 9 16 85 1 ; 8 5 13 2 10 5 15 95 2 1 5 7 1 2 6 8 10 5 10 10 to 10 11 5 1 1 2 1 1 2 125 1 1 1 13,5 1 23.5 1 1 Total 1 1 2 25 448 17 1.547 2 2 1,858 187 1,429 616 2.045 688 363 4 31 400 3 98 3 88 3 73 4 51 3 97 Variance 3 55 1 61 0 96 1 31 1 58 1 26 0 84 2 78 1 55 221 FISHERY BULLETIN VOL 77. NO I separated nearshore stations ( Figure 7 ). The regu- lar presence of bluefish juveniles in offshore wa- ters of the Middle Atlantic Bight in June was observed in three subsequent years. They occurred during 1969 only near shore; during 1970 only near the edge of the continental shelf; and during 1971 they were scattered over the shelf and slope (Figure 8b, c, d). The origin of these juveniles was puzzling, because there was no evidence of bluefish larvae in the Middle Atlantic Bight until midsummer. We had taken larvae and juveniles in April and May from Cape Hatteras south to Florida mainly offshore near the slope front. Ap- parently these fish become distributed along the slope front off the Middle Atlantic Bight in May and June and then cross the continental shelf in June as surface waters become suitably warm. Surface temperatures on the shelf are generally 15° to 20°C at this time, and most of the juveniles were taken in water >18°C. The juveniles we caught in August (Figure 7) were presumably products of recent spawning in nearby waters, for only slightly smaller larvae appeared in the plankton tows in the same area. One specimen 128 mm SL taken just outside Chesapeake Bay had probably been spawned in the spring off the South Atlantic Bight. We collected a few juveniles of widely differing sizes during two surveys in fall 1966. In a cruise conducted in 1970, we confirmed the regular pres- ence of juvenile bluefish in the Middle Atlantic Bight in fall. We then collected juveniles between Delaware and Chesapeake F^ays within 13 km of the shore ( Figure 8e); and several specimens about 200 mm SL in the same area. The juveniles from these cruises can be attributed to the summer spawning of bluefish in continental shelf waters of the Middle Atlantic Bight; and the fish about 200 mm SL to the southern spring spawning. The lat- ter fish had presumably spent the summer in mid- dle Atlantic estuaries ( Wilk") and had returned to the ocean. A 124-mm SL specimen taken in November may have originated from either spawning. No bluefish juveniles were taken in fall in the .South Atlantic Bight and neither larvae nor *Wilk,S.J. 1977. Biological and fisheries data on bluefi.sh, Pomatomus saltatrix (Linnaeus). Sandy Hook Lab. Tech. Ser. Rep. 11, 56 p. FIOIRE 7. — Months of capture lindicated by numerals) of juvenile bluefish at stations sampled by surface meter net and nndwater trawl during RV Dolphin surveys, 1965-68. 222 KENDALL and WALFORD SOURCES AND DISTRIBUTION OF BLUEFISH ■'•• ^^ J .v.>^=t^ >' ^^ . ^ i -**f /^\y,^r ^y *• tf\p^^^p'^'^ V ^-^■^-^ '^ J'. ■ K ^"""^ ■..._*°^ 5S^'. / ir ^ — """^ / ss* ./ • 1 " \- 3«",- nr- CRUISE D-69-13 JUN 10-17, ® V V n' T Y cnuise 0-70-14 JUN 15-16. 1970 (M '^y CAM I y/^' FIGURE 8.— Distribution of juvenile bluefish and surface temperatures during six cruises over portions of the Middle Atlantic Bight. Sam- pling stations indicated by dots. F*resence of juvenile bluefish in sur- face meter net or Haednch net indi- cated by circles, m midwater trawls by triangles, and under nightlight by a star. CRUISE D 70-26 OCT 29-NOV I, 1970 © © 223 FISHERY BULLETIN VOL. juveniles were taken in the Middle Atlantic Bight from late fall to June. In the winter survey, a few juveniles were taken off Florida (Figure 7). but during a follow-up cruise, none were caught (Figure 8f). DISCUSSION The patterns of distribution of young stages of bluefish off the east coast can be summarized based on our collections and those of others (Table 5). From our collections of small larvae, bluefish appear to spawn in two quite different areas — in water just shoreward of the Gulf Stream (Florida Current) from Florida to Cape Hatteras, i.e., the South Atlantic Bight, and in shelf water from Cape Hatteras to Cape Cod, i.e., the Middle Atlan- tic Bight. In the South Atlantic Bight, spawning occurs primarily during spring and apparently also to a lesser extent in fall and winter. Most of the larvae we caught were well offshorejust shoreward of the Gulf Stream in water which was 20°-26°C and had a salinity of 35-38%o. Larvae from the spring spawning in the south- ern area are evidently carried northward past Cape Hatteras in April and May and become spread out along the continental slope off the Mid- dle Atlantic Bight. As shelf waters become suit- ably warm, generally in mid-June, the young bluefish appear to cross the shelf and enter es- tuaries, where they spend the summer. There they grow from 25-50 mm SL to 175-200 mm SL (Wilk see footnote 6) and in early fall migrate south along the coast. Larvae from the fall and winter spawning in southern waters may find their way inshore south of Cape Hatteras as indicated by a few juveniles which we found in Florida in winter. The spawning in the Middle Atlantic Bight in continental shelf waters occurs in summer. The water in which larvae were found here was 3°C cooler and 5%o less saline than that in the south- T.i^BLE 5. — Collections of bluefish eggs, larvae, and juveniles, east coast of United States. Sampling period Sampling area Occurrences of bluefish Numbers Lengths (mm) Reference Years Months Eggs Marak and Colton (1961): 1951-56 Feb -June Ocean ofl New England Late May-early June 1953 tew Marak. . . Foster (1962), south of Martha's Vineyard Marak, , Miiler (1962) Norcross el al (1974) 1959-60 all except Oct Ocean oft Chesapeake Bay June, July, August 1960 and 1961 1961-62 all Ocean oft Chesapeake Bay July 1962, nearshore to slope waters many 1962 seasonally Ocean off Chesapeake Bay 1963 July Aug Ocean oft Chesapeake Bay Larvae: Selle (quoted by 1929 Apr -July Ocean Irom Cape Cod- 40'N-Chesapeake Bay, waters near many 3-21 Perlmutter 1939) Chesapeake Bay 21 C, mostly outer half of shelf Herman (1963) 195758 all Narragansen Bay July, 20 7 C 1 3 Lund' 1965 May, July-Sept Ocean oft eastern Long Island July-Sept (most in Aug ) 73 5-30 1966 June-SepI Ocean oft eastern Long Island 981 5-20 deSylva et al (1962) 1956-58 all Indian River Inlet Del Aug -Sept 2 4-28 Pearson ( 1 94 1 ) 1929-30 all Lovner Chesapeake Bay 24 July, at mouth of bay 4 4-7 Norcross el al (1974) 1959-60 all except Oct Ocean oft Chesapeake Bay May-Aug 34 3-7 1961-62 all Ocean oft Chesapeake Bay July-Sept, 441 3-11 1962 seasonally Ocean oft Chesapeake Bay July 34 5-14 1963 July, Aug Ocean oft Chesapeake Bay July-Aug, 93 4-22 Juveniles (■ 100 mm) Pearcy and Richards (1962) 1959-60 all Mystic River, Conn Seined, July-Aug lower estuary 2 75-94 Perlmutter (1939) 1938 all Waters around Long Island Throughout summer— small fish trawl Throughout summer — seined small 6 78-96 Lund' 1968 July-Sept Shmnecock Bay, N Y 200 40-100 (40 mm) fish in July and Aug deSylva el al (1962) 1958 every other Delaware River Del Seined, June-Sept, lower " estuary 130 30-100 Pacheco and Grant (1965) 1957-58 all White Creek, Del Seined May- June, Sept 45 39-104 Richards and Castagna (1970) 1965-66 all Eastern shore of Virginia Trawled, at mlets. July, Sept 5 31-85 Tagae and Dudley (1961) 1957-60 all Shoal waters near Beaufort, N C Seined, May-July, Ocl-Nov, 37 40-100 Turner and Johnson (1973) 1970 all Newport River. N C Surface, trawled, upper river May, July, Oct few 45-72 'Lund, W A . Jr Early life history of the bluelish, I'l Res Lah . Noank, Conn . 23 p sntttjtrix ( Linnaeus). (tfT the coast of" New Yurk and southern New Knjiiand, Contrib 64 Mar 224 KENDALL and WALFORD SOURCES AND DISTRIBUTION OF BLUEFISH ern area (18'-26'C and 30-32°/„o). Bluefish larvae have been reported by other authors in this area from May through September, but mostly in July and August (Table 5). Larvae have also been re- ported in the more saline areas of several estuaries of the Middle Atlantic Bight (Table 5). Although some juveniles from the Middle Atlantic Bight spawning inhabit estuaries in late summer, more seem to remain along the shore. Nevertheless, all appear to move southward and out of the bight in midfall. Their distribution in late fall and winter is still unknown. From the scarcity of juveniles (i.e., fish 50-150 mm SL) in our samples at sea, and the abundance of these fish in estuarine collections, it appears that bluefish depend chiefly on estuaries for habitat during this stage. Their dependence is de- termined by the time and place of their spawning. Those from the spring spawning spend most of their first summer in estuaries, while those from the summer spawning spend at most about a month there. Both changes in temperature and seasonal photoperiod influenced the activity and distribution of adult bluefish at least under laboratory conditions (011a and Studholme 1971, 1972 1. Thermal edges may act as barriers affecting the distribution of juvenile bluefish, as shown in recent laboratory work (OUa'). These factors, and possibly others, probably trigger movements of juveniles from the open ocean to estuaries and back to the open ocean. In order to assess the relative proportions of the two major spawning areas to the total recruitment of bluefish on the Atlantic coast in any given year, it would be necessary to sample repeatedly during the spring south of Cape Hatteras and during the summer in the Middle Atlantic Bight. Our" present limited understanding of early life history contributes to several other facets of bluefish biology. Population differences of bluefish on the U.S. Atlantic coast have been studied using meristic characters (Lund 1961), migratory pat- terns, morphometries, and scale morphology ( Wilk see footnote 6). All of these studies indicate that more than one population exists. Scale studies defined two groups of bluefish by the size of fish when the first annual ring forms in May. One group, which reaches about 260 mm by the end of 'B. L- 011a. Northeast Fisheries Center Sandy Hook Laborato- ry. National Marine Fisheries Service. NOAA. Highlands. N-J 07732, pers. commun. August 1978. its first winter, evidently represents fish spawned in spring south of Cape Hatteras. The other group, which reaches only about 1 20 mm by the end of its first winter, represents fish spawned in the sum- mer in the Middle Atlantic Bight. Body propor- tions of these two groups of fishes are statistically different (Wilk see footnote 6). Precise information on adult bluefish migration is not available, but general patterns are known ( Wilk see footnote 6). Some mature bluefish spawn near the inner edge of the Gulf Stream as they migrate northward from their wintering grounds off Florida. To a lesser extent some bluefish also spawn in the same area in fall and winter, pre- sumably on their return migration. Adult bluefish migrate to coastal waters off the Middle Atlantic Bight in spring and feed there until they migrate south coincident with fall cooling. During their stay in the Middle Atlantic Bight, bluefish spawn on the shelf, and to some extent in mouths of the larger estuaries (Norcross et al. 1974). Although spawning can take place as soon as the adults arrive in the area in May, most seems to occur in July and August, while some continues into Sep- tember. From the apparent annual variations in timing and amount of this spawning, it is depen- dent on a combination of several features of the environment including temperature, salinity, photoperiod, and food for the adults. If each mature fish spawns in both areas and in all seasons, this would indicate that there is a single stock of bluefish on the east coast of the United States. If each fish spawns in only one area, separate populations must exist. Our early life history information is consistent with other in- formation that indicates that there are separate populations. Southern and northern spawnings take place under quite different hydrographic conditions and in quite different current regimens to assist the young fish in movements to nursery grounds. In time these conditions could allow genetically distinct populations to become estab- lished. Tagging and fecundity studies would show to what extent this has happened. Since year-class strength of fishes is determined mainly during their young stages, it is important to understand the factors influencing survival of these stages. In bluefish, the eggs and larvae occur at the surface of the ocean and the juveniles occur in estuaries, areas affected by annual varia- tions in weather-related phenomena and, to an increasing extent, affected by man's activities. It is thus important to monitor these influences and 225 FISHERY BULLETIN: VOL 77. NO 1 develop models to relate them to year-class strength of the various spawnings of bluefish. ACKNOWLEDGMENTS John R. Clark, now of the Conservation Founda- tion, Washington, D.C., while at Sandy Hook Laboratory, supervised the initial work on bluefish larvae from the RV Dolphin collections. Several people helped in use of unpublished data in preparation of this paper: Stuart Wilk, NMFS, Sandy Hook, N.J.; David Deuel, NMFS, Nar- ragansett, R.L; and Sally L. Richardson, Oregon State University. Omie Tillet, Nags Head, N.C., helped make the sampling near Cape Hatteras in spring 1972 pleasurable as well as successful. LITERATURE CITED AGASSIZ, A.. .\SD C. O. WHITM.1N. 1885. Studies from the Newport Marine Laboratory. XVI. The development of osseus fishes. I. The pelagic stages of young fishes. Mem. Mus. Comp. Zoo). Harvard Coll. 14(11, 56 p. BARTLETT, M. R., and R. L. Haedrich. 1968. Neuston nets and south Atlantic larval blue marlin iMakaira nigricans). Copeia 1968:469-474. Bigelow, H. B., and W. C. Schroeder. 1953. FishesoftheGulf of Maine. U.S. Fish Wildl. Serv., Fish. Bull- 53, 577 p. BRIGGS. J. C. 1960. Fishes of worldwide (circumtropicat) distribu- tion. Copeia 1960:171-180. Clark, J. , W.G.SMITH, A. W.KENDALL, Jr.. and M. P. FAH AY. 1969. Studies of estuarine dependence of Atlantic coastal fishes. Data Report I: Northern section. Cape Cod to Cape Lookout. R.V. Dolphin cruises 1965-66: Zooplankton vol- umes, midwater trawl collections, temperatures and salinities. U.S. Bur. Sport Fish. Wildl., Tech. Pap. 28. 132 p. 1970. Studies of estuarine dependence of Atlantic coastal fishes. Data Rep. II: Southern section. New River Inlet. N.C.. to Palm Beach. Fla. RV . Dolphin cruises 1967-68: Zooplankton volumes, surface-meter net collections, temperatures, and salinities. U.S. Bur. Sport Fish. Wildl , Tech. Pap 59, 97 p. Colton, J. B., Jr., AND K. A. Honey. 1963. The eggs and larval stages of the butterfish Poronotus triacanthus. Copeia 1963:447-450. DE SYLVA, D. p., F. a. KALBER. Jr., and C. N. SHU.STER, JR. 1962. Fishes and ecological conditions in the shore zone of the Delaware River estuary, with notes on other species collected in deeper waters. Univ. Del. Mar. Lab . Inf Ser, Publ. 5, 164 p. DEUEL, D. G., J. R. CLARK, AND A. J. MANSUETI. 1966. Description of embryonic and early larval stages of bluefish, Pomatomus saltatnx. Trans. Am. Fish. Soc. 95:264-271. Fowler, H. W 1944. Results of the Fifth George Vanderbilt Expedition (1941), (Bahamas, Caribbean Sea, Panama, Galapagos Archipelago and Mexican Pacific Islands). Fishes. Acad. Nat. Sci., Phila., Monogr. 6:57-529. Herman, S. S. 1963. Planktonic fish eggs and larvae of Narragansett Bay. Limnol Oceanogr. 8:103-109. Irvine, F R 1947 The fishes and fisheries of the Gold Coast. Crown Agents for the Colonies. Lond., 352 p. LUND, W. A., JR. 1961. A racial investigation of the bluefish, Poniatomus saltatnx (Linnaeus) of the Atlanticcoast of North Ameri- ca. [Span. Abstr.) Bol. Inst. Oceanogr., Umv. Oriente Cumana 1:73-129. LUND, W. A., JR., AND G. C. M.->lLTEZOS. 1970. Movements and migrations of the bluefish. Poniatomus saltatnx, tagged in waters of New York and southern New England. Trans. Am. Fish. Soc. 99:719- 725. MARAK, R. R., and J. R. COLTON. jR. 1961. Distribution offish eggs and larvae, temperature, and salinity in the Georges Bank-Gulf of Maine area, 1953. U.S. Fish Wildl. Serv, Spec. Sci. Rep. Fish. 398, 61 P MaRAK. R. R.. J. B. COLToN. Jr., and D. B. Fo.ster. 1962. Distribution of fish eggs and larvae, temperature, and salinity in the Georges Bank-Gulf of Maine area, 1955. U.S. Fish Wildl. Serv, Spec. Sci. Rep. Fish. 41 1, 66 P M ARAK , R. R. J. B. Colton. Jr., D. B. Fo.ster, and D. Miller. 1962. Distribution of fish eggs and larvae, temperature, and salinity in the Georges Bank-Gulf of Maine area, 1956. U.S.FishWildl.Serv.Spec.Sci Rep Fish.412,95 P NORCROSS, J. J., S. L. RlCH.ARDSON, W. H. MASSMANN, AND E. B. JOSEPH. 1974. Development of young bluefish {Poniatomus saltat- nx) and distribution of eggs and young in Virginian coast- al waters. Trans. Am. Fish. Soc. 103:477-497. Oben, L. C. 1957. About the drifting approach of fingerling bluefish. Pomatomus saltatnx L.. to the shores of the Black Sea in the region of the Karadag 1 1947-1954). Translated from the Russian language by M. J. Koushnaroff and R. J. Mansueti from worksof the Daradag Biol Stn., Acad. Sci. Ukr USSR 14:155-157. OLLA, B. L., AND A. L. STUDHOLME. 1971. The effect of temperature on the activity of bluefish, Pomatomus saltatnx L. Biol. Bull. (Woods Hole! 141:337-349. 1972- Daily and seasonal rhythms of activity in the bluefish iPoniatomus saltatnxh In H. E. Winn and B. L. Olla (editors!, The behavior of marine animals. Volume 2: Vertebrates, p. 303-326. Plenum Press, NY. PACHEGO, a. L., AND G. C. GRANT. 1965. Studies of the early life history of Atlantic menha- den in estuarine nurseries. Part I — Seasonal occurrence of juvenile menhaden and other small fishes in a tributary creek of Indian River. Delaware, 1957-58. U.S. Fish Wildl. Serv,, Spec, Sci. Rep. Fish. 504, 32 p. Padoa, E, 1956. Uova, larvae stadi giovanili di teleostai: familia Z: Pomatomidae. Fauna Flora Golfo di Napoli, Monogr. 38:570-572. 226 KENDALL and WALFORD SOURCES AND DISTRIBUTION OF BLUEFISH Pearcy. W, G,, and S. W. Richards. 1962. Distribution and ecology of fishes of the Mystic River estuary, Connecticut. Ecology 43:248-259. Pearson, J. C. 1941. The young of some marine fishes taken in lower Chesapeake Bay, Virginia, with special reference to the gray sea trout, Cynoscion regalts (Bloch). U.S. Fish Wildl, Serv,, Fish. Bull. 50:79-102. Perlmutter, a. 1939. Section I, An ecological survey of young fish and eggs identified from tow-net collections In A biological sur- vey of salt waters of Long Island, 1938, Part II, p. 11-71. N.Y. Conserv. Dep., Suppl, 28th Annu Rep., 1938, Salt- water Surv. 15. RK HAKIIS, E. C, AND M. CASTAIINA. 1970. Marine fishes of Virginia's Eastern Shore I inlet and marsh, seaside waters). Chesapeake Sci. 11:235-248. Salekhova, L. p. 1959. On the development of the bluefish iPomatomus Hal- tatnx) Linne, Tr. Sevastop. Biol, Stn. 11:182-188. SETTE. 0. E. 1943. Biology of the Atlantic mackerel {Scomber scorn- 6n^it of North America. Part 1: Early life history, includ- ing the growth, drift, and mortality of the egg and larval populations. U.S. Fish Wildl, Serv., Fish. Bull. 50:149- 237. SMITH, J. L, B, 1961. The sea fishes of southern Africa. 4th ed. Central News Agency. Ltd., South Africa, 580 p. SVERDRUP, H. U., M. W. Johnson, and R. H. Fle.ming, 1942. The oceans. Their physics, chemistry, and general biology. Prentice-Hall, Inc., Englewood Cliffs. N.J,, 1087 p. Taoatz, m. e., and d. l. Dudley. 1961. Seasonal occurrence of marine fishes in four shore habitats near Beaufort, N.C., 1957-60, U.S. Fish Wildl. Serv,, Spec. Sci. Rep Fish, 390, 19 p. Turner, W, R., and G. N, Johnson, 1973, Distribution and relative abundance of fishes in Newport River, North Carolina U,S Dep, Commer,, NOAA Tech, Rep, NMFS SSRF 666, 23 p, Wrii;ht, W, R,, and C, E, Parker, 1976, A volumetric temperature/salinity census for the Middle Atlantic Bight, Limnol, Oceanogr, 21:563-571, 227 CONTRIBUTION OF 1960-63 BROOD HATCHERY-REARED SOCKEYE SALMON, ONCORHYNCHUS NERKA, TO THE COLUMBIA RIVER COMMERCIAL FISHERY Roy J. Wahle, Reino O. Koski, and Robert Z. Smith' ABSTRACT A 4-yr marking program was conducted at Leavenworth National Fish Hatchery, Leavenworth, Wash., to determine the contribution of hatchery sockeye salmon, Oncorhynchus nerka, to the Colum- bia River commercial fisheries and the economic feasibility of hatchery rearing of sockeye salmon. The study involved 1960 through 1963 brood-year fish. During the 4-vr period, 1961-64, a total of 11.5 million fish were released, of which 3.4 million were marked by the removal of the adipose fin and part ofoneof the maxillary bones — the right maxillary for 1960 and 1962 broods and the left maxillary for 196 1 and 1963 broods. Trapping at the lake outlet in the spring for the first 2 yr indicated that less than 50^f of the stocked fingerlings migrated. In 1964-67. recovery of marks from thecommercial fishery on the Columbia below and the Indian fishery above Bonneville Dam showed that an average of 13.6% of the sockeye salmon catch was composed offish raised at Leavenworth Hatchery. Adjusting for effects of marking, this represents an average fishery value per brood of $4,274.75. The average potential benefit/cost ratio for the 4 yr of the program was 0.04 to 1. Because preliminary data indicated such a low benefit/cost ratio, sockeye salmon rearing at Leavenworth was radically decreased in 1966 and terminated in 1969. In the 1930's Grand Coulee Dam was constructed on the upper Columbia River, thus barring anad- romous fish runs from 1,835 km of spawning and rearing area. The extreme height of the dam ( 106 m) precluded building passage facilities for both upstream and downstream migrants. To preserve the runs formerly utilizing the upper basin, a relo- cation of runs of affected species became neces- sary. Basic data on existing fish populations were ob- tained from 1933 through the time of dam comple- tion in 1941 (Fish and Hanavan 1948). The only relocation areas suitable for spawning and rearing were Columbia River tributaries below Grand Coulee Dam and above Rock Island Dam. The area was less than one-half the extent of that formerly available and on streams which, because of in- dustrial diversion, were for the most part inacces- sible to migrating fish. Because of general deple- tion of all the upriver salmonid runs, correction of fish passage problems was already underway in many areas. With the impetus of the relocation program, further rehabilitation was ac- complished. 'Environmental and Technical Services Division. National Marine Fisheries Service, NOAA, 811 N.E. Oregon, Portland, OR 97208. Manuscript accepted September 1978. FISHERY BULLETIN VOL. 77, NO 1, 1979. The sockeye salmon, Oncorhynchus nerka, was seriously affected by the habitat changes as its development required a lake-stream environment which has been almost completely eliminated. Annual commercial catches of Columbia River sockeye salmon ranged from '/2 to 2 million kg prior to 1900 (Gangmark and Fulton 1952). From then through the early 1920's annual catches var- ied from about 'a million to over 1 million kg. Following one more good year in 1926, the V2 mil- lion kg figure was never again reached (Figure 1). Estimates of escapement beyond the fishery were not possible until enumeration of migrating adults began in 1933 at Rock Island Dam, 755 km above the mouth of the Columbia River. An aver- age of about 19,000 adults was counted annually until 1 94 1 , when only 949 adults passed upstream. The low escapement was caused by a large com- mercial catch, low flows, and retention of water behind Grand Coulee Dam (Fish and Hanavan 1948). The relocation of runs began in 1939 for sockeye salmon as well as chinook salmon, O. tshawytscha: coho salmon, O. kisutch; and steelhead trout, Salmo gairdneri . Adult sockeye salmon were trapped at Rock Island Dam and were transported by tank trucks to the Wenatchee and Okanogan 229 FISHERY BULLETIN VOL 77, NO. 1 0,0 1890 1900 1910 1920 YEAR 19 30 1940 I960 FIGURE 1,— Commercial catch of sockeye salmon in the Columbia River, 1889-1967. (Data for 1889-1936 from Craig and Hacker (1940), for 1937 from Ward et al. ( 19631 and for 1938-67 from Fish Commission of Oregon and Washington Department of Fisheries (1968),] Lakes where they were alIowe(i to spawn natu- rally (Figure 2), Supplementary to adult relocation, an artificial propagation program was planned. A hatchery was constructed on Icicle Creek, a tributary of the Wenatchee River near Leavenworth, Wash, (Fig- ure 3). Smaller substations were built on the Entiat and Methow Rivers. The sockeye salmon production progi'am was to be concentrated at Leavenworth National Fish Hatchery, Fish produced at Leavenworth were stocked into Wenatchee and Osoyoos Lakes. Success of the sockeye salmon relocation program was indicated in 1947 when the largest run recorded since 1926 appeared. This raised the question of whether the remaining available spawning habitat was over- populated, prompting annual inventories that continued for many years (Gangmark and Fulton 1952). How much of the apparent improvement in sockeye salmon runs was attributable to hatchery production was unknown. Importance of the Wenatchee system for total sockeye salmon pro- duction was obvious. Data indicated that an aver- age of 33''f of upper Columbia River sockeye salm- on homed to the Wenatchee River in the 7 yr just prior to this study (French and Wahle 1965). Wenatchee System Sockeye Salmon Stock For over 25 yr Leavenworth Hatchery produced sockeye salmon which were stocked and reared in Wenatchee River tributaries. During this time, five major dams were built on the main Columbia River downstream. These structures, combined with growth and expansion in population and in- dustry, added greatly to existing problems which confronted both downstream migrants and return- ing adults. The Wenatchee River system was historically an excellent salmon producing system. It was comparable, for sockeye salmon production, to the Arrow Lakes, Yakima Basin, and Okanogan Lake areas, formerly the primary producers of this species in the basin (Figure 2). In the early 1900's the runs in the Wenatchee became severely de- pleted because of construction of impassable mill and power dams and unscreened irrigation proj- ects. These conditions prevailed until the early 1930's, at which time about 85% of the Columbia 230 WAHLE ET AL,. 1960-63 BROOD HATCHERY-REARED SOCKEYE SALMON Scale in kilometers Figure 2. — Portion of Columbia River Basin showing areas of past and present importance to sockeye salmon as described in t*xt. River run was being produced in the Arrow Lakes area (Fulton 1970). The Grand Coulee Fish-Maintenance Project (Fish and Hanavan 1948) began in 1933. Under this project, obstructions were removed, dams were provided with passage facilities, and irriga- tion diversions were screened. These measures were necessary to establish suitable habitat for the relocated runs in tributaries between Grand Coulee and Rock Island Dams. To reintroduce sockeye salmon to the spawning areas above Lake Wenatchee and provide eggs for 231 FISHERY BULLETIN VOL 77. NO 1 N "J' LAKE WENATCHEE N 6 T 0 N OREGON ONNEVILLE /DAM \ VTHE DALLES DAM VICINITY MAP MIGRANT' TRAP «l^ E« I LEAVENWORTH HATCHERY ROCKY REACH DAM 16 32 1 KILOMETERS ROCK ISLAND DAM Figure 3. — The Wenatchee River system and location of Leavenworth National Fish Hatchery. Leavenworth Hatchery, adult fish were trapped from 1939 through 1943 at Rock Island Dam on the main Columbia. Because the proposed hatch- eries would not be available to handle fish until 1940, adults of all displaced species were released for natural spawning in predetermined locations. Separate areas were selected for each species to prevent overcrowding and mixing. Most of the sockeye salmon transplanted undoubtedly origi- nated in the Arrow Lakes, but fish from the Okanogan and Wenatchee systems were certainly included (Fulton 1970). 232 WAHLE ET AL 1960-63 BROOD HATCHERY-REARED SOCKEYE SALMON Under the Grand Coulee Fish-Maintenance Project, sockeye salmon adults were trapped in July and August and hauled by tank truck to Lake Wenatchee, 113 km above Rock Island Dam, where a barrier was installed at the outlet. When spawning time approached, the fish ascended the White and Little Wenatchee Rivers where they spawned. When eggs were later needed for hatch- ery use, weirs were installed and adults trapped to supply the required ova. Surplus adults were al- lowed to pass upstream and spawn naturally. The offspring of these natural spawners homed back to the system to establish the new Wenatchee stock. Spawning occurred in September and October. The fry emerged from the gi-avel in spring and drifted back down to the lake to rear until the following year. Outmigration occurred in April and May, with a peak reached in early May prior to the heavy spring run-off period (French and Wahle 1959). Following 2, or occasionally 1 or3,yr at sea, the adults entered the Columbia River in late spring. The run passed Bonneville Dam in late June and early July, and several weeks later ascended the Wenatchee River to renew the cycle. The Hatchery Leavenworth National Fish Hatchery was com- pleted in 1940 as the primary station to provide hatchery-reared fish to supplement the newly es- tablished natural runs. Sockeye salmon were to be produced there and adults of other species were spawned to obtain stock to supply the satellite stations on the Entiatand Methow Rivers (Figure 2). The hatchery capacity was approximately 3.5 million eggs and 2.4 million fingerlings (Fish and Hanavan 1948). The source of eggs for the first 5 yr of operation was fish that had been hauled to Lake Wenatchee from Rock Island Dam as part of the relocation project. After this period the adult transportation was terminated and spawning operations con- tinued using fish returning to the lake naturally. After the eggs were taken and fertilized, usually in September, they were transferred to the hatch- ery for incubation. Hatching began in January and the fry began to feed about 6 wk later. Initial rearing took place inside the hatchery, and when water temperatures became suitable, they were placed in outside rearing ponds. In September or October, upon reaching an average weight of 9 to 10 g, the fingerlings were trucked to the lake. Survival from egg to stage at release ranged from 62 to 967f . After winteringover until the following April or May, the smolts migrated out of the lake. From general observations, it appeared that the hatchery operation was a success: proper rearing techniques were followed, hatchery migrants were observed leaving the lake, adults returned to the area in adequate numbers, and fish were available for commercial harvest. Data obtained through spawning surveys and downstream migrant counts at the dams indicated that the sockeye salmon population was being satisfactorily main- tained. However, it was not possible to determine whether the wild stock or the hatchery fish con- tributed most to the runs. Downstream migrant studies by Anas and Gauley 1 1956 1 pointed out the impossibility of identifying the separate stocks. There were indications that the costs of conduct- ing a sockeye salmon hatchery program were sig- nificantly higher than the values contributed to the fishery. Despite complexities of measurement of runs, some means of assessment seemed neces- sary. Thus, a study was designed to evaluate the economic feasibility of continuing artificial propa- gation of sockeye salmon at the hatchery. The study involved the marking of a proportion of the hatchery sockeye salmon production for a period of 4 yr, observations on the rearing and migration of the fingerlings, and estimation of the contribution of returning adults to the commercial fishery. An analysis of production costs and the monetary benefits to the fishermen was included. FIELD OPERATIONS Estimating Procedures The procedures used in making estimates of numbers offish are similar to those described in reports by Worlund et al. (1969) and Wahle et al. (1974). Estimates of the potential contributions and value of hatchery sockeye salmon required four steps: 1) estimation of marked and un- marked hatchery releases, 2) estimation of catch of marked adults, 3) estimation of total contribu- tion of hatchery fish to the catch, and 4) applica- tion of dollar values to the estimate of contribu- tion. Marking and Release Procedure The study began in July 1961, using 1960-brood fingerling sockeye salmon. Each year, approxi- 233 FISHERY BULLETIN VOL. 77, NO. 1 mately one-third of the total Leavenworth Hatch- ery stock was marked. In each year except the first, a circular net pocket with a metal sleeve and a tub sampler were used to obtain a sample offish for marking. Two types were employed: a 3-pocket sampler which gave an approximate 33.3'7( sample for marking, and a 10-pocket sam- pler (Worlundetal, 1969; Wahleetal. 1974) which provided a 10% sample for population estimate. In 1961, the one-third sample was obtained by mark- ing every third pond, and in the other 3 yr the fish to be marked were selected as described above. In 1961, hatchery personnel marked 1,008,310 1960-brood sockeye by removing the adipose fin (Ad) and part of the right maxillary bone ( RM). In 1962, the 1961-brood fish (600,036) were marked by removal of the adipose fin and part of the left maxillary bone (LM). The 1962-brood fish (1,146,485) were marked the same as the 1960- brood, and the 1963-brood (606, .578) repeated the 1961-brood mark. In 1961 the marked and unmarked fish were kept in separate ponds and mortality records kept for each group. The number of unmarked fish for release was estimated by using the number of eggs and the percentage of hatch, and subtracting the number marked plus pond mortality. As the fish were stocked, in order to avoid bias, the marked and unmarked fish were mixed in each truck load. In the three following years, by knowing the actual number offish marked for each brood year, and the postmarking mortality, the total popula- tion at release time was estimated. Using the 10- pocket sampler on a random group of fish from a pond, a 10% sample was obtained. Repeating this procedure on the 10% sample provided a 1% sam- ple, and a Peterson index of sample size was calcu- lated (Table 1). The fingerlings were transported by tank truck and released into Lake Wenatchee each fall. Table l. — Numbers of socke.ve released into Lake Wenatchee, Wash., during marking program. Brood Mark' No marked No. unmarked % marked Total released 1960 1961 1962 1963 Total Ad-RM Ad-LM Ad-RM Ad-LM 1 ,000,725 571.726 1.247.755 570.735 3.390.941 1.760.319 1.327.878 2.554,809 2,504,344 8.147,350 36,24 30 10 3281 18,56 29 39 2,761,044 1 ,899,604 3.802.564 3.075.079 11,538,291 'Ad - adipose fin; RM = rigiil maxillary bone, LM = left maxillary bone In the spring of 1962 and 1963, a trap was oper- ated at the lake outlet to monitor the outmigra- tion. Data obtained at the trap indicated that <50% of the marked fish migrated downstream. This amounted to 38.4% of the marked fish of the 1960-brood and 47. 9^/^ of the 1961-brood. Marked Fish Recovery Sampling for returning marked adults began in 1964 and continued through 1968. Earlier returns were not expected because prior studies at Lake Wenatchee indicated that few, if any, adults would return in their third year (Major and Craddock 1962). The search for marks was confined to the two commercial fishing areas in the lower Colum- bia River: zones 1-5, the gill net fishery below Bonneville Dam, and zone 6, the Indian set net and dip net fishery above the dam (Figure 3). Other fisheries were not sampled as Columbia River sockeye salmon rarely occur in the ocean commer- cial catch and are seldom taken by sport anglers (Koski 1964). We looked for marked fish during the commer- cial seasons. The zone 6 catch was monitored at Washington and Oregon Indian fishery buying stations. Commercial canneries in the lower river were sampled for the zones 1-5 gill net catch. Un- fortunately for the study, the commercial gill net season in zones 1-5 was closed in 1965 and 1966, and opened only for 5 days in 1964 (Fish Commis- sion of Oregon and Washington Department of Fisheries 1968). The zone 6 catch was also limited by this restriction, severely reducing the total catch (see Table 4). The catch in the 7 yr previous to the study averaged 90,900 fish. During the study period the average was only 22,500 ranging from 4,361 to 56,200 (Figure 4). Sampling Results Nearly one-half of the Columbia River commer- cial sockeye salmon catch was inspected for marks each year, except in 1966 when only a 4.2% sample was obtai ned because of the erratic nature of 1 and- ings. The extremely small sample undoubtedly biased the estimation of catch for the brood years involved. For most brood years, the majority offish were caught in their fourth year (Table 2). For all broods except the 1962 group an average of 94% was caught at age 42 (4 - total age, 2 - seaward migration age). This age-group represented only 4% of the total 1962-brood fish caught in 1966, evidence that the age 4^ fish were almost entirely missed by the fishery, although undoubtedly available. 234 WAHLE ET AL 1960-63 BROOD HATCHERY-REARED SOCKEYE SALMON 350 — m i i i I I i I ^ ^ SAMPLING YEARS THIS STUDY I ■ i I i ii i w ?^ ^ Figure 4.— Columbia River sockeye salmon commercial catch in thousands, as part of the total run. 1957-68. [Data from Fish Commission of Oregon and Washington Department of Fisheries (1968).] 65 66 67 68 Table 2— Sampling rate and marks observed in Columbia River commercial fishery for sockeye 1960-63 broods. No of marks observed by brood year 1960 1961 1962 1963 265 Catch year Fishery zone' Total catch Number sampled Percent sampled 1964 1-5 4.950 3,307 6 15,820 7,195 Total 20.770 10,502 50 6 1965 1-5 70 24 6 5.773 3,024 Total 5.843 3,048 52 2 1966 1-5 157 27 6 Total 4.204 4.361 158 185 4.2 1967 1-5 21.218 7.993 6 35,002 13.885 Total 56.220 21.878 38 9 1968 1-5 20.300 9.689 6 5.000 2,632 Total 25,300 12.321 48 7 Total 287 16 310 Vone 1-5 (below Bonneville Dam), Zone 6 (above Bonneville Dam) 235 The number of fish in the catch, the number sampled and the number of marks recovered from zones 1-5 and zone 6, were combined. CALCULATIONS Because the marks used to distinguish the groups of hatchery fish have a negative effect on survival, two different steps were employed to cal- culate the hatchery fish contribution. The deter- mination of the level of contribution required an estimation of the number of hatchery fish in the catch for each year sampled. This was calculated from the estimated number of marked fish plus the estimated number of hatchery unmarked after a correction for differential mark mortality. Poten- tial catch is that which would be expected if mark- ing did not cause postrelease mortalities. Differential Mark Mortality (Survival Factor) We suspected that there would be adverse ef- fects on the survival of the fish because of the excised fin and maxillary bone. Foerster (1968) reported that marked sockeye salmon at Cultus Lake had an estimated return of only 38'/f of the unmarked return. To obtain a mark survival factor, a modification was made to the procedure for marking the 1961- brood fish. In addition to the group that received an Ad-LM, a second gi-oup received only a chemi- cal (tetracycline) mark, while a third had both marks. In sampling returning adults, a compari- son of the three groups showed that only 40^ of Ad-LM fish expected, returned (Weber and Wahle 1969). Because we believe that tetracycline had no effect on survival, we considered that the differ- ence between returns was caused by mortality due to marking by excision. Marks in Catch To calculate the number of marks in the catch for a certain year, the number of ri marks in the sample was divided by the sampling ratio: n marks (catch) n marks (sample) I) fish (sample)//! fish Icatch) This assumed a random sample of the catch. The mark survival factor was not considered in this equation. 236 FISHERY BULLETIN: VOL, 77. NO. 1 Hatcher)' Contribution to the Fishery To determine the percent of sockeye caught in a specific year that originated at Leavenworth Hatchery, the number of (n) unmarked hatchery fish in the catch was estimated by using the number of(n) marked fish in the catch and divid- ing by the sampling ratio and the marked unmarked ratio at release, corrected by the mark survival factor. The correction was necessary be- cause this ratio changes from the time of release to time of catch due to the effects of marking: n unmarked hatchery catch = ft marks icatch) n fish (sample) n marked release „ fish (catch. "" Tiinrmarked releas^ "" «""'^^' f^'^'"'- Summing the marked and unmarked hatchery fish for a catch year and dividing by the total catch gave the estimated percent produced by the Leavenworth Hatchery. For 1964-67, contribu- tions averaged 13.&/t of the total catch (Table 3). The 21.6'7f figure for 1966 may not be representa- tive as the sample size that year was small. T.^BLE 3. — Estimated numbers and percent of hatchery sockeye in Columbia River commercial catch. Catcti Brood year Hatchery fish Total catch year Marked Unmarlted Total % all lish 1964 1960 517 1,504 2.021 Total 1961 2 519 8 1,512 10 2.031 9.8 20.770 1965 1960 42 123 165 1961 82 316 398 Total 124 439 563 96 5.843 1966 1961 24 90 114 Total 1962 189 213 638 728 827 941 21,6 4.361 1967 1962 500 1,692 2.192 Total 1963 751 1.251 5.443 7.135 6.194 8,386 14.9 56.220 1968 1963 31 226 257 (') 25.300 'Not applicable as no 1964 brood hatchery frsh were marlted Potential Hatchery Catch A potential hatchery catch figure is a theoretical number that represents what could have been caught in a given fishery assuming the same effort and no marking progi-am and was required to cal- culate benefit/cost ratios. It allows for the large number of fish failing to survive because of the mark. Potential hatchery catch (Table 4) was cal- culated by dividing the number of marks in the catch by the mark survival factor and adding the WAHLE ET AL.: 1960.63 BROOD HATCHERY-REARED SOCKEYE SALMON Table 4. — Potential number and weight of hatchery sockeye by brood year and catch year. Catch year No, with marks in sample Hatchery fish in catch Brood year Estimated no Potential no Potential wt' (kg) 1960 1964 265 2.021 2.359 4.122 Total 1965 22 287 165 2.186 192 2.551 342 4.464 1961 1964 1 10 11 16 1965 43 398 451 802 Total 1966 1 45 114 522 130 592 234 1.052 1962 1966 8 827 950 1.706 1967 191 2,192 2.518 4.085 Total 199 3.019 3,468 5.791 1963 1967 294 6.194 6,684 10.733 1968 16 257 277 479 Total 310 6,451 6.961 11.212 Grand total 841 12.178 13.572 22.519 ' The average weight of commercially caught sockeye ranged from 1 ,5 to 1 .8 kg dunng the study. number of unmarked hatchery fish in the catch: potential hatchery (catch) = n marks (catch) + unmarked hatchery (catch). survival factor ECONOMIC EVALUATION A primary purpose of this study was to deter- mine the economic feasibility of rearing sockeye salmon at Leavenworth National Fish Hatchery. An oft-employed measure of financial worth of a program is the benefit/cost ratio which compares the dollar value (benefit) of the fish returned to the amount spent (cost) in their production. Normally a favorable ratio should exceed 1:1. Cost Accounting Production costs for each brood of sockeye salm- on in this study were derived in the same manner as in Wahle et al. (1974) and consisted of two categories, amortized construction costs or capital costs and operational costs. The "annual imputed capital charge" was com- puted by amortizing the capital expenditures at the hatchery into 30 equal annual payments using an interest rate of S.S'^r . This rate was the average 3- to 5-yr government bond mterest rate weighted by the total annual capital outlay at Columbia River Program Development hatcheries from 1949 to 1970. As the hatchery reared other species inaddition to the study fish, the capital charge was apportioned by applying a percentage based on the ratio of manpower time charged specifically to sockeye salmon care. Operation and maintenance costs were divided into fish food and drugs, and other operational costs. Fish food and treatment costs were appor- tioned according to the pounds of study fish pro- duced as a percentage of the total production. Other operational costs including labor, personal services, travel, equipment, supplies, and ad- ministration were apportioned, as with capital, according to the percentage of time allotted to the care of each brood. Benefits In other economic studies involving Columbia River salmonids ( Worlund et al. 1969; Wahle et al. 1974) benefits included the accrued values from exvessel prices received by commercial fishermen engaged in the variety of catch methods, i.e.. offshore troll, purse seine, gill net, set net, etc. In addition, benefits were calculated for sport-caught fish and for sale of adult carcasses to processors. Our study included only the benefits to commer- cial fishermen on the Columbia River in the gill net (zones 1-5), and tribal dip net (zone 6) fisheries. Sport catch values were not considered as there are virtually no sockeye salmon caught by anglers in the river. The simple exvessel price paid to fishermen is a reasonable estimate of benefits as explained by Richards,- although some inadequacies exist in more intensive and complicated fisheries. For the minor fisherv involved in this studv. this method ^Richards, J. A. 1969. An economic evaluation of Columbia River anadromous fish programs, U.S. Dep. Int.. Fish Wildl, Serv,, Bur, Commer, Fish., Working Pap. 17, 274 p. 237 FISHERY BULLETIN: VOL 77. NO 1 of valuation seemed satisfactory. The commercial price paid to fishermen during the sampling years ranged from $0.68 to $0.82/kg depending on the area of catch. The benefit/cost ratio averaged 0.039:1, or approximately 4 cents returned for each dollar spent (Table 5). Table 5. — Benefit-cost ratios for Leavenworth sockeye 1960-63 broods. Brood year Total calch (kg) Hatchery fish in catch Potential Potential wt (kg) value ($) Pro- duction cost ($) Potential benelit- cost ratio 1960 1961 1962 1963 Total 41.327 49.160 97,228 75.579 263.294 4.464 3.062 1.052 858 5.791 4.456 11.212 8.723 22.519 17.099 114.123 86,823 124.321 113.541 438.808 0 027 1 010 1 036 1 077 1 039 1 DISCUSSION As our results clearly show, hatchery fish did not appear significantly in the commercial catch, averaging only 13.5% of the total harvest. Consid- ering that the hatchery fish may have utilized almost one-half of the natural rearing space avail- able, we expected their contribution would be greater. We also expected a larger proportion of hatchery fish in the returning adult run based on the ratio of hatchery to wild smolts emigrating from Lake Wenatchee. In a concurrent study, Craddock^ determined that hatchery fish made up 53% and 72% of the 1962 and 1963 total outmigra- tion, respectively. From the economic viewpoint we feel that the study produced an accurate assessment of the ben- efits provided to the commercial fishermen by the addition of hatchery fish to their catch. We are confident that the method of determining the pro- duction costs of the hatchery sockeye salmon pro- vided a valid estimate for that portion of the benefit/cost ratio. Benefits as a measure of value in this study applied specifically to those received by the com- mercial fishery. Not considered were intangible benefits derived from the preservation, mainte- nance, and enhancement of the Columbia River sockeye salmon. The return of adults to the system for a hatchery egg source is another value. Another unmeasured benefit was the contribution to the Indian subsistence and ceremonial fisheries. In short, the total benefits from the Leavenworth ^D. R. Craddock, Northwest and Alaska Fisheries Center. National Marine Fisheries Service. NOAA. Mukilteo. WA 98272, pers. Commun. April 1964. Hatchery sockeye salmon program were obviously greater than the value derived within the specific confines of the study. From the catch results it is apparent that the study period was one of an abnormally low har- vest. The river below Bonneville Dam was closed completely for two of the catch seasons and only 5 days fishing allowed in another, with almost all of the small catch taken in the Indian fishery. As the benefits were based on the number offish provided the commercial fishery, and the zones 1-5 fisher- men were almost completely denied the opportun- ity to harvest these fish, then little in the way of value could be expected under these conditions. It should be noted that the regulatory measures were in effect specifically for the protection of low runs of summer chinook salmon and summer steelhead trout which can be netted at the same time in the area. Another indication of the unusually low harvest of sockeye salmon during the study period is noted in catch/ escapement ratios ( C/E ), which in the 5 yr preceding the study were 1/1 - 2.6/1. During the study the ratio did not exceed 0.5/1 and ranged downward to 0.02/1 (Fish Commission of Oregon and Washington Department of Fisheries 1968). In addition to the low rate of return associated with adult harvest, we suspected that poor surviv- al of the released fish through various stages was a primary cause of low adult returns. Problems con- fronting the young sockeye salmon are discussed below. We could not assess any effect on the released fingerlings caused by rearing practices at Leav- enworth Hatchery, as there was no comparable rearing of sockeye salmon elsewhere. We assumed that the produced fish were of good quality, as the rearing techniques, disease control, and nutrition in effect at the hatchery were essentially the same at other Columbia River salmon hatcheries rais- ing other species. A possible hatchery-related effect on the quality of the stocked fish may have been undetected dis- ease. As reported by Guenther et al. (1959), a filterable virus disease transmitted by feeding of sockeye salmon carcasses at Leavenworth Hatch- ery caused extreme mortalities prior to 1954 when the practice was discontinued. Losses from unde- tected diseases could have had significant effect on survival following release of the fingerlings. Al- though kidney disease was not detected at the hatchery, prior to release, the senior author ob- served it in fish held in saltwater during the mark 238 WAHLE ET AL., 1960-63 BROOD HATCHERY-REARED SOCKEYE SALMON retention phase of the project. Cumulative long- term effects on outmigrants may have been sub- stantial. Other viral diseases, about which little was known at the time, may have been present. Lake Existence A high rate of mortality occurred in Lake Wenatchee during the period of lake rearing, and this was probably spread over the period from stocking until outmigi'ation. Losses similar to the 62 and 51%, found where outmigrants were enum- erated, undoubtedly occurred in the 2 yr in which outmigrants were not counted. Foerster ( 19681 re- ported that the average smolt migration from British Columbia and Alaska lakes where only fry were stocked was 44% and the survival to return ranged from 11 to 84% . The hatchery rearing at Leavenworth seemed an economic waste, as equal outmigration rates may have been obtained using fry plants. There is an extensive sport fishery in Lake Wenatchee on Dolly Varden, Sa!ve!iiu/s malma, and kokanee, a nonmigrant strain of sockeye salmon. We monitored this fishery in order to de- termine the effect on released study fish. Incidental to the trout catch, a fairly large number of sublegal ( <6-in) hatchery salmon were taken. This was determined by the presence of marked fish in a sample of sublegal fish in the angler catch. The hatchery fish were caught dur- ing the early spring of their second year just prior to their outmigration. Most sublegals were re- leased by the anglers, but mortality undoubtedly resulted from hooking and handling. Addition- ally, some of the marked sockeye salmon remained in the lake without migrating and were observed throughout the season in the creel checks of legal- sized trout. The percentage becoming resident was unknown, but in 1964 represented 1.4% of the calculated total kokanee sport catch of 17, 523 fish. Sockeye salmon becoming resident in the lake and entering the sport fishery, based on 1964 data, accounted for <1% of the stocked fish. The mortal- ity of sublegal fingerlings from angling was as- sumed to be small because of their rare occurrence in the sport catch. Health records of the hatchery fish did not indicate any expected loss from disease or parasites. Undoubtedly, the large loss of finger- lings was due to predation by larger fish and possi- bly starvation. The heaviest loss of fingerlings in the lake was certainly caused by predation. Although precau- tions were taken during release, when fish were barged to avoid shoreline concentrations. Thompson and Tufts (1967) reported heavy preda- tion both during and following release periods. Dolly Varden and northern squawfish, Ptychocheilus oregonensis, were sampled by gill net and trolling gear. Dui-ing the weeks of release, the number of captured fish containing sockeye salmon ranged from 58 to 100% . Gangmark and Fulton (1952) during experiments in 1949-51 re- ported heavy predation by the same species. Our own observations of angler-caught fish from March through July 1962 showed an average of over one sockeye salmon per stomach. No estimate of the total predation loss was possible as the total number of predators was not known. From our observations and those reported by Allen and Meekin (1973) the zooplankton produc- tion in the lake peaked in August and September each year. The hatchery fish, stocked in October, were faced with a declining food supply. Growth apparently stopped during the winter. Fingerlings of the 1961-brood averaged 97 mm FL when stocked in October whereas in the following spring, migrants trapped at the outlet, had a size range of 87-98 mm FL (Weber and Wahle 1969). Low food productivity of the lake, coupled with competition from natural resident fish for food, undoubtedly affected the fitness of the migrant sockeye salmon and possibly caused subsequent losses from stress on the seaward journey. It is highly improbable that any hatchery pro- duction program utilizing an additional rearing period in Lake Wenatchee could succeed. How- ever, even if no loss had occurred during lake resi- dence, thus doubling the number of hatchery out- migrants, no more than a twofold increase in adults could be expected. Even with such an im- provement, still more than 10 times that number of adults would be required for a favorable benefit/cost ratio. Downstream Migrant Problems With a large portion of the production sacrificed in the lake, the remaining smolts were still faced with gi-eat problems. Until recently, little was known of the causes and extent of downstream losses of sockeye salmon, although much informa- tion has been obtained for chinook salmon and steelhead trout smolts. Anas and Gauley 11956) studied the seaward migration of sockeye salmon smolts and their data suggested a wide range in 239 FISHERY BULLETIN: VOL 77, NO. 1 travel time and in size and age of migi'ants. No estimates of mortality of any given gi-oup of sock- eye salmon could be made from their data or from other studies conducted at the various dam proj- ects. However, we have assumed that extremely large losses occur in each annual outmigration of sockeye salmon, comparable to those documented for Chinook salmon and steelhead trout. Losses can occur in but a short distance during the seaward journey. Ellis and Noble (1960) re- ported losses of fall chinook salmon of 12.2 to 29.7% in the Klickitat River in a distance of only 64 km. The Wenatchee stock sockeye salmon smolts had to navigate 844 km in their seaward migration and were subjected to injuries and pos- sible death at each of seven dams, plus the myriad effects of altered flows and water quality. Major direct causes of mortality in juvenile mi- grants are gas bubble disease, a result of high dissolved nitrogen concentrations which occur throughout the river and death or injury by pass- ing through turbines (Ebel et al. 1973). At high flows with excessive spill the fingerlings are sub- jected to the nitrogen problem, while the turbine caused losses are most severe at low flows. Chaney and Perry ( 1976) reported that the juvenile losses averaged 15 to 20% at each mainstem dam from combined causes. At low flows, cumulative fish losses just from turbine mortality at a series of seven dams may exceed 90'/f . Additional mortality can be expected from sev- eral other causes. The delay of stream flow in the impoundments has reduced migration rates of juveniles by one-third according to Raymond (1969). The fish are then subject to increased pre- dation, possible loss of marine adaptability, and may become residual in the reservoir. Undoubt- edly but a small part of the outmigrants ever reach the sea in some years. Adult Problems We surmise that the sockeye salmon suffer loss- es comparable to the other species in the ocean, but there is no appreciable fishery harvest. The few tagging returns that have been reported for Co- lumbia sockeye salmon (Margolis etal. 1966) indi- cate a more southerly distribution than for Cana- dian or Washington sockeye salmon, and there is no inshore marine fishery to intercept the adults. The relatively few remaining adult sockeye salmon, after surviving the perils of sea life, still must face serious obstacles on the spawning mi- gration. Aside from the commercial harvest, a substantial mortality occurs which cannot be measured precisely. In early reports of upriver fish passage, Schoning (1948) pointed out that annu- ally an average of 36% of the Bonneville Dam count could not be located after subtracting the known harvest. "Fall-back" contributes to the loss and obscures the actual number passing the dam. Later accounts corroborate these losses (Chaney and Perry 1976). Bonneville Dam mortalities would reduce the number offish available for har- vest only in the zone 6 portion of the fishery. SUMMARY 1. The Columbia River system produced large runs of sockeye salmon prior to 1900, providing an annual commercial harvest reaching 2 million kg. 2. Deterioration of spawning areas and blockage of tributaries caused a severe decline in the sock- eye salmon population early in this century. 3. Construction of Grand Coulee Dam in 1941 blocked the sockeye salmon from 1,835 km of spawning and rearing areas, virtually eliminat- ing all natural production. 4. Compensatory measures intended to replace the lost production included relocation of the sock- eye salmon runs to suitable areas below Grand Coulee Dam and construction of hatcheries for additional production. 5. Leavenworth National Fish Hatchery on the Wenatchee River was activated in 1940 as the primary fish production station and an annual stocking program of sockeye salmon fingerlings was started. 6. For over 20 yr Leavenworth Hatchery reared sockeye salmon, releasing the fingerlings into the Wenatchee system augmenting the natural pro- duction. 7. No assessment had been made of the actual contribution of hatchery fish to the commercial fishery, thus the subject study was initiated using the 1960-63 broods of sockeye salmon. 8. During the initial 4 yr of the study, a total of 11,538,291 fish were released, of which 3,390,941 were marked by removal of the adipose fin and a part of the maxillary bone. 9. The stock used was adult .sockeye trapped in tributaries of Lake Wenatchee. Fingerlings were reared at the hatchery until fall, then released into Lake Wenatchee. 10. Surviving smolts migrated out of the lake in the spring. Outmigrant trapping in the first 2 yr 240 WAHLE ET AL : 1960-63 BROOD HATCHERY-REARED SOCKEYE SAI \ION revealed that <50^ of the stocked fish migrated downstream. 11. From 1964 through 1968, sampling for marked adults was conducted in the two Columbia River fisheries: the gill net area below Bonneville Dam (zones 1-5), and the Indian set net and dip net fishery above the dam (zone 6). An average of 43.5% of the commercial catch was examined for marks. 12. The commercial harvest was atypical during the study because of regulation restrictions. The average annual harvest for the period was only 22,500 fish compared with average landings of 90,900 for the prior 7 yr. The C/E ratio did not exceed 0.5/1. 13. Almost all hatchery fish in the catch were in their fourth year of life. The average weight offish in the catch ranged from 1.5 to 1.8 kg. 14. A mark mortality correction factor was in- cluded in calculations of hatchery fish in the catch as it was shown that the marked fish survival was only 60.52'^f of the unmarked fish. 15. During the study, hatchery fish composed an average of 13.6% of the total commercial catch. 16. The exvessel price to fishermen, used to de- termine benefits in this study, ranged from $0.68 to $0.82/kg. 17. Production costs were determined by a pre- viously developed method utilizing both capital and operational charges. 18. The benefit cost ratio for the study broods was 0.039:1 or about 4 cents returned for each dollar spent. 19. Factors contributing to poor survival of juvenile fish were: high mortality from predation and angling during lake rearing, probable disease and nutritional problems, losses during migration from turbine injury and gas bubble disease, and delay in reservoirs. 20. Reasons for the low return of adults to the fishery include: unknown ocean mortality, losses incurred while ascending Bonneville Dam, and the erratic opportunity of harvest because of sea- son restrictions. ACKNOWLEDGMENTS We are grateful for the assistance and coopera- tion of various individuals and agencies during the course of this study. Special thanks are offered the following individuals: Donald D. Worlund, National Marine Fisheries Service, for develop- ment of design and acting as primary consultant; Douglas Weber, Donovan Craddock, and Robert McConnell, National Marine Fisheries Service; Paul D. Zimmer and Eugene Maltzeff, Bureau of Commercial Fisheries; John W. Kincheloe and Steven K. Olhausen, U.S. Fish and Wildlife Service; and Arthur L. Oakley, formerly Fish Commission of Oregon, for their assistance in the design, supervision, and data collection and pro- cessing portions of this study. The aid and cooper- ation of Alfred C. Gastineau and Fredrick W. Bitle and staff of Leavenworth National Fish Hatchery is much appreciated. Helpful editorial comments were contributed by Richard T. Pressey, John I. Hodges, Steve H. Smith, National Marine Fisheries Service; William Sholes, California De- partment of Fish and Game; Robert Foster, Washington Department of Fisheries; Frederick C. Cleaver, Columbia River Fisheries Council; and F. K. Sandercock, Canadian Fisheries and Marine Service. Our thanks are due Kathleen LaBarge and Vivian Dignan for typing the text and tables for this publication. LITERATURE CITED ALLEN, R. L.. AND T, K, MEEKIN, 197.3. ColumbiaRiversockevesalmonstudy. 1972. Prog. Rep. Wash. Dep. Fish,. 61 p. ANAS, R. E.. AND J. R. GAULEY. 1956. Blueback salmon, Oncorhynchus nerka age and length at seaward migration past Bonneville Dam. U.S. Fish Wildl. Serv.. .Spec. Sci. Rep. Fish. 185. 46 p. Chaney, E., and L. E. Perry. 1976. Columbia Basin salmon and steelhead anal- ysis. Summ. Rep., Pac. Northwest Reg. Comm., 74 p. CRAIG. J. A., and R. L. H.ACKER, 1940. The history and development of the fisheries of the Columbia River. Bull. |U,S.] Bur. Fish, 49:133-216. Ebel, W. J,, D, L. Park, and R, C. Johnsen, 1973, Effects of transportation on survival and homing of Snake River Chinook salmon and steelhead trout. Fish, Bull,, U,S. 71:549-563, Ellis. C. H., and R. E, Noble, I960. Barging and hauling experiments with fall chinook salmon on the Klickitat River to test effects on survivals. Wash, Dep, Fish., 70th Annu. Rep., p. 57-71, Fish Commission of OREtMjN and Washington Depart- ment OF Fisheries, 1968. The 1967 status report of the Columbia River com- mercial fisheries. Fish, Comm. Oreg. and Wash. Dep. Fish.. 91 p. Fish. F. F,. and M, G, Hanavan, 1948, A report upon the Grand Coulee Fish-Maintenance Project 1939-1947. U.S. Fish Wildl. Serv., Spec, Sci, Rep, 55, 63 p, FOERSTER. R, E, 1968. The sockeye salmon, Oncorhynchus nerka. Fish. Res. Board Can.. Bull. 162, 422 p. 241 FISHERY BULLETIN: VOL. 77, NO 1 French, R. R., and R. J. Wahle. 1959. Biology of Chinook and blueback salmon and steelhead in the Wenatchee River System. U.S. Fish Wild). Serv., Spec. Sci. Rep. Fish. 304, 17 p. 1965. Salmon escapements above Rock Island Dam, 1954-60. U.S. Fish Wildl. Serv., Spec. Sci. Rep. Fish. 493, 18 p. Fulton, L. a. 1970. Spawning areas and abundance of steelhead trout and coho, sockeye, and chum salmon in the Columbia River basin — past and present. U.S. Dep. Commer., Natl. Mar. Fish. Serv., Spec. Sci. Rep. Fish. 618, 37 p. GANGMARK, H. a., and L. a. FULTON. 1952. Status of Columbia River blueback salmon runs, 1951. U.S. Fish Wildl. Serv., Spec. Sci. Rep. Fish. 74, 29 p. GUENTHER, R. W., S. W. Watson, and R. R. Rucker. 1959. Etiology of sockeye salmon "virus" disease. U.S. Fish Wildl. Serv., Spec. Sci. Rep. Fish. 296, 10 p. KOSKI, R. O. 1964. Management of migratory game fish. Oreg. State Game Comm., Bull. 19(6), 8 p. Major, R. L., and d. r. craddock. 1962. Influence of early maturing females on reproductive potential of Columbia River blueback salmon lOncorhyn- chus nerka). U.S. Fish Wildl. Serv., Fish. Bull. 61:429- 437. Margolis, l., f. C. Cleaver, Y. Fukuda, and H. Godfrey. 1966. Salmon of the north Pacific Ocean — Part VI. Sock- eye salmon in offshore waters. Int. North Pac. Fish. Comm., Bull. 20, 70 p. Raymond, H. L. 1969 Effect of John Day Reservoir on the migration rate of juvenile chinook salmon in the Columbia River. Trans. Am. Fish. Soc. 98:513-514. SCHONING, R. W. 1948. Trends of Columbia River blueback salmon popula- tions 1938-1947. Fish Comm. Greg., Res. Briefs l(2):33-40. THOMP.SON, R. B., AND D. F. TUFTS. 1967. Predation by Dolly Varden and northern squawfish on hatchery-reared sockeye salmon in Lake Wenatchee, Washington. Trans. Am. Fish. Soc. 96:424-427. Wahle, R. J., R. R. Vreeland, and R. H. Lander. 1974. Bioeconomic contribution of Columbia River hatch- ery coho salmon, 1965 and 1966 broods, to the Pacific salmon fisheries. Fish. Bull., U.S. 72:139-169. Ward, D., R. robison, and a. Palmen. 1963. 1963 fisheries statistical report. Wash Dep Fish., 73d Annu. Rep., p. 127-216. Weber, D., and R. J. Wahle. 1969. Effect of finclipping on survival of sockeye salmon iOncorhynchus nerka). J. Fish. Res. Board Can. 26:1263-1271. Worlund, D. D., R. J. Wahle, and P. D. zimmer. 1969. Contribution of Columbia River hatcheries to har- vest of fall chinook salmon iOncorhynchus tshauytscha). VS. Fish Wildl. Serv., Fish. Bull. 67:361-391. 242 RELATIVE ABUNDANCE, BEHAVIOR, AND FOOD HABITS OF THE AMERICAN SAND LANCE, AMMODYTES AMERICANUS, FROM THE GULF OF MAINE Thomas L. Meyer, Richard A. Cooper, and Richard W, Langton' ABSTRACT Meristic characteristics of sand lance taken from Stellwagen Bank indicated the species to be the American sand \ance, A mmodytes a menvanus. Bottom trawl data, ichthyoplankton surveys, and diver and submersible observations demonstrated a significant increase in relative abundance of sand lance since about 1975 on Stellwagen Bank; this trend was typical of the Northwest Atlantic from Cape Hatteras. N.C., to the Gulf of Maine. School shapes were constant in appearance, vertically compres- sed, tightly compacted, and bluntly linear from a dorsal and ventral view. School strengths varied from about 100 to tens of thousands of individuals with the nearest-neighbor distance ranging from '/* to 1''2 body lengths. The swimming motion is sinusoidal in form and eellike in appearance. Swimming speeds varied from 15 to over 120cmy's. Copepods were the most important food source, constituting 4 l*^f of the total weight of food consumed; sand lance feed in school formation between midwater and the surface. Sand lance bury themselves totally or partially in clean sandy substrates when not schooling. In the Northwest Atlantic, sand lance range from Cape Hatteras, N.C., to Hudson Bay. They occur over sand and fine gravel bottoms and play an important role as a trophic Imk between zoo- plankton and commercially important fish such as Atlantic cod, haddock, silver hake, and yellowtail flounder (Scott 1968, 1973; Bowman and Langton 1978). Several species of sportfish (e.g., striped bass and bluefish) also utilize the sand lance as a food source (Bigelow and Schroeder 1953). Studies of the eggs, larvae, and postlarvae of the American sand lance, Ammodytes americanus. have been reported by Covill (1959), Richards (1959, 1965, 1976), Norcross et al. (1961), Wil- liams et al. (1964), and Richards and Kendall ( 1973). Investigations on the adult sand lance in- clude taxonomic studies by Backus (1957), Richards et al. ( 1963). Leim and Scott (1966), Reay (1970), Winters (1970), Scott (1972-), and Pelle- grini^ and studies on mortality and growth by Graham ( 1956) and Pellegrini (see footnote 2). De- spite these investigations, little is known about the relative abundance, biology, behavior, and food habits of the adult American sand lance. 'Northeast Fisheries Center Woods Hole Laboratory, Na- tional Marine Fisheries Service, NOAA, Woods Hole. MA 02543. 2Pellegrini,R. 1976. Aspectsofthebiology of the American sand \ance, Ammodytes ariiencanus. from the lower Merrimack River estuary, Massachusetts. Master's problem, Univ. Mas- sachusetts, Amherst, 44 p. Manuscript accepted September 1978 fishery bulletin vol 77. NO 1. 1979 For the last 10 yr, information has been col- lected on sand lance during fishery cruises and undersea research programs conducted by the Northeast Fisheries Center, National Marine Fisheries Service, NOAA, Woods Hole, Mass. The purpose of this paper is to describe some aspects of the abundance, behavior, and food habits of the American sand lance based on bottom trawl (groundfish) survey data, observations by scuba divers and from research submersibles with photographic records, and a food-habit study. MATERIALS AND METHODS Study Area The majority of the observations on sand lance were made on Stellwagen Bank, a submarine ridge that rises to within 18 m of the ocean surface on the eastern boundary of Massachusetts Bay (Figure 1). The length of the bank is 39 km (north-south axis) and its greatest width is 13 km (at the southern end). Depths range from 18 to 77 m. Substrate characteristics by depth interval re- corded during submersible operations are: 18-43 m — sandy; 43-55 m — sandy bottom with crushed shells; 55-77 m — gravel, rocky with boulders; and below 77 m — mud/silt. Approximately 95'7c of the bank has a sandy bottom. Additional observations on sand lance were 243 FISHERY BULLETIN: VOL. .NO. 1 Table 1. — Dive locations on Stellwagen Bank and Cape Coc (Provincetown. Mass.) with observations' on presence ( + ) or absence 10) of American sand lance. Observations were made using scuba and submersible (sub). FUILIRE 1. — Study area of sand lance observations. Gulf of Maine. made on the Provincetown slope from Race Point to Wood End (Figure 1). Depths over the Province- town slope range from 0 to 46 m, with a medium- coarse sandy substrate throughout the range. Slope gradients by depth interval are: 0-9 m — 5°- 15°; 9-46 m— 30°-45°. The relatively steep slope begins between 90 and 250 m offshore. Relative Abundance Divers using scuba, or observers in submersi- bles,^ made in situ observations during various manned undersea research projects from 1968 through 1977 (Table 1, Figure 2). Camera systems aboard the submersible were: 1) a 35-mm Nikon'' camera using a 55-mm micro lens and an exter- nally mounted MK 150 Subsea stroboscopic light, and 2) a Sony AD 3400 Monochrome video camera and recorder. Dive sites Dales ol Provincelown Stellwagen Banl( observations Scuba Sub Scuba Sub 1968 1 -0 1216 July - scuba 2 0 1969 1 0 21-25 July - scuba 2 3 0 0 1970 1 0 5 - 0 06-09 July - scuba 2 3 0 0 6- 0 1971 1 0 8 - 0 4 0 1 -0 23-25 June • scuba 2 0 9 - 0 2 0 22 Sept ■ sub 3 0 10- 0 3 0 4 0 5 0 6 0 7 0 1972 1 -0 4-0 18-21 July - scuba 2-0 5 ■ 0 24-31 Ocl • scuba 3 ■ 0 60 1973 1 - 0 7 ■ 0 1 0 05-10 Ocl - scuba 2 - 0 8- 0 2 0 05-09 Ocl • sub 3 ■ 0 9 - 0 3 0 10 - 0 4 0 11-0 5 0 12- 0 6 7 8 9 0 0 0 0 10 0 1974 1 ■ 0 06-11 July ■ scuba 2-0 3 ■ 0 1976 1 - • ■ 1 ■ f-t 16-18 June - scuba 2 - ^ * 2- + 15-18 June • sub 3- . + 1977 1 - t + + 4 -t--f 08-11 Aug ■ scuba 2 --)--)- -f 3- + + -¥ 5 ■f-f 'Estimates of relative abundance are noted as 0 for no sightings, ' lor a lew sand lance observed. • • for small schools (several hundred individuals per school) with infrequent sightings, and ^ + ^ for large schools (thousands per school) and schools observed almost continuously Stellwagen Bank is included in one of the sam- pling strata covered by the spring and fall bottom trawl surveys since 1963 (Grosslein 1969). This stratum encompasses the Massachusetts Bay area, extending from Provincetown to Cape Ann and ranges in depth up to 110 m (Figure 1). Sta- tions were selected randomly within the stratum for each survey and the number of stations actu- ally occupied on Stellwagen Bank on each survey ranged from 0 to 6. Trawl survey results are pre- sented only for 1967-77, the period during which diver and submersible observations were made. Behavior ■^Research submersibles were chartered by NOAA's Manned Undersea Science and Technology Program, Rockville, Md. ■•Reference to trade names does not imply endorsement by the National Marine Fisheries Service, NOAA. Photographic and video records of sand lance behavior were made by scuba divers during a hy- droacoustic experiment from RV Albatross IV, 244 MEYER ET AL AMERICAN SAND LANCE FROM THE GULF OF MAINE Figure 2. — Dive sites and location of 1977 food habits study on Stellwagen Bank and Cape Cod (Provincetownl from 1968 to 1977. Scuba (lines), sub- mersible (dotted lines), 1977 bottom trawl (hatching) sampling areas. See Table 1 for key. (972- 1974 FOOD HABITS STUDY \ ^ m^ v- 8-11 August 1977, on Stellwagen Bank (scuba dive locations 4, 5) and along the Provincetown slope (scuba dive locations 1-3) (Figure 2C)., Divers, using a Hydro-Products Model 125 tele- vision system with a 250-W thallium-iodide light source, filmed sand lance behavior on and near the bottom. The angles and speed at which sand lance entered the bottom substrate and exited from it were estimated from slow-motion video playback. Schooling behavior was observed and photo- graphed using a Nikonos II underwater camera with a 28- or 35-mm lens and a Subsea MK 150 or 225 electronic strobe. School strength, shape, nearest-neighbor distance, and individual fish size were estimated using in situ observations, photo- graphs, or bottom trawl data. School swimming speeds were estimated at approximately 1 kn by divers swimming parallel to several schools for short distances. A speed of 1 kn is the approximate short-term sustained swimming speed of a diver. All in situ observations by diver scientists were made in daylight between 0900 and 1600 h. Food Habits A series of nine tows were conducted from Al- batross IV on the southwestern edge of Stellwagen Bank over one 24-h period beginning at 1800 h on 9 August 1977 (Figure 2D). The tows were of 5-15 min duration at 3-h intervals and were made with 245 FISHERY BULLETIN: VOL, 77, NO, 1 a Yankee #36 trawl (Grosslein^). The cod end and upper belly of the net were lined with 13-mm mesh netting, knot to knot. Only three species of fish were caught in any quantity: spiny dogfish, Squalus acanthias; silver hake, Merluccius bilinearis; and American sand lance. Sand lance were taken at random from the catch and pre- served whole in lO'^f Formalin for stomach- content analysis. In the laboratory, the stomachs were dissected out for stomach-content analysis. Ten fish from each of the nine tows were randomly selected from the preserved specimens for analysis. After the stomach was removed from each fish, the contents were examined and washed onto a fine-mesh screen. If the stomach appeared empty or had trace amounts (<1.0 mg) of food in it, it was rinsed out with seawater directly into a Petri dish. When there was a weighable quantity of prey present, the excess water was drawn off by pressing an absorbent tissue paper to the underside of the screen; the contents were weighed and then washed into a Petri dish. Using a dissecting micro- scope, the prey of each fish were identified to the lowest possible taxonomic grouping, and the per- centage composition of each of the identified groups estimated. The percentage composition and total stomach-content weight were used to calculate the percentage weight for each prey category. The data were also expressed in terms of the percentage occurrence of each prey group in the stomachs. from 30 to 31 with a mean of 30.7, SD = 0.48. The dorsal fin ray count ranged from 60 to 63 with a mean of 61.1, SD = 0.99. The vertebral count, based on radiographs of 20 fish and excluding the hypural complex, ranged from 67 to 72 and aver- aged 69.25, SD = 1.21. The mean values reported here fell into the A. americanus category given by Reay (1970). For the purpose of this paper, the classification of Reay (1970) is accepted. Relative Abundance Examination of spring and fall survey data for the past 10 yr, excluding 1967, 1969, 1971, and 1973 for spring and 1971 and 1977 for fall (Stell- wagen Bank stations were not sampled), indicates a substantial increase in sand lance abundance on Stellwagen Bank (Figure 3). The relative abun- dance increased during spring cruises from virtu- ally 0 for the 1967-75 period to 50/tow in 1976 and 10,729/tow in 1977, while increasing during fall cruises from 0 for the 1967-74 period to 4,238/tow in 1975 with a decrease to 5/tow in 1976. Spring cruises (March- May) may give a better indication of sand lance abundance since fall cruises are con- ducted from October to December, a period of les- ser sand lance activity before spawning ( Winslade 1974). In the Gulf of Maine, all bottom trawl sur- vey catches <75 sand lance/tow occurred on or along the edge of Stellwagen Bank. The catch rate RESULTS AND DISCUSSION In the taxonomic studies listed above, mor- phometric and meristic characteristics were used to distinguish between "inshore sand lance" [Ammodytesai7iericaniis -Ainmodytes hexapterus ) and "offshore sand lance" (Ammodytes dubius), although Bigelow and Schroeder (1953) ques- tioned whether such a distinction could be made. Because of the question regarding the taxonomic status of A. americanus and A. dubius. several meristic characteristics were evaluated on sand lance caught on Stellwagen Bank (Figure 2D). Dorsal and anal fin ray counts were made directly on 10 randomly chosen fish ranging from 17.9 to 22.2 cm fork length (FL) and averaging 20.0 cm, SD = 1.24. The anal fin ray count ranged 10.000 9000 J 6000 ■ 4000 SOOO 900 ' 700 , 500 : soo SPRING BOTTOM TRAWL SUBVET FALL BOTTOM TRAWL SURVEY -A/- NOSAMPLE COLLECTED oyv= 1967 ■=!^ V=^ ^Grosslein, M. D. 1969. Groundfi.sh survey methods, >fMFS, Woods Hole, Massachusetts. Lab. Ref. No. 69-02, 34 p, 246 Figure 3. — Catch of adult sand lance per standard tow on Stell- wagen Bank during the NMFS .spring and fall bottom trawl stratified sampling surveys for 1967-77. MEYER ET AL AMERICAN SAND LANCE FROM THE GULF OF MAINE declined drastically, to <1 sand lance/tow, when not fishing on the bank. In the southwest North Sea, fishermen have also noticed that better catches occur along the edges of larger banks and on the tops of smaller ones (Popp Madsen 1963). In the last 10 yr, sand lance have shown evi- dence of a population increase along the Atlantic coast from Cape Hatteras, N.C.. to and including the Gulf of Maine. Northeast Fisheries Center spring and fall bottom trawl survey results from 1968 to 1977 show large annual fluctuations in sand lance abundance since 1968 with a definite upward trend beginning in 1975 (Figure 4). The magnitude of this increase is considerably less than that recorded on Stellwagen Bank for the same period, but the yearly trends are similar. One area of concern in attempting quantitative sampling is net avoidance. Livingstone (1962) documented on film that adult sand lance were able to escape in <2.5 s from the cod end of a Yankee Modified #41 trawl net with a cod end mesh of 1 14 mm, knot to knot, and a -SS-mm cotton webbing covering. These films also showed the ease with which individuals and small schools were able to avoid the trawl net. In areas where abundance is high, the ability to avoid trawl nets maybe less effective. Scott ( 1973) found it unusual to catch adult sand lance in nets except in areas where they were very abundant. Relative abundance of sand lance on Stellwagen Bank and Provincetown slope, based on diver and submersible observations, has increased sig- nificantly since 1976 (Table 1). Although numer- - SPRING BOTTOM TRflWL SURVEr - fALL eoT TOM TRflWL SUftVE » Figure 4. — Changes in the relative abundance of adult Ammo- dytes spp. in the Northeast Fisheries Center spring and fall bottom trawl surveys from 1968 to 1977 in the area extending from Cape Hatteras northward. (Data from Grosslein et al. in press, table 3.2.) ous diving programs have been carried out over the study area since 1968, it was not until the spring of 1976 that .schools of sand lance were first observed. However, it is very likely that relatively small numbers of sand lance were present in the study area prior to 1976 but not noticed by the divers. This increase in sightings coincides with an increase in number of sand lance caught per tow during the bottom trawl survey cruises. Sand lance larvae studies, conducted by the Bos- ton Edison Company^ showed sand lance larvae were among the most abundant fish larvae occur- ring in ichthyoplankton sampling surveys con- ducted in Cape Cod Bay, Mass., d.'ring 1974-77. They were more abundant in the eastern portion of the bay and were considerably more abundant in 1976 than in the previous 2 yr. This mcrease in sand lance larvae was also observed during the Northeast Fisheries Center spring ichthyo- plankton surveys conducted in the area from Cape Hatteras to the Gulf of Maine for the past 4 yr (Figure 5). For example, the mean sand lance catch/10 m^ area in spring 1977 was 9 times great- er than in spring 1974. Bottom trawl survey results, diver and submer- sible observations, and ichthyoplankton survey results all indicate that there is a relatively large concentration of sand lance inhabiting a small section of the Gulf of Maine, i.e., Stellwagen Bank and outer Cape Cod (Provincetown slope), and that this population has increased considerably since 197.5; this increase in population is typical of the Northwest Atlantic from Cape Hatteras to the Gulf of Maine. Behavior School Structure Schools of sand lance observed on the Province- town slope were relatively small in numbers of fish, ranging from about 100 to several thousand individuals and were usually found in depths ranging from 6 to 20 m. From photographs it was calculated that individual fish on Provincetown slope ranged from approximately 12 to 17 cm long, with a mean of 15 cm. Sand lance schools observed on Stellwagen Bank were relatively large in num- bers, ranging from about .500 to tens of thousands 'Boston Edison Company. 1974-77. related to operation of Pilgrim Station. Boylston Street, Boston. MA 02199. Marine ecology studies Boston Edison Co., 800 247 FISHERY BULLETIN: VOL 77. NO I 700 600 500 400 300 I 00 - 90 80 - 70 - 60 50 - 40 30 20 Figure 5. — Changes in the relative abundance of larval Am- modytes spp. in the Northeast Fisheries Center spring ichthyo- plankton surveys from 1974 to 1977 in the area extending from Cape Hatteras northward. Data from Smith, W. G.. and L. Sulli- van. 1978. Annual changes in the distribution and abun- dance of sand lance. Ammodytes spp., on the northeastern continental shelf of the U.S. from the Gulf of Maine to Cape Hatteras. Northeast Fish. Cent.. Sandy Hook Lab., Sandy Hook, NJ 07732. Lab. Ref No. SHL 78-22. of individuals. Individuals varied from 7.4 to 24.0 cm FL (measurements from bottom-trawl catches), with a mean length of 18.2 cm. Sand lance within a given school were of similar size; slightly larger fish were observed in positions at the head or central "core" of the school, with the smaller individuals occurring at the periphery. This distribution by size within the school was observed in both study areas. Schools were ob- served on the surface, at mid-depth, and near the bottom. Inshore school strengths described by Kiihlmann and Karst (1967) for European sand lance species Hyperoplus lanveolatus and Ammo- dytes lancea were commonly 30-100 or 200-300 individuals. These smaller schools joined up to form schools of from 500 to > 1 ,000 fish and headed offshore for deeper water in the early morning. We observed schools of this size primarily in the Prov- incetown slope area. However, because the indi- vidual size of the fish and school strengths on Stellwagen Bank were larger, it is unlikely that these schools formed in the Provincetown slope area and moved out to the bank. 248 .ScIkkiI Shape The shape of sand lance schools, where indi- viduals were not engaged in feeding, was constant in appearance. As a school moved undisturbed through the water it appeared vertically compres- sed, tightly compacted, and bluntly linear from the lateral view (Figure 6). Provincetown slope schools were 1-5 m wide, 0,5-1,5 m high, and 3-20 m long; these measurements depended on school strength. This school form, where the height- width-length ratio was approximately 1 :3: 10 ( hav- ing more individuals situated ahead, alongside, and behind than above or below), is called a strat- ified school iWahlert and Wahlert 1963). This school formation was, in general, independent of .school strength. The "nearest-neighbor" distance between fish was approximately '/■!-% body length (BL) (Figure 6), This distance became greater along the school's flanks. The "nearest-neighbor" distance decreased to '4 BL when the school exhib- ited a fright reaction to divers. The fishes leading the school and ones along the flanks usually swam the deepest. School shapes described by Kiihlmann and Karst (1967) were similar to the measurements reported in this study, but a sig- nificant difference appeared in the school height and length measurements. Kiihlmann and Karst (1967) listed their school height as 15-50 cm, and their school length as s40 m. Sand lance schools encountered in our study were more than double the height and shorter in length. The European study took place in water depths of 1-6 m. and in this relatively shallow water, there may be a ten- dency for a school to flatten out and increase its length, Moxement The swimming motion of sand lance is sinusoi- dal in form and eellike in appearance from the dorsal and ventral views. Sidewise undulations begin at the head and run along the body toward the tail (Figure 7). Schools swimming undis- turbed, and not engaged in feeding, maintain an estimated speed of 30-50 cnVs. Schools exhibiting feeding behavior usually swim at about half the speed of undisturbed schools, or about 15-25 cm,s, and spread out to a little over double the normal schooling distances so that the nearest neighbor is approximately l-l'/2 BL away. Smaller schooling groups were observed to swim faster than larger schools. When approached by divers, schools ac- MEYER ET AL : AMERICAN SAND LANCE FROM THE GULF OF MAINE Figure 6. — School of sand lance encountered on Provincetown slope. Note lateral view of sand lance leaving the bottom to join school above. celerated to one side or split to avoid the divers at the part of the school closest to the divers. The forward portion of the school continued on in its original direction, while the rear portion gener- ally reversed direction. These avoidance maneu- vers were made at about 70-120 cm/s, over double the original undisturbed speed, and lasted for only a few seconds before the divided sections re- grouped and slowed down to their original speed. Feeding schools were observed in midwater and near the surface, but not on the bottom. Kiihlmann and Karst (1967) recorded the es- cape speed of larger sand lance to be 300-500 cm/s for at least a few seconds. During our study, there were many occasions when the swimming speed appeared to be >120 cm/s, but the actual speed was not calculated. Behavior Within and Near the Ocean Floor Sand lance were found in substrates conducive to burrowing, such as clean sandy bottoms, sand bottoms with crushed shells, and fine-graveled bottoms. Substrates of mud, mud/silt, medium to coarse gravel, and rock/boulder were avoided. This preference for loose porous substrate facilitates entry and exit and may relate to a sufficient supply of dissolved oxygen within at least the first few- centimeters of interstitial water. Oxygen is con- tinually replenished by tidal currents of 32-47 cm/s (0.62-0.91 kn) measured at 1 m above the bottom on Stellwagen Bank (Padan 1977). Sand lance usually disappear into the bottom in small groups. The initial penetrating angle was estimated as 60°-75° from the horizontal and con- 249 FISHERY BULLETIN VOL 77. NO. 1 < I a a 250 MEYER ET AL.; AMERICAN SAND LANCE FROM THE GULF OF MAINE sisted of a continuance of their sinuous movement until one-quarter of the body was buried, at which point the remaining three-quarters of the body was brought to a 20°-40'' angle to allow the animal to settle into its normal resting position ( Figure 7 ). Once in a resting position, the sand lance would partially emerge headfirst if disturbed (Figure 7). Sand lance on Stellwagen Bank, exhibiting this partial-emergence behavior, would retract back into the bottom when further disturbed. In con- trast, sand lance encountered along Provincetown would usually leave the substrate. Kiihlmann and Karst (1967) observed similar behavior and noted on several occasions that, after pulling back into the bottom, sand lance could turn, move laterally through the substrate, and emerge some distance away. This behavior was not observed in our study area. Sand lance leaving the bottom exited at an angle between 20° and 60° with an initial speed of 50-80 cm/s, which increased up to 120 cm/s within the first 1.5 m from the bottom (Figure 7). As divers proceeded along the bottom, sand lance would exit from the substrate and either school or swim to the end of the diver's visual range. Food Habits The results of the stomach-content analysis for A. americanus collected on Stellwagen Bank are given in Table 2. The data are presented as both the percentage occurrence of prey in the stomachs and as the percentage weight of the total prey consumed. It is evident that copepods were the most important prey, occurring in 37.8% of the stomachs examined and making up 41.4% of the total weight of the prey. The other identifiable prey groups, such as hyperiid amphipods, mysids, euphausiids, chaetognaths, salps, and animal eggs, were much less important, usually occurring in only 1-2% of the stomachs. Of these gi'oups only the chaetognath Sagitta contributed significantly to the diet on a percentage weight basis (39.9% ). This was because the stomach of one fish was quite distended with chaetognaths. "Animal remains," which are unidentifiable prey, were the most fre- quently occurring prey category; however, on a weight basis they were much less significant. The food habits of a number of different species of sand lance have been studied in Atlantic and Pacific waters. In general the diets are all very similar, with copepods being the major prey in almost every instance (Reay 1970). Around Japan, TABLF> 2. — Stomach contents of American sand lance collected on Stellwagen Bank, August 1977. The data are expressed as both the percentage frequency of occurrence of prey and as the percentage weight of the total quantity of prey consumed. Occurrence Weight Prey (%) (°o) Copepods: Calanoida 3.3 081 Calanus 8.9 9 55 Centropages 10.0 2 57 Pseudocalanus 17.8 6 28 Temora 17.8 8 06 Tortanus 17.8 6 27 Metndia 1.1 1 22 Cyclopoida Oithona 2.2 005 Unidentified 28.9 6 62 Copepod subtotal 37.8 41 43 Hyperiid amphipods 1.1 0 09 Mysids 1.1 0 32 Meganyctiphanes norvegica 1.1 041 Sagitta elegans 2.2 3991 Salpidae 1.1 0 04 Animal eggs 1.1 001 Trematodes 3.3 0 01 Animal remains 84.4 17 79 No stomachs exami ned 90 No stomachs empty or trace 32 Mean wt ot contents/stomach 15 3 mg Mean tish length 18 2 cm, SD = 1,8 for example, both Senta (1965) and Sekiguchi (1977) have shown that A. personatus is a plankton feeder relying heavily on copepods. In the North Sea, Roessingh' found that copepods were the major prey of A. marimis and occurred in roughly the same proportions in the stomachs as they did in the plankton. Macer (1966) examined the stomach contents of five species of sand lance from the North Sea. In all cases the sand lance were found to be plankton feeders, with copepods being the dominant prey for at least three of the five species. Only for A. lanceolatus was it conclu- sively shown that copepods were less significant as prey, being replaced by fish eggs, larvae, or small fish, particularly sm&W Am modytes. Two species oi sand lance are reported to occur along the Atlantic coast of North America, and only a small amount of information is available on their food habits. Richards (1963) examined the stomachs of 290 A. americanus in Long Island Sound; as for most other species of sand lance, copepods were the major prey. Centropages were preyed upon by 80% of the fish, Acartia by 55%, and Temora by 42%. Other prey included barnacle cyprids, fish eggs, dinoflagellates and diatoms, mysids, and sand lance larvae. Scott ( 1973) studied the food habits of 'Roessingh.M, 1957. Problems arising from the expansion of the industrial fishery for the sand Qe\. Ammodytes marinus Raitt, towards the Dutch coastal area. Near Northern Seas Committee, Int. Counc, Explor. Sea. 251 FISHERY BULLETIN: VOL. 77, NO. 1 A. dubiiis in the Canadian northwest Atlantic. Again, copepods, especially Calanus finmar- chicus, were the most important prey. Other prey included crustacean larvae, invertebrate eggs, polychaete larvae, larvaceans, fish eggs, pteropods, and barnacle cyprids. Comparison with plankton tows made at the time the fish were caught showed that A. dubttis had a definite pre- ference for the larger zooplankton such as copepods. From the data in Table 2, it is clear that the diet of A. americaniis from Stellwagen Bank is typical for this family of fishes. There are, how- ever, several small differences from other pub- lished results which are worth noting. For exam- ple, chaetognaths occurred rarely in the stomachs (2.2*^ ) but on a weight basis were only slightly less important than copepods. It would appear that chaetognaths are readily consumed if available. One notable exception to the list of prey is phyto- plankton. Both Richards (1963) and Scott (1973), as well asSenta ( 1965) and Macer ( 1965), reported finding diatoms or dinoflagellates in the guts of the fish they examined. In our study, no phyto- plankton was observed as part of the stomach con- tents. It is possible that at certain times of the year the occurrence of phytoplankton would be much more apparent in the guts, as might also be ex- pected for other prey such as crustacean larvae, barnacle cyprids. and larval polychaetes. SUMMARY 1. The meristic counts of sand lance reported are in agreement with published data and fall into the category of Ammodytes americaniis, the American sand lance. 2. Data on the relative abundance of sand lance from Northeast Fisheries Center spring and fall bottom trawl survey cruises indicate that there has been a substantial increase in sand lance abundance on Stellwagen Bank over the last 10 yr. This trend was also reflected by an increase in the numbers of sand lance larvae occurring in the spring ichthyoplankton results measured in the Gulf of Maine over the last 4 yr. This increasing trend in larval and adult sand lance abundance in the Gulf of Maine was typical of the northwest Atlantic from Cape Hatteras northward. 3. Sand lance encountered within the Province- town slope area ranged from 12 to 17 cm long (mean = 15 cm), and school strength numbered from about 100 to several thousand individuals. In contrast, individuals on Stellwagen Bank ranged from 7.4 to 24.0 cm FL (mean = 18.2 cm), while school strengths ranged from about 500 to tens of thousands of individuals. 4. School shapes were constant in appearance, vertically compressed, tightly compacted, and bluntly linear from a dorsal and ventral view. Provincetown slope schools were 1-5 m wide, 0.5- 1.5 m high, and 3-20 m long depending on school strengths. The nearest- neighbor distance between fish swimming in an undisturbed school was ap- proximately V2-% BL; between fish swimming in a school exhibiting a fright or avoidance reaction, 'a BL; and between fish swimming in a school en- gaged in feeding, approximately 1-1 '/2 BL. 5. The swimming motion of sand lance is sinusoidal in form and eellike in appearance. Schools swimming undisturbed and not engaged in feeding maintain an estimated swimming speed of 30-50 cm/s; during feeding they maintain an estimated speed of 15-25 cm/s; and during avoid- ance maneuvers, 70-120 cm/s. Feeding schools were observed in midwater and near the surface, but not on the bottom. 6. Sand lance were found to prefer clean sandy substrates conducive to burrowing. Sand lance usually disappear into the substrate in small groups, initially penetrating at an angle of 60°-75° from the horizontal, and continuing their sinuous movement until one-quarter of the body is buried. at which point the remaining three-quarters of the body is brought to a 20°-40° angle to allow the animal to settle into its resting position. Sand lance encountered on Stellwagen Bank were occa- sionally observed to partially emerge from the substrate headfirst and retract back into the bot- tom if approached. In contrast, sand lance along Provincetown slope would exit from the bottom when approached. Sand lance leaving the bottom exited at an angle of between 20° and 60° with an initial speed of 50-80 cm/s and built their speed up to 120 cm/s within the first 1.5 m from the bottom. Individual fish exiting would show schooling be- havior if another fish was exiting at the same time. 7. Copepods were the most important prey of A. americanus, occurring in 38'7f of the stomachs examined and making up 4Vi of the total weight of prey consumed. ACKNOWLEDGMENTS The authors gratefully acknowledge the assis- tance of the National Marine Fisheries Service, Woods Hole, Survey Unit for bottom trawl survey 252 MEYER ET AL ; AMERICAN SAND LANCE FROM THE GULF OF MAINE data; the laboratory scientific illustrator, Frank Bailey, for his many hours of patient craftsman- ship; and Rosalind Cohen and Nancy Kohler for their assistance with the stomach-content analysis. LITERATURE CITED Backus. R. h. 1957. The fishes of Labrador. Ammodytidae. Bull. Am. Mus, Nat. Hist. 113:307-308. BIGELOW, H. B., AND W. C. SCHROEDER. 1953 Fishes of the Gulf of Maine, U.S. Fish Wildl. Serv., Fish. Bull. 53. 577 p. BOWMAN. R. E., AND R. W. LANGTON. 1978, Fish predation on oil-contaminated prey from the region of the ARGO MERCHANT oil spill, //i In the wake of the ARGO MERCHANT, p, 137-141. Univ. 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PaDAN, J, W, (editori, 1977, New England Offshore Mining Environmental Study (Project NOMES), US, Dep, Commer,, NOAA Spec, Rep, NOAA ERL 1977, POPP Madsen, K, 1963, Tobis pa algediaet, Fiskeridir, Skr, .Ser, Teknol, Unders. 1963:46-47, REAY, R, J, 1970, Synopsis of biological data on North Atlantic sand eels of the genus A")"jo((v^cs..4 tobtanus, A. dubius.A. amencanus and.4 marinus. FAOFish, Synop, 82. 42 p. RICHARDS, S, W, 1959, Pelagic fish eggs and larvae of Long Island Sound. In Oceanography of Long Island Sound, p, 95- 124, Bull, Bingham Oceanogr, Collect, Yale Univ, 17(1). 1963, The demersal fish population of Long Island Sound, Bull, Bingham Oceanogr, Collect,, Yale Univ, 18(2), 101 p, 1965. Description of the post larvae of the sand lance (Ammodytes) from the east coast of North America, J, Fish. Res, Board Can, 22:1313-1317. 1976. Mixed species schooling of post larvaeof.4mmorfv(es he.xapterus and Clupea harengus harengus. J. Fish, Res. Board Can, 33:843-844, RICHARDS. S. W., AND A, W, KENDALL. jR 1973, Distribution of sand lance, Ammorfv(essp,.larvaeon the continental shelf from Cape Cod to Cape Hatteras from RV Dolphin surveys in 1966, Fish, Bull,. LI.S. 71:371-386. RICHARDS, S. W,, A. PERLMUTTER, AND D. C. McANENY 1963. A taxonomicstudyofthegenusAr?i/no(/y/es from the east coast of North America (Teleostei: Ammodytes). Copeia 1963:358-377. SCOTT. J, S, 1968, Morphometries, distribution, growth, and maturity of offshore sand launce (Ammodytes dubtus) on the Nova Scotia banks, J, Fish, Res, Board Can, 25:1775-1785, 1972, Morphological and meristic variation in northwest Atlantic sand lances (Ammodytes). J, Fish, Res. Board Can. 29:1673-1678, 1973, Food and inferred feeding behavior of northern sand lance (Ammodytes dubws). J, Fish, Res. Board Can 30:451-454. SEKIGUCHI. H. 1977, Further observation on the feeding habits of planktivorous fish sand-eel in Ise Bay, Bull, Jpn, Soc Sci, Fish, 43:417-422, SE.NTA, T, 1965, Nocturnal behavior of sand-eels, Ammodytes per- sonatus Girard. Bull. Jpn. Soc. Sci, Fish, 31:506-510. wahlert, G, v.. and h, V, Wahlert 1963. Beobachtungen an Fischschwarmen, VerofT, Inst, Meeresforsch , Bremerhaven 8:151-162, WILLIAMS, G, C, S, W, Richards, and E. G. Farnworth. 1964. Eggs of Ammodytes hexapterus from Long Island, New York. Copeia 1964:242-243, WINSLADE, P. 1974, Behavioural studies on the lesser sandeel. .4mmo- dytes marinus (Raitt), I, The effect of food availability on activity and the role of olfaction in food detection. II. The effect of light intensity on activity. III. The effect of tem- perature on activity and the environmental control of the annual cycle of activity, J, Fish. Biol. 6:565-599. WINTERS, G, H, 1970, Meristics and morphometries of sand lance in the Newfoundland area, J, Fish, Res, Board Can, 27:2104- 2108. 253 SEASONAL DISPERSAL AND HABITAT SELECTION OF GUNNER, TAUTOGOLABRUS ADSPERSUS, AND YOUNG TAUTOG, TAUTOGA ONITIS, IN FIRE ISLAND INLET, LONG ISLAND, NEW YORK' BoRi L. Olla, Allen J. Bejda, and A. Dale Martln^ ABSTRACT Results of field observations examining seasonal movements in the cunner, Tautogolabrus adspersus, and young tautog, Tautoga onitis, showed a small portion of a resident population located off Fire Island, N.Y., to disperse seasonally. Dispersal was from habitats which provide cover for both species throughout the year to seasonal habitats occupied primarily during summer. While both species exhibit a high degree of association with cover, results of experimental transfers of young tautog, monitored either ultrasonically or directly by divers with self contained underwater breathing apparatus, showed that fish will leave a suboptimal habitat even though cover is present. Dispersal and habitat selection are discussed in relation to seasonal changes in the environment and ecological requirements of the fish. Association with and dependence on cover by marine fishes have been observed for a wide vari- ety of species, exemplified by those which reside on coral reefs (e.g,, see: Hobson 1968, 1972, 1973; Sale 1969a, 1971, 1972, 1977: Smith and Tyler 1972, 1973). Although the number of species is much less, similar associations with cover also occur in temperate waters (e.g., see: Hobson 1971; Bray and Ebeling 1975; Hobson and Chess 1976; Olla et al. 1974, 1975). In both tropical (Hobson 1968, 1972) and tem- perate regions a major behavioral trait of the fam- ily Labridae is that members show a strong as- sociation with cover. Field studies on two temperate-water labrids of the northwest Atlan- tic, cunner, Tautogolabrus adspersus (Olla et al. 1975), and young tautog, Tautoga onitis (Olla et al. 1974), have demonstrated their close associa- tion with cover. Under laboratory conditions simi- lar associations have been observed for both species (cunner, Olla and Bejda unpubl. obs.; young tautog, Olla and Studholme 1975). Over several years, incidental sightings of cun- ner and young tautog always found them in as- sociation with cover. However, it was apparent that a substantial number offish were in areas in 'This work was supported, in part by a grant from the U.S. Department of Energy No. EX76-A-28-3045-A010. ^Northeast Fisheries Center Sandy Hook Laboratory, Na- tional Marine Fisheries Service, NOAA, Highlands, NJ 07732. Manu.script accepted October 1978. FISHERY BULLETIN: VOL. 77. NO. 1. 1979. which cover was present only seasonally, e.g., macroalgae and mussel beds. This suggested to us that there must be movement to these areas some- time after emergence from winter torpor (Olla et al. 1974, 1975) in March or April and movement away from these areas in the fall as the cover provided at these areas diminished. The possibil- ity of seasonal dispersal and habitat selection ap- peared likely. At least for adult tautog changes in habitat requirements with season have been es- tablished, as evidenced by the fact the fish migrate offshore to overwinter (Cooper 1966; Olla et al. 1974). In this study we have examined seasonal movements in cunner and young tautog, basing our observations on trapping and tagging, as well as surveying shelter sites seasonally by direct ob- servation with scuba or mask and snorkel. We also performed a series of transfer experiments to examine certain aspects of habitat selection. MATERIALS AND METHODS Based on previous scuba observations, six study sites (A, B, C, D, E, and F; Figure 1) within Fire Island Inlet, Long Island, N.Y., were selected at which to monitor the seasonal movements of cun- ner and young tautog. One site (A) was inhabited throughout the year and will be referred to as a perennial site. The five other sites (B, C, D, E, and F) were utilized only during late April through 255 FISHERY BULLETIN: VOL 77, NO 1 Figure l. — Location of study sites for cunner and young tautog within Fire Island Inlet, Long Island, N-Y. i see text for site descriptions!. FIRE ISLAND INLET (s) © ■'• 7 3° n' '"') ^■:^ -^^ ■I g^ ATI AN TIC OCEAN ROBERT MOSES BRIDGE FIRE ISLAND October and will be referred to as seasonal sites. A description of each site follows. Site A was the boat basin at the Fire Island Coast Guard Station, an open pentagon ( 110 ^ 52 X 47 m), constructed of tongue-and-groove planks, steel sheeting, and piles (011a et al. 1975). Along the outer perimeter was a zone of riprap (0.2- 0.4 m in diameter), 3 m wide and 2 m high. The mean water depth ranged from 2.4 to 8.8 m. Beds of the mussel, Mytilus edulis. were located along the walls, piles, and bottom. Site B was a 20.3-cm diameter drain pipe originating at the Fire Island water treatment plant. Located at a mean depth of 7.5 m, a 1.5-m section of the pipe was exposed and paralleled the bottom at a distance of 1 m. Beds of mussels sur- rounded the pipe in about a 6-m radius. Site C was one of the support piers for the Robert Moses Bridge, consisting of quarried stone and reinforced concrete. The mean water depth was 7.5 m. The pier was incrusted with mussels to a depth of 2 m below the high water mark. Sites D and E each consisted of an exposed verti- cal mud bank about 6 m long and 1 m high. Irregu- larly spaced along the face of each bank were ap- proximately 35 to 50 holes, apparently a result of erosion, varying in size from 12 to 20 cm wide and 5 to 15 cm deep. Small clumps of mussels were distributed along the top of each bank. Site D was at a mean depth of 6.0 m and Site E at 7.6 m. Site F was a grass bed which bordered a rocky shore line for 75 m and extended out from the shore 13-20 m. During the late spring and sum- mer, the area typically consisted of dense growths of eelgrass, Zostera marina, and algae iCodiurn spp., Enteromorpha spp., Polysiphonia spp., and Ulva spp.). Beds of mussels were interspersed be- tween the vegetation. Water depth throughout the area varied from 0.3 to 1.5 m. A seventh area, a small cove at the mouth of Fire Island Inlet, not designated in Figure 1, was the site of two transfer experiments involving ex- perimental cover. This site had a barren sand bot- tom, primarily dredge spoil, at a mean depth of 3.7 m. Three methods, trapping, direct visual counts, and tagging, were used to monitor, for both cunner and tautog, the periods and limits of movements as well as the types of habitats utilized. Fish traps were placed at Sites A, B, C, D, and E with two traps at Site A from March through November, one trap at Site B from May through November, and one trap each at Sites C, D, and E from June through November. Traps at each site were pulled at regular weekly intervals throughout the study and the number of cunner and tautog recorded. To compare the catch of the traps at the perennial site with the catch at the seasonal sites, we calculated the mean number offish caught per trap per week for each habitat type. Traps captured cunner rang- ing in size from 3.9 to 25.0 cm ix = 14.5 cm) and tautog from 7.3 to 35.0 cm l.v = 16.9 cm). Traps also provided the fish for the tagging portion of the study, as well as one means of recapture. Visual counts of cunner and tautog were made at Site F from the end of February through Oc- tober. A series of six transects the length of the site and 3 m wide were swum by divers, counting all 256 OLLA ET AL.: SEASONAL DISPERSAL OF CUNNER AND TAUTOC, tautog and cunner observed within each transect with the sum of the six transects being the total count. Cunner and tautog ( 314.0 cm) trapped at Sites A, B, C, D, and E were tagged throughout the study with Floy-67C^anchor tags. Tags were con- secutively numbered allowing identification of in- dividual fish and their release site. Each tag was printed with a request for fishermen catching tagged fish to return the tag, accompanied by in- formation as to the location and date the fish was caught. Fish were recaptured either in our traps or by recreational fishermen. Ultrasonic tracking was employed for short- term monitoring of movement and cover associa- tion of young tautog residing at both a perennial (Site A) and seasonal (Sites B and F) habitats. Four fish (two at Site A, one at Site B, and one at Site F) were individually tracked using the same procedures previously described by 011a et al. (1974, 1975) for capturing, handling, and track- ing. A series of transfer experiments was conducted to examine habitat selection in young tautog. All fish were captured at Site A and released at either existing, seasonal habitats (Sites B and C) or at experimental habitats which we established (see below). Fish were transferredby boat in 100-1 bar- rels of aerated seawater with the time to travel from capture to release sites ranging from 5 to 15 min. Four fish (three at Site B and one at Site C) were separately released at the seasonal habitats and tracked ultrasonically. Five transfers were made to the experimental habitats. One transfer was a single fish, released and monitored ultrason- ically. The other transfers consisted of four group releases with 10 fish/group. The response of the fish in these releases was monitored directly using scuba. While lying motionless, 5 m from the re- lease site, the observer recorded at 1-min intervals the number offish present. Cover abthe experi- mental habitats consisted of masonry structures constructed from standard cement blocks (20 x 20 X 40 cm) positioned in a manner which laterally exposed the central cavities (7 « 13 > 20 cm) ol each block. Cement blocks had been shown to be readily acceptable as cover by young tautog in the laboratory (OUa and Bejda unpubl. obs.). The structure for the single fish release was a four- block cube (40 X 40 x 40 cm). Two structures were used in the group releases. They were identical 12-block rectangular prisms ( 120 x 40 « 40 cm). RESULTS Catch and Direct Sightings at Seasonal and Perennial Habitats It was apparent from catch data and direct un derwater sightings that a majority of the habitat sites were utilized only seasonally by both cunner and young tautog. Throughout the summer, sub- stantial numbers of fish were captured at Sites A-E (Table 1) or sighted directly at Site F (Table 2). In September, there was a gradual decline in the catch of cunner and in October a sharp decline in both cunner and tautog at Sites B-E (Table 1). At Site F, direct visual counts indicated the same general trend (Table 2). However at Site A, while there was little change in catch during September, the catch of both species increased in October (Ta- ble 1). In November, Sites B-F were observed di- rectly with scuba and no fish were sighted. At Site Table 1. — Mean monthly catch of cunner and young tautog at perennial (A) and seasonal (B-E) sites. Mean catch/unit effort' Cunner Tautog Perennial Seasonal Perennial Seasons Month site sites site sites Marcii 11.0 ND^ 65 ND April 36.0 ND 27 tiJD May 6.8 9.5 25 92 June 19.7 8.5 1 3 106 July 13.8 5.3 06 11 9 August 218 61 62 98 September 21.9 2 8 86 80 October 34 0 3 0 149 10 November 97 0 38 0 'Unit eftorl = one trap fished 1 wk, -ND ^ no data Table 2.— Visual counts using scuba or mask and snorkel ot cunner and young tautog at seasonal Site F. ^Reference to trade names does not imply endorsement nt commercial products by the National Marine Fisheries Service, NOAA. Total number Total number Date Cunner Tautog Date Cunner Tautog Feb 28 0 0 July 2' 53 7 Mar 4 0 0 8^ 165 60 12 0 0 9= 93 27 20 0 0 10= 89 16 25 0 0 15 107 29 Apr 2 0 0 16' 42 13 29 17 3 29 44 24 May 20 29 11 Aug 12 63 20 22 74 20 13 169 71 29 60 15 Sept 3 42 7 June 5 65 14 24 34 6 11 79 19 Oct 2 0 0 18 10 0 20 0 0 26 69 12 29 0 0 'Mean ot two counts 'Mean of three counts 25; FISHERY BULLETIN: VOL, A, although large numbers of fish were sighted, the catch was declining (Table 1). The decline in catch at Site A may be related to lowered activity associated with decreasing temperature with the fish overwintering in torpor at this site (011a et al. 1974, 1975). Although traps were not in place in Sites B-E earlier than May, no fish were sighted directly in these areas or at Site F (Table 2 ) prior to mid- or late April. The presence offish at Site A throughout the year led us to term this a perennial habitat, while Sites B-F, where fish were only seen seasonally, we defined as seasonal habitats. Recaptures Tagged fish showed limited movements, with 91.3% of the cunner and 73. 2*;^ of the tautog recap- tures occurring at the same site at which they were released (Table 3). For the remainder of the fish, i.e., those recaptured at other sites, there were seasonal differences in where they were cap- tured. From May through August, recaptures were at seasonal as well as perennial sites (Table 3). But then from September through November, all recaptures were from sites which would be con- sidered perennial, including ones outside the study area (Table 3). Movements and Association with Cover of Young Tautog at Seasonal, Perennial, and Experimental Habitats In an earlier study, we had established that young tautog remained within several meters of cover (011a et al. 1974). Specifically, the cover re- ferred to in that study was Site A, identified in this study as a perennial habitat. To reconfirm the observation of the previous study, two fish ( no. 1,2; Table 4) were ultrasonically tracked for 48 h at Site A. Agreeing with the earlier results, both fish remained within several meters of the site. The question we next addressed was whether young tautog showed a similar association with cover at seasonal habitats. To answer this ques- tion, we captured and released two fish affixed with ultrasonic tags at Sites B (no. 4; Table 4) and F (no. 3; Table 4). The results of tracking showed the two fish to have a similar affinity to these sites as the fish had to the perennial one. remaining within 3 to 6 m of cover. The area over which the fish ranged varied with the size of the site. For example, when fish no. 3 was released at Site F, which consisted of beds of algae and eelgrass measuring about 15 ■ 75 m, it moved freely throughout the habitat, but never more than several meters beyond its perimeter. On the other hand, fish no. 4 released at Site B where cover was highly limited (0.2 x 1.5 m) ex- hibited less movement, while again remaining within several meters of cover. It appeared that the close association to cover was the same at both seasonal and perennial habitats. Thus far, all of the fish that were tracked had been released at the same site at which they were captured. Our next question was whether fish that were displaced from where they were captured T.'\BLE 4- — Size, capture and release sites i Figure 1 ». and period monitored for nine young tautog ultrasonically tracked. Tracking Number TL (cm) Capture site Release site duration (h) 1 22.5 A A 48 2 24 0 A A 48 3 20.2 F F 24 4 245 B B 48 5 21.5 A B 48 6 228 A B 72 7 23.0 A B 48 8 24.0 A C 48 9 22 5 A (') 24 'Experimental cover Table 3. -Nuinber and location of recaptures of cunner and young tautog tagged and released at perennial and seasonal sites. Release No Total no No recaptured No recaptured al otlner sites f^lay-August September Perennial ■November Perennial Seasonal Seasonal Species site released recaptured at 1 elease site sites sites sites sites Cunner A 875 176 166 5 1 4 0 B 83 13 7 0 3 3 0 C 15 0 0 0 0 0 0 D 54 6 5 0 0 1 0 E 10 0 0 0 0 0 0 Total 1.037 195 178 5 4 8 0 Tautog A 245 25 20 0 1 4 0 B 283 29 18 0 5 6 0 C 72 12 11 0 0 1 0 D 123 3 2 0 0 1 0 E 41 2 1 0 1 0 0 Total 764 71 52 0 7 12 C 258 OLLA ET AI. SEASONAI, DISPERSAL. OF IlINNER AND TAUTOC would accept and remain at a different site. Four fish captured at Site A, the perennial habitat, were affi,xed with ultrasonic tags and released at either of two seasonal sites. Three fish were released separately at Site B (no. 5-7; Table 4) and a fourth at Site C (no. 8; Table 4) and individually tracked for 48 to 72 h. The fish appeared to accept the transfer to a different habitat with all four fish remaining within several meters of the release site. The close association with cover exhibited by fish ultrasonically monitored at both perennial and seasonal habitats indicated the possibility that the apparent dependence on cover might be such that a fish would remain at any object that afforded cover. To examine whether the presence of cover was the sole determinant of habitat accep- tance, we transferred a fish from Site A to a struc- ture constructed of cement blocks, measuring 40 - 40 X 40 cm, and located on a sand bottom 50 m from a habitat with which fish were associated (Site F). The fish (no. 9; Table 4), during the first 5 min after release, circled the structure and moved farther away with each circuit, showing little, if any, attraction. When about 10 m from the struc- ture, it swam shoreward and reached Site F about 5 min later. The fish remained at this site during the next 24 h, showing the same degree of move- ment exhibited by fish no. 3 (Table 4) which had been previously captured and released at this site. It was possible that the fish moved from the structure because of its proximity to a natural habitat, therefore affording it a choice. It was also possible that social factors related to the release of a single fish rather than a group may have played a role in the rejection of the structure as a habitat. To control for these factors, we next released fish in a group of 10, 4.5 km from their home range and 100 m from the nearest natural habitat at which conspecifics were present. To broaden the scope of our queries we included the possible influence of factors such as food and naturally occurring cover on habitat selection. Two cement block structures ( 120 ' 40 > 40 cm) were placed 10 m apart. Both were identical except that while one consisted simply of bare cement blocks, the other contained clumps of mussels and algae iUlva sp.), naturally occurring food and shelter material. Two groups of 10 fish each (15-23 cm) captured at Site A, were released together at each habitat while being ob- served with scuba. Within 5 min of being released, the fish left both structures, swimming away in various directions. The habitats were then modified by the addition to each of a fish trap. To the habitat which con- tained mussels and algae the trap added was over- grown with various fouling organisms and had been in continuous use over a period of 4 to 5 mo, capturing both tautog and cunner. The fact that this trap captured fish consistently led us to con- clude that it provided an attractive stimulus or set of stimuli. The trap added to the bare structure was new. A group of 10 fish ( 10-25 cm), captured at Site A, was released at each habitat. As previ- ously, the fish left the bare habitat within 5 min. Dispersal from the other habitat was more gradual with the last fish leaving about 60 min after release. In all instances, the fish departed, indicating that factors in addition to those pro- vided were necessary for mediating habitat selec- tion. DISCUSSION It was clear from the results of trapping, tag- ging, and direct underwater observation that some portion of the cunner and young tautog popu- lations dispersed in late spring. The dispersal was from the boat basin (Site A, which we termed a perennial habitat) to habitats that were utilized only seasonally. Once adopting a seasonal habitat, the fish appeared to remain there until fall. Then there was a general movement back to a perennial habitat, but as was evident from the capture of tagged fish at perennial sites outside of the study area, not necessarily the one from which they dis- persed in the spring. Once arriving at a perennial habitat, the fish remained to overwinter in torpor, not emerging until sometime in early spring when the temperature reached 5° to 6°C (011a et al. 1974, 1975). Supporting our findings for seasonal movement, Briggs (1977) found a marked increase in the number of young tautog captured during the fall at the Kismet artificial reef, 6 km from our study area. This increase, we surmise, also reflects the movement of fish from seasonal habitats to one which appears to be perennial. In attempting to define habitat requirements for both species, it is apparent that cover is a critical factor. During the day when these fish are active, they remain within several meters of cover, and at night when quiescent and unresponsive, they are either in, against, or under cover (Olla et al. 1974, 1975). Once becoming torpid in winter, they re- main under cover until spring. It seems reason- 259 FISHERY BULLETIN; VOL. 77, NO. 1 able to assume that dependence on cover is related to protection from predation. Large adult tautog, not as vulnerable to predation because of their size, move away sometimes considerable distances from cover each day to feed (011a et al. 1974). With such a strong tendency to remain in prox- imity to cover, the question arises as to what causes a portion of the population to disperse. It is clear that environmental factors are changing with season as are the requirements of the fish. Both species in the spring have emerged from 3 to 4 mo of torpor, which has required them to live on stored energy reserves. The need for food arising from winter deprivation, coupled with the in- creased metabolic requirements resulting from the increase of temperature in late spring, might stimulate feeding and the competition for food. At least until June, the major dietary component for both species is Mytiltis cdulis 1 011a et al. 1975), and thus competition for food would be both intra- and interspecific. The spawning season for cunner also peaks dur- ing June (Dew 1976). Thus we can e.xpect that competition for participation in either group spawning (Wicklund 1970) or pair spawning (Pot- tle and Green'*) would increase. This increase would relate either to participation in gamete re- lease or male territoriality as related to pair spawning. Although the majority of tautog studied were immature and would generally not be involved in the reproductive competition, it is possible that the arrival from offshore of adults that are in spawning condition (011a et al. 1974) and which we know to be highly aggressive (011a and Samet 1977; 011a et al. 1977) may also play a role in the dispersal of the smaller fish. Competition in both species is manifested through aggression (for tautog, OUa and Studholme 1975; 011a et al. 1977, 1978; for cunner, 011a and Bejda unpubl. field and laboratory obs.). The increase in aggression that may occur at the perennial habitat as a result of competition could cause this site to become suboptimal, at least for some portion of the population. Seasonal changes in levels of aggression within a population might result in corresponding seasonal changes in the carrying capacity of the habitat. "Pottle.R. A.,andJ. M.Green. 1978. Field observation.s on the reproductive behaviour of the cunner, Tautogulahrux adspersus (Walbaumi. in Newfoundland. Unpubl. manuscr., 27 p. Department of Biology and Marine Science.s Research Laboratory, Memorial University of Newfoundland, St. John's, Newfoundland A13 3X9. 260 Support for the idea that fish will leave a subop- timal habitat is reflected in the results of the transfer experiments where young tautog left the cement block structures provided for them. Simi- lar results were obtained with juvenile cunner (Olla unpubl. obs.). In attempting to examine the mechanism for habitat selection in the manini, Acanthurus triostegus sandvicensis , Sale (1969b) performed a series of laboratory experiments and concluded from these that there was a higher in- tensity of exploratory behavior exhibited when animals were subjected to an inadequate envi- ronment. Similarly, it could be concluded that young tautog were showing greater exploratory behavior when they left the experimental cover provided for them. A portion of the fish that dis- perse will be lost, with the probability of survival decreasing as the amount of time taken to find a suitable habitat increases. Nevertheless, through this mechanism, fish are able to utilize seasonally available resources. The return to perennial habitats from seasonal ones in the fall may also be related to these becom- ing suboptimal for the fish, but for different reasons than those which caused dispersal in the spring. At habitats which exist only seasonally, as in the case with macroalgae and eelgrass beds, the actual cover that these beds provide begins to wane as they start to die back in the fall. Although some sites were structurally more permanent, such as Site B (the submerged pipe), the animals did not use them as perennial habitats, and the changes which were occurring to render them sub- optimal were not obvious. Besides changes in the environment, of prime importance for considera- tion is the change in the animals' requirements for cover. What served adequately in summer is not adequate for winter. In observing cunner and young tautog in the field during winter torpor, both species were found in deep recesses and often buried under several millimeters of sand, farther under cover than ob- served during nighttime quiescence in summer. This afforded them greater protection during the winter. The seasonal sites studied did not provide cover equivalent to that at perennial ones, which have numerous deep crevices and holes. Laboratory studies on adult tautog confirm the change in cover requirements during winter tor- por (Olla etal. 1977; 01 la and Studholme 19781. As temperature declined, the fish began to show an affinity for those structures which would serve as cover during the winter at least 1 to 2 wk before OLLA ET AL SEASONAL DISPERSAL OF CUNNER AND TAUTOG torpor was observed at which time the fish actu- ally burrowed under them being almost com- pletely covered by sand. These structures differed from the ones the fish used throughout the rest of the year at night. In the field, the offshore move- ment of the adults begins 4 to 8 wk before they would encounter temperatures that would induce torpor (011a et al. 1974), indicating a change in habitat requirements with season. About the same time that adult tautog are moving offshore, cunner and young tautog are moving to perennial sites. Association with cover is no doubt a strongly motivated behavior for young tautog and cunner, but one for which there is a considerable range of adaptation. Under seasonally changing conditions or when habitats are simply suboptimal as in the transfer experiments, the animals will disperse, leaving cover at the risk of predation until alter- nate sites are found (as discussed earlier). On the other hand, a closer association results from tran- sient environmental causes, such as the presence of predators resulting in young tautog fleeing to cover (011a et al. 1974). Similarly, elevated tem- perature stress causes young tautog to associate more closely with cover, at least under laboratory conditions (011a and Studholme 1975). ACKNOWLEDGMENTS We wish to thank the personnel of the U.S. Coast Guard, Fire Island Station, N.Y., for their assistance and cooperation. LITERATURE CITED BRAY. R. N., AND A, W. EBELINC. 1975. Food, activity, and habitat of three "picker-type" microcamivorous fishes in the kelp forests off Santa Bar- bara, California. Fish. Bull., U.S. 73:815-829. BRIGGS. P. T. 1977. Status of tautog populations at artifitial reefs in New York waters and effect of fishing. N, Y. Fish Game J. 24:154-167. Cooper. R. a. 1966. Migration and population estimation of the tautog. Tautoga onitts (Linnaeus), from Rhode Island. Trans. Am. Fish. Soc. 95:239-247. DEW, C. B. 1976. A contribution to the life history of the cunner, Tautogolabrus adspersus. in Fishers Island Sound, Con- necticut. Chesapeake Sci. 17:101-113. HOBSON. E. S. 1968. Predatory behavior of some shore fishes in the Gulf of California. U.S. Fish Wildl. Serv., Res. Rep. 73. 92 p. 1971. Cleaning symbiosis among California inshore fishes. Fish. Bull., U.S. 69:491-523. 1972. Activity of Hawaiian reef fishes during the evening and morning transitions between daylight and darkness. Fish. Bull., U.S. 70:715-740. 1973. Diel feeding migrations in tropical reef fishes. Hei- gol. wiss. Meeresunters. 24:361-370. HOBSON. E. S., AND J. R. Chess 1976. Trophic interactions among fishes and zooplankters near shore at Santa Catalina Island, California. Fish. Bull., U.S. 74:567-598. OLLA. B. L., A. J. BEJDA. AND A. D. MARTIN 1974. Daily activity, movements, feeding, and seasonal occurrence in the tautog, Tautoga onitis. Fish. Bull., U.S. 72:27-35. 1975. Activity, movements, and feeding behavior of the cimner, Tautogolabrus adspersus. and comparison of food habits with young tautog, Tautoga onitis. off Long Island, New York. Fish. Bull., U.S. 73:895-900. OLLA. B. l., and C. Samet 1977. Courtship and spawning behavior of the tautog, Tautoga onitis (Pisces: Labridae). under laboratory condi- tions. Fish. Bull., U.S. 75:585-599. Olla. B. L., C. Samet. A. J. Bejda, and A. L. Studholme. 1977, Social behavior as related to environmental factors in the tautog, roii/o^a oni/is. In Thebehavior of marine organisms: plenary papers, p. 47-99. Mar. Sci, Res. Lab. Tech, Rep, 20, Memorial Univ. Newfoundland. Olla, B. L., and a, L, Studholme 1975, The effect of temperature on the behavior of young tautog. Tautoga onitis (L,), In H, Barnes (editor!. Pro- ceedings of the ninth European marine biology sym- posium, p, 75-93. Aberdeen Univ. Press. 1978. Comparative aspects of the activity rhythms of tautog, Taw^oga onitis . bluefish, Pnmatomus saltatrix . and Atlantic mackerel. Scomber scombrus, as related to their life habits. In J, E, Thorpe (editor). Rhythmic activity of fishes, p. 131-151. Academic Press, Lond. Olla, B. L., a, L, Studholme, a, J, Bejda, C. Samet, and A, D. Martin, 1978, Effect of temperature on activity and social behavior of the adult tautogTautoga onitis under laboratory condi- tions. Mar, Biol. (Berl.i 45:369-378. Sale, P. F, 1969a, Pertinent stimuli for habitat selection by the juvenile manini, Acanthurus triostegus sandvicen- sis. Ecology .50:616-623. 1969b. A suggested mechanism for habitat selection by the juvenile manini Acanthurus triostegus sandvicensis Streets. Behaviour 35:27-44. 1971. Extremely limited home range in a coral reef fish, Dascyllus aruanus (Pisces; Pomacentridae), Copeia 1971:324-327, 1972. Influence of corals in the dispersion of the pomacen- trid fish, Dascyllus aruanus. Ecology 53:741-744. 1977. Maintenance of high diversity in coral reef fish communities. Am, Nat, 111:337-359, Smith, C, L,, and J, C, Tyler 1972, Space resource sharing in a coral reef fish communi- ty. In B, B, CoUette and S, A, Earle (editors). Results of the tektite program: Ecology of coral reef fishes, p, 125- 170, Nat, Hist, Mus, Los Ang, Cty,, Sci, Bull, 14. 1973 . Direct observations of resource sharing in coral reef fish. Helgol, wiss. Meeresunters, 24:264-275, WICKLUND, R. I. 1970. Observations on the spawning of the cunner in wa- ters of northern New Jersey. Chesapeake Sci. 11:137. 261 BIOLOGY OF WALLEYE POLLOCK, THERAGA CHALCOGRAMMA, IN THE WESTERN GULF OF ALASKA, 1973-75 Steven E. Hughes and George Hirschhorn' ABSTRACT Data on the stock composition, growth, mortality, and abundance of walleye or Alaska pollock, Theragra chakogramma , in the western Gulf of Alaska were collected during six demersal trawl surveys in 1973-75. Over 102,000 km^ of continental shelf and slope were surveyed; most of this area was covered during spring and summer. Using the area-swept technique and catchability coefficients of 1.0 and 0.5, the e.\pIoitable pollock biomass in the survey region was between 610,000 and 1,220,000 metric tons. The percentage of larger and older fish increased to the west. Sexual maturity was reached at age 3, Growth completion rates ranged from 0.2 to 0.4. Natural mortality was estimated (assuming natural mortality equals growth completion ratei at 0.33 for males and 0.30 for females. Variations in growth completion rates within year class and variable recruitment strength indicated a probable east-west separation of pollock spawning populations near Kodiak. The National Marine Fisheries Service conducted six trawl surveys of walleye or Alaska pollock, Theragra chalcogramma , and other groundfish re- sources in the western Gulf of Alaska from Cape Cleare, Montague Island, west to Unalaska Island during each spring and summer of 1973-75 (Fig- ure 1). These surveys have provided information on the geographic and bathymetric distribution and densities of species within the groundfish commmunity (Hughes and Parks 1975). An additional goal of these surveys and subject of this report was the collection of pollock life his- tory data for management purposes. METHODS Six cruises were completed. Five were con- ducted from the 28-m NOAA RV John N. Cobb, employing 400-mesh Eastern otter trawls with 30-m footropes. During these five surveys, fishing was conducted following a predetermined, strat- ified random survey pattern (Grosslein^l. Fishing densities varied from one 30-min trawl/1,370 km'-^ in strata of anticipated low densities (depths of 90 m or less) to one 30-min trawl/515 km^ in the remaining depth strata of 91-180 m, 181-270 m. 'Northwest and Alaska Fisheries Center, National Marine Fisheries Service, NOAA, 2725 Montlake Boulevard East, Seat- tle. WA 98112. ^Grosslein, M. D. 1969. Some observations on accuracy of abundance indices derived from research vessel surveys. Un- publ. manuscr. Northeast Fisheries Center, National Marine Fisheries Service, NOAA, Woods Hole. MA 02543. Manuscnpt accepted August 1978 FISHERY BULLETIN; VOL. 77, NO. 1, 1979 271-360 m, and 361-450 m. The other cruise was conducted from the 26-m chartered trawler A«/!a Marie, with similar but larger modified Eastern and Norwegian-style otter trawls with about 34-m footropes. Because the purpose of the Anna Marie survey was to determine commercial production potentials (Hughes and Parks 1975), fishing was concentrated where fish schools were detected by echo sounding; no predetermined survey pattern was followed. Consequently, the A;!na Mane data (Sanak-Unalaska. May-June 1974) were not used for pollock density or biomass studies. Stretch mesh measurements ( 1 knot included ) of all trawls ranged from 10.2- to 14.0-cm mesh in the intermediate and cod end sections. Trawls mea- sured by scuba divers at depths of 15 m indicated vertical heights of 2-3 m and horizontal spread of 11-13 m. Methods of selecting random samples of pollock for collection of biological data were consistent during all surveys (Hughes 1976a). Length- frequency fork length (FL) measurements to the nearest centimeter by sex were randomly collected from each catch with the desired sample size being 300 pollock. While processing pollock for length- frequency data, stratified subsamples of otoliths ( 10/sex per cm) and individual fish weights (5/sex per cm) were taken ( ±5 g). Otoliths were stored in ethanol in plastic boxes (Hughes 1976b) and ages were later determined as described by LaLanne (in press). Length-frequency distributions determined 263 FISHERY BULLETIN VOL 77, NO 1 Figure l.— Western Gulf of Alaska regions where trawl surveys were completed, 1973-75. from the five standard resource assessment sur- veys were weighted by catch magnitude and area within sampling strata, whereas data collected during the commercial fishing (Sanak-Unalaska, May-June 1974) trials were weighted only by catch magnitudes. Length-age data from the strat- ified otolith collections of sexed pollock in each survey region (Figure 1) were compiled into age- length keys. The proportions of observed ages on each length interval above 19 cm were applied to the weighted length frequencies. For this we used a computer program by Allen (1966! modified to exclude ex- trapolations beyond the aged length range and to include the calculation of mean length at age, as well as numbers at age. Thus numbers and size of pollock in the fishable population were estimated by region, age, and sex. Resulting analysis provided weighted age com- position data and mean length-at-age data for growth studies. Von Bertalanffy growth-in-length parameters and length-weight data were deter- mined for each region. An area-swept technique ( Al verson and Pereyra 1969) was employed to estimate the pollock exploitable biomass, using the relation Pw = (CPUE) ( A)/(f ) (a) where Pu' is equal to the aver- age standing stock, in weight, of the catchable population. A is the total area; a is the average bottom area covered by the trawl per standard tow; and c is a coefficient related to the effective- ness of the trawl in capturing pollock. Whereas earlier studies of Alaskan pollock as- sumed c = 1.0 (Alverson and Pereyra 1969), pol- lock were often acoustically detected ofT the sea bottom and above the trawl's headrope. Estimates ofc given for some gadoid species of the northeast- ern Atlantic Ocean indicated c may not exceed 0.51 (Edwards 1968). In this report, values of both 0.5 and 1.0 provide a conservative range of biomass estimates. RESULTS The surveys resulted m 144 fishing days on the grounds and 368 successful trawl hauls. Over 455,000 kg of groundfish were sampled, including 49,912 pollock which were processed for biological data. Size and Age Composition In the three regions where spring and summer surveys were conducted during the same year (Shelikof Strait 197.3; southeast Kodiak 1973; and Sanak-Unalaska 1974), seasonal variations in size and age composition were attributed to fish measuring <28 cm which represented the 1- and 2-yr-old juvenile segment of the population (Fig- ures 2, 3). However, substantial differences be- tween regions indicate that size and age of adult pollock consistently increased when moving from the southeast Kodiak and Shelikof Strait regions westward through the Chirikof region and into the Sanak-Unalaska region. The age composition data also indicated that Gulf of Alaska pollock display strong variations in year-class strength. Both 1967 and 1970 year class- es showed unusually strong recruitment. Indica- tion of a strong 1967 year class, sampled as 6-yr- olds, was noted during the May-June 1973 surveys of the southeast Kodiak and Shelikof regions. The relative strength of this year class was again noted 3 mo later during the August-September survey of southeast Kodiak and. particularly, of Shelikof Strait. Farther west, in the October 1973 Chirikof 264 HIUJHES and HIRSCHHORN BIOLOGY OF WAI.LEVE POLLOCK (%) ASNinoatid (%) ADN3no3aj (%) ADNsnoaad 265 FISHERY BULLETIN: VOL. 77. NO, 1 S E KOCIAK REGION MAY -JUNE 1973 TEMALES N. l273 = 1967 YEAR CLASS !l^' 1970 YEAR CLASS SHELIKOF SIRAIT REGION auG - SEPT 1973 EMflLE N : Sn Figure 3.— Weighted agt^frequency distributions of male and female walleye pollock by survey region and season in the western Gulf of Alaska. 1973-75. 266 HUGHES and HIRSCHHORN BIOLOGY OF WALLEYE POLLOCK survey, 6-yr-old pollock were dominant. One year later, in the most westward region (Sanak- Unalaska 1974), the prominence of the 1967 year class as 7-vr-olds was apparent during both the May-June and July-August surveys. During the May-June and August-September 1973 surveys of southeast Kodiak and Shelikof Strait, S-yr-old pollock ( 1970 year class) were dom- inant. The unusual strength of this year class was again noted 2 yr later east of Kodiak as 5-yr-olds during the 1975 Kenai survey. However, recruit- ment of the 1970 year class was not successful west of Kodiak, as shown by the low relative abundance of 3-yr-olds in the Chirikof region in 1973, of 4-yr- olds in the Sanak-Unalaska region in 1974, and of 5-yr-olds in the Chirikof region in 1975. Maturity and Sex Composition Most adult pollock ( >859c ) had spawned prior to our earliest sampling (May). Based upon a subjec- tive evaluation of gonad condition from pollock collected during May, it appeared that prime spawning periods were March and April. Ripe males and females were obtained as late as Au- gust, but these represented <0.1% of samples. Both sexes were fully recruited to the spawning population at age 3. Mature or recently spent age 2 males were encountered but represented <59e of that age-group. Mature or spent age 2 females were not encountered; however, minor gonad en- largement was noted. Means of lengths at first maturity in spring surveys were 29-32 cm for males and 30-35 cm for females. Our data indicate that sex composition fluc- tuates around 50'+^ at 20-45 cm FL but that females become progressively more dominant with larger size ( Figure 4 ). As will be shown later, the point of major difference in sex ratio (45 cm) is composed primarily of age 4, 5 females and age 5, 6 males. Length-Weight Pollock length-weight data by sex were col- lected during the May-June and August- September surveys of the southeast Kodiak and Shelikof Strait regions in 1973. Data were also collected during the September-October 1973 sur- vey of the Chirikof region. Length-weight rela- tions were determined for these survey regions and periods (Figure 5) by fitting the logarithmic form of the equation (W = aL''). where W is body weight in grams and L is fork length in centi- meters, to the mean weight per centimeter-length interval. Comparison of these curves indicates that female pollock measuring >33 cm weighed con- siderably less than males of equal length during the May-June postspawning survey. Female weight gain during summer was more rapid than in males, and differences in weight-at-length in the Shelikof Strait, southeast Kodiak, and Chirikof regions were negligible during the August-October sampling. Regional differences during spring-summer periods were also noted. Shelikof Strait pollock were heavier than southeast Kodiak pollock of equal length during spring and considerably lighter during summer. This difference may be due to a more rapid weight gain in the southeast Kodiak region or to migration of the most healthy fish out of Shelikof. An additional factor suggest- ing migration was that samples of male pollock in Shelikof actually showed a weight loss from spring to summer. Density Distribution and Estimates of Standing Stock Pollock were distributed over depth intervals of 50-360 m (Table 1). Highest densities occurred at depths of 91-270 m during spring and summer. Geographically, densities were highest at Sanak-Unalaska (181-270 m), followed by south- east Kodiak (91-180 m). Spring-summer 1973 as- sessment surveys of Shelikof Strait and southeast Kodiak indicated highest densities during sum- mer. The summer biomass of pollock exceeding 20 cm FL was estimated as 610.000-1,200,000 metric tons (t) of whole fish (Table 1). Regional biomass estimates were greatest in the Chirikof region, followed by Sanak-Unalaska, southeast Kodiak, Kenai, and Shelikof Strait. Growth Length-age data from the nine surveys were fitted by the von Bertalanffy relation /, = L^ {l - exp k(t-tf^)} following computational procedures by Fabens ( 1965). Because variation in age range affects comparability of parameters (Hirschhorn 1974), curve fits over original age ranges were supplemented: 1) with fits over a standardized age range of 2-8 yr, 2 ) with an artificial data point ( 0,0 ) 267 FISHERY BULL? TIN VOl, 77 o < is < s o V ?- in o to O m CD ~ LjJ oc o o o o E o X 1- cc o uj S cr - o o — 1- o o o UJ cc If) o X ^ X 1- C-5 n ^ z LJ _l o Y tr o o o o o o o o o o O CO ID LJ cr < ^ _,'' V <^ y 1 1 iN33H3d iN30y3d lN33a3d o c 268 HUGHES and HIRSCHHORN BIOLOGY OF WALLEYE POLLOCK 2000-1 SHELIKOF STRAIT REGION MALE MAY -JUNE 1973 CT 1500 ^ 1000 >- o o oj 500- W=2 3775»I0'l""' -I 1 1 1 1 1 1 1 8 16 24 32 40 48 56 64 SE KODIAK REGION MALE MAY- JUNE 1973 W= 3.9344 X lo'' l' '*'° ./ X -T 1 1 r — -I 1 ; 1 8 16 24 32 40 48 56 64 SHELIKOF STRAIT REGION MALE AUG -SEPT 1973 W= 3 0410 X lO'' l'"" / -1 1 1 1 1 1 1 8 16 24 32 40 48 56 2000-1 1500 * 1000- 500 SE KODIAK REGION MALE AUG -SEPT 1973 W=98I78 K IQ-' L^^"^ / X -| 1 1 1 1 1 1 1 8 16 24 32 40 48 56 64 CHIRIKOF REGION MALE SEPT.- OCT 1973 W= 20188 X I0'2 L2754I n 1 1 1 1 1 1 1 8 16 24 32 40 48 56 64 2000 -1 SHELIKOF STRAIT REGION FEMALE MAY -JUNE 1973 "S. 1500- W= 5.6136 X 10'^ l3 0627 H I CD ^ 1000- .y >- Q 2 500- ^■' n ' 1 r-' T I 1 1 1 1 SE KODIAK REGION FEMALE MAY -JUNE 1973 W = 8 2943 X 10'' L ■3 I 2 9474 ■■/■ —\ 1 1 1 1 1 1 16 24 32 40 48 56 64 SHELIKOF STRAIT REGION FEMALE AUG -SEPT 1973 W= 4 4233 X 10'' l"'^' y / ■/. —I 1 1 1 1 1 r 8 16 24 32 40 48 56 FORK LENGTH (cm) 2000-1 S E KODIAK REGION FEMALE AUG -SEPT 1973 1500- W= 1.0769 X 10'^ |_2-9252 ; 1000- / 500- / 0 y ' — 1 — 1 — 1 — 1 — 1 — 1 — 1 — 1 16 24 32 40 48 56 64 FORK LENGTH (Cm) CHIRIKOF REGION FEMALE SEPT -OCT 1973 W= 2829 X 10'^ L2.6667 Figure 5.— Length-weight rela- tionships of male and female wall- eye pollock by survey region and season in the western Gulf of Alaska. 1973-75. 16 24 32 40 48 56 64 FORK LENGTH (cm) 269 FISHERY BULLETIN: VOL, 77, NO 1 Table l. — Summary of exploitable walleye pollock biomass and density by depth strata and survey regions in the western Gulf of Alaska. Catchability coefficients 1.0 and 0,5 are used to produce a range of pollock biomass and density. Biomass estimates were calculated from the summer survey period due to limited spring survey coverage. Survey region and period Depth strata (m) Area surveyed (km^) Density (t/km') c = 1 0 c = 0 5 Exploitable b c = 1,0 iiomass (t) c = 0,5 Summer Kenai Peninsula (148 -152 W) July-Aug 1975 91-180 181-270 271-360 19.183 8.026 796 4 1 28 02 82 56 04 77.742 22.230 186 155,486 44,460 371 Regional total 28,005 100.158 200,316 SE Kodiak (152 -154'W) Aug-Sep 1973 55-90 91-180 181-270 271-360 7,302 6,143 1.475 737 22 16 1 99 0 4 4 32 2 19,8 0 16,180 99,042 14.706 0 32,360 198,085 29,412 0 Regional total 15,657 129.928 259,857 Shelikol Strait (Aug-Sep 1973) 55-90 91-180 181-270 381 3,341 2,713 02 58 10 04 11 6 20 89 19,480 2,610 178 38,960 5,221 Regional total 6,435 22,179 44.359 Chinkol (154 -159 W) July 1975 Regional total 55-90 91-180 181-270 9.439 12,749 11.661 33.849 10 136 02 20 27 2 04 9,082 173,583 11,220 193,885 18,163 347.168 22.440 387,771 Sanak-Unalaska (162-168 W) July-Aug 1974 50-90 91-180 181-270 271-360 361-450 6,647 8,935 912 703 322 27 13 1 31 8 0 0 54 26 2 63 6 0 0 18,060 117,096 29,107 0 0 36,120 234.192 58.214 0 0 Regional total 17,519 164,263 328.526 Survey total Spring SE Kodiak (148-152 W) May-June 1973 50-90 91-180 181-270 101,465 4,778 4.496 737 04 20 04 0.8 4,0 08 610.413 1.220.826 Regional total 10,011 Shelikof Strait (May- June 1973) 50-90 91-180 181-270 271-360 381 3.982 11.558 1.008 02 07 06 03 04 1 4 1 2 06 - - Regional total Sun/ey total 16.929 26,940 added on the assumption that at age 0 length is near 0 (Alverson and Carney 1975), and 3) with nominal ages or ring counts incremented by the fraction of a year between middates of spawning and sampling (A? in Table 2). Because each growth pattern in Figure 6 repre- sents a synthetic cohort, i.e., a composite of year classes, the departures from the pattern, gener- ated by members of the 1967 and 1970 year class- es, were examined in detail. According to the age composition discussed earlier, both year classes were encountered in relatively high abundance at one extreme of the survey range (Figure 3) and in low abundance at the other (the 1967 year class was prominent at Sanak-Unalaska, the 1970 year class at Kenai). To examine the evidence for a growth-density relation, the size differences be- tween the synthetic growth curves and observed mean lengths of the sampled age-groups of these year classes were calculated (lower part of Table 2). The results are shown along a schematic east- west axis in Figure 7. In the easternmost region ( Kenai), the strong 1970 year class indicates nega- tive departures from expectation (at age 5), whereas corresponding departures are positive for the relatively weak year class of 1967 (at age 8). In the westernmost region, the relative strengths of these year classes seemed to be reversed, and the direction of departures of their mean lengths at ages 4 and 7 also reversed. By this criterion, the segregation of the two components of each year class was most pronounced at the extremes and least SO in the intermediate Kodiak-Shelikof re- gion where the lines cross. Age-specific observed lengths of the 1970 and 1967 year classes were also compared directly with those of others, apparently weaker year class- 270 HUGHES and HIRSCHHORN: BIOLOGY OF WALLEYE POLLOCK Table 2.— Mean length (centimeters) at age of western Gulf of Alaska Theraga chalcogramma by survey and sex; growth parameters (L^, A', <„) for original and "selected" data sets, with standard deviation (a-) of departures from fit; departures of 1967 and 1970 year class mean lengths at age, from fit (A67YC, A70YC). Sanak Ctlirikol Kodiak May-June 74 Juiy-Aug 74 July 1975 Sept -Oct 73 May-June 73 Aug -Sept 73 M F M F 1^ F M F M F M h Item (0 17)' (0 42) (0,251 (050) (0 17) (0 42) Years of 1 _ 20.00 _ _ 1949 20 02 — — 23 07 23 09 age (0 2 25 52 24 36 29.55 29 75 24 70 24 99 27 15 27 99 25 24 2621 29 51 29 50 3 35 19 35 20 38 51 36 04 31 54 32 18 3501 3574 30 24 30 38 33 44 3385 4 39 59 40 17 41 16 42 14 33 88 34 98 39 32 40 58 3877 38 44 40 37 41 48 5 43 68 44 63 44 07 45 18 38 41 40 07 40 18 4263 40 30 43 55 41 70 44 32 6 45 16 46 81 45 01 47 05 42 10 43 05 41 36 43 82 43 26 45 15 43 37 45 91 7 47 02 48 70 44 69 47 02 42,59 44 98 43 84 48 44 47 66 50 62 46 47 48 73 8 47 50 51 01 47 27 51 65 44 67 48 02 47 37 48 37 4804 53 04 46 97 50 16 9 48 27 50 74 48 34 53 51 49 84 52 86 4685 49 39 46 67 51 62 46 41 50 77 10 53 16 55 25 47 74 52 05 50 86 54 21 4604 5273 46 03 57 03 4800 4952 11 50 11 55 56 48 13 46 79 5057 53 85 — — — — 54 10 54 00 12 — — — 57 00 — 54 00 — — — — 55 07 — Parameter L,: 50 06 5522 48 14 53 03 5236 58 40 47 26 5437 4821 66 25 58 69 56 34 sets tor K -0 47 -037 -0 47 -0 42 -025 -021 -0 38 -028 -0 38 -0 18 -0 19 -0 24 ofiginal data 'o 0 68 0 63 0 29 0 61 -0 30 0 42 0 10 -0 09 0 26 -061 -1 18 -0 75 . Percent Mean no occur- ind- occur- indi- Zooplankton category rence viduals rence viduals Fofaminrferans' 43 29 too 189 Polychaeies^ 29 0.5 too 73 Gas(ropods= 57 0 1 too 7.0 Ostracods^ 0 00 86 1 7 CalanoKJ copepods^ 0 00 too 17.7 Cydopoid copepods 0 00 43 14 HarpacOcoid copepods' 0 00 too 31 0 Mysids 0 oo 14 0.1 Cumaceans 0 00 29 06 Tanaids^ 0 0.0 86 11.9 Isopods^ 0 00 71 3.0 Cimpedian larvae 0 0.0 29 0.6 Gammarid amphipods- 0 0.0 100 40 1 Caprellrd amphipods 0 0.0 43 1.0 Candean larvae 0 00 43 609 Candean adults and juveniles 0 0.0 86 18.4 Reptaniian zoea 0 00 57 17 0 Brachyuran megalops 0 00 71 6.3 Anomuran glaucothoe 0 00 43 1.3 Chaeiognaths'" 0 00 57 59 Ascidian larvae 0 00 14 1.0 'All foraniinifefans were eittier Tretomphalus sp. {72*'-o) or Amphistigina sp. (28%) ^The rnapr polychaete was Polyophthalmus sp. ^Included one 8-mm dond opisttiobranch: the rest were prosobranchs ' 3 mm long 'The major ostracod was a species of Cytindroleberdinae -All identifiat>le calanotds were Paramisophna sp . probably undescnbed (Abraham Remingef, SCTipps Institution of Oceanography. LaJolla, CA 92038. pers commun Apnl 1978) 'All identified harpacticoids were of a species of the family Peltidndae 'All the tanaids appeared to be of a species of Leptochefia. dose to L dubia (see Hobson and Chess 1976). 'Major isopods were Ciroiana sp., laniropsis sp.. Muma sp.. anthunds. and cryptoniscid larvae 'Gammands included Aoroides sp . Dexaminoides ohentahs, UIgeborgia sp.. a eusind, an oedicefotid, and a phoxocephalid. '"All chaetognaths were Spadella gaetanoi (A. Alvanno. Fishery Biologist, Southwest Fishenes Center. NMFS. NOAA. La Jolla. CA 92038. pers com- mun Sept 1978) Discussion Our collections and collecting sites were too few to comprehensively quantify the zooplankters that emerge from the lagoon substrata at Kure anti Midway Atolls. Despite its limitations, how- ever, this study increases our understanding of the kinds of organisms that have this habit. Further- more, it indicates there may be serious problems with the more extensive studies of Alldredge and King (1977). Porter et al. il977), and Porter and Porter (1977). Certainly some of the differences between their samples and ours are unrelated to sampling prob- lems. We assume, e.g., that the zooplankton fauna at Kure and Midway Atolls is distinguishable from the zooplankton fauna in the more tropical latitudes of the western Pacific Ocean where the Alldredge and Porter groups studied. It is un- likely, however, that zoogeographic variations can account for certain of the more striking differences between their samples and ours. The predominant forms in their collections were calanoid and cy- dopoid copepods. Alldredge and King (19771 cal- culated that during the night a mean of 6.679 calanoids emerged from each square meter of the reef face, and Porter et al. (1977) reported that over 10.000 calanoids emerged during the night from each square meter of branching coral in their study area. In comparison, our night-long collec- tions from a variety of substrata, including coral, yielded a mean of only 17.7 calanoids/m^. Of course, we did not sample a well-developed reef Only two of our sites included living coral, and these were isolated heads tour traps required a bed of sand). So habitat features could have contrib- uted differences between the collections. Nevertheless, if one considers the species of calanoids and cyclopoids collected by Alldredge and King, there are strong indications that the large numbers reported were inflated by holo- planktonic forms. The only calanoids and cy- clopoids they identified were Acartia spp. and On- caea spp. Species of these two genera are exceed- ingly numerous in the water column during both day and night (see Emery 1968: Hobson and Chess 1976). and we question whether they could in fact assume a benthonic mode. As stated i Hobson and Chess 1 978:149 ) "We would expect organisms that live in the substrate by day to have morphological features reflecting this habit that distinguish them from holoplanktonic relatives at the generic level or higher." .Although the Porter group did not identify their calanoids and cyclopoids to lower taxa, they too sampled western Pacific reefs and so the copepods that similarly dominated their col- lections may well have been the same, or very similar, to those taken by Alldredge and King. All our calanoids, on the other hand, appeared to be referable to the little known genus Paramisophna (Abraham Fleminger, Associate Research Biologist, Scripps Institution of Oceanography, La Jolla, CA 92038, pers. commun. April 1978). This fact agrees with our contention that zooplankters which periodically enter the substrate should be morphologically distinctive. If the diurnal benthic mode of this species is a generic characteristic, which seems probable, then its poorly known status likely stems from failure to be sampled by standard plankton-collecting techniques. During a marine survey of the Palau Islands, Randall et al. (1978) attempted to measure the zooplankters that emerged from the sea floor using traps ". . . built according to the design of Porter 278 and Porter (1977)." Their samples, taken above coral and sand substrata, included far fewer copepods than the Alldredge and Porter collec- tions I but many more than ours»; nevertheless, they recognized the presence of holoplanktonic forms (e.g., siphonophores, crustacean and fish eggs, and fish larvae), which they assumed ". . . either swam ( or were carried ) under the base of the trap from the open water . . .." So we believe that the studies by the Alldredge and Porter groups are flawed by the unrecognized occurrence in their samples of organisms from the surrounding water column. At Enewetak .Atoll (Hobson and Chess 1978), we concluded that many of the zooplankters above lagoon reefs at night are visitors from the deeper water. If this cir- cumstance existed where Alldredge and Porter set their traps, then their collections probably in- cluded deep-water forms. If so, the figures pre- sented as measures of zooplankters that emerge from defined areas of particular nearshore sub- strata probably include not only holoplankters as- sociated by day with other nearshore substrata but also holoplankters from outside the nearshore realm. We consider our collectons conservative esti- mates of the numbers of organisms that emerge from the sampled substrata. It may be that some forms which ordinarily rise into the water column were inhibited by our trap, and undoubtedly some that rose into the trap found their way back to the sea floor. But we feel our trap should have been as effective in capturing emerging zooplankters as those used by the Alldredge and Porter groups. Possibly some strictly benthic forms entered our samples by climbing up the inside of the trap. The few prosobranch gastropods that were taken may have been trapped this way, although they were small enough to have been swept up into the water column by surge, or perhaps to possess some flota- tion device that periodically permits a planktonic mode, as is the case with certain foraminiferans (e.g., Tretomphalus and perhaps Atnphistigina). Significantly, most of the organisms collected be- long to groups that include forms we have col- lected in the water column at night elsewhere: e.g., the foraminiferan genus Tretomphalus (at Majuro and Enewetak Atolls: Hobson and Chess 1973, 1976): the polychaete genus Polyophthal- miis (at Enewetak Atoll: Hobson and Chess 1978); and the ostracod subfamily Cylindroleberdinae, the tanaid genus Leptochelia. the isopod genera Cirolana and Munna. and family Anthuridae, the gammarid genus Aoroides. and families Eusiridae, Oedicerotidae, and Phoxocephalidae I at Santa Catalina. southern California: Hobson and Chess 1976. in prepi. The forms that predomi- nated in our collections belong to groups that were only relatively minor elements in the Alldredge and Porter collections. Most, in fact, w^ere lumped by Porter et al. ( 1977) in their summarizing Fig- ure 2 as "miscellaneous." This is not because they took fewer of these forms than we did, but rather because copepods and larvaceans so dominated their collections. We believe that the major difference between our collections and those of the Alldredge and Por- ter groups is that we excluded organisms from the surrounding water column. Alldredge and King (19771 were aware that outside organisms could enter through the gaps around the base of their traps, but seemed more concerned about or- ganisms inside that might have escaped. They dismissed both possibilities as significant sources of error with the statement (p. 318 1 ". . . as many plankters may also enter the trap through these gaps as escape through them." But because these devices were, after all, traps, probably many more zooplankters came in than went out. And if in fact zooplankters entered the traps through these gaps, it seems certain that forms from the sur- rounding water, including holoplankters, were continuously captured. Porter et al. (1977) re- ported about 1.5 to 2 times as man\' zooplankters as did Alldredge and King. They attributed this difference to more effective methods and equip- ment, but their traps, tethered above the reef, may simply have been more readily entered by holo- plankters. This would also account for the rela- tively large numbers of zooplankters they trapped by day. Both studies may have suffered from a misconception about the movements of these or- ganisms. Alldredge and King doubted that many escaped through the gaps around the bases of their traps because they assumed (p. 3181". . . emerging plankton swim primarily upward . . .."The Porter group would seem to have based their trap design — inverted cones tethered above the bottom — on the same assumption. But while these animals certainly rise progressively higher in the water column after emerging from the sea floor, gener- ally they swim — some flit — in short, irregular tangents more horizontal than vertical (based on our direct observations of a wide variety of forms in many locations). In any event if holoplankton did enter these traps in significant numbers, then 279 the samples taken should not be presented as measurements of the forms that emerged from the underlying substrata. Ackniiw Iciljiiiicnts We thank Richard S. Shomura and his staff at the Southwest Fisheries Center Honolulu Laboratory, National Marine Fisheries Service, NOAA, and Robert T. B. Iverson, Southwest Re- gion, National Marine Fisheries Service, for their cooperation and logistic support. We also thank Robert Johanness, Hawaii Institute of Marine Biology; Abraham Fleminger, Scripps Institution of Oceanography; and Alan R. Emery, Royal On- tario Museum, Canada, for helpful comments on the manuscript. Kenneth Raymond, Southwest Fisheries Centei' La Jolla Laboratory, drew Fig- ure 1 and Alice Jellett, Southwest Fisheries Center Tiburon Laboratory, typed the manu- script. Littraturi- Cited Alldredge, a, L.. A.ND J. M. KlNC. 1977. Distribution, abundance, and substrate preferences of demersal reef zooplankton at Lizard Island Lagoon, Great Barrier Reef Mar. Biol. iBerl.l 41:317-333 Emery, a. R. 1968. Preliminary observations on coral reef plankton, Limnol, Oceanogr. 13:293-303. FLEMINGER. A. 1964. Distributional atlas of calanoid copepods in the California current region, Part I. Calif Coop. Oceanic Fish. Invest., Atlas 2, 313 p. Glynn, P W 1973. Ecology of a Caribbean coral reef The Ponies reef- fiat biotope: Part II. Plankton community with evidence for depletion. Mar. Biol. iBerl.i 22:1-21. HOBSON, E. S- 1968. Predatory behavior of some shore fishes in the Gulf of California. U.S. Fish Wildl. Serv.. Res. Rep, 73, 92 p. 1973. Diel feeding migrations in tropical reef fishes. Helgol. wiss. Meeresunters. 24:361-370. 1974. Feeding relationships of teleostean fishes on coral reefs in Kona. Hawaii. Fish. Bull.. U.S. 72:915-1031. 1975. Feeding patterns among tropical reef fishes. Am. Sci. 63:382-392. HOBSON, E. S., .AND J. R. CHESS, 1973. Feeding oriented movements of the atherinid fish Pranesus pinguis at Majuro Atoll, Marshall Islands. Fish. Bull., U.S. 71:777-786. 1976. Trophic interactions among fishes and zooplankters near shore at Santa Catalina Island, California. Fish. Bull., U.S. 74:567-598. 1978. Trophic relationships among fishes and plankton in the lagoon at Enewetak Atoll, Marshall Islands. Fish. Bull., U.S. 76:133-153. Porter, J. W, 1974. Zooplankton feeding by the Caribbean reef-building 280 coral Montastrea carenosa. Proc. Second Int. Coral Reef Symp. 1:111-125. Porter, J. W., ..wd K. G. Porter. 1977. Quantitative sampling of demersal plankton mi- grating from different coral reef substrates. Limnol. Oceanogr. 22:553-556. Porter, J. W.. K. G. Porter, .and Z. B.-\t.m'-C.\t.-\l.an. 1977. Quantitative sampling of Indo- Pacific demersal reef plankton. Proc. Third Int Coral Reef Symp. 1:105-112. RAND.'\LL, R. H., C. BIRKEL.AND, S. S. AMESBURY, D. LASSUY, AND J. R. EADS. 1978. Marine survey of a proposed resort site at Arakabe- san Island, Palau. Univ. Guam Mar. Lab. Tech. Rep. 44, 66 p. edmund s. hobson James R. Chess St}uthuesl Fcsfwrtes Center Tthuron Laboratory National Marine Fisheries Seruice, NOAA 3150 Paradise Drive Tihuron.CA 94920 A SIRVEV OF HEAVY METALS IN THE SL'RF CLAM, SPISVLA SOI.IDISSIMA. AND THE OCEAN QUAHOG, ARCIICA ISLANDICA, OF THE MID-ATLANTIC COAST OF THE UNITED STATES Since the mid-1940's, two varieties of clams have become increasingly important to the seafood in- dustry, the surfclam, Spisula solidissima , and the ocean quahog, Arctica islandica. Surf clams and ocean quahogs are marketed primarily by the canning industry in chowders or as minced clams, as well as in a number of specialty products, such as cakes, patties, and dips. Prior to World War II, however, these clams had been used only as ani- mal feed or fertilizer. A commercial surf clam fishery developed rapidly with an annual harvest of 5L4 million pounds of meats in 1977 (Hutchi- sonM and a peak harvest of 96.1 million pounds of meats in 1974 (Bell and Fitz Gibbon 1977). The ocean quahog fishery developed more slowly. It was not until the 1970's that a vigorous commer- cial ocean quahog fishery developed, primarily to supplement the dwindling supplies of more desir- able clams, in particular, the hard clam, Mer- cenaria inercenaria: the soft-shell clam, Mya arenaria; and the surfclam (Anonymous 1971). The ocean quahog harvest in 1977 of 16.4 million 'Roger Hutchison, U.S. Department of Commerce. Economic and Marketing Research Division. Washington, DC, pers. commun. February 1978. FLSHERY bulletin vol 77. NO 1. 1979. pounds of meats (Hutchison see footnote 1), how- ever, represents a small fraction of an estimated sustained yield of 86 million pounds of meats an- nually (Rinaldo-^). Since surf clams and ocean quahogs have re- placed many traditional species, studies are needed that reflect their economic importance. It is well documented that many molluscs, including surf clams and ocean quahogs, concentrate heavy metals (Brooks and Rumsby 1965; Pringle et al. 1968; Waldichuk 1974). Boyden ( 1973) stated that one of the nutritious qualities of shellfish may be their high metal content. However, heavy metals exhibit toxic effects that affect all life stages of shellfish, especially development stages (Cala- brese et al. 1973; Calabrese and Nelson 1974; Thurberg et al. 1975). Considerable research has been done on effects of heavy metals on more popu- lar species of bivalve molluscs, especially the American oyster, Crassostrea virginica, hard clams, and soft-shell clams (Calabrese et al. 1973; Calabrese and Nelson 1974; Thurberg etal. 1974). However, until recently, there has been little in- terest in surf clams or ocean quahogs. Concentra- tions and concentration factors for a number of metals, including cadmium, chromium, copper, lead, nickel, and zinc, have been given by Pringle et al. (1968) and Pringle and Shuster^ for surf clams taken from Atlantic coast waters (Maine through North Carolina). Thurberg et al. (1975) exposed larval, juvenile, and adult surf clams to sublethal doses of silver and measured both physiological responses and bioaccumulation. Re- searchers at the U.S. Environmental Protection Agency (EPA), Narragansett, R.I., have exposed ocean quahogs to low concentrations of cadmium and monitored toxicological, biological, and his- topathological effects, as well as bioaccumulation (Zaroogian''). Bioaccumulation distribution pat- terns associated with industrial and sewage sludge dumpsites southeast of Delaware Bay have been monitored in ocean quahogs by scientists at the EPA, Annapolis, Md. (Lear and Pesch 1975). Awareness, then, of the importance of these ^Rinaldo. R. G. 1977. Atlantic clam fishery management plan. Environmental impact statement: Mid-Atlantic and New England Regional Fisheries Management Councils. Available Fisheries Management Division, National Marine Fisheries Service, NOAA, State Fisheries Pier, Gloucester. MA 019:30. ■'Pringle, B. H.. and C. N, .Shuster, Jr. 1967. A guide to trace metal levels in shellfish. USDHEW, Public Health Serv.. Shellfish Sanit. Tech. Rep., 18 p. ■* Gerald E. Zaroogian. U.S. Environmental Protection Agency. Environmental Research Laboratoi-y. Narragansett, RI 02882, pers. commun. February 1976. species is developing, but clearly more research is needed for such an important commercial shellfishery. Nine metals were chosen for analysis: arsenic, cadmium, chromium, copper, lead, mercury, nick- el, silver, and zinc. Based upon estimates of global metal production and oceanic sedimentation rates, Bowen (1966) divided 38 metals into their pollution potentials. He categorized cadmium, chromium, copper, lead, mercury, silver, and zinc as very high potential pollutants and arsenic and nickel as moderate. Goldberg (1972) emphasized the need for measurement in benthic organisms of the most potentially hazardous trace metals. MatcriaU and Methods Sampling The area of this survey extended from approxi- mately Montauk Point, N.Y., to Cape Hatteras, N.C., and seaward to approximately the 20- fathom contour. The survey encompassed the southern distribution of both surf clams and ocean quahogs in the United States. Samples were col- lected at 151 stations for chemical analysis (Fig- ure Din June and August 1974, aboard the NOAA ship Delaware II (MARMAP'^). A small hydraulic surf clam dredge, modeled closely after larger commercial dredges, was used throughout the survey. At each station 4-6 clams of marketable size were dissected, using stainless steel equip- ment. The foot was removed from each animal, drained, then combined and frozen in plastic bags. At the laboratory the tissues were homogenized in an electric blender equipped with a glass jar and stainless steel blades then stored for analysis in plastic ointment jars. All containers and equip- ment were acid-washed prior to use. Analysis Mercury analysis was performed on a Perkin- Elmer Model 305" atomic absorption spectropho- tometer fitted with a 25 X 150 mm absorption cell with silica end windows, using the flameless method of Greig et al. (1975). Arsenic analysis, performed on a Perkin-Elmer Model 403 atomic absorption spectrophotometer. =MARMAP 1974. Surf clam survey, cruise report, NOAA ship Delaware II. 1.3-28 June 1974 and "5-10 August 1974, 9 p. •^Reference to trade names does not imply endorsement by the National Marine Fisheries Service, NOAA. 281 41° - 40° 39° 38° 37° - 36° - 6 I 76° 75° 74° 73° 72° FlCUKE 1. — Station location and number relative to the mid-Atlantic coast of the United States. 282 using a nitrogen/hydrogen flame, required an im- provisation of two simple interconnecting adapt- ers. The first, attached directly to the instrument, consisted of the female portion of a polyethylene quick disconnect (Nalgene 6150) and a nylon elbow hose connector threaded to fit the auxiliary inlet of the burner assembly. The second consisted of the male portion of the quick disconnect and a gas outlet adapter ( Rentes K- 183000). Both adapters were assembled with minimum length and bore of Nalgene tubing. The following proce- dure was used: A 5-g sample of tissue was placed into a 250-ml beaker to which 10 ml Mg(N03)2 • 6H2O (200 g/1) and 10 ml concentrated HNO3 (Baker 9603) were added. The mixture was covered with a watchglass and evaporated to dry- ness on a hot plate (130°-140°C). It was then placed into a cool mufflle furnace and the temperature raised in steps, first to 250°C for 3 h, then to 400''C for 3 h, and finally to550°C for approximately 15 h. After the beaker was completely cool, 15 ml of concentrated HCL ( reagent grade) were added and the resulting solution transferred to a 25-ml vol- umetric container and brought to volume with distilled water. A 10-ml aliquot of this solution was placed into a 24/40 jointed, 50-ml Erlenmeyer reaction flask and 2 ml of 15% (wt/vol) freshly made KI solution and 2 ml of freshly made StClj solution (20% [wt/vol] in 1:1 concentrated HCL:water) were added, waiting 2 min after each addition. Then 10 ml ofdistilled water were added. Five (5.00) grams of granular (20 mesh, no fines) low arsenic zinc (Fisher Z-15) were placed into the elbow of the second adapter, as noted above, and attached to the first adapter. This assembly was quickly inverted while attaching it to the reaction flask. The arsine generated was then analyzed at the instrument, which was equipped with a 3-slot burner and background corrector. Use of a record- er combined with full noise filtration and slow gas evolution contributed to a smooth and reproduc- ible peak upon which calculations were based. The reaction flask and the first adapter can be quickly removed for cleaning and reuse. Analysis of the remaining metals, also per- formed on the Perkin-Elmer Model 403, resembled thatof Middleton and Stuckey (1954): A sample of tissue ( 10 g wet weight) was weighed into a 250-ml beaker and 10 ml of concentrated HNO3 (Baker 9603) were added. The beaker was covered with a watchglass and heated to approximately 130°- 140°C on a hot plate until the liquid evaporated. One to two milliliters of concentrated HNO3 was added and the evaporation repeated. Again, 1-2 ml of acid was added but evaporated at 350°C or more. The hot plate was cooled and the latter acid addi- tion and evaporation was repeated until ashing was complete. The residue was dissolved in and taken up to 25 ml with 10% (wt/vol) reagent grade HNO3 after filtration through Whatman No. 2 paper. The solution was then analyzed directly in an air/acetylene flame by conventional atomic ab- sorption spectrophotometry. Results Greater average concentrations of silver, arse- nic, cadmium, copper, and zinc (122, 44.5, >230, 56.0, and 10.9% greater, respectively) were found in ocean quahogs than in surf clams for the entire survey (Table 1). Concentrations of several metals in both clams decreased southward. Concentra- tions of silver decreased steadily from 2.62 to 0.58 ppm in ocean quahogs and 1.63 to 0.19 ppm in surf clams. This is a 4.5- and 8.6-fold decrease, respec- tively, from the northernmost range of latitude to the southernmost. Concentrations of arsenic also decreased steadily, 1.6-fold, from 3.90 to 2.41 ppm in ocean quahogs. Although a steady decrease in arsenic concentrations was noted for a full 2.5° of latitude, a distinctive trend for the entire range of latitude was not evidenced. Copper concentrations in ocean quahogs decreased 2.5-fold from 7.16 to 2.84 ppm and zinc concentrations in surf clams decreased 2.0-fold from 18.5 to 9.1 ppm. Concen- trations of cadmium and zinc in the ocean quahog and copper in the surf clam did not exhibit any statistically significant trends, while the data for the remaining metal-clam combinations were in- sufficient for statistical analysis (Table 2). The results of Pringle and Shuster (see footnote 3) for cadmium and zinc (<0.20, 12.39 ppm, wet weight, respectively) in surf clams are in general agi'eement with the mean results of our study. Their result for copper (2. 39 ppm) was lower, while chromium and nickel (2.57, 1.22 ppm, respec- tively) were higher. The collection area of the former study was defined only as Maine through North Carolina; hence, geographic variations might be expected. In addition, neither the number of stations nor of surf clams analyzed was stated. Conclusions While the Food and Drug Administration (FDA) 283 Table l. — Average' heavy metal concentrations (parts per million, wet weight) found in surf clams and ocean quahogs by latitude. n Ag As Cd Cu Zn Range of lal N X SE X SE X SE X SE 7 SE Surf clams 4r00-40>30' 3 1 63 1 11 238 0 146 ■0,12 3 83 0 786 97 0 674 40 30 -40 00 6 1 42 329 263 234 0,13 0 008 287 216 18,5 481 40 00-39 30- 11 1 18 140 239 120 013 010 296 348 183 1 14 3930-39-00 11 1,05 ,130 2 17 200 0 15 015 3 45 226 148 1 1 1 39 00-38 00 13 0.94 ,120 1 91 131 ■0 13 338 211 11 3 485 38 30-38 00 13 050 082 1 57 082 ■:0,11 2 97 259 106 188 38 00-37 30 8 0 51 081 2 08 145 -0,12 354 360 9 1 253 37 30-37 00 11 0 44 071 222 122 -.0,12 3 48 478 94 228 3700 -36 30 14 0 32 046 2 17 233 <0,14 3 08 228 93 260 36 30 -36 00 3 019 053 1 46 082 .■;0,14 2 88 262 96 153 41 00-36 00 93 0 76 2 08 0 13 3 23 11 9 Ocean quahogs 41 00-40 30 8 262 0 400 3 90 0 374 054 0 069 7 16 0 837 126 0.518 40 30-4000 15 2,49 376 3 36 293 0 42 034 5 33 401 14.5 1.04 40 00'-39 30 9 1,53 296 2 97 171 0 42 035 4 71 348 139 741 3930-39'00 9 1,29 ,138 2 68 236 0 39 035 4 41 280 124 991 3900-3830' 5 1,21 371 2 65 114 0 42 059 5 10 727 132 806 38 30-36 30 6 058 120 241 326 0 39 051 2 84 434 10 4 1,38 41"00-36 30 52 1 69 3 01 0 43 504 132 'Average of n samples with 4-6 clams per sample Table 2. — Average' heavy metal concentrations ipartsper mil- lion, wet weight) found in surf clams and ocean quahogs by latitude. Range of lat N n Cr Hg Ni Pb Surf rlams 41-00-40 30 3 ■ 0 62 • 0 05 _ • 07 40 30-40 00 6 0 95 ■ 0 07 0 71 • 07 40°0O-39 30 11 0 70 0 08 ■ 0 39 ■ 07 39=30-3900 11 069 ■0 08 080 • 07 39°00 -38 30 13 065 ■0 08 0 60 ■ 0 7 38°30 -38 00 13 ■ 061 0 08 ■0 50 • 06 3B"00-37 30 8 -0 53 0 08 — • 07 37°30-3700' 11 ■ 0 49 • 007 — ■07 3700-36 30 14 -,0,48 •0,06 _ •07 36"30'-36 00' 3 • 0,48 •:0,05 — - 0 7 41 00-36 00' 93 ■ 061 ■ 0 07 ■ 0 59 ■ 0 7 Ocean quahogs 41 00 -40 30 8 1 03 ■0 09 0 91 18 40°30 -40 00 15 • : 1 ,23 - 0 06 062 1 0 40 00 -39 30 9 0 70 ■0 06 - 0 50 12 39'30-3900 9 0 80 0 07 ■ 0,50 09 39 00-38 30 5 10 008 055 • 1 2 38'30-36 30 6 1 1 ■006 ■ 059 • 09 40 00 -Se 30' 52 ■ 1 0 ■:006 <:061 • 1 1 'Average of n samples with 4-6 clams per sample has not set standards for heavy metals in U.S. fishery products (except mercury), the National Health and Medical Research Council (NHMRC) of Australia has recommended maximum con- centrations for a number of metals in seafoods (Mackay et al. 1975). Concentrations of cadmium, copper, lead, and zinc found in surf clams and ocean quahogs were well under these limits (2.0, 30, 2.0, 1,000 ppm, wet weight, respectively) and far below levels found in American oysters har- vested from Atlantic coastal waters (Pringleet al. 1968). The NHMRC recommendation of 1.14 ppm (wet weight) arsenic! 1.5 ppm as ASjOg). however, was exceeded at all but a few sampling stations. Mean arsenic concentrations for all stations were 2.1 ppm in surf clams and 3.0 ppm in ocean quahogs. The distribution of arsenic concentra- tions did not vary greatly with latitude and may indicate that background levels along the mid- Atlantic coast are higher than those in Australian waters. Concentrations of mercury were found to be well below the action limitset by the FDA (0.50 ppm, wet weight). Major fishing grounds for the surf clam industry are located off the New Jersey and Virginia coasts. Since data for mercury presented in this study are well within the existing guideline set by the FDA for U.S. fishery products and, with a single excep- tion, within the more extensive NHMRC recom- mendations for Australia, there should be little concern to consumers for surf clams or ocean quahogs harvested from these areas at present. The latitudinal cline demonstrated in this study should, however, stimulate further interest in heavy metal inputs along the mid-Atlantic coast of the United States. Data indicate that a large area of our eastern coast may be affected by the pres- ence of heavy metals. The effect on clams is impor- tant, particularly since surf clams and ocean quahogs are representative of the important shellfisheries located in this area. Literature Cited ANONYMOU.S. 1971. Ocean quahog becomes more important as surf and bay clams dwindle, Commer, Fish. Rev. 33l4):17-19. 284 BELL, T. I.. AND D. S FITZ GlBHDN (editors). 1977. Fishery statistics of the United States 1974. U.S. Dep. Commer.. NOAA, Natl. Mar. Fish. Serv.. Stat. Dig. 68, 424 p. BOWEN, H. J. M. 1966. Trace elements in biochemistry. Academic Press, N.Y., 241 p. BOYDEN. C. R. 1973. Accumulation of heavy metals by shellfish. Proc. Shellfish Assoc. G.B., 4th Shellfish Conf., p. 38-48. BROOKS, R. R., .■\ND M. G. RUM.SBY. 1965. The biogeochemistry of trace element uptake by some New Zealand bivalves. Limnol. Oceanogr. 10:521-527. Calabrese, a., R. S. Collier. D. a. Nelson, and J. R. MacInnes. 1973. The toxicity of heavy metals to embryos of the American oyster Crassoslrea virginica. Mar. Biol. (Berl.) 18:162-166. Calabrese, a., and D. a. Nel.son. 1974. Inhibition of embryonic development of the hard clam, Mercenaria njercenaria, by heavy metals. Bull. Environ. Contam. Toxicol. 11:92-97. Goldberg, E. G. (convener!, 1972. Marine pollution monitoring: strategies for a na- tional program. Deliberations of a workshop held at Santa Catalina Marine Biology Laboratory, Univ. South- ern Calif, Allan Hancock Found., Los Ang., Calif., 203 p. GREIG, R. a., D. Wenzloff, and C. SHELPUK. 1975. Mercury concentrations in fish. North Atlantic offshore waters— 1971. Pestic. Monit. J. 9:15-20. Lear, D. W., and G. G. PESCH (editorsi. 1975. Effects of ocean disposal activities on mid- continental shelf environment off Delaware and Mary- land. Environmental Protection Agency, Region III, Phila.. Pa, 204 p. MACKAY, N. J., R. J. WILLL-WIS, J. L. KACPRZAC, M. N. Kazacos, a. J. Collins, and E. H. Alty. 1975. Heavy metals in cultivated oysters iCrassostrea commercialis = Saccostrea cuculhta) from the estuaries of New South Wales. Aust. J. Mar. Freshwater Res. 26:31-46, Middleton, G., and R. E. Stuckey, 19.54. The preparation of biological material for the de- termination of trace metals. Part II. A method for the destruction of organic matter in biological mate- rial. Analyst 79:138-142. PRLNGLE, B. H,, D. E. HiSSdNG, E. L. KaTZ, and S. T. MULAWKA. 1968. Trace metal accumulation by estuarine mollusks. Proc. Am. Soc. Civil Eng., J. Sanit. Eng. Div. 94:455-475. Thurberg, F. p., W. D. Cable. J. R. MacInnes. and D. R. Wenzloff. 1975. Respiratory response of larval, juvenile, and adult surf clams. Spisiila ^olidissima, to silver. In J. J. Cech. Jr.. D. W. Bridges, and D. B. Horton (editors). Respiration of marine organisms, p. 41-52. TRIGOM Publ., South Portland, Maine. THURBERG, F. p., a. Calabrese, and M. a. Dawson. 1974. Effects of silver on oxygen consumption of bivalves at various salinities. In F. J. Vemberg and W. B. Vern- berg (editorsi. Pollution and physiology of marine or- ganisms, p. 67-78. Academic Press, N.Y. Wai.dkhuk. M. 1974. Some biological concerns in heavy metals pollu- tion. In F. J- Vernberg and W. B. Vernberg (editors). Pollution and physiology of marine organisms, p. 1-57. Academic Press, N.Y. D R. Wenzloff R. A. GREIG NorlheasI Fiaheries Center Milford Laboratory National Marine Fisheries Seniice. NOAA Milford. CT 06460 A. S. MERRILL J. W. Ropes Northeast Fisheries Center Woods Hole Laboratory National Marine Fisheries Service. NOAA Woods Hole. MA 02543 APPARENT FEEDING BY THE FIN WHALE, BALARNOPTERA PHYSALUS. AND HLIMPBACK WHALE, MEGAPTERA NOVAENGLIAE, ON THE AMERICAN SAND LANCE, AMMODYTES AMERICASLS. IN THE NORTHWEST ATLANTIC On 18 May 1977 a large group of fin, Balacnoptera p/!V.sa/(/.s. and humpback, Megaptera novaengliae, whales was observed on Stellwagen Bank north of Cape Cod (lat. 42"26'N, long. 70°26'W) by North- east Fisheries Center (NEFC) personnel conduct- ing an annual spring bottom-trawl survey aboard the National Oceanic and Atmospheric Adminis- tration RV Albatros.v IV. Nine fin and 14 humpback whales were identified and observed near the vessel. More whales were sighted in the vicinity, but were too far away to identify posi- tively or to observe conveniently. Many great black-back. Larus marinus, and herring, Lariis argcntatus, gulls were seen feeding at the surface and circling around the whales. The whales dis- played a characteristic feeding behavior described by Gunther ( 1949) and mentioned in Katona et al. (1975). The animals we observed were circling, spouting often, making short shallow dives, and not moving in any set direction. They behaved in a leisurely manner and were seemingly undis- turbed by our presence as noted by Gunther ( 1949). Echo sounding traces indicated a depth of 40 m in this area and large patches of densely concentrated small fishes throughout the water column, but particularly near the surface. During several 30-min bottom-trawl tows in the area, up to 400 kg of adult American sand lance, Ainiuo- FISHERY BULLETIN VOL 77. NO 1. 1979 285 (lytes anwncaiius, were netted per tow (Northeast Fisheries Center') with Atlantic cod, Gadus morhua, and spiny dogfish, Squalus accinthias, the only other abundant fish species. An examination of several cod stomachs showed them to be packed with sand lance while a similar inspection of sand lance showed them to be feeding on copepods. It is our contention that the abundance and behavior of whales in this area indicates that they were feed- ing on a concentration of American sand lance. Similar whale feeding behavior had been previ- ously observed on 18 June 1976 with a humpback whale located at lat. 42°09'N, long. 70°10'W, and with a fin whale located at lat. 42°04'N, long. 70°20'W, and on 20 June 1976 with a humpback whale located in the same general area ( Northeast Fisheries Center'^). During these three observa- tions many herring gulls were again seen feeding at the surface and circling around the whales. Large numbers of American sand lance were also visually observed at the surface by NEFC person- nel aboard the Alpine Geophysics RV Atlantic Twin and in the water column again by NEFC personnel aboard the General Oceanics research submersible Nekton Gamma. These latter two vessels were involved in testing the feasibility of using a research submersible to survey marine organisms (Northeast Fisheries Center-'). Bigelow and Schroeder 11953) reported that fin whales were observed feeding on American sand lance that were abundant in Cape Cod Bay in 1880. Nemoto (1959) listed American sand lance as one of the food items of baleen whales of the North Pacific, along with a variety of other fishes and euphausids. Fin and humpback whales are reported to feed on capelin, Mallotus villosus, a fish similar to the American sand lance in size, summer habitat, and schooling behavior in the continental shelf waters off Nova Scotia and New- foundland (Mitchell 1974a). Fin whales landed at Blandford, Nova Scotia, from 1967 to 1972 con- tained sand lance (May- August), and stomachs from Newfoundland fin whales had >1% sand lance (June-July) in 1970-1972 (Mitchell 1974b). There is little stomach analysis data, though, from baleen whales captured in New England waters in 'Northeast Fi.sheries Center. 1977. Cruise Results. NOAA R/V ALBATROSS IV. Cruise No, 77-02. Spnng Bottom Trawl Survey: Part III. Woods Hole, Mass.. 6 p. ^Northeast Fisheries Center. Gulf of Maine whale sighting network reports Groundfish Survey Unit. Data on tile. Woods Hole, Mass. ^Northeast Fisheries Center. 1976. Cruise Results, R/V At- lantic Twin, Cruise 76-01, Woods Hole, Mass., 8 p. the late 1880's when whaling was popular (True 1904), and no such data since the early 1900's when, for all practical purposes, whaling had ceased. Thus, it is difficult to confirm exactly what fin and humpback whales in the Cape Cod region eat. The feeding observations which we made imply that the rorqual whales off New England, particu- larly fin and humpback whales, may be utilizing the high standing stock of American sand lance that is currently available (Northeast Fisheries Center''). Additionally noteworthy is that the At- lantic herring, Clupea h. harengus, a commonly mentioned rorqual whale food (Allen 1916; Inge- brigtsen 1929; Bigelow and Schroeder 1953; Nemoto 1959), is in low abundance at this time (International Commission for the Northwest At- lantic Fisheries 1976). I.itirature Cited AU.EN, G. M. 1916. The whalebone whales of New England. Mem. Boston Soc. Nat. Hist. 8(2), 322 p. BiiiKLOw, H. B., .^ND W, C. Schroeder. 1953. Fishes of the Gulf of Maine. U.S. Fish Wild! Serv.. Fish, Bull, 53. 577 p, GUNTHER, E, R. 1949. The habits of tin whales. Discovery Rep. 25:115- 141. INTERN.ATIONAI, COMMISSION FOR THE NORTHWEST ATLAN- TIC FISHERIES. 1976, Report of standing committee on research and statistics iSTACRESi. Eighth special commission meet- ing-January 1976. Appendix II, Report ofaf//ioc working group on herring- Int, Comm, Northwest Atl, Fish,, Redb, 1976:35-50, INGEBRIGTSEN, A, 1929. Whales caught in the North Atlantic and other seas. Rapp, P,-V, Reun, Cons. Perm, Int, Explor, Mer 56, 26 p Katona, S., D, Richardson, and R, H.v.ard. 1975. A field guide to the whales and seals of the Gulf of Maine, Maine Coast Printers, Rockland. 97 p. Mitchell. E, 1974a. Present status of Northwe.st Atlantic fin and other whale stocks. In W. E. Schevill (editor). The whale prob- lem, a status report, p, 108-169, Harv, Univ. Press, Camb,. Mass. 1974b, Trophic relationships and competition for food in Northwest Atlantic whales. In M, B. U, Burt (editor), Proceedings of the Canadian Society of Zoologists annual meeting, June 2-5, p, 123-133, Nemoto, t, 1959, Food of baleen whales with reference to whale movements. Whales Res, In.st. Sci, Rep, 14:149-290, ■•Northeast Fisheries Center, Spring groundfish survey re- search cruises 1967-1977. Groundfish Survey Unit. Data on file, Woods Hole, Mass. 286 True, f. w. 1904. The whalebone whales of the western North Atlan- tic compared with those occurring in European waters, with some observations on the species of the North Pa- cific. Smithson. Contrib. Knowl. 33. 332 p. William J. Overholtz John R. Nicolas Northeast Fisheries Center Woods Hole Laboratory National Marine Fisheries Service, NOAA Woods Hole. MA 02543 entire low tide period, since only a single count was made sometime between 90 min before and 90 min after low tide. This study was initiated in fall 1973 in an effort to determine the availability of crabs and the magnitude of intertidal harvest on one high-use Puget Sound beach. From data collected, an esti- mate was made of the total use of Puget Sound beaches by sport crabbers for daylight low tides in 1974. Methods ESTIMATION OF INTERTIDAL HARVEST OF DUNGENESS CRAB, CANCER MAGISTER, ON PUGET SOUND, WASHINGTON, BEACHES' There are two major methods employed in the sport fishery for the Dungeness crab. Cancer magister, in Puget Sound, Wash. The first is a passive method. A baited pot, trap, or ring net is placed on a subtidal substrate, left for a period of time, and retrieved. The second is an active method. During periods of low minus tides, sport crabbers seek crabs by sight. The crabbers usually wade out into water between knee and waist level, then walk parallel to the beach. A round metal loop, about 1 ft in diameter, covered with wire mesh and attached to a long handle, is generally used to capture crabs. Beginners often bring fish nets, but find it difficult to extricate the crabs caught in the net. When a crab is seen, the crabber maneuvers the hoop quickly under the crab. The crab's legs go through the mesh, making escape difficult, and the hoop is then pulled from the wa- ter. Only male crabs may be taken, and they must be a minimum of 152 mm (6 in) in width, as deter- mined by a caliper measurement across the carapace, directly in front of the 10th anterolat- eral spines. The daily crab catch is limited to six per person. Knowledge of the size and distribution of the intertidal sport fishery was limited until 1969, when the Washington Department of Fisheries began aerial surveys to estimate low tide usage of Puget Sound beaches for clam digging and crab- bing. By summer 1973, enough data had been col- lected to show which beaches were being used for crabbing. However, the aerial surveys did not reflect the total use of beaches by crabbers over the 'Based on work submitted in partial fulfillment of the re- quirements for the degree of Master of Science. FISHERY Bl'LLETIN VOL 77. NO I. 1979 From preliminary aerial survey data. Mission Beach, located 60 km north of Seattle and just beyond the Port of Everett, was selected as the study site (Figure 1). The beach is 3 km long, shallow, and sandy, with eelgrass beds below the mean lower low water (MLLW) level. This beach had only one public access, cut through a 15-m bluff. This location provided me with a good view of the entire area and made it possible to interview almost all crabbers using the beach. From October 1973 to October 1974 there were 19 low tide series with tides lower than -0.30 m MLLW. These tidal series occurred in all months of the year except March and September. I visited Mission Beach during all tides lower than -0.30 m, except under adverse weather conditions in the winter months. I arrived 2.25 h before low water and walked to point 'a' ( Figure 1 ), where I entered the water and moved toward the access at a depth of 0. 15 to 0.85 m through the area most intensively utilized by the sport crabbers. For all crabs ob- served, I recorded the size to the nearest millime- ter ( taken in a horizontal measurement directly in front of the anterolateral spines on the carapace, by means of a caliper) and sex. Sampling was by the method used by most crabbers. Beginning 2 h before low tide, I made half- hourly counts of the number of crabbers at the beach, but continued beach sampling of crabs until crabbers began to leave the beach, usually about 0.5 h before the low. At this time, I interviewed the crabbers about their success and time spent crab- bing. About 9(K of all crabbers using Mission Beach, on tides checked, were interviewed. During the interviews, I measured as many crabs as pos- sible. From the interview data, I estimated the number of crabbers on the beach at any time dur- ing a period of 14 min before to 15 min after the half-hourly counts. The average time spent crab- bing was slightly over 1.5 h; thus, if all crabbers 287 48*3' Figure l. — Location of Mission Beach within Puget Sound, Wash. The area most intensively utihzed by crabbers at Mission Beach is outhned with dashes. ia'i- BEACH / ^ 5»v , i^ ACCESS \ ^ i ' KILOMETERS DEPTH IN FATHOMS ^ T" 1 2 2* 30 had been interviewed, the constructed counts would coincide with actual beach use. However, not all crabbers were interviewed, so the half- hourly counts were more accurate for the lowest period of the tide when most people were crabbing. I then constructed a table for each month which assigned the highest of the two estimates, either the constructed count from the interviews or the half-hourly beach count, to each half-hourly period. The number of crabbers using the beach was computed for each tide by dividing the total crabber hours (the sum of the half-hourly counts) by the average hours spent crabbing (obtained from crabber interviews) and totaled for each month. From the monthly table, the number of crabbers on the beach at any half-hourly interval, divided by the total number of people using the beach for each month during the low tide period, gave a percentage of people using the beach at any 288 half-hourly count. Monthly use curves were then constructed for Mission Beach (Figure 2). The methods that I employed to develop use curves were similar to those that have been used by researchers who have dealt with other recrea- tional fisheries (Miller and Gotshall 1965; Brown 1969; Tegelberg^; Jarman et al.^). In addition to the sampling that I conducted at Mission Beach, personnel from the Washington Department of Fisheries Shellfish Laboratory conducted creel sampling at six other Puget Sound beaches having differing levels of crabber use. From the survey material that they provided, I had insufficient data to construct use curves for ^Tegelberg, H C 1963 The 1962 razor clam fisheries. State Wash. Dep. Fish . 28 p. =Jarman, R.. C Bennet, C. Collins, and B. Brown 1970. Angling success and recreational use of twelve state owned lakes in Oklahoma. Paper given at 21st Annu. Meeting South. Div. Am. Fish- Soc. New Orleans. La. 100^ ^ 90- /^•^ APR M»«JUN - = 80- ^'■■■"v JUL AUG — • S 60 ■ / X:-, \\ ^ ^v •. *. S bO / \;^ \ ^ 40- / £ 30- <-'^-"^ n/- '■- \ ^ 20- xj>.. "\ S^ 10 X^.' _ **- PERIOD ABOUT LOW TIDE iMINUTES) Figure 2. — Crabber use curves for Mission Beach based on data gathered April-August 1974. April and August, but I was able to construct use curves for May -June and July, a combined total for those beaches based on 10 and 5 observations, respectively. These use curves, when superim- posed over the corresponding Mission Beach use curves, did not vary by more than approximately 10% for the period before, or 20^f for the period after, the low tide. The Washington Department of Fisheries also provided me with data from aerial surveys con- ducted over Puget Sound beaches on 27 April, 25 May, 22 June, and 20 July 1974. Most of the beaches were surveyed during the hour preceding the low tide, which corresponded to the highest beach use. Thus, the curves derived for Mission Beach were used for estimates for all beaches. While interviewing crabbers at Mission Beach, it appeared to me that both the tidal height and tidal sequence were important factors in crabbing success. I therefore analyzed the data in two dif- ferent ways. The various tidal series had from three to eight tides lower than -0.15 m(-0.5ft). I divided the low tide heights into six levels by 0.15-m increments. The first minus tide of a series to fall into a tidal height category was defined as Tide One in the tidal sequence. Each succeeding tide was consecutively numbered, with the final tide in a series designated as the last minus tide to fall into a tidal height category. Thus, low tides of equal height from different tidal series were not always the same sequence number. Results and Discussion The number of crabbers using Mission Beach during the winter nighttime tides was small com- pared with the number during the summer day- time tides. Of the estimated 762 crabbers using Mission Beach during the year, only 27 (4'7f) crabbed from October through February, while 735 (96% ) crabbed from April through August. Of the estimated 531 crabs taken for the year at Mis- sion Beach, the winter crabbers caught 60 (11%), while the summer crabbers caught 471 (89%). Stepwise multiple linear regression analysis (Poole 1974) of crabber activity at Mission Beach correlated significantly (P<0.05) with tide height, day of week, month, temperature, and wind veloc- ity (Table 1 ). However, the resultant equation was not strong enough for predictive purposes. The tide height accounted for the largest amount of the variability. The lowest three tide levels had two to four times as many crabbers as the highest three levels (Table 2). The other significant variables indicated the following: weekend use by crabbers per tide was 1.5 times greater than the average weekday use per tide; the average number of crab- bers per tide was highest in April, May, and June, with the use dropping off considerably in July and August; there were more crabbers at higher air Table L— Summary table of multiple linear regression be- tween total crabbers at Mission Beach and nine independent variables. The resultant equation was significant at P<0.001 for all steps. Variable Signif- Mult Overall step entered icance' R fl= R F 1 Tide height 0001 0 45 0 20 0 45 12 35 2 Day ol week 003 59 34 -027 1237 3 Month 005 67 45 -0 39 12 61 4 Temperature 007 73 53 0 26 12 92 5 Wind velocity 027 76 58 -006 12 37 6 Tide sequence 078 78 61 0 08 11 39 7 Previous day s catch/crabber 698 78 61 0 04 9 59 8 Precipitation 769 78 61 -0 06 8 21 9 Cloud cover 825 78 .61 -013 7 14 ^The Q level of significance for each variable as it was entered in the equation Table 2. — Crabber use and catch taken on six different tide heights (mean lower low water) at Mission Beach, Wash., Apnl-August 1974. Total Tide No ol Mean no Mean no Mean catch legal height tides crabbers of crabs legal crabs crab (m) sampled per tide caught per crabber catch -0 15 to -0 29 - 0 30 to -0 44 -0 45 10 -0 59 -0 60 to -0 74 -0 75 to -0 89 -0 90 to -1 04 6 14 16 6 13 9 25 27 1 4 79 6 1 24 7 150 54 02 06 07 1 3 06 02 7 110 92 173 62 27 289 temperatures, but this corresponded with the low- est tides in June, which occurred at midday; on days with high winds there were few crabbers. This was probably due to a lowered chance of suc- cess because waves on the beach made crabs difficult to see. The estimated use of the beach by crabbers cor- responded with the daily availability of crabs on the beach that I observed by sample crabbing. This availability appeared to be affected by current and tide height. Two hours before low tide, the water level over the eelgrass portion of the beach, where most crabs were found, was generally >1 m. As the tide went out and the water became shallower, I observed few crabs in water <0.15 m deep. The current also appeared to have effects. When the tide approached its lowest level, the current be- came slack, at which time I observed few crabs. Even on days when a large number of crabs were active an hour before the low, few would be evident at low slack. The monthly use curves enabled me to take a single aerial survey count of crabbers using a sur- veyed beach at any time during the low tide period and predict the total crabber use at the beach during the entire low tide period. I adjusted the total calculated Puget Sound beach use by crabbers during the 1974 aerial sur- veys by two factors: the number of crabbers excluded because beaches were not surveyed and the improper identification of people as crabbers who were not actually crabbing. Between 1969 and 1973, at least one aerial survey at low tide was conducted over every Puget Sound beach, and all important crabbing beaches were identified. From this data I estimated that the 1974 aerial surveys included 959( of the crabbers and other recreation- ists on the beaches at any given low tide. At the same time 1974 aerial surveys were made over Mission Beach, I made actual counts of crabbers on the beach. The average overcount of crabbers by the aerial survey was 15.5%. Total Puget Sound intertidal crabber use for all low tides from April through August was roughly estimated by dividing the total Mission Beach counts on the days of the aerial surveys, April through July, by the adjusted total Puget Sound beach count. The quotient was designated as the percentage of Mission Beach use relative to the adjusted total beach count (Table 3). Due to poor visibility on the day scheduled, no aerial survey was conducted in August, so I used averaged data from the preceding 4 mo. I estimated the total crabber use on all beaches for each month by divid- ing the percentage Mission Beach use of the total adjusted beach count into the total crabber use of Mission Beach for each month. In order to estimate the total crabs caught in Puget Sound by intertidal sport crabbers, I needed to know whether the average catch over a low tide period at other Puget Sound beaches was the same as that at Mission Beach. Six other beaches in Puget Sound that had different levels of crabber utilization were sampled on a random basis by personnel from the Washington Department of Fisheries. Their levels of crabber use ranged from a few to 70 crabbers per tide. Four of the six beaches had three or more surveys, and these were compared with Mission Beach by Wilcoxon Rank Sum Tests (Hollander and Wolfe 1973). The four beaches had W values of 13.5, 9.5, 46.5. and 106, which in all cases were greater than the computed values of 6, 6, 39, and 66. Thus the null hypothesis that there were equal catches per crabber at the different beaches could not be rejected. This im- plies that the number of crabbers at a beach is self-regulating in that crabbers tend to adjust their level of effort to the rate of return, and that rates of return for all crabbers at different beaches remains fairly constant. This same pattern of utilization was observed in the recreational trout fisheries in California lakes, where the angling effort adjusted proportionally to the numbers of catchable-size trout (Butler and Table 3.— Estimate of the total monthly crabber use in the intertidal Dungeness crab sport fishery for Puget Sound beaches, April-August 1974. — Percentage Adjusted total Puget No of crabbers at Mission Beach use Total crabbers Estimated total inler- Sound beach count on Mission Beach on of total adjusted beach count at (Col 5 - Col 4) Month monthly aerial survey monthly aerial survey (Col 3 - Col 2) Mission Beach April 433 27 6.2 79 1.274 May 829 28 3.4 229 6.735 June 954 33 3.5 279 July 805 29 36 121 3.361 August No observation '4 18 27 646 Total 735 19.987 'Average of four previous rnonths 290 Borgeson 1965). Since the catches did not differ significantly, all beaches were treated together for predictive purposes. An estimate of the total crabs caught by intertidal sport crabbers for the day- light tides in 1974 was made by multiplying the average catch per effort for April, May , June, July, and August at Mission Beach (Table 4) by the estimated total number of crabbers (Table 3) for each month. The number of crabs caught per month increased throughout the spring, reaching a maximum of 5,099 in June. Few crabs were caught after July (Table 5). When Spearman rank correlation coefficients were computed between a crabber's catch at Mis- sion Beach and a number of independent variables (Hollander and Wolfe 1973), the most significant positive correlation was with the total time spent crabbing (Table 6). Crabbing was better in April- June than in July and August. The tide height and tide sequence were not significantly correlated with the catch per crabber at P<0.05, but were significant at P<0.10. The highest average catches were on tides ranging from -0.60 to -0.74 m (Table 2). The higher tides make crabbing difficult, be- cause crabbers have to wade into deeper water to get to the area where crabs are found. In the deeper water, crabs are less visible and the mobil- ity of crabbers is impaired. The catches and number of crabbers arranged by tide sequence are shown in Table 7. The lowest tides of the year are generally four or five tides into a tidal series. The first low tides in the series have already allowed a fair amount of crabbing pressure on the beach, and many of the available crabs have been removed. Additionally, the combination of crabbers wading and less water over the beach on the previous low tides probably causes crabs to move to deeper water during the last low tides in a series. The sex and size composition of crabs that I observed while sampling are shown iti Figure 3. The numbers of legal males (152 mm and larger) include all crabs measured during crabber inter- TaBLE 4. — Monthly crabber use and mean daily catch at Mission Beach, Wash., Apnl-August 1974. Mean daily Range of Number of Number of catch per mean daily Montti tides crabbers crabber catches Table 5.— Estimated total Dungeness crab sport catch in Puget Sound on intertidal beaches. April-August 1974. April 5 79 1 76 0 4-3 0 May 11 229 86 0 0-3 4 June 14 279 64 0 0-2 2 July 14 121 59 0 0-1 7 August 6 27 30 0 0-0 5 Mean catch per Estimated Estimated crabber at total Pugel total crab Month IVtission Beach Sound crabbers catch April 1 76 1.274 2.242 May 86 6,735 5.792 June 64 7.971 5.099 July .59 3.361 1.983 August .30 646 194 Total 19,987 15,310 Table 6. — Spearman correlation coefficients between number of crabs caught per crabber and nine independent variables. Variable Time spent crabbing Month Tide height Tide sequence Wind velocity Temperature Precipitation Time of low Cloud cover Correlation coefficient 0738 -0413 0 229 -0,222 -0 175 -0 105 -0 092 0 054 0010 Significance 0001 002 .055 .061 .113 .238 .263 355 473 Table 7. — Crabber use and catch taken on different tide heights arranged according to the sequence in which they occurred in a low tide series at Mission Beach. Wash., April-August 1974. No of Mean no Mean no Mean catch Total Tide tides crabbers of crabs legal crabs legal sequence sampled per tide caught per crabber crab catch 1 6 15 76 0,5 46 2 9 23 103 0,9 163 3 8 13 9,4 0,7 85 4 8 13 6,5 0,5 52 5 8 9 89 10 71 6 7 18 63 04 44 7 3 14 27 02 8 8 1 20 20 0 1 2 2251 100 75- 50^ 25- MAIESQ FEUIAIESQ JL <108 114 121 12; 133 140 146 152 159 165 171 178 184 < LENGIH mm) Figure 3, — Size composition and sex of crabs observed during sample crabbing at Mission Beach from October 1973 through August 1974, Male crabs -">150 mm include those measured during crabber interviews. 291 In summary, the use of Mission Beach by inter- tidal crabbers is greatest 1 to 2 h before the low tide. This corresponds to the period when crabs are most readily observable. From the data collected at Mission Beach and aerial survey counts of other Puget Sound beaches, I estimated that about 20,000 crabbers utilized intertidal beaches from April through August 1974. The intertidal Dungeness crab sport fishery is, however, fairly small compared with other marine sport fisheries in Puget Sound. Acknowledgments I wish to thank G. Pauley, J. Congleton, C. Woeike, K. Chew, and T. Walker for discussion and critical readings of various stages of the man- uscript. Reviewers for the Fishery Bulletin helped improve the readability. R. Whitney, as Leader of the Washington Cooperative Fishery Research Unit at the University of Washington, provided encouragement, support, and facilities from the outset of the study. Appreciation is extended to A. Scholz and other members of the Sport Shellfish Section of the Washington State Department of Fisheries, without whose cooperation this study would not have been possible. The study was par- tially supported by funds from the Washington Department of Fisheries. Literature Cited BROWN, B. E. 1969. An analysis ofthe Oklahoma State lakecreel survey to improve creel survey design. Ph.D. Thesis, Oklahoma State Univ., 164 p. Butler, R. L., and D. P. Borgeson. 1965. California "catchable" trout fisheries, Calif Dep. Fish Game, Fish Bull. 127. 47 p. Hollander. M., and D. a. Wolfe. 1973. Nonparametric statistical methods. John Wiley and Sons. N.Y.. 503 p. MILLER, D. J., AND D. GOT.SHALL. 1965, Ocean sportfish catch and effort from Oregon to Point Arguello, California, July 1, 1957 to June 30, 1961, Calif Dep, Fish Game, Fish Bull. 130. 135 p Poole, R. w 1974, An introduction to quantitative ecology. McGraw-Hill. Inc., N,Y,. 5.32 p, JOHN G, Williams Washington Cooperative Fishery Research Unit College of Fisheries, University of Washington Seattle. WA 98195 A CONTRIBUTION TO THE BIOLOGY OF THE PUFFERS SPHOEROIDES TESTUDINEUS AND SPHOEROIDES SPENCl.ERI FROM BISCAYNE bay, FLORIDA The general biology of the checkered puffer, Sphoeroides testiidineus, and bandtail puffer, S. spengleri, is not as well known as that of the northern puffer, S. maculatus. For example, Chesapeake Bay populations ofthe northern puff- er have been examined for length-weight rela- tionships by Isaacson (1963) and Laroche and Davis (1973), for age, growth, and reproductive biology by Laroche and Davis (1973), and for fecundity by Merriner and Laroche (1977). None of this information is available on the checkered or bandtail puffer. Checkered and bandtail puffers have greater geographic ranges and are more southern in dis- tribution than the northern puffer. The checkered puffer is abundant from the Atlantic coast of southern Florida, throughout the Caribbean Is- lands, Campeche Bay, and along the coasts of Central and South America to Santos, Brazil (Shipp 1974). The bandtail puffer is common in the Caribbean Sea and along the coasts of peninsular Florida, the Bahamas, and Bermuda (Shipp 1974). I report here on growth, reproduction, and the pharyngeal dentition of these two species gathered during a study of their feeding biology (Targett 1978). The sampling habitat was a shallow seagrass bed along the southwestern shore of Virginia Key in northern Biscayne Bay, Fla. Turtle grass, Thalassia testudmum , was the dominant seagrass with small amounts of shoal grass, Halodule wnghtii, and manatee grass, Syringodium filiforme, also present. Monthly collections from September 1973 to December 1974 yielded 414 checkered puffers (15-215 mm SL; 569^ females) and 548 bandtail puffers (16-133 mm SL; 49^;^ females). Seawater temperatures ranged from 16.5° to 32.0°C and salinities from 30.5 to 38.5%o. Standard length-weight relationships (Figures 1,2) were calculated using functional regressions (Ricker 1973). Checkered puffers grow to a larger size and are heavier than bandtail puffers at a given length. Comparisons of these results with those for northern puffers from Chesapeake Bay (Isaacson 1963; Laroche and Davis 1973) was made possible by the conversion of total length to standard length using the factor: caudal fin length = 20. 2"^^, SL (Shipp 1974). Northern puffers grow 292 FISHERY Bl'LLETIN VOL 1 — I — I — \ — I — I — I — n — I— I- 20 40 60 80 100 120 140 160 180 200 220 STANDARD LENGTH ( mm ) Figure l— Standard length-weight relationship for 250 check- ered puffers from Biscayne Bay, Fla. Functional regression parameters derived by least squares fit to log transformed data, where variance about regression was S^,^ = 0.0014. to a greater maximum size than either checkered or bandtail puffers and are approximately the same weight at a given length as checkered puff- ers. Checkered puffers decreased in alDundance in June and July due to a drop in numbers of 120-169 mm SL fish (Figure 3). (Some individuals may have left the seagrass bed as early as April and May, since a greater effort was needed to catch checkered puffers at that time, ) Males and females decreased equally in abundance. The group leav- ing the seagrass bed may have been going elsewhere to spawn since their departure corre- sponded with the time of capture of ripe individu- als. Some ripe checkered puffers were captured in April and May; and by August, September, and the beginning of October the few adults caught 60 80 STANDARD LENGTH ( n FIGTRE 2 —Standard length-weight relationship for 250 bandtail puffers from Biscayne Bay, Fla Functional regression parameters derived by least squares fit to log transformed data, where variance about regression was S, ,^ = 0.0018. 20 r Hn n n n n n r-1 n ,-, CL_ n n n „ n n- n n n n n II n nn nnn nnnnn .nn n n n n .;. , , SIZE CLASS (n Figure 3.— Monthly standard length-frequency distributions for checkered puffers from Biscayne Bay, Fla , during 1974 293 were all ripe. Furthermore, Christensen (1965) found evidence that checkered puffers from Jupi- ter Inlet, Fla., spawned in low salinity waters dur- ing the fall. He found young fish (s£lO mm SL) from early November through December in waters having salinities generally <20%ii. He also ob- served that young and juveniles were abundant in the upper reaches of the Loxahatchee River ( which flows into Jupiter Inlet ) durmg winter and spring, rarely being found elsewhere. Thus, the checkered puffers leaving the seagrass bed in the present study may have been going to spawn in lower salinity waters found along portions of western Biscayne Bay or in the Miami River. This would explain why no checkered puffers <25 mm SL were captured, except for six in October. Most young likely remain in brackish water areas and move into higher salinity habitats only at larger sizes the following year. The 80-119 mm SL group appearing in August probably composed the 1-yr- old fish moving into the seagrass bed. The checkered puffer spawning season, begin- ning in the spring and concentrated during sum- mer and early fall in Biscayne Bay, occurs slightly later than the spring and summer spawning of the southern puffer, S. nephelus, at Cedar Key, Fla. (Reid 1954). The northern puffer in Chesapeake Bay has been reported to spawn during May by Hildebrand and Schroeder ( 19281 and during late May, June, and July by Laroche and Davis (1973). Fecundity analysis, using the gravimetric technique, was done on nine checkered puffer females ranging from 127 to 178 mm SL (99-256 g). Only yolky eggs, with nuclei obscured, were counted. Regression analyses of fecundity- standard length and fecundity-body weight were done using functional regressions (Ricker 1973). Total fecundity increased exponentially as a func- tion of body length (Figure 4) and linearly as a function of body weight (Fecundity = 1,431.81 [Body wt in grams] - 45,704.97; r = 0.96), Over the size range examined, relative fecundity aver- aged 1,146 eggs/g body wt. These fecundity values are greater than those found by Merriner and Laroche ( 1977) for northern puffers in Chesapeake Bay. Of the six checkered puffers <25 mm SL, two (15 and 23 mm SL) were males and the sex of the rest ( 17, 17, 18, and 21 mm SL) was undetermm- able. Thus, it was not possible to estimate the body size at which eggs become discernible. The age structure of the checkered puffer popu- lation can be inferred from the monthly length- frequency distributions (Figure 3). The 80-119 V: 0O48 X r: 88 50-1 1 1 r 120 130 140 150 180 STANDARD LENGTH (mm) Flia'RK 4— Tola) fecundity-standard length relationship for nine checkered puffers from Biscayne Bay, Fla. Functional re- gression parameters derived by least squares fit to log trans- formed data, where variance about regression wasSy.,^-0.(X)78. mm SL group appearing in August is likely 1-yr- old fish which grow to 1 20- 1 89 mm SL by the end of their second year. A comparison of the growth of checkered puffers in this population with results from the work of Laroche and Davis (1973) on northern puffers from Chesapeake Bay shows that the checkered puffers reach a smaller size at the end of each year of life and are shorter lived than the northern puffers. Eggs became discernible, by microscope, in bandtail puffers at 25-30 mm SL. Spawning sea- son, however, was not easily determined. No ripe or nearly ripe bandtail puffers were caught despite the fact that this species was abundant through- out the year and the full size range (to approxi- mately 160 mmTL(Shipp 1974)) was captured. At least one fish <30 mm SL was collected every month except September, November, and De- cember, although most were captured during March through June. This implies that bandtail puffers have a long spawning season, concentrated in the late fall and early winter, and spawn elsewhere with the young moving into the sea- grass bed shortly after hatching. Both checkered and bandtail puffers feed mainly on crabs, bivalves, and gastropods (Targett 1978). They use their beaklike jaws (paired pre- maxillary and dentary bones) to break the shelled prey. Two specimens of both species were cleared and stained, revealing that they have similar 294 pharyngeal dentition. Three pairs of dorsal pharyngeal tooth plates are present, associated with the pharyngobranchial elements of branchial arches I, II, and III, with one tooth plate of each pair being located on either side of the dorsal mid- line. Each tooth plate is slightly curved with a posteriorly directed dentigerous surface. In the 126- and 137-mm SL checkered puffers, the four tooth plates in the anterior two pairs were each 4 mm long and those in the posterior pair were each 3 mm long. In the 108- and 118-mm SL bandtail puffers, the four tooth plates in the anterior two pairs were each 3 mm long and those in the poste- rior pair were each 2 mm long. The dorsal pharyngeal tooth plates of both puffer species bear upon the pair of ventrally located, and nonden- tigerous, fifth ceratobranchial (lower pharyngeal) bones. The pharyngeal tooth apparatuses likely function to pull flesh from and to further grind and break crab and mollusc shells. The smooth puffer, Lagocephalus laevigatus, also has strong beaklike jaw teeth but has dentigerous tooth plates as- sociated with the pharyngobranchial elements of only the II and III branchial arches (Tyler 1962). In general, fishes in the Order Plectognathi have very strong jaw teeth and comparatively weak pharyngeal dentition (Al-Hussaini 1947). Acknowledgments MERRINER. J. v., AND J, L. L,-\HOCHE 1977 Fecundity of the northern puffer, Sphoeroides maculatus. from Chesapeake Bay. Chesapeake Sei. 18;81-83. REID. G K, JR. 1954, An ecological study of the Gulf of Mexico fishes, in the vicinity of Cedar Key, Florida. Bull. Mar. Sci. Gulf Caribb, 4:1-94, RICKER. W. E. 1973, Linear regressions in fishery research J Fish. Res. Board Can, 30:409-434. SHIPP. R, L. 1974. The pufferfishes (Tetraodontidael of the Atlantic Ocean, Publ Gulf Coast Res. Lab, Mus, 4, 163 p, T.ARGErr, T, E, 1978. Food resource partitioning by the pufferfishes Sphoeroides spenglen and S. testudineus from Biscayne Bay, Florida. Mar, Biol, iBerl.) 49:83-91, TYLER, J. C 1962, The general osteology of representative fishes of the Order Plectognathi, Ph.D. Thesis, Stanford Univ., Palo Alto, Calif. 388 p. Timothy E, Targett Department of Zoology University of Maine Orono. ME 04473 CORRELATES OF MATURITY IN THE COMMON DOLPHIN, DELPHl''0.10, Kendall's rank corre- lation test). Both sexually mature and immature females occur with 7-14 dentine layers (Figure 2). Testes weights are so variable in the range of 7-12 dentine layers that they cannot be estimated (Fig- ure 3), although significantly correlated over the entire range of data (PsO.OOl, Kendall's rank cor- relation). Body length is a poor indicator of sexual de- velopment. Over body lengths 175-190 cm, testes apparently undergo a transitional stage of growth. Gonad weight cannot be accurately estimated from body length over this range (Figure 4) al- though the two are significantly correlated over the entire range of data (PsO.OOl, Kendall's rank correlation). Body length and ovarian scarring are poorly correlated (P>0. 10, Kendall's rank correla- tion). Body lengths 165-182 cm include both sex- ually mature and immature females (Figure 5). 1 1 1 1 — ^T- } T ~^ 1 1 1 1 14 _ — _ • - 12 _ • — _ • - If '0 _ N = 51 • — 4 - • • - 1 6 [ • • • • - < 2 — • • • • • « • -• 0 *- • 1 1 • • 1 1 1 • • 1 1 • 1 _L • 1 * 1 1 1 1 DENTINE LAYERS Figure 2. — Ovarian corpora in relation to dentine layers in Delphinus delphis. The stippled region indicates the range of dentine layers over which sexually mature animals are indistin- guishable from immature. 1000 800 T — I — I — I — I — I — I — I — I — I — I — I — I — I — r- I ' I ' I II * I • • t • # DENTINE LAYERS FIGURE 3.— Testis weight in relation to dentine layers in Del- phinus delphis. The stippled region indicates the range of den- tine layers over which testes of mature and immature weights overlap. The FI is significantly correlated with testes weights (P=£0.001, Kendall's rank correlation) although data are missing in a narrow range (Fig- ure 6). However, inactive ovaries occur in a wide 297 lOOS 800 '^ 200 9 100 50 - 1 1 1 1 1 - N-36 • - • •• • • _ .* • • • • • _ - I 1 1 1 1 TOTAL BODY LENGTH (cmj FIGURE 4.— Testes weights in relation to body length. The stip- pled area indicates the region of overlap for mature and imma- ture testes weights. 1 ' r -T-: M, 140 160 • * • * 80DY LENGTH Figures. — Ovarian corpora related to body length mDelphinus delphis. The range of body lengths in which sexually mature and immature animals cannot be distinguished is indicated by the strippled area range of FI scores (Figure 7) and there is no sig- nificant relationship between the number of ovar- ian scars and the FI (P >0.10, Kendall's rank cor- relation). Robustness is here defined as the body length in centimeters divided by body weight in kilograms. Regardless of body length, only the most robust individuals are sexually mature. Sexual maturity occurs when the male's length/weight ratio de- 298 FLIPPER INDEX Figure 6. — Development of testes related to epiphyseal de- velopment of the pectoral appendages in Delphinus delphts as indicated by the Flipper Index, The best interpretation of the present data is that two linear phases are separated by a stage of rapid change. T ' r i ' — I — ' — r Figure 7. — Ovarian corpora related to pectoral epiphyseal de- velopment (Flipper Index) \n Delph in usdelphis. The shaded area indicates the range in Flipper Index over which sexually mature and immature animals overlap. clines to about 2.6 (Figure 8). Mature females had length/weight ratios lower than about 3.0 (Figure 9). Of the 24 females with ovarian scars in this study, 16 were pregnant. Assuming the weight of the amniotic sack is nearly equal to that of the fetus, twice the weight of the fetus was subtracted from the gross weight of the mother, leaving the weight of the nonpregnant female for calculations of robustness. The robustness of the pregnant females is not separable from the sexually mature nonpregnant females. • TESTES WEIGHT - lOOq N - It A TESTES WEIGHT >350q. N - 6 Figure 8— The body length/weight ratio as related to body length in male Delphinus delphis. Individuals with combined testes weights of 350 g are considered to be undergoing sper- matogenesis. The shading designates the weightylength ratio in which males apparently are sexually mature. 70 • • 1 1 1 • "" I I 1 • • • • IMMATURE, N"?9 i • • E « A MATURE N 7A • ^ 50 • • - t • • i " - • ••• ~ I • • • • o • i • • - -■ JO "5r * 4ft X 20 - 1 1 1 L_ 1 1 1 - BODY LENCTI FIGURE 9, — Relationship of the body length/weight ratio to body length in female Delphinus delphis. Triangles represent indi- viduals with at least one ovarian corpus. The shaded area de- notes length/weight ratios in which sexually mature dolphins predominate. Discussion The data indicate that sexual development is better correlated with parameters which indicate the individual's proximity to physical maturity than with fixed morphometric values. A large in- crease in combined testes weight from <80 g to almost 400 g corresponds with rapid skeletal growth in the individual dolphin (Figure 6). Con- sequently, the FI is better correlated with sexual maturity in males than dentine layers or body length. Robustness is also highly correlated with sexual development in males but the sample size is small. For unknown reasons, ovulation is better corre- lated with the length/weight ratio than with body length, dentine layers, or flipper bone develop- ment. Similarly, in studies of humans, it was found that girls who attained early menarche also had greater weight for height than their chronological peers who attained maturity at a later time (Simons and Greulich 1943). Data from S. attenuata (Perrin et al. 1976) also show ovarian corpora to be poorly correlated with age and length. Induced ovulation is a distinct possibility for D. delphis. Harrison and Ridgway (1971) concluded that ovulation in Tursiopa truncatus is induced but the mechanism is unknown. The present data imply that someD. delphis females never ovulate, supporting the findings of Harrison et al. ( 1972). Oliver's' examination of Delphinus from the eastern tropical Pacific showed that the smallest testes with spermatogenesis weighed 140 g. For the present study, specimens with combined testes weights >350 g were collected in March, April, July, September, October, November, and De- cember. The large testes weights throughout the year indicate that there is no seasonal rut, sup- porting the findings of Harrison et al. ( 1969). Gaps in the data occur immediately prior to maleD. delphis sexual maturity: FI scores 85-105 (Figure 6), body lengths 158-177 cm (Figure 4), 4-8 dentine layers (Figure 2). These gaps appear to be the prepuberty ranges for those indicators. Be- havior patterns may account for the absence of data in these regions. Young males of Physeter catodon (Ohsumi 1971) and Tursiops truncatus (Evans and Bastian 1969) frequently herd sepa- rately from the rest of the population. Alterna- tively, these animals may have a greater capacity to escape nets. Female specimens also are lacking in the length, age, and FI ranges just prior to the demonstration of ovarian scars. Preadolescent females, like the males, may easily escape nets, or have a social structure separate from the main herd. Acknowledgments Mary F. P. Rieger and Linda J. Harrington pro- vided assistance with the statistics and ovary examination, respectively. G. A. Bartholomew, F. G. Wood, W. E. Evans, W. F. Perrin, and J. C. Quast offered helpful suggestions on the manu- script. 'C. W. Oliver, Inter-American Tropical Tuna Commission, La JoUa, CA 92037. Unpubl. data, 299 Literature Cited EVANS, W. E . AND J, BASTIAN. 1969. Marine mammal communications; social and ecolog- ical factors. In H. T. Andersen (editor), Biology of marine mammals, p. 425-475. Academic Press, N.Y. Harrison, R. J., R. C. Boice. and R. L. Brownell. Jr 1969 Reproduction in wild and captive dolphins. Nature (Lond.) 222:1143-1147. Harrison, R, J., R, L. Brownell, Jr , and R, C. Boice 1972. Reproduction and gonadal appearances in some odontocetes. In R. J. Harrison (editorl. Functional anatomy of marine mammals, Vol 1, p 361-429 Academic Press, N.Y. Harrison, R. J., and S. H. Ridgway. 1971. Gonadal activity in some bottlenose dolphins iTur- Slops truncatus). J. Zool. (Lond. I 165:355-366. Kleinenberg. S. E., and G. A. Klevezal 1962. Towards a method for determining the age of toothed whales. \In Russ.l Dokl. Akad. Nauk. SSR Inst. Morfol. Zhivotn. OHSUMI, S. 1971. Some investigations on the school structure of sperm whale. Sci Rep Whales Res. Inst. Tokyo 23:1-25. PERRIN. W. F. 1975. Variation of spotted and spinner porpoise (genus Stenella) in the eastern Pacific and Hawaii. Bull. Scripps Inst. Oceanogr. Univ. Calif. 21, 206 p PERRIN. W. F., J. M. COE. AND J. R. ZWEIFEL 1976. Growth and reproduction of the spotted porpoise, Stenella atteituata, in the offshore eastern tropical Pac- ific. Fish. Bull., U.S. 74:229-269. SIMMONS. K., AND W. W. GREULICH 1943. Menarcheal age and the height, weight, and skeletal age of girls age 7 to 17 years. J. Pediatr. 22:518-548. SINCLAIR, D. 1973. Human growth after birth. Oxford Univ. Press. N.Y., 212p. SOKAL, R. R.. AND F. J. ROHLF, 1 969. Biometry: The principles and practice of statistics in biological research. W H. Freeman and Co.. San Franc. 776 p. Clifford a. Hui Biomedtal Branch Naval Ocean Systems Center San Diego. CA 92152 LARVAL DEVELOPMENT OF GOBIESO\ RHESSODON (GOBIESOCIDAE) WITH NOTES ON THE LARVA OF RIMICOLA MVSCARVM Seven species of clingfishes of the genera Gohiesox and Rimicola occupy the rocky inter- and subtidal areas along the California coast. Extreme mod- ification of the pelvic fins into a suction disc ena- bles them to cling to rock and algal substrates. Although all clingfish species are listed as being uncommon to rare in California by Miller and Lea (1972). clingfish larvae are collected on a regular basis (although in low numbers) by monitoring programs dealing with fish larvae (Brewer,' McGowen,^ and White^). Of the seven species re- corded in southern California, adults of only two, G. rhessodon and R. nuiscariim, are usually en- countered (pers. obs.). Knowledge of larval stages of eastern Pacific (especially Californian) fishes is largely limited to pelagic species of those coastal species with pro- tracted pelagic larval periods (Ahlstrom 1965; Moser et al. 1977). Larvae of many nearshore, coastal fishes are undescribed. Recent concern over the affects of harbor development and ther- mal discharge and entrainment from power plants on fish populations has intensified the need for proper identification of fish eggs and larvae. The principal systematic work to date on the adults of eastern Pacific clingfishes was carried out by Briggs (1955). No previous works on the larvae of eastern Pacific clingfishes have been car- ried out, although the eggs and larvae of an Atlan- tic clingfish, G. strumosus, are well known (Run- yan 1961; Dovel 196.3). Descriptions of a larval series of G. r-hessodon and early larvae of R. muscarum are presented here as taxonomic aids to larval fish investigators working in the California coastal region. Methods and Materials Eggs and adults of G. rhessndnn and R. inus- cariini were collected in June 1977 from the inter- tidal zone at low tide at Catalina Harbor and Little Harbor, Santa Catalina Island, Calif. Adults with their eggs were transported to the Catalina Marine Science Center (CMSC) operated by the University of Southern California and maintained in tanks with running seawater. The failure of hatched larvae to feed (probably due to lack of suitable food) precluded culturing past 2 days (4.0 mm). Additional specimens of G. rhessodon utilized in the series were obtained by vertical plankton tow under a night-light at the CMSC dock in Big Fisherman's Cove (4.7 mm) in June 1977; by horizontal tow in King Harbor, Redondo 'Gary D. Brewer, Institute for Marine and Coastal Studies, University of Southern California, Los Angeles, CA 90007. Pers. commun. June 1977. ^Gerald E. McGowen, Southern California Edison (Occidental Collegel, Redondo Beach, Calif Pers. commun. June 1977. ^Wayne S. White, U.S. Fish and Wildlife Service, Laguna Niguel, Calif. Pers. commun. August 1977. 300 FISHERY BULLETIN VOL Beach, Calif. (7.5 mm), in 1977; by otter trawl in Marina del Ray, Calif. (12.0 mm), in June 1977: and from the larval fish collection of the Harbors Environmental Projects (University of Southern California) taken by horizontal plankton tows in Los Angeles Harbor (specimens collected in 1972-73). A total of 32 larvae from 2.6 to 7.5 mm of G. rhessodon were examined for larval charac- teristics. An additional 311 larvae ofG. rhessodon (2.9-7.5 mm) from King Harbor were checked spe- cifically for the presence of melanophores on the head. Larvae were examined and drawn using a Wild'* stereomicroscope fitted with a camera lucida. Standard length (SL) was measured from the tip of the snout to the tip of the notochord until completion of notochord flexion and then to the posterior margin of the hypural plate. Results and Discussion Gohieiox rhesiiidiiti The most distinctive character of G. rhessodon larvae was the presence of 8-17 (mean 12) stellate melanophores, which ran laterally in two or three rows from the pectoral fin region to just posterior to the anus (Table 1, Figures 1-3). The dorsum of the gut was also heavily pigmented with stellate melanophores (not included in the lateral melanophore counts). The gut pigmentation often obscured the well-developed swim bladder. Myo- mere counts ranged from 24 to 29 (mean 27) but were difficult to count, especially in early stages. All specimens up to 6.9 mm had four to seven ■•Reference to trade names does not imply endorsement by the National Marine Fisheries Service, NOAA. Table l. — Summary of larval measurements and adult counts for Gobiesox rhessodon andRtrnicola muscarum (Miller and Lea 1972 and present study). Gobiesox Rimicola Item rhessodon muscarum Larvae No. lateral melanophiores 8-17 (X = 12) 40-50 in in 2-3 rows 4 rows Myomere count 24-29 (X = 27) (') No ventral tail melanophores 4-7 Absent Size (mm) at onset ot pelvic fin development S.S 9 Adults No visible dorsal tin rays 10-12 6-8 No visible anal tin rays 9-10 6-8 No pectoral tin rays 19-21 14-17 No vertebrae '28- 29 ^35-36 regularly spaced melanophores along the ventral portion of the tail region. The length of the gut averaged approximately 35*7^ of body length in all specimens examined. Head length ranged from 19 to 25'7f SL in most specimens <6.5 mm. Individu- als 5^6.5 mm had a much larger head of about 33'7f of SL. All specimens had a stellate melanophore at the base of each pectoral fin which was covered by the opercular flap in later stages ( >6.9 mm). The larvae from Catalina and Los Angeles Harbor pos- sessed from zero to four spots on the dorsal portion of the head. Forty-two percent (mean 24, range 2.6-6.9 mm) of the larvae had head pigmentation in the form of spots. Of the larvae examined from King Harbor, 79^f (mean 311) lacked this head pigmentation. The larvae with and without head spots were very similar in every other respect. The larvae of G. rhessodon hatched at about 4.0 mm (three specimens ranged from 3.9 to 4.1 mm) from attached, monolayered eggs laid under rocks and cobble in the intertidal zone at Catalina Is- land. Nest guarding adults have been found from spring to early summer by Lavenberg.^ The rela- tively advanced larvae possessed well-developed jaws and pectoral fins at hatching and a laterally bilobed yolk, which was absorbed within the first 24 h. The gut had two or three constrictions giving it the appearance of being looped. The constric- tions were characteristic of the larvae up to 6.9 mm. Notochord flexion occurred between 5.5 and 6.9 mm, and caudal fin rays started to develop just prior to flexion. Dorsal and anal fin ray develop- ment began around 6.2 mm and the fins were de- veloped sufficiently for positive identification at about 6.9 mm. The development of the pelvic fins began at 5.5 mm and the characteristic suction disc was formed at about 7.0 mm. Transformation and settling probably occur between 8 and 12 mm as evidenced by an 8-mm planktonic specimen from King Harbor that possessed juvenile pigmen- tation (McGowen see footnote 2) and the 12-mm juvenile (Figure 3) which was collected by benthic otter trawl. This latter specimen exhibited the ability to cling to surfaces after capture. Larvae of G. rhessodon appear to be the most common Gobiesox encountered in several near- shore plankton sampling programs in southern California (Brewer see footnote 1; McGowen see footnote 2; White see footnote 3). This is to be expected in that previous species lists of adult/ 'Lateral melanophores obscurred myomeres so that accurate counts could not be taken ^Counts from Los Angeles County Museum specimen X-rays — G rhessodon (LACM1998), (ourspecimens, R rrruscarum (LACMW70-16). six specimens ^Robert J. Lavenberg. Curator of Fishes. Los Angeles County Museum of Natural History, Los Angeles, CA 90007. Pers. com- mun. June 1977. 301 4 . 7 WW 5.5 mm 6.2 wm Figure 1. — Developmental stages ofGobiesox rhessodon . The 3,9-mm larva was reared in the laboratory i <24 hi. The remainder are from plankton collections. juvenile fishes in southern California coastal areas have included G. rhessodon exclusively (Horn and Allen 1976). RiniiLoU. I numiirnm postanal myomere, and the absence of pigmenta- tion on the ventral tail region (Table 1). Yolk-sac larvae do not have head pigment. Adult counts are also markedly different from G. rhessodon (Table 1). Yolk-sac larvae of R. niuscarum (Figure 4), shortly after hatching, can be distinguished from G. rhessodon larvae at this stage by the greater number of lateral, stellate melanophores (40-50) in four rows that continue to the sixth or seventh Comparison Three species oiGobiesox, in addition to G. rhes- sodon. have been reported in southern California: G. macndricus, G. paplllifer, and G. eugrammiis. 302 Figure 2. — Pelagic larvae of Gobiesox rhessodon . 6 . 9 mm 7.5 nun Figure 3— Late pelagic larva (upper) and benthic juvenile (lower) of Gobiesox rhessodon . &,^X J2.0 mm The larval stages of G. maeandricus have recently been described by Marliave ( 1976). Based on Mar- liave's description and data from Richardson,^ G. maeandricus larvae differ from G. rhessodon mainly in that G. maeandricus lack lateral melanophores and possess more myomeres (31-33). In addition, adults of G. maeandricus are rare south of Point Conception, Calif. (Miller and Lea 1972). Gobiesox papillifer and G. eugrammus are also rare in southern California. Gobiesox papil- lifer has been reported only once in southern California, and G. eugrammus only ranges as far north as San Diego County (Miller and Lea 1972). The larvae of these two species of Gobiesox have ^Sally L. Richardson, School of Oceanography, Oregon State University. Corvallis, OR 97331. Pers. commun. May 1978. not been described, however, it is unlikely that any of these forms were among the specimens examined considering the distributions of the adults. The Atlantic species of Gobiesox, G. strumosus, studied by Runyan (1961) and Dovel (1963) was similar in appearance to G. rhessodon , but does differ in that the Atlantic species had 10-15 saddle melanophores (as opposed to lateral) and dis- played no ventral midline pigment in the early stages (<3.9 mm). Later larvae of G. strumosus also appeared to be more heavily pigmented on the trunk portion of the body (4.73-8.78 mm). The presence or absence of head pigmentation has been used by some investigators to separate Gobiesox larvae collected in southern California into two types. This character is variable in G. Figure 4. — Yolk stage larva ofRinncola mus- carum . 4 . 0 mm 303 rhessodon and, therefore, is not useful in distin- guishing it from other species. Acknowledgments For their advice and instruction, I thank Robert J. Lavenberg and H. Geoffrey Moser. Gary D. Brewer and Gerald E. McGowen gave advice and field and laboratoiy assistance, and provided speci- mens. Brian White, Marty Meisler, Marianne Ninos, Layne Nordgren, A. Kubo. Delaine Wink- ler, Sarah Swank, Scott Ralston, and Tina Beh- rents assisted in the field collection of eggs, larvae, and adult clingfishes. Michael H. Horn, Robert J. Lavenberg, H. Geoffrey Moser, and Sally L. Richardson greatly enhanced the manuscript through their critical reviews. Literature Cited AHLSTROM. E. H. 1965. Kinds and abundance of fishes in the California Cur- rent region based on egg and larval surveys. Calif Coop. Oceanic Fish. Invest. Rep. 10:31-52. BRIGGS. J. C. 1955. A monograph of the clingfishes (order Xenop- terygiii. Stanford Ichthyol Bull. 6:1-224. DOVEL, W. L. 1963. Larval development of clingfish, Gobiesox strumosus, 4.0 to 12.0 millimeters in total length. Chesapeake Sci. 4:161-166. HORN, M. H., .'^ND L. G. ALLEN. 1976. Numbers of species and faunal resemblance of marine fishes in California bays and estuaries. Bull. South. Calif Acad. Sci. 75:159-170, MARLIAVE. J. B. 1976 The behavioral transformation from the planktonic lar\'al stage of some marine fishes reared in the labor- atory. Ph.D. Thesis, Univ. British Columbia, Van- couver. 231 p. Miller, D. J., and R. N. Lea. 1972. Guide to the coastal marine fishes of California Calif Dep. Fish. Game, Fish Bull. 157, 235 p. Moser, H. G., E, H. Ahlstrom, and E. M. Sandknop. 1977. Guide to the identification of scorpionfish larvae I family Scorpaenidae) in the eastern Pacific with com- parative notes on species oiSebastes andHeltcolenus from other oceans U..S. Dep. Commer., NOAA Tech. Rep NMFS Circ, 402, 71 p, RUNYAN, S. 1961. Early development of the clingfish, Gobiesox strumosus Cope. Chesapeake Sci. 2:113-141. SPRING AND SUMMER FOODS OF WALLEYE POLLOCK, THERAGRA CHALCOGRAMMA, IN THE EASTERN BERING SEA The walleye (Alaska) pollock, Theragra chalco- grainma (Pallas 1811 ), is the most abundant com- mercial fish species in the eastern Bering Sea (Pereyra et al.M and plays an important role in ecosystem trophodynamics of the region. To obtain better knowledge of the role of the pollock as a predator, we have studied the stomach contents of pollock from the eastern Bering Sea collected on U.S. research vessels in the summer of 1974 and on Soviet and Japanese fishing vessels in the spring of 1977. Results from this study contribute to our under- standing of feeding habits; information on sea- sonal and size-dependent changes in feeding be- havior are used to model interactions between species (trophodynamics), and to predict the influence of commercial fisheries on the abun- dance of populations in the eastern Bering Sea (Laevastu and Favorite-'*). Methods Pollock stomachs were collected by U.S. fisheries observers, on an opportunistic basis, aboard Soviet and Japanese motherships in the eastern Bering Sea. Samples were collected in the region of the continental shelf break in April and May 1977 (Figure 1, Table 1). The stomachs were removed, tied in cheesecloth, and preserved in di- lute Formalin'' (ca. 5Vf ) and sent to the Northwest and Alaska Fisheries Center, National Marine Fisheries Service, NOAA, Seattle, Wash., for analysis. Identifiable matter was separated by major taxa. Wet weight for each taxa was deter- mined after blotting with paper towels. Uniden- LARRY G. ALLEN Department of Biological Sciences University of Southern California Los Angeles. CA 90007 'Pereyra, W. T., J. E Reeves, and R. G. Bakka- la. 1976 Demersal fish and shellfish resources of the eastern BeringSeain the baseline year 1975. Unpubl. manuscr, vol. 1, 619 p. Northwest and Alaska Fisheries Center, National Marine Fisheries Service, NOAA, 2725 Montlake Blvd. E., Seattle, WA 98112. ^Laevastu. T. and F. Favorite. 1976. Evaluation of .stand- ing stocks of marine resources in the eastern Bering Sea. Un- publ. manuscr.. .35 p. Northwest and Alaska Fisheries Center, National Marine Fisheries Service, NOAA, 2725 Montlake Blvd. E., Seattle. WA 98112. ^Laevastu, T, and F Favorite. 1976. Dynamics of pollock and herring biomasses in the eastern Bering Sea. Unpubl. manuscr., 50 p. Northwest and Alaska Fisheries Center. Na- tional Marine Fisheries Service, NOAA, 2725 Montlake Blvd. E., Seattle, WA 98112. ''Reference to trade names does not imply endorsement by the National Marine Fisheries Service, NOAA. 304 FISHERY Bl'LLETIN VOL 77. NO I.Ii)79. 180° 178° 176° 174° 172° 170° 168° 166° 164 162° 160° 158° 156° Figure l. — Location sites where walleye pollock stomach samples were collected in the eastern Bering Sea. Table l. — Summary of walleye pollock stomach samples col- lected in the eastern Bering Sea. No of Depth Average Sampling stomachs range (m) depth Vessel penod collected of bottom (m) Oregon (US) July 1974 352 71-132 99 Chiltubu Maru (Jpn) Apr 1977 180 124-210 194 Tiraspol (USS.R) Apr 1977 225 128-256 167 7enyo Maru #3 Apr -May (Jpn.) 1977 Total 92 849 110-165 132 tifiable matter was classed as "digested material" and also weighed. Percentage of food weight for each major food category, by fish-length group, was calculated as was the weight for each major food category per fish for each length group. Empty stomachs were not included in the analysis. Detailed length data from foreign fishing ves- sels were available only from the Japanese fishing vessel Tenyo Maru. These data were analyzed by 10-cm fork length classes. Fish lengths from the Japanese fishing vessel Chikuhu Maru and the Soviet fishing vessel Tiraspol were recorded only as greater or less than 35 cm (the approximate length at sexual maturity). This is also the size at which pollock become markedly cannibalistic (Takahashi and Yamaguchi 1972). Data from all three observer cruises were combined using these two major size categories to obtain sufficient sam- ple sizes for comparison with the data collected in 1974. Data collected in 1974 (RV Oregon) were examined by 5-cm length classes. The larger number of stomach samples collected during this cruise allowed a finer analysis of size-related changes in feeding habits. The methods used for processing samples from this cruise were approx- imately the same as for samples from the foreign vessels. Results An examination of stomach content weight by fish-length group provided evidence of related shifts in principal food categories in the diet of pollock (Figures 2, 3). In both spring 1977 and summer 1974, the percentage of copepods as food biomass tended to decrease with increasing size of pollock. The percentage offish in pollock stomachs tended to increase with the size of pollock. Euphausiids were important food components in most length classes in both sampling periods. Am- phipods, however, were only abundant in 305 lOOr FIGURE 2— Percent biomass of stomach contents by taxa per 5-cm length group of Bering Sea walleye pol- lock, summer 1974, CO <50 o III FISH SHRIMP DIGESTED MATTER EUPHflUSIIDS AMPHIPOOS COPEPODS 519 20-24 25-29 30-34 35-39 40-44 45-49 50' LENGTH (cm) 100 80-- 60 5 O 40 20- 0^ DIGESTED MATTER FISH EUPHAUSIIDS AMPHIPOOS COPEPODS 1 52'» 25-34 35-44 LENGTH (cm) Figure 3. — Percent biomass of stomach contents by taxa per 10-cm length group of Bering Sea walleye pollock, spring 1977 stomachs collected in summer 1974. and the per- centage of amiphods as food biomass tended to increase with increasing pollock size. Other food organisms that appeared in the diet are listed in Table 2. The analysis of stomach contents by weight-per- centage masks the behavioral aspects of pollock feeding due to size differences in food organisms. More information can be obtained from the data when analyzed as grams of food organisms per fish for each length class (Tables 3, 4). From this analysis it appears that larger pollock tended to exclude smaller food items from their diet. As the pollock grew larger they fed more on euphausiids, amphipods, and fish. 306 Table 2. — Proportion of taxa observed in walleye pollock stomachs in the eastern Bering Sea. Taxa Fish Copepods Euphausiids Amphipods Chaetognaths Cephalopods Mollusks Ostracods Larvaceans Annelids Shrimp Cumacean Nemerteans Mysids Crab Unidentified Digested Total Table 3. — Grams of food organisms per fish mot including fish with empty stomachsl in each size class, Tenyo Mam, spring 1977. Observei cruises. Oregon cruise. spring 1977 summe 1977 Weight (g) °o biomass Weight (g) °o biomass 277 07 28 53 223 21 25 94 349 81 36 02 44 60 518 210 02 21 62 81 70 949 2 15 0 22 235 63 27 38 0 47 0 05 17 77 2 07 0 30 0 03 — — 0 15 0 02 0 89 0 10 0 02 — _ _ 0 08 0 01 008 001 3 99 0 42 3 40 0 40 1291 1 33 979 1 14 — — 001 _ — — 092 0 11 — — 0,55 0 06 — _ 456 053 — — 1 64 0 19 114.09 11 75 235 83 27 40 971,06 100 00 860 58 100 00 Fork length ( :m) of pollock Item 15-24 25-34 35-44 •45 Grams copepods/fish 008 097 0,66 0 14 Grams euphausiids./fish 0 04 0 09 035 082 Grams tish,fish _ — 0 69 528 Grams total food,'fish 0 20 122 2 04 6 50 No of fish with food 6 28 14 19 Percentage of fish with empty stomachs 57 26 18 17 Data on the species composition offish in pollock stomachs were available from the summer cruise of 1974 [Oregon). Fish ingested were identified from the stomachs of 27 pollock ranging in fork length from 26 to 57 cm (mean = 40 cm). Of the fish ingested, 89^/f by weight and 39^f by number were Table 4. — Grams of food organisms per fish (not including fish with empty stomachs) in each size class, Oregon, summer 1974. Fork length (cm) of pollock Item •20 20-24 25-29 30-34 35-39 40-44 45-49 ■49 Grams copepods/ftsh 0 42 0 26 0 14 0 16 0 13 0 02 _ _ Grams amphipods/fish 0 04 0 04 0 27 0 33 080 2 90 2 20 1 23 Grams euphausiids/lish — — 0 20 038 030 0 25 0 31 031 Grams shrimp/(ish — — — — 001 — — 0 40 Grams fish/dsh — — 001 0 40 0 73 0 02 718 0 71 Grams total loodlish 0 62 0 70 1 27 1 97 291 4 57 1 1 24 4 00 No ot tish with food 20 14 94 64 70 22 18 22 Percentage of fishi witti empty stomactis 35 0 7 2 4 8 14 4 pollock. Other fishes identified included gadids, cottids, hexagrammids, and zoarcids. Pollock food composition in summer 1974 and spring 1977 can be compared although geographic locations of stomachs collected varied (Figure 4). Pollock were observed with more copepods as a percentage of food biomass in spring 1974 than in summer 1977. Amphipods were nearly absent from stomachs collected in spring 1974 but were an important food component in summer 1977. 100 D iscussion Previous studies on the food of the walleye pol- lock in the eastern Bering Sea indicated that in winter 1972, juvenile pollock fed mainly on euphausiids, while adult pollock fed on euphausiids, small pollock, and other fish (Mito 1974). In summer 1970, juvenile pollock fed on copepods and euphausiids, while adult pollock fed on euphausiids, small pollock, and other fish (Takahashi and Yamaguchi 1972). Our study in- dicates that in summer 1974 juveniles fed mostly on copepods, euphausiids, and amphipods, while adults fed on euphausiids, amphipods, and fish. In spring 1977, juvenile pollock fed mostly on copepods and euphausiids, while adult pollock fed on copepods, euphausiids, and fish. The results of these studies indicated that euphausiids are an important year-round food source of both juvenile and adult pollock. Fish appear to be an important year-round resource to adult pollock. The relative importance of other prey organisms in the diet of pollock seems to fluctuate between the studies. Adult pollock tend to obtain a greater percen- tage of their food biomass from larger prey or- ganisms than juvenile pollock, by ingesting more fish, euphausiids, and amphipods as they grow larger (Figures 2, 3). Additionally, larger pollock tend to exclude copepods from their diet (Tables 3, 4). These observations could result from an active process, based on preference or capture efficiency. < 5 o 50 FISH SHRIMP DIGESTED MATTER ANNELIDS CHAETOGNATHS EUPHAUSIIDS AMPHIPODS COPEPODS t35cm >35cm SUMMER 1974 t35cm >35cm SPRING 1977 FIGL'RE 4. — Percent biomass of stomach contents by taxa for adult and juvenile walleye pollock in summer 1974 and spring 1977 in the Bering Sea. or a passive process, resulting from spatial dis- tribution. Additional information is needed to understand the complexities of pollock feeding behavior, in- cluding: 1 ) seasonal variations in feeding behavior, 2) geographical variations, and 3) effects of alter- nate prey on cannibalism and grazing on other fish. This information would be useful in eco- system modelling to understand the natural com- petitive and predatory interactions between fish populations and the potential effects of heavy exploitation. Acknnw Icdgnients We thank the following persons at the North- west and Alaska Fisheries Center: Donald Day for collecting and making preliminary analysis of 1974 data, Robert French for arranging the collec- tion, and Beverly Vinter and Jay Clark for iden- 307 tifying the contents offish stomachs collected in 1977. Literature Cited MITO, K. 1974. Food relationships among benthic fish populations in the Bering Sea on the Theragra ckalcograninia fishing ground in October and November of 1972. (In Jpn.l M.S. Thesis, Hokkaido Univ.. Hokkaido, Jpn.. 135 P Takahashi, Y., and H. Yamaguchi. 1972. II — 2. Stock of the Alaska pollock in the Bering Sea. [In Jpn., Engl. summ. on p. 418-419, J In Svmposium on the Alaska pollock fishery and its resources, p. 389-.399. Bull, Jpn. Soc Sci. Fish. 38. KEVIN Bailey Jean Dunn Northwest and Alaska Fisheries Center National Marine Fisheries Sennce. NOAA 2725 Montlake Boulevard East, Seattle. WA 98112 FECUNDITY OF THE ATLANTIC MENHADEN, BREVOORTIA TY'RANNVS Although some work has been done to determine the time and place of spawning, age of spawning, and fecundity of Atlantic menhaden, Brevoortia tyrannus (Higham and Nicholson 1964), no at- tempt has been made to relate fecundity and age. In this study, I 1 ) examined the ovaries offish 1 to 5 yr old collected during autumn 1970, in the vicin- ity of Beaufort, N.C.; 2) estimated the number of ripening ova in sexually mature fish; 3) calculated the mean number of ova spawned by fish of each age; and 4) determined the reproductive potential and the net reproductive rates for the 1 954-63 year classes. Atlantic menahden, family Clupeidae, consti- tute a single biological population (Nicholson 1972, 1978; Dryfoos et al. 1973) inhabitating coastal waters from Florida to the Gulf of Maine. It is subjected to an intensive purse seine fishery from Florida to New England. Fish are landed daily at reduction plants and processed into meal, oil, and solubles. Fishing begins in Florida and North Carolina in late April, in New Jersey coast- al waters in early June, and in New England wa- ters in late June. Fishing usually ends in mid to late November, except in the vicinity of Beaufort where schools of migrating fish of all ages from northern areas provide an intensive fishery from November to late December or early January. Atlantic menhaden make extensive coastal movements and during the fishing season are stratified along the coast by age and size. In au- tumn most fish north of Virginia move southward and by January are concentrated in offshore wa- ters from Cape Hatteras to northern Florida. About mid-March they begin a northward move- ment and by mid-June are stratified in coastal waters by age and size, the younger and smaller farther south and the older and larger farther north (Nicholson 1971). South of Cape Hatteras and in Chesapeake Bay most fish are ages 1 and 2. Age-2 fish dominate in coastal waters off New Jersey, ages 3 and 4 in Long Island Sound, and age 4 and older north of Cape Cod. Although they may live to age 9, few older than age 6 are caught. Menhaden spawn in offshore coastal waters where the eggs hatch in 36 to 48 h (Reintjes 1962). Larvae, carried inshore by ocean currents, enter estuaries where they metamorphose to the adult form at about 35 mm total length. Although some spawning occurs in summer and early autumn in Long Island Sound and New England waters — the only areas where fish of spawning age are found during that time — most spawning occurs in the South Atlantic area from January to March and in the Middle Atlantic area from October to December and March to May. Although there ap- pears to be only one spawning cycle each year, evidence is uncertain as to whether Atlantic menhaden are fractional spawners (Higham and Nicholson 1964). As the population size decreased in the 1960's age structure also changed. Fish older than age 3 became extremely scarce, and most plants in the northern areas that were dependent on older fish closed. By 1969 few fish older than age 4 were landed, even in the North Carolina fall fishery, which traditionally had been dependent on older fish (Nicholson 1975). Collection and Preparation of Ovaries Ovaries were collected from 17 November to 29 December 1970 during the North Carolina fall fishery at the same time catches were being sam- pled routinely for age and size (June and Reintjes 1959). Sampling personnel measured and weighed the fish, removed scales for aging, and removed the ovaries. Only ripening ovaries fitting the 308 FISHERY BL'I.I.ETIN VOL 77. NO I.li)7() Stage III classification of Higham and Nicholson (1964) were retained. They were blotted on paper towels to remove excess moisture, weighed to the nearest 0.1 g, split longitudinally and turned in- side out, and placed in individual jars of Gilson's fluid modified by Simpson (Bagenal 1967). The jars were shaken to liberate all eggs. After the Gilson's fluid was poured off, along with most pul- verized ovarian tissue, the ova were washed and decanted in water several times and forced through a sieve to remove remaining fragments of ovarian tissue, spread on large trays covered with paper towels, and dried under incandescent lamps. Higham and Nicholson (1964) described four stages in the maturation of ovaries. Ovaries in the immature and intermediate stages contain only undeveloped ova; ovaries in the maturing and ripe stages contain developing as well as undeveloped ova. They concluded that only maturing ova ripened during each spawning period. Maturing ova were described as being opaque and yellow and between 0.35 and 0.78 mm in diameter. I fol- lowed this description to separate immature from maturing ova. I also measured fecundity by es- timating the number of maturing ova in both ovaries. Instead of counting ova in sample sections of the wet ovary, however, I counted ova in two replicate samples of the dried ova that had been separated from connective tissues. Before being weighed, eggs were allowed to equilibrate with air humidity. Each sample was weighed to the nearest 0.01 mg. If both ovaries weighed more than 12 g, two samples, each weighing 1/350 of the total weight, were taken. If the ovaries weighed 1 2 g or less, two replicate samples, each weighing 0.035 g, were taken, since fecundity would have been difficult to estimate in samples smaller than 0.035 g. Proportional sampling tended to minimize the counting error for a fixed amount of counting effort. Ova in each sample were counted under a stereoscope. The number of ova in both ovaries, A^, was estimated by multiplying the number of ova in the two samples, N,, by the ratio of total dry weight of eggs, W, , to dry weight of eggs in samples, W^ (N =A^sW,/W,). To minimize count- ing error between samples, a coefficient of varia- tion of 3.0^f or less was maintained. Preliminary calculations indicated that fecun- dity could be estimated with a precision of about 159c if 30 fish were selected randomly from each age-class. The ultimate number in each age-group was age 1, 21; age 2, 34; age 3, 33; age 4, 12; and age 5, 1 (Table 1). Table l. — Mean number of eggs (thousands! and mean ovary weight (grams), by age. for Atlantic menhaden sampled from the North Caro: Ima fall fishery, 1970. No Mean Mean of no of cv ovary C-V. Age fish eggs Range (%) wt Range (%) 1 21 115 8 26 5-250 7 47 179 4 0-43 5 54 2 34 177 4 39 2-368 8 50 30 1 5 0-62 5 55 3 33 302 8 127 7-458 3 30 50 9 21 1-96 9 34 4 12 308 6 142 7-514 0 36 48 5 22 0-74 8 36 5 1 568 4 - - 900 - — 'Coefficient of variation Fecundity The regressions of fecundity on ovary weight, F = 6,908(OW) - 17.937(OW)2, and fecundity on total fish weight, F = 293(TW) + O.'ZUiTW)^, were curvilinear, but fecundity on body weight only,F = 488(BW), was linear. Thefl^ values were 0.981, 0.675, and 0.916, respectively. Although the rela- tive merits of predicting fecundity from different variables are debatable (Bagenal 1967), these three models seem less useful than fecundity on age, which can be used to determine reproductive potential and calculate life table estimates, and fecundity on fish length, which can be used to predict the number of eggs spawned by different size classes. A statistical test failed to support the curvilinear relation implied by a plot of fecundity on age, perhaps because of the few fish in older age- groups. Of the two linear models tested for es- timating fecundity at age, I selected F = 92,592( Age ) as the better estimator (r^ = 0.879; SE slope = 3,440; SE regression = 89,110). It had tighter confidence limits and a higher r^ than the model F = a + bL. A logarithmic model (log F = a + bL) was selected to describe the curvilinear relation be- tween fecundity and length and was fitted to both my data and the data of Higham and Nicholson ( 1964) (Figure 1). Values predicted by this model fit observed values more closely over the entire range than those predicted by the nonlogarithmic model (F = fcjL -H 6.2L^). The difference in the slope coefficients of the logarithmic model fitted to the two sets of data was significant (P<0.001). Esti- mated fecundities were in reasonable agreement for fish up to 275 mm, but diverged for large fish. For 3.50 mm fish the model fitted to Higham and Nicholson data predicted about 1.75 as many ova as the model fitted to my data. Differences in fish ages or in the time of year fish were collected, or actual changes in fecundity might account for differences in estimates of ova 309 log f= 7 2227 + 0 0I76FL IHighom and Nicholson) 0 V 200 250 275 300 FORK LENGTH (mm) Figure l— Regression of fecundity on fork length for Atlantic menhaden showing confidence limits on the mean at 95'? level ForlogF = 7.2227 + 0.0176^,^ = 38, SE regression = 0.3069; SE regression coefficient = 0.001 1, r^ = 0.726; for logf" = 8.6463 + 0.012QFZ,, Af = 101. SE regression = 0.3330, SE regression coefficient = 0.0007, r^ =0.871 for larger fish. Higham and Nicholson { 1964), e.g., had four fish with between 400,000 and 500,000 ova, four with between 500,000 and 600,000, and one with over 600,000, whereas from nearly three times as many fish I had only two with over 500,000 and six with between 400,000 and 500,000. I believe, however, that differences in counting techniques caused the differences in ova estimates. I used proportional sampling, whereas they did not. I separated the eggs from each other and from the connective tissue, dried and weighed the eggs, and then counted those in a sample. They counted the eggs in a sample from the wet ovary. Also, a certain amount of subjectivity is involved in distinguishing between maturing and non- maturing ova. Reproductive Potential and Net Reproductive Rate Since the sex ratio of Atlantic menhaden is about equal (Nicholson and Higham 1964), I was able to calculate the annual numbers of females of each age in the population, 1955-68, by dividing half of the number offish caught at each age by the exploitation rate for all ages (Schaaf and Huntsman 1972). When I collected my material in 1970, recording the maturing stage offish in catch samples had been discontinued, but Higham and Nicholson (1964) estimated that about 10'7f of age-1 fish, 909c of age 2, and lOf/i of age-3 or older fish examined during the North Carolina fall fishery in October-December from 1955 to 1959 had maturing ovaries. From these figures I calcu- lated the number of females of each age that would spawn each year and multiplied it by the mean number of ova spawned by fish of each age to estimate the number of eggs spawned each year (Table 2). The net reproductive rate, R„,oi' a population is defined as the sum of the products of the age- specific survival rate 4, and the age-specific natal- ity rate w,, of females (Odum 1971). A value of 1.0 for each generation would indicate that the popu- lation is stable and that there is a balance between births and deaths. In fish populations it is nearly impossible to obtain accurate counts or estimates of the number of offspring produced by each age- group. It is possible, however, to estimate the mean number of eggs spawned for fish of each age. If this variable is used for m, in the formula given by Odum and ifi/,"!, is called, /?o*. then the recip- rocal of /?„* should be a rough estimate of the survival rate of female eggs, providing the popula- tion is approximately stable. Although the Atlan- tic menhaden population declined after about 1960. 1 think in view of the imprecise estimates of other parameters, that it can be assumed stable for the purpose of estimating egg mortality. Ro* values were calculated for the 1954-63 year classes. I assumed a 0.65 survival rate up to age 1, which I divided into the estimated number offish that were age 1 (Schaaf and Huntsman 1972) for an estimate of the number of fish at the postlarval stage. Since the sex ratio is equal, this number divided into the estimated number offish surviv- ing to each age iSchaaf and Huntsman 1972) Table 2. — Estimated number of eggs (multiply by 10"! spawned by Atlantic menhaden, by year and age. Age in ^ears Year 1 2 3 4 5 6 7-9 Total 1955 83 0 377.6 723 2 1195 43.6 87 35 1.359 1 1956 69 7 443 9 1037 465 1 1188 31 1 10 7 1.243 0 1957 106 9 136.6 1667 127 2 144 9 197 60 708 0 1958 161 1 1313 510 62.8 429 28 8 30 480 9 1959 73.0 599.2 85.9 40 7 530 234 106 885 8 1960 329,8 205.3 457 9 142 0 59.4 21 1 68 1,222 3 1961 44 8 1,938 4 51 2 1046 127 43 1 5 2,1575 1962 57 7 270 2 877 6 85 0 85 0 124 34 1.391 3 1963 422 143 8 88 0 136 6 34 0 130 26 460 2 1964 38 4 95 3 34 1 199 210 50 1 4 215 1 1965 322 108 0 28 2 56 4 7 34 04 1825 1966 31 2 44 0 90 1 1 04 05 02 86 4 1967 20 5 101 1 11 8 1 5 — — — 134 9 1968 41 3 91 2 247 30 02 — — 160 4 310 yielded age-specific-survival fractions (/, ) for females of each year class. Ro* for each year class ranged from 7,100 to 25.800 (Table 3). The recip- rocal of these numbers, 0.000141 and 0.000039, respectively, indicate a survival rate ranging from 39 to 14 1 females, or 78 to 282 fish of both sexes, for each 1,000,000 eggs spawned. Any estimate based in turn on a series of rather imprecise and arbitrary estimates must be viewed with caution, and this one is no exception. Yet it is in line with current knowledge that the survival rate of pelagic fish eggs is extremely low. Table 3.— Net reproductive rates (/?„*! and their reciprocals (1/ffo*) for the 1954-63 year classes of Atlantic menhaden. Year Year class flo- l/flj- class fio- 1'flo- 1954 16.546 0 000050 1959 22,297 0000045 1955 7.109 0 000141 1960 10,120 0 000099 1956 25.932 0 000039 1961 14,073 0 000071 1957 11.850 0 000084 1962 11.024 0 000091 1958 21.856 0 000046 1963 11,181 0 000089 Literature Cited Bagenal, T. B. 1967. A short review offish fecundity. In S. D. Gerking (editor). The biological basis of freshwater fish production, p. 89-111, Blackwell Sci. Publ,. Oxf , Engl DRYFOOS. R, L., R. P, CHEEK, AND R. L. KROGER 1973, Preliminary analyses of Atlantic menhaden, Bre- voortia tyrannus, migrations, population structure, survi- val and exploitation rates, and availability as indicated from tag returns. Fish, Bull., U.S, 71;719-734. HIGHAM, J, R., AND W. R, NICHOLSON 1964. Sexual maturation and spawning of Atlantic menhaden. U,S, Fish Wildl. Serv., Fish, Bull. 63:255- 271. JUNE, F, C AND J, W. REINTJES 1959. Age and size composition of the menhaden catch along the Atlantic coast of the United States, 1952-55; with a brief review of the commercial fishery. U.S, Fish Wildl, Serv,, Spec. Sci, Rep, Fish, 317. 65 p. NICHOLSON. W. R. 1971. Coastal movements of Atlantic menhaden as in- ferred from changes in age and length distributions. Trans, Am, Fish, Soc, 100:708-716, 1972, Population structure and movements of Atlantic menhaden, Brevoortia tyrannus, as inferred from back- calculated length frequencies. Chesapeake Sci, 13:161- 174, 1975, Age and size composition of the Atlantic menhaden, Brevoortia tyrannus, purse seine catch, 1963-71, with a brief discussion of the fishery. US, Dep, Commer,, NOAA Tech. Rep, NMFS SSRF-684, 28 p. 1978, Movements and population structure of Atlantic menhaden indicated by tag returns. Estuaries 1:141- 150, NICHOLSON, W, R., AND J, R, HiGHAM, JR 1964. Age and size composition of the menhaden catch along the Atlantic coast ofthe United States, 1959, with a brief review ofthe commercial fishery, U,S. Fish Wildl, Serv,, Spec, Sci. Rep. Fish 478, 34 p, ODUM, E. P, 1971. Fundamentals of ecology, 3d ed W B, Saunders Co,, Phila,, Pa,, 574 p REINTJES. J, W, 1962. Development ofeggs and yolk-sac larvaeofyellowfin menhaden. U.S.Fish Wildl, Serv., Fish, Bull, 62:93-102, SCHAAF W. E., AND G. R, HUNTSMAN 1972. Effects of fishing on the Atlantic menhaden stock: 1955-1969. Trans, Am, Fish, Soc 101:290-297, CHARLES S, DIETRICH. jR Southeast Fisheries Center Beaufort Laboratory National Marine Fisheries Service, NOAA PO Box 570, Beaufort, NC 28516 ROLE OF LAND AND OCEAN MORTALITY IN YIELD OF MALE ALASKAN FUR SEAL, CALLORHINVS URSINVS The annua! commercial harvest of male fur seals has fluctuated widely and declined since the early 1950's, This has occurred despite a fairly stable harvesting regime and efforts to maintain the population near the level believed to be consistent with maximum sustainable productivity (Chap- man 1961, 1964, 1973). Variations in early natural mortality are mainly responsible for these changes in the harvest of males which occurs at ages 2-5 yr (mostly 3-4 yr). Kenyon et al. (1954) and Chapman' emphasized that natural mortal- ity between birth and age 3 yr is high and that most of it probably occurs during the first winter just after weaning. This report gives estimates of male survival from natural mortality of pups on land and from the first 20 mo of life at sea, a total interval of approximately 2 yr. The importance of pup num- bers and early survival rates in determining an- nual variations in abundance at age 3 yr is quan- tified also. Methods Data for survival estimates are in Table 1. The age composition of annual kills before 1950 cannot be determined accurately because an aging technique was not available until then (Scheffer 'Chapman, D. G, 1975, Methods of forecasting the kill of male seals on the Pribilof Islands. Background paper for the 19th Annual Meeting ofthe North Pacific Fur Seal Commission, 10 p- (Unpubl. rep.) FLSHERY BULLETIN VOL 77, NO 1, 1979. 311 Table l .—Estimated numbers of male pups (born, dead, and livmg at the time of migration! and age-specific commercial kill of males from the 1950-70 vear classes on St. Paul Island, Pribilof Islands. Alaska.' Number ot pups (thousands) Number killed at age Year class Born Dead Living 2 3 4 5 2-5 1950 225.5 26 7 199 855 40.656 15,365 332 57,208 1951 223.5 353 188 1.384 32,350 18,083 3,057 54.874 1952 219.0 20 4 199 1.735 30,773 31,410 675 64,553 1953 222.5 39 1 183 839 38,312 8,855 54 48.060 1954 225.0 48 1 177 2,918 23,473 5,599 554 32.544 1955 230.5 37 8 193 1,015 27,863 10,555 115 39.548 1956 226.5 49 4 177 885 10,671 2,762 532 14.650 1957 210.0 30 8 179 2.590 24,283 15,344 773 42.990 1958 193.5 156 176 1.977 48.458 14,149 1,587 66,171 1959 167.5 20 0 148 2.820 26.456 14,184 1,764 45,224 1960 160.0 314 129 1,619 14.310 10,533 1,240 27,702 1961 168.4 29 0 139 1,098 22,468 12,046 1,270 36,882 1962 139.2 22 6 117 2,539 19,009 12,156 1.287 34,991 1963 132.0 163 116 1,264 25,535 11,785 1.542 40,126 1964 142.5 108 131 3,143 26,991 13,279 1.469 44,882 1965 133.4 196 113 2,200 18,706 10,565 731 32,202 1966 150.0 107 138 1,673 17,826 11,548 1.338 32,385 1967 142.0 70 135 2,640 22,176 12,503 2.185 39,504 1968 117.5 126 105 1,725 12,888 14.932 721 30,266 1969 116 8 66 110 323 15.024 10.800 1.631 27.778 1970 1158 103 105 916 16.337 15.533 1,402 34,188 'Sources tor data in Table 1 and tootnotes are given belov^r Pups born 1 950-60 table 1 1 2 Irom Ctiapman 1 1 973) . 1 961 -65 and 1 969-70, table 1 4 from Marine Mammal Biological Laboratory ( 1 971 ■). 1 967-68, table 1 0 from l^anne lulammal Division (1976^) A 1 1 sex ratio is assumed (Kenyon et al 1954, H Kaiimura pers common ) Dead pups 1 950-60 (except 1 952), appendix table 39 from Marine Mammal Biological Laboratory ( 1 961 ) . 1 952, counts (Irom same source) on sample rookenes only, extrapolated to island total Irom average contribution ol these rookeries to known totals in 1951 and 1953 1961-69 table A.12 Irom Manne Mammal Biological Laboratory (1971) A 1 1 sex ratio is assumed (Kenyon et al 1954, M C Keyes pers common ) Living pups Pups born less dead pups, rounded to nearest thousand Kill by age 1950-56 year classes, table 1 trom Marine Mammal Biological Laboratory (1961'), 1957-64 year classes, table 1 trom Manne Mammal Biological Laboratory (1971), 1965-70 year classes table 1 from Marine Mammal Division (1976^) "Marine Mammal Biological Laboratory 1 971 Fur seal invesligation, 1 970 Unpubl manuscr , 1 55 p US Dep Commet . Natl Mar Fish Serv Northwest Fish Cent , Seattle, WA 98112 "Marine Mammal Division 1976 Fur seal investigations, 1975 Unpubl manuscr , 1 15p US Dep Commer Natl Mar Fish Serv , Northwest Fish Cent , 'Marine Mammal Biological Laboratory 1961 Fur seal investigation, Pribilol Islands, Alaska Unpubl manuscr , 148 p US Fish Wildl Serv , Bur Commer Fish 1950). However, the average numbers of pups migrating from land and of seals harvested at age Syr are approximated for the 1920-22 year classes in order to include in the yield-pup relationship a data point for the relatively small pup population then present. It should be mentioned that basic data were not taken during 1925-46 from which to estimate annual pup production. The 1920-22 averages are based on kill data from Lander and Kajimura^ and on pup data from Kenyon et al. ( 1954). The average number of pups born annually on St. Paul Island during 1920-22 was approximately 150,700. Their mean mortality rate on land was 2.2'7f , so an average of about 74,000 male pups migrated to sea annually. Be- cause the harvest always has been selective for animals the size of 3- and 4-yr-olds, these 1920-22 year classes contributed to the kills mainly in 1923-26. The annual average kill then was 14,300, of which about 9,100 were age 3 yr assuming the same average (64'7f ) as in the kills from the 1950- 70 year classes (Table 1). 'Lander, R. H, and H Kiyimura, 1976 Status of northern fur seals. Food and Agriculture Organization of the United Nations, Scientific Consultation on Marine Mammals, Bergen, Norway, August 31-September 9, 1976, 50 p. (Unpubl. rep. I The kill of 3-yr-olds is used as an index of abun- dance at that age. The assumption is justified reasonably well by the generally stable harvest- ing regime and the usual predominance of this age group in the kills. Annual population monitoring and behavioral data (Bartholomew and Hoel 1953; Peterson 1968) show the median date of birth on St. Paul Island is about 8 July, pup mortality on land is essentially over by mid-August, and the median date when pups migrate to sea is around 1 November. Survi- val of pups on land is calculated as the ratio of living pups to pups born (Table 1). Few seals haul out on land until 24 mo of age, and survival is estimated for the first 20 mo at sea. These ocean survival rates are calculated from the data for living pups and age-specific kills (Table 1) and from the model of Lander (1975) with time intervals appropriately modified. Results Figure 1 shows wide fluctuations in the kill at age 3 yr around the regression line for pups born. After the effects of pup mortality on land are re- moved, high variability persists around the line 312 40 z < in o 20- PUPS BORN 50 •53 Ul •58 UJ > PUPS MIGRATING < FROM LAND X 40- 53 '50 t/1 ' _J < 51 ^^ UJ U1 ^^ •s? LU _) 63 61 59 y^ •ss < 5 6 7A , .'57 ll- 20- ^1^ ^ 54 o 70, ^^ • 56 cc ly* .69 UJ y •60 CD ^y^ 68 2 ^^ •56 3 *20-22 2 90 150 210 NUMBER OF MALE PUPS (THOUSANDS) FiGLTRE 1.— Yield-pup relation for male fur seals of the 1920-22 and 1950-70 year classes from St Paul Island Least squares regression lines are shown for pups bom (a = 2.341. 6 = 0.126) and for pups migrating from land (a = 3.740, b = 0.188). for pups migrating from land. Most of the varia- tion in abundance at age 3 yr is evidently due to changes in the ocean survival rate undergone by the different year classes, not to changes in the rate of pup survival on land. Estimated survival rates for the 1950-70 year classes are in Table 2 (ocean survival could not be estimated for the 1920-22 year classes without age composition data). The means and ranges of survi- val estimates in Table 2 are 87<7f ( 78-95'7f ) for pups on land, 40% (18-497^ ) for the first 20 mo at sea, and 35^?^ (14-45'7f ) for both stages between birth and 2 yr of age. Figure 2 shows a statistically significant associ- ation between the ocean and land survival esti- mates (r = 0.67,P<0.01). Conditions of weather, feeding, and disease which promote good survival Table 2. — Estimated natural survival rates of male fur seals from St. Paul Island in two stages from birth to age 2 yr, 1950-70 year classes. Year class < o 45 o 5 35- 25- Pups on land First 20 mo at sea until start ot kill at age 2 yr Birth to age 2 yr 1950 0 88 041 036 1951 084 0 42 035 1952 0,91 0 46 0 42 1953 082 0 38 031 1954 0 79 0 30 0 24 19SS 0 84 0 33 0 28 1956 0 78 0 18 0 14 1957 0 85 0 37 0 31 1958 0 92 0 49 0 45 1959 0 88 0 43 0 38 1960 0 81 0 34 0,28 1961 083 0 39 0 32 1962 0,84 043 0 36 1963 088 0 47 041 1964 0 92 0 47 0 43 1965 085 041 0 35 1966 0.92 0 36 0.33 1967 0 95 0 42 0 40 1968 089 0 42 0 37 1969 0 94 0 38 0 36 1970 091 0 46 042 All 0 87 0 40 0 35 78 86 94 ESTIMATED SURVIVAL OF PUPS ON LAND (%) Figure 2. — Relation of estimated survival rate during first 20 mo at sea to estimated survival rate of pups on land for male fur seals of the 1950-70 year classes from St. Paul Island. Functional regression line shown (Ricker 1973) has intercepts = 0.830 and slope [' = 1.425. of pups on land apparently equip them to survive relatively well at sea. As in Figure 1, however, the wide scatter about regression is prominent — emphasizing again that events at sea contribute 313 heavily to fluctuations in the survival of different year classes. Values in Tables 1 and 2 were also analyzed under the multiple linear regression model Y = A + B,Xi + 52^:2 + B3X3 + E where y = kill at age Syr in thousands, Xj = male pups born in thousands, X2 = survival rate pups on land, and X3 = survival rate during the first 20 mo at sea. £ is a random error term; the intercept A and slopes fi, are parameters to be estimated. Table 3 shows that multiple regression is highly significant (F = 26.60, P<0.001). Given that the pup survival rate on land is not significant (dele- tion of A'2 causes no change in R^ here), 100 R'^ = 82% of the annual variation in estimated abun- dance at age 3 yr, as indexed by the kill, is explained by annual changes in pup production and in the survival rates of different year classes during their first 20 mo at sea. The remaining variability, 18%, is due to random sampling errors and possibly to systematic errors. Discussion This report helps to quantify the importance of early ocean mortality in determining the average number of males available for harvest at age 3 yr and their pronounced annual fluctuations. Ken- yon et al . (1 954 ) speculated that only half the pups survive the attempted transition from a milk diet T.\BLE 3. — Statistics and tests for linear regression of male seals killed on St. Paul Island at age 3 yr( thousands) from the 1950-70 year classes (V ) on pups born (A', . thousands), estimated survival rate of pups on land i.Vji, and estimated survival rate during the first 20 mo at sea until age 2 yr (Xj ). Hem Calculated value Source of sum of squares, degrees of freedom, and mean square Multiple regression Deviations Total Test of multiple regression Square ot multiple correla- tion Parameter estimates and variances a.s'. Tests of individual regresions Pups born Land survival rate Ocean survival rate 1.53160/3 = 510 53 326-2617 = 19 19 1.857 86/20 ^ 92 89 F -- 510 53/19 19 ^ 26 60" R' = 1,53160/1.857.86 = 0.82 -70 355. 533 294 21 389, 753 857 103012, 350 151 on the Pribilof Islands to the quest for fishes and squids in a stormy environment after the islands are left behind. The authors stated that starvation during prolonged storms is a direct cause of death and noted that unusually large numbers of young seals from the 1949 year class were washed ashore on the Washington coast in emaciated condition during the severe winter of 1949-50. Ichihara ( 1974) postulated that the apparently higher mor- tality of males between birth and age 3 yr (Chap- man 19641 was due to the greater proportion of males wintering in stormy northern areas than in calmer waters to the south where females pre- dominate. Literature Cited Bartholoiview, G. a., Jr., and p. G. Hoel. 1953. Reproductive behavior of the Alaska fur seal, Cal- lorhinus ursinus. J. Mammal. 34:417-436. CHAPMAN, D. G. 1961. Population dynamics of the Alaska fur seal herd. Trans. North Am. Wildl Nat. Resour. Conf. 26:356-369. 1964. A critical study of Pnbilof fur seal population esti- mates. U.S. Fish Wildl. Serv., Fish. Bull. 63:657-669. 1973, Spawner-recruit models and estimation of the level of maximum sustainable catch. Rapp. P.-V. Reun. Cons. Int. Explor. Mer 164:325-332. Ichihara, T. 1974, Possible effect of surface wind force on the sex- specific mortality of young fur seals in the eastern Pa- cific, Bull, Far Seas Fish, Res, Lab, (Shimizul 11:1-8, Kenyon, K. W., V, B. Scheffer, and D. G. Chapman, 1954, A population study of the Alaska fur-seal herd. US. Fish Wildl. Serv., Spec. Sci. Rep. Wildl. 12, 77 p. Lander. R. H. 1975, Method of determining natural mortality in the northern fur seal \Callorhinus ursinus) from known pups and kill by age and sex. J. Fish. Res. Board Can, 32:2447-2452. Marine Mammal Biological Laboratory, 1971, Fur seal investigations, 1969. U.S. Dep. Commer., Natl Mar. Fish. Serv., Spec. Sci. Rep Fish. 628, 90 p. Peterson, R, S, 1968. Social behavior in pinnipeds with particular refer- ence to the northern fur seal. In R. J. Harrison et al. (editors), The behavior and physiology of the pinnipeds, p. 1-53. Appleton-Century-Crofts, N.Y. Richer, W, E, 1973. Linear regressions in fishery research. J. Fish. Res. Board Can. 30:409-434. SCHEFFER. V. B. 1950, Growth layers on the teeth of Pinnepedia as an indi- cation of age. Science (Wash,, DC) 112:309-311 ROBERT H. Lander t, = 0 203/v_0 0qi 6 42" , = 21 389/v'753857 =^0 78 ■ 103 012'v'350,157 = 550" Northwest and Alaska Fisheries Center National Marine Fisheries Sennce, NOAA 212h Montlake Boulevard East Seattle. WA 98112 314 NOTICES NOAA Technical Reports NMFS published during the last 6 mo of 1978. Circulars 414. Synopsis of biological data for the winter flounder, Pseudopteuronectes americanus (Walbaum). By Grace Klein-MacPhee. November 1978. ill + 43 p., 21 fig., 28 tables. Also FAO Fisheries Synopsis No. 117. 415. A basis for classifying western Atlantic Sci- aenidae (Teleostei: Perciformesl. By Labbish Ning Chao. September 1978, v + 64 p., 41 fig., 1 table. 416. Ocean variability: Effects on U.S. marine fishery resources- 1975. Jul ien R. Goulet.Jr. and Elizabeth D. Haynes, editors. December 1978, iii + 350 p. 417. Guide to the identification of genera of the fish order Ophidiiformes with a tentative classification of the order. By Daniel M. Cohen and Jorgen G. Nielsen. December 1978, vii + 72 p., 103 fig., 2 tables. 418. Annotated bibliography of four Atlantic scom- brids: Scomberomorus brasiliensis, S. cavalla, S. maculatus, andS. regalis. By Charles S. Manooch III. Eugene L. Nakamura, and Ann Bowman Hall. De- cember 1978, iii + 166 p. Special Scientific Report — Fisheries 726. The Gulf of Maine temperature structure between Bar Harbor, Maine, and Yarmouth, Nova Scotia, June 1975-November 1976. By Robert J. Pawlowski. De- cember 1978, iii -I- 10 p., 14 fig., 1 table. NOAA Technical Reports NMFS are available free in limited numbers to Federal and State government agencies. They are also available in exchange for other scientific and technical publications in the marine sciences. Individual copies, if available, may be obtained by purchase from the Superintendent of Documents or by writing to User Services Branch (D822.), Environmental Science Information Center. NOAA, Rockville, MD 20852. 315 INFORMATION FOR CONTRIBUTORS TO THE FISHERY BULLETIN Manuscripts submitted to the Fishery Bulletin will reach print faster if they conform to the following instructions. These are not absolute requirements, of course, but desiderata. 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The accuracy of the literature cited is the re- sponsibility of the author. Abbreviations of names of periodicals and serials should conform to Bio- logical Abstracts List of Serials with Title Abbrevi- ations. (Chemical Abstracts also uses this system, which was developed by the American Standards Association.) Common abbreviations and symbols, such as mm, m, g, ml, mg, °C (for Celsius), %, °/oo and so forth, should be used. Abbreviate units of mea- sure only when used with numerals. Periods are only rarely used with abbreviations. We prefer that measurements be given in metric units; other equivalent units may be given in parentheses. FORM OF THE MANUSCRIPT The original of the manuscript should be typed, double-spaced, on white bond paper. Please triple space above headings. We would rather receive good duplicated copies of manuscripts than car- bon copies. The sequence of the material should be: TITLE PAGE ABSTRACT TEXT LITERATURE CITED APPENDIX TEXT FOOTNOTES TABLES (Each table should be numbered with an arable numeral and heading provided) LIST OF FIGURES (Entire figure legends) FIGURES (Each figure should be numbered with an arable numeral; legends are desired) ADDITIONAL INFORMATION Send the ribbon copy and two duplicated or carbon copies of the manuscript to; Dr. Jay C. Quast, Scientific Editor Fishery Bulletin Northwest and Alaska Fisheries Center Auke Bay Laboratory, National Marine Fisheries Service, NOAA P.O. Box 155, Auke Bay, AK 99821 Fifty separates will be supplied to an author free of charge and 100 supplied to his organiza- tion. No covers will be supphed. Contents-continued OLLA, BORI L., ALLEN J. BEJDA, and A. DALE MARTIN. Seasonal dispersal and habitat selection of cunner, Tautogolabrus adspersus, and young tautog, Tautoga onitis, in Fire Island Inlet, Long Island, New York 255 HUGHES, STEVEN E., and GEORGE HIRSCHHORN. Biology of walleye pollock, Theraga chalcogramma, in the western Gulf of Alaska, 1973-75 263 Notes HOBSON, EDMUND S., and JAMES R. CHESS. Zooplankters that emerge from the lagoon floor at night at Kure and Midway Atolls, Hawaii 275 WENZLOFF, D. R., R. A. GREIG, A. S. MERRILL, and J. W. ROPES. A survey of heavy metals in the surf clam, Spisula solidissima, and the ocean quahog, Arcfjca islandica, of the Mid-Atlantic coast of the United States 280 OVERHOLTZ, WILLIAM J., and JOHN R. NICOLAS. Apparent feeding by the fin whale, Balaenoptera physalus, and the humpback whale, Megaptera novaengliae, on the American sand lance, Arnmodytes americanus , in the northwest Atlantic . 285 WILLIAMS, JOHN G. Estimation of intertidal harvest of Dungeness crab, Cancer magister, on Puget Sound, Washington, beaches 287 TARGETT, TIMOTHY E. A contribution to the biology of the puffers Sphoeroides testudineus and Sphoeroides spengleri from Biscayne Bay, Florida 292 HUI, CLIFFORD A. Correlates of maturity in the common dolphin, Delphinus delphis 295 ALLEN, LARRY G. Larval development ofGobiesox rhessodon (Gobiesocidae) with notes on the larva oi Rimicola muscarum 300 BAILEY, KEVIN, and JEAN DUNN. Spring and summer foods of walleye pollock, Theragra chalcogramma, in the eastern Bering Sea 304 DIETRICH, CHARLES S., JR. Fecundity of the Atlantic menhaden, Brevoortia tyrannus 308 LANDER, ROBERT H. Role of land and ocean mortality in yield of male Alaskan fur seal, Callorhinus ursinus 311 Notices NOAA Technical Reports NMFS published during the last 6 mo of 1978 315 , GPO 696-364 ..< °?^ c Fishery Bulletin Mariiie BiolDgical laliordiOJj LIBRARY OCT 24 1979 Vol. 77, No. 2 Woods Hole, Mass. April 1979 ■^ CLARK, COLIN W., and MARC MANGEL, Aggregation and fishery dynamics: a theoretical study of schooling and the purse seine tuna fisheries 317 WEINSTEIN, MICHAEL P. Shallow marsh habitats as primary nurseries for fishes and shellfish, Cape Fear River, North Carolina 339 SCOTTO, LIBERTA E. Larval development of the Cuban stone crab, Menippe nodi- frons (Brachyura, Xanthidae), under laboratory conditions with notes on the status of the family Menippidae 359 PELLA. JEROME J., and TIMOTHY L. ROBERTSON. Assessment of composition of stock mixtures 387 WURSIG, BERND, and MELANY WURSIG. Behavior and ecology of thebottlenose dolphin, Tursiops truncatus, in the South Atlantic 399 METHOT, RICHARD D., JR., and DAVID KRAMER. Growth of northern anchovy, Engraulis mordax, larvae in the sea 413 SIEGEL, ROBERT A., JOSEPH J. MUELLER, and BRIAN J. ROTHSCHILD. A linear programming approach to determining harvesting capacity: a multiple species fishery 425 WENNER, ELIZABETH LEWIS. Some aspects of the biology of deep-sea lobsters of the family Polychelidae (Crustacea, Decapoda) from the western North Atlantic 435 PRATT, HAROLD L., JR. Reproduction in the blue shark, Prionace glauca 445 ANNALA, JOHN H. Mortality estimates for the New Zealand rock lobster, Jasus edivardsii 471 REPPOND, KERMIT D., FERN A. BULLARD, and JEFF COLLINS. Walleye pol- lock, Theragra chalcogramma: physical, chemical, and sensory changes when held in ice and in carbon dioxide modified refrigerated seawater 481 Notes HOLLIDAY, D. V., and H. L. LARSEN. Thickness and depth distributions of some epipelagic fish schools off southern California 489 BRILL, RICHARD W. The effect of body size on the standard metabolic rate of skipjack tuna, Katsuwonus pelamis 494 HINES, ANSON H. Effects of a thermal discharge on reproductive cycles in Mytilus edulis and Mytilus californianus (MoUusca, Bivalvia) 498 (Continued on back cover) Seattle, Washington U.S. DEPARTMENT OF COMMERCE Juanita M. Kreps, Secretary NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION Richard A. Frank, Administrator Terry L. Leitzell. Assistarit Administrator for Fisheries NATIONAL MARINE FISHERIES SERVICE Fishery Bulletin The Fishery Bulletin carries original research reports and technical notes on investigations in fishery science, engineering, and economics. The Bulletin of the United States Fish Commission was begun in 1881; it became the Bulletin of the Bureau of Fisheries in 1904 and the Fishery Bulletin of the Fish and Wildlife Service in 1941. Separates were issued as documents through volume 46; the last document was No. 1103. Beginning with volume 47 in 1931 and continuing through volume 62 in 1963, each separate appeared as a numbered bulletin. A new system began in 1963 with volume 63 in which papers are bound together in a single issue of the bulletin instead of being issued individually. Beginning with volume 70, number 1, January 1972, iheFishery Bulletin became a periodical, issued quarterly. In this form, it is available by subscription from the Superintendent of Documents, U.S. Government Printing Office, Washington, DC 20402. It is also available free in limited numbers to libraries, research institutions, State and Federal agencies, and in exchange for other scientific publications. EDITOR Dr. Jay C. Quasi Scientific Editor, Fishery Bulletin Northwest and Alaska Fisheries Center Auke Bay Laboratory National Marine Fisheries Service, NOAA P.O. Box 155, Auke Bay, AK 99821 Editorial Committee Dr. Elbert H. Ahlstrom Dr. Merton C. Ingham National Marine Fisheries Service National Marine Fisheries Service Dr. Bruce B. Collette Dr. Reuben Lasker National Marine Fisheries Service National Marine Fisheries Service Dr. Edward D. Houde Dr. Jerome J. Pella University of Miami National Marine Fisheries Service Dr. Sally L. Richardson Gulf Coast Research Laboratory Kiyoshi G. Fukano, Managing Editor The Fishery Bulletin (USPS 090-870) is published quarterly by Scientific Publications Office, National Marine Fisheries Service. NOAA, Room 450, 1107 NE 451h Street. Seattle. WA 98105. Controlled circulation paid to Finance Department, USPS. Washington, DC 20260 Although the contents have not been copyrighted and may be reprinted entirely, reference to source is appreciated. * The Secretary of Commerce has determined that the publication of this periodical is necessary in the transaction of Ihe public • business required by law of this Department Use of funds for printing of this periodical has been approved by the Director of the Office of Management and Budget through. 31 March 1982 J \ Fishery Bulletin CONTENTS Vol. 77, No. 2 April 1979 CLARK, COLIN W., and MARC MANGEL. Aggregation and fishery dynamics: a theoretical study of schooling and the purse seine tuna fisheries 317 WEINSTEIN, MICHAEL P. Shallow marsh habitats as primary nurseries for fishes and shellfish. Cape Fear River, North Carolina 339 SCOTTO, LIBERTA E. Larval development of the Cuban stone crab, Menippe nodi- frons ( Brachyura, Xanthidae), under laboratory conditions with notes on the status of the family Menippidae 359 PELLA, JEROME J., and TIMOTHY L. ROBERTSON. Assessment of composition of stock mixtures 387 WURSIG, BERND, and MELANY WURSIG. Behavior and ecology of the bottlenose dolphin, Tursiops truncatus. in the South Atlantic 399 METHOT, RICHARD D., JR., and DAVID KRAMER. Growth of northern anchovy, Engraulis mordax, larvae in the sea 413 SIEGEL, ROBERT A., JOSEPH J. MUELLER, and BRIAN J. ROTHSCHILD. A linear programming approach to determming harvesting capacity: a multiple species fishery 425 WENNER, ELIZABETH LEWIS. Some aspects of the biology of deep-sea lobsters of the family Polychelidae (Crustacea, Decapoda) from the western North Atlantic 435 PRATT, HAROLD L., JR. Reproduction in the blue shark. Prionace glauca 445 ANNALA, JOHN H. Mortality estimates for the New Zealand rock lobster, Jasus edwardsii 471 REPPOND, KERMIT D., FERN A. BULLARD, and JEFF COLLINS. Walleye pol- lock, Theragra chalcogramma: physical, chemical, and sensory changes when held in ice and in carbon dioxide modified refrigerated seawater 481 Notes HOLLIDAY, D. V., and H. L. LARSEN. Thickness and depth distributions of some epipelagic fish schools off southern California 489 BRILL, RICHARD W. The effect of body size on the standard metabolic rate of skipjack tuna, Katsuwonus pelamis 494 HINES, ANSON H. Effects of a thermal discharge on reproductive cycles in Mytilus edulis and Mytilus californianus (Mollusca, Bivalvia) 498 (Continued on next page) Seattle, Washington 1979 For sale by the Superintendent of Document.^. U.S. Government Printing Office. Washington, DC 20402— Subscription price per year $12 00 domestic and $15 00 foreign. Cost per single issue. $3.00 domestic and $3,75 foreign Contents-continued SHERBURNE, STUART W., and LAURIE L. BEAN. Incidence and distribution of piscine erythrocytic necrosis and the microsporidian, Glugea hertwigi, in rainbow smelt, Osmerus mordax, from Massachusetts to the Canadian Maritimes 503 WINSTEAD, JAMES T. A simple method to obtain serum from small fish 509 IRVINE, A. BLAIR, MICHAEL D. SCOTT, RANDALL S. WELLS, and JAMES G. MEAD. Stranding ofthe pilot whale, Globtcephala macrorhynchus, in Florida and South Carolina 511 GALT, CHARLES P. First records of a giant pelagic tunicate, Bathochordaeus charon (Urochordata, Larvacea), from the eastern Pacific Ocean, with notes on its biology 514 Vol. 77, No. 1 was published on 30 May 1979. The National Marine Fisheries Service (NMFS) does not approve, rec- ommend or endorse any proprietary product or proprietary material mentioned in this publication. No reference shall be made to NMFS, or to this publication furnished by NMFS, in any advertising or sales pro- motion which would indicate or imply that NMFS approves, recommends or endorses any proprietary product or proprietary material mentioned herein, or which has as its purpose an intent to cause directly or indirectly the advertised product to be used or purchased because of this NMFS publication. AGGREGATION AND FISHERY DYNAMICS: A THEORETICAL STUDY OF SCHOOLING AND THE PURSE SEINE TUNA FISHERIES' Colin W. Clark^ and Marc Mangel^ ABSTRACT This paper describes mathematical models of exploited fish stocks under the assumption that a certain portion of the stock becomes available through a dynamic aggregation process. The surface tuna fishery is used throughout as an example. The effects of aggregation on yield-effort relationships, indices of abundance, and fishery dynamics are discussed. The predictions of the theory are notably different from those obtained from general-production fishery models, particularly in cases where the available substock has a finite saturation level. Possible effects include fishery "catastrophes" and lack of significant correlation between catch-per-unit-effort statistics and stock abundance. Various man- agement implications of the models are also discussed. The relationship between fishing effort, catch rate, and stock abundance is of fundamental im- portance to the management of commercial fisheries. To a first approximation, it is usually assumed that catch per unit effort (ClE ) is propor- tional to stock abundance (P), with a fixed con- stant of proportionality (catchability coefficient). C = qEP, (1) where C denotes catch per unit time and E denotes fishing effort. By combining this relationship with an appropriate model of population dynamics, one obtains a dynamic fishery model which can then be used as a basis for management policy (Schaefer 1957). The form of Equation (1 ) is predicated on certain underlying assumptions pertaining to the fishing process, particularly a) that fishing consists of a random search for fish and b) that all fish in the stock are equally likely to be captured. More pre- cisely, by introducing an explicit stochastic model of the fishery based upon such assumptions, one can deduce Equation ( 1 ) for the expected catch rate C. But such models can also be employed to inves- tigate the consequences of alternative, and possi- bly more realistic, assumptions. For example, 'Research performed under contract to NOAA, National Marine Fisheries Service, Contract No. 03-6-208-35341. ^Department of Mathematics, University of British Columbia, Vancouver, B.C., Canada V6T 1W5. ^Center for Naval Analyses, 1401 Wilson Boulevard, Ar- lington, VA 22209. Manuscript accepted October 1978 FISHERY BULLETIN VOL 77, NO 2, 1979 Stochastic models of purse seine fisheries, incor- porating detailed descriptions of the operation of fishing vessels, have been discussed by Neyman (1949), Pella (1969), and Pella and Psaropulos ( 1975). On the other hand, the effects of concentra- tion offish and of fishing effort have been studied by Calkins (19611, Gulland (1956), and others. In this paper we discuss fishery models in which the assumption of equal availability of all portions of the stock is relaxed. Specifically, we are con- cerned with fisheries that exploit aggregations of fish; these aggregations are assumed to constitute a dynamically changing substock of the entire population. Although a general class of such mod- els could be developed, we shall restrict the discus- sion here to the case of the tuna purse seine fisheries, in which aggregation apparently occurs through the process of surface school formation. Several alternative models of the interchange pro- cess between surface and subsurface tuna sub- populations will be presented, and the effects of the surface fishery will be investigated for each model. Evidence arising from studies carried out at the Inter-American Tropical Tuna Commission (Sharp 1978), and at the Southwest Fisheries Center, National Marine Fisheries Service, shows that yellowfin tuna, Thunnus albacares, captured in surface schools in the eastern tropical Pacific Ocean do in fact spend part of their time below the surface. Little seems to be known, however, about the dynamics of the interchange process; our analysis of alternative models indicates that such knowledge could become crucial to the manage- ment of the fishery. 317 FISHERY BULLETIN: VOL 77. NO, 2 Fisheries for various other pelagic, schooling species, such as anchoveta, herring, and mackerel, also appear to involve aggregative processes. Sev- eral of these fisheries have in fact experienced collapses which are qualitatively similar to those predicted by our aggregation models. Other mechanisms, however, may be involved in these fisheries, including: predation (Clark 1974); com- petitive exclusion (Murphy 1966); increased catchability (Fox ); depensation in stock- recruitment relationships (Clark 1976). In some cases, stocks have failed to recover following a collapse, even when fishing has been greatly cur- tailed (Murphy 1977). Dynamic behavior of this kind is not consistent with any of the traditional models employed in fishery management. On the other hand, discontinuous behavior of continuous nonlinear systems is a well-known phenomenon in applied mathematics. Thus the term "bifurcation" refers to such discontinuous changes induced by continuous parameter shifts in explicit mathematical models. More recently the subject "catastrophe theory" has been de- veloped as an abstract approach to these phenomena (Thom 1975; Zeeman 1975; see also the report in Science by Kolata (1977)). A discussion of catastrophe theory as it applies in the fishery setting appears in Jones and Walters (1976). Indeed these authors assert that ". . . the tropical tuna fisheries have almost certainly moved into a cusp region, . . . where small changes in investment policy or failure to rapidly adjust catch quotas could lead to fishery collapse." (Jones and Walters 1976:2832). Since no specific biologi- cal (or technological) catastrophe-inducing mechanism has been suggested by Jones and Wal- ters, their assertion stands only as a plausible conjecture — a warning that possible nonlinear system effects ought to be investigated more fully. In this paper we shall investigate in some detail the interactions between the schooling behaviour of tuna and the operation of the purse seine fishery. Since current knowledge about the school- ing strategy of tuna is limited, we shall construct a variety of models in order to investigate the possi- ble effects of and interactions with the fishery. In particular, we shall discuss the following topics: ^Similar collapses have not occurred in tuna stocks, perhaps because of their relative diflfuseness. ^Fox, W. W., Jr. 1974 An overview of production model- ling. Unpubl. manuscr. Southwest Fisheries Center, Na- tional Marine Fisheries Service, NOAA, P.O. Box 271, La JoUa. CA 92038, 1. yield-effort relationships, 2. indices of stock abundance, 3. fishery dynamics, 4. management implications. The results turn out to be highly, perhaps sur- prisingly, sensitive to the assumptions and parameters of our models. Of particular impor- tance is the way in which the size of surface tuna schools depends upon the overall abundance of tuna. If it is the case that school size ( as unaffected by the fishery) is relatively independent of total tuna abundance, then our models indicate the pos- sibility (under certain additional conditions) of a catastrophic collapse of the tuna fishery as the intensity of fishing passes some critical level. That such a prediction could arise from a potentially biologically realistic tuna model was completely unexpected at the beginning of the study, in spite of the theoretical investigations mentioned above. Another significant result of our analysis is that, under our model assumptions, the catch- per-unit-effort(CPUE) statistic may constitute an extremely unreliable index of stock abundance. The bias may be in either direction depending on the model adopted — CPUE may severely either underestimate or overestimate the decline in abundance as the fishery develops, while in other cases CPUE may quite accurately represent abundance. Following the description and analysis of our various models, we shall present some simple simulated development paths for the tuna purse seine fishery, based upon the models. The first simulation that we performed utilized our best guesses as to realistic parameter values. In this simulation the fishery experiences a catastrophic collapse when effort is increased to 18,000 stan- dardized vessel days per annum. The decline of the tuna population itself occurs quite gradually, but is not reflected by any significant decline in catch or in CPUE, until the fishery is virtually de- stroyed. In other words, the collapse of the fishery involves not an abrupt change in the stock, but rather an abrupt change in the input-output rela- tionship. TUNA PURSE SEINE FISHERY The commercial fishery for tuna in the eastern tropical Pacific Ocean began in the years following World War I, the two main species taken being yellowfin tuna and skipjack tuna, Katauivonus 318 CLARK and MANGEL: AGGREGATION AND FISHERY DYNAMICS pelamis. Annual catches in the between-war period rose to a total of about 70.000 short tons. Following World War II "there was a great up- surge in the fishery" (Schaefer 1967:89). which has continued to the present time, see Figure 1. The entire period has also seen a progressive expan- sion of the fishery into the offshore waters, con- comitant with progressive developments in technology. Of particular significance is the switchover from bait boats to purse seiners, which occurred in the early 1960's and has resulted in substantial continuing increases in the catch of yellowfin tuna. Much of this increase has resulted from the offshore fishery on porpoise-associated tuna schools. The purse seine tuna fishery operates by locat- ing schools of tuna at or near the surface of the sea. The main types of schools encountered are: a) non- porpoise associated schools (pure yellowfin tuna, pure skipjack tuna, or mixed schools) and b) por- poise schools (yellowfin tuna only). Schools of tuna that are not associated with porpoise are some- times associated instead with concentrations of floating debris ("log schools"). Management of the yellowfin tuna fishery has been complicated by the controversial problem of limiting the incidental kill of porpoise, but this question will not concern us here. Figure L— Annual catches of yellowfin i YFl and skipjack iSK) tuna in the eastern tropical Pacific Ocean, 1945-75. Schools of tuna are normally located by visual search, often by noting the presence of flocks of sea birds. After sighting and approaching a school, the vessel attempts to capture tuna by setting its purse seine net about the school. During a set on porpoise schools, speedboats may be lowered into the water to assist in concentrating the porpoise so that the school can be encircled by the net. Of the daylight hours spent on the fishing grounds, perhaps 70% are spent in searching for schools and 30% on setting of nets. According to biological observations (Sharp 1978),only a portion of the total tuna population is available to the fishery, as schooled fish, at any given time. It appears that the magnitude of this available portion may be related to environmental conditions, particularly the depth in the ocean of certain thermal isoclines. Furthermore, it seems evident that there must exist a dynamics of school formation and exchange. The fishery interacts with this dynamic process by removing some of the schools. To our knowledge, the implications of such a dynamic availability phenomenon have not been previously investigated in detail. Since present knowledge about the schooling strategy of tuna is limited, we shall discuss a coterie of submodels for the formation of schools. The models have been chosen in an attempt to "bracket" the possible range of schooling strategies; a wide variety of alternative models could obviously also be set up (see Appendix B). We next describe a submodel for the purse seine fishery. In order to keep the length of this paper within bounds we discuss only a single fishery submodel, in which vessels search at random for randomly distributed surface schools. Finally we introduce our submodel of tuna population dynamics, which will be the standard Schaefer model. In the main body of the paper we employ the continuous-time version of the Schaefer model, but a discrete-time version will be dis- cussed in Appendix A. In Appendix B we describe several more de- tailed models pertaining to the schooling strategy of tuna, using techniques known from chemical kinetics. This approach yields as special cases the two submodels described in the text proper and also gives rise to a number of interesting new details. Although the background of our schooling and fishery models is stochastic, we concern ourselves only with expected values, so that the analysis remains essentially deterministic. (Explicit 319 FISHERY BULLETIN: VOL, 77, NO, 2 stochastic considerations are taken up in a forth- coming paper by Mangel. ) Two important omis- sions from our models are: a) age structure and b) spatial distribution of the tuna population; the multispecies aspect is also not covered. These omissions were dictated by our desire to concen- trate on the novel features of our work, viz the schooling strategy and its implications. Further research will be required (probably based primar- ily on simulation techniques) if more sophisti- cated, disaggregated models are to be studied. SCHOOL FORMATION SUBMODELS We imagine a given number, K, of school "at- tractors," such as porpoise schools, or collections of floating debris. (Our models also apply to nonpor- poise and nonlog schools provided that the ex- change process between subsurface and surface schools satisfies the appropriate hypotheses, see Equations (10).) Tuna from an underlying, or "background," population associate with these at- tractors according to one of the submodels A or B below; the attractors are independent of one another and do not interchange associated tuna. Let N denote the number of tuna present in the background (subsurface) population. The number of tuna in an individual generic school is denoted by Q = QW). (A full list of variables and parame- ters is given in Table 1.) Table l — Basic parameters and variables of the models. Sym- bols endemic to the appendices are pven below. Units of Item Meaning measurement Parameters a schooling rale per atlractor day ' H deschooling rate day ' Q- maximum equilibrium school size tons b catchability ol attractors (standard ves- sel day) ' K numtier ol attractors — to capture ratio _ r intrinsic growth rate day ' N carrying capacity tons Variables: 0 school size tons t time days N sutjsurtace tuna population tons E lishing etlort standardized vessels Y catch rate tons ■ (day ') S surface tuna population tons s- carrying capacity ol S tons » net rate of transfer tons ■ (day ') G growth rate tons ■ (day ') Appendix A Parameters T length ol fishing season days P carrying capacity tons 9 growth parameter (day 'l Variables R recruitment tons p escapement tons Appendix B Parameters y number ol core schools per complex — So weight of core schools tons Variables: T number of core schools _ C number of complexes — Q(0 = Q* d-c-oe" '), (4) Model A where Cq = 1 - QqIQ* . Tuna associate with a given attractor at a rate aN proportional to the background population, and dissociate at a rate /3Q proportional to the current school size: — =OrN m. (2) (The dissociated tuna return to the background population, see Equation (15).) For fixed N the resulting equilibrium school size Q* is given by aN (3) If Q(0) = Q„, Equation (2) has the solution (for fixed AT): Thus in model A, the equilibrium size of schools is directly proportional to the background tuna population. (Since we treat the number of attrac- tors, K, as fixed, we do not discuss the possibility that school size could also depend on K .) Model B In this alternative submodel, we assume that the maximum school size is a constant, Q *, which is independent of the background tuna population. Equation (2) is replaced by (5) •Mangel, M. 1978. Aggregation, bifurcation, and extinc- tion in exploited animal populations. Cent. Nav Prof Pap 224. Center for Naval Analyses, 1401 Wilson Boulevard, Ar- lington, VA 22209. where Q' = fixed maximum school size. Thus we now have (for fixed N) 320 CLARK and MANGEL AGGREGATION AND FISHERY DYNAMICS Qil) = Q* -{Q* -Qo)e-"'^'/^*. (6) As will be seen in the sequel, the characteristics of our purse seine fishery model are severely inflenced by the choice of the schooling submodel A or B. Which of these submodels more accurately reflects the actual schooling strategy of tuna is a question we are not qualified to answer. It may be the case that neither extreme (school size Q* strictly proportional to tuna abundance N in sub- model A, and Q* strictly independent ofN in sub- model B) is realistic. For example, school size may saturate for large A'', but exhibit density depen- dence at low N, giving rise to a combination of models A and B. Submodels involving more gen- eral links between Q* and N could easily be con- structed, but we will not attempt to work through the details here. A more general class of schooling submodels is discussed in detail in Appendix B. Let us remark here that models A and B assume in effect a uniformly distributed "background" tuna population. The models discussed in Appen- dix B assume instead that the background popula- tion consists of "core" schools; according to Sharp (1978) the latter assumption is more realistic. In certain cases the core-school models reduce to the models A and B described above. MODEL OF THE PURSE SEINE FISHERY We shall use a simple Poisson model to describe the process whereby the fishing fleet searches for schools of tuna. The h3TDotheses underlying this model are well known (see, e.g., Ludwig 1974) and will not be specified here. Let us note, however, that our model pertains to a single type of school (e.g., porpoise school, log school); a more refined model might allow for a random intermingling of school types. A nonrandom distribution of school types, on the other hand, would lead to the as yet unsolved problem of attributing allocation of ef- fort by fishing vessels. The probability that the fishing fleet locates exactly /f school attractors with the expenditure of t days of searching effort, is given by where X = (a/A)K a = area searched per day A = total area of fishing ground K = number of school attractors. If searching effort is properly standardized, we will have a/A = bE, where E = effort 6 = a constant. Hence \ =bE K. (8) 'Broadhead and Orange 1 19601 imply that Q' is nearly con- stant, although It may in some cases be slightly density depen- dent. However, for skipjack tuna, in the eastern Pacific, school size and population size as indexed by CPUE are highly corre- lated (but the two estimates are not independent), J, Joseph. Director of Investigations. Inter-American Tropical Tuna Com- mission, La Jolla, CA 94720, pers. commun. July 1978. The average number of attractors located by the fleet in time t is k = \t =bEKt. Thus the total catch rate of tuna, Y. is given by Y = bEKxoQ <9) where \q = capture ratio (average fraction cap- tured w-hen a school is encounter- ed). LetS(t) denote the total number of tuna present at time t in surface schools: S = KQ. Our model then implies that ds \aKN- /« - b\oES (Model A) ^^ ]aKN(l-SIS*)-bxoES (Model B) where S* = KQ* represents the total "carrying capacity" of the surface school attractors. (Note that, replacing oKN by pN = flow rate from sub- surface to surface populations, we could simply adopt Equation (10) as the basic hypothesis of our model, eliminating any particular assumption re- garding the attractive mechanism for surface schools.) Let us assume for the moment that an equilib- rium is achieved rapidly in the surface fishery, relative to adjustments in the underlying popula- tion N. (The dynamics of the underlying popula- 321 nSHERY BULLETIN VOL 77. NO 2 tion will be modeled below.) Setting dS/d? = 0, we obtain the following "catch equations": bXpaKEM (Model A) y = (11) )bxoaKQ*EN {oiN+bxoQ''E (Model B) . These equations appear not to be of a standard form, as encountered either in ecology (where YIN would be termed the "functional response," see Fujii et al. ), or in economics (where Y would be termed the "production function" of the fishery, see Clark 1976, sec. 7.6), or in the fisheries litera- ture (Paloheimo and Dickie 1964; Rothschild 1977 ). This unfamiliarity is perhaps to be expected since, as far as we know, the peculiar "skimming" process of the purse seine fishery has not previ- ously been modeled. Equations (10) are however closely analogous to the Michaelis-Menten equa- tion of enzyme kinetics (White et al. 1973) as might be expected from the observation that the attractors serve to "catalyze" the purse seine fishery, see Appendix B. Regarding the catch Equations (11), let us ob- serve that both submodels exhibit a saturation effect with respect to fishing effort £, whereas only submodel B exhibits a saturation effect with re- spect to tuna abundance N . For a fixed background population level N, the catch rate Y bears an asymptotic relationship with fishing effort £. For small E we have, from Equations (11): [bXoaNK pxoQ* KE (Model A) (Model B) (12) Since Q* = aA^//3 in Model A, these expressions are in fact the same for the two submodels, and concur with the standard Schaefer fishery production function. For large E we have lim y oNK (13) »Fuju, K., P. M. Mace, and C. S. Holling. 1978. A simple generalized model of attack by predator. Unpubl. manuscr., 39 p University of British Columbia, Institute of Animal Re- source Ecology, Vtmcouver, B.C., Canada V6T 1W5. 322 for both submodels. For submodel B we also have (for fixed £) lim y = bxoKQ*E (Model B). (14) AT-^oo FISHERY DYNAMICS As our submodel of population dynamics of the subsurface tuna population, we adopt the familiar Schaefer logistic model (Schaefer 1957): ■^ = rN{l-N/N)-i at (15) where r = intrinsic growth rate N = environmental carrying capacity e = net rate of transfer to the surface pop- ulation. The net rate of transfer, 6, is obtained from Equa- tions (2) and (5): {aNK - I3S (Model A) 6= { (16) [oNKa -SIS*) (Model B). Our dynamic models of the surface tuna fishery then consist of the simultaneous system of Equa- J tions(10)and (15). For convenience we rewrite the ' two systems as follows: dS = aiiw — ps — oxo^.^ I (17) Model A: ^= aKN-fiS-bxoES at dN dl dS G(N)-{aKN-iiS)} Model B: -^ = aKN{l- S/S* ) - bxoES | dN dl G(N)-aKN(l-S/S*) where G{N) = rA?(l -N/N). (18) (19) Although the difference between these two models may appear minor, their qualitative be- havior turns out to be quite dissimilar. Their be- havior is also quite different from the standard Schaefer model (Schaefer 1957). As indicated by results discussed in the appendices, however, the qualitative behavior of the above models seems to be characteristic of a wide variety of alternative CLARK and MANGEL; AGGREGATION AND FISHERY DYNAMICS models of both population dynamics and the school-formation process. We next discuss the be- havior of our models in detail. Model A Figure 2(a) and (b) show the system of solution trajectories (Nit), S(t)) for the Equation system (17), for the two cases In these Figures, the effect of an increase in the effort parameter E is to rotate the isocline S = 0 in a clockwise direction, thus decreasing both popu- lation levels N^ andS^. The corresponding yield- effort curves are shown in Figure 3(a) and (b) re- spectively. The shape of these yield curves is easily explained. Note from Equations (16) that the con- stant oK < r and aK > r aK respectively. The system has a unique stable equilibrium at the point {N^,Sj; the correspond- ing sustained yield from the fishery is given by y = bx„ES^. N =0 3 Q. o < Lj_ IT 3 to (a) aK < r N = 0 S = 0 (b) aK > r SUBSURFACE POPULATION (N) Figure 2. — Trtyectory diagram for model A: a stable equilib- rium exists at the point IN^, S^). Case (a): intrinsic schooling rate less than intrinsic growth rate; population cannot be de- pleted below N by surface fishery. Case (b): intrinsic schooling rate greater than intrinsic growth rate; population can theoreti- cally be fished to arbitrarily low levels (see also Figure 3). represents the maximum net rate at which the subsurface population A'^ aggregates to the sur- face; this may be referred to as the "intrinsic aggregation rate" (or "intrinsic schooling rate" in the present model). If the intrinsic aggregation rate p is less than the intrinsic growth rate r (see Figures 2(a), 3(a)), then the population cannot be exhausted by the surface fishery; in this caseN -> TV > 0 and y -►F > 0 as effort £ -♦ -^-. (Figure 3(a) shows yield increasing to a maximum level and then declining as effort increases. This situation arises if N < N/2, i.e., if p > r/2; otherwise, Y simply increases to an asymptotic value Y .) (0 ) aK < r (b) aK > r EFFORT ;e ) Figure 3. — Equilibrium yield-effort curves for model A. Case la): intrinsic schooling rate less than intrinsic growth rate; yield approaches a positive asymptotic value as effort approaches infinity. Case (bl: intrinsic schooling rate greater than intrinsic growth rate; yield approaches zero at finite effort level. 323 On the other hand, if p > r (Figures 2(b), 3(b)) then exhaustion is possible at sufficiently high levels of effort. This case is similar to the Schaefer model. For model A, CPUE is a seriously biased index of total stock abundance. The instantaneous CPUE is, of course, simply an index of abundance for the surface population. Sustained CPUE progres- sively overestimates the decline in abundance at high levels of effort. Conversely, particularly if the aggregation rate is large, CPUE may underesti- mate the decline in abundance at intermediate levels of effort. It is clear in general that no simple transformation of the CPUE index can provide an unbiased estimator of abundance, for this model. Any fishery exploiting a substock of a biological population necessarily provides only partial in- formation concerning total abundance; in the event that the fishery itself affects the relation- ship between the substocks, the interpretation of a time series of catch-effort data becomes extremely difficult. To summarize, if the present model realistically represents the process of aggregation (via surface schooling) of tuna, then CPUE data may ulti- mately overestimate the decline in abundance of tuna. Management policy based on such data may then be unduly restrictive. The situation may be very different, however, if model B is the more realistic representation. We now turn to this case. Model B The solution trajectories of Equations (18) are illustrated in Figure 4(a) and (b), again corres- ponding to the cases aK < r and aK > r respec- tively. The corresponding yield-effort curves are shown in Figure 5. In case (a), aK < r, the system has a unique stable equilibrium (iV^, Sj. As in model A, we haveA'^^-»'iV -OasE -> + ==. The yield-effort curve for this case has the same shape as for model A. A new phenomenon arises, however, in the case that aK > r. For small E (see Figure 4(b)) there now exist two stable equilibria, at iN.,.S,) and at ( 0,0), separated by a point of unstable equilibrium. As E increases, the stable and unstable equilibria coalesce and then disappear, leaving only the sta- ble equilibrium at (0,0). In mathematical ter- minology, the Equation system (18) undergoes a "bifurcation" at the critical effort level E = E^ where the two equilibria coalesce. The graph of systainable yield vs. effort (Figure 5(b)) becomes 324 FISHERY BULLETIN: VOL. 77. NO, 2 0 3 = 0 (b) aK > r SUBSURFACE POPULATION (N) Figure 4.— Tr^ectory diagrams for model B: a stable equilib- rium exists at point ( N», S^); in diagram (b) an unstable equilib- rium also exists for small E, but both equilibna disappear for large E. Case la): intrinsic schooling rate less than intrinsic growth rate: population cannot be depleted below N by surface fishery. Case (bi: intrinsic schooling rate greater than intrinsic growth rate population can theoretecally be shed to arbitrarily low levels; the transition from N = N^ toN = 0 is "catastrophic"; see also text and Figure 5(b), multivalued for this case. Model B exhibits an explicit mathematical "catastrophe." The significance of multivalued yield-effort curves for fishery management has been discussed by Clark (1974, 1976); see also Anderson (1977). As effort E expands from a low level, the catch follows the upper stable branch (Figure 5(b)), pos- sibly with some lag. But onceE exceeds the critical level £, , sustainable yield drops discontinuously to zero and the fish population goes into a steady decline. Subsequent decreases in effort do not necessarily result in recovery of the fishery, which may become "trapped" at a position of low abun- dance. This behavior is characteristic of the "catastrophe" situation (here the so-called "fold" catastrophe (Zeeman 1975)). In general, once a catastrophic jump has occurred, a large-scale change in the control variable (effort) is required CLARK and MANGEL AGGREGATION AND FISHERY DYNAMICS POPULATION ( N ) (a) aK < r LU >- ( b) aK > r EFFORT ( F ) Figure 5. — Equilibrium yield-effort curves for model B. Case (a); intnnsic schooling rate less than intrinsic growth rate; yield approaches a positive asymptotic value as effort approaches infinity. Case lb); intnnsic schooling rate greater than intrinsic growth rate; yield undergoes a catastrophic transition when effort exceeds critical level E,.. in order to return the system to the original stable equilibrium. The behavior of our model (submodel B) can be described in terms of Figure 6, in which the hori- zontal plane represents the "control space," with efforts as the basic control and intrinsic schooling rate aK as a parameter (which in some cases might also be subject to manipulation, or to stochastic variation). The vertical axis represents subsurface stock size A^. The surface S is the locus of equilibrium solutions for our model. Two possible paths for the development of the fishery are also shown in Figure 6. (Simulated versions of these paths will be presented below.) Path I, corresponding to Figure 5(a), occurs if «A' < r; here there is a steady decline in the equilib- rium population level N = N as the effort parame- ter increases. (If £ varies rapidly over time, then equilibrium conditions will not prevail, and the actual development path will diverge from Path I lying on i.. Figure 6 is still useful for understand- ing the dynamics in this case, however.) Path II, with aK > r, behaves similarly to Path I INTRINSIC SCHOOLING RATE (aK ) Figure 6. — Catastrophic surface il) corresponding to model B; This surface describes the eauilibrium population level (N) as a function of effort I E) and intrinsic schooling rate faK) Path I represents the development of the fishery, as effort increases, in thecase that aK < r, while Path II corresponds to the case oK > r In the latter case the fishery experiences a catastrophic col- lapse at point P. for small levels of effort, but then suddenly falls over the "edge" of the catastrophe surface 1, at point P. I Notice that for aK - r the surface 5i folds under itself, the upper sheet N = N and the lower sheet N = 0 being stable equilibria, while the middle sheet N = N' is unstable. This surface shape is the typical "cusp" catastrophe of Thorn 1975.) The management implications of the theory will be discussed later; the question of robustness of the models will be taken up in the appendices. Figure 6 stresses the significance of the parame- ter p = aK for the interactive dynamics of aggre- gation and fishing. For tuna, p may be age- dependent, as suggested by the differences in age distribution between longline and purse seine catches. Also, as noted previously, p may vary over time and space as a result of environmental gra- dients. The theoretical consequences of such com- plexities have yet to be investigated (Mangel see footnote 6). A "cusp" catastrophe surface similar to that de- picted in Figure 6 can also be used to describe the response of the tuna fishery to simultaneous exploitation of the surface schools and the subsur- face (background) population. If a given level of fishing mortality f\ is applied to the subsurface population, the effect will be to replace our dynamic Equation (15) by 325 FISHERY BULLETIN VOL dM dl nV(i -^)-A.iv-e N = r N (/■-/■,).V(1--— r^ '■-/■.SiV )-o. Thus the net biological gi'outh rate becomes r - f^ and the condition for catastrophic behavior in submodel B becomes aK > r fs- If we now consider effort E in the surface fishery and mortality/', in the subsurface fishery as con- trol variables (now assuming aK = constant), it is clear that the surface of equilibrium A''-values has the same nature as shown in Figure 6. Thus while the surface fishery might be "subcatastrophic" in the absence of any subsurface fishery, the de- velopment of the latter might transform the sys- tem into a catastrophic region. One further possibility is worth noting. As re- marked earlier, the schooling behavior of tuna may be influenced by environmental factors, par- ticularly the depth of certain thermal isoclines. If so, the system might switch randomly between catastrophic and noncatastrophic states. Under these circumstances the fishery might exist for sometime at a level of stable sustained yield, but could suffer a catastrophic collapse induced by un- usual, or unusually protracted environmental conditions. The practical importance of these possibilities is increased by the fact that CPUE is likely severely to misrepresent the decline in abundance of the tuna population. In the first simulation reported below, for example (Figure 7), CPUE falls by only 2(y/r even though the tuna population declines by over 997f . A SIMULATED CATASTROPHE Figures 7 and 8 show the outcome of two simula- tions based on submodel B. (These simulations employed the discrete-time version of the population-dynamics submodel, as described in Appendix A. Qualitatively the results are the same as for the continuous-time model.) The fol- lowing parameter values were utilized: K = 5,000 attractors Xo = 0.5 EFFORT (SDF ) FIGURE 7. — Simulation re.sults: model B. "catastrophic" case. EfTort (measured in standardized days fishing iSDF'i is increased at years 1, 5. and 9. The final effort level produces a catastrophic but gradual declme in the tuna population, which is not "picked up" by thecatch-per-unit-effort iCPUEi index until the population has been essentially eliminated, i Scales for the four curves are Imear but not related; see initial values shown . I 326 CLARK and MANGEL AGGREGATION AND FISHERY DYNAMICS FIGURE 8— Simulaion results. Model B, noncatastrophic case. In this case, CPUE (catch per unit effort) seriously overestimates the decline in tuna abun- dance. SDF = standardized days fishing. EFFORK SDF ) E5CAPEMENTI TONS! CATCH I T0N5 ) CPUE I TONS/SOF) Q* = 50 tons 6 = 2 X lO""" per vessel day r„ =1.5 per annum N = 10« tons. In the first simulation (Figure 7) we set a = 10 '', implying an intrinsic schooling rate of 5'7f per day. Since this is well in excess of the intrinsic growth rateofO.ll'X per day, a catastrophe is observed. In the second simulation (Figure 8) we set a = 1.5 ^ 10 ', implying an intrinsic schooling rate of 0.075% per day, which is below the intrinsic growth rate. In Figure 7, effort is fixed at 6,000 vessel days for years 1-4, then 12,000 vessel days for years 5-8, and finally 18,000 vessel days for all later years. The escapement population stabilizes at about 890.000 tons by year 4, and stabilizes again at about 735,000 tons by year 8. However in years 9-17 the effort level is above £, s 15,000 vessel days, and the population is steadily reduced, ulti- mately to a level <100 tons. Although the popula- tion decline itself occurs gradually, neither catch nor CPUE shows any marked decline until the tuna population has crashed. For example, the decline in catch (and CPUE) in year 14 is 2.5'^f relative to the level for year 1, and in year 15 is 5.4'^ relative to the .same level. Even in year 16, when the tuna population is virtually destroyed, the catch (and CPUEl falls by only 20'7, . The same effort profile was used in the simula- tion shown in Figure 8, except for an additional increase in effort at year 12. In this simulation, CPUE declines significantly, but the population level is only slightly reduced. The biological ex- planation lies in the low rate of schooling in com- parison with the first simulation. Because of this low schooling rate, increased effort mainly has the effect of reducing the surface population, and (at the levels shown here) has little effect on the sub- surface population. This also explains why CPUE is much lower, at any fixed E. than in the first simulation. Finally, Figure 9 shows the results of a simula- tion based on submodel A, using the same parame- ter values as for Figure 7. This simulation indi- cates that, as expected, submodel A behaves quite similarly to traditional fishery models. MANAGEMENT IMPLICATIONS The models described above, and in the appen- dices, indicate that traditional methods of fishery management may be inappropriate in cases where aggregation processes significantly affect the fishery. On the one hand, such processes may be the source of bias in CPUE indices of stock abun- dance. On the other hand, these processes may also lead to a catastrophic relationship between fishing effort and sustainable yield. The latter situation will be especially serious in the event that CPUE underestimates declines in abun- dance. In addressing the management implications of 327 Figure 9. — Simulation results: Model A. The behavior of the model is similar to that of traditional fishery models. SDF = standardized days fishing. CPUE = catch per unit effort. FISHERY BULLETIN VOL 77, NO, 2 EFFORT (SDF) in 862.000 CATCH (TONS) ESCAPEMENT(TONS) CPUE ITONS/SOF) these theoretical results, for a particular fishery, we face two main problems. First, what is the likelihood that the fishery in question does involve an aggregation process, and if so, that catastrophic conditions may prevail? (We remark again that catastrophic conditions may be the result of pro- cesses other than aggregation.) Secondly, given that such conditions may exist, what are the im- plications for management policy? If an aggregation process is known to exist, our models suggest that the next question that ought to be addressed is whether aggregation is density dependent, and if so, to what extent it depends on population abundance? Also, the rate parameters of the process should be determined. Unfortu- nately this information may be extremely difficult to obtain, and the question arises whether infer- ences can be drawn from data supplied by the fishery, such as catch-effort data, school size, den- sity of schools, size composition of catches, and so on. For example, if aggregation is density depen- dent, then the size of the aggregated (surface) population will decrease with the size of the re- sidual (subsurface) population. For the case of tuna, either the number or the size of schools (or both) should decrease as the fishery develops. But the converse implication cannot be made: school size and/or number may decrease merely because the surface population is reduced by fishing pres- sure. Unless a direct, independent abundance es- timate of the subsurface population is available. the interpretation of such fishery data may remain ambiguous." The possibility that aggregation may lead to catastrophic yield-effort relationships lends a sense of urgency to the question of achieving a fuller understanding of the dynamics of the aggre- gation process. But whenever such catastrophic relationships seem possible, for whatever reason, a conservative approach to management appears appropriate. In view of the uncertainties involved, quotas should probably be established at a level lower than the estimated maximum sustainable yield. Furthermore, since depletion may neverthe- less occur unexpectedly, emphasis should be placed on achieving a high degree of controllabil- ity of the fishery. To a certain extent this necessity has been recognized by the Inter-American Tropi- cal Tuna Commission, the Director of Investiga- tions now being empowered to close the yellowfin tuna fishery in the event of a sharp decline in CPUE. However, if the decline were truly "catas- trophic," more drastic measures, such as a moratorium of some duration, might become necessary. Although the possibility may seem re- mote at present, we feel that further attention 'Various alternative indicators of depletion, involving size composition of the catch and the results of cohort analysis, are in fact employed by the Tuna Commission and have demonstrated no severe change that can be attributed to the fishery. The validity of such indicators should not be affected by the presence of an aggregation process, but we have not attempted to extend our model to include cohort structure. 328 CLARK and MANGEL; AGGREGATION AND FISHERY DYNAMICS needs to be given to these problems. Experience gained from other fishery failures suggests that control may be extremely difficult to achieve un- less expansion of the fishing industry is kept under control. For domestic fisheries operating within 200-mi zones, such control is now a possibility. For international pelagic fisheries, such as the tropi- cal tuna fisheries, however, the problem of entry limitation remains unresolved. ACKNOWLEDGMENTS This research was performed under contract to Southwest Fisheries Center, National Marine Fisheries Service, under contract number 03-6- 208-35341. For valuable discussions and correspondence about the tuna fisheries we are indebted to many people, including particulai'ly Robin Allen, Wil- liam Fox, Robert Francis, Paul Greenblatt, John Gulland, Daniel Huppert, James Joseph, Peter Larkin, William Perrin, Gary Sakagawa, Gary Sharp, Carl Walters, and Norman Wilimovsky. Responsibility for errors and expressed opinions, however, lies solely with the authors. LITERATURE CITED ANDERSON, L, G, 1977. The economics of fisheries management- The Johns Hopkins Univ. Press. Baltimore. Md.. 214 p. ARONSON, D.. .\ND H. WEINBERGER. 1975. Nonlinear diffusion in population genetics, combus- tion and nerve pulse propagation. In J. A, Goldstein leditori, Partial differential equations and related topics, p. 5-49, Lecture notes in mathematics 466. Springer- Verlag, N.Y. BRO.'\DHEAD. G. C, .'\ND C. J. ORANGE. 1960 Species and size relationships within schools of yel- lowfin and skipjack tuna, as indicated by catches in the Eastern Tropical Pacific Ocean, Inter-Am, Trop Tuna Comm,, Bull, 4:447-492, Calkins, T, P, 1961. Measures of population density and concentration of fishing effort for yellowfin and skipjack tuna in the East- em Tropical Pacific Ocean, 1951-1959. Inter-Am. Trop. Tuna Comm . Bull 6:69-152. CLARK. C- W. 1974, Possible effects of schooling on the dynamics of exploited fish populations, J, Cons. 36:7-14. 1976, Mathematical bioeconomics: The optimal manage- ment of renewable resources. Wiley-Interscience. N,Y.. 352 p. GULLAND. J. A. 1956. The study of fish populations by the analysis of commercial catches. Cons, Perm, Int. Explor. Mer Rapp. P.-V. 140:21-27. Jones, D. D., and C. J. Walters. 1976. Catastrophe theory and fisheries regulation. J. Fish. Res, Board Can, 33:2829-2833, KOLATA, G. B. 1977, Catastrophe theon,': the emperor has no clothes. Sci- ence (Wash., DC) 196:287, 350-351. LL'DWIG. D. 1974, Stochastic population theories. Lecture notes in biomathematics 3 Spnnger-Verlag. N,Y,. 108 p. May, R, M, 1974. Biological populations with nonoverlapping genera- tions: stable points, stable cycles, and chaos. Science (Wash,. DC, I 186:645-647, Moore, W, 1972, Physical chemistry. Prentice-Hall, Englewood Cliffs, N.J,, 977 p. Murphy, G. I, 1966, Population biology of the Pacific sardine tSard:nops caerulea). Proc, Calif Acad, Sci,. Ser, 4, 34:1-84, 1977. Clupeoids. In J. A. Gulland (editor). Fish popula- tion dynamics, p. 283-308. Wiley. NY, NEYMiVN. J, 1949. On the problem of estimating the number of schools offish. Univ. Calif, Publ, Stat, 1:21-36, PALOHEIMO, J. E., AND L. M, DICKIE, 1964, Abundance and fishing success. Cons, Perm, Int. Explor, Mer Rapp P,-V, 155:152-163, PELLA. J. J, 1969, A stochastic model for purse seining in a two-species fishery. J, Theoret, Biol, 22:209-226. PELLA, J. J., AND C, T. PSAROPULOS. 1975. Measures of tuna abundance from purse-seine oper- ations in the eastern Pacific Ocean, adjusted for fleet-wide evolution of increased fishing power. 1960-1971, Inter- Am, Trop, Tuna Comm,, Bull, 16:281-400, ROTHSCHILD. B- J. 1977, Fishing effort, /n J, A, Gulland (editor). Fish popu- lation dynamics, p, 96-115, Wiley. NY, SCHAEFER, M. B. 1957. A study of the dynamics of the fishery for yellowfin tuna in the Eastern Tropical Pacific Ocean, Inter-Am, Trop. Tuna Comm,, Bull, 2:245-285. 1 967 , Fishery dynamics and present status of the yellowfin tuna population of the Eastern Pacific Ocean, Inter-Am, Trop, Tuna Comm,. Bull, 12:87-137, SH.'^RP, G, D, 1978, Behavioral and physiological properties of tunas andtheireffectson vulnerability to fishing gear, /n G, D, Sharp and A, E, Dizon (editors), The physiological ecology of tunas. Academic Press, NY. THOM. R, 1975, Structural stability and morphogenesis. Benj'a- min. Inc. Reading. Mass., 348 p. White, a., P. Handler, and E, L. Smith, 1973, Principles of biochemistry, McGraw-Hill, NY., 1296 p. ZEEMAN, E, C. 1975, Levels of structure in catastrophe theon," illustrated by applications in the social and biological sciences, Proc, Int Congr, Math.. Vancouver, B.C., p. 533-546. 329 FISHERY BULLETIN: VOL, 77. NO, 2 APPENDIX A The purpose of these appendices is to test the robustness of our models, by introducing alterna- tive submodels for population dynamics (Appen- dix A) and for the schooling process (Appendix B). In this appendix we replace the continuous-time Schaefer model by a discrete-time stock- recruitment model. We postulate a fishing season of given length, during which the stock is fished down, followed by an interim season which results in the replenishment of the stock. The purpose of this exercise is not particularly to provide a more realistic model of tuna population dynamics, but simply to enquire whether our main results are independent of the type of model employed. (See Clark 1976, chapter 7, for a general discussion of models of the sort considered here, i Our alternative Model A is governed by the equations dt dN_ dt = -(aKN-j]S) /V(0) = R,S{0) = aKR/li 0 1 s 1, Exhaustion of the stock by the surface fishery is thus possible if and only if / / o- ESCAPEIVIENT ( P ) FiC.URE 10. — Fishery dynamics for the discrete-time modeLs; schooling model B G = net population growth curve; Y - catch curve; Y, = limiting position of Y; P' = population equilibrium forgiven Y. Case (a): intrinsic schooling rate less than intrinsic growth rate; escapement population cannot be reduced below level P by .surface fishery. Case (bl: intrinsic schooling rate greater than intrinsic growth rate; population can be fished to arbitrarily low levels; P* denotes an unstable equilibrium. (The corresponding yield-effort curve is similar to Figure 5(bl.l 3.30 CLARK and MANGEL: AGGREGATION AND FISHERY DYNAMICS exp \aKT) > g, i.e., if and only if'the intrinsic schooling rate (over the duration of the fishing season) exceeds the intrinsic growth rate. It is also clear that the yield-effort curves for this model have the same appearance as in Figure 3. Hence the behavior of the two models is closely analogous; bifurcations do not arise. The discrete-time version of model B is obtained by replacing the expression ( aKN ~ fiS) in Equa- tion ( Al I by «A'A'( 1 - SIS- ). This gives rise to a nonlinear escapement-recuitment relationship ^'^AR) It can be shown (we omit details i that limR.o^K («) = exp(-aKr) lim£.,.vl'e {/?) - exp(-aKT)-R limfi,„ (/?-*£-(/?)) = bxnS'TE. The resulting dynamics can be described in APPENDIX B terms of Figure 10. If aAT < a = \ng the model is noncatastrophic (Figure 10(a)), having a single equilibrium P* (escapement) which approaches P > 0 as £ -► +-^-. (If g > 2 the equilibrium at P* may be unstable, even "chaotic," for small E ( May 1974), but this possibility will not concern us here.) But if aKT > era second, unstable, equilib- riumP ' emerges, and a bifurcation occurs at some critical effort level E = E. To summarize, this appendix has demonstrated that the qualitative predictions of our schooling strategy models are independent of the basic popu- lation dynamics of the tuna population. Although we have explicitly established this fact only for two specific models, it should be clear that the theory will remain valid for a large variety of other models, including alternative forms of the growth and stock-recruitment functions and in- cluding delayed-recruitment models as well as cohort models. In all cases, the nature of yield- effort curves will depend critically upon a) the relationship between intrinsic schooling rate and biotic potential and b) the schooling strategy of tuna to the extent that school size is sensitive to the total tuna population. In this appendix, we present two detailed, kinetic models of the schooling behavior of tuna and tuna-porpoise complex formation. The models are more general that either model A or model B. which are in fact special cases of the models de- veloped in this appendix. Since our basic assump- tions are quite different from those used in the body of the paper, it is interesting that equivalent results can be obtained, at least in special cases. The models are based on the following assump- tion: in some large area of ocean, 11, there are Ttt^ core tuna schools and Kit) "attractors" (porpoise schools or logs) at time I . We assume that the core schools move independently of each other and that the motion is random. We first assume that when an attractor and y ( y s 1 ) tuna schools "collide" (i.e., come within some critical distance), a tuna-attractor complex is formed. Let C(n denote the number of tuna- attractor complexes at time I. The fishery is as- sumed to fish only on these complexes. We shall postulate different mechanisms of complex forma- tion and analyze the resulting kinetic equations. The kinetic equations are derived assuming a law of "mass action'" similar to the one used in chemi- cal kinetics (Moore 1972). We shall not consider the mechanism by which the core tuna schools are formed. Whenever it is necessary for the analysis, we shall assume that the number of core schools has a logistic grow-th function. This assumption is derived by firstly as- suming that the biomass of tuna, Af(/), has a logis- tic growth function. Namely, if no fishing occurred and no complexes formed: f-*" N/No) (Bl) where .V„ is the carrying capacity of H, in terms of biomass of tuna. LetS,, denote the weight of a core school. Then we have dT dt = rT(l -T/To) (B2) where 7"(n = .V(nS|, is the number of core schools at time I. A model in which the tuna-attractor complex is formed by one collision between y tuna schools and one attractor is first analyzed. Submodel A of the paper is a special case of this model. We show that 331 the harvest rate is a nonUnear function of effort and saturates asE -> ^-. Consequently Y/E is not a valid biomass estimate. We discuss other possible biomass indices, the behavior of ^(^ £i as a func- tion of effort and the sensitivity of the results to the parameters which appear in the kinetic equa- tions. Next, a multistep complex formation process is considered. A two-step model is analyzed in full detail. Submodel B is contained as a special case. In addition to exhibiting all of the features of the one-step model a multistep mechanism may lead to "catastrophic" behavior. The catastrophic be- havior was not built into the model but arises naturally from the dynamics. The models presented in this appendix ( particu- larly the multistep model) are based on what ap- pear to be reasonable assumptions about the schooling behavior of tuna and formation of the complexes. The ultimate behavior of the system (fishery + tuna + porpoises) does not appear to be an artifact of the models, but a result of the basic assumptions that the tuna form into schools and that the fishery seeks tuna schools associated with attractors. In fact, Thom's ( 1975) theorem on the structural sta- bility (robustness! of unfoldings asserts that small modifications of our models will not alter the qual- itative behavior. The analysis of discrete-time versions of our models is relatively intractable. Numerical studies are underway. We do not expect the results will be qualitatively different from the continuous-time results. The analysis presented in Appendix A supports this expectation. We have not included spatial effects (e.g., diffu- sion) in our kinetic equations. The addition of dif- fusion greatly complicates the analysis of the kinetic equati(ms. However, preliminary work based on the recent theory of Aronson and Wein- berger (1975) has been carried out. treating the kinetic equations with spatial dependence. We ex- pect that if diffusion is added to the models in this appendix, the transitions between high and low- tuna steady states may occur at effort levels lower than those predicted by the models without diffu- sion. Single-.Stt'p ( ollision Model In this model we assume that y tuna schools collide, at once, with one attractor to form a com- plex: K+yT-' FISHERY BULLETIN: VOL, 77, NO, 2 a (B3! The rate constants a, fj measure the association and dissociation rates of the complex. The com- plexes are fished at a rate/)/? with capture ratio x„: \obE C K + harvest of 7 schools. (84) Elquation iB.3) indicates that y schools must be present for a complex to form. In particular, if -y > 1 this model does not allow for the formation of "partial" complexes, with fewer than y tuna schools in the complex. It is clear that this assump- tion is restrictive; later we relax it and allow for complexes with 1,2 y tuna schools. The kinetic equations corresponding to Equa- tions (B.3) and (B4) are f = gr -aKT' + ^yC (B5) k = gn -aKT' +liC + hE\„C (B6) C = aKT'' -iiC-bE\oC: (B7) in p]quations (B5) and [BGigj. and^'^. are the tuna and attractor growth functions, respectively (^^. = 0 for logs). The term proportional to T^arises in the follow- ing way. Consider a small area of ocean, a. The probability,/), that a tuna school is in a should be proportional to alii and to T: T = h'T. (B8) If a complex containing y tuna schools is to form, y schools must be in o. Since the tuna schools move | independently and randomly, the probability of finding y schools in a is proportional top'' = /^T'. (A more precise analysis would lead iokTiT - 1) (T-2)...(7'-y-i-l) instead of^7'\ since once a school is in a specified area of ocean, there remain I r - 1 schools to be distributed over the ocean. ' Once the location of two schools has been specified, there remain T - 2 schools, etc. When T is large, as we are assuming, ^T'' is a good approximation to the exact expression.) The steady-state number of complexes is deter- mined by setting C = 0. We obtain C aKT' (3 + bExo (89) 332 CLARK and MANGEL. AGGREGATION AND FISHERY DYNAMICS The instantaneous rate of harvest, Y, is the prod- uct of (the number of complexes) X (the encounter rate bE) x (the capture ratio Xo' ^ ' the number of schools per complex). Thus Y = bExoyaKT^Sp P + bE\o If y = 1. Equation iBlO) becomes y = bExoaKTSg i5 + bE\o (BIO) (BID which is, with the exception of S^. identical to Equation (llA). The additional factor S„ arises here because we are considering numbers of tuna schools, whereas model A of the main part works directly with tuna biomass. Model A is thus a subcase of the model in this section. Hence, we have provided a second physi- cal picture for the mechanism which generates model A used in the paper. Equation (Bll) exhibits a saturation as E in- creases and is similar to results obtained in the Michaelis-Menten approach to enzyme kinetics (White et al. 1973). This is not unexpected, since our models are based on the assumption that the attractors "catalyze" the fishery. The tuna and attractor steady states are deter- mined from the steady-state versions of Equations iB5i and (B6i. Adding Equations (B6) and (B7) gives Sk 0, (B12) w^hich we assume has a solution A' = K,.. (Note that this model does not allow for the loss of attractors due to fishing.) The steady-state tuna population satisfies 0=,,-aKr^.^, [^^] (B13) gr = oAT'[ bExo-ii{y-l) a + bExo = aAT7(£,7). tB14) Since the case in which 7 = 1 was analyzed in the body of the paper, we shall not consider that case here. We shall briefly consider the case of -y a 2. This case may be of little interest in the actual tuna fishery, but there may be other instances where y 3= 2 is interesting le.g., animal popula- tions). When E is small, so that ^^Xu < f^^y - H- the coefficient /'(£',>') is negative. Equation (B14) has a graphical solution sketched in Figure 11. The steady-state tuna level, 7",, is greater than the "natural level" T^, but this is explained as follows. At any time there are a certain number of tuna schools bound in the complexes. The remaining, uncomplexed, tuna achieve the steady state level r,|. The total number of tuna, however, is T„ plus the number in the complexes. AsE increases, a level of effort is reached so that /"(£,y) = 0. At this point. Equation iB14) becomes 8t 0. (B15) The tuna level is at the natural steady state, be- cause tuna are removed from the complexes as quickly as they enter the complexes. AsE increases further, /"(S.y) -►/■,, where/'j = 1 is the limit as E -*■ ^ of /(fi.y). Equation (B14) becomes g^ = uKT\ (B16) The graphical solution of Equation (B16) is < < I u < aKT' f (E,y ) NUMBER OF CORE SCHOOLS (T) Figure U. — Graphical determination of the steady-state tuna population I Tj I for the one-step kinetic model, when the natural dissociation rate is greater than fishing mortality isee text). 333 FISHKRY BULLETIN VOL 77, NO a sketched in Figure 12. When 7^2, it is impossible to overfish the tuna into extinction (compare Fig- ure 12 with Figure 2, which corresponds to the case y = 1 ). The reason for this behavior is that, as the tuna level decreases, the rate of formation of complexes, aKT^. decreases much more rapidly since y s^ 2. When T is small, it is unlikely that a complex will form. This result should be con- trasted with the case of y = 1, in which is it possi- ble to overfish the tuna to extinction. From Fx]uation (RlOi we have Y/E hxoyaKT Sp a + bE\o Thus, if /i • ■ hE\„ we obtain r' cc YIE (B17I iBISi In the intermediate region /J ~ hEx^^ it appears that no simple biomass index is available. The determination of the appropriate biomass index depends upon the size q{ hE\„l(i. This is a natural measure since it compares the rate at which complexes are dissociated due to fishing with the natural dissociation rate /i. Miiltistep (jjllision Model The model in the last section is somewhat un- realistic in that the complex with y tuna schools is formed only if the y schools collide siniultaiiei}usl\' w ith an attractor. Hence, the model did not allow lor complexes with y - 1, y - 2. ... ,1 tuna school per complex. A more realistic model is one in which the tuna-attractor complexes form by a multistep mechanism: so that T cc (y/£:i'>. iBU)i Thus (V''£i' ^ is a possible biomass index, if /i > hExu- U liEx„ fi. then y,T + A': C, 73^ + C2^^C..j (B21i y/E * ^—^^ So. (B20) In this limit a possible biomass index is (Y')'^. Thus, the catch itself is a biomass index. < a: < cc UJ X S o I- •- — < cr o UJ a kt'' aKT't(E,y) bE\o K -^ harve.st of I 7 schools i = \ where / = 1 , More detail could lie added, e.g., when a complex C'l is fished, / = 1, ,/ tuna schools might be re- NUMBER OF CORE SCHOOLS (T; moved with probabilities p,,. When all y/,. = 1, Equation iB21i is undoubtedly the most realistic model presented here. (Since the probability that two core schools are added at the same instant is essentially zero, the idea of stepwise addition of schools seems justified.) The kinetic equations cor- responding to the reactions in Equation (B21) are I for y ^ 1 for all / ) Ci = Q , AT - (/iiCt + hExnC\ + 02^1 T) + {i^Co Figure 12. — Graphical determination of the steady-state tuna population (T^i for the one-step kinetic model, when fishing mortal ity is greater than the natural dissociation rate i see text). C„ = a„C„_ir-(/3„C„ + 6£xoC„ + Q„.^ir„7') +/i„.nC„„, (n>2) (B22I 334 CLARK and MANGEL AGGREGATION AND FISHERY DYNAMICS K = -aiKT+bExo{^^ C,} +|3iCi +gK{K). Steady states of the system are obtained if we set the left-hand sides in Equation i B22) equal to zero. We then find that the steady states are determined bv: C (n>2) (B23I gK(K) = 0 J=i Equations (B22l and (B23) seem to represent a fairly realistic model of the fishery dynamics. A full analysis of these equations would be quite illuminating. However, as it is, the analysis of this model quickly becomes intractable. In order to illustrate the behavior of this model, we will analyze the case /; = 2 (for arbitrary y, , y.^); Pi C■^ +7,r. -Co P2 bE\a Cj ^ A' + harvest of 7 J tons (B24) bE\n C2 "A + harvest of 71 +73 tons. The results of the analysis of three-(or higherJstep mechanisms should be similar to the analysis of the two-step mechanism. The multistep model provides a picture of the tuna-porpoise bond which appears to be relatively realistic. For example, we may imagine that the first Vi schools are bound strongly to the complex (a, large, /^, small) and that the next y.^ schools are bound less strongly (a.^ < a,. /32 ^" /^i '■ Sharp's (19781 discussion of the effect of the thermocline on the tuna-porpoise association supports this model. In particular, it seems likely that the a, and 13, depend upon the location of the thermocline. The kinetic equations corresponding to the mul- tistep model are f = gr -OiT' ' A-ttaT'^ Ci + /3i Cj + /^2C2 + 7il3iCi +72(^2C2 'B25) ^ = ^h- -ai r" A + (JjCi + 6£xo(Ci + Cg) (B26i + 1^202 - bE\oC\ (B27I C2 = ttaCiT'^ -^2C2-bE\QC2 ■ (B28i In the steady state, we have azCiT'' Co (^2 + bExo ■ (B29) Adding the steady-state version of Equations (B25)-iB28) gives f^K = 0 (B30) which we assume has the solution K = A,, ■ 0. The steady-state version of Equation (B27), using Equation (B29), is: 0 = ttiAT'' -l^iCi -asCiT'-' - bExoCi +a2^2T'"C^I(^2 + bE\o) which can be solved to give the steady-state level ofC, complexes; <"l = aiKT^' i3i ^a2T'' + bExo -a2p2T^ ' IW2 + ^^Xo) (B31) The instantaneous harvest rate is given by: Y = 6£Xo(7iCi +(72 + 7i)C2)So (B32) bExoSoaiKT'- |3i +a2T"- + 6£:xo -ot2ii2T" IW2 + ''^Xo) X (7i +72a2r"7(|32 + 6£\o))- (B33) 335 FISHERY BULLETIN VOL 77. NO 2 Note that if we set /3, = fi., = 0 and y, = y., = 1 . Equation (B33) becomes bExoSoOiKT bExo + oc2T With the exception of the multiplicative term ( 1 + a.,T/hEx„). Equation (B34) is equivalent to Equa- tion 111) (model B) in the body of the paper. We shall show that the model presented in this section contains model B as a special case and also exhibits "abrupt" transitions, between multiple steady states. As E -► ^, the harvest rate saturates and y-y„ = ai7iSoX,r'' (B35) Hence, when E is large, iV)' ''' is a biomass esti- mate. When E is small. Equation iB33) becomes bExoSoOiiKT'' 720 2 Y^ 7. (7i+-^T'M, IB36) Pi P2 which can be written as Y/E ^ hiT" +h2T'' where h-^ bXoSoO^iKyi /Ji72"2 ■,/'2 12& (837) iB38) 2P2 Unlike the one-step model, in the multistep model YIE is not a useful biomass estimate at any level of effort. The steady-state tuna level is determined from the steady-state version of Equation (B25). After Equations (B29) and (B32) are used for the values of C| and C, and the resulting expression is sim- plified, we obtain gr = aiT' K A{aJ.E,T) iB39) p{a,li,E,T) where A = (7i + 1) [)3i/32 + |3i bExo 1 + (y2-W2T'' + dibExo + (bExo)^ lB40) P = ^S,i32 (B41) ^bExoifii *li2 + bExo+oi2T'' ). Because A and p are so complicated, Equation (B39) is difficult to analyze as it stands. To simplify the analysis, we assume that /3, = fi^ ~ 0. Physically, this means that the rate of dissociation of complexes due to fishing is much greater than the natural dissociation rate of complexes. Since our major interest is in the qualitative behavior of Equation ( B39), this assumption seems acceptable. If /3, = li.2 = 0. Equation (B39l becomes gr a^T" KbExo bExo+a2T'' {B42) which can be analyzed. We denote by /■(£, y^,y2,T) * the right-hand side of Equation (B42). The solu- tions of Equation (B42) will be discussed according to the values of y, and y.,- A complete analysis of Equation (B42) is very involved. We shall present a partial analysis, in order to illustrate the types of behavior which may occur. We first consider the casein which y, = yj = 1. Equation (B42) becomes gr = a^KbExoT bExo -^ 02T ' (B43) which is analogous to Equation ( 1 IB) of the body of the paper. Consequently, we shall not pursue the analysis here. In the analysis of Equation (IIB), we showed that Equation ( B43 ) may have multiple steady states. As effort increases, a transition be- tween the steady state where the tuna level is high and the steady state where 7" = 0 is possible if «,A' '> gT' *0' 'the "catastrophe" condition). In the one-step model, a complex containing two tuna schools was formed only if the two schools, at once, came into close contact with an attractor. That model did not exhibit multiple steady states, or even the possibility of overfishing the tuna into extinction. On the other hand, if the complex that contains two schools is formed by a stepwise process, so that schools are added to an attractor one at a time, "catastrophic" behavior and extinction of the tuna are possible. Sudden transitions in population (catastrophes) are usually difficult to predict. However, the model presented here leads to a natural measure of overfishing. From Equations (B29) and (B31), when E is large we have 336 CLARK and MANGEL AGGREGATION AND FISHERY DYNAMICS 1 bExo {bExo)^ (B44) Consequently, if overfishing is occurring, the number of complexes with two tuna schools is much less than the number of complexes with one school. As effort increases further, the fishery will find more and more attractors without any as- sociated tuna schools. Such observations should act as a warning that the tuna are being over- exploited. We note that it is possible that CPUE will not decrease, even though the number of tuna schools per complex is decreasing (see Figure 7). A host of complex solutions and bifurcations can be determined if the values of y, , y.^ are not 1 . Since y, > 1, y., > 1 do not have an immediately obvious interpretation for fishery dynamics, we will not consider those cases here. In this Appendix, we have taken an approach to modelling the fishery that is substantially dif- ferent from the approach in the main part of the paper. The results obtained here complement the main results, and extend them. We have shown that models A and B presented in the paper arise as special cases of the kinetic models in this Ap- pendix. It is clear that these models could be greatly elaborated and many other details explored. 337 SHALLOW MARSH HABITATS AS PRIMARY NURSERIES FOR FISHES AND SHELLFISH, CAPE FEAR RIVER, NORTH CAROLINA Michael P. Wein'stein' ABSTRACT Seine and rotenone collections taken during 1977 from the upper reaches of tidal creeks and along the marsh fringe m the vicinity of the Cape Fear River, N.C., indicated that these areas serve as primary nursery habitats for postlarval and juvenile fishes and shellfish- Average densities i number 400m2i for several ocean-spawned species at the peak of postlarval or early juvenile recruitment were high: spot, Leiostomus xanthurus. 3,099; Atlantic menhaden, Brevoortia lyrannus. 839; striped mullet, Mugil cephalus. 711; white mullet, Mugil curema. 52.5; and brown shrimp, Penaeus aztecus. 329. Standing crops for the majority of species studied further indicated that lower productivity per unit area occurred in high salinity marshes closest to the ocean In addition, distribution patterns for several species were significantly correlated with salinity and substrate characteristics or combinations of them and seasonal effects also were evident so that related and potentially competing species were separated temporally Community analyses demonstrated that each niar.sh complex was unique; however, overall similar- ity for the most abundant species was high. The diflferences were related to salinity gradients and to the presence of an "edge effect" where marshes closest to the river mouth were species rich due to seasonal invasion by low densities of reef, nearshore, and shelf marine .species. Similarly, freshwater fishes invaded brackish marshes during periods of high river flow Patterns of distribution of estuarine species have often been correlated with environmental gra- dients (Remane 1934; Hedgepeth 1957; Gunter 1961; Khlebovich 1969; Gainey and Greenberg 1977) and have also been described in terms of characteristic estuarine zones: marshes, tidal flats, sounds, bays, and channels. Within these areas, organisms are frequently associated with specific habitats; for example, the marshes can be divided into the high marsh and tidal creeks, the latter characterized by soft muds at their head- waters and by more scoured areas downstream. Several properties of the water column also vary in these creeks, being generally more stable near the creek mouth (Hackney et al. 1976), and the presence of food organisms is often correlated with sediment properties so that predators may fre- quent one area more than another (deSylva 1975). On the basis of individual tolerances, some species will frequent habitats under a wide range of condi- tions, while others will be more restricted in their distribution. These tolerances may change with the age of the individual so that a given species may be a member of several different communities during its life cycle. 'Lawler, Matusky & Skelly Engineers, One Blue Hill Plaza, Pearl River, N.Y.; present address: Department of Biology, Vir- ginia Commonwealth University, Richmond. VA 23284. When the nursery role of estuaries is considered in this framework, it becomes evident that infor- mation is lacking on age-specific utilization of es- tuarine zones. Few investigators have studied the primary nursery areas where the youngest mem- bers of many ocean-spawned species first take up residence (Herke 1971; Parker 1971; Purvis-), In one such area, the tidal salt marshes, comprehen- sive sampling efforts have demonstrated that a temporal succession takes place with many spe- cies residing in the upper reaches of tidal creeks during their earliest days and then moving gradu- ally downstream as they grow (Herke 1971; Dunham 1972; Purvis see footnote 2). A similar successional pattern occurs in the upper reaches of the Chesapeake Bay (Haven 1957; McHugh 1967; Chao and Musick 1977 1 and in open bay waters near the heads of estuaries in South Carolina (Bearden 1964), Louisiana (Thomas and Loesch 1970), and Florida (Hansen 1970). The present study details the composition of the nekton community of several shallow marsh areas, including tidal creeks and marshes adjacent to the river shoals. Consideration is given to the role of these habitats as primary nurseries, and patterns Manuscript accepted January 1979 FISHERY BULLETIN: VOL, 77, NO. 2, 1979. ^Purvis. C, 1976, Nursery area survey of Northern Pamlico Sound and tributanes, Div. Mar. Fish, Rep. (prepared for U.S. Dep. Commer.. NOAA, Natl. Mar. Fish. Serv.l, 62 p. 339 FISHERY BUI. LFTIN VOI, 77, NO of distribution of individual species are described. An attempt is also made to correlate these dis- tributions with both biotic and abiotic parameters. STUDY AREA All sampling stations were situated within the Cape Fear River, N. C, located at approximately lat. 33° N (Figure 1 1. The estuary is relatively narrow, averaging only 1.6-3.6 km wide and ex- tending 45 km from the general location of the salt boundary at Wilmington, N.C., to the river mouth at Baldhead Island. A 12 m deep ship channel is maintained from Wilmington to the river en- trance, and numerous spoil islands are found adja- cent to this channel over its entire length. Tidal velocities in the Cape Fear are high, averaging 1 .5 m/s at the river mouth during ebb. Tidal salt marshes cover approximately 8,900 ha and form the largest contiguous system of this type in North Carolina (U.S. Army Corps of En- gineers-''). Dominant plant species include the smooth cordgrass, Spartina alterniflora , and black needle rush, J uncus roemerianus, with giant reed grass, Spartina cyanosuroides, prevalent up- stream at lower salinities. Tidal creeks cover an estimated 648 ha, and shallow open water areas (shoalsi between the channel and salt marshes contribute an additional 7,285 ha of suitable nur- sery habitat. MATERIALS AND METHODS Nine stations were established within several major marsh systems and along the river shoals (Figure 1; Table 1). Suitable interior marsh sites could not be located in the middle reaches of the estuary, since the few available creek systems were inaccessible or could not be sampled without great difficulty. Salinities at the chosen sites ranged from 0 to 35%o, and a wide variety of sub- strata were included, ranging from soft organic ooze, approximately 10-20 cm deep, to sandy areas containing little organic material. Stations were sampled on a monthly basis from January through December 1977 with several exceptions (Table 1 ). Because of ice cover, the Dutchman and Walden Creek rotenone stations were not sampled in January, and new stations were established at Shellbed Island and Hechtic Creek in February and at Barnards Creek in April. Two collection methods were employed throughout this study: seining, where footing was satisfactory, and rotenone application i5'^f emul- sifiable Fish-Tox-*), where softer mud or snags pre- dominated. Before either method was attempted, an area of tidal creek was isolated utilizing large blocking seines. Nets were extended from shore to shore and were anchored with U-shaped lengths of concrete reinforcing rods, especially helpful in pinning the leadline along the contours of the banks on each side of the station (at several sites, one shoreline was always bordered by a bar forma- tion!. In addition, a length of heavy chain was affixed to the leadline of each block net to ensure direct contact with the substrate. Initially, 6.5 mm mesh block nets were employed; beginning in April 1977 these were replaced with fine mesh (approxmiately 1.0 mm) nets capable of retaining the smallest ocean-spawned larvae. The enclosed area then was swept repeatedly with a 7.6 m, 6.5 mm mesh, seine or treated with sufficient rote- none to kill all fish present. To determine the number of seine sweeps re- quired, a study was conducted in October 1976 when nekton diversity remained near a yearly maximum. After the block nets were set at the Dutchman Creek site, a total of 13 sweeps were i taken, and the contents of each sweep kept sepa- rate. The results were plotted (Figure 2) as the cumulative number of species, the expected number of species (ENS) (Hurlburt 1971) and the ' cumulative diversity (H', Shannon and Weaver 1949 ). As seen in the figure, little new information was gained after the eighth sweep, i.e., an asymptote was approached. A separate study at Baldhead Creek in September 1977 confirmed these results, and a procedure requiring eight sweeps was instituted at each seine station.'^ In addition, three overlapping sweeps with a 7.6 m, approximately 1.0 mm mesh, seine were taken at each site. These served to capture the smallest fish present, those capable of passing through the 6.5 mm meshes. A preliminary experiment indicated that these seines were capable of significantly re- ducing the lower size range of key species studied (Table 2). ^U.S. Army Corps of Engineers. 1977. Maintenance of Wilmington Harbor, North Carolina. Final environmental statement. U.S. Army Engineers District, Wilmington. NC. 97 p. 340 ^References to trade names does not imply endorsement by the National Marine Fisheries Service. NOAA. ^A50-ft 1 1.5-2 m) seine was used on the last sweep, this was the original down.stream blocknet. WEINSTEIN SHALLOW MARSH HABITATS AS PRIMARY NURSERIES Figure l. — Seine and rotenone sampling sites. Cape Fear River estuary, N.C. 341 FISHERY BULLETIN: VOL. 77. NO, 2 Table l. — Sampling localities and dates for collections of fishes and invertebrates, Cape Fear River estuary, N.C., including physicochemical data. D = approximate distance from river mouth to creek entrance; SD = standard deviation; MPS - median particle size; SC = sorting coefficient. Location Sampling schedule D (km) Average salinity -SD Average temperature :SD Sediment parameters Sand (%) Organics (%) MPS (mm) SC Station Medium Fine Silt- clay No. ol cores Baldhead Cr Tidal seme creek Jan -Dec 09 257±70 21 1-76 13 86 1 1 88 0 23 065 7 rotenone Jan -Dec 09 25 9-6 7 21 3-78 34 65 1 1 13 0,34 0,80 6 Sheilbed Is River seme shoal Feb -Dec 46 26 6 ■ 5 9 23 1 -6 8 7 92 1 0 77 0 23 0 60 3 Dutchman Cf Tidal seme creek Jan -Dec 66 25 1 i6 9 199:83 10 86 4 2 67 021 0 79 7 rotenone Feb -Dec 66 18 1 -8 7 20 4-8 9 20 66 14 10 42 0 20 1 31 4 Walden Cr Tidal seme creek Jan -Dec 97 86±48 21 4.8 1 12 87 1 0 80 021 059 6 rotenone Feb -Dec 97 92-54 21 2'77 12 87 1 0 43 0 25 0 56 3 Hechtic Cr River seme shoal Feb -Dec 33 6 6 0-55 21 4-98 27 66 7 2 30 0 28 1 13 6 Barnards Cr Brackish rotenone stream Apr -Dec 33 9 61 i56 223:76 8 86 6 33 17 024 0 72 3 SWfcfcl' NUMflER Figure 2. — Dutchman Creek. N.C., survey (October 1976) de- signed to determine the number of seine sweeps required to pro- duce a representative sample. Cumulative number of species I ENS) and Shannon-Weaver diversity IH') are plotted on sepa- rate axes. At rotenone sites, sufficient toxin was intro- duced to kill all fishes present; this quantity was determined by the presence of certain "indicator" species in the collections, especially killifish iFundulus spp.) and eels (e.g., speckled worm eel, Myrophis piinclcifns; American eel, Anguilla ros- trata) which are resistant to rotenone and may also burrow in the substrate. Stricken fishes were dipnetted as long as they were visible on the sur- face, and the downstream block nets were also picked at the end of the survey. During winter, additional rotenone was added to ensure that toxi- city remained uniform, and in all months, potas- sium permanganate (KMnO^) was added down- stream to detoxify rotenone carried below the sites. During this study, no attempt was made to account for rotenone losses due to settling. All collections were initiated near low tide to reduce the effects of current and to sample post- larval fishes that were not swept downstream by tidal flows. To ensure uniformity of water volume between the block nets, staff gauges and land- marks were used to standardize the volume/area sampled. Throughout this paper, all catches will be reported as the number of individuals per 400 m-, the average surface area of the stations. Temperature was recorded prior to each collec- tion with a calibrated stick thermometer or tem- perature mode on a Beckman (model RS 5-3) salinometer; surface salinity was measured with the same instrument. The salinometer was cali- brated prior to each monthly sampling trip with a T.^BLE 2. — Comparison of length-frequency distributions from 6.5 and 1.0 mm mesh, seine collections. Cape Fear River estuary, N.C. A = 6.5 mm mesh seine, seven sweeps; B = 1 .0 mm mesh seine, three sweeps. Lower one-tailed /-test; ** =P 0,01. ns = not significant. Specimens '-28 mm are not included in mean values. Species Length (mm) 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 28 Total Mugtl cephatus Leiostomus xanthurus Paralichthys spp 4 36 37 62 41 20 15 13 7 1 2 5 9 10 1 1 1 2 1 4 20 7 5 42 49 9 6 24 19 3 2 9 4 2 7 2 3 1 8 253 21 4 3 30 21 1 ns 1 170 199 33 184 •■ 8 14,9 39 130 •• 342 WEINSTEIN: SHALLOW MARSH HABITATS AS PRIMARY NURSERIES known resistor and periodically checked against salinity standards. Fishes and shellfish were pre- served in 10'7f Formalin and lengths (standard length for fishes, carapace width for crabs, and total length for shrimp) recorded for selected species. Subsampling for lengths was employed when sorted collections contained more than 100 individuals of a given species. Sediments were collected with a 0.01 m'-^ plug sampler. Three to seven cores, 5 cm deep, were taken at each site, with the actual number at any one location governed by the expected homogeneity of the substratum. Where the bottom was uniform, three evenly spaced cores were taken along a diagonal across the site; where bar forma- tions formed a border of the site, six or seven evenly spaced cores were collected along two transects located parallel to each shore. Cores were processed according to prescribed methods of the American Society for Testing and Materials (American Society for Testing and Materials 19631. Hydrometer analysis was used for the fine ft-action, and particle size descriptions were based on the unified scale (U.S. Corps of Engineers 1953). The degree of similarity among sites was com- pared with the percent similarity index (PSI) (Whittaker and Fairbanks 1958): PSI = 100 i(p ,p ) wherep^ andp^^ are the proportion of species i in samples a and b, respectively. Since species with single occurrences (singletons) and taxa not iden- tified to species contributed little to similarity among sites or to an understanding of their role in the community, they were omitted from the analyses. Separate matrices were constructed for pooled monthly data at each site on the basis of station and species affinities (recurring species groups) and clustered by the unweighted pair group-average method (Sneath and Sokal 1973). Data were logj^, transformed prior to these analy- ses to give added emphasis to less common species and decrease the effect of extreme values (Clifford and Stephenson 1975). Three separate dendro- grams were constructed — a station association dendrogram in which all nine stations were com- pared, and a pair of dendrograms which reflected station and species associations for seine sites. Results for the latter comparisons were then cross-referenced by construction of a two-way coincidence table (Clifford and Stephenson 1975). Partial correlations were calculated with physi- cochemical data and monthly abundances for selected species (Fisher 1973). The latter were based on sufficient sampling densities (taken as at least 10 individuals collected among all sites in any given month) and served to reduce the effect of zero catches in the data. Prior to the analyses, abundance data were \og^^^ transformed in order to stabilize variances (Winsor and Clark 1940). RESULTS Physicochemical Parameters Among the seine sites, two distinct salinity pat- terns were observed (Table 1); high salinity sta- tions (Baldhead and Dutchman Creeks and Shell- bed Island) generally ranged above 15%ii, while Hechtic Creek (well upriver) and Walden Creek (part of a fairly extensive freshwater drainage ba- sin) ranged downwards from this value. Seasonal patterns also were evident, with salinity depres- sions occurring in the spring, especially in March and April, and again during the fall. Although the pattern for rotenone stations was not as distinct as that for seine sites, results were similar, with the exception of the Dutchman Creek station (located at the headwaters of this creek system) which reflected local runoff. Sediment characteristics (Table 1) represent means for all cores taken at each site. Fine sands (1.25-3.75 3.75 ) were minor components of the substratum at stations located in the Baldhead Island complex, although this percentage increased in Dutchman Creek, with a maximum ( lA'i ) at the rotenone site. Both upriver stations. Hechtic and Barnards Creeks, also con- tained more silts and clay. Organic fractions were similarly distributed, with the lowest station mean recorded for the well-scoured Walden Creek system. Dutchman Creek and upriver sites gener- ally had sediments with high organic content, with a maximum at Barnards Creek of SS.l?*^. Sorting coefficients (a, ) were calculated (Table 1 ) for each site according to the methods of Folk (1974). Sediments were poorly sorted at the Dutchman Creek rotenone station, located at the 343 FISHERY BULLETIN VOL. 77 NO 2 headwaters of the marsh creek where flows were minimal throughout the tidal cycle, and at Hech- tic Creek which also "dead-ends" a short distance upstream. Median particle size, computed as the geometric mean for all core samples collected at the site, generally fell within a narrow range, with the exception of the Baldhead Creek rotenone sta- tion where larger particles were associated with the medium sand fraction. The percentage of this fraction was considerably greater (349; ) than at other localities. Intcrstation Comparisons Species richness was greatest at the Baldhead Creek stations, closest to the ocean entrance, while the total number of individuals captured varied among sites (Table 3). The low catch at Barnards Creek is reflected in the reduced sam- pling effort at this station which was first sampled in April. Catches at Walden Creek were similar tp those at Baldhead Island, although fewer taxa were collected. On a seasonal basis, peak total abundance occurred mainly in the winter and early spring, coincident with the presence of win- ter-spawned species, primarily spot, Leiostomus xanthurus; Atlantic menhaden, Brevoortia tyran- nus; mullets, Mugil spp.; and flounders, Para/ic/i- thyi^ spp. Differences in relative numbers of species in monthly collections were tested with the Wilcoxon signed rank test (Table 4). Seine and rotenone stations were treated separately, and in compari- sons involving Barnards Creek, only the months April to December were used. Among seine sta- tions, Baldhead Creek yielded greater numbers of species than all sites except Hechtic Creek, while Table 3. — Total number of individuals and species collected at seine and rotenone sampling sites. Cape Fear River estuary. N.C. Samptmg site No ol individuals No ol species Sample see Baldhead Creek Seme Rotenone Shellbed Island: Seme Dutchman Creek: Seme Rotenone Walden Creek Seme Rotenone Hechtic Creek Seine Barnards Creek Rotenone 15,320 52 12.259 58 23.611 43 25,964 36 36.750 30 14,929 35 18.183 37 23.113 44 8.063 39 12 11 12 11 12 11 the Baldhead Creek rotenone site produced sig- nificantly more species than other rotenone sta- tions. The upriver sites, Hechtic and Barnards Creeks, were also richer in species than either Dutchman or Walden Creek, but did not yield more species than the station at Shellbed Island. The most abundant species ( collectively compos- ing O.S*^ or more of the total number of individu- als) were essentially similar among stations (Ta- ble 5), differing only in their order of abundance. For example, Leiostom us xanthurus; mummichog, Fundulus hcteroclitus; and striped mullet, Mugil cephalus, were ubiquitous, and Brevoortia tyran- nus\ white mullet, M. curema; and Atlantic silver- side, Menidia rnenidia, nearly so. Other abundant species seemed more closely associated with .specific habitats; the striped killifish, F. majalis, for example, was restricted mainly to high salinity areas, while the Atlantic croaker, Micropogonias undulatus. and hogchoker, Trinectes maculatus, were collected more frequently in brackish water with bottoms high in organic matter. It should be emphasized that seine and rotenone methods used here differed somewhat with respect to gear ef- ficiency and selectivity (Weinstein and Davis in prep.) and, in addition, invertebrates such as brown shrimp, Penaeus aztecus, and blue crab, Callinectes sapidus, were not considered to be sampled quantitatively with rotenone. These species, however, were common at all seine sites except Shellbed Island. The effects of the extreme cold in January and February 1977 along the eastern seaboard were reflected in the data with severely reduced catches of organisms in these months. Although catches might have been expected to be higher at this time of year, ice covered the headwaters of several marsh creeks, and water temperatures in the shal- lows hovered between 0' and 2' C. These tempera- T.ABLE 4. — Species richness comparisons among seine and rotenone stations. Cape Fear River estuary, N.C. The test statis- tic IS the Wilcoxon signed rank test, * = significant at a = 0.05; ns = not significant. Seme station Baldhead Shellbed Dutchman Walden Creek Island Creek Creek Hechtic Creek Baldhead Creek Shellbed Island Dutchman Creek Walden Creek Hechtic Creek Rotenone Baldhead Dutchman Walden Barnards station Creek Creek Creek Creek Baldhead Creek • Dutchman Creek — ns • Walden Creek — Barnards Creek — 344 WEINSTEIN SHALLOW MARSH HABITATS AS PRIMARY NURSERIES Table 5 —Pooled species abundance for all collections at seine and rotenone sites in the Cape Fear River estuary, N.C.. listed in order of abundance- Only species composing 0.5'7c of the total number of individuals and their corresponding percentages are shown. Bamards Creek was not collected until April 1977. Location/ species No % Location/species No % Location'species No % Seine Mugil curema 83 06 Tnnectes maculatus 92 11 Baldhead Creek Menidia beryllina 82 06 Penaeus duorarum 79 1 0 Anchoa mitchilli 4,330 28 2 P setilerus 70 0 5 Citharichthys spilopterus 54 07 Leiostomus xanthurus 3.918 25 5 Shellbed Island; Gobionellus sp 52 06 Mugtl curema 1.668 109 A mitchilli 8,927 37 8 Syngnathus louisianae 42 05 Menidia menidia 1.510 98 M menidia 8,758 37 1 Dutchman Creek Fundutus heteroclitus 938 6 1 Leiostomus xanthurus 3,023 128 L xanthurus 12.436 33 7 Penaeus duorarum 657 43 F heteroclitus 730 3 1 F heteroclitus 9,278 25 1 F maialis 541 35 Mugil cephalus 525 22 Mugil curema 8.546 232 Brevoortia tyrannus 287 1 9 E argenleus 450 1 9 M cephalus 3.713 101 P aztecus 266 1 7 M curema 354 1 5 B tyrannus 909 25 Mugit cephalus 263 1 7 A hepsetus 295 1 2 Lagodon rhomboides 677 1 8 Callinectes sapidus 162 1 1 B chrysura 115 0 5 Flops saurus 273 07 Gobiosoma bosci 114 0 7 Hechtic Creek Menidia menidia 242 0 7 Bairdella chrysura 108 07 Brevoortia tyrannus 7,967 34 4 Walden Creek Eucinostomus argenleus 106 07 L xanthurus 7,953 34 4 Leiostomus xanthurus 1 1 .093 61 0 C simitis 91 06 M cephalus 3.009 130 8 tyrannus 2.531 139 Lagodon rhomboides 70 05 P aztecus 1.199 52 F heteroclitus 910 5.0 Dutchman Creek A mitchilli 660 29 Mugil cephalus 733 4,0 Leioslomus xanthurus 8,534 32 8 F heteroclitus 590 26 Lagodon rhomboides 708 39 M cephalus 4,160 160 C sapidus 265 1 1 M curema 677 37 F heteroclitus 3,056 11 7 P duorarum 247 1 1 Eucinostomus argenleus 329 1 8 M curema 2,582 99 M curema 199 09 Menidia menidia 318 1 8 Menidia menidia 2.510 96 Menidia beryllina 199 09 M beryllina 241 1 3 Brevoortia tyrannus 1,387 53 P setilerus 171 0 7 Paralichthys spp 142 08 C sapidus 938 36 Bairdiella chrysura 160 07 Bairdiella chrysura 88 05 F maialis 824 32 Micropogonias undulatus 122 05 Bernards Creek P aztecus 741 28 F heteroclitus 2,996 24 4 Bairdiella chrysura 502 1 9 Rotenone Leiostomus xanthurus 2.750 22 4 E argenleus 231 09 Baldhead Creek M menidia 2.486 20,2 A mitchilli 151 06 L xanthurus 1.969 24 2 Mugil curema 855 70 P selilerus 132 05 Brevoortia tyrannus 1,260 155 Lagodon rhomboides 519 42 Walden Creek. Mugil cephalus 1.181 145 Mugil cephalus 406 3,3 L xanthurus 7.410 496 F heteroclitus 799 98 G boleosoma 373 30 Brevoortia tyrannus 1,666 11 1 Micropogonias undulatus 446 55 B chrysura 343 2.8 F heteroclitus 1,240 83 A mitchilli 373 46 Gobiosoma bosci 223 1 8 P aztecus 1,217 8 1 Symphurus plagiusa 334 4 1 Anchoa mitchilli 211 1 7 A mitchilli 1,050 70 Paralichthys spp 250 31 Eucinostomus argenleus 205 1 7 Mugil cephalus 780 52 Gobionellus boleosoma 213 26 Brevoortia tyrannus 158 13 E argenleus 304 20 Angullla rostrata 209 26 Paralichthys spp 123 1 0 C sapidus 284 1 9 C sapidus 179 22 F maialis 85 07 Lagodon rhomboides 192 1 3 Gambusia aftinis 134 1 6 Penaeus duorarum 69 06 Menidia menidia 175 12 Penaeus aztecus 117 1 4 Symphurus plagiusa 64 05 Bairdiella chrysura 112 07 Paralichthys lethosligma 100 1 2 Orthopnstis chrysoptera 56 05 P duorarum 101 07 tures might be fatal to the young of many species, especially since they were prolonged (Gunter and Hildebrand 1951; June and Chamberlain 1959; Massman and Pachecho 1960; Joseph 1972). Seasonality and Growth In the Cape Fear estuary tidal marshes, peak seasonal abundance ( Figure 3 ) for young commer- cially and recreationally important species was always associated with the recruitment of postlar- vae or early juveniles into the area and sub- sequent decreases in numbers were due to mortal- ity and/or emigi-ation from the primary nurseries. Although very few postlarval Micropogonias un- dulatus were captured in early 1977, recruitment was improved at the beginning of the 1977-78 lar- val year, with densities in November 1977 at up- river sites reaching a mean of 31 mdividuals/400 m^ (Figure 3, upper left). Concentrations of this species in the river mainstem were much higher than in the marshes (Hodson"). Red drum, Sci- aenops ocellata. were captured in relatively low numbers in the fall although their density ap- proached 34 individuals/400 m^ in the Dutchman Creek collections in October. Leiostomus .xanthu- rus postlarvae dominated the sciaenid catches with average densities in March of 3,099 individuals/400 m^. Except during the cold period in early 1977, Mugil cephalus were fairly common throughout the estuary (Figure 3, lower left), with primary recruitment of early juveniles occurring in March and April. Mugil curema, however, displayed a "R. G. Hodson, Director, Cape Fear Estuarine Laboratory, North Carolina State University, Southport, N.C, pers. com- mun. July 1978. 345 FISHERY liL'I.LKTIN VOL. 77, NO 2 e o o (/) en 10 r 3 10 2 10 10 0 ■ilO # LEIOSTOMUS XANTHURUS D MICROPOGONiaS UNDUL&TUS A SCLIENOPS OCELLATA I I I I I T I I I I • BREVOORTia TYRANNUS D PARALICHTMYS Spp •tj--o- 1 r 1 — rn — r-r TT < o a: o ti. o a: UJ CQ 3 UJ o < cr UJ 10 • UUGIL CEPHALUS O MUGIL CUR E M A A M J MONTH 0 N D • PENAEUS AZTECUS □ PENAEUS DUORARUM A PENAEUS SETIFERUS ■ CALLINECTES SAPIDUS ■-■'1 I 1^ M I I I M J J S 0 MONTH N D FKU'RK 3. — Seasonality for selected estuary species in the Cape Fear River, N.C., 197 346 WEINSTEIN SHALLOW MARSH HABITATS AS PRLMARY NURSERIES more distinct seasonal presence in the Cape Fear estuary, with young arriving in May and emigrat- ing nearly completely from the estuary in late fall. The more southerly distribution of this species (Anderson 1957; Moore 1974; Richards and Cas- tagna 19761, perhaps related to temperature tol- erance, may be responsible for this pattern. Other winter-spawned species also were com- mon in the Cape Fear. Flounders of the genus Paralichthyf! were most abundant in March and April when postlarvae first entered the marshes (Figure 3. upper right). Brevnortia tyrannus reached peak densities in April and May and were fairly abundant throughout summer and early fall, then they generally migrated out of the shal- lows in October when temperatures decreased markedly. The pooled data for the Atlantic men- haden, however, do not indicate the large monthly variation observed for catches of this species. In a given creek, densities varied over more than an order of magnitude between months, and peaks of abundance were not coincident among marshes. The only consistent pattern e.xhibited by the At- lantic menhaden was their generally greater as- sociation as postlarvae and early juveniles with intermediate to lower salinities. Except for their brief stay in brackish-water marshes as juveniles, Atlantic menhaden did not seem to establish long-term residency in any area, but instead tended to range throughout the lower salinity por- tions of the estuary, especially the river mainstem. Their mode of feeding may have con- tributed to this phenomenon (June and Chamber- lain 1959; Jefferies 1975; Durbin and Durbin 1975). All three species of commercial shrimps (Figure 3, lower right) exhibited distinct seasonal pres- ence: Penaeus aztecus was recruited to the marsh- es as early as May, and white, P. setiferiis, and pink, P. duorarum. shrimp were first captured in July. For all three species, peak densities were recorded during the month of first appearances, and young adults emigrated from the shallow- marshes during the fall, especially after October. Callinectes sapid us (Figure 3, lower right) gener- ally were abundant in all months, with a peak of recruitment in November and December. Appar- ently, the absence of early juveniles in January and February 1977 catches reflected heavy mor- tality or emigi'ation due to the extreme cold in these months. Length-frequency data for abundant 0 year class fishes and brown shrimp indicated that most of these species resided in tidal creeks at relatively small sizes and grew rapidly after April (Table 6). The smaller increments of gi-owth occurring prior to this month for winter-spawned species resulted from the effects of low temperatures and the mask- ing effect of continued recruitment through March. Extended recruitment periods created a similar "lag" in gi'owth for species spawned in other sea.sons. Standing Crops at Peak Recruitment Patterns of distribution for selected species at the peak of postlarval recruitment are shown in Table 7; in all cases, more than 1 mo was averaged since a plateau was indicated in the data. Catches generally were lower at Baldhead Island stations (including Shellbed Island) for most dominant fishes, suggesting the inability of these marshes to support as much juvenile production per unit area as other Cape Fear marshes or perhaps indicating greater predation pressure in this area. Leiosto- mits xanthiiriis was relatively evenly distributed although catches of this species and those oiMugU cephalus and M. cureina were lower at Baldhead Island; M. ciirema also was captured in reduced numbers at low salinity sites. In addition, both species of mullet were collected where the sub- strate contained high levels of organic matter. Atlantic menhaden postlarvae and early juve- niles ( 17-32 mm) predominated upriver at brack- ish salinities and also were abundant in Walden and Dutchman Creeks. Although salinity was rel- atively low in Dutchman Creek in April (11.5 and V2.6X,i at the rotenone and seine sites, respec- tively) the high catch of menhaden in May at the seine site (742 individuals/400 m^) occurred at a time when salinity (35"/(mi) was at a yearly maximum. Interestingly, the majority of these fish were of a different age-class (probably yearlings, 50-109 mm) than were the postlarvae and early juveniles that predominated in the April and May collections at other stations. These individuals may have already completed their early develop- mental period in brackish waters (June and Chamberlain 1959) and were moving freely throughout the Cape Fear estuai'y. They also ap- parently made forays into the Walden Creek sys- tem, and in other months contributed to the patch- iness at all stations described previously. Penaeid shrimp were an important component of the marsh nekton community during the late spring and summer months. Maximum densities 347 FISHERY BULLETIN: VOL. 77. NO- 2 Table 6. — Length data for 0 year class individuals of selected species. Cape Fear River estuary, N.C.. all station collections combined. — = data were not available. Species Jan. Feb. Maf Apr May June July Aug Sept, Oct Nov Dec Leiostomus xanthurus ; Mean length 14,3 19.5 22.4 24 6 334 41 3 43 8 49 1 58 4 686 89,8 109,4 Range 13-16 13-25 14-30 12-41 16-60 21-69 29-71 36-73 38-98 48-109 54-162 63-174 Sample size 3 412 1,969 1,778 1,275 709 524 373 376 193 41 35 Brevoortia tyrannus Mean length — — 277 27 0 31 9 333 47 3 372 52 3 56 8 68 0 67 3 Range — — 22-31 17-32 24-44 20-46 37-60 41-43 32-64 43-69 42-86 50-82 Sample size 0 0 300 674 693 306 146 5 54 57 3 3 Mugil cephalus : Mean length 21 0 21 9 228 25 6 36 0 45,8 62.1 62 3 69 3 76 1 836 78.5 Range 19-22 18-28 16-29 17-37 24-62 28-67 35-92 37-94 40-113 48-131 49-118 55-127 Sample size 4 235 1.025 853 816 403 553 382 277 355 149 372 M curema Mean length — — — — 258 37 0 56 3 61 6 63 1 70 5 75 1 — Range — — — — 15-38 21-60 18-87 18-90 18-121 17-135 25-114 — Sample size 0 0 0 0 718 751 665 392 327 67 71 0 Sciaenops oceliata Mean length _ _ — — — — — 143 175 24 8 39 5 33 5 Range — — — — — — — 13-15 5-30 12-40 23-47 23-48 Sample size 0 0 0 0 0 0 0 3 39 80 13 10 Paralichthys spp.' Mean length — 131 154 176 — — — — — — — — Range — 9-19 12-21 10-30 — — — — — — — — Sample size 0 68 100 169 0 0 0 0 0 0 0 0 Anchoa mitchilli: Mean length — — — — — 173 20 2 21 0 22 3 22 2 26 5 24 6 Range — — — — — 8-23 10-35 10-34 11-53 15-53 17-61 19-48 Sample size 0 0 0 0 0 473 540 391 844 715 447 85 Penaeus aztecus^ Mean length — _ — — 37 7 70 1 88.6 97.6 — — — — Range — — _ — 18-64 24-113 30-130 24-127 — — — — Sample size 0 0 0 0 663 421 370 169 0 0 0 0 'Probably mostly Paralichthys lethostigma which was abundant at upriver stations: 0 year class identitied to species after April ^Penaeus sp was collected down to 1 1 mm TL in May probably P aztecus Table v. — Relative densities (mean number of individuals/400 m^) for selected species at the peak of postlarval and early juvenile recruitment in the Cape Fear River estuary, N.C. Rotenone collection data are not presented for shrimp, Penaeus spp. Baldhead Creek Species Peak recruitment months Seme Rotenone Seme Shellbed Island Hechtic Bernards Creek Creek Seme Rotenone Seine Rotenone Seme Rotenone Dutchman Creek Walden Creek Leiostomus xanthurus Brevoortia tyrannus Mugil cephalus M curema Penaeus aztecus P duorarum P setiferus Mar -Apr Apr -May Mar -Apr May-June May-June July-Aug. July-Aug. 1.781 110 80 712 113 266 0 3,474 4,520 16 109 179 24 172 148 0 373 1,788 979 257 2 60 439 970 2,251 505 209 21 525 31 26 153 24 73 3,821 909 71 538 92 85 618 803 0 'April data only of brown shrimp occurred at Hechtic and Walden Creeks. Except for a single individual in August, none were collected at Shellbed Island, and catches were also low at the Baldhead Creek site. The presence of shrimp in high densities in Wal- den Creek is of interest since the organic (detrital) content of the substratum is the lowest of any of the Cape Fear stations. Except for one tributary where nearby construction activities have added large quantities of fine sediments, this creek is well scoured almost its entire length. White shrimp (P. setiferus ) were most abundant at Hech- tic and Dutchman Creeks, where the sediment contained considerable quantities of organic mat- ter and were absent from the high salinity stations in Baldhead Creek and Shellbed Island. On the other hand, pink shrimp reached maximum abun- dance in Baldhead Creek, while intermediate numbers were also collected at Hechtic Creek. Community Patterns Numerical classification analysis was employed to detect underlying patterns among marsh nek- ton communities (Figure 4). Two primary station clu.sters were discerned by this procedure, a group consisting of the Baldhead Island sites (i.e., Bald- head Creek seine and rotenone stations and Shell- bed Island) and a second group composed of the Walden and Hechtic Creeks and the Dutchman Creek seine station. The latter cluster was joined bv the Walden and Dutchman Creek rotenone sta- 348 WEINSTEIN SHALLOW MARSH HABITATS AS PRIMARY NURSERIES BALOHEAO I SEINE I BALDHEAO L ROTENONE 1 SHELLBEO ( SEINE 1 BARNARDS ( ROTENONE < DUTCHMAN 1 ROTENONE ) WALDEN i ROTENONE 1 HECHTIC 1 SEINE ) DUTCHMAN 1 SEINE 1 WALDEN 1 SEINE ) PERCENT SIMILARITY FIGL^RE 4. — Similarities among all stations collected from Feb- ruary to December 1977 m the Cape Fear River estuary, N.C. Associations m dendogram are based on pooled monthly collec- tions. Sampling was not initiated at Bamards Creek. N.C. until April. tions and by the Barnards Creek site which exhib- ited the lowest overall degree of association. Although the physicochemical factors at the Bar- nards Creek site differed in some respects from those of other stations ( particularly with respect to percent organics, Table 1), it should be em- phasized that this station was not collected until April and, therefore, did not reflect a large portion of winter recruitment. Since the rotenone stations were not collected uniformly throughout the year, they were omitted from further analysis. Data for individual species, however, are used to support conclusions drawn from seine studies. A two-way coincidence table (Table 8) was pre- pared for seine data collected from February to December 1977 by first clustering the matrix for seine station associations and comparing these with a dendrogram for species associations. In this way, comparisons among stations was facilitated by direct cross-referencing against the charac- teristics species associations at each site. The five seine stations fell into two clusters at the 659! similarity level, designated A and B in the table. Twelve species association clusters were recog- nized at this same level. Clearly, several subcate- gories of marsh communities may be distin- guished for the Cape Fear region, although the marshes also share many commonalities, as indi- cated in Figure 4 by the generally high similarity values among station clusters { >55'7(). Members of Group III (Table 8) were generally ubiquitous, with most difference being reflected in relative numbers. Leiostomus xanthurus, Mueil cephalua, and Brevoortia tyrannus, for example, were more prevalent at Hechtic, Walden, and Dutchman Creeks, while the bay anchovy, An- choa mitchilli. and Mcnidia menidia dominated at Baldhead Island stations. Species groups I, IV, and X were characterized by the lower salinities at Hechtic and Walden Creeks and included species present in relatively higher densities, such as the tidewater silverside, M. heryllina, and species normally associated with lower salinities, such as gizzard shad, Dorosoma cepedianum; mosquito- fish, Gambi/sia affinis; AnguiUa rostrata; and juvenile Micropogonias undulatus. Two freshwa- ter fishes, the bluegill, Lepow/s macrochiriis, and golden shiner, Notemigonus crysoleucas , also were captured at these sites. In rotenone collections, by comparison, tidewater silverside were absent from Baldhead Creek collections and only six speci- mens were captured at Dutchman Creek. In Wal- den Creek, this species was a relativley abundant member of the community, contributing 1.3% of the total number of individuals (Table 5). At Bar- nards Creek, however, only 15 individuals were captured. Several other species were also more abundant in low salinity rotenone collections, postlarval and juvenile M. undulatus (9-83 mm), for example, were the fifth most abundant species captured in Barnards Creek samples, and A. ros- trata and G. affinis contributed 2.6 and 1.6'7f of the total number of individuals, respectively (Table 5). The Baldhead Creek and Shellbed Island sites form a complex that is influenced by the nearby marine environment. Groups VII, VIII, and IX included many species associated with intermedi- ate to higher salinities and probably also reflected additional parameters such as the substratum composition and proximity to the ocean entrance. Several stenohaline marine species were collected only at these locations. These included rough sil- verside, Mcmbras martinica; several species of searobins, Pnonotus spp.; windowpane flounder, Scopthalmus aquosus; summer flounder, Paralichthys dentatus; fringed flounder, Etropus crossotus: gag, Mycteroperca microlepis: southern blue crab, Callinectes similis: inshore lizardfish, Synodus foetens; and pigfish, Orthopristis chrysoptera. Except for Scopthalmus aquosus and E. crossotus, these species were also recorded in low to intermediate densities from Baldhead Creek rotenone collections (e.g., pigfish ranked 17th in abundance out of a total of 61 taxa col- lected). Members of the genus Prionotus were not 349 FISHERY BUI.LKTIN VOL Table 8. — Two-way coincidence table comparing dendograms for station and species associations in the Cape Fear River estuary, N.C.. February-December 1977. The two station clusters, desig- nated A and B. are cross-referenced against 12 species clusters derived from previous calculations. Dendrograms are not shown. B A Dutctiman Walden Hecriiic Shellbed Baldhead Creek Creek Creek Island Creek Species 2 Notemgonus crysoleucas 3 Mofone saxatilis _ 10 Alosa aesii\/alis 1 1 Tnnectes maculatus ~ 2 1 2 5 Cynoscion nebulosus 2 26 16 3 1 Stronglyura manna 741 1,217 1,199 1 266 Penaeus aztecus 2,510 175 57 8. 758 1.510 Menidia menidia 231 304 6 405 106 Eucinostomus argenteus 824 50 7 46 541 Fundulus maialis 2,582 83 199 354 1.668 Mugil curema 67 lot 247 31 657 Penaeus duorarum 24 192 89 55 70 Lagodon rhomboides ^ 1,387 1,666 7,967 71 287 Brevoortia tyrannus 938 ■284 265 41 162 Calinectes sapidus 4,160 780 3,009 525 263 Mugil cephalus 502 112 160 115 108 Bairdiella chrysura 3,056 1.240 590 730 938 Fundulus heteroclitus 8,534 7410 7.953 3.023 3.918 Leiostomus xanthurus 1 29 14 19 48 Paraltchlhys spp 151 1,050 660 8.927 4.330 Anchoa mttchilli 1 21 13 Gambusia alfinis 1 6 10 Dorosoma cepedianum 1 82 199 Menidia beryllina 4 3 122 3 Micropogonias undulatus 3 3 8 2 Caranx hippos < 2 1 3 2 Pomatomus saltatnx 6 2 49 1 Anguilla rostrata 27 4 22 2 Slops saurus 132 70 171 Penaeus setiferus 1 15 32 Syngnalhus louistanae 1 1 9 9 Gobionellus boleosoma 13 3 114 Gobiosoma bosci • 20 t 7 Lutianus gnseus 2 5 Cithanchlhys spilopleius ^^ 2 4 Caranx latus — 21 Membras martinica < 3 Cithanchlhys macrops ^ 1 2 2 27 48 Symphurus plagiusa 1 1 2 1 5 1 9 5 2 16 1 3 2 1 Monacanthus hispidus Myrophis punciatus Paralichthys dentalus Mycleroperca microlepis Eiropus crossotus 295 1 1 Anchoa hepsetus *^ 3 1 Scophthalmus aquosus ^ 3 1 Pfionotus carolmus 1 9 18 Synodus toetens 34 91 Calhnectes similis 19 1 3 29 2 10 Orthopristis chrysoptera Pnonotus scilulus Pnontus Inbulus 4 Opsanus tau 21 Syngnalhus tuscus 3 Pnonotus evolans X 2 Lutjanus synagris 5 Aslroscopus y-graecum 1 15 Gobiosoma ginsburgi 2 Lepomis macrochirus 2 Lucania pan/a X 2 Evorlhodus lyncus 2 1 1 Chaetodipterus laber X 62 1 2 Sciaenops ocellata 3 Pogonias cromis y. 3 Gobionellus hastatus 2 Trachinotus falcatus 350 WEINSTEIN SHALLOW MARSH HABITATS AS PRIMARY NURSERIES recorded from low salinity sites with the exception of the two very small, unidentified species from Walden Creek in August (salinity 18.3"/(iu). Also absent from low salinity rotenone collections were S. aquDnufi. E. (.-rossotug, and P. clentatiis; on the other hand, the southern flounder, P. lethostigma , was common at low salinity stations and was the 14th most abundant species at Barnards Creek, composing 1.2'7f of the total captured. A winter visitor to the estuary, striped cusk-eel, Rissula niarginata , was present in Baldhead Creek rotenone collections; a total of 1.5 specimens were captured during February-April, and a single specimen was also captured at the seine site. At least three estuarine species with a previously reported preference for higher salinities were col- lected in larger numbers at Baldhead Island sta- tions, the Atlantic silverside (Johnson 1975). striped killifish (Griffith 1974), and blackcheek tonguefish, Symphurus plagiusa (Gunter 1945; Reid 1954), which also was taken in substantial numbers in Dutchman Creek. The affiliation of Dutchman Creek presents an interesting case among marshes. Recent construc- tion activities nearby have effectively reduced the input of freshwater to this orginally brackish water creek (Birkhead"). Thus, apparently in the process of change, Dutchman Creek retains both original similarities to Walden Creek, and "new- er" associations with higher salinity marshes (e.g., for the Atlantic silverside and white mullet). DISCUSSION Tidal Creeks as Nurseries Due partly to sampling difficulties, the nursery role of tidal salt marshes, especially the shallow upper reaches of tidal creeks, has seldom been investigated (Herke 1971; Copeland and Bechtel 1974; Cain and Dean 1976). Nevertheless, it is this very habitat that has been defined by Purvis (see footnote 2) and others (Kilby 1955; Herke 1971; Dahlberg 1972) as one of the primary nursery zones where initial postlarval development takes place. Populations of marine-spawned species in the areas Purvis studied in Pamlico Sound, N.C., (low salinity, shallow tributaries with mud or mud-grass bottoms) were uniformly of very early 'W, Birkhead. Associate, Cape Fear Estuarine Laboratory, North Carolina State University, Southport, N.C., pers. com- mun, Apnl 1978. juveniles. In the past, several investigators have pointed to the relationship between the size of organisms in an area and salinity as an indicator of the primary nursery grounds (Gunter 1945, 1961, 1967; Herke 1971; Dahlberg 1972; Copeland and Bechtel 1974). Others, however, have noted that the size-salinity relationship is not a simple one, and that interactions with food supplies, sub- stratum characteristics, and other physicochemi- cal factors dictate preferred zones for nursery utilization (Kilby 1955; Reid 1957; Simmons 1957; Dawson 1958; Reid and Hoese 1958; McHugh 1967; Parker 1971). Results of my study demonstrate that shallow tidal creeks and marsh shoals of the Cape Fear River estuary harbor dense populations of post- larvae of several marine-spawned species. Field observations showed that young fishes and shell- fish were actively seeking the creek headwaters, that in effect, the marshes fill up backwards dur- ing recruitment. Postlarval spot, Mugil spp., Paralichthys spp., red drum, and other species ac- cumulated in great numbers in the upper reaches of the creeks and gi'adually decreased in densities downstream. Ichthyoplankton tows in the mouths and a short distance upstream in these same creeks yielded much lower concentrations of post- larvae than collections closer to the headwaters (Hodson see footnote 6). Although the gear de- ployed in these surveys differed, recent studies of gear efficiency indicated that the methods are reasonably similar ( Weinstein and Davis in prep. ). The period of residency in these habitats is appar- ently lengthy; winter recruits of several species were abundant throughout the summer (Figure 3); and a mass exodus did not seem to take place until the following fall. Other studies have shown, however, that larger members of the population tend to move downstream as they grow, leaving behind slower growing individuals and newer re- cruits (Herke 1971; Dunham 1972; Purvis see footnote 2). Parallel conclusions on the comparative rich- ness of shallow marsh habitats were reached by Marshall (1976). Employing similar sampling techniques, including the use of 1 mm mesh seines, he reported densities of spot, Mugil spp., Atlantic menhaden, and brown shrimp in two marsh areas altered by ditching for mosquito con- trol to exceed 0.1/m-. Standing crops of most species in the natural creeks and ditches he studied were among the highest ever reported for small estuarine nekton. A survev of the literature 351 FISHERY BULLETIN VOL 77. NO 2 by Marshall (1976) supported this observation, even higher densities for total nekton were noted in the studies of Turner and Johnson (1974) in South Carolina tidal marshes. However, Marshall cautioned that the efficiency and selectivity of gear used to study various estuarine areas may, in part, be responsible for some of the differences seen among areas. Average densities in my study for the same species listed by Marshall all ex- ceeded 0.1 organism/m^ except for brown shrimp. When seine data alone were considered for this species, however, densities of 0.1/m- were re- corded. The utilization of the marsh shallows does not, however, hold for all postlarvae that inhabit the Cape Fear region. Atlantic croaker, for example, occurred primarily in the deeper water of the river from the vicinity of the salt boundary through the mesohaline zone. As postlarvae, this species was noticeably absent in the downstream marshes and densities generally were low at upstream stations. The Atlantic croaker was not listed among the 10 most abundant species captured in each of two marsh areas near Beaufort, N.C., by Marshall (1976), nor was it among the 10 most abundant species collected in six tidal creeks located near Port Royal Sound, S.C. (Turner and Johnson 1974). In my study, only one specimen of the 1976-77 year class was collected before May, when juveniles (27-35 mm) appeared at low salinity sta- tions. In the early stages of recruitment for the 1977-78 year class, however, low densities of post- larval and early juvenile croaker (9-19 mm) were collected, principally at Hechtic and Barnards Creeks. Haven (1957) and Wallace (1940) ob- served a similar distribution in the Chesapeake Bay, and for most Atlantic and Gulf coast es- tuaries containing deeper channels, this relation- ship seems to hold (Welsh and Breder 1923; Suttkus 1955; Nelson 1969). However, the Atlan- tic croaker also utilizes the marsh shallows exten- sively in some of the (iulf states, including Louisiana, Texas, and Mississippi (Herke 1971; Parker 1971; Arnoldietal. 1974; Yakupzack et al. 1977). In the Cape Fear region, where there are extensive marshes, the Atlantic croaker is simply absent. Perhaps minimum temperatures during winter recruitment in the Cape Fear and other middle Atlantic coast estuaries are limiting for this species (Joseph 19721. Another species that seems to prefer open waters is the Atlantic menhaden, which was captured in lower numbers in the interior marshes than on the river shoals 352 and in the ship channel (Hodson see footnote 6). Since postlarvae feed primarily on zooplankton (Thayer et al. 1974) which are found in higher concentrations out in the estuary (Jefferies 1975). this preference for open waters is not surprising. These observations lead to conjecture as to the mechanisms that may reduce potential competi- tion among the early life stages of species with similar food requirements (Thayer et al. 1974; Kjelson et al. 1975). The results of recent studies (May 1974; Thayer et al. 1974; Lasker 1975; Houde 1977; Laurence 1977) suggested that food supplies are potentially limiting in estuaries and nearshore areas and that critical densities of food items were required at several larval developmen- tal stages. If species were undergoing diffuse com- petition (MacArthur 1972), they might, therefore, benefit from behavioral patterns that resulted in temporal and/or spatial segregation on the nur- sery grounds. There are apparently two major nursery areas in the Cape Fear estuary: the in- terior marshes, including the shallow marsh fringe, and the river mainstem at the head of the estuary. Related or potentially competitive species, by utilizing either one of these zones, may remain spatially segregated. Seasonal presence also may enhance survival of many species; the data showed this clearly for white and striped mullet and for penaeid shrimp although local variables within each major nur- sery zone also influenced patterns of distribution for these groups. For example, white and pink shrimp were recruited at similar times of the year, yet they separated within the marsh zones on the basis of salinity. White mullet were much more abundant at high salinities in areas with sedi- ments containing considerable quantities of or- ganic matter; striped mullet were distributed throughout the estuary although they, too, were most abundant where sediments contained a high level of organics. Salinity preferences for several dominant spe- cies are treated statistically in Table 9. Although consistent relationships appeared in the data, I monthly values reflected local variations in fresh- I water flow. In September, for example, heavy rain- I fall in the vicinity of Dutchman Creek depressed salinities 16"iiii below the previous collection date. The resident population of white mullet appar- I ently remained in the area and catches were high (1,112 individuals 400 m'-^ at the rotenone sitei. Along with lower catches for this species elsewhere in the system, this observation suggests WEINSTEIN: SHALLOW MARSH HABITATS AS PRIMARY NURSERIES Table 9. — Partial correlations i given tempera turei of species abundance with salinity in with < 10 individuals of a given species in any month were omitted from the calculations. Aug the Cape Fear River estuary, N.C. Collections N.C. = >10 individuals collected. **P<.01. Species Feb, Mar Apr. May June July Sept. Oct Dec Pooled Leiostomus xanthurus -0,449 -0.808 -0 582 0 176 -0.237 -0 493 -0 783 -0751 -0210 -0 449 0577 -0 409-- 13870 10 Menidia menidia .387 983 ,747 856 799 546 673 676 722 799 732 TIT- 10 244 10 M beryllma - 509 NC NC NC - 547 - 604 - 719 - 755 - 469 - 820 - 855 - my 2 705 Mugil cephalus 525 - 132 080 637 - 501 118 304 - 769 374 - 418 060 - 291 8312 10 M curema NC NC NC 769 .757 627 624 067 252 NC NC 560- • 3 783 5 Symphufus plagiusa NC NC NC NC N.C - 018 - .217 068 - 625 523 NC - 092 4 428 4 Brevoonta tyrannus NC - 001 - 736 - 570 - 555 - 274 334 - 537 - .110 N.C NC - 426- • 3243 / Fundulus heteroclitus 293 - 397 269 - 675 438 343 ^41 094 169 043 082 060 7 622 10 F maiaiis 665 669 .887 514 700 544 600 873 453 460 654 673-- 4 827 10 Micropogonias undulatus NC NC NC - 765 - 724 - 781 NC NC - 580 - 648 - 576 688- • 0 732 b Bairdiella chrysura NC NC NC NC 146 015 518 628 NC NC NC 353 1 761 3 Anchoa mitchilli NC NC NC 449 537 - 271 084 109 - 058 030 242 130 3 090 / A hepseius. NC NC NC NC 355 324 542 585 NC NC NC 459 0421 3 Lagodon rhomboides - .111 - 474 - 032 - 099 162 289 384 290 332 NC 857 003 11 804 y Sample size (stations) 7 8 9 9 9 9 9 9 9 9 9 'v^ values are based on lasts of equality among correlations ot the 1 1 monthly collections; none were slgnl^ca^l, therefore, all individual correlation values were pooled a lack of correlation of distribution with salinity. This effect occurred in other months for other species and is consistent with the patterns of dis- tribution of estuarine organisms and their ability to withstand wide ranges of salinity, at least over the short term. What is important, however, is that during the course of residency in the marshes, the presence of several species was significantly correlated with salinity. Gunter (1961) draws a similar conclusion by stating that correlation is not necessarily with a given salinity but rather with the gradient as a whole. Of the species tested (Table 9), striped mullet; blackcheek tonguefish; mummichogs; silver perch, Bairdiella chrysura; pinfish, Lagodon ' rhomboides; bay anchovy; and striped anchovy, A. hepsetus, were distributed independently of salin- ity. In several instances, a considerable portion of the variance associated with abundance data was explained by salinity alone; this was true for the Atlantic and tidewater silversides and for the striped killifish and Atlantic croaker. Although other/- values were significant (P<0.01) it is obvi- ous that factors other than salinity ~were con- tributing to patterns of distribution. Substrate characteristics have been shown to influence invertebrate populations and the struc- ture of fish communities (Mills 1975). In this study, the distribution of several species also ap- peared influenced by properties of the sediment (Table 10). The abundance of Menidia menidia and M. heryllina was negatively correlated with per- cent organics. and the former species displayed a similar relationship with sorting coefficient. This is not at all sm-prising in light of their mode of feeding and the presence of currents which proba- bly act to carry food items through the area. On the Table 10.— Partial correlations (given salinity) of species abundances with several sediment parameters in the Cape Fear River estuary. N.C. Collections with < 10 individuals of a given species in any month were omitted from the calculations. Values in parentheses do not include Bamards Creek. ** =P<.01. Percenl Sorting Fine Species organics coefficient sand Menidia menidia -0.410-- -0.468- ■ 0,234 M beryllma - .655- • - .123 - .009 Mugil cephalus .065 (.562") .588" .364 M curema - 136 (.743- •) 620- - - .399-- Symphurus plagiusa .628" - .326 .210 Micropogonias undulatus .553" .366 - .193 Fundulus heteroclitus 297 .565-- - 353" Anchoa milchilli - .031 - 310 .511-- Other hand, young striped mullet which relies heavily on detritus in its diet (Odum 1968) was expected to display a positive association with per- cent organics, but this did not occur with respect to all creeks concerned. If Barnards Creek was omit- ted from the calculations, however, the relation- ship became highly significant. The extremely high organic content of Barnards Creek sediments probably is indicative of highly reducing condi- tions, and may, in fact, have contributed to the low total fish catch in this creek. Two other species exhibited a positive relation- ship with percent organics, the blackcheek tonguefish and the Atlantic croaker. The blackcheek tonguefish commonly is associated with muddy bottoms and high salinity (Gunter 1945; Kilby 1955) although salinity did not seem to play a role in governing its distribution in the Cape Fear region (Table 7). Darnell (1958) has described the feeding preference of young croaker for organic matter and since this species tends to accumulate toward the headwaters of many sys- 353 FISIIKRY BULLETIN: VOL, 77, NO, 2 tems (where deposition is greatest), this result may have been expected. Thus, both spatial and seasonal programming seem to play an integral role in habitat partition- ing among ocean-spawned recruits utilizing Cape Fear estuary primary nurseries. Whether or not this partitioning results in enhanced survival of otherwise competing species remains an area for fruitful research. Communit) (Composition Each marsh community in the Cape Fear es- tuary displayed several unique characteristics. In addition to seasonal differences in species rich- ness, abundance relationships varied among marsh complexes (Tables 5, 8 1. Although some species appeared in relatively low numbers, they only occurred in certain areas or were much more abundant in a specific marsh complex. The Atlan- tic croaker, southern flounder, mosquitofish, and the seasonal capture of freshwater species includ- ing white catfish, Ictaliirus caliis. bluegill, golden shiner, Noti'iiiigonuti crysoleucas, and largemouth bass, Microptcrus! salmoidcs. were associated with low salinity sites ( Walden, Hechtie, and Barnards Creeks). More abundant members of these com- munities also seemed to display a preference for lower salinities including t idewater sil verside and Oyear class Atlantic manhaden (see also Table 9). Two groups apparently set the high salinity marshes apart from other areas. Several species, usually associated with estuaries during the early part of their life cycle, were restricted mainly to the polyhaline zone. Pigfish. white mullet, red drum, and southern blue crab were in this cate- gory and along w-ith two permanent marsh resi- dents. Atlantic silverside and striped killifish were much more abundant or were only captured at high salinities. The predominance of sandy areas near Bald- head Island, in combination with higher salinity, attracted several species — e.g.. the windowpane. rough silverside, spotted whiff, Cithanchthys niacrops, inshore lizardfish, and bighead sea rob- in, Prionotiis tnbulus — were in this group. The proximity of the Baldhead Island marsh to the ocean entrance also provided suitable condi- tions for invasion by several stenohaline species not usually associated with estuaries. Many of these species were seasonal visitors to the area and their general rarely suggests that the marsh is not a primary nui-sery habitat. Young sergeant 354 major, Abudcfduf xuxatilis; great barracuda, Sphyraena barracuda: Atlantic spadefish. Chae- todipti-rus faher: lookdown, St'lc/ic roiuer; lane snapper. Liitjaniis syna^ns; gag. and others are seldom collected in marshes and, in fact, would probably be classified as reef species. McHugh ( 1967) has described these species as adventitious invaders of the estuary. The majority of community dominants captured in this study were transient in the marshes, being resident for only part of their life cycle. The only permanent residents which were dominant mem- bers of the marsh community were mummichog. striped killifish, and Atlantic silversides. Thus, energy flow at higher trophic levels is predomi- nantly through those species that utilize the marsh nurseries in the first year of life. Although larger individuals of these species probably make feeding forays into the upper tidal creeks, their importance in these areas is not known. Not surprisingly then, species richness was greatest in areas (Baldhead Island and upriver) influenced by the marine and freshwater biotas. It IS tempting to relate higher species diversity to more stable physicochemical conditions existing at these sites, yet as indicated in Table 1. salinity and temperature variations were generally simi- lar at all stations. A more plausible explanation of these phenomena may lie in what has been de- scribed as an "edge effect" (Odum 1971). Thus. Baldhead Island forms a mixing zone for es- tuarine. shelf, and reef faunas as evidenced by the seasonal invasion of the latter forms. Similarly, Barnards and Hechtie Creeks are influenced by fresh and brackish faunas at various times of the year. It is a remarkable observation that if all the transient members of the shallow marsh commu- nity were removed, that the remaining, perma- nent estuarine residents would form a community distinguished by the paucity of its members (Em- ery and Stevenson 19.57L The importance of the link, or continuum, between the estuary and the nearshore marine environment and the energy transfers therein, is highlighted by this observa- tion. It seems obvious that the functional integrity of the estuarine eco.system is as much dependent on the marine fish community as the members of that community are dependent on the estuary for part of their life cycle. Continued productivity, within the estuary and marine environment for certain species important to man may indeed, de- pend on the continued health of this relationship. WEINSTEIN: SHALLOW MARSH HABiTATS AS PRIMARY NURSERIES CONCLUSIONS Shallow marsh habitats are demonstrably criti- cal areas for the earliest developmental stages of fishes and shellfish. Postlarvae of most species im- portant to man were found to reside in immense numbers at the headwaters of shallow tributary creeks and along the marsh fringe at the rivers edge. With few exceptions these species were the community dominants at all study sites. Salinity seemed to play an important role in governing spatial distributions of many species and to a lesser extent substratum characteristics interacted with salinity to restrict certain species to a narrow range of habitats. Based partly on these observations, a hjrpothesis has been estab- lished whereby sea.sonal programming and spatial distributions mediated by salinity and sub- stratum preferences (and probably other factors) may serve to reduce competition among species recruited to the estuary throughout the year. Similarly, these and other physicochemical parameters, which affect individual tolerances, create unique conditions in each marsh complex that affects the composition of the nekton com- munity. Species richness was highest in the marshes closest to the ocean entrance where higher salinities allowed seasonal invasion by marine forms otherwise unable to reside in the estuary. An apparently similar phenomenon, more limited in extent, occurred at the head of the estuary for freshwater species. Despite the sea- sonal progression of species, it is apparent that marsh communities in the Cape Fear are highly structured and are able to maintain a specific identity throughout the year. ACKNOWLEDGMENTS I am grateful to J. P. Lawler of the Lawler, Matusky & Skelly iLMS) Engineers and W. T. Hogarth of the Carolina Power and Light Co. for the opportunity to conduct these studies. I am also grateful to the biotechnicians of LMS, in particu- lar, R. Beatty, R. Davis, L. Gerry, J. Hecht, W. Pollard, and P. Woodard for their conscientious efforts in the field and laboratory; the quality of their work added measurably to the success of this study. Several individuals have provided con- structive criticism of the manuscript including K. L. Heck, J. P. Lawler, G. W. Thayer, R. L. Wyman, and two anonymous reviewers. S. Weiss contrib- uted significantly with his expertise in statistics, and J. Berkun, B. McKenna, and S. Kaufman pro- vided editorial and typing assistance. This pro- gram was funded by the Carolina Power and Light Co. LITERATURE CITED ANDERSON, W. W, 1957. Early development, spawning, growth, and occur- rence of the silver mullet {Mugd curema I along the south Atlantic coast of the United States. U.S. Fish Wildl. Serv., Fish, Bull. 119:397-414. AKNOLDI, D. C, W. H. HERKE, AND E. J. CLAIRAIN. JR. 1974. Estimate of growth rate and length of stay in a marsh nursery of juvenile Atlantic croaker, Micropogon undulatus (LinnaeusI, "sandblasted" with fluorescent pigments. Gulf Caribb. Fish. Inst. Proc. 26th .'\nnu. Sess., p. 158-172. AMERICAN SOCIETY FOR TESTING AND MATERIALS. 1963. Standard method for particle-size analysis of soils. Am. See. Test. Mater. D422-63. p. 200-211. BEARDEN, C. M. 1964. Distribution and abundance of Atlantic croaker, Micropogon undulalus. in South Carolina. Contrib. Bears Bluff Lab. 40, 23 p. Cain, R. L., and J. M. Dean. 1976. Annual occurrence, abundance and diversity offish in a South Carolina intertidal creek. Mar. Biol. iBerl.) 36:369-379. CHAO, L. N., and J. A. MUSICK. 1977. Life history, feeding habits, and functional mor- phology of juvenile sciaenid fishes in the York River es- tuary, Virginia. Fish. Bull., U.S. 75:657-702. Clifford, H. T., .and W. Stephen.son 1975. An introduction to numerical classification. Aca- demic Press, N.Y., 229 p. COPELAND, B. J., AND T. J. BECHTEL. 1974. Some environmental limits of six Gulf coast es- tuarine organisms. Contrib. Mar. Sci. 18:169-204. Dahlberc, M. D. 1972. An ecological study of Georgia coastal fishes. Fish. Bull. U.S. 70:323-353." Darnell. R. M 1958. Food habits of fishes and larger invertebrates of Lake Ponchartrain. Louisiana, an estuarine communi- ty. Publ. In.st, Mar, Sci, Univ, Tex,'5:353-416. Dawson, C. E. 1958. A study of the biology and life history of the spot, Leiostomus xanthurus Lacepede. with special reference to South Carolina. Contrib. Bears Bluff Lab. 28. 48 p. m: SYLVA, D P. 1975. Nektonic food webs m estuaries. In L. E. Cronin (editor), Estuarine research. Vol, I, p, 420-447, Aca- demic Press. N.Y. Dunham, F, 1972. A study of commercially important estuarine- dependent industnal fishes. La. Wildl. Fi.sh, Comm. Tech, Bull. 4. 63 p. DURBIN. A. G.. AND E. G. DURBIN. 1975, Grazing rates of the Atlantic menhaden Breuoortia [yrannus as a function of particle size and concentra- tion. Mar. Biol. (Berl.) 33:265-277. 355 FISHERY BULLETIN VOL, 77. NO 2 EMERY. K. O.. M'Vl R. E. STEVENSON. 1957. E.stuaries and lagoons. /« J. \V. Hedgpeth (editor). Treatise on marine ecology and paleoecology. Vol. 1. p. 673-693. Geol. Soc. Am. Mem. 67. Fisher. R. a. 1973. Statistical methods for research workers. Hafner Publ. Co., N.Y., 362 p. Folk. R. L. 1974. Petrologj' of sedimentary rocks. Hemphill Publ Co., Austin. Tex., 182 p. Gainey, L. F., Jr., .^nd m. J. Greenberg. 1977 Physiological basis of the species abundance-salin- ity relationship in molluscs: A speculation. Mar. Biol. iBerl.l 40:41-49 Griffith, R. w. 1974. Environment and salinity tolerance in the genus Funi. Copeia 1974:319-331. GUNTER. G. 1945. Studies on marine fishes of Texas. Publ. Inst. Mar. Sci. Univ. Tex. 1:1-190. 1961. Some relations of estuarine organisms to salini- ty. Limnol. Oceanogr. 6:182-190. 1967. Some relationships of estuaries to the fi.sheries in the Gulf of Mexico. In G H. Lauff (editor). E,stuaries, p. 621-638. Am. Assoc. Adv. Sci., Publ. 83, Wash.. D.C. GI'nter. G.. and H. H. Hildebrand. 1951. Destruction of fishes and other organisms on the South Texas Coast by the cold wave of January 28 - Feb- ruary 3, 1951. Ecology 32:731-736. Hackney, C. T., W. D. Burbanck, and 0. P. Hackney. 1976. Biological and physical dynamics of a Georgia tidal creek. Chesapeake Sci. 17:271-280. Hansen, D. J. 1970. Food, growth, migration, reproduction, and abun- dance of pinfish, Lagodon rhomhoides, and Atlantic croaker, Micropogon undulatus, near Pensacola, Flonda, 1963-65. Fish. Bull., U.S. 68:135-146. Haven, D. S. 1957. Distribution, growth, and availability of juvenile croaker, Micropogon undulatus, in Virginia. Ecology 38:88-97. HEDGPETH. J. W. 1957. Biological aspects. In J. W. Hedgpeth (editon. Treatise on marine ecology and paleoecology. Vol. 1. p, 693-749. Geol. Soc. Am. Mem. 67. HERKE.W. H. 1971. Use of natural, and semi-impounded, Louisiana tidal marshes as nurseries for fishes and crustaceans, Ph.D. Thesis, Louisiana State Univ., Baton Rouge, 264 p HOUDE. E- D. 1978. Critical food concentrations for larvae of three species of subtropical marine fishes. Bull, Mar, Sci, 28:395-411, HURLBERT, S. H. 1971. The nonconcept of species diversity: a critique and alternative parameters. Ecology' 52:577-586. Jeffries, H. P. 1975. Diets of juvenile Atlantic menhaden \Brevoortia tyrannus ) in three estuarine habitats as determined from fatty acid composition of gut contents. J. Fish. Res. Board Can. 32:587-592. Johnson. M. s. 1975- Biochemical systematics of the atherinid genus Mentdia. Copeia 1975:662-691. Joseph, E. B. 1972. The status of the sciaenid stocks of the middle At- lantic coast. Chesapeake Sci. 13:87-100. June, F. C, and J. L. Chamberlin. 1959. The role of the estuary in the life history and biologv" of Atlantic menhaden. Proc. Gulf Caribb. Fish. Inst 11th Annu. Sess.. p. 41-45. KHLEBOVICH, V. V. 1969. Aspects of animal evolution related to critical salin- ity and internal state. Mar. Biol. (Berl.) 2:338-.345. KILBY. J. D. 1955. The fishes of two Gulf coastal marsh areas of Flori da. Tulane Stud Zool. 2:173-247. K.JELSON, M. A., D. S. Peters, G. W. Thayer, and G. N, JOHNSON. 1975. The general feeding ecology of postlarval fishes in the Newport River estuary. Fish. Bull.. U.S. 73:137-144 Lasker, R. 1975. Field criteria for survival of anchovy larvae: The relation between inshore chlorophyll maximum layers and successful first feeding. Fish. Bull. U.S. 73:453-462, Laurence, G. C. 1977. A bioenergetic model for the analysis of feeding and survival potential of winter flounder. Pseudopleuronectes amencanus . larvae during the period from hatching ti that of short, ventrally curving lateral spines. A minute seta found pos- terior to and at base of dorsal spine throughout all zoeal stages. A dorsal tubercle present in all stages midway between bases of dorsal and rostral spines. Eyes unstalked. Ah(/(mu-ri (Figure lA. B). Five somites and tei- son; second through fifth with 2 small setae on posterodorsal margin (remaining throughout all zoeal stages); second with small pair of lateral spines or knobs curving anteriorly; third with pair curving posteriorly (both pair present in all stages); fifth with pair of large ventrally curved spines at dorsolateral angle, present in all zoeal stages. 360 SCOTTO: LARVAL DEVELOPMENT OF CUBAN STONE CRAB FUiL'RE 1. — First zoeal stage oiMenippe nodifrons- < A) Ventral view; (B) lateral view; (C) telson; (D) antennule; (El antenna; (F) left mandible (in ventral view as illustrated here and throughout all zoeal stages); (G) maxillule; (H) maxilla; (I) maxilliped 1; (J) maxilliped 2. 361 FISHERY BULLETIN VOL Tclson (Figure IC). One dorsal and two smaller lateral spines present on median portion of each upcurved furca. Three spines, each with three rows of spinules, on inner margin of each furca (present in all zoeal stages); setae replace spinules at midpoint of innermost spines, number variable but setae present in all zoeal stages. Antcnmih' (Figure ID). Conical rod with 4 un- equal aesthetascs terminally. Antenna (Figure lEi. Protopodite a slender pro- cess bearing two rows of small teeth from about midlength to one-fifth from the distal tip. Exopo- dite tapered, approximately 0.75 ^ length of pro- topodal process, with a slender spine (present in all zoeal stages) near distal end extending almost as far as tip of protopodal process; slender spine about 0.4 • length of exopodite. Mandible (Figure IF). Assymetrically dentate, scoop-shaped process. Incisor process elongate with indistinct dentation. Molar process irregu- larly serrate on outer margin; left molar process with 2 or 3 small prominences along inner margin and at junction with incisor process: right side either smooth or with a prominence. Maxillule (Figure IG). Endopodite with two segments, proximal short with 1 long feathery seta laterally, distal with 4 long setae: 2 terminal, 2 subterminal. Coxal endite with 7 plumodentate setae (armed with hair proximally, spinules dis- tally ). Basal endite with 5 plumodentate setae, 2 of which are stouter: lower margin of endite with rows of fine hairs. Maxilla (Figure IHi. Endopodite bilobed. each with 3 setae. Coxal and basal endites with 5 and 4 setae respectively, placed as shown. Anterior and posterior margins of endopodite, as well as basal and coxal endites. pubescent. Scaphognathite with 4 plumose setae on outer margin; distal por- tion tapering to a thin plumose process. Maxilliped 1 (Figure II). Coxopodite with 1 seta; basipodite with 10 ventral setae progressing dis- tally 2,2,3,3. Endopodite five-segmented, ventral setae 3.2,1,2,4 t I (Roman numeral denotes dorsal setae). Exopodite two-segmented; 4 natatory setae terminally. Maxilliped 2 (Figure IJ ). Coxopodite naked; 362 basipodite with 4 ventral setae. Endopodite three-segmented, ventral setae progi-essing dis- tally 0,1,4 (3 terminal plus 1 subterminal). Exopo- dite two-.segmented. 4 natatory setae terminally. Color. Zoeae transparent, appearing gold with emerald green eyes under reflected light. Chromatophore position follows Aikawa (1929) Single brown chromatophores placed as follows: precardiac, occasionally one at posterior tip of dor- sal spine, postcardiac. carapacial (posterolateral margin of cephalothorax), labral, mandibular, and maxillipedal (distally on the basipodites of the first and second maxillipeds). Two brown chromatophores placed ventrally on all abdominal somites and telson. Singular orange chromatophores placed as follows: precardiac, postcardiac, and carapacial (posterolateral mar- gin of cephalothorax). Second Zoeae Carapace length: 0.68 mm. Number of specimens examined: 10. Carapace (Figure 2 A, B). Cephalothorax as in stage I, but with additional setae placed as follows: 1 on lateral, 2 on posterolateral margin, a pair of minute setae posterolateral to dorsal tubercle, 2 minute interocular setae. Dorsal and rostral spines increased in length, now 2 x longer than lateral spines. Eyes stalked. Abdomen (Figure 2A, B). First somite with 1 or 2 dorsal setae; second unchanged; third and fourth with an additional pair of small spines at postcro- ventral angle; fifth often with small blunt tooth at posteroventral angle. Telson (Figure 2C). Dorsal and lateral spines on medial portion of elongate furcae now minute. A pair of small setae along posterior telsonal mar^ gin. Six spines between furcae as previously de- scribed and illustrated. Antenniile (Figure 2D). Similar in form to first stage; basal region swollen; aesthetascs increased to 5 or 6. unequal in length. Antenna (Figure 2E). Similar in form to first .stage; protopodal basal region produced as a small hump I = endopodite primordium ); exopodite spine SCtrrXCJ LARVAL DEVELOPMENT OF CUBAN STONE CRAB ft FIGURE 2. — Second zoeal stage of Menippe nod if rons. lAl Ventral view;iB) lateral view; (C) telson; iDi antennule; (E) antenna; (F) mandible; (G) maxillule; (Hi maxilla; (I) maxilliped 1; ( J> maxilliped 2 363 FISHERY BULLETIN VOL equal to or surpassing protopodal process, about 0.5 X length of exopodite. Mandible (Figure 2F). Incisor process stouter, dentation irregular. Left molar process with 3 ir- regular teeth along inner margin to junction with incisor process, right molar process with 1 tooth. Maxilhde (Figure 2G). Setae on endopodite and coxal endites unchanged; basal endite now with .5 spines and 2 setae, plus 1 long feathery seta later- ally. Maxilla (Figure 2H). Setae on endopodite; coxal and basal endites unchanged. Scaphognathite with 1 1 plumose setae, no elongate distal process. Maxilliped 1 (Figure 21), Coxo-, basi-, and en- dopodites unchanged. Exopodite with 6 natatory setae. Maxilliped 2 (Figure 2J). Coxo-, basi-, and en- dopodites unchanged. Exopodite with 6 natatory setae. Color. Darker orange-brown, though chroma- tophore number and position unchanged from first stage; eyes with an orange-rose hue. Third Zoeae Carapace length: 0.80 mm. Number of specimens examined: 10. Carapace (Figure 3A, B). Cephalothorax inflated, posterolateral border with 8 (7-9) setae. Three pair of minute setae alongdorsal midline as in stage II. Dorsal and rostral spines increased in length, usually 3.5^ longer than lateral spines. Buds of third maxillipeds and thoracic appendages barely visible through carapace. Abdomen (Figure 3 A, B). Now with 6 somites, sixth with 2 dorsal setae posteriorly but no spines. Posterolateral spines of third, fourth, and dor- solateral spines of fifth somites elongate. Three dorsal setae on first somite. Tel son (Figure 3C). Dorsal and lateral spines on median portion of furcae miniscule. Spination and setation of posterior margin as before, occasion- ally an additional median seta. Furcae >0.75x length of telson. Antennule (Figure 3D). Similar in form to second stage; terminal aesthetascs usually 4 (3-5): 3 long. 1 short. Antenna (Figure 3E). Endopodal bud enlarged. Exopodal spine extended slightly beyond slender protopodal process, and equal in length to exopo- dite. Mandible (Figure 3F). Incisor process similar in form to second stage, 3 or 4 irregular teeth on left side, 2 on right. Maxillule (Figure 3G). Basal endite with I addi- tional seta, now 5 spines, 3 setae, plus lateral seta as before. Setae of endopodite and coxal endites unchanged. Maxilla (Figure 3H). Endopodal setation as in stage II: basal endite lobes 5,5; coxal endite lobes usually 5,4 (6,4). Scaphognathite with 19 or 20 marginal plumose setae. Maxilliped 1 (Figure 31). Similar in form to sec- ond stage; coxo- and basipodal setae unchanged; exopodite with 8 natatory setae; endopodite usu- ally with an additional lateral seta on the distal segment (formula now 3,2,1,2,5-1-1; rarely 3,2,1,2,4 + 1). Maxilliped 2 (Figure 3J). Similar in morphologv- to second stage; exopodite with 8 natatory setae. Color. Two orange chromatophores ventrally on first through fifth abdominal somites; other chromatophores as before. Entire zoea dark orange-rose; rose coloration concentrated on pos- terior and posterolateral margins of cepha- lothorax. Lateral carapace and abdominal spines, now pale orange-rose. Dorsal carapace spine clear except for orange-rose hue at base and along pos- terior margm. Mandible and labrum dark brown. Eyes with rose coloration concentrated dorsally. Abdominal somites 1 through 5 darker orange- brown than in previous stage. Sixth somite pale orange-brown. Fourth Zoeae Carapace length: 1.0 mm. Number of specimens examined: 10. Carapace (Figure 4A, Bl. Cephalothorax 364 SCOTTO LARVAL DEVELOPMENT OF CUBAN STONE CRAB Figure 3. — Third zoeal stage ofMenippe nodifrons. lAl Ventral view; iBl lateral view; iC) telson; (Dl antennule; lE) antenna; (F) mandible; iG) maxillule; iHl maxilla; (II maxilliped 1. (Jl maxilliped 2. 365 FISHERY BULLETIN VOL 77. NO 2 globose, enlarged, posterolateral border with 1 1 or 12 setae; three pairs of minute interocular setae; other setae as in stage III. Bud of third maxilliped and thoracic appendages enlarged, more evident under carapace. Abdomen (Figure 4A, B). Pleopod buds now present on second through sixth somites, but much reduced on sixth. First somite with 5-7 setae on dorsal posterior margin; sixth with a pair of small posterolateral spines or knobs. Posterolateral spines on third, fourth, and dorsolateral spines on fifth somites more elongate than in previous stage. Telson (Figure 4C). Similar in form to third stage; 4 setae on posterior telsonal margin. Dorsal and lateral spines on median portion of furcae miniscule as in previous stage. Antennule (Figure 4D). Similar in form to third stage aesthetascs increased to 7 or 8, arranged in three tiers progressing distally: 2 small, 1 small, 3 large plus 1 or 2 small. Antenna (Figure 4E). Exopodal spine usually ex- tending 0.1 X beyond protopodal process and only 0.75 X length of exopodite. Terminal tip of en- dopodal bud extending to base of lateral spinules of protopodal process and about 0.4 x its length. Mandible (Figure 4F). Left molar process un- changed, right molar process with 2 or 3 irregu- larly rounded prominences which join margin of incisor process. MaxUlulc (Figure 4G). Endopodal setation un- changed; basal endite with 12 setae (6 or 7 strong, 5 or 6 thinner) plus a long plumose lateral seta as in previous stage; coxal endite with 8 setae (5 strong plus 3 thinner). Maxilla (Figure 4H). Endopodite unchanged; setae on each basal endite usually 6,5 (5-7, 5-6); coxal endite setae 6,4 (uncommonly 7,4). Scaphognathite with 25-29 plumose setae. Maxilliped 1 (Figure 41). Coxopodite now with 2 setae; basi- and endopodite setae unchanged. Exopodite with 10 natatory setae. McLxilliped 2 (Figure 4J). Coxo-, basi-, and en- dopodal setae unchanged. Exopodite with 10 natatory .setae. Maxilliped 3 (Figure 4K). Bilobed, rudimentary process, without setae, visible through cara- pace. Color. Zoeae similar in color to third stage. Basipodite of first and second maxillipeds now orange-yellow. In lateral view, abdomen gold dor- sally, brown medially, deep orange-rose ventrally. Ommatidia more evenly rose colored, cornea emerald green. Other chromatophore placement and color unchanged. Fifth Zoeac (ultimate) Carapace length; 1.55 mm. Number of specimens examined: 11. Remarks: Ultimate fifth stage zoeae molted directly to megalopae without an intercalated molt to sixth stage. Carapace ( Figure 5A, B). Distinctly increased in size from fourth stage. Carapace length, as in pre- vious stages, about 1.2-1.3* longer than dorsal and rostral spines. Posterolateral margin witli 15-20 setae. Other carapacial setae as described and illustrated for fourth stage. Third maxilliped and pereiopods increased in size, visibly extended from beneath carapace, segmentation evident. Abdomen (Figure 5A, B). First somite usually with 10 (8-10) dorsal setae. Setae on second through fifth somites unchanged, each bearing 2 on posterodorsal margin. Small lateral spines on second and third, posteroventral spines on third and fourth, and dorsolateral spines on fifth somite elongate. Posteroventral prominence of sixth so- mite broad, unlike slender spines of preceding so- mites. Pleopods on second to fifth somites, each with well-developed exopodite and a rudimentary endopodite; sixth rudimentary. Telson (Figure 5C). An additional fifth seta may occur on the posterior margin of the telson. When exopodite of the second maxilliped has 12 plus 1 setae, telson exhibits 2 small medial setae dorsally near telsonal posterior margin as shown; if there are only 12 natatory exopodal setae, telson is naked. Antennule (Figure 5D). Endopodal bud now present below tiers of aesthetascs, latter progress- ing distally 7,7,1,5; basal region swollen but un- segmented, with 2 small basal setae. 366 SCOTTO LARVAL DEVELOPMENT OF CUBAN STONE CRAB Fir.URE 4— Fourth zoeal stage ofMenippe nodifrons. (A) Ventral view; (B) lateral view; (C) telson; iDl antennule; (E) antenna; (Fl mandible; (Gl maxillule; iH) maxilla; (I) maxilliped 1; (J) maxilliped 2; iK) maxilliped 3. 367 FISHERY BULLETIN VOL 77. NO 2 FIGURE 5.— Fifth (ultimate) zoeal stage o( Menippe nudifrons (A) Ventral view; (B) lateral view; iC) telson; (D) antennule; (E) antenna; (F) mandible; iG) maxillule; (H) maxilla. 368 SCOTTO LARVAL DEVELOPMENT OF CUBAN STONE CRAB Antenna (Figure 5E). Exopodal spine extending (as in stage IV) beyond distal tip of protopodal process and remaining 0.75 y length of exopodite. Endopodal bud elongate, unsegmented, about 0.7 * length of protopodal process. Mandible (Figure 5F). Palp bud now present on anterior surface. Left molar process with 4 or 5 rounded to angular prominences along margin of inner angle and junction with incisor process, right molar process with 2 or 3 prominences. Maxillulc (Figure 5G). Endopodite unchanged. Lateral margin of basal endite with 2 long feath- ery setae; usually 8(8-10) spines and 8(8-10) setae terminally; coxal endite with 6 strong plus 5 thin- ner setae distally and 1 long feathery seta basally. Maxilla (Figure 5H). Endopodite unchanged; basal endites with 7,7 processes; coxal endite lobes with 8 or 9, and 4 or 5 processes, respectively. Scaphognathite with 36-45 plumose setae. Maxilltped 1 ( Figure 6A). Coxopodite with 5 ( 5 or 6) setae; basi- and endopodal setae unchanged. Exopodite with usually 11 distal plus 1 lateral natatory setae. Maxilliped 2 (Figure 6B). Coxopodite with 1 seta; basi- and endopodal setae unchanged. Exopodite with 12 distal and commonly 1 smaller lateral setae. Maxilliped 3 (Figure 6C). Exopodite two- segmented, distal segment with up to 6 terminal setae of variable length; endopodite indistinctly four- or five-segmented; unsegmented naked epipodite now present, commonly with 1 seta. Color. Cephalothorax and abdominal coloration similar to fourth stage. Placement artd color of chromatophores unchanged except for additional orange chromatophore at the posterior margin of the yellow telson. In lateral view, abdomen gold dorsally, brown medially, and orange ventrally; pleopods colorless carapace rose-gold dorsally, brown medially, rose posteroventrally, and brown anteroventrally. Ommatidia light rose through- out but concentrated dorsally; cornea reflecting emerald green to irridescent turquoise depending on the position of the larvae. Mandibles and lab- rum dark brown; antennules and antenna color- less. On the first day in stage V, chelae barely visible and colorless except for dark brown chromatophores on the interior margin of each manus. Chelae progressively turn deep orange- rose and continue to extend beneath the carapace by the fourth day. Fifth Zoeae (penultimate) Number of specimens examined: 10. Remarks: Penultimate fifth stage zoeae molted to an atypical sixth stage before molt- ing to megalopae. The morphological charac- ters compared and discussed below are the ones that differ from the regular fifth stage and may be used as a guide to distinguish between the two fifth stages. The abdominal setation should be one of the first characters to check in distinguishing between the two fifth stages. Carapace. Carapace similar to ultimate fifth stage zoeae. Setation on the posterolateral border of penultimate fifth stage zoeae 15 or 16 (15-20 in ultimate stage). Abdomen. First abdominal somite usually with 8 (7-10) dorsal setae (10 in ultimate stage). Antennule. Endopodal bud less developed, its distal tip not extending beyond the midpoint be- tween the base of the first tier of aesthetascs and the base of the bud itself (ultimate stage bud ex- tends about one-fourth past this midpoint). Aes- thetascs arranged in tiers: progressing distally 3-7,7,1,5 ( the ultimate stage proximal tier usually has 7 aesthetascs). Antenna. Endopodal bud less elongate, often not reaching distal end of protopodal spinules, never surpassing them (as in ultimate stage). Mandible. Palp bud smaller in penultimate stage, other prominences equal in both fifth stages. Maxilliped 1 . Coxopodite with 4 setae (5 in ulti- mate stage). Exopodite with either 1 1 or 1 1 plus 1 natatory setae (latter condition usual in ultimate stage). Maxilliped 2 . Exopodite exhibits either 12 or (as usual in ultimate stage) 12 plus 1 natatory setae. 369 FISHERY BULLETIN VOL 77. NO IJ FKU'RE 6.— Fifth I ultimate) (A-C) and sixth (D-F) zoeal stagesof Menippe nodifrons . (A) Maxilliped 1 ; iBi maxilliped 2; (C) maxillipcd 3; (Dl maxilliped I; (El maxilliped 2; iF) maxilliped 3, 370 SCOTTO LARVAL DKVELOPMENT OF CUBAN STONE CRAB MaxilUpcd 3. Epi- and endopodites usually naked. Sixth Zoeae (intercalated) Carapace length: 1.60 mm. Number of specimens examined: 5. Carapace. Cephalothorax little inflated from previous stage. Posterolateral border with 20-22 setae, other setation and armature unchanged. Abdomen. Pleopods elongate, one specimen with setae partially extruded. First abdominal somite with 11-14 dorsal setae. Telson. Similar in morphology to fifth stage. Antenniile (Figure 7A). Endopodal bud elongate with up to 3 setae on distal end. Exopodite showing evidence of five segments; aesthetasc number var- iable, arranged in tiers: (progressing distally) 0,6-11,9-10,7-9,2 subterminal plus 5 terminal (note: not all aesthetascs illustrated); unseg- mented basal region swollen with 2 small setae placed as shown. Antenna (Figure 7B). Endopodite surpassing protopodal spinous process, showing evidence of five segments; setation variable, 0 or 1 on proxi- mal segment, 0-3 on remaining four. Distal tip of exopodal spine surpassing protopodal process but attaining length of endopodal distal tip. Exopodal spine now 0.5 ■ length of exopodite; latter about equal in length to protopodal process. Mandible (Figure 7C). Palp unsegmented, elon- gate, with up to 3 distal setae. Molar process simi- lar in form to fifth stage, 4 or 5 rounded to angular prominences along margin of inner angle and junction with incisor process; right molar process with 2 or 3 prominences. Ma.xillule (Figure 7D). Proto- and endopodal se- tation unchanged; basal endite with 11 spines plus 10-12 stout setae plus 2 laterally; coxal endite with 6 strong plus 7 thinner setae plus 1 basally. Maxilla (Figure 7E). Endopodite unchanged; basal endite lobes with usually 8 (8 or 9), 10 (8-10) setae respectively; coxal endite setae usually 1 1,7. Scaphognathite with 43-50 plumose setae on outer margin plus 2 small setae on lower surface of the blade. Maxilliped 1 (Figure 6D). Coxopodite with 6 setae; basipodal setal formula similar to fifth stage with 2-4 additional setae dispersed as illustrated; endopodal setae 3,2,1,2-3,5 + 1; exopodite with usually 1 1 ( 11 or 12) plus 1 lateral natatory setae. Maxilliped 2 (Figure 6E). Coxo- and basipodal setation unchanged. 1 and 4 setae, respectively; endopodal setae 0,1,5; exopodite with 12 plus 2 natatory setae. Maxilliped 3 (Figure 6F). Exopodite two- segmented with S setae on distal segment; unseg- mented endopodite unchanged from previous stage; epipodite with up to 6 setae. Color. Entire zoea much lighter orange-rose than in previous stage. Eyestalks each with one brown-orange chromatophore anteriorly. Ros- trum pale rose. Proximal segment of exopodites of maxillipeds 1 and 2 now yellow. Brown-orange postcardiac chromatophores, present in first five zoeal stage, now absent. Megalopae Carapace length '-^ width: 1.50 ^ 1.31 mm. Number of specimens examined: 10. Remarks: Megalopae (VI) molting from stage VI zoeae differed only slightly from those megalopae (V) molting from stage V zoeae. These differences are noted under the appro- priate headings. Carapace (Figure 8A). Cephalothorax subquad- rate overall, sparsely covered with hairs as shown; posterior and posterolateral border with up to 60 setae. Frontal region rectangular, rostrum strongly deflexed, nearly vertical, bluntly rounded with distinct median cleft, slightly expanded lat- erally to meet bluntly angular interorbital promi- nence. Orbit excavated, nearly rectangular; eyes large, eyestalks with 5 anterior setae. Abdomen (Figures 8A, 9A), Pleurae 1 through 5 with lobes at posteroventral angles, that of somite 6 subquadrate. First abdominal somite with up to 32 setae arranged in a transverse row, somites 2 through 6 sparsely covered with setae. 371 FISHERY BULLETIN VOL 77, NO 2 FICURE?.— SixthlA-ElzoealstageofAfenippenodi/T-on*. (A) Antennule (not all aesthetascs illustrated); (Bl antenna; (C) mandible; (Di maxillule; (El maxilla. Megalopa iF-Jl: (F) Antennule (not all aesthetascs illustratedi; (G) antenna; (Hi mandible; (II maxillulc (Ji maxilla 372 SCOTTO LARVAL DEVELOPMENT OF CUBAN STONE CRAB Figure 8. — Megalopal stage o( Menippe nodifrons. (A) Dorsal view; iB) maxilliped 1; iC) maxilliped 2; (Dl maxilliped 3. 373 FISHERY BULLETIN: VOL. 77, NO 2 Telson (Figure 9A). Subquadrate, posterior an- gles rounded, 5 setae on posterior margin, other setation variable. Antennule (Figure 7F) Biramous. Peduncle three-segmented; bulbous basal segment partially bilobed; middle segment subcylindrical, smaller than proximal segment, setae appearing distally as shown; distal segment ovoid, setation variable in all segments. Lower ramus one-segmented with 8 setae; upper ramus five-segmented, aesthetascs arranged in tiers: usually 0,12,10,8 ( + 2 setael, 5 subterminal plus 3 terminal (note: all aesthetascs not illustrated). Antenna (Figure 7G). Peduncle with lateral lobe extending to about midpoint of the first basal seg- ment. First basal segment the largest; setation of the 11 flagellar segments variable, usually 4,3,2,0,0,4,0,4,0,4,5. Mandible (Figure 7H). With truncately spade- shaped cutting edge: palp two-segmented, setae 0, 10-13. Maxillule (Figure 71). Protopodite with 1 long feathery seta on the dorsal margin; endopodite two-segmented, longer and more swollen proximal segment with 1 lateral seta, distal segment with 4 setae; basal endite with 28-33 spines and setae; coxal endite with 15-19 setae. Maxilla (Figure 7J). Endopodite now unseg- mented with 4-6 setae; setation of basal endites variable: 10-13, 11-15, setae on coxal endites also variable: 9-15, 4-10. Scaphognathite of megalopae (V) usually with 66 plumose setae on the outer margin plus up to 12 small setae on blade, megalopae (VI) with 76 plus 18. Maxilliped 1 (Figure 8B). Exopodite two- segmented, proximal segment usually with 5 (4-6) setae distally, distal segment usually with 6(5-7) setae. Endopodite unsegmented, usually with 6 (6-9) setae. Basal endite setation variable, 30-34 on megalopae (V), 40-44 on megalopae (VI); coxal endite setae 12-18 on megalopae (V), 20-25 on megalopae (VI). Epipodite with naked processes ( in appearance similar to antennular aesthetascs), 12-20 on megalopae, (V), 26 on megalopae (VI). Maxilliped 2 (Figure 8C). Exopodite two- segmented, proximal segment with 2 small setae 374 medially, distal segment with 8 terminal setae. Endopodite four-segmented, setation variable usually: 8-12, 0-5, 6-10, 9-12, placed generally as shown. Epipodite with up to 10 naked aes- thetasclike setae. Maxilliped 3 (Figure 8D). Exopodite two- segmented, 4 medial setae on proximal segment, 6-10 on distal segment. Endopodite five- segmented, third and fourth segments partially bilobed, setation on all segments variable, usu- ally: 25, 14, 10, 11, 8. Epipodite usually with 18 naked aesthetasclike setae on distal two-thirds plus 8 normal setae on proximal one-third in megalopae (V); 28 plus 8 in megalopae (VI). Pro- topodal setation variable (example illustrated). Pereiopods (Figure 9B, C, c, D, d). Chelipeds (B) elongate, equal; dactyl with 4 irregular teeth in gape, propodus with 3, the curved tips overlapping distally. Second to fourth pereiopods (e.g., C) simi- lar; dactyls with 5 teeth ventrally. Fifth pereiopod dactyl (D, d) with 3 long pectinate setae distally (= brachyuran feelers) in megalopae (V), 4 on megalopae (VI). Pleopods (Figure 9A, E, F). Pleopods of decreas- ing size on second to sixth abdominal somites; pleopods (uropods) of sixth somite without en- dopodite. Megalopae (V) with 20-21, 20-21, 20-21, 16-17, and 11 plumose setae on the exopodite re- spectively; megalopae (VI) with 22-23, 22-23, 21-22, 19-20,and 12 plumose setae. Endopoditesof pleopods ( = appendices internae) 1-4 and both (Vl and (VI) megalopae with 3 hooked setae. Color. Under incident light, the megalopae exhibit a rose-orange coloration especially pro- nounced around posterolateral borders of carapace. Eyes iridescent turquoise. Eyestalks with black chromatophores dorsally, rose colored posteriorly. Cephalothorax with iridescent tur- quoise chromatophores on epibranchial, pos- terolateral, and entire gastric region. Abdomen with 1 large black chromatophoreon first somite, 2 each on second to sixth somites. Second to fifth J pereiopods light rose, darker at joints. Chelipeds " deep orange-rose with black chromatophores in- terspersed, teeth of hand colorless. DISCUSSION OF REARING RESULTS Few brachyuran decapod larvae exhibit vari- SCOTTO LARVAL DEVELOPMENT OF CUBAN STONE CRAB 1.0mm 0.25mm c,d,E,FH FIGURE 9.— Megalopal stage ofMenippe nodifrons. ( Ai Abdomen; IB) cheliped; (C) third pereiopod; (c) third pereiopod dactyl; (D) fifth pereiopod; (d> fifth pereiopod dactyl; lE) first pleopod; (F) fourth pleopod. 375 FISHERY BULLETIN VOL 77. NO 2 ability in number of larval stages. Callinectes sapidus, Drornidia antillensis , Rhithropanopeus harrisii, Menippe mercenaria, and now M. nodi- frotiK larvae have exhibited an extra instar at the end of larval development iKnowlton 1974). In summarizing earlier studies, Knowlton (1965, 1974) speculated that the amount of food, temper- ature, and photoperiod contribute to controlling the number of instars in decapod crustaceans. Knowlton (1974) reared Palaemonetes rulgaris, a caridean shrimp, under varying environmental conditions and concluded that "larvae maintained at increasingly higher temperature levels were inclined to pass through more instars." In con- trast, Sandifer (1973) found that larvae of P. vul- garis "passed through fewer instars at the moder- ate temperature (25°C) than at higher or lower temperatures " Menippe nodifrons has five or (uncommonly) six zoeal stages, and one megalopal stage, as does its congener M. mercenaria (Porter 1960; Ong and Costlow 1970). As expected (Ong and Costlow 1970; Costlow and Bookhout 1971; Gore 1971: Christiansen and Costlow 1975) larval develop- ment of A/, nodifrons was substantially slower at 20' C than at 30° C. The first five zoeal stages exhibited modal durations ranging from 5 to 8 days at 20" C, 4 to 5 days at room temperature (£ = 24,5° C), and 2 to 4 days at 30° C (Table 1). A decrease in the number of zoeal stages was ob- served concomitant with this decrease in duration of each stage at the higher temperature, i.e., only five zoeal stages were attained at 30° C, while an atypical sixth stage was infrequently obtained at both room temperature and 20° C. In summary, duration of larval development, duration in days of each stage, and number of zoeal stages of M. nodifrons, are all temperature- dependent (Figure 10). Although similar results were obtained by Ong and Costlow (1970) with regard to larval development of M. mercenaria . a difference in survival rate can be noted. At 30° C none of the M . nodifrons larvae survived to crab stage 1, while 30 (60% ) M. mercenaria larvae (in 35%n) attained crab stage 1. At similar room tem- peratures (about 25° C), 1 M. nodifrons larva (27?) reached crab stage 1, while 37 (74%) M. mer- cenaria larvae attained crab stage 1. At 20° C, M . nodifrons exhibited the highest survival with 7 (15%) megalopae molting to crab stage 1, while survival of M. mercenaria sharply decreased to O^t with no first crab stages reached ( Ong and Costlow 1970). Table 1. — Duration of larval stages of Menippe nodifrons at three temperatures. Total no Temp Duration (days) moiling to ( C) Stage Mm Mean Mode Max next stage 20' Zoeae ( 5 58 6 7 48 II 3 43 5 5 42 III 4 5 1 5 7 39 IV 5 60 6 7 38 V(P)' 5 52 5 6 5 V(u)' 6 76 8 9 24 VI 8 8 7 9 9 3 Megalopa (V)^ 15 168 175 18 6 (VI)' 16 160 160 16 1 24 5" Zoeae 1 3 4 7 5 6 48 (mean II 3 39 4 6 44 room III 3 5 1 5 8 28 lemp) IV 3 42 4 5 25 V(p)' 3 4 4 5 5 7 V(ul= 5 63 5 11 9 VI 6 60 6 6 1 Megalopa (Vl)" 13 130 13 13 1 30 Zoeae 1 3 32 3 4 46 II 2 25 2 5 3 48 III 1 26 3 4 47 IV 2 3 1 3 5 46 V 3 40 4 5 35 Megalopa (') (9) 0 'Zoea V moiling lo Zoea VI (penultimale). ^Zoea V moiling to Megalopa (ultimate) ■"Megalopa moiled Irom Zoea V 'Megalopa molted Irom Zoea VI ( ) Died in stage Ong and Costlow ( 1970) suggested that 30° C is the optimum survival temperature for the larvae of M. mercenaria with optimum salinity ranging from 30 to 35"/oii. The megalopal stage was attained in 14 days, first crab on day 21, with total larval survival ranging from 60 to 72% . Conversely, my results indicate highest survival of M. nodifrons ( 15% ) at 20° C. The megalopal stage was attained in 28-34 days and first crab on days 45-49 from fifth stage zoeae. Because of the additional sixth stage, the megalopal stage in that series was at- tained in 36-37 days and first crab on day 52. DISCUSSION Comparative Morphology oi Meni[)[)e Larvae The only other species of Menippe whose com- plete larval development has been described is M. mercenaria. Hyman ( 1925) described the prezoeal and first zoeal stages of that species, and Porter (1960) obtained a complete series of five (atypi- cally six) zoeal stages. Menippe nodifrons also at- tains five and atypically six zoeal stages, depend- ing on the rearing temperature. There is but one easily observed and recurring feature which may be used to distinguish between all zoeal stages of M .nodifrons and M .mercenaria. The fourth abdominal somite of M . mercenaria has 376 SCOTTO LARVAL DEVELOPMENT OF CUBAN STONE CRAB 100 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 44 46 48 50 52 54 DAYS IN STAGE FIGI'RE 10— Percentage survival and stage duration ofMenippe nodifrons larvae reared under laboratory conditions. N - number of larvae cultured at each temperature; * = combined stages; u = ultimate stage; p = penultimate stage. 377 FISHERY BULLETIN VOL 77. NO :; a dorsolateral spine not found in M. nodifrons. Additionally, in the first zoeal stage several differ- ences (Table 2i include: antennular aesthetasc number, maxillulary coxal endite setation. and segmentation of the exopodites of the first and second maxillipeds. Setation differences in other stages are relatively minor (Table 3), and include: setation of the first maxilliped, in zoeal stage 2; setation of the maxillary basal endite and endopo- dite of the second maxilliped, in zoeal stage 3; and setation of the maxillulary basal endite, in zoeal stage 4. Setation on the larval appendages of Af. nodi- frons becomes particularly variable in the fifth stage: because of this, distinguishmg characters between M . nodifrons and.M. tnercenaria in this stage are not discussed. However, in M . nodifrons there are several differences between ultimate fifth stage zoeae [ZV(u)| that molt directly to megalopae and penultimate fifth stage zoeae [ZV(p)l that molt to sixth stage. These include (Table 4): coxopodal setation of the first maxil- liped, antennular aesthetasc number, exopodal se- tation of the third maxilliped, and setation on the first abdominal somite. In addition, the antennal endopodite bud reaches the tip of the protopodite in ZViu); in ZV(p) it is less elongate, reaching only to distal end of protopodite process spinules. Differences between the sixth zoeal stages of M. nodifrons and M. mercenaria concern setation ol' the maxillary scaphognathite and first maxil- lipedal basipodite (Table 5). Other distinguishing characters include evidence of antennular exopo- dite and antennal endopodite segmentation, also observed in Callinectes sapidus (Costlow and Bookhout 1959). Kurata"* described the complete larval develop- ment, including the megalopal stage, of M. mcr- ■^Kurata. H. 1970. Part IH. Larvae of decapod Crustacea of Georgia. In Studies on the life histories of decapod Crustacea of Georgia. UnpubL manuscr.. 274 p. University of Georgia, Marine Institute. Sapelo Island. GA 31327. Table 2. — Taxonomically important first zoeal characters in three species o{ Menippe ? Character M rumphii (Prasad and Tampi 1957) M mercenaria (Porter 1960) Carapace Rostrum Dorsal spine Lateral spine Margin Antennule Exopodite Antenna Exopodite Mandible Maxillule Endopodite Basa! endite Coxal endite Maxilla Endopodite Basal endite Coxal endite Scaphognathite Maxilliped 1 Coxopodite Basipodite Endopodite Exopodite Maxilliped 2 Coxopodite Basipodite Endopodite Exopodite Straight, unarmed Posteriorly curved Venlrally curved Unarmed Conical rod 4 aesthetascs Exopodite ^4 protopodite Tapered, long subtermmal spine Scoop-shaped, incisor and molar processes indistinctly dentate and serrate, no palp Two-segmented 1 , 4 seiae 5 hirsute setae 7 hirsute setae Bilobed 3,3 setae Biiobed 5,4 setae Bilobed 5,4 setae 4 plumose setae, distal plumose process 1 seta 10 setae. 2,2,3.3. Five-segmented 3.2.1,2.5 Two-segmented. 4 natatory setae Naked 4 setae Three- segmented 0 1,4 setae Two-segmented, 4 natatory setae Somites 2 to 5 with 2 posterodor- sal setae, somite 4 without spines in all stages Straight, unarmed Posteriorly curved Ventrally curved Unarmed Conical rod 4 aesthetascs Exopodite - protopodite Tapered, single spine Cutting edge serrate, no palp Two-segmented 1, 4 setae 5 hirsute setae 6 hirsute setae Bitid 3,3 setae Bifid 5,4 setae Bitid 5.4 setae 4 plumose setae, posterior plumose process 1 seta 6 setae Five-segmented 2,2.1,2,4 4 natatory setae Not given Few setae Three-segmented 0.2.4 setae 4 natatory setae Somites 2 to 4 with a pair of short hairs; somite 4 without spines Straight, unarmed Posteriorly curved Ventrally curved Unarmed Conical rod 6 aesthetascs Ratio not given Tapered. 1 long heavy spine Lateral and posterior cutting edge indistinct teeth, no palp Two-segmented 1 , 4 setae 5 stout hairy setae 6 stout hairy setae Bilobed 3,3 setae Bilobed 5 4 setae Bilobed 5.4 setae 4 plumose setae, distal plumose process Not given 10 setae Five-segmented 2.2.1.2.5 Partially bisegmenled. 4 natatory setae Not given 4 setae Three-segmented 0,1,4 setae Partially bisegmenled. 4 natatory setae Somites 1 to 5 with 2 posterodor- sal setae, somite 4 with pair of dorsolateral spines m all stages 'Characters taken from authors descriptions and illustrations 378 SCOTTO LARVAL DEVELOPMENT (IF CUBAN STONE CRAB Table 3. — Taxonomically important zoeal characters in two species of Menippe. Data on M . mercenaria taken from Porter (1960). Stage II Stage III Stage IV Character M nodifrons M mercenaria M nodifrons M mercenana M nodifrons M mercenana Carapace Margin 3 setae Several setae 8 setae 5 setae 11-12 setae 1 2 setae Aniennule aesthetascs 5-6 5 4 5 Base swollen, 7-8 Base svnollen, 7 Antenna Endopodite Small hump Not given Bud Hump Bud terminal tip at mid- point o( an- tenna Terminal tip bud at mid- point ot an- tenna Maxillule setation Endopodite Basal endite Coxal endue 1.4 7*1 laterally 7 1,4 7 . 1 laterally 7 1,4 8 . 1 laterally 7 1,4 8 ■ 1 laterally 7 14 12-1 laterally 8 1,4 12 * 2 laterally 8 rvtaxilla setation Endopodite Basal endite Coxal endite Scaphognathite 3,3 5,4 5,4 1 1 plumose 3.3 54 5,4 11-12 plumose 33 5,5 5,4 19-20 plumose 3.3 5,4 5,4 18 plumose 3,3 6.5 6,4 25-29 plumose 3.3 6,5 6,4 27-28 plumose Maxilliped 1 setation Coxopodite Basipodite Endopodite Exopodite 1 2,2,3,3, (10) 3,2,1,2,5 6 natatory Not given 10 2,2,1.2,5 6 natatory 1 2,2,3,3, (10) 3,2,1,2,6 8 natatory Not given 10 3.2,1,2,5 8 natatory 2 2,2,3.3, (10) 3.2.1.2,6 10 natatory Not given 10 3.2 1.2,6 10 natatory Maxilliped 2 setation Coxopodite Basppodite Endopodite Exopodite Maxilliped 3 Nalied 4 0,1 4 6 natatory Not given 4 0,1,4 6 natatory Naked 4 0 1,4 8 natatory Not given 4 0,1,4 8 natatory Naked 4 0,1,4 10 natatory Bilobed bud Not given 4 0,1 4 10 natatory Bud Abdomen First somite Sixth somite 1-2 setae 1 setae 3 setae 2 dorsal setae 3 setae Unarmed Pleopod buds 5-7 setae 2 dorsal setae Pleopod buds 5-7 setae Unarmed cenaria. His data show that difference.s between megalopae of the two species are exhibited chiefly in the spination of the pereiopods. Menippe mer- cenaria has 5 or 6, 2 or 3, and 1 small spine on the ischia of walking legs, one, two, and three, respec- tively; and 2 small spines on the proximal inner edge of the merus of the first walking leg. Menippe nodifrons exhibits variable setation on these same segments but lacks spines. Kurata also stated that the ischium of the third maxilliped of M. mer- cenana has 9 small spines; in M . nodifrons vari- able setation occurs, but 25 setae are usually found. Among other species of Menippe only the first zoeal stage of the Indo-Pacific M. /•;/ mph ii has been described (Prasad and Tampi 1957). As indicated in Table 2, the three congeners have a similar first stage, but differ in antennular aesthetasc number, .setation of the maxillary coxal endite. setation of the basi- and endopodite of the first maxilliped. and endopodite setation of the second maxilliped. As noted in the introduction, there is some ques- tion as to whetherM. rumphii is synonymous with M . nodifrons. The complete larval development of M . rumphii is needed to establish the status of this species and its taxonomic relationship to M . nodi- frons. Distinguishing Morphology of Xanthidae Larvae According to Lebour ( 1928), larvae of the family Xanthidae exhibit the following characters: 1. One prezoeal and four zoeal stages. 2. Carapace with dorsal, rostral, and one pair of smaller lateral spines. 3. Antenna with rudimentary exopodite, or with one nearly as long as the spinous pro- topodal process. 4. Abdomen with lateral knobs on somites 2 and 3, somites 3-5 or 6 with lateral spines in all stages. 5. Telson furcae with 3 lateral spines or with 1 tending to disappear in later stages. Wear 1 1970) reviewed the diagnostic characters of certain xanthid larvae and enumerated sev- eral conclusions about Menippe. Known larvae of the genus Menippe. reared under laboratory con- 379 FISHERY BULLETIN: VOL. 77, NO, 2 Table 4. — Taxonomically important characters of the fifth zoeal stage in two species otMenippe. Character M nodilrons (ultimate) M. nodilrons (penultimate) M. mercenaria (Porter 1960) Carapace: Margin 1 5-20 setae 15-16 setae 20-22 setae Antennule Endopodite Exopodite Bud 7,7,1.5 Bud less elongate 3-7.7.1,5 Bud elongate 2-7,6-8,1,4-5 Antenna Endopodite Bud elongate Bud less elongate Bud elongate Mandible Palp present Palp smaller Palp present Maxillule setation. Endopodite Basal endite Coxal endite 1.4 16.2 laterally 11-1 basally 1,4 16^2 laterally 11*1 basally 1,4 14-17 '2 laterally 11-12 Maxilla setation Endopodite Basal endite Coxal endite Scaphognalhite 3,3 7,7 8-9. 4-5 36-45 plumose 3.3 7.7 8-9. 4-5 34-42 plumose 3,3 8,7 6-10,4-5 36-39 plumose Maxilliped t setation Coxopodite Basipodite Endopodite Exopodite 5 2,2,3,3 (.10) 3.2,1.2.6 11-1 natatory 4 2.2,3.3 (10) 3,2,1,2,6 1 1 or 1 1 - 1 natatory Nol given 10 3,2,1,2,6 11^1 natatory Maxilliped 2 setation Coxopodite Basipodite Endopodite Exopodite 1 4 0.1.4 12-1 natatory 1 4 0.1.4 12 or 12 • 1 natatory Not given 4 0.1.4 12+1 natatory Maxilliped 3 setation Endopodite Exopodite Epipodile Indistinctly 4-5 segmented Two-segmented 0. 0-5 Unsegmented. naked Reduced Naked Reduced Partially tive-segmented Unsegmented Unsegmented. naked Abdomen selation First somite Usually 10 Usually 8 8-9 Pleopoos Pair 1 to 4 with exopod and rudi- mentary endopod. pair 5 a bud Pair 1 to 4 with exopod and rudi- mentary endopod, pair 5 a bud Pair 1 to 4 with protopod. exopod and endopod. pair 5 a bud ditions, are distinguished from other xanthid gen- era by attaining five and atypically six zoeal stages; other xanthid larvae exhibit only four zoeal stages. Larvae of the genus Menippe (and Eriphia ) are distinguished from other xanthids by antennal development, i.e., the larval exopodite is about 0,75 ■ the length of the spinous protopodal process (see Aikawa 1937; Porter 1960; Sandifer 1974), Menippe (and Sphaerozius) larvae are dis- tinguished from other closely related xanthid gen- era by the absence of setae on the basal segment of the second maxillipedal endopodite (Aikawa 1937; Porter 1960), Number of Zoeal Stages According to descriptions to date, every genus of xanthid crab has four zoeal stages ey^cept Menippe. In this study, M. nodifrons attained five zoeal stages, occasionally a sixth, and a prezoeal stage occurred. These stages also appeared in the larval development of A/, mercenaria (Porter 1960). The prezoeal stage exhibited by both M. mercenaria and M. nodifrons was never observed to molt to a first stage zoea. Larvae of both species, collected within seconds after hatching, were almost always found to be in the first stage, indieatmg that the observed M . nodifrons prezoeae were those zoeae too weak to molt to stage L Porter also indicated that M. mercenaria prezoeae. which were seen most often when subsequent survival was poor, may not be a normal stage in planktonic existence of the larvae. However, Lebour (1928), Chamber- lain (1957), and Wear (1970) established that lar- vae of other xanthid genera hatch from the egg as prezoeae. Based on data obtained in this experi- ment, it seems possible that the prezoeal stage of M. nodifrons may occur in nature under certain conditions, as may the sixth zoeal stage. Porter ( 1960) suggested that, based on the var- iability of morphological characters and the fact that no stage VI zoeae molted to megalopae. the sixth stage in M. mercenaria may not be a true stage but an advanced fifth stage. As noted in the rearing results, the observation of temperature- dependency in relation to number of zoeal stages 380 SCOTTO: LARVAL DEVELOPMENT OF CUBAN STONE CRAB Table 5. — Taxonomically important characters of the sixth zoeal stage in two species of Menippe. Data on M. mercenaria taken from Porter 1 1960). Character M nodifrons M. mercenaria Carapace Margin 20-22 setae 20-22 setae Antennule Endopodite Bud elongate, 0-3 Bud elongate, occa- setae sional setae Exopodite Five-segmented, 0, Unsegmented. 4-6 6-11, 9-10, 7-9. 6-8. 1. 4-5 2 subterminal * 5 terminal Antenna' Endopodite Five-segmented, 0-1 0-3. 0-3, 0-3, 0-3 Unsegmented Mandible Palp elongate, 0-3 setae Palp as in stage 5 Maxillule setation Endopodite 1.4 1.4 Basal endite 22-23 + 2 laterally 23-29+2 laterally Coxal endite 13 11-12 Maxilla setation Endopodite 3,3 3.3 Basal endite 8(8-9), 10(8-10} 9-11, 8-9 Coxal endite 11,7 8-11. 4-5 Scaphognathile 43-50^2 plumose 39-44 plumose Maxilliped 1 setation CoKOpodite 6 Not given Basipodite 12-4 10 Endopodite 3,2,1,2-3,6 3.2,1.2.6 Exopodite 11 - t natatory 11-1 natatory Maxilliped 2 setation Coxopodite 1 Not given Bastpodite 4 4 Endopodite 0,1,5 0.1.4 Exopodite 12*2 natatory 12*1 natatory Maxilliped 3 setation Endopodite Unsegmented. naked Not given Exopodite Two-segmented, 0-8 0-8 Epipodile Unsegmented, 0-6 Not given Abdomen setation First somite 11-14 9-11 Pleopods Exopodite setae only Exopodites with setae partially extruded on all or only last pair indicates that his supposition may not hold for all members of the genus, notably for M. nodifrons. Regardless of whether a sixth zoeal stage is a laboratory artifact, the appearance of which seems to be temperature-dependent, it is apparent that larvae of at least two species of Menippe undergo at least five zoeal stages. The ramifications of this fact will be discussed below. Few other brachyuran species e.xhibit an incon- sistent number of instars in their larval develop- ment. Boyd and Johnson ( 1963) reported that out of 20 species of brachyuran crabs observed by Costlow, only two species, both Portunidae, exhib- ited variation in the number of zoeal stages. The phylogenetically primitive Portunidae have at least seven and sometimes eight zoeal stages iBookhout and Costlow 1974, 1977). The extra stages resulted in reduced viability, with only a few zoeae developing to megalopae. Boyd and Johnson ( 196.3) also suggested that the sixth stage in some normally five-staged Brachyura is a result of laboratory conditions because the extra stage has never been found in the plankton. This sup- ports Gurney's ( 1942) and Porter's 1 1960) conten- tions that laboratory conditions produce aberrant larval forms. However, Boyd and Johnson (1963) also stated that extra stages might possibly occur in nature under certain conditions. Now that lar- vae of A/, iiodifrona are known it should be rela- tively easy to identify a sixth stage zoea of this species in the plankton based on criteria produced earlier in my study. Plesiomorphy and Larval Development Lebour (1928) set forth the genus Portun us as the most primitive of the Brachyrhyncha, based on the following characters: many zoeal stages (up to eight, Bookhout and Costlow 1977); telson with 6 long internal setae plus 3 lateral spines on each furca, making 7 spines on each side, with 2 extra pair of internal setae in later stages; knobs on the second and third abdominal somites, those on the third disappearing in later stages; and antenna with a well-developed exopodite, about one-half as long as the spinous protopodital process. Larvae of the western North Atlantic species of Menippe also exhibit these characters, differing only in the number of larval stages (up to six) and in the retention of the knob on the third abdominal somite. Larvae of the Cancridae, considered to be more primitive than the Xanthidae (Rathbun 1930; Gurney 1939) and by some authors (Bor- radaile 1907; Lebour 1928; Glaessner 1969) than the Portunidae, also exhibit the primitive charac- ters enumerated by Lebour for the Portunidae, differing mainly in number of zoeal stages (five), armature of the telson (2 lateral spines on each furca), and possession of a knob only on the second abdominal somite. Based on the assumption that a gi-eater number of zoeal stages is a primitive character, I agree with the phylogenetic arrangement of Rathbun ( 1930 ) and Gurney ( 1939), both of whom placed the Cancridae primitive to the Xanthidae but more advanced than the Portunidae. However, in com- paring the number of larval stages, the genus Menippe shows a closer relationship to the Can- cridae than to the Xanthidae. This relationship is discussed below in light of additional larval characters. Excluding Menippe. the laboratory cultured genera of xanthids have four zoeal stages (e.g.. 381 FISHKRY BULLETIN Vol. Piliannus danypodu.^, Sandifer 1974; Eurypuno- pcus depresstis, Costlow and Bookhout 1961a). These xanthids usually possess 8 or 9 natatory maxillipedal setae in the third zoeal stage and pleopod buds first appear in this instar. However, third zoeae oiMenippe, which also possess 8 nata- tory maxillipedal setae, lack pleopod buds and the latter do not appear in known Mcnippc larvae until the fourth stage (10 natatory maxillipedal setae). Menippe larvae, as do other xanthid larvae, otherwise attain the sixth abdominal somite in the third stage. A similar situation is found among known lar- vae of the Cancridae (e.g., Cancer borcalis. Sastry 1977b; C. irniratiis,Sa»try 1977a), which exhibit 8 natatory maxillipedal setae but no pleopod buds in the third zoeal stage, while 10 natatory maxil- lipedal setae and pleopod buds are exhibited in the fourth stage, as in Mcnippc. Thus Mcnippc again shows, in this respect, a closer relationship to the Cancridae than to the Xanthidae. Another heterochronic feature is the mandibu- lar palp, which appears in the fourth (i.e., last) zoeal stage in all xanthid genera except Mcnippc. Fourth stage Menippe larvae in the western North Atlantic may thus be distinguished from other stage IV xanthid larvae in lacking a mandibular palp as well as in possessing 10 natatory maxil- lipedal setae, as noted above. In all other laborato- ry cultured xanthid genera with 9 or 10 natatory maxillipedal setae the mandibular palp is present. Again, Menippe larvae seem closer to cancrid lar- vae than to xanthid larvae, in that the mandibular palp appears in the fifth (usually the last) zoeal stage. Comparison of M. nodifrons maxillipedal coxopodal setation with that of other xanthid and cancrid larvae, which may be a significant feature, was not analyzed because of the lack of descrip- tions and illustrations of this larval character. The coxopodal setation has been described for only one other xanthid, Neopanope texana (McMahan 1967). Setal number of M. nodifrons agreed with that of A^. le.xana for the first four zoeal stages, increasing in the fifth and sixth stages of M. nodi- frons . Assuming then, that data just presented are evidence of retained, primitive features, it can then be postulated that Menippe larvae are re- capitulating, in the sense of retarded het- erochronic maturation (Gould 1977), a larval development now accelerated in other xanthid lar- vae. The presence of the fifth zoeal stage, the ir- regular occurrence of the sixth stage, the delayed appearance of mandibular palp and pleopod buds, and retention of coxopodal setation in cultured species of .V/. nodifrons and M . merccnaria are all evidence which indicates this might have hap- pened. Evolution has apparently acted in the lar- vae of other xanthid genera to reduce the number of zoeal stages. In summary, because of the greater number ol' zoeal stages and the tardy appearance of both pleopod buds and mandibular palp, Menippe may lie the most primitive genus of the family Xanthi- dae. Whether the genus is transitional between the Cancridae and the Xanthidae remains speculative. As noted above, larvae of the family Cancridae, phylogenetically primitive to the Xan- thidae. also exhibit five zoeal stages and pleopodal and mandibular features which appear in a similar developmental sequence to those of Menippe. The more advanced xanthid larvae, on the other hand, pass through only four zoeal stages and exhibit sequential features typical of larvae of the family Gimeplacidae, a group considered to be more advanced than xanthids (Lebour 1928; Kurata 19681. Carapacial Armature Mcnippc larvae have well-developed dorsal, rostral, and smaller lateral spines, a feature found in all cancrid and most xanthid larvae. Thus, little can be inferred regardmg phylogenetic relation- ships using these features. The reason for such spines remains conjectural. Lebour (1928) stated that these well-developed carapacial spines were used "in directing move- ment and keeping up |the larvae in] the surface- layers, and their reduction appears to be associated with habits near the bottom." Her sup- position may be correct. Menippe nodifrons larvae reared in this study were active swimmers near the surface in earlier stages. Their locomotion was usually in a forward direction with the dorsal spine pointed anteriorly. Antennal Morjiliology In considering antennal features, xanthid lar- I vae were first divided into either two (Hyman 1 925) or three ( Lebour 1 928) groups. In the former, l)()th authors noted that the length of the antennal exopodite is either about equal to the protopodite (primitive) or rudimentary (advanced). In the :W2 SCOTTO I,AR\A1. I)p;VKL( )['MKNT < )K CUBAN STONE CRAB third group, also considered primitive, the anten- nal exopodite is about three-fourths the length of the protopodal process (this group was established by Lebour to include Me nippe andEriphia ). There- fore, regardless of classification scheme (Hyman's or Lebour's), larvae of the genus Mtvn'ppe exhibit a primitive antennal morphology. However, as will he seen, the degree of primitiveness is relative. Aikawa ( 1929) classified four types of antennae (A, B, C, and D) based on the ratio of length of peduncle to that of exopodite. In the A type an- tenna the exopodite and peduncle i = protopodal proce.ss) are nearly equal in length. Aikawa also considered this to be the most primitive condition because other authors (e.g.. Caiman 1909) have noted that the long exopodite is homologous with the antennal scale of the Caridea. Xanthid larvae exhibiting A type antennae are Pilumnus (considered by Hyman 1925 to be the most primitive xanthid I, Hetcropan:sn>i (Costlow and Bookhout 1961a), and Hexcipanopeus angiistifrons (Costlow and Bookhout 1966), all more advanced forms than Menippe. These data lend further support to the primitive status of Menippe as compared with other xanthid genera. In summary, using larval characters suggested by Lebour (1928) to determine the primitive or advanced status of decapod larvae, the genus Menippe is phylogenetically more primitive than 383 most of the Xanthidae. It appears to be closer, in most features, to the family Cancridae. Status t)f the Family Menippidae Ortman (1894) established the family Menip- pidae, which included the subfamilies Menip- pinae, Myomenippinae, and Pilumninae. based on the following adult characters: a) the second seg- ment of each antenna is short, not overreaching the frontal region; and b) the palate is with or without a ridge. However, because of the reigning taxonomic confusion in this group, this familial rank was not recognized by other authors of that time. Indeed, many present day xanthid species were placed under differing familial and subfami- lial names (e.g., Pilumnidae, Cancridaei before the taxon Xanthidae became firmly established (Rathbun 1930). Later authors notwithstanding, Aikawa (1929, 1937), using Lebour's larval characters (with emphasis on antennal develop- ment), again recognized the family Menippidae, considering it to be more primitive than the Xanthidae. Subsequent study of the larval de- velopment oi Menippe . reported by Porter (1960) and in this paper, supports Aikawa's phylogenetic arrangement based on larval morphology, as well as adding evidence using larval development, i.e., the fact that Menippe attains up to six zoeal stages (more stages = primitive). The establishment by Ortmann (1894) of the Menippidae as a family, although based only on adult characters, seems to be supported also by larval traits. Guinot (1977) proposed a new classification scheme for brachyuran decapods based on place- ment of female and male genital openings. She divided the brachyurans into three sections as fol- lows: 1) Podotremata — female and male openings coxal, a primitive condition (i.e., Homoloidea); 2) Heterotremata — female openings sternal, male openings either sternal or coxal, an intermediate condition (i.e., Xanthoidea); 3) Thoracotremata — female and male openings sternal, an advanced condition (i.e., Gecarcinoidea). Guinot'* listed the family Menippidae under the superfamily Xanthoidea, based on adult characters emphasiz- ing genital opening placement. Thus she provided additional evidence, based on adult gonopore/ gonopod characters, for the reestablishment of the 'Guinot. D. 1977. Project d'une nouvelic classification des Brachyoures Unpubl. Uihies. Museum National d'Histoire Naturellc. Labortoire de Zoologie lArthropodes). Paris. Fr. FISHERY BULLETIN: VOL, 77. No 2 family Menippidae. Investigations of the larval development of other species of Menippe could provide further support warranting reestablish- ment of the family. NOTE ADDED IN PROOF After this paper was sent to the printer, a publication — Larval development of Epixanthiis dentatus (White) (Brachyura, Xanthidae) by M. Saba, M. Takeda, and Y. Nakasone published 1978 in Bulletin of the National Science Museum (Tokyo), Series A (Zoology) 4(3):151-161— was re- ceived indicating that three genera of xanthids developed through less than four zoeal stages. Epixanthus dentatus and HcteroziiiK rotundifrons attain two larval stages, while PUuninus lum- pinus attains only one larval stage. These three species live in specialized and restricted habi- tats. ACKNOWLEDGMENTS I wish to express my appreciation to the Smith- sonian Institution for granting a summer intern- ship and use of the facilities at the Fort Pierce Bureau. I also thank the members of my thesis committee: Robert H. Gore, Smithsonian Institu- tion, Fort Pierce Bureau; and Frank M. Trucs- dale, William H. Herke, Clyde H. Moore, Louisiana State University, for their assistance. I express my gratitude to Anthony J. Provenzano, Jr. and Paul A. Sandifer who also critically re- viewed the manuscript. I also wish to thank Joan Dupont, Applied Biology. Inc., Atlanta, Ga., for pointing out morphological differences between M. nudifr-ons and M. mercenuricr, and Suzanne Bass, Karen Rodman, and Kim Wilson who pro- vided moral support and aid in the laboratory. LITERATURE CITED AIK,\\V.\, H. 1929. On larval forms of some Brachyura, Rec Oceanogr, Works Jpn. 2:17-55. 1937. Furttier notes on brachyuran larvae, Rec, Oceanogr, Works Jpn, 9:87-162, BOOKHOl'T. C. 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E., and J. D. CO.STLOW, jR. 1975. The effects of salinity and cyclic temperature on larval development of the mud-crab Rhttkropanopeus karnsu (Brachyura:Xanthidae) reared m the laboratory. Mar. Biol. (Berl.l 32:215-221. Co.STI,OW, J. D., AND C. G. BOOKHOLT. 1959. The larval development of Callinectes sapidus Rathbun reared in the laboratory, Biol. Bull. (Woods Hole) 116:373-396. 1960. A method for developing brachyuran eggs in vitro. Limnol. Oceanogr. 5:212-215 1961a. The larval development of £'urvpanopcusc/cprcssi/.s' (Smith) under laboratory conditions. Crustaceana 2:6- 15. 1961b. The larval stages of Panopeus herhstii Milne- Edwards reared in the laboratory. J. Elisha Mitchell Sci. Soc. 77:33-42. 1962. The effect of environmental factors on larval de- velopment of crabs. In C. M. Tarzwell (Chairman), Biological problems m water pollution. Third Seminar, p. 77-86. U.S. Publ. Health Serv., Cine, Ohio. 1966. Larval development of the crab, Hexapanopmis angustifrons. 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MONOD, TH 1956. Hippideaet Brachyura ouest-africains. Mem. Inst. Fr. Afr. Noire 45, 674 p. Ong, K.-S., and J. D. Costlow, Jr. 1970. The effect of salinity and temperature on the larval development of the stone crab, Mentppc rnenenana (Say), reared in the laboratory. Chesapeake Sci. 11:16-29. Ortmann, a. 1894. Die Decapoden-Krebse des Strassburger Museums. VII. Theil. Abtheilung:Brachyura (Brachyura genuina Boas) II. Unterabtheilung; Cancroidea, 2. Section: Can- crinea, 1. GruppeCyclomctopa. Zool. Jahrb. Abt. Syst. DeKol. Geogr. Tiere 7:411-495. Porter, H. J. I960. Zoeal stages of the stone crab, Menippe mi'nenarw Say. Chesapeake Sci. 1:168-177. PR.-\SAD, H. J., AND P. R. TAMPI. 1957. Notes on some decapod larvae. J. Zool. Soc. India 9(l):23-39. 385 FISHERY BULLETIN VOL 77. NO, 2 PROVEN'/.ANO, A. J., Jr. 1967. Recent advances in the laboratory culture of decaptxi larvae. In Symposium on Crustacea, p. 940-94.5. Mar. Biol. Assoc. India, Symp. Ser. 2. RATHBUX. M. J. 1930. The cancroid crabs of America of the Families Euryalidae. Portunidae, Atelecyclidae, Cancridae and Xanthidae. U.S. Natl. Mus. Bull. 152. 609 p. Sasdifer, p. a. 1973. Effects of temperature and salinity on larval de- velopment of grass shrimp, Palaemonetes vulganx (De- capoda, Caridea). Fish. Bull., U.S.71:115-123. 1974. Larval stages of the crab, Pilumnus dasypmliis Kingsley (Crustacea, Brachyura, Xanthidae), obtained in the laboratory. Bull. Mar. Sci. 24:378-391 Sastrv, a. N. 1977a. The larval development of the rock crab, Canivr irroralus Say, 1817, under laboratory condition.? iDe- capoda Brachyural. Crustaceana 32:1.55-168. 1977b. The larval development of the Jonah crab. Cancer boreatis Stimpson, 1859, under laboratory conditions (De- capoda Brachyura). Crustaceana 32:290-303. Say, T. 1818. Appendix to the account of the Crustacea of the United States. J. Acad. Nat. Sci. Phila. 1:445-458. STIMPSO.N. W. 1859. Notes on North American Crustacea. No. 1. Ann Lyceum Nat. Hist. N.Y. 7(1862) (21:49-93. 1871. Notes on North American Crustacea in the Museum of the Smithsonian Institution. No. Ill Ann. Lyceum Nat. Hist. N.Y. 10:92-1.36. VILEI.A, H 1951. Crustaceos decapodes e estomatopcxles da Guine Portuguesa. An Junta Invest. Colon. Lisboa 4i 19491:47-70. WEAR, R G. 1970. Notes and bibliography on the larvae of xanthid crabs. Pac. Sci. 24:84-89. 386 ASSESSMENT OF COMPOSITION OF STOCK MIXTURES Jerome J. Pklla' and Timothy L. Robertson^ ABSTRACT Stocks offish can occur in mixtures, and knowledge of the composition of such a mixture may be needed. An estimate of the proportion of the mixture arising from each stock potentially present as well as a measure of the precision of this estimate may suffice. To develop these estimators, we posit that the d istnbutions of characters of individuals differ among the stocks and that rules have been developed by others with which some success in stock identification of individuals can be had. We require test samples of individuals from each stock included in the mixture with which to evaluate the rules; these samples must be other than the learning samples used to develop the rules. The rules are also appi led to a sample from the mixture. Using the numbers of individuals in each test sample and sample of the mixture which are assigned to each stock, we can e.stimate the composition of the mixture and the precision of this estimation. Approximations based on large samples underlie the estimation. Numerical studies provide some idea of the sample sizes required for the approximations to be satisfactory as well as of the behavior of the estimators as related to performance of rules and sample sizes. We note that the roles of the learning and test samples from the segregated stocks may be inter- changed, allowing a repetition of the procedure. Stocks offish frequently occur in mixtures. When these stocks are of the same species at the same life stage, the stock identity of an individual may be difficult or impossible to ascertain. Yet if the dis- tributions of characters of individuals differ among stocks, some success may be had in iden- tification of individuals in a mixture by use of discrmimant analysis (e.g.. Hill 1959; Fukuhara etal. 1962; Anas and Murai 1969; Parsons 1972; Cook and Lord 1978) or more simply by a verbal key iKonovalov 1975). In most important applica- tions the correct identification of individuals is not of direct value. Rather the accurate determination of the proportions of the mixture belonging to each stock is desired. Critical to accurate assessment of composition of a mixture are the rules of assignme,nt of indi- viduals to stocks. The rules applied to a vector of measurements on an individual assign the indi- vidual to one stock of those possible. Among rules, those with lowest error rates of assignments pro- vide the most accurate assessments, of course. If individuals of known stocks, either those used in 'Northwest and Alaska Fisheries Center Auke Bay Laborato- ry, National Marine Fishenes Service, NOAA. P.O. Box 155, Auke Bay, AK 99821. -Division of Fisheries, University of Alaska, Juneau, Box 1 447 , Juneau . AK 99802; present address: Alaska Department of Fish and Game, Division of Commercial Fisheries, 333 Raspberry Road, Anchorage, AK 99502. developing the rules or new individuals, are as- signed to stocks using the rules, a measm-e of error rates is provided. Although some sense of the ac- curacy of the rules is obtained, this does not pro- vide a satisfactory evaluation of possible errors in estimates of stock proportions from new mixtures. Worlund and Fredin ( 1962) began to attack this problem. They developed an estimation procedure for stock proportions in a mixture of an arbitrary number of stocks. Further, under restrictive as- sumptions concerning knowledge of the accuracy of assignments, Worlund and Fredin developed an approximate variance expression for the esti- mates of stock proportions in the mixture when only two stocks composed the mixture. We extend their approach now, developing methodology to estimate stock proportions in mixtures of an arbi- trary number of stocks as well as the variances of such estimates under less restrictive conditions. BACKGROUND SITUATION AND SAMPLING THEORY We assume A' stocks are known to potentially occur in the mixture. Random samples of indi- viduals are taken from each stock at a time when the stocks are completely segregated; these may be taken before or after the mixing. A random sample of individuals from the mixture is also taken. Manu.'^cnpl acci-pttKl November 1978. FISHERY BULLETIN: VOL. 77, NO. 2, 1979. 387 FISHERY BULLETIN VOL. 77. NO, 2 The sample from a stock at time of segregation is partitioned into two subsamples, called the learn- ing and test samples after Cook and Lord ( 1978). Learning samples from the K stocks are used to develop rules of assignment; the assumptions and methods used are arbitrary for our purpose. The realism of the assumptions forming the basis of the rules is not critical; performance of the rules and some knowledge of this performance is impor- tant. Performance of the rules is determined by their application to the test samples. The rules are also applied to the sample of the mixture. Using the numbers assigned to each of the stocks by application of rules to the test samples from the segregated stocks and the sample from the mix- ture, we can estimate the composition of the mix- ture and the precision of this estimation. A caveat concerning situations in which the methodology is not appropriate is needed before we begin. What follows presumes the individuals of a stock in both the test sample and mixture sample are drawn from a common distribution of characters used in the rules. When the condition is violated, performance of the rules would differ im- permissibly between test samples and that of the mixture. We must avoid characters on which a selection process occurs between the mixture and the separate stocks. Test Sample Theory and Analysis Once particular rules have been established from the learning samples (e.g., using discrimi- nant analysis), individuals forming each stock in effect have been partitioned into K mutually ex- clusive gi'oups corresponding to those assigned by the rules to one of each of the K stocks. We define 4>i;i to be the proportion of the individuals compris- ing the ^th stock which is assigned by the rules to the jth stock. Also we let ?t, be the number of individuals in the test sample from stock k as- signed by the rules to stockj, and let T\ = (^^j, t/,.,. . . . , t/^). Assuming the number of individuals in the test and learning samples is small as compared with the number of individuals composing the stock, the probability of the occurrence of vector T'j.is, to a good approximation, given by the mul- tinomial probability function, i.e.,'' ^The dot notation implies summation over the subscript. Thus ^' ( is the size of the test sample from the ^th stock. Pin) '/; 1 'fc 2 ■ • • '),■ K 0fc 1 <^h2 kK (1) Because the probabilities 4>i. are usually un- known, we estimate them from 7"^ by the well- known maximum likelihood estimator 'I'fe = {thiltkJk2ltu /;ck/';.-) (2) . corresponding to the parameter vector 't)'^, = (4>i,i, t/)^.,, . . . , <^,,l- 'fcj, is unbiased and has the variance-covariance matrix ~'K = <>hi('^-<>i!i) 0M0;,-; ')..■ t„- <>k2<>kl 0/;2(l-0fe2) ll.-- <>)n<>kK k 2^k K <>k KC^-'h k) (3) Test samples from different stocks are statistically I independent and covariance between elements of <1j^ and *^ are zero for /; ^ k' . Mixed Sample Theory and Anahsis The mixture of stocks at the time of sampling is comprised of possibly as many as K stocks. Ignor- ing for the moment the actual stock composition of the mixture, our rules established from the learn- ingsamples partition the mixture into A' mutually exclusive groups again corresponding to the K stocks to which individuals are assigned. We define A , to be the proportion of the individuals composing the entire mixture which would be as- signed to the,/th stock by the rules. Also we let w, be the actual number offish in the sample from the mixture which are assigned to stocky. If the size of the sample from the mixture is small compared with the number of fish composing the mixture, the probability of observing the vector ,Vf' = i/?; ,, ;?! ^ m^\ is given by the multinomial probability function, i.e.. 388 PELLA and ROBERTSON ASSESSMENT OF STOCK MIXTURES P(M) = AK Al A2 (4) We can estimate the probabilities \, from M by the maximum likelihood estimator A' = (mi/m , m2lm , .... m^^lm} (5) corresponding to the parameter vector A ' = ( \j , Xj- . . . , A^-). A is unbiased and has the variance- covariance matrix -A = Ai(l-Ai) m m A2A1 A2(l-As m (6) X 1 A 2 A 1 A K- m I A2AK m ■ ■ ■ m Ak(I-Ak) m A is a natural estimator of stock composition of the mixture. Unfortunately as we see next, its expected value, A, depends not only on stock composition, but also on the behavior of the rules. Basic Relation Between Parameters of Test Samples and Those of the Sample from the Mixture We know the mixture consists of individuals from at most K stocks. Let H,, be the proportion of the individuals composing the entire mixture which are of the ktVi stock, where 0 /,' and H. s 1 for all K 1 . The parameter vector 9' = {H^.ft., W^i is un- known: its estimation is our objective. If the indi- viduals of each of the stocks occurring in the mix- ture are a random sample from the character distribution of that stock, then the probability that a randomly sampled individual from the mix- ture is assigned to thejth stock, A ,, is related to previously defined probabilities by the equation system l! = l J = 1,2, K. (7) The term, Wj.^,, represents the probability a ran- domly sampled individual from the mixture is of stock k and assigned to stocky; summing over the K stocks gives the total probability the individual is assigned to stocky. This basic set of relation- ships can be expressed in matrix notation, A = *e (8) where '1> ( I'l < I' 2 = < I'K_ 011 012 . ■ .011 <>K 1 0K 2 ■ • • <>K K ESTIMATION OF STOCK COMPOSITION OF MIXTURE If lj 7^ 0, we can solve Equation (8) for 0, e = (') ' A. (9) When the rules assign individuals from the stocks without error, = 7, and H = A. Then the natural estimator .\ is appropriate. But the rules will usu- ally be imperfect, yet Equation (9) shows we can still solve for H without error provided <1> and A are known. Unfortunately neither (t' nor A is known in usual circumstances; however, we saw how to es- timate them from the test and mixed samples using Equations (2) and (5). When \ and in Equation ( 8 ) are replaced by estimates from Equa- tions (2) and (5), the problem of estimating B is a special case of estimation of the solution of a sys- tem of linear equations with random coefficients. Fuller'' has provided several solutions for the gen- eral problem; these are applicable in the present case for large test and mixed samples. Later we indicate how large these samples must be. ■"Fuller, W. A. 1970. Mimeographed class notes. Statistics 638, winter 1969-70. Iowa State Univ, Stat. Lab.. 56 p.. on file at the library of Northwest and Alaska Fisheries Center Auke Bav Laboratory. National Marine Fisheries Service, NOAA, P.O. Box 1,5.5. Auke Bav. AK 99821. 389 Fuller l =0 must be impossible. The asymptotic variance-covariance matrix of 6, S ,•, , is given by v,^ =(*')-' a, + Siotl'' 0,2^n(l-<^n) 111) FISHERY BULLETIN: VOL 77, NO 2 and i^ is defined by Equation (6l We remark that variation in estimates of O arises additively from two sources: 1) sampling variation in estimation of the assignment compo- sition of the mixture which is represented by S \; and 2) sampling variation in estimation of the probability of assignment matrix 4^ which is rep- resented by i,,,,|- The diagonal elements of the 1,, are the variances of the elements of (i; the square roots of these are the standard errors. where -,i S,~4>i24>ii Oi'^4>iK4>n 0, <>i\0,2 fli20,2(l-0,2) Oi'^,K<>i2 0,2 0,,. (1-0,^,) I ' ;■ Bias in estimation of (* is approximately given by B ^( /.•?I 'l- /.•^2 '1- h^zK '1- 12, ^''■'01101/,. 0'^02l(l-021 0'''^02102/.- I;. fc^l 22, 0''''0120W,- 0^^022(1-022) 0''"^02202/.- /.■^2 0 '01K01;. 0''''02k(1-02k) 0''^02K02/,- /■,, /oq£K '2- '■• K . 0"\'>Ki(l-0Ki) 0"''0ki0k;,- h 0^'^'0K2(1-0K2) 0^'^0KK(l-0K-h-) ;,-^i /.•:^2 0, 0 '■"''' 0K 2 0K/,- 0''''''0K-K0Kfc kz^K 390 PELLA and ROBERTSON: ASSESSMENT OF STOCK MIXTURES and 'r'(J] ($')' A. (14) it. When only two stocks occur in the mixture, this set of simultaneous intervals reduces to the famil- iar univariate normal approximation for setting confidence intervals: ^2 -2 a 12(022^)'^' <02<02 +^0/2(022 2vV! (16) Here G is obtained by substituting the estimates for the unknown parameters of G. To the order of approximation provided by Fuller, these estimators have the same variance-covariance matrix as O. An internal estimate of this variance-covariance matrix ^(, can be obtained by substitution of observed values for parameters in Equation (11). We can substitute in Equation (11) for elements of O the corresponding elements of either 0, O, or (i To distinguish between these possibilities, we label the internal estimators of X,-, as 1|-|, i|i, or i|,, respectively. With the internal estimate of i|,, we can estimate not only H but also how precisely the estimation is accomplished. To establish confidence intervals on the ele- ments of B, we assume test and mixed samples are sufficiently large so that the estimators B, B, or O are each approximately distributed as the mul- tivariate normal with mean B and known variance-covariance matrix i,„ i,). or S,,, respec- tively. Then a 100(1 - aW set of confidence inter- vals such that all the unknown elements of B are simultaneously covered by their respective inter- vals with a probability 1 - « is for the estimator B (say) as follows (see Morrison 1967, section 4.4): where^ ,„ is the standardized normal deviate such that 100(a/2)'7f of the distribution lies below -2,^,2 and 100(a/2)"7r lies above Zui-z. These expressions are in terms of the estimator B; they apply as well to the other estimators when elements of B or B replace those of B within them. Worlund and Fredin (1962) developed the es- timator B in Equation (10). To translate their no- tation to ours, let 0,7 = Pij (17) ft, and permit the subscripts to take on letter values a,h,c, . . . .In the special case when the mixture is comprised of only two stocks, they developed an asymptotic expression for the variance of H, (the variance of H2 necessarily equals that of H, since H2 = 1 - f^i ). In deriving the variance expression, they assumed >!> is known without error so that i,i,i, is a null matrix: such is approximately true as t and I., become large. h-(Ollh.:K-l^f'<01 <»! +(Oii\„;K-i')'' 2 - (022^,, ;K-1 ^Y" <- 6 2 < d 2 + (a22^X „ ;K-1 ^) Sk -{0,k\.:K-ir' <0, ■( 1 XjXs m 1 -1 -1 1 '^"011012 ^2 021022 (24) 1 -1 -1 1 (25) G, 1^, and !„■,.„ are obtained by substituting estimates for the corresponding parameters. Then ('I' )' >i A, 0" o'' _0 " <;>" 011022 -012021 O = ( )~iA m2lm U^ ('1' )-' {^\ ■())• (26) (19) (20) (21) provides internal estimates of the variance of W, or H., as well as their covariance. Expressions for 6 and B follow directly from specialization of Equations (13) and (14) to two stocks; substitution of their elements into Equa- tion (26) in place of those of B provides i;-, and Sj-^, respectively. Numerical Computations for Three Stocks To illustrate the computations for a three-stock situation, we use the information reported by Cook and Lord ( 1 978) regarding stock composition of high-seas mixtures of sockeye salmon, On- vorhynchus nerka. Their purpose was to estimate proportions of the mixture arising from each of three river systems — Egegik, Kvichak, and Nak- nek — of the Bristol Bay region of Alaska. Actu- 392 PELLA and ROBERTSON: ASSESSMENT OF STOCK MIXTURES ally the application of our methods is inappropri- ate because Cook and Lord used individuals of test samples from the segregated stocks both to modify an original set of rules from the learning samples as well as to estimate 4>. Because our purpose is only to illustrate the computations, we will treat their observations as though the test samples had been used exclusively to estimate "t". Using the test samples in developing the rules, as Cook and Lord did, should produce greater precision in estima- tion of composition of a mixture: the disadvantage at present is the inability to assess the precision of these enhanced estimates. In developing the variance-covariance matrix i,:,, we assumed 't> and A are statistically independent. Such is un- true if the test samples are used as by Cook and Lord both to develop the rules used to estimate .\ as well as to estimate ^. Test samples from the segregated stocks of the three rivers were assigned by the rules to these stocks iTable li. Then the rules were applied to 101 fish caught on the high seas. Of these, 25 were assigned to Egegik, 22 to Kvichak, and 54 to Nak- nek. We identify Egegik, Kvichak, and Naknek as the first, second, and third streams in our sub- script use. Computations using these data produce the following results: cU G = H 1.30019 -0.07801 -0.22218 0.03641 1.49782 -0.53422 -0.35885 -0.47847 1.83732 " 0.00480 -0.00086 -0.00424' -0.00154 0.00737 -0.00666 _-0.00326 -0.00651 0.01090_ 0.138 '0.145" '0.145' 0.051 e = 0.062 B = 0.062 0.811 0.793 0.793 (Our B is f7 of Cook and Lord (1978): their errors in evaluating /?^^ are responsible for the discrepancy with our estimate B.) 0.00184 0.00197 0.00975 -0.00053 0.00169 -0.00050 0.00230 0.00208 0.014.54 -0.00131 -0.00115 0.00246 -0.00146" -0.00180 0.00326 -0.01184' -0.01662 0.02846 = 0.80000 0.04000 0.16667 0.08000 0.74000 0.20833 0.12000 0.22000 0.62500 (Our have misgivings of probable occurrence of additional unaccounted stocks in the high-seas mixture. BEHAVIOR OF ESTIMATORS AND ASYMPTOTIC FORMULAS Of interest to investigators beginning studies of stock composition of mixtures is the behavior of our estimators as test and mixed sample sizes vary for fixed rules and the influence of rules on the estimators. Further, we remarked that our solu- tion of the stock mixture problem assumes large test and mixed samples. Of concern is how large specifically the samples must be for the asymptotic expressions to be reasonably accurate. This examination will be restricted to the two-stock case which is genera! for our purpose in that any number of stocks can be partitioned into two groups; that is. we can evaluate the estimators for a particular stock when the remaining stocks are lumped into a second group after assignment by the rules to the individual stocks. Bias and var- iance for the particular stock would be unchanged then even if the stocks of the second group were treated severally. We evaluate estimation behavior and asympto- tic approximation for three choices of "t" represent- ing rules of increasing accuracy: Case 1. 0) = 0.75 0.25 _0.25 0.75 Case 2. * = "0.75 0.25" _0.10 0.90 Case 3. = ~0.9() o.io" 0.10 0.90 We let ()' = i0.6, 0.4) for all three cases. Based on experience in identification of sockeye salmon in Bristol Bay. Alaska, using discriminant functions on scale features, the ranges of elements of 4> are realistic. The choice of O is arbitrary, of course. Given , O, and sample sizes ?, , /., , and m . we can enumerate all possible sample points — Z^. /j._,, /^,, t.22, "i,, and in.^ — as well as compute their probabilities of occurrence. In om- evaluations, we always used equal test sample sizes. For each sample point, we can compute B, 6, (). ii,, 1,-,, and i,i. With these calculations for each pomt we can compute the mean and variance of each estimator by weighting its value at a sample point by the probability of that point. Estimation of 6 by 6, 0, or O requires the prob- ability that I 4) ] = 0 be zero; this condition is not met. If we supplement the procedure by assigning arbitrary values to the estimators when j 'l> j = 0, means and variances of such modified estimators will approach the values we obtained by omission of such sample points. The probability that | 1 = 0 rapidly decreases with increasing test sample sizes. For case 1 with test samples of 20, it is <5 x lO"*, and with test samples of 40, about 5 x lO''. The probability also decreases with improved identification of stocks. For case 3 with test sam- ples of 20, the probability is <4 X 10''. Weighting the arbitrary values of the estimators correspond- ing to such points by their probabilities makes their contributions to expectation computations negligible. We found these numerical studies to be expen- sive, especially with large sample sizes. Therefore, we began omitting sample points whose probabil- ity was small even if | « and fc«,l. Absolute value of bias of ^, is less than that of either f), or (\. Generally, abso- lute value of bias of 6^ is also less than that of H, ; the sole exception is case 1 with test samples of only 20. Bias of W, or H^ decreases with improved rules as we go from case 1 to case 2 to ca.se 3, holding test and mixed sample sizes fixed. Biases computed for f> decreased between case 1 and case 3 for which the 4>-matrices are both symmetric; however, for 394 PELLA and ROBERTSON: ASSESSMENT OF STOCK MIXTURES Table 2. — Biases, ibt, , Hh . and 6^ *• of estimators and asymptotic bias. 61, from Equation ( 12t for indicated 4>-matrices, indicated test and mixed sample sizes, and B' = (0.6,0.4). Tesl sample sizes Mixed sample size [0.75 0 25 0 25 0 75 '20 230 240 '20 •30 •'40 •40 -001077 • 01076 • 01076 • 00637 • 00637 - 00636 ■ 00438 -0.00363 - 00362 - 00364 - 00123 - 00124 - 00124 00063 -0 01873 - 01873 ' 01873 - 00381 - 00381 • 00382 - 00108 • 0 00750 - 00750 - 00750 - 00500 - 00500 - 00500 • 00375 [■ Case 2 -, 0 75 0 25 0 10 0 90 20 30 40 '20 '30 '40 01053 - 00090 00660 - 00037 00481 - 00022 - 00186 - 00905 - 00060 - 00604 - 00033 - 00453 Case 3 20 '20 • 00155 - 00014 00018 . 00141 0 90 0 10 30 '30 ■ 00099 - 00007 00008 - 00094 _0 10 0 90_ 'Evaluated at all sample points except when 'l" 1 - 0 'Evaluated only at sample points for whicti probability ot observing this outcomes of the test samples ■10-6 and I*! * 0 two of three combinations of test and mixed sam- ple sizes, repeated under case 1 and case 2, bias increased between case 1 and case 2, the latter not having a symmetric ft>-matrix. The predicted bias of 0^ from the asymptotic formula [Equation (12)] agrees with actual bias of H reasonably well. The approximation obviously becomes more accurate as size of test samples in- creases or as rules improve. Biases would appear negligible in comparison with magnitude of variances of the estimators next considered. Absolute value of bias in the situ- ations evaluated represents at most 3.1'V of the parameter value. ^, = 0.6. Random errors in esti- mation are the main concern. Variances of the estimators (H. H, and ih de- crease as test samples become larger, agreeing in behavior with biases; in contrast to biases, var- iances also decrease as size of mixed samples in- creases. We computed variances under case 1 for the same test and mixed sample sizes described for bias evaluation (Table 3, lines 1 to 6). Although variance of any of the estimators (^1, W, , and H, ) decreases with size of test or mixed samples, the rate decreases with size of either type when that of the other is fixed. For example, at test samples of T.ABLE 3. — Variances ( th,'. -matrix. As rules of assignment improve and the -matrix approaches the identity matrix, precision of estimation at fixed test and mixed sample sizes increases. In our evaluations, variance of ^j is always less than that of f)^. In this respect tt^ also enjoys con- siderable advantage over fi, when rules are poor, case 1 , and sample sizes are small. As test or mixed samples increase, the advantage diminishes until fi^ has the smaller variance. However, differences among variances of the three estimators (W, , ()^, and W, ) become negligible either as rules improve or samples sizes become large. Predicted variance of the estimators of 0^ from the asymptotic formula (Equation (11)] describes variance of ^, remarkably well, even when rules are poor and sample sizes are small (Table 3, com- pare lines 1 to 7 of column cr, ,^ with column „ - ( i.e., of the element in the first row and first column of 1,,) for the cases of and sample sizes used in the previous evaluations of bias and variance (Table 4). The mean of this in- ternal variance estimator, £'((j^l, of internal variance estimator. & n^; and percent bias for indicated ■{'-matrices; for indicated test and mixed sample sizes; and O' = (0.6,0.4). * Tesi sample sizes Mixed sample size ""' E(*„') Per- cent bias Case 1 0 75 0 25 20 '20 '30 '40 0 11232 08685 07417 0 24894 19693 17096 122 127 130 0 25 0 75 30 '20 '30 '40 07957 05904 04877 10171 07707 06450 28 31 32 40 '40 04051 04289 59 Case 2 20 '20 04640 04894 55 0 75 0 25 0 10 0 90_ 30 40 '30 '40 02892 02111 02931 02125 1 3 0 7 Cases 20 •20 02425 02394 -13 0 90 0 10 30 '30 01579 01562 -1 1 0 10 0 90. 'Evaluated at all sample points except when | | = 0 'Evaluated only at sample points tor wtiicti probability ot observing ttie outcomes ot ttie test samples ■ 10'^ and | "t" I ^0 4, lines 1 to 7); conceivably omission of sample points in our evaluations underlies the slight in- crease with mixed sample size. Under any case of , the internal estimator or variance of W, becomes nearly unbiased at the largest sample sizes examined. Our last computations are of the mean and var- iance of the internal variance estimators (o-,,^^, (T„ ^, and (T „^) (i.e., of the elements in the first row and column of i^-|, i,-,,and Xy, respectively) for the three cases of with test and mixed samples all of size 20. Also we determined the actual probability that 9(y7i and 95*^^ simultaneous confidence inter- vals from Equation (16) using either (), i), or (), each with its internal variance estimator, S,-,, i,-,, or i||, cover the actual composition vector O' -= (0.6, 0.4) (Table 5i. Comparison of actual variances of the es- timators (6* ,, «,,and (*,) (Table 5, line 1) with the mean of the corresponding internal variance es- timators (Table 5, line 2) shows the positive bias of each internal estimator diminishes as rules im- prove. Only the internal estimator of variance of ^, becomes negatively biased. Percent bias (Table 5, line 3) of each estimator decreases sharply with improvement of rules. Variance of the internal variance estimators of «, and H^ are manyfold greater than that of ^, under case 1 and case 2. With improved rules of case 3, all internal variance estimators have com- parable variance. Probabilities that simultaneous confidence in- tervals for each estimator ((), O, and ()) cover the 396 PELLA and ROBERTSON: ASSESSMENT OF STOCK MIXTURES TABLE 5— Variances of the estimators (»,.#,, and »,). means of mtemal variance estimators, percent bias of interna] variance estimators, variances of internal variance estimators, anci probabilities of coverage of B' = (0.6, 0.41 by simultaneous 90 and 95-^ confidence intervals for three cases of 4> when test and mixed samples are all of size 20.' fo 75 0 25 0 75 0 25 0 90 0 lOl 025 075 0 10 0 90 0 10 0 9oJ Esttmator H^ "i H, H, H, H, H^ H^ «, Variance oi estimator 0 11221 0 06740 0 86543 0 04634 0 04009 0 04259 0 02425 002293 0 02290 Mean ot internal variance estimator 0.24824 0 12030 7 75453 0 04859 0 04683 0 07374 0 02394 0 02387 0 02386 Percent bias ot internal variance estimator 121 78 796 49 168 73 ■1 3 4 1 42 Variance ot internal variance estimator 25 2471 0 10567 125 688 0 11388 0 00175 439 969 9 521 X 10- 5 9 166 X 10-5 9 140 X 10-5 Probability ot coverage by 90°o confidence i ot H ntervals 0^33 0 949 0.950 0906 0917 0917 0 890 0 897 0 897 Probability of coverage by 95°o confidence i of H ntervals 0 976 0 981 0981 0 956 0960 0 960 0 947 0 950 0 950 'Evaluations only include sample points for wfiich probability ot observing the outcome of the test samples 10-' and | * | * 0 parameter vector G' = (0.6. 0.4) approach the in- tended levels of confidence as rules improve (Table 5. lines 5 and 6). For rules of case 1 or case 2. the level of confidence provided by any of the es- timators exceeds that intended; such is preferable to the converse because the intervals provide at least the level of confidence the investigator in- tends. Our normality assumption used to con- struct confidence intervals will be better satisfied as mixed and test sample sizes increase. Appar- ently the internal variance estimators become less biased as test sample size increases. Therefore, we anticipate the level of confidence of intervals from any of the estimators will more closely approach the intended level as test sample size increases even when rules are poor. Limited as these numerical studies are, they demonstrate that when sample sizes are small and rules are poor, 6 should be used to estimate com- position of a mixture. We found then that 6 is least biased, has smallest variance, and its internal var- iance estimator itself has smallest variance. With larger sample sizes or good rules of assignment, the estimators 6, B, and ("> appear more nearly equivalent. Decisions on sample sizes depend on desired precision and the rules characterized by . The closer O is to an identity matrix or, equivalently, the better the identification of stocks, the fewer required individuals in test and mixed samples to achieve desired precision of composition estima- tion. With an accurate initial estimate of from the learning samples, the corresponding asympto- tic variance-covariance matrix at Equation ill) can be used to estimate sample sizes needed to achieve required precision. We recall that var- iance of B^ is well described by the asymptotic variance-covariance matrix even when rules are poor and sample sizes are smal 1, providmg another reason for preferring H to () or () in that cir- cumstance. AFTERWORD Withholdmg individuals of samples from the separate stocks to form test samples must result in less effective rules than if the learning and test samples were pooled for rule formation. Although the practice is repaid in part by the ability to evaluate precision of composition assessment, the penalty at rule development can be further al- leviated. Roles of the two samples from each of the separate stocks can be interchanged; either can be the learning or test .sample. If each of the samples from the segregated stocks is partitioned into two approximately equal sized subsamples, two sets of rules can be formed; two estimates of "t obtained; two estimates of B computed by any of B. B, or G; and two internal estimates of the variance- covariance matrices (!„, I,-,, or S„) calculated. The pairs of estimates are statistically dependent. Nonetheless, means of pairs of estimates of B and i have the same expectation and presumably greater precision than the individual members of the pairs. Exact evaluation of that enhanced pre- cision for estimates of the composition vector 0 does not appear easy; however, use of the mean of internal estimates of the variance-covariance matrix in calculation of the confidence set Equa- tion! 15) provides an unknown but greater level of confidence than the indicated 100(1 - an value. LITERATURE CITED AN.\S, R. E., AND S. MURAl. 1969. Use of scale characters and a discriminant function 397 FISHERY BULLETIN VOL 77. NO for classifying sockeye salmon lOncorhynchus nerkci) by continent of origin. Int. North Pac. Fish. Comm., Bull 26:157-192. Cook, R. C and G. E. Lord. 1978. Identification of stocks of Bristol Bay sockeye salm- on. Oricorhynchus nerha . by evaluating scale patterns with a polynomial discriminant method. Fish. Bull.. U.S. 76:415-423. FUKUHAR.-\, F. M., S. MLRAI, J. J. LaLANNE. AND A Sribhibhadh. 1962. Continental origin of red salmon as determined from morphological characters. Int. North Pac. Fish, Comm., Bull. 8:15-109. Hill, D. R. 1 959. Some uses of statistical analysis in classifying races of American shad iAliisa sapidissima I. U.S. Fish Wildl. Serv., Fish. Bull. 59:268-286. KONOVALOV. S. M 1975. Differentiation of local populations of sockeye salm- on Oncorhynchus nerka (Walbaum). (Translated from Russ. by Leda V. Sagen.i Univ. Wash. Publ. Fish., New Ser . 6, 290 p. MORRISON, D. F. 1967. Multivariate statistical methods. McGraw-Hill. N.Y,, .338 p. PAR.SON.S. L. S. 1972. Use of meristic characters and a discriminant func tion for classifying spring- and autumn-spawning Atlan- tic herring. Int. Comm. Northwest Atl. Fish. Res. Bull 9:5-9. WOKLLNI), D. D.. AND R. A. FKEDIN, 1962. Differentiation of stocks. In N. J. Wilimovsky leditorl. Symposium on pink salmon, p. 143-153. H.R. Mac.Millan Lectures in Fish , Univ. B.C.. Vancouver. Can. 398 BEHAVIOR AND ECOLOGY OF THE BOTTLENOSE DOLPHIN, TURSIOPS IRUNCATUS, IN THE SOUTH ATLANTIC Bernd Wursig and Melany Wursig' ABSTRACT Bottlenose dolphins observed nearshore in Golfo San Jose, Argentina, spent 92% of their time in water less than 10 m deep. They moved into deeper water, up to 39 m depth, mainly during midday in nonsummer for brief ( 16 mm ) penods. They moved more rapidly m deeper water, and may have been feeding on schoolmg fish at that time. During summer they stayed in shallow water, 2-6 m deep. Dolphins moved parallel to shore and in consistent depth of water at almost all times. They changed direction at predictable locations and patrolled certam nearshore waters for up to several hours. Their movement was mfluenced by tide and by nearshore rocks. Slow movement and apparent restmg occurred mainly during the morning, while most aenal behavior, apparent sexual and social behavior, and rapid-movement feeding occurred in the afternoon. The Atlantic bottlenose dolphin, Tursiops triin- catus , is undoubtedly the best studied of any of the toothed cetaceans. It was successfully kept in cap- tivity over 60 yr ago (Townsend 1914). and has since that time served as the "white rat" of cetol- ogy, with a great deal known about its behavior in captivity, but until relatively recently practically nothing known about its behavior in the wild. Long-term behavioral studies of stable bottlenose dolphin colonies in captivity were mainly carried out at Marine Studios/Marineland of Florida from the mid-1930's to mid-1950's (McBride 1940; McBride and Hebb 1948; McBride and Kritzler 1951; Essapian 1953, 1963; Tavolga and Essapian 1957; Tavolga 1966). These studies showed that bottlenose dolphins have a complex social organi- zation, often with a male-dominated social hierar- chy. From some of these studies also developed the idea that bottlenose dolphins, and other odonto- cete species as well, use echolocation (McBride 1956). This concept was validated by numerous workers in the 1950's and 1960's (Schevill and Lawrence 1956; Kellogg 1961; Norris et al. 1961). Other research on captive bottlenose dolphins in general (including the species T. gilli and T. adtincus, as well as T. truncatus) was reported by Brown and Norris ( 1956), Caldwell et al. ( 1965), D. K. Caldwell and M. C. Caldwell (1972). M. C. Caldwell and D. K. Caldwell (1972), Tayler and Saayman (1972), and Saayman et al. (1973). The 'State University of New York al Stony Brook. Program for Neurobiology and Behavior; present address: Center for Coastal Marine Studies. University of California, Santa Cruz, CA 95064. first reports of behavior in the wild consisted mainly of anecdotal information gathered oppor- tunistically while capturing dolphins or pursuing other activities (Gunter 1942; Brown and Norris 1956; Norris and Prescott 1961; Brown et al. 1966). This led to more detailed field studies, most of which have been made within the past 10 yr, and all of which relied heavily on shore-based or small-boat operations close to shore (Saayman et al. 1972; Tayler and Saayman 1972; Irvine and Wells 1972; Saayman et al. 1973; Saayman and Tayler 1973; Shane 1977; Wursig and Wursig 1977; Castello and Pinedo 1977; Wursig 1978; Wells et al. in press; Irvine et al.^). At the same time, and also close to shore, behavioral investiga- tions of other odontocete genera have been carried out. Thus, Norris and DohF studied the Hawaiian spinner dolphin, Stenella longirostris, Saayman and Tayler (in press) described Indian Ocean humpback dolphin, Sousa sp., behavior and social organization, and Wursig and Wiirsig^ performed similar work on the South Atlantic dusky dolphin, Lagenorhynch us obscurus. iUanuscnpt accepted December 197H, FISHERY BULLETIN VOL 77. NO 2. 1979. ^Irvine, A. B., M. D. Scott. R. S. Wells, J, H, Kaufmann.and W. E. Evans. 1978. A study of the movements and activities of the Atlantic bottlenosed dolphin, Tur^iiops truncatus. including an evaluation of tagging techniques. Final report for U.S. Marine Mammal Commission Contracts MM4AC004 and MM.5AC0018. .53 p. 'Norris. K. S., and T. P. Dohl. The behavior of the Hawaiian spinner porpoise, Stenella longirostris (Schlegel, 1841). Unpubl. manuscr .. 66 p. Center for Coastal Marine Studies. University of California. Santa Cruz. ■* Wursig, B. G. , and M. A. Wursig. The behavior and ecology of the dusky dolphin, Lagenorhychus obscurus. Unpubl. man- user.. 64 p. Center for Coastal Marine Studies, University of California, Santa Cruz. 399 -^^'-^ FISHERY BULLETIN VOL, 77, NO, 2 Detailed work on the social organization of bottlenose dolphins was carried out by Irvine et al. (see footnote 2) and Wells et al. (in press). They captured many animals for tagging, and thus gained size and sex information. They found that a resident herd in the Sarasota-Bradenton area of West Florida consisted of groups whose individual membership was constantly changing by influx and efflux in a "kaleidoscopic manner." Such changes were not random, however, and several patterns of association were observed. Within a relatively stable herd occupying a well defined home range, each age and sex class frequented particular regions and interacted with other classes to varying degrees. Females of all ages and adult males ranged through the northern portion of the home range and interacted more with each other than with subadult males, which formed bachelor groups or groups with one or more adult females in the southern portion. Females with young moved throughout the home range and in- teracted with adult males to a lesser extent than did other females. A given group generally re- mained intact for only a matter of hours or days. At least superficially similar group instability was documented for Argentine bottlenose dol- phins by Wiirsig and Wiirsig (1977) and Wiirsig (1978), for Texas bottlenose dolphins by Shane (1977), for Hawaiian spinner dolphins by Norris and Dohl (see footnote 3), and for humpback dol- phins by Saayman and Tayler (in press). These studies present the first detailed accounts of some aspects of social organization of odontocete ceta- ceans, and make comparisons of these animals with terrestrial mammals such as bovids and pri- mates possible. The present analysis of South Atlantic bottle- nose dolphins represents an attempt to describe the general movement patterns, aerial and social behavior, and ecology of this population. We made no attempt to capture animals for sex and size information as we were loathe to disturb their "natural" movement and social behavior. Instead, we observed them mainly from cliffs lining the shore. Earlier, we reported on some aspects of sea- sonal occurrence patterns, group stability, surfac- ing associations, and calving seasonality of the same population discussed here (Wiirsig and Wiir- sig 1977; Wiirsig 1978). This paper presents addi- tional information, with the primary purpose of providing background data on the natural history of bottlenose dolphins, and hopefully also with future application to other species as further studies unfold. MATERIALS AND METHODS Bottlenose dolphins were observed at Golfo San Jose ( lat. 42°23' S., long. 64°03 ' W.) from July 1974 through March 1976. We made observations through binoculars and a 20-power transit monocular from two points, 14 m and 46 m high at mean low water ("Camp" and "Cliff Hut," respec- tively. Figures 1, 2). To describe the movements of dolphin sub- groups (averaging 15 animals) which were present near the observation point anywhere from several minutes to several hours, we plotted their posi- tions with the help of a Kern= model DKMl sur- veyor's theodolite. The theodolite had a 20-power monocular through which the animals were fol- lowed visually. A separate eyepiece showed hori- zontal degrees and vertical degrees which rep- resented the location of the dolphins, and which we read at 15 s to several-minute intervals into a cassette recorder. In the laboratory, data from the theodolite were plotted on a depth map (Figure 2), by a Hewlett-Packard Model 9830A desk cal- culator and plotter. Besides plotting the animals' positions, the computer program also supplied their distance from the observer, their heading in degrees relative to true north, and their speed. 'Reference to trade names does not imply endorsement by the National Marine Fisheries Service. NOAA. /?_^22122l5 FIC.URE 1.— Map of Golfo San Jose on Peninsula Valdes. Argen- tina, The bay is approximately 750 km^ with a 7 km wide mouth opening to the Atlantic, The lined area in the southeast portion . of the bay represents the study area. The crosshatched subsec- | tion is shown m detail in Figure 2. • 400 WURSIG and WURSIG. BEHAVIOR AND ECOLOGY OF Tl'RSIOPS TRrXCATUS n 1 LOS CONOS CAMP + TUR5IDP5 TRPEL FILE 13 10/24/75 0707. MI 075G.I5 97 ENTRIES 8000 9000 10000 IIOOO 12000 13000 Figure 2. — Depth contour map of one-fourth of the study area. Margin numbers represent meter distances relative to a zero location on land. Crosses foiTn 1 km squares. "Cliff Hut" and "Camp" are the locations from which most observations were made. Depth contours are in meters at mean low water (ML Wi. The usual distance for good observation of a moving dolphm group was at least 3 km. At a normal tide height of 5 m above MLW. water depth of 40 m was 1 km from Cliff Hut, and thus clearly visible. The solid Ime above Cliff Hut represents a sample track of a bottlenose dolphin group, and the printed information gives computer file location, date of track, time of day, and number of theodolite entries. About 200 such tracks were obtained of bottlenose dolphins during the 21-mo study. The map is from a larger area map which was by courtesy of Roger Payne, New York Zoological Society; Oliver Brazier. Woods Hole Oceanographic Institute; and Russ Charif Harvard Universitv. Since dolphins often did not travel in straight line, speed information from theodolite readings separated by several minutes was lower than the actual speed traveled. To minimize erroi's in speed calculations, only readings made within 30 s of each other were used. The accuracy of the transit (±30" of arc) allowed for placement of position within ±100 m at 5.5 km distance. RESULTS Preferred Depths To determine whether dolphins prefer a specific depth of water, and to map their movement pat- terns, theodolite readings were obtained whenever bottlenose dolphins came within sight- ing range of shore ( 1-10 km, depending on visibil- ity). Within that range, the depth of water varied from 1 to 65 m. Bottlenose dolphins occurred 92% of the time in water <10 m deep (2,655 of 2,883 theodolite readings), within 1 km of shore (Figure 3). None were ever sighted in water >39 m. Visi- bility at almost all times extended to at least 3 km from shore, where water depth was 45-50 m (see Figure 1), and we consistently tracked dusky dol- phins in much deeper water (Wiirsig and Wiirsig see footnote 4). Furthermore, we traversed the study area by boat in waters 1 to 10 km from shore on 109 occasions and never saw bottlenose dol- phins in water >39 m. For these reasons we be- lieve that the data for shallow nearshore travel are not biased by sighting error. In general, dol- phins moved in shallow water in the morning and 401 FISHERY BULLETIN VOL, 77, NO, 2 1800- 10 m deep, SD = 7.1, n = 230) and was interspersed with longer shallow-water travel. As a result, the increase in mean depth around noon of Figure 4a and b was not because animals consistently traveled in deeper water at those times. Instead, they more often moved for brief periods into deep water, and therefore the mean depths increase at those times. When the data were divided into months (Figure 4b, c), the nonsummer months of March, July, October, and November account for the movement into deeper water shown in Figure 3a. This trend was particu- larly strong for July (midwinter in Argentina), with a peak of 23 m depth at 1300 h. On the other hand, no increase in depth of water during midday took place in summer (December and January, Figure 4c). It would appear that there are predict- able seasonal and daily variations in depth of water in which the dolphins move. Speed of Movement The overall mean speed of the dolphins calcu- 402 lated from the 1.545 theodolite readings made within 30 s of each other was 6.1 km/h. Speed of travel was significantly correlated with depth of water; speed was 5.7 km/h in water <10 m deep, and 13.9 km/h in deeper water (Figure 5). But, was speed directly influenced by depth of water, or was it due to distance from shore, which in general increased with increasing depth? To solve this ambiguity, we took random samples of 10 readings each from 1) >600 m from shore and slO m depth, 2) <600 m from shore and 5^10 m depth, and 3) <600 m from shore and slO m depth, and compared their speeds (Table 1). If speed were influenced by distance from shore, we would ex- pect speeds of li and 2) to be different. Instead, speeds of 2) and 3) were significantly different (P<0.005, Wilcoxin two-.sample test, Sokal and Rohlf 1969), indicating that depth of water, not distance from shore, was probably the prime de- terminant of speed increase. Table l ,— Samples of bottlenose dolphin speeds i kilometers per hour! in three different water conditions, selected at random from the data. 600 m from shore 600 m from sfiore - 600 m from shore ^^10 m deptti 5=10 m depth •10m depth 78 16,1 43 15,3 21 8 2,5 14,2 28 8 5,2 13.7 20 4 7.0 12,8 13 1 4.7 14,2 120 4,5 16,1 16 1 3.8 11,4 137 5.6 21,8 175 6,1 21 4 143 5,9 Mean 114 174 5,0 Speed of travel appeared uniform throughout the day (Figure 6a), but a further subdivision into months (Figure 6b, c) shows that there was an increase around noon in nonsummer months, with the average speed over 14 km/h at 1300 h during October. During December and January, no such midday peak was evident, but instead animals traveled more rapidly during late afternoon than at other times of day. Movement Patterns In water <10 m deep, bottlenose dolphins al- most always moved parallel to the depth lines; that is, they stayed in consistent depth (Figure 71. In deeper water, movement was more random and dolphins at times rapidly crossed into different depths. Nevertheless, a tendency to follow depth contours was still present. WURSIG and WURSIG. BEHAVIOR AND ECOLOGY OF TCRSIOPS TRIWCATUS 8 X 1- Q. Q 390 369 Figure 4. — Mean depth of water in which bottlenose dolphins were found during different times of day (al- The numbers near points represent number of theodolite readings gathered for that hour of day. The higher number of readings around midday is a result of increased work with the theodolite at that time; it does not represent an increase of dolphins in the area. Instead, the incidence of dolphin sightings was about equal for all daylight hours. These data were divided into different months lb. c i. Average depths ■ 10 m are clumped toward midday 1 10-13 h,P =0.014, Raleigh test. Greenwood and EKirand 195.5(. These deeper water peaks are significantly different from shallow-water travel during the rest of the day for March, July, October, and November (P<0.01 in all 4 mo. Kruskal-Wallis test in lieu of one- way ANOVA,Sokal and Rohlf 1969). In December and January, dolphins stayed in shallow water all day, and this trend is different from data in b (P<-0.001, Mann-Whitney U test, Sokal and Rohlf 1969). 403 FISHERY BULLETIN VOL 77. NO, 2 to- 1-5 b-IO 10-15 15-20 20-25 25-30 50- J5 DEPTHS (m) FUU'RE 5- — Average speed of travel of bottlenose dolphins in different depths of water. Numbers represent number of theodo- lite readings per depth category for which speed information was available. Shallow-water i-lO mi'speeds are significantly dif- ferent from those in deeper water lP<0.01, Mann-Whitney U-test. Sokal and Rohlf 19691. Movement of dolphins was also affected by tidal fluctuations. Animals were found in progressively shallower water as the tide ebbed. Thus, dolphins tended to remain the same distance from the high tide line. When the tide was 6 m above mean low water, dolphins were found in 9 m depth. At mean low water, they were found at a depth of 3 m (Figure 8a). At low wateras the tide began to flood, the dolphins remained in shallow water (3 m) but as the tide continued to rise from 1 to 3 m, they moved into deeper water. At a tide height of 4-7 m, they moved into waters 5-10 m deep (Figure 8b). Depths over which dolphins were when flood tide was between 1 and 3 m were quite variable, indi- cating that the animals moved in all depths near shore at those times, and moved into deep water more often than at other tide heights. Thus, on a lowering tide, dolphins were found in progres- sively shallower water, while on a rising tide the reverse trend appeared, but with a dramatic inter- ruption in this trend at tide heights of about 1-3 m. At those heights, dolphins more often moved into deep water for brief periods. Bottlenose dolphin subgroups often moved back and forth longitudinally within a confined area near shore, thus at times staying within sight of our observation points all day. Within 0..5 km of shore, they turned (changed direction by 180°±10") on the average every 673 m (SD = 980, n =104), and farther than 0.5 km from shore they turned every 1,382 m(SD = 1,094?; = 11). Despite the large standard deviations in these readings, dolphins farther from shore traveled significantly longer distances before turning than when they lOr 8 6 10 E 8 10 8 10 12 14 16 18 20 10 12 14 HOUR OF DAY 20 Figure 6. — Mean speed of travel at different times of day 0.5 km = 10.0 min). Thus, dolphins changed direction about every 9 or 10 min. The increase in distance covered appeared to be a con- sequence of the greater speed in deeper water. Changes in direction by 180'±10' were often made at the same locations on different days, and 404 WUR8IG and WURSIG BEHAVIOR AND ECOLOGY OF TVRSIOPS TRrXCATLS TYPE OF MOVEMENT IN WATER 'lOm DEEP 10 I 6 I- a UJ o 4 2 Movement Observed % Expected % Porallel 796 77 258 25 Interm. 196 19 517 50 Perpend. 41 04 258 25 Tolol 1033 100 1033 too TYPE OF MOVEMENT IN WATER JlOm DEEP Movement Observed % Expected % Porollel 13 38 8.5 25 Interm. 19 56 17.0 50 Perpend. 2 06 8.5 25 Total 34 100 34 too Figure 7. — Movement relative to depth contours In "parallel" movement, dolphins stayed in the same depth between theodo- lite readings, in "intermediate" movement they crossed contour lines at an angle, and in "perpendicular" movement they moved perpendicular to depth contours, and therefore changed depths rapidly In shallow i <10 m) water, dolphins moved parallel to depth lines I ±22.5) significantly more than they moved perpen- dicular to them I ±22.5'.P<0.001,chi-squaregoodnessoffit testi and in deeper 15^10 m) water this trend was weaker but still present iP < 0.03. test as above! . The circles to the right show the divisions of movement, where parallel lines indicate movement parallel to depth lines, and an inverted T represents movement perpendicular to them. Only one-half circle is shown for shallow water because it is likely that animals near shore cannot travel into shallower water. However, the expected percentages of movement relative to depth contours remains the same in shal- low and deep water. therefore after a while could be predicted. Near camp there were three locations where subgroups turned more often than expected if turns were made at random (P<0.005, ehi-square goodness of fit test). All three of these locations were marked by rocks which were submerged during medium and high tides. When the tide was low enough to uncover these rocky areas, leaving only an even, sandy bottom covered, the preference for turning at those areas disappeared. It appears, therefore, that the animals used these rocks as underwater landmarks which, at least at times, stimulated them to change direction. It is unlikely that the dolphins turned at these locations simply to avoid bumping into the rocks, since one of the three areas was marked by rocks only 5-10 cm above the sandy substrate. All three areas formed distinct discontinuities in the bottom topography, how- CORRELATION COEFFICIENT t ) = 0.928 10 8 I 6 0 12 3 4 TIDE HEIGHT (m) -10 1 2 3 4 5 6 TIDE HEIGHT (m) Figure 8. — Average depth of water in which dolphins traveled at different tide heights during a lowering lor ebbi tide (a). Bars above and below points represent QS'^/r confidence limits. A least-squares regression line through the means shows that dol- phins were found in progressively shallower water as the tide ebbed (correlation is statistically significant. P- 0.01 1. Average depth of water in which dolphins traveled at different tide heights during a rising (or flood) tide ib). The rising trend was interrupted between tides 1 and 3 m by animals more often moving into greater depth (shown by increase in mean depth and by larger SS':? confidence limits, because variability increased!. ever, and may have served as cues to turn at the boundary of the area traversed. The tongue of land called Los Conos i Figure 2 ), 6 km north of camp, appeared to be the northward boundary of the present population's range. In 260 h of observation, dolphins were never observed traveling north of this point. When they were lost from sight, it was either due to bad visibility or because the animals traveled out of range in the southwest portion of the study area. In addition, when the animals were first spotted coming into the study area, they always came from the south- west, never from the north. As was described earlier, bottlenose dolphins in the present study exhibited two distinct move- ments. Usually, they moved slowly and very close to shore, in shallow (<10 m deep) water. They moved for brief ( 16 min) periods, mainly during midday in nonsummer seasons, into deeper ( >10 405 FISHEKY BULLETIN VOL 77, NO 2 m) water, and moved more rapidly at that time. These two distinct movements were marked as well by a difference in group formation. While slowly traveling near shore, the dolphin subgroup was 87'^r of the time (226.2 h of 260 h) in a tight formation about 10-15 m wide and 50-75 m long. Because of this narrow formation, no individual was far from shore, and all were in similar depth. On the other hand, when dolphins moved into deeper water they advanced as a wider than long rank, with each animal separated from the next by as much as 25 m on its flank, yet the entire group presented one wide front. In this manner, the sub- gi'oup was able to cover a large swath of sea (up to about 300 m I as it rapidly moved ahead. During 13 of 134 times (9.7'^f ) that rapid movement was ob- served, we noted 1-12 terns and at times gulls flying in front of this advancing dolphin line and diving into the water to pick up 10-15 cm long fish. We suspect that they may have been near parts of schools of southern anchovy, Engraulis anvhoita. because of the abundance of this fish in the area. The wide front movement in deeper water may thus be a searching pattern by bottlenose dolphins for such schooling fish. When the subgroup slowed at the end of an individual-abreast run, the ani- mals milled in different locations (122 of 134 times, 91% ), giving us the impression that they were feeding in that location. However, such mil- ling after rapid movement was usually short (60 s±30 s), and never lasted more than 5 min. At the end of milling, the subgroup usually (115 of 122 times, 94^/ I continued to move slowly in shallow water, but less often (7 of 122 times, &7c ) began a new period of 16-min-long rapid movement in deep water. Aerial Behavior Aerial behavior was not as frequent in the bottlenose dolphin population we studied as in many other species of cetaceans ( e.g., see Saayman and Tayler in press; Norris and Dohl see footnote 3; Wiirsig and Wiirsig see footnote 4). Individuals engaged in any form of aerial display <5'^f of the observed time. These displays were the 1 1 leap, 2) headslap, 3) noseout, 4) tailslap, and 5) kelp toss. For the sake of conformity, the aerial displays discussed below, except for 5l, follow the names and descriptions of aerial behavior given for Hawaiian spinner dolphins by Norris and Dohl (see footnote 3): 1. Leaping either produced a loud sound when the animal fell back into the water onto its belly or side ("noisy leap"), or was relatively silent when the animal arched its body during the leap and reentered nose first ( "clean leap" ). Noisy and clean leaps occurred at any time of day when the ani- mals were moving slowly close to shore. However, noisy leaps were most often performed by calves and subadults (calves leaped approximately 3 times as often as adults), and occurred more often in the afternoon ( morning, 24 leaps in 1 17 h, mean = 0.21/h; afternoon, 70 leaps in 143 h, mean = 0.49/h; significant difference at P<0.001, testing equality of percentages, Sokal and Rohlf 1969). Clean leaps were performed only by adults and usually occurred when the gi'oup was relatively stationary in medium-deep (10 m±5 m) water. At times (about 25'f , not adequately quantified for exact numbers) such leaps were attended by terns diving in the vicinity and feeding on small fish, leading to the inference that such clean leaps, which allow animals to rapidly descend headfirst, may be food-related. No daily or seasonal pattern was evident for clean leaps. 2. The headslap was seen only twice in 260 h of observation, each time performed by a subadult while the subgroup slowly moved along shore. 3. Noseouts, when dolphins poked their heads out of the water to beyond at least one eye, were about as frequent as noisy leaps and usually oc- curred at the same time (i.e., more often in the afternoon). 4. Tailslaps were the most frequent form of aer- ial behavior. They also occurred at any time dur- ing the day, but were frequent only when some disturbance occurred. Thus tailslaps were noted a) when our outboard engine was started 300-500 m from the dolphins, b) 14 of 95 times ( 15'y ) our boat initially approached a subgroup of dolphins, c) when the subgroup had been split into two adja- cent groupings for several hours and then rejoined (this happened five times), and d) once when a light plane flew overhead at low altitude. In these cases, the tailslapper was always an adult, and most of the time was a large, recognizable indi- vidual who was part of a stable subunit of five individuals which consistently stayed together (dolphin no. 1 in Wiirsig 1978). Unlike any of the other forms of aerial behavior, which usually were performed only once by one animal at a particular time, tailslapping occurred from 10 to 20 times during one bout. 5. "Kelp tossing" usually was accompanied by J high incidences of noisy leaps and noseouts. Dur- ' 406 WURSIC; and WURSIG BEHAVIOR AND ECOLOCY OF TURSIOPS TRI'XCATl'S ing kelp tossing, an animal would balance a piece of Macrocystis sp. on its melon or forehead, flip it to its tail with a sudden head jerk, flip it to the dorsal fin with its tail, or any variation of the above. Kelp tossing was observed nine times during the study, and lasted an average of 15 min bout. Social Behavior Because most observations were done from a distance, and usually only dorsal fins were visible above the water, little insight was gained into social behavior. Nevertheless, a few major trends were apparent. When noisy leaps, noseouts. and kelp tossing occurred, animals were also often seen swimming side by side while touching, with at least one of the animals in an upside down position ("belly-up"). Viewed from directly over- head, as when the subgroup passed close beneath our observation cliff, individuals could be seen nudging each others' bodies with their snouts. As with leap frequency, most of this behavior was observed in the afternoon (12 of 17 times. "Vi: significant difference from morning at P<0.Q'2. testing equality of percentages, Sokal and Rohlf 1969). It appeared as well that belly-up and rub- bing behavior were more frequent when two sub- groups which had moved separately for several hours joined again. However, this did not happen often enough (five times m total i for statistical analysis. Five calves were observed during the study. Each stayed close to a particular adult (see Wiirsig 1978), and we assume that this adult was the mother. Calves and mothers were also observed engaging in rubbing behavior with other adults. Bottlenose dolphins associated with the south- ern right whale. Euhalacna glacialis, which were seen near shore from June through November. While moving along shore, dolphins veered from their previous path by as much as 300 m to join one or more right whales. Once with the whales, they rapidly swam back and forth across the whales' head. Whales invariably became very active when dolphins were present, blowing and "snorting" loudly in air as well as underwater. Whales also rapidly surged or lunged ahead in the direction of dolphins crossing their heads. The dolphins then rode (or surfed) on the pressure waves created by these lunges, riding along the crest of either wave cascading to the side of the whales. This associa- tion appeared to us to be play, and occurred 24 of 26 times (92'* ) that whales were directly in front of the path of moving dolphins. It lasted an aver- age of 1.5 min.. after which the dolphins left the whales and continued in the direction in which they had been traveling beforejoining the whales. Further interspecific associations occurred with the sea lion. Otaria flaret^cens, and, on one occa- sion, with a subadult male elephant seal. Mlrotin- f>a leontna. The pinnipeds joined a subgroup of dolphins and traveled with it for up to 1 km. rapidly moving among the dolphins. Dolphins also at times approached our 4.5 m rubber Zodiac boat and swam underneath the boat for brief (up to 5 min) periods. During 86 of 95 (9Kc) boat approaches, however, bottlenose dol- phins appeared to ignore our boat, neither ap- proaching nor avoiding it. When winds rose above 20-30 km h, dolphins were often observed rapidly riding down the ad- vancing crest of waves in the surfline. It appeared that they were surfing the waves much as human surfers do, and much as dolphins did with "bow" waves of whales. Possible Predation We saw no direct evidence for predation on bottlenose dolphins, but one of the animals, TS ( for "tiger stripes," Wiirsig and Wiirsig 1977) ap- peared in January 1975 with a series of scratched lines along its left dorsum. From the regularity and spacing of the lines, we bel ieve that they were made by killer whale. Orriniis area , teeth. It seems possible that this individual narrowly escaped a killer whale. Furthermore, on two separate occa- sions, we observed killer whales approaching within 0.5 km of bottlenose dolphins. In each case, the bottlenose dolphins rapidly swam away and toward the open sea. Their swimming was so rapid at these times that the dolphins leaped clear of the water and covered 2 or 3 times their own length out of the water during low forward leaps. Hertel (1963) suggested from mathematical models that this type of movement is most efficient for rapid surface swimming. Theodolite readings taken at these times indicate that the dolphins were mov- ing at speeds of at least 30 km/h; however, no definitive upper limit speed information was ob- tained because it was difficult to follow rapidly moving animals accurately in a .short- time period. DISCUSSION The bottleno.se dolphin population studied here 407 FISHERY BULLETIN: VOL. 77, NO 2 spent 92''6 of its time in water < 10 m deep, and was never seen in water -39 m during the 21 -mo study. "Coastal dolphins" is therefore truly an ap- propriate label. Various investigators have men- tioned the presence of bottlenose dolphins farther from shore and in deeper water populations dis- tinct from the nearshore populations seen in the same general geographic area (e.g., Norris and Prescott 1961 ). We never saw Tursiopn in offshore waters >3 km from land despite over 100 attempts to find them lay boat in deeper water. Instead, a different animal, the dusky dolphin. Lagenorhyn- chus obacurua. was seen farther offshore during the entire year ( Wiirsig in press; Wiirsig and Wiir- sig see footnote 4i. The bottlenose dolphins studied here were al- most always found in water ■ 10 m deep; however, in autumn, winter, and spring they moved into deeper water for brief periods during midday. At that time, they sped up and moved as fast as 24 km h. Because terns were seen feeding near such movement, and because of the wide swath of sea covered by the dolphins while rapidly advancing in this manner, we believe that during these times they were searching for and at times feeding on aggregations of schooling fish. Although adult southern anchovy are apparently not abundant in the area in winter (Brandhorst et al. 1971), juve- niles are present near shore in small schools at this time (Brandhorst and Castello 19711. Similar group feeding by bottlenose dolphins has been re- ported on numerous occasions (Morozov 1970; Hoese 1971; Tayler and Saayman 1972; Saayman and Tayler 1973; Busnel 1973; Leatherwood 1975; Hamilton and Nishimoto 1977). We could not de- termine, however, whether the dolphins were ac- tively herding fish into a tight unit against the surface of the water, as dusky dolphins are thought to do (Wiirsig and Wiirsig see footnote 4). The daily periodicity of deepwater movement dur- ing nonsummer indicates that the schooling prey of bottlenose dolphins may be more abundant in those waters during midday. However, this is at present only conjecture. At any rate, no such mid- day increase in speed and depth of water was evi- dent in summer. During summer, southern an- chovy are not found very often in coastal waters less than approximately 40 m deep (Ciechomski 1965; pers. obs. ). Instead, these schooling fish are found in deeper (and cooler) offshore waters, where dusky dolphins feed on them. The present population, however, does not go into these deep waters in the southeast portion of (}olfo San Jose, and thus does not appear to have this resource available in this area during summer. Whether or not there is active competitive e.xclusion between bottlenose dolphins and dusky dolphins is not known. During summer afternoons, Tursiops moved more rapidly and in slightly deeper water than at other times of day. We do not know whether they were cooperatively hunting and feeding on school- ing fish as in the manner described above. It is possible that the animals were moving into some- what deeper water to avoid very warm water ( up to 25' C, pers. obs. ) present in 0-4 m depth during hot summer weather, but as bottlenose dolphins live in warmer water elsewhere, it is more probable that their daily movement pattern was food- related. Average speed of travel by bottlenose dolphins was 6.1 km h. This represents one of the first times that such a speed has been reported for an undis- turbed group of wild dolphins. It is similar to speed estimates made for the Indian Ocean bottlenose dolphin, Tiirsiops (ultincus (9.9 km h) and for Soiisa sp. (4.8 km h) during normal progression (Saayman et al. 1972; Saayman and Tayler in press). As an interesting sidelight, which may be recognized as having general significance as more population studies of dolphins unfold, bottlenose dolphins studied by Saayman et al. 1 1972) were usually found in deeper water while humpback dolphins were almost always Ibund in shallow wa- ters. While moving near shore, .south Atlantic bot- tlenose dolphins moved roughly as fast as did humpback dolphins, and while farther from shore, they moved roughly as fast or faster than the In- dian Ocean bottlenose dolphin. The same trend is true for dusky dolphins in the south Atlantic wa- ters ( Wiirsig and Wiirsig see footnote 4 ). A possible explanation may be that nearshore searching for food and feeding are more often functions of indi- viduals, while deeper water prey search appears often to utilize the combined sensory abilities of the entire group as it actively echolocates for whole schools of fish. A similar pattern of dis- persed individual feeding near shore and group feeding offshore has been found by Irvine, et al. (see footnote 2). The nearshore search for food re- quires looking in detail at the prey possibilities near rocks, plants, and on the bottom, while mo.st efficient search in open water is likely to be facili- tated by covering as large an area as possible within a small space of time. Possibly more impor- tant intraspecifically is a recent suggestion that 408 WURSIG and WURSIG: BEHAVIOR AND ECOLOGY OF TURSIOPS TRUSCATUS coastal dolphins at times rest close to shore (and move slowly while resting) to avoid deeper water predators such as sharks and killer whales i Norris and Dohl see footnote 3; Wiirsig and Wiirsig see footnote 4). They more often feed farther from shore and in deeper water, and are more active at that time. In this study there was evidence that bottlenose dolphms near shore paid attention to bottom to- pography. While they in general moved over con- sistent water depth for brief periods, they often moved back and forth over the same bottom topog- raphy durmg a falling tide. As a result, they traveled in progressively shallower water as the tide receded. Furthermore, they changed direction over particular underwater landmarks, usually consistmg of groups of rocks. This type of move- ment associated with bottom topography may be strongest while the animals are searching for bot- tom-dwelling prey. However, we do not know what their food was at such times. The intertidal areas in which they were traveling had abundant snails, and part of the area was covered by mussels. Mus- sels were especially abundant on the rocky out- croppings where dolphins turned (and at times milled or lingered for several minutes), but we have no direct evidence for feeding on shellfish. Norris and Prescott (1961) reported that Tursiops in California waters feed at times on hermit crabs and shellfish. Also present in and around rocks were larger — up to 1 m long — fish. Pinguipet: fas- ciatus. We observed individual dolphins shaking these fish in their mouths and repeatedly tossing them into the air on three separate occasions. Al- though this behavior at first looked like "play" before feeding on the fish, it is likely that the dolphins were tossing and shaking them to soften the fish and possibly to separate the head from the edible body (as reported by Brown and Norris 1956). It thus appears that this fish constitutes a nearshore prey item, and it may be part of the reason that bottlenose dolphins often turned and lingered near rocks. During intermediate flood tides dolphins trav- eled more often into deep water than at other tide stages. Since deepwater movement appeared cor- related with group feeding on schooling fish, feed- ing may have occurred more often during such intermediate rising tides. We therefore suspect that schooling fish were also more often present in nearshore waters during rising tides, perhaps brought into the area from deeper water by the tidal currents. Although we have no evidence for this postulated movement of bottlenose dolphin prey, it is a common behavior of many fish species to come in with the tide, and thus a reasonable possibility in the present case. Tide-related movements ofTursiops sp. have been described by McBride and Hebb (1948). Norris and Prescott ( 1961 ). D. K. Caldwell and M. C. Caldwell ( 1972), Irvine and Wells ( 1972 ), Shane ( 1977 ), and others. Most of these descriptions involved the move- ments of bottlenose dolphins into and out of coast- al channels or canals and are therefore not strictly comparable with the present study. However, dol- phin movement appeared often to be food-related in these studies. Saayman and Tayler (in press) found a peak in Sousa sp. feeding 2 h before high tide, presumably also because prey fish were being brought into their study area by the tide. Near shore, dolphins changed direction by 180° approximately once every 700 m. This was the average distance between rocky outcroppings of cliffs. The turns often tended to keep the animals in a restricted area within sight of our observation points for several hours. When farther than 0.5 km from shore, dolphins traveled about twice the nearshore distance before turning, possibly be- cause they encountered no rocks or outjuttings of cliffs in such deeper water. Nevertheless, because travel in one direction lasted on the average only 9 or 10 min whether near or far from shore, deeper water travel also usually kept the animals in a particular area. Although we were able to describe the move- ments of bottlenose dolphins in some detail within an approximately 50 km^ area, we do not know- where the dolphins went when they moved out of our area. They did not travel beyond a certain point (Los Conos. Figure 2) within the study area, but at least once individuals traveled as far as 300 km away from the study site (Wiirsig and Wiirsig 1977; Wiirsig 1978). However, a more accurate definition of range awaits further data. It was mentioned previously that slow move- ment near shore may at times be associated with feeding on large solitary fish as well as on smaller bottom-dwelling organisms. Dolphins also en- gaged in other activities while moving near shore. During the morning, we observed very little aerial behavior such as leaping, noseouts, belly-ups, and kelp tossing. As a result it appeared that their activity level was less during the morning than during the afternoon, and that much of the time the animals were resting as they moved back and forth close to shore. A similar pattern of rest dur- 409 FISHERY BULLETIN: VOL 77. NO ing morning has been reported for Hawaiian spin- ner dolphins by Norris ( 1974), Norris and Dohl l in press), and Norris and Dohl (see footnote 3) and for dusky dolphins by Wiirsig and Wiirsig (see foot- note 4). Norris and Prescott ( 1961) also mentioned that T. gilli off California appears more active in the late afternoon than during the early part of the day. Why this period of rest should be concen- trated in the forenoon in at least three different coastal species is not known. It contrasts in the present population with a greater amount of feed- ing activity in the afternoon, and it may be that schooling prey is more available in the deeper offshore waters in which these porpoises feed in the afternoon. As a result, they rest more fre- cjuently when prey is not .available. During the afternoon, activity level increased. Aerial displays were generally performed singly, however, and were often spaced in time, with only a few leaps or noseouts per hour. This amount of aerial displaying was less than for the spinner dolphins which spread out over large distances and for which the omnidirectional splashing sounds attendant to most aerial behavior is thought to serve a possible communication func- tion (Norris 1974). Such communication would be most important when the animals are not close together as a tightly knit unit, which the present individuals were at almost all times. Neverthe- less, it is still possible that noisy leaps, e.g., served to attract the attention of the rest of the subgroup in a highly efficient manner. The exact meaning, however, of these leaps is not clear. Noseouts, belly-ups, kelp tossing, and clean leaps make little noise. These also occurred with higher frequency in the afternoon. Clean leaps, with individuals reentering the water headfirst, as has been mentioned previously, appeared to precede steep dives in intermediate and deep wa- ters. They may be correlated with feeding on or near the bottom. Noseouts, belly-ups, and kelp tossing occurred when individuals were close to- gether, often touching, and may be associated with "play" and copulatory activity. Especially during times when individuals moved upside down (belly-up) for 50 m or more, they were attended by one or more individuals rubbing along their flanks and dorsum. These close interpersonal associa- tions need not necessarily indicate copulatory be- havior, however. They were also performed on several occasions by adults and their small calves, and may represent a form of nonsexual social communication as has been proposed by several other works (Caldwell and Caldwell 1967; Bate son''; and others). Especially significant for thi> hypothesis may be the fact that we observed more of these behaviors when two subgroups which had been separated for several hours or longer re- joined. Rubbing behavior and attendant aerial displays may at least in part serve a gi-eeting func- tion, where individuals renew and strengthen so- j cial bonds in a manner analogous to many social terrestrial mammals (for a review, see Wilson 1975). , Belly-up movement was described by Leather- wood ( 1975) for T. trunaitiis , and by Saayman and Tayler (in press) for Sausa sp. as being performed by individuals while pursuing fish near the sur- face of the water. Although we saw belly-up be- havior only in conjunction with other behavior which we assumed to be social, it may also occur for feeding in the present population. A final form of aerial behavior which also made a loud sound was tailslapping. It was performed at any time that the group may have been disturbed, such as upon the approach of our boat. We there- fore concur with other researchers (Norris and Pre.scott 1961; D. K. Caldwell and M. C. Caldwell 1972) who believe that tailslapping by dolphins in general serves as a warning signal or fright reac- tion. It was performed with highest frequency by a | large adult who was part of a "core" of individuals present throughout the 21-mo study. We suggest that this individual may have been a "leader" of the subgroup of animals, posssibly dominant over other individuals. This suggestion is based only on this one behavioral pattern, however, and must therefore be treated with caution. Dolphins associated with whales by riding on the waves created by the larger cetaceans, and rode on wind-driven waves and the pressure wave of the boat. This type of behavior has been seen in many species, and was described for dolphins rid- ing near whales by McBride and K ritzier (1951), j for dolphins riding wind-driven waves by Wood- cock and McBride ( 1951 ), and for dolphins riding boat bow waves by Matthews ( 1 948 ) and Woodcock (1948). Especially insightful analyses of this be- havior have been provided by Scholander (1959) and Norris and Prescott ( 1961 ). They showed that dolphins could travel with less muscle movement, and therefore presumably less expenditure of "Bateson, G. The cetacean community in Whaler's Cove - Sea Life Park. Unpuhl. manuscr., 16 p. Center for Coastal Marine Studies, University of California, Santa Cruz. 410 WURSIG and WURSIG BEHAVIOR AND ECOLOGY OF TURSIOPS TRVNCATUS energ>', by surfing in this manner. How much pure play (and perhaps play as a part of learning) is involved, and whether or not dolphins really ride waves to get a "free ride" to a different location are questions which remain unanswered. In the present paper, we made an attempt to describe some of the behavior patterns which we saw most often from above the water surface, and suggested various possible functions for them. We realize, however, that most social interactions go on under water, and that dolphins probably com- municate with sound at least as extensively as with observed movements. Tyack ( 1976) found dif- ferences in quality and quantity of sounds pro- duced by the bottlenosed dolphins of the present study depending on whether they appeared to be feeding, socializing, or resting. Although this is a promising beginning, much more sound-behavior correlation is necessary before biological meaning can be ascribed to specific sounds. In this paper, we have described certain move- ment patterns and behavior, and ascribed possible functions to them. However, the present analysis raises many more questions than it answers, and may be regarded as a first step in understanding the behavior of these animals. ACKNOWLEDGMENTS Jen and Des Bartlett, Peter Tyack, Marty Hyatt, and Russ Charif helped gather data. Jan I. Wolitzky wrote the computer program for analyz- ing theodolite track data, and Matt Lamishaw pa- tiently worked at the computer. Roger and Katy Payne provided material and intellectual support. Kenneth Norris, Jay Quast, George C. Williams, J. L. McHugh, Randall Wells, William Perrin, Douglas Smith, and an anonymous reviewer for the Fishery Bulletin critically read the manu- script. Charles Walcott supported and encouraged all phases of the research. We are especially gi-ate- ful to him. This study was supported by the New York Zoological Society, the Committee for Research and Exploration of the National Geographic Soci- ety, and the Progi-am for Neurobiology and Behav- ior of the State University of New York at Stony Brook. LITERATURE CITED BRANDHORST, W., AND J. P. CA.STELLO. 1971. Evaluacion de las recursos de anchoita iEngraulis anchoita^ frente a la Argentina y Uruguay. II. Abundan- cia relativa entre las latitudes 39" y 45° S en relacion a las condiciones ambientales en febrero-marzo de 1970. Proyecto DesarroUo Pesq.. Ser. Inf. Tec, Publ. 32, 47 p. BRANDHORST. W , J. P. CASTELLO, R. PEREZ HABIAGA, AND B. H. ROA, 1971. Evaluacion de los recursos de anchoita (Engraulis anchoila) frente a la Argentina y Uruguay. III. Abundan- cia relativa entre las latitudes 34'40' S y 42'10' S en relacion a las condiciones ambientales en may-junio de 1970. Proyecto DesarroUo Pesq., Ser. Inf Tec, Publ. 34, 39 p. BROWN, D. H., D. K. CALDWELL, AND M. C. CALDWELL. 1966. 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D.C.) 198:755-756. 412 GROWTH OF NORTHERN ANCHOVY, ENGRAULIS MORDAX, LARVAE IN THE SEA Richard D, Methot, Jr. and David Kramer' ABSTRACT Northern anchovy larvae froml2 samples collected at :3.0°-16.2° C in the Southern California Bight were aged using daily growth increments in sagittal otoliths, and growth rates were calculated from size at age data. In nine samples, growth rate at 8 mm was very similar, ranging from 0.34 to 0.40 mm per day. Growth in the other three samples ranged from 0.47 to 0..55 mm per day. There was no correlation between growth rate and temperature within this set of field samples, but the range of growth rates was similar to the range expected from laboratory rearing experiments in this tempera- ture domain. In no case was growth in the sea as slow as growth in the laboratory on severely limited rations. Anchovy larvae which obtain enough food to survive apparently obtain enough food to grow rapidly. The presence of daily growth increments in some hard tissues of various plants and animals has been known for several decades (Neville 1967i. Despite the fact that fish otoliths have been examined for annual growth marks throughout this century (Blacker 1974), daily growth incre- ments were only recently identified in fish (Pan- nella 1971). The daily nature of these increments was verified in the laboratory by Brothers et al. (1976) using marine fish larvae. Taubert and Coble ( 1977) showed that increment formation in centrarchids is linked to the diel light cycle, not a feeding rhythm. Although studies have been con- ducted on the gross growth of otoliths (Degens et al, 1969; Mugiya 1974, 1977) the physiological mechanism responsible for daily growth incre- ment formation in fish is unknown (Simkiss 1974), Regardless, daily growth increments provide the ecologist with a tool for determining age and growth of specimens from the field iStruhsaker and Uchiyama 1976). The objective of this project was to estimate growth of larval northern anchovy, Engraulis mordax, in the sea. Many laboratory studies dem- onstrate that growth of young fish is limited by temperature and ration (Riley 1966; Brett et al. 1969; O'Connell and Raymond 1970; Houde 197.5). Because food availability is frequently considered to be one of the major factors controlling larval survival (Gushing and Harris 1973; Jones 1973: 'Southwest Fisheries Center LaJolla Laboratory, National Marine Fisheries Service, NOAA, P O Box 271, La Jolla, CA 92038. May 1974; Lasker 197.5; Arthur 1976), growth in the sea may frequently be limited by food. How- ever, when collections of measured larvae are used for indices of spawner abundance or larval mortal- ity studies, growth is assumed to be constant (Houde 1977) or a function solely of temperature (Bannister et al. 1974), Determining growth rates of larval fish in the sea should resolve this con- tradiction between theoretical and applied fishery science. Anchovy larvae can be reared to metamorphosis and beyond in the laboratory (Kramer and Zweifel 1970; Hunter 1976; Sakagawa and Kimura 1976), Growth in these experiments was described best by the Gompertz growth equation, equation 1 (Kramer and Zweifel 1970; Zweifel and Lasker 1976), The effect of temperature on embryonic de- velopment and larval growth was incorporated by making the Gompertz gi-owth parameters. .4„ and a, increasing functions of temperature (Zweifel and Lasker 1976; Zweifel and Hunter^). We com- pared the size at age of anchovy larvae in each field sample with that predicted by this temperature dependent model of anchovy growth in the laboratory, assuming that the temperature mea- sured at the time of collection represented the temperature experienced by the larvae through- out their lifetimes. Manuscript accepted .lanuarv 1979 FISHERY BULLETIN: VOL 77. NO 2, 1979. ^Zweifel. J. R., and J. R. Hunter Temperature specific equa- tions for growth and development o( anchovy. Engraulis mordax , during embryonic and larval states. (Manuscr. in prep.) Southwest Fisheries Center La Jolla Laboratory, NMFS. NOAA, P.O. Box 271, LaJolla. CA 92038. 413 FISHERY BULLETIN: VOL, 77. NO 2 METHODS Ichthyoplankton samples were collected from the Southern California Bight in March 1976, May 1976, and March 1977 with the NOAA ship David Starr Jordan. The sampling gear consisted of a CalCOFI (California Cooperative Oceanic Fisheries Investigations) ring net (1 m mouth diameter), MARMAP (Marine Resources, Moni- toring, Assessment, and Prediction Program) Bongo net (60 cm mouth diameters), and a Manta neuston net: all with 505 ;um mesh. Oblique tows were made from the depth indicated in Table 1 to the surface. Samples were drained of excess sea- water and preserved in 85% ethanol. (Recently we found that preservation is greatly improved if the alcohol is changed at least once after initial pres- ervation; the otoliths may dissolve in poorly pre- served samples with large plankton volumes. We change it once within 24 h and again within a few weeks.) Surface temperatures were measured with a bucket thermometer, and vertical tempera- ture profiles were obtained with expendable bathythermographs. The 12 samples analyzed in this study are from a limited part of the spawning range of the northern anchovy, but the Southern California Bight in March is an important spawning area for the cen- tral population of the anchovy (Smith 1972). Sam- ples A1-A3 and Bl were collected near Los Angeles and the Channel Islands in 1976 (Figure 1 ) and were selected because of the wide size range of anchovy larvae found in each. Samples CI and C2 were collected in this same region in March 1977. They were selected to represent the widest temperature range possible. Samples D1-D6 were collected in March 1977 along a transect extend- ing seaward from San Diego and were the only samples containing anchovy larvae on this tran- sect. Additional station data are in Table 1. All fish eggs and larvae were sorted from the plankton samples chosen for analysis and anchovy larvae were processed in a manner similar to that described by Brothers et al. ( 1976). The standard length, tip of snout to tip of notochord or hypural plates, of each larva was measured to the nearest 0.1 mm. Sagittae were removed and placed on a microscope slide with the lateral (flat) side up. A polarizing filter and analyzer in the dissecting microscope made the otoliths more visible during dissection. The slide was air-dried and the otoliths were mounted under a coverglass with a clear mounting medium iPro-texx'M. Daily growth in- crements were counted in otolith images on a video screen; the total magnification by the micro- scope and video camera was 600 ^ or 1 ,500 x . Each otolith was counted by 1-3 observers until the range of accepted counts for the two otoliths was =s2. Accepted counts were averaged over all ob- servers and both otoliths. The shrinkage of sea-caught larvae in preserva- tive (Blaxter 1971) and the lag between hatching and first increment formation must be considered before comparing the size at age of sea-caught larave with laboratory-reared larvae. Shrinkage of anchovy larvae depends upon the elapsed time between death and preservation (Theilacker''). There is no shrinkage when live larvae are placed directly into ethanol but a 5-15 mm larva could shrink about 0.6 mm if dead throughout the 6 min duration of the net tow. No shrinkage correction was applied because the elapsed time between death and preservation probably was <6 min and highly variable. Anchovy larvae tend to stay above the thermocline ( Ahlstrom 1959) so are cap- ^Reference to trade names does not impl.v endorsement by the National Marine Fisheries Service. NOAA. "H^heilacl^er. G. H, Preservative shi'inltage of larval anchovy. Engrauhs mordax: laboratory versus field. Paper presented Nov. 1, 1978 at CalCOFI Conference, USC, Idyllwild, Calif. Table l — Data on samples of larval northern anchovy taken from the Southern California Bight, spring 1976 and 1977. Depth Tempera- Sample Date Time Lat, N Long. W Gear (ml ture (°C) N At 29 Mar 1976 2150 33 35 9 117 566 Ring 10 158 106 A2 31 Mar 2205 33 43 5 118 28 0 Ring 5 15 0 38 A3 1 Apr 1850 33 42 0 118 20 5 Ring 5 150 29 Bl 8 May 1835 33 27 5 1 18 400 Mania 0 162 146 CI 20 Mac 1977 1915 33 30 3 118 01 5 Bongo 70 151 35 C2 24 Mar 2320 33 29 4 1 1 7 54 1 Bongo 70 130 112 D6 27 Mar 0235 32 41 5 119 01 5 Ring 70 132 18 D1 27 Mar, 1830 32 00 0 119 120 Ring 70 14 0 13 D2 27 Mac 2100 32 05 8 118550 Ring 70 140 25 D3 28 Mar 0140 32 28 8 118 35 0 Ring 70 144 18 D4 28 Mar 0405 32 39 5 117595 Ring 70 152 22 D5 28 Mar 0630 32470 117385 Ring 70 15 1 25 414 METHOT and KRAMER GROWTH OF NORTHERN ANCHOVY LARVAE 33°N Figure l. — Sampling sites for north- ern anchovy larvae off southern California. Box indicates the region shown in detail in Figure 4. 34''N 32°N I19°W tured primarily during the last 1 or 2 min of an oblique tow, and some large larvae were still alive at the time of preservation. Brothers et al. (1976) found a 5-day difference between posthatch age and number of increments for anchovy larvae reared in the laboratory at 16' C. At 19' C the lag is 3 days and at 12.5= C it is about 9 days ( Methot unpubl . data ). These lags are very close to the age at completion of yolk absorp- tion (19° C, 2.9 days; 16° C, 4.7 days; 12.5= C, 8 days — Zweifel and Hunter (see footnote 2)); the larvae are about 4.2 mm at this age. Since de- velopmental events, such as a functional jaw, occur at a constant size at all temperatures in this range (Zweifel and Lasker 1976), we assume that increment formation also begins at a constant size of 4.2 mm at all temperatures. The number of increments represents the age in days after yolk absorption. RESULTS Standard length of each larvae in a sample was plotted against the mean number of increments (Figure 2). Each data point represents the integral of the growth rate of an individual larva over its lifetime, and a trend line through these points estimates the average growth history of larvae in the region sampled. Possible biases in this esti- mate of growth rate are discussed below. 415 FISHERY BULLETIN VOL 77. NO According to the null hypothesis, the laboratory growth curve corresponding to the temperature at which the sample was taken should provide the best fit to the data. A suitable parametric proce- dure for testing this goodness of fit was not avail- able. The nonlinear least-squares method for fitting the Gompertz growth function to size at age data (Zweifel and Lasker 1976) does provide esti- mates of confidence intervals on the parameters, but the probability levels associated with these intervals are only approximate (Conway et al. 1970). We found these confidence intervals to be rather broad. We tested the goodness of fit by using a modifica- tion of the median regression procedure of Tate and Clelland ( 1957), replacing their estimated re- gression line by the laboratory derived Gompertz growth curve specified by our null hypothesis. Only curves at 1' C intervals were considered. Each larva in a sample was classified into a 2 x 2 contingency table, according to whether it was to the left or right of the median age of larvae in the Al I5 8°C _!_, 1 l_l I i I U 15 l-C II II „ - 15* LAB, - ^^ --^TED - , > •^^^ ^•■' -r*"^*"^*^^^ -^^--^^ A3 - ISCC 1 1 I 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 NUMBER OF INCREMENTS NUMBER OF INCREMENTS 416 METHOT and KRAMER GROWTH OF NORTHERN ANCHOVY LARVAE 18 ~ 16 - E E 14 - FITTED, I .0 - • . ^^^^^ ■'^'L^% -J o a. ^ ^ Q q: 2 Z < 6 6 - • • 4 1 i 111111:1 1111 1 1 D5 I5I°C. 1 1 1 1 1 1 1 1 NUMBER OF INCREMENTS NUMBER OF INCREMENTS FIOURE 2. — Relationship between standard length of northern anchovy larvae and the number of daily growth increment.s ( age postyolk absorption I in their otoliths. Two growth curves are shown. One I LAB I is the laboratory growth curve which was expected to fit the data because of the temperature at which the sample was collected. The other iFlTTEDi was fit to the data using a nonlinear least-squares method. sample and whether it was above or below the laboratory growth curve (line labelled LAB in Figure 2). Points which fell on lines were split equally between the cells on either side of the line. A chi-square statistic with 2 degrees of freedom was calculated using the expectation of equal numbers of larvae in each cell of the table. The results of these tests are in Table 2. In general, larvae collected between Los Angeles and the Channel Islands in March 1976 (samples A1-A3) grew slower than expected while those collected there in March 1977 (CI, C2) grew 417 FISHERY BULLETIN; VOL, 77. NO, 2 Table 2. — Results of chi-square test of the hypothesis (see text) that tempera- ture-specific grovrth in the northern anchovy is the same m sea and laboratory (A-Ei and the parameters of the Gompertz growth curve fit to the data in each sample (F-I). A, sample size; B, surface temperature in degrees Celsius; C. growth curve compared with data; D, probability that growth curve fits data; E. sign of significant deviations l0.05 level i from laboratory curve; F and G, Gom- pertz parameters, A 0 and a; H, standard error of regression; 1. growth rate at 8 mm (in miUimeters/day). Last row shows results for combined data (samples with *). Sample A B C D E F G H 1 Ar 106 158 16 0 001 0 060 0 024 0 094 0 356 A2- 38 150 15 ■ 0 01 - 0 059 0 025 0 089 0 341 A3- 29 150 15 0 25 0 0 067 0 029 0 086 0 387 B1 146 162 16 0 001 0 093 0 037 0 111 0 552 CI 35 15 1 15 0 001 0 089 0 038 0 074 0515 C2 112 130 13 0 001 0 080 0 033 0 083 0 471 D6- 18 132 13 0 001 0 067 0 029 0059 0 389 or 13 14 0 14 0 25 0 0 061 0 024 0-109 0358 D2- 25 14 0 14 0 025 0 068 0 029 0 120 0 397 D3- 18 14 4 14 0 25 0 0 059 0 025 0 092 0348 D4- 22 152 15 0 10 0 0 061 0 027 0 105 0 348 D5- 25 15 1 15 0 25 0 0 064 0 063 0 027 0 027 0 103 0 097 0 371 0 370 faster than expected. The larvae collected in March 1977 along the transect extending seaward from San Diego (DI-D61 grew about as fast as expected, given the surface temperature at which the sample was collected. Since the data in 7 of 12 samples deviated sig- nificantly from the predicted Gompertz growth curve, we fit the Gompertz growth function (Zweifel and Lasker 1976) log,, iSL) = log,, iSL^) + An (1 ■) (1) where SL = standard length in millimeters t = number of increments = age in days postyolk absorption SL„ = initial size, fixed at 4.2 mm A„, a = parameters to be estimated to each using a nonlinear least-squares method (Conway et al. 1970). The parameters of the fitted curves (Table 2) were used to calculate a linear approximation of the growth rate of 7.5-8.5 mm anchovy larvae (Figure 3). The range of growth rates among the 12 samples collected at 13°- 16.2" C was bounded by the growth rates of anchovy larvae grown in the laboratory at 14° and 17.5° C. Growth was very similar in all but three samples (Bl, CI, C2) al- though the temperatures associated with these nine samples spanned a range of 2.5° C. The growth rate of 8 mm larvae calculated from a Gompertz curve fit to the combined data of the nine similar samples was 0.37 mm day. The mean 09 y 0 9 - / ® 07 - ®X foe E tf 05 cr I I 1 CI 1) ® 0 01 D6 01^03 *oa Al @ 02 -© ® 01 1 > ' 1 1 1 © 1 1 1 1 TEMPERATURE rc) Figure 3. — Relationship between growth rate imillimeters/day at 8 mm) and temperature for northern anchovy larvae from the field (bare symbolsl and in the laboratory i circled symbols I. Field samples, this study, A1-D6; composite of nine field samples, Bl, CI, and C2 not included. iJ; Hunter 1976, laboratory-reared prey. H; Kramer and Zweifel 1970, wild plankton for food, K; Lasker et al, 1970, dinoflagellates only, LD, dinoflagellates plus veliger, LV; Sakagawa and Kimura 1976, S; unpubl. data avail- able at Southwest Fisheries Center, low temperature experi- ment, E, periodic starvation experiment, F. Curve was derived from the model of Zweifel and Hunter (see text footnote 21; it was not fit to the growth rate data presented here. temperature of these nine samples (weighted by number of larvae) was 15.04' C. The model of Zweifel and Hunter (see footnote 2) predicts that 8 mm larvae reared at 15° C would grow at 0.395 mm/day. 418 METHOT and KRAMER GROWTH OF NORTHERN ANCHOVY LARVAE Standard deviation of log,, (size) at age. calcu- lated from the set of combined data, ranged from 0.045 at 4 increments to 0.144 at 19 increments with a mean of 0.0904. The standard error of re- gression (standard deviation of residuals) of the Gompertz curves fit to the data (Table 2) were similar to these estimates of standard deviation of size at age. Any difference in growth rate between these samples, small scale environmental hetero- geneity integrated by our nets, or random error in the aging of the larvae causes the standard error of regression to overestimate variability in the growth process. Over the same age range in a laboratory experiment (Hunter 1976), standard deviation ranged from 0.064 to 0.15.3 with a mean of 0.115. EVALUATION OF POTENTIAL BIASES The conditions under which larvae are reared and growth is measured in the laboratory may differ sufficiently from conditions in the sea to bias the comparison of growth in the sea with growth in the laboratory. In the laboratory, growth is esti- mated from a time series of samples from a cohort. The exact age of each larva is known; temperature rarely varies >1°C: prey concentration is rather constant; and mortality is low (about S'/r/day in Hunter 1976) and except for cannibalistic species, not influenced by size-selective predation. Growth of sea-caught larvae is estimated from one sample containing larvae of several ages. The age of each is estimated from the number of daily growth in- crements in its otoliths, the environmental condi- tions are measured only when the sample is taken, mortality is over lO'^f/day (Smith and Lasker 1978 ) and probably size selective, and large larvae avoid the net disproportionately. Age Determination Anchovy larvae deprived of food at the normal time of first feeding may delay deposition of daily growth increments until food is provided and growth resumes (Theilacker-^), but if larvae are still about 4.2 mm when the first increment ap- pears, estimates of the growth rate of larger larvae will be unaffected. Taubert and Coble ( 1977 ) found that increment formation in late larval and juvenile centrarchids stopped if growth was ^G. H. Theilacker, Southwest Fisheries Center La Jolla Laboratory, NMFS, NOAA, P.O. Box 271. La Jolla, CA 920.38, pers. commun. June 1978. slowed sufficiently by low temperature. We examined the otoliths of some anchovy larvae whose growth was drastically retarded by a reduc- tion in rations (Methot unpubl. data) (F in Figure 3 ). The slowest growing of these larvae had fewer increments than expected, so increment formation can stop before the point of no return is reached. However, if we use number of increments rather than known age to estimate growth rate of these laboratory-reared larvae, the resulting overesti- mated growth rate is still slower than that ob- served in any field samples used in this study. We conclude that the sea-caught larvae were growing fast enough to deposit a growth increment every day. Temperature Determination Anchovy larvae usually remain above the thermocline ( Ahlstrom 1959). so surface tempera- ture probably accurately represents the tempera- ture they experience. Growth was slower than ex- pected in March 1976. but it is unlikely that the surface temperature overestimated the tempera- ture experienced by the larvae because these sam- ples were all collected shallower than 10 m (Table 1). Positive deviations in growth rate, equivalent to a temperature change of up to 3° C, were ob- served in March 1977, but additional temperature data collected at that time indicate that the mea- sured surface temperature accurately represented the temperature experienced by the larvae throughout their lifetimes. The relative surface temperature field determined from satellite ob- servations of infrared radiation (Bernstein et al. 1977 ). taken just before and after this 2-wk cruise, was entirely consistent with the temperature field measured during the cruise; there was no cooling trend. The resolution of the satellite observations was insufficient to distinguish details of the eddy structure in the region of samples CI and C2, but here the greater intensity of surface temperature determinations allowed contouring of isotherms for the first 4 days of the cruise and the next 5 days (Figure 4). Samples CI and C2 were taken within persistent water masses of about 10 km width, not in regions with steep horizontal gradients in tem- perature. Because of the shallow thermocline in this region ( ■- 5 m at some stations), we may have overestimated the temperature experienced by the larvae but this would cause a negative devia- tion from the model, not the observed positive de- viations. 419 FISHERY BI'1J,ETIN VOL 77, NO II8°W MARCH 17-20,^977 10 km Figure 4. — Surface isotherms in de- grees Celsius between Los Angeles and Santa Catalma Island, Calif., in March 1977, Selective Mortality If mortality rate is a function of size, then growth rates determined from size at age data will provide a biased estimate of the true growth rate of the survivors which are sampled iRicker 1969). The effect of size selective mortality on our esti- mates of growth is difficult to assess. Few sets of data are extensive enough to even consider the question of ontogenetic changes in mortality rate of larval fish. All available estimates are based upon sized but not aged specimens. They depend upon an assumed growth curve (Farris 1960) and are susceptible to bias by size selective avoidance of the sampler. Smith ( 1973) found a difference in mortality rate between sardine eggs and young sardine larvae, but mortality in plaice was essen- tially constant through the egg and larval stages (Bannister et al. 1974), Laboratory experiments show that older, more active yolk-sac anchovy lar- vae are less susceptible than newly hatched larvae to some invertebrate predators (Lillelund and Lasker 1971; Theilacker and Lasker 1974). As a rough estimate of the magnitude of the maximum effect of size selective mortality on our growth estimates, we examined the interaction between variable growth and size selective mortality and determined the effect of this mortality on mean size of anchovy larvae at 25 days after yolk absorp- tion. 420 METHOT and KRAMER GROWTH OF NORTHERN ANCHOVY LARVAE Suppose variation in growth is such that indi- viduals of age 25 days range in size from 11.4 to 16.6 mm and that the exponential growth rate parameter which gives rise to this variation has an uniform statistical distribution. If mortality during this 25-day period is random with respect to size, the mean size of individuals which survive to age 25 days will be 13.86 mm. However, if the instantaneous daily mortality rate is related to size by Af = 3.5L " (this is consistent with current estimates of egg, young larvae, and adult mortal- ity rates for anchovy (MacCall 1974; Smith and Lasker 1978)), the mean size of individuals which survive to age 25 days will increase only slightly to 14.08 mm. We conclude that an overestimate of growth because of size selective mortality is un- likely to occur. Another possibility is that mortality is related to growth rate rather than size, the mortal fraction being that portion of the population which is slow growing and weak and therefore more susceptible to predators (Isaacs 1964). If we make the extreme assumption that the daily mortal fraction is the slowest growing lO^f ofthe cohort, the survivors at age 25 days will be the fastest growing !"< ofthe original cohort, but this extreme model unrealisti- cally predicts that variations in size at age would decline as the slow growing larvae die. Some in- termediate degree of growth rate selective mortal- ity could affect estimates of growth rate in the sea, especially if mean growth rate is slow and the slower growing individuals are near starvation. Net Avoidance Avoidance ofthe ring net by anchovy larvae in daylight begins at a length of about 5 mm and increases with size iLenarz 1973; Murphy and Clutter 1972). The Bongo net catches larvae more effectively but avoidance still occurs in the larger size classes. The degree to which we underesti- mated mean size at age depends upon how rapidly avoidance increases with increasing size. We at- tempted to minimize this bias by only considering larvae with fewer than 25 increments ( lengths less than about 15 mm) and samples taken at twilight or dark. There was no difference in size at age between the twilight samples (Dl. D5) and the night samples (D2-D4) along the transect. Al- though fast growth was observed only in samples taken with the Bongo or neuston net (Bl, CI, C2), we do not believe this was an artifact caused by size-selective avoidance of the ring net. If this were an artifact, then ranges in size at age in samples taken by the less selective gear would have been broader and overlapped the distribution of size at age in samples taken with gear which allowed larger larvae to escape. This was not ob- served. DISCUSSION Growth rates of larval northern anchovy < 1 mo old were determined with size at age data. In 9 of 12 samples, growth rates at 8 mm were very simi- lar, ranging from 0.34 to 0.40 mm/day. The growth rate estimated from the combined data of these samples was 0.37 mm/day. Growth in the three other samples was faster. 0.47-0.55 mm/day. Var- iation in size at age between individuals was small. A typical 95% confidence interval for larvae with 12 daily growth increments was 6.5-9.5 mm. When the trend of growth rate on temperature, obtained from several rearing experiments, was compared with the field results (Figure 3) it was obvious that growth in the sea was similar to growth in the laboratory. The range in growth rate between field samples at the same temperature was similar to the range in growth rate between laboratory rearing experiments conducted at the same temperature (Kramer and Zweifel 1970). Variation of size at age was also similar in the sea and the laboratory. In no case were sea-caught larvae growing as slowly as larvae reared in the laboratory on inadequate rations (LV, LD, F in Figure 3). At 17.5° C (Lasker etal. 1970) anchovy leirvae fed only a dinoflagellate grew at about 0. 15 mm/day (LD) and larvae fed dinoflagellate and veligers ( LV) grew still slower than larvae fed wild plankton (K) (Kramer and Zweifel 1970). Al- though the availability of suitable prey may limit the feeding success rate of first feeding anchovy larvae (Lasker 1975), larvae which get enough food to survive apparently get enough food to grow rapidly. There was no obvious relationship between growth rate and temperature. This is not surpris- ing considering the narrow temperature range considered, the variation in growth rate between laboratory experiments at the same temperature, and the uncertainty in our measurement of the temperature experienced by the larvae in the sea. The samples we examined came from near the center of distribution of northern anchovy larvae with respect to space, time, and temperature. As samples from the periphery of this species range 421 FISHERY BULLETIN: VOL. 77, NO. 2 become available, we expect to find increased var- iation in growth rate. Correlations between the spatial-temperature pattern of variation in growth rate and environ- mental parameters may provide clues to the events which control larval survival. This analy- sis will require that the measured growth rates reflect the larvae's response to the environmental factors measured at the time the sample was col- lected. We estimated the growth rate of larvae in a sample by determining the relationship between size (L) and age [T). This technique is susceptible to several biases discussed above and is not sensi- tive to changes in growth conditions occurring a few days before the sample is taken. If the instan- taneous growth rate of each individual could be measured, then the same growth rate parameters could be estimated from the relationship between ilLldT and L. This alternative method would reflect growth conditions at the time of sampling and would be independent of changes in growth conditions during the lifetime of the older larvae in the sample. Ottaway and Simkiss (1977) de- veloped a relative measure of the instantaneous growth rate of adult fish using the in vitro rate of incorporation of '•'C labelled glycine into scales, but this technique may not be adaptable to larval fish. Another approach is to correlate the width of a daily growth increment with the growth of the fish on that day. A measurement of the width of the outer increments could provide an absolute measure of growth rate during the few days before capture. In addition, the radius of each increment in an individual's otoliths could be used to back calcu- late its growth history (Ricker 1969). The differ- ence between the back calculated growth histories of older individuals, the survivors captured with nonselective gear, and the distribution of size at age of all younger individuals supplies informa- tion on differential mortality and size dependent net avoidance by the larvae. Ultimately, analysis of daily growth increments in the otoliths of larval fish may provide a means of determining whether larval survival is limited primarily by predation or food and how these two factors interact. ACKNOWLEDGMENTS David Kramer passed away in December 1977 during the early stages of this paper's preparation. The personnel at the Southwest Fisheries Center are indebted to him for his contributions to the CalCOFI program, in particular for his early work on the taxonomy and rearing of larval fish and for his devotion to this project on the aging of larval fish. We will miss him. He was a friend and a model to many of us. I want to thank Ken Plummer for his assistance in the preparation of many of the otoliths used in this study. Special thanks are due John Hunter for his helpful comments on early versions of this manuscript. LITERATURE CITED AHLSTROM. E. H. 1959. Vertical distribution of pelagic fish eggs and larvae off California and Baja California. U.S. Fish Wildl. 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Growth rate and body composition of fingerling sockeye salmon, Oncorhynchus nerka. in relation to temperature and ration size. J. Fish Res. Board Can. 26:2363-2394. Brothers. E. B., C. p. M.^^thews. and R. Lasker. 1976. Daily growth increments in otoliths from larval and adult fishes. Fish. Bull., U.S. 74:1-8. CONWAY, G. R., N. R. GLASS, AND J. C. WlLCOX. 1970. Fitting nonlinear models to biological data by Mar- quardt's algorithm. Ecology 51:503-507. Gushing, D. H., and J. G. K. Harris. 1973. Stock and recruitment and the problem of density dependence. Rapp. P.-V. Reun. Cons Int Explor. Mer 164:142-155. DEGENS, E. T., W. G. DEUSER, AND R. L. HAEDRICH. 1969 Molecular structure and composition of fish oto- liths. Mar. Biol. (Berl. I 2:105-113. Farris, D. a. 1960. The effect of three different types of growth curves on estimates of larval fish survival J. Cons. 25:294-306. HOUDE. E. D. 1975. Effects of stocking density and food density on survi- val, growth and yield of laboratory-reared larvae of sea 422 METHOT and KRAMER GROWTH OF NORTHERN ANCHOVY L.'^RVAE bream, Archosargus rhomboidalis iL.I (Sparidael. J. Fish. Biol. 7;115-127. 1977. Abundance and potential yield of the round herring. Etrumeus teres, and aspects of its early life history in the eastern Gulf of Mexico. Fish. Bull., U.S. 75:61-90. HUNTER, J. R. 1976. Culture and growth of northern anchovy, Eiigraulis mordax. larvae. Fish. Bull., U.S. 74:81-88. Isaacs, J. D. 1964. Night-caught and day-caught larvae of the Califor- nia sardine. Science iWash.. D.C.i 144:1132-11.33. JONES. R. 1973. Density de[)endent regulation of the numbers of cod and haddock. Rapp. P.-V. Reun. Cons. Int. Explor, Mer 164:156-173. KRA.MER, D., AND J. R. ZWEIFEL. 1970. Growth of anchovy larvae {EngrauHs mordax GirardI in the laboratory as inflenced by tempera- ture. Calif Coop. Oceanic Fish. Invest. Rep 14:84-87. LASKER, R. 1975. Field criteria for survival of anchovy larvae: The relation between inshore chlorophyll maximum layers and successful first feeding. Fish. Bull, U.S. 73:453-462. LASKER, R., H. M. FEDER, G. H. THEILACKER, AND R. C. MAY. 1970. Feeding, growth, and survival of Erigraulis mordax larvae reared in the laboratory. Mar. Biol. iBerl.l 5:34.5- 353. LENARZ, W. H. 1973. Dependence of catch rates on size of fish larvae. Rapp. P.-V. Reun. Cons. Int. Explor. Mer 164:270-275. LILLELUND, K., AND R. LASKER. 1971. Laboratory studies of predation by marine copepods on fish larvae. Fish. Bull., U.S. 69:655-667. MacCall. a. 1974. The mortality rate ofEngrauhs mordax in southern California. Calif Coop. Oceanic Fish. Invest. Rep 17:131-135. May. R. C. 1974. Larval mortality in marine fishes and the critical period concept. In J. H.S. Blaxter{ editor). The early life history offish, p. 3-19. Springer- Verlag. Berl. MUGIYA. Y. 1974. Calcium-45 behavior at the level of the otolithic organs of rainbow trout. Bull. Jpn. Soc. Sci. Fish 40:457-463. 1977. Effect of acetazolamide on the otolith growth of goldfish. Bull. Jpn. Soc. Sci. Fish. 43:1053-1058. MURPHY. G. I., AND R. I. CLUTTER. 1972. Sampling anchovy larvae with a plankton purse seine. Fish. Bull.. U.S. 70:789-798. Neville, a. C. 1967. Daily growth layers in animals and plants. Biol Rev. (Camb.l 42:421-441. O'CONNELL. C. P.. AND L. P. RAYMOND. 1970. The effect of food density on survival and growth of early post yolk-sac larvae of the northern anchovy iEn- graulis mordax Girard) in the laboratory. J. Exp Mar. Biol. Ecol. 5:187-197. OTTAW.^Y. E. M.. AND K. SlMKlSS, 1977. "Instantaneous" growth ratesof fish scales and their use in studies offish populations. J. Zool. iLond.) 181:407-419. PANNELLA. G. 1971. Fish otoliths: daily growth layers and periodical pat- terns. Science (Wash.. D.C.) 173:1124-1127. RICHER. W. E. 1969. Effects of size-selective mortality and sampling bias on estimates of growth, mortality, production, and yield. J. Fish. Res. Board Can. 26:479-541. RILEY, J D. 1966. Marine fish culture in Britain. VII. Plaice iPleuro- nectea platessa L. i post-larval feeding on A rfcmiasa/ina L. nauplii and the effects of varying feeding levels. J. Cons. 30:204-221. SAKAGAWA, G. T.. and M. KIMI'RA. 1976. Growth of laboratory-reared northern anchovy. En- graulis mordax, from southern California. Fish. Bull.. U.S. 74:271-279. SIMKISS. K. 1974. Calcium metabolism of fish in relation to ageing. In T. B. Bagenal (editor), Ageing offish, p. 1-12. Unwin Bros. Ltd.. Old Woking Surrey. SMITH. P. E. 1972. The increase in spawning biomass of northern an- chovy. Engraulis mordax. Fish. Bull. U.S. 70:849-874. 1973. The mortality and dispersal of sardine eggs and lar- vae. Rapp. P.-V. Reun. Cons. Int. Explor. Mer 164:282- 292. SMITH. P. E., AND R. LASKER. 1978. Positionof larval fish in an ecosystem. Rapp P.-V. Reun. Cons. Int. Explor. Mer 173:77-84. STRUHSAKER, p., and J. H. UCHIYA.\U. 1976. Age and growth o{ the nehu. Stolephorus purpureas (Pisces: Engraulidae), from the Hawaiian Islands as indi- cated by daily growth increments of sagittae. Fish. Bull, U.S. 74:9-17. T.ate, M. W., and R. C. Clelland. 1957. Nonparametric and shortcut statistics in the social, biological, and medical sciences. Interstate Printers and Publishers. Inc., Danville, III, 171 p. Taubert, B. D., and D. W. Coble. 1977. Daily rings in otoliths of three species of Lepomis and Tilapia mossamhica. J. Fish. Res. Board Can. 34:332-340. THEILACKER, G, H., AND R. LASKER. 1974. Laboratory studies of predation by euphausiid shrimps on fish larvae In J H. S. Blaxter (editor). The early life history of fish, p. 287-299. Springer-Verlag., Berl. ZWEIFEL, J. R., AND R. LASKER. 1976. Prehatch and posthatch growth of fishes— a general model. Fish. Bull, U.S. 74:609-621. 423 A LINEAR PROGRAMMING APPROACH TO DETERMINING HARVESTING CAPACITY: A MULTIPLE SPECIES FISHERY Robert A. Siegel," Joseph J. Mi'Ki.i.er,^ and Brian J. Rothschild^ ABSTRACT The U.S. Fishery Conservation and Management Act of 1976 (P.L. 94-265) requires that fishery management plans specify the capacity of a fishing fleet. However, the Act does not provide a definition of capacity. This paper considers .some of the problems of defining and measuring capacity in the harvesting sector of the fishing industry and suggests an estimation procedure A linear programming model is used to estimate the economic capacity of a fishing fleet. The model provides estimates of the expected output in a multiple species fishery. Measurement of capacity in the U.S. fishing in- dustry has become of increasing importance as a result of the passage of the Fishery Conservation and Management Act of 1 976 (FCMA). The FCMA requires (Section 303 (a) (4i (A)) fishery manage- ment plans prepared by Regional Fishery Man- agement Councils or the Secretary of Commerce to; "assess and specify . . . the capacity and the extent to which fishing vessels of the United States, on an annual basis, will harvest the op- timum yield . . . ." The FCMA, however, does not provide a func- tional definition of capacity that can be used in the preparation of fishery management plans. This raises operational difficulties since "capacity" can be based on economic or physical concepts. For example, physical capacity can be measured in terms of the hold space of a fishing vessel, al- though this generally exceeds the catch. An economic measure would simply be past catches (assuming these reflect equilibrium conditions), but this does not necessarily provide an accurate indication of future catches. It is apparent that the hold space or past catches are only "first" approximations to "capacity" and that better indicators are needed in order to have meaningful estimates of the expected catch of the fleet. Since estimates of capacity are of obvious 'National Marine Fisheries Service, Office of Resource Con- servation and Management. Washington, DC 20235. ^National Marine Fisheries Service, Federal Building, 14 Elm Street, Gloucester, MA 01930. 'National Oceanic and Atmospheric Administration, Office of the Administrator, Washington, DC 20230. Manuscript accepted October 1978 FISHERY BULLETIN. VOL. 77, NO. 2, 1979, importance in determining U.S. -foreign alloca- tions, it is essential that the measurements of capacity and expected catch be accurate. Thus, a major effort must be made to develop meaningful estimates of capacity that are consistent and to indicate what these measures are designed to rep- resent. Analysis of the capacity problem must address four issues: 1) development of a definition and measure of capacity, at least initially, relevant to the harvesting sector of the fishing industry: 2) development of appropriate methods of es- timating capacity; 3) estimation of what the fleet will catch under a set of economic and environmental condi- tions (it will be suggested that the expected domestic catch is indeed the appropriate no- tion of "capacity" in the short run); and 4) the time frame for the analysis. This paper will consider some of the problems of measuring capacity in the harvesting sector of the fishing industry and suggest possible estimation procedures. Section I focuses on economic and technical concepts of capacity. Section II presents a linear programming model which can be used to estimate the output of a fishing fleet in a multi- species fishery. Section III contains an example problem which shows the applicability of this model to a multispecies fishery such as the New England otter trawl fleet. Section IV provides a summary of the paper and briefly describes areas of further research. 425 CONCEPT OF CAPACITY: FISHING INDUSTRY General Capacity Characteristics In general, a firm's productive capacity refers to the quantity of output that can be produced during a given time with existing plant and equipment. This definition is characterized by physical and time dimensions. The physical dimension requires that output be specified in terms of a measurable quantity. The time dimension reflects what "can be produced" during the period of operation of the plant. An important aspect of the time dimension centers on the interpretation of "what can be pro- duced." For example, plant and equipment can be u.sed to produce a certain quantity of output if operated continuously 24 h a day, for 7 days a week, assuming no resource input constraints; and another quantity of output if operated 8 h a day, 5 days a week, taking into account the most economical combination of inputs. Because of these characteristics and the variability of output given different economic and environmental con- ditions, there does not appear to be a unique number for capacity. Fishing Fleet Capacit)- Measures Technical Capacity While it may not be possible to define the con- cept of capacity in precise detail, a distinction can be made between technical and economic capacity. A technical interpretation can be formulated in terms of the following question: how much fish can be caught by a given vessel on each trip, utilizing the entire physical hold space and with no con- straints on resource abundance? Capacity in this context is associated with the physical hold space of a fishing vessel. It represents an upper limit on the physical capabilities of the vessel, assuming no input constraints. However, a technical defini- tion of capacity as described above has limited applicability under the FCMA because the capac- ity problem is to determine the amount offish the fleet can be expected to catch during a given time period. In other words, the physical notion relates to "assess the capacity" but does not provide any guidance on the "extent to which" this capacity will be utilized. FISHERY BULLETIN: VOL 77, NO J Economic Capacity of a Fishinj; Fleet Economic theory contains several different con- cepts of capacity. These are briefly described as follows: 1) the output that can be produced at minimum average cost in a competitive model (Klein and Pre,ston 1967); 2) the production flow associated with the input of fully utilized manpower, capital, and labor, and other relevant factors of production (Klein 19601; 3) the maximum sustainable level of output the industry can attain withina very short time if the demand for its product were not a con- straining factor, when the industry is operat- ing its existing stock of capital at its custom- ai-y level of mtensity (Klein and Summers 19661; 41 the greatest level of output that a plant can achieve within the framework of a realistic work pattern (U.S. Bureau of the Census 19761. The first concept has generally been used in theoretical discussions about capacity. The other concepts have been applied in the measurement of capacity in the manufacturing sectors of the economy. In addition, there are several concepts pertaining to agricultural capacity, although none of these have gained universal acceptance (Spiel- mann and Weeks 1975). After reviewing these concepts and taking into account the specific re- quirements of the FCMA, it is nevertheless possi- ble to develop a concept of capacity applicable to the harvesting sector of the fishing industry. Harvesting ( apacitj Under the FCMA The FCMA requires that estimates be made of U.S. harvesting capacity which are clearly short run in nature. This is due to the fact that, in a particular year, total allowable catch constraints are established, and the problem then is to deter- mine the catch of the U.S. fleet under different economic conditions. In the short run, economic capacity is related to the quantity offish that can be caught with a fishing vessel in order to maximize profits or other objectives during a spec- ified period of time. The concept of capacity in this context reflects the behavior of the vessel in the 426 SIEGEL ET AL LINEAR PROGRAMMING APPROACH short run corresponding to the level of output that can be produced as determined by market condi- tions, input prices, technology, vessel hold space, and a normal fishing pattern. In effect, economic capacity, other things being equal, moves with price. If prices rise, capacity or output of those vessels already in the fishery will be expected to increase. If prices drop, it will fall.^ Conversely, if the catch per unit effort increases, and factor costs and output prices remain un- changed, then capacity rises. The important point to note about the economic concept of capacity is that it is not necessarily the full utilization of the hold space of a fishing vessel. If there are changes in cost conditions, market prices, and stock abun- dance, then capacity output will also change. Thus, the technical notion of capacity described what can be produced based on the physical characteristics of a fishing vessel and the fleet. This concept, however, does not incorporate con- straints on output or the quantity of landings be- cause of economic or environmental factors. In contrast, the economic concept of capacity de- scribes what will be produced given technical rela- tionships, factor prices, and product price informa- tion, and it is essentially what is implied in the FCMA regarding the "extent to which the (physi- cal) capacity will be utilized." The definition of fleet capacity used hereafter in this report is as follows: Capacity is the amount of fish that the fleet is expected to harvest during a specified period with the existing stock of capital (vessels and gear) and technology, given catch quotas, processing capabilities, and market condi- tions. Clearly, the expected domestic catch is synonymous with the "extent to which" notion contained in the Act, and both of these are synonymous with the notion of short run economic capacity as defined above. SPECIES ALLOCATION OF CAPACITY USING A LINEAR PROGRAMMING (LP) FRAMEWORK This section outlines an approach that can be used to estimate short-run capacity (output) in a multispecies fishery. The LP Problem for a Multispecies Fishing Fleet A complete generalization of the problem of es- timating the "extent" or the expected catch of the fleet is to determine the allocation of resources (over species, vessel category, fleet capacity, fishing area, and time period) that maximizes a stated objective. The following LP model is based on a model formulated by Mueller.^ The statement of the objective function and the associated constraints of the model are presented below; Maximize Z = S PjjfL„—ll Cij,Ljj, (1) or Z = S L,j, (Pjjt—Ciji) i.J.I where Z = net revenue received at the harvest- ing level L,„ = pounds of species; in area / landed in a directed fishery for that species during period / P , = revenue realized per pound of species / landed in a directed fishery for species ; in area j during period t (includes value of bycatch) C,,, = cost associated with catching a pound of species ; (and its associated bycatch ) in area j during period t in a directed fishery for species (. Equation (1 ) is the objective function to be maximized. It shows the number of pounds of each species that should be caught in a directed U.S. fishery in each area during a particular time period in order to maximize net revenues. These net revenues include the value of the target species and the associated bycatch. In this LP problem formulation, the price per pound landed and cost per pound landed are invariant with the quantity of output.*^ However, these can be al- lowed to vary. ■•This assumes that there is no entry or exit in a fishery during a given fishing season. If prices rise, vessels may shift from other fishenes; but it is not clear whether the shift will occur in the current or following season. ■■^Mueller, J. J. 1976. A linear programming discussion model for maximizing the net revenues from a multiple species fishery. Unpubl. manuscr., 13 p. National Marine Fisheries Ser- vice. Federal Building. 14 Elm Street, Gloucester. MA 01930. 'An alternative formulation of the objective function could involve substitution of a demand function for a given price in each time period. In addition, instead of the assumption of a constant average cost per pound of fish landed, costs could be allowed to vary with the quantity offish landed and with the 427 Total Allowable Catch Constraint Presumably there will be a year's total allow- able catch (TAG) set for each species for each area. However, because of the bycatch problem, if the number of pounds of each species taken in a di- rected fishery equaled the TAG for each species, then all of the TAC's would be exceeded. To deal with this problem the following constraint is for- mulated: ^ A I ■^ "^ mijl '-'ijl (2) where A, number of pounds of species m caught per pound of species ; in a directed fishery for species ; in area / during period t. It is as- sumed that these A„„y, are the same for all vessel categories. TAG for species m in areaj for all periods. . Processing Capacity Generally there exists an upper bound on the total amount of species processing capacity avail- able during a particular ti me period. To reflect this situation the following constraint was formulated: S b„ L„ B, (3) where b,, B, - the number of pounds of processing capacity required when a pound of species ( is caught in a directed fishery for species i in areaj during period t = the number of pounds of processing capacity available during period /. Harvesting Capacity The final restriction used in this model is a phys- ical upper limit on the amount offish that can be caught by the fleet in a particular time period or season. To address this problem, the following constraint was formulated: fishing area. If these changes were incorporated into the LP model, they would certainly make the problem more realistic However, the purpose of this was to initially formulate a simple problem and then to develop more complex models m future research. A drawback to this assumption of a given price in each time period js that the quantity landed would be expected to influence pnce. At the time of this analysis, appropriate demand functions had not been estimated. FISHERY BULLETIN: VOL 77. NO. 2 (4) S d,„ L,_„ ^ FC„ where rf,„ = the number of units of physical harvesting capacity required when a pound of species ; is caught in a directed fishery for species / in area j during period t. FCi, = the total number of pounds of fish that a fleet consisting of a specified number of vessels (given technol- ogy and gear) is physically capable of catching in area / during a par- ticular time period t . AN APPLICATION TO THE NEW ENGLAND OTTER TRAWL FLEET New England Otter Trawl Fisher>' The fishery to be studied is the otter trawl fishery in New England. The output consists of landings by vessels using otter trawls in Maine, Massachusetts, and Rhode Island during the 1955-74 period (Table 1). In the late 1950's land- ings in this fishery averaged more than 304,000 metric tons (t). However, by 1972 landings had declined sharply to about 126.8 thousand t. The catch per gross registered ton (CGRT) reached a maximum value of 9.03 t in 1957 (Table 2 1. The total associated catch in 1957 also peaked at 3 18.5 thousand t. By 1973 both GGRT and land- ings sharply declined to 3.45 t and 127.4 thousand t, respectively. This decrease can be generally at- tributed to a lower stock abundance of target T.^BLE 1 . — Landings (metric tonsi of fish by otter trawl vessels in Maine, Massachusetts, and Rhode Island. (Sources: U.S. De- partment of Commerce 1971-77, US. Fish and Wildlife Service 1957-69.) Year Maine Massachusetts Rhode Island Total 1955 51.341 208.495 39,470 299,306 1956 49,920 207,514 53,281 310,715 1957 44,200 224,436 49.827 318,463 1958 49.525 213,007 42.066 304,598 1959 50,769 198,544 40,846 290,159 1960 46,438 179,805 15.417 241,660 1961 46,094 180,201 23.151 249,446 1962 43,473 190,430 26,550 260.453 1963 40,454 184,294 25.837 250,585 1964 42.167 180,006 11.090 233,263 1965 42,788 177.877 15.435 236,100 1966 45.634 162,307 25.361 233.302 1967 41.716 136,194 29.648 207,558 1968 42,709 127,465 27.494 197,668 1969 34,774 105,859 35.644 176,277 1970 31,872 103,152 26.288 161,312 1971 29.154 96.984 24.838 150,976 1972 24,485 79.457 22,954 126,896 1973 22,049 77,309 28.044 127,402 1974 17,766 72,263 27.051 117.080 428 SIEGEL ET AL LINEAR PROGRAMMING APPROACH Table 2. — Estimates of potential output (capacity) based on prices, costs, and stock abundance. Gross registered tons (GRT) Catch per gross Potential capacity (t) Abundance index Potential capacity (t) Year registered ton (t) 1957 abundance (Clark and Brown 1977) adjusted for abundance 1955 37,472 6.93 338.820 1 000 338.820 1956 36,362 8.42 323.335 1 000 323.335 1957 35,269 9.03 318.463 1 000 318.463 1958 35,192 8.66 317.762 1,000 317.762 1959 34.786 8.34 314.099 1 000 314.099 1960 39,280 6.15 354.469 1,000 354,469 1961 36.833 6.77 332.571 1 000 332,571 1962 38,677 6.73 349.226 1 000 349,266 1963 38,839 6.4S 350.691 1 000 350,691 1964 39,155 5.96 353.557 1 000 353,557 1965 39,256 6.01 354.503 0 3639 128,984 1966 42,216 5.53 381.212 0,7315 278,848 1967 42,237 4.91 381.316 1 0561 402,787 1968 37,698 5.24 340,217 0.8741 297,548 1969 40,629 4.38 363.456 0 5761 211,353 1970 40,093 4.02 361 .734 0 7011 253,818 1971 39,452 3.83 356.071 0,3844 136,936 1972 39.383 3.43 333.933 03739 132.957 1973 36.918 3.45 333.512 0,4923 164.116 1974 39,016 3.00 352.283 0,3693 130.098 '1975 38,972 3.54 351.901 02693 94.767 '1976 38.972 3.54 351.901 0.4041 142.203 'Based on 1970-74 average species in the otter trawl fishery resulting from the entry of foreign effort in these fisheries in the late 1950's and early 1960's. The LP model formulated in the previous sec- tion required data on species, prices, harvesting costs, bycatch ratios, and physical capacity esti- mates for both the harvesting and processing sec- tors. Data are generally available for these items except for harvesting costs. In the absence of har- vesting cost data, the objective function in the model was specified to only maximize gross rev- enues. Because of this, the solution variables would probably be overestimates of actual ex- pected catches. In this report the method of incorporating cost factors is to deflate the peak CGRT by an index of relative species abundance (Clark and Brown 1977). The index of stock abundance is being used to adjust the expected level of catch for changes in cost conditions for the 1955-77 period. Since the level of catch is, among other factors, a function of abundance, any declines m abundancfe would be expected to result in a lower level of catch (other things being equal). Reductions in abundance, therefore, would be expected to result in declining CGRT and increased costs per unit of output. A more realistic measure of factor productivity would be catch per unit of effort; this information is not available. Data in Table 2 indicate that GRT has not changed significantly since 1955 for this otter trawl fishery. The assumption was made that the number of days fished per GRT has not changed.' The year 1957 was chosen as the base year because CGRT reached a maximum value and stock abun- dance was probably relatively high. Table 2 also shows an index of stock abundance for the Interna- tional Commission for the Northwest Atlantic Fisheries (ICNAF) designated subarea 5 and statistical area 6 for finfishes and squids. In order to devel op a measure of expected output relative to 1957, it is noted that catch in sub- sequent years will vary as a function of fishing effort and stock abundance. If the catchability coefficient relative to GRT can be assumed to be the same, at least as a first approximation for each year, then the catch in any year is: II ^0 where T, is the GRT in the iih year, and T„ and €„ are, respectively, the GRT and catch for the year 1957." Furthermore, it is assumed that catch would depend on the abundance of the stock and, therefore, the catch in any vear should be modified by: where A, denotes the abundance in the ;th year and A„ the abundance in the base year (1957). Thus, an estimate of expected output relative to the base year is: ^Data are not available to verify this assumption. ^Using this approach, it is necessary to choose a base year. Asa result, physical capacity and economic capacitv were identical for 1957. 429 Ti A; TfrX-T-XCQ An underlying feature of this simple index (A, /A,,) is that while catches should rise and fall with effort (T/s), they should also increase and decrease with abundance. Consequently, abundance is a factor influencing output or capacity when the other inputs, except for effort (GRTi, are fixed. Example Problem An example problem is presented below utiliz- ing the model formulations in the previous sec- tion. In this problem it is assumed that there are: 1)11 species, 2) 1 vessel category (all otter trawl- ers), 3) 1 time period (1 yr), and 4) 1 area. The objective of the problem is to maximize the gross revenues to the otter trawl fleet assuming the 1977 catch restrictions, the most recent bycatch ratios, and an estimated U.S. deflated harvesting capacity as developed in the previous section." The species that were used and their associated bycatch ratios are in Table 3. The interpretation of the entries in the table is as follows: when a pound of cod is sought in a directed fishery for cod, 1 lb of cod, 0.0.59 lb of haddock, 0.012 lb of redfish, etc., are caught.'" The total pounds caught when seek- ^For the purpose of this problem, gross revenues were used in the objective function since the separable costs of catching these species has not yet been determined. The costs of traveling to and from the fishing grounds should also be included in the objective, but these are not available at present. "The bycatch ratios used in the LP problem were not con- verted from pounds to metric tons. The basic data for the compu- tations in the LP problem were specified in pounds. FISHERY BULLETIN: VOL. 77. NO 2 ing to catch a pound of cod in a directed fishery for cod is 1.344. Table 4 presents the total gross revenue realized for each species when attempting to catch that species in a directed fishery. For example, when attempting to catch a pound of cod in a directed fishery, the total of 1.344 lb offish actually caught is worth a total of 35.2 cents and includes the value of the cod and the value of the bycatch. Table 5 presents the amount of processing capacity re- quired per pound of each species caught in a di- rected fishery and includes the bycatch require- ment. Cod, haddock, and pollock are the only species of those listed that are landed drawn and a loss of 15% by weight is assumed. A total pro- cessing capacity of 500 million pounds (226,796 t) was assumed. Estimates i)f Landings Adjusted for Abundance Estimates of adjusted landings (incorporating cost factors) were made (Table 2) using the ap- Table 4. — Gross revenue per pound in a directed fishery. (Source: U.S. Department of Commerce 1976.) Total revenue per pound caught in a directed fishery (includes value o( bycatch) Species (c'lb) Atlantic cod Haddock Redlish Silver hake Red hake Pollock Yellowtail flounder Other flounders Other finfish Atlantic mackerel Squid 35.2 52.7 16.G 16.2 20.3 22.6 46.4 55.6 28.7 13.3 10.0 T.^BLE 3.- -United States otter trawl bycatch ratios in 1974 for ICNAF areas. (Source: Northeast Fisheries Center. National Marine Fisheries Service, NOAA. Woods Hole, Mass.) Species caught (pounds) Species Atlantic Sliver Red Yellowtail Other Other Atlantic sought cod Haddock Redfish hake hake Pollock flounder flounder finfish mackerel Squid Total Atlantic cod 10 0,059 0012 0002 0 0 07 0 041 0 108 0 052 0 0 1,344 Haddock 0214 too 0 022 0 027 0 0 027 0 038 0049 0 0 0 1377 Redtish 0 04 0-011 10 0 002 0 0059 0 0 001 0 046 0 0 1.159 Silver hake 0 051 0 003 0 004 1 0 0 081 0 005 0 061 0 073 0 106 0 009 0 04 1,433 Red hake 0 021 0 0 0496 10 0 0 054 0 082 0 350 0 001 0 098 2 112 Pollock 0213 0 032 0 035 0 009 0 022 10 0 003 0 003 0 073 0 001 0085 1 476 Yellovirtail flounder 0 101 0015 0 0 001 0 0 003 1 00 0 058 0 004 0 0 004 1 186 Other flounders 0 266 0 036 0 0 054 0 005 0 007 0 296 10 0 170 0002 0 112 1 948 Other finfish 0 313 0 078 0 06 0 152 0 048 0 153 0 07 0 124 10 0019 0 046 2.063 Atlantic mackerel 0 009 0 0 0024 0 0012 0 0 0.042 10 0051 1 138 Squid 0 0 0 0 0 0 0 0 001 0002 0 1.0 1,003 430 SIEGEL ET M LINEAR PROGRAMMING APPROACH Table 5. — Processing requirements per pound of each species in a directed fishery. iSource; National Marine Fisheries Service, Statistics Branch, Gloucester, MA 01930.1 Species Processing requirement Atlantic cod Haddock Redfish Silver hake Red hake Pollock Yellowtail flounder Other flounders Other finflsh Mackerel Squid 1 1745 1 19085 1 1425 1 42415 2 10885 1 2895 1 1911 1 8935 1 98135 1 3485 1 003 The estimate of 142,000 t for 1976 also could be modified to take into consideration the changes in technology of the fleet. The changes include, among others, the utilization of stern trawlers. pair trawls, improved loran, and increase in horsepower. It is assumed for this example that these changes account for an estimated 5,000 t of additional harvesting capacity under current conditions of abundance. Table 6 shows the simplex tableau for the LP calculations for the base model. proach outlined in the previous section." In 1976, for example, the deflated estimate of landings was 142,000 t under current conditions of abundance. Another way of explaining this figure is as follows: if we assume that the relationship between aggre- gate production prices and aggregate factor costs have been unchanged since 1957, then we would expect that 142,000 1 offish would be landed by the otter trawl fleet (given the current level of abun- dance). It should be noted that in 1965 and 1971 the actual catch was larger than the estimated potential catch adjusted for abundance. These dis- crepancies could be due to reasons such as in- creased fishing intensity or possibly large sam- pling errors given the stochastic nature of the stocks. Estimates of undeflated catch are also provided in Table 2. These indicate what could be caught if 1957 productivity conditions prevailed. However, these estimates are not particularly meaningful since they do not reflect changes in stock abun- dance and cost conditions. "Data on catch per gross registered ton were not available for 1975-76. The estimates of deflated capacity m 1976 for this example were based on 1973 data on catch per GRT and the 1976 index of abundance ( A, 'A o'- It is interesting to note that the 1974 forecast was within 5^V of the actual 1974 catch bv otter trawls. RESULTS The base model computations are presented in Table 7. Column 2 (Directed catch) shows the catches of each of the species in the directed fisheries. Column 3 (Bycatch) presents the resul- tant incidental catches of each of the species that are implied by the directed catches in column 2. The total gross revenues that would accrue to the otter trawl fleet by employing this fishing strategy, as predicated on the optimal LP solution, would be $68.5 million. This is the maximum gross revenue that the fleet could obtain given the as- sumptions of the LP model. In other words, there is no other fishing strategy (allocation of harvesting capacity) that would result in a larger level of gross revenues. The FCMA requires that foreign fishing be al- lowed on those stocks for which surpluses have been identified. This LP model can be used to esti- mate foreign surpluses. Column 4 (Total catch) presents the estimated total U.S. catches of each of the species. Column 5 (Quota) indicates the rec- ommended quotas for 1977. Column 6 (Estimated surplus) shows the resultant surplus or the excess of each species quota over the probable U.S. catch of the particular species as identified by the model. Table 6. — Basic computational form or simplex tableau for LP calculations. Decision van ables XI X2 X3 X4 X5 X6 X7 X8 X9 X10 X11 Constraints 1 0 0214 0 04 0 051 0021 0213 0 101 0 266 0313 0 009 0 55,125,000 0 059 10 0 011 0 003 00 0 032 0015 0 036 0 078 0 0 13,230,000 0012 0 022 1 0 0 004 0 0 035 0 0 0 060 0 0 19,845,000 0 022 0 027 0 002 1 0 0 496 0 009 0 001 0 054 0 152 0 024 00 264,600,000 0 0 0 0 081 1 0 0 022 0 0 005 0 048 0 0 97,020.000 0 070 0 027 0059 0 005 0 1 0 0 003 0007 0 153 0012 0 66,150,000 0 041 0 038 0 0 061 0 054 0 003 1 0 0 296 0 07 0 0 30,870,000 0 108 0 049 0 001 0 073 0 082 0 003 0 058 to 0 124 0 0 001 44,100.000 0 052 0 0 046 0 106 0 360 0 073 0 004 0 170 1 0 0 042 0 002 269.000.000 0 0 0 0 009 0 001 0 001 0 0 002 0019 1 0 0 165,375,000 0 0 0 0 040 0 098 0 085 0 004 0 112 0 046 0 051 1 0 174,195,000 1 344 1 377 1 159 1 433 2 112 1 476 1 186 1 948 2 063 1 138 1003 325,000,000 1 1745 1 19085 1 1425 1.42415 2 10885 1 2895 1 1687 1 8935 1 98135 1 150 1 003 500,000,000 0352 0 527 0.166 0 162 0.203 0,226 0464 0,556 0287 0 133 0,1004 Objective function 431 FISHERY BULLETIN: VOL 77. NO Table 7. — Results of the base mode! showing estimated U.S. catches and surpluses in the otter trawl fisheries in ICNAF Areas 5 and 6. Harvesting capacity - 325 million pounds (147.565 tl; gross revenues = $68,605,600. Species Directed catch Bycatch Quota Estimated surplus Actual surplus Millions or pounds — — Atlantic cod 27 28 55 55 — 0 Haddock 8 5 13 13 — 0 Redfish 17 3 20 20 — 0 Silver tial(e — 4 4 265 261 188 Red hake — 2 2 97 95 77 Pollock 62 4 66 66 — 0 Yellowtail flounder 18 13 31 31 — 0 Ottier flounders 40 4 44 44 — 0 Ottier finfisli — 16 16 269 253 132 Atlantic mackerel 61 61 165 104 152 Squid — 13 13 174 161 94 Total 233 92 325 1.199 874 643 The results of the model (Table 7) indicate that all of the cod, haddock, redfish, pollock, yellowtail flounder, and other flounders be allocated for ex- clusive U.S. exploitation since the sum of the di- rected catches and the bycatches for these species are equal to the quotas. The results from the model did identify the exis- tence of surpluses for silver and red hake, Atlantic mackerel, squid, and other finfish. Coincidentally, the species or species groupings for which surpluses were identified in the Preliminary Management Plans (PMP'sl for the Fishery Con- servation Zone in the northwest Atlantic were for these same species identified by the model. All of the surpluses, except for Atlantic mackerel, are larger than the actual surpluses specified in the PMP's. (These surpluses appear in column 7 of Table 7.) This would be expected since the model only considered the otter trawl fleet capacity in New England and did not include harvesting capacity by other gear types in New England and in the Mid-Atlantic area. An important implication of the optimal solu- tion for the LP model was the calculation of shadow prices for certain species for which the constraints were binding (i.e., there were zero surpluses).'^ The optimal solution indicates that the quotas for Atlantic cod, haddock, redfish, pol- lock, yellowtail flounder, and other flounders were harvested. In addition, the entire harvesting capacity was utilized. Therefore, all of these species quotas were binding constraints and the resources had positive shadow prices in the opti- mal solution. Furthermore, harvesting capacity was also a binding constraint. Shadow prices are shown in Table 8. For the species in excess supply Table 8. — Shadow prices for binding constraints. Resource Stiadow pnce (S/lb) i^Shadow prices show the changes in the objective function for a unit change in the constraint (see column RHS in Table 6). 432 Atlantic cod Haddock Redfisti Pollock Yellowfail flounder Othier flounders Harvesting capacity 0-14 0,32 0.02 0,01 0,30 0 19 0 12 (as evidenced by surpluses) there are no shadow prices. This is to be expected since the correspond- ing shadow price is zero because the excess supply is of no value to the U.S. fleet if it cannot be har- vested and sold. In this particular problem, the shadow price for cod can be interpreted as follows: if the Atlantic cod quota was increased by 1 lb, the objective func- tion would increase by 14 cents. This 14 cent,>^ includes the imputed value of Atlantic cod (shadow price) and the other species caught as bycatches with cod less the value of a pound of lower valued species that the new mix replaces. As can be seen from Table 8, the shadow prices vary since the exvessel prices shown in the simplex tableau (Table 6) are different. In the optimal so- lution, the shadow price for harvesting capacity is lower than most of the other species in Table 8. This is because if the harvesting capacity was in- creased by 1 lb, the only species available to har- vest are the lower valued species. Shadow prices play an important role in the development of resource management strategies. For example, a decision to rebuild the stock for a particular species could be based on the shadow- price that indicates the greatest return when a constraint is increased by one unit. The LP model in this paper, given the shadow prices from the optimal solution, shows that in the multispecies otter trawl fishery, cod, haddock, and yellowtail SIEGEL ET AL. LINEAR PROGRAMMING APPROACH flounders would be likely candidates for rebuild- ing. An area of further interest in this model is to determine how sensitive the optimal solution (Ta- ble 7) is to changes in the prices, bycatch ratios, and quotas. If the optimal solution is not particu- larly sensitive to changes in these parameters, this means that it may not be necessary to be overly concerned with very precise estimates of technical parameters. Consequently, the bounds on the technical parameters in the LP model may not result in a large impact on changes in the objective function. A sensitivity analysis was not performed for this LP model, but the implication for future research is that estimates of certain technical parameters may not have to be as precise as researchers believe before there is a significant change in the optimal solution to the LP problem. SUMMARY The purpose of this paper was to discuss alterna- tive approaches used to measure capacity, to de- velop a definition of capacity for the harvesting sector of the commercial fishing industry, and to present a model that could be used to estimate this capacity in a multispecies fishery. We have argued that the concept of capacity contained in the FCMA is identical to short-run economic output. We feel the suggested methodology and the model presented in this paper can be used to address the issue of capacity in a multispecies fishery. The model can be used to examine other scenarios than presented here, by incorporating seasonal quotas, alternative mesh sizes, and stock rebuilding con- siderations. ACKNOWLEDGMENTS The authors express their appreciation for the helpful suggestions and comments on the work to Barrel Hueth, Joel Dirlam, and Ivar Strand. All omissions and errors are, of course, the responsi- bility of the authors. REFERENCES Clark, S. H., and B. E. Brown. 1977. Changes in biomass of finfishes and squids from the Gulf of Maine to Cape Hatteras, 1963-74, as determined from research vessel survey data. Fish. Bull., U.S. 75:1-21. DeLEEUW, F. 1961. The concept of capacity. American Statistical As- sociation. Proc. Bus. Econ. Stat, Sect., p. 320-329. 1966. A revised index of manufacturing capacity. Fed. Reserve Bull. 52:1605-1615. Hertzberg, M. p., a. I. Jacobs, and J. E. Trevathan. 1974. The utilization of manufacturing capacity, 1965- 1973. Surv. Curr. Bus. 54(7);47-57. Klein, L. R. 1960. Some theoretical issues in the measurement of capacity. Econometrica 28:272-286. Klein, L. R., and R. S. Preston. 1967. Some new results in the measurement of capacity utilization. Am. Econ. Rev. 57(l):34-58. Klein, L. R,, and R. Summers. 1966. The Wharton index of capacity utilization. Univ. Pennsylvania, Wharton School of Finance, Dep. Econ., Philadelphia, Pa., 94 p. PERRY, G. L. 1973. Capacity in manufacturing. Brookings Papers on Economic Activity 3:701-742. PHILLIPS, A. 1963. Industrial capacity: an appraisal of measures of capacity. Am. Econ. Rev. 53(21:275-292. Quance, L., and L. Tweeten. 1972. Excess capacity and adjustment potential in U.S. agriculture. Agric. Econ. Res. (U.S. Dep. Agric.) 24(31:57-66. RADDOCK, R. D., and L. R. FOREST. 1976. New estimates of capacity utilization: manufactur- ing and materials. Fed. Reserve Bull. 62:892-905. Rothschild, B. J. 1972. An exposition on the definition of fishing effort. In Economic aspects of fish production, p. 257- 271. Organization for Economic Cooperation and De- velopment, Paris. Rothschild, B. J., and J. W. Balsiger. 1971. A linear-programming solution to salmon manage- ment. Fish. Bull,, U.S. 69:117-140. Spielmann, H., and E. Weeks. 1975. Inventory and critique of estimates of U.S. agricul- tural capacity. Am. J. Agric. Econ. 57:922-928. U.S. BUREAU OF THE CENSUS. 1976. Survey of plant capacity. 1975-MQ-Cl(75l-2. U.S. Gov. Print. Off., Wash., DC U.S. DEPARTMENT OF COMMERCE. 1971-77. Fishery statistics of the United States 1968 |to 19741. (Various editors and pagination.! National Marine Fisheries Service. National Oceanic and Atmos- pheric Administration. Wash.. DC 20235. U.S. FISH AND WILDLIFE SERVICE. 1957-1969. Fishery statistics ofthe United States 1955 [to 1967]. (Various editors and pagination.) Yeh. C, J., L. G. Tweeten. and C. L. Quance. 1977. U.S. agricultural production capacity. Am. J. Ag- nc. Econ. 59:37-48. 433 SOME ASPECTS OF THE BIOLOGY OF DEEP-SEA LOBSTERS OF THE FAMILY POLYCHELIDAE (CRUSTACEA, DECAPODA) FROM THE WESTERN NORTH ATLANTIC ' ^ Elizabeth Lewis Wenner^ ABSTRACT Stereomastis nana was the most abundant species of Polychelidae collected by otter trawl on the continental slope of the Middle Atlantic Bight, off the eastern United States. Total catches were almost four times greater than those of its congener, S sculpta. Other polychelid species, Poiycheles ualidus and P. granulatus, were caught infrequently . Si^reomasds nana was abundant at depths of 1,400-2,599 m, and S. sculpta occurred at 486-2,257 m. Stereomastis nana and S. sculpta appear to spawn year round, and both may be deep-sea scavengers. The Polychelidae are the only extant members of the superfamily Eryonoidea, a group represented in fossil records from the mid-Triassic period (Glaessner 1969; Firth and Pequegnat'*). The fam- ily is currently placed by Glaessner (1969) within the infraorder Macrura, along with the spiny lobsters (Palinuridae) and the shovel-nosed lobsters (Scyllaridae). Although the Polychelidae are not of commercial importance, interest in these lobsters dates back when Bate (1888) dis- cussed uniqueness of the family because its mem- bers lack eyes and are related to forms thought to be extinct since the Mesozoic. In addition, some species live at extreme depths. Since that time, Andrews (1911) indicated the occurrence of exter- nal spermatophores and discussed sperm transfer among male and female polychelids; Santucci (1933) and Bernard (1953) suggested that Poiycheles typhlops performs reproductive migra- tions up slope; and Firth and Pequegnat (see foot- note 4) investigated taxonomic relationships of the entire family Polychelidae as well as certain aspects of its biology. Otter trawl collections of Polychelidae have been made by the Virginia Institute of Marine 'Based on part of a dissertation to be presented to the School of Marine Science, College of William and Mary, Williamsburg, Va. ^Contribution No. 881, Virginia Institute of Mairine Science, Gloucester Point, Va. 'Virginia Institute of Marine Science, Gloucester Point, Va.; present address: South Carolina Wildlife and Marine Resources Department, P.O. Box 12559, Charleston. SC 29412. ■•Firth, R.W., Jr., and W.E. Pequegnat. 1971. Deep-sea lob- sters of the families Polychelidae and Nephropidae (Crustacea, Decapodal in the Gulf of Mexico and Caribbean Sea. Texas A&M Res. Found. Ref 71-1 IT, College Station, 106 p. Science on the continental slope near Norfolk Canyon, off the eastern United States from 1973 to 1976, which confirmed their importance as benthic slope crustaceans. In this paper, I give new biological information on this interesting group of decapods that has come to light as a result of these collections. Species from the western North Atlan- tic which are discussed include Po/yc/?e/Musick,J.A.,C A. Wenner, andO.R. Sedberry. 1975. Ar- chibenthic and abyssobenthic fishes. In May 1974 baseline in- vestigation of Deepwater Dumpsite 106, p. 229-269. NOAA Dumpsite Eval. Rep. 75-1, 388 p. Manuscript accepted December 1978. FISHERY BULLETIN: VOL. 77, NO. 2, 1979. 435 FISHERY BULLETIN VOL 77, NO .' low, but these samples were used in length- frequency distributions and reproduction analyses. All specimens were identified by me from Firth and Pequegnat's (see footnote 4) key to the Polychelidae. Short carapace length (SCLi, i.e., the distance from the median posterior margin of the carapace to the orbit, was measured to the nearest millimeter. Sex and gonad condition were recorded for all polychelids, and gonads representative of stages of development were obtained for histological examination and placed in Davidson's fixative (Humason 1972). Validity of female gonad stages was determined by gross ovarian morphology, ovarian histology, and oocyte diameter. The longest horizontal diameter of 15 oocytes ran- domly chosen from excised ovaries of each lobster was measured with an ocular micrometer. Fecundity was estimated from total external egg number. I stripped eggs from the pleopods, placed them in a graduated tube, and adjusted the volume to 10 ml w^ith water. After mixing, I took three 0.5 ml aliquots and counted eggs from the aliquots on a gridded Petri dish. I then noted the degree of embryological development of eggs, similar to descriptions by Meredith (1952) and Allen ( 1966), and measured the longest horizontal diameter of 15 randomly chosen eggs. I also removed stomachs from preserved lobsters and sorted and identified their contents where possible. The importance of food taxa was then determined from their numerical abundance. RESULTS Stereoniastis tniiui (Smith) the Middle Atlantic Bight collected 459 S. nana from depths of approximately 613-2,642 m and temperatures of 2.4°-5.0° C. Analysis of variance showed a significant difference (Table 1 ) between abundance of S. nana for depth intervals shown in Figure 1. Scheffe's multiple mean comparison test iSnedecor and Cochran 1967) showed the mean catch rate, expressed as log,,, (.v + 1) 0.5 h tow, to be significantly higher at depths of 1 ,400-2,599 m. There was no discernible change in depth distribu- tion of this species with season. There was also no apparent segregation of sex with depth since both male and female S. nana occurred throughout the depth range. Chi-square analysis using Yates correction (Woolf 1968) showed females and ovigerous females to be sig- nificantly more numerous than males at arbitrar- ily chosen depth strata of 1,200-1,999 and 2,000- 2,800 m (Tables 2, 3). There was no significant relationship between average size of S. nana and depth of capture (F = 0.056, df = 1,460). Males (mean = 22 mm SCL), females (mean = 25 mm SCL), and ovigerous females (mean = 2(S mm SCL) differed significantly from each other in size by analysis of variance (Table 4) and Scheffe's multiple mean comparison test. Sex ratios varied significantly with size, with females predominat- ing at lengths >26 mm SCL and males at lengths <22 mm SCL (Table 5). Among the Polychelidae, sperm transfer is accomplished by attachment of spermatophores to the surface of the posterior sterna of the females ( Andrews 1911). Most ovigerous and nonovigerous females >23 mm had externally attached sper- matophores (Figure 2). All ovigerous females except five damaged individuals had spermato- phores attached. It is probable that spermato- Stereomastis nana is found in the three major oceans but not in the Mediterranean and Carib- bean Seas or the Gulf of Mexico (Firth and Pequegnat see footnote 4). Its bathymetric dis- tribution within the western North Atlantic off the east coast of the United States was reported to be 1,289-3,506 m (Smith 1884, 1887); off Green- land and Iceland, specimens have been taken from 1,271 to 2,271 m (Hansen 1908). Abundance data based on our 13.7 m otter trawl catches show that S. nana constitutes 20^t by number of the total benthic decapod fauna at depths below 1,200 m. Its importance within the benthic decapod community diminishes to 0.3'/^ at depths between 400 and 1,199 m. Trawls within Table I — One-way analysis of variance on abundance, expres- sed as logio (* -^ 11 per 0.5 h tow, of Stereomastts nana and .S. ^culpta by depth interval (see Figure 1 for description of depth intervals). Source of variation S nana Among groups (depth interval) Wittiin groups Total S sculpta Among groups (depth interval) Within groups Total 'SS - sum of squares. 'MS = mean squares, ■■P- 0 01 dl SS' MS' 10 133 13 16 23' 126 104 01 136 23 7 9 15 0,17 2 88 129 76 006 138 91 436 WENNER: BIOLOGY OF DEEP-SEA LOBSTERS Figure l. — Abundance oi Stereomastis nana and S. scuplta by depth, expressed as tog U + 1) per 0.5 h tow, where x is number of individuals. Ratios over bars indicate number of stations where Stereomastis spp. were captured to total number of stations within depth intervals. Table 2. — Summaries for three depth strata of morphological and reproductive data on Stereomastis nana and S. sculpta from the continental slope, .v = arithmetic mean; SCL = short carapace length in millimeters; 95'7f confidence limits (CL* follow the means. Percent ovigerous females is based on total female samples only. 400-1 199 m 1.200-1.999 m 2.000-2.800 m Item S nana S sculpta S. nana S sculpta S nana S sculpta No successful tows 9 36 32 15 21 3 Temperature (' C) 4.5 48 37 3 8 3 1 29 No individuals 14 107 239 20 209 3 N (Percent) males 5(357) 48(45 1) 73(305) 12(60.0) 79(37 8) 1(333) N (Percent) lemales 9(54 3) 59(54 9) 166(69 5) 8(40 0) 130(62 2) 2(66 7) N (Percent) ovigerous females 3(33 3) 8(14 0) 92(55 4) 0 36(27 7) 0 X (CL) SCL all individuals 24(18:29) 34(31.37) 26(26:27) 30(24:35) 24(23.25) 35(0,78) Size range 18-34 16-69 17-37 19-72 16-38 19-54 X (CL) SCL males 21(15:27) 33(31:36) 22(22.23) 27(24:31) 22(22,23) 20(ND') Size range 18-26 16-52 17-28 19-37 18-26 ND X (CL) SCL females 27(20:33) 35(32:38) 27(26,28) 33(20.47) 25(24,25) 42(0:192) Size range 19-34 18-55 18-37 22-72 16-38 30-54 X (CL) SCL ovigerous females 29(16:41) 52(48.56) 29(28,29) ND 29(28,30) ND Size range 25-34 45-58 25-35 ND 24-38 ND 'ND = no data Table 3. — Chi-square test for goodness of fit. using Yates correc- tion for continuity of male: female ratios of Stereomastis nana and S. sculpta by depth interval. Depth interval (m) Frequency Sex S nana S sculpta S nana S sculpta 400-1.199 M 5 48 F 9 59 1,200-1,999 M 73 12 F 166 8 2,000-2,800 M 79 1 F 130 2 •■p19 mm were also found with a hardened secretion of spermatophores projecting out of the gonopore at the base of the fifth pereopod (Figure 2). Ovigerous females, nonovigerous females, and males with external spermatophores occurred at all depths, with maximum numbers at 1,400-2,199 m. No males or females with external spermatophores. and only one ovigerous female occurred deeper than 2,400 m. By examination of ovaries, I defined six stages of ovarian development in Stereomastis spp. (Figure 437 FISHERY BULLETIN: VOL. 77. NO 2 Table 4. — One-way analysis of variance on short carapace length otStereomastis nana and S sculpta by sex imale. female, and ovigerous female). ITH SPERMATQPHORES PRESENT Source of variation dl SS' MS^ F S nana Among groups (sexes) Within groups 2 459 3,010 9,304 1.506 2 20 3 74,25" Total 461 12,314 S sculpta Among groups (sexes) Witllin groups 2 122 3,592 12.964 1.796 2 1063 16 90-- Total 124 16,556 'SS = sum of squares ^MS = mean squares ■*P 0 01 Table 5. — Percent of ma\e Stereomast is nana by size interval. Size groupmgs result from chi-sqirare analysis of male and female frequencies by 2 mm size intervals. SCL (mm) Males Females Mates 1%) x' 16-21 9 69 23 75 2201" 22-259 72 67 52 0 11 26-39 9 14 210 6 171 SO" Total 155 300 34 4557-- SHORT CARAPACE LENGTH (mm) Figure 2. — Length-frequency distribution ofStereomastis nana pooled for all months of collection. 3 ). Immature ovaries were threadlike and difficult to remove from the specimens because of their adherence to the dorsal portion of the digestive gland. In cross section, the oocytes appeared very small (0.05-0.2 mm, mean =0.1 mm) with the nucleus composing most of the oocyte. Resting ovaries had oocytes (0.1-0.3 mm, mean = 0.2 mm) with a large nucleus and no yolk granules (Figure 4A). The intermediate ovary had fewer densely packed oocytes (0.1-0.4 mm, mean = 0.3 mm). A distinct basophilic nucleus with condensed chromosomes was visible in cross section. Yolk granules partially filled the cytoplasm. The ger- minative zone was well developed and filled with developing, basophilic oocytes (Figure 4B). In the ripening ovary, the oocytes were irregularly shaped (0.3-0.8 mm, mean = 0.5 mm), with the cytoplasm partially filled with yolk granules. There was a visible nucleus. The germinative area within the ovary was larger than in ripe individu- als. In gravid individuals, the ovary occupied much of the thoracic cavity, with anterior and posterior horns extending laterally. The oocytes (0.5-0.9 mm in diameter, mean = 0.7 mm) were tightly packed and irregularly shaped, yet they were easily dislodged from the ovary with slight probing. Histological sectioning revealed oocytes to be filled with yolk granules. The nucleus was generally not visible and the central germinative zone of the ovary was compressed (Figure 4C). Individuals with ovaries judged to be spent were usually ovigerous females. The ovaries contained a few atresic (0.3-0.4 mm) oocytes, but much of the ovary was filled with resting stage basophilic oo- cytes (0.1-0.2 mm (Figure 4D)). Most nonovigerous females <26 mm had imma- ture and resting ovaries (Figure 5). Individuals with ripening and gravid ovaries first appeared at 21 mm, and the percentage of females in these stages increased with increasing size. Approxi- mately 58"^'^ of the 65 nonovigerous females with external spermatophores were ripe. The remain- ing individuals had immature (&7c ), resting (99f ), intermediate 1 1 1'* ), ripening (8'^? ), or spent (8'? ) ovaries. A large percentage of ovigerous S. nana 21 mm or larger were spent, but there were some ovigerous individuals with ovaries in each stage of development (Figure 5). In most cases, ovigerous females with ripening or gravid ovaries had ad- vanced eggs (eyes and a discernible abdomen), cor- responding to C or C+ stage designated by Meredith ( 1952). Spent individuals had eggs that were newly deposited (stages A-A-(-) or gastru- lated (stage B + ). Ovigerous and other female S. nana with exter- nal spermatophores attached were found during 438 WENNER BIOLOGY OF DEEP-SEA I,OBSTERS A Figure 3. — Cephalothoracic position and relative size of the ovary of Polychelidae during ovarian development stages (dorsal view); A. Immature; B. Resting; C. Intermediate; D. Ripen- ing; E. Gravid; and F. Spent. OV = ovary; DG = digestive gland; M = muscle; and S = stomach. every month of collection (Table 6). Individuals with advanced eyed (stages C-C + ) eggs and egg remnants (stage D), indicative of imminent or re- cent hatching, were also collected each month. Similarly, there were gravid and ripening females and spent ovigerous females present throughout the year (Figure 6), but there was no indication that seasonal peaks in oviposition occurred. The estimated number of eggs on the pleopods ranged from 1,015 to 7,580 (mean = 3,392. /; = 10) with a mean diameter of 0.7 mm. There was no apparent relation between body size and fecundity for 10 individuals examined. I examined 127 males (17-36 mm SCL) for pres- ence of external (protruding from gonopores) and internal ( present in vas deferens ) spermatophores. T.ABLE 6. — Summary of data on reproductively mature individuals and advanced egg development mSterenmastis nana and.S Miilpta by month of collection. Item September January April May-June July ssssssssss, ss nana sculpta nana sculpla nana sculpla nana sculpla nana sculpta nana sculpta Males Sample size Percent total catch Percent witti spermatophores exuding Nonovigerous females Sample size Percent with spermatophores attached Ovigerous females: Sample size Percent of total females 10 15 58 16 19 8 23 5 13 13 34 2 20 45 35 53 26 50 39 28 36 59 42 33 40 13 5 6 5 0 26 20 46 31 50 0 13 17 70 11 30 7 24 11 10 8 27 4 77 29 37 9 17 29 46 9 40 12 37 25 Sfi 1 37 3 24 1 12 2 13 1 19 0 67 5 35 21 44 12 33 15 57 11 41 0 439 FISHERY BULLETIN: VOL. 77. NO. 2 FiGLiRE 4. — Photomicrographs of four ovarian stages of Stereomastis scutpta and S. nana. Harris hematoxylin-eosin stain. A. Resting ovary from S. nana showing preponderance of developing (D) oocytes, x 165. B. Intermediate stage ovary fromS. nana. Note presence of developing iD) oocytes among more advanced oocytes with yolk granules (YGl present. x52. C. Gravid ovary from S sculpta showing compacted yolk filled oocytes, x 52. D. Spent condition of S. nana showing atresic tAT) oocyte surrounded by developing (D) oocytes, x 52. 440 W KNNER BIOLOGY OF DEEP-SEA LOBSTERS 100 90 80 70 60 50 40 30 ^ 20 n:2l n:62 11 = 70 m 100 -I £ 90 cr u 80 ■ a. 70 - 60 50 40 30 20 10 ^ m n:7 n:94 M 21-25 26-30 31-35 36-40 SHORT CARAPACE LENGTH (mm) ntermediote Gravii Ripening tl I t 1 Spent Resting Figure 5. — Percent occurrence of ovigerous and nonovigerous Stereomastis nana in ovarian development stages for five length intervals. 100- 90 ■ 80 • 70 ■ 60 50 40 30 ' 20 10 100 I 90 I 80 70 60 50 40 30 20 10 n:IO n:22 n:8 n:58 n-.2l I i I n=l3 n=l8 WA m MAY/JUNE JULY SEPT NOV JAN MONTHS OF COLLECTION □ Immoture Resting Ripening Gravid l\l\ Intermediate Spent l« Figure 6. — Percent occurrence of ovigerous and nonoviger- ous S/(?rcomas//s nana in designated ovarian development stages bv month of collection. All individuals were sexually mature with sper- matophores present within the vas deferens, and there were also some males at each season with spermatophores protruding from the gonopores I Table 6i. Analysis of stomachs from 438 S. nana showed Si^/f of them were empty. Among the remainder, 3% contained sediment with some Foraminifera, 2'7f contained either polychaete fragments or crus- tacean body parts, and 'i"c had unrecognizable paste. Single occurrences offish scales ( VA ), shell fragments (IVf), and one entire fish (Myc- tophidae?) ( 1% ) were also noted. Stereoniasth aiilptii (Smith) Stereomastis sculpta has a wide geographic dis- tribution, captures having been reported from the Atlantic and Indian Oceans, the Arabian, Mediterranean, and Caribbean Seas, and the Gulf of Mexico. It has been reported off the east coast of North America from lat. 35°49'-43'10' N at depths of 460-1,568 m. It has not been reported from the Pacific Ocean, where it is replaced by the sub- species S. sculpta pacifica (Firth and Pequegnat see footnote 4). Roberts ( 1977) found S . sculpta to 441 KISHKKY BL'l.LKTIN: VOL be the most abundant polychelid collected by benthic skimmer in the Gulf of Mexico, and Firth and Pequegnat confirmed it as the most commonly caught polychelid both in that region and in the Caribbean Sea. Although Firth and Pequegnat stated thatS. sculpta is one of the most commonly reported species in the Polychelidae and probably one of the most important polychelid species nu- merically on the continental slope, it was much less abundant thanS. nana in my Middle Atlantic Bight collections (Figure 1 1. Abundance data based on 13.7 m otter trawl catches showed S. sculpta constituted 6. 5''f of the total benthic deca- pod catch. Its importance diminishes at lesser and greater depths within its bathymetric range of 486 (5.7' C) to 2,257 m (2.9" C). Analysis of variance showed no significant difference in abundance by depth intervals for 115 S. sculpta (Table 1). The overall ;' : 9 ratio (1:1.1) and se.\ ratios for depths of capture did not differ significantly from 1:1 (Tables 2, 3). There was also no apparent rela- tionship between average size of S. sculpta and depth of capture (F = 2.321, df = 2,122, P =0.05). Ovigerous females (mean = 54 mm) were sig- nificantly larger (Table 4) than males (mean = 32 mm I and other females (mean = 35 mm), based on analysis of variance and Scheffe's multiple mean comparison. Spermatophores occurred only on females 45 mm and larger and were found protruding from the gonopores of males 32 mm and larger. Oviger- ous females were 45 mm and larger, and all had attached spermatophores (Figure 7). Ovigerous females and most males and females with exter- nally located spermatophores were found at the shoaler depths sampled; none were obtained below 1,199 m. Ovarian development stages of .S. sculpta were similar to those described for.S. nana. Immature gonads were found in all nonovigerous females in = 36) 36 mm and larger. Ripening and gravid individuals occurred only at sizes 38 mm and larger. Seven ovigerous females were spent, and one 54 mm individual was ripening. Since ovigerous females were obtained each month, except July (Table 6), I conclude there was no clearly defined spawning season. Nonovigerous females with spermatophores attached occurred at all months. There was no relation between ovari- an stage and month of capture. Fecundity o( (our S. sculpta varied from 10,093 to 19,080 with a mean of 15,541. Eggs had a mean diameter of 0.6 mm. All males were found to have spermatophores in the vas deferens. Males with external sper- matophores were present during all months ex- cept January and July (Table 6). Sixty-eight percent of 114 S. sculpta stomachs were empty. Stomachs of other individuals con- tained sediment with Foraminifera (13%), fish body parts ( 50^ ), polychaete parts (39f), crustacean parts (5'r ), and unidentifiable gurry i6%). ) EXTERNaL SPERMATOPHORES PRESENT lb. m r—^-H^rg-a^ ^ 5 ^^l^^iT] XI J I , rrr:r> p^^ P^ ^ k£^ OVIGEROUS ^ FTTja .JE?L_ Fl« 16 20 24 26 32 36 40 44 48 52 56 60 64 66 72 SHORT CaRfiPACE LENGTH 1mm) ;URE 7.— Length-frequency distribution of Sterenmastifi acultpa represented in catches included in this study. 442 WENNER: BIOLOGY OF DEEP-SEA LOBSTERS Other Polychelid Species Polycheles validus (A. Milne-Edwards) is found in the eastern and western Atlantic, the Mediter- ranean and Caribbean Seas, and the Gulf of Mexico. Its distribution in the western North At- lantic extends northward to lat. 42° N at 2,211- 2,393 m (Firth and Pequegnat see footnote 4). My Middle Atlantic Bight collections recovered 10 P. validus at depths between 1,698 and 2,337 m and temperatures of 3.8'-2.9° C. Males ranged from 21 to 48 mm with spermatophores present in gono- pores of two individuals, 32 and 44 mm SCL. Two females were collected, 21 and 28 mm SCL, and both were immature. Small catches of P. validus are best attributed to its deep-living existence, having never been reported shallower than 1,280 m. Polychelt'sgranulatus(Faxon)has been reported from the Atlantic, Pacific, and Indian Oceans at depths of 347-2,505 m (Firth and Pequegnat see footnote 4). Captures of this species were reported at 349-799 m in the western North Atlantic by Squires.*^ I collected 11 individuals from the Mid- dle Atlantic Bight at depths between 932 (4.4° C) and 2,068 m (3.4 'C). Nine males, none with exter- nal spermatophores, were 16-22 mm SCL. Two immature females 18-28 mm were also captured. The presence of ovigerous fema.\e P. granulatus off the Nova Scotian Shelf at 350-440 m (Squires see footnote 6) and the fact that this species has not been reported from the' Gulf of Mexico or the Carribbean Sea ( Firth and Pequegnat see footnote 4) is evidence that reproducing populations of this species occur in the northerly reaches of the west- ern Atlantic. DISCUSSION Although Stereomastis nana andS.sculpta were both represented in catches from the Middle At- lantic Bight, it is evident that relative abundance and bathymetric distribution of the two species are markedly different. Stereomastis nana was the most abundant species collected, total catches being almost four times greater than those of S. sculpta. Haedrich et al. (1975) collected only S. nana during trawling with a 4.9 m ( 16-fti net on the continental slope south of New England. From further trawls in this location, they obtained 92S. nana at 24 stations between 828 and 3,642 m, and only 2 S. sculpta at 2 stations between 1,328 and 1,938 m (Haedrich et al.''). Farther north. Squires (see footnote 6) collected 15 S. sculpta off the slope of the Grand Banks at depths of 420-810 m (4.1°- 4.5° C). The lack of S. nana in his samples probably resulted from confinement of trawls to depths shallower than 800 m. Stereomastis sculpta is the most commonly caught polychelid in the Gulf of Mexico (Firth and Pequegnat see footnote 4). Roberts (1977) reported density estimates of 394 individuals/ha (565-918 m), 343 individuals/ha (1,061-1,829 m), and 88 individuals/ha (2,744- 3,256 ml for the northeastern Gulf of Mexico. It appears, therefore, thatS. nana is more abundant in the Middle Atlantic Bight while S. sculpta is more plentiful in southern latitudes. Bathymetric distributions of the two species also differ, withS. nana found deeper on the conti- nental slope than S. sculpta. Separate bathymet- ric distributions of these species as proposed by Barnard (1950) formed the basis for rejection of Smith's (1884) hypothesis that S. nana was a dwarf deep-sea form of S. sculpta. Stereomastis nana and S. sculpta appear to spawn year round, producing large numbers of small eggs. There is no indication that increased numbers of ovigerous females occur at certain months, as suggested by Santucci (1933) and Squires (see footnote 6). Santucci ( 1933) found the greatest number of ovigerous female Polycheles typhlops were taken between April and July, while mostS. sculptawere ovigerous in May, Oc- tober, and November (Squires see footnote 6). Squires (see footnote 6) concluded from a study of 15 individuals that annual breeding occurs in S. sculpta. Collections ofS. nana from my study indi- cate spawning occurs year round. Reproduction in S. sculpta appears also to be year round, but the small sample size limits interpretation of repro- duction in this species. There is also no evidence to indicate that the reproductively mature females perform upslope migrations similar to those Santucci (1933) and Bernard (1953) suggested for P. typhlops. These investigators found that ovigerous females and other females with well-developed ovaries ascend to shallower depths where their eggs are released. ^Squires. H. J. 196.5. Decapod crustaceans of Newfound- land, Labrador and the Canadian eastern Arctic. Fish Res. Board Can. Manuscr. Rep. Ser. 810, 212 p. 'R. L, Haedrich. G. T. Rowe, and P. T. Polloni, Biological Oceangraphers. Woods Hole Oceanographic Institution, Woods Hole. MA 02543, pers. commun. October 1977. 443 Firth and Pequegnat (see footnote 4) suggested a similar pattern for P. crucifer and S. sciitpta but cautioned that other polychelid species may not perform migrations to shallow waters. There was no evidence to support this hypothesis among S. nana or S. sculpta since ovigerous and reproduc- tively mature females occurred within depths of maximum abundance for the species. Lack of sup- port for the hypothesis is also indicated by failure to find any correlation between size of individuals and their depth range. If such migrations occur, larger individuals, such as ovigerous and sexually mature females, would have been found at shal- lower depths. Size at sexual maturity for Stereomastis spp. examined in my study agrees with Firth and Pequegnat's (see footnote 4) observations. How- ever, they founds. .s-c(//p/a as small as 18 mm with spermatophores protruding from the genital pores. In the present study, the smallest male in this condition was 32 mm. Feeding habits among the Polychelidae are also not resolved. Firth and Pequegnat (see footnote 4) indicated the polychelids are detritus scavengers but Lagardere (1976) found P. typhlops exists by almost exclusive predation on mobile crustacean prey, such as mysids, euphausiids, and pelagic amphipods. He did note, however, presence of benthic polychaetes (Aphroditidae) in several stomachs. Stomach content analysis from the present study is most inconclusive since sediment, detritus, polychaetes, and fish body parts were found. Since polychelids have seldom been seen in bottom photographs and are thought to bury in sediment (Firth and Pequegnat see footnote 4), it appears that a scavenging mode of existence along the bottom is likely forS. nana and S. sculpfa. ACKNOWLEDGMENTS I would like to thank J. Musick for providing ship time through National Science Foundation (NSF) Grants GS-37561 and GS-27725. Special thanks go to F. Perkins and P. Berry for providing histological sections. Information on catches of Stereomastis from the slope off New England were provided by R. Haedrich, G. Rowe, and P. PoUoni (Woods Hole Oceanographic Institution) under NSF Grant OCE-74-22339. This research was completed while the author was recipient of an NSF award (OCE-77-05698) for support of doctoral dissertation research in bio- logical oceanography. 444 FISHERY BULLETIN VOL. 77. NO, 2 LITERATURE CITED .\LLE.N'. J. A. 1966. The dynamics and interrelationships of mi.Ked popu- lations of Caridea found off the north-east coast of Eng- land. In H. Barnes (editor), Some comtemporary studies in marine science, p. 4.5-66. Hafner Publ. Co., N.Y. ANDREWS, E. A. 1911. Sperm transfer in certain decapods. Proc. U.S. Natl. Mus. 39:419-434. B.ARNARD, K. H. 1950. Descriptive catalogue of South African decapod Crustacea. Ann. S. Afr. Mus. 38:1-837. BATE.C. S. 1888. Report on the Crustacea Macrura collected by H.M.S. Challenger during the years 1873-76. Rep. Sci. Res. Voyage H.M.S. Challenger. 1873-76, Zool. 24, 942 p. BERNARD, F. 1953. Decapoda Eryonidae [Eryoneicus et Wille- moesia). Dana Rep. Carlsberg Found. 37, 93 p. GLAESSNER, M. F. 1969 Decapoda. In R.C. Moore leditori, Treatise on in- vertebrate paleontology, Part R, Arthropoda 4. Vol. 2, p. 399-533. Geol. .Soc. Am., Inc., and Univ. Kans. Haedrich, R. L.. G. T. Rowe, and p. T. Polloni. 1975. Zonationandfaunal composition of epi bent hie popu- lations on the continental slope south of New Eng- land. J. Mar. Res. 33:191-212. Hansen, H. J. 1908. Crustacea Malacostraca. I. Dan. Ingolf-Exped. 3(2), 120 p. HUMASON, G. L. 1972. Animal tissue techniques. 3d ed. W. H. Freeman and Co., San Franc, Calif.. 641 p. Lagardere, J. P. 1976. Recherches sur la distribution verticale et sur Talimentation des crustaces decapodes de la pente con- tinentale de I'Atlantique nord-oriental. These, I'Uni- versite d'Aix-Marseille. France, 188 p. Meredith, S. S. 1952. A study ofCrangnn crangun L. in the Liverpool Bay area. Proc. Trans. Liverp. Biol. Soc, 58:75-109. Roberts, T. W. 1977. An analysis of deep-sea benthic communities in the northeast Gulf of Mexico. Ph.D. Thesis. Texas A&M Univ. College Station. 270 p. SaNTUCC'I, R. 1933. Biologia del fondo a "Scampi" nel mare ligure, I, - Polycheles typhlops. Heller R, Comit. Talassograf, Ital, Mem, 199, 48 p. S.MITH, S, 1. 1884. XV-Report on the decapod Crustacea of the Alba- tross dredgings off the east coast of the United States in 1883. U.S. Comm. Fish Fish. Rep. Comm, for 1882 10:345-426. 1887, XXI-Report on the decapod Crustacea of the Alba- tross dredgings off the east coast of the United States during the summer and autumn of 1884, US, Comm, Fish Fish, Rep, Comm, for 1885 13:60.5-705. SNEDECOR, G. W.. AND W. G. COCHRAN. 1967. Statistical methods. 6th ed, Iowa State Univ, Press,. Ames, 593 p, WOOLF, C. M. 1968. Principles of biometry. D. Van Nostrand Co., Inc., Princeton, N.J., 359 p. REPRODUCTION IN THE BLUE SHARK, PRIONACE GLAUCA Harold L. Pratt, Jr.' ABSTRACT In the male blue shark. Prionace glauca, paired testes produce spermatozoa year round which are stored first in the epididymides, then as spermatophores in the lower ductus deferentia. Spermatazoa are transferred to the female through paired claspers employed singly. Spermatozoa are injected into the upper vagina and pass through the uterus and isthmus into the shell (oviducall gland, where they are stored until the female is ready for fertilization. Male blue sharks reach maturity at 183 cm fork length when 5(K^ possess spermatophores. Females pass through a subadult phase (145-185 cm), when the organs for copulation and sperm storage are developed but the ova are undeveloped. During this phase females receive numerous toothcuts in their thickened dermis as a prelude to mating and frequently copulate. I examined reproductive organs from 160 subadult female blue sharks, caught in shelf waters off southern New England during summer months, by histological sectioning to determine if spermatozoa were present. Of these females, 79 had spermatozoa in the oviducal gland, establishing successful copulation. Inseminated females then emigrate offshore where fertilization occurs the following spring during ovulation. Blue sharks are viviparous and bear young after 9 to 12 months gestation. Thirty- eight new or unpublished accounts of gravid females are investigated, as well as one 192 cm hermaph- roditic blue shark. In shelf waters during the summer the sex ratio for subadults is nearly equal while males dominate the adult sizes due to the emigration of inseminated females. The blue shark, Prionace glauca, is the most abundant of the larger oceanic sharks in the At- lantic (Bigelow and Schroeder 1948). It is fre- quently among the incidental catch of tuna and swordfish longliners in temperate, subtemperate, and tropical parts of the world ocean. Nichols and Murphy (1916) reported seeing "hundreds, even thousands" of them swimming free and attracted by the activity of the sperm whale fishery in the tropical Atlantic. Longline fishing operations con- ducted by National Marine Fisheries Service biologists in the offshore areas between Cape Cod, Mass., and Cape Hatteras, N.C., reveal the blue shark to be more numerous in this area than any other large shark or big game fish (Casey and Hoenig^). Like other elasmobranchs, blue sharks have a complex reproductive cycle which contributes to their success as a species. Suda (1953), Strasburg ( 1958), Aasen ( 1966), and Stevens ( 1974) have all contributed information about blue shark repro- 'Northeast Fisheries Center Narragansett Laboratory, Na- tional Marine Fisheries Service, NOAA, Narragansett, RI 02882. ^Casey, J. G., and J M. Hoenig. 1977 Apex predators in deepwater dumpsite 106. In Baseline report of environmental conditions in deepwater dumpsite 106. NOAA Dumpsite Evaluation Report 77-1, p. 309-376. duction, but many of the details concerning anatomy, maturity, and the sexual cycle were in- complete. New information is presented on the mechanism of spermatozoa storage in the male and female blue sharks and adaptations for mat- ing in the female. In this study, the reproductive systems of west- ern North Atlantic blue sharks have been investi- gated to better understand the life history of this important apex predator. MATERIALS AND METHODS Blue sharks sampled from October 1969 to April 1977 came from two sources: 1) longline catches made by research and commercial vessels and 2) anglers' catches landed during shark fishing tour- naments. The area sampled extended from Cape Hatteras to east of Georges Bank, both on the continental shelf and in the Gulf Stream. Three fish were also collected north of St. Thomas, V.I. Throughout this paper I use fork length (FL), a straight line measurement from the tip of the snout-to the fork of the tail. Measurements involv- ing the upper caudal (such as total length, TL) are variable due to its flexibility. Fork length is an easier and more accurate measurement for one person to make at sea. Many authors cited use Manuscript accepted November 1978 FISHERY BULLETIN: VOL. 77. NO. 445 FISHERY BULLETIN: VOL. 77. NO. 2 total length, defined by Bigelow and Schroeder ( 1948) as a caliper measurement along the body axis from the snout to a perpendicular extended from the upper caudal. I have converted all refer- ences to blue shark total lengths in the literature to fork lengths in centimeters using a regression^ derived from a sample of 554 males and females between 93 and 282 cm FL (r = 0.995). Clasper length (posterior free tip to the free trailing edge of the pelvic fin lateral to each clasper) and internal organs were measured with calipers to the nearest millimeter. Sharks were dissected as soon as possible after being caught. Several adults were frozen whole and dissected in detail at the laboratory. Speci- mens for analysis and anatomical description ranged in size from 1.1 to 264 cm and included 210 females and 114 males. A single ventral incision from cloaca to pectoral girdle permits access to the body cavity. The size and condition of internal organs of both sexes were noted. To determine maturity and insemination, both oviducal glands were excised carefully, with- out squeezing, with several centimeters of adja- cent oviduct. Oviducal glands and other histolog- ical samples were preserved in Bouin's fixative because it is compatible with the primary stain (Mallory's Triple Stain). Larger organs were pre- served in 107f Formalin.'' Tissues were prepared by the paraffin method and sectioned to 10-15 /j.m. In the latter part of the study a smear technique was developed to quickly determine insemination. This new technique, which obviates the need for histological sectioning, is discussed in a later sec- tion. RESULTS AND DISCUSSION Male Anatomy Testes and Epigiinal Organ The male blue shark has two equally developed testes each embedded in the anterior portion of a long irregular epigonal organ which has no known reproductive function other than to support the testes (Figures 1,2). Dissected from the epigonal organ, the testis is cylindrical with rounded ends. It is packed with tiny spheres averaging 0.3 mm in HEAD OF EPIDIDYMIS DUCTUS EFFERENS TESTES MESORCHIUM EPIDIDYMIS EPIGOhlAL ORGAN DUCTUS DEFERENS AMPULLA DUCTUS DEFERENS URE TER DUCTUS DEFERENS SPHINCTER UROGENITAL SINUS UROGENITAL PAPILLA COELOMIC PAPILLAE (ABDOMINAL PORES) Figure l. — Male reproductive system in the adult blue shark, general ventral view. DUCTUS £FFER£fJS TESTIS EPIGONAL OPCa^ LfrO/GS GiaND ^Computed regression: FL = 1.73872 + 0.82995 TL. 'Reference to trade names does not imply endorsement by the National Marine Fisheries Service. NOAA Figure 2. — Testes, epididymis, and epigonal organ of the adult male blue shark 446 PRATT REPRODUCTION IN BLUE SHARKS diameter, the seminiferous ampullae (Figure 3). The only other macroscopic structures are suppor- tive partitions of connective tissue radiating in- ternally from a band on the mediolateral surface of the testes. A double mesorchia suspends the testes from the midline of the dorsal body wall. The duc- tus efferens is a series of fine tubules which crosses the mesorchium at its anterior edge and com- municates with the head of the epididymis. Epididymis Above the testes on the dorsal abdominal wall lie the paired epididymides. They are attached on either side of the dorsal aorta in the hollow of the ventrolateral processes of the vertebral column. In the adult blue shark the epididymis is approxi- mately 3 cm wide, 30 cm long, and 0.5 cm thick. In sharks captured from March to November it is turgid with spermatozoa in a matrix of supportive tissue secreted by accessory glands on the dorsal surface. The epididymis originates just forward of and adjacent to the testes as a firm subspherical "head" which narrows to a short "neck" and then expands to form a long straplike organ (Figure 2). The tubules of this organ describe a path of con- volutions so complex that its surface appears cere- briform. Tubule diameters range from 1.5 to 1.75 mm adjacent to the testes, expanding to >2 mm at the junction of the ductus deferens. Here it enters Leydig's gland, the modified anterior section of the mesonephric kidney. At this level the function of the ductus changes from spermatozoa storage to spermatophore formation and storage. Ductus Dctcrens The ductus deferens (Figure 4) is the storage organ for male seminal products. The ductus gradually increases in diameter as it penetrates the kidney, finally enlarging in strong convolu- tions to form the ampulla ductus deferens which is 10-15 mm in diameter in the adult blue shark. The ampullae are lined with partitions or septa similar to those noted by Matthews ( 1950) in the basking shark, Cetorhtnus maximus. The thin-walled ure- ter becomes entwined with the ductus deferens in the last 20 cm of its length and roughly parallels its sinuous course. The ureter and ductus deferens terminate in a common double papilla which pro- jects into the anterior wall of the urogenital sinus. The ductus occupies the central orifice of the papilla and is closed by a sphincter muscle. The ureter has a crescent-shaped sphincterless duct on the dorsal edge of the cone of the papilla. The urogenital sinus vents into the common cloaca by means of a single large (2 cm) papilla that projects from the dorsal bodv wall. ^ .m ' rl \^' ^s^' Figure 3. — Seminiferous ampullae of mature testes in the blue shark ( ■< 160). Spermatozoa arranged radially inside spheres (seen in cross section). vx„.--- \.y0.] 447 KIDNEY FISHERY BULLETIN: VOL 77. I DUCTUS DEFERENS POSITION OF KIDNEY IN SHARK Figure 4. — Male urogenital complex in the blue shark. Sperm Sac The sperm sac ( Figure 4 ) is not well developed in the blue shark. This paired organ communicates with the anterior end of the urogenital sinus through an opening between the paired terminal papillae of the ductus deferens. The diameter in a mature 200 cm male was 16 mm at the sinus. The sperm sacs lie along the dorsal midline of the body cavity and extend anteriorly into the kidney ap- proximately 15 cm, where the tubes taper down to threads and end blindly. Siphon Sacs and Claspcr In the adult blue shark the paired claspers are heavily calcified scroll-shaped appendages which transfer sperm from the lower ductus through the urogenital papilla to the vagina of the female dur- ing copulation. Propulsive force is provided by a water piston driven by the muscular subdermal siphon sac associated with each clasper. An accu- rate description of clasper morphology and func- tion is given by Leigh-Sharpe (1920). The clasper is similar in form to that of the basking shark, which has been described in detail by Matthews ( 1950) and to the tope, Galeorhinus galeus (Leigh- Sharpe 1921). The blue shark lacks a distinct spur or clasper hook and uses instead the sharpened edges of the terminal parts, which are splayed open after insertion to secure the clasper in the 448 1 - ' i ) i \ X . • \ iV . ' J • ' ■ ■ . . • • • ' • h i fv* ■••• '.f/ « .1 "^ ^' f » .> < FIGURE 5 —Spermatozoa of the blue shark < x 1,600). PRATT REPRODUCTION IN BLUE SHARKS vagina during copulation. The siphon sacs origi- nate on the surface of the pelvic fin at the proximal end of the clasper and extend anteriorly under the dermis to end blindly just short of the pectoral girdle. They are approximately 25 mm in diameter and 60 cm long. Spermatoza Sperm cells (Figure 5) develop in expendable spheres of germinal tissue, the seminiferous am- pullae described by Romer (1962). They form ra- dially, then clump together in groups of 60-70 (Fig- ure 6). When the sperm mature the ampullae disintegrate, liberating individual spermatozoa into the interstitial spaces of the testis. They pass through the ductus efferens (Figure 2) and into the epididymis. Secretions from the accessory glands flow into the epididymis and form a matrix which supports the individual spermatozoa. Sper- matozoa are stored in the epididymis which usu- ally appears swollen in adult males. This is the most convenient location to obtain a sperm smear. In the lower epididymis the spermatozoa again aggregate, with heads aligned parallel until groups of 60-70 are formed in the anterior section of the ductus deferens. Hundreds of these packets then aggregate into spermatophores (Figure 7), which are stored in the expanded terminal am- pulla of the ductus deferens. Spermatophores In mature males the entire lumen of the lower ductus deferens is usually turgid with seminal products. Most noticeable macroscopically are snow-white clumps of a gelatinous substance 3-4 mm in diameter and containing no spermatozoa. This evidently is a supportive and possibly nutri- tive material for the smaller spermatophores. The blue shark spermatophore (Figure 7) is an ivory white ovoid, 0.5-2.0 mm across its largest diame- ter. When the ampulla is cut at midkidney, sper- matophores flow freely and copiously from the incision and are interspersed with the white gel- atinous clumps. Several hundred milliliters may be expressed from the two ductus deferens of an adult male. Matthews (1950) gave a good account of the structures and functions involved in spermato- FIGURE 6. — Spermatozoa in seminifer- ous ampullae of the blue shark (X 1,600). 449 Figure 7. — Spermatophore of the blue shark (xlOO). FISHERY BULLETIN: VOL. 77. NO- 2 w^^vf Tl >*-i~^- ^ •>.;.•* 'V^bm... f ^-.••.'*«v- _^ 1, N w-^i-i'j.- phore formation in the basking shark. He specu- lated that spermatophores preserve the sperm from loss in leakage to the surrounding water dur- ing copulation. Blue shark spermatophores break down in seawater, liberating individual sper- matozoa, so rapid transfer is necessary. The sper- matophore may simply be an efficient way to store spermatozoa in the male's ductus deferens. Indicators of Sexual Maturity in Males The simplest technique to determine maturity is to compare external secondary sexually dimor- phic characteristics that occur in large animals with those same characters as they appear in less developed members of the species. In male elas- mobranchs changes in relative size, hardness, and development of the claspers is the most frequently 4,50 employed method for determining sexual matur- ity. Clark and von Schmidt (1965) considered a male mature when: 1) the distal end of the clasper and rhipidion are fully formed and can be spread open on a fresh specimen, 2) the clasper proximal to the head is rigid due to calcification of the sup- porting cartilage, 3) the base of the clasper rotates easily and the clasper can be directed anteriorly, and 4) the siphon sacs are fully elongated. Aasen (1966, footnote 5) used clasper length exclusively as a maturity index in his work on blue and por- beagle sharks. Springer (1960) noted that the claspers of the sandbar shark become hardened or calcified at about the same time that the testes enlarge. ^Aasen. O. 1961. Some observations on the biology of the porbeagle sharkLamna nasus. Bonnaterre. Int. Counc. Kxplor. Sea, CM. 1961, 109:1-7. PRATT REPRODUCTION IN BLUE SHARKS Blue shark claspers exhibit these characteris- tics (Figure 8) in a gradual transition with body growth rather than the abruptness noted by Clark and von Schmidt (1965) for thecarcharhinids. It is therefore difficult to distinguish maturity in sub- adult blue sharks based on external organs. Another valid index of sexual maturity is the presence or absence of sex products such as eggs and sperm. Several authors have used the pres- ence of male sexual products as indicators of maturity. Kauffman (1950) working on the tiger shark observed ". . . the release of milt from the gonoduct when pressure was applied." Matthews (1950) stated that a basking shark of 622 cm ". . . was just approaching sexual maturity, for though the testis was showing incipient activity, the ampullae of the ductus deferentia were rather small, completely empty of spermatophores and showing no signs of having contained any." Olsen ( 1954) recognized that maturity took place over a fairly extensive size range. He noted that in the school shark, Galeorhinus australis, seminal fluid flows freely from the cut surface of the enlarged testes and the seminal vesicles contain active spermatozoa in early summer. In borderline cases Olsen histologically sectioned the testis. He considered those fish to be mature that had ". . . enlarged seminiferous tubules [sic] which carried bundles of ripe spermatozoa . . . ." Bonham et al. (1949) and Templeman (1944) working on the spiny dogfish, Squahis acanthias. combined clas- per length with the presence of spermatozoa in the seminal vesicles to determine maturity. In the blue shark, two organs which enlarge as the male matures are the testes and the epididy- mides. Unfortunately, testes length ( Figure 9) and epididymis width (Figure 10) follow the same gradual size increase as the claspers (Figure 8). Because they do not exhibit major inflections, these relationships are of little use for determin- ing the onset of sexual maturity. The most reliable method that I have found for determining maturity in the difficult subadult to adult sizes is to assess the ability of a shark to produce spermatophores. Many sharks with clas- pers that appear mature lack spermatophores and have small ductus deferentia. The spermatophore is the last tissue to mature and it develops abruptly in blue sharks. Of 193 male blue sharks examined, 74 (38. 3*^) contained some quantity of spermatophores. The sharp increase in spermatophore occurrence be- tween 175 and 205 cm body length is the transition ■ tf/rn SPERMATOPHORES o WITHOUT SPERMATOPHORES .*• *, • ■ ° J>-° ° . . Zr' 80 100 t20 140 160 160 200 2Z0 240 260 FORK LENGTH (cm) Figure 8. — Clasper-body length relationship compared with spermatophore development in the blue shark. o o o 205 cm and lOC^ >235 cm were mature. These data agree well with Aasen's (1966) length at sexual maturity for the male blue shark. He cited 196.6 cm as the point of maturity as determined by an analysis of clasper length and my observations show 80% of the males contain spermatophores at this size. Stevens' ( 1974) sam- ple contained only one mature male blue shark. He drew no conclusions regarding male maturity. Stevens speculated that all of his blue sharks were either immature or in a resting stage, except the largest one which was in poor condition. By my criteria, all of his sharks were immature except this individual. Bigelow and Schroeder (1948) suggested that both sexes mature in the range of 177-203 cm which agrees well with my finding of 183 cm. Afield test for the presence of spermatophores is accomplished by making a cross-sectional cut through the kidney at its thickest part. Four large ( 10-15 mm) ducts are visible ventral to the kidney at this level. Two of these are the thin-walled ureters, usually filled with a clear fluid. The thicker walled pair are the ampullae ductus defe- rens containing several hundred cubic centime- ters of spermatophores, 0.5-2.0 mm in diameter, and their associated white flocculent supportive tissue. The presence or absence of spermatophores 140 160 laO 200 BODY FORK LENGTH (cm) provides a positive answer to the question of sex- ual maturity in an individual male blue shark. I observed no obvious seasonal fluctuations of sperm production in the blue shark as have been noted by Olsen (1954 ) and other authors for differ- ent species of sharks. Female Anatomy Ovan and Epij;150 cm and suggests that this is the size at sexual matur- ity for the blue shark. Northwest Atlantic blue sharks bear dermal wounds similar to those described as courtship scars by Stevens (1974). Distinct tooth cuts have been observed on females of 134 cm. (The smallest female carrying sperm is 136.5 cm.) Occasionally slashes and wounds resembling mating marks occur on females as small 118 cm. External tooth cuts are most extensive in female blue sharks from 145 to 200 cm long (Figure 16). Pregnant females generally bear only older healed scars. Males of all sizes are usually free of cuts. Wounds are so con- sistently present on females that the fish being tagged during longline or sportfishing operations may be sexed from the dorsal surface without examination of the pelvic appendages. To accommodate the male's aggressive mating behavior, the skin over most of the body of the mature female is more than twice as thick as that of the male (Figure 17). The skin is thicker than the males' teeth are long and only occasionally do the wounds penetrate the dermis and involve the musculature. Tooth cuts are generally punctures or slashes made by the upper jaw only. Resistance to infection and healing rates are apparently high in the blue shark. Despite injuries that seem very serious, evidence of infection and necrotic tissue are notably absent. Matthews (1950) noted internal lacerations on the thick vaginal pads of female basking sharks. They are caused by the male's clasper claw, a structure common to several families of elasmo- branchs. The blue shark clasper does not bear a claw. After insertion, the terminal end of the clasper is flexed about 45°, unfolding and expanding the sharp-edged rhipidion to form an anchor in the vagina. The female often bears hematose abra- sions on the otherwise light colored walls of the vagina as a result of copulation. Specimens from the Middle Atlantic Bight possess vaginal wounds during all seasons examined (March-October). Fresh marks are more frequent in summer months while older dark purple scars are observed in spring and fall. Spermatozoa have been found in young females lacking vaginal wounds indicating 454 PRATT REPRODUCTION IN BLUE SHARKS Figure 14. — Oviduca! gland of female blue shark- Dark contents of central tubes are spermatozoan masses. Cross section ( x8). 455 FISHERY BULLETIN: VOL. 77, NO. 2 Figure is.— Oviducal gland of female blue shark with spermatozoa clumped in tubules. Enlargement of Figure 14. Cross section ( > 80). Figure 16. — Subadult female blue shark 185 cm FL with tooth cuts (mating scars). 456 I'KATT REPRODUCTION IN BLUE SHARKS Figure n. — Skm thickness compari- son, cross sections of pelvic region of similar-sized male (left) and female (right) blue shark. that insemination is not always accompanied by internal lesions. Hermaphroditic Blue Sharks Hermaphroditic blue sharks have not been mentioned in the literature and are apparently as rare as in other species of elasmobranchs. The only hermaphroditic blue shark I have examined was caught off central Long Island, 14 July 1973. It was 192 cm long and weighed 94 lb. There were many severe dermal lacerations (mating scars), some so recent as to be freshly clotted. There were two similar-sized claspers on the inner margin of the pelvic fins. They were much too short for the body length (17 mm from the margin of the fin to the free tip) and were not calcified. Internally, a small patch of ovary bearing four large (11 mm) ovarian follicles was found in the normal position on the epigonal organ. All of the reproductive or- gans were reduced; the upper oviduct diameter was 4 mm. Paired oviducal glands were present as 10 mm swellings in the oviducts. Caudally the 4 mm oviduct expanded to a 10 mm uterus. Two small testes were suspended in the usual position forward in the abdominal cavity. Histological sec- tions revealed spermatozoa in the seminiferous ampullae of the testes. The epididymis and vas deferens were identifiable as undeveloped white tubes 1 mm in diameter. Judging from mating scars on the dorsal surface, this fish was treated by at least some of its conspecifics as a female. Al- though the ovary and testes were developed, the oviduct, ductus deferens, and claspers were too underdeveloped to permit this specimen to be functionallv mature as either a male or female. Indicators of Sexual Maturity in Females Nearly every structure of the female reproduc- tive tract has been used in the past to determine sexual maturity. Most authors rely on a combina- tion of indicators that account for several stages in the reproductive cycle. Bonham et al. ( 1949) noted that the length of the ovary increased only slightly faster than did the body length of Squaliis acan- thias. Springer (1960) and Kauffman (1950) used the appearance of the elasmobranch ovary as an indicator of maturity. The development of the oviduct has been considered an index by Springer (1960) and Olsen (1954); the oviducal gland by Olsen (1954) and Nalini (1940); and the uterus by Olsen (1954), Templeman (1944), and Aasen (see footnote 5). In the carcharhinids studied by Clark and von Schmidt (1965), the development of the vaginal opening proved to be the most useful ex- ternal indicator of maturity. In young carchar- hinids the vaginal opening begins as a slit in the urinary papilla. Defining sexual maturity in female blue sharks is difficult because they pass through a distinct subadult phase in which the organs necessary for copulation are developed and those required for generation are dormant or developing. The sub- adult stage lasts for two summer seasons and most female blue sharks on the continental shelf in the western North Atlantic are in this stage. Examination of sex organs in female blue sharks of various sizes reveal that like the male claspers, growth is quite regular in the ovary and oviduct. The oviducal gland exhibits some differ- ential growth after 100 cm body length is attained 457 FISHERY BULLETIN VOL 77, NO (Figure 18), but growth is nearly constant through the subadult sizes. The vaginal opening is occluded by a partial membrane only in the juve- niles, disappearing by 135 cm. The membrane may be lost with growth. The first attempt at copu- lation would remove it. Sex Products Another method for determining size at sexual maturity is to examine the sex products (follicles, ova, embryos) in relation to body length. The presence of mature ova in the ovary is one of the most widely used indicators of elasmobranch sexual maturity. Metten (1941), Bonham et al. (1949), Kauffnian 1 19.501, Olsen (1954), and Springer ( 1960) have all partially utilized the con- dition of ovarian eggs for this purpose. In the mature blue shark a generation of 100- 130 large ova of fairly equal diameter ( 15-20 mm) visually dominate the hundreds of smaller folli- cles in the ovary. In a 243 cm mature gravid female, the most distinctive ovarian features were 123 yolked ova from 6 to 20 mm in diameter. The larger ova were found at the anterior end of the ovary. A second group of nearly 1.000 follicles, from 0.1 to 1.0 mm in diameter, were found between and attached to the covering of the larger ova. The diameter of the largest generation of ovar- ian eggs is a valid index of first maturity when compared with body length (Figure 19). First 1 — I — \ — I — r 40 60 80 100 120 140 160 180 200 220 240 260 FORK LENGTH (cm) Figure 18 — Oviducal outside diameter-body fork length relation.ship in the blue shark. 458 PRATT REPKODUCTION IN BLUE SHARKS 100 2 0 - • • "i 5 18 1 • UJ '^ - 1 , • • 1- i UJ 14 _ , 1 2 1 < . 1 1 Q 1 2 - • O / O 10 — • llj H 8 - • (D . ' . . •• ^ A / _ .'• • • ..^2 < • . . ,,■; ^^ ^ _i 14 • _:--'■'-''' 2 - • 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 120 140 160 180 200 220 FORK LENGTH (cm) 240 260 280 Figure 19. — Largest egg diameter-fork length relationship in the blue shark. Hand tit curve follows the first generation of eggs in the subadult population Egg diameters accompanying lengths >200 cm are from mature or gravid females that have released or absorbed one or more generations of eggs and are producing subsequent generations. maturity is reached at 180-190 cm body length by this criterion. Egg diameters accompanying body , lengths -200 cm are from mature or gravid fe- males that have released or absorbed one or more generations of eggs and are producing subsequent generations. Gravid Females The smallest recorded gravid females should be slightly longer, due to elapsed gestation time, than females carrying their first generation of ripe ovarian eggs (Figure 19). Gravid blue sharks with the smallest fork lengths reported in the literature from the Atlantic are as follows: 166 cm (Tucker and Newnham 1957), 193.3 cm (Aasen 1966), and 177-203 cm (Bigelow and Schroeder 1948); from the Pacific: 168cm(Suda 1953) and 173.3 cm (Strasburg 1958). Blue sharks carrying embryos are encountered infrequently in the world ocean. Suda (1953) ex- amined 115 Pacific blue shark females bearing embryos and concluded that gestation lasts 9 mo and birth occurs between December and April. At this time the embryos have attained a maximum length of 39 cm. Strasburg (1958) examined 18 large females from the Pacific of which at least 10 were pregnant. The largest embryos were also 39 cm and occurred in March and May. Francis Williams" caught eight pregnant fe- male blue sharks while longlining in the eastern Pacific. His sample was unique because the size range of gravid females was small (153.3-171.6 cm). The embryos also were in a narrow size range (21.9-34.7 cm). Gubanov and Grigor'yev (1975) reported small embryos (3.2-28 cm) from February to July in the equatorial Indian Ocean. They speculated that birth of young blue sharks occurs outside of this area. "Williams, F. 1977. Notes on the biology and ecology of the blue shark iPrionace glauca L.) in the eastern Pacific Ocean and a review of data from the World Ocean (unpubl. manuscr.l. Pers. commun. via John Casey, Northeast Fisheries Center Nar- ragansett Laboratory. National Marine Fisheries Service, NCAA, Narragansett' Rl 02882. 1977, 459 FISHERY BULLETIN VOL, 77. NO, 2 There are few published accounts of gravid female blue sharks in the North Atlantic. Aasen ( 1966) examined 48 caught by longline primarily around the Canary Islands. He reported lengths of 11 individuals and embryo lengths from only 2 specimens with means of 28.1 and 40.0 cm. The largest embryo length he measured was 43.0 cm. From these lengths he concluded that birth oc- curred between February and April. Beebe ( 1932) reported a gravid female taken off Nonsuch Island, Bermuda, in September of 1931. She carried 50 embryos averaging 8.3 cm long. Tucker and Newnham (1957) reported a small ( 166 cm) gravid female caught in the sport fishery off Looe, England. They summarized the eastern Atlantic and Mediterranean observations of gravid females with embryos. From 1967 to 1975, 1 examined 19 gravid female blue sharks from the western Atlantic. These specimens include a blue shark taken in January approximately 300 mi northeast of the Windward Islands (lat. 21°20' N, long. 58°52' W); 2 caught in the Gulf Stream south of Sable Island in May; and 16 obtained from off the coast of Long Island, N.Y. These fish were caught within 50 mi of shore dur- ing June and July. The embryos from 13 fish were examined, the remainder having been lost or aborted during capture. In addition, Richard Backus' has supplied information on 19 gravid females. Embryos Growth of the placentally viviparous embryos appears to be linear, gestation taking 9-12 mo. Figure 20 combines all available North Atlantic and Mediterranean data for a summary of embryo length and season. The trend line seems to indi- cate a gestation of 12 mo, 3 mo longer than re- ported by Suda (1953). A 12-mo gestation also agrees with my proposed sexual cycle. However, since the left-hand data points are from offshore observations and the right-hand points are from inshore fish, it is quite possible that the offshore embryos may be born in March while embryos from inshore females could have been conceived in September and born in June, 9 mo later. These data cannot therefore resolve gestation time. On 23 July 1978, a female blue shark in the first stages of pregnancy was examined at Montauk. It contained two embryos 11 and 13 mm long at- tached to 22 mm yolks with 38 less-developed eggs arranged in a dorsoventral series in both uteri. 'Original data from Richard H. Backus of Woods Hole Oceanographic Institute. Pers. commun, via John Casey. I I- a. o o >- tc m UJ 1 1 1 1 1 1 1 1 _L 1 1 - o 48 - EMBRYO SIZE/MONTH O o 44 - N ATLANTIC a MEDITERRANEAN o ^^ - ALL SOURCES • ■ ^^f ° 40 - Y-- 017139 + 0 09816 X n • .^ r -- 0. 841 .^'^'^ o 36 - • ^^ • * y^ 32 - o% ^-^ A ■ ^ • c. 28 - • 24 - ^ • ^^ '■'"^ o PRATT 20 — • n BACKUS (U1PUBI AASEN 1966 16 — ■ o ■ LOB IAN CO 1909 A TUCKER a NEWNHAM 195? 12 - ^^^' \ * OODERLEIN IS SI 8 - ^^^^^ a • O BENE DEN 13 n ^•^ • £3 BEEBE 1932 4 - ^.^ • * - *2 0 - 1 1 1 1 1 1 1 "T" 1 1 MAY 1 JUN 1 JUL i AUG 1 SEP 1 OCT 1 NOV DEC JAN 1 FEB MAR 1 APR 1 MAY 1 JUN 1 JUL AUG MONTH OF CAPTURE Figure 20. — Embryo length-month relationship for North Atlantic and Mediterranean blue sharks 460 PRATT REPRODUCTION IN BLUE SHARKS The embryos taken during June and July were full term (mean lengths 37.1-46.6 cm). Some were larger than any reported in the literature (42-46.6 cm) except for one 49 cm embryo reported by Be- neden (1871) and cited by Tucker and Newnham (1957). The range of smaller embryo sizes reported by other authors as "full term" may result from examination of young "in utero" or aborted on deck. Judging from my January sample, after only 4-5 mo gestation embryo blue sharks have lost branchial gills and yolk sacs, and appear to be full-term replicas of the adults. When returned to the ocean they are active and quickly swim away. Premature embryos (up to 30 cm) have a propor- tionally thin body for the size of the head giving them a tadpolelike appearance. Full-term em- bryos (Figure 21) have a girth that equals or ex- ceeds the head circumference. The pregnant female sampled in January carried 82 embryos averaging 13 cm long. Suda (1953) indicates this 264 cm female could be between 4 and 5 mo preg- nant. Only the report of Gubanov and Grigor'yev (1975) of 135 young exceeds this observation. Minimum number of young could not be deter- mined due to reports of premature parturition while the fish were being boated. Gubanov and Grigor'yev (1975) agreed with a proposition of Liibbert and Ehrenbaum (1936) that embryo blue sharks develop and are born in stages. No evidence was found in the Atlantic to support this hypothesis. Embryos occurred in the same relative stage of development in each female. This is apparent in Figure 22. The 37 cm (.V ) embryos ventral to the 232 cm pregnant female appear slightly smaller due to camera parallax. Nearly every litter contains one stunted or decom- posing embryo. The explanation may be failure to attain placentation, dislodgement, or tangling of the umbilical cords. A stunted embryo is 10th from the left in the ventral row of embryos (Figure 22). The smallest free-swimming young have been observed in the Pacific by Francis Williams (see footnote 6) at 35 cm and Strasburg ( 1958) at about 38 cm. The smallest Atlantic specimen is Bigleow and Schroeder's (1948) report of 44 cm. These lengths resemble lengths of the largest embryo sizes, and available evidence suggests that size at birth for the blue shark is between 35 and 44 cm. The pupping season can be interpolated from Fig- ure 20 to occur from March to July. The apparent lack of "young-of-the-year" blue sharks suggests an offshore pupping. The blue shark is the most prolific of the large oceanic sharks (Bigelow and Schroeder 1948), yet I have seen only one free- swimming fish that was <1 m FL. Blue sharks in the first and second year of life must, therefore, inhabit an unknown niche. Structure and Function of the Oviducal Gland The oviducal gland (Figure 23) as defined by Metten (1941) has also been referred to as the FIGURE 21— Ovary and 43 cm FL full- term embryo from 220 cm FL gravid blue shark. tf.,* 461 FISHERY BULLETIN VOL, 77. NO. 2 Figure 22.— Gravid female blue shark. VENTRAL CROSS- SECTION LATERAL FlOURE 23.— Schematic views of the oviducal gland in the blue shark I 0mm lOmm I 0 mm nidamental or nidamentary gland and as the shell gland. The term "nidamental" is inappropriate since it is derived from the Latin "to nest" which is not a trait of elasmobranchs. Since a functional shell is produced in only a few species of shark, oviducal is a more accurate term for this speciali- zation of the oviduct. A sagittal section of the oviducal gland reveals the two major tissues (Figure 24), an anterior albumen-secreting zone and a posterior shell- 462 PRATT: REPRODUCTION IN BLUE SHARKS CRAINIAL OVIDUCT LUMEN OF OVIDUCT ALBUMEN SECRETING ZONE CENTRAL LUMEN LAMELLAE SHELL SECRETING ZONE - ANTERIOR HALF SHELL SECRETING ZONE- POSTERIOR HALF CAUDAL OVIDUCT Figure 24.— Sagittal section of the oviducal gland in the blue shark i ^5 cross section). secreting zone. The mucus-secreting zone found in some elasmobranchs is reduced or absent in the blue shark, perhaps because of the limited shell that is produced. Secretory tubules originate blindly around the circumference of the gland and extend inward, parallel to one another. In the course of their travel they bow posteriorly for sev- eral millimeters, then return to the latitude of their origin where they communicate with the central lumen. The albumen-conducting tubules enter the lumen as a series of 13-15 evenly spaced lamellae with irregularly flattened ends. The shell-secret- ing tubules terminate in tufted pockets bordering the central lumen. The posterior half of the shell-secreting section communicates with the lumen through paired caudal protuberances of secretory tissue (Figure 24). They are embedded in a stroma of connective tissue and run a shorter, more irregular course to the lower central lumen where they end in larger and less uniform lamellae. As the gland matures the lumen branches into two diverticula, which extend around its circum- ference and into each lateral horn in a medial cross section. These two diverticula give the lumen a symmetrical S-shaped appearance (Figure 1.3i. Of those sharks studied by Prasad ( 1944, 1945, 1948), the oviducal gland of the blue shark most closely resembles that of Carcharhinus dus- 463 FISHERY BULLETIN VOL 77, NO '.' sumieri. This is to be expected because both C. dussurnieri and P. glauca are viviparous forms in which a yolk-sac placenta has been developed. (See Prasad 1944, for a discussion of phylogenetic significance.) Metten (1941) observed that the oviducal gland of Scyliorhinus canicula has a function beyond that of albumen and shell production. He found active male spermatozoa in every mature female oviducal gland that he dissected. In S. canicula this gland is a seminal receptacle. Eggs are fer- tilized, not in the anterior oviduct as had been previously suggested, but in the oviducal gland itself It is not known how many species of elas- mobranchs share this trait. Matthews ( 1950) could not find sperm in the oviducal gland of the basking shark. Prasad (1944) observed the presence of spermatozoa in the oviducal glands of four vivip- arous species from the Indian Ocean: Car- charhinus dussurnieri . Hemigaleus balfouri, Sco- liodon palasorrah , and S. sorrakowah. He also gives an excellent account of the search for a "re- ceptaculum seminis" and its existence in other animals. Prasad (1945) observed spermatozoa in the oviducal gland of the tiger shark, Galeocerdo cuvieri. Stevens ( 1974) found that IG""! of female British blue sharks had tooth cuts. Of these, three were dissected and oviducal glands examined for sper- matozoa. His failure to find spermatozoa could re- sult from technique, sample size, or the dynamics of the British blue shark population which con- tains very few males (Stevens 1974). Only 4''^ of the males in his sample reached sexual maturity as defined by my criteria based on the spermato- phore development of western Atlantic blue sharks. I have found spermatozoa in the oviducal glands of 79 of 160 female blue sharks collected over a 3-yr period (Figure 25). In all cases sperm was detected in a cross section of the posterior third of the oviducal gland using light microscopy. Fifteen micrometer sections were examined at 120-500 diameters magnification and the presence of brightly stained sperm confirmed at 1,250 diame- ters (Figure 26). In the last year of field collections, comparative tests were conducted to determine if the presence 28 26 24 22 > 20 o 18 LiJ 16 3 14 O LJ 12 10 Li. 8 6 4 2 0 uU TlM B I _ I X EGG DIAMETER I ^*^ FOR INSEMINATED $'S. N=62 r-n — \'""{""V'''\ 1 — I — r^ "h ^ r^^ 100 140 ISO BODY LENGTH (cm) I I r — I I I 220 260 m CD CD 20 o IH > lb s 14 m 1? H m lU :d 8 -•"^ 6 3 4 3 w,__^ ^. 0 Figure 25, — Frequency of occurrence of female blue sharks off Bay Shore, N.Y.. with data on insemination, egg diameter, and body length relationship: Ai uninseminated females, Bi adult females. Cl insemmated females. 464 PRATT REPRODUCTION IN BLUE SHARKS '**«r wl % TV- ,J«W» Figure 26. — Spermatozoa in tubules of oviducal gland in the blue shark (x 2,500). 465 FISHERY BULLETIN VOL. 77. NO. L' of spermatozoa in the oviducal gland could be de- tected using a smear technique as an alternative to the time-consuming process of embedding and sectioning. The oviducal gland was excised with a few centimeters of oviduct attached. The posterior one-third of the gland was removed by cross- sectioning with a clean scalpel. The anterior two- thirds of the gland was then squeezed and the expressed fluid was smeared on a microscope slide. Slides were dried and later fixed and stained with the Harleco Diff-Quik stain system. Oviducal glands from 21 sharks were prepared. One from each fish was sectioned; the other gland cut and smeared. Both techniques revealed sper- matozoa in 15 and both methods proved negative for the other 6. The presence of spermatozoa can therefore be determined from fresh smears of the oviducal gland. Like Metten (1941), I found varying amounts of spermatozoa in the inseminated glands. Females >200 cm contained relatively few spermatozoa in the tubules. Some fish in the 160-180 cm gi-oup had obviously just copulated, because the tubules of the posterior oviducal gland were distended with sperm (Figure 14) and additional sperm was present in the central lumen. The spermatozoa are stored in the lower lobes of tubules which probably once were shell-secreting in function but now are actively evolving into a seminal receptacle. Since sperm may be stored for over 1 yr and possibly two (see Sexual Cycle below) these tubules must have a mechanism for sperm preservation and nour- ishment. Ducts from the lower lobes also run an- teriorly into the upper ends of the lumen's diver- ticula. I suspect that the ova are fertilized at this upper level of the oviducal gland. The exact sequence of events is difficult to understand because of the complex nature of the lumen. Sperm Retention in the Female Blue Shark Many diverse animals can store spermatozoa for varying lengths of time (Prasad 1944). The pres- ence of spermatozoa in the oviducal glands of pregnant blue shark females would suggest extended storage. Histological examination re- vealed spermatozoa in the oviducal gland of the Sargasso Sea specimen. The other gravid females examined histologically are from northern waters caught in May, June, and July. A total of nine gravid females contained spermatozoa. Two females did not contain spermatozoa and it is pos- sible that the glands lacking spermatozoa were poorly fixed, or the spermatozoa was destroyed because these sport-caught fish often hang in the sun for hours before dissection. Alternatively, it is possible that the reservoir of sperm has been naturally depleted and another copulation is necessary. If the female could physiologically sense this depletion, the presence in coastal wa- ters of 225-240 cm nongravid females would be explained. In any case, it may be concluded from the above that spermatozoa can persist in the oviducal gland for at least the length of gestation (9-12 mo). If delayed fertilization is a part of the sexual cycle, then storage for 18-22 mo would be necessary for sperm to be found in a gravid female. Since the oviducal gland is at the anterior end of the uterus it is doubtful that spermatozoa could reach the gland if copulation took place while the female was carrying young. In addition to these physical obstacles to the transfer of spermatozoa, the presence of 110-120 ripe ovarian eggs also suggests that the gravid female is ready for fertili- zation and development of a second litter im- mediately after pupping. The offshore distribution ofmost pregnant females (Aasen 1966; Backus see footnote 7) in areas not frequented by adult males and perhaps unreceptive behavior in the female very likely act to prevent males from copulating with pregnant females. Therefore, it is possible that the quantities of spermatozoa found in the nine gravid female oviducal glands are sufficient for fertilization of the ripe ovarian eggs. Sexual Cycle The high incidence of mating scars and presence of sperm in the oviducal gland indicate a summer IMMATURE M » 3U8ADULT MATURE i: 1 ; ^ '. 1^0 .40 it.0 ISO ..'00 ??0 BODY FORK LENGTH (cm) Fk; L'RE 27. — Blue shark sex ratio in June off Bay Shore, Lon^ Island, N.Y., 196.5-72, n = 2,174. 466 PRATT REPRODUCTION IN BLUE SHARKS breeding season for the blue shark on the conti- nental shelf off southern New England. The length-frequency histogram of these inseminated females approximates a curve of normal distribu- tion with a peak at 175 cm (Figure 25). The phenomenon of carrying spermatozoa seems to separate an age-class from the combined length frequency of the female population. If this is an age-class, then Stevens' (1975) age curve for the blue shark indicates that the inseminated females are 5 yr olds and the uninseminated fish are primarily fours and fives. Since most of my sam- ples were taken in June and July, it is possible that the unfertilized 5 yr olds would be insemi- nated later in the season. Since all nongi-avid females on the continental shelf bear tooth cuts and many have vaginal scars, it would appear that only females >4 yr have organ systems developed enough to retain spermatozoa. The growth curve ofovarianeggsin inseminated females (Figure 25) shows the eggs as half-mature in 5 yr olds. Five- yr-old inseminated females that I sampled as late as October in continental shelf waters off southern New England do not contain mature ova or em- bryos. Due to immature egg size and the lack of developing embryos, 1 conclude that this age class is not ready to bear young during the summer of insemination. If fertilization occurred during the winter, the 9-mo gestation proposed by Suda ( 1953) and Aasen ( 1966) would produce full-term embryos in gravid females through the following summer and into the fall. This is not the case. Full-term females occur most frequently during the spring and early summer (Figure 20). The age-6 female length-frequency mode (190 cm; Stevens 1975) is conspicuously absent from the shelf waters in the summer months (Figure 27), while males of this size are numerous. Backus (see footnote 7) caught two females offshore that could be 6 or 7 yr old by Stevens' (1975) criteria (197.4 and 209.5 cm); each carried 11.0 cm em- bryos in September and October, respectively. I examined one gravid female in July with two em- bryos 1 1 and 13 mm. The uterine eggs were other- wise undeveloped. Typically, gi^avid females in this population are of lengths indicating 7 yr of age and older. Based on these findings, the sexual cycle of the female blue shark in the western North Atlantic would start as 4- and 5-yr-old fish arrive on the feeding/mating grounds of the continental shelf in late May and early June. Here they interact with males receiving dermal punctures and lacerations (tooth cuts). The 5-yr-old females and some 4 yr olds, copulate with the males of 180 cm and larger judging from the size of the tooth interspace reflected in bite marks and male sexual maturity. This process is known to continue as late as November and may continue year round in Baha- mian waters (Stephen Connett*). The followmg spring, the 6-yr-old females remain offshore and fertilize their eggs (May, June). Embryos reach full term in 9-12 mo. Puppingisfrom April to July. At this time the female is 7 yr old. This is the probable trend for most female blue sharks. There are many exceptional bits of data such as reliable reports of small (165 cm) gravid females (Suda 1953; Tucker and Newnham 1957) and embryo sizes that depart from the trend, especially in the eastern North Atlantic ( Figure 20). These are to be expected in a wide ranging, abundant species with a long breeding season. A small number of females in the inshore population have very advanced or- gans and egg development for their length. It is possible that these precocious individuals bear young a year earlier than their siblings or shift completely out of phase by bearing young at ran- dom seasons. Stray gravid females occur regularly in south- ern New England shelf waters. Their diminuitive numbers are an insignificant part of the spawning population. Too little is known of the early life history and feeding habits of the blue shark to determine whether the young would fare better in the rich waters of the continental shelf or offshore along the margins of the Gulf Stream. Sex Ratio Suda ( 1953) reported the blue shark sex ratio at birth to be 1:1. Data from a population of 2,174 males and females sampled at Bay Shore, Long Island, from 1965 to 1972 is presented in Figure 27. In this sample immature females consistantly outnumber the males until a fork length of 150 cm is reached because unlike females, the males only move inshore when the sex organs start to mature. The sex ratio then becomes equal in the subadult sizes when a large number of mating wounds and inseminated oviducal glands are prevalent. In the adult size group ( 180-250 cm) the sex ratio shifts rapidly to a preponderance of males. The inflexion point at 180 cm coincides with the size at which 'Stephen Connett. instructor, summer oceanography program St. George's School, Newport. R.I., pers. commun. April 1977. 467 FISHERY BULLETIN: VOL 77, NO ■> ovarian eggs are reaching maturity (Figure 18) and the greatest number of females are becoming inseminated (Figure 27). Larger females are caught in decreasing numbers on the mating grounds on the shelf. Their absence probably indi- cates a successful insemination and offshore mi- gration. Since courtship and copulation are not without peril to the female, it is reasonable that they should move offshore at this time. The sex ratio remains between 5 and 10% female, from 200 to 230 cm where a second peak occurs. These are mostly postpartum and gi-avid females in their first pregnancy. They have probably followed the main population inshore for its summer feeding migration. It is possible that since their eggs are ripe they may also need to supplement the amount of spermatozoa in the oviducal gland. CONCLUSION The blue shark's success as a species is partly dependent on a highly evolved system for repro- duction. The blue shark differs from other car- charhinids in having a steady growth rate for the sexual organs, a lack of seasonality in the genera- tion of sex products, and a distinct female subadult stage. A different approach has been necessary to discern the size at sexual maturity for both sexes: an analysis of spermatophore development for the male, and an examination of the seminal recepta- cle present in the female oviducal gland. There are many stages between the generation of sexual products (sperm, eggs, embryosi and the time of their delivery. Elaborate capabilities have been developed by both sexes for lengthy storage and nourishment of spermatozoa, first in the epididymis, then as spermatophores in the ductus deferens, and finally in the oviducal gland of the female where they are retained for months and possibly years. Sexual maturity occurs for both sexes at a simi- lar body length when they are together on the continental shelf for the summer season. While the details of mating and copulation are obscure, it is highly successful since not a single female of age was observed without evidence of mating activity and 49% were inseminated. With the exception of the strays examined op- portunistically during this study gravid females occupy a niche that is different from the continen- tal shelf population. The release of young and their early development apparently occur in oceanic areas. Little is known of this important period in their life history. SUMMARY Males The internal anatomy of the male blue shark is similar to other carcharhinids. The vas deferens is enlarged and convoluted for the storage of sperm and spermatophores. The clasper lacks a spur and resembles that of the basking shark and tope. Juvenile and small mature males 4 and 5 yr old ( 153-180 cm) are the most commonly encountered size group on the continental shelf off southern New England from June to October. Male blue sharks reach maturity at 180 cm and probably copulate frequently through the summer. Only about 2'7( of all males caught have claspers swollen and discolored by mating. Females The internal anatomy of the female blue shark is similar to other species of placentally viviparous carcharhinids. The single right ovary delivers ova up to 20 mm in diameter to paired oviducts. They are fertilized as they pass through the oviducal gland by stored spermatozoa and develop in paired uteri. Female blue sharks can be grouped into imma- ture, subadult, and adult categories based on size, behavior, and development. 1 . Immature females range from 46 cm (birth) to a maximum of 145 cm long. The ovary is small with many undeveloped follicles. The oviducal gland and uterus are undifferentiated from the oviduct. The vagina is sealed by a membrane which may persist to a fork length of 135 cm. 2. Subadult females range from 145 to 185 cm long and possess differentiated though not com- pletely functional reproductive organs. The ovary contains follicles between 2 and 6 mm. Externally, the oviducal gland is heart shaped and roughly twice the diameter of the oviduct. The uterus is differentiated from the oviduct but not >2 cm in diameter and never contains embryos. The skin begins to thicken to receive the courtship wounds of the males. There are several reasons for consid- ering these females as a separate group. Fish in this condition are the most common group of females on the continental shelf from Hudson 468 PRATT: REPRODUCTION IN BLUE SHARKS Canyon to Georges Bank, They are sexually active with obvious external mating wounds on every individual in shelf waters. The presence of male spermatozoa in the oviducal gland indicates that a large proportion have successfully copulated. Subadults were found inseminated at a minimum size of 135 cm. They bear abrasive scarring on the lateral walls of the vagina in fish as small as 158 cm. 3. Mature females range from 185 to >300 cm long. They possess fully differentiated organ sys- tems that are actively developing eggs, embryos, or both. The ovary is robust with over 100 ova from 16 to 21 mm in diameter and hundi'eds of smaller follicles. The oviducal gland is large and heart- shaped with the anterior horns slightly coiled. The uterus when empty is long and flaccid. Skin thick- ness is increased to over twice that of similar-sized males. Recent internal and external mating wounds are usually not present on mature fe- males. Old healed scars are often present on fins and body. gravid female that I have examined suggests that another fertilization is imminent. ACKNOWLEDGMENTS My thanks to the staff of the Oceanic Gamefish Task of the Northeast Fisheries Center Narragan- sett Laboratory, National Marine Fisheries Ser- vice, NOAA, for help in data collection and analysis; to John Casey for guidance and sugges- tions; to Charles Entenmann and the Bay Shore Tuna Club for providing the opportunity to sample at their annual shark tournament; and also to Carol Kroupa and Carl Darenburg, of the Mon- tauk Marine Basin, who made sampling possible during their tournament. Thanks also to Bob Benway and Steve Szlatenyi for photogi'aphy, to Jennie Dunnington for manuscript typing, and to Lianne Armstrong for illustrations and artwork. I am grateful to John Colton who reviewed the manuscript, and to Richard Backus and Francis Williams for permission to use unpublished data. Spermatozoa Storage Both sexes store spermatozoa. It is first stored in the epididymis of the male in a matrix of suppor- tive tissue, then as spermatophores in the lower ductus deferens. After copulation, spermatozoa is stored as clusters of individuals in tubes of the oviducal gland of the female. Histological sections of oviducal glands from a full size range of 160 females revealed spermatozoa stored in 79. Sexual Cycle Four- and five-year-old female blue sharks ar- rive on the continental shelf off southern New England in late May and early June. Here they sexually interact with males, receiving tooth cuts. The 5 yr olds and some 4 yr olds copulate with males of 180 cm ( 6 yr olds I and larger. The 4-yr-old females are too undeveloped to store spermatozoa. Five-year-old females actively mate and retain copious amounts of spermatozoa. The following spring, this age-group, now 6 yr old, remain off- shore and fertilize their eggs in May or June. Em- bryos reach full term in 9-12 mo. Pupping is from April to July with up to 82 young being born. It is probable that the 7-yr-old female again copulates as the oviducal glands of gravid females contain a relatively small amount of spermatozoa. The full complement of ripe ovarian eggs present in every LITERATURE CITED Aasen, O. 1966. B\ahaien, Prion ace g la uca (Linnaeus! 1758, Fis- ken Havet 1:1-16, BEEBE, W, 1932, Nonsuch: Land of Water, Brewer, Warren & Put- nam, N,Y„ 259 p, BENEDEN, P, J, VAN, 1871, Les poissons des cotes de Belgique, leurs parasites et leurs commensaux, Mem, Acad, R, Med, Belg, 38, 100 p. BlGELOW. H, B,. AND W, C, SCHROEDER, 1948, Sharks, In A, E, Parr and Y, H, Olsen (editors). Fishes of the western North Atlantic, Part One, p, 59-546. Sears Found, Mar, Res,, Yale Univ, Mem, 1, BONHAM, K,, F, B, SANFORD, W, CLEGG, AND G. BUCHER, 1949, Biological and vitamin A studies of dogfish landed in the state of Washington iSqualus suckleyi ), Wash, Dep Fish,. Biol, Rep, 49A:83-114, CLARK. E., AND K, VON SCHMIDT, 1965, Sharks of the central Gulf Coast of Florida, Bull. Mar, Sci, 15:13-83, DODERLEIN. P, 1881, Manuale Ittiologico del Mediterraneo, Vol, 2. 119 p, Soc. Sci, Nat, Econ,, Palermo, GUBANOV. YE, P,, AND V. N, GRIGORYEV, 1975, Observations on the distribution and biology of the blue shark Prionace glauca (Carcharhinidae) of the In- dian Ocean, J, Ichthyol, 15:37-43, KAUFFMAN, D, E, 1950, Notes on the biology of the tiger shark (Galeocerdo arclicus) from Philippine waters, U,S, Fish Wildl, Serv,, Res, Rep, 16, 10 p LEIGH-SHARPE, W. H, 1920, The comparative morphology of the secondary sex- 469 FISHERY lU'LI.ETIN VOL 77. NO ual characters of Elasmobranch fishes. 1. J. Morphol. 34:245-265. 1921. The comparative morphology of the secondao' sex- ual characters of Elasmobranch fishes. II. J. Morphol. 35:359-380. Lo Bianco. S. 1909, Notizie biologiche riguardianti specialimente il periodo di matunta sessuale degli animale del golfo di Napoli. Mitt. Zool. Stn. Neapel 19:513-761. LUBBF.RT, H.. AND E. EHRENBAUM. 1936. Handbuch der Seefischerei Nordeuropas. B. II. E. Schweizerbart'sche Verlagsbuchhandlung, Stuttgart, 357 P M.'MTHEWS, L. H. 1950. Reproduction in the basking shark. Ci'lorhinus maximus (Gunner). Philos. Trans. R. Soc. Lond., Ser. B, Biol. Sci. 234:247-316. METTEN, H. 1941. Studies on the reproduction of the dogfish. Philos. Trans. R. Soc. Lond.. Ser. B, Biol. Sci. 230:217-238. Nalini, K. p. 1940. Structure and function of the nidamental gland of Ckilosiyllium gnseum (Mull and Henlel. Proc. Indian Acad. Sci., Sect. B 12:189-214. Nichols, J. T.. a.nd R. C. Ml'rphy. 1916. Long Island fauna IV. The sharks Brooklyn Inst. Arts Sci., Brooklyn Mus. Sci. Bull. 3:1-34. Olsen, a. M. 1 954. The biology, migration , and growth rate of the school shark, GaU'nrhinusaustralls (Macleay* (Carcharhanidae) in south-eastern Australian waters. Aust. J. Mar. Freshwater Res. 5:353-410. Prasad, r. r. 1944. The structure, phylogenetic significance, and func- tion of the nidamental glands of some elasmobranchs of the Madras coast. Proc. Natl. Inst. Sci. India, Part B, Biol Sci. 11:282-302. 1945. Further observations on the structure and function of the nidamental glands of a few elasmobranchs of the Madras coast. Proc. Indian Acad. Sci., Sect. B 22:368- 373. 1948. Observations on the nidamental glands of Hy- dnilaaiis coltiei. Raja rhma and Platyrhinoidis trisenatus. Copeia 1948:54-57. Romer. A. S. 1962. The vertebrate body. 3d ed. W. B. Saunders Co., Phila.. 627 p. SRINGER, S. 1960. Natural history of the sandbar shark. £H/amia tntl- herlt. U.S. Fish Wildl. Serv., Fish. Bull. 61:1-38. STEVENS, J. D. 1974. The occurrence and significance of tooth cuts on the blue shark iPnonace glauca L.I from British waters. J. Mar. Biol. Assoc. U.K. .54:373-378. 1975. Vertebral rings as a means of age determination in the blue shark iPrionace glauca L.J. J, Mar. Biol. Assoc. U.K. 55:657-665. .STRASBURG, D. W. 1958. Distribution, abundance, and habits of pelagic sharks in the central Pacific Ocean. U.S. Fish Wildl. Serv., Fish. Bull. 58:335-361. SUDA, a. 1953. Ecological study on the Blue shark [Prumace glauca Linnel. South Sea Area Fish. Res. Lab Rep. 26:1-11. TEMPLEMAN, W. 1944. The life-history of the spiny dogfish iSqualus acan- thtas) and the vitamin A values of dogfish liveroil. New- foundland Dep. Nat. Resour , Fish. Res. Bull. 15, 102 p. Tucker, D. W.. and C. T. Newnham. 1957. The blue sharkPnonacegtouca (L.lbreedsin British seas. Ann. Mag. Nat. Hist., Ser. 12, 10(1171:673-688. 470 MORTALITY ESTIMATES FOR THE NEW ZEALAND ROCK LOBSTER, J/\5L/5 EDWARDSII John H. Annala' ABSTRACT The instantaneous total mortality rate and instantaneous fishing mortality rate were estimated for an exploited population ofmale New Zealand rock lobster. Jasusedivardsn , Instantaneous total mortality rate estimates were made from the seasonal size-frequency distribution of landed rock lobsters using three different methods and ranged from 0.64 to 1.07. Estimates of both mortality rates were also made from the rate of return of tagged rock lobstersover an entire year and by adjusting the rate for an 8- or 9-month fishing season. These estimates of the instantaneous total mortality rate ranged from 1.92 to 3.13 and were considered too high to be representative of the entire exploited population. Instan- taneous fishing mortality rate estimates from the tag returns ranged from 1.17 to 1.85, with the lower rates based on an 8- or 9-month fishing season. Using the results from both types of analyses, and the observed lifespan of rock lobsters m the fishery, the best estimates of the instantaneous total mortality rate are between 1 .00 and 1 .50 and of the instantaneous fishing mortality rate between 0.90 and 1 .40. assuming the instantaneous natural mortality rate equals 0.10. Knowledge of the total mortality rate, and its components of fishing and natural mortality, is essential for an adequate understanding of the population dynamics of an exploited population. Mortality rates are generally estimated from 1) the age composition of the population, with the age composition of the catch serving as the population sample; 2) the results of mark and release experi- ments; or 3) some relationship between catch and effort. The purpose of this investigation is to derive and compare estimates of mortality rates for an exploited population of the New Zealand rock lob- ster, Jas;/s edwardsii . Rock lobsters do not contain any structural parts retaining annual marks, so estimates of mortality rates cannot be made from the age composition of the catch. However, the total mortality rate can be estimated by analysis of the size-frequency distribution of th& catch, and three different methods are employed. The results of these analyses are compared with estimates of the total mortality rate derived from a tag- recapture study conducted over the same fishing season and in the same area from which the size- frequency distributions were drawn. The results of the marking experiment are also used to estimate the fishing mortality rate, which is then compared with the estimates of the total mortality rate using 'Fisheries Research Division, P O. Box 19062, Wellington, New Zealand. Manuscript accepted December 1978 FISHERY BULLETIN: VOL. 77. NO. 2, 1979. a previously derived estimate of the natural mor- tality rate. METHODS AND RESULTS Analyses of Size-Frequency Distributions The three methods used to estimate the total mortality rate from the size-frequency distribu- tion were: 1) the approximate method of separat- ing a polymodal size-frequency distribution into its component distributions described by Bhat- tacharya ( 1967); 2 ) Method 2 of Van Sickle ( 1977), where growth and size-frequency data were used to estimate mortality on a size specific basis; and 3 ) the partitioning of a size-frequency distribution by the average annual growth increment into com- ponents approximating age classes (average an- nual growth increment method) described by Hancock (1965). Mortality rates were estimated from the size- frequency distribution of male rock lobsters landed from the Gisborne local area during the 1976-77 fishing season. Females constitute only a small proportion of the landings from this area, so their mortality rates were not estimated. Gisborne is a major fishing port located on the east coast of the North Island (Figure 1). The Gisborne local area is defined as encompassing the rock lobster fishing grounds extending from Young Nicks Head in the south to Gable End Foreland in the 471 FISHERY BlILLETIN VOI. 77, NO Gable End Foreland 30 Young Nicks Head 39° S 30' Figure l, — Location of the study area between Young Nicks Head and Gable End Foreland on the east coast of the North Island, New Zealand. north ( Figure 1 ). The landings from this area were chosen for analysis because it has been the site for a series of tag-recapture studies, which were also used to estimate mortality rates. The results re- ported here are part of an extensive study of the biology of J. edwardsii in the Gisborne area. Size-frequency distributions in the landings were determined on a monthly basis from July 1976 to February 1977, with the exceptions of Au- gust and January, during the 1976-77 season. The fishing .season is defined as extending from 1 June to 31 May of the following year. There is a natural break between seasons due to a period of low catchability and resulting low effort expenditure during April and May. During each month the landings were chosen on a nonrandom basis for sampling, and the entire landing on a given day for an individual boat was measured. The mea- surement used was the carapace length taken from the base of the antennal platform to the dor- sal, posterior margin of the carapace along the midline. These individual samples were given equal weights and combined directly to yield a monthly sample. The monthly samples were then weighted by the proportion of the total seasonal landings landed during that month and combined to give a weighted seasonal size-frequency dis- tribution (Table 1, Figure 2). This weighting pro- cedure was applied to average out changes in the size-frequency distributions due to fluctuations in catchability, recruitment, and mortality to permit estimation of the average annual total mortality rate. The approximate method of separating the com- ponent distributions of a polymodal size-frequency distribution described by Bhattacharya ( 1967) in- volves a cubic approximation of density within a size class and a quadratic approximation to the logarithm of the frequency of each class. It was assumed that the frequency distribution is com- posed of Gaussian component distributions that are adequately separated so that each component has a sufficiently broad region where the effects of Table l. — Weighted seasonal size-frequency distribution of male New Zealand rock lobsters from the Gisbome local area during the 1976-77 season. Observed frequency values are weighted frequencies x 10-'. Class niidpoint Observed frequency (mm) W) log,/ AlOQe/ 94,5 17 2 8332 0 4990 95.5 28 3 3322 0 3814 96 5 41 3 7136 0 5059 97 5 68 4 2195 0 1872 985 82 4 4067 0 1300 995 72 4 2767 0 5108 1005 120 4 7875 0 1335 101 5 105 4 6540 0 1107 102 5 94 4 5433 -0 2126 1035 76 4 3307 - 0 3989 1046 51 3 9318 -0 0198 1055 50 3 9120 -02484 106 5 39 36636 -0,1979 107 5 32 3 4657 0 3302 108 5 23 3 1355 0 8329 109 5 10 2 3026 0 4700 1105 16 2 7726 0 2877 1115 12 2 4849 -0 2877 1125 9 2 1972 0 2007 1135 11 2.3979 1 0116 114 5 4 1 3863 02231 1155 5 1 6094 0 2231 1165 4 1 3863 0 0000 1175 4 1 3863 0 2231 1185 5 1 6094 0 9163 1195 2 0 6931 0 0000 120,5 2 0 6931 0 0000 121 5 2 0 6931 0 0000 1225 2 0 6931 0 0000 123 5 2 0 6931 0 6931 124 5 1 0 0000 0 0000 125 5 1 0 0000 0,0000 1265 1 0 0000 472 ANNALA: MORTALITY OF ROCK LOBSTER 105 110 115 Coropace iengfh ( FlGLTRE 2. — Weighted seasonal size-frequency distribution of male New Zealand rock lobsters from the Gisbome local area landed during the 1976-77 season. all other components are negligible. Moreover, the class range should be small , and the sample should be of a sufficient size so that the class frequencies are not small in the area of the distribution where the components are being separated. If the class intervals are assumed to be constant, direct graphical procedures can be used, as simple differencing reduces the quadratic to a straight line. The midpoints of the size classes were plotted on the abscissa and the logarithmic difference in the frequency between successive classes on the ordinate. Each of the regions on the graph contain- ing straight lines with negative slope corresponds to the separate components of the distribution. The natural logarithms of the abundance of each of the 1 mm size classes and the logarithmic differences between successive size classes are also shown in Table 1. The logarithmic differences plotted against the midpoints of the size classes are shown in Figure 3 , as well as the lines fitted by eye through adjacent points. This procedure in- volved fitting a straight line with a negative slope through successive points and required a certain amount of subjectivity when choosing the posi- tions of the lines. However, the line-fitting was aided by using the average annual growth incre- ment as a guide in determining the positions of the lines and by fitting the lines more closely to the points with the larger than the smaller frequen- cies. Using Bhattacharya's (1967) terminology, the revelant parameters from Table 1 and Figure 3 are: h = the class interval = 1 mm 90.5 95.5 100.5 105.5 110.5 Midpoint of class (mm) 115.5 Figure 3. — Logarithmic difference in abundance plotted against the midpoints of successive mill imeter size classes from the weighted seasonal size-frequency distribution of male New Zealand rock lobsters landed from the Gisbome local area during the 1976-77 season b d K K Or 0, i^-r M, the scale of .v = 1 the scale of v = 20 the .r-intercept of the rth line 100.7 ^2 = 105.0 110.5 = the angle the rth line makes with the negative direction of the .v-axis = 82.0° So = 78.5° «3 = 79.5° (the mean of the rth component) = K + h/2 = 101.2 M2 = 105.5 As = 1110 (the SD of the rth component) = \/ Idh cot 6r/b) - (h^/12) = 1.6513 ^2 = 1-9967 6-3 = 1.9033. Using Method iv, and following the steps out- lined in table 8, of Bhattacharya (1967), the number of individuals {N, ) in each of the first three fully recruited components of the seasonal size- frequency distribution from the Gisbome local area was estimated as shown in Table 2. Male rock lobsters less than the carapace length size class from 100.0 to 100.9 mm were not fullv recruited 473 FISHERY BULLETIN VOL 77, NO Table 2.— Estimation of the number in each component (iV, ) and the annual instantaneous total mortality rate iT ) from the 1976-77 weighted seasonal size-frequency distribution of male New Zealand rock lobsters from the Gisbome local area using Method iv of Bhattacharya 1 1967). Component /) 0, + /r,'121 n 24o,' A/. log, — n, A/, A/, T 1 5 1 6513 28 1000 4 5184 0 3719 0 0153 5.3047 20128 332 0 36 2 5 1 9967 20 8000 3 6217 0 7217 0 0105 4 7530 115 93 231 1 75 3 5 1 9033 22 2360 2 5200 0 1237 00115 3 0543 21 20 40 Average 1 06 into the fishery, so these smaller size classes were not included in the analysis. Moreover, only the first three components were used because the small number of individuals of larger sizes in the sample made it difficult to accurately distinguish any further components. Assuming that each component approximates an individual year class, the annual instantaneous total mortality rate be- tween components 1 and 3 is 1.06. Estimates of the annual instantaneous total mortality rate were also derived from the six monthly samples (see Table 5). These estimates ranged from 0.00 to 1.15, with a weighted mean (weighted by the proportion of the seasonal land- ings taken during the month) of 0.49 and 9.5'; confidence limits of 0.06 and 0.92. The model used by Van Sickle ( 1977) describes the exact shape of the size distribution of a sta- tionary or steady state population, with the shape expressed as a function of size-specific mortality and growth rates. His Method 2 requires com- prehensive growth and size-frequency data to es- timate mortality on a size-specific basis. However, it does not require the explicit determination of the age distribution nor a fitted gi-owth curve, which is advantageous for this species. The size distribution was divided into size class- es (indexed by,/), and it was assumed that the mortality rate ( /x, ) was the same for all individuals in size class,/. The size classes can be of any width, but the growth rate and number density must be known at the boundaries of each class. Using the terminology of Van Sickle ( 1977), let ./stand for the size interval (^,,2,.l). If the growth ratesgiz, ),giz, . i ) and the number dnesitiesN, (2,), A^^(2,.,) at the boundaries plus N, *, the total number or proportion of organisms in classy are known, then /x^ is calculated from his equation 8: Estimates of the annual instantaneous total mortality rate applying Method 2 of Van Sickle ( 1977) to the seasonal size distribution of Table 1 are shown in Table 3. The growth rate of 4.8 mm used at the boundaries is an initial estimate of the average annual growth increment of males in the Gisbome local area, and was based on the molt increment of 204 tagged rock lobsters recaptured during 1976-77. The tagged individuals were all in the size range 80-106 mm, due to difficulties ex- perienced in obtaining larger animals for tagging, so growth estimates were not available for the upper part of the size distribution. However, ini- tial growth information from other areas indicates it is not unreasonable to assume a constant molt increment for males between 80 and 115 mm carapace length. Some difficulty was experienced in determining the lOO/; retention length for rock lobsters using a carapace measure because the minimum legal size is based on a tail length measure (Annala 1977). The carapace length class from 100.0 to 100.9 mm had the highest proportion of any single mil- limeter class in the size-frequency distribution ( Table 1 , Figure 2 ) and was therefore chosen as the smallest size class fully represented in the land- ings. The size-frequency distribution was then partitioned into 4 mm and 5 mm size groups, be- ginning with the 100 mm size class, to bracket the average annual growth increment of 4.8 mm. The T..\BLE3.—E.stimation of the annual instantaneous total mortal- ity rate I /i, ) from the 1976-77 weighted seasonal size-frequency distribution of male New Zealand rock lobsters from the Gis- bome local area using Method 2 of Van Sickle ( 1977). Size grouping |z,,.2, .,1 W ' IgU,). 9(f ■)) M,(yr ) 1 g{Zj)NAz,)-g(^,+ iWj^,+ i) 4 mm (100. 103) 395 (4 8, 4.8) 0,53 (104, 107) 172 (4 8,4 8) 0,53 (108. Ill) 61 (4 8, 4 8) Average 0,86 0,64 5 mm (100, 104) 446 (4 8,4 8) 0,74 1105. 109) 154 (4,8, 4,8) 124 (110, 114) 52 (4 8. 4,8) Average 1 11 1,03 474 WNALA: MORTALITY OF ROCK LOBSTER estimates of the annual instantaneous total mortality rate were 0.64 and 1.03 for the smaller and larger groupings, respectively. Estimates of the annual instantaneous total mortality rate from the monthly samples (see Table 5) using the 4 mm grouping ranged from 0.46 to 1.00, with a weighted mean of 0.69 and QSVf confidence limits of 0.50 and 0.88. The monthly estimates using the 5 mm gi-ouping ranged from 0.90 to 1 . 18, with a weighted mean of 0.99 and 95'7f confidence limits of 0.89 and 1.09. Hancock (1965) estimated the total mortality rate of Cancer pcigurus in the Norfolk (England) fishery by partitioning the size distribution into approximate year classes based on the average annual growth increment. If the natural loga- rithms of numbers are plotted against size, a line whose slope is proportional to the total mortality rate is obtained over the size range where growth is constant. Annala (1977) also used this method for estimating the total mortality rate of J. ecl- wcnxlsii in the Otago fishery of New Zealand. The average annual growth increment of 4.8 mm was rounded to the nearest millimeter, and the seasonal size-frequency distribution of Table 1 and Figure 2 partitioned into 5 mm size classes. The results are shown in Table 4, with the annual instantaneous total mortality rate estimated to be 1.07. The estimates from the monthly samples (Table 5) ranged from 0.78 to 1.25, with a weighted mean of 1.11 and 959^ confidence limits of 0.97 and 1.25. Analyses of Tag Return Data Mortality rates were also estmiated from the rate of return of tagged male rock lobsters released in the Gisborne local area in July 1976 and recap- tured during the following 12 mo. The instanta- neous total mortality rate was estimated using the method derived by Robson and Chapman (1961) for analyzing a segment of the catch curve. The Table 4. — Estimation of the annual instantaneous total mortal- ity rate iZ) from the 1976-77 weighted seasonal size-frequency distribution of male New Zealand rock lobsters from the Gis- borne local area using the average annual growth increment method of Hancock (1965). Size class (mm) N, £_ 100 0-104 9 446 1050-1099 154 110 0-114 9 52 Table 5. — Estimates of the annual instantaneous total mortal- ity rate from the monthly size-frequency distributions of male New Zealand rock lobsters landed from the Gisbome local area during the 1976-77 season. The methods used were Method iv of Bhattacharya (19671. Method 2 of Van Sickle (19771, and the average annual growth increment method of Hancock ( 1965), AT = sample size. Van Sickle Van Sickle (4 mm (5 mm IVIonlh (N) Bhattacharya grouping) grouping) Hancock Jjly (325) 0 00 063 1 14 1 25 Sept (399) 0 45 1 00 1 18 0 78 Oct (1,155) 0 54 0 95 0 90 1 09 Nov (506) 1 03 0 45 0 96 0 92 Dec (247) 0 32 0 82 0 94 1 18 Feb (627) 1 15 0 46 0 91 1 04 Weighted mean mortality rate 0 49 0 69 0 99 1 11 95°o confidence limits of Ifie weighted mean 0 06, 0 92 0 50, 0 88 0 89, 109 0 97, 1 25 Average 1 06 1 09 1 07 instantaneous fishing mortality rate was esti- mated by ] ) a method developed by Paulik ( 1963) for use with recaptures grouped into time inter- vals, and 2) a method described by Ricker (1975) where estimates are available for the instanta- neous total mortality rate and rate of exploitation. A total of 444 male rock lobsters were caught by pots, tagged using the western rock lobster tag (Chittleborough 1974), and released on the fishing grounds. All of the returned rock lobsters were taken in pots by commercial fishermen. Fishing effort was not constant throughout the 1976-77 season, so the rate of return of tags was adjusted by the effort expended in each month. The best mea- sure of effort available was the average number of days fished per month per boat for 12 selected boats in the Gisborne local area. The average number of days fished in June 1976 (9.9 days/boat) was used as the basis for determin- ing relative effort. The number of recaptures for July 1976 was not included in the analysis because tags were not returned over the entire month. The number of males recaptured, the relative effort, and the number of recaptures per unit of relative effort for each month are shown in Table 6. The method of Robson and Chapman (1961) used for estimating the total mortality rate de- pends on determining a mean coded age,.r accord- ing to the terminology of Jones (1976), wherex = X/1\\ . The total coded age iX ) was calculated from X = il; = l)y, for i = 1,2 J. where J = the number of samples, and y, = the number of recap- tures per sample. Using the number of monthly recaptures per unit relative effort from August 1976 through April 1977 is shown in Table 6 as an example, 475 FISHERY BULLETIN VOL 77. NO 2 Table 6. — Recaptures of male New Zealand rock lobsters tagged and released in the Gisbome local area in July 1976. efTort expenditure during 1976-77. and the number of recaptures per unit relative effort (v, ). Average no Year and No of of days Relative month recaptures fished boat eflon V 1976: Aug. 64 15.4 1.56 41 03 Sept. 31 55 056 55 36 Oct. 26 125 1 26 20 63 Nov. 40 13 5 1 36 29 41 Dec 23 128 1 29 17 83 1977: Jan. 13 158 1 60 8 13 Feb. 23 133 1 34 17 16 Mar. 12 89 090 13 33 Apr. 1 40 0 40 250 May 0 1 0 Oil 000 June 2 108 1 09 I 83 July 8 170 1 72 4 65 S(i _ lyy^ = 41.03(1 - 1) + 55.36(2 - 1) + 20.63(3 - 1) + 29.41(4 - 1) + 17.83(5 - 1) + 8.13(6 - 1) + 17.16(7 - 1) + 13.33(8 - 1) + 2.50(9 - 1) = 513.09 Sv, = (41.03 + 55.36 + 20.63 + 29.41 + 17.83 + 8.13 + 17.16 + 13.33 + 2.50) = 205.38. Thus, the mean coded age ix) = 513.09/205.38 = 2.4982. The proportion of tagged individuals remaining free after the last monthly sampling period was too large to be neglected, so the estimate of mean coded age was equivalent to Estimates of the survival rate (S) that will satisfy a given value of x for any given J were determined from table 3 of Robson and Chapman (1961). In this examples = 2.4982 and J = 9, so the value of S which satisfied was 0.786. This was a monthly value for S, so an estimate of S for the entire year, assuming total mortality acts uniformly over the 12-mo period, was San^uai = (SmonthLvH^ = (0.786)'2 = 0.0556. Thus, the annual instantaneous total mortality rate (Z) measured over the 12-mo period = 2.89. However, with fishing effort concentrated in the 9-mo period from mid-June to mid-March and with a low initial estimate of instantaneous natural mortality rate {M) of approximately 0.10 (Annala 1977), it was assumed that mortality acted primarily during the 9-mo fishing season. An estimate of annual total mortality based on this 9-mo period was S.nnual = (S,„„„,hlv)" = (0.786)« = 0.1145, with Z = 2.17. The results of this analysis, as well as the re- sults of grouping the tag returns bimonthly and quarterly are shown in Table 7. Estimates of the instantaneous fishing mortal- ity rate (F) were made using equation 26of Paulik (1963) for grouped observations, whereF = -/j.ln S/(l - §'^), and /i = n.lN, where n. = the total number recaptured over the period of observation, and A^ = the total number of tags released. In the example cited above, where tag returns were grouped on a monthly basis from August 1976 to April 1977, ii = 223/433 = 0.5381, where the number recaptured in July (11) was subtracted from the number released (444) to estimate the number still at large at the beginning of August (433). Using the monthly value of S = 0.786, the monthly value oi f = -0.5381 x -0.2408/[l - (0.786)''] = 0.1464. On a 12-mo basis, the annual estimate of F = 1.76. However, based on a 9-mo fishing season, the annual estimate oi P = 1.32 (Table 7). The value of F was also estimated from the equation F = iiZIA , which was derived from equa- tion (1.13) of Ricker (1975), where u = rate of exploitation, Z = instantaneous total mortality rate, and A = actual total mortality rate. The value of u was estimated on an annual basis from the equation ;/ = RIM. where/? = number of recaptures during first year after release and M -= number of tags released. For the July 1976 tagging, u = 251/444 = 0.5653. Thus, for the tag returns grouped on a monthly basis, the annual estimate of F = uZ/A = 0.5653 X 2.89/0.9444 = 1.73 over a 12-mo period. T.XBLE 7. — Estimates of the annual instantaneous total (Z) and fishing (Fl mortality rates of male New Zealand rock lobsters from the Gisbome local area derived from tag returns of those tagged and released in July 1976. (?) Robson and (H (F) Chapman Paulik Ricker tjlethod 119611 (1963) (1975) Returned tags grouped lulonthly, Aug 1976- Apr 1977 '289(217) 1 76(1 32) 1 73(1 30) Bimonthly, Aug 1976- July 1977 3 13(2,09) 1 84(1 22) 1 85(1 35) Quarterly. Aug, 1976- July 1977 2 56(1,92) 1,56(1.17) 1 57(1.27) 'The figures m parentheses are estimates of Z and F taken over 9 mo for the monthly and quarterly groupings and 8 mo for the bimonthly grouping. 476 ANNALA MORTALITY OF ROCK LOBSTER On the basis of a 9-mo fishing season, the annual estimate of F = 1.30 (Table 7). DISCUSSIOiN The weighting procedure used to derive the sea- sonal size-frequency distribution was designed to average out changes in the monthly distributions due to fluctuations in catchability, recruitment, and mortality, which affect the estimates of total mortality rate. The estimates derived from the seasonal size-frequency distribution using the methods of Hancock ( 1965) and Van Sickle ( 1977) were similar to the means of the respective monthly estimates (Table 5). The estimates from the monthly samples using the method of Bhat- tacharya (1967) were highly variable, probably due to the small sample sizes, and the mean of the monthly estimates was considerably less than the estimate from the seasonal distribution. The factor having the greatest potential effect on the estimates of mortality derived from the size-frequency distributions is probably the influx of new recruits into the fishery by growth over the minimum legal size. Male rock lobsters in the Gis- borne local area exhibit marked periodicity in the molt cycle, with most molting between October and December. However, the monthly estimates using the methods of Hancock (1965) and Van Sickle (1977) do not indicate any changes in mor- tality rate associated with this molting period. Therefore, estimation of the total mortality rate from the weighted seasonal size-frequency dis- tribution is considered valid in this example. The estimates of total mortality rate from the weighted seasonal size-frequency distribution using the three methods gave similar results. The method of Bhattacharya (1967) is considered adequate when the sample size is large and an estimate of growth rate is available to aid in fitting the lines. However, when used in analyzing size- frequency distributions whose sample sizes were small, such as those from other areas (my unpubl. data) and the monthly samples in this example (Table 5), the results varied widely. Moreover, when used with data without definite modes, the abundance of the first component often appears to be underestimated, perhaps due to the difficulty of determining the 100'7f retention length, and greater consistency is obtained if the first three components are included for analysis. Method 2 of Van Sickle (1977) also requires comprehensive size-frequency and growth data. One of Van Sickle's key assumptions is that the method be applied to a stationary or steady state population, which he defines (after Seber 1973) as one having age and size structures that are cyclic, with a period usually of 1 yr. Thus, size distribu- tions observed at yearly intervals will appear identical. However, he argues that the method can be applied to annual "average" size distributions rather than a distribution at one point in time (Van Sickle 1977, quoting Van Sickle 1975). Growth and mortality rates should not vary with time, and seasonal and year-to-year changes in recruitment and growth should be "averaged out" of the data used. Estimates derived using the smaller of the mil- limeter size groupings bracketing the annual growth increment for this example (Tables 3, 5) and for samples from other areas (my unpubl. data) were usually lower than those derived using the larger millimeter size grouping. These lower es- timates may be due to the violation of one or more of the above assumptions. Van Sickle's method is very dependent on accurate estimates of growth rates and densities at the boundaries of each size class, and even minor fluctuations in recruitment and for samples from other areas (my unpubl. data) were usually lower than those derived using the larger millimeter size grouping. These lower estimates may be due to the violation of one or more of the above assumptions. Van Sickle's method is very dependent on accurate estimates of growth rates and densities at the boundaries of each size class, and even minor fluctuations in recruitment could affect the estimates of the num- bers in the boundaiy size groups. The success of the average annual growth in- crement method of Hancock (1965) is also depen- dent on the assumptions of constant recruitment and growth rate over the size range considered. However, this method is probably not as suscepti- ble to fluctuations in recruitment as that of Van Sickle ( 1977), because the use of broad size classes based on average annual growth increments should smooth out any small fluctuations. The ac- curacy of both these methods may be improved by combining size-frequency distributions obtained over a number of years to reduce the effects of changes in recruitment and growth rates. Con- tinuous monitoring of size-frequency distributions in the Gisborne fishery should result in improved estimates in the future. In summary, the analyses of the size-frequency distributions using the three methods gave gener- 477 FISHERY BULLETIN VOL, 77, NO J ally consistent results. The method of Van Sickle (19771 requires the most detailed information on the size distribution and growth rates, and the results are susceptible to the size groupings cho- sen. Hancock's (1965) method requires less de- tailed information on growth, as average annual growth increments can be used, but still requires an accurate description of the size-frequency dis- tribution. Bhattacharya's (1967) method does not require information on growth, although knowl- edge of the annual growth increment does aid in analysis of the data, but again requires an accu- rate description of the size-frequency distribution. The instantaneous total mortality rate can also be estimated from length composition data using the expression derived in Appendix B of Beverton and Holt (1956) based on the von Bertalanffy (1938) growth parameters. This method is most accurate when there is a rapid increase in length with age over the important size range and a minimum of overlap between the length distribu- tions of adjacent age groups. Saila et al. (in press) found that growth of male rock lobsters from the Gisborne area during the first few years after re- cruitment to the fishery (the important size range in this study) is slow relative to earlier years as described by an empirical growth curve. This curve was considered to be a more realistic de- scription of growth than the von Bertalanffy curve at this stage of the species' life history. Moreover, the great variability found in the individual growth increments probably results in a high de- gree of overlap between the lengths of adjacent age classes. Thus, the conditions for the best use of the Beverton and Holt method do not appear to be met, and it was not applied to this species. Polymodal frequency distributions may also be separated into their component groups using com- puter techniques such as ENORMSEP (Extended Normal Separator Program) ( Yong and Skillman 1975). An important advantage of this technique over the method of Bhattacharya (1967) is that the goodness of fit of the estimated component dis- tributions to the original polymodal distribution can be determined. However, the accuracy of both techniques is reduced when the modes of the size- frequency distribution are not well separated. The size-frequency distributions analyzed in this example do not exhibit any well-defined modes, so ENORMSEP was not used as it is considered that this technique would not improve the accuracy of the estimates. The estimates of total mortality rate from the rate oftag returns using the method of Robson and Chapman ( 1961) are much higher (even when ad- justed for an 8- or 9-mo fishing season) than the estimates derived from the size-frequency dis- tributions. Morgan (1974a) suggested that the western rock lobster, Pan!///r;/,s cygntis, caught by pots have a higher probability of recapture by pots than rock lobsters initially captured and released by diving. He further suggests that rock lobsters previously caught by pots, marked, and released, have a greater probability of recapture by pots than the probability of capture by pots of the total population. All of the rock lobsters tagged and released in this study were caught by pots, so they may have been more vulnerable to capture by commercial pot fishermen than the untagged in- dividuals in the population. Moreover, due to the nature of the fishing grounds, the tag and release procedure was not conducted in a strictly random manner, and the resulting distribution of tags in the fishery may have led to a greater susceptibility to capture for the tagged rock lobsters. The estimates of total mortality rate from the tag returns also may be affected by changes in the catchability of the rock lobsters. Laboratory ex- periments indicate feeding activity is lowest for individual J. edwardsii immediately prior to and after molting (my unpubl. results). Morgan (1974b) found a significant negative correlation between premolt stage Dl animals and catchabil- ity for the western rock lobster. Fluctuations in the number of recaptures per unit relative effort between August and April (Table 6) indicate that catchability may vary considerably. Any decrease in catchability during the molting period would act to increase the estimate of the total mortality rate. Other factors affecting estimates of the total mortality rate (Type B errors, Ricker 1975) in- clude: 1) tag loss, 2) extra mortality of tagged rock lobsters, and 3) emigration of tagged rock lobsters from the fishing area, with all three acting at a steady, instantaneous rate throughout the exper- iment. These factors all result in an overestimate of the total mortality rate. Preliminary laboratory and field experiments on the rates of initial tag loss and mortality due to tagging indicate these effects are minimal (my unpubl. data). However, rock lobsters are most susceptible to tag loss and mortality due to the presence of the tag while molting. Laboratory ex- periments are being conducted to determine the long-term rates oftag loss and mortality. 478 ANNALA: MORTALITY OF ROCK LOBSTER The third factor, emigration out of the area, does not appear to be important. None of the males tagged in July 1976 had been recaptured outside the Gisborne local area. The inshore fishing grounds outside the Gisborne local area are all heavily fished, so the movement of significant numbers of tagged animals would probably be de- tected, unless they were migrating to deeper, unfished areas. The methods of Paulik 1 1963) and Ricker 1 1975) used to estimate the fishing mortality rate from the tag returns (Table 7) are both dependent on estimates of the total mortality rate. Any bias in the estimates of total mortality rate will affect the estimates of fishing mortality rate. If the tagged rock lobsters were more susceptible to capture then the untagged individuals, then the estimates of fishing mortality rate may be overestimates. Other factors affecting estimates of fishing mor- tality rate (Type A errors, Ricker 1975) include: 1) the death of tagged rock lobsters due to the pres- ence of the tag, or the loss of their tags, shortly after marking; and 2) incomplete reporting of tags recaptured by fishermen. As mentioned previ- ously, preliminary experiments indicate the ef- fects of the first factor are minimal. However, pre- dation by fish on the newly released animals may be important and warrants further investigation. It is known that some of the recaptured tags went unreported by fishermen, although the numbers were not large. This would result in an underesti- mate of the fishing mortality rate. The estimates of fishing mortality rate adjusted for an 8- or 9-mo fishing season (1.17-1.35) are considerably lower than the unadjusted estimates (1.56-1.85). If the estimate of M = 0.10 (Annala 1977) applies to the Gisborne fishery, then Z = 1.27 to 1.45 based on the estimates ofF for an 8- or 9-mo season. These estimates of Z are more com- parable to those derived from the analyses of the size-frequency distributions (0.64-1.07) than to the estimates derived using the method of Robson and Chapman (1961) (1.92-3.13). Moreover, these lower estimates are more consistent with the es- timated lifespan in the fishery than are the higher estimates. Based on the average annual growth increment of 4.8 mm and the seasonal size- frequency distribution in Table 1 and Figure 2, rock lobsters appear to survive for about 4 or 5 yr in the fishery. The preliminary empirical growth model developed by Saila et al. (in press) also indi- cates that male rock lobsters from the Gisborne local area remain in the exploited phase for a minimum of 4 to 5 yr. In summary, the estimates of total mortality rate for the entire exploited population from the rate of tag returns are considered too high. The estimates of total mortality rate from the size- frequency distribution analyses, and those based on the estimates of F over an 8- or 9-mo fishing season with the addition of M = 0.10, are more consistent with the observed lifespan in the fishery. Thus, the best estimates of Z are between 1.00 and 1.50, and ofF are 0.90 and 1.40, assuming M = 0.10. ACKNOWLEDGMENTS I would like to thank the National Research Advisory Council of New Zealand for fellowship aid during part of this study. Saul Saila provided many helpful suggestions on the application of these methods. J. Booth, R. Francis, J. McKoy, S. Saila, G. D. Waugh, and two anonymous reviewers made many constructive comments on the manu- script. B. Bycroft. B. Hvid, and J. McKoy provided valuable assistance in the field. Finally, I would like to thank the commercial fishermen for their excellent cooperation in returning tagged rock lobsters, and the staffs of the fish processing sheds and the Ministry of Agriculture and Fisheries Office in Gisborne for leceiving and holding the same. LITERATURE CITED ANNALA, J. H. 1977. Effects ofincreases in the minimum legal size on the Otago rock lobster fishery. N.Z. Fish. Res. Div, Occas. Publ. 13, 16 p. BEVERTON, R. J. H.. AND S. J, HOLT. 1956. A review of methods for estimating mortality rates in exploited fish populations, with special reference to sources of bias in catch sampling. Rapp. P.-V. Reun. Cons. Perm. Int. Explor, Mer 140:67-8,3. BH.ATTACHARYA. C. G. 1967. A simple method of resolution of a distribution into Gaussian components. Biometrics 23:115-135. Chittleborough, R. G. 1974. Development of a tag for the western rock lob- ster. Aust.C.S.I.R.O. Fish.Oceanogr.Div.Rep.56. 19p. Hancock, D. a. 1965. Yield assessment in the Norfolk fishery for crabs [Cancer pagurus). Rapp. P.-V, Reun. Cons. Perm. Int. Explor. Mer 156:81-94. Jones R, 1976. The use of marking data in fish population analysis. FAO Fish. Tech. Pap. 153. 42 p. 479 FISHERY BULLETIN; VOL^ 77. NO. 2 MORGAN, G. R. 1974a. Aspects of the population dynamics of the western rock lobster, Panulirus cygnus George. I Estimation of population density. Aust. J. Mar. Freshwater Res. 25:235-248. 1974b. Aspects of the population dynamics of the western rock lobster, Panulirus cygnus George. II. Seasonal changes in the catchability coefficient. Aust. J. Mar. Freshwater Res. 25:249-259. PAULIK, G. J. 1963. Estimates of mortality rates from tag recoveries. Biometrics 19:28-57. RlCKER, W. E. 1975. Computation and interpretation of biological statis- tics offish populations Fish. Res Board Can., Bull. 191, 382 p. ROBSON, D. S., AND D. G. Chapman. 1961. Catch curves and mortality rates. Trans. Am Fish. Soc. 90:181-189. SAILA S. B , J. H. ANNALA, J L. MCKOY, AND J. D. BOOTH. In press. Application of yield models to the New Zealand rock lobster fishery. N.Z J. Mar. Freshwater Res. SEBER, G. A. F. 1973. The estimation of animal abundance. Co. Ltd. Lond., Engl., 506 p. C. Gnffin & Van Sickle, J. 1977. Mortality rates from size distributions. The applica- tion of a conservation law. Oecologia 27:311-318. VON BERTALANFFY, L. 1938. A quantitative theory of organic growth (inquiries on growth laws. II). Hum. Biol. 10:181-213. YONG, M. Y.Y., AND R. A. SKILLMAN. 1975. A computer program for analysis of polymodal fre- quency distributions (ENORMSEPi, FORTRAN IV. Fish. Bull., U.S. 73:681. 480 WALLEYE POLLOCK, THERAGRA CHALCOGRAMMA: PHYSICAL, CHEMICAL, AND SENSORY CHANGES WHEN HELD IN ICE AND IN CARBON DIOXIDE MODIFIED REFRIGERATED SEAWATER Kermit D. Reppond, Fern A. Bullard, and Jeff Collins' ABSTRACT Walleye pollock. Theragra chalcogramma , were held in the round in ice and in CO2 modified refriger- ated seawater and periodically examined for physical and chemical changes as well as changes in the palatability of baked portions of blocks of fillets- Taste panel evaluation revealed that satisfactory fillets were obtained from fish that would have been judged spoiled if based on examination of the fish in the round. Sensory evaluation of baked fillet portions indicated that fish were acceptable for consump- tion to 6 days if heavily iced. The fish held in modified refrigerated seawater were judged acceptable only to 4 days because of lower sensory scores for salt content and flavor. Yield of fillets and protein content did not change significantly with time of holding m either medium. The total volatile acid and trimethylamine data indicated that these tests may prove useful as chemical indicators of spoilage for ice-held fish whereasdetermination of trimethylamine oxide or extractable protein nitrogen may prove useful for fish held in modified refrigerated seawater. Round weight and dimethlyamine content increased in fish from both systems with time of holding as did the salt content offish held in modified refrigerated seawater. Total volatile base, formaldehyde, and free c«-amino-nitrogen content remained unchanged but nonprotein nitrogen and total sil-.ds content decreased with time of holding. Walleye pollock. Theragra chalcogramma, have been the subject of several studies concerning changes that occur in frozen storage, and how these changes affect the suitability of pollock in traditional Japanese products (Iwata and Okada 1971, Okada and Noguchi 1974). Uchiyama et al. (1972) and Kramer et al. (1977) reported on changes that occur when pollock are held in ice. If pollock are to be held more than a few hours, ice or some type of refrigeration is needed to retard de- terioration in quality. The advantages and disad- vantages of refrigerated seawater (RSW) for hold- ing fish and shellfish are well established (Roach et al. 1967). In recent years, reports have appeared on holdmg fish or shrimp in RSW modified by the addition of dissolved CO2 (MRSW) (Bafnett et al. 1971: Bullard and Collins 1978). These authors reported that deterioration occurred at a slower rate in MRSW than in ice. Lemon and Regier (1977) noted similar results with Atlantic mac- kerel. Stow ier scombrus, held in either ice, RSW, or MRSW. Experiments with Atlantic ocean perch, Sebastes marinus. (Longard and Regier 1974) also confirmed the superiority of MRSW over RSW or ice as a holding medium. The objec- 'Northwest and Alaska Fisheries Center. National Marine Fisheries Service. NOAA, P.O. Box 1638. Kodiak. AK 9961.5. tives of this study were to generally characterize the changes that occur in walleye pollock with time of holding in ice and in MRSW, to determine which holding medium is superior, and to deter- mine if some of the common chemical indices for spoilage could be useful for pollock. METHODS Sampling A catch of various species of bottom fish includ- ing approximately 135 kg each of walleye pollock and Pacific cod, Gadus macrocephahis, was made on 2 November 1976 by the RV Oregon near Cape Barnabas, Kodiak Island, Alaska, and shall be referred to as Lot 1. Lot 1 was evaluated by physi- cal and chemical methods and by informal subjec- tive observation on whole fish and their raw fillets. No formal sensory evaluation of cooked pollock was possible because of the limited amount offish. To obtain fish for formal sensory evaluation, a second catch was made 1 yr later on 13 October 1977 at the same location and shall be referred to as Lot 2. Most of the chemical analyses conducted on Lot 1 were repeated on Lot 2 to see if the lots were similar. Analyses for total volatile base (TVB) and free a-amino acids were conducted on Manuscript accepted December 1978 FISHERY BULLETIN; VOL. 77. NO 2, 1979. 481 FISHERY BULLETIN: VOL 77, NO Lot 1 only. Analyses for dimethylamine (DMA), trimethylamine oxide (TMAO), and formaldehyde (FA) were conducted on Lot 2 only. Analyses for total volatile acid (TVA), trimethylamine (TMA), total nitrogen, total solids, chloride, extractable protein nitrogen (EPN), and nonprotein nitrogen (NPN) were conducted on both lots. Fish in Lot 1 were held on a sorting table until arrival at the laboratory 6 h later. Ambient air temperature was about 4° C. Pollock and cod were separated from the rest of the catch, individually weighed, tagged, and transferred to the previously described ice or MRSW systems (Bullard and Col- lins 1978). To simulate a commercial operation, the pollock and cod were not segregated by species within the holding systems. This paper deals with pollock; cod will be discussed in a subsequent arti- cle. At regular intervals up to 15V2 days, pollock were selected in such a manner that the average weight per fish in a particular sample was close to the average for all the pollock (495±175 g SD). Each sample from the ice system consisted of 1.3 fish and each sample from the MRSW system con- sisted of 14 fish. Prior to loading with fish, carbon dioxide was injected into the refrigerated brine until the pH leveled off at 4.3. Subsequent intermittent addi- tion of carbon dioxide kept the pH between 5 and 6 throughout the experiment. Temperature was maintained at -1° C. The brine to fish ratio was 1.5:1. In the ice system, the fish were mixed in a fivefold excess of ice and fresh ice was added as necessary to replace melted ice. Great care was taken to insure the fish did not touch each other. Although commercial icing conditions are not as thorough, this procedure was used so the data ob- tained would be based on ideal icing conditions. A control sample was taken 6 h after arrival at the dock. After removal of a sample from a holding sys- tem, the fish were washed briefly to remove slime or ice, drained on a rack for 5 min, and the weight of the individual fish recorded. The fish were filleted by hand and the fillets were rinsed briefly, drained on an inclined screen for 5 min, and weighed. Notes were made on the appearance of the round fish and the condition of the gills, fillets, and viscera. The fillets were then ground using the coarse blade on an Oster'-^ food grinder. A compos- ite of 800 g was frozen at -34° C. The remaining ^Reference to trade names does not imply endorsement by the National Marine Fisheries Service, NOAA. ground flesh was washed with cold water ( 1 flesh:2 water) for 15 min on a reciprocating shaker. The flesh was drained for 30 min on an inclined 16- mesh plastic screen, then weighed and frozen at -34° C for later analysis. All analyses were com- pleted within 2 mo and we assumed no changes took place during frozen storage. Formal Sensory Evaluation Pollock (Lot 2) were separated from the rest of the catch and stored on the deck of the boat. The fish were frequently sprayed with fresh seawater to keep them cool. About 6 h after capture, the fish were transferred into the ice and MRSW holding systems. A control sample was taken at this time. The icing was less thorough than in Lot 1. Tem- perature and pH of the MRSW holding system were maintained at the same values as in Lot 1. At regular intervals, fish were removed from each holding system and filleted by hand. About 7 kg of fillets were frozen as blocks in plastic bags at -34 C for formal sensory evaluation. The remaining fillets were ground and stored at -34" C for later chemical analysis. Chemical and sensory analyses were completed within 2 mo. The last sample ( 12 days) was not large enough for the taste panel test and was evaluated by chemical methods only. The blocks were sawed into portions measuring 80 X 50 X 12 mm and thawed at room tempera- ture. The control sample and samples from fish held in ice were salted by immersion in a 5% NaCl solution for 1.5 min. The portions were cooked in individual sealed aluminum pans at 232° C for 20 min in a commercial oven. Because of the difficulty in equalizing the salt content, samples from the two holding systems were not directly compared. Judges were asked to note if a sample were too salty. The results of the sensory tests were evaluated by analysis of variance. If analysis of variance indicated a change had occurred with time of holding, the Student-Newman-Keuls test was used to determine which samples were differ- ent. Chemical Analyses The frozen samples were tempered overnight in a refrigerator at 3° C and ground twice using the fine blade of an Oster food grinder. Analyses were carried out for total nitrogen, total solids, chloride (Horwitz 1975), total volatile acid (TVA, 482 REPPOND ET AL : WALLEYE POLLOCK CHANGES WHEN HELD IN SEAWATER Friedemann and Brook 1938), total volatile base iTVB, Stansby et al. 1944), and extractable pro- tein nitrogen (EPN.Dyeretal. 1950). Analyses for formaldehyde I FA, Castell and Smith 1973), trimethylamine oxide (TMAO, Bystedt et al. 1959), free «-amino-nitrogen (Pope and Stevens 1939), and nonprotein nitrogen (NPN, Nikkila and Linko 1954) were carried out on a 5'/ trichloroacetic acid extract. An aliquot of the ex- tract was neutralized and analyzed for di- methylamine (DMA) by Dowden's (1938) method modified by increasing the time of extraction to 15 min and by using a mechanical shaker. Analysis for trimethylamine (TMA) in fish in Lot 1 was carried out using Dyer's original method (Dyer 1945). For fish in Lot 2, Dyer's method and the modification by Tozawa et al. (1971) were used. RESULTS AND DISCUSSION Physical Appearance and Yield Changes in odor, degree of decomposition of vis- cera, and physical appearance of fish from Lot 1 and Lot 2 occurred at the same time of holding. Ice-held fish were generally free of slime whereas fish held in MRSW were covered with a thin layer of slime throughout the experiment. After a few days, the gills and fins offish held in ice were firm but those in MRSW were soft and swollen. After 4 days in ice, the pollock had soft livers and after 6 days, decompostion of the viscera could be detected externally. Softening of fillets became noticeable in 2 or 3 days in fish from both holding systems. An unpleasant odor became noticeable after 3 days in ice and predominant after 4 days. Browning of the fillets appeared after 6 days in ice and seemed to be enhanced by grinding. Based on this informal sub- jective observation on the physical appearance and odor of the fish in the round and the raw fillet, pollock could be held a maximum of 4 days under ideal icing conditions before becoming unaccept- able for human consumption. Pollock held in MRSW showed the same changes as those held in ice but they occurred several days later. The maximum time the fish could be held in MRSW and still be acceptable for consumption was 8 days based on evaluation of the fish in the round and the raw fillets. The amine odor usually associated with deterioration of fish was not present but there was a distinct and un- pleasant smell in the fillets offish held more than 12 days in MRSW. The changes in odor and tex- ture occurred gradually in fish from either system, so the exact time for onset of spoilage based on these informal, subjective evaluations could not be reliably determined. Pollock held in either medium gained weight steadily throughout the experiment (Table 1 ). The increase was more than 6% of the initial weight after 5 days in MRSW but only 3V( in ice. The yield of fillets averaged 36% in both media and re- mained fairly constant. Solids content of the flesh decreased from IS'i initially to 16% and 17'r after 10.5 days in ice and in MRSW, respectively (Table 1 ). Solids contents of fish in Lot 2 were similar. The higher solids content of fish held in MRSW was probably caused by the uptake of salt (Table 1). Sensor}' Assessments Differences in odor and firmness were highly noticeable in raw fillets from fish held different lengths of time in the same holding system or Table l. — Change in weiglit, salt, and total solids content of fillets and washed ground flesh of walleye pollock iLot li with time of holding in- ice and in modified refrigerated seawater. ce holding system Modified refr gerated seawater Round Initial weiqtil' Final Fillets Washed ground fillets Weight- NaCI Solids Round Initial weight' Final Fillets Washed groun Weight- NaCI J fillets Time Weight NaCI Solids Weight NaCI Solids Solids (days) (g) ig) (9) (°«) (°.) (g) I'o) (°°) (g) (g) (g) (%) (°.) (g) (%) (%) 0 6.383 6.383 2,268 013 182 2,661 007 123 6.383 6.383 2,268 0 13 182 2,661 0 07 12,3 05 6,616 6,615 2,356 0 14 180 2,384 0 05 125 — — — _ _ _ — — 1 5 6299 6,324 2,333 0 13 176 2,718 0 05 126 7,456 7.655 2,541 0 58 19 1 2,730 0 23 14 5 25 6,433 6.520 2,262 0 14 175 2,487 0 07 130 6,910 7,244 2,618 0 76 185 2,695 0 29 148 35 6,180 6,271 2,331 0 14 17 1 2,637 0 05 129 7,038 7.386 2,642 0 94 183 2,685 0 38 15,2 45 6,428 6,583 2,483 0 14 174 2,947 0 05 124 6.835 7.270 2,571 1 07 184 2,550 0 42 157 65 6,630 6,816 2.510 0 15 168 2,837 0 04 126 7,264 7,882 2,828 1 21 180 2,773 0 46 150 85 6,372 6,713 2,376 Oil 16 6 2.685 0 04 124 7,352 8,022 2,872 I 34 179 2,805 058 152 10 5 6,674 6,986 2,441 0 10 164 2,799 0 05 124 7,017 7777 2,591 1 55 175 2.473 066 157 12 5 6.845 7,755 2,535 1 64 176 2,395 064 152 135 7.096 8,003 2,715 1 64 174 2,578 069 15 3 155 6.750 7,727 2.597 169 17 1 2.497 070 148 'Total round weight of the fish that composed the sample ^Weight of ground, washed flesh if no portion had been reserved for analysis of fillets. 483 FISHERY BULLETIN VOL 77. NO 2 equal lengths of time in (different holding systems, but were almost absent in the cooked samples (Table 2). The flavor scores of iced pollock did not change significantly until after 6 days and texture remained unchanged throughout the experiment. Kramer et al. ( 1977) reported that pollock can be held 12 days in ice with only a small decrease in flavor scores and none in texture scores. The pol- lock used in that experiment were larger than those used in our work, and preparation and cook- ing of the fish were different. The flavor scores for the MRSW samples re- mained unchanged to 4 days and were acceptable to 8 days except for the high salt content. The increased salt content, in addition to the develop- ment of a disagreeable taste noted by some panel members, was probably the reason sensory scores decreased after 4 days in MRSW. The scores for texture remained unchanged throughout the ex- periment. These conclusions on holding characteristics of pollock were based on fish obtained from one loca- tion at one time of year but pollock caught at different locations may have different holding properties (Kramer et al. 1977). Not only does the size of walleye pollock vary from one location to the next (Kizevetter 1973) but there is some evi- dence of distinct breeding groups (Iwata 1975). Variation due to the yearly reproduction cycle may also affect the holding qualities. 16.57f in either system for both lots. The nonpro- tein nitrogen content was 1 W of the total nitrogen content initially and did not change with time of holding in ice but slowly decreased to 79; after 10 days in MRSW. The free a-amino-nitrogen content did not change significantly during the experi- ment, averaging 7.1 ±0.7 (SD) and 6.2±0.9 (SD) mg N/100 g sample in the fillets offish held in ice and in MRSW, respectively. Several chemical analyses were performed to determine which, if any, could be used as an index of spoilage. TVB changed little and never ex- ceeded 10 mg N/100 g sample making it unsuit- able as an index of spoilage. Tokunaga (1964) re- ported TVB values of 10-13 mg N/100 g sample for freshly caught pollock. Analysis for TVA in fish from Lot 2 gave values essentially the same as in Lot 1. Except for the 2.5-day sample, values for TVA content of ice-held fish remained largely un- changed at <0.20 meq H'/lOO g flesh to 4.5 days but then began to increase (Figure 1 ). The increase at 4 days coincided with the change in quality as determined by informal subjective evaluation of the raw fillets but preceded by at least 2 days the decrease in flavor scores of the cooked fillets. Therefore, TVA content could be used as an index of spoilage for pollock held in ice if supplemented by subjective sensory examination of cooked fish. For MRSW-held samples, a rapid increase in TVA content occurred after 12 days while a significant Chemical Analyses While the salt content of pollock held in ice remained relatively unchanged with time of hold- ing, it increased rapidly in MRSW-held fish (Table 1 ). Salt contents offish from both lots were similar. The protein contents (6.25 x <7c total N) of the fillets varied little with holding time and averaged Table 2. — Change in mean sensory analysis scores for baked portions of blocks of fillets of walleye pollock (Lot 2) with time of holding in ice and m modified refrigerated seawater i MRSW). SD are in parentheses. Panel had 12 judges. Flavor and texture scores were on the following scale: Very good, 5; Good, 4; Fair, 3; Borderline, 2; and Poor. 1. Time o( Flavor Percent responding too salty (days) Ice' MRSW Ice MRSW Ice MRSW 0 2 4 6 8 4 0(0 5) 3 9(0 5) 3 6(0 5) 3 8(0 6) 3 2-(0 8) 4 0 (0 5) 3 7(0 5) 4 1 (0 5) 2 9-(0 9) 3 2-10 7) 4 0 (0 3) 3 9(0 5) 3 8(0 5) 3 8(0 6) 3 8(0 5) 4 0(0 7) 3 9 (0 5) 4 0(0 7) 3 9(0 7) 3 8 (0 4) 0 0 0 0 0 0 0 0 33 75 'Values viiltl aslerisl* were signiticanlly (P - 0 05) diHerent Irorn zero holding time values 8 10 1 .:> HOLDING DAYS FIGURE 1.— Change in total volatile acid iTVA I content of fillets from walleye pollock (Lot li with time of holding in ice and in modified refrigerated seawater (MftSWi. 484 REPPOND ET AL WALLEYE POLLOCK: CHANGES WHEN HELD IN SEA WATER decrease in quality was detected at 8 days in the raw fillets, and at 6 days in the cooked fish. There- fore, TVA could not be used as an index of spoilage for pollock held in MRSW. In both lots, the TMA values (Dyer 1945) were higher for ice-held fish than for MRSW-held fish (Figure 2). A higher TMA content should have occurred in the fish held in ice if their flesh was at a higher pH because Castell and Snow (1949) showed the rate of formation was higher in a more basic medium. The pH of a 2:1 distilled water- ground flesh mixture was 7.25 and 6.45 for ice- held and MRSW-held fish, respectively, and changed little with time of holding. Another reason for the higher TMA content in iced fish was that the lower pH of the brine should inhibit the proliferation of bacteria. For fish held in MRSW, there was little difference in TMA content be- tween lots but for fish held in ice, values for Lot 2 are about twice the corresponding values in Lot 1. This difference in TMA values between lots was probably due to the fish in Lot 2 being iced in o 2 O 2 4 6 8 10 12 14 16 TIME OF HOLDING DAYS Figure 2.— Change in trimethylamine (TMA) content of fillets from walleye pollock with time of holding in ice and in modified refngerated seawater (MRSW). layers while those in Lot 1 were individually iced. Kramer et al. ( 1977) reported TMA values on iced pollock that were similar to that of Lot 1 . Although there was no statistically significant correlation between flavor of iced fish and TMA content, the rapid change in TMA content for iced fish from Lot 2 occurred at the same time as the flavor score decreased. The change in rate of accumulation of TMA in iced fish in Lot 1 was not as discernible but probably occurred between 4 and 6 days. Kramer et al. (1977) reported a large increase in TMA content in pollock after 8 days in ice. Differences in analytical technique, sample preparation, or icing procedure could account for the different times for the sudden increase in TMA. For MRSW-held fish in Lot 2, no rapid change in TMA content was noted even after the flavor scores decreased. Con- sequently, TMA content may provide a useful index of spoilage for ice-held pollock but may not be usefull for fish held in MRSW. Using the modification by Tozawa et al. ( 197 1 ) of Dyer's (1945) method for determining TMA has reduced the interference from DMA but has not always provided as reasonable or as useful data (Botta and Shaw 1975; Shaw et al. 1977). Fish from Lot 2 were analyzed by both methods and though TMA values were generally lower using the method of Tozawa et al., there was no differ- ence in the way TMA content varied with time of holding. Consequently, the methods of Dyer and Tozawa et al. were equally useful as chemical in- dices of spoilage for pollock during fresh storage in ice. The TMA values as determined by the method of Tozawa et al. were not included in this report. The TMAO content (Lot 2) of the zero holding time sample was 69 mg N/100 g flesh. Tokunaga (1964) has reported TMAO values which averaged about 100 mg N/100 g flesh. The TMAO content of the ice-held fish remained essentially unchanged to 8 days but dropped to 36 mg N/100 g flesh on the last day (Figure 3). The TMAO content offish held in MRSW was about the same as that offish held in ice to the fourth day then rapidly decreased. Al- though there was no significant statistical correla- tion between TMAO values and flavor scores, the decrease in TMAO content coincided with the de- crease in flavor scores for MRSW-held fish. The TMAO content of the ice-held fish had not changed significantly at the eighth day of holding even though the flavor score had decreased sig- nificantly. The DMA content was also determined on fish in Lot 2 (Figure 4). The rate of accumulation of DMA 485 FISHERY BULLETIN VOL 77. NO 2 4 6 8 TIME OF HOLDING DAYS FIGURE 3.— Change in trimethylamine oxide iTMAOl content of fillets from walleye pollock I Lot 2) with time of holding in ice and in modified refrigerated seawater iMRSW). 4 6 8 10 TIME OF HOLDING DAYS FIGURE 4.— Change in dimethylamine iDMAl content of fillets from walleye pollock iLot 21 with time of holding in ice and in modified refrigerated seawater (MRSWl. was linear and equal in both systems and there- fore had little usefulness as an index of spoilage. Because of the leaching ability of both the melt water in the ice system and the brine in the MRSW system, the rate of accumulation of DMA in the flesh may be different from the rate of formation of DMA. In the dissociation of TMAO, FA should be formed in equal molar proportion to DMA. The results for analysis for FA in fish from Lot 2 re- vealed that FA content was 4 ppm in both systems and did not change with time of holding. The lack of an increase in FA content was probably due to its reaction with proteins. Castell et al. (1973) noted that addition of FA lowered the solubility of the protein so the formation of FA can be inferred by a decrease in EPN with time of holding (Figure 5). Results from an experiment on a control sample to which NaCl was added indicated that the low EPN values of MRSW-held fish were not due to their high salt content. Like the TMAO content, the values for EPN are about the same for either holding system until after 4 days when the values for MRSW-held fish decreased rapidly (Figure 5). Data from fish in Lot 1 also indicated that there was a similar difference in solubility after 4 days of holding. Although there was no significant statistical correlation among EPN values, TMAO content, or the flavor scores, all three of these experimentally determined values decreased at the same time in fish held in MRSW, i.e., after 4 days. With ice-held fish, the decrease in flavor preceded the decrease in TMAO and there was no decrease in EPN values. Evidently, analysis for TMAO and EPN may provide and index of spoil- age for MRSW-held fish but not for ice-held fish. Tokunaga (1964) reported data similar to that 4 6 8 TIME OF HOLDING DAYS Figure 5.— Change in extractable protein nitrogen (EPNl of fillets from walleye pollock I Lot 2) with time of holding in ice and in modified refrigerated seawater I MRSW). 486 REPPOND ET AL.: WALLEYE POLLOCK: CHANGES WHEN HELD IN SEAWATER presented here on the accumulation of DMA and FA in the flesh of walleye pollock stored as fillets at l"-3° C. Kramer et al. (1977) reported much lower values of DMA but this was probably due to differences in sampling and analytical technique. Effects of Washing Ground Flesh Washing improved the appearance of minced pollock (Miyauchi et al. 1977) and is a common procedure in the utilization of pollock in tradi- tional Japanese products lOkada and Noguchi 1974). The water to flesh ratio of 2:1 used in this experiment was much smaller than the 5;1 or larger values used by other investigators. Wash- ing the ground flesh of ice-held pollock increased the apparent yield but no change in yield occurred for samples held in MRSW. If yield data are con- verted to a salt-free, constant 187? solids basis however, the washing procedure actually de- creased the yield to 3(>7f for samples from either system. Yamamoto et al. ( 1975) reported that 209'( of the protein content of ground pollock can be lost under certain washing conditions. Consequently, for commercial pui-poses, any beneficial results from washing would have to be balanced against a sizable decrease in yield. The advantages of wash- ing are that the product is lighter in color, has less odor, and, in the case of fish held over 4 days in MRSW, has an acceptable salt content (Table 1). TMA, TVA, and NPN content are also reduced by about half on washing. CONCLUSIONS Walleye pollock can be held to 6 days if iced thoroughly and still be acceptable for human con- sumption. Palatable fillets can be obtained from ice-held fish whose physical appearance in the round would probably cause them to be rejected for human consumption. In MRSW, the rapid ac- cumulation of salt in the flesh would prohibit hold- ing pollock more than 4 or 5 days at the 1.5:1 brine to fish ratio utilized in this experiment. The de- velopment of a disagreeable taste other than sal- tiness may be responsible for some of the decrease in flavor scores. The beneficial results of washing the ground or minced flesh of pollock will probably be negated by the decrease in yield and the prob- lems associated with disposing of the wash water. Analysis for TMA or TVA may provide a chemical index of spoilage for pollock held in ice; for pollock held in MRSW, analysis for TM AO or EPN may be useful. Further work is needed before limiting values for TVA, TMA, TMAO, or EPN can be pro- posed as objective indicators of the acceptability of fresh pollock. LITERATURE CITED BARNETT, H. J., R. W. NELS( )N, p. J. HUNTER. S. BAUER, AND H, Groninger. 1971. Studies on the use of carbon dioxide dissolved in refrigerated brine for the preservation of whole fish. Fish. Bull.. U.S. 69:433-442. BoTTA, J. R., AND D. H. Shaw. 1975. Chemical and sensory analysis of roughhead gre- nadier {Macnmrus berglax) stored in ice. J. Food Sci. 40:1249-1252. BULLARD, F. A., AND J. COLLINS. 1978. Physical and chemical changes of pink .shrimp. Pon- dalus borcalis. held in carbon dioxide modified refriger- ated seavater compared with pink shrimp held on ice. Fish. Bull.. U.S. 76:73-78. BVSTEDT, J., L. SWENNE, AND H, W. AAS. 1959. Determination of trimethylamine oxide in fish mus- cle. J. Sci. Food Agric. 10:.301-304. CaSTELL, C. H., AND B, SMITH, 1973. Measurement of formaldehyde in fish muscle using TCA extraction and the Nash reagent. J. Fish. Res. Board Can. 30:91-98. Castell, C. H., B. Smith, and W. J. Dyer. 1973. Effects of formaldehyde on salt extractable proteins of gadoid muscle. J. Fish. Res. BoardCan. 30:1205-1214. Castell, C. H., and J. M. Snow. 1949. The effect of pH on the enzymatic reduction of trimethylamine oxide J. Fish. Res. Board Can. 7:561- 562. DOWTIEN, H. C. 1938. LVIII, The determination of small amounts of di- methylamine in biological fluids. Biochem. J. 32:455- 459. DYER, W. J. 1945. Amines in fish muscle. I. Colorimetric determina- tion of trimethylamine as the picrate salt, J, Fish, Res. Board Can. 6:351-358, DYER, W, J., H. V. FRENCH, AND J. M. SNOW. 1950. Proteins in fish muscle. I. Extraction of protein frac- tions in fresh fish. J. Fish. Res. Board Can. 7:585-593. FRIEDEMANN, T. E,, AND T. BROOK. 1938. The identification and quantitative determination ofvolatilealcoholsandacid, JBiolChem, 123:161-184, HORWITZ, W, (editor), 1975, Official methods of analysis of the Association of Official Analytical Chemists, 12th ed, Assoc. Off. Anal. Chem., Wash,, D.C.. 1094 p. IWATA, K., AND M. OKADA, 1971 . Protein denaturation in stored frozen Alaska pollock muscle — I. Protein extractability and Kamaboko form- ing ability of frozen surimi. Bull. Jpn. Soc. Sci. Fish. 37:1191-1198. IW'ATA, M. 1975, Population genetics of the breeding groups of wal- leye pollock ^Theragra chalcogranima) based on tet- razolium oxidase polymorphism, Sci. Rep. Hokkaido Fish. Exp. Stn. 17:1-9. 487 KlZEVETTEK, 1. V. 1973. Chemistry and technology of Pacific fish. Isr. Prog. Sci. Transl. Ltd., Keter Press Binding. Jerusalem, 304 p. KR-AMER, D. E., D. M. A. NORDIN, .•\ND L. J. G.ARD.N'ER. 1977. A comparison of the quality changes of Alaska pol- lock and Pacific cod during frozen storage at -28° C. Can. Fish. Mar, Serv. Tech, Rep, 753, 63 p. LEMON, D. W., AND L, W, REGIER, 1977. Holding of Atlantic mackerel iScomberscomhrus) in refrigerated sea water. J. Fish. Res. Board Can. 34:439- 443. LONGARD, A. A., AND L. W. REGIER. 1974. Color and some composition changes in ocean perch {Sebastes martriu:^) held in refrigerated sea water with and without carbon dioxide. J. Fish. Res. Board Can. 31:456-460, MlYAUCHI, D,, G, KUDO, AND M, PATASHNIK, 1977 Effect of processing variables on storage characteris- tics of frozen minced Alaska pollock. Mar, Fish, Rev. 39(51:11-14, NIKKILA, O. E., AND R. R. LINKO. 1954. Denaturation of myosin during defrosting of frozen fish. Food Res. 19:200-205. OKADA, M., AND E. NOGUCHI. 1974. Trends in the utilization of Alaska pollock in Ja- pan. In R.Kreuzerleditorl.Fisheryproducts.p. 189-193. Fishing News (Books), Ltd., Lond. fishery bulletin vol, 77. no, 2 Pope, C. G., and M. E. Stevens. 1939. CXXX. The determination of amino-nitrogen using a copper method. Biochem, J. 33:1070-1077. Roach, S. W., H. L. a, Tarr, N. Tomlinson, and J. S. M. Harrison. 1967, Chilling and freezing salmon and tuna in refriger- ated sea water. Fish, Res, Board Can., Bull. 160, 40 p SHAW, D. H,, R. L. GARE, .and M. A. KENNEDY, 1977, Chemical and sensory changes during storage of witch flounder [Glyptocephalus cynoglossus) in ice. J. Food Sci, 42:159-162, Stansby, M, E, R. W. Harrison, J. Dassow, and M. Sater. 1944. Determining volatile bases in fish. Ind. Eng. Chem., Anal. Educ. 16:.593-596. TOKUNAGA, T. 1964, Studies on the development of dimethylamine and formaldehyde in Alaska pollock muscle during frozen storage. Bull. Hokkaido Reg. Fish. Res. Lab. 29:108-122. TOZAWA, H., K. ENOKIHARA, AND K. A.MANO. 1971. Proposed modification of Dyer's method for trimethylamine determination in cod fish. In R. Kreuzer (editor). Fish inspection and quality control, p, 187-190, Fishing News (Books) Ltd,, Lond, UCHIYAMA, H,, N, KATO, AND S, EHIRA, 1972, Freshness preservation of Alaska pollock in fishing boats in the North Pacific, Bull, Tokai Reg, Fish, Res. Lab, 72:1-8, Yamamoto, M., a. Barnes, Y. C. Lau, and J. Wong, 1975, Consequences of washing deboned fish flesh upon appearance and on protein loss. Can. Fish. Mar. Serv. Tech. Rep. 580, 10 p. 488 NOTES THICKNESS AND DEPTH DISTRIBUTIONS OF SOME EPIPELAGIC FISH SCHOOLS OFF SOUTHERN CALIFORNIA Many schooling fish species such as northern an- chovy, Engraiilis morda.x; jack mackerel, Trach- iiriis symmetrictis; and Pacific mackerel. Scomber japonicus, are adept at avoidance of surface ves- sels, even those moving at relatively high speeds. Evasion behavior has complicated measurement of the vertical extent, thickness, and distribution in depth of such fish schools using standard echo sounding techniques. In addition, hull-mounted echo sounders are usually 3 to 4 m below the sur- face, are blanked for the duration of the transmit- ted pulses and are relatively ineffective for another 5 to 10 m due to high surface and volume reverberations immediately following the pulse transmission. The combination of evasion be- havior and transducer mounting and operation often results in poor sampling of the upper 10 to 20 m of the water column by hull-mounted echo sounders. Commercial fishermen routinely use air spot- ters to guide them to school groups (Squire 1972). Fishermen often set their gear visually in water so rich with plankton that visibility is severely re- stricted. An awareness of these practices and of the implication that many of the fish landed com- mercially are caught at relatively shallow depths emphasizes the need for a good tool for studying shallow schools. Determination of fish size from swim bladder resonance data requires accurate measurement of the depth and thickness of schools, including those in the upper 20 m (HoUi- day 1977). When operating an echo sounder in shallow wa- ter, multiple "bottom" echo traces often appear. The second "bottom" in these traces is an image of the sea surface as reflected by the sea floor. With appropriate attention to signal processing it is possible to make measurements on subsurface targets detected via sound which has been reflect- ed from the seabed. Under these conditions, a school of fish near the surface will appear just above the second "bottom." The procedure used to obtain the data presented in this paper is a varia- tion on this observation. Materials and Methods Measurements of the mean depth and thickness of schools or aggregations of marine organisms were made at three locations in the California Current near the southern California coast. Each location was occupied during a different season, the first in December 1976, the second in May 1977, and the last durmg September 1977. The December and May work was done near Santa Catalina Island and the September data were taken about 15 mi southwest of Oceanside, Calif In December, only 17 schools were studied, be- cause the location of the ship at that time did not coincide with the presence of a large school group. All measurements were made during daylight hours. The schools studied were previously de- tected on the 30 kHz sonar in its normal side-look- ing mode. In May, 121 schools were studied and in September measurements were made on 221 targets. Our bottom bounce system was implemented using the sonar aboard the NOAA ship David Starr Jordan. The procedure involved a 30 kHz sonar, steerable in the vertical and horizontal planes, with a capability for depression to 90°, i.e., vertical as in the standard echo sounding mode. Over a flat bottom, the sonar was normally oper- ated at a depression angle of 80° to 85°, depending on water depth. The horizontal steering was to either port or starboard, that is, normal to the ship's track. This allowed sampling of a path whose width varied with water depth on the selected side of the ship and parallel to the ship's track (Figure 1). As an example, for a flat bottom, a depression angle of 80° and a water depth of 500 m, a path was studied with an inner edge which inter- sected the surface 70 m from the ship's track, and an outer edge which extended to 275 m. These limits were derived from the sonar's 12° beam width, defined as the -6 dB point on the two way (transmit and receive) beam pattern. The data reported in this note were acquired using 1 ms CW pulse waveforms. It was deter- mined that reliable measurements could be made in water depths up to 500 m with bottom slopes of up to 1.4° using a source level of 216 db//l/xPa at 1 m. Bottom characteristics were thought to be FISHERY BULLETIN VOL 77. NO 2. 1979 489 Volume Reverberation Bottom Echo School Echo via Bottom Reflection Surface Echo via Bottom Reflection FHU'RK 1. — Illustration of bottom bounce technique geometry and typical time-amplitude graph of sonar echo. either mud or mud and sand in the operating areas , (Revelle and Shepard 1939:247), but no bottom samples were taken. Relative to that over a flat bottom, performance appeared to be slightly im- proved in areas with a gentle slope, presumably because of a change in bottom composition or roughness. Schools were easily detected when sur- face waves were <3-5 ft, but acoustic measure- ments became more difficult when the wind in- creased in strength and whitecaps were formed. This was partly due to uncertainties in the precise location of the surface reflection which is used as a reference in determining target depth. The sur- face reflection was substantially more diffuse when moderate numbers of whitecaps were visi- ble. This effect may have been due to increased surface scattering and absorption by small air bubbles entrained by wave action near the sur- face. Although we made no direct measurements of school target strengths, our best estimates range between -5 dB and +10 dB for side aspect target strengths of the schools studied. These es- timates are based on earlier measurements made for schools similar in size and suspected composi- tion ( Larsen' ). Ventral aspect target strengths are possibly 3-6 dB less (Love 1977) based on mea- surements for individuals rather than schools. 'Larsen, H. 1974. Distributions of target strengths and horizontal dimensions for aggregations and schools of marine organisms. Tracor Doc No T74-SD-1054-U. 66 p. Results antl Discussion Examination of the bottom bounce data for the depth distribution of schools (Figure 2) revealed an apparent preference of the schools for depths near the seasonal thermocline. The accumulation of the number of observations per depth interval, when normalized to achieve a display with a unit area under the curve, is one means of estimating the probability density function (p.d.f.) for a quan- tity such as school mean depth (Feller 1971:36). The most probable value (depth, thickness) of a random variable is defined as the value of the quantity at the largest peak in its p.d.f. (Papoulis 1965:140). Though the thermocline was less well defined in May than in December and September, the most probable depth at which a school was found in each survey generally coincided with the ma.ximum thermal gradient (Table 1; Figure 2a, f, k). In order to quantify the apparent relation of fish school distribution and the thermal profile, the mean depth of each school was determined. The data were sorted into 10 m depth intervals. Because of the sonar's beam shape, the volume searched by the bottom bounce procedure varied for a given school depth interval as the bottom depth changed. For a bottom depth of 300 m, about 40'/^ more water was searched for schools at 5 m depth than for schools at 150 m. The number of schools observed during each survey in a particu- lar depth interval (Figure 2a, f, k) was normalized 490 "T I — i — r J I . I 0 25 so 75 100 c - J L 10 15 20 1 1 1 1 u 5 1 in Ul z 10 *: u X 1- e '' ^ z o A»» r S : L - 1 so - H 1 1 / - 3 - 5 - (0 f trt 1 2 ?^ a Ul a: ELAPSED TIME (MIN) Figure l. — Changes in metabolic rate, heart rate, and red muscle temperature of a 1.456 kg skipjack tuna during an experiment to determine standard metabolic rate (SMR), The predicted metabolic rate is based on a least-squares fitted second degree polynomial. The minimum predicted metabolic rate (i.e,, SMRl is .50.5mgO2h ', 495 significantly. Red muscle temperature was moni- tored to test if changes in metabolic rate reflected changes in it. All fish showed red muscle tempera- tures as stable as those shown in Figure 1. Fish were in the respirometry box approximately 15 to 30 min before data recording began and red mus- cle temperatures generally approached thermal steady state during this period. The SMR of 33 fish (0.317-4.737 kg) was success- fully determined. A regression line of SMR versus body weight was fitted by Gauss-Newton iteration technique (Biomedical Computer Programs, pro- gram number BMDP 3R), rather than by a linear regression technique based on log-log transforma- tion of the data (Figure 2). The advantages of the former method and disadvantages of the latter have been discussed by Zar (1968) and Glass (1969). The best-fitting allometric equation was found to be: SMR 412.0 ( ±27.1) W 0.563( *0,07) (1)2 where SMR = standard metabolic rate in milli- grams O2 per hour and W = body weight in kilograms; values in parentheses are the standard deviations of the parameters. The coefficient of determina- tion (r2) is 0.72. The exponent in the allometric equation de- scribing the effect of body size on the SMR of other teleosts ranges from approximately 0.65 to >1 (Winberg 1956; Fry 1957; Beamish and Mookher- jii 1964; Beamish 1964; Glass 1969; Brett 1972). The lower value for the exponent in Equation (1) indicates that the weight specific SMR (i.e., mil- ligrams O2 per gram per hour) of skipjack tuna decreases more steeply as body size increases than does the weight specific SMR of other species. The strong influence of body size on the SMR may be a unique characteristic of thermoconserv- ing species such as skipjack tuna. However, the value of the weight exponent could also be influenced by the technique used to measure SMR. For comparative purposes, it would be useful to determine the SMR's (and corresponding allomet- ric equation) of species (e.g., salmonids) where ^If the allometric equation to describe the effect of body size on whole body SMR is: SMR =aW'' then the corresponding equation to describe weight-specific SMR versus body weight is: SMR; W = aW-WorSMR' =oH"' 'whereSMR' = weight-specific SMR. W = body weight, and a and h are fitted parameters. 0 3 04 0 5 10 2 0 3 0 4 0 50 10 0 BODY WEIGHT (kg) Figure 2. — A double logarithmic plot of the standard metabolic rate (SMR) versus body weight (W). The line represents the allometric equation SMR = 412.0 w" 56.) jy^^ coefficient of de- termination IS 0.72. these parameters are already known, but employ- ing the methodology outlined in this study. The SMR has been postulated to be a function of: the diffusing capacity of the respiratory system, whole blood sugar concentration, and the rate at which the circulatory system can deliver sub- strates and oxygen to the cells (Schmidt-Nielsen 1970; Ultsch 1973; Coulson et al. 1977; Wilkie 1977; Hughes 1977; Umminger 1977). Specifically which of these factors most influence the SMR of skipjack tuna is unknown at this time. Selection pressures apparently favor significant reductions in the weight-specific SMR of skipjack tuna as body size increases (hence the lower exponent m Equa- tion (D). How the factors that determine SMR could be affected by such selection pressures is also unknown. The SMR's for skipjack tuna are approximately 5 to 10 times greater than those reported for other teleosts of equal body size (Pritchard et al. 1958; Beamish 1964; Brett 1965, 1972). However, the great difference in the effect of weight on SMR, and the unique methodolog>' employed in this study, makes direct comparisons tenuous. Application of the Results Careful application of my results in energetics models is advised for several reasons. First, skip- jack tuna attain maximum body size of approxi- mately 22 kg iKitchell et al. 1978); although the weight range of fish I used in this study covers more than an order of magnitude, there is still a large untested size range. Because skipjack tuna 496 >4 to 5 kg are extremely difficult to capture and transport, it is unlikely that specimens larger than this will be tested in the foreseeable future. Second, the SMR includes the energetic cost of osmoregulation and cardiac work. The energy re- quirement of both processes comprises a sig- nificant fraction of the SMR (Heath 1964) and more importantly, the energy demand of these processes is dependent on swimming speed (Rao 1968; Farmer and Beamish 1969; Nordlie and Leffler 1975). Therefore prediction of energy de- mand as a function of swimming speed may not be adequately determined by simple addition of the SMR and the energj' cost of swimming based on a theoretical estimate of hydrodynamic drag: an es- timate of the increased internal work, due to activ- ity, should also be included. Third, the scatter in the SMR's presented in Figure 2 is due, in part, to the difficulty of working with animals such as skipjack tuna, which are both highly active and physiologically delicate. There are, however, also at least two distinct sub- populations of skipjack tuna that occur around the Hawaiian Islands ( Sharp-' i. It is reasonable to sus- pect the SMR of individuals from the various sub- populations might be significantly different when measured under identical conditions. Again, reasonable caution in application of the data pre- sented here is urged. ■Acknow ledgments I thank the following people for helpful criti- cisms of the manuscript and useful discussions: Andrew Dizon, Gary Sharp, Don Stevens, Causey Whittow, and Carol Hopper. Randolph Chang, Douglas Davies, and Victor Honda provided tech- nical assistance. Literature Cited BEAMSH, F. W. H. 1964. Respiration of fishes with special emphasis on stan- dard oxygen consumption. II. Influence of weight and temperature on respiration of several species. Can. J. Zool. 42:177-188. Beamish, F. W. h., and p. S. Mookher.jii. 1964. Respiration of fishes with special emphasis on stan- dard oxygen consumption. I. Influence of weight and temperature on respiration of goldfish, Carassius a;/ ra/us L. Can. J. Zool. 42;161-175. ^G. D. Sharp, Inter-American Tropical Tuna Commission, La JoUa, CA 92038, pers. commun. 1978. Brett, J. R. 1965. The relation of size to rate of oxygen consumption and sustained swimming speed of sockeye salmon iOn- corhynckus nerka}. J. Fish. Res. Board Can. 22:1491- 1501. 1972. The metabolic demand for oxygen in fish, particu- larly salmonids, and a comparison with other vertebrates. Respir. Physiol. 14:151-170. CouLSON, R. A., T. Hernandez, and J. D. Herbert. 1977. Metabolic rate, enzyme kinetics in uivo. Comp. Biochem- Physiol, 56A:251-262. Farmer, G. J., and F. W. H. Beamish. 1969. Oxygen consumption of Tilapia nilolica in relation to swimming speed and salinity. J. Fish. Res. Board Can. 26:2807-2821. Fry, F. E. J. 1957. The aquatic respiration of fish. In M. E. Brown (editor). The physiology of fishes. Vol. 1, p, 1-63. Acad, Press. N.Y. 1971. The effect of environmental factors on the physiol- ogy offish. In W.S. Hoar and D.J, Randall (editors). Fish physiology, Voi. 6, p. 1-98. Acad. Press, N,Y. Glass, N. R. 1969. Discussion of calculation of power function with spe- cial reference to respiratory metabolism in fish. J. Fish. Res. Board Can. 26:2643-2650 HEATH, A. J. 1964. Heart rate, ventilation, and oxygen uptake of a marine teleost in various oxygen tensions. Am. Zool. 4:386. Hughes, G. m. 1977. Dimensions and the respiration of lower verte- brates. In T. J. Pedley (editor). Scale effects in animal locomotion, p. 57-81. Acad. Press, N.Y. KITCHELL, J, F,,J, F. KOONCE, R. V. O'NEILL, H, H. SHUOART, Jr., J. J. Magnl'slin, and R. S. Booth. 1974. Model of fish biomass dynamics. Trans, Am. Fish. Soc. 103:786-798. KITCHELL, J. F., W. H. NEILL, A. E. DiZON, AND J. J. Magnuson. 1978, Bioenergetic spectra of skipjack and yellowfin tunas. In G. D, Sharp and A. E. Dizon (editors). The physiological ecology of tunas, p. 357-368. Acad, Press, NY KITCHELL, J, F., D. J. STEWART, AND D. WEININGER. 1977. Applications of a bioenergetics model to yellow perch iPerca flai'escens 1 and walleye iStizostedion uitreum vitreum). J. Fish. Res. Board Can. 34:1922-1935. Magnuson, J, J. 1969. Digestion and food consumption by skipjack tuna {Katsuwonus pelamis). Trans. Am, Fish. Soc. 98:379- 392. MuiR. B. S., G. J, Nelson, and K. W. Bridges. 1965. A method for measuring swimming speed in oxygen consumption studies on the aholehole Kuhlia sandvicen- sis. Trans. Am. Fish. Soc. 94:378-382. NaKAMURA. E. L. 1972, Development and uses of facilities for studying tuna behavior. In H. E Winn and B L. OUa (editors). Be- havior of marine animals. Current perspectives in re- search. Vol. 2, p. 245-277. Plenum Press, N.Y. Nordlie, F. G., and C. W. Leffler, 1975. Ionic regulation and the energetics of osmoregula- 497 tion in Mugil cephalus Lin. Comp, Biochem. Physiol. 51A:125-131. Pritchard, a. W., E. Florey, and a. W. Martin. 1958. Relationship between metabolic rate and body size in an elasmobranch iSqualus sttckleyi) and in a teleost {Ophiodon elongatus). J. Mar. Res. 17:403-411. Rao, G. M. M. 1968. Oxygen consumption of rainbow trout iSalmo gairdneri ) in relation to activity and salinity. Can. J. Zool. 46:781-786. Schmidt-Nielsen, K. 1970. Energy metabolism, body size, and problems of scal- ing. Fed. Proc. 29:1524-1532. Sharp, G. D., and R. C. Francis. 1976. An energetics model for the exploited yellowfin tuna, Thunnus alhacares, population in the eastern Pacific Ocean. Fish. Bull., U.S. 74:36-51. SHARP, G. D., AND W. J. VLYMEN III. 1978. The relation between heat generation, conservation and the swimming energetics of tunas. In G. D. Sharp and A. E. Dizon (editors), The physiological ecology of tunas, p. 212-232. Acad, Press, N.Y. Snedecor, G. W., and W. G. Cochran. 1967. Statistical methods. 6th ed. Iowa State Univ. Press, Ames, 593 p. Stevens, E. D. 1972. Some aspects of gas exchange in tuna. J. Exp. Biol. 56:809-823. ULTSCH, G. R. 1973. A theoretical and experimental investigation of the relationships between metabolic rate, body size, and oxy- gen exchange capacity. Respir. Physiol. 18:143-160. UMMINGER, B. L. 1977. Relation of whole blood sugar concentrations in ver- tebrates to standard metabolic rate. Comp. Biochem. Physiol. 56A:457-460. WEIHS, D. 1973. Optimal fish cruising speed. Nature (Lond.i 245: 48-50. 1977. Effects of size on sustained swimming speeds of aquatic organisms. In T. J. Pedley (editor), Scale effects in animal locomotion, p. 333-338. Acad. Press, N.Y. WILKIE, D. R. 1977. Metabolism and body size, /n T. J. Pedley (editor). Scale effects in animal locomotion, p. 23-36. Acad. Press, N.Y. WINBERG, G. G. 1956, (Rate of metabolism and food requirement of fishes.) lln Russ.] Nauchn. Tr, Belorussk. Gos, Univ. Minsk, 253 p, (Transl. 1960. Fish. Res. Board Can., Transl. Ser. 194, 202 p.) ZaR,J. H. 1968. Calculation and miscalculation of the allometric equation as a model in biological data. Bioscience 18:1118-1120. Richard W. Brill Southwest Fisheries Center Honolulu Laboratory National Marine Fisheries Service, NOAA P.O. Box 3830. Honolulu. HI 96812 Present address: Department of Zoology The University of British Columbia 207.5 We.'ibrook Mall. Vancouver, B.C. V6T IWS. Canada EFFECTS OF A THERMAL DISCHARGE ON REPRODUCTIVE CYCLES IN MYTILUS EDL'LIS AND MYTILUS CALIFORSIANL'S (MOLLUSCA, BIVALVIA) One principal concern about thermal effluents is the effect of altered temperatures on the repro- ductive biology of organisms near the discharge (e.g., Hedgpeth and Gonor 1969). In marine mus- sels of the genus Mytilus. the role of temperature in regulating the reproductive cycle and the ef- fects of temperature stress on the energy budget for growth and reproduction have been particu- larly well studied (Bayne 1975; Gabbott 1976; Seed 1976). Mytilus edulis has a seasonal cycle of gametogenic activity that is conditioned by tem- perature and is linked with the storage and utiliza- tion of reserve materials in the body (Bayne 1975). Metabolism and filtration rate show complete temperature acclimation from 5° to 20° C, and the scope for growth is relatively independent of temperature over this range (Widdows and Bayne 1971; Widdows 1973, 1978a). However, above 20" C the mechanisms of temperature adaptation break down, producing an increase in the metabolic rate, a decline in filtration rate, and thus a reduced scope for growth (Widdows 1976, 1978a). Above 25° C this scope is so reduced that there is no energy for growth, and energy reserves are depleted in order to survive (Widdows 1978b). This study examined the effect of a thermal dis- charge from a coastal steam-electric power plant on reproduction in M. edulis and M. californianus in central California. The reproductive cycles and gonadal weights of these mussels in the warmwa- ter outfall and in control regions of naturally oc- curring temperatures were compared using body component index methods. Water temperatures in the outfall exceeded 20° C much of the late sum- mer and early fall, while plant intake tempera- tures were usually in the 12-15° C range and rarely exceeded 17° C, Methods This study was conducted at the Pacific Gas and Electric Company fossil-fuel power plant at Morro Bay, Calif (Figure 1). The 1,030-MW plant used ocean water for once-through cooling and dis- charged warmed water into a canal about 80 m long. The canal released water into the surf, form- ing a plume with an isotherm 5° C above naturally occurring temperatures of about 0.6-3.0 acres sur- 498 fi.shery bulletin vol . NO, 2, 1979, Figure l. — Locations of the intake and outfall of the Morro Bay power plant in California and the collecting sites for mussels in this study. In addition to outfall samples of both species, control samples of Mytilus eduUs were taken from site 1, and control samples of M. caltforntanus were taken from site 2. face area depending on plant load and weather conditions. The mean temperature differential be- tween the intake and outfall was about 7" C and ranged from about 3° C in spring to about 15° C in late summer and fall (Figure 2). The intake showed a seasonal cycle of low temperatures around 11-12° C in winter and high temperatures around 14"-15°C in summer and fall. Mean outfall temperatures exceeded 20° C from May through January and varied seasonally from around 18° C in spring to around 26° C from July through Oc- tober. Daily temperature fluctuations in the out- fall were much greater (up to 11°C) than those in the intake (up to 3°C). Also, heat treatment every few weeks to kill organisms fouling the cooling tubes raised outfall temperatures in places to as high as 36° C for about an hour. Mytilus californianus and M. ediilis, were col- lected from the warmwater outfall and from nearby control areas of normal temperatures at about monthly intervals from November 1972 to November 1973 (Figure 1). Mytilus edulis were collected from shallow ( 1-2 m) subtidal rocks mid- way along the discharge canal and from the un- dersides of floats near the intake. Mytilus califor- nianus were collected intertidally at 1-3 ft above mean lower low water at the mouth of the dis- charge canal and at equivalent tidal heights from the jetty at the Morro Bay harbor entrance. High surf made collecting impossible on the jetty and difficult at the mouth of the discharge canal at Figure 2. — Temperature records from the outfall and intake of the Morro Bay power plant. Weekly mean temperatures were calculated from continuous temperature recorders positioned at mean lower low water near the power plant's intake screens and discharge tubes. The dashed line marks the temperatures above 20' C. which are energetically stressful to Mytilus edulis. (Re- drawn from Hines 1978.) times during the winter. Neither outfall nor con- trol M. edulis were exposed to significant surf at any time, but the outfall had much stronger cur- rents (up to 0.7 m/s) than the control areas. Salinities in the control and discharge areas did not differ significantly from seawater. The temperature records closely reflect the thermal environments of the samples of M. edulis, because they were collected at nearly the same locations as the recorders. However, the records do not represent as closely the thermal regimes of the samples of M. californianus. which were collected from intertidal positions above the recorders and were therefore exposed to air temperatures part of the time, or which were collected at locations dis- tant from the recorders. Seawater temperatures for the control sampling site for M. californianus were sometimes l°-2° C lower than intake temper- atures, and temperatures at the mouth of the dis- charge canal where outfall samples were taken were often 2°-4° C lower than the records show due to dilution of the warmwater discharge by incom- ing surf. Monthly samples of 12 mussels 70-1 10 mm long from outfall and from control populations of each species were processed. For each mussel, the shell length and the internal shell volume determined by the volume (milliliters) of water required to fill the empty valves were recorded. Total wet tissue weight (grams) and wet weight of the gonad tissue dissected from the mantle and body mass were recorded for each mussel. From these data the gonadal index was calculated as: (gonad wt x 499 lOOVtotal tissue wt. The body weight/shell volume index was calculated as: (total wt - gonad wti/ shell volume. The gonadal index reflects reproduc- tive condition and the body weight/shell volume index reflects nutritional condition (Giese and Pearse 1974). Preliminary work showed that in- dexes calculated from wet and then dry weights did not have significantly different variances. Resulfi Mytiltis edulis and M. californiaru/s longer than about 50 mm were sexually mature, and the gonadal indexes of both species had large var- iances. Because gonadal indexes of both species were calculated for a large' size range (70-110 mm shell length) in each population, the covariance of gonadal index on shell volume was analyzed for each species. However, regressions of the arcsine transformation of the gonadal index on shell vol- ume calculated for each monthly sample did not have significantly different slopes for either species (ANCOVA, P>>0.05): for M. califor- nianus the common regression slope = 0.09, ^(18.1901 = 0.206; for M. edulis the common regres- sion slope = 0.08,F,.,,22o, =0.217. Therefore, mus- sel size was ruled out as a significant source of variability in gonadal index for this study. Rather, the variability was probably a result both of the difficulty in precisely dissecting the diffuse gonad from the body tissues and of a large degree of inherent reproductive asynchrony in the popula- tions. The gonadal indexes of M. edulis from the out- fall and from the control populations showed the same distinct cycle of gonads increasing in size during summer and fall and dropping to a low in spring (Figure 3). However, gonadal weights of the outfall population were lower than the controls, as can be seen by the generally lower level of the outfall gonadal index, particularly in the April through November samples. Similarly, the body weight/shell volume index for M. edulis showed an annual cycle which peaked in summer and dropped in fall and winter to a low in spring ( Figure 3). The phase of this body weight/shell volume index was slightly in advance of the gonad cycle. As with the gonad cycle, the outfall population had the same basic body weight/shell volume cycle as the control, but it showed a generally lower level than the controls and indicated that the outfall mussles were in poorer nutritional condition than the controls. NDJFMAMJJASOND 1973 M J J A S 1973 0 N D FiGliRE 3. — Monthly mean values for the gonad index and body weight/shell volume index for Mytilus edulis. Circles = control population; dots = outfall population. Vertical lines are the 95'» confidence limits of the means. Each sample was 12 mussels. In contrast to M. edulis. the gonadal index of M. californianus did not show a distinct annual cycle (Figure 4). The April and May control samples probably represented a peak of reproductive activ- ity, but the erratic fluctuations of the index made this uncertain without histological information or field observations of spawning. Except for this brief spring peak, the outfall population showed a consistently higher level of ripeness throughout the year than the control mussels. The body weight/shell volume index of A/, californianus ap- peared to show a slight annual cycle with a low in March and April and higher levels in late sum- mer (Figure 4). However, this trend was not pro- nounced and did not appear to correlate with the gonadal index. Contrary to the trend shown by gonadal index levels, outfall body weight/shell volume indexes were consistently lower than the 500 50 40 X uj 30 o Q 20 < o 10 f\'4. i no data high surf J I I L J I 1 I L NDJ FMAMJJ ASOND 1973 501- E X lij o 40 30 O > d o CD no data high surf 20 - X J I L _I L. J L. N D J F M A M J J A 1973 S 0 N D Figure 4. — Monthly mean values for the gonad index and body weight/shell volume index for Mytilus californianus. Circles = control population; dots = outfall population. Vertical lines are the 95'7f confidence limits of the means. Each sample was 12 mussels. controls, indicating that the control mussels were in better nutritional condition. For any given body weight, a larger shell vol- ume will result in a lower body weight/shell vol- ume index. Therefore, the relationship of shell volume to shell length was examined for each of the mussel populations. Over the size range of mussels sampled in the study, this relationship was closely approximated by linear regressions, even though it would probably have been cur- vilinear if much smaller mussels were included in the samples. Shell volumes of outfall M. califor- nianus were proportionally larger than the con- trols over most of the sizes sampled (Figure 5), such that the slope and the intercept of the regres- sion of shell volume on shell length for outfall mussels were significantly different from those of 80 - / ^ 70 - J^ y 60 M. edulis outfall + control ^J^^ Z fSO \ .V ^y-./ ^ yy> -> \ ■^■'■if' ^^^ -1 y^^j^ y.' ' ^^ o 40 >■ > "y^^^/^y ^^ry _l III 30 - ^^^^^S^\ M colifornianus — outfall I V) 20 10 n _^/_l 1 — _1_ ■ — control 1 1 70 80 90 SHELL LENGTH 00 (mm) 110 Figure 5. — Regressions of shell volume on shell length for all Mytilus edulis sampled and for outfall and control samples of Af. californianus. Dashed lines indicate the 95'>'r confidence limits of the mean predicted shell volumes. For each population of mus- sels the sample size, correlation coefficient, and regression equa- tion with the 95'7f confidence limits of the slopes and intercepts in parenthesis was as follows. Mytilus californianus outfall: n = 132, r = 0.94, Vol = 1.48( ±0.09)Length - 85. 8( ±8.5l; control: n = 96,r = 0.91, Vol = 1.13( ±0.11lLength - 63.0>±9.0>. Mytilus eduhs outfall: n = 132, r = 0.94, Vol = 1.07(±0.07)Length - 47. 2( ±5.2); control: n = 132, r = 0.85, Vol = 1.12( ±0.12lLength - 48,4(±10.8); combined: n = 264, r = 0.88. Vol = 1.10(±0-07lLength - 47.9(±6.2). the regression for the control mussels (Mests, P<0.05). However, for M. edulis the slopes and the intercepts were not significantly different be- tween regressions of shell volume on shell length for outfall and control populations (^-tests, P>0.05). Therefore, a single, combined regression for both populations of M. edulis was calculated (Figure 5). The difference in the shells of M. californianus may partly account for the apparent differences in the nutritional condition of the out- fall and control populations. Discussion The reproductive cycle of M. edulis varies with geographical location, but reproductive activity is generally correlated with rising water tempera- tures (Kinne 1970; Seed 1976). Bayne (1975) showed that gametogenesis is regulated by chang- ing temperatures in terms of increasing "day- degrees." In the present study M. edulis from both the outfall and control populations also 501 showed the same cycle of increasing gonad activity in the late spring and early summer when temper- atures were increasing, in spite of the temperature differential between the two areas. However, the outfall population did not attain as high gonadal index levels as the control, probably because stressful temperatures above 20° C were reached in June, leaving less energy available for gamete production (Widdows 1976; 1978a. b). Food avail- ability interacts with temperature to influence the energy budget of mussels (Bayne 1973; Widdows 1978a, b), but food availability estimated by dry weight of suspended matter is not significantly different in the outfall and intake water at Morro Bay (Hargreaves 1977). In July through October outfall temperatures exceeded the energetically extremely stressful! level of 25° C (Widdows 1978a, b), and the body weight/shell volume index declined to levels well below the controls. Al- though the reduced gonadal index of the outfall population at Morro Bay strongly indicated a re- duced reproductive output, M. ediilis under stress apparently conserve the gonad up to a point at the expense of other tissues, so that stressed mussels continue to produce some gametes (Gabbott and Bayne 1973; Bayne 1975). However, gametes from stressed mussels result in embryos and larvae that are less viable than those produced by adults not under stress (Bayne 1972). In M. californianus the relationship of tempera- ture to the energy budget for growth and reproduc- tion is not well studied as it is in M. ediilis, nor have the critically stressful temperatures been de- termined for M. californianus. Mytilus california- nus is reported to reproduce year-round with peak periods of more intense spawning at various times, particularly in spring and fall (Seed 1976). In the present study the control population showed a peak of gonadal activity in spring, corresponding with the period of rising ambient temperatures. The outfall population showed higher gonadal index levels than the controls year-round, indicat- ing that in M. californianus higher absolute tem- peratures, rather than a temperature change as in M. edulis, stimulate gametogenesis and increased reproductive output. However, the body weight/ shell volume index of M. californianus in the out- fall was consistently lower than the control popu- lation. If M. californianus conserves its gonad at the expense of other tissues under the increased energetic stress of elevated temperatures in the same manner as M. edulis, this would explain the lower body weights of the outfall mussels. It is not clear why all but the smallest outfall M. californianus in my samples had relatively larger shell volumes at the same shell length than the controls. The difference may reflect greater shell erosion of the control mussels, resulting from high surf levels on the jetty, rather than reflecting a temperature effect on the form of shell growth. Seed ( 1968) showed that shell growth in M. edulis is extremely variable, depending upon population density and physical conditions. Mytilus califor- nianus also shows great variation in shell form from one locality to another (Coe and Fox 1944), and intertidal height and latitude also affect shell growth (Dehnel 1956). It is often difficult to apply results from control- led laboratory conditions directly to field situa- tions, where there are multiple and fluctuating variables. I must acknowledge that the ability to interpret the results of the present paper speaks well for the realistic analysis of energetics and stress in marine mussels in recent laboratory work by others. However, very few marine inver- tebrates have received this level of study critical for the assessment of complex sublethal effects of environmental disturbances such as thermal effluents. Acknowledgments I am grateful to Cadet Hand, Virgil Schrock, Ralph Smith, and George Trezek for their advice and support. Bruce Hargreaves, Chris Harrold, and John Pearse gave valuable comments on the manuscript. Linda Hines, Brian Jennison, Marg Race, Jim Rutherford, Jon Standing, Chris Tarp, and John Warrick helped in many ways. The Pacific Gas and Electric Company gave gener- ously of their time and facilities. This study was funded by National Science Foundation Grant GI-34932 to George Trezek and Virgil Schrock of the Department of Engineering, University of California, Berkeley; Sea Grant NOAA 04-5- 158-20 to Ralph I. Smith and Cadet Hand of the Department of Zoology; and a grant from the Pacific Gas and Electric Company. Literature Cited Bayne. B L 1972. Some effects of stress in the adult on the larval development of Mytilus eduhs. Nature(Lond.i 237:459. 1973. Physiological changes in Mytilus edulis L induced by temperature and nutritive stress. J. Mar. Biol. Assoc. U.K. 53:39-58. 502 1975. Reproduction in bivalve molluscs under environ- mental stress. In F. J. Vemberg (editor*. Physiological ecology of estuarine organisms, p. 259-277. Univ. S.C. Press. Columbia. COE. W. R., AND D, L. FOX. 1944. Biology of the California sea-mussel iMytilus call- fornianus)- III. Environmental conditions and rate of growth. Biol. Bull. (Woods Hole) 87:59-72. DEHNEL. P. A. 1956. Growth rates in latitudinally and vertically sepa- rated populations of Mutilus californianus. Biol. Bull. (Woods Hole) 110:43-53. Gabbott. p. a. 1976. Energy metabolism. In B. L. Bayne (editor), Ma- rine mussels: their ecology and physiology, p. 293-355. Camb. Univ. Press, Lond. Gabbott. P. A., and B. L. Bayne. 1973. Biochemical effects of temperature and nutritive stress in Mytilus edulis L. J. Mar. Biol. Assoc. U.K. 53:269-286. GIESE, A. C, AND J. S. PEARSE. 1974. Introduction: general principles. In A. C. Giese and J. S. Pearse (editors). Reproduction of marine inver- tebrates. Vol. 1. p. 1-49. Acad. Press. N.Y. HARGREAVES, B. R. 1977. Growth of two marine mussels. Myttlus edulis and Mytilus californianus. Ph.D. Thesis, Univ. California, Berkeley, 119 p. HEDGPETH. J. W., .\ND J. J. GONOR. 1969. Aspects of the potential effect of thermal alteration on marine and estuarine benthos. In P. A. Krenkel and F. L. Parker (editors). Biological aspects of thermal pollu- tion, p. 80-122. Vanderbilt Univ. Press. Nashville. Hikes, a. H. 1978. Reproduction in three species of intertidal barnacles from central California. Biol. Bull. (Woods Holei 154:262-281. KlNNE, O. 1970. Temperature. In O. Kinne (editor). Marine ecol- ogy. Vol. I. p. 321-616. John Wiley and Sons. N.Y. Seed, R. 1968. Factors influencing shell shape in the mussel Myti- lus edulis. J. Mar. Biol. Assoc. U.K. 48:561-584. 1976. Ecology. In B. L. Bayne (editorl. Marine mussels: their ecology and physiology, p. 13-65. Camb. Univ. Press, Lond. WIDDOWS. J. 1973. Effect of temperature and food on the heart beat, ventilation rate and oxygen uptake of Mytilus edulis. Mar. Biol. (Berl.) 20:269-276, 1976. Physiological adaptation of Mytilus edulis L. to cyc- lic temperatures. J. Comp. Physiol. 105B:115-128. 1978a. Combined effects of body size, food concentration and season on the physiology oi Mytilus edulis. J. Mar. Biol. Assoc. U.K. 58:109-124. 1978b- Physiological indices of stress in Mytilus edulis. J. Mar. Biol. Assoc. U.K. 58:125-142. WIDDOWS, J., AND B. L. Bayne. 1971. Temperature acclimation of Mytilus edulis with re- ference to its energy budget J, Mar. Biol. Assoc. UK, 51:827-843. ANSON H. HINES Department of Zoology. University of California Berkeley, Calif Present address: Center for Coastal Marine Studies Unwersity of California Santa Cruz, CA 95064 INCIDENCE AND DISTRIBUTION OF PISCINE ERYTHROCYTIC NECROSIS AND THE MICROSPORIDIAN, GLVGEA HERTWIGI. IN RAINBOW SMELT, OSMERUS MORDAX. FROM MASSACHUSETTS TO THE CANADIAN MARITIMES Since the first discovery by Laird and Bullock (1969) of piscine erythrocytic necrosis (PEN) in the red blood cells of the Atlantic cod, Gadus morhua: seasnail, Liparis atlanticiis; and long- horn sculpin, Myoxocephalus octodecemspinosus , 15 genera of fishes, including 17 marine species along the North Atlantic coast of North America have been found to be affected by PEN. Sherburne (1977) reported PEN in the alewife, A /osapseurfo- harerigus, and smelt, Osmerus mordax. Walker and Sherburne (1977) reported PEN in the Atlan- tic herring, Clupea harengiis harengiis; Atlantic tomcod, Microgadiis torncod; spot, Leiostomus xanthurus: tautog, Tautoga onitis; rock gunnel, Pholis gunnellus; sea raven, Hemifripferus americanus; fourspot flounder, Paralichthys ob- longus; and winter flounder, Pseitdopleumncctes americanus. Sherburne and Bean (unpubl. data) have found PEN in pollock, Pollachius virens; At- lantic menhaden, Brevoortia tyrannus; American shad, A/osa sapidissima: and blueback herring, A. aestivalis. PEN has been confirmed by electron microscopy as an erythrocytic icosahedral cytoplasmic deoxy- ribovirus (EICDV) infection in two of the above species — the Atlantic cod (Walker 1971; Appy et al. 1976; Walker and Sherburne 1977) and the Atlantic herring (Philippon et al. 1977; Reno et al. 1978). During our investigations of PEN in the Atlan- tic cod, other marine species were examined for evidence of PEN. especially those forming the diet of the cod. One of these was the rainbow smelt, Osryierus mordax. Smelt were examined for both PEN and the pathogenic microsporidian parasite, Glugea herticigi. This report shows the incidence and geographi- cal distribution of PEN and Glugea hertwigi in smelt populations from Massachusetts to the FISHERY BULLETIN VOL 77, NO 2, 1979 503 Canadian Maritimes and indicates that current management practices result in the transfer of PEN and G. hertwigi from one area to another via infected smelt. Materials and Methods For evidence of PEN, blood samples of 1,412 anadromous Osmerus mordax (12.7-27.3 cm total length. TL) were collected at 42 sites from 15 coastal smelt streams from Massachusetts to the Canadian Maritimes (Figure 1) between 3 November 1976 and 17 November 1977: Kittery, Maine (Spruce Creek); Boothbay, Maine (Hodgdon Cove and Boothbay Harbor); Bath, Maine (Whiskeag Creek); Dresden, Maine (Eastern River); Damariscotta, Maine ( Damariscotta River); Wiscasset, Maine (Montsweag Creek): Warren, Maine (St. George River); Addison, Maine (Harrington River); Winterport, Maine (Penobscot River); Newington, N.H. (Great Bay); Kingston, Mass. (Jones River); Hingham, Mass. (Weir River); Quarryville, New Brunswick, Canada (Miramichi River); Portapique, Nova Scotia, Canada (Portapique River); and Oxford, Nova Scotia, Canada (Philip River). In addition, blood samples from 256 landlocked O. mordax (7.6-27.0 cm TL) were collected in nine samples from five Maine lakes between 15 Jan- uary and 5 May 1977: Damariscotta (the lake is approximately 10 mi long, begins at Jefferson, Maine, and empties into the Damariscotta River at Damariscotta); Wyman (Bingham, Maine); South Twin and Millinocket ( Millinocket, Maine); and East Musquash (Topsfield, Maine). For evidence of G. hertwigi. 1,692 anadromous O. mordax (12.7-27.3 cm TL) were collected in 42 samples from 16 localities (the above ISplusCasco Bay, Maine) between 3 November 1976 and 17 November 1977. In addition, 254 landlocked O. mordax (7.6-27.0 cm TL) were collected in eight samples from the above five lakes between 15 January and 5 May 1977. Smelt were obtained from our own catches, from those of fishermen and from Massachusetts Divi- sion of Marine Fisheries personnel. Depending W)NTERPORT 28% (7/ 25) BINGHAM 0% (0/25)® DRESDEN 73% (59/81) BATH \ 65%(135/208)- KITTERY, ME 37%(I5/41) NEWINGTON N, 627o(l5/24 HINGHAM, MAV 99%(99/IOO) A Ji QUARRYVILLE 21% (48/ 223 MILLINOCKET ®®0% (0/77) TOPSFIELD 0%(0/50)® ^(^Vaddison ^^ ;^r,'^ioo%(ioo/io(5v' J. " ' WARREN \ y I07o (40/50) ^ p^ DAMARISCOTTA LAk'^ 4% (4/104) DAMARISCOTTA RIVER 46% (52/114) BOOTHBAY 50% (56/ I -WISCASSET 447o (11/25) -KINGSTON, MA 100 7o 1100/ 100) I) (•) denotes locations of inland lakes Figure l. — incidence and distribution of piscine er>'throcytic necrosis (PEN) in anadromous rainbow smelt from the Canadian Maritimes to Massachusetts and landlocked rainbow smelt from five Maine lakes (two lakes are located at Millinocket). 504 upon the location and season, smelt were caught by handline and by dip, cast, bag, and gill nets. Except for a few instances the same individuals were examined for both PEN and G. hertwigi. For evidence of PEN, live smelt were measured for total length, and the caudal peduncle was wiped free of water and mucus with a clean towel and then severed and a smear made from a small drop of blood placed on a clean slide. Smelt were sexed and given a gross external and internal examina- tion for evidence of G. hertwigi and other abnor- malities. Microscopic examination of unstained and Giemsa-stained spores from cysts was ini- tially made to confirm the presence of G. hertwigi . Air-dried blood smears were fixed in absolute methanol for 3 min and stained with diluted Giemsa for 30 min. Smears were examined thoroughly under oil immersion at 1,000^ to de- termine the presence of PEN. ^:-/?^~'?:;w;y ' i • % •*• • # • '^ ' ..• Results PEN - Anadromous smelt — Of the anadromous smelt sampled, 55. 7"^^ (786/1,412) were infected with PEN (Table 1 1. By light microscopy, PEN lesions of smelt red cells resemble those of EICDV infected Atlantic cod (Figure 2). Infected smelt occurred in every stream sampled (Figure 1 ). The highest incidences were in Kingston (100/100), Addison (lOQ/lOO), and Hingham (99/100). Lower incidences were evident from Nova Scotia and New Brunswick than from Maine, New Hamp- shire, and Massachusetts. Individual infections were light; of the 786 in- fected smelt, the highest infection was 8'f in a smelt from Kingston. Overall, 87.7'7f (689/786) of the infected smelt had <1.0% of their red cells infected: 12.3'7f (97/786) had from 1 to m. The two areas with the highest incidences, Kingston and Addison, also had the highest indi- vidual infections and accounted for 87.Q'7( (85/97) of the smelt in this study with V7c or more infected erythrocytes. Kingston had 64/100 smelt with in- fections >V7c\ Addison had 21/100. In contrast, Hingham with an incidence of 99/100 had only- four smelt with infections >V7c. From a total of 1,387 anadromous smelt sexed, 54. 3% of the males and 58.39; of the females had PEN. PEN - Landlocked smelt — Damariscotta Lake was the only lake with PEN infected smelt, 3.8'/f (4/104). Individual infections were <\'7( . Because of the design of the fishway at Damariscotta, ana- % < Figure 2. — Rainbow smelt erythrocytes with PEN lesions re- sembling those of PEN (EICDV I infected Atlantic cod. Infected cells show characteristic chromatin condensation and nuclear degeneration. Unlike cod, cytoplasmic virions were not visible by light microscopy in infected smelt erythrocytes. dromous smelt are unable to negotiate the fishway leading into the lake. However, there is a possibility that some of the smelt we sampled could have been from a coastal population. Live coastal smelt are used by ice fishermen as bait for salmon and togue, and there is a possibility that unused bait could have been released into the lake with a resultant intermingling of coastal and landlocked smelt. Glugea hertwigi -Anadromous smelt — Overall, 8.09f (135/1,692) of the anadromous smelt were infected with G. hertwigi (Table 1). Infected smelt occurred mail 16 coastal areas sampled (Figure 3). Distinctive white, spherical cysts were found primarily along the intestinal tract but often on other internal organs such as liver and gonads. Cysts varied from pinhead size to 5 mm (Figure 4). Degree of infection varied from one cyst to severe infections where the abdominal cavity was nearly filled. Areas with highest incidences were at Kit- tery 49';;- (20/41) and Kingston 289'^ (28/100). The lowest incidence was at Boothbay with 0.9% ( 1/ 505 Table 1. Incidence of piscine erythrocytic necrosis (PEN) and Glugea hertuigi in anadromous and landlocked rainbow smelt from Massachusetts to the Canadian Maritimes. 3 November 1976-17 November 1977. G hertwtgi Sample source and categorY Anadromous 'Kittery. Maine Boothbay, Maine 3 Nov 1976 6 Nov 1976 19 Nov 22 Nov 23 Nov 6 July 1977 6 July 7 July 5 Aug 25, 26 Aug Boothbay Total Casco Bay, Maine Bath, Maine 9 Dec 1976 14 Dec 1976 15 Dec 16 Dec 20 Dec 6 Jan 1977 6 Jan 11 Jan 13 Jan, 17 Jan 3 Feb 17 Nov 'Bath Total 27 Dec 30 Dec 4 Jan 11 Jan Dresden Total 17 Jan 21 Jan 23 Jan 5 Feb 19 Feb, Damariscona Total Wiscasset, Maine 28 Jan 1977 Warren, Maine 1 Feb 1977 8 Feb Warren Total Dresden, Maine Damariscotta Maine 1976 1977 1977 'Addison, Maine Newinglon, N H Winterpon, Maine 'Kingston, Mass 'Hingham, Mass Quarryville, N B 10 Feb 1977 27 Feb 1977 8 Mar 1977 15 Apr 1977 15 Apr 1977 30 Apr 1977 1 May 2 May Quarryville Total Total no examined Portapique. N S Oxford, N,S 3 May 1977 3 May 1977 65 4 12 5 3 7 111 52 46 23 25 8 15 7 9 19 208 25 35 15 6 81 3 70 27 1 13 114 25 25 25 50 100 24 25 100 100 100 70 53 223 110 100 366 50 0 500 100 0 446 500 500 60 0 67 0 86 0 50 4 65 4 89.1 73.9 76 0 500 37.0 60.0 42.8 44.4 15.8 649 64,0 82 8 60 0 83 3 728 48 6 51.8 30.8 45.6 440 80 0 80 0 80 0 100 0 62 5 28 0 100,0 99 0 23 0 20 0 207 21 5 191 28 0 Total no, examined 10 4 1 65 4 12 5 3 7 52 46 51 114 29 4 12 15 7 9 19 358 25 35 15 6 81 3 70 27 100 25 25 33 58 100 24 84 100 100 100 97 53 250 110 100 488 25,0 09 too 65 20 53 35 75,0 83 67 143 22,2 158 6 1 40 86 67 167 74 129 18 5 140 80 30 1 7 50 83 24 28 0 100 1 0 38 1 2 64 70 Mean length, SD, and range (cm) 16,6i1,8 18,3±1,3 20,711,3 18,8±0 18.9±2.1 16.2±1,4 18.0±2,3 16,9±0,7 18,1±1 4 199-1,8 168i26 20.8l24 21,3±2,8 20,9±2,2 20,6±1 9 20,5 ±2,6 17,0±1-9 19,8=:1,8 18,3±2,3 20,4±1,6 20,32:2,1 20,3±2,1 I8-8±l 6 19,5±2,0 17,8ll-B 18,5±1 5 18 1:2,7 19.712,8 20,4 ±2,0 16,2±0 19 1±1 3 18,7±1,8 18.0*2-0 18.6±2,1 20-4±2,3 189120 185±2.9 18,5±1,3 189±22 197±1,8 193±1 5 196±1 6 20.2 ±1,9 16,4±1,5 13 8 22 0 160 21 3 19 7 22 7 188 15,2-25.0 14.2-17.5 15,9-22,9 15,9-17,9 165-192 178-230 127 21 6 15 6-26 7 17,8-273 17,8-260 159-248 15,9 26,7 146-18,5 159-21 6 134-22 1 18 1-22 9 17,8-22,9 16,3-24,3 162-223 15-6-24 4 152-20,7 16,5-203 15,6-20,9 15 0-26,6 1 7 1 - 24 1 162 178-22,9 160-23 4 14 9-24 8 14 6-22.2 140-267 152 21.6 140-26.7 12.7-21.9 12.7-23.8 15.6-25.4 15.9-23 5 16 5-24 1 15,9-263 12 7-20 3 TOTAL 55 7 1,692 Landlocked JeHerson, Maine (Damariscotta Lakel 15 Jan 1977 9 Feb 18 Feb 23 Feb 24 Feb 10 Mar Jefterson Total Bingham, Maine 19 Jan 1977 'Millinockei, Maine 12 Feb 1977 ^Topsfield, Maine 5 May 1977 7 — — 10 10 100 12 83 12 83 18 — 18 — 32 _ 32 — 25 120 25 80 04 38 97 4 1 25 — 25 56,0 77 — 82 56.1 50 _ 50 — 19.8±2.0 21 0±2.9 18.0±1.4 19.5±2.8 18.9±1.6 22 1 ±2.6 139±1 1 86±1 7 9.1 ±0 4 17.8-235 184-267 16.5-203 16 5-26 3 159-235 17 1-270 114-159 7 6-12 1 8.2-102 TOTAL 'Areas that include individual PEN infections of 1% or greater ^Smelt from Millinockel and TopsSeld. Maine, were within normal size ranges lor populations in these lakes and were sexually mature. 506 WINTERPORT 2% (2/84) BINGHAM 56% (14/25: DRESDEN 7% (6/8 BATH 6% (22/358) CASCO BAY 10% (5/50) KITTERY, ME 49% (20/41) ,j NEWINGTON.NM 8% (2/24) ^v^y L—-'" QUARRYVILLE N 8 y I.27ol3/250) . ■^"^ MILLINOCKET 56%(46/82) TOPSFIELD 07o(a/50), U'CiS^JXaddison C^ 5%(5/100 WARREN 2% (1/58 AMARISCOTTA L 4% (4/97) DAMARISCOTTA RIVER 14% (14/100) BOOTH BAY 0.9% ( I/Ill) WISCASSET 8% (2/25) OXFORD N.S. 7% (7/ 100) PORTAPIOUE 6.47o(7/IIC (•) denotes locations of inland lokes KINGSTON MA 287o ( 28 / 100 ) Figure 3. -Incidence and distribution of Glugea hertwigi in anadromous rainbow smelt from the Canadian Maritimes to Mas- sachusetts and landlocked rainbow smelt from five Maine lakes (two lakes are located at Millinocket). FIGURE 4. -A rainbow smelt mfected with Glugea hertwigi showing large (up to 5 mm) white spherical cysts associated with this infection. 111). From a total of 1,663 ana(iromous smelt sexed, 1 .&'/( of the males and SA'^'/c of the females had G. hertwigi. Glugea hertwigi - Landlocked smelt — Infected smelt were found in four of the five lakes sampled. Overall, 25.2% (64/254) were infected. Heavy incidences occurred at Wyman, South Twin, and Millinocket Lakes — each lake had 56% of the sampled smelt infected, ( 14/25), (5/9), and (41/73), respectively. Infections varied from one cyst to severe infections. 507 Discussion PEN and G. hertwigi infected smelt will un- doubtedly be found in other areas, both within and beyond the geogi'aphical range sampled in this study. Management practices involving anadro- mous alewives have inadvertently contributed to the spread of PEN within the State of Maine (Sherburne 1977). Haley ( 1954b) reported similar circumstances for G. hertwigi infected freshwater smelt in New Hampshire. Glugea hertwigi was found in rainbow smelt from Lake Winnisquam, N.H., as well as in other localities where smelt populations were established from the Winnis- quam stock. Smelt that were being transported by the Massachusetts Division of Marine Fisheries from Hingham to Cape Cod, Mass., to initiate new runs during the time of this study had incidences of 99'7f (99/100) PEN and lOV^ (10/100) G. hertwigi . Because of the known pathogenicity of G. hertwigi (Haley 1954a, b; Chen and Power 1972; Nepszy et al. 1978), localities with relatively high incidences may warrant further investigation. At the time of the decline of the smelt population in the Great Bay region of New Hampshire in the 1950's, 23.3':'f (308/1,3231 of the smelt examined had G. hertwigi (Haley 1954a). Although our samples were considerably smaller, 33.89? (22/65) of the smelt sampled from Kittery and Great Bay were infected with G. hertwigi. The high inci- dences of G. hertwigi (56'7f) at Wyman, South Twin, and Millinocket Lakes were unexpected. However, Chen and Power ( 1972) reported that of 1,691 smelt sampled from Lake Erie 62.77f were infected with G. hertwigi. They reported that apart from actual mortality the real significance of G. hertwigi infection lies in its effect on smelt fecundity. In females, parasitic cysts replaced ovarian tissue, causing a serious reduction in the number of maturing eggs. There was no apparent relations between G. hertwigi and PEN in the populations sampled in this study. Although smelt at Kingston had high incidences of both PEN and G. hertwigi ( 100/100 and 28/100, respectively) other populations with high incidences of PEN did not have high inci- dences of G. hertwigi, i.e., Hingham had 99'100 with PEN, 10/100 with G. her-twigi; Addison had 100 100 with PEN, 5/100 with G. hertwigi: War- ren had 40 50 with PEN, only 1 58 with G. hertwigi . There was no apparent relation between G. hertwigi and PEN infections in individuals. Of 135 andaromous smelt with G. hertwigi. 71 (52.6"^'?) likewise had PEN. Chen and Power (1972) reported seasonal fluc- tuations in G. hertwigi infection from Lakes On- tario and Erie, with the highest incidence during the winter, when smelt were undergoing the most active phase of gonadal maturation. Most of our sampling was confined to winter; therefore, we have no evidence of seasonal fluctuations of PEN and G. hertwigi infections in this study. However, since different areas were sampled at similar times and all fish sampled were adults, the data obtained should afford a representative compari- son between areas. This study has determined that PEN and G. hertwigi are widely distributed in rainbow smelt populations along the North Atlantic coast from Massachusetts to the Canadian Maritimes, that the incidence of PEN in each population is high but the intensity of individual infections is low, and that higher incidences of G. hertwigi occur in inland lakes of Maine than in coastal populations. These findings differ from previous studies on the Atlantic cod and Atlantic herring where lower incidences of PEN have been evident but indi- viduals have had nearly every red cell infected (Walker and Sherburne 1977; Sherburne 1973). .-Vcknciw kdj;ments We thank M. J. Hogan of the Department of Marine Resources and D. C. Harmon of East Boothbay, Maine, for assisting in the field work. Joseph DiCarlo of the Massachusetts Division of Marine Fisheries obtained smelt for us from Hingham and King.ston. We thank Roland Walker of Rensselaer Polytechnic Institute, Jay C. Quast of the Northwest Alaska Fisheries Center Auke Bay Laboratory, NMFS, NOAA, and an anony- mous reviewer who critically reviewed the manu- script and made helpful suggestions to improve clarity of presentation. This study was supported by Public Health Service Grant #5R01HL19163 from the National Heart and Lung Institute, Na- tional Institutes of Health and Grant #PCM75- 22746 from the National Science Foundation. Literature ( ited APPY, R. G., M. D, B. BURT. AND T. J. MoRKIS. 1976. Viral nature of piscine erythrocytic necrosis (PEN) in the blood of Atlantic cod (Gac/i;smf)r/iHH ). J. Fish Res. Boarti Can. 33:1380-1,38.'5. 508 CHEN. M., AND G. POWER. 1972. Infection of American smelt in Lake Ontario and Lake Erie with the microsporidian parasite Glugea hertwigi (Weissenberg). Can. J. Zool. 50:1183-1188. Haley, a. J. 1954a. Microsporidian parasite, Glugea hertwigi, in American smelt from the Great Bay region. New Hamp- shire, Trans, Am, Fish, Soc, 83:84-90, 1954b, Further observations on Glugea hertwigi Weissen- berg 1911, 1913 (microsporidial in fresh water smelt in New Hampshire. J. Parasitol. 40:482-483. Laird. M., and W. L. Bullock. 1969. Marine fish haematozoa from New Brunswick and New England. J. Fish. Res. Board Can. 26:1075-1102. NEPSZY. S. J.. J. BUDD, AND A. O. DECHTIAR. 1978. Mortality of young-of-the-year rainbow smelt (Os- merus mordax) in Lake Erie associated with the occur- rence ofGlugea hertwigi. J. Wildl. Dis. 14:233-239. PuiLiPPON, M,. B, L. Nicholson, and S. W, Sherburne. 1977. Piscine Erythrocytic Necrosis I PEN) in the Atlantic herring iClupea harengiis harengus): evidence for a viral infection. Fish Health News 6:6-10. Reno, P., M. Philippon-Fried, B. L. Nicholson, and S. W. Sherburne. 1978. Ultrastructural studies of piscine erythrocytic ne- crosis (PEN) in Atlantic herring iCIupea harengus haren- gus). J. Fish. Res. Board Can. 35:148-154. Sherburne, S. W. 1973. Erythrocyte degeneration in the Atlantic herring. Clupea harengus harengus L. Fish. Bull. U.S. 71:125-134. 1977. Occurrence of piscine erythrocytic necrosis (PEN) in the blood of the anadromous aXevjiie, Alosa pseudoharen- gus, from Maine coastal streams. J. Fish. Res. Board Can. 34:281-286. Walker. R. 1971. PEN, a viral lesion offish erythrocytes. Am. Zool. 11:707. Walker, R.. and S. W. Sherburne. 1977. Piscine erythrocytic necrosis virus in Atlantic cod. Gadits morhua, and other fish: ultra-structure and dis- tribution. J. Fish. Res. Board Can. 34:1188-1195. Stuart W. Sherburne Laurie L. Bean State of Maine Department of Marine Resourees Fisheries Research Station West Boothhay Harbor. ME 04575 A SIMPLE METHOD TO OBTAIN SERUM FROM SMALL FISH It is desirable to obtain blood serum information from small fish due to their extensive use in pol- lutant and disease studies (Snieszko et al. 1969; Snieszko 1974; Mulcahy 1975). It is well known that gross observations cannot detect subtle changes in blood chemistry caused by environ- mental factors such as stress, diet, or inflamma- tion (Mulcahy 1975) and some pesticides (Walker 1963). Techniques to obtain fish blood for study have been described in reviews by Hesser (1960) and Blaxhall (1972). Cardiac and venous puncture are the most commonly used techniques for fish >150 mm, while severance of the caudal peduncle and insertion of a capillary tube to draw blood is usu- ally employed for smaller fish. Fish <60 mm pre- sent problems because the quantity of blood ob- tainable is small (generally <0.2 ml), coagulation time is quick, and tissue fragments or clots can clog collecting tubes, causing loss of serum in the transfer from one container (or collecting tube) to another for centrifugation. In most cases an- ticoagulants are used to eliminate some of these problems. Sodium oxalate, heparin, or dipotassium ethyl- enediaminetetraacetate (EDTA) are the most commonly used anticoagulants. Unfortunately, oxalate and EDTA anticoagulants can interfere with serum ion determinations, such as calcium, and produce misleading data (Tietz 1976). When many blood serum components are to be mea- sured, especially on instrumentation such as an amino acid auto analyzer, a quantity of serum (at least 0.5 ml and preferably free of anticoagulant) must be obtained for the numerous tests these analyzers can do. Heparinized tubes, excellent for single serum component tests, are limited because the volume of serum they can obtain is generally not enough for use with sophisticated instrumen- tation. This note describes a simple method to obtain pooled serum samples, without anticoagu- lants, from fish <60 mm when hepau-inized tubes are not practical. Materials and Methods Small fish <60 mm fork length should be anes- thetized, if desired, and blotted to remove excess water on the fish's body. A dry Kimwipe' is wrap- ped around the fish, covering the vent to prevent contamination of the sample, leaving approxi- mately 2.5 cm of the tail exposed (Figure IB). A small portion of the Kimwipe is allowed to overlap the fish's head. The caudal peduncle is severed with sharp scissors, leaving a slight point at the caudal region (Figure IC). The fish is rapidly in- ' Reference to trade names does not imply endorsement by the University of Southern Mississippi or by the National Marine Fisheries Service, NOAA. FISHERY BULLETIN: VOL, 77, NO 2. 1979 509 Figure l. — Diagrammatic representation of the centrifuge method for extracting serum from small fishes. A. Blotted fish ready for bleeding. B. Fish is wrapped with Kimwipe, leavmg overlap at top. Vent is also covered to prevent contamination of the sample. C. Caudal peduncle is cut at an angle with sharp scissors. D. Fish is fit snugly into a 15 ml centrifuge tube, usmg more or less Kimwipes to obtain a proper fit, and taped so the fish will not be pulled into the tube. E. Fish , in the tube, is spun at 400 g for 3 min. F. Covered tube with blood is kept in an ice water bath until another fish can be processed in the same tube. serted, tail first, into a 15 ml Pyrex centrifuge tube and secured by taping the overlapping Kimwipe to the side of the tube (Figure ID). (The fit must be snug but not too tight). Varying fish sizes can be compensated for by wrapping with more or less Kimwipes; fish will not be pulled into the tube if the wrapping is correct. Fish are spun in a cen- trifuge at 400 g for 3 min. After each fish is cen- trifuged, the tube of blood obtained (one tube for all fish) is covered and quickly placed in a beaker of ice water to inhibit evaporation of serum ob- tained and hemolysis of red blood cells. A total pooled sample of approximately 1 ml can be col- lected from 20 fish. The blood is allowed to clot and the serum drawn off. From 1 ml of pooled whole blood, 0.5 ml of serum can be obtained. Discussion Contamination by tissue fluid, lymph, and cell debris is unavoidable but exists in any method which severs the caudal peduncle. Proper wrap- ping of fish and the use of sharp scissors help to reduce this contamination. The amount of lymph and intracellular fluid gained from the cutting action of the scissors and centrifugation is mini- mal and does not prejudice one's results sig- nificantly. Cellular debris from the actual wound is insignificant because the serum is separated from it before analysis. Careful placement of Kimwipes around the vent eliminates urine or feces contamination of the sample. This method has the advantage of simplicity, speed, and no anticoagulant contamination. Red blood cell hemolysis is minimal, and larger pooled blood samples can be obtained in a single container with little serum loss during unnecessary transfers when heparinized collecting tubes are unfeasible. This technique should be helpful in pathologic studies of small fish used in toxicity tests when it is desirable to monitor many blood serum parame- ters and where there is no objection to the use of pooled samples. Acknowledgments I thank Lee Courtney for help with the figure and John Couch for critical review of the manu- script. Literature Cited Bl..\XH.\LL, P. C. 1972. The haematological assessment of the health of freshwater fish. A review of selected literature. J. Fish. Biol. 4:593-604. HESSER. E. F. 1960. Methods for routine fish hematology. Prog. Fish- Cult. 22:164-171. MUU'AHY, M. F, 1975. Fish blood changes associated with disease: a hematological study of pike lymphoma and salmon ul- cerative dermal necrosis. In The pathology of fishes, p. 925-944. Univ. Wis. Press, Madison. SNIESZKO, S. F. 1974. The effect of environmental stress on outbreaks of infectious diseases of fishes. J. Fish. Biol. 6:197-208. 510 SNIESZKO, S. F.. J. A. MILLER, AND C. R. ATHERTON. 1966. Selected hematological and biochemical tests per- formed with blood and serum of adult rainbow trout tSalmo gairdnen) with a high incidence of hepato- ma. Ann. N.Y. Acad. Sci. L36:191-210. TIETZ, N. W. 1976. Methods for the determination of calcium in body fluids. In N. W. Tietz (editor). Fundamentals of clinical chemistry, p. 903-904. W. B. Saunders Co., Phila. WALKER, C. R. 1963. Toxicological effects of herbicides on the fish envi- ronment. Univ. Mo. Bull. 64:17-34. James T. Winstead University of Southern Mit^sissippi Hattieshurg. Miss. Present address: U.S. Environmental Protection Agency Sabine Island Laboratory Gulf Breeze. FL 32561 STRANDING OF THE PILOT WHALE, GLOBICEPHALA MACRORHYNCHL'S. IN FLORIDA AND SOUTH CAROLINA An opportunity to observe the behavior of strand- ing pilot whales occurred in February 1977. Be- fore dawn on the 6th, 175-200 pilot whales moved with the rising tide into the Fort George River, 1.5 km north of the mouth of the St. Johns River (lat. 30'=25' N, long. 81°29' W), near Jacksonville, Fla. The weather was clear, calm, and cold; minimum air temperature was 0° C at Jacksonville Beach (Environmental Data Service 1977:6). Once inside the river mouth, the animals turned south into a small, shallow embayment (Figure 1). A chronol- ogy of the events that followed is presented below. Events of 6 February were summarized by Willard Patrick. 1 6 February 1977. — Sometime prior to dawn the whales began moving onto the southeast shore (Figure 1, Site A), where they were stranded either by their movements or by the falling tide. Throughout the day, many of the whales were refloated repeatedly by Florida Marine Patrol (FMP) officers and local volunteers, but many were immediately stranded again. Some whales thrashed vigorously during attempts to refloat them. By 2100 h, 21 whales were dead on the beach and the remainder were milling around near the middle of the bay in water 1-2 m deep. During the night of 6-7 February, what was thought to be the remainder of the herd approached the surf zone at high tide and an estimated 25 whales moved into the ocean. Those whales not exiting through the surf are believed to have returned to the embay- ment although some may have stranded and died, then drifted out to sea. 7 February 1977. —At 0845 h, 23 whales, includ- ing the 21 from the previous day, were dead on the beach, most near Site A (Figure 1). Two groups of 40 to 60 whales were milling around in the bay, one group approximately in the center and one near Site B (Figure 1). Several smaller groups of up to five animals each were also sighted. At about 1030 h, the large groups restranded at Sites A and B. Many of the animals near Site A were pushed off by volunteers; approximately 40 whales near Site B died within an hour. 'Willard Patrick, Sergeant, Florida Marine Patrol, District 8, 4124 Boulevard Center Drive, Jacksonville, FL 32207, pers. commun. March 1977. FIGURE 1 .—Pilot whale stranding sites ( A-C) in the Fort George River, Duval County, Fla., lat. 30°25' N, long. 81°24' W. FISHERY BULLETIN, VOL. 77. NO, 2, 1979. 511 The whales appeared disoriented and lethargic, but moved steadily ashore. Their behavior and movements appeared similar to the responses of trained dolphins in a strange environment (Irvine 1971 ). Most animals offered little resistance when pulled by their flukes and turned away from the beach, but they usually turned and again moved slowly toward shore. Some whales grounded on shoals in the bay and either floated off on the rising tide, or died there when the tide ebbed. The whales pushed off from Site A were pre- vented from moving toward shore by a FMP motorboat moving around the pod. The whales were herded towards the river mouth and by late afternoon, using the combined action of two FMP boats, the volunteers helped 20-30 whales move past the surf line. Another 10 were counted in the river at dark, and an additional 20-35 whales re- stranded and died at various locations between Site A and the outer surf zone, including 10-15 at Site C. Other whales apparently moved out to sea without human assistance, or died and drifted out. Between 0930 and 1440 h, we measured, sexed, and tagged 17 whales (9 males and 8 females) with 16 roto tags (Jumbo Size, Nasco Inc., Ft. Atkinson, Wis.)2 and three spaghetti tags (Model FH69A, Floy Tag & Manufacturing, Inc., Seattle, Wash.). We worked opportunistically on animals close enough to deep water to be refloated. Seven tagged whales (4 females, 3 males) eventually stranded and died in the Fort George River area. Total lengths of the tagged whales that restranded and died were males: 308, 450, and 468 cm; females: 277, 3.50, 380, and 385 cm. Total lengths of unre- covered whales were: males 375, 443, 440, 446, 478, and 547 cm; females: 353 and 374 cm. Two females were tagged but not measured. 8 February 1977— At 0800 h, 1 whale was alive near Site A, as were 10-15 whales near Site C, but all died within a few hours. The whales near Site C apparently drifted inland with the rising tide. Aftermath —Between 8 and 16 February, about 40 dead whales were recovered from adjacent areas, including river branches and tidal creeks as fai-as6-8km northwest of the principal stranding sites. Several groupsof 5-10 whales traveled north up the river on 6 February, but we know neither how many animals stranded and died there, nor how many carcasses were moved to their recovery location by currents. Single whales stranded at Anastasia State Park (lat. 29°53' N, long. 81 16' W), 56 km to the south on 9 February, and at Jacksonville Beach (lat. 30n8' N, long. 80°12' W), 10 km to the south on 1 1 February. A total of 135 dead whales were ultimately recovered (Figure 2) and examined by Mead. The size and sex composi- tion of this group is similar to that of other mass strandings of this species (Mead unpubl. data) and probably represents a normal social aggregation. On the same morning ( 6 February ) that the initial stranding took place on Fort George Island, a group of 1 5 pilot whales stranded on the south end of Cumberland Island, Ga. (lat. 30°45' N, long. 81 °28' W ) 40 km to the north. This group may have separated from the larger school prior to strand- ing. Figure 2.— Length-frequency distributions of male and female pilot whales stranded at Fort George River. Duval County, Fla, Three decomposed carcasses, thought to be G. macrorhvnchiis. were seen, but not recovered, near Mayport (lat. 30°23' N, long. 8r29' W) at the mouth of the St. Johns River in June 1977 (D. Gicca^). Two whales stranded on 13 February on Wadamalaw Island (lat. 32'35' N, long. 80°11' W) near Charleston, S.C, some 220 km (straight-line distance) to the northeast. Interestingly, the ani- mals entered the mouth of the North Edisito River and moved into Bohicket Creek before stranding at Rockville, 7.5 km from the coast. One was a 478 cm male, tagged near Site C with spaghetti and ''Reference to product names does not imply endorsement by the National Marine Fisheries Service, NOAA. 'D. Gicca, Biological Technician, Gainesville Field Station. National Fish and Wildlife Laboratory, 412 NE 16th Avenue. Room 250. Gainesville. FL 32601, pers. commun. June 1977. 512 roto tags. The other was an untagged 406 cm female that later died. After both tags were re- moved from the male, it was refloated by local residents. The whale was followed by P. Laurie-^ for 15-20 min and reported to be respiring without difficulty as it moved seaward. As with most mass strandings of marine mam- mals, the cause was not clear. A cold weather frontal system passed through the area on the day prior to the stranding, but was not unusual for that time of year and probably was not related to the stranding. None of the whales were obviously injured and none appeared to follow a lead indi- vidual ashore. A combination of the passage through the surf into the river and the shallows in the bay may have confused and disoriented the animals, thus increasing the probability that they would strand. The whales appeared to tire with time, as evidenced by their less vigorous response to being pulled off the beach on 7 February; but why some animals died quickly after stranding on 7 February while others remained alive for hours on the beach or stranded repeatedly is unknown. On the west coast of Florida, groups of G. mac- rorhynchiis (Fehring and Wells 1976) and Pseiidorca crassidens lOdell et al. = ) have re- stranded at different locations, but this is the first report of restrandings at different locations on the Atlantic coast. Until now identification of previ- ously stranded individuals has been based on rope marks and dorsal fin shapes. The use of tags on stranded cetaceans would facilitate the identifica- tion of individuals on the shore and the study of herd structure of refloated animals at the strand- ing site, and would also help identify resighted or restranded individuals. Motor boats seemed effective for herding the whales and may be a means to keep refloated ani- mals together and prevent immediate beachings at future strandings. Boats have been used effec- tively to herd P. crassidens (Odell et al: see foot- note 5), although attempts to drag whales up to 1 km offshore at other strandings have not been totally effective because the animals often im- mediately restranded. More data are needed to determine why mass strandings occur and how to deal with the animals once they are on the beach. If efforts to save mass stranding victims prove futile because the ani- mals immediately restrand, euthanasia may be the most humane alternative. As shown by this report, however, some animals may survive a mass stranding and potentially can be a source of valuable data if resighted elsewhere. It would also seem that the spirit of the Marine Mammal Pro- tection Act of 1972 obligates American citizens to save stranded marine mammals if practical. An effort is therefore needed to get experienced people to a mass stranding site quickly so the rescue techniques can be evaluated and data collection can be maximized. Acknowledgment We thank R. Jenkins, P. Laurie, and W. Patrick for providing information on the stranding events. D. K. Odell and F. G. Wood offered constructive suggestions on earlier versions of this report. Literature Cited EWIRONMENTAL DATA SERVICE. 1977. Climatological data, Florida. 81(2), 12 p. NOAA. Environ. Data Serv., Asheville. N.C. Fehring, W. K., and R. S. Wells. 1976. A series of strandings by a single herd of pilot whales on the west coast of Florida. J. Mammal- 57:191-194. Irvine. B. 1971. Behavioral changes in dolphins in a strange envi- ronment Q J. Fla. Acad. Sci. 34:206-212. A. Blair Irvine MICHAEL D. SCOTT National Fish and Wildlife Laboratory Gamesnlle Field Station 412 NE 16th Avenue. Gainesville. FL 32601 Randall S. Weli^ Department of Zoology. University of Florida Gainesville. FL 32611 James G. Mead National Museum of Natural History Smithsonian Institution. Washington. DC 20560 ■■P. Laune. Information Specialist. South Carolina Wildlife and Marine Resources Department, Charleston, SC 29412. pers. commun. February 1977. ^Odell. D K., E. D. Asper. J. Baucom. and L. H. Cornell, A summary of information derived from the recurrent mass stranding of a herd of false killer whales, Pseudorea crassidens (Cetacea: Delphinidae). Unpubl. manuscr. 513 FIRST RECORDS OF A GIANT PELAGIC TUNICATE, BAIHOCHORDAEVS CHARON (UROCHORDATA, LARVACEA), FROM THE EASTERN PACIFIC OCEAN, WITH NOTES ON ITS BIOLOGY Recent studies iHamner et al. 1975; Alldredge 1972, 1976a; Silver et al. 1978) have demonstrated the importance of gelatinous macroplankton and their mucous secretions in planktonic com- munities as sources of particulate organic carbon and surface habitat in an otherwise homogeneous environment. Pelagic tunicates of the Class Lar- vaeea appear to be especially important members of this assemblage because they periodically se- crete and release numerous external, mucous, feeding structure.s or "houses." In midwater trawl- ing off southern California we obtained several specimens of a unique, giant larvacean, Bathochordaeus charon Chun 1900. This species may be a major source of suspended organic aggregates, or "marine snow" (Silver et al. 1978), as well as a major consumer of living and detrital particulate organic carbon in mesopelagic regions. Only eight specimens of this unusual tunicate, whose trunk may reach 25 mm long, have been reported. The present material increases the number of known intact specimens to 13 and rep- resents a major extension of the range of the monotypic genus. Histon, t BalhoihoriLitin ihitroii The present specimens iTable 1, Figure 1) con- form generally to published accounts of B. charon, detailed descriptions of which were given by Chun (1900), Lohmann (1931), Garstang (1937, as B. stygius ), and Thompson ( 1 948). Final confirmation must await careful morphological study of the new material. The conspicuous feature of this species is its •} B Figure 1. — The pelagic tunicate Bathochordaeus charon. A. Preserved specimen, trunk and tail, dorsal view. Tail is short- ened from shnnkage during fixation. B. Preserved specimen, trunk, dorsal view. 5 mm 515 Figure 2. — Composite diagram o( Balhochordaeus charon . anterolateral view, c, caecum; cp, cheek pouch of epidermis; e, esophagus; g. gonad; gs, gill slit; i. intestme; m, mouth, mb, muscle band; n, notochord; p, pharynx; s, stomach great size relative to other larvaceans, whose adult trunk lengths are usually < 5 mm. The pres- ent specimens are the largest collected since Chun's ( 1900) first two giants (Table 1). The ratio of tail length to trunk length ranges from 2.1 to 3.9, but damage to the tail and shrinkage after fixation make these figures unreliable. The mean ratio of 3.0 for all 12 intact specimens indicates that, in contrast to other Oikopleuridae.B. charon has a relatively short, broad tail whose width is about one-third its length. The lateral epidermal fin is usually torn or absent, but when present it is widest distally, unique in the Oikopleuridae. The notochord is clearly visible as the central axis of the tail, sandwiched between the two broad mus- cle bands. In contrast to other Oikopleuridae, the trunk is strongly compressed dorsoventrally and is nearly as broad as long (Figure 2). The epidermis is thin and often diaphanous, and it protrudes on either side of the oral region as a pair of "cheek" pouches. The mouth, unique in its dorsal and subterminal position, lies atop a low buccal cone and leads into the short, narrow pharynx. The long, spindle- shaped openings of the two stigmata (gill slits) arise from the floor of the pharnyx just behind the level of the dorsal mouth and ventral endostyle. The gut, the only conspicuous internal structure, is light brown in Formalin'-preserved material and lies free in the body cavity. The pharynx opens 516 via the esophagus into the large stomach that is expanded laterally as a blind caecum on the left and a right lobe which gives rise to the narrow intestine and rectum. The anus opens ventrally just anterior to the base of the tail . Small masses of gonadal tissue lie in the hemocoel in three of the specimens. In mature individuals the gonad forms a U-shaped mass which protrudes into the cheek pouches. Distribution of BjthoihorJtiens charon Only one specimen of B. charon was taken with a closing net, thus the depth distribution of the species cannot be determined with certainty. However, all of the remaining 13 specimens were taken well off the bottom in vertical or oblique tows from at least 200 m or in horizontal tows whose time at maximum depth greatly exceeded the time for haulmg in the net. This and the lack of specimens in surface tows support the belief of Chun (1900), Lohmann (1931), and Garstang ( 1937) thatB. charon is a deep-living, mesopelagic species. Few specimens have been collected and it is premature to conclusively describe the areal dis- tribution ofB. charon on the basis of known rec- ords (Figure 3). Since the eight previously re- ported specimens came from the North and South 'Reference to trade names does not imply endorsement by the National Marme Fisheries Service, NOAA Figure 3. — Known collection sites oi Bathochordaeus charon Numbers correspond to specimen number listed in Table 1. Atlantic, Indian, and southwestern Pacific Oceans, this report represents the first clearly es- tablished record of the species in the eastern Pacific Ocean. On the basis of the known material, it appears thatB. charon has a circumglobal dis- tribution in tropical and subtropical oceanic wa- ters between lat. 35° N and 35° S. Forneris ( 1957) classified it as a "eurythermic thermophile," but such a characterization seems unwarranted, as it was based on only eight specimens obtained from widely separated local ities and without associated physical oceanographic data. D iscussion All known larvacean species secrete a mucous feeding device, the house. The structure of the house varies considerably among the three larva- cean families, but in the Oikopleuridae it contains mucous filters which remove particulate matter from the water. Periodically, when the filters be- come clogged, the animal abandons the old house and within a few minutes produces a new one from a mucous rudiment secreted while in the old house. The type of house produced byB. charon is not yet known. Chun (1900) believed it was as large as a pumpkin and that it completely enclosed the animal, as in other Oikopleuridae. Lohmann (1931)believed that the house was probably of the "nose bag" type, as in Fritillariidae, in which a mucous net is cast out from the buccal region and the animal is free in the water. Barham (1969) observed spherical, mucous structures, at least 25 to 50 cm in diameter, from deep submersibles off San Diego, Calif., at about 200 m. Inside some of these structures, the swim- ming motions of a large, tadpolelike animal were visible. The structure and size of these "busted balloons" leave little doubt that they were oc- cupied and abandoned larvacean houses, very likely those of S. charon . Because the houses have not been collected in nets, Barbara's account rep- resents the only observation of them. Studies of photographs from such in situ observations and of the secretory apparatus of the animals themselves may elucidate the structure of the house of B. charon. Bathochordaeus charon is considered to be rare because of sparse records obtained since its discov- ery in 1900. However, current evidence indicates that the animals and their houses may be rela- tively common, comparable with other species of similar, large size, at least at certain depths, loca- tions, or times. Barbara^ estimated the densities of presumed giant larvacean houses off Cape Cor- rientes, Mexico, to be on the order of 1 to 3/m'' within narrow layers near the thermocline, be- tween about 50 and 300 m. At least six of the known specimens occurred in pairs in the same plankton sample. Thus, despite their large size, ^Eric G. Barham, Southwest Fisheries Center, National Marine Fisheries Service. NOAA, P.O. Box 271, La Jolla, CA 92038, pers. commun. March 1978. 517 they may be difficult to collect because of a verti- cally stratified distribution or they may remain unrecognized in midwater plankton samples be- cause of their fragility, transparency, and devia- tion from typical larvacean structure. Epipelagic larvacean relatives of B. charon filter feed on nanoplankton, especially cells <10 Mm (Lohmann 1899; Alldredge 1975). The muscu- lar tail pumps water through the house and per- mits the concentration of suspended particles from larger volumes of water than would be possible using ciliary currents alone. Since food is selected only on the basis of size, detritus may constitute a significant fraction of the food in some locations (Gerber and Marshall 1974). In waters below the euphotic zone, particulate organic carbon is scarce, generally present at levels from 10 to 10^ ixg C/1, compared with roughly 10^ to 10^ /xg C/1 in the euphotic zone (Holm-Hansen et al. 1966; Hobson 1967; Menzel 1967). Most of the particulate carbon below 200 m contains little or no chlorophyll (Holm-Hansen et al. 1966) and is composed mainly of detritus. How- ever, Fournier ( 1971 ) and others have reported the presence of living, pigmented cells ("olive-green cells," or OGC's) averaging 3.5 fj-m in diameter in virtually all waters sampled deeper than about 50 m in the Atlantic and Pacific Oceans. These cells reach their maximum density of about 10^/1 at 300 to 500 m and may contribute up to about 1 /Lig C/1, or up to 10% of the total particulate organic carbon in aphotic marine environments. Fournier (1971) suggested that copepods are not likely to be major consumers of OGC's because of their limited abilities to filter such small particles at low con- centrations and that pelagic tunicates, which filter water through mucous sheets, may be better suited to utilize such particles. Fournier (1973) demonstrated that the gut contents of colonies of the pelagic tunicate, Pyrosoma, from below the euphotic zone consisted mainly of OGC's. If B. charon is indeed a resident of midwaters, as suggested above, and if it, like its epipelagic rela- tives, filters particles < 10 to 20 /am in size, then it may be a major consumer of OGC's as well as detritus. The localized occurrence of dense layers of S. charon indicated by the in situ observations of Barham ( 1969) may depend on the presence of peak concentrations of OGC's between 200 and 1,000 m, as observed by Fournier ( 1971). Alterna- tively, the filter meshes of the house of B. charon may be larger than those of smaller, epipelagic larvaceans and the food may then consist largely of slow zooplankton. Knowledge of house structure and analyses of gut contents of additional speci- mens may clarify the role of B. charon in meso- pelagic food webs. Bathochordaeiis charon may contribute large amounts of mucus to the water column in the form of its discarded houses. Oikopleura clioica secretes and discards four to six houses per day (Paf- fenhofer 1973). Such occupied and empty houses are sources of particulate food and surface habitat for microorganisms in planktonic ecosystems (Alldredge 1972, 1976a) and, along with other or- ganic aggregates, may serve as a barrier to the downward flux of particulate matter and sub- stances adherred or adsorbed to them ( Silver et al. 1978). Moreover, such "marine snow" provides a trophic link between large consumers and nano- plankton, protozoa, and microcrustaceans, allow- ing the former to tap an otherwise unavailable food source (Hamner et al. 1975). Larvaceans and their houses are known prey for fish and planktonic invertebrates (Alldredge 1976a, b; Bailey et al. 1975; Hobson 1974; Hobson and Chess 1976). Bathochordaeiis charon produces large mucous structures, although the size and frequency of pro- duction of the houses is not known. The rate of turnover of houses is probably less than in O. clioica because of lower temperatures and lower concentrations of particulates which could clog the house filters. Other Oikopleuridae produce houses which are roughly 5 to 15 times the trunk length (Alldredge 1975). If this ratio holds forB. charon, then a 25 mm individual would produce a house about 10 to 40 cm in diameter, comparable with in situ estimates (Barham 1969). IfB. charon is con- centrated in layers just above the thermocline, as suggested by in situ observations (Barham see footnote 2), then its houses may form a major com- ponent of mesopelagic marine snow. Note Added in Proof I am grateful to A. Biickmann and H. Kapp for calling my attention to their paper (Unter- suchungen am Zooplankton von der Atlantischen Kuppenfahrt der „Meteor", Marz bis Juli 1967, published 1973 in „ Meteor" Forschungsergeb- nisse, Reihe D, No. 13:11-36) in which they de- scribed and illustrated two additional specimens, referred to as B. stygius. The specimens were taken April 1967 in the North Atlantic (lat. 30°18' N, long. 29^20' W) between 100 m and the surface. 518 One specimen was 6.1 mm ti-unk length and the other was not measurable. The authors provided a valuable discussion of the taxonomic problems of the genus and suggested that B. stygius should be applied at least to all known juvenile specimens. Acknowledgments Thanks to Eric Barham for sharing his unpub- lished observations and for critically reading the manuscript; to Janie Layton, Suzanne Latauska, Robert Freligh, and Michael Schaadt for technical assistance; and to Theodore Pietsch, Laurie Stuart, Jay Quast, and an anonymous reviewer for commenting on the manuscript. This work was supported in part by a grant-in-aid from the Office of Graduate Studies and Research, California State University, Long Beach. Literature Cited ALLDREDGE, A. L. 1972. Abandoned larvacean houses: A unique food source in the pelagic environment. Science (Wash., D.C.) 177:88.5-887. 1975. Quantitative natural history and ecology of appen- dicularians and discarded appendicularian houses. Ph.D. Thesis, Univ. of California. Davis, 149 p. 1976a. Discarded appendicularian houses as sources of food, surface habitats, and particulate organic matter in planktonic environments. Limnol. Oceanogr. 21:14-23. 1976b. Field behavior and adaptive strategies of appen- dicularians (Chordata: Tunicata), Mar. Biol. (Berl.) 38:29-39, Bailey, J. E.. B. L. Wing, a.nd C. R. M.^^ttson. 1975. Zooplankton abundance and feeding habits of fry of pink salmon, Oncorhynchus gorbuscha . and chum salmon, Oncorhynchus keta. in Traitors Cove, Alaska, with speculations on the carrying capacity of the area. Fish. Bull., U.S. 73:846-861. Barham, E. G. 1969. A window in the sea. Oceans Mag. 1( 11:54-60. Chun, c. 1900. Aus den Tiefen des Weltmeeres. Gustav Fischer, Jena, p. 519-521 (2d ed,, 1903, p, 554-5571, Fenalix, R. 1966. Synonymie et distribution geographique des Ap- pendiculaires. Bull Inst, Oceanogr (Monaco) 66(1363), 23 p. FORNERIS, L. 1957. The geographical distnbution of the Copelata. An. Acad. Bras, Cienc, 29:273-284, FuURNIER, R, O. 1 97 1 , Studies on pigmented microorganisms from aphotic marine environments, II, North Atlantic distribu- tion. Limnol. Oceanogr, 16:952-961, 1973, Studies on pigmented microorganisms from aphotic marine environments. III, Evidence of apparent utiliza- tion by benthic and pelagic tunicata, Limnol. Oceanogr 18:38-43. GARSTANG, W. 1936. On a new Appendicularian, Bathochordaeus sp., from Bermuda, with a revision of the genus. (Ab- stract.) Proc. Linn. Soc. Lond. 148:131-132. 1937. On the anatomy and relations of the Appendicula- rian Bathochordaeus. based on a new species from Ber- muda (S. stygius. sp. n.). J, Linn, Soc, Lond, Zool. 40:283-303. Gerber, R. p., and N. Marshall. 1974. Ingestion of detritus by the lagoon pelagic communi- ty at Eniwetak Atoll. Limnol. Oceanogr. 19:815-824. HaMNER, W, M, L, P, MADIN, a. L. ALLDREDGE, R. W. GiLMER, AND P. P. HA.MNER. 1975. Underwater observations of gelatinous zooplankton: Sampling problems, feeding biology, and be- havior. Limnol. Oceanogr. 20:907-917. HOBSON, E. S. 1974. Feeding relationships of teleostean fishes on coral reefs in Kona, Hawaii, Fish, Bull,, US, 72:915-1031, HOBSON, E, S, , AND J, R, CHESS. 1976. Trophic interactions among fishes and zooplankters near shore at Santa Catalina Island, California Fish. Bull., U.S. 74:567-598, HOBSON, L, 1967, The seasonal and vertical distribution of suspended particulate matter in an area of the Northeast Pacific Ocean Limnol. Oceanogr. 12:642-649. HOLM-HANSEN, O, J, D, H, STRICKLAND, AND P. M. WILLIAMS. 1966 A detailed analysis of biologically important sub- stances in a profile off southern California. Limnol. Oceanogr. 11:548-561 LOHMANN, H. 1899. Das Gehause der Appendicularien, sein Bau, seine Funktion und Entstehung. Schr. Naturwiss. Ver. Schleswig-Holstein 11:347-406, 1914, Die Appendicularien der VALDIVIA Expedi- tion, Verb, Dtsch, Zool, Crts, 24:157-192, 1931, Die Appendicularien der Deutschen Teifsee- Expedition, Wiss, Ergeb, Dtsch, Tiefsee-Exped. 211- 158. LOHMANN, H., AND E. HENTSCHEL, 1939. Die Appendicularien im Siidatlantischen Ozean. Wiss. Ergeb, Dtsch, Atl, Exped, 13:153-243, MENZEL, D, W, 1967, Particulate organic carbon in the deep sea, Deep- Sea Res. 14:229-238. Silver, M. W., a. L. Shanks, and J. D. Trent. 1978. Marine snow: Microplankton habitat and source of small-scale patchiness in pelagic populations. Science (Wash., D.C.) 201:371-373, Thompson, H. 1948. Pelagic Tunicates of Australia. Commonw. Counc. Sci. Ind. Res,, Aust,, 196 p, TOKIOKA, T, 1960 Studies on the distribution of appendicularians and some thaliaceans of the North Pacific, with some mor- phological notes, Publ. Seto Mar. Biol. Lab. 8(2)129- 221. Charles P. Galt Biology Department California State University Long Beach. CA 90840 519 INFORMATION FOR CONTRIBUTORS TO THE FISHERY BULLETIN Manuscripts submitted to the Fishery Bulletin will reach print faster if they conform to the following instructions. These are not absolute requirements, of course, but desiderata. 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A simple method to obtain serum from small fish 509 IRVINE, A. BLAIR, MICHAEL D. SCOTT, RANDALL S. WELLS, and JAMES G. MEAD. Stranding of the pilot whale, Globicepkala macrorhynchus, in Florida and South Carolina 511 GALT, CHARLES P. First records of a giant pelagic tunicate, Bathochordaeus charon (Urochordata, Larvacea), from the eastern Pacific Ocean, with notes on its biology 514 . GPO 696-364 .<< °'X Fishery Bulletin Woods Hole, Mass. Vol. 77, No. 3 HUBBS, CARL L., and ROBERT L. WISNER. Revision of the sauries (Pisces, Scomberesocidae) with descriptions of two new genera and one new species .... 521 JOHNSON, JOHN KENNETH. Effects of temperature and salinity on production and hatching of dormant eggs of Acartia californiensis (Copepoda) in an Oregon estuary 567 BARHAM, ERIC G., JAY C. SWEENEY, STEPHEN LEATHERWOOD, ROBERT K. BEGGS, and CECILIA L. BARHAM. Aerial census of the bottlenose dolphin, Tursiops truncatus, in a region of the Texas coast 585 WEIHS, DANIEL. Energetic significance of changes in swimming modes during growth of larval anchovy, Engraulis mordax 597 PREZANT, ROBERT S. An antipredation mechanism of the polychaete Phyllodoce mucosa with notes on similar mechanisms in other potential prey 605 SCARNECCHIA, DENNIS L., and HARRY H. WAGNER. Contribution of wild and hatchery-reared coho salmon, Oncorhynchus kisutch, to the Oregon ocean sport fishery 617 HAYNES, EVAN. Larval morphology of Pandalus tridens and a summary of the principal morphological characteristics of North Pacific pandalid shrimp larvae 625 HUNTER, J. ROE , and STEPHEN R. GOLDBERG. Spawning incidence and batch fecundity in northern anchovy, Engraulis mordax 641 HEALEY, M. C. Utilization of the Nanaimo River estuary by juvenile chinook salmon, Oncorhynchus tshawytscha 653 JUDKINS, DAVID C, CREIGHTON D. WIRICK, AND WAYNE E. ESAIAS. Com- position, abundance, and distribution of zooplankton in the New York Bight, Sep- tember 1974-September 1975 669 KROUSE, JAY S. Distribution and catch composition of Jonah crab. Cancer borealis, and rock crab. Cancer irroratus, near Boothbay Harbor, Maine 685 Notes SCHLIEDER, RODRIC A. Effects of desiccation and autospasy on egg hatching success in stone crab, Menippe mercenaria 695 HOWE, KEVIN M., DAVID L. STEIN, and CARL E, BOND. First records off Oregon of the pelagic fishes Paralepis atlantica, Gonostoma atlanticum, and Aphanopus carbo, with notes on the anatomy of Aphanopus carbo 700 (Continued on back ctwert Seattle, Washington U.S. DEPARTMENT OF COMMERCE Juanita M. Kreps, Secretary NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION Richard A. Frank, Administrator Terry L. Leitzell, Assistant Administrator for Fishieries NATIONAL MARINE FISHERIES SERVICE Fishery Bulletin The Fishery Bulletin carries original research reports and technical notes on investigations in fishery science, engineering, and economics. The Bulletin ofthe United States Fish Commission was begun in 1881; it became the Bulletin of the Bureau of Fisheries in 1904 and the Fishery Bulletin ofthe Fish and Wildlife Service in 1941 . Separates were issued as documents through volume 46; the last document was No. 1103. Beginning with volume 47 in 1931 and continuing through volume 62 in 1963, each separate appeared as a numbered bulletin. A new system began in 1963 with volume 63 in which papers are bound together in a single is.sueof the bulletin instead of being issued individually. Beginning with volume 70, number 1, January 1972, theFis/iery Bulletin became a periodical, issued quarterly. In this form, it is available by subscription from the Superintendent of Documents, U.S. Government Printing Office, Washington, DC 20402. It is also available free in limited numbers to libraries, research institutions. State and Federal agencies, and in exchange for other scientific publications. EDITOR Dr. Jay C. Quast Scientific Editor. Fishery Bulletin Northwest and Ala.ska Fisheries Center Auke Bay Laboratory National Marine Fisheries Service, NOAA P.O. Box 155, Auke Bay, AK 99821 Editorial Committee Dr. Elbert H. Ahlstrom National Marine Fisheries Service Dr. Bruce B. Collette National Marine Fisheries Service Dr. Edward D. Houde University of Miami Dr. Merton C. Ingham National Marine Fisheries Service Dr. Reuben Lasker National Marine Fisheries Service Dr. Jerome J. Pella National Marine Fisheries Service Dr. Sally L. Richardson Gulf Coast Research Laboratory Kiyoshi G. Fukano, Managing Editor The F/she/y Bulletin (USPS 090-870) is published quarterly by Scientific Publications Office. National Marine Fisheries Service. NOAA. Room 450. 1107 NE 45th Street. Seattle. WA 98105 Controlled circulation paid to Finance Department. USPS. Washington, DC 20260. Although the contents have not been copyrighted and may be reprinted entirely, reference to source is appreciated The Secretary of Commerce has determined that the publication ot this periodical is necessary in the transaction of the public business required by law of this Department Use of funds for printing of this periodical has been approved by the Director of the Office of fyfanagement and Budget through 31 lylarch 1982, Fishery Bulletin CONTENTS Vol. 77, No. 3 July 1979 HUBBS, CARL L., and ROBERT L. WISNER. Revision of the sauries (Pisces, Scomberesocidae) with descriptions of two new genera and one new species .... 521 JOHNSON, JOHN KENNETH. Effects of temperature and salinity on production and hatching of dormant eggs of Acartia californiensis (Copepoda) in an Oregon estuary 567 BARHAM, ERIC G, JAY C. SWEENEY, STEPHEN LEATHERWOOD, ROBERT K. BEGGS, and CECILIA L. BARHAM. Aerial census of the bottlenose dolphin, Tursiops truncatus, in a region of the Texas coast 585 WEIHS, DANIEL. Energetic significance of changes in swimming modes during growth of larval anchovy, Engraulis mordax 597 PREZANT, ROBERT S. An antipredation mechanism of the polychaete Phyllodoce mucosa with notes on similar mechanisms in other potential prey 605 SCARNECCHIA, DENNIS L., and HARRY H. WAGNER. Contribution of wild and hatchery-reared coho salmon, Oncorhynchus kisutch, to the Oregon ocean sport fishery 617 HAYNES, EVAN. Larval morphology of Pandalus tridens and a summary of the principal morphological characteristics of North Pacific pandalid shrimp larvae 625 HUNTER, J. ROE, and STEPHEN R. GOLDBERG. Spawning incidence and batch fecundity in northern anchovy, Engraulis mordax 641 HEALEY, M. C. Utilization of the Nanaimo River estuary by juvenile chinook salmon, Oncorhynchus tshawytscha 653 JUDKINS, DAVID C, CREIGHTON D. WIRICK, AND WAYNE E. ESAIAS. Com- position, abundance, and distribution of zooplankton in the New York Bight, Sep- tember 1974-September 1975 669 KROUSE, JAY S. Distribution and catch composition of Jonah crab. Cancer borealis, and rock crab. Cancer irroratus, near Boothbay Harbor, Maine 685 Notes SCHLIEDER, RODRIC A. Effects of desiccation and autospasy on egg hatching success in stone crab, Menippe mercenaria 695 HOWE. KEVIN M., DAVID L. STEIN, and CARL E. BOND. First records off Oregon of the pelagic fishes Paralepis atlantica, Gonostoma atlanticum, and Aphanopus carbo, with notes on the anatomy of Aphanopus carbo 700 (Continued on next page) Seattle, Washington 1980 For sale by the Superintendent of Documents. U S Government Printing Office. Washington. DC 20402 — Subscription price per year $12 00 domestic and $15 00 foreign Cost per single issue: $3 00 domestic and $3 75 foreign Contents-continued BUCKLEY, L. J. Changes in ribonucleic acid, deoxyribonucleic acid, and protein content during ontogenesis in winter flounder, Pseudopleuronectes americanus, and effect of starvation 703 SCHERER, MICHAEL D., and DONALD W. BOURNE. Eggs and early larvae of smallmouth flounder, Etropus microstomus 708 LANCRAFT, THOMAS M., and BRUCE H. ROBISON. Evidence of postcapture ingestion by midwater fishes in trawl nets 713 NEWKIRK, G. F., and D. L. WAUGH. Inhibitory effect of the alga Pavlova lutherii on growth of mussel, Mytilus edulis, larvae 715 Notices NOAA Technical Reports NMFS published during the first 6 mo of 1979 719 Vol. 77, No. 2 was published on 9 October 1979. The National Marine Fisheries Service (NMFS) does not approve, rec- ommend or endorse any proprietary product or proprietary material mentioned in this publication. No reference shall be made to NMFS, or to this publication furnished by NMFS, in any advertising or sales pro- motion which would indicate or imply that NMFS approves, recommends or endorses any proprietary product or proprietary material mentioned herein, or which has as its purpose an intent to cause directly or indirectly the advertised product to be used or purchased because of this NMFS publication. REVISION OF THE SAURIES (PISCES, SCOMBERESOCIDAE) WITH DESCRIPTIONS OF TWO NEW GENERA AND ONE NEW SPECIES Carl L. Hubbs and Robert L. Wisner' ABSTRACT The extant members of the Scomberesocidae are: 1) Scomberesox saurus saurus of the North Atlantic, ranging into the Arctic north of Europe, and Scomberesox saurus scom Oroides, of disjunct occurrence in the Southern Hemisphere; and 2) Cololabis saira of the North Pacific (with one record attributed to release of bait in the Indo-Pacific tropics), two dwarf species, Nanichthys simulans, new genus and species, of the central Atlantic and the Indian Oceans, and Elassichthys (new genus) arfoccrus , of the eastern centra] Pacific. Some other names applied to Miocene fossils from southern California have been referred, we believe erroneously, to the Scomberesocidae. Elassichthys adocetus is particularly dwarfed but both dwarfs are distinguished by having no gas bladder and by having a single ovary which, at maturity, very largely fills the body cavity with few large ova. All members of the group are epipelagic, and they constitute a major element of that assemblage over a large share of the tropical and temperate world ocean. Fishes of the family Scomberesocidae form a well-defined unit, due principally to the presence of separated finlets posterior to the dorsal and anal fins (as commonly found in scombroid fishes) and in having a slender, pikelike body with these me- dian fins set far back (Figure 1). We interpret the scomberesocids as more or less akin to the Be- lonididae, Hemiramphidae, and Exocetidae, largely on the basis of having the lower pharyngeal bones united, and the lateral line low, near the ventral profile, rather than (as in most fishes) high on the lateral aspect of the body. The ordinal classification of the family has been variously interpreted since the turn of the cen- tury. For example, it was placed in a division called the "Scombresocidae microsquamatae" by Schlesinger (1909); in the subfamily Scombere- socinae of the Exocoetidae by Regan (1911); in the family Scomberesocidae of the order Synen- tognathi by Jordan (1923) and by others of his school; in the Scomberesocidae of the suborder Microsquamati of the order Synentognathi by Nichols and Breder ( 1928); in the suborder Scom- beresocoidei, including also the Belonidae, in the Beloniformes by Berg (1940); and, more recently, in the family Scomberesocidae of the superfamily Scomberesocoidea in the suborder Exocoetoidei and order Atheriniformes by Rosen ( 1964) and by 'Scripps Institution of Oceanography. University of Califor- nia, San Diego. La Jolla, CA 92093. Carl L. Hubbs died on 30 June 1979. Manuscript accepted April 1979 nSHERY BULLETIN; VOL 77, NO 3, 1980 Greenwood et al. (1966), who deleted the super- family. Bailey et al. (1970) in general followed Greenwood et al., as did Nelson (1976). Gosline (1971) preferred to recognize the order Beloni- formes, suborder Scomberesocoidei, families Scomberesocidae and Belonidae, and suborder Exocoetoidei, families Exocoetidae and Hemi- ramphidae; Gosline did not refer to Greenwood et al. (1966). Despite varied opinions on the ordinal level, all authors retained the scomberesocid fishes as a familial unit. The Scomberesocidae appear to comprise a com- pact group to which we add two new genera and one new species. The genera and their species are characterized in Table 1. Scomberesox and Col- olabis are relatively large fishes (about 350-450 mm), have paired ovaries and a gas bladder, while Elassichthys and Nanichthys are dwarfed (not known to exceed 126 mm, and one species not exceeding 68 mm standard length (SL)), have a single ovary, and lack a gas bladder. Also, they have fewer pectoral and procurrent caudal fin rays, gill rakers, and vertebrae. Several of the authorities cited above, and others, have indicated that the Scomberesocidae represent an evolutionary line highly specialized for active life at the surface. The modifications of the posterior dorsal and anal rays into finlets, as in various scombroids, is evidence for this view. As a corollary, it seems obvious that a strong swimmer like Cololabis saira or Scomberesox saurus, rather than the smaller, probably weaker Elassichthys 521 FISHERY BULLETIN: VOL, 77, NO c D 200 Figure l. — Adults of the four genera and species of scomberesocid fishes: (A) Scomberesox saurus: B Cololabis saira; (C) Nanichthy simulans; iD) Elassichthys adocetus. Table l. — Differential characters of the four genera and species of Scomberesocidae. Characters Cololabis saira Scomberesox saurus^ Nanichthys simulans Elassichthys adocetus Ovanes (Figure 8) Paired; bilateral Paired; bilateral Single, median Single: median Testes (Figure 9) Paired, bilateral, neither Paired, bilateral; neither Paired but forming Paired but forming overtopping other overtopping other coherent mass, left overtopping right coherent mass, left overtopping right Gas bladder Large, thin-walled Large, thm-walled Completely lacking Completely lacking Maximum known length Ca. 400 mm Ca. 450 mm 68 mm 126 mm Developed gonads Dorsolateral to gut; at- Lateral lo gut; attached Dorsolateral to gut; Dorsolateral to gut: tached to wall ot coelom to wall ol coelom unattached unattached Filaments on eggs Many at pole, single distant one None None None Upper beak Pointed, short, stout, over- Greatly produced, very Moderately produced. No beak, upper )aw lapped slightly by lower fragile, slightly overlapped by lower fragile, ca half length of lower broadly curved Lower jaw (in adult) Pointed, short, stout Greatly produced, ca, equal Much produced, ca twice Very short, bluntly point- to postorbital head length length of upper jaw ed, tubercular at tip Teeth on upper )aw All uniseriat Biserial on beak, Unisenal behind: bisenal Unisenal. few, widely unisenal behind forward spaced Teeth on lower )aw Obsolete, except developing Well developed throughout Bisenal near gape. Essentially unisenal. forward only in adults, life, bisenal on beak, unisenal forward fewer anteriorly unisenal unisenal behind Cartilaginous loops be- Few, but very well Numerous over long area Few over short area Wholly lacking tween mandibular rami developed Intermandibular tissue Covered by upper jaw Covered by upper jaw Covered by upper jaw Tissue largely exposed Lateral line Extending to over anal Extending to over anal To slightly past pelvic Completely lacking finlets finlets base^ Tubes and pores of head Numerous and much branched Numerous and much branched Intermediate Few. little branched Fiber bundles of body Fine Fine Moderately coarse Relatively very coarse muscles (Figure 7) Caudal peduncle^ Short Short Long Long Procurrenl caudal rays 5-7 5-7 4, rarely 3 or 5 2-3 Gill rakers" 37-38 (32-43) 45 5(39-51) 22-24(19-26) 17-18 (15-21) Pectoral rays" 12-14 (12-15) 13-14 (12-15) 10-11 (10-11) 9-10(8-11} Vertebrae* «65-67 (64-69); 63-67 (62-68) 65-67 (64-70) 59-62 (58-62) 56-57 (54-59) Scales, lateral midline 128-148. rather firmly attached 107-128, rather firmly attached 77-91. very caducous 70-88, very caducous 'Except for gill rakers (5), characters refer to both subspecies ^The lateral lines are incomplete on all our specimens except on the 121.2 mm one from Funchal, Madeira ^Length of caudal peduncle, measured as interval between bases of last finlet and first precaudal ray, is either "short" (about equal to depth of peduncle) or "long (about twice that depth) ■"Minimum and maximum values, the most common values first with total ranges in parentheses ^Values in parentheses are those for S, s scombroides «First values for western Pacific, mean 66.05 (tor 248 counts): second values for eastern Pacific, mean 65 11 (for 3,060 counts). 522 BBS and WISNER REVISION OF THE SAURIES adocetus or Nanichthys sunulans, is the basic type of the family, and that the dwarf forms are deriva- tive. DEVELOPMENT OF BEAK In their early ontogeny, the Scomberesocidae, like other synentognathous fishes, pass through changes in physiognomy (Figure 2), involving especially the upper and lower beaks. The degree of metamorphosis varies greatly among the four species. The most dwarfed scomberesocid, E. adocetus, exhibits the least change, retaining rather heavy, little-produced jaws throughout life. The upper jaw remains relatively short, and rounded in top view, and the lower jaw increases with growth of the fish only very slightly in production and slen- derizing. Next in degree of age changes is C. saira, in which the premaxillaries become more pointed forward and the dentaries become slightly pro- duced and slenderized, but not to a degree fully warranting the designation of either jaw as a beak. In contrast with Scomberesox and Nanich- thys, the snout does not further increase in rela- tive length after the fish reaches the standard length of about 50 mm i Figure 2 ). In contrast, the snout increases in relative length throughout the life span of Nanichthys and in Scomberesox until a length of about 200 mm has been attained. Next in the series we may rate the largest, and in many other respects the most extreme form, S. saurus. Very small juveniles have a short muzzle, with the lower jaw, as in all the species, the heavier (Figure 2). Very early the jaws both be- come sharper forward and begin to elongate. The process is initially somewhat more accelerated in the lower jaw, but at no stage do the developing beaks simulate the condition found in halfbeaks, for the developing upper beak is always much more than half as long as the lower. Liitken's ( 1880) indication to the contrary resulted from his inclusion of TV. sunulans into what he treated as the developmental series of S. saurus (see p. 533). In fact, the relative projection of the lower jaw decreases but little with age (Figure 2). The most extreme ontogenetic changes in physiognomy are displayed by the next-to-most dwarfed form, N. simulans (Figure 2). Until it reaches about 30 mm SL the jaws are scarcely produced. Soon, however, the premaxillaries be- come pointed forward and begin to elongate, but slowly. The dentaries become very slender and, in juxtaposition, elongated forwai-d far beyond the slender conjoined tips of the premaxillaries. When the standard length has reached 60 mm, the lower beak ofNanichthys, in contrast with Scomberesox, is more than twice the length of the upper. Nanichthys thus displays the closest approach to the halfbeak condition, but it can hardly be said to pass through a halfbeak stage, as do the belonids and two genera commonly (Oxyporhamphus) and/or regularly (Fodiator) placed in the Exocoe- tidae (Lutken 1880; Nichols and Breder 1928; Breder 1932, 1938; Hubbs 1933; Parin 1961). The projection of the lower jaw as a proportion of length offish increases sharply with age, at least for the usual standard lengths of about 90 mm in the specimens available to us. PHYLOGENY Only two extant genera of the family Scom- beresocidae, Scomberesox Lacep'ede 1803, and Cololabis Gill 1895, have been recognized. They have been differentiated primarily on the basis of the degree of development of the jaws into beak- like structures; in Scomberesox each jaw is definitely prolonged, very slender, fragile, and elongate, whereas in Cololabis the jaws remain short, less fragile, and only moderately pointed (Figures 1, 2). In each genus the lower jaw projects slightly beyond the upper. Both genera comprise slender, elongate fishes, bearing, as do the unre- lated Scombridae, a file of separated finlets that largely fill the interval between the caudal fin and the main parts of the dorsal and anal fins. Scom- beresox attains a standard length rarely in excess of 450 mm, although there are undocumented re- ports of 500 mm. Cololabis reaches about 350 mm SL. Despite the several expressed opinions to the contrary (below), we regard the merely pointed muzzle, with projecting chin, as in Cololabis and Elassichthys (Figure 2), as a primitive feature, and as also in Arrhamphus, Chriodorus, and Melapedalion of the halfbeaks. We also regard the beaks of Scomberesox and Nanichthys as deriva- tive therefrom. Jordan and Evermann (1896) surmised that Cololabis "represents the immature state of Scomberesox" — a view repeated by others of that school. Schlesinger (1909) definitely treated the jaws of Cololabis as secondarily foreshortened. Nichols and Breder ( 1928) went so far as to characterize Cololabis as "... a recogniz- 523 FISHERY BULLETIN VOL 77. NO ;) ft B Q I HUBBS and WISNER REVISION OF THE SAURIES able fixed larva of Scomberesox ." Knowing C. saira well as a moderately large and extremely active surface fish leads us to emphatically disre- gard its consideration as a larva. There is nothing in the ontogeny of the four species of the family to support the view that beaklessness arose from the beaked condition. Thus, we arrive at the concept of a relatively large and strong, beakless. surface-swimming fish as the phyletically basic member of the Scombere- socidae: Cololabis alone fits this concept. We therefore assume that an immediate ancestor of C saira gave rise to the other members of the family and remains as a relic in the temperate waters around the North Pacific, where it appears to re- place Scumberesox completely. The Cololabis ancestor presumably gave rise to Scomberesox through the development of a long beak, by the loss of filaments on the egg, and through a moderate increase in size and in aver- age numberof gill rakers and vertebrae. Perhaps a stock of the ancestor crossed equatorial waters in some past cool period and became isolated when the tropics again became warm; differentiation may then have taken place. From cool South Pacific waters the West Wind Drift may be as- sumed to have transported the saury to the south- ern parts of the Atlantic and Indian Oceans. From the Cape region of Africa it could have been car- ried far northward on the Benguela Current and may somehow, at some time, possibly even in the Pleistocene, have transgressed the tropics to gain the favorable waters of the North Atlantic. Such movements, however, are hypothetical. The origin of the dwarfs from a type or types more like Cololabis and Scomberesox seems hardly subject to doubt (as is indicated above). While recognizing the many features, some deep- seated and fundamental, wherein Elassichthys and Nanichthys closely agree, and jointly contrast with Cololabis and Scomberesox (Table 1), we strongly favor, albeit somewhat intuitively, the hypothesis that they are the products of conver- gent evolution: that Elassichthys stemmed from Cololabis (or an immediate ancestor of that genus), and that (Nanichthys is an offshoot from Scomberesox (or its immediate ancestor). Circumstances favoring the concept of a dual origin of the two dwarf species follow. 1) Characters held jointly by Elassichthys and Nanichthys, in contrast with Cololabis and Scom- beresox, are of the sort that might well be related to dwarfing, and hence be susceptible to indepen- dent origin. The lack of the gas bladder seems compensated for by the greatly reduced size of the fish ( yielding relatively more surface and viscosity per weight), and by the apparently weaker muscu- lature. The single ovary may be related to the minute size of the organ and the proportionately immense size of the few ova containable at any one time. The degeneration of the lateral line is a common feature of dwarfed fishes. The great re- duction in number of gill rakers would be ex- pected, as the smaller number should give adequate straining in a space so greatly reduced. Reduced number of vertebrae and rays is a feature of dwarfing, as Te Winkel (1935) showed in her study of a neotenic goby, and as she and the senior writer showed in an unpublished study of the ex- cessively neotenic fish genus Schindleria (which was originally misplaced in the Synentognathi, though it is not so related — as Gosline ( 1959) has shown). 2) The agreement between Elassichthys and Cololabis in the mere sharpening of the jaws (the upper rounded in Elassichthys), without any real beak development, is a compelling reason to re- gard them as closely related. 3) The circumstance that the gill rakers and vertebrae are fewer in Cololabis than in Scom- beresox. and about proportionately fewer in Elas- sichthys than in Nanichthys is at least suggestive evidence. 4) The circumstance that Cololabis is some- what smaller than Scomberesox , and that Elas- sichthys is proportionately smaller than Nanich- thys, seems to provide similar confirmatory evidence. 5) The mutual occurrence oi Elassichthys and Cololabis in the Pacific Ocean, in part sympatri- cally, and the mutual occurrence o^ Nanichthys and Scomberesox in the Atlantic and Indian Oceans, again in part sympatrically, provides strong confirmatory evidence that Elassichthys is the dwarf derivative of Cololabis and that Nanich- thys stemmed similarly and independently from Scomberesox. This hypothesis is diagrammed in Figure 3A. On this concept, dwarfing and various structural changes (diagrammed as "d g o"), in- cluding the loss of the gas bladder and the change to a single ovary, occurred twice, whereas the evolution of a beak (marked as "b") occurred only once. No such body of evidence seems advanceable for the alternative hypothesis (Figure 3B) that dwarfing and the ancillary changes occurred but 525 Scomberesox V A Nanichthys Cololobis (d go) Elassichthys Scomberesox B Cololobis Elossichfhys Xb) Nanichthys Figure 3.— Diagrams (A and B) of hypothetical divergent evolution within the Scomberesocidae: b — well-developed beak; d— dwarfism; g— gas bladder lost; o— ovary smgle. (A) The larger Scom6eresax and the dwarfed Nanic/if/iys, and the larger Cololabis and the dwarfed Elassichthys, derived respectively from beaked and beakless ancestors; development of a beak occurred but once, dwarfism and structural changes id g ol twice. (B) The beaked and beakless larger forms. Scomberesox and Cololabis. derived from a common ancestor, as did the beaked and beakless dwarfs. £iissicAr/i_vs and A'an^cAMvs ; development of a beak occurred twice, dwarfism and the structural changes but once. once, SO that Elassichthys and Nanichthys are of immediate common origin. On this hypothesis, the beak would have developed independently in Nanichthys and Scomberesox . The differences be- tween the two genera in the lengths of the upper and lower beaks could be cited as confirmatory evidence. As another item of evidence it could be stated that agreement between Elassichthys and Cololabis breaks down when the structure of the egg is considered. For some years we have known that there is a distinct dwarf genus i Nanichthys) having many FISHERY BULl.ETIiN VOI. 77, NO :i characters in common with Scomberesox. as well as another dwarf genus {Elassichthys) having much in common with Cololabis. The species in- volved we name Nanichthys simulans, new spe- cies, and Elassichthys adocetus (Bohlke 1951). These conclusions have been rather widely shared with colleagues. Parin (1968a, b) in par- ticular, has discussed these putative relation- ships, using the names "Scomberesox sp." and "Cololabis adocetus" for the respective dwarfs; he cited only superficial distinctions, along with re- duced numbers of gill rakers and vertebrae, in the dwarf form. Dudnik (1975bl, likewise using the name "Scomberesox sp.." also discussed Nanich- thys; he noted one internal morphological feature, that one of the ovaries is rudimentary. We have consistently found, however, no trace of a second ovary in either Elassichthys or Nanichthys. Our findings have been mentioned al.so by Collette ( 1966) as the second case of paedomorphism in the order, during his indication of a third case, that of a "paedomorphic or neotenic" belonid. The first case he indicated as the suggestion by Nichols and Breder ( 1928) that the scomberesocid genus Col- olabis is a permanently arrested stage in the on- togenetic development of Scomberesox. Table 2. —Numbers of gill rakers for the scomberesocid fishes. Gill Scomberesox ^^"'"= Cololab,s Nanichthys Elassichthys takers scomoroides saurus saira simulans adocetus 15 _ 12 16 — _ _ _ 6l 17 _ — — — 120 18 — — — — 135 19 — — _ 1 53 20 _ _ _ 3 27 21 — — _ 8 5 22 — _ _ 24 __ 23 — — — 19 _ 24 — _ _ 12 — 25 — — _ 8 _ 26 — — _ 4 — 32 — — 2 _ _ 33 — — 5 _ _ 34 _ 1 23 _ _ 35 — 5 34 _ _ 36 — 11 47 _ _ 37 — 9 84 — — 38 — 17 63 — — 39 6 18 50 _ _ 40 12 20 43 — — 41 28 18 16 _ _ 42 36 6 8 _ _ 43 47 5 3 _ _ 44 41 3 - _ _ 45 43 1 — — _ 46 35 — — — _ 47 19 _ _ _ _ 48 11 — _ _ _ 49 11 _ _ _ _ 50 4 _ — — _ 51 3 — — — — N 296 114 378 79 403 X 44.11 39.19 3753 22.84 17,66 526 HUBBS and VVISN'ER REVISION OP THE SAURIES Tables. — Numbers of pectoral fin rays (both sides counted) and of total anal and dorsal fin rays (including finletsl for the scom- beresocid fishes. Fin rays Scomberesox Cololabis Nanichthys Elassichthys saurus ' saira simulans adocetus 9 — — — 203 10 — — 99 122 11 — — 54 1 12 8 124 _ _ 13 108 962 — — 14 37 388 _ — 15 1 8 — — N 154 1,482 153 332 X 13.20 13.19 10.35 9.36 Doisal 14 -~ 3 14 31 15 6 97 49 183 16 45 422 16 136 17 28 185 _ 19 18 1 15 — 6 N 80 722 79 375 X 16.30 16.16 15.03 15.43 Anal 16 _ 1 17 1 _ 1 13 18 18 24 9 103 19 84 250 48 188 20 30 370 20 49 21 11 67 — 2 N 144 711 78 356 X 19.22 19,68 19.11 18.78 'Counts for al II fin rays of the no rttiecn and soi ittiern subspecies of Scorn- beresox saurus are combined The much reduced size of Nanichthys and the even more extreme dwarfing of Elassichthys strongly support the hypothesis that they exhibit neotenic or paedomorphic tendencies, certainly dwarfism; we hold that they are not neotenic, in the strict sense, but merely dwarfed. The reduced numbers of gill rakers, pectoral rays, vertebrae (Tables 2-5), scales, and procurrent caudal rays provide confirmatory evidence (no marked differ- ences were found in the numbers of dorsal and anal rays, either in the main fin or in the finlets). The loss of one ovary (or the complete fusion of the T.ABLE 4. — Numbers of vertebrae for the scomberesocid fishes. Number of Scomberesox Colotabis Nanichthys Elassichthys vertebrae saurus saira simulans adocetus 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 2 11 30 46 14 74 224 186 52 6 — 12 21 _ — 115 _ _ 9 672 _ _ 73 1.212 — _ 149 840 — — 83 187 — — 20 21 _ _ 3 1 1 — — 338 3,060 110 556 66 13 65 14 6066 5637 'Counts for the southern and northern subspecies are combined pair), and a tremendous decrease in the production of ova, the more notable in Elassichthys, may well be correlated with the dwarfing of the two new genera (the ova, however, have not been notably decreased in size). The less extreme dwarfing of Nanichthys could be interpreted as reflecting the larger size of its presumed progenitor, Scum- hereso.x (Figure 1, Table 1). The concept of Na- nichthys and Elassichthys being the respective de- rivatives of Scomberesox and Cololabis could be interpreted as being supported by their similar beak structures (Figure 2). and by the common occurrence of Scomberesox and Nanichthys in the Atlantic and Indian Oceans and of Cololabis and Elassichthys in the Pacific, north of the range in that ocean of Scomberesox. Herein we describe, discuss, and differentiate the two new dwarfed genera, Nanichthys and Elassichthys, and the new species A^. simulans, distinguish the Southern Hemisphere population of Scomberesox as a subspecies, fo.r which the T.^BLE 5. — Correlated counts of precaudal and caudal vertebrae of the four genera of Scomberesocidae. Counts not otherwise marked represent Ehssichthys; counts in italics refer to /Nanichthys; counts in parentheses represent Cololabis; and counts in bold face type refer to Scomberesox. Precaudal vertebrae Caudal vertebrae Genus 21 22 23 24 25 26 27 28 29 Elassichthys 32 _ 1 1 1 _ _ _ _ _ 33 2 7 23 8 34 1 21 52 8 _ Nanichthys 35 — 7 5 1 2 ; — _ _ 36 — — 1 4 2) 14 2 Cololabis 37 — I 7 47 22 (7) (8) (6) — 38 ; 7 3 (37) (64) (21) (1) Scomberesox* 39 — — — — (3) 1 (37) (63) 1 (10) (1) 40 — — — — 12 13 (11) (15) (4) _ ■ 41 — — — 17 63 31 1 42 — — — 6 19 6 1 1 43 — - - 2 2 - - - - 'Counts for the southern and northern subspecies are combined. 527 FISHERY BULLETIN VDL name S. saurus scomhrotdes (Richardson 1842) appears to have priority, and we portray the zoo- geography of the four genera of the Scomberesoci- dae that we now recognize. Also, we append a discussion of Miocene fossils from California re- ferred to the Scomberesocidae. MATERIALS AND METHODS We have examined material from the following repositories: AMS (Australian Musuem, Sydney); BCFL (Bureau of Commercial Fisheries Labora- tories (now NMFS), at Brunswick, Ga.; Honolulu Hawaii (formerly POFI); Seattle, Wash.; and Woods Hole, Mass.); BMNH (British Museum (Natural History)); BU (Boston University); CAS (California Academy of Sciences); CF (Carlsberg Foundation); CFG ( California Fish and Game, San Pedro); CNHM, FMNH (Chicago Natural History Museum, Field Museum of Natural History); LACM (Los Angeles County Museum); MCZ (Museum of Comparative Zoology, Harvard Uni- versity); MMF (Museo Municipal do Funchal, Madeira); SAM (South African Museum, Cape TowTi); SIO (Scripps Institution of Oceanography ); SOSC (Smithsonian Oceanographic Sorting Center); SU (Stanford University; collections now at CAS); TABL (Tropical Atlantic Biological Laboratory, Miami); UMMZ (University of Michi- gan Museum of Zoology); USNM (United States National Museum); UW (University of Washington, Seattle); WHOI (Woods Hole Oceanographic Institution); ZMUC (Zoological Museum, University of Copenhagen); and ZSZM (Zoologisches Staatsinstitute und Zoologisches Museum, Hamburg). Counts of dorsal and anal rays include the suc- ceeding finlets because the last rays of the main fin proper are often too much like those of the first finlets for definitive separation, particularly in adults; usually the last rays of the fin proper are thickened at the base and much branched and fanlike distally — in shape much like that of the first finlet. In young and subadults a space greater than that between the last rays of the fin proper usually separates the last ray and the first finlet, but this space is often obscured by a membrane or is not apparent in large specimens, particularly of Scomberesox and Cololabis. Pectoral rays of small and juvenile fish were counted using an air jet, or when submerged. Vertebrae were counted from radiographs or stained material (the latter method was used primarily for juveniles of Col- olabis). The urostyle was included in the count. Numbers of gill rakers for specimens oi Scom- beresox and Cololabis -70 mm SL and ofNanich- thys and Elassickthys <30 mm SL are not included in the tabular data because at shorter sizes the anterior rakers fade gradually into diminishing nubs of tissue that require highly subjective in- terpretation. Lateral lines scales were removed from the left side within a distance no >10 mm anterior to the origin of the pelvic fin. To enhance visibility of circuli the scales were lightly stained in a weak solution of Alizarin Red S and visually monitored for adequate uptake of stain. The scales of both Scomberesox (particularly! and of Cololabis were quite tenacious, so much so that they needed to be cut away from the body and the adhering tissue manually removed. Remaining bits of tissue often were so firmly attached that they could not be pulled off with forceps; immersion in 2% KOH eroded the scales without removing the bits of tissue. As most specimens of Scomberesox examined had the tips of the beaks broken off, proportions in all the species are based on body length rather than standard length. Body length is defined as the distance from the posterior margin of the orbit to the end of the hypural plate; this end point was determined by flexing the caudal fin until a crease appeared, approximately at the end of the hypural. KEY TO SPECIES OF SCOMBERESOCID FISHES la. Gill rakers numerous (.34-.51I, very closely spaced. Pectoral rays 12-15. Procurrent caudal rays 5-7. Depth of caudal peduncle equal to or less than its length 2 lb. Gill rakers fewer ( 15-26), less closely spaced. Pectoral rays 8-11. Procurrent caudal rays 2-5. Depth of caudal peduncle one-half to less than its length 3 2a. Both jaws produced into long, slender beaks in specimens -100 mm SL, the lower slightly longer. Maximum size about 450-500 mm SL. Known from temperate waters of North Atlantic and all southern oceans Scomberesox saurus 528 HUBBS and WISNER REVISION OF THE SAURIES 2b. Jaws only moderately produced into blunt beaks, the lower slightly longer. Maximum size about 400 mm SL. Native only in North Pacific Ocean Cololabis saira 3a. Jaws of adults produced as slender beaks, the lower about twice the length of upper. Gill rakers 22-24 (19-26). Procurrent caudal rays 4 (3-5i. Maximum size to 126 mm, usually about 100 mm. Known only from warm-temperate waters of Atlantic and Indian Oceans Nanichthys simulans 3b. Upper jaw very little produced, bluntly rounded, the lower jaw slightly more produced and more pointed at all sizes. Gill rakers 17-18 (15-21). Procurrent caudal rays 2-3. Maximum size to 68 mm SL. Known only from eastern tropical Pacific and westward to Hawaii Elassichthvs adocefiis AIDS TO IDENTIFICATION If the specimen is determined to be one of the larger species, pertinence to S. saurus or C. saira will be obvious from the oceanic source of the material, and, for all but the very young, from the presence or absence of a beak (Figure 2); even if the long beaks of Scomberesox are broken off near the base the stubbed condition will be obvious. However, if the very young of one or both species should be taken in the eastern Pacific Ocean in the upwelling area along the Equator (which now seems unlikely from the distributional evidence discussed below), it would hardly be feasible to arrive at a certain identification on the basis of beak development alone until the beak begins to develop at about 40 mm SL; but the reduced num- bers of pectoral and procurrent caudal rays and of gill rakers (rather short and widely spaced) read- ily distinguish Elassichthvs from Scomberesox and Cololabis. The development of the beak is the most trenchant distinction between Scomberesox and Cololabis; counts (Tables 2-5) and mor- phometric values (Table 6) overlap widely. If the specimen is determined to be a dwarf, its pertinence to E. adocetiis or N. simularts will probably always be determineable from the local- ity of capture, and, for specimens longer than about 50 mm, from the incipient to full devel- opment of the beak (Figure 2); in fact, in Elassichthys the upper jaw never becomes really beaklike, only broadly rounded, not moderately pointed as in C. saira of comparable size (Figure 4). If further check is desired, separations may be attained by counting gill rakers, pectoral rays, or vertebrae (Tables 2-5). Ueyanagi and Doi (1971) showed that in young of Elassichthys (^=30 mm) the depth of the caudal peduncle was one-half or less of its length, but was about equal in S. saurus and C. saira. We find (original data) N. simulans to have a ratio of depth to length of caudal pedun- cle similar to that of £. adocetus. These ratios hold for all sizes of the four species. The scomberesocid fishes inhabiting the Atlan- tic or Indian Oceans may be either N . simulans or S. saurus. determinable by the meristic counts (Tables 2-4). At lengths greater than about 60 mm, the relative development of unbroken beaks should ordinarily be decisive (Figure 2). Table 6.— Selected body proportions from 36 1 specimens each of the four species of scomberesocid fishes (thousandths of body length). ScomberBsox Scom6e/-esox s Nanichthys Elassichthys Cololabis saurus I saOrus scombroides simulans adocetus saira (26-223 mm) X Range (63-300 mm) X Range (32 -77 mm) (29-60 mm) X Range (5C X 1-239 mm) Body proportion X Range Range Orbit lengtti 49 36-39 45 37-59 52 41-64 50 43-58 43 35-53 Posiorbital head (englh 104 82-124 105 92-120 99 88-111 89 80-102 113 103-126 Body depth at origin of 132 109-160 128 115-139 113 95-135 115 95-131 136 121-153 petvic fin Distance from origins of dorsal and anal fins 127 105-143 123 111-137 108 98-119 107 93-116 127 111-147 Posterior margrn of orbit to origins of Peivic fin 513 474-525 501 475-536 460 444-487 447 417-485 478 457-502 Anal fin 661 611-692 669 642-707 621 604-645 628 606-654 643 620-668 Dorsal fin 684 650-715 685 658-723 648 631-672 652 630-673 679 661-707 End of hypural to origins of: Pelvic fin 512 487-538 515 483-542 549 529-565 560 529-586 529 518-546 Anal fin 354 317-396 343 314-371 388 363-406 380 351-400 361 326-381 Dorsal fin 330 298-369 322 281-350 359 341-379 357 330-374 329 312-350 529 FISHERY BULLETIN VOL. 77, NO 3 Figure 4— Upper— Dorsal view of bluntly rounded tip of upper beak ofaduhElassichthys adocetus, 59.0 mm SL. Lower— Dorsal view of moderately pointed tip of upper beak of juvenile Cololabis saira, 58.0 mm SL. DESCRIPTION OF NEW TAXA Nanicbthys Hubbs and Wisner, new genus New genus, Hubbs and Wisner. — Collette 1966:4, 6, 7, 20 (reduced counts; neotenic [this seems to be the only published reference to Nanichthys as a genus]). Genotype. Namchthyn simtilans, new species. Diagnosis. — A dwarfed scomberesocid ( maximum known standard length 126 mm), agreeing with 530 Elassichthys in having a single median ovary, when ripe largely filling the expanded coelom, and the testis folded together into a single median band. Gas bladder completely obsolete. Lateral line developed only anteriorly. Premaxillary and mandibular tooth rows closely approximated at front. Upper jaw produced as an extremely slender beak about half as long as in S. saurus and much slenderer (in both lateral and dorsal aspects) than the much stronger but still slender lower beak, which is only about half as long as, and much less attenuate than, that in adult S. saurus. The major HUBBS and WISNER: REVISION OF THE SAURIES counts are much reduced: vertebrae 58-62, trans- verse scale rows along midlateral line 70-88. pro- current caudal rays 4 (rarely 3 or 5), pectoral rays 8- 11, rakers on first gill arch 19-25 (usually 22-24). Derivation of generic name. — From the Greek pavocr (nanos), a dwarf, and iilidva (ichthys) a fish. Nankhthys simtilaui Hubbs and Wisner, new species Figure 5 o l-I to Derivation of species name, simulans (imitating). -From the Latin, Holotype.SlO 63-546, an adult male 89.5 mm SL, dipnetted at surface under a light in the south central Atlantic Ocean at 24=02.5' S, 15=32.0 ' W, on 9 June 1963; deposited in the Marine Verte- brate Collection of the Scripps Institution of Oceanography. Paratypes. — All dipnetted in the southern Atlan- tic Ocean at night under a light. Marine Verte- brate Collection of the Scripps Institution of Oceanography; SIO 63-545, 8 (46-69 mm), 12 June 1963, 29 51.5' S, ir07' W; SIO 63-546, 17 (47-90 mm), 19 June 1963, 24°02.5' S, 15°32.0' W; SIO 63-548, 16 (20-76 mm), 20 June 1963. 23°42,0' S, 12=12.5' W; SIO 63-549, 6 (55-87 mm), 22 June 1963, 2r21.0' S, ir34.5' W; SIO 63-550, 7 (45-80 mm), 24 June 1963, 2010.5' S, 11 30.5' W; SIO 63-553, 4 (67-90 mm), 26 June 1963. 17"39.0' S, 12°22.0' W; SIO 63-555. 11 (38-66 mm), 28 June 1963, 15''48.0'S,16°50.0'W; SIO 63-571, 2 (38 and 44 mm), 22 July 1963, 11=35.0' S. 44=01.0' W. USNM 204257, 2 (68 and 101 mm), 15°45' S, 08''45' E; USNM 204258, 4 (42-66 mm), 32°57' N, 39°21' W. CO We plan to transfer some of the Scripps para- types listed above to USNM, MCZ, Philadelphia Academy of Natural Sciences ( ANSP), CAS, and BMNH. We do not assign paratype designation to many additional specimens, mostly very small, from the mid-Atlantic, nor to the few examples seen from the Indian Ocean, nor to two specimens, unusually large for this dwarf species, from Funchal, Ma- deira (these two are discussed on p. 541). Synonymy of Nankhthys iimiilaiis a a D I 3 O Scomhresox scuteUatus (not Scomberesox sciitul- 531 FISHERY BULLETIN: VOL 77. NO :i latum LeSueur 1822:132-133^)— Valenciennes 1846:477-479 (description: "en le retirant de restomac d'un coryph'ene iConphaena eqtiise- tis) . . . venait de pecher a vingt-cinq lieues [ca. 2.76 mil au nord de Sainte-Helene |St. Helena Isle, about 16° S in mid-Atlantic Ocean i; nous avons un second exemplaire de la meme espece ... fit a risle-de-France (Mauritius Island, In- dian Ocean] ou pendant sa traversee de retour" [to France]. Scombresox saurus (misidentification). — Giinther 1866:257-258 ("Atlantic, 3' N of the line"; St. Helena; probably also 20° N, 22°53 ' N and other series); 1889:34 (". . . fry and young . . .belong to most common forms of pelagic life . . . from the Atlantic . . . .").^ Sauvage 1891:526 (listed from near Madagascar, between 3° and 26° S, 42° and 65° E; presumed from locality). Murray and Hjort 1912:89, 90, 94, 607, 613 (14 stations listed), 633, 635, 644, 670, 741, 747-748, figs. 541-542, all in part or questionable, listed both as "Scombresox" and as "Scombresox saurus," from open Atlantic in area between Iceland, Morocco, and Newfoundland; size to 50 cm. Bar- nard 1925:259, fig. 16b (St. Helena record only). Cadenat 1950:298 (presumed from locality off lies du Cap Vert). Scomberesox saurus (misidentification). — Liitken 1880:564-569, 1 fig., repeated by Murray and Hjort, see above ( in part: in Atlantic Ocean from 11°30' to 48° N, 9° to 40° W, and from 12° to 40 32 ■ S, 52 W to 16 30' E; in Indian Ocean from 27° to 38°20' S, and from 24°30' to 10r40' E; measurements and counts presumably also in part). Regan 1916:142 (postlai-vae from south of Azores, at 29°10' N, 33 36' W, identification dubious). Bigelow and Welsh 1925:166, fig. 71 (range, 11°-12° to40° N in Atlantic (presumably in part), figure repeated from Murray and Hjort, see above). Hildebrand and Schroeder 1928:151-152 (range, in part, and description of young, from Bigelow and Welsh 1925). Sivert- sen 1945:6 (in part, St. Helena record only). Bigelow and Schroeder 1953:170-171, fig. 83 (in part, doubtful, description; young — 100 to 150 ^LeSeuer's type-specimen was "small." with upper beak about half of other; it was " . . found in the stomach of a fresh codfish which had been brought to Boston from the Bank of Newfound- land." therefore in the appropriate range oi Scomberesox sauru:^ and far north of the range o( Nantchthys simulans. ^At least in part; one of three specimens involved, but not mentioned, from Tenerife (one of the Canary Islands) has been identified for us as N. simulans by G. Palmer of the British Museum i Natural History), using characters outlined by us. mm "hemiramphus stage," most numerous in open Atlantic between 11° or 12° and 40° N). Smith 1955:308 (presumptive, listed from Al- dabra Island). Fowler 1956:141-142 (reference to Borodin's 1930 dubious (unverified) Red Sea record; South Africa, description taken from New England and New York material of S. saurus and not "Indo-Pacific" entry). Briggs 1958:264 (presumptive, in part, western Atlan- tic from Newfoundland and Bermuda to Argen- tina, 35° to 30° S). Rodriguez-Roda 1960:115 (presumed from locality; southern Spain, Strait of Gibralter). Hotta 1964:4-5 i in part, presump- tive, distribution). Leim and Scott 1966:168 (in part, presumptive, in western Atlantic south to West Indies; fry abundant between 11° and 40° N;jaws do not reach full length until fish are 4 to 6 in long). Sauskan and Semenov 1969:250-252, fig. 157 (two populations inferred in North At- lantic, 32° to 36° N, 50° to 70° W, and near Azores; feeding migration) (in part, presumed from locality). Zilanov and Bogdanov 1969, fig. 158 (size groups, migrations, northeast Atlan- tic, 30° to 60° N, 8° to 40° W) (in part, presumed from locality). Hartmann 1970 (2.0 mm eggs in 68 mm scomberesocids from northeastern At- lantic can refer to only N. simulans). Scomberesox sp. — Parin 1968b, fig. 31 (plank- tonic, records mapped in tropical eastern Atlan- tic and north of Madagascar, Indian Ocean); 1968a, fig. 1 (undescribed species under study by Hubbs and Wisner). Parin and Andriashev 1972 (dwarf Atlantic species, along 26 W between 24° and 30° S, and in western cruise track off South America in area of 32° S, temperature 20.4° to 22.4° C). Parin 1973 (reference to Parin 1968a; to be described by Hubbs and Wisner; abundant, epipelagic, Atlantic off Madeira, Canaries, Morocco, Portugal, to 40° N). Ueyanagi et al. 1972, fig. 1, 2 (sizes graphed, distribution in Atlantic mapped). Suda 1973, fig. 7 (life history presumably similar to that of Cololabis adocetus: not suitable for commercial fishery). Dudnik 1975b, fig. (general discussion; comparison with S. saurus in range and charac- ters; one ovary developed, second rudimentary; ova sizes; spawning prolonged). Wisner 1977, fig. (description, key; compared with S. saurus, Belonidae, and Hemiramphidae; distribution in northwestern central Atlantic). Hardy 1978, fig. 29-34 (in part. North Atlantic; "Scomberesox sp." in reference to Hartmann, 1970, .statement of 2.0 mm eggs in females 68 mm and over). 532 HUBBS and WISNER REVISION OF THE SAURIES Discussion of Synonymy. — It has been consis- tently overlooked that Valenciennes [1846 iXVIIIl:477-479] recognizably described this dwarf scomberesocid, from 25 leagues north of Saint Helena Island in the tropical Atlantic Ocean and from Mauritius Island in the Indian Ocean or on the return journey I to France!. He misidentified this species as Scomhreso.x sciiteHatttm LeSeuer. However, Scombresox scutellatum LeSueur( 18221 was based on a small specimen, obviously of Scomberesox saurus. that was taken from the stomach of a cod brought to Boston from the bank of Newfoundland. The Atlantic specimen de- scribed by Valenciennes also was supposed to be a young saury that had been eaten by a dolphin fish, identified as Coryphaena equisetis, caught "a vingt-cinq lieues au nord de Sainte-Helene." As- suming this to be the island on w'hich Napoleon was confined, on the basis of 2.76 mi to a league, from the old French system, the location was ap- proximately 14°48' S, 05"42' W (marked as an open circle on Figure 12). This location is obvi- ously within the now known habitat of Ncinichthys simulans and far from the range of S. saurus. whereas the specimen treated by LeSueur was centered within the area where S. saurus alone occurs, in abundance. That Valenciennes had an example of the dwarf Atlantic saury is obvious from his description of the beak in a small specimen. Valenciennes wrote: "La brevite du museau est aussi non moins remar- quable; car le longueur du bee n'est quere moitie du reste de la tete; le bee superieur lui-meme n'est pas beaucoup plus prolonge que celui des plusieurs hemiramphes." He further stated (p. 478), "Ce petit poisson, long de deux pouces neuflignes . . . ." Since the old French "pouce" was 27.07 mm long, and a "ligne" one-twelfth of a pouce, we compute the length of the fish as about 75 mm. A scom- beresocid of this size, with beak scarcely half the length of the head behind the beak, and with snout comparable with that of a hemiramphid, could scarcely be other than a Nanichthys. Since the specimen collected at "I'lsIe-de-France" [Mauri- tius], or on the return journey, was described as of the same size and of the same species, and since A'^. simulans is now known to occur in the southern Indian Ocean, it has seemed highly probable that it also pertains to that species. This assumption has been verified for us, very kindly, by Marie- Louise Bauchot'' who has found that the two specimens, respectively 66.9 and 67.1 mm SL, have 1 1 and 10 pectoral rays, 23 and 22 gill rakers, and 59 and 60 vertebrae (within the range for A^. simulans but far below the range for S. saurus). It is now clear that Liitken (1880:564-569, fig. a-h) unknowingly included A'^. simulans as well as Scomberesox s. saurus in his account of S. saurus. This is evident from his statement of latitudinal distribution in the Atlantic Ocean from 11 30' to 48" N and from 12° to 40'32' S. and in the Indian Ocean from 27° to 38°20' S, as well as from his figures; figures c,d, and e represent fish 51, 60, and 100 mm TL from tip of mandible to caudal-fin fork (corresponding to standard lengths of about 47, 55, and 89 mm, from tip of upper jaw to base of caudal fin). Beaks of specimens f-h (170 mm to full adult) pertain to Scomberesox. Comparison of these three figures with our illustrations of growth changes in the four species (Figure 2 1 demonstrates agree- ment only with N. simulans. The divergent ap- proach toward hemiramphine beak structure in this developmental series of Nanichthys appar- ently did not disturb Liitken, for he showed in the same compilation of figures the development of Belone vulgaris from the beakless very young through the halfbeaked juveniles to the nearly full-beaked adult stage. In the lack of locality data it is not clear which species are represented by Liitken's figures a and b, which represent pre- juveniles, 16 and 30 mm in fork length, with al- most no beak development. The epochal treatise of Atlantic epipelagic fishes by Mui-ray and Hjort ( 1912), expanding that of Liitken ( 1880), recognized the preponderance of Scomberesocidae in the mid-Atlantic but failed to distinguish between S. sQi/ri/.s and N. simulans. Evidence in these classics, however, renders it clear that both accounts dealt with both species. Murray and Hjort's figure 541 of a 6. 2 cm saury (on p. 747) almost surely represents A', simulans by reason of the better development of the beaks at that size (although the body was drawn too deep). Their figure 542 is a copy of Liitken's figure 567 (discussed above). The well-filamented egg labeled "Egg of Scomberesocid" (fig. 531) was obviously misidentified and very probably represents an exocoetid (Orton 1964). The treatment of sauries by Murray and Hjort pertains almost wholly to young (the maximum size given, 50 cm, was pre- sumably drawn from some other source); they ^Marie-Louise Bauchot, Fish Division, Museum National d'Historia Naturelle, Rue Cuvier, 57, Paris, France, pers. com- mun 2 Mav 1968, 533 KISHEKY BULLETIN VOL 77, NO :i stated that only "young scomberesocids" were taken on the cruise. The accounts of S. sniirus by Bigelow and Welsh (1925) and by Bigelow and Schroeder (1953i definitely also involved N. simulans. The figure of the young, after Murray and Hjort, definitely rep- resents the dwarf species, as does the text account of the "young": "The most interesting phase in the development of the skipper is that its jaws do not commence to elongate until the fry have grown to about 1% inches (40 mm.), and that the lower jaw out-strips the upper at first, so that fry of 4 to 6 (100 to 150 mm.) inches look more like little halfbeaks ('Hemiramphus' stage) than like their own parents" (quoted from Bigelow and Schroed- er). These confusions were also expressed by Hil- debrand and Schroeder (1928). Inclusion of Scomheresox s. saiirua (Giinther 1889) in part, in the synonymy of this species, and the inclusion of this species in the British Museum collection, have been verified for us by G. Palmer'' by examination, with our findings at hand, of the following specimens: six young, .31-61 mm, from St. Helena; three. 64-68 mm, from "Atlantic" (Godfrey); three, 29-93 mm, collected by Jones; one of 96 mm of the two without locality collected by Haslar; one of 69 mm taken by Vallentin at 18*32' N, 2909 ' W; one of 52 mm, with two of S. .s. saunis . taken at Tenerife (Canary Islands) by the Chal- lenger; and one of 131 mm ( total body length— see p. 541) by G. Maul in Funchal Harbor, Madeira. Giinther ( 1866, vol. 6:257) reported Sci>mheresox saurus "From 1 '/2 to 7 inches long" from "Atlantic, 3°N. of the line," which, on distributional grounds, assuming correct latitude, would be expected to be Nanichthys. However, G. Palmer reports an ex- tant specimen 156 mm long, listed with three of 66-98 mm, from "Atlantic (Godfrey)" that is prob- ably the 7-in specimen, but Palmer finds it to be Scorn beresox. Zoogeographical considerations might lead to the citation in the synonymy of Nanichthys simu- lans of the material recorded as Scomberesox sau- rus by Arnoult et al. (1966) from off Liberia and Equatorial Guinea llles Principe], but Marie- Louise Bauchot (see footnote 4) has informed us that a reexamination of the five specimens in- volved led her to reidentify them as Strongylura senegalensis (Valenciennes) and Platybehme ar- galus (LeSueur). Although Valenciennes ( 1846) applied the name Scomheresoxscutullatus to what now seems surely to be Nanichthys simulans (q.v.), we regard the original Scomberesox scutullatum LeSueur as having been based on S. .s. saurus. The locality "Bank of Newfoundland" is in the range of that form and probably far outside the range of its dwarfed relative. The one pertinent key character given, that of 13 pectoral rays, confirms pertinence to Scomberesox. Eliissichthys Hubbs and Wisner, new genus New genus, Hubbs and Wisner. — Collette 1966:4, 6, 7, 15, 20 ( reduced meristics; neotenic | this seems to be the only published reference to Elassichthys as a genus]). Genotype. Cololabis adocctus Bohlke 1951. Diagnosis. — A greatly dwarfed scomberesocid (maximum known standard length ca. 68 mm), agreeing with Nanichthys in having a single me- dian ovary largely filling, when ripe, the expanded coelom, and the paired testes folded together into a single median band with the division on the right side. Gas bladder and lateral line scales obsolete. Upper jaw very broadly and evenly rounded in dorsal aspect and only moderately pointed in lat- eral view; lower jaw only moderately pointed at the tuberculate tip (Figure 4). Premaxillary and mandibular tooth rows very broadly separated at front. Counts minimal for the family: vertebrae 52-59, usually only 56 or 57; transverse scale rows along midlateral line 70-78; procurrent caudal rays reduced to only 2 or 3; rakers on first gill arch 15-21, usually 17 or 18. Derivation. — From the Greek, eKdmronw, smaller, less, and t\th''(r. a fish. Elassichthys itdocetiis Biihlke 195 I Figure 5B Scomhresox sp. — Kendall and Radcliffe 1912:84, 167 ( in part).'" ^G. Palmer. Department of Zoology. British Museum I Natural History I, Cromwell Road. London SW7, England, per.s, commun 3 Mav'l968. "Young of Scomheresiix saurus scomhroides may well have been included; only three specimens on Mu.seum of Comparative Zoology), among those listed, have been examined by us and aU were found to be E. adocetus from Albatross stations 46.57 i07°I2;iO" S. 84'09' Wi, 4708 (11 40' S. 96 .'").'")' Wl. and 47.30 ( 17' 19' S, 100°.52 '30 " Wi. Scomherescjx s. scomhroides also occurs in these areas. 534 HUBBS and WISNER REVISION OF THE SAL'KIE.S Cololabis saira (misidentification). — Schaeferand Reintjes 1950:164 (between California and Hawaii at 28' 22' N, 137"12' W; 25n4' N, 144°41' W; 23°52' N, 148°41' W; 23"04' N. 153°19' W; compared with "Cololahis adocetus." these records thought [erroneously! to confirm reference ofCololabis bi-evirostr-is to C. saii-a by Hubbs 1916:157 and by Schultz 1940:2701. Ramirez Hernandes and Gonzales Pages 1976:74 (reference to Peru only). Cololahis sp.— Clemens 1955:165 (3"3r S, 81 11' W [presumptive identification due to locality |i. King and Iversen 1962:301, tables 19-20, ap- pendix table 8 (one 86 mm specimen taken in Equatorial Counter Current) [identification presumed from locality |." Scomberesocidae. — Mais and Jow 1960:131 (02 54' S, 99 37' W) [identification presumed from locality |. Cololahis adocetus.— B'oUke 1951:83-87 (original description; comparison, phylogeny; from 160 misouthwest of San Juan, Peru ( 17 S,76'50' W) (holotype); and off Peru at 10°0r S, 80°05' W; west of Chincha Isles, Peru, 13=35' S, 76=50' W; arrested development). Knauss 1957:236 (in oceanic front at about 3 N, 120 W). Gosline 1959:73 (neotenic); Gosline and Brock 1960:128, 318 (Hawaii; compared with C. saira). Chyung 1961:277 (reference to Bohlke 1951). Koepcke 1962:197 (references; knownonly from Peru, 10 to 17° S). Clemens and Nowell 1963:251-255 (records offEcuador, Peru, Chile). Hotta 1964:4, fig. 22 (distribution off Peru). Orton 1964:144- 145, 148- 149 (description of pelagic and ovarian eggs from off Peru, 8°07' to 10' 51' W; range overlaps that of S. saurus; vertebral numbers). Lindberg and Legeza 1965:209 translation, 1969:201 (Peru). CoUette 1966:3, 15 (neoteny; meristic reduction; phylogeny; generic status). Ebeling 1967:599 (distribution mainly in cen- tral water mass in eastern Pacific Ocean ). Parin 1967b:150 (117 in translation) (larvae may be caught near surface at any time of day); 1967a: many pages (distribution in very warm water) Rass 1967:58, 60, 63-66, 129 (distribution). Parin 1968b:many pages (an epipelagic fish said to be limited to tropical waters of eastern Pacific and near Hawaii); 1968a: many pages, fig. 2,3, 5 (comparisons, relationships; distribution and ecology). ChirichignoF. 1969:40 (vernaculars in Peru, Chile). Parin 1969a:715, 719, fig. (epipe- lagial; distribution, dwarf fish, false pike; east- ern tropical Pacific); 1969b:577 (462 in transla- tion), fig. 2 (northern part of area surveyed off west side of South America; numerical abun- dance charted; as many as 1,000 trawled in 20 min with pleuston net south of Galapagos Is- lands). Ueyanagi et al. 1969:6-7, fig. 12 (occur- rence off Peru). Ueyanagi and Doi 1971:17-21, fig. 15 (distribution in southeastern Pacific mapped; characters distinguishing juveniles of C. adocetus from C saira and S. saurus). Ahlstrom 1972:1192, 1196, fig. 14 (occurrence of larvae in eastern tropical Pacific). Suda 1973:2134-2135, fig. 7 (range in eastern Pacific; dwarf species; not suitable for a commercial fi.shery). Chirichigno F. 1974:318-319, 331, fig. 628 (characters in key; Peru, 10° to 12"' S). Nel- son 1976:172 (neotenic). Parin 1975:314-316 (records near Equator at about 97= W). The Southern Subspecies of Scotnheresox iaiirns We have found that the disjunct, widespread, circumglobal Southern Hemisphere population of Scombereso.x saurus is slightly differentiated from the topotypic Northern Hemisphere Atlantic form, as Parin (1968a) has tentatively suggested. Before presenting the evidence we list, with anno- tations, the rather complicated synonymic refer- ences that apply distinctively to the southern form, and here eliminate references in which the names used are synonyms of the North Atlantic subspecies Scomberesox saurus saurus, namely Scombresox, Scomberesox, or Scombresose, equi- rostrum or aequirostrum, Scombresox or Scom- beresox rondeletii , or Scomberesox storeri. We have, however, retained carded citations to those references. Sconiheresnx saurus scotiihroides (Richardson 1842)'^ Esox saurus. — Schneider ;/; Bloch and Schneider 1801:394 (in part; "J. R. Forster MSS. II. 63"; New Zealand). 'The general area of the Equatorial Countercurrent, in which the small specimen was taken, is stated as between about 05° ani 10° S (fig. 12). No coordmat^s were given fer the capture but the area sampled within this current extended from about 108° to 160° W (fig. 4). 'The synonsTny of what we treat as the Southern Hemisphere subspecies of Scomfeert'soj: saurus lists in sequence of first usage the varied names that have been applied thereto, whether ongi- nally based on the Northern Hemisphere form or on Southern Hemisphere material. 535 FISHERY BULLETIN: VOL, 77, NO 3 Scombresox saurus. — Giinther 1866, vol. 6:257 ( in part; records from Cape of Good Hope only'. McCoy 1888:135, fig. 2 (description; Queens- land). Jordan and Evermann 1896:726 (in part; reference for S.forsteri only). Gilchrist 1901:152 (occurrence off South Africa). Miranda-Ribeiro 1915:22 (reference to C. Berg's original account of the species in South America); 1918:16 (characters and range, in part; Montevideo; no Brazil locality included). Barnard 1925:259- 260, fig. 16 (in part; references; characters; St. Helena Bay, Table Bay, and Cape Point to Mos- sel Bay, South Africa; New Zealand; Australia; synonymy; general remarks). Ehrenbaum 1936:75 (Pacific and Indian Oceans only). Bar- nard 1950:72 (characters; St. Helena Bay to Mossel Bay in South Africa, southern Australia, and New Zealand; large schools near surface; leaping; prey). Scomberesox saurus. — Berg 1895:25 (in part; Montevideo). Schreiner and Miranda-Ribeiro 1902:37 (in part; habitat: Atlantic from coast of North America to Montevideo (Berg), Africa and Europe). Gilchrist 1904:145-147, 152, pi. 10 (eggs and larvae; off Cape Point, South Africa). Devincenzi 1924:190 (reference to Berg; counts; apparently rare in Uruguay). Devincenzi and Baratini 1928:152, pi. 18, fig. 4, 5 (Uruguay). Hildebrand and Schroeder 1928:152 (in part; New Zealand). Pozzi and Bordale 1935:159 (35'30' S to Argentina, habitat). Fowler 1936:436-438, fig. 216 (in part; synonymy; de- scription based on North Atlantic material; South Africa record from Barnard 1925); 1942a (Brazil)-'. Sivertsen 1945:6 (in part; description; from stomach of Dininedia; North Atlantic; St. Helena, South Africa, New Zealand, S. Austra- lia). LozanoRey 1947:597 (in part; New Zealand and South Africa in range). Smith 1949 (and 2d ed., 1953):129, fig. 224 (along most of South Africa; remarks). De Buen 1950:92 (in part; reference to Montevideo reports). Fowler 1956:141-142 (characters; in part; South Af- rica; Indo-Pacific). Lopez 1957:145-151, fig. 1-8 (synonymy and records for South American 'Fowler entered, under the species name, merely "Brasil iRibeiro, 1915)," but Miranda-Ribeiro (1915). in his Fauna Brasiliense, Scombresocidae, p. 21. the 16th or 22d page of the book, gave as the basis for including the species in his treatise on Brazilian fishes the range statement; ". . . habita o Atlantico desde Cap. Cod. na America do Norte, costas da Europa e da Africa e foi constatado em aguas de Montevideo pelo Dr. Carlos Berg." This circumstance was probably the basis for the 1 isting of the Scomberesocidae in Brazil bv Fowler 1 1942b:.384l. Atlantic; mouth of Rio de la Plata at 36"'52' S, 54°02' W; development of beak; mucus canal system of head; digestive canal). Briggs 1958:264 (Atlantic, Indian, and western Pacific Oceans; in western Atlantic to Argentina). Wheeler and Mistakidis 1960:334 ( in part; Tris- tan da Cunha, record only). Clemens and Nowell 1963:253-255 (17°30' S, 7r30' W; 20°25' S, 70°43' W). Hotta 1964:4-7, fig. g. 2-5, table 1 (in part; distribution mapped, southern oceans). Parin and Gorbunova 1964:224 (translation, 1966:237) (Indian Ocean; mentions S. saurus having pelagic eggs in open ocean, reference to Haeckel 1855 and Sanzo 1940). Parin 1967a (translation 1971): many pages (in part; epipelagic fish; distribution in Pacific; develop- ment); 1967b:150 (117 in translation) (among most plentiful fishes in moderately warm wa- ters of both hemispheres; larvae common at sur- face day and night). Penrith 1967:524. 544-545 (Tristan da Cunha, at 37 05' S, 17 40' W [error for 12'=17' W); surface-living). Rass 1967:58-66, fig. 10 (in part; distribution in Pacific; general remarks). Parin 1968b (and translation 1970): many pages (in part; world distribution in epipelagic zone); 1968a:275-290,fig. 2-5 (inpart; development and numbers of gill rakers; dis- tribution, with records; synonymy); 1969a:719, fig. (in part; place in high-seas fauna; distribu- tion mapped in North Atlantic and in Southern Hemisphere); 1969b:577, 579 (462, 464 in trans- lation), fig. 2 (in part of area surveyed off west coast of South America; numerical abundance charted). Ueyanagi et al. 1969:6-7, fig. 12 (oc- currence in all southern oceans). Tortonese 1970:366 (in part; temperate region of whole ocean). Ben-Tuvia 1971:10, 29, 35 (cosmopolitan [in part]). Ueyanagi and Doi 1971:17-21, fig. 15 (distribution in southeastern Pacific mapped; characters distinguishingjuveniles of Cololahis adocetus. C. saira. and S. saurus). Parin and Andriashev 1972:963 (866 in translation) (along 26 W between 37' and 39 S, and along west profile off South America between 34 and 45° S; temperature from 14.3° to 20.4' C). Chigirinsky 1972:151-165, fig. 1-13 (size and composition in .southeastern Pacific); 1973:198-215, fig. (in part; "winter" range 5°-7° S in southeastern Pacific; spawning intermittent throughout year; stock and catch estimated). Ueyanagi et al. 1972:15-19, fig. 1-2 (size of fish graphed; dis- tribution in Atlantic Ocean mapped). Parin 1 973:261 -262 I in CLOFNAMh in part; southern 536 HUBBS and WISNER REVISION OF THE SAURIES form in synonymy; reference to Parin's (1968a) use of S. s. scombroides). Suda 1973:2134-2135. fig. 7-9 (in part; distribution of larvae and pre- adults; potential fishery). Kawamura 1974: many pages (in food of southern sei whale; seems to swarm at surface, probably at patches of Crustacea on which it may feed). Kusaka 1974:26, 111, fig. 163 (urohyal of 318 mm speci- men from off Cape Town similar to that of C. saira I. Dudnik 1975a:203-210 ( 182-188 in trans- lation), fig. 1-2 (limits of distribution of larvae, fingerlings, and juveniles in winter in South Atlantic from South America to Africa); 1975b:738-743 ( 503-506 m translation, in which names were misspelled Scombresox and Scom- bresocidae), fig. (S. saurus compared with Scomberesox sp. Parin [= Nanichthys simu- lans]; distribution in Atlantic Ocean). Robertson 1975:7, 18, fig. 4a (planktonic egg; offshore waters around New Zealand). Smith 1975:22 (southern Africa; Afrikaans and En- glish vernaculars). Wheeler 1975:324 (circum- polar in Southern Hemisphere; off South America, South Africa, South Australia, and across Pacific to American continent). Paxton in Allen et al. 1976:387 (references; circumglobal in Southern Hemisphere, including eastern Australia and New Zealand as S. forsteri; North Atlantic and Mediterranean). Sairis scombroides. — Richardson 1842:26 (syn- onymy; valid characters adopted'" verbatim from manuscript on "Esox scombroides , Solan- der, p. 40; Esox saurus G. Forster [MS], ii. t. 233; J. R. Forster, MS II 65, apud Bl. Schneider, p. 394 .. . lat39''2S,204'4=W, [sic] between New Zealand and New Holland .... The specimen figured by G. Forster was captured ... in Dusky Bay [New Zealand]. The aborigines named it 'he-eeya.' "). Scombresox scombroides. — Scott 1962:77, 1 fig. (brief description; western and southern Aus- tralia, Victoria, New South Wales, and Tas- mania; vernaculars). Scomberesox saurus scombroides . — Parin 1968a:284 (tentative name for Southern Hemi- sphere subspecies of S. saurus, based on fewer gill rakers). Chirichigno F. 1974:90, 318, 349, fig. 18-19 on p. 91 (characters in key; Punta Aguga. Peru, to Chile; Isla Juan Fernandez and |in error] Isla de Pascua)." Scombr-esox Rondeletti (misidentification on sub- species level). — Valenciennes 1846:475 (in part; Cape of Good Hope record only). Bleeker 1860:56 (Cape of Good Hope only). Scomberesox rondeletti . — Gilchrist 1901:152 (South Africa). Scombresox equirostrum (misidentification on subspecies level). — Valenciennes 1846:479-481 (description based on specimen from Chile re- ported by Guichenot in 1848). Guichinot 1848:318-319 (description; rarely found in Chile). Rendahl 1921:50-51 (Isla de Juan Fer- nandez; also off Peru, New Zealand, southeast Australia, and [in error] Japan). Scomberesox equirostrum. — Fowler 1940:757, fig. 27 (Valparaiso); 1944a:491 (Valparaiso and Isla de Juan Fernandez, Chile); 1944b:30-31 (synonymy; republished in book form under same title, 1945:78-79). Mann 1950:25 (key; dis- tribution, Arica to Valparaiso, Islas de Juan Fernandez; found in markets of central Chile, May-July; vernaculars). Fowler 1951:282 (in key; Chile). Mann 1954a:47, 79, 169-171 (de- scription; distribution; restricted to pelagic warm water, Arica and Islas de Juan Fernandez and [in error] Isla de Pascua; vernaculars); 1954b:77 (listed off Chile in subtropical waters). De Buen 1955:154 (listed off Chile as food of Germo alalunga I. Scombresox aequirostrum. — Gijnther 1866:258 (references; Chile; Chilean fish described by Valenciennes may prove distinct). Reed 1897: 18 (listed for Chile). Delfin 1900:4 (listed for Chile; generic name misprinted as Scomhresose). Quijada 1912:95 (Valparaiso). Scomberesox aequirostrum. — Delfin 1901:45 (synonymy; in part; Islas de Juan Fernandez). Quijada 1913:84 (listed for Chile; edible; com- mercial importance). Scomberesox storeri. — Storer 1853:268 and 1867:137-139 (status of LeSueur's "S. equiros- trum" from Chile). Scombresox forsteri . — Valenciennes 1846:481-482 (original description [indicated by "nob"]; re- ceived from Forster; New Zealand). Giinther 1866:258 (synomy; diagnosis; validity doubted; New Zealand). Hector 1872:118 (rare in New Zealand waters; compared with "Half Beak"). '"Not all "nomina nuda" as stated by Whitley (1968:351; applicable characters were given. "The Isla de Pascua record of a 480 mm "Scomberesox" listed by Wilhelm and Hulot (1957:1481 was referred to Belone iEurycauIust platyura by de Buen (1963a:16l, who, we presume, examined the specimen (43Cl. 537 FISHERY BULLETIN VOL. 77, NO ,1 Macleay 1881:244 (description; Melbourne and Sydney). Giinther 1889:34'^ (unable to separate young of saurus and forsteri). Hutton 1872:53 (description; 12-in specimen; New Zealand); 1889:283 (New Zealand). Sherrin 1886:305 (New Zealand). Hutton 1904:50 (New Zealand). Stead 1906:70 (Australia); 1908:39 (characters; immense shoals of half-grown fish inside Port Jackson Heads). Regan 1916:134 (northern New Zealand and Three Kings Islands). Phillipps 1921:120 (food value; highly esteemed edible fish at Bay of Islands; probably spawns in mid- May). Waite 1921:64 (South Australia; often netted with garfish); 1923:88, fig. 96 (length to 15 in; surface skipping and jumping). Scomberesox forsteri. — Brevoort 1856:281 (New Zealand; seems closest to S. saira). Jordan et al. 1930:197 (questioned synonymy with S. saurus: New Zealand). Munro 1938:55, fig. 389 (diag- nosis; habitat: New South Wales, Victoria, Tasmania, South and West Australia). Berg 1939:207, and 1941 (reprint):654 (closely re- peated species; New Zealand and southern Aus- tralia). Whitley 1948:15 (off Albany and Perth, Western Australia). Andriashev 1961:345, 348 — as "Scomberesox forsteri"; 397, 422, 424, 442— as "Scomberesox"; 421, 426, 442, 443, 445 — as "Scomberesox sp" (taken at "Ob" sta- tions in southern Pacific Ocean); 1962:285 (north of 46"S in "Zone of Scomberesox"). Whit- ley 1962:52, fig. (habits; characters: southeast Australia, New Zealand, and Tasmania to West Australia, and elsewhere). Moreland 1963:18, fig. (general remarks). Parin 1963:134, 139 (at- tracted to light at night). Heath and Moreland 1967: 16, fig. 17 ("needlefish" and other vernacu- lars; general remarks; New Zealand). Parin 1967a:58 (42 in translation) (doubtful status as species). Berman and Ryzhenko 1968:10, 12, fig. (young and adults off Chile and Perii; potential fishery). Whitley 1968:35 (synonymy). Scott et al. 1974:88 (descriptitm; distribution; West and South Australia, Victoria, New South Wales, and Tasmania; uncommon off South Australia). '^Giinther referred the pelade fr>' and young sauries i"up to Iva inche.s in length"!, taken in the Pacific Ocean, to S. fnrsten while acltnowiedging that he could not di-stinguish them from .S saurus. But he stated that these specimens were taljen m July 1875, during which month the ship was runnmgeast from Japan near .35 N, thence due south to Hawaii (Mosely 1879:495 and track chart; also p. 750 and Sheet 36 of Part' 1 of Vol. 1 ol Challenger Report I. Although the specimens are apparently no! extant in the British Museum (see footnote 5). it seems safe to conclude that the record was based on Colnlabis .■iairii- 538 Scomberesox sourus forsterii. — Chirichigno F. 1969:40, fig, 85 (vernaculars; Peru, Chile, Islas de Juan Fernandez; detailed description). Scomberesox stolatus. — de Buen 1959:262-264 (original description; synonymic references to Scomberesox and Scomberesox equirostrum and aequirostrum; types from 35°20' S, 75°23' W; vernaculars). Chirichigno F. 1962:2, 8-9, fig. 6 (Callao and Isla Chincha, Perii; from Arica to central zone of Chile; Islas de Juan Fernandez, and I in error] Isla de Pascua; not previously known from Peru). Koepcke 1962:196-197 (ref- erences; high seas; west coast of South America from central Chile to Callao, Peru; Islas de Juan Fernandez, and (in errorl Isla de Pascua [sec footnote 111). De Buen 1963b:81, 83, 85 (key; brief description; Antofagasta). Medina 1965:260-261 (habitat; central Chile from Cal- lao, Perii, and Juan Fernandez Islands, and |in error] Isla de Pascua). Cololabis saira (misidentification). — Chirichigno F. 1962:9, fig. 7 (description of young; Paita, Peru). Koepcke 1962:197 (in part; reference to Chirichigno's Paita record only). Fourmanoir 1971:492 (87 specimens, 8-30 mm, from 180 mi west of Port Macquarie, New South Wales, Aus- tralia). Scomberesocidae. — Lcinnberg 1907:15 (Straits of Magellan, "Smyth Channel, Eden Harbour"). Fowler 1942b:384 (Brazil, Patagonia, West Af- rica). Scombere.wx. — Bbhlke 1951:85-86 (Chile; Col- olabis adocetus compared). Needlefish.— McKenzie 1964:14, 1 fig. (in part; vernaculars; color; size; habits; New Zealand). Discussion of Synonymy. — The synonymy of Scomberesox has some complications but in gen- eral is relatively clear taxonomically and nomen- claturally. The name was spelled as Scomberesox twice by Lacepede (1803), hence can hardly be treated as a misprint, though in naming the species Scomberesox Camperii he gave the French vernacular as Scombresoce camperien. Many au- thors, beginning apparently with Rafinesque ( 1810), adopted the classically more correct but un- acceptable (unauthorized) emended spelling Scombresox for the genus, and this spelling is still occasionally followed in Europe (viz. Zoological Record (Pisces), 1956-59). The type-species of Scomberesox, by monotypy, is S. camperii Lacepede, a synonym of S. saurus saurus (Wal- baum). UBS and WISNER: REVISION OK THE SAURIES The earliest synonym, Sayris, was proposed by Rafinesque 1I8IO1, with the statement: "Cosris- l)(inde al genere Scombresox di Lacepede, il di cui Home essendo formate dall'unione di due altri nomi generici e talmente contra la leggi della nomenclatura zoologica, . . . ." Since Sayris was iihviously proposed as a replacement name for Scomberesox, it takes, according to Article 67 (i) of the International Code, the same type-species, namely Scomberesox camperii Lacepede. The type-species has been designated (Jordan and Evermann 1896) as Sayris "reciirvirostra = cam- peri," obviously on the basis of the original indica- tion of Sayris recurvirostra as a replacement name for S. camperii. This type of designation was re- peated by Jordan (1917). Jordan et al. ( 1930) gave the type as "S. recurvirostra Rafinesque = Esox saurus Walbaum," but Camperii is not an objec- tive synonym of saurus. Gramminocotus Costa ( 1862) is clearly a subjec- tive synonym of Scow beresox . The type-species, by monotypy, is G. bicolor, an obvious synonym of Scomberesox saurus saurus. The statement by Jordan et al. ( 1930) that Grammiconotus is "said to lack the air bladder" seems to have no basis other than the erroneously indicated lack of the gas bladder as a character of Scomberesox in the Mediterranean, from which the 40 mm type of G. bicolor came. Various authors have reported on the presence or absence of a gas bladder in S. saurus from the Mediterranean. Valenciennes (1846) based S.ffondeto?;; on the beliefthat it had no gas bladder; Giinther (1866:258) and Moreau (1881) accepted this action. Liitken (1880) and subsequent authors accepted the presence of the bladder, but Supino ( 1935) failed to find it. Scordia (1936, 1938) found it in specimens from Messina and Naples. Further supporting its presence, En- rico Tortonese'-' stated: "Personally, I believe it is present, as I have found it in all the dissected specimens from Nice and Genoa. Its walls are thin and easily broken; this may perhaps explain why it was sometimes overlooked." One of us (Wisner) hasfound the gas bladder in a 197 mm SLsubadult from the Straits of Messina, as has N. B. Mar- shall'-". There was also no basis for the indication (Jor- " Enrico Tortonese, Director, Museo Civico di Storia Natu- relle. 16121 Genova. Via Brigala Liguria N. 9, Italy, pers. com- mun. 8 July 1968. '^N.B. Marshall. Curator of Fishe.s. British Museum i Natural History '. Cromwell Road, London SW7, England, pers. commun 21 .June 1968. dan 1921) that the genus Grammiconotus lacks a beak (it had not yet elongated in Costa's type, "Long. coip. millim. 40"). The generic recognition by Jordan and by Golvan (1962, 1965) was an anachronism. JUSTIFICATION OF SUBSPECIFIC SEPARATION Parin ( 1968a) reported differences in the num- bers of gill rakers of Scomberesox saurus between 7 specimens from the North Atlantic and Mediter- ranean (average 40.75) and 64 specimens from the Southern Hemisphere (average 44.67). On this rather limited basis he concluded that the two populations may be separable, at least at the sub- specific level, and, if so, the southern subspecies should be named "S. saurus scombroides (Richardson)." Parin also stated: "There are no significant morphological differences between populations inhabiting southern regions of the At- lantic, Indian and Pacific oceans." We concur in this latter statement and include populations from the Northern Hemisphere (not included by Parin, perhaps due to limited material, seven specimens). Furthermore, we agree with Parin that the populations of the two hemispheres may be separable as subspecies and that the name Scomber-esox sau7-us scombroides (Richardson 1842) is applicable to the Southern Hemisphere form. While we are aware of the highly subjective criteria for subspecific separations, and despite the extensive overlap in counts of gill rakers be- tween populations of the two hemispheres (Table 7), we favor the distinction of the two populations as subspecies. We base this action both on proba- bly highly significant statistical differences (un- tested) in numbers of rakers and on the presently known distribution of the genus (see below). We cannot conceive of any recent intermingling across the equatorial region of the Atlantic Ocean, at least since the glacial period; the species does not occur in the North Pacific, and, presumably, the northern Indian Ocean is too warm for it. The statistical reasoning on which we base sub- specific distinction involves both a method of graphical analysis of variation (Hubbs and Perl- mutter 1942, revised by Hubbs and Hubbs 1953) (Figure 6) and a value, "coefficient of difference (CD.)," from Mayretal.( 1953); this latter value is derived by dividing the difference between means bv the sum of their standard deviations. 539 FISHERY BULLETIN: VOL, 77. NO, 3 Table 7. — Numbers of gill rakers, by areas, for the two Scomberesoz saurus subspecies. Scomberesox saurus saurus Scomberesox saurus scombroides Gill rakers Southwestern Atlantic Soulti Pacific' Atlantic' Atlantic canean' Total Atlantic Africa New data Par n (1968a) Ocean' Total 34 _ 1 1 _ 35 1 2 2 5 — — — — — — 36 4 4 3 11 — — — — — — 37 6 1 2 9 — — — — — — 38 8 5 4 17 — — — — — — 39 13 — 5 18 — — 5 1 — 6 40 13 4 3 20 — _ 10 2 — 12 41 13 2 3 18 — 1 23 4 — 28 42 3 1 2 6 1 6 21 5 3 36 43 5 — — S 1 4 34 7 1 47 44 2 1 — 3 2 10 19 2 8 41 45 1 1 8 8 17 4 6 43 46 _ _ _ 11 4 10 3 7 35 47 — — — 4 5 5 2 3 19 48 _ _ — 2 3 3 1 2 11 49 — — — — 4 3 — 3 1 11 50 — — — — 1 1 — 1 1 4 51 — — — — 1 1 — 1 — 3 N 69 21. 24 114 35 46 147 36 32 296 X 39.70 38.24 38.58 3919 4629 45,13 43 01 44,17 45,28 44,11 SD 2,13 2,61 2,08 228 1.93 2 38 2,35 2,95 2,76 2 52 'Counts by Parin (1968a 280, fig 3) for specimens 75 mm and longer are included mtfie above counts tor Northwest Atlantic (5 specimens) and Mediterranean (5 specimens) 'Data from Peru. Chile, Central Pacrfic, and Australia-New Zealand are combined since counts from each area are very similar, the means ranging from 42 87 to 43 08 gill rakers 1 ^ 2 ^^H 3*7 ^ 3 • 4 _^-_-_- 6 -^^^ 7 i« 35 3& 3r 38 39 40 41 42 43 44 45 46 47 4Q 49 50 5l GILL RAKERS Figure 6. — Graphed variation in numbers of gill rakers o{ Scomberesox saurus saurus and of S. s. scombroides. by area. Scomberesox s. saurus: 1— Northwest Atlantic, N = 69; 2 — Northeast Atlantic and Mediterranean, A^ = 45; 1 + 2 — total for Northern Hemisphere, N = 114. Scomberesox s. scombroides: 3 + 7— total for Southern Hemisphere, N - 296; 3— Southwest-central South Atlantic, N = 35; 4— Atlantic near South Africa, N = 46; 5— South Pacific (new data), iV = 147; 6— South Pacific (Parin 1968a), N = 36; 7— Indian Ocean, Af = 32 1 26 from Parin 1 1968a), 6 new data). In each sample the baseline shows the total range in variation, and the short vertical line the mean of the sample; open (white) bars del ineate 1 SDon each side of the mean, and the solid (black) bars 2 SE of the mean on each side of the mean. The difference between means for gill rakers (39.19 vs. 44.11) of the total populations of S. s. saurus and S. s. scombroides (Table 7; Figure 6, lines 1+2 and 3+7) appears to be highly sig- nificant, the probable odds (untested) being bil- lions to one against the two areas comprising a single, homogeneous population. Despite a large overlap in numbers of rakers, the calculated CD. 540 HUBBS and WISNER REVISION OF THE SAURIES value is 1.025, a value approaching subspecific distinctness (as interpreted by Mayr et al.), in that it indicates a joint nonoverlap of about 85%. Of even greater significance, perhaps, is the differ- ence in means (7.93 rakers) between populations from the southwestern-central Atlantic and the combined northeastern Atlantic-Mediterranean areas (46.29 vs. 38.36 rakers); the graphed data (Figure 6, lines 1 and 3) indicate again probable odds (untested ) of billions to one that the two popu- lations are not homogeneous; in addition, the CD. value of 1.88 indicates about 99% joint nonoverlap in numbers of rakers — virtually that of separation at the species level. As sampled (Table 7, Figure 6). the total popula- tion of S. s. saurus appears to be relatively homo- geneous, but that of S. s. scombroides may be less so. Heterogeneity of populations in the Southern Hemisphere is indicated by a difference of 3.28 rakers between the areas of southwestern-central South Atlantic and the entire South Pacific (new data) (46.29 vs. 43.01 ); this may indicate that little or no intermingling occurs around the tip of South America. Conversely, the close agreement in means for rakers between specimens from the South Atlantic near South Africa and from the Indian Ocean (45.13 vs. 45.28) may indicate that considerable, if not complete, intermingling oc- curs around South Africa. The entire South Pacific area (as sampled) appears to contain a homoge- neous population; a difference of only 0.21 rakers was found between samples of about 50 specimens each from the Peru-Chile, central, and Australia-New Zealand areas. DESCRIPTION OF GENERA AND COMPARISONS Inasmuch as we treat each of the four obviously distinct saury species as constituting a monotypic genus, the comparisons of these genera, as previ- ously discussed, and epitomized in Table 1, pro- vides a comparison oi Nanichthys simulans with each of the three other scomberesocid species. It certainly ranks as one of the two dwarfed species. The largest specimens of this species examined by us were taken in Funchal Harbor, Madeira ( 126.2 mm SL, Museo do Funchal No. 2866, shown in Figure 1, and 121.2 mm SL, BMNH 1953 ■ 3 ■ 13 ■ 7). No other specimens >101 mm SL (USNM 204257 ) have come to our attention and none other among hundreds examined by ushave exceeded 90 mm. Parin (1968a) recorded 90 mm SL as the largest of his material. Dudnik (1975b) reported that the longest of about 200 specimens of "Scom- beresox sp" was 1 12 mm. The occurrence of the two "giants" in Funchal Harbor leaves us to wonder if the inshore habitat may have led to increased or sustained growth. G. E. Maul''* has told us that the genus is rare near Funchal. Nanichthys simulans, unlike Elassichthys ado- cetus, has retained the lateral line; it extends to about midway between the origins of the pelvic and anal fins, but not, as in Sconiberesox and Col- olabis , to opposite some one of the anal finlets. The upper and lower jaws, instead of remaining short and pointed as they do in Cololabis. or short and rounded (in the upper) asin Elassichthys (Figures 5, 6), become definitely elongated as beaks, but remain shorter than in Scomberesox; the upper is about half as long and produced as the lower, and much less slender and fragile than they are in Scomberesox. Counts for N. simulans are given in Table 2 (gill rakers), Table 3 (fin rays), and Tables 4 and 5 (vertebrae), and are contrasted with similar data for E. adocetus and for the larger forms, C. saira and Scomberesox; numbers of gill rakers are given for both subspecies oi Scomberesox in Table 7. The pectoral rays ofN. simulans, numbering 10 or 11, average more than in Elassichthys (8-11, usually 9 or 10), but fewer than in Cololabis and Scomberesox (12-15 in each). The procurrent caudal rays number 4, rarely 3 or 5, vs. 2 or 3 in Elassichthys or 5-7 in Cololabis and Scomberesox. The vertebral counts are 58-62, mean 60.68, con- trasting with 54-59, mean 56.37, in Elassichthys, 62-69 in 3,160 specimens of Cololabis, with means of 66.05 for 248 counts for the northwestern Pacific and of 65.03 for 2,812 counts for the northeastern Pacific, and 66-70, mean 66.13, for 338 counts for Scomberesox (both subspecies). Scale counts (lateral midline rows) number 77-91 vs. 70-88 in the other dwarf species, E. adocetus, as mutually contrasting with counts of 128-148 in Cololabis and of 107-128 in Scom- beresox. Counts of gill rakers in Nanichthys (19- 26, mean 22.80) average higher than for Elas- sichthys { 15-21, mean 17.64), but much lower than in either Cololabis (32-43, mean 37.53) or S. s. saurus (34-45, mean 39.19) and 39-51 (mean 44. 1 1 ) for S. s. scombroides (Table 7 ). The ovary, as in Elassichthys, is single instead of paired (as '^G. E. Maul. Curator of Fishes. Museu Municipal do Funchal, Madeira, pers. commun. 5 May 1978. 541 FISHERY BULLETIN VOL noted below in the general description of the ovary in the two dwarf species). In life Nanichthys is silvery ventrally and later- ally, becoming greenish with brown specks dor- sally; this is also the basic coloration of the other three genera. In preserved specimens the anal fin is essentially colorless, but the dorsal, pectoral, and caudal fins bear microscopic spots of dark pigment along the edges of the outer rays. The caudal fin. in addition, is pigmented in the crotches of the first branching of the rays and sometimes in the second branching of both dwarf species (the resulting streaking shows in Figures 5, 8, 9). In preserved specimens of this (and of other) scomberesocid species, a dusky underlying streak parallels the dorsal margin of the body (evident in Figure 5). Elassichthys adocetus has basically the same coloration. JUSTIFICATION OF GENERIC SEPARATION In recognizing a separate genus for each of the four species of Scomberesocidae we are cognizant of the circumstance that we are in a period when lumping is prevalent. We hold, however, that the grounds for the recognition of the four genera ai"e compelling, and consistent with other generic rec- ognitions on similar grounds. The distinctive fea- tures stand out sharply in the generic comparisons (Table 1). The complete lack vs. strong development of the gas gladder and the single vs. paired ovaries, supplemented by a series of minor characters, primarily the striking differences in body muscu- lature (Figure 7), and bolstered by the vast differ- ence in body size, seem to provide fully adequate grounds for distinguishing both Elassichthys and Nanichthys from either Colo! abis or Scomberesox. The sagittal sections of the four genera of scom- beresocid fishes (Figure 7A-D). taken from close behind the bases of the pelvic fins, portray these striking differences. The 59 mm SL adult oi Elas- sichthys and 60 mm SL adult ofNanichthys clearly show the lack of the gas bladder; also, there is no evidence of even a weak septum that might indi- cate a paired condition of the ovaries. Even in the young of Cololabis (59.4 mm SL) and of Scom- beresox (59.7 mm SL) the roughly triangular ga^ bladder is plainly evident just above the liver and gut; these young specimens are too immature ti, have recognizable gonads. Also evident and notable is a difference in thi arrangement of the myotomes; those of the young Cololabis and Scomberesox (and of adults) are separated by distinct septa. However, in the adults of the dwarf forms the myotomes are much more massive and the dividing septa are greatly re- duced in number in Nanichthys (virtually non- existent in Elassichthys). Perhaps this reduction is a reflection of the weak-swimming, surface- pelagic habits of these small fishes. The development of filaments of a peculiar well-formed type on the egg of Cololabis strength- ens the basis for the separation of that genus from Scomberesox, with unfilamented eggs. The large literature on Cololabis and its great commercial importance are additional incentives for retaining the familiar and well-established nomenclature; Scomberesox now approximates qualification in both categories. The generic separation of the two dwarf forms also seems to be well justified. The feature of the well-developed beak in Nanichthys vs. its lack in Elassichthys (Figure 2 1 calls for generic separa- tion, as it does for retaining Cololabis distinct from Scomberesox. The apparent total lack of an external lateral line in Elassichthys and its con- siderable development in Nanichthys provides sustaining evidence. Furthermore, the high prob- ability that Nanichthys and Elassichthys are of separate origin (Figure 3), owing their resem- blances to convergent evolution, seems to us clinching reason for generic separation. Description of Gonads The one ovary and the two testes o( Nanichthys are essentially like those of Elassichthys (Figures 8, 9). Instead of being pendant from the dorsolat- eral walls of the coelom, they form, as they de- velop, a coherent median mass, occupying, with maturity, a very large proportion of the coelom from the middorsal line to the ventrally displaced liver, intestine, and other visceral organs. In the specimen figured for this discussion, the length of the ovary composes 38^^ of the standard length of the fish; the greatest depth of the ovary 20% of its length; and its greatest width 60% of its greatest depth. The development of a single functional ovary in "Scomber-esox sp" |= Nanichthys simulans\ has been noted by Dudnik ( 1975b), who, however, mentioned that "the second lovaryl is rudimen- tary and can barely be discerned" |a translation!. We. however, have found not even a rudimentary 542 HUBBS and WISNER: REVl.SION OF THE SAURIES •a E tn W 8 <^ ~. Q en — ^ .. >^ i CO X 60 2 *\ ; en 1 1 Ed K g 543 FISHERY BULLETIN: VOL. 77. NO. 3 a> a c I 2 a O I 00 u O -9 til U3 E E o i s a E 2: I 544 HUBBS and WISNER: REVISION OF THE SAURIES ovary in this species (nor in the other dwarf, E las- sie hthys adocetus). In cross section the maturing and mature ovaries of both dwarfs are rather ovate in section. They very nearly fill the whole coelom between the much expanded body walls, particularly in Elas- sichthys (Figure 8). As they ripen, the ova fill the entire ovary so tightly that many of the ripe ova and even some of those in developmental stages are compressed into angular forms throughout the ovary. Forward, the ovai-y narrows dorsoventrally where the liver broadens to fill much of the coelom. Gentle probing readily discloses that the ovary lacks any structural connection with the coelom wall (except at the genital opening), although, with development, the ovary completely fills the body cavity above the visceral organs and lies closely appressed to the body wall, both dorsally and laterally. Dislodging the ova by probing dis- closes no trace of any internal septum. The ova in the mature ovary of Nanichthys and Elassichthys appear on gi'oss examination to rep- resent at least four stages of development, but a major difference in size exists between the largest category (readily visible in Figure 8) and the next largest, as though an acceleration in growth pre- cedes the extrusion of the brood. Since the ova of the largest category are usually markedly irregu- lar in shape (presumably due to crowding), mea- surements are approximations. However, after discharge the ova are probably normally spherical rather than ovoid in shape, as the eggs oi^Cololabis saira have been described to be (Mito 1958; Mukacheva 1960). The largest egg size in the Nanichthys series studied ranged in diameter from 2.0 to 2.5 mm. The smaller and presumably younger size groups seemed to group around 0.80, 0.40, and 0.10 mm. Similar size groupings ap- peared to hold for Elassichthys. The positioning of the largest eggs in the ovaries of the dwarfs seems to be quite random among the smaller ones (Figure 8). These large eggs were noted to be arranged generally mostly two abreast (three abreast once in Elassichthys). The random distribution of the large eggs within an ovary otherwise filled with smaller eggs invites specula- tion on how the anteriormost eggs of the largest size category move past the smaller ones to become extruded. None of the eggs of the dwarfs, even of the largest and presumably soon-to-be-extruded cate- gory, show any sign of bearing filaments. Their surfaces, however, are sculptured with closely set, round, and extremely minute tubercles which are colorless (in preservative) and produce, under strong magnification, a finely pebbled effect. It has not been determined whether the single ovary of the two dwarfed scomberesocids is the result of the fusion of bilateral primordia oris due to the failure to develop, or to the atrophy, of one ovary. The presence of but one gonad in synentog- nath fishes has been reported. Collette ( 1968) indi- cated that in the Belonidae Strongyliira marina differs from a closely related species, S. timiicu , in having only the right gonad developed. Collette ( 1974) reported that in the freshwater needlefish, S. hubbsi, 48 males had both testes developed but 2 apparently lacked the left one, and of 45 females, 2 had a tiny left ovary but all others lacked any trace of a left ovary. In contrast with the ovary, the testis of both Nanichthys and Elassichthys . at apparent matur- ity, occupies only about one-third instead of about three-fourths of the height of the fleshy body (Fig- ure 9). The testis agrees with the ovary, however, in occupying virtually the entire ( limited ) width of the coelom, forming from body wall to body wall a compact and compressed organ of seemingly homogeneous reproductive tissue. However, close inspection and some probing with a fine dissecting needle clearly discloses that the dorsally rounded mass comprises both testes. As seen from the right side, on removing the body wall (Figure 9), a fine, somewhat wavy longitudinal line, nearer top than bottom, indicates that the essentially homogene- ous structure comprises the paired testes, and gen- tle probing confirms the indication. The left testis is definitely the larger, but both are well de- veloped and are obviously functional. The two are essentially co terminal along the ventral edge, but the left testis definitely and sharply overtops the right. Ventrally the two organs form, at about the same level, symmetrical ridges on a rather broad base. At front, the paired testes are clearly distinct as lobes, of which the right one ends distinctly as a point, at that side of the left one. Anterior to the end of the right organ, the left one broadens on the ventral surface and forms a pair of bilaterally paired ridges, the left one of which seems to struc- turally replace the lost end of the right testis. Mucus Pores and Canals of the Head Numbers and arrangement of mucus pores and canals of the head vary notably among the scom- beresocids (Figure 10, items 1-6). Adults of the two 545 FISHERY BULLETIN VOL 77. NO, H larger forms, Scomheresux and Cololabis (Figure 10. items 1, 41, have a much greater number and complexity of pores and canals on the side and particularly on the top of the head, than do adults of the dwarfed forms, Nanichthys and Elan- sichthys (Figure 10, items 3, 6). Also juveniles of the larger forms (Figure 10, items 2, 5) show a greater pore-canal development than do the adult dwarfs, although they are of virtually identical size. This reduction of pores and canals in the dwarfs may be interpreted as an arrested state of development, perhaps neotenic or paedomorphic in character, as very small (20-24 mm SL) speci- mens of the larger forms bear a pore-canal struc- ture similar to those of the adult dwarfs (Figure 10, items 3, 6); or, it may be that neither numbers nor complexity of pores is necessary at such small sizes and (perhaps) less active habits. Lopez (1957i provided the first figure of the pores and canals of the head of an adult (size not stated) Scornheresox sauriis ( = S. s. scomhroides) from near Nechochea, Argentina. Our specimen, from the Peru-Chile area, bears a much greater profusion ol pores and complexity of canals, par- ticularly dorsally. than shown by Lopez. Collette (1966) illustrated interorbital canals and pores of four species of belonid fishes. These canals, rather simple and unbranched, which he reported to be representative of the Belonidae, are basically like those of Elatisichthys and Nanich- thys, although those of the latter show slight branching (Figure 10, item 3). Collette (his figure 7D) figured a complete joining of the left and right canals dorsally on Behmion dihranchodon , with both median and lateral pores present. He re- ported this condition to be unlike that of any other synentognath. Despite the profusion of pores and canals atop the heads of Scomberesox and CdI- olahis (Figure 10. items 1. 4), no joining of the left and right canals is apparent, although some ca- nals very closely approach the median line. Lateral Line Scales The lateral line scales of Scomberesox and Col- olabis are basically similar, but those of the dwarfed Nanichthys differ notably, both in shape and in numbers and development of circuli ( Figure llA-C). We have found no trace of lateral line scales in Elassichthys. All scales were removed from within 1 cm anterior to the pelvic fin. The basic similarity in the scales of the three genera involves the secondary tube on each scale that leads posteroventrally from the main tube and opens to the external surface of the scale. The primary (main) tube of each scale, in contrast, overlies the lateral line canal which extends along the body. The lateral line scale of the adult Scomberesox (270 mm BL (body length); Figure llA) lacks cir- culi, but they are present, though very weakly developed, on fish about 200 mm BL. Development of circuli appears to decrease as the fish grows; the circuli on scales on a 100 mm fish are notably better defined than on the 200 mm specimen. These early developed circuli occur in areas rather similar to those that are better developed in Col- olabis. A principal feature distinguishing the Scomberesox scale from that of Cololabis is a well-developed baselike structure on the ventral aspect of the scale (Figure IIC). As the Scom- beresox scale is much more tenacious than that of Cololabis, perhaps this structure serves as an an- chor to the body. Another difference between the scales of Scomberesox and Cololabis is a narrow median band of tissue at about the center of the scale (and main tube) that does not absorb the weak solution of alizarin red S stain. When remov- ing it, the highly tenacious scale usually breaks at this band. The Scomberesox scale figured is about 0.9 mm thick at the main tube. The lateral line scale of the adult of Cololabis (262 mm BL; Figure IIB), in addition to differing in form from that of Scomfeeresojc, differs in having at least weakly formed circuli on the anterodorsal and anteroventral aspects (these circuli do not show clearly, probably due to a slight canting of the scale during mounting and to the extremely short depth of focal field inherent in photomicros- copy). The scale has a thicknessatthe main tube of about 0.4 mm. The circuli are better developed on smaller fish and extend farther posteriad along both the ventral and dorsal aspects of the scale in about the same areas as in the adult scale. Some, but notall, lateral line scales of adults of Co/o/a/);.s bear the nonstaining band of tissue found in Scomberesox, but it is much less strongly de- veloped. The lateral line scale of Nanichthys (106 mm BL; Figure IIC, from the 121.2 mm Funchal "gi- ant") differs notably from that of its two larger relatives. The shape is quite different and the cir- culi are much more numerous and more strongly developed and extend over most of the scale, being absent only on the central portion of the basal (exposed) area. The thickness of the scale at the 546 HUBBS and WISNER. REVISION OF THE SAURIES Figure lO. — Dorsal and lateral views of mucus pores and canals of heads of adults and young of scomberesocid fishes: (1) adult Scomberesox saurus scombroides , 240 mm BL; (2) young of S. s scombroides. 70.8 mm BL; (3) adult o(Nanichthys simulans, 70.0 mm BL; (4) adult of Co/o/a6issaira, 243 mm BL; (5) young of C. saira, 54.0 mm BL; (6) adult of Elassichthys adocetus , 54.6 mm BL. Each scale line represents 1 cm. 547 FISHERY BULLETIN: VOL. 77. NO. 3 B Figure ll.— Lateral line scales of adults: lA) Scomberesox saurus scombroides; (B) Cololabis saira; (C) Nanichtkys simulans. The apical (cov- ered) portion is to the left. All scale lines repre- sent 1 mm. No lateral line scales have been found on Elassichthys adocetus. 548 HUBBS and VVISNER REVISION OF THE SAURIES main tube is about 0.1 mm. The tube is relatively more fragile than it is in the larger forms, and there is only a hint of the stain-resisting band of tissue. Phar\ngeal Bones and Teeth The first pair of upper pharyngeal arches I bones) is absent in all the scomberesocid fishes. Also, the second pair of upper bones are so closely appressed as to appear as a single unit and are not notably larger than the third pair, which are not closely appressed; the lower pharyngeal bones are fused into one, as in the Synentognathi. Absence of the first upper pair of pharyngeals in synentog- nathous fishes has been reported by Collette ( 1966) who figured the pharyngeal bones and teeth of six species of the Belonidae: Belonion dibran- chodon, B. apodion, Potomarraphis guianerisis, Strongylura notata,Pseudo.stylusangiisticeps, and Xenentodon cancila. Of these six. only B. apodion and -Y. cancila lack the first (lower) pair of upper pharyngeals: they also lack the second pair, re- taining only the third (uppermost) pair. As figured by Collette, but not discussed, the pharyngeal teeth of these belonid species appear to have only a conical type of tooth, with no cuspate or lobate features. In apparent contrast, many of the pharyngeal teeth of the scomberesocid species treated below have more or less well-developed lateral lobes or cusps, or are distinctly tricuspid. Cololabis isaira, 281 mm SL, 225 mm BL, from the Gulf of Alaska (SIO 57-198). The greatest length of the lower pharyngeal arch is 12.8 mm. the greatest width 8.6 mm. The teeth are moder- ately strong and curved. The marginal ones are all slender and unicuspid but those within the margin in the wider part are definitely widened, slightly to greatly, medially, with usually on each side a marginal lobe grading from rudimentary to. rarely, a rather definite cusp. There is oftly a trace of alignment (the arrangement is more nearly quite indefinite). Along the interior, greatly nar- rowed half of the length, the teeth, reduced in size, are very roughly in three or four rows. The lateral teeth do not form a definite row and are not mark- edly enlarged. Toward the posterior margin the teeth are large and irregularly crowded. Most of the larger teeth bear a more or less well-developed median, lengthwise, rather rounded ridge. Each bone of the second pair of upper pharynge- als is 11.8 mm long and 3.0 mm wide. Anteriorly and marginally the teeth are slender, moderately curved, and almost strictly unicuspid. Over the major portion of each bone, however, the teeth are, for the most part, definitely tricuspid, with the lateral cusps submedian and occasionally rep- resented by weak to strong lobes. Between the left and right arches there is, posteriorly, a triangle of dermal ridges, medially a low ridge, and an- teriorly a high ridge reaching to the surface with a strong fimbriation. As in the lower pharyngeal, the teeth are crowded and irregularly show just a trace of oblique seriation. Each bone of the third pair measures about 2.3 ^ 6.7 mm. The teeth are nearly concealed in the strong fimbriation of the surface, and all are small, irregularly arranged, moderately curved, and un- icuspid. Elassichthys adocetus, 58.0 mm SL, 49 mm BL, from off Peru at 08°07 ' S, 84°58 "W (SIO H 52-380). The lower pharyngeals are about 2.6 mm long and 1.1 mm wide. The teeth are relatively few, not more than about 10 across at the widest part of the arch. Most of the relatively large teeth in the me- dian portion of the broad posterior region are broadened and to a varying degree tricuspid, with the central cusp much stronger than the lateral ones. The teeth along the posterior edge are rather broadly lanceolate rather than very slender as in Cololabis. Anteriorly, where the arch narrows, the teeth become weak. In the rows along the outer margins the teeth are relatively conical and mod- erately curved. The teeth across the posterior field are much larger than others and bear a median lengthwise ridge. Near the middle of the arch are only about four teeth in cross section. Each bone of the second pair measures approxi- mately 0.6 X 1.5 mm. The teeth are relatively robust and uniformly the sharp, definitely unicus- pid tip is bent sharply. On the broad part of the bone there are only about five teeth in cross sec- tion. A membranous septum, very weakly pat- terned, extends the whole length between the two bones. Each of the third pair of bones measures about 0.4 ■ 0.9 mm. The relatively few teeth are all unicuspid with the tips bent backward. Sconi beresox saurus scombroides . 290 mm SL, 205 mm BL. from off Chile. 34' 30 ' S, 79"30 ' W ( SIO 58-263). The lower pharyngeal has a midline length of 11.4 mm. a maximum width of toothed area (at posterior edge) of 7.3 mm. and a width 549 FISHERY Bl'LLETIN VOL over teeth at midlength of 1.0 mm. The teeth are strongly heterodont and are rather definitely aligned, especially marginally, in rows. The teeth along the posterior margin number 41; those near the middle on each side are in nearly a single series alternating in proximity to the edge, whereas those toward either end tend to be ar- ranged in oblique, separate rows of 2-4 teeth. All of these teeth are essentially erect, fairly stout, and pointed, with the tips not bent backward. The teeth along the two margins tend to form a rather even row; they are all sharply pointed, rather strongly bent backward, tend to flare outward, and are, in general, especially forward, larger and stronger than the teeth within; toward the an- terioi' angles of the arch the marginal teeth tend to have a rather weak lobe on each side below the tip, and thus intergrade toward the median teeth. In the anterior half of the length of the arch the whole set of teeth grade from nearly triserial to unise- rial. with only the very strong marginal teeth of each side occupying much of this space. After some intergradation, both anteriorly and laterally, the teeth occupying the major triangular part of the arch are dilated and bear on each side, well below the tip, a lobe or a cusp; they are strongly bent backward. Anteriorly the margins of the arch are rather strongly concave. The length of each dental surface of the second pair is 8.9 mm; the maximum width of each, near the posterior end, is 2.7 mm. The teeth are ar- ranged on each bone in about 16 rather regular rows extending from near the midline outward and backward in a weak curve. Teeth of reduced size, but otherwise similar, also curved, are found on a fimbriate pad immediately behind each bone. All of the teeth are bent backward. A number of teeth at the anterior end are simply conical, and especially strong. Virtually all of the other teeth, including those along the median and lateral edges, are tricuspid, with the median cusp very much stronger than the lateral pair, which arise well below the tip. The two bones are narrowly separated and a strongly fimbriate compressed membranous ridge intervenes, grading both for- ward and backward into several papillate rows. The length of each bone of the third pair is 5.8 mm, the width of each 1.9 mm. The small teeth ari.se from a strongly papillate surface. They are directed mesiad and are strongest on the median margin, but definitely weakening laterally. They are all conical, without any trace of marginal en- largement. Ncinichlhys siniulans, 85.0 mm SL, 68.0 mm BL. from the central South Atlantic. 24 02.5' S. 15 32.0' W (SIO 6.3-5461. The lower pharyngeal measures 1.9 ■ 3.3 mm. As in Elassichthys. but contrasting with the two large species, the arch is less attenuate forward and the posterior border is definitely convex instead of being slightly con- cave. There is no definitive alignment of the teeth. and a band about three or four teeth wide extends virtually to the fi-ont tip. The teeth rather regu- larly and strongly increase in size backward. About 20 teeth in one very irregular row. or in twn rows, occur along the posterior margin; these are essentially erect, mostly very large, relatively, and show barely a trace of the lateral enlarge- ments. Toward the front end the teeth are conical and less curved backward than the following teeth (excluding the posterior marginal ones). Most of the other teeth bear on each margin, well below the tip. either a lateral swelling or a definite cusp. Each second pharyngeal measui-es 0.9 « 3.1 mm. with the greatest width well behind the mid- dle. The teeth are scattered without definite alignment. Those in the narrow front end of the arch and those along the outer margin are conical or nearly so. with the tips bent backward, .some- what as in the other species. The remaining teeth, however, are vastly different, actually submolar. These rather lobular teeth seem to have been built on a much swollen and rounded version of the corresponding teeth in the other series, sometimes showing a trace of the lateral enlargements or cusps; but essentially they are irregularly round- ed domes, but grading forward, outward, and backward into the more conventional, weakly tricuspid type. Each third pharyngeal measures approximately 0.6 X 1.6 mm. The arch is widest behind the mid- dle. The teeth are rather hidden in the papillae and all are simply conic, weakly curved backward. They are quite strong along the inner margin but grade into extremely minute ones on the outer margin. DISTRIBUTION The distributions of the .scomberesocid fishes have been depicted by various Russian and Japanese authors. The Russian data are sum- marized by Parin (1968a. b, 1969a). Parin (1968a, b) received from us many of his data on "Scom- heresox sp" ( = Nanichthys simtilans) and on Col- nlahis ndncetus ( = Elassichthvsndoretus). Dudnik 550 HUBBS and WISNER REVISION OF THE SAURIES (1975a) charted the distribution of Scomberesox saurus ( = S. s. scombroides ) in the South Atlantic Ocean, and (1975b) of Scomberesox sp. in the North and South Atlantic. Ueyanagi and coau- thors have reported many captures of all the scomberesocid species, primarily juveniles and postlarvae, in the Pacific and Atlantic Oceans and the Mediterranean Sea. In Figures 12-17 we attempt to show the known captures of all four species of scomberesocid fishes. In each figure the solid circles represent material examined by us. The large open circles in the North Atlantic and southwestern Pacific Oceans refer to literature records (specimens not seen by us); we have not used this symbol for literature records from the Pacific coasts of North and South Figure 12 — Distribution of Nanichthys simulans. Solid circles represent material examined by us; solid triangles represent localities mapped by Ueyanagi et al. (1972); the large open circle in the southwestern Atlantic indicates 18 closely spaced collections (111 specimens), and the small open circles represent unpublished localities furnished by Parin; open squares refer to records mapped by Dudnik <1975b); letters L and M refer to records from Lampe ii914) and by Murray and Hjort (1912). The question mark near Madagascar represents Smith's 1955 record o{ Scomberesox saiinis from Aldabra Island, which seems to represent this species. The query in the Red Sea refers to Borodin's 1930 record of a yount; "Scomberesox saurus." 551 FISHERY BULLETIN VOL. 77. NO. 3 Figure 13. — Distribution ofElassichthys adocetus. Solid circles represent material examined by us; solid triangles, records mapped by Ueyanagi et al. (1972); open triangles, localities by Ahlstrom (1972); small open circles, unpublished records furnished by Parin. America because either we have seen many of these specimens or have numerous captures from closely adjacent localities. The sauries are essentially antitropical in dis- tribution. This is particularly true for two larger forms. Scorn beresox and Cololabis, which mostly inhabit cold to warm-temperate waters (Figures 14, 15). The dwarf genera Nanichthys and Elcifi- sichthys occupy much more tropical waters and occur much nearer the Equator than do their larger congenors. The one exception to this generalization is that of the northerly extension of juveniles and young of S. s. scombroides along the coast of Ecuador to about 02" S (Figure 15), where these young stages and the adults and young of Elassichthys have been taken together. This far northern extension of the young of S. s. scom- broides is interpreted as due to transport by the northerly flowing Pcrii Current. Along the coastof Peru and northern Chile the ranges of Elas- sichthys and S. s. scombroides overlap to about 22 S (Figure 17). 552 HUBBS and WISNER: REVISION OF THE SAURIES 60- rr h i ■\ \ 20- w ACT /| / ■> -^ — — 1 — 1h\ \ 1 ■ J ( ^ w 4 Q- 1 30- 20* 0 ; ic /i. 60* 70- 1 90* « 5-i U S , c r / ■\^ - tt '- 1 A 1 1 1 J I n \ 1 1^ 7 J=f ^ 1 if^ 4 TrtTW- \ 1. \ 1 1 I i 1 -ffZIy ^\ FIGURE 14— Distribution of the northern and southern populations o{ Scomberesca saurus in the Eastern Hemisphere. Solid circles represent material examined by us; small open circles, records published by Parin ( 1968a); large open circles represent other published records (specimens not examined by us); solid triangles, records mapped by Ueyanagi et al. (1972); small open squares, localities mapped by Dudnik ( 1975a), additional and closely spaced records by Dudnik off southwestern Africa are indicated by two open ellipses. Letters L and M refer to records published by Lampe (1914) and Murray and Hjort (1912). The far-southern locality off Chile for S. s. scombroides, at 47" S, 81" W (Figure 15), is based on seven juveniles (56-67 mm SL) in the Hamburg Museum (No. 10601) examined by us. This south- ern occurrence is not readily explained. It lies well within the portion of the West Wind Drift that forms the northerly flowing Peru Current; per- haps these specimens were waifs carried south into the edge of this current by the counterclock- wise southeastern eddy of subtropical water that extends to between about 20" to 40'-45 ' S and 120''-80° W. The southern localities listed by Parin (1968a) to 48° S, about 110° W, are apparently attributable to a similar extension of subtropical water (Figure 15). The questioned locality near the Straits of 553 FISHERY BULLETIN: VOL. 77, NO, :i Figure 15. — Distribution of Cololabis saira and of Scomberesox saurus in the Western Hemisphere. Solid circles represent material of C.saira in the North Pacific, S. saurus scombroides in the South Pacific, andS. s. saurus in the extreme northeastern Atlantic Oceans examined by us. For the two areas bounded by heavy lines the records for C. saira would virtually blacken the areas and are omitted. Solid triangles refer to mapped records by Ueyanagi etal. ( 1972) for C. saira in the North Pacific and for S s. scombroides in the .south; small open circles represent both published and unpublished records of S. s. scombroides by Parin; large open circles are for other published records; open diamonds refer to records by Ahlstrom (1972). The question mark near 'i'raits of Magellan refers to Lonnberg's (1907) record for a scomberesocid. The large open hexagon near New Guinea refers to the record of C, saira by Kailola (1974), Magellan (Figure 15) refers to a statement by Lonnberg (1907) in a report on fishes from the Straits (Smyth Channel, Eden Harbor): "In der Sammlung befanden sich ausser den oben au- fgefiihrten Spezies [Macruronus magellanicus n. sp. I noch Junge von mehreren Arten, die sich wegen der Jugend der Examplare nicht bestim- men liessen. Unter diesen fanden sich auch einige Reprasentanten fiir Scorn beresociihte . so dass sich die Zugehorigkcit dieser Familie zu der magalhaensischen Fauna als sicher annehmen lasst." We question Lonnberg's identification of "Scomberesocidae" at a locahty so far south, but we are at a loss to know with what other species his 554 HUBBS and WISNER REVISION OF THE SAURIES Figure 16. — Overlapping distributions of Scomberesocidae in the Eastern Hetnisphere. Lines sloping downward to the left refer to Nanichthys simulans; lines sloping downward to the right refer to Scomberesox saurus in the Atlantic and Indian Oceans. "young" specimens could have been confused. Mann ( 1954b, 1960) listed no scomberesocids or beloniforms from the Patagonian area. Also, there appears to be confusion as to the locality of the capture stated by Lonnberg: Smyth Channel and Eden Harbor appear to be about 240 mi apart. According to Defense Mapping Agency Chart 22ACO 22390, Eden Harbor mow Puerto Eden) lies on a narrow channel along the east side of Isla Wellington, about 49'09' S, 74 24' W. This is far inland from the open sea and is a seemingly im- probable place to find a synentognath fish. Smyth Channel ( Defense Mapping Agency Chart 22XH A 22404) opens to the Pacific Ocean at about 52°50' S, 73'50' W (about the center of its wide mouth) and extends northerly to about 52 23' S, where it merges with Mayne and Gray Channels. If scom- beresocid fishes of any size occur in the area, the mouth of Smyth Channel is a more probable place than the inland Eden Harbor. The taking of seven young of S. s. scomhroidet^ at 47 S, 81' W, cited above, lends some credence to the possibility of the 555 FISHERY BULLETIN; VOL. 77, NO. 3 FIGURE 17.— Overlapping distributions of Scomberesocidae in the Western Hemisphere. Lines sloping downward to the right refer to Cololabis saira in the North Pacific and near New Guinea, and to Scomberesox ssp. in the South Pacific and extreme northwestern Atlantic; lines sloping downward to the left refer to Elassichthys adocetus. species being taken in the wide oceanic mouth of Smyth Channel some 400 mi farther south. Our findings on the distribution of S. s. scom- broides westward across the South Pacific differ little from that shown by Parin (1968a). The northern subspecies, S. s, saurus, occurs widely in the North Atlantic Ocean, north of about 30' N, but rather sparsely in the central area, where it is very largely replaced by Nanichthys (Figures 12, 14, 16). It ranges along North 556 America from Florida (rarely) to Newfoundland, and well into the Gulf of St, Lawrence ( Vladykov and McAllister 1961) and to Iceland (Saemunds- son 1949). The species occurs uncommonly along the eastern shores of the United States south of New Jersey. It occurs at the oceanic islands of the eastern North Atlantic, throughout the Mediter- ranean, Aegean, and Adriatic Seas, the British Isles, and along Norway to near Nordkapp. It has been reported from the Barents Sea, and from the HUBBS and WISNER: REVISION OF THE SAURIES White Sea in Kandalaksha Bay, about 67° N, 32°45' E (Andriashev 1954, after Novikov). Berg (1939) reported it from the western entrance to the Strait of Matochkin Shar, Novaya Zemlya Island labout 73 = 16' N, 56°27' E); Andriashev (1954) gave the length of this specimen as 25 cm. Pre- sumably the species is rare that far north and is a summer migrant. However, it has been reported (Anonymous 1970) that four Russian vessels cap- tured 7 to 10 metric tons per vessel per day of "saury" in late September 1969 near Novaya Zem- lya. W. L. Klawe'*^ feels that these large catches of Scorn beresox so far north actually represented either "saida" (Pollachius virens, the Atlantic pol- lock) or "saika" (Boreogadus saida, the Arctic cod), and that the use of the Russian vernacular "saira" ( = saury) was either a misprint or misinterpreta- tion. The southern extension of S. s. saurus into the central North Atlantic, to 15° N (Figure 14) is probably due to the southeasterly flowing currents of the huge gyre that extends across the ocean between about 40° and 20° N; the southern border of this gyre forms the northern boundary of the west-flowing North Equatorial Current; its south- erly boundary reaches to about 5° N. Nanichthys is common in the more central parts of the North and South Atlantic Ocean but is not common in the Indian Ocean (Figure 12). We enter on the distributional chart (Figure 12) a question mark in the Red Sea on the dubious basis of Boro- din's (1930) record of "Scomberesox saurus, young" from the "Red Sea" (accepted by Fowler 1956). The record is questioned because Borodin's identifications have proved to be commonly inac- curate, and we have not seen the specimen (which has been reported to us as no longer extant in the Vanderbilt Museum). If the record was not based on a juvenile hemiramphid or other nonscom- beresocid synentognath, it may have been based on Nanichthys, which we have seen from Zan- zibar. We also enter a question mark (Figure 12) in reference to the record of S. saurus reported by J. L. B. Smith (1955). Smith" has stated: "With re- gai-d to the Aldabra record, I regret that we cannot find the specimen. In our field notes this species is entered as 'Juvs. in stomach of Tunny.' Neither my wife nor I can remember whether that material was kept or not; it probably was in a bad state." The records of capture of Nanichthys in the In- dian Ocean are too few to warrant more than con- jecture as to limits of distribution there; it is either uncommon or has been very infrequently taken. No specimens resulted from the broad station coverage of the International Indian Ocean Ex- pedition, 1963-64. N. V. Parin'* did not encounter any specimens of Nanichthys, although he did re- port many captures of S. s. scoinbroides (Figure 14). Sauvage (1891) listed "Scombresox saurus" from near Madagascar, within a rather broad area bounded by "3^ et 26^ paralleles et les 42^ et 65"^ meridiens." Misidentification is possible as Sauv- age included species of Belonidae, Hemiram- phidae, and Exocoetidae in his "Scombresocidae"; no size or number of specimens was given. In most of the records of Nanichthys from the North Atlantic Ocean, the greatest number of cap- tures lie within the large eddy system and easterly of about 40° W, extending to the African coast. The southern border of the range, ca. 10° N, is at about the middle of the North Equatorial Current, and the northern border, at ca. 35° N, at the northern margin of the eddy and the southern margin of the Gulf Stream and of its continuation — the North Atlantic Current. There is little difference in cur- rent structure between winter and summer in the southern portion of the North Atlantic (Anony- mous 1965), and the currents are relatively slow during both periods. Oddly, Nanichthys is in- frequently taken west of about 40° W, the most westerly occurrence being near St. Thomas Island, West Indies (Figure 12 1. Nanichthys appears to be more antitropical in distribution than does Elas- sichthys. Ueyanagi et al. (1972) mapped the oc- currence of a juvenile at about 02° S, 10° W (Figure 12). In the Atlantic, in both hemispheres, this dwarfed form has often been confused by authors with the young of Scomberesox. The material re- ported by Murray and Hjort ( 1912) ("M" in Figures 12 and 14), and by Liitken ( 1880) from the North Atlantic in part represent Nanichthys. Each au- thor stated that the young of Scomberesox were taken in great numbers in collections from the open Atlantic; each figured (as young of Scom- beresox saurus) the distinctive beak structure of '^W. L. Kla we, Inter- American Tropical Tuna Commission. La JoUa, Calif., pers. commun. 20 March 1970. "J. L. B. Smith, Department of Ichthyology, Rhodes Univer- sity, Grahamstown, South Africa, pers. commun. 20 November 1964. '*N. V. Parin, P. P. Shirshov Institute of Oceanology, Akademia 117218 Moscow. Krasikowa 23, U.S.S.R., pers. commun. 14 Sep- tember 1978. 557 FISHERY BULLETIN: VOL adult or semiadult Nanwhthya — the upper beak notably shorter than the lower. We have examined most, if not all, of these specimens and found them to be referable to Nanichthys. Also, most of the reports of Scorn beresox saurus from the South At- lantic and Indian Oceans by Lampe ( 1914) ("L" in Figure 12) may, on the basis of geographical evi- dence, be referable to Nanichthys. We have, how- ever, not seen the specimens, but many of Lampe's collections occurred in the area of overlap (Figure 16). Dudnik ( 1975a) reported on an extensive col- lection of "Scomheresox saurus" from the South Atlantic (about .3,000 specimens, from 8 to 460 cm). In general his data agree well with ours and with Parin's (1968a, b) but he shows (Dudnik 1975a, fig. 2) the species to extend northward to about 18° S along the coast of Africa. This is nota- bly farther north of the expected range but is well within that o( Nanichthys. He did not discuss the dwarf {"Scomberesox sp") in his study (Dudnik 1975a), submitted for publication on 20 January 1974, nor did he compai'e it with its larger relative, although presumably he was aware of the form and of Parin's 1 1968a) study for he submitted his own (Dudnik 1975b) concerning it on 20 Novem- ber 1974. As no tabular or descriptive morphologi- cal data were offered in the first study (on Scom- beresox saurus), it is not entirely clear whether or not Dudnik 1 1975a) dealt only with the larger form, for he indicated that only smaller specimens, larvae to juveniles up to 100 mm (a size range encompassing most adults of Nanichthys), occur- red north of 20° S. Also, in his later work on Scom- beresox sp. (= Nanichthys simulans), Dudnik (1975b) showed collections of the dwarfed form between about 10 and 15 S in this same area off Africa. The dwarfed form, Elassichthys adocetus, of the eastern Pacific Ocean also has been confused with the young of Cololabis .sa;ra. Roedel (1953) and Chirichigno F. ( 1962) reported C. saira (as young) from off northern Peru. Schaefer and Reintjes ( 1950) reported (as young of C. saira ) specimens of E. adocetus from between the Hawaiian Islands and the western coast of North America. Elassichthys adocetus appears to be less anti- tropically distributed than is Nanichthys simu- lans in the Atlantic Ocean. A few specimens have been taken between the two principal areas of occurrence north and south of the Equator ( Figure 13); perhaps these are strays from the main groups (presumably from the southern) and transported there by the complex current systems of the area and/ or associated with oceanic fronts, as reported by Knauss ( 1957) in the vicinity of 03° N, 120° W. An interesting aspect of the distributions of the northern population of £. adocetus is its absence from the large area bounded by about 1 15° W and the Equator. Also, it has not been taken within hundreds of miles of the coast of Baja California, Mexico. In contrast, the species is very common in the coastal waters of Ecuador and Peru. One reason for the avoidance (or absence) of the area westerly of Baja California may be the still cool water of the California Current, between 18° and 25° N. This broad current is evident out to about 120° W and flows southerly to about 22 N between January and June-July before turning westerly and mixing with the North Equatorial Current; from August to December these two currents merge at or north of 20° N. Temperatures within this large area range between 25 and 29° C (Wyrtki 1964) and are probably above the op- timum tolerated by the species. Also, this area is one of very low oxygen content (0.05 ml/1), but this may not be a factor in the distribution of E. adoce- tus as it is an entirely surface form and probably remains well above the upper depth limit of the O^ minimum layer, between 50 and 200 m (Wyrtki 1967). The occurrence of £. adocetus (and S. saurus scombroides ) near the coasts of Ecuador and Peru, and its westward extension of range to about 1 15 W near the Equator, are no doubt due to the still cool water of the Peru Current; the temperatures range to about 20-26° C in summer and 16 -24 C in winter, between about 0° and 22 S (Wyrtki 1964). In the northeastern Pacific Ocean the ranges of C. saira (again mostly juveniles and young) and the northern population of £. adocetus overlap in an extensive area roughly bounded by about 20 to 30' N, 115° to 155° W (Figure 17); perhaps the overlap is primarily seasonal but often the two have been taken together in the northern portion of the overlap area. King and Iversen ( 1962:320, app. table 8) reported one specimen (86 mm) of "Scomberesocidae" from the Equatorial Counter Current (ECC) in 1955-56. No coordinates were given but the collection was made between about 108° and 160° W within the ECC. the boundaries of which these authors indicated to be between about 5° and 10° N (p. 286, fig. 12). The stated size ("86 mm") is notably longer than the largest of hun- dreds examined by us (about 68 mm SL). but it can scarce! V be other than Elassichthvs, which is 558 HUBBS and WISNER REVISION OF THE SAURIES common within the ECC. The southernmost known occurrence of C. saira is some hundreds of miles to the north. Cololahis saira apparently does not occur south of about 20° N (Figure 15), based on our data and those of Parin (1960). North of this latitude it ranges throughout the North Pacific to the Aleu- tian chain, but apparently not into the eastern and central Bering Sea. In the far western area it oc- curs in the eastern portion of the Yellow Sea. the entire Sea of Japan to well along Sakhalin, into the southern Okhotsk Sea, and northerly along the Bering Sea coast of Kamchatka to Olyutorsky Bay, at about 60= N (Farm 1968a, b) (Figure 17). Along the North American coast C. saira is very common from Alaska to at least central Califor- nia, but only sporadically so to about the Cedros Island region of Baja California, Mexico; it is rela- tively uncommon south of that region, particu- larly adults, but young and juveniles have been taken at about 19° N in the eastern Pacific. Cololabis saira juveniles (8-30 mm) were re- ported from 180 mi east of Port Macquarie (New South Wales, Australia) by Fourmanoir (1971); however, we have examined these small fishes and determined them to be S. s. scombroides. One ap- parently valid capture of C. saira near New Guin- ea (kindly communicated to us by N. V. Parin, 14 September 1978) was reported by Kailola (1974): ". . . one specimen. East of Kavieng [New Ireland! (2°34' S, 150°49' E) Dipnetted by night light, 1967. — 205 mm SL." The count of dorsal and anal finlets (5 each) indicates the specimen is a scom- beresocid, and certain proportions listed can per- tain only to Cololabis: "Eye 5, 1.8 in snout. Snout 2.7 in head." falling far outside the range for Scomheresox of similar size. The stated size, 205 mm, is far too large (or Elassichthys. This locality (Figure 15, large hexagon) is about 1,800 miles south of any other known occurrence of C. saira in the western Pacific. Parin believes, andwe concur, that this specimen was very probably lost from a Japanese longline vessel; Fourmanoir and La- boute (1976) describe the use of frozen sauries (C. saira) as bait by longliners operating in the area. Intriguing questions arise concerning this ap- parently valid capture in the Southern Hemi- sphere. We assume that the specimen was alive ( at least it was not stated otherwise). Kailola ( 1974) postulated that "abnormal extensions of cold cur- rents south of the Equator may thus account for the southern record of the species." An alternative explanation is that the specimen was transported alive from northern waters in a bait tank aboard a vessel. However, C. saira does not keep well in live-bait tanks; they are "wild" and dash them- selves to death against the walls, particularly of small tanks. And, to our knowledge, there are no recorded instances of a Japanese longline vessel carrying large live-bait tanks. ACKNOWLEDGMENTS Our efforts have been aided by many persons — so many that no doubt we will fail to list at least a few; in that event we hereby express our great appreciation for any effort made to further our work. We are deeply indebted to our Russian col- league Nikolai Parin for deferring to us the nam- ing of his "Scombercsux sp" and for persuading his fellow- workers also to refrain; also, we are indebt- ed to him for providing many unpublished capture localities for all four species of the family. Our Japanese colleagues, Shoji Ueyanagi, Shigeru Odate. Keiichiro Mori, Hiroshi Hiyama, and To- kiharu Abe, have provided information on dis- tribution of Cololabis saira: Ueyanagi, in addi- tion, provided much information on Scomberesox, Nanichthys. and Elassichthys. We are very grate- ful to Philip Sloan, formerly a student at Scripps Institution of Oceanography, for his efforts on the Scripps expedition LUSIAD in gathering the nuc- leus of the material on which we base the new genus and species, Nanichthys sinnilans. Specimens and information have been provided by Bruce B. Collette and Robert H. Gibbs, Jr. lUSNM), G. Palmer (BMNH), Enrico Tortonese (Museo Civico di Storia Naturale, Genoa), W. Ladiges (ZSZM), P. Fourmanoir (New Caledonia), Frank Talbot ( AMS), Frederick H. Berry (TABL), Myvanwy Dick (MCZ). E. Bertelsen and J0rgen Nielsen (ZMUC), and Marie-Louise Bauchot (Pans). Leslie W. Knapp (SOSC) and Leonard P. Schultz ( USNM) have kindly provided much study material. We are grateful to Camm C. Swift (LACM) and Peter U. Rodda (CAS) for the loan of fossils that have been referred to the Scom- beresocidae. Bruce B. Collette critically reviewed the man- uscript and offered valuable suggestions. Eliza- beth N. Shor typed the final manuscript and otherwise provided assistance. To all these per- sons (and those we have forgotten) we offer our very great appreciation and deep thanks. 559 FISHERY BULLETIN VOL 77. NO 3 ADDENDUM Fossil Fishes from California Referred to Scomberesocidae We are uncertain of the synonymic status of the nominal genus Scomberessus. based on a fossil from the Miocene (Monterey) formations, intro- duced by Jordan (1920). By context, Jordan pro- posed Scomberessus as a new genus, as follows: "Scomberessus Jordan, 571 [referring to the same item in The Genera of Fishes \. orthotype SCOMBERESOX ACUTILLUS J, & G. (fossil). Differs from the living genus ScOMBERESOX in the much larger dorsal, of 16 rays." But an examination of the text and figures of the two fossil specimens described by Jordan and Gilbert ( 1919: 37-38, pi. XIV, fig. 2. and XVIII — Scomheresox acutilliis and S. edwardsi ) indicate a serious confusion. The one item of diagnosis (dorsal fin) was obviously drawn not from the account and figure of Scorn beresox acutillus Jordan and Gilbert ( 1919:37-38, pi. XIV, fig, 2 [the paratype]), but from the description and figure of Forfex hypuralis Jordan and Gilbert (1919:36-37, pi. XIV, fig. 3). The description of S. acutillus states only "dorsal obliterated," also, the paratype (a complete skeleton examined by us) shows no remaining trace of a dorsal fin. The de- scription of F. hypuralis lists the dorsal rays as "apparently I, 16 in number" and the figure shows a long-based dorsal of approximately the stated number of rays and beginning before the middle of the body (without head). The juxtaposition of the two figures on the plate presumably led the aged master astray. Despite the nonapplicability of the one stated character, the generic name Scom- beressus must, we assume, rest on the designated type-species, Scomberesox acutillus. Regardless, we are more concerned with the ref- erence of these fossils to the family Scomberesoci- dae. We have examined the paratype of Scom- beresox acutillus (a complete skeleton but with crushed head), and five essentially complete skele- tons referable (presumably) to S. edwardsi (the holotype is a head and anterior few vertebrae) and have failed to find any finlets — a key character of the family — this despite the listing by Jordan and Gilbert (1919) of". . . traces of five finlets" for S. acutillus (the paratype); under high magnification these traces proved to be isolated scales. David ( 1943) may have inferred the presence of finlets by listing counts forS. edwardsi of "Dorsal fin 14. V; anal fin 18. VI . . . ."As Roman numerals have long been used to designate spiny or unseg- mented rays, and as living scomberesocids and related fishes all have segmented rays, we assume that David was referring to finlets. However, on examination of David's and other material la- belled S. edwardsi, we find nothing to substan- tiate a count including any "V" or "VI," particular- ly for finlets. Each finlet of the Scomberesocidae and Scom- bridae (mackerels and tunas) arises from a single base (ray) that branches into a fanlike structure that is much more robust than a slender, single ray of the dorsal and anal fins proper. Since the individual rays of these fins are distinctly evident on some of these fossils, it is reasonable to expect the heavier finlets also to be preserved or that an imprint at least would have remained. The lack of imprint of finlets is substantiated by the absence of any (or imprint) of the supporting bones associated with them. In present scom- beresocids these supporting bones are robust, flat- tened laterally, and lie embedded somewhat parallel to the surfaces of the caudal peduncle rather than extending more or less vertically be- tween the neural and haemal spines, as do those of the rays of the main portions of the fins. Thus, since the supporting rays of the main portions of the fins are often visible in the fossils, it is reason- able to expect such rays of the finlets also to be visible, if present. In addition to the appai'ent lack of finlets on these fossils (labeled as of Clarendonian stage), there are notable differences in proportions in lengths of anal bases and caudal peduncle between them and present Scomberesox. In two fossils on which the anal fins appear to be entire ( none have complete dorsal fins) the length of this fin is slightly shorter than the length of caudal peduncle (23.7 vs. 26.5 and 28.5 vs. 33.2 mm). In present Scomberesox the caudal peduncle is about 2.5 times the length of either the dorsal or anal fin base, exclusive of finlets. In this regard the fossils approach the condition found in the Belonidae, wherein the length of the caudal peduncle is one- half or less as long as the fin bases; in Ablennes hians the peduncle is scarcely more than one- fourth the length of these bases. Thus, among known marine fishes with both jaws greatly pro- longed into beaks, these fossils are about midway between pre.sent belonids and Scomberesox in the ratio of lengths of caudal peduncle to the base of either dorsal or anal fins < exclusive of finlets in the latter group). An additional difference is a notable 560 HIIBBS and WISNER REVISION OF THE SAURIES reduction in numbers of vertebrae in those fossils with complete skeletons, 54-58 vs. 64-70 in pres- ent Sco7nbereso.x, and 62-69 in Cololahis. Due to the apparent absence of finlets and the discrepancy in lengths of caudal peduncle and anal fin base, and the many fewer vertebrae, it seems justifiable to remove these fossils from the family Scomberesocidae. To retain them therein would require acceptance of development of finlets and drastic modification of the peduncular region since the Miocene period (7-26 million years BP [Before Present]) and a gain of at least six verte- brae; we hold these to be improbable occurrences. In any event, the name Scomberessus appears to have no bearing on the new generic names pro- posed herein. Furthermore, we find no sound basis for even the doubtful reference of Praescomberesox paci- ^ci/s David (1946:58-59, pi. 2, fig. 3, and pi. 3, fig. 2) to the Scomberesocidae on the basis of isolated scales found in a core from oil-well drilling at a depth between 3,895 and 3,907 feet (holotype). LITERATURE CITED AHLSTROM. E. H. 1972. 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Biol, (for 1968i 25:252-255. 566 EFFECTS OF TEMPERATURE AND SALINITY ON PRODUCTION AND HATCHING OF DORMANT EGGS OF ACARTIA CALIFORNIENSIS (COPEPODA) IN AN OREGON ESTUARY John Kenneth Johnson' ABSTRACT Experimental results indicate that induction of dormancy in Acartia californiensis eggs is temperature dependent and occurs below 15^ C in two ways: 1 ) Cold adapted females spawn true resting eggs which exhibit major differences in hatching and survival rates from nondormant eggs under similar condi- tions. 2) Nondormant eggs spawned above 15° C may become dormant and have short-term viability at temperatures below 15° C. Salinity does not induce dormancy. Hatching results offield-collected resting eggs at naturally occurring temperature- salinity combina- tions demonstrate that termination of dormancy is also primarily temperature dependent. Salinity, however, regulates rate and success of hatching. In addition, heavy naupliar mortality occurs following hatching at low salinities. Substantial hatching must occur in the field over much of the year. Since subsequent survival and population growth depends on the presence of favorable temperature and salinity conditions, nauplii which hatch during the low salinity winter and spring months in Yaquina Bay must be lost. This phenomenon is viewed as a "leaky" population diapause. Resting eggs were also demonstrated for Epilahidocera longipedata and Eurytemora affinis, an occurrence previously undescnbed in the literature. Resting eggs have been known to be a common adaptation in freshwater zooplankton since the turn of the century (see reviews in Hutchinson 1967 and Elgmork 19671. The existence of a com- parable resting egg phase in the life cycle of marine neritic species was postulated for many years to explain the seasonal disappearance of coastal species from the water column (e.g.. Fish and Johnson 1937; Barlow 1955: Conover 1956). Preliminary evidence of marine calanoid resting eggs was first reported by Sazhina ( 1968) for the species Pontella mediterranea and Centropages ponficiis. Zillioux and Gonzalez 1 1972) conclusively dem- onstrated with laboratory and field evidence that the seasonal disappearance of Acartia tonsa , a common coastal species, coincides with the pro- duction of overwintering eggs as water tempera- tures fall below 14.5' C. Subsequent research has shown that egg dormancy is an important adapta- tion in many boreal and temperate neritic calanoids, including both summer-fall species (e.g., Tnrtanus fnrcipatus, Kasahara, Onbe, and Kamigaki 1975; Lahidocera aestiva , Grice and Gibson 1975) and winter-spring species (e.g., .4. 'School of Oceanography, Oregon State University, Corvallis, OR 97331. clausi , Uye and Fleminger 1976; C. ahdominalis. Pertzova 1974). Egg dormancy probably enables most coastal species to survive periods during which conditions in the water are unfavorable. Environmental factors such as temperature or photoperiod usually govern the induction of dor- mancy in arthropods (Lees 1955). Both the adult and/or the egg may be responsive to adverse en- vironmental changes. Egg dormancy may result from a physiological response of the female to a changing milieu which modifies the eggs. Con- versely, dormancy may develop as a response of the egg to changes in conditions as it sinks through the water column into the bottom sedi- ments. There is evidence for both mechanisms in marine copepods. Zillioux and Gonzalez (1972) demonstrated that the production of resting eggs by A. tonsa is a response of the female to low temperatures. However, Uye and Fleminger (1976) examined egg development of four Acar- tiaspecies (including A. tonsa) from southern California waters at various temperature and sa- linity combinations and concluded that dormancy is primarily a response of the egg to the milieu. Their results led them to hypothesize that expo- sure of the eggs to abnormal salinities may be necessary to induce dormancy in at least two of the species of Acartia . Once buried in the sediments. Manuscript accepted March 1979 nSHERY BULLETIN: VOL 77. NO 3. 1980, 567- FISHERY BULLETIN: VOL, 77. NO, :) egg dormancy is maintained by low oxygen levels (Kasahara, Onbe, and Kaniigaki 1975; Uye and Fleminger 1976). Light is also required to break dormancy in at least one species, A . clan si ( Landry 1975a; Uye and Fleminger 1976). Further work is required to fully demonstrate the factors regulating dormancy in coastal calanoids. A localized summer-fall population of A. californiensis in Yaquina Bay, Oreg., affords an excellent opportunity to examine this phenome- non, since the entire winter-spring period is passed in the resting egg stage. A field research program provided data for the correlation of popu- lation dynamics with temperature and salinity. Laboratory experiments were carried out to de- termine the relative importance of temperature and salinity in the formation and subsequent hatching of dormant eggs of A. californiensis . Analysis of the data provides additional informa- tion on the role of the female versus that of the egg in development of dormancy. Acartia californiensis , a newly described species (Trinast 1976), is useful for comparative studies in egg dormancy since it displays close affinities to A . tonsa in both physiological and morphological fea- tures. Earlier studies in Yaquina Bay (Zimmer- man 1972; Frolander et al. 1973; Johnson and Miller 1974; Miller et al. 1977) identified the species as A. tonsa in the belief that it represented a smaller, ecophenotypic variant of the larger, offshore, A. tonsa present in the northerly David- son Current during the winter months. Further- more, the unidentified "Acartia sp. I" discussed by Uye and Fleminger ( 1976) has been recently iden- tified as A. californiensis Trinast by A. Fleminger,^ thus permitting comparison of egg dormancy in northern and southern populations. METHODS The seasonal population cycle of A. californien- sis in Yaquina Bay was determined by the collec- tion of plankton samples twice weekly at Stations 21, 29, 39, 45, and 57 (Figure 1). Sampling was done from June to November in 1972-74 with a Clark-Bumpus sampler (mouth diameter 12.5 cm) fitted with a 112 ;um mesh net which quantita- ^Abraham Fleminger, Scripps Institution of Oceanography. University of California, La JoUa. CA 92037, pers. commun. June 1978. I24<'00'W FK,:l:RE 1, — Sampling stations for Acartia caltforntrnsis in Yaquina Bay estuary. Oreg. 568 JOHNSON EFFKCTS OF TEMPERATIRE AND SALINITY ON ACAHTIA CAUFdRMEXSIS EGGS tively retained all copepodite stages. Tows were oblique in a stepwise pattern from just above the bottom to near surface at midchannel. A cali- brated propeller flowmeter in the mouth of the net was used to estimate the quantity of water filtered. volumes filtered were typically 5-6 m*. Tempera- ture measurements and salinity samples were taken at the surface and just above the bottom at each station. Salinities were later determined by inductive salinometer in the laboratory. RESTING EGG PRODUCTION October Experiment Adult A. californicnsia were collected at Station 39 (Figure 1 ) on 9 October 1975, using a 239 ^m mesh net towed slowly at 1-2 m depth. Surface temperature and salinity were 14.9 C and 26.8"™., respectively. Laboratory cultures were estab- lished the same day by sorting 50 female and 25 male adults into each of eight 1,400 ml beakers containing 1,200 ml of Millipore^-filtered water (25"'i.i.i. Water temperature increased to room temperature (16.8' C±0.3°) during this time. Upon completion of sorting, all newly spawned eggs were removed by screening and discarded. Replicate cultures were then transferred to water baths and maintained at 21", 17\ 13\ and 9" C ( ±0.1°). Continuous overhead lighting (low level) was used throughout the experiment. Adults were fed daily with a mixture of Pseiidoisochrysis sp., Isochrysis galhana, and Thalassiogira fluviatilis at a concentration of approximately 200,000-250,000 cells • ml' Phytoplankton cultures were maintained in log- phase at 16.8 C. Viability of the algal species over the temperature range of 9 -21 C was not deter- mined but assumed to be unimportant in the ex- perimental design since A. californiensis adults were provided excess food daily. In addition, adult mortality was moderately low (estimated at ■20*5) during the acclimation and spawning period with similar losses observed in all cultures. Thus, selection of adults in response to tempera- ture or food during the acclimation period was not likely a factor in influencing the type of egg spawned. After the third day of adult acclimation, ac- cumulated eggs were removed by gentle screen- ^Reference to trade names does not imply endorsement by the National Marine Fisheries Service, NOAA. ing. The eggs were used in a preliminary experi- ment on hatching success which differed from the main experiment in that fewer hatching tempera- tures were tested for eggs produced at each accli- mation temperature. The main experiment was established with eggs collected on the eighth day of adult acclimation. Maximum egg age ranged from 5 days at 9° C to 1 day at 21" C because of differences in egg develop- ment rate as a function of temperature. Eggs from replicate cultures at a given acclimation tempera- ture were mixed together in a Petri dish for sorting by pipette. Water temperature was maintained as close as possible to acclimation temperature dur- ing sorting. Depending on the number of eggs available, 10-15 replicate batches of 50 eggs each were placed in small 6 ml Petri dishes ( 1 cm depth, 3.5 cm in diameter) containing 4-5 ml of Millipore-filtered water (25";...). Dish bottoms were marked in a grid for ease in counting at 25 • with a dissecting scope. Salinity changes caused by evap- oration were prevented by floating the small dishes in transparent, tightly capped 100 ml beak- ers filled with 80 ml of water (also 25'Kh,). Two and usually three or more replicate dishes of 50 eggs were then placed in each of five water baths at 21", 17 , 13 , 9°, and 5° C, respectively. This procedure was repeated for eggs produced at all four acclima- tion temperatures C2V , 17', 13", 9°C), resulting in an experimental design (Table 1 ) using over 2,500 eggs. Hatching success was determined daily by mak- ing separate counts of eggs remaining and hatched nauplii. Nauplii were captured and removed daily with a pipette. Every 5th day, water was changed by pipette with minimum disturbance to the re- maining eggs. Unhatched eggs were maintained at the experimental temperature well past the time expected for normal hatching (Table 2) and then transferred to a favorable temperature (21° C) to determine subsequent hatching success. November Experiment Animals collected on 4 November 1975 at Sta- tion 39 ( 12° C, 21%o) were used to repeat the exper- iment at the prevailing field temperature and sa- linity conditions. By this time, the field population of A. californiensiswas greatly reduced and egg production was assumed to be primarily resting eggs. Females were kept at 12° C and 2 l%u during transfer to the laboratory and subsequent cultur- ing. Eggs were collected on the fourth day of 569 FISHERY BULLETIN VOL 77, NO :l 5 3 to OD V 1h ^ 0) "ti ?n X « -g k t^ « o> S CO ki be 1 ^ c\i ■2 o O LO o> o . w tS| 0.0 ^^ 1 S *to •r "a. 1^ 6 CO Is 52 s H V a> c - ^ « -S 5 rt O" 0) S -^ U) "i ^ ^ "« O 3 c o if «E CVJ 1 s "5 c o O in S -M J 'tn It "0 ?n " & ■- T ■2 iS f^ CNJ ■§- c 1i in '■C eC s s &) ^^ ■^ I& (M^g ^ <" S >. _ S c o OD -ro ^1 eg b. X) c E q o C TJ .s 0 f 0 Si s e c B c 0) Q. a; > nj E E LU il il 0 s Oq. 2 at CO X 1- s O J= _ «j C 33 ■a 2 1) B ta " « 3 E 1. >5 3" UJ <5 "5 -J = s 0- O) CQ E o 0 in < (31 000000 ooooo 000000 000 ooocviCMcn mm 000000 ooooo O — f^'I'J'^ ^^ 0 r- '- in ^ c\j -- (\j n in r-- eg CD CD CD 0 O) en CD CD O) 0 CO (D CD CD 0> CD CD 01 CD (D 0 u^ eg Cn (D CM CM CM en ■^ in en en u? 0 0 01 CD 0 0 CD (D O) 0 0 O) CD 0 -^ 0 CO 0 0 C\J CD cn 01 r- r- h~ - CVJ CO ^ in CD ' ^ ^ h- '" in CO CO to m CD O) CO "" 0 CD 0 0 cn CD 0 r-> m (M "" in *" C) r- 0 0 CD 0 0 r^ Tl r 0 m — ±. OJ c (11 f. m F 5 cn u. Table 2- — Nondormant egg development time for A cart la tonsa and A. clausi as a function of temperature, and time that un- hatched eggs of A. californiensis were initially held at the same experimental hatching temperature (October expenmentl. Incubation lime (days) null Temp (' C) A fonsa' A clausi^ 21 ■17 C= lJ-9" C 21 13 12 5 20 17 1 9 1,5 3 20 13 3 1 22 11 11 9 85 38 15 15 5 45 1 120 120 spawning at 12° C and sorted into replicate batches of 50 eggs each. Hatching rate and success weredeterminedat2r'. 17", 15', 13°, 9\and5°C in 'Data based on prediction of Beletiradek function (Zillioux and Gonzalez 1972) ^Data Irom experimental observations of Landry (1975b) ^Temperatures at wtiicti A californiensis eggs were spawned 25\i) water. Other procedures were as described above. HATCHING OF RESTING EGGS COLLECTED IN THE FIELD A series of preliminary experiments (J. K. Johnson, unpubl. data) had demonstrated that resting eggs of A. californiensis and A. clausi occur in similar numbers in the surface sediments in the vicinity of Station 39 (Figure 1). Unfortu- nately, the resting eggs of the two species are not distinguishable from each other on the basis of diameter, shape, or color. Therefore, the following hatching experiments include resting eggs of both species at unknown ratios. Much information and insight were gained in spite of this serious ex- perimental limitation. Salinity Experiment Resting eggs were obtained by collecting mud with an Eckman-Birge grab 500 m upstream of Station 39 on 7 February 1976 during low tide. The upper 1-2 cm of sediments were saved for later screening. Temperature and salinity values near the bottom were 9.8° C and 4.1%o. An accompany- ing series of plankton tows from Station 21 to Station 45 verified that no copepodite stages of A. californiensis were present in the upper estuary, as expected from earlier field work. Acartia clausi was present in low numbers only at Stations 21 and 29 (<50-m"^). It does occur at Station 39 during January to April but only at extremely low densities (ca. 5-20 • m ') during periods of high tides (Zimmerman 1972). Thus, few recently spawned eggs were likely to be present in the sediments collected at Station 39. Sediment samples were maintained at field temperature (10° C) during transport to the 570 JOHNS(JN EFFECTS OF TEMPERATURE AND SALINITY ON ACARTIA (--Al.lFORyiENSIS EGGS laboratory and storage in the dark for 1 mo. Rest- ing eggs were removed (10 March 1976) by first sieving the sediments through 119 /xm and 64 /xm mesh nylon screens. This size fraction was diluted with water (5%"), stirred well, and allowed to set- tle. Appro.ximately 5-6 ml of the surface sediments were then slowly introduced by pipette onto the sui-face of 8-10 ml of a 2.8 M aqueous sucrose solution (suggested by Brewer 1964) in each of several 15 ml centrifuge tubes. Following cen- trifugation at 1,000-2,000 rpm for 1-2 min, rest- ing eggs of Acartm spp. and other species (includ- ing calanoids, harpacticoids, and rotifers) were removed by pipette from the water-sucrose inter- face. These eggs were nearly free of detritus. A thorough rinse with Millipore-filtered water (5'!?V^^ A 20- K^f ^^^xA^ V^^;£3. ■ 15- sJ "y ^\/ ''^t/ "^^H, *§.'' 10- / 29 ^^*^-— 30- » Ay^yvr?- Cx„- 20 /v -A A^^ ^^^v/^ ^jr^ 10- A^ 1 ^45 - 0 1 1 I 1 1 i I'l .. 1 ; .i .', 1 ; i M 1 S ig M ' 5 ■ n ' ^ IB I) Figure 2. — Seasonal population cycle o^ Acartia californiensis in Yaquina Bay ( I972i based on maximum abundance of adults and copepodites (I-Vi observed on successive sampling days. JUNE JULY AUG SEPT OCT NOV 1972 Figure 3.-~Temperature lAl and salmity (B) profiles at Sta- tions 29 and 45 during June to November 1972. Points represent means of surface and bottom values. Envelopes correspond to general range of most favorable physical conditions for Acartia californiensis population growth at a given time. 572 JOHNSON: EFFECTS OF TEMPERATURE AND SALINITY ON AC.ARTIA CAUFORNIENSIS EGGS 1972 Figure 4. — Annual profile of bottom temperature 1° C) and sa- linity (%»i at Station 39 in 1972. Values represent general range of temperature-salinity experienced by resting eggs m surface layer of sediments. December-May values from unpublished data of H. F. Frolander (School of Oceanography, Oregon Stat* Univ.. Corvallis. OR 97331). September (19°-22° C, 25-30%o) was followed by a gradual decline to complete absence in late November. Production of nondormant eggs re- mained important throughout September, as evi- denced by the large numbers of copepodites pres- ent in the water column. However, copepodite recruitment nearly ceased by the first week of October, indicating that most reproduction was likely in the form of resting eggs. Some nondor- mant eggs were still produced, however, since a small pulse of copepodites was seen in the last half of October. Mean temperature had dropped to 13°- 15° C at the end of September when recruit- ment began to fail. The population was gone by December at a field temperature of 9°- 10° C. Salin- ity remained high, relatively stable, and presum- ably in a favorable range (25-30'U) during the September-October decline and disappearance. Salinity began to drop only in November when A. californiensiswas essentially absent from the water column. Resting Egg Production October Experiment (Preliminan.) Eggs collected on the third day of adult acclima- tion to 21°, 17°, 13°, or 9°C had essentially similar hatching rates and cumulative hatching success at a given temperature to eggs collected on the eighth day . The similarity in results indicates that A. californiensis can shift from production of non- dormant eggs to production of resting eggs in only 1-2 days in response to a significant lowering of water temperature. The absence of significant changes in egg hatching time and viability with increasing adult acclimation time demonstrates that the eggs produced were not adversely affected by the rapid change in water temperature (2-4 h) at the beginning of the acclimation period. The only effect observed was an initially lower fecun- dity in those females which experienced the largest temperature changes ( 16.8° C to 21°C or 9° Cl. In these latter two cultures, fecundity in- creased with acclimation time. October Experiment (Main) Hatching successes of eggs spawned over the range of 9°-21° C give evidence that the type of egg spawned is a function of ambient temperature (Figures 5, 6). Experimental conditions and re- sults are also summarized in Table 1. Females which spawned at 21° and 17° C (typical midsum- mer temperatures at Stations 29-45) produced nondormant summer eggs that developed nor- mally at 21° and 17° C (Figure 5A, B). Develop- ment time was <36 h with nearly 100% of the eggs hatching. Lower hatching temperatures (13°, 9°, 5° C), however, were found to arrest development of summer eggs which then entered dormancy. The incidence of dormancy increased with de- creasing hatching temperature: eggs spawned at 17° C had a total hatching success of 71% at 13° C compared with 35% at 9° C (Figure 5C, D) and 5% at 5° C (Figure 6). Thus dormancy in summer eggs is a response to low, unfavorable tempera- tures and may occur independently of parental influence. More than adequate time (Table 2) was allowed in these experiments for "normal" hatching, given the prediction from a Belehradek function for A . tonsa (Zillioux and Gonzalez 1972) and the ob- served development rates for A. claiisi (Landiy 1975b). A subsequent increase in water tempera- ture to 21° C broke the dormancy of the summer eggs previously incubated at 13° and 9 C (Figure 5C, D). Hatching resumed within a few hours at a rate similar to that observed earlier at 17° and 21° C (Figure 5A, B). Mortality of summer eggs spawned at 17° C was low during the 1 1- and 15-day "holding" periods at 13° and 9° C (Figure 5C, D), evidenced by a final hatching success of 90-96% after increase to21°C. However, dormant 21° C summer eggs experi- enced substantial mortality during the 15-day 573 FISHEKY BULLETIN VOL. 77. NO, :i 5 10 15 20 Incubation Time (days) Figure 5. — Hatching success of Acartia californiensis eggs at: (A) 21° C, (B) 17° C, (C) 13° C, ID) 9° C in 25%« salinity. Eggs spawned at different parental acclimation temperatures of 21°. 17°, 13°, and 9° C. Spaw-ning temperatures are designated by I Si. Hatching temperatures increased to 21° C on day II iCi and 15 iDi holding period at 9° C (Figure 5D). Only GCK* of the remaining eggs hatched following the tempera- ture rise, resulting in a cumulative total of 74*^^. E o 20 Hatching Temperature (5°C) 2r(S) 17-(S1 ^-: -;-v- -:--:-4 .III/ 1 \ '< \ -^ 0 4 6 120 124 126 Incubotion Time (days) Figure 6. — Hatchmg success of Acartia californiensis eggs at 5° C in 25%o .salinity. Eggs spawned at 21°, 17°, 13°, and 9° C, Spawning temperature is designated by (S). Hatching tempera- ture increased to 21° C on day 120. Long-term survival of summer eggs was negli- gible at low temperature ( 120 days at 5° C). Only l'7r of the 17° C spawned eggs subsequently hatched at 21° C. Many of the eggs remained nor- mal in appearance, being greenish yellow, throughout the 120-day period. However, within 3-4 days at 2 rC, nearly all dormant summer eggs had disintegrated. Most eggs probably died long before day 120, given the high mortality of 21° C spawned eggs after 15 days at 9 C (Figure 5D). In comparison with dormant summer eggs, the eggs spawned at 13° and 9° C appear to be true resting eggs with an overwintering capacity. The final cumulative hatch of the two types of eggs was similar over the temperature range of 21 -9° C. However, there were major differences in hatch- ing rates between eggs spawned at 9°-13° C and 17°-21° C at all five hatching temperatures tested (Figures 5, 6). For example, the 9°-13° C spawned eggs required 11 and 20 days at 21° and 17° C, respectively, to reach the final comparable hatch of 87-99%. This period was 10-20 times longer than that required by summer eggs. While none of the 9°-13° C spawned eggs exhi- bited dormancy at 17° and 21° C, few hatched at the lower incubation temperatures. Only 3-49( hatched at 13° C in contrast to 70-90% for the summer eggs. Likewise only 0-1% at 9° C and 0% at 5° C hatched versus 35% and 5-109f, respec- tively, for the summer type (Figures 5D, 6). Temperature was increased to21°C on days 11, 15, and 120 for the 13°, 9°, and 5° C hatching treatments, respectively. Hatching resumed in all cases at a rate and with success similar to those of summer eggs. However, a l-1.5day delay occurred in each case before hatching resumed (Hgures 5C, 574 JOHNSON EFFECTS OF TEMPERATURE AND SALINITY ON ACARTIA CAUFORNIE.\SIS EGOS D; 6). This delay, absent from the data on hatching of summer eggs following an identical tempera- ture increase, is evidence of a difference in the character of dormancy in the two types of eggs. Resting egg mortality was low during the 11- and 15-day incubation periods (Figui'es 5C, D). Approximately 96'/c and SOf/c final hatch occurred for eggs spawned at 13' and 9 C. respectively. The somewhat lower viability of the 9 C spawned eggs was also seen at hatching conditions of 17' and 21' C (Figure 5A, B). Survival remained high (71'/f ) for 9° C spawned eggs following 120 days incuba- tion at 5" C (Figure 6). In comparison, the 13° C spawned eggs had only 30% survival. This sub- stantial difference in survival may not be impor- tant, as opposite results were found for the hatch- ing success of resting eggs from the preliminary experiment under equivalent conditions (9° C spawn = 45'7f ; 13° C spawn = 60''^ survival). The implication is that resting egg survival is about 50'/f after a 4-mo dormant period. In most cases, hatching success at a given tem- perature was similar for eggs of a given type (summer or resting) spawned at different temper- atures (Figures 5, 6). For example, 21 C spawned eggs displayed little difference in hatching time or success from 17°C spawned eggs at 21°, 17°. and 9° C. The discrepancy in summer egg hatching times and cumulative totals at 13° C was likely an ex- perimental artifact since it was absent in the re- sults of the preliminary expermient. Uye and Fleminger (1976) similarly reported finding no difference in hatching success at a given tempera- ture for A. claust eggs spawned at 17.5" and 13.5° C. A notable exception to this pattern occurred for 13° and 9° C spawned eggs which were incubated at 21° and 17° C (Figure 5A, B). In both cases, the 9° C spawned eggs had a higher initial rate of hatching than 13° C spawned eggs. By day 5, this was reversed, and the rate for 13° C spawned eggs exceeded that for 9° C spawned eggs. It is possible that some of the 9° C spawned eggs had an en- hanced metabolic rate relative to 13° C spawned eggs, caused by cold acclimation (suggested by Landry 1975b). Uye and Fleminger (1976) also found evidence that cold-acclimated eggs of A. tunsa, spawned at 6.5° C, tended to hatch more quickly at temperatures below 12.5 C than eggs spawned at 17.5° C. Long-term exposure to low temperature re- sulted in abnormal development for some resting eggs. This was only seen in 5-129c of the 9 C spawned eggs incubated at 9° or 5° C for 120 days. Abnormalities of the newly hatched NI nauplii ranged from mild to strong structural deforma- tion. Some nauplii possessed an enlarged labrum or fused appendages (e.g., second antennae and mandible); some lacked appendages of one side of the body. One nauplius had two severe constric- tions which divided the body into three lobes. Many of the abnormal nauplii were alive, though weak, at the time of observation. Uye and Fleminger (1976) also reported finding deformed NI nauplii and postulated that osmotic stress from abnormal salinities may have caused the deforma- tions. In this case, however, deformation must have resulted from long exposure to low tempera- tures, since salinity was maintained at a favorable concentration of 25%o. November Experiment Different hatching results were obtained using eggs spawned by females acclimated at the November field temperature of 12° C. Hatching patterns (Figure 7) indicate that both nondormant and resting eggs were produced concurrently in the population. This is in contrast to production of resting eggs only in the 13° and 9° C treatments of females collected in October for the main experi- ment (Figures 5, 6). The evidence for the presence of both egg types is the two different hatching rates which occurred at summer temperatures (Figure 7). The initial hatching at 21° and 17° C occurred within the first day, similar to summer eggs at identical temperatures (Figure 5A, B). "> — ' — r 10 15 Incubation Time (days) Figure 7. — Hatching success of Acartia califorrnensis eggs spawned by November-collected females at the field acclimation temperature of 12" C. Hatchmg temperatures varied from 21° C to 5" C; salinity was 25%o. Temperature increased to 21° C (de- noted by vertical line) after variable periods of incubation below 17° C. 575 FISHEKY BULLETIN VOL. 77. NO However, after reaching a total of 61-66% hatched, the rate decreased sharply with hatching continu- ing at a low, constant rate to a final total of 90-91% at day 16. The latter pattern resembles that found for resting eggs (13°, 9° C spawn) hatched at sum- mer temperatures (Figure 5A, B). A comparable 56% hatch also occurred at 15° C within the first 2.5 days. However, development then ceased until temperature was increased to 21° C. Thus, at all three temperatures, approximately 60% of the eggs behaved as nondormant summer eggs, while the remaining 40% had characteristics of resting eggs. Dormancy increased from 409i at 15"C to 98% at 5° C (Figure 7), presumably as a result of dor- mancy induced by low temperatures in otherwise nondormant eggs. This result is similar to that seen for summer eggs hatching at the lower tem- peratures (Figures 5C, D; 6). Egg viability during short- and long-term dor- mancy was determined by increasing temperature to 21° C on days 9, 11, 15. and 102 for the 15 , 13°, 9°, and 5° C hatching treatments, respectively (Fig- ure 7). Mortality was low during the 9-15 day incubation period at 15°, 13°, and 9° C with a final cumulative hatch of 85-91% . In contrast, only 45% of the dormant eggs incubated for 102 days at 5° C completed development into NI nauplii following temperature elevation. Probably few dormant summer-type eggs survived the long holding period at 5° C, given that about 40% of the eggs exhibited characteristics of resting eggs in 21°, 17°, and 15° C water. This conclusion is supported by the high mortality ( 99-100% ) found for summer eggs incubated at 5° C for 120 days in the October experiment i Figure 6). Hatching of Resting Eggs Collected in the Field Salinit) Expc-riment The effect of salinity on hatching of resting eggs collected from field sediments was initially deter- mined at 17" C, a temperature favorable for egg hatching (Figure 5) and population growth of A. californiensis (Figures 2, 3). Results presented in Figure 8 are the combined data for both A. califor- niensLs and A. clausi. since their respective over- wintering eggs could not be separated. Hatching occurred at all salinities from 23.5"'im to 0%o (Figure 8). Rates decreased only slightly with decreasing salinity from 23.5%o (37%'day ') - 20 0 y< ••^.^s:*-*"'*^--?"" 10 0%. ^__,„..— — * 8^" I50j^^ y ^^__,^--'''^ ^,.65 IT'C 125^^ x' /^ ,_- •'" - lif ^ / -'' — -— • 5 0 -\l/ ''< /" ^^^^-^ - /'/ '*/ -—-"^^ t'l !/ ---'"'Z^^ — '"'^^ °'" 0 5 10 1 1 1 r 15 IncuboTion Time Idoys) Figure 8. — Hatching succe,s.s of field-collected resting eggs of Acartia spp. as a function of salinity (0-23.5'Kki) at 17° C. to 12.5%o(31%-day'; day 2.5). Final hatch in this salinity range was 91-96%. Initial hatching rates below 12.5%ii decreased markedly, ranging from 26% -day"' at' 10%,, to 1.8% -day' at 0%„. These latter rates, while reduced, were nevertheless substantial over a 2-wk span. Overall hatching success by day 12 was 21%, 61%, and 88% of the resting eggs at 0"/oo, 5%o, and 8%o, respectively. Furthermore, hatching was continuing, even in freshwater, as indicated by the slopes of the curves, when the experiment was ended. Ii: com- parison, resting eggs of Tortanus forcipattis do not hatch in freshwater when temperature is favor- able (Kasahara, Onbe, and Kamigaki 1975). The retarding effect of low salinity on hatching appeared to be limited to the actual process of naupliar escapement from the eggshell. Em- bryogenesis proceeded at similar rates (subjective observations) in all treatments (0-23. 5%o), appar- ently independent of external salinity concentra- tion. Developmental arrest, when present, nor- mally occurred after the fully formed nauplius was visible inside the eggshell. Exposure to low salinity (0-5"/,)o) for varying periods during dormancy was not fatal for the majority of prehatch nauplii. In each case, high rates of successful hatching (Figure 9) quickly fol- lowed a salinity increase to 23.5%o. However, pre- hatch mortality of "holding" nauplii increased substantially as a function of salinity reduction when compared at equal time. This is seen in a final hatch of 79%, 71%, and 59%, following a salinity increase (day 12) to 23.5%ofor eggs previ- ously incubated at 5%o, 2.5%o, and 0%o, respec- tively. Thus, an approximate 10% increase in mor- tality occurred for each 2.5%n decrease in salinity below 5%(,. 576 JOHNSON: EFFECTS OF TEMPERATLTRE AND SALINITY ON ACARTIA CALIFORMENSIS ECWS Incubation Time (days) Figure 9. — Hatching success and viabi lity ( "holding" success! of Acartia spp. at 23.5%o (Figure IIC), diapause did not persist in eggs of either A. californiensis or A. clausi exposed to 5%o at 10° C. The reason for this difference is not known. While only 2'7f of the eggs had hatched, nearly all re- maining eggs had broken diapause and were in the final prehatch holding state many days before the temperature increase on day 13. The difference in the nature of dormancy is reflected by the rapid hatching rate with no delay period following the temperature increase. In spite of high viability seen after day 13, the termination of diapause and the failure to hatch at 5%o and 10° C demonstrate that egg survival of both Acartia species was short-term and limited by available energy re- serves. Posthatch naupliar mortality within the first 24 h as a function of salinity at 15°, 12.5°, and 10° C was very similar to that shown for 17° C (Figure 10). The mortality range in 15%.., 10%.., and 5%o water, for example, was 2-7%, 12-22%, and 80- 100%, respectively, as compared with 2%, 15%, and 78% at 17° C. Typically, the percent survival decreased slightly at a given salinity as tempera- ture decreased. Therefore, at salinities -10%ii, survival was high with mortality primarily in- creasing with decreasing temperature. Below lO'Km, the NI nauplii experienced increasingly heavy mortality primarily as a function of de- creasing salinity. Additional information on hatching behavior and fraction of A. californiensis resting eggs were obtained by a comparison of the proportions of copepodites reared from nauplii which initially hatched from unsorted egg mixtures at each temperature-salinity combination (Table 3). Hatching at the most optimal of the given experi- mental conditions for both species (15°C, 25-15%o) resulted in copepodite proportions of 51% and 62% A. californiensis. A similar percentage (54%) was observed at 12.5° C and 25"/oo. As these estimates are based on independent rearing treatments, it is reasonable to conclude that roughly 55% of the field resting eggs were those of A. californiensis. This result corresponds very well with other esti- mates of percent abundance determined in earlier unpublished experiments. Copepodites of A. californiensis were absent in the cultures which initially hatched in 10"/oo and 5'U at both 15° and 12.5° C (Table 3). As nearly all resting eggs were previously found to terminate diapause at these lower salinities (Figure 11 A, B), the absence of A. californiensis is the result of mortality during either prehatch holding or subsequent naupliar stages. This is verified, in part, by the increasing mortality of NI nauplii {Acartia spp.) below 12. 5"/(m (Figure 10). Further- more, hatching rate differences over the range of 25-10%ip were small as shown in Figure llA, B. For example, at 15° C, a total hatch of 86% and 81% was observed at 15%o and 10%o, respectively. Yet, the proportion of A. californiensis copepodites was 62% at 15"/oo and 0% at 10%.. (Table 3). Similarly at 12.5° C, only 6% survived to copepodites when hatched at 15"/.... as compared with 54% at 25%o. It must be reemphasized that the temperature and salinity values referred to here and in Table 3 are hatching conditions only. Rearing was under more favorable conditions (see Methods). Therefore, as Table 3. — Proportion of Acar/m californiensis and A. clausi copepodites that survived following hatching at 12 temperature-salinity combinations. Temperature and salinity levels for rearing to copepodite stages were gradually increased to 1.5° C and 25%o to increase p.">sthatch survival (see text for further details.. i(r c 12 5 C 15 C Sal.nity A clausi A calit A clausi A calil A clausi A calif iXo) n (°») (%) n (%) (%) n ("<.) 1%) 5 0 0 0 4 100 0 0 0 0 10 16 100 0 24 too 0 119 100 0 15 15 100 0 71 94 6 40 38 62 25 235 100 0 28 46 54 183 49 51 579 FISHERY BULLETIN: VOL diapause was ended at all salinities at 12.5°-15°C, it is evident that individuals hatching from rest- ing eggs of A. californiensis exposed to salinities below 15%o experienced early death, even when temperature and salinity were increased to more favorable levels following hatching. As a result, these data can be used to define minimal hatching conditions for growth to maturity and can be corre- lated with the fall disappearance and summer re- population of A. californierislfi in Yaquina Bay. Acartia californiensis copepodites were absent at all salinities at lO'C (TableS). Absence over the range of 25-10%(i was probably the result of con- tinued diapause of the resting eggs of A. califor- niensis . as previously demonstrated (Figure 1 IC). Some of the latter eggs may have hatched at 25%o, given the likelihood of a 62% hatch (Figure IIC) and an estimated resting egg ratio of 55% (Table 3). However, egg hatching at 15"/im and 10"/on (40- 33%; Figure IIC) can be completely attributed to A. clausi since it composed ca. 45% of the resting eggs. An unrelated but important observation con- cerns the hatching of a few Epilabidocera lon- gipedata Sato (= E. amphitrites McMurrick) 10° C, 25%o) and Eurytemora affinis (Poppe) (10-15° C, 5-25%o) from the unsorted resting egg mixtures used to obtain Acartia spp. ratios. Identification was made at the late copepodite stages. Neither species has previously been reported as possessing a resting egg stage. Both species are absent at Station 39 in Yaquina Bay during the winter months, insuring that the eggs were in diapause when collected. DISCUSSION Environmental Conditions Resulting in Egg Dormancy Many shallow-water neritic and estuarine calanoid species with multivoltine life cycles are now known to survive long periods of adverse environmental conditions by facultative produc- tion of resting eggs. Field observations and laboratory results have demonstrated that this is true for A. californiensis in Yaquina Bay. After 4 or 5 successive generations with substantial recruitment (July-September 1972; Figure 2), the planktonic population declined rapidly and was gone by mid-November. The failure of recruitment in early October coincided with a decline in temperature below 15° C. Salinity remained rela- tively high and stable at 25-30%.., during the popu- lation disappearance, implying temperature de- pendence for the production of resting eggs (Fig- ures 3, 4). Experimental results confirmed the hypothesis that diapause in A. californiensis eggs is essen- tially a response of the spawning females to low temperatures, similar to that shown for A. tonsa (Zillioux and Gonzalez 1972), Tortanus forcipatus (Kasahara, Onbe, and Kamigaki 1975) and possi- bly Pontella meadi (Grice and Gibson 1977). The shift from summer egg to resting egg production occurred between 15° and 13° C (Figure 5), a tem- perature range comparable to that observed in the field. Salinity was not a factor, since it was main- tained at a constant and favorable level (25%o) in all treatments. Food quantity and quality were excluded as factors by daily providing the adults with an ample ration consisting of three prey species. Photoperiod is known to influence induc- tion of diapause in some cladocerans (cf.: Daphnia magna, Bunner and Halcrow 1977; D. pulex, Stross and Hill 1965). However, it was eliminated as a possible extrinsic factor by the use of continu- ous lighting. The production of overwintering eggs was most likely initiated by changes, possibly hormonal, within the female in response to the extrinsic stimulus of adverse temperature. Extensive re- search on the physiology of insects has confirmed the regulation of diapause by hormones ( e.g.. Lees 1955; Slama et al. 1974). Moreover, Carlisle and Pittman (1961) found differences in forebrain neurosecretions between summer and over- wintering "dormant" CV copepodites of Calanus finmarchicus that resembled diapause in insects. Watson and Smallman (1971) similarly reported significant changes in small tissue patches in the head region of the cyclopoid copepod, Diacylops navus, that correlated with induction and cessa- tion of diapause. Since dormant egg production can be rapidly induced in A. californiensis by low- ering water temperature, it is probable that the controlling physiology is somewhat different. The temperature-dependent maternal role in the induction of dormancy in A. californiensis eggs is contrary to results reported by Uye and Fleminger ( 1976) for A. californiensis ( = Acartia sp. I) in a southern California lagoon. They con- cluded that egg dormancy in A. californiensis must occur independently of maternal influence since 90-100% of the eggs hatched at all tempera- tures in the annual field range (10°-25° C). Expo- 580 iHN'SON EFFECTS OF TEMPERATURE AND SALINITY ON ACARTIA CAUFnR.XIENSlS EGGS sure to salinity extremes was suggested as a possi- ble cause of induced dormancy. Their conclusion, however, was based upon the hatching behavior of A. californiensis eggs which were spawned at 17.5" C. On the basis of my observations (Figure 5), these latter eggs were most likely all summer eggs which exhibited increasing dormancy below 10' C. It is likely that female-induced dormancy would have been observed if a spawning temperature below 15 C had been used. Summer eggs of A. californiensis possess the capacity for short-term facultative dormancy when exposed to temperature below 15° C (Figure 5). Hatching resumed within hours following temperature elevation above 15° C. This type of arrested development, temporarily induced by unfavorable external conditions and ended with the return of a favorable environment, represents a state of "quiescence" as the term is used by An- drewartha ( 1952), Lees ( 1955), and Wigglesworth (1972) for other arthropod groups. Quiescence of nondormant eggs at low tempera- tures is probably a characteristic of most calanoid species which inhabit highly variable environ- ments such as estuaries and lagoons (Uye and Kasahara 1978). For example, Uye and Fleminger (1976) found that A. tonsa eggs which were spawned at 17.5° C (a favorable temperature) exhibited dormancy only at 7.5° and 5' C, a result which they also demonstrated for A. californien- sis. In both species, survival during dormancy at 7.5° and 5°C wasof short duration, since no hatch- ing occurred following a temperature elevation after 28-30 days. The lack of long-term viability is supporting evidence that the respective eggs were in a quiescent state and not true resting eggs. In each species, the percentage of quiescent summer eggs increased as temperature decreased. However, quiescence occurred at significantly higher temperatures in eggs of A. californiensis from Yaquina Bay, shown by a 359^ hatch at 10° C (Figure 5D), as compared with 1009c fortTie south- ern California population (Uye and Fleminger 1976). Both sets of eggs were spawned at 17 or 17.5° C. The considerable difference in thermal induction of quiescence in summer eggs may rep- resent a genetic gradient reflecting the latitudinal separation of the two populations. Selection for quiescence in this warmwater species is probably more important in Oregon estuaries because of lower water temperatures (2°-22° C range) and longer winters (Figure 4). Less of a selective ad- vantage would exist in California estuarine and lagoonal waters with a narrower annual range of 10°-25° C (from Uye and Fleminger 1976). Fur- thermore, any genetic gi'adient caused by differ- ential selective pressures would be reinforced by the localized confinement of populations within estuaries or lagoons, which must greatly reduce gene flow. The adaptive value of quiescence may be greatest in temperate estuaries (e.g., Yaquina Bay) where eggs in the bottom sediments typically experience large variations in temperature over successive tidal cycles. However, since viability of A. californiensis eggs in the quiescent state at low temperatures is limited to 1-2 mo, as shown above (Figures 5, 6) and in figure 5F of Uye and Fleminger ( 1976), the importance of quiescence in overwintering must be considered negligible. Summer and resting eggs of A. californiensis may cooccur in equal proportions in the cumula- tive spawn at temperatures below 15 C as shown in the November experiment with females which spawned at their field acclimation temperature of 12° C (Figure 7). Zillioux and Gonzalez (1972) re- ported similar spawning results for A. tonsa females at acclimation temperatures of 9°, 11.4°, and 14.5° C. In each case, approximately 50-60'7f of the eggs were nondormant and hatched. It is not known from these data if the same female can produce both egg types at once. It is likewise not known if a female producing only resting eggs at lower temperatures can switch back to summer egg production if temperature increased above 15° C. These questions will need to be resolved by observations on individual females. There is an apparent discrepancy between the November and October observations. Females col- lected from 15° C water in October produced exclu- sively dormant eggs when rapidly cooled to 13° or 9 C. It is reasonable to have expected all of the November eggs spawned at the field acclimation temperature of 12° C to have also been dormant, given the October results. Perhaps there are ef- fects upon the initiation of dormant egg produc- tion from both low temperature to which a female is fully acclimated and from sudden temperature reductions. Response to the latter stimulus would protect against more than usually moderate cool- ing rates in the fall. Given normal field conditions, however, there probably is considerable variation between individual females in the population in the threshold temperature which induces dormant egg production. As a result, cooccurrence of both egg types would be expected during a significant 581 FISHERY BULLETIN VOL 77, NO :i portion of the fall population decline. Some field evidence of this is seen in the weak pulse of copepodites found in late October, indicating that substantial hatching did occur below 15° C earlier in the month (Figures 2, 31. Termination of Diapause and Population Reappearance Hatching of field-collected resting eggs ofAcar- tia spp. at various temperature-salinity combina- tions indicates that termination of dormancy is essentially temperature dependent. However, hatching rates and survival are regulated by sa- linity. My conclusions with respect to A. cali- fornienf:is, based on the often disparate observa- tions, are: 1. Appro.\imate!y half of the experimental rest- ing eggs were A. californiensis. 2. Embryogenesis and hatching occurred at all salinities tested at 12..5'-15' C (5-257oo) and 17= C (0-23.5%"). 3. Diapause persisted at 10' C over the range of 10-25%o, while embryogenesis occurred at 5"U. 4. Hatching was retarded at low salinities, par- ticularly below 10"/oo. 5. Developmental arrest in low salinity nor- mally occurred at the last stage of embryogenesis. Viability of "holding" prehatch nauplii was limit- ed to 1-2 mo, depending on temperature. 6. Mortality losses were increasingly severe below 10""" for hatched nauplii and substantial for "holding" eggs. 7. No nauplii survived to reach the copepodite stages at salinities below 15%" at 12.5" C or at any salinity at 10"" C. Exposure to low temperatures over a prolonged period (comparable to cold stratification for seeds of many temperate, deciduous plants) is unneces- sary forthe release of diapause in A. californiensis overwintering eggs. This is probably the normal condition for most Acartia species (see Zillioux and Gonzales 1972 and Uye and Fleminger 1976). It is not universal, however, as the resting eggs of Po/!/e//amrarfi, a neritic species, require a chilling period before hatching can occur (Grice and Gib- son 1977). A similar requirement is implied but not conclusively demonstrated for resting eggs of P. mediterranea and Centropages ponticus (Sazhina 1968). Overwintering eggs of some freshwater calanoids (e.g., Diaptomus oregonen- s(.s, Cooley 1971 ) are also known to require expo- sure to low temperatures prior to hatching. While chilling is unessential for termination of diapause in A. californiensis resting eggs, some effects from chilling were observed. For example, all field-collected eggs were found to commence development at 12.5° C (Figure 11) while labora- tory-spawned eggs terminated diapause only above 15° C (Figures 5, 6, 7). Thus, exposure to winter temperatures appears to lower the hatch- ing threshold. The time required is unknown but may be quite short. Newly spawned resting eggs initially hatched at vei-y low rates when incubated at 17°or2rC(Figure5). However, after Hand 14 days of chilling, hatching rates approached those of summer eggs when placed in favorable temper- atures. The "holding" phenomenon induced by low sa- linities represents a second type of short-term quiescence in A. californiensis resting eggs. It dif- fers from the temperature-induced quiescent state seen in summer eggs in that quiescence does not set in until the final stage of embryogenesis. In addition, salinity-induced quiescence is much weaker, since hatching continues at low levels. In these aspects, it closely resembles the dark inhi- bition of summer egg hatching of A. clausi (Landry 1975a). Development of A. c/af/.s: eggs in the dark proceeds to the prehatch naupliar stage before "holding" occurs. Viability of eggs in this darkness-induced quiescence is even shorter than that of A. californiensis in low salinity-induced quiescence. Uye and Fleminger (1976) and my own data (unpubl.) indicate it is 20-25 days. On the basis of field collections in February, experimental results and the temperature and sa- linity cycles in the field, significant hatching (or embryogenesis followed by holding) of resting eggs must occur over much of the year. Low oxy- gen tension in sediments, while important in in- hibiting hatching (Kasahara, Onbe, and Kami- gaki 1975), is probably not a critical factor, since resting eggs in the bottom sediments are continu- ally exposed to oxygenated surface layers by turbulence and erosion. Termination of diapause does not always coincide with the presence of favorable environmental conditions for naupliar growth. Those resting eggs which undergo development and then either enter quiescence or hatch during the winter-spring months, a period of very low salinities, must be soon lost. Such a pro- cess would partially account for the seasonal de- cline in resting egg numbers in the sediments with 582 JOHNSON EFFECTS OF TEMPERATURE AND SALINITY ON ACAItll\ CAUFORNIENSIS EGGS increasing time as observed by Kasahara, Uye, and Onbe ( 1975). Successful repopulation is possi- ble at any point in spring that daily mean salinity is in excess of 10%i), which usually occurs in early June. Production of resting eggs in the annual cycle of A. californiensis is thus viewed as a "leaky" population diapause that is consistent with the opportunistic nature of estuarine copepod species. It is possible that the leaky character of the diapause is retained because of the occasional suc- cess of the early-hatching portion of the popula- tion in years with early termination of winter rains. In those years, this fraction of the popula- tion would be strongly favored by the end of the growing season because of its early start. In years with prolonged spring rains, the late-hatching fraction would be favored. Variations in the weather cycle, thus, may prevent development of absolute and restrictive requirements for termi- nation of diapause. ACKNOWLEDGMENTS I wish to thank Charles B. Miller for the invalu- able assistance provided in discussions of the experimental results and in reviewing the manu- script. Special thanks are also due Abraham Fleminger and Peter Sertic for their aid in resolv- ing the taxononiic status of Acartia populations from Los Penasquitos Lagoon, La Jolla, Calif, and upper Yaquina Bay. This research was supported by the Oregon State University Sea Grant College Program, under the Office of Sea Grant (NOAA), #04-6- 1,58-44094. LITERATURE CITED ANDREWARTHA. H, G. 1952. Diapause in relation to the ecology of insects. Biol. Rev. (Camb.l 27:50-107. Barlow, J. P. 1955. Physical and biological processes determining the distribution ofzooplankton in a tidal estuary. Biol. Bull. (Woods Holei 109:211-225. BREWER. R. H, 1964. The phenology of Diaptnnjiis stagnalis (Copepoda: Calanoida): The development and the hatching of the egg stage, Physiol. Zool. 37:1-20. BUNNER, H. C, AND K. HALCROW. 1977. Experimental induction of the production of ephip- piaby Daphnta magna Straus iCladocera). Crustaceana 32:77-86. BURT, W. v., AND W. B. MCALISTER. 1959. Recent studies in the hydrography of Oregon es- tuaries. Res, Briefs Fish Comm. Oreg. 7(11:14-27, Carlisle, D. B., and W. J. Pitman. 1961. Diapause, neurosecretion and hormones in Cope- poda. Nature (Lond.l 190:827-828. CONOVER. R- J. 1956. Oceanography of Long Island Sound, 1952-1954, VI, Biology o( Acartia clausi and A. tonsa. Bull. Bingham Oceanogr. Collect., Yale Univ. 15:156-233. COOLEY. J, M. 1971. The effect of temperature on the development of resting eggs of Diaptnmus oregonensts Lill; (Copepoda: Calanoidal. Limnol. Oceanogr. 16:921-926. ELGMORK. K, 1967. Ecological aspects of diapause in copepods. In Symposium on Crustacea, p. 947-954. Mar. Biol. Assoc. India, Symp. Ser. 2. FisH.C. J., andM. W.Johnson. 1937. The biology of thezooplankton population in the Bay of Fundy and Gulf of Maine with special reference to production and distribution, J. Biol. Board Can, 3:189- 322, FROLANDER, H. F., C. B. MILLER, M. J. FLYNN, S. C. MYERS, AND S.T.Zimmerman. 1973. Seasonal cycles of abundance in zooplankton popu- lations of Yaquina Bay, Oregon, Mar Biol (Berl.i 21:277-288. Grice, G. D., and V. R. Gibson. 1975, Occurrence, viability and significance of resting egg* of the calanoid copepod Labidocera aestwa. Mar Biol, (Berl) 3I:335-.337. 1977. Resting eggs in Pontella meadi (Copepoda: Calanoi- da). J. Fish. Res. Board Can. 34:410-412. HlTCHINSON, G. E. 1967. A treatise of limnology. Vol. II, Introduction to lake biology and the limnoplankton, Wiley, N,Y., 1115 p, Johnson, J, K,, and C. B. Miller. 1974. Dynamics of isolated plankton populations in Yaquina Bay, Oregon. Proc. 3d Annu. Tech. Conf Es- tuaries Pac, Northwest, p. 27-35. Oreg. State Univ, Eng, Exp, Stn. Circ. 46. Kasahara. S., T. Onbe. and M. Kamigaki. 1975. Calanoid copepod eggs in sea-bottom muds. III. Ef- fects of temperature, salinity and other factors on the hatching of resting eggs of Tortanus forctpatus. Mar. Biol (Berl.) 31:31-35. Kas.-uiara, S., S. Uye, and T, Onbe, 1975. Calanoid copepod eggs in sea-bottom muds. II. Sea- sonal cycles of abundance in the populations of several species of copepods and their eggs in the Inland Sea of Japan. Mar, Biol, (Berl,) 31:25-29, Landry, M, R. 1975a. Dark inhibition of egg hatching of the manne cope- pod Acartia clausi Giesbr. J. Exp. Mar. Biol. Ecol 20:43-47. 1975b. Seasonal temperature effects and predicting development rates of marine copepod eggs. Limnol. Oceanogr. 20:434-440. Lees, a. D. 1955. The physiology of diapause in arthropods. Camb. Univ, Press, Engl., 151 p. MILLER, C- B., J. K. Johnson, .-wd d. r. Heinle. 1977. Growth rules in the marine copepod genus Acartia. Limnol. Oceanogr. 22:326-335, 583 Pertzova, n. m. 1974. Life cycle and ecology of a thermophtlous copepod Centropages hamatus in the White Sea. [In Russ.l Zool. Zh, 53:1013-1022. SAZHINA. L. I. 1968. Hibernating eggs of marine Calanoida. Zool. Zh. 47:1554-1556. iTransl , 1969. Fish. Res. Board Can. Transl.Ser. 1259.) SLAMA, K., M. ROMANUK, AND F. SORM. 1974. Insect hormones and bioanalogues. Springer- Ver- lag. N.Y., 477 p. STROSS, R. G., and J. C. HILL. 1965. Diapause induction in Daphnia requires two stimu- li. Science (Wash., D.C.i 150:1462-1464. TRINAST, E. M. 1976. A preliminary note on Acartia californiensis. a new calanoid copepod from Newport Bay. Cali- fornia. Crustaceana 31:54-58. Uye, S., and a, FLEMINGER. 1976. Effects of various environment factors on egg devel- opment of several species of Acartia in southern Cali- fornia. Mar. Biol. (Beri.) 38:253-262. fishery bulletin: vol. 77, no. 3 Uye, S., and S. Kasahara. 1978. Life history of marine planktonic copepods in nentic region with special reference to the role of resting eggs. Bull. Plankton Soc. Jpn. 25:109-122. Watson, N. H. p., and B. N. Smallman. 1971. The physiology of diapause in Diacyclops navus Herrick (Crustacea, Copepoda). Can. J. Zool. 49:1449- 1454. wigglesworth, v. B. 1972. The principles of insect physiology. 7th ed. Chapman and Hall, Lond, 827 p. Zillioux, E. J., AND J. G. Gonzalez. 1972. Egg dormancy in a neritic calanoid copepod and its implications to overwintenng in boreal waters. In B. Battaglia (editor), Fifth European Marine Biology Sym- posium, p. 217-230. Piccin Editore, Padova, Italy. Zimmerman, 8. T. 1972. Seasonal succession of zooplankton populations in two dissimilar marine embayments on the Oregon coast Ph.D Thesis, Oregon State Univ., Corvallis, 212 p. 584 AERIAL CENSUS OF THE BOTTLENOSE DOLPHIN, TURSIOPS TRUNCATUS, IN A REGION OF THE TEXAS COAST Eric G. Barham,' Jay C. Sweeney,^ Stephen Leatherwood, Robert K. Beggs,'' and Cecilia L. Barham' ABSTRACT On five replicate aerial surveys in late March 1978, the bottlenose dolphin. Tursiops truncatus, herds were sighted and their numbers estimated in 21 strip transects flown across bays and channels between barrier islands and the coast from Port Aransas northeast to Matagorda, Texas. The transects were spaced at 4.63 km intervals and herds were scouted in about 800 m wide strips totaling 436 km in length, providing approximately 17% coverage of the area. On surveys 1-4 (survey 5 was excluded from , population calculations because it was conducted in adverse weather) 133 bottlenose dolphin herds were sighted, containing an estimated 916 animals. Within these strips the mean heard size was 6.95 animals and mean herd density was 0.0947/km^, extrapolating to a population estimate of 1,319 dolphins and a density estimate of 0.752/km^ for the entire area. These figures are relatively high in contrast to recent studies in other environments. About half the herds were feeding and approximately one- third were traveling. Sightings were most frequent in ship channels, shallow areas inside barrier islands, and near shore. There were several sources of bias in our measurements, and we consider the results to be conservative. In the waters under jurisdiction of the United States, live capture of marine mammals is now limited by law to those species that are used for public exhibition and scientific research. With the exception of certain pinnipeds, the greatest de- mand is for the bottlenose dolphin, Tursiops trun- catus Montagu, the most tractable of the smaller cetaceans. This recent management regime has generated a need for assessment of marine mammal stocks that consider population size and reproductive rates of potentially impacted species (Odell et al. ). Obviously, rigorous density estimates are an es- sential starting point for such studies, but despite the long history of a live fishery for bottlenose dolphins (Townsend 1914) there are scant popula- 'Southwest Fisheries Center. National Marine Fisheries Ser- vice. NOAA, P.O. Box 271. La Jolla. CA 92038. ^Dinnes Memorial Veterinary Hospital, 16133 Ventura Boulevard, Encino. CA 91436. ^Biomedical Branch, Naval Ocean Systems Center, San Diego, Calif.; present address: Hubbs-Sea World Research Institute, 1700 South Shores Road, San Diego, CA 92109. "Sea Arama Manneworld. P.O. Box 3068. Galveston. TX 77552. 'Department of Fisheries and Wildlife. Oregon State Univer- sity, Corvallis, OR 97331. «Odell. D. K., D. B. Siniff, and G. H. Waring (editors). 1975. Tursiops truncatus assessment workshop. Final Report. U.S. Marine Mammal Commission, Contract MM 5AC021. 141 p. Rosenstiel School of Marine and Atmospheric Science, Univer- sity of Miami, 4600 Rickenbacker Causeway , Miami, FL 33149. tion data on which to base management decisions lOdell 1975). The majority of bottlenose dolphins that are readily available for capture dwell in the coastal and inland waterways of Florida and the other states bordering the Gulf of Mexico. In such envi- ronments several factors make T. truncatus, in contrast to pelagic odontocetes, ideally suited for synoptic studies from aircraft: many of the envi- ronments are semienclosed waters of limited di- mensions, the herds are usually small thus indi- viduals can be relatively accurately counted, and T. truncatus is generally the only small cetacean in the area and therefore easily identified. Accord- ingly, recent studies of bottlenose dolphins off the northern Gulf of Mexico and the Indian River area of Florida have used and refined aerial survey tactics and methods (Leatherwood et al. 1978; Leatherwood 1979; Leatherwood and Platter'; Odell and Reynolds"). Using similar procedures M.'inuscnpt attt-pted .March 1979 FISHERY BULLETIN: VOL. 77. NO. 3. 1980, 'Leatherwood, S.. and M. F. Platter. 1975. Aenal assess- ment of bottlenosed dolphins off Alabama. Mississippi and Louisiana In D K. Odell. D. B. Siniff. and G. H. Waring (editors). Tursiops truncatus assessment workshop, p. 49- 86. Final Report. U.S. Marine Mammal Commission. Contract MM5AC021. Rosenstiel School of Marine and Atmospheric Sci- ence, University of Miami, 4600 Rickenbacker Causeway, Miami, FL 33149. "Odell.D K, and J. E.Reynolds in. 1978. Distribution and abundance of the bottlenose dolphin, Tursiops truncatus, on the west coast of Florida. Draft - Final Report, Marine Mammal Commission, Contract MM5AC026, 55 p. Rosenstiel School of Marine and Atmospheric Science, University of Miami, 4600 Rickenbacker Causeway, Miami, FL 33149. 585 FISHERY BULLETIN: VOL, 77. NO, we report here on the size and density of the bottlenose dolphin population in the Port Aransas Pass-Matagorda Peninsula region of the Texas coast as observed in late March 1978 and compare the density figures with those obtained in the previous studies. Observations on T. truncatus distribution, behavior, sighting cues, and the per- pendicular distances of the sightings, and alterna- tive procedures and results are also presented and discussed. STUDY AREA AND METHODS Based on previous research (Leatherwood el al. 1978), a strip transect was designed (Eberhardt 1978). The dolphin herds were sighted and their numbers estimated within strips theoretically 804.5 m wide (0.435 n.mi.). All sightings, regard- less of the numbers of animals, were statistically considered as a herd, and the term is used here in the general sense of a grouping of animals without implying more complex behavior. To achieve pre- cision the same area was surveyed during five replicate flights. The extent of the area surveyed was limited to dimensions that could be covered in 7-8 h of flying time and that would provide approx- imately 17^Y coverage of the area on any one repli- cate survey. The surveyed territory extended along 160 km (86 n.mi.) of the central Texas coast from Port Aransas at the northern end of Corpus Christi Bay to the base of the Matagorda Peninsula (Figures 1-3). This terrain is a complex of bays, bayous, lakes, and channels bordered seaward by long, low- barrier islands. Convoluted arms of the larger bays extend inland into river deltas surrounded by agricultural lands. Marshes fringe much of the barrier and outer bay shorelines and numerous sand and shell reefs, small islands, and spoil dumps interrupt the water areas. Extensive shoals are covered by water of < 1 m, and the deeper parts of the bays are limited to about 4 m depths. Oil well platforms and well heads are numerous in some parts of the bays and man-made Mission Bay I ' ,^ Aransas SURVEY DATE SYMBOL I 3/26/78 O n 3/27/78 • m 3/28/78 i m 3/30/78 A I 4/1 /78 D I I I I I I I I I I I 0 5 10 (km) FlIilKE 1,- 586 -Distribution of bottlenose dolphin herds and their estimated numbers from Aransas Pass to MesquiteBay (transects l-8l, Texas. BARHAM ET AL AERIAL CENSUS OF THE liOTTLENOSE DDLPHIN Figure 2. — Distribution of bottlenose dolphin herds and their estimated numbers from Ayres Bay to Pass Cavallo (transects 9-14). Texas. Figure 3. — Distribution of bottlenose dolph'in herds and their estimated numbers from Port O'Connor ship channel to Tres Palacios Bay (transects 15-21), Texas. 587 FISHERY BULLETIN: VOL 77. NO .3 cuts and channels run through the area. Five channels, two man-made, open to the Gulf of Mexico. Operating from Aransas County Airport, a high-wing, four-seat airplane was flown along 21 transect lines spaced at approximately 4.63 km (2.5 n.mi.) intervels across the study area (Figures 1-3 ). With some exceptions the transect lines were oriented due east to west. To provide a reference point with a previous population study (Shane 1977) the first two lines were bent to conform to the narrow Corpus Christi and Aransas ship channels (Figure 1). Line 8 was jogged slightly to the north over the Lamar Peninsula so that its western extension would cross Mission Bay (Fig- ure 1). Lines 14 and 15 were altered to overfly the Pass Cavallo and ship channel entrances into Matagorda Bay in the region of Port O'Connor, the location of a proposed T. truncatus study. In 12 cases the transects were interrupted by land that divided them into two or more parts, so that in all, 42 overwater crossings were flown. Eight of these crossings were 2 km or less in length while the longest was 42 km. Their average length was 10.2 km. Time of these crossings ranged from < 1 to about 18 min. Most transects were flown at 167 km/h and an altitude of approximately 152 m (500 ft). The first part of transect 1 was flown at 213 m (700 ft) to safely maneuver around large cranes and other structures. When not fully occupied with flying the plane, the pilot searched for bottlenose dol- phins. An observer sat in the right front seat next to the pilot. This observer also functioned as the "navigator," talking the pilot onto transect land- marks, calling out the start and stop times for each transect, and charting the dolphin sightings. Two observers sat in the rear of the plane. The observer in the right seat mainly functioned as a recorder who kept a transect log noting the time of starting and ending of each transect and comments on visi- bility, weather, and other observations of interest. A sighting form was also kept in which was noted: the observer making the sighting, the nature of the observation which first alerted us to the pres- ence of a dolphin herd, the sighting cue; the esti- mated numbers of adult animals and calves and their assumed behavior; and the estimated right angle, or perpendicular, distance of the sighted dolphin herds from the plane's track. While a strip transect design had been planned, the perpendicu- lar distance estimations were essential for alter- native dolphin density calculations utilizing line transect theory (Saber 1973). If time allowed, the herd configuration relative to the environment was also sketched. Because of the low flying speed, the airplane was relatively quiet and voice communication between party members was feasible. The shortness of the transects and rest intervals between transect lines alleviated observer fatigue. Observers searched outward to about 400 m (we estimated distances in yards). This distance was estimated with the aid of tape markings on the wing struts that had been calibrated against range marks on the landing strip. When a dolphin sighting was made, the pilot deviated from the transect line and usually orbited the herd twice while all observers counted the animals and noted the presence of calves. A consensus opinion was scored for these counts. Rarely only one circle was necessary, and on occasion three or more circuits were flown before the observers felt confident with the count. On occasion, individual animals or small herds could not be relocated and limited data based on the original sighting were logged. Two observers worked all the flights, whereas one person was relieved as recorder-observer for the last three flights. The same pilot flew the plane on surveys 1-4. A different pilot took over on the last survey. RESULTS Operations The survey design called for six replicate tran- sect runs on successive days. The period of the operation (26 March-1 April 1978), however, was plagued by strong winds ( 33-46 km/h) that caused a 1-day postponement of survey 4, cancellation of survey 6, and affected the results of survey 5 to the extent that those data are of limited value (the specific effects of weather on the survey will be discussed later). Weather conditions were good to excellent on two runs, surveys 2 and 4, and mar- ginal to fair on surveys 1 and 3. A malfunctioning airplane engine caused curtailment of the last three transects on survey 2. These were made up at the end of survey 4 under similar environmen- tal conditions. A total of 436 track kilometers ( 235 n.mi.) was flown on each survey. Assuming a 402.25 m scan on each side of the aircraft, an area of 351 km^ (102 n.mi.^) was searched. With the 4.63 km transect line spacing, this would repre- 588 BARHAM ET AL AERIAL CENSUS OF THE BOTTLENOSE DOLPHIN sent about IV/f coverage of the survey area on any one replicate. Dolphin Counts During the first four survey flights 133 dolphin herds were sighted, containing an estimated 916 animals. A mean of 33.3 herd sightings per survey, composing 229 dolphins, was calculated for the four flights (Table 1). On survey 5, affected by adverse weather, only 19 herds estimated to con- tain 107 dolphins were sighted. Because these scores fell well below two standard deviations of the mean that was calculated for the first four replicates (Table 1). the results of survey 5 were excluded from our population calculations. Data from the last survey were used, however, for analyzing behavioral observations, sighting cues, and the perpendicular distances of dolphin herds from the trackline. T.ABLE 1. — Bottlenose dolphin herd sightings, individuals, and calves estimated on surveys 1-4 Port Aransas to Matagorda. Texas. Date Survey Total no. Total no Total no Percent (1978) number ol herds of animals ol calves of calves Mar 26 1 36 175 17 97 Mar 27' 2 36 260 17 65 Mar 28 3 29 209 20 96 Mar 30 4 32 272 31 11 4 Total 133 916 85 Mean 333 229 0 21 3 93 SD 34 45.2 6.7 20 on 1 ; J 4 5 6 ^ e 3 10 (£ p? la 15 16 I - " ^^ 2j ^6" 35 HERD SIZE FIGURE 4. — Frequency distribution of bottlenose dolphin herd sizes on surveys 1-4, Port Aransas to Matagorda, Texas. The mean herd size for each daily survey repli- cate was computed as: 1=1 "; (1) where h , = mean herd size, hi, = herd size of the ith sighted herd on replicate 7, rij = the number of herds sighted during replicate J. The estimated herd density for each replicate was obtained from: Dj = (2) 'Tfie last four transects were run on Marcti 30 Calves Among the animals sighted in surveys 1-4, some 8.5 were classified as calves, and they represented 9.3"f of the total population observed (Table 1). Because the surveys were made just prior to the peak of the calving season, it was not always pos- sible to differentiate between older calves of the year and young yearlings. Some 13 animals were in this questionable category. Herd Size and Herd Density While the estimated sizes of herds ranged from 1 to 42 animals, generally the aggregations were small. Groups of two and three T. truncatus rep- resented the mode and composed 28.6% of all sightings, and 96 of the 133 sightings (72.2% ) were composed of 7 or less animals (Figure 4i. where D, = the estimated herd density on rep- licate 7, a = the surveyed area in km'^, Hi = is defined as before. These calculations produced a mean herd size of 6.95 and a mean herd density of 0.0947/km^ (Table 2). Estimated Population Size (Numbers of Dolphins) In previous aerial assessments of bottlenose dolphin populations by Leatherwood and his co- workers, variance of the population size was calcu- lated according to Goodman's (1960) equation for estimating the variance of a product of two inde- pendent variables. However, in these cases Good- man's equation was used to estimate variance of the mean population size over all the replicates 589 FISHERY BULLETIN VOL 77. NO :i Table 2. — Basic terms and figures for population size and density estimates of bottlenose dolphin m the Texas bays resulting from replicate surveys 1-4. Survey number (replicale) Mean Variance mean herd size herd size (h/) (Varh,) Herd density (no, km') (D/) No of dolphins yV/) Variance no of dolphins' (VarN,| Dolphin density (no„'km2) idj) Variance dolphin density-' (Vard,) 1 4.86 0613 0 1026 1.008 58,828 0 575 00175 2 7.22 0918 0 1026 1,498 100,613 0854 0 0326 3 7.21 1 967 0 0826 1,204 103.000 0 685 0 0334 4 8.50 2,994 00912 1.567 175,232 0,893 0 0569 Mean 6.95 0 0947 1.319 0 752 SD 1.52 0 0097 260,4 0 148 SE 0 76 0 0049 1302 0074 SE from theory J189 43 "0 1080 'From Equation (9) 'From Equation (12) ^From Equation (10) "From Equation (13)- andnot the variances of'each replicate. Quinn has suggested a more refined treatment that is appli- cable if two conditions are met: the numbers of sightings for each replicate follows a Poisson distribution, and no real differences exist in the replicate herd densities. If these assumptions hold, a variance can then be legitimately com- puted for each replicate survey and these numbers pooled to produce a more precise estimate of mean population size variance. Accordingly, we pro- ceeded as follows. The estimation of the popula- tion size for each replicate was calculated as: N, ADjhj (3) where N^ = estimated population size on repli- cate^, A = total area assumed to be 5.76 x of the searched area (a), t)j = estimated herd density on replicate hj = mean herd size on replicate j. Results are shown as "number of dolphins" in Table 2. The computed variance of the estimated popula- tion size for each replicate was: VarATj = A'^Var(bjhj) which simplifies to: VarjV, = ■-(^r Var {rijhj) (4) (5) wherea is assumed to be l?"/; of the total area l/\ ). The estimated variance of mean herd size within replicates was then estimated from: 'Terrance J. Quinn II, Center for Quantitative Science, Uni- versity of Washington, Seattle, WA 98195, pers. commun. to S, Leatherwood, March 1978. Var/i; y (6) Following Elliott (1971), a chi-square value utilizing the index of dispersion was computed for the number of herd sightings on replicate surveys 1-4 to test agreement with a Poisson series. The index of dispersion was 0..'i.5 with a resulting x- value of 1.05. These values support the Poisson distribution assumption. This allows us to con- sider the variance of replicate herd sightings as equal to the numbers of herd sightings. Thus: Var (?, (7) Using the chi-square test again we also found that there was no difference at the 5% significance level in the herd densities of the replicate surveys. The mean herd size [hj ) and the numbers of herds sighted (/?,). however, were obtained from the same set of observations, and as one reviewer has rightly pointed out, it is not known if in fact these estimates were independent. We therefore tested for interrelationship using Spearman's Rank Cor- relation Test (Zar 1974). Finding no demonstrable correlation at the 5% significance level, we pro- ceeded to treat the results of the replicate surveys generated from Equation (5) in terms of Good- man's ( 1960) equation for estimating the variance of a product as suggested by Leatherwood et al. (1978). Thus: Var N: 5^{n/ Var hj + h-^ Var Oy - Var rij Var h,) , (8) and substitution of/?, for Var n. results in: 590 BARHAM KT AI. AERIAL CENSUS OF THE BOTTLENOSE DOLPHIN Var Nj = 5^(nj^ Var h^ + /j/ rij - nj Var hj) . (9) Before proceeding, a one-way analysis of var- iance with unequal sample sizes was performed on herd sizes with a logm transformation for counts. No significant differences i« = 0.05) between replicate herd sizes were found, thereby allowing the pooling of the four variances as: Var dj = — (n,'^ Var h, + hj^ nj - iij Var h,) (12) VarN = Var Var (Nj) .(10) These computations produced an estimated mean T. truncatus population size of 1,319 with a standard error (SE) of 189 (Table 2). The susceptibility of the above analysis to possi- ble nonindependence of the mean herd size and herd density parameters was recognized by Leatherwood et al. ( 1978), and they suggested that mean herd size be established in preliminary flights before the herd counting phase of the sur- vey is initiated. In the case of our work, however, because of inclement weather and limited re- sources we decided to make as many replicate sur- veys as possible rather than dividing the flight functions. Despite the assurance of ranking tests, if inde- pendence between /?, and n, does not hold, use of Equation (9i will probably underestimate the var- iance of iV, . An alternative more robust approach suggested by one reviewer was to compute the SE of the replicate estimates of numbers of dolphin on the four surveys (Table 2). This procedure pro- duces a SE of 130.0 which is reasonably close to the theoretical value of 189 obtained from Equation (9) and tempers to some extent doubts of the valid- ity of this approach. Estimated Dolphin Density For comparative purposes we also estimated the density of dolphins in the study area from: dj = Djhj = — hi . ' ' ' a (11) The same rationale and procedures for calculat- ing the replicate and overall variances of popula- tion estimates were used to calculate the var- iances for dolphin density. Thus: and Varrf =(j) V Yard,. (13) This treatment gave an estimate of 0.752 dolphins/km" with an SE of 0.074. The SE calcu- lated from the variance of the mean of the repli- cates was 0.108 (Table 2). Comparisons with Other Population Studies We can roughly compare our counts from the Aransas Pass area with those of Shane's (1977) who counted T. truncatus in the same area from a skiff run on a meandering course through the ship channels and cuts almost on a daily basis over a 1-yr period. For March and April 1977, her mean was 95 dolphins. The mean of our scores for tran- sects 1 and 2 that covered part of her study area was 53. Considering the differences in methods and area covered, the results do not seem unrea- sonably diverse. Our mean density estimate for all transects is compared with the results of recent aerial surveys of T. truncatus populations in waters adjacent to Florida, Mississippi, and Louisiana in Table 3. While it is clearly tenuous to contrast densities from different environments, it is worth noting that the two semienclosed areas, Indian River, Fla., and the Texas bays, appear to support similar densities, 0.52 dolphins/km^ and 0.75 dolphins/ km^, respectively. The mean percent of the calves Table 3. — Density estimates of bottlenose dolphin populations in southeastern US, coastal waters, based on recent aerial sur- veys. There are considerable differences in the nature and extent of the areas covered in these studies, thus the results are not strictly comparable. Dolphins Dolphins Location Reference per km^ per n.mi.2 Florida Indian River Leatherwood 1979 052 1 79 Florida' Odell and Reynolds West coast (text footnote 8) 0 27 0 93 Mississippi Leatherwood el al. Gulf coast 11978) 023 0 79 Louisiana Leatherwood et al. Gulf coast (1978) 0.44 1.51 Texas Gulf coast This paper 0.75 2 57 ^Derived from their table 10 by computing the product of mean herd size (5 43) and mean herd density (0 0497) 591 to the total number of animals counted (9.3 ±2.0%) is about the same as previously reported (Leath- erwood 1979). Distribution and Behavior As can be seen from Figures 1-3 the distribution of dolphin herds in the area was hardly homogen- ous. Some 28 herds i'Zn ) of the total were sighted in the narrow Aransas Pass ship channels (mainly transect 1) and 211 (2.3'-; i of the animals counted were in these herds. (This marked difference in densities is discussed below.) Transect 18 across Matagorda Bay was another area of high dolphin density. While we noted only eight herds on this line they were relatively large and accounted for I49c of the dolphins sighted.. In general, aside from the ship channels, the shoreward side of the bar- rier islands and locations close to the beach ap- peared to be favorable situations for T. truncatiis, whereas sightings were rare in the middle of large bays. When possible, the apparent behavior of the herds was coded as either traveling, playing, feed- ing, or resting. Of the 97 herds classified, about half i48..5'^r ) were considered to be feeding. Side or upside down swimming by dolphins actively pur- suing prey as reported by Leatherwood ( 197.5) was frequently observed. This was particularly true in the shallow regions inside the barrier islands where Gunter ( 1954) reported that bottlenose dol- phins frequently chase mullet, Mitgil cephalus. Feeding appeared to be associated with herd size, for of the 17 herds composed of 15 or more indi- viduals, 13 (76.59; ) were considered to be feeding. The next most common behavior was "traveling," and 36 herds (37.1'*) were assigned to that be- havioral mode. Perpendicular Sighting Distances and Sighting Cues As previously indicated, in most cases we esti- mated the perpendicular distance from the plane's track to the sighted herd. In addition we also log- ged the nature of the observation which first alerted us to the presence of a dolphin herd, the "sighting cue" (Figure 5). During the field work. 11 different codes were used but these could be reduced to four classes: 1) surface perturbations such as mud trails or boils, scars, and splashes; 2) an animal's body seen below the water (most eas- ily noted when the dolphins are rolling or swim- jH suRFiCe PERTunemiONS. 12 5% I I ANIMAL BELOW SU«f«E. Z I 5% I 1 ANIMAL OR SLOW AflOvE SLIREACE, 58 5*4 I I UNCERTAIN OR UNNOTED, 76% '-tuMm-i^-S ESTIMATED PERPENDICULAR DISTANCE: i i SIGHTING FROM TRANSECT LINE (ml Fir.lfRp: 5 — Frequency distribution of estimated perpendicular distances of bottlenose dolphin herd sightings from transect lines on surveys 1-5, Port Aransas to Matagorda. Texas. Histo- grams are divided into the relative ratios of sighting cue classes. ming upside down and their contrasting light ven- tral surfaces are showing); 3) an animal's body, or part of it, or its condensed respiratory exhalation "blow" noted above the water surface; and 4) "cue uncertain or unnoted." The "animal above surface" cue was effective at all ranges and was the predominant sighting cue, accounting for 58.3'r of all sightings (Figure 5). The "animal below surface" instigated 21.,5'i of the sightings, but was more important at ranges under 200 m, contributing 28 of the 96 sightings (29.2''7f ) at these ranges, whereas, at ranges -200 m, only 3 of 48 sightings (6.29r ) were signaled by this cue. As will be discussed later, the effective- ness of both underwater sightings and surface per- turbations appeared to be vulnerable to weather conditions. Most questionable or unrecorded sighting cues occurred on the initial survey. DISCUSSION Possible Biases to Population Estimates Several factors, both operational and analytical, influenced the results, in some cases prejudicing the counts upward and in others to lowering them. We first discuss two factors, effects of weather and inability to sight all herds, that tended to cause underestimates. Relatively strong southwest winds (22-41 km/h) blew constantly for several days during the field operations. The wind's major effect on searching efficiency was not sea state, as is the case in the open ocean, for splashes were seldom the sighting cue, but rather the stirring of bottom materials into suspension creating large areas of highly tur- 592 ; ARHAM ET AL AERIAL CENSUS OF THE BOTTLENOSE DOLPHIN bid water. On such days the only clear water was in the lee of barrier islands and headlands where the fetch was limited. Increased turbidity limits the observer's chances of sighting underwater animals and not- ing mud boils and trails. For underwater animals, however, the overall effect on the number of sight- ings was tempered because submerged dolphins will frequently be spotted when they eventually surface. More important was the negative influence of high turbidity on the observer's abil- ity to note surface signs. For example, on the two low-wind days 12 out of 68 ( 17. 7<^ ) sightings were cued by surface perturbations. In contrast, on the three medium to high-wind days only 8 of 83 (9.6%) of sightings were signaled by this cue. The effect was probably more important than those data indicate, for frequently the observer's atten- tion was drawn to an area by subtle surface signs and then, if a dolphin's body showed at the surface, it was usually the second rather than the first cue that was logged. As stated earlier, we have re- duced the effects of weather on the population estimates by excluding the results of survey 5, when the wind effects were extreme, from the den- sity computations. Regarding our inability to sight all herds, the supposition that all target animals will be seen is basic to the strip transect method (Eberhardt 1978). However, in terms of line transect theory ( Seber 1973), which assumes that the herds will be randomly distributed, the frequency histogram of the estimated perpendicular sighting distances (Figure 5) gives strong evidence that one of these assumptions was incorrect, probably the former, as follows. First, only 3 of 144 sightings were made at under 50 m range. The aircraft's configuration which severly limits searching the water directly under and adjacent to the flight path was the major cause of this discrepancy. (A secondary fac- tor was discomfort to the observer's necli caused by attempting to look down at a steep angle.) The only sightings made directly under or close to the track were when the aircraft was in a steep turn, and frequently herds were noted at moderate ranges when we were circling on a previous sight- ing. Secondly, the systematic decrease of the sight- ing frequencies from 50 to 200 m, suggesting a negative exponential curve, and the "tail" out to 400 m must at least in part reflect the inherent inefficiency of the observers to see beneath the water's surface at low angles or to detect relatively small, low-contrast objects at even moderate dis- tances. Three factors, dolphin movement, nature of the terrain, and observer experience, may have had mixed effects on the estimates, as follows. Regarding effects of dolphin movement between the open Gulf of Mexico and the bay behind the barrier islands, it was originally planned that vol- unteer observers stationed adjacent to the passes would note the numbers and directional move- ments of bottlenose dolphins during the hours of the survey. However, a week's delay in starting the field work and the subsequent resumption of college classes following Easter vacation made it necessary to cancel that observational phase. At the termination of survey 4, however, we flew homeward just outside Matagorda Peninsula and Island. Outside Pass Cavallo at least 50 T. trun- catiis were seen lolling in small herds in and just outside the surf zone. These dolphins may have either been moving in from the Gulf or out of the bays, but their proximity to the beach and the pass indicates that there was frequent movement of dolphins between the two environments. Factors of bathymetry of the bays and the na- ture of the terrain were not considered by the analysis. While T. truncatus were occasionally noted in shallow water just inside the barrier is- lands, extensive regions in the middle of the bays and in the shoreward areas were covered with a thin layer of water over sand and mud flats and there are numerous reefs and islands. Thus, within most of the 800 m swaths used to compute the density estimates there was territory that was not available to the dolphins that could legiti- mately be subtracted from the area searched. On the other hand, by multiplying the searched area by 5.76 (Equation (3)) to obtain an estimate of the total number of dolphins we were sometimes at- tributing dolphin habitat to dry land. This is par- ticularly true for the Port Aransas ship channels that were limited to about 600 m width and were surrounded by large land areas. We feel that observer experience possibly also biased the accounts. Tursiops triincati/s herds ap- pear to occupy a home range (Caldwell 1955; Shane 1977) and we frequently sighted herds that were of similar size and in the same approximate location of herds noted on previous surveys. The observers tended to concentrate their attention on these areas and thus searched them more efficiently in the latter surveys. 593 Despite the smalliiess of the herds, it was not easy to accurately count animals that were some- times spread over a relatively large area, and in subgroups that only showed for brief periods at the surface. Obviously, accuracy of such counts will also improve with experience. However, by scor- ing a consensus opinion the judgment and bias of the most experienced observer probably carried more weight, and as a result we feel that in all cases the counts were conservative. Because of the experience factor we also think that, other influences being equal, the latter surveys were probably the more accurate. Last, one factor, the "gerrymandered" lines of transects 1 and 2, clearly tended to influence the counts upward. Our rationale for altering the line of these transects was based on the desirability of obtaining data in an area for which baseline in- formation already was available (Shane 1977). Unfortunately, the terrain was not ideal for tran- sect sampling, and flying an east-west line over the ship channels would have resulted in gross underestimation of an area known to hold a rela- tively large number of dolphins. Clearly, the results for transects 1 and 2 (23"^"^ of the animals sighted in only 6.6'J of the total area) were strikingly different from those data for the rest of the tran.sects. Estimated dolphin density for the ship channels was 2.6.33/km^, some 4.25 times greater than the 0.619/km''^ estimated for tran- sects 3-21 (Table 4). Based on these densities the total population estimate could be partitioned into 304 dolphins for the ship channels and 1,015 ani- FISHERY BULLETIN: VOL. 77. NO 3 mals in the rest of the area. Shane's (1977) maximum estimate for the ship channel area for any month of the year was about 280, thus the two estimates are in reasonable agi'eement. We still feel, however, that there were some unresolvable problems with our survey methodology as it applied to the Aransas Pass ship channels, and that the soundest procedure was to lump the re- sults from the minority area with those from the major region, as we have done. Alternative Density Estimate As previously discussed, the decrease in the number of dolphin sightings at increasing ranges of the herds from the flight path (Figure 5) indi- cated violation of strip transect theory assumption that all herds within the delineated area were sighted. Line transect theory (Seber 1973) pro- vided an alternative method of analyzing the re- sults. Because there were few observations in the 0-50 m increment, creating a marked gap in the frequency distribution, and the "tail" of the fre- quency distribution was truncated, in part be- cause we limited observations to about 400 m range, our data were not strictly applicable to line transect theory, either. Despite these discrepan- cies, however, we obtained for comparative pur- poses a rough approximation of the level of bias by applying a simple modification of the so-called ex- ponential estimator (Gates et al. 1968) which cor- rects for the gap in the 0-50 m frequency distribu- tion interval as follows: Table 4.— The basic terms and figures for comparing the estimated bottlenose dolphin density i n two parts of the survey, the Port Aransas ship channels (transects 1 and 2) and rest of the area (transects 3 to 21). Survey number (replicate) Total no. ol (lerds Total no ol animals Mean herd size Cl;) Herd density no./) 100 m, strongly indicate violation of the strip transect assumption that all herds within the delineated strip were noted. If this is true then the population has been underestimated to some degree, al- though the inclusion of transects 1 and 2 would tend to compensate for this. Conversely, one as- sumption of line transect theory is that the targets are randomly distributed. We found, however, that the distribution of the dolphin herds was strongly nonrandom. This factor may have caused an upward bias to those calculations, but the pre- cise impact of this violation is presently unclear. These questions cannot be resolved until further surveys are done simultaneously with adequate "gi'ound truth" counts. ACKNOWLEDGMENTS This study was a collaborative effort among or- ganizations within the NOAA's National Marine Fisheries Service, the Marine Mammal Commis- sion, Dinnes Memorial Veterinary Hospital, Sea Arama Marineland of Galveston, and the Naval Ocean Systems Center. We thank the adminis- trators of these organizations for expediting the work. We are also indebted to James McGrew for his excellent piloting and Terrance Quinn II for his suggestions. Gary Stauffer advised on statisti- cal matters; the art work was done by Kenneth Raymond and typing by Lorraine Prescott, all of the Southwest Fisheries Center. The originally submitted draft of this paper was read by William Fox, Joseph Powers, and Nancy Lo of the South- west Fisheries Center and Pat Tomlinson of the Inter-American Tropical Tuna Commission. Fol- lowing editorial review, Tim Smith of the South- we.st Fisheries Center consulted with the senioi' author on additional statistical work in response to suggestions by the referees. We also thank Lee Eberhardt of Battelle Pacific Northwest Laboratories as well as an anonymous reviewer and the editor for their constructive comments and suggestions. Despite the many contributions from the junior authors, advisors, and reviewers, the senior author, of course, assumes full responsibil- ity for the contents of this paper. LITERATURE CITED Caldwell, D. K. 1955. Evidence of home range of an Atlantic bottlenose dolphin. J. Mammal. 36:.304-305. Eberhardt. L. L. 1978. Transect methods for population studies. J Wildl Manage, 42:1-31. ELLH)TT, J, M. 1971 . Some methods for the statistical analysis of samples of benthic mvertebrates. Freshwater Biol. Assoc, Sci. Publ. 25, 144 p. Gates, C. E., W. H. Marshall, and D. P. Olson. 1968. Line transect method of estimating grouse popula- tion densities. Biometrics 24:135-145. Goodman, L. a. 1960. On the exact variance of products. J. Am, Stat Assoc, 55:708-713. GL'NTER, G. 1954. Mammals of the Gulf of Me.\ico, U,S, Fish Wildl Serv., Fish, Bull. 55:543-551. LE.-^THERWOOD, S. 1975. Some observations of feeding behavior of bottle- nosed dolphins ^Tiirsiops truncatus I in the northern Gull of Mexico and ( Tursiops cf T. gilli ) off southern California, Baja Cahfornia, and Nayant, Mexico Mar. Fish. Rev. 37(91:10-16. 1979. Aerial survey of populations of the bottlenosed dol- phin, Tursiops truncatus . and the West Indian manatee. Tnchechus manatus, in the Indian and Banana Rivers. Florida, Fish, Bull., U.S. 77:47-59, Leatherwood. S,, J, R, Gilbert, and D, G. Chapman, 1978. An evaluation of some techniques for aerial censuses of bottlenosed dolphins, J, Wildl, Manage, 42:239-250. ODELL, D. K. 1975, Status and aspects of the life history of tht bottlenose dolphin, Tursiops truncatus, in Florida, J Fish. Res, Board Can. 32:1055-1058, SEBER, G. a. F. 1973. The estimation of animal abundance and related parameters. Charles Griffin, Lond., 499 p. SHANE, S. H. 1977. The population biology of the Atlantic bottlenose dolphin, Tursiops truncatus, in the Aransas Pass area of Texas. M.S. Thesis, Texas A&M Univ.. 238 p. ToWNSEND, C. H, 1914. The porpoise in captivity, Zoologica (N,Y,) 1:289- 299. Zak, J, H, 1974, Biostatistical analysis. Prentice-Hall, Inc., En glewood Cliffs. N.J. ,620 p. 595 ENERGETIC SIGNIFICANCE OF CHANGES IN SWIMMING MODES DURING GROWTH OF LARVAL ANCHOVY, ENGRAULIS MORDAX Daniel Weihs' ABSTRACT The swimming behavior of larval northern anchovy, Engrauhs mordax, in the first few days after hatchmg is different from the intermittent beat-and-glide mode used by older larvae and later stage fish. It is shown mathematically that the bursts of continuous swimming typical of these yolk-sac larvae is the more efficient form of locomotion at this stage, because of their small size. This advantage changes as the larva grows out of the size range in which water viscosity is the dominant factor (small Reynolds numberl. When the larva reaches a length of 5 mm, typical Reynolds numbers are such that intermittent swimming gradually becomes the more economical mode, and this mode is dominant when the larvae reach 15 mm. These analytical results compare well with observed behavioral changes. Swimming behavior of the northern anchovy, En- graulis mordax, changes dramatically during growth in the larval stage (Hunter 1972). At hatching, the motion of yolk-sac larvae consists of bouts of continuous, very energetic swimming. This behavior persists for the first 3-4 days of growth, changing to beat-and-glide swimming at the close of the yolk-sac period. The beat-and-glide mode is then retained during the rest of the fish's life. Intermittent swimming, or beat and glide, is an efficient mode of locomotion for adult fish, enabl- ing increases by a factor of two or more in the range achieved for a given energy expenditure (Weihs 1974). The problem addressed in the pres- ent paper is whether the changes in swimming behavior mentioned above also have an energy- saving function. The energetic advantage of in- termittent swimming may not exist during the early life stages of fishes because of the importance of viscous effects on small organisms. This study includes setting up a theoretical framework for the analysis of energetics of swimming during the various stages of the fish's life history. The forces and energy required for swimming in the continu- ous and intermittent modes are then calculated and compared at different stages of larval de- velopment. These stages are hydrodynamically distinguished by the nondimensional Reynolds number. Re, which is a function of both length and 'Southwest Fisheries Center La Jolla Laboratory. National Marine Fisheries Service, NOAA, La Jolla. Calif; present ad- dress; Department of Aeronautical Engineering, Technion, Haifa, Israel. speed. The value of the Re defines the relative importance of viscous and inertial effects on the hydrodynamic resistance to motion. THEORETICAL MODEL Consider a fish swimming in a straight line at constant depth. We shall assume the fish to be neutrally buoyant so that the only forces acting are in the horizontal plane. Fish of negative buoyancy can be included in the following analysis by equating the excess weight of the fish in water ( which is usually not more than 6% of its weight in air) and lift forces produced on the body and fins. However, this is not directly relevant to the pres- ent discussion as these forces are perpendicular to the plane of motion, and shall therefore be left out for simplicity. Returning to the horizontal plane, the forces acting are the thrust applied by the fish, T',and the drag on the fish, D, acting in the opposite direc- tion. The drag is a combination of viscous drag due to friction and form drag, which also is an indirect result of the friction caused by areas over which the flow is separated from the fish body. The drag force can be written (Hoerner 1965) as D -^pACoU^ (1) Manuscript accepted Marc)i 1979 FISHERY BULLETIN: VOL. 77, NO, 3. 19 where p is the water density; A the frontal area (seen in frontal projection); Cjj a nondimensional drag coefficient dependent on shape, roughness, and other factors to be discussed below; and ;/ the relative velocity between the fish and the water 597 FISHERY BULLETIN: VOL 77. NO 3 some distance away, which is not disturbed by the fish's passage. The drag coefficient C^ has been found experi- mentally to be a similar function of Re for various shapes. Thus, for all shapes tested (Hoerner 1965, chapter 3 >, the coefficient C p is a decreasing func- tion up to Re 200-300, being a constant for larger Re up to the turbulent regime which starts at about Re = 500,000, where a new, lower, constant value is obtained. Thus when Re>200, hydro- dvnamic drag becomes proportional to the veloc- ity squared, as the other factors in Equation ( 1) do not change for a fixed body. The Re>200 regime was examined by the au- thor ( Weihs 1974 ) previously and will therefore be mentioned here for comparisons only. When Re<200, two main regimes are observed, that of Re<10 and 101, i.e., for the speeds and sizes at which viscous effects dominate continuous swimming is always more efficient. This calculation is based on the relation Cq « Re"' and is therefore valid for Re up to 10. Larval anchovy tend to swim at speeds of about 0.8 body length/s (Hunter 1972) when swimming intermittently. Thus the Re typical of 3-day-old larvae whose length (Zweifel and Hunter^) is about 4 mm at 18° C is also about 10. At age 3 days, larvae spent <20% of the time swim- ming intermittently, but 2 days later (Hunter 1972, fig. 1) about 90*7^ of the time is spent in beat-and-glide motion. This level of intermittent swimming is retained thereafter. This sharp change coincides with the time the animal "grows out" of the viscous regime (the Re is essentially proportional to fish length squared ), e.g., when the larvae is 5 mm long, the Re is 20. Recalling that at high Re, beat-and-glide swimming is the more efficient motion (Weihs 1974), the energy saving obtained is probably one of the reasons for the observed change in swim- ming behavior. The fact that the average continuous speeds are much higher also results in savings of energy. For a 3-4 mm long larva, swimming at over 1 cm/s brings it again to Re of over 20, so that the drag coefficient is smaller, and some coasting at the end of the bout of continuous swimming is possible. At lower Re, in the purely viscous regime, no coasting is possible as the inertial effects are negligible and motion ceases immediately when oscillations stop. It is therefore advantageous for the fish, for hydro- dynamic reasons, to swim continuously during the first few days of the larval phase, changing to beat-and-glide swimming later on. It should be noted here that the present calculations and data are for a water temperature of 17°-18° C. Both viscosity of water and the growth rate of larvae (see footnote 2) depend on the temperature, so that data collected under different ambient conditions might lead to a later (or earlier, if the temperature is higher) change of swimming mode. Further examination of Figure 1 shows that for each terminal velocity in the beating stage there is a value of U^ for which the ratio S attains a minimum (marked by the dashed line). The value of this minimum approaches unity and the curves become more shallow as Uf increases. Thus, if an anchovy larva swims intermittently at low Re, it should do so at high average speeds, so that the energy penalties incurred due to swimming in the beat-and-glide mode are minimal. Figure 1 also shows that the lowest penalties for using intermittent swimming are obtained when Uf approaches unity, for the whole^range of aver- age speeds. Therefore, the value Uf = 0.995 was chosen for calculations of the effect of varying a. (the ratio of swimming to coasting drag). These appear in Figure 2, where the dependence of S on U^ is shown. The range of values of a to be expected in nature is described by the shaded area, showing as expected that the smaller the a the more advan- tageous is continuous swimming. When a>2, which can only happen at higher Re, a range of values of [7;. and Uf exists where S is smaller than unity, i.e., intermittent swimming is more efficient. This is shown by the dashed curve on Figure 2 where for Of = 0.995 and 0.79<[/,15 mm long). The results presented a = 3\ ^Zweifel, J. R., and J. R Hunter 1978. Temperature specific equations for growth and development of anchovy {En- graulis mordax) during embryonic and larval stages. Unpubl. manuscr., 13 p. Southwest FisheriesCenter.NMFS.NOAA, P.O. Box 271, La Jolla, CA 92038. 05 Figure 2. — influence of changes m ratio of swimming drag to gliding drag a on the energy ratio S, versus nondimensional average speed Uc Shaded area is the range of possible a at low Reynolds numbers, tjf = 0.995 (See Figure 1 for definitions). 601 FISHERY BULLETIN; VOL. 77, NO. 3 stem from calculations based on the analysis in Weihs ( 1974 ). The ratio of energy per unit distance traversed in intermittent swimming to that of con- tinuous swimming at the same average speed R, can be shown to be, in present notation, intermittent swimming relatively more efficient than carangiform swimmers as a is greater for anguilliform swimming in which most of the body is oscillated. Another result is that for greatest gains, the average speed during the whole beat- tanh R = Uf-Uj tanh In { cosh tanh Ur - U, [/,.[/, + t/, sinh tanh ^ U, - U. - - 1^ + a In —~ (251 The computed values of /?, for a = 2, appear in Figure 3. Each full line describes the values of i? for a gi\er\Uf as a function of the average velocity C/j.. Each of these curves ends at U ^ = [/^and, in a similar manner to Figure 1, has a minimum for a lower value oiU ^ . Here, however, all curves have a large section in the range R' \, i.e., intermittent swimming is more efficient. In fact, the slower the average velocity, the higher the possible gains, as shown by the dashed line which is the locus of lowest values of i? as a function oitj^ . As already mentioned in Weihs (1974)^ this curve goes monotonously from unity at t/^ = 1 (continuous swimming by definition) to 1/aat t/,, -►O. One can therefore predict that fish species using the an- guilliform swimming mode (Breder 1926) will find 12 _ \\ \o 8 \ U, = 0995 08 _ ,'" - :?- ^--■"^ 04 - on 0.0 0 25 0 5 0 75 10 Uc Figure 3.— The ratio of energy required per unit distance R. for intermittent and continuous swimming at high Reynolds num- bers, respectively, versus nondimensional average speed Uc Dashed lines shows locus of minimum values of /? attainable as a function of Uc. See Figure 1 for definitions 602 and-glide should be as low aspossible, with small differences between U, and Uf. Anchovy, which swim in the anguilliform mode, fulfill both these predictions as adults and more mature larvae usually swim by means of a single beat followed by a long glide, so that 1 ) t7, and Of are not too different and 2) [/,. is rather low. Having examined the low and high Re domains, where the drag coefficient is porportional to the reciprocal of Re, and constant, respectively, we now look at the transition regime between them. Based on average swimming speeds of 0.8 body length/s, larvae will be in this regime when they are from 5 to 15 mm in length. Analysis of the forces and energy is much more complicated here because the hydrodynamic drag is C[) a Re" (26) where fi is not constant, but itself is a function of both Re and body shape. This results in Equation (4) taking the form T = du_ dl + aKu' (27) a differential equation that has to be solved nu- merically when /3 is not zero or one (the two cases discussed previously). While this in itself is a rela- tively straightforward task, the generality and accuracy of the previous solutions is immediately lost as numerical values for the mass and K have to be included. K especially is known very inaccu- rately as it includes the numerical drag coefficient and the frontal area (which varies at different speeds and times). The setting of /3 is even more problematical as it depends on the instantaneous swimming speed in an empirical manner (which WEIHS: ENERGETIC SIGNIFICANCE IN ENGRAULIS MORDAX is, however, not known at the present time), thus changing during the beat-and-glide cycle. No single value may therefore be taken to describe a given beat-and-glide behavior and an average value has to be used. This adds greatly to the inaccuracy as ji is an exponent. Bearing especially the latter factor in mind, no smooth curves of the type appearing in Figures 1-3 can be expected. In order to try and make clear how the transi- tion regime influences the energetics of swim- ming, in spite of the difficulties mentioned, curves such as those from Figures 1 and 3 are reproduced in Figure 4. The purpose of this Figure is to show that by using the correct nondimensional descrip- tion, curves for the viscous and nonviscous re- gimes can be compared. Both the dashed and full curves have similar shape, going to infinity for Uc -> 0 and having a minimum at the higher values of Uc, the values increasing again for U ,■ -* Uf. One must recall that the absolute speeds and sizes are very much different for the two cases, this result- ing from the difference in Uo. the maximum sus- tained speed. t/„ is much larger for the full curves. The dashed curves have (i = \ while the full lines are for 13 = 0. Therefore, calculations at any inter- mediate values of /3 are expected to fall between them. Some calculated values appear in Figure 4, for two values of average /3. While they show the ex- pected behavior, their actual values are, as men- R,S 05 Figure 4. — Energy ratio versus nondimensional speed at vari- ous Reynolds numbers. Dashed lines show the low Reynolds number I viscous) regime, full lines are for high Reynolds num- bers (boundary layers) and. ' , + are at mtermediate Reynolds numbers, for U f = 0.7 and Uf = 0.8, respectively. See Figures 1 and 3 for other definitions. tioned before, unreliable, because they are based on rough estimates of various coefficients which do not have to be made when /3 = 0 or 1 . These compu- tations are to be taken only as an indication that the expected gradual transition actually occurs and are not to be used for actual calculations. Keeping these limitations in mind, one can ten- tatively come to the conclusion that the inter- mediate Re regime is one of gradual transition. The advantage of beat-and-glide intermittent swimming becomes more and more significant as the larva grows, after the 4th day after hatching. This conclusion can be strengthened, in a roundabout manner, by a different approach. The ratio of swimming to gliding drag for a given ani- mal is 2 in the low Re regime, and up to 4 for high Re. Therefore taking a higher value of a for the viscous domain calculations can indicate, in a dif- ferent manner, the trend of results when increas- ing Re. This appears in Figure 2, where the dashed line stands for a = 3. It can be seen that this curve is intermediate between typical curves for the vis- cous (Figure 1) and inertial regimes (Figure 3). CONCLUDING REMARKS It was demonstrated in the previous section that the change in swimming style observed when an- chovy larvae reach the age of 4-5 days is correlated with the passage of the animal ft-om the highly viscous regime to the boundary layer regime. My calculations show that this behavioral change is an adaptive energy sparing mechanism. When the larva is <5 mm long, it can only progress by ac- tively swimming as the enhanced effect of viscos- ity will bring it to a rapid halt when coasting. The yolk-sac, which still exists as a spherical protru- sion, increases the drag even further at this stage. The drag coefficient here is inversely proportional to the velocity so that any low-speed motion is very costly in terms of energy. As a result, interspers- ing coasting and accelerating is not an efficient way of progressing. When the larva is larger (>5 mm) and moving faster, viscous effects are concen- trated in a thin layer surrounding the fish and the influence of speed and shape on drag changes. At this stage, it is shown that intermittent motion is the more efficient for fish species such as anchovy which swim in the anguilliform mode. Intermit- tent motion is much less efficient for carangiform swimmers at all sizes (Weihs 1974) which may explain why species such as mackerel swim con- tinuously at all phases of life. 603 ACKNOWLEDGMENTS I would like to thank John Hunter and Reuben Lasker for their hospitality as well as for very helpful discussions and comments. This work was done while I was a NRC-NOAA Senior Resident Research Associate, on leave from Technion, Is- rael Institute of Technology, Haifa. I am grateful to the NRC, and especially R. C. Kinney, for mak- ing this visit possible. LITERATURE CITED Breder, C. M., Jr. 1926. The locomotion of fishes. 297. Zoologica (N.Y.) 4:159- FISHERY BULLETIN: VOL. 77, NO. 3 HOERNER, S. D. 1965 Fluid dynamic drag. S. F. Hoemer, N.J , 420 p. HUNTER, J. R. 1972. Swimming and feeding behavior of larval anchovy, Engraulis mordax Fish Bull., U.S. 70:821-838. VLYMEN, W. J. m. 1974. Swimming energetics of the larval anchovy, En- graulis mordax. Fish. Bull., U.S. 72:885-899. WEBB, P. W. 1975. Hydrodynamics and energetics of fish propulsion. Fish. Res. Board Can , Bull. 190, 158 p. WEIHS, D. 1974. Energetic advantages of burstswimming of fish. J. Theor. Biol. 48:215-229. Wu, T. Y.-T., C. J. BROKAW, AND C. Brennen (editors). 1975. Swimming and flying in nature. Vol. 1, 421 p. num Press, N.Y. Ple- 604 AN ANTIPREDATION MECHANISM OF THE POLYCHAETE PHYLLODOCE MUCOSA WITH NOTES ON SIMILAR MECHANISMS IN OTHER POTENTIAL PREY' Robert S- Prezant^ ABSTRACT The polychaete Phvllodove mucosa exhibits an antipredation response via the extrusion of a repulsive mucoid secretion. The mucus, secreted by largeglandular regions of the dorsal and ventral parapodial cirri, prevents immediate ingestion of the worm by several species of small or juvenile fish. A sipunculid, Phascoleopsis gouldr. a nemertean. Ltneus ruber; and a large flatworm. Stylochus zebra. are also distasteful to some potential predators. Antipredation responses found in some organisms may play an important role in regulating benthic community dynamics by mediating the feeding habits of certain predators during at least some stage of their development. Feeding habits of many species offish have been well established, but few studies have extended analyses beyond stomach contents. Results of such research frequently lead to labeling food found in the stomach as "preferred" (Onyia 1973; Smith and Daiber 1977). Reports of selective feeding be- havior based mainly on stomach contents reveal the major types of food eat«n by a fish but do not add substantially to our understanding of the in- teractions between predator and prey. Ivlev (1961), discussing selective feeding by fishes, included the role of "constitutional de- fenses" of potential prey species as a mechanism which may contribute to predatory selectivity. Selectivity in food thus entails not only "prefer- ence" but avoidance of specific potential food items (Berg 19791. Bakus ( 1966) considered the possible role of antipredatory responses by some tropical reef inhabitants. He noted that several members of a reef community that are not readily able to retreat into the security of a coral crevice or not naturally protected by skeletal armor are either poisonous, venomous, or distasteful to predators. Acidic secretions from epidermal glands of some opisthobranch gastropods (Graham 19.57; Thompson 1960, 1969) and some nemerteans (Gibson 1972) function as predatory deterrents. In view of the fact thatpredation isa well established cause of quantitative changes in a population of prey species, the ability of some members of a 'University of Delaware, College of Marine Studies Contribu- tion No. 130' ^University of Delaware. College of Marine Studies, Lewes, DE 19958. M.inu.-icript aiiepti-d April 1979 FISHERY BULLETIN: VOL. 77. NO. 3, 1980. community to thwart extensive predatory crop- ping by using inherent protective devices may also affect community structure. An accurate picture of community dynamics demands a closer examination of direct interac- tions between potential prey and predatory species. A start in this direction has been made on a limited number offish. Hynes( 1950), Tugendhat ( 1960), and Beukema ( 1968) examined some of the behavioral feeding patterns of the threespine stickleback, Gasterosteus aculeatus. They found that selective feeding of the stickleback is influenced by degree of satiation and palatability of food. This may have implications extending into the natural environment with regard to seasonal, predatory, or man-induced changes in community structure. In food-limited situations "selectivity" may decrease. The presence of a predatory deter- rent in an organism may thus be functionally operative only in a nonstressed community with nonstarved predators. Polychaetes often dominate marine benthic communities (Sanders et al. 1965) and many bot- tom feeding fish eat substantial quantities of these worms (Qasim 1957; Nikolsky 1963; Kislalioglu and Gibson 1977). Obscurance of taxonomic characters due to digestion often prevents iden- tification of prey to species, so food items tend to be listed in terms of higher taxonomic levels (Hynes 1950; Kneib and Stiven 1978). This is especially true for soft bodied prey organisms and means that accurate feeding records are often nonspecific and possibly biased relative to the researcher's taxonomic expertise. 605 FISHERY BULLETIN: VOL, 77. NO. 3 Phyllodocid polychaetes secrete copious amounts of mucus when irritated (Fauchald 1977). Pettibone (1963) briefly noted that the mucoid secretion oi' Phyllodoce maculata may be offensive to predators. Preliminary observations of P. maculata and P. mucosa (Prezant 1975, un- publ. data) have confirmed that an epitheUal, mucoid secretion acts as an antipredatory mechanism against at least one species offish, the rock gunnel, Pholis gunnel! us. The present study extends these observations by quantitative experiments on behavioral interac- tions of Phyllodoce mucosa with several species of small or juvenile fish, and examines the possible defensive mechanism of this polychaete. Initial observations concerning antipredatory mechanisms in the phyllodocids Eumida san- guinea and P. maculata, the large flatworm Stylochus zebra, the sipunculid Phascoleopsis gouldi, and the nemertean Lineus ruber are also reported. METHODS Phyllodoce mucosa (Phyllodocidae) was col- lected in late August 1978 in Nahant Bay, Mass., by epibenthic sled from a fine sand substratum at a depth of about 17 m. Eumida sanguinea and the orbiniid Scoloplos fragdis were collected intertid- ally from Henlopen Flat, Lewes. Del., in early September 1978. Scoloplos fragdis was used as a control in the behavioral experiments because, de- spite its overall gross similarity to phyllodocids (i.e., long, thin worms of similar proportions), S. frogilis produces considerably less external mucus than P. mucosa. Worms were maintained in sepa- rate finger bowls on a running seawater table at 17= C and 32%o salinity. Fish used in behavioral experiments (Table D were collected in July 1978 and allowed to acclimatize for 30-60 days in separate compart- ments on the seawater table. During acclimatiza- tion, the fish were fed a variety of foods from a widemouthed glass pipette. Foods included bits of fresh blue mussel, Mytilus edulis\ and American oyster, Crassostrea virginica; live tubificid oligochaetes, Tubifex spp.; brine shrimp, Artemia manna; and, infrequently, frozen brine shrimp. Phyllodoce mucosa, typically found on fine sand substrata from low water to depths over 500 m, ranges from Labrador to Mexico (Pettibone 1963) thus geographically overlapping with all fish species used in this study (Table 1). Since this research dealt principally with the inability of certain predators to eat P. mucosa, it was important to insure that the fish used would actively feed throughout the experimental period. Accordingly, several other species of polychaetes Table l. — The range, habitat, food habits, and collection sites of the species offish used in the feeding experiments. The last column lists the test organisms offered to fish. Quantitative results are available only (or Phyllodoce mucosa . Range, habitat, and feeding habit data for the fish are from Hildebrand and Schroeder ( 1928), Bigelow and Schroeder (1953), Chao and Musick (1977). and Kneib and Stiven(1978). Fish species Range and habitat Feeding habits Fish collection site Test organism Atlantic silverside. Menidia menidia Weakfish, Cynoscion regahs Windowpane flounder, Lophopsetta maculata Sheep shead minnow. Cypnnodon variegatus Mummichog, Fundulus heteroclitus Threespine stickleback. Gasterosteus aculeatus Striped sea robin. Pnonotus evolans Rock gunnel. Pholis gunneius Nova Scotia to northern Flonda. often over sandy or gravelly shores Nova Scotia to Florida, shallow coastal waters in summer Gulf of St Lawrence to South Carolina, sand bot- toms from low water to 50 m Cape Cod to Mexico, shallow waters ot inlets and bays, salt marshes Labrador to Mexico, shallow coastal waters especially salt marshes Labrador to Virginia; salt and fresh waters Gulf ol Maine to South Carolina, coastal bottom dweller Hudson Strait to Delaware, generally on rocky bot- toms from low Water to over 200 m Small crustaceans and molluscs, annelids, small fish, eggs, and plant malenal Fish, crabs, amphipods, mysids, shnmp, mol- luscs, annelids Mobile prey such as mysids. fish, shrimp, errant polychaetes Mobile epifauna including annelids Omnivorous (at least when -30 mm) including small crustaceans, annelids, and carnon Small invertebrates, fish fry, eggs Crustaceans, molluscs, annelids, small fish Molluscs, crustaceans, annelids Lewes Beach. Lewes. Del Lewes Beach Lewes Beach and near Delaware Bay mouth at 1 8 m Lewes Beach Canary Creek. Lewes. Del East Point. Nahant, Mass , tide pool Near Delaware Bay mouth at 18 m East Point. Nahant tide pool Phyllodoce mucosa Scoloplos fragilis P mucosa Phascoleopsis gouldi S fragilis Phyllodoce mucosa Eumida sanguinea S fragilis P mucosa S fragilis P mucosa Phascoleopsis gouldi S fragilis Phyllodoce mucosa S fragilis Stylochus zebra Phascoleopsis gouldi Uneus ruber Phyllodoce mucosa P maculata Nephtys incisa 606 PREZANT: ANTIPREDATION MECHANISM OF PHYLLODOCE MUCOSA were fed to the fish before and following be- havioral experiments. These worms, which were fi'om various size classes, included: Spio filicornis (Spionidae) and Nephtys incisa (Nephtyidae) col- lected from Nahant Bay: and Glyccra amencana ( Glyceridae), Ner-eis virens iNereidae), Scolecolepides viridis ( Orbiniidae), and Hydr-oides dianthus (Serpulidae) collected from Henlopen Flats. The feeding behavior of each species of fish, e\c\uAmg Prioi^otuaevolans and Phol is giinnellufi, was tested quantitatively viithPhyllodoce mucosa and Scoloplos fragUis. Fish were starved for 24-48 h prior to testing. An individual fish was then placed in a separate 4 1 glass aquarium or in a small compartment on the seawater table and al- lowed to acclimate for 60 min prior to experimen- tation. Each test session was composed of two sets of observations separated by a 5-min interval. A set consisted of five 1-min trials each separated by a 2-min interval. The trials entailed repeated ex- posure of randomly chosen worms to potential predation by each fish by dropping the worm from a widemouthed glass pipette in close proximity to the head of the fish. Since the fish were previously fed from a pipette, they showed no hesitation m accepting potential food items delivered in this manner. Following release from the pipette, sev- eral possible combinations of behavioral responses of the fish were noted: 1) ingestion of the worm, 2) rejection of the worm following an active attempt at ingestion, 3) presence or absence of investiga- tions of the worm by the fish (investigation is defined here as an obvious "enticement" of the fish to the worm without an attempt at ingestion), and 4) avoidance of the fish to the worm. The behavior of P. mucosa was also noted following release from the pipette and after rejection or avoidance by the fish. If the worm sank to the floor of the aquarium, either after rejection or without any contact with the fish, it was taken off the bottom and again dropped in front of the fish. This process was re- peated as often as a l-min trial would allow. Dis- counting delays due to behavioral interactions, this averaged one exposure every 6 s. Prior to the start of the first set of each test session and 1 min after each trial ended, the fish was fed a small portion of frozen brine shrimp to ensure active feeding. If at any time during a test the fish re- fused to eat the brine shrimp, the experiment was terminated. Because of terminations, the number of sessions per species offish varied. Initial qual- itative tests subjecting various other test or- ganisms found on Henlopen Flats to potential predation are also noted on Table 1. To test whether the mucoid secretion truly acts as the predatory inhibitor in P. mucosa, two further tests were carried out. First, mucus was removed from the surface of P. mucosa by re- peatedly sucking the worm in and out of a narrow-mouthed glass pipette and then gently dabbing it with a clean, lintless cloth. The worm was then fed to a rock gunnel. Second, mucus from P. mucosa was collected by placing several of the worms in a small, dry stendor dish, allowing the worms to physically irritate each other and thus produce a copious supply of mucus. After the phyl- lodocids were removed from the dish, a small Nephtys incisa, which secretes very little external mucus, was placed in it and allowed to accumulate a thick mucoid coat. The nephtyd was then fed to the rock gunnel. For histological .study of the mucus-producing organs of P. mucosa, entire worms were fixed in Zenker's or Hollande's fixatives and embedded in polyester wax. Blocks were cut at 5 ixm and sec- tions stained with Mallory's "Azan" or toluidine blue in l.O'ii borax. To examine the ultrastructure of the parapodial cirri of P. mucosa, small worms were fixed for 1 h in cold Anderson's fixative, cut into 2 mm sections with a razor blade, thoroughly rinsed with phos- phate buffer (pH 7.2), and postfixed for 1 h in 2.0% osmium tetroxide in a phosphate buffer. Following dehydration in a gi'aded acetone series, the speci- mens were embedded in Spurr's low viscosity medium and polymerized at 60 C for 48 h. Thin sections, cut on a Porter-Blum'' MTl ultramicro- tome using glass knives, were stained with uranyl acetate and Sato lead citrate. Sections were examined with a Philips EM201 transmission electron microscope at an accelerating voltage of 80 kV. RESULTS Response of Fish Results of the feeding experiments for the vari- ous species offish being fed P. mucosa along with the length of each are summarized in Tables 2 and ^Reference to trade names does not imply endorsement by the University of Delaware, College of Marine Studies or by the National Mai'ine Fisheries Service. NOAA. 607 FISHERY BULLETIN: VOL 77. NO 3 Table 2, — Number of attempts to ingest Phyllodoce mucosa by several species offish An attempt is defined as a single intake and expulsion of the worm. The number following the ab- breviated fish binomial stands for an individual fish and the small letter that follows stands for an individual worm. The two numbers in parenthesis in the first column are the standard lengths of the fish and maximum length of the worm, in mil- limeters, respectively Fh = Fundulus heteroclitus. Ga = Gas- terosteus aculealus. Mm = Menidm mentdia, Cv = Cypnnodon variegatus, Lm ^ Lophopsetta maculata, Cr = Cynoscion re- galia, t =experiment terminated, * = worm eaten. Set A. trial Session 1 Total Fhia (63.22) Ftilb (63.29) Fh2c (66.18) Fh3d (52,19) Fh4e (61,19) Gala (18.9) Ga2a (18.15) Ga2b (18.12) Ga3c (18.13) Ga3d (18.24) Ga4e (18.12) GaSe (18.12) Mm la (44.24) Mm2b (37.22) Mm3c (51.17) Mm4d (54.14) MmSe (64.18) Mm5l (64.23) Mm6g (67.13) Cvia (46.24) Cvlb (46.24) Cv2c (46.14) Cv2d (46.12) Lm1a (69.29) Lmlb (69.21) Lm2a (91.29) Lm2c (91.17) Lm2d (91.21) Crla (42.24) Crib (42,16) Crlc (42,26) Cr2d (46,14) Cr2e (46.22) Cr2( (46.17) 3 5- 9 4- 4 2- 13- 10- 21 2 29 0 14 10 3 r 2- 4' 3 2 3 6 2 2 7 1 2 2 2 Ot 2 6 Ot 2 4 0 6 5 1 20 5- 1 20 5- 0 Ot Ot 1 0 Ot 1 4 5 6 4 5 4 5 3 5 4 13 6 13 10 26 53 34 34 1 19 8 12 11 18 7 1 2 4 15 16 8 24 11 31 13 22 27 6 23 0 44 0 40 3. The large number of ingestive attempts in a given trial (Table 2) resultetd from the rapici, re- petitive actions of a fish not allowing the worm to settle to the floor of the aquarium following initial attempts. Results of the control series using S. fragilis and sizes of fish and worms are given in Table 4. Of the six species offish quantitatively tested, only the mummichog, Fundulus heteroclitus, con- sistently ingested P. mucosa early in set A (Table 2). This species of fish showed no investigative behavior before taking the worm into its mouth. Nevertheless, F. heteroclitus did show some dis- taste for this polychaete; in two cases the mum- michog sucked the worm in and out 13 times prior to ingestion. When F. heteroclitus did eat the worm, ingestion was immediately followed by a variable period ( 10-45 si of choking or "coughing" Table 3.— Number of investigations undertaken by four species of fish when exposed to Phyllodoce mucosa This table excludes Fundulus heleroclitus and Cypnnodon rariegatus because these species showed no or insignificant investigatory behavior with- out attempts at ingestion. Abbreviations and notations as in Table 2. Set A. trial Set B. trial Session Total Gala (18.9) Ga2a (18,15) Ga2b (18,12) Ga3c (18.13) Ga3d (18,24) Ga4e (18,12) GaSe (18,12) Mmla (44.24) Mm2b (37.22) Mm3c (51,14) Mm4d (54.14) Mm5e (64.18) Mm5f (64.23) Mm6g (67.13) Lmla (69,29) Lmlb (69,21) Lm2a (91.29) Lm2c (91.17) Lm2d (91.21) Crla (42.24) Crib (42.16) Crlc (42.26) Cr2d (46,14) Cr2e (46.22) Cr2t (46.17) 14 2 5 0 9 6 5 6 5 5 0 0 0 0 3 0 12 23 23 0 23 0 19 Table 4.— Number of attempts to ingest the control polychaete Scoloplos fragdis and size offish and worm used. Abbreviations and notations as in Table 2 Session Session Ft.lx (48,15) Fhly (48.20) Galx (18,11) Ga2y (18. 9) Mmlx (37,14) Mm2y (64,13) Cvix (46.13) Cv2y (46.26) Lmlw (69.16) Lmlx( 69,25) Lm2y (91,17) Lm2z (91.23) Crix (42.14) Crly (42.17) 12 lit (rapid protraction and retraction of jaws and in- take and expulsion of water). In session Fhla, the worm was held in the mouth and only partially ejected many times prior to ingestion. During trial 2 of set A in session Fhlb, the fish, on the fourth attempt, took in the worm and exhibited a choking response which lasted 15 s before spitting out the posterior portion of the worm. The remain- ing portion of the polychaete was eaten after two further attempts. The maximal number of at- tempts prior to ingestion by F. heteroclitus was demonstrated by the smallest mummichog (Fh3d) and in trials involving the largest phyllodocid (Fhlb) (Table 2). Scoloplos fragilis was consumed on the first attempt by F. heteroclitus in each con- trol test (Table 4). 608 PREZANT: ANTIPREDATION MECHANISM OF PHYLLODOCE MUCOSA While only one size class of Gasterostetis aculeatus was used, there was no trend between size of the worm and ingestion by the fish ( Table 2 ). The largest as well as some of the smaller worms were not consumed. Sessions Gala, 2b, and 3a all resulted in ultimate ingestion of P. mucosa but involved 34-53 prior ingestive attempts. Of the seven sessions observed with G. aculeatus, these three sessions showed the highest number of at- tempted ingestions prior to consumption. In ses- sion Ga2a, there was a renewed expression of the antipredation mechanism at the start of set B (Ta- ble 2). Thus, sets A and B start with 21 and 20 attempts, respectively, followed by a decrease in the number of attempts in set A and consumption in trial 2 of set B. In most of the sessions between G. aculeatus and P. mucosa, lack of ingestive attempts seemed to correspond with the presence of investigative re- sponses (Tables 2, 3). These investigations in- volved a close approach to the worm as it sank through the water column, and in some cases a recoil from the worm without evidence of direct contact. In cases where the worm was consumed, the fish exhibited a coughing response which lasted several seconds. Gasterosteus aculeatus readily consumed S. fragilis (Table 4). A correlation between the size of the Atlantic silverside, Menidia menidia, and its ability to con- sume P. mucosa is suggested (Table 2). Smaller fish showed little interest in the worms following initial experiences in set A. while the larger fish often consumed the worm very early in the first set. During set A. fish <50 mm initiated several attacks on the phyllodocids. and the worm was easily taken into the buccal cavity before rejec- tion. A rejected worm was often so densely covered with mucus that it would cling to the lower lip of the fish by a mucus thread for several seconds. Menidia menidia also exhibited coughing reac- tions following attempted and succegsful inges- tions. Larger silversides were quick to respond to potential food items released into the aquarium and swiftly sucked them in. In set Mm5f, a 64 mm fish was fed a 23 mm worm. On the first attempt at ingestion by the fish, the worm was quickly taken, whereupon the fish reacted with a coughing re- sponse lasting 45 s. The fish also exhibited a vio- lent lateral head shaking during this time. Fol- lowing this, the worm was totally ejected but the fish continued reacting as described for several seconds. This was the only case where an entire worm was injured prior to ejection. The worm. though alive, lost several parapodia and cirri and appeared sluggish. This same worm was again placed in the aquarium with the fish and was again set upon, producing a coughing response lasting 30 s but was not rejected. This fish did postfeed on A. marina and M. menidia showed no hesitation in consuming S. fragilis. Only a single size class of sheepshead minnow, Cyprinodon variegatus, was available. This species was exposed to P. mucosa ranging in size from 12 to 24 mm and showed a consistent rejec- tion of each size class (Table 2i. In no case was a coughing reaction noted. Cyprinodon variegatus appeared able to distinguish between P. mucosa and A. marina from short distances (up to 15 cm). The fish showed almost no investigatory behavior after initial ingestive attempts in a given trial but did quickly swim over to feed on A. marina in every case of exposure. Scoloplos fragilis was eaten on the first attempt in each control test with C. variegatus (Table 4). The windowpane flounder. Lophopsetta maculata, was the largest fish used in this study. This species rejected the phyllodocids without fail, showing 1 1-31 attempts at ingestion (Table 2) and also exhibited coughing responses following in- gestive attempts. The two sessions with L. maculata, making the greatest number of at- tempts to ingest (Lmlb and 2d) (Table 2), also registered the greatest degree of inquisitiveness (Table 3). There was no relation between size of fish and size of worm in these interactions. As Table 4 shows, there was some hesitation by the larger L. maculata in the control series when of- fered S. fragilis. In all of these control tests but one (Lm2z was terminated), the fish eventually ate the worm, but in Lm2y the fish made 21 attempts and ran into the second trial of set A prior to ingestion. Less than 1 h later, this same fish actively and quickly fed on 12 mm Scolecolepides viridis and 31 mm Ner-eis virens. Juvenile weakfish, Cynoscion regalis, also re- fused to eat P. mucosa (Table 2). There may be a relationship between the number of attempts to ingest and the size of the worm in these cases (Table 2i. In Crlc and 2e, the worms used were among the three largest (26 and 22 mm, respec- tively), and in both cases the fish showed a violent headshaking respon.se to void its buccal chamber. It thereafter became "nervous" and would not feed on A. marina. In Crla a 24 mm worm was used, and in the entire session only six attempts at in- gestion were made. All the remaining P. mucosa 609 FISHERY BULLETIN: VOL 77, NO. 3 tested with C. regal is were <20 mm long, and in- gestive attempts ranged from 23 to 44/session. Cynoscion regalis exhibited frequent investiga- tive responses (Table 3) which, unlike those of most of the other fish, usually involved direct con- tact with the worm by bumping it with its snout. In some cases following this contact, the fish would show a headshaking reaction similar to that pro- duced by attempted ingestion. Cynoscion regalis consumed Scoloplos fragilis during the first trials of the control series (Table 4). During the course of these experiments, indi- viduals of each species offish were given the op- portunity to feed on several other species of polychaetes. These included Spio filicornis, Neph- tys incisa. Nereis virens. Glycera americana, Scolecolepides viridis. and- Hydroides dianthus. Each fish readily consumed each of these species from several size classes, in almost every case on the first attempt. Preliminary data has also been collected on Eumida sanguinea tested with L. maculata. Test worms ranged from 9 to 13 mm long and were consistently rejected. A 69 mm L. maculata re- jected a 13 mm long E. sanguinea 20 times over a single session, while a 91 mm flounder rejected a 12 mm long worm 38 times in a session. Investiga- tions ranged from 6 to 10/session and showed no obvious relationship with ingestive attempts. In qualitative observations, it was also noted that the rock gunnel rejected both P. mucosa and P. maculata. Removal of the mucus coat from P. mucosa re- sulted in quick consumption by P hoi is gunnellus. Emplacement of the phyllodocid mucus on a small Nephyts incisa, which were previously a quick meal for P. gunnellus. resulted in rejection of the nephtyd polychaete by the rock gunnel many times prior to ingestion. Initial observations were also made on the sea robin, Prionotus evolans. fed Stylochus zebra. Lineus ruber, and Phascoleopsis gouldi. Fundulus heteroclitus and C. regalis were also tested with P. gouldi. In each case the fish showed adverse reac- tions (coughing, headshaking, and rejection) after ingestive attempts. The sea robin rejected S. zehi-a 75 times over eight trials before consuming the flatworm. In many cases, the turbellarian was held in the buccal chamber for as long as 21 s before ejection. Both the nemertean and the flat- worm produced copius quantities of mucus when irritated, whereas the sipunculid did not. Behavior of Phyllodoce mucosa Phyllodoce mucosa showed relatively consistent reactions upon release into the aquarium and fol- lowing rejection. When first released, the worm fell slowly through the water in a semicurl posi- tion, or curled in a tight ball and fell at a slightly faster rate. After a worm was taken and rejected by a fish, it was covered with a thick layer of viscous mucus. Immediately after rejection, the worm coiled into the tight, spheroid position. In this position, it was either retaken by the fish and the process repeated until the worm was eaten, or the worm was dropped, after initial attempts, to the floor of the tank. If the worm drifted unharmed to the floor of the aquarium, it usually started what appeared to be an exploratory phase which consisted of several short excursions in various directions before setting out on a single, straight path toward one of the corners of the aquarium. During this exploratory period, the worm held its dorsal parapodial cirri folded against its dorsum. Histology and Ultrastructure of Phyllodoce mucosa Parapodial Cirri The glandular and sensitive dorsal and ventral parapodial cirri of P. mucosa are the primary sources of externally released mucoid secretion. The dorsal cirrus possesses a large nerve which runs along the cirral axis and then radiates cen- trally into several smaller nerves which wind be- tween the large cirral mucocytes (Figure 1). Numerous free neural extensions penetrate the cirral epithelium. Large, ovoid mucocytes, which stain beta-metachromatically with toluidine blue (Figure 1, lower), fill most of the cirrus. These broad and elongated cells have small basal nuclei. In worms that have been irritated prior to fixation, the previously metachromatic mucocytes appear as large, empty vacuoles surrounded by many immature mucus cells (Figure 1, upper). The lat- ter are usually small, irregularly shaped cells which are densely packed with basophilic but or- thochromatic secretory granules. The outer, cen- tral portion of the dorsal cirrus has a narrow bank of melanic pigment cells. There are also thin mus- cle bands which enter the cirrus along the dorsal region of the cirral peduncle. Electron microscopy reveals a dense microvillar and ciliary border lining the short, columnar epithelium of the dorsal cirrus (Figure 2). The epithelial cells have large, irregular nuclei with 610 PREZANT. ANTIPREDATION MECHANISM OF PHYLLODOCE MUCOSA 30 pm iii 30tjm /•• Figure l. — Upper: An oblique-frontal section of the dorsal parapoidial cirrus of the polychaete Phyllodoce mucosa. This specimen was irritated prior to fixation resulting in the loss of the mucoid secretion produced by mature cirral mucocytes. The vacuolated regions mark the remnants of the mature muco- cytes. The large cirral nerve is also evident. Zenker's fixative, "Azan" stain, m = immature mucocyte; n = neural extension; N = cirral nerve; V = vacuolated mucocyte. Lower: The dorsal parapodial cirrus of a relaxed specimen of P. mucosa in trans- verse section, fixed without excessive mucus loss. The cirral mucocvtes show a beta-metachromatic reaction with toluidine blue HoUande's fixative, toluidine blue stain. M = meta- chromatic mucocyte. abundant heterochromatin material. Many im- mature secretory inclusions are present near the epithelial surface as well as subepithelially. The immature secretory droplets occur in a loose for- mation and are surrounded by a dense array of smooth endoplasmic reticulum. The larger, less electron dense, mature secretory droplets occur in tighter, membrane bound accumulations. Figure 2 shows a portion of a vacuolated mucous cell bounding a central nucleus. Both the mature and vacuolated secretory cells have numerous, small mitochondria associated with them. The smaller, ventral cirrus is histologically and cytologically similar to the dorsal cirrus, and is equipped with oblong mucocytes in both mature and immature stages. Also present is a large cirral nerve and thin longitudinal muscle bands. Melanic pigmentation is not obvious in sections of the ventral cirri. DISCUSSION AND CONCLUSIONS Many factors influence successful predation. Griffiths (1975) believed that prey abundance and prey size are two of the prime variables affecting predation success but that situations do occur in which predators react to prey characteristics other than body size. These characteristics include phys- ical avoidance by potential prey (Fagade and Olaniyan 1973) which may be chemically mediated by a secretion released by the predator (Mackieetal. 1968: Doering 1976; Mayo and Mac- kie 1976), physical deterrents of the potential prey species such as spines (Hoogland et al. 1956; Bakus 1966), or innate defen.se mechanisms of the potential prey such as toxicity or unpalatability (Thompson 1960; Bakus 1966, 1968; Gibson 1972; Rahemtulla and Lovtrup 1974). An epidermal, mucoid secretion is responsible for the protection of at least some phyllodocid polychaetes from ac- tive predation by some small or juvenile fish. Since phyllodocids are relatively small benthic worms, it is unlikely that many large fish would expend the energy needed to use them as a primary food source; thus only smaller fish would potentially make any notable impact on the phyllodocid popu- lations. Russell (1966) tested the palatability of tissues from 48 species of marine organisms with two marine iPelatus quaclrllincntus and Torquigener hamiltoni) and two freshwater {Gambusia affinis and Carassius atiratus) species of fish ranging from 25 to 90 mm. This involved choice experi- ments with the fish simultaneously offered a known palatable organism and a test organism of unknown palatability. The results revealed many unpalatable species which were rejected by the fish. The majority of these tests involved only three or fewer trials and there is little note con- cerning specific reaction of fish to potential prey items. Among the palatable items found by Rus- sell was Phyllodoce malgremi. Phyllodocids, as all other test organisms, were cut to acceptable sizes based on preliminary trials which noted size limits of prey for each fish. Phyllodoce malgremi might indeed be consumed by these particular fish but the limited number oftrials( two per fish) and lack of corresponding worm size data plus the previous treatment of the worms (i.e., sectioned into frag- ments) may have led to misleading data concern- ing palatability. Few reports list phyllodocids as a major portion of a fish's diet; however, Wigley ( 1956) did list four 611 FISHERY BULLETIN: VOL 77, NO 3 » . • 5 nm Figure 2— The ultrastructurc of the dorsal parapodial cirrus of thepolychaete f/iyWorfoce mucosa. The micrograph shows the dense array of cilia and microvilli which line the cirral epithelium as well as mature and immature secretory droplets and associated organelles. Anderson's and osmium tetroxide fixation, uranyl acetate, and Sato lead stain. S = mature secretory droplets; A = mitochondria; E = smooth endoplasmic reticulum. Other abbreviations as in Figure 1 species of phyllodocids in the food of the haddock, Melanogrammus aeglefinis. No phyllodocids were among the 11 dominant prey species of the larger fish examined. VVigley noted, however, that be- cause of the small, subterminal mouth, most of the haddocks' prey were small and thin. Small inver- tebrates, including phyllodocids, were listed as dominant foods of the few smaller 1 14-.30 cm) had- dock examined. Annelids composed only 1.9'/i of the prey items found in the haddock study and no note was made of the diet offish •14 cm. Data for small juveniles is found in only a few studies in- volving bulk analysis of fish stomach contents iStickney et al. 1975; Chao and Musick 1977). In nature, initial rejection and adverse reaction of a fish to P. mucosa may give the potential prey sufficient time to retreat from harm. Chiszar and Windell (1973) found that satiated bluegill, Lepomis inacrochirus, have more selective feeding habits than starved fish. This may imply that in natural conditions a normally feeding fish may not persist in an attack on an unpalatable prey or- ganism. Murdoch et al. ( 1975) suggested that predators distribute attacks among prey species in response to the prey's relative densities. These authors broke down events leading to final ingestion of prey into a series of predatory behaviors, includ- ing "choosing" to attack the prey species. Once a potential prey is perceived and located, the "choice" is up to the predator whether to attack or not. If the organism is attacked and successfully 612 PREZANT: ANTIPREDATION MECHANISM OF PHYLLODOCE MUCOSA consumed, the predator may set up a "specific searching image" iTinbergen 1960), which would increase its chance of locating additional speci- mens provided more of the same prey species can be found while remforcement is still fresh. Thus, this pattern is only relevant when prey species occur in relatively high densities. Phyllodoce mu- cosa is found in moderately high densities in Na- hant Bay with many other polychaetes such as Prionospw malmgreni, Scoloplos armiger, and Nephtys spp. If a small fish encounters and at- tempts to eat a Phyllodoce mucosa but is repulsed by the worm's defenses several times, the fish may eventually set up a negative searching image and thus avoid further "discomfort" caused by at- tempted ingestion. While simultaneous choices of food may be a rare event in nature (Beukema 1968), when it does occur between a phyllodocid and another tvpe of prey of similar size, a fish with a negative image may "select" the nonphyllodocid prey. This is indicated in the present data by the relationship between ingestive attempts and in- vestigations of Gasterosteus aculeatus and the "loss of interest" shown by the smaller Menidia menidia. Kneib and Sti ven ( 1978 ) recently found that the diet of F. heteroclitus in a IJorth Carolina salt marsh varied with the size of ;;he fish (smaller fish were carnivorous while laiger individuals were omnivorous). In this case, alteration in diet seemed to reflect a physiological and morphologi- cal change in the fish with growth. This conversion of food habits may be based upon the ability of the fish to eat different food items because of its pro- portionally larger size or it might indicate a change in the "ability" of the fish to consume less appeal- ing food items if the "need" arises. Data presented here indicate that larger M. menidia might be more effective in consuming phyllodocids than smaller M. menidia. Smaller fish may not be able to "handle" a phyllodocid of a size that a larger fish might readily consume. This is based solely upon the reaction of the fish to the mucoid secretion since smaller fish were able to consume compara- tively large nonphyllodocid polychaetes. The largest fish used in the present study, a juvenile Lophopsetta maculata, about 9 cm long, consistently rejected P. mucosa. Lophopsetta maculata is an active predator of mobile prey (Ta- ble 1 ). The large buccal chamber and distensibility of the esophagus of this flounder preclude the pos- sibility that the phyllodocid mucus acts as a physi- cal barrier to ingestion (i.e., an occlusive plug) but instead indicate that the mucus contains some irritating or obnoxious substance which repels the fish. The high sensitivity and secretory nature of the parapodial cirri is reflected in the complex ultra- structure shown in Figure 2, however, P. mucosa does not seem able to continually produce an adequate supply of protective mucus. This is indi- cated by ingestion of the worm by G. aculeatus following numerous rejections from this fish's small, sharply toothed buccal cavity which may have removed the protective cover. Similar results are obtainable with a smallmouthed pipette, which simulates this. The large, empty vacuoles in the dorsal cirri surrounded by immature muco- cytes indicate a lag between total loss of available secretion and maturation of additional, functional mucocytes. Beukema (1968) suggested that G. aculeatus hunts by sight only and its sense of smell plays little if any role in finding food. This is supported in the data presented here by the correlation be- tween investigations and ingestive attempts. In- vestigations involved no direct contact but only close observation of the worm by the fish. Ejectory behavior by G. aculeatus feeding on clumps ofTubifcx spp. oligochaetes was discussed by Tugendhat (1960) who found that this action caused a breakdown of the clumps into individual worms which were easily ingested. Hynes ( 1950) noted that young G. aculeatus feed on proportion- ally smaller prey items and that the diet changed to larger prey as the fish grew. The largest phyl- lodocid fed to a G. aculeatus in the present study was 24 mm long, and it was investigated but only one attempt at ingestion was made. In this case, the worm probably was too large for the fish to deal with. The only species of fish tested which consis- tently ate P. mucosa wasF. heteroclitus. Fundulus heteroclitus, a well-known inhabitant of salt marshes, is only rarely found in strictly saline environments iHildebrand and Schroeder 1928). Vinceet al. ( 1976) showed thatF. heteroclitus may cause an impact on the abundance and distribu- tion of some prey species, and Eraser ( 1973) found that Fundulus spp. would consume prey items in proportion to prey densities. Since P. mucosa is not a normal resident of salt marshes the question must be asked: does the fact that these two or- ganisms occur in different environments influence the predator-prey interactions between these species when brought together? According to Tin- 613 FISHERY BULLETIN VOL 77. NO 3 bergen il960), there may be an obvious delay in the attack on a potential prey if it is new to the predator. No such delay was seen in these experi- ments using semistarved fish. It is unlikely that P. mucosa has developed a defense mechanism which is specific in its action only to marine fish. The ability of F. heteroclitus to consistently consume P. mucosa probably reflects the predaceous mum- michog's lack of sensitivity or its ability to over- come the irritation or unpalatability of this worm. Cypnnodon variegatus always rejected the phyl- lodocids and rarely investigated the worm without attempted ingestion. The small, terminal mouth of this fish, with its large tricuspid teeth and pro- tractile premaxillaries, was quite efficient at quickly devouring all nonphyllodocid polychaetes offered to the fish during these experiments. Cynoscion regalis is primarily an active pelagic predator (Table 1). There has been some research concerning the feeding habits of juvenile sciaenids (Thomas 1977; Chao and Musick 1977) which found that small C. regalis feed mainly on mysids, copepods, and small fish. Annelids do form, how- ever, a portion of the weakfish's diet (Table 1). Bigelow and Schroeder (1953) noted that the diet of C. regalis varies with locality and availability of prey. Small weakfish reject P. mucosa as a food item. Cynoscion regalis showed active investiga- tory behavior which usually consisted of tapping or bumping the sinking worm with its snout. Di- rect contact often resulted in a rapid shunning of the worm by the fish. This may indicate the pres- ence of sensitive nares chemoreceptors. The juvenile fish would not be a major threat to these worms even were they readily available. Preliminary work indicates that antipredation responses are active in P. maculata.E. sanguinea, Phascoleopsis gouldi. Stylochus zebra, and Lineus ruber. All these organisms, except the sipunculid, secrete large quantities of mucus. The epidermis of many sipunculids is densely packed with gland cells (Tetry 1959) and some secretion from these glands may serve to protect the animal from pre- dation. Stylochus zebra, is a commensal of pagund crabs; abundant production of mucus by this worm may tend to keep this relationship commensal. The role of secretory defense mechanisms is well established in many species of marine animals (Graham 1957; Thompson 1960, 1969; Bakus 1 968 ), but many questions concerning the broader aspects of antipredational responses remain un- answered. Are antipredation responses reflected in the composition of marine benthic com- munities? How does effectiveness of antipredation mechanisms vary with size of predators or degree of predator satiation? In similar-sized predators, what differences allow one species to prey on a given organism and not on the other? What changes in diet would be found if feeding studies involving analyses of stomach contents typically were extended to include all size classes offish? Does previous exposure to an antipredation mechanism produce "learning" in potential marine predators? In responding to slow-moving predators many potential prey species have evolved escape reac- tions (Doering 1976). In dealing with highly mobile fish predators, many species of potential prey have developed such defense mechanisms as protective secretions. Lagler et al. (1977:142) stated, "In general the esophagus (offish) is so distensible that it can accommodate anything that the fish can get into its mouth . . . . " With the dis- covery of the repulsive characteristics of certain phyllodocids, the indications of antipredation mechanisms in a sipunculid and turbellarian re- ported here, added to what is known of nemerteans and opisthobranchs, it is clear that a closer exami- nation must be made of interspecific molecular interactions which occur within marine com- munities. ACKNOWLEDGMENTS I gratefully acknowledge the many helpful suggestions concerning this manuscript which were received from M. R. Carriker, F. C. Daiber, B. Brown, R. Palmer, and L. Williams. I also thank L. Watling and G. Entrot for constructive criticisms of an earlier draft of this paper. Harlan Dean, G. Entrot, S. Howe, P. Nimeskern, F. Prezant, J. Vargas, and W. Wehling helped in the collection of animals used in this study, and I thank them for their efforts. The use of the RV Clione and facilities at the Marine Science Institute, Nahant, Mass., were kindly supplied by N. W. Riser. Thanks also to P. Savage for typing the manus- cript. LITERATURE CITED B.AKL'S. G, J. 1966 Some relationships of fishes to benthic organisms on coral reefs. Nature iLond.l 210:280-284, 1968, Defensive mechanisms and ecology of some tropical holothurians Mar Biol (Berl I 2:23-32. 614 PREZANT; ANTIPREDATION MECHANISM OF PHYLLODOCE MVC Berg, J. 1979 Discussion of methods of investigating the food of fishes, with reference to a preliminary study of the prey of Gobiusculus flavescens (Gobiidae). Mar. Biol. (Berl.) 50:263-273. BEUKEMA. J. J. 1968. Predation by the three-spined stickleback iGa.s/cros- teus aculeatus L.): the influence of hunger and experi- ence. Behaviour 31:1-126. BIGELOW, H. B-, AND W. C. SCHROEDER. 1953. Fishes of the Gulf of Maine. U.S. Fi.sh Wild! Serv.. Fish. Bull. 53, 577 p. Chad. L. N., and J. A. Musick. 1977. Life history, feeding habits, and functional mor- phology of juvenile sciaenid fishes in the York River es- tuary. Virginia. Fish. Bull., U.S. 75:657-702. CHISZAR, D., and J. T. WINDELL. 1973. Predation by bluegill sunfish (Leopomis mac- rochirus Rafinesque) upon mealworm larvae [Tenehno molitor). Anim. Behav. 21:536-543. DOERING, P. H. 1976. A burrowing response of Mercenuria mercenaria (Linnaeus, 17581 elicited by Asterias forbesi (Desor, 1848). Veliger 19:167-175. Facade, S. 0.. and C. L O. Olaniyan. 1973. The food and feeding interrelationship of the fishes in the Lagos Lagoon. J. Fish. Biol. 5:205-225. Fauchald, K. 1977. The polychaete worms. Definitions and keys to the orders, families and genera. Nat. Hist. Mas. Los Ang Cty.. Sci. Ser. 28:1-190. FRASER. A. 1973. Foraging strategies in three species of Fun- dulus. M.S. Thesis. Univ. Maryland, College Park, 54 p. Gibson, r. 1972. Nemerteans. Hutchinson Univ. Library, Lond. 224 p. GRAHAM, A. 1957. The molluscan skin with special reference to Proso- branchs. Proc. Malac. Soc. Lond. 32135-144. Griffiths, d. 1975. Prey availability and the food of predators. Ecol- ogy 56:1209-1214. HILDEBR^ND, S. F., AND W. C. SCHROEDER. 1928. Fishes of Chesapeake Bay. Bull. U.S. Bur Fish 43. 366 p. HoooLAND. R.. d. Morris, and N. Tinbergen. 1956. The spines of sticklebacks iGasterosteus and Pygos teus) as a means of defence against predators (Perca and Esnx). Behaviour 10:205-2.36. HYNES. H. B. N. 1950. The food of fresh-water sticklebacks iGaslerosteu>^ aculeatus and Pygosteus pungittus), with a review ol methods used in studies of the food of fishes. J. Anim Ecol. 19:36-58. IVLEV. V. S. 1961. Experimental ecology of the feeding of fishes (Translated from Russ. by D. Scott). Yale Univ. Press New Haven. 302 p. KISLALIOGLU. M.. AND R. N. GIBSON. 1977. The feeding relationship of shallow water fishes in a Scottish sea loch. J. Fish. Biol. 11:257-266. KNEIB. R. T.. AND A. E. Stiven. 1978. Growth, reproduction, and feeding of Fundulut keteroclitus (L.I on a North Carolina salt marsh. J. Exp Mar. Biol. Ecol. 31:121-140. Lagler, K. F., J. E. Bardach, R. R. Miller, and D. R. M. PASSING. 1977. Ichthyology. Wiley, N.Y., 506 p. Mackie, a. M., R. Lasker. and p. T. Grant. 1968. Avoidance reactions of a mollusc Buccinum un- datitm to saponin-like surface-active substances in ex- tracts of the starfish Asterias rubens and Marthasterias glacialis. Comp. Biochem. Physiol. 26:415-428. Mayo, p., and a. M. Mackie. 1976. Studies of avoidance reactions in several species of predatory British seastars (Echinodemata: Asteriodea). Mar. Biol. (Berl.) 38:41-49. MURDOCH. W. W.. S. Avery, and M. E. B. Smyth. 1975. Switching in predatory fish. Ecology 56:1094- 1105. Nikolsky. G. v. 1963. The ecology of fishes. (Translated from Russ. by L Birkett). Acad, Press, London and NY.. 352 p. Onyia. a. D. 1973. A contribution to the food and feeding habit of the threadfin Galeoides decadatylus. Mar. Biol. (Berl.i 22:371-378. PETTIBONE, M. H. 1963. Marine polychaete worms of the New England re- gion I. Families Aphroditidae through Trochochaetidae U.S. Natl. Mus. Bull. 227, 356 p. Qasim, S. Z. 1957. The biology of Centronotus gunnellus (L.) (Teleos- tei). J. Anim. Ecol. 26:389-401. R.\HEMTULLA. F., AND S. L0VTRUP. 1974. The comparative biochemistry of invertebrate mucopolysaccharides. II. Nematoda; Annelida. Comp. Biochem. Physiol. 496:639-646. RUSSELL, E. 1966. An investigation of the palatability of some marine invertebrates to four species offish. Pac. Sci. 20:452-460 SANDERS, H. L.. R. R. HESSLER. AND G. R. HAMPSON. 1965. An introduction to the study of deep-sea benthic faunal assemblages along the Gay Head-Bermuda tran- sect. Deep Sea Res. 12:845-867. Smith. R. W.. and F. C. Daiber. 1977. Biology of the summer flounder, Paro/ic/i(Ay.«rfi?ni from three Oregon hatcheries, we selected eight characters that we believed were potentially use- ful in separating hatchery from wild fish (Table 3). Characters were selected based on the assumption that the freshwater rearing environments for hatchery and wild coho salmon are distinctly dif- ferent and differences in scales between the two groups would be manifest during this period. We selected for analysis preocean radius and preocean circulus counts on the basis of results of Peck ( 1970) and on data on weights of smolts being T.ABLE 1 —Number of adipose clipped and unmarked coho salm- on sampled for scales at Oregon ports in 1977 Ports are arranged from north to south. Port Marked Unmarked Port Marked Unmarked Hammond 5 356 Coos Bay 9 165 Garibaldi 43 188 Gold Beach 0 30 Depoe Bay 64 516 Brookings 0 56 Newporl 33 412 Winchester Bay 24 331 Total 178 2.054 Table 2. — Ongin of scales of wild coho salmon, brood year, and number of scale samples from each geographic location. "Berry, R, L. 197,5. Spawning surveys in coastal water- sheds, 1974. Oreg, Dep. Fish Wildl. Coastal Rivers Inf Rep 75-4. P.O. Box 529, Tillamiwk, OR 97141. County ot Brood Number of River system collection year samples Necanicum Clatsop 1974 3 Salmon Lincoln 1973 46 Salmon Lincoln 1974 16 Alsea (Flynn Creek) Lincoln 1962 ' Alsea (Flynn Creek) Lincoln 1963 32 Alsea (Needle Branch) Lincoln 1963 27 Alsea (Deer Creek) Lincoln 1963 28 Coos and Coquille Coos 1974 4 Total 162 618 liCARNECCHlA and WAC.NER CONTRIBUTION OF COHO SALMON To OCEAN SPORT FISHERY ITaBLE 3. — Description of scale characters measured or counted in this study from known hatchery and wild coho salmon- All measurements are made at angles ventral to the longest axis. ) Character Description 1 Radius of preocean zone at 20 2 Number o( circuli in the preocean zone at 20 3 Distance between circuli 1 and 5 ol the preocean zone at 90 4 Distance between circuli 1 and 10 of the preocean zone at 90 5 Distance between circuli 1 and 15 of the preocean zone at 90 ji 6 Radius of preocean zone at 90 ■ 7 Number of circuli in preocean zone at 90" 7 3 Number of broken or branched circuli within precise- ly defined zone (see fvlethods) released by hatcheries of the Oregon Department of Fish and Wildlife. Most hatchery-reared smolts currently being released by Oregon's hatcheries are larger than wild smolts (Oregon Department of Fish and Wildlife"). Because radii of scales and number of circuli appear to be well correlated to length of Pacific salmon smolts (Clutter and Whitesel 1956), they are logical selections for scale characters to use in separating hatchery and wild fish. .Some scales had no "plus" (Anas and Murai 1969) or estuarine growth whereas others had substantial amounts. We chose to measure total freshwater growth plus any spring and estuarine growth and to call that distance the "preocean" zone. We chose three spacing characters, 3 through 5 (Table 3), to determine whether the plentiful food supply of hatchery coho salmon would yield differ- ent spacing of circuli than that observed for wild fish. We measured these characters at 90 to the longest axis of the scale because breaking and branching of circuli is less at that angle than at lower angles to the longest axis. The number of broken or branched circuli (character 8, Table 3) was used to determine if circuli of hatchery fish were more or less branched than circuli of wild fish. It was postulated that regular feeding by hatchery fish would result in less breakmg and branching of circuli. For this character an acetate sheet with thin parallel lines 1 cm apart and a dotted line parallel to and mid- way between these lines was used as a guide. A small point at the end of the dotted line was placed at the center of the focus of the scale and a dotted line extended outward at 90" ventral to the longest axis. The two solid outer lines then enclosed a rectangular area. Within this area, we counted circuli 5 through 12 inclusive in the preocean zone of the scale and recorded the number of these cir- culi that were broken or branched. The eight characters in Table 3 were measured and counted from scales of known hatchery fish (Table 1) and known wild fish (Table 2). These measurements were subjected to discriminant function analysis, which reduced all characters for each scale to a single value and then, through a linear model, classified the scales as hatchery or wild (Nie et al. 1975). Assumptions in this analysis were that data were multivariate normal and had common variance-covariance matrices. Plotting the data for each of the eight characters individually showed that only character 8 de- viated somewhat from normal. Although normal- ity of individual characters does not imply joint normality, it indicates that the data conform fairly well with the assumption of multivariate normal- ity- From the discriminant function analyses, it was concluded that preocean radius at 20° ( character 1 ) was the most efficient individual character for separating hatchery and wild fish. Preocean radius at 20° is generally larger in hatchery fish than in wild fish. By using the character, we reli- ably separated S'2f7c of the hatchery fish and 89'/f oi the wild fish. While characters 1, 3, and 8 in combination would do as well, there would be no benefit to their use except that a slightly higher percentage (1.1) of hatchery fish would be correctly classified at the expense of a lower percentage (1.2) of wild fish correctly classified (Table 4). Since preocean radius at 20° was the most useful character for discriminating between adult hatch- ery and wild coho salmon, this character was mea- T.ABLE 4. — Combinations of scale characters to which discrimin- ant function analysis was applied and effectiveness at classify- ing coho salmon as to wild or hatchery origin. Percentage correctly classified 'Oregon Department of Fish and Wildlife. Unpubl. slat, of the Fish Culture Division. 17330 SE Evelyn Street. Clackamas. OR 97015. 1 , 8, and 3 1 and 2 1 through 8 1. 8. 3.2, and 5 Hatchery Wild Total 81.5 88,9 85 0 69.7 82.1 756 74.7 72.8 738 69.1 81.5 75 0 7S.3 75.3 75 3 78.7 85.8 82 1 70.2 69.1 69.7 68.0 85.4 66.8 82.6 87.7 B5 0 79.8 88.9 84 1 82.6 87.0 847 81,5 87.0 84 1 619 sured from scales from 2,054 unmarked coho salm- on (Table 1). In all scale readings only scales that had one or more ocean annuli were read. Fewer than 0.5% of the fish were age 2.1, and the scales indicated that the fish grew slowly in their first year of life.' These scales were assumed to be from wild fish. Wild and hatchery fish were assumed to have similar numbers of regenerated scales, most of which were regrown because of scale loss during freshwater rearing. If wild fish tend to lose more scales because of their more rigorous rearing envi- ronment in freshwater, the numbers of wild fish are slightly underestimated, since those samples taken from unmarked salmon that were discarded for lack of useable scales would have been biased toward being wild fish. Once we had classified scales from unmarked fish as hatchery or wild we weighted the number of unmarked fish that were landed at each port dur- ing 2-wk periods (sampling strata) for the season by our estimated percentages of hatchery and wild fish for that stratum. The estimated catch of known marked fish was then added to the un- 'Most adult coho salmon caught off Oregon are age 1.1, where numbers left and right of the decimal indicate number of fresh- water and marine annuli on the scales, respectively. Age 1 . 1 fish are in their third year of life. FISHERY BULLETIN VOL 77. NO ;l marked hatchery fish to find the total number of hatchery fish caught in that stratum (Table 5). Because of the small number of scales available from unmarked fish for several strata, we com- bined 2-wk periods for a given port where neces- sary to obtain a sample of at least 50 fish. Small sample sizes necessitated combining samples for Brookings and Gold Beach. The observed percentage of hatchery coho salm- on in the unmarked sample was corrected for wild fish incorrectly classified as hatchery fish, and hatchery fish incorrectly classified as wild fish. Confidence levels were also computed. Both proce- dures are described by Worlund and Fredin ( 1962 ). RESULTS The percentages of hatchery fish contributing to Oregon's sport fishery were highest near the Co- lumbia River and decreased steadily southward (Table 6). The percentages of wild fish in the catch were highest late in the season at Garibaldi, Depoe Bay, Newport, and Winchester Bay and near midseason at Hammond. Total estimated percentages of hatchery fish landed at each port from mid-June to mid-September 1977 were 85 at Hammond, 83 at Garibaldi, 79 at Depoe Bay, 77 at Newport, 61 at Winchester Bay, 65 at Coos Bay, Table 5. — Estimated number of coho salmon landed Oregon sport fishery by port in 1977. Data are for and the catch per angler day (in parentheses) by 2-wk periods from 16 June to 15 September. Port 16-30 June 1-15 July 16-31 July 1-15 Aug 16-31 Aug 1-15 Sept. Hammond 5.548 10.058 12.701 11.810 5,056 1.845 Garibaldi (1 34) 217 (133) 859 (135) 2,285 (0 88) 1,438 (0 45) 1,625 (0,36) 279 Depoe Bay (0,06) 1.090 (028) 2.624 (045) 7.909 (0 24) 2.927 (028) 5,032 (0 09) 616 Newport (0 24) 568 (0 32) 2.447 (0 70) 4,349 (0 28) 4.492 (0 46) 3,283 (013) 516 Winchester Bay (Oil) 2.602 (027) 5,328 (041) 10,175 (0.59) 9.217 (0 43) 1,639 (0,16) 1.287 Coos Bay (0,65) 641 (057) 1.923 (0 99) 3,522 (0.65) 1,553 (024) 638 (0,27) 244 Gold Beach (0 23) 9 (0 33) 2 (0 60) 812 (035) 337 (0 13) 68 (0 14) 17 Brookings (0 05) 33 (0 00) 19 (0 29) 8,603 (0 08) 2,141 (0 02) 96 (001) 180 (001) (0 00) (049) (0 16) (003) (0-04) Table 6. — Estimated percentages and 95% confidence intervals of hatchety-reared coho salmon in the total catch landed in 1977 by the Oregon sport fishery. Port 16-30 June 1-15 July 16-31 July 1-15 Aug. 16-31 Aug. t-15Sopt Hammond Bay /Brookings ( nin-Sfi ) 69,2±11.7 9n9-BP ( qnfi-^S.I ) Garibaldi ( MM±7.a ( SnB-RO ) Depoe Bay 79-7±67 95-714.4 100,0^0.2 92.3r5,5 ( Ri'.^U? ) 88,3 ±6.4 ( - 74 1 707±7.3 62 8 68,6*12.0 ( 64.1*7.8 ) Newport -6 1 ) ( 79n-in9 ) Winchester Coos Bay ( 58 9r10,3 _) B7a*in.i ) Gold Beact -mi ) 620 SCARXECCHIA and WAGNER CONTRIBUTION OF COHO SALMON TO OCEAN SPORT FISHERY and 63 at Brookings/Gold Beach. An estimated 75% of all coho salmon landed by the entire sport fishery from mid-June to mid-September 1977 originated from hatchery releases. Percentages of hatchery coho salmon by port and period, along with confidence intervals, are shown in Table 6. Since the sport fishery is mainly composed of private and charter boats on day-long trips, our estimated percentages of hatchery and wild fish by port probably reflect fairly well the actual per- centages occurring near each port, assuming simi- lar catchability of hatchei-y and wild fish. DISCUSSION Of the estimated 140,660 coho salmon caught in the ocean in 1977 by Oregon sport fishermen from mid-June to mid-September, 35,300 were wild fish. Although scales from fish caught by the com- mercial troll fishery were not analyzed in 1977, it is likely that the overall percentages of wild and hatchery fish were similar to those of sport fishery. To evaluate this likelihood, we compared observed percentage of marked fish in the monthly catch of the sport fishery for six Oregon ports with the percentage of marked fish in the corresponding commercial catch. In only 7 of the 18 comparisons for which sample sizes were adequate did percent- ages of marked fish caught in a given strata by the sport fishery differ from those of the commercial fishery (P<0.05), which indicates that overall per- centages of hatchery and wild fish are similar for the two fisheries. We can explain the north to south trend toward increasing percentage of wild fish in the catch (Table 6) by assuming a northward movement of hatchery and wild coho salmon as the season pro- gresses, as Van Hyning (1951) concluded, with wild fish from south and north coastal streams ceasing their northward movement near their natal streams. Since over 80% of the coho salmon produced by hatcheries in California, Oregon, and Washington ( excluding Puget Sound ) are released in the Columbia River and its tributaries (Oregon Department of Fish and Wildlife see footnote 7), many of the hatchery fish off the Oregon coast are probably headed for the Columbia River. These hatchery fish continue northward and concentrate near the mouth of the Columbia River. The argu- ment for south to north movement of coho salmon is supported by the occurrence of lower percent- ages of hatchery fish late in the fishing season in catches off of Garibaldi, Depoe Bay, Newport, and Winchester Bay (Table 6). Late in the season, hatchery fish may be proportionately less abun- dant along the south and central coast, since most Columbia River fish would have moved northward by this time, leaving mostly coastal hatchery and wild fish contributing to the south and central coast fisheries. The lowest percentage of hatchery fish noted was 49.7 at Winchester Bay, from 1 August to 15 September. Another possible factor contributing to lower percentage of hatchery coho salmon in the fishery to the south is that a substantial portion of adult hatchery fish released as smolts from Columbia River hatcheries do not migrate far southward along the Oregon coast. The argument is sup- ported by the large number of coho salmon caught per angler day at Hammond early in the fishing season (Table 5), perhaps indicating that coho salmon returning to the Columbia River are con- centrated near the river in early summer. The high percentage of hatchery fish caught at Ham- mond from 16 June to 15 July further supports this hypothesis (Table 6). The total catch of coho salmon and catch per angler day were low after mid-August 1977 from Winchester Bay southward, and were low for all ports after August (Table 5), so that while the percentage of wild coho salmon caught rose late in the season, the numbers caught were low, espe- cially along the southern coast. Closing the season for salmon fishing after mid-August would not have protected many wild coho salmon, and would have made only a small sacrifice in catch of hatch- ery fish. Almost twice as many chinook salmon, O. tshawytscha, would have been lost to the sport fishery. Combined data obtained from the Oregon De- partment of Fish and Wildlife from Winchester Bay to Brookings from mid-August to mid- September showed that an estimated 1.8 chinook salmon were caught for every coho salmon landed by sport fishermen. During years of higher abun- dance of coho salmon, fishermen may tend to fish more for coho and less for chinook salmon than they did in 1977, which would increase fishing pressure on wild stocks of coho salmon late in the season. If wild and hatchery fish are distributed differ- ently in oceanic areas, fishing pressure could be adjusted to meet management goals. If, however, there is substantial variability in the localities of capture of wild fish, either because of the fishery or because of environmental factors, and if hatchery 621 FISHERY BULLETIN: VOL, 77. NO :i fish intermingle extensively with wild fish, it will be difficult to protect wild stocks while maintain- ing high rates of harvest of hatchery fish in the ocean. Total Oregon troll and sport catch of coho salm- on in the ocean plus the Columbia River commer- cial catch was only 645,000 fish in 1977. Assuming that 75% are hatchery fish, only 162.000 of the fish originated from natural production. Average an- nual catch of coho salmon by the Oregon troll fishery alone from 1952 to 1956 was 312,000 fish, probably almost all wild fish. The lowest catch over the 5-yr period was 227,000 fish in 1954. This figure excludes fish caught in the ocean by sportsmen and also excludes the Columbia River catch. The average catch from 1952 to 1956 was 1.9 times higher than the catch of wild coho salm- on from the combined ocean troll and Columbia River net fisheries in 1977. Yet, the catch of wild fish in the 1950's was considered low enough to warrant closure of commercial gill net fisheries in all Oregon coastal streams to increase the es- capement of wild stocks. The efficient net fisheries of the 1950's were considered a primary threat to the production of wild salmon by some biologists. Recent analyses of marking experiments with coho salmon show some Oregon coastal stocks of hatchery fish with a catch to escapement ratio of 6 (Pacific Fishery Management Council 1978). As- suming wild fish are as readily catchable as hatch- ery fish, the effectiveness of the troll and offshore sport fisheries in harvesting coho salmon now ri- vals that of many terminal fisheries. Despite elimination of coastal Oregon net fisheries, abun- dance of wild coho salmon, from all indications of catch and escapement, is at an alltime low. The catch of wild fish might be considerably les,"- if it were not for the natural spawning of some hatchery fish and later rearing of their progeny ir streams. The number of wild coho salmon that results from natural spawning of hatchery fish that fail to return to hatcheries is unknown. Con- sidering the large numbers of smolts being re- leased, even a small percentage of straying by returning adults could lead to significant produc- tion in the wild, assuming that the progeny do not differ significantly in fitness from the progeny ot wild parents. ACKNOWLEDGMENTS We thank John D. Mclntyre, Carl B. Schreck James A. Lichatowich, and James D. Hall for of- fering valuable comments; Robert Mullin. Robert McQueen, and District Biologists of the Oregon Department of Fish and Wildlife for providing the scales; Stephen Lewis, Malcolm Zirges, and David Loomis for providing unpublished data on the sport and troll fisheries; Norbert Hartmann. David Niess, Allyson Macdonald, and Tumi Toinasson for assistance with the statistics; and Jan Ehmke for typing the manuscript. LITERATURE CITED AN.\s. R. E.. .A.\'D S. MfR.XI. 1969. Use of scale characters and a discnnunanl f'uiK'tioii for classifying sockeye salmon iOncorhyruhus ricrkat In continent of origin. Int. North Pac. Fish. Comm. Bull 26:157-192. CLUTTER, R. I., AND L. E. WlHTESEL. 1956. Collection and interpretation of sockeye salmon scales. Int. Pac. Salmon Fish. Comm. Bull. 9. 1.59 p. He.nry, k. a. 1961. Racial identification of Eraser River sockeye salmon by means of scales and its applications to salmon man- agement. Int. Pac. Salmon Fish. Comm, Bull. 12, 97 p. M.VJOR. R. L.. K. H. MosHKR, .\.\D J. E. M.A.SO.N. 1972. Identification ofstocks of Pacific salmon by means ol their scale features. In R. C Simon and P A. Larkin (editors). The stock concept in Pacific salmon, p. 209-231, H. R. MacMillan Lect. Fish.. Univ. B.C.. Vancouver. MOSHER. K. H. 1963. Racial analysis of red salmon by means of scales. Int. North Pac. Fi.sh- Comm, Bull, 11:31-56, NIE. N.H., C.H.Hull. J. C.jE\KLNS,K.STEINBREN.\KR,.\Nn D. H. Bent. 1975, Statistical package for the social sciences. 2d ed. McGraw-Hill. 675 p. Oregon Dep.'\kt.ment of Fish .and Wildlife .\nd Washington Depakt.me.nt of Fisheries. 1976, Status report: Columbia River fish runs and fisheries 1957-75. 2(ll. 74p, Pa( iFic Fishery Management Colincil, 1978, Final environmental impact statement and fishen. management plan for commercial and recreational salm- on fisheries ofl' the coa.st of Washington, Oregon, and California commencing in 1978. Pac. Fish. Manage, Counc, Portland. Oreg., 1229] p. Plck.T. H. 1970. Differentiation of hatchery and stream juvenile coho salmon iOncorhynckus kisutch) from Washington and Oregon by the use of scales and otoliths. M.S. Thesis. Univ. Washingtxjn, Seattle. 67 p, Phinney. L. a., and M, C, Miller 1977, StatusofWashington's ocean sport salmon fishery in the mid-1970s. Wa.sh, Dep, Fish, Tech Rep, 24. 72 p, TaNAKA. S.. M. P, SlIEl'ARD. AND H, T, BiLTON. 1969. Origin of chum salmon iOnvorhynchus keta i in offshore waters of the North Pacific in 1956-1958 as de- termined from scale studies. Int. North Pac. Fish, Comm. Bull. 26:.57-155. Van Hyning. j. m. 1951. The ocean salmon troll fishery of Oregon. Pac Mar. Fish. Comm. Bull. 2:4.3-76. 622 -1 ^KNECCH1A and WMAEK C'U.\TRIHI!T|C )N OF COHO .SALMON I'O OCKAN SPORT FISHERY WoKLUNIl, D. D., AM) R. A, FRKDIN. WRIOHT.S. G- 1962. DifTerentiation of stocks. In N J. Wilimovsky 19"6. Status of Washington's commercial troll salmon (editorl, Symposium on pmk salmon, p. 143-153. H. R. fishery in mid 1970's. Wash. Dep. Fish. Teen. Rep. MacMillan Lect. Fish . Univ B.C . Vancouver. 21, 50 p. 623 LARVAL MORPHOLOGY OF PANDALUS TRIDENS AND A SUMMARY OF THE PRINCIPAL MORPHOLOGICAL CHARACTERISTICS OF NORTH PACIFIC PANDALID SHRIMP LARVAE Evan Haynes' ABSTRACT Larval stages I- VII of Pandalus tndens from plankton of lower Cook Inlet, Alaska, are most similar morphologically to larvae of P. borealis. P goniurus. P. jordani, and P. stenolepis from the North Pacific Ocean. Larvae of P- tndens are distinguished from larvae of P. borealis, P goniurus, and P. jordani by the shape of the rostrum and antennal scale, and spination of the abdominal somites. Larvae of P Iridens differ from larvae of P stennlepis by shape of the carapace, abdominal somites, and telson; length of the antennal flagellum and rostrum; and setation of the antennal scale. Differences in larval morphology support classification of P. tndens as a species rather than a subspecies ofP. montagui. A summary of the pnncipal morphological characteristics of the described larvae of pandalid shrimp found in the North Pacific Ocean is provided. In 1976, the Northwest and Alaska Fisheries Center Auke Bay Laboratory of the National Marine Fisheries Service and the Alaska Depart- ment of Fish and Game conducted a survey to determine the seasonal distribution of larvae of king crab and pandalid shrimp in the Kachemak Bay-lower Cook Inlet area (Haynes^). During the survey, Stages I-VII zoeae oiPandalus tridens ( = P . montagui tndens Rathbun 1902) were captured in plankton tows in lower Cook Inlet. Except for Stage I, zoeae of P. tridens have not been described in the literature. In this report I describe and illus- trate each of the seven zoeal stages captured and compare my descriptions with those of pandalid shrimp zoeae given by other authors. 1 also discuss the evidence from larval morphology that sup- ports raising the subspecies, P. montagui tridens, to full species status, P. tridens Rathbun 1902. A summary of the principal morphological charac- teristics of described pandalid shrimp larvae of the North Pacific Ocean is also given. METHODS During the 1976 survey, plankton was collected by hauling 61 cm bongo samplers vertically from about 1 m above the ocean bottom to the surface at a velocity of slightly <1 m/s. Nets with 0.333 mm mesh and cod end jars with 0.571 mm mesh were used. Zoeae of P. tridens were collected in water 120-160 m deep about 16 km west of the Kenai Peninsula in lower Cook Inlet. The terminology, methods of measurement, techniques of illustration, and nomenclature of gills and appendages are those used by Haynes (19791. Identification of the zoeae is based on de- scription of Stage I zoeae hatched from known parentage by Ivanov( 1971) and undescribed Stage I specimens hatched from known parentage by Ethelwyn Hoffman of the Auke Bay Laboratory's staff. Only those morphological characteristics useful for readily identifying each stage are given. For clarity, setules on setae are usually omitted from the figures, but spinulose setae are shown. 'Northwest and Alaska Fisheries Center Auke Bay Laboratory, National Marine Fisheries Service, NOAA, P.O. Box 155, Auke Bay, AK 99821. ^Haynes, E, 1977. IV Summary status on the distribution of king crab and pandalid shrimp larvae in Kachemak Bav-lower Cook Inlet, Alaska, 1976 In L. L. Trasky, L. B. Flagg. and D C Burbank i editors i, Environmental studies of Kachemak Bay and lower Cook Inlet, vol. 4. 52 p. Alaska Dep Fish Game. Anchor- age. Manuscript .uit-pted -March 1979 FISHERY BULLETIN: VOL 77. NO. 3. 1980 STAGE I ZOEA Total length of Stage I zoea (Figure lA) 3.2 mm (ranges. 1-3. 5 mm; Gspecimensi. Rostrum slender, somewhat sinuate, without teeth, about two- thirds length of carapace, and projects horizon- tally. Carapace with small, somewhat angular dorsal prominence at base of rosti'um and smaller 625 FISHERY BLILLETIN VOL 77. NO ;i rounded prominence near posterior edge. These two prominences occur in all seven zoeal stages. Pterygostomian spines present, but minute and usually hidden by sessile eyes. Three to four mi- nute denticles on ventral margin of carapace im- mediately posterior to pterygostomian spine, and about 12 somewhat larger denticles along pos- teroventral margin of carapace. Denticles in Stages Mil, but rarely in Stage IV. Denticles vary in number among stages and among individuals in 0.25 mm 626 HAYNES LARVAL MORPHOLOCY OF PAATMLCS THinEXS Figure l. — Stage I zoea ofPandnlus tndrns: A, whole animal, right side; B. antennule, dorsal; C. antenna, ventral; D, mandibles (li It and rightl, posterior; E. maxillule, dorsal; F, maxilla, dorsal; G, first maxilliped. lateral; H, second maxilliped, lateral; 1. thii.i maxilliped, lateral; J. second pereopod, lateral; K. telson. dorsal. 627 FISHERY BULLETIN: VOL. 77. NO, 3 each stage. Posterior margins of abdominal so- mites fringed with spines. ANTENNULE (Figure IB).— First antenna, or antennule, has a simple, unsegmented, tubular basal portion; plumose seta terminally; and ter- minal conical projection bearing four aesthetascs: one long, one short, and two of intermediate length. ANTENNA ( Figure IC ).— Consists of inner flagel- lum (endopodite) and outer antennal scale (exopo- dite). Flagellum spiniform, unsegmented, about three-fourths length of scale, and spinulose dis- tally. Protopodite bears spinous seta at base of flagellum, but no spine at base of scale. Antennal scale distally divided into four joints, fringed with 17 heavily plumose setae along terminal and inner margins. Distinct seta on outer margin at base of terminal segments; another seta on outer margin, near the protopodite. MANDIBLES i Figure ID).— Without palps m this stage and all later zoeal stages examined. Incisor process of left mandible has six teeth in contrast to triserrate incisor process of right mandible. Left mandible bears movable premolar denticle (lacinia mobilis) and subterminal tooth only on left mandible in all zoeal stages examined. MAXILLULE (Figure IE).— First maxilla, or maxillule, bears coxal and basial endites and an endopodite. Proximal lobe (coxopodite) has seven spinulose spines terminally. Median lobe (basipo- ditei bears five spinulose spines and a lai"ge setose seta proximally. Endopodite originates from lat- eral margin of basipodite and has three terminal and two subterminal spines; two of the spines have especially long spinules. MAXILLA (Figure IF). — Bears platelike exopo- dite (scaphognathite) with six long plumose setae: three on distal margin and three on proximal margin. Endopodite has 10 nonplumose setae: 7 bear distinct setules. Basipodite and coxopodite bilobed. Basipodite bears four setae on each lobe; each seta has distinct pattern of setules. Coxopo- dite bears 12 setae: 2 on distal lobe and 10 on proximal lobe; 6 distal setae of coxopodite some- what plumose, remaining 6 setae have few, if any, setules. FIRST MAXILLIPED (Figure IG).— Most setose 628 of natatory appendages. Protopodite not seg- mented, bears 11 setae (7 of them spinulose i. En- dopodite distinctly four-segmented; setation for- mula 3, 4, 1, 1. Exopodite is long slender ramus, segmented at base; exopodite bears two terminal and four lateral natatory setae. Epipodite a single lobe. SECOND MAXILLIPED (Figure IH).— Protopodite not segmented; bears seven sparsely plumose setae. Endopodite distinctly five- segmented; fourth segment expanded somewhat laterally; setation formula 5, 2, 1. 1, 3. Exopodite with two terminal, eight lateral natatory setae. No epipodite. THIRD MAXILLIPED (Figure II).— Protopodite unsegmented, bears two setae. Endopodite dis- tinctly five-segmented, about the same length as exopodite; setation fon..ula 5, 3, 1, 1,3. Exopodite has 2 terminal and 10 lateral natatory setae. No epipodite. PEREOPODS.— Poorly developed, not segment- ed, directed under body somewhat anteriorly (Figure lA). First three pairs biramous (second pereopod shown in Figure IJ). last two pairs uni- ramous and slightly smaller than pairs 1-3. All pereopods without setae. PLEOPODS.— Absent until Stage IV. TELSON (Figure IK).— Continuous with sixth abdominal somite; slightly emarginate distally; bears seven pairs of densely plumose setae. Fourth pair of setae longest: length about one-half maximum width of telson. Minute spinules at base of each seta except lateral pair. A few larger spinules on distal margin between bases of four inner pairs. Enclosed uropods visible. No anal spine. STAGE II ZOEA Total length of Stage II zoea (Figure 2AH.2 mm ( range 3.9-4.6 mm; 5 specimens). Rostrum without teeth, sinuate, projects somewhat dorsally. Carapace bears two prominent, supraorbital spines, one on each side of carapace; antennal and pterygostomian spines clearly visible. All zoeal stages examined except Stage I bear supraorbital, antennal, and pterygostomian spines. Epipodite slightly larger than in Stage I, but not bilobed. No HAYNES: LARVAL MORPHOLOGY OV PA.\DAU'S TRIDE.WS pleurobranchiae. Spines on posterior margins of abdominal somites similar in size and number to spines in Stage I. ANTENNULE i Figure 2B).— Three-segmented; bears large lateral flagellum and smaller inner flagellum on terminal margin. Inner flagellum unsegmented, conical, and has one long spine ter- minally. Outer flagellum has five aesthetascs of various lengths and one plumose .seta. Proximal segment bears four setae laterally near base, single seta subdistally. and two setae distally. Second segment has two setae distally. Distal segment has four plumose setae laterally near inner flagellum and has small seta laterally and subdistally. ANTENNA i Figure 2C i.— Flagellum styliform, about one-third length of scale. Antennal scale about 5'2 times as long as wide and fringed along distal and inner margins with 22 long, thin plumose setae. Antennal scale still divided dis- tally into four joints; bears two setae on lateral margin: one at base of proximal joint, one proxi- mally. Protopodite bears spine at base of flagellum but no spine at base of scale. MANDIBLES (Figure 2D).— Incisor proce.sses of both mandibles more pronounced and have more teeth than in Stage I. Molar processes somewhat more developed than in Stage I, especially forw-ard lip of truncated end. MAXILLULE. — Similar in shape to maxillule of Stage I, except coxopodite and basipodite each bear additional spine. MAXILLA. — Shape similar to Stage I maxilla, ex- cept scaphognathite is slightly longer proximally, bears 9-11 marginal plumose setae, and large plumose seta at proximal end. Endopodite same as endopodite of Stage I. Lobes of basipodite bear either 6 + 6 or 7 -i- 5 setae; lobes of coxopodite bear 3 + 11 or 3 + 12 setae. THIRD MAXILLIPED.— Dactylopodite (Figure 2Fi narrower, longer than in Stage I. FIRST AND SECOND PEREOPODS (second pereopod shown in Figure 2Gi. — Endopodites of first and second pereopods functionally developed, five-segmented and terminating in simple conical dactylopodite. Exopodite of first pereopod is longest exopodite of pereopods. Exopodites of first and second pereopods have two terminal and eight lateral natatory setae. THIRD PEREOPOD ( Figure 2H ).— Exopodite and endopodite nonfunctional but segmented at base. Endopodite tipped by four simple setae. FOURTH AND FIFTH PEREOPODS (Figure 21 1. — Poorly developed, unsegmented. and with- out exopodites. TELSON (Figure 2Ji.— Telson similar in shape to Stage I, but distinctly segmented from sixth ab- dominal somite. Telson has eight pairs of densely plumose setae. Uropods still enclosed. Anal spine present but minute. STAGE III ZOEA Total length of Stage III zoea 5.9 mm (range .5.6-6.3 mm; 7 specimens!. No change in shape of rostrum from Stage II. Spines along anteroventral and posteroventral margin of carapace still pres- ent, but minute and fewer than in Stage II. Epipo- dite on first maxilliped still only gill structure present. Spines on posterior margins of abdominal somites smaller than in Stage II. ANTENNULE.— Similar in shape to antennule of Stage II but bears several additional setae; a spine projects downward from ventral surface of proximal segment. From this stage on, change in antennule slight: inner flagellum lengthens, more setae on antennule. FIRST MAXILLIPED (Figure 2Ei.— Epipodite of first maxilliped longer than in Stage I. Setation formula of endopodite 3, 2, 1, 3. Protopodite un- segmented, bears about 20 setae. SECOND MAXILLIPED.— Same as Stage I, ex- cept each segment of endopodite may have an ad- ditional seta. ANTENNA.— Flagellum styliform, two- segmented, still only about one-third length of scale. Antennal scale about six times as long as wide; two complete joints at tip (Figure 3A). Ter- minal spine on lateral margin of scale does not quite reach tip of scale. Protopodite bears small spine at base of flagellum and minute projection at base of scale. 629 FISHKin 111 l.l.ETlN vol. 77. \' 0.25 mm 6:^0 HAYNES LARVAL MORPHOLOGY 0¥ PA^DAirS TRIDEXS 0.25 mm 0. 5 mm Fl()URE2. — StagellzoeaoiPandalus tridens: A, whole a.n\ma\, right side; B,aiitennule, ventral; C. antenna, ventral; D, mandibles (left and right), posterior; E. first maxilliped, lateral; F. third maxilhped (distal segments), lateral; G, second pereopod, lateral; H, third pereopod. lateral; I. fourth and fifth pereopixis. lateral; J. telson. dorsal. FIRST AND SECOND PEREOPODS.— Essentially same as Stage II, except exopodite of second pereopod bears additional pair of setae. THIRD PEREOPOD i Figure 3Bi.— Functional, five-segmented. Exopodite bears two terminal and eight lateral natatory setae. FOURTH PEREOPOD (Figure 3C).— Functional. Dactylopodite tipped by spine and simple seta. FIFTH PEREOPOD.— Similar to fourth pereopod except terminal spine not as fully developed. TELSON (Figure 3D).— Uropods free. Endopodite 631 FISHERY BULLETIN VOL, 77, NO, 3 0.25 mm 0. 5 mm Figure 3,— Stage III zoea of Pnnrlalus tridens: A. antennal scale (distal portion), ventral; B, third pereopod. lateral; C, fourth pereopod. lateral; D, telson, dorsal. 632 HA'i'NES: LARVAL MORPHOLOGY OF PANDALUS TRIDENS undeveloped, less than one-half length of exopo- dite, bears three setae distally. Anal spine clearly visible. STAGE IV ZOEA Total length of Stage IV zoea 7.8 mm (range 7.0-8.4 mm; 9 specimens). Rostrum (Figure 4Ai projects horizontally but curves slightly down- ward at tip, bears two teeth at base. A few minute spines still on anteroventral and posteroventral margins of carapace. Epipodite of first maxilliped bilobed. Posterior margins of abdominal somites fringed as in Stage III. Figure 4. — Stage IV zoea ofPandalus tridens: A, rostrum, right side; B, antennal scale (distal portion), ventral; C, second pereopod Iterminal segments), lateral; D, third pereopod (distal segments), lateral; E, telson, dorsal. 633 FISHERY BULLETIN; VOL. 77. NO . ANTENNA.— Flagellum .still styliform, only about one-third length of scale. Antennal scale about seven times as long as wide, no joints at tip; terminal spine projects considerably beyond tip of scale (Figure 4B). Pro topodite bears small spine at base of flagellum and antennal scale. SECOND PEREOPOD.— Distal joint of propodite (Figure 4C) widened, projects distally in later stages. THIRD PEREOPOD.— Dactylopodite lengthened (Figure 4D); exopodite has an additional pair of setae. PLEOPODS.— Minute buds. TELSON (Figure 4Ei.— Endopodite of uropod about three-fourths length of exopodite and fringed with about 15 setae. Lateral margins of telson widen posteriorly, have two spines each. Distal margin emarginated, bears 6 + 6 spines. STAGE V ZOEA One specimen with rostrum broken and exopo- dites of third pereopods missing. Posterior mar- gins of abdominal somites minutely fringed. ANTENNA.— Flagellum slightly rounded at tip, two-thirds length of antennal scale, five-seg- mented. SECOND PEREOPOD.— Chela partially formed; distal joint of propodite projected somewhat dis- tally, tipped by .spine (Figure 5A). SECOND PLEOPODS.— About one-fourth height of second abdominal somite. TELSON (Figure .5B).— Uropods fully developed, no evidence of transverse hinge. Lateral margins somewhat parallel but widen slightly posteriorly. STAGE VI ZOEA Total length of Stage VI zoeae 10.7 mm (range 10.2-1 1.2 mm; 2 specimens). Rostrum (Figure 6A) about one-third length of carapace, projects hori- zontally, bears six teeth dorsally, tip bears hump indicating future location of distal tooth. A few minute spines on posterior margin of fifth somite. 0. 5 mm FKII'RE .5. — Stage V zoea o( Pandalus tnilrns: A. .second pereopod idistal segments), lateral; B, tel.son. dorsal Bud of epipodite on second maxilliped. Pleuro- , branchiae at base of all five pereopods. I ANTENNA. — Inner flagellum nearly as long as antennal scale, about 25-segmented. SECOND PEREOPOD.— Chela well formed (Fig- ] ure 6Bl. Terminal spines of propodite and dac- I tylopodite each bear single spine at base. 1 634 HAYNES: LARVAL MORPHOLOGY OF PANDALVS TRIDENS 0.25 mm B 0.25 mm 0. 5 mm Figure 6.— Stage VI zoea ofPandalus tndens: A, rostrum, right side; B, second pereopod (distal segmentsl, lateral; C. third pereopod (distal segments), lateral; D. second pleopod, lateral; E, telson, dorsal. THIRD PEREOPOD.— Dactylopodite well de- about one-half height of second abdominal somite veloped; has two distinct spines along inner mar- (Figure 6D). gm (Figure 6C). TELSON (Figure 6E). — Lateral margins some- PLEOPODS. — Pleopods segmented at base; no what parallel, but not as much as in Stage VII; setae or appendices internae. Second pleopod each margin bears two spines. Posterior margin 635 FISHERY BULLETIN: VOL. 77, NO. 3 slightly emarginated and bears 6 + 6 spines dis- tal ly. Transverse hinge of exopodite of uropod not evident. STAGE VII ZOEA Total length of Stage VII zoea 13.0 mm ( 1 speci- men). Rostrum (Figure 7A) curved slightly up- ward, slightly less than one-half length of carapace; bears seven teeth dorsally, tooth near tip not developed. No change in number of gill structures from Stage VI. PLEOPODS.— Exopodite and endopodite of pleopods tipped by a few setae; no appendices in- ternae. Second pleopod (Figure 7B) about two- thirds height of second abdominal somite. TELSON (Figure 7C). — Lateral margins essen- tially parallel, each bears two spines. Transverse hinge of exopodite of uropod partially complete. COMPARISON OF LARVAL STAGES WITH DESCRIPTIONS BY OTHER AUTHORS SECOND PEREOPOD.— Terminal spine of dac- tylopodite may bear two spines at base instead of one spine, as in Stage VI; carpopodites unseg- mented. The only previously published description of larvae of Pandalus tridens is that of Ivanov (1971) who described and figured Stage I zoeae reared from known parentage. My description of the Figure 7. — Stage Vll zoea ofPandalus tridens: A, rostrum, right side; B, second pleopod, lateral; C, telson, dorsal. 636 HAYNES: LARVAL MORPHOLOGY OF PANDALUS TRIDENS Stage I zoeae agrees in all essential aspects with Ivanov's description. Larvae of P. tridens are similar to larvae of P. borealis, P.goniiirus, P. jordani, and P. stenolepis: all have poorly developed pereopods and exopo- dites on pereopods 1-3 in Stage I. Larvae of P. borealis (described by Haynes [1979]), and P. goniurus (described by Haynes [1978]), andP.jor- dani (described by Modin and Cox [1967]) are readily distinguishable from larvae of P. tridens by the lack of spines on the posterior margins of the abdominal somites and by the rostrum, which in early stages is spiniform and projects downward rather than being sinuate and projecting upwards as in P. tridens. In addition, the antennal scales of larvae of P. borealis, P. goniurus, and P. jordani are markedly shorter and wider than in larvae of P. tridens. Zoeae of P. tridens described in this report are most similar to zoeae ofP. stenolepis described by Needier (1938), especially in Stage L In Stage I zoeae of both species the carapace bears denticles, the abdominal somites are fringed with spines, and the antennal scale is relatively long and nar- row. The Stage I zoeae of these species differ: the carapace and abdominal somites of Stage I zoeae of P. stenolepis are flared laterally, and the antennal scale bears 9-12 plumose setae; the carapace and abdominal somites of Stage I zoeae of P. tridens are not flared, and the antennal scale bears 17 plumose setae. Also, the telson of Stage I zoeae of P. stenolepis is considerably wider and the posteri- or margin more emarginate than the telson of Stage I zoeae of P. tridens. Other morphological differences between zoeae of the two species are the antennal flagellum and rostrum. The antennal flagellum in all zoeal stages of P. stenolepis is longer than the antennal scale; the antennal flagellum of zoeae of P. tridens remains shorter than the antennal scale through at le^st Stage V. The rostrum of P. stenolepis zoeae is as long as, or longer than, the carapace and bears teeth as early as Stage II; the rostrum of P tridens zoeae remains shorter than the carapace as late as Stage VII and does not bear teeth until Stage IV. The morphology of Stages I-VII zoeae of P. tri- dens from lower Cook Inlet confirms the opinion llvanov 1971; Squires^) thatP. montagui tridens, the Pacific subspecies of P. montagui Leach, 'Squries. H, J. 1965. Decapod crustaceans of Newfound- land, Labrador and the Canadian Eastern Arctic. Fish. Res. Board Can., MS Rep. Ser. Biol. 810:1-212. Biological Station. Nanaimo, B.C. V9R-.5K6. should be given the full specific rank of P. tridens Rathbun 1902. Rathbun's (1902, 1904) separation of the Pacific subspecies, P. montagui tridens, from the Atlantic species, P. montagui, was based on slight differences in adult morphology. For in- stance, the rostrum of the Pacific subspecies was lVi-1% times the length of the carapace compared with P/s-l'/o times the length of the carapace for the Atlantic species. Also, termination of the dor- sal rostral spines of the Pacific subspecies was behind the middle of the carapace rather than in the middle or in front of the middle of the carapace as in the Atlantic form. Squires' (see footnote 3) conclusion that the Pacific subspecies should be given specific status was based on coloration of adults. Ivanov's (1971) conclusion was based on morphological differences between Stage I larvae of P. tridens from the Gulf of Alaska and Pike and Williamson's (1964) description of Stage I larvae of P. montagui from the North Atlantic. In Stage I P. montagui the margins of the carapace and ab- dominal somites are smooth; in Stage I P. tridens the carapace bears pterygostomian spines, the an- tero- and posterolateral margins of the carapace bear denticles, and the posterior margins of the abdominal somites bear minute spines. In P. tri- dens, the rostrum is longer and the number of setae and spines on the antennal scale is greater than in P. montagui. Also, P. tridens larvae are larger than larvae of P. montagui. My comparison of the seven zoeal stages of P. tridens from Cook Inlet with the zoeae of P. montagui raised in the laboratory and collected from North Atlantic plankton by Pike and Williamson ( 1964) confirms the morphological differences found by Ivanov (1971) for Stage I and shows that these differences persist through later stages. SUMMARY OF PRINCIPAL MORPHOLOGICAL CHARACTERISTICS Certain characteristics of larvae of pandalid shrimp from the North Pacific Ocean change form as the larvae develop. I discuss changes of these characteristics and categorize the larvae by number of stages. I also discuss the probable mor- phology of larvae of Pandalopsis ampla Bate, P. aleutica Rathbun, andP. longirostis Rathbun and larvae tentatively identified as Dichelopandalus leptocerus (Smith). Although the number of pereopods bearing exopodites does not change during larval de- velopment, the exopodites themselves degenerate 637 FISHERY BULLETIN VOL. 77. NO. 3 during later stages, usually at the molt to the megalopa. In Table 1, poorly developed pereopods in Stage I are unsegmented pereopods that are directed anteriorly under the cephalothorax. Usu- ally pereopods become functional by Stage III. Denticles on the carapace and spines on the ab- dominal somites are most prevalent in Stage I and tend to disappear during larval development. Thus, inPandaltis platyceros most ofthe denticles and spines have disappeared by Stage III; in P. stenolepis and P. tridens most have disappeared by Stage VI. For most pandalid shrimp larvae, the typical number of telsonic spines is 7 -I- 7 in Stage I and 8 -^ 8 in later stages. In the latest stage another pair may be added. The total nurnber of telsonic spines of P. kesslen varies from 30-34 (Stage I) to 14-15 (Stage V); Pandalopsis coccinata has 55-56 tel- sonic spines inStageI(Kurata 1955, 1964). Stage I Pandalus kessleri and Pandalopsis coccinata usu- ally have 16 + 16 and 28 + 28 telsonic spines, respectively (Table 1). The number of larval stages oi'Pandalopsis dis- par, P. coccinata , Pandalus tridens. and P.jordani has not been verified. Seven zoeal stages are known for Pandalopsis dispar and Pandalus tri- dens. Based on morphological development. Stage VII ofPandalopsis dispar is probably the last lar- val stage. Pandalus tridens probably has an addi- tional stage before the larvae molt to the first juvenile stage. Only the finst zoeal stage of Pan- dalopsis coccinata is known, but development of this stage is so far advanced that only one or, at the most, two more stages probably appear before the larvae molt to the first juvenile stage. For Pan- dalus jordani . I have estimated six larval stages based on development of larvae of morphological ly similar species, P. borealis, P. goniurus. and P. tridens. rather than the 1 1-13 stages obtained by ModinandCox ( 1967) or the 8+ stages obtained by Lee (1969) in the laboratory. Modin and Cox (1967) noted that the 11-13 larval stages of P. jordani obtained by them in the laboratory were nearly twice the number of larval stages of the closely related P. borealis. Artificial laboratory conditions may have caused a greater number of larval stages than natural conditions. The numbers of larval stages cited in Table 1 include the megalopa stage because the transition from zoea to megalopa is not always abrupt and may extend over several molts. For example, P. hypsinotus has functional pleopods in Stage VII, but other morphological characteristics normally associated with postzoea occur earlier (Haynes 1976). Also, the number of larval stages of some species vary slightly depending on geographical origin. Larvae of P. hypsinotus, P. goniurus, and P. borealis from the western North Pacific Ocean and P. borealis from British Columbia waters have one or two more stages than larvae of these species from Alaskan waters (Haynes 1976, 1978, 1979). Geogi'aphical variation in larval morphology has not been verified for other species of pandalids from the North Pacific. The number of larva! stages given in Table 1 refers to development in the sea rather than in the laboratory. Development in the laboratory often results in molt retardation and extra stages. Al- though the number of molts required to reach a specific point in development may vary in wild pandalid shrimp (Haynes 1978), the stages are, for the most part, remarkably constant and limited in number (Gurney 1942). For identification purposes, pandalid shrimp larvae of the North Pacific Ocean can be catego- rized into two groups on the basis of morphological Table l . — Principal morphological characteristics and number of larval stages of known larvae of pandalid shrimp ofthe North Pacific Ocean. + = yes; - = no. (Only the most complete references on larval morphology are given.) Species Pereopods bearing exopodites Pereopods poorly developed in Stage I Spines on abdominal somites Denticles on carapace margin No of telson spines in Stage I No of larval stages Pandalopsis coccinata P dispar Pandalus kesslen P danae P hypsinotus P platyceros P tridens P stenolepis P borealis P goniurus P lordani 1-2 1-2 1-2 1-2 1-2 1-3 1-3 1-3 1-3 1-3 1-3 28 -r 28 3 4 12 + 12 7 1 16 - 16 4 3.4 7 » 7 6 1 7 + 7 7 1. 10 8+8 5 1. 9 7 + 7 8 8. 13 7 + 7 6 2 7+7 6 1. 4, 12 7*7 6 5. 11 7 + 7 6 6. 7 ' References 1 ) Berkeley ( 1 930) ; 2) Needier ( 1 938) . 3) Kurata ( 1 955) : 4) Kurata ( 1 964) : 5) Ivanov ( 1 965) , 6) Modm and Cox ( 1 967) , 7) Lee ( 1 969) . 8) Ivanov ( 1 971 ) . 9) Price and Chew |1972). 10) Haynes (1976), 11) Haynes (1978); 12) Haynes (1979). 13) this repon 638 HAYNES LARVAL MORPHOLOGY OF PANDALUS TRIDENS characteristics: species with exopodites on pereopods 1-3 and species with exopodites only on pereopods 1 and 2. Species with exopodites on pereopods 1 and 2 are characterized by well- developed pereopods in Stage I. and no spines on the abdominal somites or denticles on the carapace margin. For three of the species with exopodites on pereopods 1 and 2 iPandalopsis coc- cinata. P. dispar, and Pandalus kessleri), the numbers of telsonic spines in Stage I are consider- ably greater than for species with exopodites on pereopods 1-3. Fewer thoracic exopodites usually indicate fewer stages before the megalopa (Pike and Wil- liamson 1964). This is not always true for pandalid shrimp larvae of the North Pacific Ocean. For in- stance, larvae of P. danae, P. hypsinotus, andPa«- dalopsis dispar also bear exopodites on first and second pereopods; but, the number of their larval stages is 6, 7. and 7, respectively. Also, Stage I larvae of P. dispar have dorsal and ventral teeth on the rostrum, 12 + 12 spines on the telson, and a long, jointed antennal flagellum that is about six times the length of the antennal scale; but the pleopods are not tipped with setae until Stage V, and Stage VII zoeae still bear a supraorbital spine. A greater number of telsonic spines in Stage I is associated with fewer larval stages in develop- ment of the Caridea (Gurney 1942; Pike and Wil- liamson 1964). This is true for Pandalus platycer(>s,P. kessleri, and Paridalopsis coccinata . which have 8 + 8, 16 + 16, and 28 + 28 telsonic spines in Stage I and 5, 4, and 3 larval stages, respectively. An exception is P. dispar, which has 12-^12 telsonic spines in Stage I, but may have as many as seven larval stages. Four species of pandalid shrimp in the North Pacific Ocean are not listed in Table 1: Pandalnp- sis ampla, P. aleulica, P. longirostris , and Dichelopaiidalus leptocerus. Larvae of P. amphi. P. aleutica. and P. longirostris have not been de- scribed. If larvae of P. ampla, P. aleutica, and P. longirostris undergo typical development of larvae of the genus Pan da I ops is (Kurata 1964; Berkeley 1930), they will be characterized by advanced de- velopment, especially their large size and long antennal flagellum. Stage 1 Pandalopsis spp. lar- vae are at least 10.0 mm long and the antennal flagellum is longer than the body and segmented throughout its length. For comparison. Stage I larvae oi' Pandalus are 8.0 mm or less in length and the antennal flagellum is usually unseg- mented and shorter than the length of the carapace. Stage I and II larvae of/), leptocerus have been tentatively identified from western Greenland waters (Pike and Williamson 1964). The larvae identified as D. leptocerus are most similar to larvae of P. stennlepis and P. platyceros: in Stage I and II, D. leptocerus, P. stenolepis. and P. platyceros bear prominent denticles on the antero- ventral margin of the carapace, the anteroventral margin of the carapace and posterior margin of the third abdominal somite are flared, the rostrum is about as long as the carapace, and exopodites are present on pereopods 1-3. Larvae of D. leptocerus can be distinguished, however, from the identified pandalid shrimp larvae of the North Pacific Ocean, including larvae of P. stenolepis and P. platyceros , by the presence of posterolateral spines on the fifth abdominal somite. LITERATURE CITED Bkhkki.ev. a. a. 1930- The post-embryonic development of the common pandalids of Briti.sh Columbia. Contnb. Can. Biol. 6:79-16.3. Gurney, R. 1942. Larvae of decapod Crustacea. Ray Soc. iLond.i Publ. 129, 306 p. Haynes, E. 1976. Description of zoeae of coonstripe shrimp. Pandalus hypsumtus, reared in the laboratory. Fish. Bull., U.S. 74:323-342. 1978. Description of zoeae of the humpy shrimp, Panrfa/u.s goniurus. reared in situ in Kachemali Bay, Alas- ka, Fish. Bull., U.S. 76:235-248. 1979. Description of larvae of the northern shrimp, Pan- dalus bitrealis. reared in situ in Kachemak Bay, Alas- ka. Fish. Bull. US. 77:1.57-173 IVANdV, B. G. 1965. A description of the first larva of the far-eastern shrimp {Pandalus goniurus). [In Russ., Engl, summ.j Zool. Zh. 44:12.55-1257. iTransl. by U.S. Dep. Commer., NOAA, Natl. Mar. Fish. Serv., Off. Int. Fish. Affairs, Code No. F44,l 1971. The larvae of some eastern shrimp in relation to their taxonomic status. [In Russ., Engl, summ.l Zool. Zh, 50:657-665. (Transl. by U.S. Dep. Commer., NOAA, Natl, Mar. Fish Serv,, Off, Int, Fish, Affairs. Code No. F44.) Kurata, H 1955. The post-embryonic development of the prawn, Pandalus kessleri. |In Jpn., Engl, synopl Bull, Hok- kaido Reg, Fish. Res, Lab, 12:1-15. 1964. Larvae of decapod Crustacea of Hokkaido. 3, Pan- dalidae. [In Jpn , Engl synopl Bull. Hokkaido Reg. Fish, Res, Lab 28:23^34, LEE, Y. J. 1969. Larval development of pink shnmp, Pandalus jor- dani Rathbun reared in laboratory. M.S. Thesis, Univ. Washington, Seattle, 62 p. 639 FISHERY BULLETIN: VOL, 77. NO 3 MoDlN. J. C. AND K. W. Cox. platyceros) and description of stages. J. Fish. Res. Board 1967. Post-embryonic development of laboratory-reared Can. 29:413-422. ocean shrimp. Pn;irfo/i/s./orrfQ/!/ Rathbun. Crustaceana RathBUN M J ^ 1902, Descriptions of new decapod crustaceans from the NEEDLKR. a. B. ^pj,j j,„3j.j ^f fj^^^ America, Proc, U.S. Natl. Mus, 19.38. The larval development of Pnni/0.2 mm in diameter). Eggs are often distributed in one to three modes and the number of eggs in the most advanced mode has been as- sumed to be equal to the number of eggs produced per spawning (Clark 1934; MacGregor 1968). Another approach has been to count all yolked oocytes in reproductively active females and to 'Supported in part by the Marine Research Committee of the State of California. ^Southwest Fisheries Center La JoUa Laboratory, National Marine Fisheries Service, NOAA. P.O. Box 271, La Jolla, CA 92038. 'Department of Biologv, Whittier College, Whittier. CA 90608. assume that these are equal to the number of eggs spawned in a season (Macer 1974). Neither ap- proach provides conclusive evidence for the number of spawnings nor total egg production. All eggs in the most advanced mode may not ovulate (Clark 1934; Yamamoto and Yamazaki 1961) and atresia may reduce the number of eggs per spawning (Macer 1974; Ivankov 1976). Further, the total number of yolked oocytes may not pro- vide an estimate of total fecundity because some of the small unyolked oocytes, not included in such counts, could mature later during the same breed- ing season. It has long been known in teleost fishes (Cun- ningham 1898) that at ovulation a remnant of the ovulated follicle (empty or postovulatory follicle) remains in the ovary. Postovulatory follicles are believed to be transitory because of their rarity in field-collected material (Wheeler 1924; Yamamoto 1956; Gokhale 1957; DeVlaming 1972; Goldberg 1977; Andrews'*), but actual measurements of their longevity are rare because the time of spawn- ing must be known. Yamamoto and Yoshioka ( 1964 ), using Oryzias latipes which spawns every 3 days, reported postovulatory follicles were barely distinguishable on the third day after spawning. They suggested that the frequency of spawning ^Andrews, C. B. 1931. The development of the ova of the California sardineiSardina caerijlea\ Llnpubl. manuscr., 88 p. Stanford University, Stanford, CA 94305. Manuscript accepted March 1979 FISHERY BULLETIN: VOL. 77. NO. 3, 1980. 641 FISHERY BULLETIN. VOL. 77, NO 3 could be determined by the presence of postovula- tory follicles but the estimate would have to be made soon after spawning. Through techniques of Leongi 19711 it was possible to induce spawning in the northern anchovy, Engraulis mordax, in the laboratory, making it possible to characterize the histological degeneration of postovulatory folli- cles on a time basis. Thus, it seemed feasible that spawning frequency of natural populations oi E. mordax could be estimated from incidence of post- ovulatory follicles in females once the period in which they could be detected was established. Moreover, once recently spawned fish were iden- tified, the rate of maturation of subsequent egg batches as well as the number of eggs produced per batch could be estimated. The objectives of this study were to establish the detection period for postovulatory follicles in northern anchovy and to estimate the incidence of natural spawning through histological examina- tion of these structures. In addition, by using this information to guide our selection of specimens, we provide a new estimate of the number of eggs released per spawning or batch fecundity, and the time required for subsequent spawnings. Previous estimates for anchovy based on frequency dis- tributions of yolked oocytes include those of Mae- Gregor (1968) and Norberg.'^ METHODS The period over which postovulatory follicles can be detected in the ovary was determined from anchovy held in the laboratory. Groups of anchovy reared to sexual maturity were induced to spawn using the method of Leong (1971). A total of 119 females were sampled; fish were killed at the time of spawning and thereafter at 24-h intervals up to 9 days after spawning. Ovaries were fixed in Bouin's fixative or 10% neutral buffered Forma- lin"^ and embedded in Paraplast. Histological sec- tions were cut at 6 ixm and stained with Harris' hematoxylin followed by eosin counterstain, Mas- son's trichrome, periodic acid-Schiff reagent, or Heidenhain's iron hematoxylin. A classification system for postovulatory follicles was established and laboratory specimens were classified without prior knowledge of their age to estimate the accu- racy of the technique. Field samples were then classified using the same criteria. Three field col- lections of anchovy females from the Southern California Bight were examined to determine the frequency of spawning in natural populations: 3 commercial purse seine samples of 38-65 temales each from March 1977; 4 research trawl samples of 1-11 females from September 1977; and 29 re- search trawl samples of 10 or 11 females from February 1978 (Figure 1). ■■^Norberg, R. H, 1975. Investigations on the fecundity of northern anchovy, jack mackerel and Pacific maciter- el. Unpubl. manuscr., 2,3 p. Calif. Dep. Fish Game, 350 Golden Shore. Long Beach, CA 90802. "Reference to trade names does not imply endorsement by the National Marine Fisheries Service, NOAA. 1 2r 120° 119° 1 1 M 1 I ! 1 I I 1 1 1 1 1 1 1 I 1 118" II7» ! 1 I 1 i 1 1 1 1 1 1 M 1 1 1 1 1 1 W— •'"•^-''t**.,^^ Sonto Barboio X^^ • FEBRUARY 1978 "_ • Y A MARCH 1977 34" M.0o»« X,.^ sonto ^"' ■ SEPTEMBER 1977 Santo Crui # \ Rosa ^Pt v^nte • •§ • ^-Vj'''^V • • • '■< N • • 'ti,- .\ ; San Nicolo*^^^ Son.o • V - • • \ 33° • • \ .-..k; Son 9 9 • £. - ^^, ^^, Cl»m«ni» LJ\ \~'''\ ~ Tonntf • • |i ] «,^ '-^ Bonfc I - • "''-. ""\ V - Corltl \ - 32'- Banh '' ^ i 1 i M 1 1 1 1 1 1 1 1 1 1 1 TT 1 I 1 1 1 FiCURE I. — Location of samples of fftnaie northern anchovy taken off southern California in March and Sep- tember 1977 and February 1978. 642 HUNTER and GOLDBERG: SPAWNING INCIDENCE OF NORTHERN ANCHOVY The number of eggs per mode was estimated for 117 of the field-caught specimens by fixing a weighed sample in Gilson's fluid and determining the size-frequency distribution of yolked oocytes (MacGregor 1968; Macer 1974). One-hundred and fifty of the oocytes >0.20 mm on the major axis were measured to the nearest 0.05 mm from each sample and all the remaining oocytes ( >0.20 mm) were counted. We shall use "diameter" to refer to these measurements but since anchovy eggs are longer than wide, it is not a diameter in a strict sense but the major axis of an oblate spheroid. The form of the distribution of egg diameters within an ovary was similar to those illustrated for other multiple spawning fishes (Macer 1974). Distributions varied from ones composed of two to three distinct modal groups of eggs to ones with only a single mode. Even in those with very dis- tinct modal gi'oups the tails of adjacent modes often overlapped. We used the program NORMSEP (Abramson 1971) to separate modal groups, estimate the mean egg diameter within a mode, and estimate iteratively the number of eggs within a mode. Although one must arbitrarily as- sume egg diameters within a mode are normally distributed, the program does eliminate some of the subjectivity in judging the range of diameters to include within a mode and how the tails of adjacent modes should be proportioned. Just prior to ovulation and spawning the modal group of eggs about to be spawned takes up fluid and swells to three or four times its former volume (Fulton 1898). These hydrated eggs greatly in- crease the ovary weight and increase the total weight of the female. To avoid this bias in female weight we used female weight less ovary weight (ovary-free wet weight) to express fecundity- weight relations. We also provide fecundity esti- mates based on total weight in tabular form so that conversions can be made if desired. CLASSIFICATION OF OVARIES Ovaries of laboratory matured females that had spawned within 24 h in all cases contained post- ovulatory follicles. They were similar in appear- ance to those described for a variety of teleosts (Cunningham 1898; Wheeler 1924; Bowers and Holliday 1961; Yamamoto and Yoshioka 1964; Moser 1967; Scott 1974). In specimens killed 0-6 h after spawning, postovulatory follicles consisted of irregularly shaped structures composed of colum- nar follicle cells and an underlying connective tis- sue theca (Figure 2A, B). In some cases the colum- nar cells had hypertrophied slightly. The lumen characteristically contained eosinophilic granules of uncertain origin. Degeneration was pronounced in material examined 24 h after spawning. The postovulatory follicle (Figure 2C) had greatly shrunken or col- lapsed on itself, vacuoles had become common, and walls of the follicle cells were no longer distin- guishable (Figure 2D). The granular material that was observed in postovulatory follicles taken at the time of spawning was still present but not as abundant. The prominent underlying connective tissue theca seen in new postovulatory follicles was no longer distinct. Degeneration had progress- ed further, 48 h after spawning. The follicle was one-half to one-fourth smaller than at 24 h, the lumen was very small or indistinguishable, eosinophilic granules were absent, and nuclear sizes were gi'eatly reduced. Owing to their rapid degeneration, postovula- tory follicles were difficult to age in laboratory specimens sampled 48 h after spawning. At this time they may be confused with intermediate stages of atretic oocytes (Lambert 1970). On the other hand, classification of postovulatory follicles into age 0 day and age 1 day was done with an accuracy of 76 to Si'^i (Table 1). In view of this, the following system was established for classification of ovaries from field-caught specimens; Hydrated: ovaries with many hydrated eggs (eggs enlarged by fluid uptake just prior to ovula- tion) and no postovulatory follicles. (Spawn- ing considered to be imminent.) Age 0 day: new postovulatory follicles, showing no sign of degeneration as described above (Figure 2A, B). Hydrated eggs may occa- sionally be present. Elapsed time from spawning <24 h. Age 1 day: regressing postovulatory follicles, showing degeneration as described for specimens (Figure 2C, D) sampled 24 h after spawning. Elapsed time from spawning 3=24 h but <48 h. Nonspawning (mature): ovaries with many yolked oocytes; may contain post- ovulatory follicles in advanced stages of de- generation which cannot be readily distin- guished from other atretic structures. Elapsed time from spawning 48 or more hours. Immature: few or no yolked oocytes. 643 FISHERY BULLETIN VOL 77, NO. 3 FICUKK 2. — Photomicrographs of northern anchovy ovaries from laboratory specimens: A (400x) and B (l.OOOx), postovulatory follicles i elapsed time from spawning 0-6 h); C 1 400 ■ I and Dd.OOOx I. postovulatory follicles (elapsed time from spawning 24 h). Arrow indicates lumen of postovulatory follicle. 644 HUNTER and GOLDBERG SPAWNING INCIDENCE OF NORTHERN ANCHOVY Table l. — Results of blind classification* (number of females) of postovulatory follicles of female northern anchovy spawned in the laboratory. n Classification Elapsed time from Postovulatory lollicles Postovulatory lollicles older than 2 days or no evidence of spawning Percent correctly classified (days) 0 day 1 day 0 1 2 3 4-9 21 19 23 20 38 16 0 0 0 0 5 16 0 0 0 0 3 23 20 38 76 84 100 100 100 'Elapsed time from spawning was unl0.2 mm, whereas, in less mature fish a significant propor- tion of the oocytes in the second mode were <0.2 mm, and thus below the lower limit of our mea- surements. The average diameter of eggs in the ovary in the most advanced mode immediately after spawning was 0.46 mm; 1 day after spawning it had in- creased to 0.51 mm and was 0.59 mm in nonspawn- ing females. Figure 4 illustrates how growth in the diameter of eggs in the most advanced mode and Table 5.— Sex ratio in samples (femalesrt males + females)) and percent of spawning northern anchovy taken in February 1978 off southern California. Sex ratio Percent of temales Number Sex ratio class Class mean 0 25 054 0 84 Number samples' 7 10 12 Spawning on night o1 capture^ Spawned day before capture^ No evidence of spawning females classified 0 10-0 39 0 40-0 69 0.70-099 39 16 10 15 12 20 46 75 70 72 101 122 'Twenry-five fish per sample were used to calculate sex ralio and 10 or 1 1 females were examined histologically. ^Includes females with hydrated eggs and those witti recent postovulatory follicles- ^Females with 1-day-old postovulatory follicles. 648 HUNTER and GOLDBERG: SPAWNING INCIDENCE OF NORTHERN ANCHOVY 08 0 7 OG 05 0 4 Spawning -Spawning ELAPSED TIME FROM SPAWNING (days) Figure 4. — Growth of oocytes in female northern anchovy dur- ing an assumed 6-day spawning cycle. Open circles are the mean diameter of eggs in the most advanced mode for: females with hydrated eggs Ihydrated eggs excludedi combined with those with recent postovulatory follicles (''spawning"!; females with day-old postovulatory follicles (second open circle): and for nonspawning females i third open circlet- Horizontal bar indi- cates period in a 6-day cycle that females would be classified as nonspawning; and the point is plotted at the midpoint of that interval. Vertical bars are ±2 SE of mean and solid circle indi- cates the mean diameter of eggs in the least advanced mode for the nonspawning class. that in the second mode could produce a 6-day spawning cycle, the second mode becoming the most advanced mode at the time of spawning. The mean diameter of the eggs in the most advanced and the second mode for the nonspawning class, when plotted at 3.5 days, seems in a reasonable position relative to the other points, indicating that the cycle may be about 6 days. A linear trajec- tory of oocyte growth of 0.04 mm/day indicates spawning at a diameter between 0.6 and 0.7 mm. in keeping with laboratory findings. This analysis indicates that the mean diameter of yolked oocytes of females in various reproductive stages is consis- tent with a 6-7 day spawning cycle. Batch Fecundity MacGregor ( 1968) estimated the number of eggs in the most advanced mode in northern anchovy ovaries to be 574 eggs/g wet weight, from an analysis of frequency distribution of eggs in 19 females. Norberg (see footnote 5) concluded that northern anchovy fecundity was 556 eggs/g, from an examination of 119 females. The supposition underlying both estimates was that the number of eggs in the most advanced mode represents the number of eggs spawned. Owing to the importance of batch fecundity in any estimate of spawning biomass from egg and larval production, we de- cided to reexamine spawning batch fecundity in the northern anchovy. The assumptions underlying batch fecundity es- timates are: all eggs in the most advanced mode are spawned; fecundity is directly proportional to weight; and no bias exists in the estimation of the number of eggs within the most advanced mode nor in the selection of mature females for analysis. We consider these assumptions for females taken in February 1978 using fecundity estimates for each reproductive class. Histological examination of females with post- ovulatory follicles indicated that very few hy- drated eggs were retained after spawning. Thus, the number of hydrated eggs within ovaries prior to ovulation (females with no postovulatory folli- cles) should give the most accurate estimate of the number of eggs spawned. Another advantage of using hydrated eggs was that they stand out as an isolated class, distinct from all others; they differ in appearance and are as much as 2-3 times larger than yolked oocytes. Hence, they only need to be counted; neither statistical techniques nor one's judgment need be used to separate overlapping modes. The mean number of hydrated eggs per gram of female (ovary free) was 389 ±59 ( ±2 SE) eggs and was only T^k less than that estimated for females with the most mature ovaries (nonspawner class) (Table 6). Thus, nearly all eggs in the most ad- vanced mode were destined to be hydrated and spawned. Fecundity estimates were substantially higher and more variable in the other three repro- ductive classes. Many of the females in these classes had only one mode of yolked eggs whereas about %W( of those classified as nonspawners had two modes. Fecundity estimates for the less ma- ture females tend to be higher because the eggs destined to form a second mode have not grown sufficiently to be separated from the rest of the yolked oocytes. More variability exists because of variation among females in the extent of the dif- ferentiation of the second modal group of eggs. In summary, we believe our most accurate esti- mate of batch fecundity is 389 hydrated eggs/g ovary-free female weight. If an estimate based on total female weight is needed, we recommend the one for nonspawning fish (Table 6) reduced by the fraction of eggs which may not be hydrated (7%). The adjusted fecundity for nonspawners is 368 eggs/g female weight. Fecundity as estimated above is a function of female weight, ovary weight, and the number of 649 Table 6. FISHERY BULLETIN: VOL, 77. NO 3 -Fecundity (eggs per gram female) eEtimates for northern anchovy females collected in February 1978 off southern California. Number of females Fecundity Ovary-tree female weigfit J SD Total female v»eight Percent of females with two modal groups of Sample X SD nonhydrated eggs Most advanced nonhydrated eggs of females with Hydrated eggs' Day 0, postovulatory follicles' Day 1 , postovulatory follicles None of the above |nonspav»ners) Hydrated eggs lyfacGregor (1968) 23 13 19 33 23 19 530 693 619 418 389 606 360 387 313 186 141 151 462 497 592 396 340 574 309 201 294 171 114 131 39 69 69 91 'Only the nonhydrated eggs m most advanced mode are included 'Females having both hydrated eggs and postovulatory follicles were included advanced eggs in a weighed sample of the gonad. The number of hydrated eggs per gram of ovary did not vary with fish weight and was 2,880 ±373 ( ±2 SE) eggs/g of ovary. If any weight-related bias existed, it probably was related to the gonad weight-female weight relation. To ascertain how ovary weight varied with female weight, we sepa- rated the data into three classes on the basis of mean diameter of eggs in the most advanced mode and plotted ovary weight as a function of female weight for each class (Figure 5). The relation was slightly curvilinear; the departure from linearity was most ovbious in the 0.51-0.60 mm egg diame- ter class. Considering the variability in the number of mature eggs per gram of ovary, and the slight departure from linearity, no practical pur- pose is achieved in expressing fecundity as a func- tion of female weight rather than as a direct pro- portion of weight, although direct proportionality is somewhat less accurate for extreme weight classes. The relation between gonad weight and female weight differed somewhat among the diameter classes as can be seen in Figure 5. This might be expected because the weight of the ovary should increase somewhat with the average diameter of the eggs in the most advanced mode. We analyzed the data using multiple regression to determine if the In doge) gonad weight (G) could be estimated from the diameter of eggs in the most advanced mode(D), In ovary-free female weight (W), and the interaction term (D In G ). Both female weight and the interaction term had a significant effect on gonad weight, whereas diameter alone did not. The final multiple regression equation was: D = In G + 4.213 - 1.069 In W 0.555 In W InG -4.213 + 1.069 In U' + 0.555 D In W where r^ = 0.92. Solving for diameter we obtain 650 This equation may be useful for estimation of maturity stages for anchovy from weight relation- ships; 60% of the estimates of mean diameter were within ±0.1 mm of the observed values and thf residuals were distributed evenly. The equation is more useful than gonad index (ovary weight female weight), which is commonly employed to assess maturity, because it produces a number that can be directly related to reproduction and avoids a weight bias for extreme weight classes. The weight bias in gonad index is apparent by examination of data in Figure 5 (lowest); a 30 g female with eggs of 0.65 mm in the most advanced mode has a gonad index of 0.064 whereas that of a 10 g female at the same stage of maturity has an index of 0.040. The equation also identifies females with hydrated eggs; the average diameter of eggs estimated by the equation for females with hydrated eggs was 1.20±0.12 mm in = 22) and is close to the mean of spawned eggs ( 1.34 mm). Ob- viously, such equations would be specific to popu- lations having similar weight relations, but it does seem a useful approach for assessing maturity. DISCUSSION This paper provides a method for direct estima- tion of the frequency of spawning of a multiple spawning pelagic fish population. From such es- timates it may be possible to directly estimate spawning biomass from the abundance of eggs and larvae over a short segment of the breeding sea- son. One of the major assumptions underlying the estimate is that a representative sample of females is obtained. Spawning frequency would be overestimated if nonspawning females were in re- HUNTER and GOLDBERG: SPAWNING INCIDENCE OF NORTHERN ANCHOVY 2 0 1.5 1.0 0.5 - 0.0 EGG DIAMETER 0.30 - 0.50 mm I i I i I I I I I I I I I 0.43 mm I I I I I I I I I I I I 10 15 20 25 30 35 2.0 I- 1,5 - I (J3 1.0 I 0.5 > o ao 2.5 EGG DIAMETER 0.51 - 0.60 mm 2.0 1.0 0.5 0.55 mm I I I I I I I ''' I ' I I I I I I I I I I I ' I I I I 'i I ' 5 10 15 20 25 30 35 EGG DIAMETER 0.61 - 0.76mm 0.65 mm QQ t ' I I I I I I 1 '■ I I I I I I I I I I I I i I I I I ' I I I I 5 10 15 20 25 30 35 OVARY FREE FEMALE WEIGHT (g) Figure 5. — Relation between wet weight of ovary and o- ary- free wet weight of female northern anchovy classed into three groups, based on the mean diameter of eggs m the most advanced mode. Each pomt is a value for a single female. The lines repre- sent multiple regressions, described in the text, for the mean egg diameters given by the arrows. gions or at depths not sampled by the" trawl or commercial purse seine. Studies need to be con- ducted at other times of the year and employing other sampling techniques to answer these ques- tions. This paper also describes a new method for es- timation of batch fecundity in a multiple spawn- ing fish. Our estimation for northern anchovy based on hydrated eggs ( 389 eggs/g female weight, less ovary), was substantially less than that of MacGregor (1968) (606 eggs). This difference could be attributed to annual variation in fecun- dity because variations of this size are known to occur in fishes (Bagenal 1973). On the other hand, our selection of females on the basis of reproduc- tive state also may have been responsible for at least part of the difference. Our estimates for females that had recently spawned (day 0 and day 1 postovulatory follicles. Table 6i were close to MacGregor's estimate. In recently spawned females, modal groups of eggs were less distinct, and often one mode was considered to exist when the eggs may have been destined to form two spawning batches. If MacGregor (1968) used such females, this could explain in part why his esti- mate was higher than our estimates based on hy- drated eggs or on fish classed as nonspawning. In addition, our technique of partitioning eggs occur- ring between two modal groups according to an assumed normal distribution may have decreased our estimate somewhat relative to past methods. Use of hydrated eggs avoids these problems, but it does require histological examination to insure that none of the females used for the estimate have begun ovulation. Apparently, some of the females we captured were spawning because their ovaries contained many new postovulatory follicles as well as many hydrated eggs. We usually examined only one set of histological sections to determina- tion if ovulation had occurred; histological exami- nation of an entire ovary was impractical. We be- lieve our examination was adequate because our estimate based on hydrated eggs was close to the one based on females with the most advanced ovaries (nonspawning). In addition to the obvious application to the estimation of spawning biomass, this work pro- vided insights into the reproductive biology of E. mordax. The high spawning frequency, the ability to rapidly mature new batches of yolked oocytes. and the long breeding season of the northern an- chovy (Lasker and Smith 1977), indicate that energy reserves and the availability of food may set the limit to the number of spawnings and hence to total fecundity. The analysis has also provided a possible explanation for the variability in the sex ratio of catches of anchovy. ACKNOWLEDGMENTS We thank Kenneth Mais (California Depart- ment of Fish and Game) for providing the speci- mens and data on sexual composition of schools from his February 1978 cruise. We are indebted to Roger Leong (Southwest Fisheries Center ( SWFC ) ) who maintained and spawned anchovy in 651 FISHERY BULLETIN; VOL, 77. NO, 3 the laboratory. Beverly Macewicz (University of California, San Diego) did all microtechnique work and assisted in the histological classification of the ovaries. Thomas Mickel (University of California, San Diego) assisted in the analysis of fecundity and estimation of ovum diameters. We thank James Zweifel (SWFC) for permitting us to use his unpublished method for estimating confidence intervals for the mean of a negative binomial distribution and for his analytical work on estimating ovum diameters from the gonad weight-female weight relation. LITERATURE CITED ABR.-\MSON, N. J. 1971. Computer programs for fish stock assess- ment. FAO Fish. Tech, Pap, 101:1-11,(11,2,10, BAGENAL. T. B. 1973, Fish fecundity and its relations with stock and re- cruitment, Rapp, P.-V, Reun, Cons. Int. Explor. Mer 164:186-198. BOWERS, A. B., AND F. G, T, HOLLIDAY. 1961. Histological changes in the gonad associated with the reproductive cycle of the herring iClupea harengus L.). Mar. Res., Dep. Agric, Fish. Scotl. 1961i5):l-16. Brewer, G. D. 1978, Reproduction and spawning of the northern an- chovy, Engraulis mordax, in San Pedro Bay, California. Calif. Fish Game 64:175-184. Clark, F. N. 1934. Maturity of the California sardine (Sardina caerulea) determined by ova measurements. Calif. Dep. Fish Game, Fish Bull, 42, 49 p. Clark, F, N,, and J, B. Phillips, 1952, The northern anchovy iEngraulis mordax mordaxf in the California fishery. Calif Fish Game 38:189-207. Collins, R. a. 1969. Size and age composition of northern anchovies lEn- graults mordax) in the California anchovy reduction fishery for the 1965-66, 1966-67 and 1967-68 seasons. Calif Dep. Fish Game, Fish Bull. 147:56-74. Cunningham, j. t, 1898. On the histology of the ovary and of the ovarian ova in certain marine fishes. J, Mier. Seig, New Ser., 40:101-163. DEVLAMING, V. L. 1972, Reproductive cycling in the estuarine gobiid fish. GiUwhthys mirabilts^ Copeia 1972:278-291. Fulton, T. w. 1898. On the growth and maturation of the ovarian eggs of Teleostian fishes. Annu, Rep, Fish, Board Scotl. 16:88- 124. GOKHALE, S. V. 1957. Seasonal histological changes in the gonads of the whiting (Gadus merlangus L) and the Norway pout (G. esmarkii NiLsson). Indian J. Fish. 4:92-112, Goldberg. S. R. 1977. Seasonal ovarian cvcle of the tidewater goby, Eucyc- logobius newberryi iGobiidae). Southwest. Nat. 22:557-558. 652 Ivankov, v. N. 1976, The formation of ultimate fecundity in intermit- tently spawning fish with reference to the southern one- finned greenling, Pleurogrammus azonus and the wild goldfish, Carassius auratus gibelio. J. Ichthyol, 16:56- 62. (Translated from Vopr. Ikhtiol.l JllHNSON, N, L,, AND S. KOTZ. 1970. Continuous univariate distributions - 2. Houghton Mifflin Co., Boston. 306 p KLINl'.BEIL. R. a. 1978. Sex ratios of the northern anchovy, Engraulis mor- dax. off Southern California Calif Fish Game 64:200- 209. Lambert, J. G. D. 1970. The ovary of the guppy,P(ifr(7;a re^icu /a/a The atre- tic follicle, a Corpus atreticum or a Corpus luteum praeovulationis. Z. Zellforsch. 107:54-67. Lasker, R., and p. E. S.MITH. 1977. Estimation of the effects of environmental varia- tions on the eggs and larvae of the northern an- chovy. Calif Coop. Oceanic Fish. Invest. Rep. 19:128- 137. Leong, R. 1971. Induced spawning of the northern anchovy, En- graulis mordax Girard. Fish. Bull., U.S. 69:357-360. Macer. C, T, 1974, The reproductive biology of the horse mackerel Trachurus trachurus (L.I in the North Sea and English Channel. J. Fish. Biol. 6:415-438. MacGregor, j. S. 1968, Fecundity of the northern anchovy, Engraulis mor- dax Girard. Calif Fish Game 54:281-288. Magnuson, j. j., and j. H. Prescott. 1966, Courtship, locomotion, feeding, and miscellaneous behavior of Pacific bonito {Sarda chiltensts). Anim. Be- hav. 14:54-67. MOSER, H. G. 1967. Seasonal histological changes in the gonads of Sebastodes paucisptnus , an ovovivi parous teleosKFamily Scorpaenidael. J. Morphol. 123:329-353. NIKOLSKY, G. V. 1963, The ecology of fishes. Academic Press, N.Y. 352 p. Qasim,S. Z, 1956, Time and duration of the spawning season in some marine teleosts in relation to their distribution. J. Cons. 21:144-154. SCOTT, D. B. C. 1974. The reproductive cycle of Mnrmyrus kannume Forsk. (Osteoglossormorpha, Mormyriformes) in Lake Victoria, Ueanda. J. Fish. Biol. 6:447-454. Wheeler, j, F, G, 1924, The growth of the egg of the dab iPleuronectes limanda). Q. J. Microsc, Sci. 68:641-660, YAMAMOTO. K. 1956. Studies on the formation offish eggs. I. Annual cycle in the development of ovarian eggs in the flounder, Liop- setta obscura. J.J. Fac. Sci. Hokkaido Univ.,Ser.6,Zool. 12:362-373. YA.MAMOTO, K., and F. YAMA7.AKI. 1961. Rhythm of development in the oocyte of the gold- fish, Carassius auratus. Bull. Fac. Fish., Hokkaido Univ. 12:93-110. YA.MAMOTO, K., AND H. YOSHIOKA. 1964, Rhylhm of development in the ooc.vte of the medaka, Oryzias latipes. Bull. Fac. Fish., Hokkaido Univ. 15:5-19. UTILIZATION OF THE NANAIMO RIVER ESTUARY BY JUVENILE CHINOOK SALMON, ONCORHYNCHUS TSHAWYTSCHA M. C. Healey' ABSTRACT Chinook salmon are considered, normally, to spend from a few months to a year rearing in freshwater before migrating to sea. Although large downstream movement of fry, recently emerged from spawn- ing gravels, has been observed in several river systems, it has been suggested that most of these migrant fry are lost to the population. This report describes the fate of downstream migrant chinook salmon fry in the Nanaimo River, British Columbia. In 1975 and 1976 most of the potential fry production from the river system was estimated to have passed by a trapping location near the river mouth. Many of these fry were subsequently found rearing in the intertidal area at the river mouth where salinity was commonly above 20%o. Very few chinook salmon fry were captured at other sampling sites within a 10 km radius of the river mouth. Juvenile chinook salmon were present in the intertidal area of the estuary from March to July each year, but peak numbers occurred in April and May. Peak estuary population was estimated to be 40.000-50,000 in 1975 and 20.000-25,000 in both 1976 and 1977. While in the estuary, chinook salmon grew about 1.32 mm per day or 5. 8'7r of their body weight per day. Individual fish probably spent an average of about 25 days rearing in the estuary and left the estuary when about 70 mm fork length. While in the estuary, juvenile chinook salmon fed on harpacticoid copepods, amphipods, insect larvae, decapod larvae, and mysids. After leaving the es- tuary, they fed mainly on juvenile herring. The stomach content of chinook salmon captured in the estuary averaged 5% of body weight or less, and varied seasonally and between years. It appears that in the Nanaimo and probably in other systems with well-developed estuaries, that the estuary is an important nursery for chinook salmon fry. After they emerge from the spawning gravel in early spring, chinook salmon, Oncorhynchus tshawytscha, are considered, normally, to spend from a few months to a year in freshwater before migrating to sea (Reimers and Loeffel 1967; Stein et al. 1972; Mehan and Siniff 1962; Lister and Walker 1966). Recently, Reimers (1971) and Dun- ford (1975) showed that juvenile chinook salmon may also spend considerable time rearing in es- tuaries after their downstream migration and be- fore moving into high salinity water. Although juvenile chinook salmon are known to occur in a number of British Columbia estuaries ( Goodman^; Hoos and Vold^; Bell and Kallmann Bell and 'Department of Fisheries and Oceans, Resource Services Branch, Pacific Biological Station Nanaimo, B.C., Canada V9R 5K6. ^Goodman, D. 1975. A synthesis of the impacts of the pro- posed expansion of the VIA. and other developments on the fisheries resources of the Fraser River estuary. Unpubl. man- user., 137 p. -(- append. Environ. Can., Fish. Mar. Serv., Van- couver 'Hooe, L. M., and C. L. Void. 1975. The Squamish River estuary: Status of environmental knowledge to 1974. Environ. Can., Fish. Mar. Serv. Spec. Estuary Ser. 2, 361 p. 'Bell, L. M., and R. J. Kallman. 1976. The Cowichan- Chemainus River estuaries: Status of environmental knowledge to 1975. Environ. Can., Fish. Mar. Serv. Spec. Estuary Ser. 4, 328 p. Kallman^), the importance of estuarine habitats as nursery areas for young chinook salmon is not well documented. The purpose of this report is to pre- sent information on the utilization of the Nanaimo River estuary and adjacent marine areas by juvenile chinook salmon and to consider the im- portance of the estuary to the stock. Specifically, I shall discuss the timing of downstream movement and abundance of chinook salmon fry in the river; their distribution, abundance, and length of resi- dence in the estuary and in marine waters adja- cent to the estuary; and their growth rate and food habits. In this report the term "fry" refers to juvenile chinook salmon that recently emerged from the spawning gravel, often still with exter- nally visible yolk. METHODS River Sampling Downstream migrating chinook salmon fry were captured in seven inclined plane fry traps Manuscript accepted March 1979 FISHERY BULLETIN: VOL. 77, NO. 3, 1980 ^Bell.L.M., and R.J. Kallman. 1976. The Nanaimo River estuary: Status of environmental knowledge to 1976. Environ. Can., Fish. Mar. Serv. Spec. Estuary Ser. 5, 298 p. 653 FISHKRY BULLETIN, VOL 77. NO. 3 anchored in two narrow stream channels near the mouth of the Nanaimo River (Figure 1). (These traps were similar in design to those described by Lister etal. 1969.) The mouth opening of each trap was 30 cm wide by 60 cm deep. Four traps were set side by side in one channel and three in the other. Nylon netting of 5 cm mesh was run between the traps and shore in an attempt to lead additional fry into the traps. The traps were operated in 1975 and 1976 and were set and fished the same way each year. In 1975 the traps were in place from early March to late May, while in 1976 they were in place from early April to late May. Although the main river flow was down a third channel to the west of the traps, a significant fraction of the Chinook salmon run passed down the trapping channels and, as will be shown later, the traps captured about l.S'^r of the run. Figure l. — The Nanaimo River estuary. Vancouver Island, showing the location of the fry traps (20) for juvenile chinook salmon; the stations sampled weekly on the east arm of the river and Holden Creek, (28), (29), (30), (31); the general location of seine sets made to determine the distribution of chinook salmon fry in the estuary, ^■, and the location of purse seine sets made over the intertidal flats at high tide, 0. Small circles show the location of pilings to which log rafts are moored Most raft stor- age is on the west side. 654 Fry captured in the traps between 0800 h of 1 day and 0800 h of the next were counted as a single day's catch. In 1975 the fry were held in live pens in the river and marked a few hours after capture by spraying with fluorescent grit (Healey et al.*^). After they were sprayed, the fry were held a further 24 h to recover and then were released in the late evening into the river about 2.5 km up- stream from the traps. Most mortality from mark- ing occurred in 24 h and was normally <5% (Healey etal.'). Each daily catch was examined for marked fry, and total daily run was estimated by mark recapture techniques (Ricker 1975; Healey et al, see footnote 7). In 1976 the fry captured each day were counted and released downstream from the trapping site. By changing the color of marking grit several times during the run I determined that, on aver- age, 75'7r of recaptures from a single release were made the night of release, a further 17% on the next night, and the remaining8'7f over the next 14 nights. I assumed that these percentages repre- sent the proportions of the marked fry which mi- grate the night of release or delay migration one or more days. Also, <100''^ of sprayed fry received a mark. Samples of marked fry examined a few days after spraying showed that usually 95*^^ or more of the fry were marked. The total number of marked fry migrating downstream each night was, there- fore, estimated to be the number of fry released, corrected for the proportion unmarked, minus the number expected to delay migration, plus the number expected to be migrating from previous releases. Total daily run was estimated as the product of daily catch and the estimate of marks migrating divided by the number of recaptures. Trap efficiency was the ratio of recaptures to esti- mated marks migrating. During about half the trapping days in 1975 no recaptures were made. On these days the run was estimated as the trap catch divided by the overall estimate of trapping efficiency for the year (total recaptures/total marks migrating). Total run in 1976 was estimated from the overall estimate of efficiencv for 1975. "Healey, M. C, F. P. Jordan, and R M Hungar 1976. Laboratory and field evaluating of fluorescent grit as a marking material for juvenile salmonids. Fish. Res. Board Can. Manuscr. Rep. 1392, 17 p. 'Healey, M. C, R. V Schmidt, F P Jordan, and R. M Hun- gar. 1977. Young salmon in the Nanaimo area 1975: I. Dis- tribution and abundance. Fish. Res Board Can. Manuscr Rep 1369, 161 p. HEALEY: UTILIZATION OF THE NANAIMO RIVER ESTUARY During April and May 1975, samples of downstream migrant chinook salmon were mea- sured for fork length (millimeters) and wet pre- served weight ( iO.Ol g) to provide an estimate of the body size of downstream migrants. During 1975 and 1976 the temperature of the river near the trapping site was measured morn- ing and evening. Daily discharge of the river was available from Inland Waters Directorate, Envi- ronment Canada, Ottawa. The measurements were made about 12 km upstream from the traps. Estuary- Sampling In the intertidal area of the estuary most sam- pling was by beach seine ( 18 m long x 3 m deep of 12 mm mesh I. Stream channels crossing the inter- tidal mud flat and the delta front were sampled at low tide, and the edges of the tidal marshes at high tide. During March and April 1975 widely scat- tered locations on the estuary were sampled, but during the latter half of April and May. sampling was concentrated in the east channel of the river and Holden Creek (Figure 1) at low tide. During 1976 and 1977 four specific sampling sites were established in the east channel of the river and Holden Creek and these were fished weekly (Sta- tions 28-31; Figure 1) except that Station 28 was not fished until June 1976, and fishing at Stations 30 and 31 was discontinued after the chinook salmon disappeared from these stations. Sampling at other locations at high and low tide was per- formed occasionally, as time permitted, to deter- mine the distribution of chinook salmon in the estuary. In addition to beach seining, five sets with a 90 ■ 7 m hand-hauled purse seine were made over the intertidal mud flat at high tide on 12 May 1976 to determine if juvenile chinook salmon re- mained over the mud flat at high tide. Catch data are presented as average catch-per-set (CPUE) in this report. Estuary sampling began during the second or third week of March of each year. In 1975, sam- pling terminated in early June; in 1976, in mid- July; and in 1977, at the end of June. In 1975. samples of chinook salmon for analysis of length, weight, and stomach contents were preserved in only 6 of 12 sampling weeks. In 1976 and 1977. however samples of 20 or more were preserved each week. In 1977, temperature (°C) and salinity (per mil) were measured at the time of beach seining at each sampling location in the east channel of the river and Holden Creek with a Yellow Spring Instru- ments Model 33 Thermister/Salinometer*. In 1977 the total population of chinook salmon in the estuary was estimated twice by mark and recapture techniques. Between 18 and 21 April, 3,187 chinook salmon were captured along the east channel of the river and Holden Creek, mainly at Stations 30 and 31, marked with a left pelvic fin clip, and released at the point of capture. Catch and recaptures were recorded on 19-22 April, and on all subsequent sampling days. Between 16 and 19 May, 1,554 chinook salmon captured mainly at Stations 28 and 29 were marked with a right pel- vic fin clip. Recaptures of these marks were re- corded on 17-19 May. 22 May. and all subsequent sampling days. Recaptures after the final mark release for each fin clip provided an estimate of the rate of disap- pearance of marked fish from the sampling area. This rate was assumed constant for each mark and was calculated as the slope of the regression of loge (CPUE marks) on days since marking. In calculat- ing the rate for left pelvic clips, catches during the second marking period were ignored since sam- pling on these days was performed in a way to maximize catch, and was different from our nor- mal sampling procedure. The number of marks released was reduced each day in accordance with these estimated rates of disappearance to give an estimate of the total marks present on each sam- pling day. Population estimates for each day were, therefore, the product of total catch and estimated marks present divided by recaptures. Left pelvic marks were still present at the time of the second marking, so that it was possible to make two inde- pendent estimates of population size at this time. A sample of chinook salmon was preserved from those captured each day for marking, and these provided an estimate of the average size of marked fish at the time of release. Marked fry captured after the last release of each fin clip were pre- served and their fork length and weight measured to provide an estimate of growth rate. Marine Sampling Up to 18 different locations within a 10 km radius of the river mouth were sampled in 1975 and 12 locations in 1976 (Figure 2). In 1975 nine 'Reference to trade names does not imply endorsement by Fisheries and Oceans, Canada, or by the National Marine Fisheries Service, NOAA. 655 FISHERY BULLETIN: VOL 77. NO. 3 STRAIT OF GEORGIA KILOMETERS Figure 2. — Map of the Nanaimo area, Vancouver Island, show- ing the locations where beach seine and purse seine sets were made for juvenile chinook salmon (circled numbers). locations ( 1, 2, 4, 5, 8, 9, 15, 16, 17; Figure 2) were sampled during the second and third week of May by beach seine! 18 x 3 m). Twelve locations! 1,2,5, 6, 7, 8, 9, 10, 11, 13, 15, 17; Figure 2), were sampled weekly from March to July by hand-hauled purse seine (90 x 7 m). Sixteen locations ( 1, 2, 3, 4, 5, 6, 7a, 8, 9, 10, 1 1, 12, 13, 2 1, 22, 23, 24; Figure 2) were sampled weekly from April to July by drum seine !216 ■' 18 m), except locations 21-24 which were sampled at 2-wk intervals from late May until early July. In 1976 seven locations !1, 2,4,5, 6, 16, 17; Figure 2) were sampled weekly from April to June by beach seine. Ten locations II, 2, 4, 5, 6, 7a, 10, 23, 24, 27; Figure 2) were sampled by drum seine weekly from early April until the end of July, then approximately monthly until March 1977. In 1977, Area 10 was sampled weekly from late April to late August by the 90 m hand-hauled purse seine. Sample Processing Fork length and weight of preserved fish were measured in all years, and in 1976 and 1977, stomach analyses were also performed. The lengths offish in small catches at sea were occa- sionally measured at the time of sampling and the fish released. This was especially true of early catches in 1975. In 1977, fish captured by the hand-hauled purse seine in Area 10 were all mea- sured for length, and a subsample of 15-20 was preserved for weight and stomach analyses. Scales of some of the preserved fish from both 1976 and 1977 were examined under 20 » magnification to determine age structure of the catch. Preserved samples were sometimes not analyzed until weeks or months after capture so preserved weights are likely to overestimate live weights. Length, how- ever, is only slightly affected by preservation ! Parker 1963). Wet weights of the stomach contents of indi- vidual fish from the intertidal area of the estuary were measured in 1975. Sample size was small except for the 9 May sample !see Table 6). In 1976 and 1977, dry weight of the stomach contents of 10-20 fish from the estuary and a similar sample from off the estuary was recorded each week and converted to percent of body weight by assuming that preserved fish were 20^? (average of >20 de- terminations) dry matter. Detailed taxonomic analysis of stomach con- tents was not made. However, in 1976 and 1977 the dominant components of the stomach contents of each sample were recorded. DESCRIPTION OF STUDY AREA The Nanaimo River discharges into the Strait of Georgia just south of the City of Nanaimo on the east coast of Vancouver Island (Figure 2). It sup- ports spawning populations of chinook; coho, O. kisutch; and chum, 0. keta, salmon as well as steelhead, Salmo gairdnerii, and cutthroat trout, S. clarki. Since 1950, chinook salmon escapement has averaged 2,100 spawners, and there has been a gradual decline in abundance from 3,700 spawn- ers between 1950 and 1954 to 1,400 between 1972 and 1976 (Aro^; Canada, Fisheries and Marine Service'"). Adult chinook salmon enter the river between April and October, and spawn from Sep- tember to November ( Aro see footnote 9). In 1974, 1975, and 1976 (the brood years reported in this study) escapement was estimated to be 2,400, 525, and 1,100 respectively. The delta estuary of the river occupies about 9 km^ of which about 6 km^ is intertidal mud flat (Figui-e 1). At the southern margin ofthe delta the 'Aro, K. V. 1973. Salmon and migratory trout of the Nanaimo River and adjacent streams (Revised 1973). Fish. Res. Board Can. Manuscr. Rep. 1284, 15 p. '"Amiua! stream bank estimates of spawning escapement available from Fisheries and Oceans. Canada, Field Services Branch, 1090 West Pender Street. Vancouver, B.C.. 656 HEALEY: UTILIZATION OF THE NANAIMO RIVER ESTUARY river divides into two main channels which cross the intertidal mud flat on the east and west sides. The west channel carries most of the flow, how- ever, and during low river flows in the spring and summer a gi'avel berm blocks the east channel, probably preventing any fish movement down this channel. Holden Creek flows across the delta on the east side and joins the east channel of the river about half way across the intertidal mud flat. Hong Kong Creek and Chase River enter the delta from the west and join the west channel of the river near the upper margin of the mud flat. The mud flat between the two main channels of the river is dissected by numerous small stream chan- nels fed by seepage from the main river channels. The smaller streams contributing to the delta do not support chinook salmon spawning but do sup- port chum and coho salmon. Salt marshes at the top of the delta are dominated by black grass, J uncus gerardii. The intertidal area has three floral associations: Fucus-Salicornia in the upper tidal area, Ulva- Enteromorpha in the midtide area, and Zostera- Ulva in the low tide area (Foreman^'). Zostera extends in a band across delta front, and well up the east channel of the river. The intertidal area of the delta is used for log storage by local sawmills and a pulp mill. Part of the northwest corner of the estuary has been filled in during development and expansion of the Port of Nanaimo. Intermittent dredging occurs at the delta front to keep the shipping lane into Nanaimo Harbor open. Some dyking has occurred along the southern margin of the delta to create farm land. Further details of physical and biological features of the estuary and adjacent lands are given in Bell and Kallman (see footnote 5). Seaward from the intertidal area of the delta a wide variety of habitats provide potential nursery area for juvenile salmon, from sheltered bays and lagoons to exposed rocky or sandy beaches. Many of these habitats were sampled during 1975 and 1976 to estimate the extent of utilization of habitats away from the river mouth as nursery areas (Figure 2). Some details of the physical and biological features of the habitats sampled are given by Healy et al. (see footnote 7). Apart from sampling locations 10, 11, and 17, within the Nanaimo Harbor area (Figure 2), salinity was usually above 27%ii, while spring and summer temperature ranged 6°-15° C (Healey et al. see footnote 7). RESULTS AND DISCUSSION Downstream Run of Fry Downstream movement of the chinook salmon fry had two peaks in 1975, the first on 19 April and the second 14 days later (Figure 3). Fry were mov- ing in small numbers throughout March, but most movement occurred in April and May. A total of 10,876 fry entered the traps between 10 March and 24 May. Trapping began on 8 April 1976, and chinook salmon were already moving downstream. One peak occuiTed in the 1976 run, although isolated large catches occurred before and aifter the peak (Figure 3). Only 4,360 fry entered the traps in 1976 suggesting that the total run was about half that in 1975. Downstream migrants averaged 38.3 mm long (0.57 g) and ranged 33-45 mm long (0.33-1.02 gl. Many of the fry still had visible yolk. River discharge during the the fry run in 1975 ranged 16-100 m^/s, and increases in fry run were generally associated with increases in discharge. 1976 60- 1975 1-° 70- 1 A " 60- ) IV- 50- oj "^'j V 40- l\ °'^l' 1 Vw V 30 ./ V J 5- 20- L-" .-JV-^ 4- "Foreman, R. E. 1975. Nanaimo River estuary mac- rophyte study: Seasonal aspects of macrophyte distribution and standing crop on the Nanaimo River estuary mudflats. BERP Rep. 75-3, final report on Fish. Mar. Serv. Contract OSU4-0217 prepared by R. E. Foreman. Botany Dep., Univ. B.C., 41 p. Figure 3.— The trap catch of chinook salmon fry (upper panels), river discharge (solid line lower panels), and weekly average river temperature (circles, lower panels) in 1975 and 1976 in the Nanaimo River. Trap catch and discharge are averaged at 2-day intervals for ease of plotting. 657 FISHERY BULLETIN VOL 77, NO 3 Temperature in 1975 ranged 3.1-11.2" C and was increasing during the run. Greatest fry movement in this year occurred when river temperature was 6°-9° C (Figure 3). In 1976 discharge ranged 18- 91m% and was higher early in the season than in 1975. Increases in the 1976 fry run often preceeded increases in discharge (Figure 3). River tempera- ture ranged 5.0°-13.3° C and greatest fry move- ment was when temperature was 8^-11" C (Figure 3). In addition to temperature and discharge, the catch of chinook salmon in the traps was probably influenced by tide. The traps were set very near the river mouth and at high tide flow past the traps was often negligible. To examine the potential contribution of discharge, river temperature, and tide height to variations in trajD catch, I performed a stepwise multiple regression analysis on the data. The dependent variable was trap catch and the independent variables were river discharge, river temperature (morning and evening mea- surements averaged), average tide height during three periods of the "trapping day" (0800-1800 h, 1800-0000 h, 0000-0800 h), and Julian day of cap- ture. I performed separate analyses on catches preceding and following the peak catch each year. The hypotheses tested were; 1) catch is positively correlated with discharge and temperature and negatively correlated with tide height for all data sets; 2) catch is positively correlated with day of capture prior to peak catch and negatively corre- lated after peak catch. The regression analysis failed to confirm or re- ject either of these hypotheses unequivocally. Dis- charge was positively correlated with trap catch while catches were increasing, but was not corre- lated while catches were decreasing (Table 1). Temp)erature was not significantly correlated with catch in any of the analyses. Tide height was nega- tively correlated with trap catch while catches were increasing as predicted. While catches were decreasing, however, tide height was uncorrelated with trap catch in 1975 and positively correlated in 1976 (Table 1). The correlation of trap catch with Julian day was positive while catches were increasing and negative while catches were de- creasing, as predicted, except that the correlation with increasing catch was not significant in 1976 (Table 1). The multiple correlation coefficients were highly significant and explained 50-79% of the variation in trap catch {R^. Table 1). Some of the results, like the positive correlations between trap catch and tide height, were counterintuitive, however, and cast doubt on any interpretation of the regression analysis. In spite of these difficul- ties the regression analysis suggests that dis- charge and tide height may have influenced trap catch, while temperature probably did not. Recaptures of marked fry in the traps in 1975 ranged 0-16. 6*^^ of the daily estimate of marks migrating. The ratio of recaptures to marks mi- grating for the whole run was 0.0175, indicating an overall trap efficiency of 1.757( (Table 2). Peterson estimates of total daily run were made Table l . —Results of stepwise multiple regression analysis of fry trap catch of juvenile chinook salmon regressed on river discharge, river temperature, average tidal height during three daily time periods (0800-1800 h, 1800-2400 h, 2400-0800 h) and Julian day of capture. Only the regression coefficients for the variables that made a significant (P<0.05) contribution to the multiple regression are shown. Independent variable Partial Regression coefficient Standardized partial regression coefficient Multiple correlation coefficient (fl) 1975 1976 1975 1976 1975 1976 Analysis 1 ; trap catch from first capture to maximun- capture n = 53, 1975 n = 24. 1976 Discharge + 0,20 +0,40 0,481 0800 Tidal height 0800-1800 1800-2400 24000800 Julian day All significant variables - -150 -78,0 - ♦63 - - 0160 0 162 - 0,507 - 0 873 0 710 Analysis 2 trap catch from maximum capture to last capture, n = 22, 1975: n = 31, 1976 Discharge Temperature Tidal height: 0800-1800 1800-2400 2400-0800 Julian day All significant variables — +159,8 - +122.0 -22,3 -14,2 — 1.77 — 1,55 0,705 1,10 0,705 0891 0.50 658 HEALEY: UTILIZATION OF THE NANAIMO RIVER ESTUARY Table 2. — Trap catch, estimate of marks migrating downstream, recaptures in the traps, and estimated daily run of chinook fry in the Nanaimo River in 1975. Population estimates in italics were derived from trap catch divided by average trap efficiency (0.0175). All other estimates are Peterson type estimates. Trap Marks Recap- Population Trap Marks Recap- Population Date catch migrating tures estimates Date catch migrating tures estimates Mar 10 2 0 0 1U Apr, 17 200 251 3 16.733 11 2 0 0 114 18 481 254 8 1 5,272 12 1 0 0 57 19 776 206 10 15.986 13 6 0 0 342 20 261 265 21 3,294 14 6 1 0 342 21 152 569 9 9.610 15 2 2 0 114 22 100 309 4 7,725 16 3 5 0 171 23 166 179 0 9,474 17 2 3 0 114 24 227 116 2 13,166 18 4 3 0 228 25 372 162 8 7,533 19 7 2 0 400 26 56 120 0 3,)96 20 11 4 0 628 27 425 107 0 24,255 21 9 6 1 54 28 190 66 0 10,844 22 6 10 0 342 29 249 333 2 41 ,459 23 8 8 0 457 30 396 210 2 41.580 24 15 6 0 856 May1 324 233 6 12.582 25 5 8 1 40 2 509 337 5 34.307 26 6 11 0 342 3 822 326 2 133,986 27 2 6 0 114 4 167 383 6 10.660 28 2 6 0 114 5 202 684 19 7,272 29 9 3 0 S14 6 133 284 4 9,443 30 11 3 0 628 7 272 202 5 10,989 31 61 1 0 3 481 8 234 144 4 8.424 Apr. 1 14 15 0 799 9 497 238 11 10.753 2 49 49 0 2.797 10 440 218 6 15.987 3 27 22 0 1.541 11 312 409 2 63.804 4 54 39 0 3 082 12 104 397 2 20.644 5 36 29 1 1.044 13 48 327 2 7.848 6 57 49 3 931 14 65 150 1 9.750 7 75 37 0 4.280 15 51 78 0 2.9!I 8 67 35 0 3.824 16 47 60 1 2.820 9 92 64 2 2.944 17 48 59 0 2.739 10 173 66 2 5,709 18 66 48 0 3,767 11 194 81 0 11.072 19 20 45 0 1,141 12 381 138 1 52.578 20 14 59 0 799 13 293 177 2 25.930 21 5 29 1 145 14 215 311 3 22.288 22 4 18 0 228 15 276 288 3 26.496 23 3 6 0 171 16 256 210 3 17.920 24 1 6 0 57 for .37 days of the 1975 run and ranged 40-133,986 fish/day. The sum of these estimates was 687,568 chinook salmon, and total trap catch for the days when estimates were made was 9,188. The ratio of catch to total run for the Peterson estimates was 0.013, indicating only 1.3^^ trap efficiency. This estimate was strongly influenced, however, by the large population estimate for 3 May, which re- sulted from a large catch in which there were few recaptures (Table 2). Ignoring this estimate, the ratio of trap catch to Peterson population esti- mates was 0.0151, closer to the average efficiency based on mark recaptures. Population estimates for all days of the run to- taled 784,155 in 1975. Assuming trap efficiency was similar in 1976, the run was about 300,000 during the trapping period. Although most chinook salmon are expected to go to sea after about 2 mo of residence in their natal stream, downstream movement of fry shortly after emergence has been observed in other systems. In the Big Qualicum River, 100 km north of the Nanaimo, between 3,000 and 241,000 fry migi'ated downstream mainly in March and April from 1961 to 1965, although the time ol greatest movement varied from late March to early May (Lister and Walker 1966; Lister and Genoe 1970). The fry migration was followed by a fingerling migration in June which was usually larger than the fry migration. In the Cowichan River, 50 km south of the Nanaimo River, a large downstream movement of fry was recorded during March and April in 1966 and 1967 followed by a smaller fingerling movement in June (Lister et al.'^). The survival of these fry and their contribu- tion to the adult population were unknown, but presumed to be slight (Lister and Walker 1966). The number of chinook salmon fry, estimated to have migrated downstream in the Nanaimo River in 1975 and 1976, was 5-10 times greater than in the Big Qualicum River which has a simi- lar escapement (Lister and Walker 1966). This '^Lister, D, B,,C. E.Walker, and M.A.Giles. 1971. Cow- ichan River chinook salmon escapement and juvenile production 1965-1967 Can. Dep. Fish. For. Tech. Rep. 1971-3, 48 p. 659 FISHERY BULLETIN: VOL. 77, NO. 3 raises the question: What proportion of the fry population migrates out of the Nanaimo River each year? Information on sex and age of the 1974 and 1975 spawning population in the Nanaimo River is not available so egg deposition can only be surmised. If one assumes, however, that of the 2,400 escapement in 1974, 800-1,000 were females, and that of the 525 spawners in 1975, 200-225 were females, and that the fecundity of Nanaimo River chinook salmon is in the range 6,000-8,000 (Godfrey'-''; Schutz'-*), then potential egg deposition in 1974 was on the order of 6-6.5 million, and in 1975 on the order of 1.2-1.6 million. (The female population was estimated to be <50% of the escapement because of the "jacks.") In the winters of 1974 and 1975 there were no extreme freshets, so survival was probably quite good, perhaps as high as 15-207f (Lister and Walker 1966; Coots "^). Fry production may be estimated to be, therefore, on the order of 0.9-1.3 million in 1975 and 0.18-0.32 million in 1976. These values are similar to the estimated fry migration each year and indicate that a high proportion of Nanaimo River chinook salmon left the river as recently emerged fry. 9 16 23 30 6 13 20 27 4 II 18 25 I 8 15 22 29 6 13 20 MARCH APRIL MAY JUNE J(JLY Figure 4.— Catch of chinook salmon fry per beach seine set at Stations 28-30 on the Nanaimo River estuary in 1975 (dots), 1976 (circles), and 1977 (triangles). Distribution and Relative Abundance of Chinook Salmon in the Estuary- Sampling in the intertidal area of the estuary revealed chinook salmon were abundant there in spring and early summer of each year (Figure 4). Juvenile chinook salmon were first captured at the beginning of April 1975, were most abundant in May, and had declined in abundance by early June when sampling terminated (Figure 4). Chinook salmon were captured from mid-March until late July 1976 but increased in abundance later than in 1975, and were generally less than half as abundant as in 1975. Juveniles were already abundant in the estuary when sampling began in late March 1977 and reached maximum abun- dance in early April, 3 wk earlier than in 1975 and 1976 (Figure 4). "Godfrey, H. 1968. Ages and physical characteristics of maturing chinook salmon of the Nass, Skeena, and Fraser rivers in 1964, 1965 and 1966. Fish. Res. Board Can. Manuscr. Rep. 967, 38 p. "Schutz, D. C. 1975. Rivers Inlet chinook sport fishery, 1971-1974. Environ. Can Fish. Mar. Serv. Tech. Rep. PAC/T- 75-9, 24 p. "Coots, M. 1957. The spawning efiBciency of king salmon ^Oncorhynchus tskawytscha) in Fall Creek, Siskiyou County 1954-55 investigations. Calif. Dep. Fish Game, Inland Fish. Branch. Inland Fish. Adm. Rep. 57-1:1-15. Greatest catches of chinook salmon were in the east channel of the Nanaimo River and Holden Creek. Catches in other stream channels crossing the intertidal mud flat and along the delta front at low tide were small by comparison. Catches in the stream channels in the center of the mud flat aver- aged only two fish/set, and on the west side of the delta only one chinook salmon was captured in eight sets. Catches across the delta front at low tide aver- aged eight fish/set. At the same time catches in the east channnel and Holden Creek averaged 20-40 chinook salmon, set. Catches along the edges of the salt marshes at high tide were lower than in the east channel in 1975, but of similar size in 1977. Purse seine sets over the intertidal flats at high tide, even near locations 29 and 30 where chinook salmon were abundant at low tide, produced no chinook salmon (Figure 1). Catches at Stations 28-31 in 1 976 and 1977 indi- cated that the area of greatest concentration of juvenile chinook salmon moved seaward along the channel as the season progressed (Table 3). The difference in time of maximum abundance be- tween Station 31 and Station 28 was about 5 wk. Physical conditions during low tide at the sam- pling stations along the east channel and Holden 660 HEALEY: UTILIZATION OF THE NANAIMO RIVER ESTUARY Table 3. — Catch of juvenile chinook salmon per beach seine set at different points along the east channel of the Nanaimo estuary during 1976 and 1977. Station locations are shown in Figure 1. Sampling StaCon Sampling week starts Station week starts 28 29 30 31 28 29 30 31 Maf, 21. 1976 Mar 20. 1977 22.5 5.5 4.0 28 27 16.0 22.0 30.0 Apr 4 0.0 05 1 0 Apr 3 6.5 7.5 1.5 18 5 11 0.3 00 05 10 05 158.5 76.5 995 18 0.5 3.5 80 17 12,0 31.4 76.0 58 9 25 20 0 130 100 24 12,0 79.5 23.0 May 2 20 155 370 May ■ 1 350 35,0 75 1,5 9 345 63,7 31 0 8 20.0 24.0 11 5 00 16 645 24.0 30 15 63.8 47.9 35 2,0 23 50.0 90 10 22 31 0 23.0 7 5 2.0 30 68 0 0.0 29 360 05 1 5 1.5 June 6 85 7 32.5 June 5 60 45 0,0 0.0 13 3.0 7.3 12 135 05 20 1.5 25.0 19 00 1 0 00 0.0 27 31.5 5.0 26 11.5 0.0 July 4 21 5 13.0 11 2.0 0.0 18 1.0 0.5 Creek varied considerably with season in 1977. Temperature ranged 9.5°-26.0' C and salinity 2-24%o (Table 4). In general, temperature in- creased at all stations from April through June, but this was strongly influenced by variations in river discharge and weather conditions on the day of sampling. Salinity increased throughout the season, but was also dependent on river discharge and local conditions. Large, local variation in physical conditions was indicated by measure- ments of temperature and salinity at two locations at Stations 28 and 30 in May and June. At Station 28 a small steam channel joined the main east channel. Temperature of the river above where this stream entered was usually lower, and on one occasion 4.5° C lower, than below the entrance. Salinity above the entrance of this stream channel was sometimes higher and sometimes lower than below the entrance, the greatest observed differ- ence being 6%i, (Table 4). At Station 30. Holden Creek joined the east channel of the river. The river was usually cooler than Holden Creek, al- though on one occasion it was warmer, and salinity of the river was usually lower than Holden Creek. Temperature and salinity values reported, there- fore, should be taken as indications of the kind of conditions in which the fish lived at low tide, with considerable latitude for selection by the fish. The appearance of juvenile chinook salmon in the intertidal area of the estuary was coincident with the buildup of the downsteam run and the rate of increase in catch on the estuary was similar to the cumulative increase in the number of chinook salmon which had moved downstream. In both 1975 and 1976 the estuary population con- TaBLE 4.— Temperature (° C) and salinity (%o) at sampling loca- tions for juvenile chinook salmon on the Nanaimo estuary dur- ing 1977. Station locations are shown in Figure 1. Sampling station 28 Station 29 Statw in 30 Station 31 week starts ■c V C V •c V 'C %. Apr 3 12.0 160 12.0 14 8 13.0 9,5 12.0 10.5 10 105 95 155 15.3 17 130 200 13.6 17.8 12.7 13.0 17.8 11.0 24 11.8 2.0 17.0 10.4 17.2 11.3 May 1 17.0 228 15.0 12.8 15.8 14.3 20 0 17.0 8 18 0 208 18,2 19.8 21.3 17 0 21 6 181 21.4 20.4 15 167 182 '22 1 24.5 16 1 222 15.0 14.6 '190 20,0 154 178 22 15,8 182 '20.0 245 15,2 208 15.6 151 '22,2 20 4 169 18 3 29 130 130 '20.0 14,0 132 21 6 133 16 1 '20.6 20,4 138 19 1 June 5 190 235 '175 140 190 20 0 25 1 19.9 '198 189 260 19.4 12 190 19.3 '178 17 4 187 182 19.9 '18.9 19 21.0 24.6 20.2 24 6 20.5 24.0 240 24.0 26 21.0 20.3 '22.3 23.2 190 22.0 19.9 '189 'Upper measurement above small tributary, lower below small Inbutary 'Uppef measurement in Holden Creek, lower m mam river channel tinued to increase after the peak in the down- stream run. These observations indicated that the fry which migrated downstream remained in the estuary for some time. At low tide the chinook salmon population in the estuary was clearly concentrated in the east chan- nel of the river and Holden Creek. Some juveniles were found in stream channels crossing the center of the mud fiat, and some also found their way down to the delta at low tide. The channels cross- ing the western side of the mud flat, however, were little used by juveniles. With the incoming tide the chinook salmon moved to the landward margin of the mud flat and at high tide were found in scattered schools all 661 nSHERY BULLETIN VOL, 77, NO 3 across the landward margin of the intertidal area. Apparently no chinook salmon, or very few, re- mained over the intertidal flats at high tide The redistribution of chinook salmon on each tidal cy- cle, and their concentration in one of several low tide refuges implied active habitat selection. Ac- tive selection of habitats at low tide is further indicated by the seaward movement of the center of the population in the east channel and Holden Creek as the season progressed. The habitats in which chinook salmon were cap- tured ranged from a few centimeters to a meter or more in water depth, on gravel, sandy, or muddy substrates, with and without eelgrass, Zostera sp. In the east river channel, concentrations of fry were found mainly in pools and back eddies. There were, however, no obvious qualitative differences between preferred sites in Holden Creek where chinook salmon were abundant and stream chan- nels crossing the central and west sides of the intertidal area where chinook salmon were scarce. The upstream portions of the stream channels in the central area of the delta, where they cut through the marsh areas, were used as low tide refuges in early spring. Where these stream chan- nels cross the intertidal mud flat deep pools are scarce and the water flow small. These features may have made them unsuitable as refuges during May. The absence of chinook salmon from the west branch of the river could not be explained in this way; however, disturbance of the estuary by log rafting is greatest along the west branch and this may have influenced chinook salmon distribution. Temperature and salinity in the east channel of the river and Holden Creek indicated that the chinook salmon were tolerating moderate salinities and relatively high temperatures. Occa- sional measurements of temperature and salinity in other areas sampled at low and high tide were comparable with those in the east channel at low tide. Weisbart (1968) reported that juvenile chinook salmon (parentage not identified) were intolerant of direct transfer from freshwater to 31.8%o seawater, but that they had greater resist- ance to seawater than either coho or sockeye salmon, O. nerka. Mclnerney (1964) reported that juvenile chinook salmon from the Samish hatch- ery, Washington State, avoided all salinites above 0%o except for a brief preference for about 5%o salinity in September tests. Presumably both tol- erance and preference for salinity will vary among stocks of salmon, and Nanaimo River chinook salmon appear adapted to life in moderate salinity on the estuary. Temperatures experienced by the chinook salmon at low tide were within their tol- erance range but were generally above the 12°-13° C reported to be their preferred temperature (Brett 1952). Seasonal changes in the low tide distribution of chinook salmon were not obviously correlated with temperature and salinity in the east channel and Holden Creek. Temperature at the upstream stations often, though not always, exceeded that at the downstream stations. Chinook salmon were not captured at Stations 30 and 31 when tempera- ture there exceeded 20° C. They were present at Stations 28 and 29, however, when temperature was 20"-21''C. Salinity wasonly slightly higher on the average at the downstream stations, and often the salinity at the upstream stations was the same or slightly higher than downstream (Table 4). In- creasing adaptation to salinity, therefore, ap- peared not to be a factor in this seaward move- ment. Possibly the disappearance of chinook salmon from the shallow sampling stations in Holden Creek as the season progressed was an avoidance of the high temperatures that occurred there on sunny days. The seasonal pattern of abundance of juvenile chinook salmon in the Nanaimo estuary was the same as that observed by Dunford (1975) in the Fraser River, but different from that in the Sixes River, Oreg. (Reimers 1971). In the Sixes River, most chinook salmon apparently spent some weeks in the river before moving into the estuary, although some were considered to have moved di- rectly to the estuary, and some even directly to the sea. Reimers ( 1971 ) did not present information on the temperature and salinity of the estuary habi- tats he sampled. Dunford ( 1975) gave temperature measurements for two habitat types in the Fraser estuary, and these were lower than in similar areas of the Nanaimo River. Chinook salmon dis- appeared from Fraser River marsh habitats when temperature reached about 15° C (Dunford 1975). Size and Growth of Chinook Salmon in the Nanaimo Estuary Length and weight of chinook salmon captured in the intertidal area of the estuary were only slightly greater than those of downstream mi- grants throughout the fry run. Toward the end of the fry run, however, average length and weight of chinook salmon captured in the estuary increased rapidly and leveled off at around 70 mm fork 662 HEALEY: UTIUZATION OF THE NANAIMO RIVER ESTUARY length (FL) and 4.2 g (Figure 5). Chinook salmon captured in 1976 were slightly smaller on the av- erage, than those captured in 1975, while those captured in 1977 were the largest of all. Average size of Chinook salmon captured in 1977 increased rapidly 3-4 wk earlier than in 1975 and 1976, in keeping with the apparently earlier downstream run in 1977. The differences in size of chinook salmon captured in the 3 yr were not large, at least early in the sampling, and probably reflected dif- ferences in the timing of migration rather than differences in growth rate. The small change in length and weight of chinook salmon in the es- tuary during March and April probably resulted from continued recruitment of downstream mi- grant fry to the estuary population, while the in- crease in May and June reflected growth of the fish residing in the estuary. Seventy millimeters fork length is apparently the size at which chinook salmon leave the estuary and disperse into the marine environment. No young-of-the-year <70 mm were captured away from the estuary. The smallest young-of-the-year captured in area 10 were 70-75 mm FL. Weisbart (1968) commented that 70 mm was about the size at which juvenile 70 60 I I— o UJ 50- p 40- ,«'° /A. n I I I 1 1 1 1 1 1 1 1 r 15 25 4 14 24 4 14 24 3 13 23 3 13 23 4 0-1 E o o> 30- I O 20- UJ 10- V '\' \...-,» ;,'9-«'-0.-5» „/ T 1 1 1 1 1 1 1 1 1 1 1 r 15 25 4 14 24 4 14 24 3 13 23 3 13 23 MAR APRIL MAY JUNE JULY Figure 5. — Average fork length and round weight of juvenile chinook salmon captured on the Nanaimo River estuary in 1975 (dots), 1976 (circles), and 1977 (triangles). chinook salmon became physiologically capable of tolerating high salinity water. The increase in size of chinook salmon on the estuary in June was not representative of their true growth rate, as it was influenced by both the continued immigration of small fish from the river and the emigration of fish reaching 70 mm FL. Recaptured fin clipped fish in 1977, however, pro- vided an estimate of the growth rate of a known group of juveniles. Total mark recaptures sampled for length and weight were 36 left pelvic clips and 19 right pelvic clips. Left pelvic clips averaged 44 mm and 0.92 g when marked, and five of these recovered 47 and 57 days after marking averaged more than 100 mm and 13 g (Table 5). Right pelvic clips averaged 63 mm and 3.36 g when marked, and increased to more than 100 mm and 13 g after 29 days (Table 5). The linear regressions of length or logp weight on days since marking indicated no significant difference in the rate of growth between the two marked groups. The data were, therefore, combined by scaling to 0 length and weight at the day of release and growth rates were calculated for the combined data. Growth in length was 1.32 mm/day. Instantaneous daily growth in weight was 0.0566, or about 5.8% of body weight/day. Estimates of Total Estuary Population Although the beach seine samples taken in this study provided an adequate measure of distribu- tion and relative abundance of chinook salmon, they do not permit an estimate of the total number of chinook rearing in the estuary. Mark and recap- ture estimates of abundance in 1977 provided a reference point for comparing catches between years and for comparing the downstream run of fry with the estuary population. Between 18 and 21 April 1977, 3,187 fish marked with a left pelvic clip were released at Stations 29-31 of the east Table 5. — Size at release and recapture of fin-chpped juvenile chinook salmon in the Nanaimo River estuary in 1977. Le« pe Vic clips Right pelvic clips Days Aver- Aver- Days Aver- Aver- since age age since age age n marlelvic clip. Population estimates are the product of total catch and estimated marks present divided by marks recaptured. Tolal catch Total marks released Marks recaptured LV RV CPUE recaptures Estimated marks present Population estjr LV RV nates Date LV RV LV RV LV RV Bottl Both Apr 18 589 370 19 875 827 18 329 15.993 20 858 791 55 1,028 16.037 21 1,344 1,199 127 1.619 17,133 22 609 104 8.00 2.506 14,675 25 229 23 3.63 1.764 17,563 May 3 168 10 1.25 692 11.558 9 111 2 022 343 18.648 16 233 203 6 0.75 151 5.708 17 340 335 17 13 1 55 1 18 134 177 311 2.680 4,629 3,525 18 749 691 23 35 2 66 3 89 120 446 566 3,908 9,544 7,309 19 412 325 22 48 275 600 106 992 1.098 1,985 8,515 6,463 2C 127 2 13 0,25 1 62 67 761 828 4,254 8,089 7.010 31 79 0 3 0 00 038 26 254 280 6,689 7,373 June 6 21 0 1 000 012 13 112 125 2,352 2,625 13 28 0 1 000 0.25 6 43 49 1,204 1,372 20 2 0 0 0 00 000 3 16 19 28 13 0 0 0,00 0,00 1 5 6 664 HEALEY: UTILIZATION OF THE NANAIMO RIVER ESTUARY estimated marked population for the week was 655, giving a population estimate of 22,148 for the whole estuary. The average population of the east channel for the week was about 15,000, or about 68% of this estimate. Total estuary population may. therefore, be about 32% greater than the esti- mate for the east channel and Holden Creek. Comparing beach seine catches for 1975-77 with the mark recapture estimates indicated that the peak population on the estuary was on the order of 20,000-25,000 in 1976 and 1977 but was probably closer to 40,000-50,000 in 1975. These estimates are comparable with a single day's fry migration in 1975 and 1976. However, the slow rate of disap- pearance of marked fry from the east channel indi- cated a relatively long residence of fry on the es- tuary (about 60 days). An accumulation of fry on the estuary during downstream migration would, therefore, be expected. Treating each daily run of fry as a single cohort arriving on the estuary, and reducing that cohort by 11-12%/day (the rate of disappearance of marked fry from the east chan- nel), produced estimates for the estuary popula- tion of around 100,000 in 1975 and 50,000 in 1976, or about twice the estimate based on mark recap- ture results for 1977. Estimates of downstream run are for the release point of the marks, how- ever, and significant mortality might occur bet- ween the release point and the estuary (Hunter 1959). Alternatively, the rate of disappearance of marked fry may underestimate the rate of disap- pearance of recent downstream migrants. A dis- appearance rate of 11-12%/day suggested an aver- age residence time of about 60 days, whereas growth rates suggested that most fry should spend only 25 days in the estuary. If downstream migrants spend only 25 days in the intertidal area, and their rate of disappear- ance is constant during that' time, then peak es- tuary populations are 40,000 in 1975 and 20,000 in 1976, comparable with the estimate based on mark recaptures in 1977. The estimate of disap- pearance rate from mark returns has rather wide confidence limits, 25 days being within the range of 95% probability in estimates of residence time. The apparent discrepancy between mark recap- ture estimates of estuary population size and downstream run can be resolved by assuming re- sidence of 25 days, therefore. The assumption of a constant rate of disappearance of chinook salmon from the estuary population, however, implies the disappearance of many juveniles <70 mm FL. Al- though high mortality of salmon fry is a common assumption, no predators or important diseases were obviously present in the Nanaimo estuary to justify the assumption of heavy losses of small fish. The tentative agreement between the various es- timates of population size may therefore be spuri- ous, and these estimates should be regarded as preliminary at best. By comparison with the Fraser and the Sixes Rivers, chinook salmon were rare in the Nanaimo River. Dunford (1975) reported maximum densi- ties in excess of 2 fish/m^ in Fraser River marshes, compared with average densities of about 0.1 fish/m^ in the east channel and Holden Creek. For the Sixes River estuary, an area about twice as large as the east channel and Holden Creek, Reimers (1971) reported maximum population es- timates of 100,000-150,000. However, Reimers' estimates were made 5 days after the release of marked fish into the estuary, and, assuming his marked fish were disappearing at a rate similar to those in the Nanaimo River, the population in the Sixes River estuary may have been closer to half the values he reported. Nevertheless, this still represents a population significantly more dense than that in the Nanaimo estuary. In terms of suitable habitat, however, the Sixes River may not be greatly different from the Nanaimo River, as it is about twice as large as the east channel and Holden Creek, and probably supported about twice the population of chinook salmon. Population of Juvenile Chinook Salmon Outsicie the Estuary Beach seine samples in areas other than the intertidal area of the estuary produced few- juvenile chinook salmon. In 1975, 19 sets made in mid-May yielded only 3 juveniles, and in 1976, 61 sets made during April-June yielded only 26. Twenty-four of these were captured in the lagoon behind Duke Point (area 16), adjacent to the es- tuary. Apparently onshore areas away from the estuary were not used by chinook salmon fry, al- though all the beaches sampled were used by pink and chum salmon fry. Juvenile chinook salmon were captured in most locations sampled by the two purse seines in 1975 and 1976. Not all chinook salmon captured were young-of-the-year, however. Catches prior to May were mainly yearlings. In late May and early June there was a large influx of young-of-the-year and a subsequent decline in the catch of yearlings. The influx of young-of-the-year (Figure 6) coincided 665 nSHERY BULLETIN VOL. 77. NO. 3 with the decline in abundance of chinook salmon in the intertidal area of the Nanaimo estuary. The periodicity of catches in the estuary and adjacent marine areas is indicative of a stage movement away from the estuary and into deeper water by young-of-the-year. Sampling by drum seine after July 1976 indicated the persistence of moderate numbers of juvenile chinook salmon in the Nanaimo area until the end of October, after which catches declined to the low levels observed in spring (Figure 6). Catches of chinook salmon by the 92 m purse seine in 1975 were mainly in area 10 (338 of 434 chinook salmon captured ), with smaller catches in areas 6, 7, 8, and 11 and few elsewhere. Catches by the 218 m drum seine in 1975 were also mainly in area 10(101 of 205 captured), with the remaining catch scattered throughout the sampling areas. Chinook salmon were more scattered in 1976, area 10 yielding only 79 of 245 captured by drum seine between April and July and areas 1.2, 5, and 6 also providing good catches. Chinook salmon were of similar abundance in drum seine catches between 60- l\ ^H ,, OCEAN ^™ TYPE 40- / \ ESTUARY HD '^V.T'' 20h / \ 1 Iq^OCEAN 1 ^'^^TYPE n_ / ^ MARINE 4-10 meter depth -°- ^'"""'^ MARINE \ > 20 metef depth Figure 6.— Catch per set of juvenile chinook salmon by age and life history type, by beach seine on the estuary, and by shallow and deep purse seine in marine waters adjacent to the Nanaimo River e.stuary. Data are averages for 1975-77, April and June 1975 and 1976 (CPUE 0.73 in 1975 and 0.83 in 1976) but were significantly less abun- dant in July 1976 compared with 1975 (CPUE 3.30 in 1975 and 2.28 in 1976 x^ = 6.43, P<0.051. The greater catch in July 1975 presumably reflected the greater contribution of young-of-the-year from the estuary in 1975. The presence of juvenile chinook salmon in the Nanaimo area throughout the year in 1976 indi- cates a local resident population that is supplemented by young-of-the-year in June. The appearance of juveniles in large numbers in area 10 coincident with their disappearance from the intertidal area of the estuary indicates that these fish were from the estuary population. The evi- dence is not conclusive however, and e.xamination of the catch at area lOin June and July 1977 for fin clips from the estuary produced only 8 marked fish out of 555 examined. This compares with approx- imately 10%' of the estuary population marked in April and May. Possible reasons for the low number of marks in the catch at area 10 include differential mortality of marks (the percentage of mark returns in the estuary declined after each marking), rapid dispersal of chinook salmon away from the estuary, dilution of the fish of local origin by fish from other systems, or dilution of the es- tuary population by late migrants from the Nanaimo River. In my view the most likely expla- nations are rapid dispersal of juveniles from the estuary population, and dilution of the estuary population by late migrants from the Nanaimo River. Chinook salmon reared in the intermediate salinity of the estuary are probably already adapted to seawater by the time they are ready to leave the estuary while late migrants from the river might be expected to stay close to the river mouth for some time, adapting to salt water. Sam- ples from area 10 may, therefore, contain a dispro- portionate number of late migrants. An unknown proportion of the Nanaimo River population probably disperses rather quickly away from the Nanaimo area after leaving the river. Some young-of-the-year, however, remain in the Nanaimo area, at first concentrated rather close to shore, but later moving to more offshore sampling locations where they persist until at least November (Figure 6 1. During the winter these fish decline in numbers until by the follow- ing spring there are only a few 1 + ocean fish in the local area. Most of these disappear from the sur- face waters in May coincident with a small influx of yearling smolts from the Nanaimo River (Fig- 666 HEALEY: UTILIZATION OF THE NANAIMO RIVER ESTUARY ure 6). The yearling smolts dominate samples taken in late May and early June, after which they disappear and are replaced by young-of-the-year, presumably from the Nanaimo River. This se- quence of events in which 1+ ocean fish are re- placed by 1 -I- stream fish which in turn are replaced by 0-1- ocean fish is not unique to the Nanaimo area but appears to be typical for the Gulf Islands region as a whole (Healey"'). Food Habits and Feeding Rates A growth rate in excess of 5'7f body weight/day implies good feeding conditions in the estuary (e.g., LeBrasseur 1969). Diets of juvenile chinook salmon were similar in 1976 and 1977, and five taxonomic groups made up the bulk of the diet in the estuary. Harpacticoid copepods were impor- tant in March and early April, decapod larvae and amphipods in April and May, and mysids and in- sect larvae in May-July. Off the intertidal area of the estuary fish larvae, chiefly herring, dominated the diet of juvenile chinook salmon from May through August, while calanoid copepods, decapod larvae, and insects were occasionally important. A shift from a predominantly invertebrate diet to a predominantly fish diet, therefore, occurred as the young chinook salmon dispersed away from the intertidal area of the estuary. Average weights of stomach contents varied considerably from sample to sample; nevertheless, some generalizations appear possible. Weights of stomach contents of juvenile chinook salmon cap- tured on the estuary in 1975 ranged about 3-5'5f of body weight in April but dropped rapidly to a low of about O.lVf of body weight as the chinook salm- on population on the estuary increased in May (Table 7). Weights of stomach contents of juveniles on the estuary were uniformly low in 1976, never rising above 2.V7< of body weight (Table 7). Stomach contents of juveniles captured in 1977 ranged 2-Wi of body weight except during the peak of fry abundance when contents dropped to 0.5% of body weight (Table 7). Assuming that stomach contents are a reflection of feeding condi- tions, it appears that feeding conditions were poorest in 1976, better in 1977, and possibly best of all in 1975 when the population was greatest. Peak population densities were associated with a decline in stomach contents, and by inference, a Table 7. — Stomach contents as a percent of body weight for juvenile chinook salmon captured in the intertidal area of the Nanaimo River estuary and off the intertidal area 1975-77. Sampling week dates are for 1976. Add 2 days for 1975 and subtract 1 day for 1977 to get the correct starting date for those years. Sampling weeK On the estuary ( 3lf the estuary 1975 1976 1977 1976 1977 starts n °'o n % n % n % n % Mar 14 1 1 4 21 15 1 6 28 1 1 7 19 34 Apr. 4 9 33 2 20 24 24 11 3 4 1 6 10 20 26 18 t 29 20 1 4 57 1 9 25 5 50 20 17 15 06 May 2 1 3.8 20 1 6 18 20 9 25 0 1 20 2,2 20 22 25 26 16 3 23 20 1 2 36 4 1 23 20 1 4 15 2 1 30 20 1 1 12 40 5 25 June 6 20 22 10 3.3 1 0 1 13 6 50 13 20 14 25 20 ,,- 20 1 9 2 20 3 1 3 27 20 20 5 40 15 34 July 4 20 20 3 08 17 30 11 24 1 8 20 1 2 18 3 1 0 24 13 29 27 25 8 1 2 19 1 4 Aug 15 4 2.3 22 10 1 2 '^Healey. M. C, 1978. The distribution, abundance and feeding habits of juvenile Pacific salmon in Georgia Strait, British Columbia. Fish. Mar. Serv. Tech. Rep. 788, 49 p. decline in food intake in the years of good feeding conditions. Weights of stomach contents of juvenile chinook salmon captured away from the intertidal area of the estuary were similar to those in the estuary during May and early June, but in mid-June dropped below those from the estuary. Weights of stomach contents of chinook salmon captured offshore were lower in 1976 than in 1977, as was observed for the estuary population (Table 7). The composition of the diet of juvenile chinook salmon in the Nanaimo estuary was similar to that reported by Sibert and Obrebskii 1976) for the Nanaimo estuary in 197.3 and to that recorded by Dunford ( 1975) in similar habitats on the Fraser estuary. The relative timing and importance of specific items in the diet was different than in the Fraser, but this probably reflects differences in abundance of the different diet items and the op- portunistic feeding behavior of the fish. The change in diet of juvenile chinook salmon from invertebrates while in the intertidal area of the Nanaimo estuary, to larval fish when away from the intertidal area was consistent with observa- tions on the Fraser estuary. Juveniles in the Fraser River and marsh area fed mainly on inver- tebrates, but those on Roberts and Sturgeon Banks fed mainly on juvenile herring (Goodman see footnote 2). 667 FISHERY BULLETIN: VOL. 77, NO, 3 Seasonal changes in the diet of chinook sahnon in the intertidal area of the estuary indicated that a combination of size selection and availability influenced the diet. Very small organisms (har- pacticoids and cladocerans) occurred in stomachs only in the early spring when the fish were 50 mm or less in length. Larger organisms (amphipods. mysids) were important later in the season when the fish were considerably larger. Insects were important diet items throughout, presumably be- cause of their widespread availability in the habitats sampled. CONCLUSIONS The Nanaimo River population of juvenile chinook salmon is composed offish which go to sea in their first year and fish which remain in freshwater for 1 yr, with those which go to sea in their first year most numerous. Chinook salmon which migrate to sea in their first year are the most common life history type in British Colum- bia (Milne'^; Godfrey see footnote 13). In the Nanaimo River many of those chinook salmon which go to sea as young-of-the-year move downstream as recently emerged fi^y and rear to smolt size in the intermediate salinity of the es- tuary. Large numbers of chinook salmon fry are found in the marshes of the Fraser estuary in spring and summer (Dunford 1975) and in the estuaries of other rivers in which chinook salmon spawn (Healey unpubl. data). Estuaries, there- fore, are important nursery areas for chinook salmon, a fact which has not hitherto been ap- preciated. ACKNOWLEDGMENTS Technical staff who contributed to the collection and analysis of data presented include R.V. Schmidt, F. P. Jordan, and R. M. Hungar. Fry trap- ping was performed by R. Wilson under contract. Robin Le Brasseur and T. G. Northcote criticized a draft of the manuscript. LITERATURE CITED Brett, J, R. 1952. Temperature tolerance in young Pacific salmon. "Milne, D. J, 1964. Sizes and ages of chinook (Oncorftvn- ckus tshawytscha) and echo (O. kisutch^ salmon in the British Columbia troll fisheries 1 1951-19591 and the Fraser River gillnet fisheries (1956-1959). Fish. Res. Board Can. Manuscr. Rep. 776, 36 p. genus Oncorhynchus. J Fish Res, Board Can, 9:265- 323. DlNFORD, W, E, 1975. Space and food utilization by salmonids in marsh habitats of the Fraser River estuary. M, Thesis, Univ, British Columbia. 81 p HlWTER. J, G. 1959. Survival and production of pink and chum salmon in a coastal stream J, Fish. Res. Board Can, 16:835-886, LkBk,\s,ski'R, R, J 1969, Growth of juvenile chum salmon [Oncorhynchus keta) under different feeding regimes, J, Fish, Res, Board Can, 26:1631-1645, LISTER, D. B., .\s\) H S GKXDE 1970, Stream habitat utilization by cohabiting underyear- lings of chinook {Oncorhynchus tshauytscha ) and coho lO, kisutch I salmon in the Big Qualicum River, British Colum- bia, J, Fish, Res, Board Can, 27:1215-1224, LISTER, D. B,, R, A, L, H,-\RVEV, ,\.\D C, E, W.ALKER, 1969. A modified wolf trap for downstream migrant young fish enumeration. Can. Fish Cult. 40:57-60. LISTER. D, B,, AND C, E, WALKER, 1966, The effect of flow control on freshwater survival of chum, coho and chinook salmon in the Big Qualicum River, Can. Fish Cult, 37:3-25. MclNERNEY, J. E. 1964, Salinity preference: an orientation mechanism in salmon migration, J, Fish Res, Board Can, 21:995-1018, MEHAN, W, R,, AND D, B, SiNIFF, 1962, A study of the downstream migrations of anadro- mous fishes in the Taku River, Alaska, Trans, Am, Fish, Soc, 91:399-407. Parker, R. R. 1963, Effects of formalin on length and weight of fishes, J, Fish, Res, Board Can, 20:1441-1455, REIMERS, P, E, 1971, The length of residence of juvenile fall chinook salm- on in Sixes River, Oregon, Fish Comm, Oreg, Res, Briefs, 99 p, REIMERS, P, E,, AND R, E, LOEFFEL, 1967, The length of residence of juvenile fall chinook salmon in selected Columbia River tributaries. Fish Comm, Oreg, Res, Briefs 13:5-19. RICKER, W. E, 1975, Computation and interpretation of biological statis- tics of fish populations. Fish, Res, Board Can, Bull, 191, 382 p, SIBERT, J,, AND S, OBREBSKI 1976, Frequency distributions of food item counts in indi- vidual fish stomachs. In C, Simenstad and S, Lipovsky leditorsl. Fish food habits studies, 1st Pacific Northwest Technical Workshop Proceedings, p, 107-114, Washington Sea Grant, Univ, Wash,, Seattle, STEIN, R. A., P, E, REIMERS, ANTJ J D, HALL, 1972, Social interaction between juvenile coho (Oncor/ivn- chus kisutch ) and fall chinook salmon (O, tshawytscha) in Sixes River, Oregon, J, Fish, Res, Board Can, 29:1737- 1748, WEISBART, M. 1968, Osmotic and ionic regulation in embryos, alevins, and fry of the five species of Pacific salmon, Ctm, J, Zool, 46:385-397, 668 COMPOSITION, ABUNDANCE, AND DISTRIBUTION OF ZOOPLANKTON IN THE NEW YORK BIGHT, SEPTEMBER 1974-SEPTEMBER 1975 David C. Judkins,' Creighton D. Wirick,' and Wayne E. Esaias^ ABSTRACT Zooplankton taxa were counted in 8 to 19 samples from each of 11 cruises in the New York Bight between September 1974 and September 1975. Meyor seasonal events were an influx into the region of tropical-subtropical copepod species during autumn 1974 and summer 1975, an offshore ( >50 m water depth) zooplankton abundance maximum in March dominated by the pteropod Limocina retroversa, a second offshore maximum in May characterized by high abundance of the copepods Pseudocalanus sp., Calanus finmarchicus, and Oithona similis, and an onshore ( <50 m water depth) maximum in July characterized by high abundance of the copepods Centropages typicus and Temora longicornis. The offshore maxima occurred during or shortly after the local spring phytoplankton bloom (March-April). Advection of pteropod and copepod stocks into the region from the northeast probably contributed to these peaks. The July C. typicus-T. longicornis peak was associated with summer warming of the water column within the highly productive waters in the Bight apex and off the New Jersey coast. Comparison of our results with those of a study conducted in 1959-60 shows that the most abundant species of copepods were essentially the same during the two periods. The New York Bight is the section of continental margin and overlying water within the bend of the Atlantic coastline bounded by Long Island on the north and New Jersey on the west (Figure 1). It is one of the most heavily used coastal regions of the world for a variety of human activities, including transportation, fisheries, recreation, and waste disposal (Gross et al. 1976). Exploration for and exploitation of potential offshore petroleum de- posits may place additional burdens on the re- gion's environment. Efforts to document changes in the biota because of these activities have gener- ally been inadequate, especially in regards to the zooplankton. In a recent review, Malone (1977) observed that studies of the zooplankton of the New York Bight generally have been restricted to small geographic areas and to short periods of time, and consequently little data on species abundance and distribution exist for most of this heavily exploited area. In this paper, we examine seasonal and onshore-offshore trends in occurrence and abun- dance of zooplankton taxa in waters of the New York Bight. These observations are based on analysis of the most comprehensive set of zoo- plankton samples obtained to date within the re- gion and thus are invaluable for comparison with 'Oceanographic Sciences Division, Brookhaven National Laboratory, Upton NY 11973. ^Marine Sciences Research Center, State University of New York, Stony Brook, NY 11794. future studies. We compare our results with previ- ous studies for evidence of the year-to-year varia- tions in mean abundance of dominant species and in timing of peaks in their standing stocks. Fi- nally, we examine occurrences of offshore water within the study area, and discuss zooplankton abundance maxima in relation to seasonal and regional variations in temperature and phyto- plankton standing stocks and the environmental requirements of the dominant species. METHODS The station grid (Figure 1) was occupied 13 times between 25 July 1974 and 15 September 1975, vidth a cruise every month except December 1974 and January 1975. These cruises were part of an ichthyoplankton survey by the National Marine Fisheries Service (NMFS) Laboratory at Sandy Hook, N.J., funded by the Brookhaven Na- tional Laboratory. Zooplankton were analyzed in collections from the 11 cruises between 24 Sep- tember 1974 and 15 September 1975 (Table 1). Standard NMFS MARMAP gear was used that consisted of 60 cm diameter paired 333/xm and 505 fim mesh nets mounted on a "bongo" sampler without an opening-closing mechanism. Sampling accessories (flovraneters, depth recorder, depres- sor, towing cable) were rigged as specified by Smith and Richardson (1977). To obtain better estimates of small-bodied copepods, nets with 253 iVlanuscnpt accepted Februar\' 1979. FISHERY BULLETIN: VOL.77, NO. 3, 1980. 669- FISHERY BULLETIN: VOL 77. NO 3 I 7no 40"30- *2 C2 ^ D3 A4 I I, • GRID STATIONS + TRANSECT STATIONS G2 + + + Gt + y +'' /' + S6 40°00- 39°30- 74*00' I 73°30' I 7300' ^i'" F7 0 20 kilometers 40 72° 30' 72°00' 7f30' 1 Figure l.— New York Bight with stations for oblique net tows for zooplankton ignd) and chlorophyll, nutrient, and hydrographic measurements igrid and transect). or 223 yLtm mesh were added to the sampling array in 1975. These nets were 20 cm in diameter and mounted as pairs on a bongo sampler rigged with a flowmeter in one mouth. The 20 cm sampler was attached to the towing wire immediately above the 60 cm frame, and the entire array was towed obliquely at 3.5 kn (6.5 km/h) from near bottom to surface, except at stations exceeding 200 m where tows were from 200 m to the surface. The samples from the two nets on the 20 cm frame were com- bined before preservation. From 8 to 19 of the 20 grid stations (Figure 1) were sampled for zooplankton during the 11 cruises of the survey (Table 1). Samples were not available for every station because of gear failure, adverse weather, or contamination by algae or sediments. At all grid and transect stations (Fig- ure 1) XBT's and nonmetallic sampling bottles were used to obtain temperature, salinity, nutri- ent, and chlorophyll data at discrete depths. Samples were analyzed separately for chaetog- naths, copepods, and "other" zooplankton ( i.e., all taxa other than chaetognaths and copepods). We used only samples from 253 \xm. and 223 /itm mesh nets to estimate the abundance of copepods and other zooplankton in 1975 but had to rely on 333 /nm mesh nets for abundance estimates in 1974. In the separate analyses of copepods and other zooplankton, we removed aliquots from a sample with a piston pipette until a total of 500 or more individuals were identified and counted. We counted chaetognaths only in collections from 333 /xm mesh nets , which retained most size classes of these large-bodied animals. We used a Folson plankton splitter to subsample collections with large numbers of chaetognaths until a total of 200 670 JUDKINS ET AL.: ZOOPLANKTON IN THE NEW YORK BIGHT Table l. — Zooplankton sampling data for the New York Bight region. 1974-75. Net mesh aperatures and mouth diameters indicated by letters: A. 333 ;um, 60 cm; B, 253 ^cm (February 1975 only) or 223 /Am, 20 cm. For station locations see Figure 1. Depth' Cmise 74-11 74-13 74-15 75-1 75-3 75-4 75-5 75-6 75-7 75-8 75-14 Station (m) 24-26 Sept. 23-28 Oct 19-23 Nov 1-6 Feb. 5-11 Mar. 2-10 Apr 6-12 May 2-9 June 7-12 July 12-16 Aug 8-15 Sept A2 27 A A _ A, B A A. B A.B A.B A.B A. B B A4 26 A A — A, B 6 A. B A,B A, B B A.B A, B B3 40 A A A A, B A, B A, B A, B A.B A.B A, B A, B B5 37 A A — — A. B A.B A, B A.B A.B B A.B C2 33 A A A A. B A. B A. B A, B A. B A. B A. B A, B C4 49 A A A A A, B A.B A.B A.B A, B A.B A.B C6 59 — A — — B A. B A. B A. B A A. B A. B D1 29 A A A A, B A. B A. B A.B A, B A, B A.B A.B D3 49 A A A A, B A A.B A, B A. B A, B — A. B D5 64 A A — A. B A, B A A, B A B A, B A.B A.B E2 48 A — A A. B A, B A.B A.B A, B A.B A.B A.B E4 66 A A A A, B A. B A, B A.B B A, B A, B A, B E6 124 A A — A, B A, B A.B A.B A, B A, B A.B A, B F1 49 A A A A A, B A. B A, B A. B A. B A, B A, B F3 71 A A — A, B A, B — A, B A.B A.B A.B A, B F5 128 — A — A, B AS B A.B A, B A, B A.B A.B F7 2,800 A A — A. B A, B A, B A.B A, B A, B A.B A, B G2 71 A A — A, B A, B — A.B A, B A.B A.B A.B G4 146 A A — A. B — A. B A, B A.B — A, B A. B G6 1.600 — - — - — — — — B A. B — 'Maximum sample depth - 200 m, or more individuals were counted. Abundances of taxa within individual samples and related data are available in a data report ( Judkins^) and from the senior author. In our treatment of the cross- shelf distribution of zooplankton, we divided the study region into two sectors of equal area, an onshore zone shoreward of the 50 m depth contour and an offshore zone seaward of that contour. Each sector contained 10 zooplankton grid stations (Figure 1). This division yielded approximately equal numbers of onshore and offshore samples and provided an easy test for cross-shelf differ- ences in species abundances. In Tables 2 and 3, we list abundances as both concentrations (numbers/cubic meter) and stand- ing stocks ( numbers/square meter ). We calculated concentrations primarily for comparison with the historical data which have been reported almost exclusively in that manner. However, it would be an error to compare concentrations from different locations in the New York Bight because of the wide range of depths of stations and the vertical stratification of zooplankton. Estimates of numbers/cubic meter from oblique tows are aver- age values for the entire water column, and these would be adequate for comparisons of tows from different depths only if zooplankton were evenly distributed throughout the water column. How- ever, if a species is restricted to a narrow depth stratum, then its concentration would be underes- ^Judkins, D. C. Zooplankton sampling program and da- ta. In E. Wold (editor), Atlantic coastal experiment survey cruises (July 1974-September 1975) data report Vol. 2. Zoo- plankton and ichthyoplankton, p. 2-129. BNL 24771. Brookha- ven National Laboratory, Upton. N.Y, timated by deeper tows relative to shallower ones (Peterson and Miller 1977). Vertically discrete samples show that most species in the New York Bight are concentrated in the upper 20 to 30 m ( Judkins unpubl. data). To avoid underestimating species abundances in samples that extended below about 30 m, we calculated standing stocks and were then able to obtain mean values for com- binations of tows from different depths and to test for significant differences between these means. RESULTS Frequency of Occurrence of Zooplankton Taxa We identified 88 copepod species, 10 chaetog- nath species, and 26 other holo- and meroplank- tonic taxa (Table 4). By season, 100 taxa occurred in samples taken in autumn (September- November) 1974, 68 in samples from winter to spring (February-May) 1975, and 91 in samples from summer (June-September) 1975. These taxa can be grouped on the basis of sea- sonal and cross-shelf patterns in occurrence. The taxa in one group occurred commonly during all seasons and included the copepods Centropages typiciis. Pseudocalanus sp. .Calanus finmarchicus, Paracalanus parvus, Oithona atlantica, Metridia lucens, and Clausocalanus pergens, the chaetog- naths Sagitta elegans and S. serratodentata, and pteropods, appendicularians, medusae, poly- chaete larvae, bivalve veligers, and euphausiid furcilia and calyptopsis stages (Table 4). The copepod O. similis was uncommon only during au- 671 FISHERY BULLETIN: VOL, 77. NO. 3 Table 2.— Mean abundance (no. Im', no. Im'. and percent total no. /m^), frequency of occurrence (% of samples), average rank, and dominance of the 20 most abundant zooplankton taxa in the New York Bight, September 1974-September 1975. Taxa ranked within each sample on basis of number per square meter 1 1 = most abundant, ties averaged ); ranks for each taxon averaged over all samples (n = 178 for chaetognaths. n = 183 for copepods and others). Dominance: proportion of samples in which taxon was among those making up SOT of the individuals; summation in each sample was begun with the most abundant species (Fager and McGowan 1963). Taxa Pseudocafanus sp Reropods Centropages typicus Paracalanus parvus Penilia avirostns Temora longicornis Calanus ftnmarchicus Olthona similis Appendicularians Gastropod veligers Evadne spp Doliolids Methdia lucens Plutei O atlantica Clausocatanus pergens Medusae Acartie tonsa Sagitta elegans Polychaete larvae Total copepods Total chaetognaths Total "others" Grand total no.'m^ Aburidance no ;m^ Frequency 25.566 25.532 25.135 15.342 14.613 11.365 11.245 8.293 7.076 4.833 3,901 3,600 2.498 2.239 1.979 1.821 1.419 1.345 1.311 926 114.383 2.222 67.769 184,174 521 479 655 312 454 373 146 146 126 113 91 90 21 51 22 16 27 43 26 20 2.406 43 1.511 3.960 138 13 8 136 83 79 62 6 1 4 5 3,8 2 6 2 1 20 1 4 1 2 1 1 1 0 08 07 07 05 62 0 1 2 36 8 % Average rank Dominance 91 157 56 98 117 42 97 8,9 57 79 282 49 28 82 9 15 61 50 8 11 91 17,3 36 81 28,7 9 84 27,2 14 61 523 5 46 65,9 9 32 795 6 58 52,4 8 31 805 5 72 367 17 51 59 4 8 74 40.7 0 24 858 0 96 30,9 3 84 33,6 0 tumn 1974, and that may have been due simply to escapement of this small-bodied species through the coarse-mesh (333 fxm) net used then. Metridia lucens, C. pergens, and euphausiid calyptopsis and furcilia stages were generally common only offshore, but all others in this group tended to be common throughout the Bight. A number of taxa were common only during portions of the year. The oceanic copepod Calocalanus tenuis, cladocerans of the genus Evadne, hyperiid amphipods, and doliolids were common in autumn 1974 and again in summer 1975 but were uncommon during the intervening winter-spring period (Table 4). The neretic copepod Temora longicornis, ectoproct larvae, and copepod nauplii occurred commonly during au- tumn 1974 and winter-spring 1975 but were un- common during summer 1975. The cold-water oceanic copepod Pleuromamma borealis occurred commonly only during the winter-spring period and then only offshore. Another oceanic copepod characteristic of warmer waters, Mecynocera clausi, was common offshore during winter-spring and summer 1975. Gastropod veligers were com- mon both onshore and offshore during 1975 but were uncommon throughout the Bight in 1974. A large group of taxa were common only during au- tumn 1974. This assemblage consisted of copepods Candacia armata, Oncaea venusta, Acartia tonsa, A. danae, Nannocalanus minor, Centropages bradyi, Rhincalanus nasutus, Eucalanus sewelli, Paracalanus aculeatus, Clausocalanus furcatus, C.jobei, Corycaeus clausi, C. speciosus, Temora stylifera, Scolecithrix danae, and Oithona plumi- fera, the chaetognath Sagitta enflata, the clado- ceran Penilia avirostris, echinoderm plutei, and siphonophores (Table 4). With the exception of the coastal-estuarine species A. tonsa and P. aviros- tris (and probably most of the plutei), members of this group typically inhabit the slope region and adjoining warm oceanic waters (Grice and Hart 1962; Owre and Foyo 1967; Bowman 1971). The majority of copepods (61) and chaetognaths (7) were uncommon or rare in our samples, and most of these (43) were recorded most frequently or exclusively in autumn 1974 and/or summer 1975. Some of these rare and uncommon species are coastal-estuarine forms (e.g., Centropages hamatus, Acartia longiremis, A. hudsonica, Paracalanus crassirostris, Tortanus discaudatus, Labidocera aestiva, Anomolocera opalus, Sagitta hispida) and a few inhabit boreal offshore waters (e.g., Calanus helgolandicus, Heterorhahdus norvegicus), but the majority typically have 672 JUDKINS ET AL.i ZOOPLANKTON IN THE NEW YORK BIGHT Table 3.— Seasonal variations in mean abundance (no./m^ and no./m") and frequency of occurrence CJ of samples) of the 20 most abundant zooplankton taxa in the New York Bight, 1974-75. Values in parentheses are percents of total zooplankton Ino./m') during periods. Asterisks indicate significant differences in mean no./m^ between periods (• =P<0.05,** =P<0.01,NS = not significant, NT = not tested because of different mesh aperatures of nets used in 1974 and 1975). 1974 1975 Sept. Oct.-Nov Feb-Mar Apr. -May June-July Aug -Sept No samples (chaetognaths) 17 26 32 35 34 34 No samples (copepods. others) 17 26 30 35 37 38 Taxa Item Pseudocalanus sp . No./m' 1.692(1.0) NS 507(1 0) NT 116,340 (8 5)" 64.184(24 1)- 40.855 (18 0)-- 9.981(63) No,/m' 33 11 374 1.163 900 245 *'o frequency 71 69 97 100 100 95 Pleropods No/m^ 712 (0 4)" 308 (0 6) NT 81.837 (42 4) NS 43.100(16 2)-- 12,553 (5.6)NS 5.801 (3 7) No./m^ 13 8 1.215 937 335 149 % frequency 100 100 100 100 95 97 Centropages No,/m! 16,818(9 7) NS 19.838 (40 61 NT 30,077(15 6) " 8.702 (3 3)- 50.801(22,4)NS 18.143 (11 6) lypicus No./m^ 445 606 700 104 1498 451 % frequency 100 92 100 97 97 97 Paracalanus No./m' 2.834 (16) NS 6.168 (126) NT 17.388 (9 0) NS 5,402 (2,0) NS 13,820(6 1)" 36.395 (23 2) parvus No./m' 74 188 299 41 295 784 % frequency 94 96 90 31 73 100 Penilia avirostris No./'m^ 74,658 (43.0)- 794 (16) NT .;1(.-0.1)NS -NS — - 36,434 (23.2) No./mJ 2,278 24 <1 — — 1,152 % frequency 94 35 3 — — 63 Temora tongicornn ; No./mS 139 (0,1) NS 246 (0 5) NT 855(0 4)" 6.875 (2 6)- 48,173 (21,3)-- 529 (0 3) No .'m' 3 5 30 204 1,605 16 % frequency 53 62 53 80 84 29 Calanus No m^ 4,031 (2,3) NS 1.895(3 9) NT 824 (0 4| NS 26.651 (9 8) NS 16.640 (7,3) NS 9.636 (6 1) finmarchicus No.:m5 70 32 12 261 231 173 % frequency 76 81 90 100 95 92 Oithona simihs No/m2 128 (CI)- 34(0 1) NT 11.199 (5 8) NS 18.947(7 1)- 9.836(4 3)" 3.739(2 4) No./m3 3 .:! 221 265 227 68 % frequency 53 31 83 100 97 95 Appendlcularians No/m» 4.293(2.5)- 586(1 1) NT 11.894 (6 2) NS 19.205(7 2)" 3,136 (1 4) NS 1.623 (1.0) No./m^ 115 6 204 316 60 39 % frequency 100 62 60 100 89 92 Gastropod veligers No./m' 1(<0.1) NS 2(<01)NT 6.848 (3 5) NS 13.674 (5 1) NS 5.253 (2.3) NS 159(0.7) No,/m^ <1 <1 431 324 149 2 % frequency 12 4 100 97 70 47 Evadne spp No,/m2 3,846 (2.2)- 72 (0.1) NT — " 13,116(4 9)- 3.884 (17) NS 1.156(0.7) No./m3 127 2 — 306 77 23 % frequency 76 35 _ 69 68 34 Doliolids No./m' 22.022(12.7)" 65 (0,1) NT -NS -NS 389(0,1) NS 6.191 (4.0) No,/m= 552 1 — — 4 183 % frequency 100 58 — — 30 39 Metrldia lucens No/m! 221 (0 1) NS 247 (9 5) NT 1.533(0 8)- 8.195 (3 1)- 1 .683 (0 7) NS 1.327 (0 8) No,/m= 2 4 23 58 15 12 % frequency 32 62 70 69 47 58 Pljtei No./m! 14,682 (8 5) NS 2.745(5 6) NT -NS 1.635(0 6) NS 48 (-0 1) NS 784 (0 5) No./m' 308 90 — 22 1 25 % frequency 59 54 — 54 14 21 0 aVamca No/m2 1.354 (0 8) NS 1.742 (3 6) NT 1.498(0 8) NS 2.350(0 8) NS 1.963 (0 8) NS 2.497 (1.6) No,/m= 18 31 27 18 14 24 % frequency 88 88 100 57 41 76 Clausocalanus No./m' 142(0 1)NS 81 (0 2) NT 1.494 (0 8) NS 3.740 (1 4) NS 1.304 (1 4) NS 2,807(18) pergens No;m' 1 1 21 27 15 21 % frequency 41 50 80 29 43 63 Medusae No./m2 128 (0 1) NS 540(1 1) NT 511 (0 3)" 4,411 (1 7)- 1.927 (0 9)" 63 (<0.1) No./m3 4 16 10 87 33 2 % frequency 66 85 70 97 78 50 Acertia tonsa No,;m2 4,195(2.4) NS 435 (0 9) NT -NS 41(<;01) NS — 4,264(2.7) No/m^ 140 14 — <1 132 % frequency 71 58 — 6 _ 39 Sagitta elegans No.'m' 1,006(0 6) NS 277 (0 6) NS 478(0 2)-- 1.581 (0 6)" 2.850 (1 3)-- 1.220(0,8) No./m' 19 5 9 55 61 19 % frequency 100 100 100 94 91 91 Polychaete larvae No./m^ 140(01) NS 71(0 1) NT 227(0.1)-- 2.835 (1 1)- 577(0 3) NS 1.205(0 8) No/mJ 3 1 4 57 12 26 % frequency 76 81 88 97 85 74 Total copepods No m' 49.149(28 3)NS 38.212(78 1) NT 89.074(462)- 159.725(60 0) NS 191.772(84.6)- 96.930(61 8) No.;m5 1.089 986 1.879 2.260 4.930 2,047 Total No./m' 1,934(1 1) NS 1.721(3 5) " 797(0 4)-- 2.627(1 0) NS 3.502(1 5) NS 2.393(1 5) chaetognaths No./m> 34 31 12 53 94 43 Total others No./m^ 122.617(70 6)" 8.975(18 4) NT 103.115(53 4) NS 104.226(39 1)-- 31.386(13 8) NS 57.401(366) No/m3 3,441 215 1.582 2.138 733 1.662 Grand total No,/m' 173.697" 49.008 NT 1 94.238 NS 266.575 NS 226.313 NS 156.472 No,;m= 4,564 1.232 3,473 4.451 5.757 3.752 673 FISHERY BULLETIN; VOL. 77. NO. 3 Table 4— Zooplankton taken in onshore (on) l<50 m) and offshore (offl O50 m) waters of the New York Bight during period 1 (September-November 1974), period 2 (February-May 1975), and period 3 (June-September 1975). Taxa within the msgor categories (copepods, chaetognaths, others) listed in order of decreasing overall frequency of occurrence. C = common, occurrence in ^50% of samples; U = unusual, occurrence in €50% of samples; R = rare, occurrence in =£3 samples. Period 1 Period 2 Period 3 Taxa Period 1 Period 2 Peri< On )d3 Taxa On Off On " ai On Oft On Oft On Off OH Copepods Ctausocalanus arcuicornis _ R _ — — — Centropages typicus C c C c C c L acutilrons — — — — — R Pseudocalanus sp,' C c C c C c Corycaeus latus R R — — — — Calanus finmarchtcus C c C c C c Anomolocera opatus — — — — R R Oilhona similis U u C c C c Scotecithricalta minor — — — — — R Paracalanus parvus C c U c C c Neocalanus gracilis — — — — — R 0 atlantica C c C c U c 0 minuta — — — R — — Temora longicomis C c C u U u Ctausocalanus mastigophorus R R — — — — Metndia lucens U c C c U c Corycaeus catus R — — — — — Clausocalanus pergens U c U c U c C elongalus R R — — — — Mecynocera clausi U u U c u c Pontella pennata R — — — — — Candacia armata C c u u u u Sapptinrina opalina — R — — — — Calocalanus tenuis C c — u — c Lucicutia flavicornis — R — — — — Oncaea venusta C c R u — u Calocalanus pavionius — R — — — — Pleuromamma boreatis R u U c — u Scolecithricetla vittala — R — — — — Acartia danae C c - — R u Centropages velificatus — — — — — R Nannocalanus minor C c — — R u Paracalanus pusillus — — — — — R A tonsa C u R — U u Microsetella norvegica R — — — — — Centropages bradyt C c R R — u Chiridius obtusilrons — — — — — R C tiamatus R — U U u u Lubbockia squillimania — — — — — R Rhincalanus nasutus U c R U — R S tenuiserrata — — — — — R Eucalanus sewelli C c R R — R Scottocalanus secunfrons — — — — — R Paracalanus aculeatus C c — R — — Sapphinna ovatolanceolata — — — — — B Ctausocalanus lurcatus C c — R R R P quasimodi — R — — — — C. iobei C c — — — R Scottocalanus thomasi — — — — — R Corycaeus clausi C c — — — — Chaetognaths Scdecithrix danae C c — R R — Sagitta elegans C C C c c c A longiremis — — U U U u S serratodentata c C c c u C Corycaeus speciosus c c — — — R S enllata c c R u R u T stylilera c c — — — — Pterosagitta draco R u R — — R C- danae — — u U — — Eukrotinia hamata — — — R — R Torlanus discaudatus — — u u U — S. maxima — — R R — R Calocalanus styliremis R — R u — U S tiexaptera R R — R — R A. hudsonica R — U R R - S decipiens — R — — — R Oithona plumilera C R — — — — S riispada — R — — — — R. cornutus U u — — — — E fowleri — R — — — — Oncaea mediterranea U u — — — — Others: E. pileatus U u R — — R Pteropods C C C C C C Labidocera aestiva U R — — U R Appendicularians C C c C c C Aetideus armatus — R — R — U Medusae c C c C c c Paracalanus crassirostris R — — — u U Decapod larvae c C u u c c Corycaeus venustus R u — R — R Polychaete larvae c C c c c c Euchaeta marina U u — R — R Bivalve veligers c C c c c c Undinula vulgaris R u — — R — Euphausiid furcila stages u C c c u c Calocalunus pavo — u — — — — Gastropod veligers — R c c c c Ischnocalanus plumulosus — u — — — - Ectoproct larvae c C c c u u Calanus tenuicorms R R — R R R Hypenid amphipods c C u u u c 0 conitera R U — — — — Copepod nauplii u C c c u u Macrosetella gracilis R U — — — — Evadne spp c u u u c c Ctausocalanus parapergens — R — R — R Anthczoan laroae u u u u u c Sapptiirina angusta R U — — — — Euphausiid calyptopsis stages R c u c R c C paululus — — — R — R Doliolids c c — — c c Eucalanus subtenuis R u — — — — Plutei c u u u u R Pleuromamma robusta — — _ — — R Siphonophores c c R R u u Faranula gracilis — R — — — — Penilia avirostris c u — R u u Calanus tielgolandicus R — — — R R Conchoecia spp. u c R U — u Paracalanus pygmaeus — — — R R R EuphausiKJ nauplii — u R U R u E ttyalinus R U — — — — Barnacle cypnses — — U U U u E crassus R R — R — R Heteropods u u — — — — F cannata R — — — — R Podon spp u — u — R R Ctausocalanus lividus — R — R — R Salps — u — — — u Capita mirabtis — R — — — — Barnacle nauplii — — R u — u Heterorhabdus norvegicus — — — — — R Stomatopod larvae R — — — R — H papilliger — R - — — 'Atlantic representatives of the genus Pseudocalanus are not adequately described. They are being studied by B Frost, Department of Oceanography, University of Washington. Seattle 674 JUDKINS ET AL : ZOOPLANKTON IN THE NEW YORK BIGHT warmwater oceanic distributions (Pierce 1953; Grice and Hart 1962; Jefferies 1967; Pennell 1976; Fleminger and Hulsemann 1977). Mean Abundance, Frequency, Average Rank, and Dominance We calculated mean abundances for various taxa and found that copepods, on the average, composed 62% of the zooplankton in our samples (Table 2). Pteropods and gastropod veligers to- gether contributed 15% to the total, and cladoce- rans (Penilia avirostris plus Evadne spp.) and urochordates (doliolids and appendicularians) yielded another 10 and &fc, respectively. No other group (e.g., echinoderm plutei, medusae, polychaete larvae, chaetognaths), on the average, composed more than about \% of the zooplankton. At the species level, Pseudocalanus sp. and Cen- tropages typicus were codominant in 1974-75, their annual mean abundances (number/square meter) each equaling approximatesly 13% of the annual mean for total zooplankton. Pteropods composed another 13% of the zooplankton, and these consisted almost exclusively of one species, Limacina retroversa (Wormuth'*). Paracalanus parvus, Penilia avirostris, Calanus finmarchicus, and Temora longicornis each composed between 5 and 10% of total zooplankton over the period, and severalother taxa had values exceeding 1% (Table 2). In addition to mean standing stocks and con- centrations, we calculated frequency of occurrence, average rank (rank of most abundant taxon in a sample = 1), and an index of dominance (Pager and McGowan 1963) for the 20 taxa having the highest mean abundance in our samples (Table 2). These measures showed similar trends, and, in general, frequency of occurrence and dominance tended to decline and average rank to increase as mean abundance decreased. There were, however, a number of exceptions to this pattern. For in- stance, the highly seasonal species P. avirostris and T. longicornis had high mean abundances but disproportionately low frequency and dominance values and high average ranks. Conversely, other taxa, which were seldom abundant, nevertheless occurred frequently (e.g., S. elegans, O. atlantica, polychaete larvae, medusae). 'J. H. Wormuth, Department of Oceanography. Texas A&M University. College Station, pers. commun. August 1978. Seasonality in Abundance Total zooplankton in the New York Bight de- clined nearly fourfold in mean abundance between late summer (September) and autumn (October- November) 1974 (Table 3), primarily because of a drastic decline in the abundance of P. avirostris after September. In 1975, numbers of total zoo- plankton did not vary as greatly between seasons, and the highest mean value (April-May) differed from the lowest (August-September) by less than a factor of two. Copepods were least numerous in winter (February-March), but increased through spring (April-May) to an early summer (June- July) peak before declining in late summer (August-September). Other zooplankton com- bined exceeded copepods in mean abundance only during winter, and this primarily was due to the large standing stocks of the pteropodL. retroversa present in the Bight during that period. We calculated mean abundances by season for the 20 taxa having the highest overall mean val- ues in our samples (Table 2) and found thatmost of these taxa underwent marked and often statisti- cally significant (P<0.05) seasonal fluctuations in standing stock (Table 3). Penilia avirostris, doliolids, echinoderm plutei, and Acartia tonsa reached maximum or near maximum levels of abundance in late summer 1974 and again in late summer 1975. With the exception of echinoderm plutei, these taxa were virtually absent from our samples during the intervening winter and spring. The relatively low numbers of small copepods in 1974 may have been due to escape- ment through the coarse mesh (333 /xm) nets used then. We found that Paracalanus parvus, Pseudocalanus sp., O. similis, and Clausocalanus pergens were significantly less abundant (paired sample /-test, P<0.05) in collections from 60 cm diameter 333 /u.m mesh nets than in simultaneous samples from 20 cm diameter 253 and 223 nm mesh nets. Only 1 taxa (L. retroversa) peaked in winter 1975, but 10 taxa [Pseudocalanus sp., Calanus finmarchicus, O. similis. Metridia lucens. Clausocalanus pergens, Evadne spp., appen- dicularians, gastropod veligers, medusae, and polychaete larvae) reached their highest levels of abundance during spring 1975. Centropages typicus, T. longicornis, and S. elegans attained maximum levels of abundance in early summer, and Paracalanus parvus peaked in late summer 1975. Among the 20 taxa listed in Table 3, O. at- 675 FISHERY BULLETIN: VOL. 77, NO 3 lantica varied the least in mean abundance during the study, showing only slight increases during spring and late summer 1975. Onshore-Offshore Distribution Several of the more abundant zooplankton taxa in the New York Bight showed statistically sig- nificant (P<0.05) differences in mean standing stocks between the onshore (<50 m) and offshore ( >50 m) sectors of the region (Table 5). Taxa which on the average were significantly more abundant onshore during 1974-75 were C. typicus, Penilia avirostris, T. longicornis, Evadne spp., A. tonsa. and doliolids. Those which were significantly more abundant offshore were Calanus finmarchicus, O. similis, O. atlantica, M. lucens, and Clausocalanus pergens. Significant onshore-offshore differences on an annual basis were not observed for Pseudocalanus sp., pteropods, Paracalanus parvus, appendicularians, gastropod veligers, echinoderm plutei, medusae, and S. elegans. Neither total copepods nor total chaetognaths differed sig- nificantly between the two regions, but other zoo- plankton combined were significantly more abun- dant offshore (Table 5). Substantial seasonal changes occurred in the onshore-offshore distribution of many of the aforementioned taxa (Figure 2). Certain copepod species which peaked or were otherwise very abundant in the offshore region during winter and spring were much less abundant onshore at those times. However, during the summer, onshore stocks of these species increased to levels ap- proaching those in offshore waters. Species exhibiting this pattern were M. lucens. C. pergens. O. atlantica, Calanus finmarchicus, and P. parvus (Figure 2). Several other taxa which reached maximum levels of abundance during the spring tended to be equally abundant onshore and offshore during most times of the year. This group of ubiquitously abundant taxa included Pseudocalanus sp., O. similis, S. elegans, medusae, appendicularians, pteropods, gastropod veligers, and polychaete larvae (Figure 2). Doliolids and the coastal-estuarine speciesPen(7ia avirostris, T. longicornis, and A. tonsa all peaked in the onshore environment during summer or autumn and were seldom, if ever, abundant offshore (Figure 2). Although Centropages typicus also reached its highest levels of abundance on- shore during the summer, it was usually abundant offshore as well, especially during March and April (Figure 2). Echinoderm plutei peaked in on- shore waters during autumn 1974 but also exhib- ited a secondary offshore peak during spring 1975 (Figure 2). Evadne spp. exhibited maxima in both the onshore and offshore environments during spring and summer 1975 but were abundant only onshore during autumn 1975 (Figure 2 1. Zooplankton Maxima, Phytoplankton Blooms, and Temperature We observed distinct peaks in zooplankton abundance in both onshore and offshore environ- ments in 1975 (Figure 3). In the offshore region, there were two maxima, in March and May. The March peak was dominated by L. retroversa which composed nearly 60% of all offshore zooplankton during that month. The remaining 40'/( of offshore zooplankton in March was composed primarily of the copepods Pseudocalanus sp., O. similis, Paracalanus parvus, and M. lucens. The May maximum was dominated hy Pseudocalanus sp., Calanus finmarchicus, and O. similis, and these species tended to be most abundant over the outer shelf at the eastern end of the study area (e.g., stations F3, F5, G2, G4). The March pteropod- dominated maximum occurred similtaneously with the beginning of the spring phytoplankton bloom when chlorophyll a standing stock biomass (milligrams/square meters) was high (Figure 3) and discrete depth chlorophyll a concentrations exceeded 4 ixg/l throughout the water column at virtually all stations. However, during May when copepods peaked in abundance offshore, the phytoplankton bloom was in decline (Figure 3). In the offshore region, water temperatures in the upper 20 m remained low ( =£10° C) through May. We observed a single peak in zooplankton abun- dance in the onshore environment during 1975 (Figure 3). This peak occurred in July and was the result of marked increases in the abundance of Centropages typicus and T. longicornis. In July, these two species constituted about 67^^ of all on- shore zooplankton and were especially abundant at stations near the apex of the Bight and off the New Jersey coast (e.g., A2, A4, B3, B5). The early summer rise in C. typicus and T. longicornis stocks occurred during a period when surface water temperatures rose from about 10° to 20° C but when onshore chlorophyll a biomass was low ( Fig- ure 3). At other times during this study various other taxa were dominant onshore, e.g., Penilia 676 JUDKINS ET AL : ZOOPLANKTON IN THE NEW YORK BIGHT T.ABLK 5. — Onshore-offshore variations in mean abundance (no./m^ and no./m-'i and frequency of occurrence i"* of samples! of the 20 most abundant zooplanl 151 140 % frequency 85 77 Appendiculanans No/m^ 6,576(3 2) NS 7,666(4 6) No/m^ 157 89 °o frequency 80 88 Gaslropod veligers No /m* 6,556(3 2) NS 2,804(1 7) No /m^ 173 41 °<, frequency 58 65 Evaane spp No 'm'' 5,891(2 9)" 1,557(09) No/m3 149 22 °o frequency 49 41 Doliohds No m^ 6.497(3 2)- 185(0.1) No 'm^ 165 2 % frequency 29 34 Metridia lucens Nolm' 178(0 1)" 5.232(0,3 No 'm^ 4 41 °» frequency 37 83 Plulei No/m^ 3,591(1 7) NS 680(0 4) No/m' 86 9 % frequency 35 25 0 atlantica Noi'm' 564(0 3)" 3,646(2.2) Nolm' 13 31 % frequency 57 90 Clausocalanus pergens No 'm^ 161(0 1)" 3,777(2 3) No 'm^ 4 31 "o frequency 28 78 Medusae Nolm' 1.454(0 7) NS 1,378(0 8) No /m^ 35 19 *b frequency 76 73 Acartia lonsa No Im' 2.432(1 2)- 63( 0 1) No/m= 78 1 % frequency 35 11 Sagftta elegans No /m- 1.407(0 7) NS 1.187(0,7) No ;m' 34 17 °'o frequency 95 96 Polychaete larvae No ;m- 989(0 5) NS 946(03) No m^ 26 13 °o frequency 65 68 Total copepods Nolm' 115,284(57 7) NS 113,104(68 2) No/m' 3,358 1,284 Total chaetognaths No !m' 2,175(1 1) NS 2,282(1 4| No ;m3 52 32 Total "others' Nolm' 82,510(41 3)- 50.396(30 4) No./m= 2,663 626 Grand total Nolm' 119,943 NS 165,590 No Im' 6.073 1,942 677 5 4 + 3 — 2 o I 0 5 4 + 3 —' 2 o I Pseudocalanus sp FISHERY BULLETIN: VOL, 77, NO. i '-i< S'74 0 N D J'75 FMAMJJAS S'74 0 N D j'75 FMAMJJAS 5 4 + 3 ■^ 2 a- o I 0 Metridia lucens .\-. 1^. / '^1-1-' s'74 0 N D J'75 FMAMJJAS 5 4 + 3 — 2 I 0 Oilhona simihs S'74 0 N D J'75 FMAMJJAS Clousoca/onus pergens S'74 0 N D J'75 FMAMJJAS 5 4 + 3 -— 2 en 1 0 Sogitta elegans ^^i s'74 0 N D J'75 FMAMJ JAS Oithona atlantica -^' a:^xt-^-^-r- -}--, s'74 0 N D J'75 FMAMJ JAS 5 4 + 3 —' 2 I 0 Pteropods v^--'^ s'74 0 N D J'75 FMAMJJAS r Paracalanus parvus I ^ -^ /^^ !^ ^ f ■ i^-f- \ ^' 1 / s'74 0 N D J'75 FMAMJJAS 5 4 + 3 ■— 2 I 0 Pplychaete lorvoe -i-Ji' S'74 0 N D J'75 FMAMJ JA S 678 JUDKINS ET AL ZOOPLANKTON IN THE NEW YORK BIGHT 5r Medusae S'74 0 N D J'75 FMAMJJAS 5 4 + 3 ^1 E — ' 2 w o ~ I 0 s'74 0 N D J'75 FMAMJ JAS S'74 0 N D J'75 FMAMJJA S Ob S'74 0 N D J75 FMAMJ JAS 5 Gos ropod ve igers 4 I -i/"^ 1 ( I + 3 1 >v/\ \ §1% — 2 T \ \; M cr o 1 n _jl: \ _ 1 1 1 1 1 1 i 1 S 74 0 N D J'75 FMAMJJA S Cenlropoges fypicus _j 1 I S'74 0 N D j'75 FMAMJ JAS S'74 0 N D J'75 FMAMJJA S S'74 0 N D J'75 FMAMJJAS 5 4 + 3 — 2 cr o I 0 Acartia tonsa ■ K \1 , / / \ \ \ / A.^ / / \ s'74 0 N D j'75 FMAMJJAS Evodne spp . n. s'74 0 N D j'75 FMAMJ J A S Figure 2— Onshore ( <50 m) and offshore ( '50 m) monthly mean abundances of 20 most abundant zooplankton taxa in the New Yori Bight, September 1974-September 1975. Circles = onshore means; dots = offshore means; vertical bars -^ 1 SE above and below mean 67! 20 10 FISHERY BULLETIN: VOL, 77. NO, 3 OFFSHORE TEMPERATURE 2 2 X el e ' zl E OFFSHORE CHLOROPHYLL OFFSHORE ZOOPLANKTON !\- Pseudocalanus sp B-C finmarchicus C-P. parvus 0-0. similis E- Other Copepods F- Pteropods G-Other Zooplankton -F S'74 0 N 20 10 - ONSHORE TEMPERATURE ^^^^„^20m surface' ^,^_ Figure 3.— Onshore (<50 ml and offshore ( >50 ml monthly means for temperature at surface and 20 m, chlorophyll a integrated water column biomass. and zooplankton abundance (showing cumulative contribu- tion of dominant laxai in the New York Bight, September 1974-September 1975, en CVJ el e onshore CHLOROPHYLL zl e onshore ZOOPLANKTON A-C. typicus ^-Pseudocalanus sp. C-r. longicornis D- Other Copepods E-Pteopods F-Other Zooplankton S'74 0 D J'75 F M MONTH 680 JtlDKINS ET AL.: ZOOPLANKTON IN THE NEW YORK BIGHT avirostris (September 1974), L. retroversa (March, April), Pseudocalanus sp. (May), and Paracalanus parvus (August, September 1975). DISCUSSION Previous zooplankton studies in the New York Bight have been based on relatively few samples, usually taken from a restricted area over a limited period of time (of. review in Malone 1977). Grice and Hart's (1962) study is closest to ours in taxonomic coverage, net mesh size, geography, and quantitative analysis. They collected a total of 14 samples with vertically hauled 230 /xm mesh nets from New York Bight shelf waters on cruises in September and December 1959 and March and July 1960. These samples were part of a larger study of zooplankton along a transect between Montauk, N.Y., on eastern Long Island and Ber- muda. Comparison of mean concentrations of sev- eral abundant species of copepods in their samples (table 4, Grice and Hart 1962) with our mean concentration values (Table 2) is informative. The eight most abundant copepods during 1959-60 (in order of decreasing abundance: Pse£/c?oca/a;!i/s sp., C. typicus, O. similis, T. longicornis, Paracalanus parvus, Calanus finmarchicus, M. lucens, Can- dacia armata) correspond closely with the eight most abundant species in 1974-75 (Centropages typicus, Pseudocalanus sp., T. longicornis, Paracalanus parvus, Calanus finmarchicus, O. similis, Acartia tonsa, O. atlantica). Furthermore, the mean densities of the two most abundant copepods in both studies, Centropages typicus and Pseudocalanus sp., were very similar for both species during the two periods (i.e., the mean den- sity of C. typicus was 450/m^ in 1959-60 and 650/m^ in 1974-75; the mean density of Pseudo- calanus sp. was 560/m^ in 1959-60 and 520/m^ in 1974-75). This comparison suggests that zoo- plankton in the New York Bight had not changed substantially in the 15 yr between the two studies. The degree of similarity is somewhat surprising in view of the evidence that considerable year-to- year variations may occur in the timing, duration, and amplitude of abundance maxima in important zooplankton taxa (Bigelow and Sears 1939; Sears and Clarke 1940). Grice and Hart (1962) observed an influx of warmwater oceanic species into the New York Bight in September 1959, and this is similar to the high incidence of subtropical-tropical species in autumn 1974 and summer 1975. This apparently annual phenomenon is probably associated with intrusions of the Gulf Stream over the continental slope which occur most frequently during the warm seasons (Wright 1976; Bowman 1977). Our hydrographic data reveal the occurrence of salini- ties ( s=36'7( ) characteristic of Gulf Stream water (Wright 1976) in the slope region during Sep- tember 1974, and in June, August, and September 1975 (Figure 4), and the National Environmental Satellite photos show Gulf Stream water imping- ing along the outer edge of the study area in Au- gust 1974 and in May, July, and August 1975. A shoreward increase in the abundance of sev- eral common offshore copepods (e.g., Calanus finmarchicus, O. atlantica, Clausocalanus pergens, M. lucens) also occurred during warm portions of the year. This onshore increase in abundance of common forms and the frequent oc- currence over the shelf of less common oceanic species are probably the result of shoreward mix- ing of slope water with shelf water. Slope water is thought to move onshore along isopycnals during late summer and autumn (Wright and Parker 1976; Gordon et al. 1977), and during September 1974 we observed slope water (35%o ssalinity <36%o, Wright 1976) on the shelf (Figure 4). Limacina retroversa, Pseudocalanus sp., O. similis, and Calanus finmarchicus, the species re- sponsible for zooplankton abundance maxima in the New York Bight during spring 1975, are low- temperature forms whose distributions are cen- tered north of the region (Fish 1936a, b,c; Redfield 1939; Bigelow and Sears 1939; Fleminger and Hulsemann 1977). Their geographical distribu- TOTAL SAMPLE NUMBER 181 71 245 270 253 132 154 , 195 147 256 261 _ 370 ? 36.0 < 1/) 350 i S'74 0 N Al 1— 1 1 r 1 • • • • r : 1 • : . 1 : ! / 1 1 1 1 1 1 X 1 lX F 75 M A MONTH Figure 4.— Occurrences of Gulf Stream water (salinity s3e%.>) over slope (sslOO ml. and of slope water (35%o 9 S 3 5 7 I ' I I I I I I L YEAR Figure l. — Catch and ex-vessel price of Jonah and rock crabs (species combined* landed in Maine, 1919-77. 69°40 69°3( Figure 2. — Boothbay Harbor region and loca- tion of sampling sites. n^HING Siti 9 686 KROUSE DlSTRrBUTION OF JONAH AND ROCK CRABS Additional commercial catch data were pro- vided by Joel Cowger, Maine Department of" Marine Resources, West Boothbay Harbor, Maine, who obtained measurements of 299 commercially caught Jonah crabs from the Maine coast (Sep- tember 1977-March 1978). Carapace widths were measured between the tips of the outermost an- terolateral spines. These long carapace width measurements can be converted to short carapace width (distance between notches) by the linear regression Y = -1.669 + 0.973X where Y = short CW and A' = long CW (Carpenter 1978). RESULTS AND DISCUSSION Size Ciiinposituin Jonah crabs captured with research traps (mean 104.8 mm CW for females and 113.7 mm for males) were significantly smaller (^-test, P<0.01) than those crabs commercially landed at either Boothbay Harbor (mean 114.0 mm CW for females and 128.6 mm for males) or at other Maine ports (mean 114.0 mm CW for females and 141.1 mm for males) (Figures 3-5). At first it was thought that disparities in size composition might be associated to variations in selectivity of the research and commercial gear for crabs <95 mm CW; however, since similar proportions of small crabs appeared in both the research and commercial catches (Figures 3-5), the effects of gear selectivity must be minimal. The near total absence of crabs -95 mm CW in the commercial catch from Boothbay Harbor (Figure 4) was the result of fishermen discarding the smaller crabs before their landed catches were measured; whereas, the catches shown in Figures 3 and 5, which were measured at sea, included all crabs caught. Thus, I attribute these size disparities to spatial variations in the distribution of different size crabs. For instance, research traps were fished at depths of 3-20 m, whereas, most com- mercial traps were fished at depths of 12-91 m. In support of this contention, different size groups of Jonah crabs have been observed to be distributed within the Mid-Atlantic Bight according to depth (Haefner 1977; Carpenter 1978). Male Jonah crabs averaged larger than females in all catches (Figures 3-5); similarly, male rock crabs generally averaged larger than females (Krouse 1972). Unlike female rock crabs, which have no commercial value because of their small size (rarely >100 mm CW, Krouse 1972), female Jonah crabs, which approximate the size of male rock crabs, are commercially harvested along with male Jonah crabs. 6r 60 80 100 110 CARAPACE WIDTH (mm) 20 140 FIGURE 3.— Width-frequency distributions of male and female Jonah crabs caught with research traps in the Boothbay Harbor region, 1968-74, 687 FISHERY BULLETIN: VOL. 77. NO. 3 15 14 13 12 II >- <-> 10 z UJ UJ £ 8 Q: 6 UJ Q. 5- 4 - 3- 2- z MALES N = 110 i = 128 6 S_= 0 85 X ^ ^ FEMALES N = 90 X = 114,0 S-= 0 87 120 130 CARAPACE WIDTH 140 150 160 (mm) Figure 4.— Width-frequency distributions of male and female Jonah crabs caught by commercial fishermen in the Boothbay Harbor region, 1973-76. 110 120 130 CARAPACE WIDTHIniTi) 160 Figure 5. — Width-fVequoncy distributions of male and female Jonah crabs caught by commercial fishermen at various locations along the Maine coast, 1977-78. 688 KROUSE: DISTRIBUTION OF JONAH AND ROCK CRABS The total commercial and research catch of 954 Jonah crabs included only 27 i2.8'f ) individuals ■ 90 mm. This might be related to gear selectivity, but this explanation loses credibility given that numerous rock crabs (equivalent catchability to Jonah crab) from 40 to 60 mm CW have been sampled previously with conventional and mod- ified lobster traps (Krouse 1976). Moreover, the fact that no Jonah crabs 67 mm CW were ob- served while hand-collecting 2,426 rock crabs (mean 23.9 mm CW) during a 3-vr intertidal study (Krouse 1976) or hauling research gear over a 9-yr period (juvenile rock crabs were frequently seen in traps) is evidence that small Jonah crabs in Maine waters, unlike juvenile rock crabs, inhabit deeper water exclusively. In the Mid-Atlantic Bight, Car- penter (1978) reported that Jonah crabs <30 mm CW were most abundant in depths ■ 150 m, while Haefner (1976) found crabs =s40 mm CW to be most numerous between 75 and 150 m. Both inves- tigators noted that the maximum abundance of the larger crabs ( >40 mm) occured in the 150-400 m strata. Distribution From July 1968 through 1974, 459 Jonah crabs were captured in 7,055 trap hauls (0.07 crab/trap haul) wdth research gear fished near Boothbay Harbor (Table 1). Fluctuations in the catch in as- sociation with temporal and spatial variations in fishing effort were assessed by plotting mean monthly values of catch in numbers per trap haul (catch per unit of effort, CPUE) for each fishing area (Figure 6). In areas with relatively high CPUE (average >0.1), catches gradually in- creased throughout the summer, peaked in the fall, and then diminished rapidly. Because most crabs in the research catch were at least two molt increments larger than the lower size limit of the gear's selectivity range, the seasonal rise in CPUE - Upper Mark Uland ■24 '5^^- ..39. ,;<^39' Middle Mark Island >/ ^■^. Powderhorn Island ., -:_-- --^. ^oj^- — < «T ^■_ Green Island r Q- < ■- ,431 "2i^ ■'-~ — 1661 !7Ti ':0) 1321 (531 QC Cat Ledges y^ 1/1 (66, 1 ./ S Capilol Island ,- 2- ■— , !163! .. "-^.. . .... .-""""^ ^''■^•- — . Eost Booihbay / \ ----.--' >„. Squirrel Island /'\ .2- '3; . /■ \._ Damonscove Island / N. • / \. ■l- '.8' ,'. .L .A. a' .,' ,1 ,1, .1 cl J .,' J Jon Feb Mar Apr May June July Aug Sepr Oct Nov Dec MONTH Figure 6. — Monthly catch per unit of effort values for Jonah crabs collected at various stations in the Boothbay Harbor region, 1968- 74. Number of trap hauls are in parentheses. Catch per unit of effort outliers are marked by arrows. may be explained by recruits migrating into the fishing areas. Conversely, the decline in CPUE in winter may be attributed to the effects of fishing mortality as well as emigration. Jonah crabs have been reported by Jeffries ( 1966) to move into the warmer waters of Narragansett Bay, R.I., from spring through fall, followed in winter by a move- ment to deeper, relatively warmer waters as in- shore water temperature declined. The closely re- TaBLE 1. — Trap catch-effort values of Jonah and rock crabs caught in research traps at various stations near Boothbay Harbor, Maine, 1968-74. Depth range Jonah crab Rock crab Total no. No, per Total no No, per Area (m) Substrate Hauls caught haul caught haul Upper Mark Island 5-15 Mud 157 5 0 03 645 4 11 Powderhorn Island 3-10 Mud 271 8 0 03 2,062 761 Green Island 3-10 Mud 396 4 001 1,025 259 Middle Mark Island 10-20 Mud-rock outcroppings 522 65 012 671 1 29 Gal Ledges 5-15 Sand-bedrock 656 41 0 06 660 1 01 Capitol Island 5-15 Mud 2 794 75 0,03 4.869 1,74 Easi Southport 5-15 Mud-rock outcroppings 253 30 0 12 318 1 25 Squirrel Island 5-20 Mud-rock outcroppings 1,267 149 0 12 2,674 2,11 Damariscove Island 5-20 Sand-bedrock 739 82 Oil 535 072 Tolal 3-20 7,055 459 0 07 13,459 1 91 689 FISHERY BULLETIN: VOL. 77, NO. 3 lated European edible crab, C. pagurus, have also been observed to undertake similar seasonal movements off the coast of England (Brown^). Li- mited population movements of Jonah crabs has also been suggested by Haefner (1977). Althiiu^h .Jonah cralis weiX' caught at each sta- tiiin, their relative abundance varied markedly liy area as reflected by CPUE values which ranged from 0.01 to 0.12 (Table 1 ). Jonah crabs were more numerous at the generally deeper, more seaward station.s i East Southport, Sc|uirrel Island, and Damariscove Island) characterized by rocky sub- strates and within the Sheepscot River at .Middle Mark Island where the fishing area borders rela- tively deep water (45 ml and the bottom is hard- packed mud interspersed with rock outcroppings. Conversely,. Jonah crabs were sparsely distributed at the otherstations in the Sheepscot estuary ( Up- per Mark Island. (Jreen Island, and Powderhorn Island! which in contrast to Middle Mai k Island are c|uite shallow with soft mud bottoms. Thus, the data indicate that the distribution and abundance of Jonah cralis reflects bottom type as well as depth. Comparisons (jf CPUE for rock crabs with those for Jonah crabs at different sampling sites re- vealed an inverse relationship iTable Ii. Rock crabs were very abundant at those stations within the Sheepscot River (CPUE: 2.6-7.6) where Jonah crabs were scarce; whereas, at other areas where Jonah crabs were more plentiful rock crabs were less common (CPUE: 0.7-2.1 1. Based on these ob- servations, rock crabs seem to prefer inshore areas with mud bottoms while Jonah crabs favor sea- ward locations with rocky substrates. This agrees with Jeffries ( 1966i findings that the same two cancrid crabs are separated spatially in Nar- ragansett Bay according to bottom type: rock and Jonah crabs inhabit sand and rock substrates, re- spectively. Interestingly, in the more northern latitudes, juvenile rock crabs, unlike the adults, show preference for coarse, rocky bottoms (Scar- ratl and Lowe 1972; Krou.se 1972; Reilly and Saila 197H). where protection from predators would be optimum. Distribution of both cancrid crabs is not only related to substrate type and depth, but is also dependent upon water temperature. For example, in the mid-Atlantic region, Carpenter (1978) found Jonah crabs at temperatures from 5° to 15° C ■'Brown. C;. C;. IflT.'i. Nciilnlk ctmIi inve..itigatu>ns I969-7:i I.al). I.i'afl .ill, 12 p Fi,-h I.ah . Lmvc.'^tcilt, .SiilTolk, Kngland with ma,\imum abundance between 6" and 12° C, Similarly, Haefner ( 1977) reported Jonah crabs to be most numerous in the temperature range of 8°-14° C. The more eury thermal rock crabs have been observed to be widely distributed over the continental shelf of the Mid-Atlantic Bight and most abundant inshore particularly during winter when temperatures are lowest (as low as 2° C) iMusick and McEachran 1972; Haefner 1976). In Chesapeake Bay rock crab abundance increases markedly in winter (2°-8° C ) and declines in spring as temperatures warm (Shotton 1973; Terretta 1973). In view of these data, the distribution of the two cancrid crabs along the Maine coast may be further e.xamined in relation to temperature. Rock crabs have been found to be most abundant in shallow nearshore waters where temperatures may vary from near 0° C in winter to 18° C in summer (Welch''); whereas, Jonah crabs are more numerous at greater depths where temperatures are more stable. Likewise, in the Gulf of St. Law- rence where the temperature regime is great ( -2° to 20° C [Lauzier and HuU'l), rock crabs are com- mon and Jonah crabs are nonexistent (Squires 1966; Scarratt and Lowe 1972). Thus, it appears that the distribution of these congeneric species in the northern part of their range is dependent upon substrate, depth, and temperature. Sex Ratios Initially, I examined ratios of male to female Jonah crabs in monthly catches at each fishing site; however, due to the small sample sizes for several of the groups, area catches were combined by month ( Table 2 ). The chi-square test, which was usedonly when the monthly N was slO, indicated that July through September ratios deviated sig- nificantly (P = 0.05) from 1:1. Males dominated in July while during August and September there was a preponderance of females. This shift in sex ratios may be attributed to an apparent movement of female crabs into warmer shoal water during summer and early fall as the result of behavior associated with molting and copulating. The closely related Dungeness crab, C. magister, and ■•W. R. Welch, Marine Resources Scientist, Maine Department of .Marine Re.sdurce.s, West Boothbay Harbor, MK MWl^. pers commun. February 1979. "Lauzier, I,. M., and .J H. Hull 1969. Coastal .station data temperatures along the Canadian Atlantic coast 1921- 19H9. Ki.sh Res. Board Can. Tech. Rep. l.iO. 2.5 p. 690 KROUSE: DISTRIBUTION OF JONAH AND ROCK CRABS Table 2. — Monthly captures and sex ratios of Jonah crabs caught with research traps. 1968-74. Asterisks denote sig- nificant deviation from 1:1 Ichi-square). Upper Sheepscot River ■ ■486'' Ratio Ratio Month i (-■ .) Montti ( ■■ 0 Dec -Apr 10 4 25:1NS Aug 39 81 1:2 1" May 7 3 23 INS Sept 38 1 17 1:3, 1" June 8 T 4 1NS Oct 44 45 1 INS July 24 7 34 1- Nov 1 1 19 1 1 7NS NS = not significant • = PcO.05 •• = P- 0 01 European edible crab have been reported to move inshore in spring and offshore in fall (Dewberry 1956; Hoopes 1973; Brown see footnote 3). In fact, mature female European edible crabs have been observed to move considerable distances ( ^225 km) along the coast of England (Brown see foot- note 3). Sex ratios of rock crabs caught with research gear varied not only by season but also by area (Figui-e 7). From July through September females generally outnumbered males, throughout the fall many of the sex ratios approximated a 1;1 relation, and then in winter males were dominant except in the upper Sheepscot River where they predomi- nated only in May. Similar to Jonah crabs, sea- sonal variations in rock crab sex ratios may best be explained by changes in the crabs' availability and vulnerability to the research traps in association with shedding and mating behavior. For instance, peak catches of females during summer and early fall coincided with egg hatching (summer) and molting (fall) in Maine waters (Krouse 1972). Higher proportions of male rock crabs in winter and spring catches may be attributed to: 11 re- cruitment of males as the result of winter-spring shedding (Krouse 1972) and, possibly, inshore movement (Haefner [1976] suggested that male rock crabs in the Mid-Atlantic Bight undertake seasonal inshore-offshore migrations); 2) in- creased feeding activity of newly molted crabs; and 3) a reduction in the availability and vulnera- bility of females during the winter spawning period (Dewberry [19561 noted that ovigerous female C. pagurus consume little food). Through- out summer the number of male rock crabs, par- ticularly those 90 mm CW, diminished due to fishing mortality and, perhaps, an offshore move- ment. The upper Sheepscot River sites, unlike the other locations, had a preponderance of female.^ during fall and winter, yet in spring, similar to other areas, males were more numerous (Figurt 7). Perhaps this relatively high abundance of Jan Feb Mar Apr May June July Aug Se'pl Oct Nov Dec MONTHS Figure 7. — Monthly percent frequencies of female rock crabs caught by research traps at different locations in the Boothbay region. 1968-74. Numbers in parentheses represent total number of males and females. Those ratios differing sig- nificantly from 1:1 (P = 0.05 by chi-square) are marked with asterisks. Blank bars represent no fishing effort. females may be related to the Sheepscot River sites' soft mud substrate, which females apparent- ly seek during the spawning season. From laboratory observations it appears that unless females are burrowed in the substrate at the time of egg extrusion, many eggs will not become at- tached to the pleopods resulting in a significantly reduced complement of eggs. Edwards and Early ( 1972) reported that female C. pagurus also show preference for soft substrates during the spring. Lindsay (1973) also noted that sex ratios ol Maine rock crabs vary by locality and sea.son. He also found males to be more abundant in the winter and spring. \\ id th- Weight Relations Because the overlap of data of males and females composed only a small segment of the total range of sizes, I applied analysis of covariance to the total regressions as well as the partial regressions derived from the data that 691 FISHERY BULLETIN VOL, 77. NO 3 overlapped. Significant differences (P = 0.05) were found between the v-intercepts of either sex for both the complete and partial regressions, so males and females were treated separately. Plots of the predictive regressions show that male Jonah crabs averaged about 8% heavier than females of the same CW over the range 115-130 mm (Figure 8). SUMMARY FromJuly 1968 through March 1978, 419 male (67-168 mm CW) and 535 female (74-136 mm) Jonah crabs were collected from research traps and commercial fishermen. Even though male Jonah crabs attain larger sizes (mean sample 113.7-141.1 mm CW) than females (mean sample 104.8-114.0 mm), many female Jonah crabs are harvested commercially whereas, rock crab land- ings are chiefly composed of males. No Jonah crabs <67 mm CW were caught and only 2.79^ of the total catch were <90 mm CW. This with other evidence indicates that small Jonah crabs inhabit greater depths (>20 m) than those sampled. Catch per unit of effort values for Jonah crabs caught with research gear generally increased during summer, peaked in fall, and then declined sharply. Fluctuations in the catch were attributed primarily to movement. Catches were highest at the deeper, more seaward sampling sites where the substrate was predominantly rocky. In con- trast, rock crabs were more abundant at those relatively shallow estuarine stations having soft BOOr 550- 500 X X Figure 8.— Carapace width-weight rela- tionships calculated for 110 male and 90 female Jonah crabs from the Boothbay Harbor region. Standard errors of the re- gression coefficients are 0,1793 (a) and 0.0850 (b) for males and 0,2023 (a) and 0.0984 (6) for females. 450 _ " / 27444 W=0.0006CW 400 - . "."/ . X « I / K K u> « « X«XX M £350 ~ s ■ yo O UJ 0« XiWtfM t' MALES X ^300 - FEMALES 0 250 200 - XX OOOQOOO ooooaoCoooo 0006000 rfwoo 0 0 Jboo 0000 000'^ 0 0 0 oo ^ a/T 27721 Zo W=0.0005CW ■ 150 'S o 0 o ■ L 1 1 J... _l — 1 1 I 1 1 1 95 100 105 110 115 120 125 130 135 140 145 150 155 CARAPACE WIDTH (MM) 692 KROUSE DISTRIBUTION OF JONAH AND ROCK CRABS mud bottoms. Distribution of both cancrid crabs appears to be controlled by substrate type, depth, and temperature. Male Jonah crabs outnumbered females in the catch in July; the opposite occured in August and September; during the remaining months, sex ratios did not differ significantly from 1:1. In com- parison, female rock crabs generally predomi- nated July through September, during fall most ratios approximated 1:1, and in winter and spring males usually dominated with the exception of most estuarine locations where males were only in the majority during May. ACKNOWLEDGMENTS I thank the many summer assistants who helped collect, compile, and tabulate several years data. I also thank Joel Cowger for providing me wdth his field data and Clarence Burke for drafting many of the figures. LITERATURE CITED Carpenter, R. K. 1978. Aspects of growth, reproduction, distribution and abundance of the Jonah crab, iCancerborealts) Stimpson, in Norfolk Canyon and the adjacent slope. M.A. Thesis, Univ. Virginia, Charlottesville, 68 p. DEWBERRY, E.B. 1956. The characteristics, habits and life history of the edible crab. Naturalist (Leeds! 858:91-96. EDWARDS, E., AND J. C. EARLY, [1972.] Catching, handling and processing crabs. Dep. Trade Ind., Torrv Res. Stn., Torry Advis. Note 26 (rev. I. 17 p. H.AEFNER.P. A.,JR 1976. Distribution, reproduction and moulting of the rock crab. Cancer irroratus Say, 1917, in the mid-Atlantic Bight. J. Nat. Hist. 10:377-397. 1977. Aspects of the biology of the jonah crab. Cancer borealis Stimpson, 1859 in the mid-Atlantic Bight. J. Nat. Hist. 11:303-320. HOOPES,D. T. 1973. Alaska's fishery resources — the Dungeness crab. U.S. Dep. Commer., NOAA, Natl. Mar. Fish. Serv.,Fish. Facts-6, 14 p. Jeffries, H. P, 1966. Partitioning of the estuarine environment by two species of Cancer. Ecology 47:477-481. Km USE, J. S. 1972. Some life history aspects of the rock crab. Cancer irroratus. in the Gulf of Maine. J. Fish, Res, Board Can. 29:1479-1482. 1976. Size composition and growth of young rock crab. Cancer irroratus. on a rocky beach in Maine. Fish. Bull., U.S. 74:949-954. Lindsay, B. P, 1973. Some aspects of mobility and feeding activity of the rock crab. Cancer irroratus. M.S. Thesis, Univ. Maine. Orono, 57 p. MUSU K, J, A,. AND J. D. MCE.ACHRAN. 1972. Autumn and winter occurrence of decapod crusta- ceans in Chesapeake Bight. US .■\, Crustaceana 22:190-200, REILLY, P, N,, AND S. B. SAILA. 1978. Biology and ecology of the rock crab. Cancer ir- roratus Say, 1817, in southern New England waters (De- capoda.Brachyura). Crustaceana 34:121-140. S.ASTRY, A. N. 1977. The larval development of the Jonah crab. Cancer borealis Stimpson, 1859, under laboratory conditions (Decapoda Brachyura), Crustaceana 32:290-303. SCARRATT, D. J., AND R. LOWE. 1972. Biology of rock crab (Cancer borealis) in Northum- berland Strait. J. Fish. Res. Board Can, 29:161-166. SHOTTON, L. R, 1973. Biology of the rock crab. Cancer irroratus Say. in the coastal waters of Virginia. M.A, Thesis, Univ. Vir- ginia. Charlottesville. 72 p. Squires, H.J. 1966. Distribution of decapod Crustacea in the northwest Atlantic. Ser. Atlas Mar, Environ. Am. Geogr. Soc. Folio 12, unpaged, Terretta, R. T, 1973, Relative growth, reproduction and distribution of the rock crab. Cancer irroratus. in Chesapeake Bay durmg the winter, MA, Thesis, Coll. William and Mary, Wil- liamsburg, Va., 104 p. 693 NOTES EFFECTS OF DESICCATION AND AUTOSPASV ON EGG HATCHING SUCCESS IN STONE CRAB, MEMPPF MERCES ARIA The stone crab. Menippe mercenaria, is found from North Carolina to Yucatan, Mexico, Cuba, Jamaica, and the Bahamas; commercial fishing occurs principally in the State of Florida. Crabs are captured in wooden or plastic traps (40 ■ 40 ■ 28 cm) baited with available fish scraps. Present Florida laws allow harvest of both claws from all crabs, including ovigerous females, provided each claw is of legal size (70 mm propodus length). Sale of whole crabs is prohibited, and declawed crabs are relea.sed to allow regeneration of lost claws and renewal of fishable stocks. Regeneration of another legal claw can occur within 18 mo (Sulli- van'). The commercial season extends from 15 October to 15 May. Spawing occurs during the warmer months (Noe 1967; Cheung 1969), and females with large external egg masses (sponge) of up to 600,000 eggs are observed from early March to late November. Newly extruded eggs, attached to abdominal pleopods, are red-orange and progress to yellow then grey over a 9-12 day maturation period. Larvae generally hatch directly from eggs attached to pleopods. Most commercial operations maximize daily marketable claw yield by pulling traps continuously and declawing crabs only dur- ing the return trip to port. This necessitates keep- ing whole crabs in large fish boxes or containers on deck that are exposed to air for up to 8 h. Claw removal from air-exposed ovigerous females and desiccation of exposed egg masses may reduce lar- val hatching and recruitment. Since these proce- dures violate Florida law requiring crabs to be declawed immediately and released in the same area where captured, this study was conducted to provide scientific data to implement change in current fishing methods and protect future stocks. Mtthiids Gravid stone crabs were captured in the Gulf of Mexico (5-9 ml west of Pass-A-Gnlle Beach, St. Petersburg, Fla., between March and September 1977. Females with large egg masses were trans- ported in 4 1 containers by ship to the Florida De- partment of Natural Resources Marine Research Laboratory. St. Petersburg. Container water, ex- changed frequently with Gulf water while sampl- ing, was not changed for approximately l'/2 h dur- ing transport through low salinity waters. Unfed crabs were kept individually in plywood tanks divided into compartments (45.7 x 30.5 x 30.5 cm), sealed with fiber glass'tape and epoxy, and leached 2-4 wk prior to use. Water in the closed system was maintained at 15 cm depth by removable standpipes, and overflows were di- rected into individual glass tanks where eggs or larvae were retained before water entered two 1,000 1 undergi-avel filter vaults (Dugan et al. 1975) (Figure 1). Overflow splash and two airlift standpipes maintamed aeration. Hatching tank Glass tank screen 'J. R. Sullivan, Florida Department of Natural Resources. Marine Research Laboratory, pers. commun. May 1977. FliU'UK I— Hatchint; lank i4.") 7 ■ .30..') ■ :30,.5 cml and glas.s larval capture tank (15 x 15 x 30 cm) for desiccation and auto- spasy experiments with ovigerous stone crabs. FISHERY BULLETIN VOL. . NO :). 1980, 695 Optimum survival conditions for egg develop- ment and hatching success for M. mercenaria (30° C and 34%o salinity) were determined by Ong and Costlow ( 1970). Salinity in the present study var- ied between 32.0 and 36.0%o and averaged 34.4"/oi) in all experiments. Air and water temperatures in the control room fluctuated from 27° to 33° C with water temperature generally 0.5°-1.0° C lower. Dissolved oxygen levels were measured twice monthly. Nitrites and ammonia levels were evaluated weekly and never exceeded 0.089 and 0.073%o, respectively. Lighting was regulated for 16 h light: 8 h dark and utilized Vita-Lite- bulbs which simulated the natural spectrum of sunlight (Dugan et al. 1975). Experiment 1(13 April-31 July) Crabs were divided into three test groups, with similar ranges of animal size and egg mass color (maturity) and were acclimated to tanks for at least 18 h. Initially, individual crabs were exposed to ambient indoor air conditions in separate cages. This procedure was modified after the first series to simulate commercial holding techniques more closely by placing crabs from a single group into loosely covered wooden slat boxes located in direct sunlight. After desiccation, crabs were returned to holding tanks and observed every 24 h until all eggs hatched. Group I (control) crabs remained in water throughout the experiment. Group II and Group III crabs were desiccated for 2 and 5 h, respectively. Total number of crabs for each group was: 35-Group I, 34-Group II, 33-Group III. Experiment II (S August-21 September) Desiccation procedures were identical to mod- ified procedures in Experiment I; added stress from claw removal was introduced after desicca- tion. Claws were removed using commercial har- vesting methods by inducing autospasy (loss of appendage through externally applied pressure). In this technique, claws were grasped firmly and ventral pressure applied until the fused basis- chium stopped against the coxa. Further flexion strained the autotomizer muscle, and separation of the limb occurred at a natural fracture plane. Excessive hemorrhaging is prevented by swelling ^Reference to trade names does not imply endorsement by the Marme Research Laboratory, FDNR or the National Marine Fisheries Service, NOAA. of a hypodermal diaphragm located at the fracture plane. Group IV (control) crabs remained in water throughout the experiment and had similar treatment as Group I. Group V and Group VI crabs were desiccated for 2 and 5 h, respectively, then declawed. Declawed crabs were placed im- mediatedly into holding tanks and observed every 24 h as in Experiment I. Total number of crabs for each group was: 30-Group IV: 34-Group V; and 35-Group VI. Crabs continuously discarded eggs from egg masses. Single eggs were shed when females raised their bodies on claws and legs and preened (combed) egg masses with rear legs. Egg stalks containing up to several hundred eggs (clumps) were also frequently shed. Aeration of eggs by rapid abdominal movement also occurred at this time. Detached eggs, larvae, and other egg mass products retained in individual glass tanks were removed daily and preserved in 10*"^ Formalin prior to counting. .\nalysis Hatching occurred from 0 to 9 days after day of experimental stress. Complete hatching generally required 24-48 h, and organic matter retained in glass tanks after that time was principally dead eggs, deformed larvae, or empty egg cases cleaned from pleopods. The day with highest number of normal first- stage larvae was called major hatch. Days before and following major hatch were called prehatch and posthatch. Eggs from a single ovigerous female were ob- served microscopically to determine normal hatching process and identify normal first-stage larvae. Initial breaking of the chorion enabled larvae to emerge head first from the egg. Vigorous abdominal flexing by the larvae cast off the egg case and induced shedding of the prezoeal cuticle and full extension of the rostral and lateral spines. In a few instances, spinular extension was delayed until complete seperation from the egg, but all prezoea yielded normal, active free-swimming first-stage larvae within minutes of initial hatch. Eggs removed from the same female after desicca- tion were observed for comparison. Increased numbers of inviable eggs and partial hatches were evident. Numerous prezoea, unable to cast off pre- zoeal cuticles, died after continued struggle. Suc- cessful first-stage development was reduced, and 696 larval activity was sluggish, frequently ending in death. Aliquots from individual daily crab samples ( 1 or 2 ml; count ^ 200) were sorted under a dissect- ing microscope and classified. Normal first-stage larvae ( Hyman 1925; Porter 1960) were denoted as viable; whole eggs, partially hatched eggs, prezoea (Hyman 1925; no rostral or lateral extension), and deformed first-stage larvae were denoted as invi- able. Stein's two-stage sample test i Steel and Tor- rie 1960) indicated that six replicate aliquots from each sample provided reliable counts (within 95% confidence limits) of total numbers of viable and inviable eggs and larvae present each day. Because results of aliquot counts were inconsis- tent when samples contained clumps of eggs, 1-8 ml of chlorine bleach (5.25% sodium hypochlorite) were added to dissolve stalks and dissociate eggs uniformly before aliquots were taken. Number of eggs carried by individual crabs at time of capture was estimated by combining daily totals of viable and inviable eggs and larvae. Total hatching success was expressed as percent of orig- inal egg mass that hatched viably. Total egg mass mortality was expressed as the percent not hatch- ing or hatching inviably. Average daily mortality (per group) was calculated by dividing total mor- tality per day by the number of crabs yielding inviable eggs and larvae that day. Crabs not yielding any larvae were eliminated from analysis; two crabs in Group I and one crab each m Groups III, IV, and VI were so eliminated. Comparison among groups was made by pre- senting prehatch, posthatch, and total egg mass mortality for each group. I chose this method be- cause inviable eggs and larvae were evident in some form in all daily samples, but viable larvae were present for only 24-48 h. Results and Discussion Experiment 1 Initial egg loss from crabs in Group I (Figure 2) was probably caused by handling at capture and stress from transport to laboratory. With acclima- tion to holding tanks, average daily mortality de- creased until major hatch, when highest egg and larval mortality coincided with maximum first- stage larval survival. Crabs desiccated for 2 h (Group II) showed im- mediate preening activity upon return to water and daily prehatch mortality peaked at 3.6%, 3 Posthotch Days after MH FK^IUI^E 2. — Average daily percent egg mortality in ovigerous stone crabs as related to desiccation. Group I crabs untreated I control ), Group II crabs exposed to 2-h desiccation and Group III crabs exposed to 5-h desiccation. DD - day of desiccation: MH - day when major hatching occurred; Prehatch - days following DD; Posthatch ■ days following MH. Starred points represent percent mortality excluding one of three crabs which accounted for 96% total mortality on posthatch days 4 and 5. days after desiccation (Figure 2). Thereafter, daily percent mortality decreased until major hatch. Posthatch mortality was similar to, but slightly higher than that of Group I. Total prehatch mor- tality ( 12.1% ) was four times greater than that of Group I (Table 1) and posthatch mortality (9.3%) was nearly twice that of Group I. Total mortality for Group IK 2 1.4% ) was 13.0% higher than control (Group I). Desiccation for 5 h (Group III) caused temporary lethargy in crab mobility; sponge care and initial mortality were below those of Group I (Figure 2). Crabs recovered slowly during prehatch, resulting in 5 days of generally increasing daily egg mortal- ity. Maximum daily egg and larval mortality usu- ally occurred on the day of major hatch, but was delayed 2 days for most Group III crabs. Improper maternal care of eggs during prehatch and through posthatch may have prolonged oxygen 697 Table l— Percent egg mortality in ovigerous stone crabs as related til desiccation and autospasv. Experiment I comparesegg mortality after effects of desiccation and experiment 11 compares egg mortality after desiccation followed by removal of both claws (autospasy). Crabs Group and trealmenl (no) Prehatch Posthatch Total Experiment 1 1 (controll 33 33 51 84 II |2-ri desiccation) 34 12 1 93 21 4 III l5-h desiccaiion) 32 59 33 8 39 7 Experiment II IV (conlroll 29 70 67 137 V (2-h desiccation/autospasy) 23 85 18 1 VI (5-h desiccalion/aulospasy) 16 98 50 4 60 2 deficiency within the egg mass and lack of abdom- inal movement may have hindered successful lar- val hatching. Davis (19651 separated eggs from female blue crab, Callincctcs sapiclus. and noted a decrease in hatching success if eggs remained in small clusters, presumably due to insufficient oxygen. Rice and Williamson (1970) found that decapod larvae hatched from ovigerous females were weakened if oxygenated water could not be replenished. Prehatch mortality for Group III (5.9^r ) was less than that of Group II, but was still greater than that of Group I (Table 1), Posthatch mortality (33.8%) was considerably higher than Group I or Group II. Total mortality for Group III 139,7%) represented a mean increase of 18.3% mortality above that of Group II and a mean increase of 31,3% above that of Group I (Table 1). Expcrinicnl II Autotomizer muscle reflexes were adversely af- fected in crabs subjected to air exposure, and de- clawing often resulted in jagged wounds and severance of the artery proximal to the hypoder- mal diaphragm. Unrestricted hemorrhaging caused death in 8 crabs in Group V and 14 crabs in Group VI. Death in seven additional crabs (three in Group V, four in Group VI) could not be explained as above, but also occurred after deelaw- ing. Resulting 100% egg mass mortality for 34,4% of Group V and 52,9% of Group VI notably reduced group mean hatching success related to control Group IV (Table D, Wood and Wood (1932) found any treatment which weakened brachyurans affected muscular responses, preventing normal autotomic reflex; they further stated that American crayfish (As- tacidae) held captive for any length of time were vitiated and lacked normal reflex. Davis^ related wound size and body fluid loss in reporting 53.79; death in M. mercenaria held for 10 days in labora- tory tanks and then declawed using commercial methods. Loss of both claws after desiccation reduced preening of eggs by surviving crabs, resulting in an apparent initial egg mass mortality below that of Group IV (Figure 3i, Group V crabs (2-h desiccation) recovered quickly and compensated for claw loss by propping themselves against sides of compartments; rocks and shells common where stone crabs occur may be used similarly in nature. Prehatch mortality peaked 3 days after desiccation, Posthatch mortal- ity was higher and more erratic than that of con- trol Group IV. Prehatch mortality (8,5%) was slightly higher than that of Group IV (7,0%), but posthatch mortality (18,1%) was almost three times higher than that of control group (Table II, Total mortality for Group V (26,6%) was 12,9% above control (Group IV I, ^Davis, G. E, Interim report June, 1977. National Park Service Stone Crab Studv. Everglades National Park, Box 279, Homestead, FL;«030. S 120 E ! too-- 80 60 4 0 20 GROUP H GROUP I GROUP Vl -H — I — I — I — I — I — I — I — ^ 2 3 4 5 6 Prehatch Doys after DA H — I — I 1— I — I 1 — I — I t—l MH I 2 S 4 5 6 Posthatch Days after MH Fli.lKK :i,— Average daily percent egg iniirtality in ovigerous stone crabs as related to desiccation and autospasy. Group IV crabs were untreated (control). Group V crabs had both claws removed lautospasyi after 2-h desiccation, and Group VI crabs had both claws removed after .>h desiccation n.-\ - day of desic- cation and autospasy; MH - day when major hatching occurred; Prehatch - days following DA; Po.sthatch ■ days following MH. 698 After 5-h desiccation, surviving declawed crabs (Group VI) recovered more slowly than did crabs of Group V. Maternal preening was delayed and egg mortality during prehatch did not peak until 6 days after desiccation (Figui'e 3). As noted previ- ously, maximum egg and larval mortality nor- mally occurred at major hatch, but difficulty in maintaining body elevation probably inhibited preening for Group VI during posthatch. Con- sequently, maximum egg and larval mortality oc- curred 3 days after major hatch and time needed to clean pleopods was extended to 9 days. Group VI recovery from stress was sufficient to produce prehatch mortality of 9.8%, an increase of 2.8'r above control Group IV (Table 1). Extended posthatch yielded 50. 4'^> egg and larval mortality, the highest of any group. Total mortality for sur- viving crabs in Group VI (60. 2'/? i was a marked increase of 46.5'^f above that of control Group IV (Table 1) even excluding lOQ'i mortality values from 18 dead crabs. A 1 r— t— 1 n m 1 H B E"Pef>ment ail cobs n r-t-i |2 , o 51 C f iperim.?nt dbs S 1 1 1 H 1 Figure 4. — Hatching success in ovigerous stone crabs as re- lated to desiccation and autospasy Mean (vertical line), range (horizontal line! and 95'7f confidence intervals (bar) about the mean. Set A includes untreated Group I crabs. Group II crabs exposed to 2-h desiccation and Group III crabs exposed to 5-h desiccation; Set B includes untreated Group IV crabs. Group V crabs, both claws removed after 2-h desiccation and Group VI crabs, both claws removed after 5-h desiccation; Set C includes only crabs that survived desiccation and autospasy in Groups V and VI. Mean Hatchinj; Success Mean hatching success for control crabs in Ex- periment I (Group I) was 91. G*;?. Desiccation from air exposure for 2h (Group II) decreased success to 78.6'7f and desiccation from 5-h air exposure (Group III) decreased success to 60.3'?. Mean hatching success for control crabs in Experiment II ( Group IV) was 86.3'r . Stress from 2-h desicca- tion plus autospasy (Group V) decreased success from Group IV to 49. 69^ and stress form 5-h desic- cation plus autospasy (Group VI) decreased suc- cess to 18.8'7f (Figure 4). Sunim.iry Desiccation of eggs by air exposure of ovigerous females caused reduction in larval hatching suc- cess that was directly related to length of expo- sure. Desiccation weakened normal crab autotomic muscular reflex, and experimental de- clawing resulted in death of 34.4'f of crabs ex- posed 2 h and 52.9% of crabs exposed 5 h. Stress from autospasy after 2-h desiccation did not increase mean egg and larval mortality for surviving crabs above that for crabs desiccated only. Related to controls. Group II (2-h desicca- tion) and Group V ( 2-h desiccation'autospasy) had nearly identical total mortalities, 12.9% and 13.0%, respectively. Claw loss delayed maternal egg mass preening, and reversed the prehatch posthatch egg mortality ratio of crabs desiccated 2 h from 12.1:9.3 (Group II) to 8.5:18.1 (Group V). Effects of stress after 5-h air exposure were less definitive. Egg and larval mortality for surviving declawed crabs exposed to 5-h desiccation was 15.5% higher than was mortality for similarly ex- posed whole crabs when related to controls. Ma- ternal egg preening by declawed crabs was obvi- ously affected by claw loss, but small sample size (16) in surviving declawed crabs and overlap in confidence intervals for the 5-h desiccation groups made differences in mortalities inconclusive. The stone crab fishery, unlike the blue crab fishery which allows permanent removal of whole animals, realizes high stability and recruitment by release of reproductively active crabs capable of claw regeneration. Present harvesting techniques adversely affect this stability by subjecting crabs to air exposure and desiccation. When crabs are ovigerous, desiccation causes a definite reduction in larval hatching succe.ss and is related to crab death and reduced overall population recruit- ment. Protection of ovigerous females by im- mediate release or by use of methods to dampen crabs while on deck is therefore warranted. .■\tkn<)\\ Icdynicnts This study was funded in part by the U.S. De- partment of Commerce, NCAA, National Marine Fisheries Sei-vice under PL 88-309, Project No. 699 2-278-R. I thank F. S. Kennedy, Jr., M. E. Berri- gan, J. R. Sullivan, D. G. Barber, and S. M. Foster for helping to collect and process the data, J. Hinkle and D. Richardson for laboratory assist- ance, and W. G. Lyons, D. K. Camp, and J. A. Huff for editorial review. Special thanks to Deb, my wife, who spent immeasurable time assisting me on weekends. Literature Cited Cheung, T. S. 1969. The environmental and hormonal control of growth and reproduction in the adult female stone crab Menippe mercenaria (Say). Biol. Bull. (Woods Hole) 136:327-346, D.^VIS.C, C, 1965. A study of the hatching process in aquatic inverte- brates: XX. The blue crab, Callinectes sapidus, Rathbun. XXI. The Nemertean, Carcinonemetes carcinophica (Kolliker). Chesapeake Sci. 6:201-208. DUGAX. C. C. R. W. H,-\GO0D. .-WD T. A. FR.AKES. 1975. Development of spawning and mass larval rearing techniques for brackish-freshwater shrimps of the genus Macrobrachium iDecopoda Palaemonidae). Fla. Mar. Res. Publ. 12, 28 p. Hym.ax. 0, W. 1925. Studies on the larvae of crabs of the family Xan- thidae. Proc. U.S. Natl. Mus. 67(3), 22 p. NOE, C. D. 1967. Contributions to the life history of the stone crab A/. mercenaria with emphasis on the reproduction cy- cle, MS, Thesis, Univ, Miami, Coral Gables, Fla,, 55 p ONG, K. S., and J. D. COSTLOW. JR 1970. The effect of salinity and temperature on larval de- velopment of the stone crab. Menippe mercenaria (Say), reared in the laboratory. Chesapeake Sci. 11:16-29, PORTER, H, J, 1960. Zoeal stages of the stone crab Menippe mercenaria (Say). Chesapeake Sci. 1:168-177. RICE, A. L.. .AND D, 1, WlLLI.AM.SOX 1970, Methods for rearing larval decapod Crustacea. Helgol. wiss. Meersunters. 20:417-434. STEEL, R, G, D,, .AXD J, H, TORRIE 1960. Principles and procedures of statistics, with special reference to biological sciences. McGraw-Hill, N. Y., 481 P- Wood, F. D., .\xd H. E. Wood. 1932. Autotomy in decapod Crustacea J Exp, Zool 62:1-55. RODRIC A. SCHLIEDER Florida Department of Natural Retiources Marine Research Laboratory 100 Eighth Avenue SE St. Petersburg. FL 33705 FIRST RECORDS OFF OREGON OF THE PELAGIC FISHES PARALEPIS ATLAMTICA, GONOSTOMA ATLANTICUM, AND APHANOPVS CARBO, WITH NOTES ON THE ANATOMY OF APHANOPVS CARBO' The species covered in this report are common in parts of the Atlantic Ocean and all are known to occur in the Pacific Ocean. We fill a gap in knowl- edge of the distribution of two species known formerly only north and south of Oregon, extend the northward range of Gonostoma atlanticum Norman, and report inshore occurrences of Paralepis atlantica Kr0yer. The unusual gross anatomy surrounding the gas bladder of Aphanopus carbo Lowe is worthy of description. Methods Counts and measurements followed those of Hubbs and Lagler (1958) and all measurements were taken to the nearest 0.1 mm. Specimens are catalogued in the fish collections of the Depart- ment of Fisheries and Wildlife (OS) or the School of Oceanography (OSUO), Oregon State Univer- sity. Anatomical terminology follows that of Lag- ger et al. (1962) and Romer (1970). Four speci- mens of A. carbo from Oregon were dissected and two were radiographed. Two specimens from the Atlantic Ocean off Madeira were dissected and radiographed. Complete vertebral counts could not be made from the radiographs due to poor resolution of the small posterior caudal vertebrae. Notes on Distribution and Morphology Paralepis atlantica has been recorded in the eastern Pacific from Baja California and Califor- nia (Rofen 1966) and from the vicinity of Willapa Bay, Wash. (Kajimura 1969). Bakkala (1971) re- ported the species from surface waters of the cen- tral Pacific at lat. 48°00' N, long. 165°00' W. Two specimens of P. atlantica were found on shore in northwestern Oregon. One (OS 956:456 mm SL) was taken alive on the beach at Netarts, Tillamook County, on 7 October 1963. Another (OS 5160:466 mm SL) was found dead on the beach 29 km north of Seaside, Clatsop County, on 16 May 1960. A specimen ofG. atlanticum (OSUO 2402:59 mm SL) was captured on 30 July 1977, 65 'Technical Paper No. 5082, Oregon Agncultural Experiment Station, Oregon State University, Corvallis, OR 97331. 700 nSHERY BULLETIN: VOL 77, NO. 3, 1980 km west of Newport (lat. 44°38' N), between 335 and 400 m deep with a small Cobb midwater trawl ( 10 m mouth opening) with an opening and closing cod end (Pearcy et al. 1977). This female fits the descriptions by Grey (1960, 1961, 1964) and Mukhacheva (1972). Maximum diameter of eggs in the ovary was 0.16 mm. Grey (1964) con- sidered fish of this size to be mature. Gonostoma atlanticum is usually distributed in warm water of the Atlantic, Pacific, and Indian Oceans. It is found in the eastern and central North Atlantic, and it has usually been recorded from equatorial waters in the Pacific and Indian Oceans. The northernmost previous record (lat. 34°18.6' N) for its occurrence in the Pacific Ocean was that of Berry and Perkins (1966), who cap- tured several individuals off southern California. The temperature of the water in which the OSUO specimen was captured was 5.37°-5.70° C. Backus et al. (1965) reported the occurrence of G. atlan- ticum in the Atlantic Ocean in waters of 10°-11°C. Aphanopus carbo was first reported from the Pacific Ocean off Bodega Bay and Fort Bragg, Calif., in 1969 (Fitch and Gotshall 1972). Peden (1974) reported a specimen from off the Strait of Juan de Fuca. Clarke and Wagner (1976) col- lected larvae and juveniles off Hawaii. Five specimens were taken off Oregon in 1976: OS 5381 (476 mm SL), about 29 km off Cape Meares, at about 183 m; OS 6115 (639 mm SL), about 37 km off Florence, at about 146 m; OSUO 2352 (570 mm SL), 2353 (558 mm SL), 2354 (547 mm SL), 120 km west of Newport, at about 400-480 m, in an opening and closing net. Our specimens compared with those from Madeira, had slightly smaller horizontal orbit, slightly wider suborbital head width, and slightly shorter anal spines. Otherwise the Atlantic and Pacific Ocean specimens are very similar. Gas Bladder Anatomy in Aphanopus'carho Although Maul (1954) mentioned that on re- trieval to the surface the gas bladder in A. carbo expands greatly, causing the skin of the abdomen to split, none of our specimens exhibited this characteristic. ShepeF stated that none of the specimens examined by him had their skin split, but that the stomach in most specimens (all from the Atlantic Ocean) were everted. Only one of our ^L. I. Shepel, Fishery Reconnaissance, Murmansk, U.S.S.R.. pers. commun. 15 November 1977. specimens had an everted stomach. These differ- ences led us to examine the gas bladder and as- sociated structures in A. carbo. Bone ( 1971) described the anatomy and histol- ogy of the gas bladder of A. carbo. Tucker (1953) briefly mentioned the ribs and provided partial radiographs of the ribs and vertebral column in A. carbo and A. schmidti. However, we found no descriptions of the relationship of the bladder to the vertebral column, ribs, kidneys, and coelom. Our examination of A. carbo shows that the gas bladder of this species, and the structures as- sociated with it, has several unusual characteris- tics. Little variation in anatomy was noted in our specimens. The position of the gas bladder in A. carbo is typical of that in most fishes; it is ventral to the vertebral column and kidneys and dorsal to the peritoneal (abdominal) cavity (i.e., retroperi- toneal) (Figure 1). The anterior end of the gas bladder is below the sixth vertebra. From it, two minute extensions proceed anterolaterally at 45°, but the size of the extensions did not allow us to trace them forward more than a few millimeters. Posteriorly, the gas bladder extends to a blunt end between vertebrae 42 and 45, directly dorsal or slightly anterior to the vent. Although the dor- soposteriad portion of the peritoneal cavity nar- rows and curves ventrally, the gas bladder con- tinues to parallel the vertebral column except for a slight dip near the posterior end. The region be- tween the gas bladder and the peritoneal cavity is filled with hypaxial muscle. The bladder is slightly narrowed at its anterior and posterior ends. It is oval in cross section and slightly small- er than the diameter of vertebral centra in our preserved specimens (Figure 1). The kidneys extend anteriorly from the region dorsal to the vent to the posterior portion of the skull. They are enlarged in the area above the vent, and between the anterior of the gas bladder and posterior of the skull, and lie ventrolateral to the vertebral column and dorsolateral to the gas bladder. They terminate in a urinary duct that appears to empty into a urogenital sinus. The ventral ribs are intimately associated with the gas bladder and kidneys. A pair of ventral ribs is present on all trunk vertebrae, but those anterior to the gas bladder are short and thin. These ribs are difficult to find but may be seen readily in radiographs. From immediately an- terior to the gas bladder to about the ninth ver- tebra the ribs become progressively longer and 701 .r<^ SKIN SEPTUM VERTEBRA KIDNEY GAS BLADDER RIB GONAD NTESTINE STOMACH W of the protein. During the period from hatching to the end of the yolk-sac stage (day 5), DNA and RNA content remained essentially constant while a decrease in protein was observed. Although plankton was added on day 4 to aquaria containing fed larvae, visual observation of the gut indicated that the majority of the larvae had 704 1.5— X _i < _i 3 < Q 3 — Q > > 2 Z O' CT> < z 1.0 — o cr Q. .5 — EGGS LARVAE Qv. RNA STARVED PROTEIN STARVED — .35 .30 25 — .20 — .15 —.10 — .05 D ■z. > < o c > 2 4 6 8 DAYS AFTER SPAWNING 10 4 6 8 10 DAYS AFTER HATCHING Figure l , — Time course of development of DNA, RNA, and protein content per individual winter flounder egg or larva, a) SC/c hatch; b) starved larvae transferred to filtered seawater; c) most larvae showed no visible yolk; di food visible in gut of fed larvae. not begun feeding until day 7. Between the end of the yolk-sac stage and initiation of feeding iday 7) DNA content increased sharply while RNA and protein decreased. Of the protein present in the egg just prior to hatching, 45'7f was lost by the time of feeding initiation. After feeding initiation DNA, RNA, and protein content increased stead- ily (Figure 1; Tables 1, 2i. The RNA and protein content of winter flounder larvae transferred to filtered seawater prior to feeding initiation continued to decrease until a lOC^f mortality was observed between day 11 and 14 (Figure 1 1. Starved larvae did show an increase in DNA content on day 7 similar to that observed in fed larvae. The RNA-DNA ratio of both starved and fed larvae decreased from the end of the yolk- sac stage through day 9. However, the RNA-DNA ratio was significantly higher in fed larvae than starved larvae on day 9. The RNA content of a second group of larvae transferred to filtered seawater 28 days after hatching decreased within 2 days, while both DNA and protein content appeared to increase (Table 1). After 4 days a decrease in all three components was observed. A SO'/f mortality, con- sisting almost entii'ely of the smaller individuals Table l. — RNA. DNA, and protein content of starved and fed winter flounder larvae 28 to 36 days after hatching. Age (days) Starvation stanOard lengthMmm) RNAMMqla'va) DNAJ (^q larva) ProlemMfq larva) RNA DNA' (days) Fed Starved Fed Stan/ed Fed Slan/ed Fed Starved Fed Starved 28 30 32 0 2 4 C 8 C'' 5 61 ±0 60 5 64=0 66 5 68 = 0 54 5 83=0 72 5 84=0 66 5 44=0 80 6 53 = 0 92 6 41=0 45 6 23 = 0 94 4 74=0 73 4 75 = 0 1 4 3-95=0,22 8 91 ±0 66 8-15=267 3 32=0 51 2 59=0 61 0 99=0 13 1 21=0 16 0 99=0 05 2 17=041 1,92=0-46 1 04=0 11 093=0 13 37= 3 79= 4 43= 4 1 73 = 0 18 94= 4 86 = 24 44=5 36-7 427=042 4 81=0 56 3 16 = 0 26 3 99=0 50 2 78=0 29 3 98=0 06 419=043 214=016 420 = 034 ^Number ot days starved fisti were m filtered seawaier ^Data are means = 1 SD for 40 to 50 larvae 'Data are means =1 SD ot three replicates containing 10 larvae eacti ^Fish removed from fed population and transferred to filtered seawater 18 hi prior to sampling to clear stomach contents 705 -z. Q \ 3 < tr 2- Table 2. -RNA, DN A, and protein content of wild and cultured (fed winter flou nder. Age (days after hatching) Standard length (n- m) RNA (/igilarva) DI^JA (//g/ larva) Protein (^rg/ larva) Range Mean SD RNA DNA Cultured larvae'. 42 4 98-607 560 0 39 3,55r0.23 — 44: 1 — 6 27 6 89 6 50 20 919±0.75 199r006 99:10 4 61 :0.09 7 00 8 77 7 77 57 21 83 ±1.98 3 91 *0 70 200:15 5.62:052 43 5 26 6 35 5 76 30 3 35*0 61 082±013 44: 5 4 10:007 6 36 7 26 6 82 26 7 75*0 98 1 85:025 91 : 5 418:003 7 29 8 54 6 19 33 27 42:0 28 4 84*0 00 274: 5 5 67:0 06 50 4 10 6 54 601 55 5 32 •0 40 1 27 ■_ 0 08 49: 4 4.19:003 6 31 7 69 7 00 34 11 08:0.29 2 52 '0 02 115: 1 4.40:0.08 '7 50-8 67 8 83 56 32 82 ±2 83 6 1 9 ■ 0 69 370:37 5 31:0 14 58 5 79-6 91 S31 27 5 70^0 03 1 35:0 07 64- 1 4.23±0.20 6 67 8 35 7 27 47 14 33:1.03 3 18:008 153: 1 4.50:0.21 ^7 40 849 7 33 ,31 37 08 : 1 02 705:0 10 434^ 3 5.26:0 07 Wild larvae'' Group 1 7 29 7 45 7 34 09 19 05 4 19 212 4 55 II 5 80-6 71 641 53 — 248 131 — III 6 54 7 54 6 95 41 25.36±3.20 5 45:0.34 376:43 465±0.41 'Standard length data (or cultured larvae are means ' 1 SD for 50 to 150 larvae Chemical data are (or two replicates consisting of 10 larvae each except lor the largest size group on days 43. 50, and 58 when only 5 larvae were used per replicate ?ln this sample, 6 of the lO fish had metamorphosed ^In this sample, all ftsh had metamorphosed •"Data for Groups land II represenlvalues tor pools of three larvae each Data for Group III are means • i SD for five larvae analyzed individually END FEEDING YOLK-^AC INITIATION STAGE # FED C) STARVED Figure 2.— RNA-DNA ratios of starved and fed winter flounder larvae. Open circles indicate values for larvae transferred to filtered sea water on day 3 and diiy 28. Brackets indicate ^ 1 SD. "1 — r 2 1 \ r I I I '■'" n — \ — TT" 30 32 DAYS AFTER SPAWNING in the group, occurred 7 days after transfer to filtered seawater, accounting for the high DNA, RNA, and protein values observed on the final day of sampling (day 36). The RNA-DNA ratio of lar- vae transferred to filtered seawater decreased con- tinually until a 100'* mortality was observed. No significant change in the RNA-DNA ratio of fed larvae was obser-ved during the same period (Fig- ure 2). The DNA, RNA, and protein content of different size groups of wild and cultured larvae through metamorphosis is shown in Table 2. Discussion The DNA, RNA. and protein content of winter 706 flounder eggs reported in this study are total val- ues for the yolk plus the embryo. Any increase in the amount of a particular component must there- fore result from synthesis rather than transfer from the yolk to the embryo. The continual net accumulation of DNA from fertilization to hatch- ing is probably correlated with an increa.se in cell number (Regnault and Luquet 1974) although the content of DNA per cell may decrease (Neyfakh and Abramova 1974). The small increase in pro- tein content during the same period is evidence that protein is not an important energy source during early development in winter flounder. The 46'; decrease in protein content between the maximum .3 days prior to hatching and the minimum at initiation of feeding on day 7 indi- cates that protein is probably an important energy source during this period although this includes a 22'7f decrease in protein upon hatching, the major- ity of which may be lost with the chorion. Two periods of decrease in RNA content were observed. One occurred just prior to hatching; the other just prior to feeding initiation. No significant net de- crease in the DNA content of eggs or fed larvae was observed between any sampling periods. The decrease in protein and RNA content (Fig- ure 1) as well as the decrease in the RNA-DNA ratio (Figure 2) prior to feeding initiation resem- bles the pattern observed for starved larvae. Even in the presence of excess food the RNA-DNA ratio fell from 4.9 at the end of the yolk-sac stage to 3.0 at initiation of feeding on day 7. The critical im- portance of food availability at the initiation of feeding capability was demonstrated 2 days later when fed larvae contain almost lOO'^'i more RNA and 55'''f more protein than larvae held in filtered seawater. The RNA-DNA ratio was the most reliable and sensitive index of nutritional state evaluated in this study which included relationships between RNA, DNA, protein, standard length, and dry weight. RNA content was the most labile, decreas- ing within 2 days after removal of food. DNA con- tent was generally conserved except in the final stages of starvation prior to death. The protein- DNA ratio, which is an index of the amount of protein per cell, generally decreased as starvation progressed and the protem-RNA ratio generally increased. The RNA-DNA ratio was particularly useful as an indicator of condition since unlike other indices it fell within well-defined limits throughout most of the period studied. Winter flounder larvae established a mean RNA-DNA ratio of between 4.0 and 4.8 3 wk after initiation of feeding (Figure 2). This range is similar to the RNA-DNA ratio values reported by Bulow ( 1970) for golden shiners. The RNA-DNA ratio was not greatly affected by either the age or size of the larvae until metamorphosis when the RNA-DNA ratio increased to between 5.3 and 5.7 and re- mained at this level until the experiment was terminated on day 58 (Table 2). This is particu- larly important since the age of sea-caught larvae is difficult, if not impossible, to establish and a large size range is observed in larvae of the same age. This point was demonstrated on day 36 when a large mortality of smaller larvae resulted in an increase in the mean DNA. RNA, and protein con- tent of starved larvae. The RNA-DNA ratio, how- ever, was unaffected by the change in size dis- tribution and continued to decrease. Results from larvae transferred to filtered seawater 18 h prior to sampling and allowed to empty their stomachs (Table 1) indicate that the RNA-DNA ratio is not significantly affected by stomach contents at the time of sampling. The RNA-DNA ratios of winter flounder larvae captured in Narrow River fell within the range of values observed for fed winter flounder in the laboratory. The high RNA-DNA ratios indicated that the larvae were in good nutritional condition. This observation is supported by visual examina- tion of the larvae and the high growth and survi- val rates of laboratory-reared winter flounder held in situ in Narrow River with a semiopen environ- mental chamber (Laurence et al. 1979). Before measurements of RNA-DNA ratios are useful in the field, the effect of changing environ- mental conditions such as temperature, salinity, and possibly various pollutants as well as low prey concentrations and intermittent feeding should be evaluated. Although adult golden shiners, lar- val winter flounder, and larval cod, Gadiis morhua, (Buckley unpubl. datal showed a similar decline in RNA-DNA ratio when food is withheld, the response of other species should be deter- mined. .•\c k 111 1 \\ letlg mc n[ s I would like to thank G. C. Laurence and E Jackim for their critical review of the manuscript. Lit(.-r.iturc ( ituil BL.AXTEK, J. H .S 1971. Feeding and condition of Clyde herring lar vae. Rapp. P.-V. Reun. Cons. Int. Explor. Mer 160:128- 136. BLII.OW, F. J. 1970. RNA-DNA ratios as indicators of recent growth rate.s of a fish. J. Fish Res Board Can. 27:2343-2349. CERIOTTI. G. 1952 A microchemical determination of desoxyribonu- cleic acid. J. Biol. Chem. 198:297-303. DACfi, M. J., AND J. L. LlTTLEPAGE. 1972. Relationships between growth rate and RNA. DNA, protein and dry weight in Artenmi aalina and Euchaetu etoiigata. Mar Biol. iBerl i 17:162-170 EHRLICH, K. F 1974a. Chemical changes during growtli and starvation oi \aT\a\ Pleuronectes platessa. Mar. Biol. iBerl.i 24:39-48 1974b, Chemical changes during growth and starvation ol herring larvae. In J, H, S, Blaxterleditori, The early life history offish, p. 301-323. Springer- Verlag, Berl 707 EHRLICH. K. F, J. H. S, BLAXTER, AND R. PEMBERTON. 1976. Morphological and histological changes during the growth and starvation of herring and plaice larvae. Mar Biol. (Berl.) 35:105-118. HARTREE. E. F. 1972. Determination of protein: A modification of the Lowry method that gives a linear photometric re- sponse. Anal. Biochem. 48:422-427. HINEGARDNER. R. T. 1971. An improved fluorometnc assay for DNA. Anal. Biochem. 39:197-201. HOLM-HaNSEN, O., W. H. SUTCLIFFE, JR., AND J. SHARP, 1968. Measurement of deoxyribonucleic acid in the ocean and its ecological significance. Limnol. Oceanogr. 13:507-514. LAURENCE. G. C. 1975. Laboratory growth and metabolism of winter floun- der Pseudopleuronectes americanus from hatching through metamorphosis at three temperatures. Mar. Biol. (Berl.) 32:223-229. LAURENCE, G. C. T. A HALAVIK, B R. BURNS, AND A. S. SMIGIELSKI. 1979. An environmental chamber for monitoring "in situ" growth and survival of larval fishes. Trans. Am. Fish. Soc. 108:197-203. MUNRO, H. N., AND A FLP:CK. 1966. The determination of nucleic acids. Methods Biochem. Anal. 14:113-176. NEYFAKH, A. A., AND N. B. ABRAMOVA. 1974. Biochemical embryology of fishes. In M. Florkin and B. T. .ScheerieditorsI, Chemical zoology. Vol VIII, p 261-286. Acad. Press, N.Y. O'CONNELL, C. P. 1976. Histological criteria for diagnosing the starving condition in early post yolk sac larvae of the northern anchovy, Engraulis mordax Girard. J. Exp. Mar. Biol. Ecol. 25:285-312. REGNAULT, M., AND P. LUgUET. 1974. Study by evolution of nucleic acid content of pre- puberal growth in the shnmp Crangon vulgaris. Mar. Biol. (Berl.) 25:291-298. SMIGIELSKI, A. S. 1975. Hormonal-induced ovulation of the winter flounder, Pseudopteuronectes arnericanus. Fish. Bull., U.S. 73:431-438. SUTCLIFFE, W. H.. JR. 1965. Growth estimates from ribonucleic acid content in some small organisms. Limnol. Oceanogr. I0:R253- R258. 1970. Relationship between growth rate and ribonucleic acid concentration in some invertebrates. J. Fish. Res. Board Can 27:606-609. THEIL.ACKER, G. H. 1978. Effect of starvation on the histological and mor- phological characteristics of jack mackerel, Trachurus symmelncus. larvae. Fish. Bull., U.S. 76:403-414. L. J. BUCKLEY Northeast Fifihcries Center Narragansett Laboratory National Marine Fisheries Service, NOAA ft «. 7A.Box522A Narragansett. RI 02H82 EGGS AND EARLY LARVAE OF SMALLMOUTH FLOUNDER, lilROPi'S MICROSTOMUS Smallmouth flounder, Etrnpus microstomas (Gilll, ranging from early postlarvae to adult were de- .scribed and illustrated in detail by Richardson and Joseph (1973). Eggs and larvae through yolk-sac absorption had yet to be identified. During a 197.5-76 ichthyoplankton survey of Block Island Sound conducted by Marine Re- search, Inc. small unidentified planktonic fish eggs were taken. Through subsequent rearing of a number of these eggs and completion of a length series with larger, known larvae, we identified the specimens as E. microstomiis eggs. Our descrip- tions of eggs and yolk-sac larvae together with the work of Richardson and Joseph (1973) provide a complete developmental series for identification of this species. Methods Sampling was conducted in Block Island Sound at five stations along each of three transects run- ning from Charlestown and East Beach, R.I., to Block Island, a distance of approximately 14.8 km. Collections were made with 60 cm, 0.505 mm mesh, bongo nets. All tows were made obliquely, bottom to surface at approximately 2.5 kn for about 5 min. Digital flowmeters provided volume estimates and quantitative density estimates. Periodically, a 30 cm, 0.505 mm mesh, plankton net was fixed above the bongo net to collect sam- ples of live eggs. These were returned to the laboratory in aerated 4 1 thermos jugs and incu- bated at 20°-21° C. Etropus microstomas eggs and larvae were stored in 3-5'X buffered Formalin' solutions before examination. Descriptions of the Egg Etropas microstomas eggs (Figure 1, Table 1) are small, 0.561-0.740 mm in diameter (.f = 0.64) with a single small oil globule, 0.051-0.165 mm (.r = 0.12). The egg is spherical with a transparent, unsculptured chorion. The oil globule is also spherical. Occasonally two oil globules were noted or a single one with several surrounding oil parti- cles were found. This condition has commonly been noted for other species (Ahlstrom and Ball ■Reference to trade names does not imply endorsement by the National Marine Fisheries Service, NOAA. 708 nSHERY BULLETIN: VOL. 77. NO. 3, 1980. Figure l. — Etropus microstomus eggs; mean diameter = 0.64 mm: a) middle stage; b-dl development of pigmentation during late stage. Table i. -Egg, yolk, and oil globule diameters (millimeters) for Etropus microstomus eggs taken m Block Island Sound. 1975. Egg diameter Oil glob jle diameter Yollt diameter stage n Mean SD Range n' Mean SD Range n' Mean SD Ranqe Early Middle Late Total 449 261 111 821 0 64 0 65 0 65 0 64 0 02 0 02 0 03 0 02 0 59-0 73 0 59-0 71 0 56-0 74 0 56-0 74 435 257 102 794 0 12 0 11 0 11 0 12 0 01 001 0 02 0 02 0 08-0 17 0 05-0 13 0 08-0 1 5 0 05-0 17 111 239 103 453 0 52 0 55 0 56 0 54 003 0 03 0 05 0 04 0 43-0 59 0 49-0 61 049-069 0 43-0 69 'Discrepancies in sample sizes resulted from shattered oil globules and yolks which were not measured 1954; Smith and Fahay 1970; Berrien 1975) and is generally believed to result from shattering dur- ing collection or preservation. About 75% of the early stage eggs in our preserved samples also contained broken yolks which could not be accu- rately measured. To facilitate descriptions, eggs were separated into three stages following Ahlstrom and Ball (1954): early (.fertilization to 709 closure of the blastopore), middle (blastopore clo- sure to tail separation), and late (tail separation to hatching). Early Stage During this stage, eggs were distinguishable by measurement of egg and oil globule diameters. The yolk occupied about 81'7r of the egg diameter. It appeared translucent and yellow-to-amber in color with transmitted, incandescent light. With closure of the blastopore the embryo encompassed about half the circumference of the yolk. Middle St.igc Faint melanophores began to appear on the dor- sal surface of the embryo (F'igure la). They were widely spaced, appeared randomly distributed, and were easily overlooked at magnifications under 50 x. No pigment was noted on either the yolk or oil globule. Myomeres ( 12-22) became visi- ble but were difficult to count with any accuracy. The optic vesicles became clearly visible but lacked pigment. By the end of this stage the number of melanophores increased although they were still present only on the dorsum. In some eggs they began to appear more numerous just behind the head while a few developed on the occiput. As the tail developed free of the yolk material, traces of finfold became visible on the posterior edge of the embryo. Laif Stage Melanophores enlarged so they became clearly visible (Figure lb). Some developed along the sides and in some cases a few were noted on the yolk near the embryo. Melanophores along the dorsum commonly migrated into a more or less straight middorsal row extending from the nape to the tip of the tail. As the embryo developed, the portion of this line of pigment posterior to the vent migrated into the dorsal finfold while the lateral melanophores migrated into the ventral finfold (Figure Ic). As this occurred, little pigment re- mained on the trunk except for the anterior por- tion of the middorsal row. Numerous small dots persisted on the nape and dorsal surface of the head. Once melanophores had migrated into the finfold they began to coalesce into four distinct spots — two in the dorsal and two in the ventral finfolds; the dorsal pair aligned above the ventral pair. An additional group of melanophores aggre- gated ventrally near the tip of the notochord (Fig- ure Id). Much of this pigment spot appeared to be in the finfold but it was always in contact with the trunk and often extended upon it. Some of the small melanophores remaining on the anterior dorsum coalesced and moved into the dorsal finfold approximately midway between the vent and head. In some embryos a portion of the finfold melanophores became dendritic before they coalesced. The oil globule was located posteriorly in the yolk near the developing vent where it remained through hatching. In some advanced, late stage eggs, one or two melanophores formed on the sur- face of the oil globule. No additional pigmentation developed on the yolk. Shortly before hatching the embryo encircled the yolk with the tip of the tail almost reaching the snout. De^cnptKin ol Early Larvae Two recently hatched larvae measured 1.4 mm NL (notochord length! and were essentially identical to advanced late stage embryos. Three dark spots were present near the margin in the dorsal finfold, two near the margin in the ventral finfold, and one along the ventral body margin near the tip of the notochord. Small melanophores were scattered over the dorsum from the occiput to a point about halfway to the tip of the tail. The eyes remained unpigmented. The oil globule was located at the posterior edge of the yolk sac. By 2.0 mm NL (Figure 2a) no change in pig- mentation had occurred. The yolk was reduced in size by about 50'* and the gut and vent more clearly defined. Specimens 2.0 mm NL were obtained from preserved plankton samples where the finfold and its pigmentation were frequently lost. Between 2.1 and 2.3 mm NL (Figure 2b) the yolk sac was fully resorbed, eye pigmentation developed, and larvae developed many of the characteristics de- scribed by Richardson and Joseph ( 1973) for 2.3- 2.5 mm larvae. Melanophores developed along the ventral body margin from the gut to the pro- nounced spot near the tip of the notochord. As these melanophores developed, most or all of the pigmentation on the dorsum was lost. The distinc- tive markings in the dorsal and ventral finfolds of yolk-sac larvae remained with the exception of the posterior dorsal spot. This spot was either lost as the caudal band, described by Richardson and 710 Figure 2. — Etropus muro^tomus early larvae; a) 2.0 mm NL; bt 2.2 mm NL. Joseph, formed or the inelanophores migrated ventrally to form all or part of the band. The mid- caudal band was found in larvae as early as 2.1 mm in our collections; it was never observed in larvae still displaying the posterior dorsal finfold spot. The finfold markings appear to have been lost in the 2.5 mm SL (standard length) specimen illustrated by Richardson and Joseph due to finfold mutilation but do appear in their illustra- tions of 3.5 and 4.5 mm specimens. The smallest specimen containing pigmenta- tion on the gas bladder in our collections was 2.4 mm. Preopercular spines were first observed at about 2.3 mm. Gas bladder pigmentation and pre- opercular spines were described by Richardson and Joseph (1973) for their smallest specimen (2.5 mm). Occurrence Etropus microstonitis eggs were found in our Block Island Sound samples from 11 June until 10 September 1975; sampling was weekly through August, monthly thereafter. Samples taken again on 140ctober 1975did notcontain£. microstomus eggs. Surface water temperatures during this period ranged from a low of 15.3" C in June to a high of 22.3 C in early August. Larvae were taken from 9 July to 14 October 1975 at which time water temperatures were 15.6° C. In our weekly 1976 collections, eggs were taken beginning 1 June, larvae beginning 17 June. Both eggs and larvae were found regularly until 26 August when sampling ended. Surface water temperatures averaged 11.9° C on 1 June, 13.2° C on 17 June, and 20.0 C on 26 August. Similar Species Prior to formation of the distinctively pig- mented embryo in E. microstomus . some confu- sion may occur in separating similar stage eggs of the fourbeard rockling, Enchelyopus cimbnus; hakes, Urophycis spp.; and butterfish, Peprilus /nacanthiis. According to Scotton et al. ( 1973), E. cimbnus spawns from Nova Scotia to Block Island and Urophycis spp. spawn from Nova Scotia to South Carolina, depending upon the species. Pep- rilus triacanthus spawns from Nova Scotia (Scot- ton et al. 1973) to Chesapeake Bay (Peai-son 1941). We regularly collected eggs and larvae of these species in Block Island Sound at the same time that Etropus microstomus eggs were taken. Most early and middle stage E. microstomus eggs may be distinguished on the basis of their smaller egg and oil globule diameters. Although ranges over- lap to some extent (Table 2) mean values for egg and oil globule diameters are fairly distinctive. Only 2'Z of the 794 eggs we measured contained oil globule diameters 3=0.13 mm, the smallest oil 711 Table 2. — Egg and oil globule diameters (millimeters) as reported in the literature for species which might be confused with Etropus microstomus eggs. References represent only a portion of those available. Recent literature summaries may be found in Hardy (1978) and Martin and Drewry 1 1978). Species E99 Oil Source Enchelyopus cimbnus Urophycis chuss Urophycis regius Pepntus tnacdnthus 065075 0 740 89 (X = 0 82) 0 72-0 76 (X = 0 74) 0.62-0 97 (X = 0 76) 0 67-0 81 (X = 0 73) 0 69-0 80 (X = 0 75) 0 75-0 79 (X =0 77) 0 13-0 15 0 13-0,20 (i » 0 16) 0.15-0 17 0.15-0.22 (X = 0,19) 0,14-0,22 (X = 018) 0 14-0 22 (X = 0 18) 0 17-0 21 (X = 0 20) Battle (1929) Colton and Marak' Bigelow and Welsh (1925) Colton and Maral<' Barans and Barans (1972) Wheatland (1956) Colton and Honey (1963) 'Colton. J B.Jr.andR R Marak 1969 Guidefondentificationotthecommonplanklonicfisheggsandlarvaeof continental shelfwaters. Cape Sable to Block Island Bur Commer Fish Lab Rel 69-9. Woods Hole Biol Lab . 43 p. globule diameter reported for the other species. Once pigmentation appears on the embryo, dis- tinction is greatly facilitated. Enchelyopus cim- brius and Urophycis spp. are easily separated by their heavier and more numerous melanophores. Heavy mealonophores are always scattered on the yolk and oil globule of Urophycis spp. while E. cimbrius have pigmented oil globules and occa- sionally pigmented yolk. Peprilus triacanthus are somewhat more difficult to separate because, like Etropus microstomus they have fine melanophores located on the dorsum. However, this pigment generally forms two distinct rows from the eyes to the tail in P. triacanthus and does not migrate into the finfold as it does in E. microstomus. Eggs of Gulfstream flounder, Citharichthys arctifrons, may resemble E. microstomus eggs since the early larvae are quite similar (Richard- son and Joseph 1973). Diameters of unfertilized eggs given by Richardson and Joseph ranged from 0.70 to 0.82 mm (x = 0.74) which is considerably larger than E. microstomus. Presumably water hardening would increase this diameter even further. Acknowledgments We are grateful to Masahiro Dojiri for the illus- trations. Literature Cited AHLSTROM, E. H., .^ND O. P. B.^LL. 1954. Description of eggs and larvae of jack mackerel (rracAurussvmme^ncu.s land distribution and abundance of larvae in 1950 and 1951. U.S. Fish Wildl Serv, Fish. Bull, 56:209-245. Bara.njs, C. a., and a. C. Barans. 1972. Eggs and early larval stages of the spotted hake, Urophycis regius- Copeia 1972:188-190. Battle, h. i. 1929. Effects of extreme temperatures and salinities on the development oi Enchelyopus cimbrius (L.). Contrib Can. Biol. Fish.. New Ser, 5:109-192. Berrien, p. L. 1975. A description of Atlantic mackerel. Scomber scorn- brus. eggsand early larvae. Fish. Bull.. U.S. 73: 186-192. Bigelow, H. b., and W. W. Welsh. 1925. Fishes of the Gulf of Maine, Bull, U.S. Bur. Fish. 40(1). 567 p. (Doc. 965.) Colton, J. B.. Jr.. and K. A. Hon-ey. 1963. The eggs and larval stages of the butterfish. Poronotus triacanthus. Copeia 1963:447-450. Hardy. J. D. Jr. 1978. Development of fishes of the Mid-Atlantic Bight. An atlas of egg, larval, and juvenile stages. Vol. II. Anguil- lidae through Syngnathidae. U.S. Fish Wildl. Serv., Biol. Serv. Program, 458 p. M.-\RTiN, F. D.. AND G. E. Drewry. 1978. Development of fishes of the Mid-Atlantic Bight. An atlas of egg, larval, and juvenile stages. Vol. VI. Stromateidae through Ogcocephalidae. U.S. Fish Wildl. Serv.. Biol. Serv. Program, 416 p PEARSON. J. C. 1941. The young of some marine fishes taken in lower Chesapeake Bay, Virginia, with special reference to the gray sea trout. Cynoscion regalis (Bloch). U.S. Fish Wildl. Serv.. Fish. Bull, 50:79-102. Richardson. S. L.. and E. B. Joseph. 1973. Larvae and young of western north Atlantic bothid flatfishes Etropus microstomus and Citharichthys arcti- frons in the Chesapeake Bight. Fish, Bull., U.S. 71:735-767. Scotton. L. N., R. E. S.mith. N. S. S.mith. K. S. Price, and D. p. DE SYLVA 1973. Pictoral guide to the fish larvae of Delaware Bay with information and bibliographies useful for the study of fish larvae. Delaware Bay Rep. Ser. 7. Coll. Mar. Stud.Univ, Del. 206 p. Smith, w. g,. and m, p, Fahay. 1970. Description of eggs and larvae of the summer floun- der, Paralichthys dentatus. U.S. Fish Wildl. Serv.. Res. Rep. 75.21 p. WHE.-\TLAND, S. B. 1956. Oceanography of Long Island Sound. 1952-1954. VII. Pelagic fish eggs and larvae. Bull. Bingham Oceanogr. Collect., Yale Univ. 15:234-314. Michael D. Scherer Donald W. Bourne Marine Research. Inc. 141 Falmouth Heights Roatl Falmouth. MA 02.^40 712 EVIDENCE OF POSTCAPTURE INGESTION BY MIDWATER FISHES IN TRAWL NETS The ingestion of food items by midwater fishes in trawl nets, if it occurs at appreciable levels, may pose serious bias problems for dietary studies based on stomach content analyses. In a recent discussion of "net feeding," Hopkins and Baird (1977) reviewed the available evidence and found that while it may occur to some degree, net feeding is probably not extensive. In an earlier field study, Hopkins and Baird ( 1975) used side-by-side nets that provided captured fishes with different levels of exposure to captured zooplankton. On one side the fish were allowed to enter the cod end of the net and mingle with the zooplankton concentrated there. In the adjacent net fishes were excluded from the cod end by an 11 mm mesh bag at its mouth. Their results from 19 intraspecific com- parisons of 700 myctophid and gonostomatid fishes showed little significant data that indicated net feeding. All of the evidence to date, both for and against postcapture ingestion, has been indirect. This is because there was no sure way to determine whether a food item had been ingested in the net. The following study was conducted in order to provide a more direct investigation of stomach content contamination. Methods Experiments were conducted by introducing bogus food items into the cod end of a net before launching it, and then examining the stomach contents of captured fishes after recovery. Eleven such hauls were made with Tucker-type midwater trawls in deep water off southern California (Ta- ble 1). The nets had a main scoop of 6 mm nylon mesh and a rear section of 0.333 mm plankton netting. The 9 m^ net utilized an enclosed, bag- type cod end (Baker et al. 1973) on two hauls ( 10, 11) and a rigid closing cod end (Childress et al. 1978) on three hauls (7, 8, 9). Both of these cod ends are of the flow- through variety and allow the passage of water out the rear. The 2.3 m^ net had a rigid, nonclosing, 3.7 1 plastic jug cod end that restricted flow. Prior to launching the trawl, approximately 100 ml (or about 3,000 pieces) of artificial prey were placed in the cod end. In all cases, the amount of bogus prey introduced was much less than the eventual catch of similarly sized zooplankton in Table l. — Trawling data for the ingestion experiments at Santa Barbara (SB) and San Clemente (SC) Basins, and off Guadalupe Island (GI), Calif. Date 1977 Mouth opening Day/ Location (m^) night Depth (m) Duration (min) 1 Apr 12 SB 23 N 0-190 60 2 12 SB 2.3 N 0-130 50 3 13 SB 23 N 0-150 50 4 13 SB 2.3 D 0-500 95 5 14 SB 2,3 D 0-400 100 6 14 SB 23 D 0-590 145 7 Feb. 22 SC 9 D 0-425 80 8 22 sc 9 Evening 483-891 180 9 24 SC 9 D 526-634 165 10 Aug, 10 Gi 9 D 450-480 90 11 13 G( 9 N 0-150 135 the cod end. The material consisted of rubber band fragments and bits of filter paper, between 2 and 15 mm in greatest dimension. Their individual volumes ranged between 0.5 and 60 mm^, which falls within the size range of natural prey items. Upon recovery, the cod end samples were pre- served initially in 10% formaldehyde then trans- ferred to 50% isopropanol. In the laboratory, fish stomachs were removed from the body cavity be- fore being opened for examination. Only material from intact stomachs was counted, material found in the mouth and esophagus was not recorded. Data from haul 23 are biased toward larger indi- viduals because the smallest specimens in the catch were not examined. Percent net feeding rep- resents the relative number of individuals of any species which had ingested at least one bogus prey item. It is necessarily a conservative representa- tion because zooplankton from the cod end may also have been ingested after capture but could not be distinguished from naturally ingested prey. Results A total of 1,211 specimens were examined, rep- resenting 15 midwater fish species. Fifty-nine in- dividuals (5% of the total) from 10 species were found with artificial prey in their stomachs (Table 2). Most of the bogus prey ingested (92%) were small (0.5-6 mm'*) and only four fish had swal- lowed artificial items >12 mm^. Generally, the average number per stomach was low ( Table 2 ) but a few fish had their stomachs packed with arti- ficial prey. Only 5 of the 59 fishes containing bogus prey had stomachs which were otherwise empty; all others also contained zooplankton, some por- tion of which may have been ingested in the cod end. Notable differences in net feeding occurred both interspecifically and intraspecifically. The two nSHERY BULLETIN; VOL. 77, NO, 3, 1980, 713 Table 2. — Occurrence of bogus prey items in the stomachs of midwaterfishes. Sizes are standard lengths in miUimeters. No. of Fish that net fed ':„ net fed Species fish (range) Number Percent lulean size bogus prey night'day Balhylagus weselhi 35 50(27-84) 0 _ _ — Leuroglossus stilbius ■ 20 60(45-100) 1 50 100 10 0/100 Cyclolhone acclinidens 64 45(26-57) 1 16 56 1 0 — C signata 89 20(17-38) 0 — — — — Poromitra crassiceps 6 44(34-75) 1 167 75 30 — Scopelogadus m bispinosus 13 55(43-69) 0 — — — — Lampanyctus ritten 14 77(39-100) 7 500 68 38 0/50 L regalis 15 42(35-53) 0 — — — — Parvilux ingens 11 71(35-172) 0 — — — — Stenobrac^tius leucopsarus 138 52(24-82) 32 23 2 61 23 5/47 Symbolophofus califormensis 6 48(30-62) 2 33 3 60 35 0.'67 Tnphoturus mexicanus 742 56(19-67) 11 15 50 12 12 Ceratoscopelus townsendi 22 42(33-48) 2 9 1 44 195 0 100 Sternoptyx diaphana 20 29(14-37) 1 50 37 10 Idtacanlhus aniroslomus 16 175(63-318) 1 63 231 10 0/25 Total 1.211 59 Table 3. — Haul by haul comparisons of postcapture ingestion by Stenohrachius leucopsarus. Measurements are standard lengths in millimeters. N ighttime hauls Daytime hauls Item 1 2 4 5 6 Number of fish examined 48 25 21 26 13 fi/lean size (range) 46(26-68) 50(30-81) 60(32-79) 53(34-70) 51(36-69) Number net fed 3 1 12 10 6 Percent net fed 6,3 40 57.1 38-5 462 fwlean size net fed 54 59 64 59 60 Number ol fish -51 mm 23 15 19 17 11 Percent fish '51 mm net fed 130 67 63.2 58.8 54.5 f^ean number bogus prey/stomach 1 3 1 0 20 3.4 1.7 Number of fish net led/hour 3.0 1-25 7.5 5.9 2.5 most abundant fishes in the collection, myctophids Stenohrachius leucopsarus and Tnphoturus mexicanus, showed a large difference in the per- centage of individuals which had ingested the bogus prey items (23.2% vs. 1.5% respectively). In 8 of the 10 species that showed net feeding, larger-than-average individuals were more likely to contain artificial prey than smaller ones. A haul by haul comparison of data on S. leucop- sarus (Table 3) shows a greater degree of net feed- ing in daytime hauls than at night; although the average size of specimens in nighttime hauls is smaller (/-test,P<0.001). If we consider only those specimens which were equal to or larger than the smallest individual found with bogus prey in its stomach (51 mm), the trend for greater daytime net feeding still, holds. All other species also showed a higher incidence of daytime net feeding (Table 2). Discussion The ingestion of bogus prey items by midwater fishes is direct evidence that the contamination of stomach contents can and does occur in the cod ends of midwater trawls. The degree to which it occurs, and thus the seriousness of the bias im- 714 parted to dietary studies, is apparently variable. Within a collection of midwater fishes, our data and that of Hopkins and Baird (1975, 1977) indi- cate that overall the bias may be low. However, the data from the present study showed that im- portant levels of contamination can occur within some species. Hopkins and Baird (1975) based their low estimates of net feeding on intraspecific comparisons of their paired net data. The same data, when e.xamined interspecifically, reveals that in 14 of 19 comparisons (700 fish from 11 species), fishes prevented from reaching the cod end had a lower average number of prey items in their stomachs than fishes which had entered the cod end. The probability of finding no difference in the number of prey items between these samples (i.e., no net feeding) is <10% (Wilcoxon matched pair signed rank test); thus their data indicating net feeding is significant to at least the 90% level of confidence. Several factors may be responsible for the ob- served variations in degree of net feeding. The condition and viability of captured fishes is cer- tainly a key factor; hardy species such as S. leucopsarus and Symbolophorus califormensis commonly survive capture and arrive at the sur- face alive and active. The survival of other fishes (e.g., T. mexicaniis, Cyclothone acclinidens, C. sig- nata, Sternoptyx diaphana) is usually quite low. Obviously a dead fish cannot swallow cod end material while a stressed but living fish may. The survival factor may have caused some of the dif- ferences between our results and those of Hopkins and Baird ( 1975); off California the survival rate of trawled specimens is relatively high (Childress et al. 1978) while in the Gulf of Mexico it is very low (T. L. Hopkins and R. C. Baird, pers. com- mun.). Survival rate is probably influenced by haul duration, the depth and temperature range sampled, cod end design, and net construction. It is also apparent that specimen size can influence the degree of net feeding. It is not clear whether this is due to the greater survival rate of larger individuals or to their larger mouth size. Within the limits of survival rate and size vari- ables, the degree of exposure to prey in the cod end is a function of haul duration, the depth strata sampled, and the amount of time a fish spends in the cod end. Discrete-depth hauls probably de- crease the degree of exposure by limiting the number and diversity of prey items while oblique hauls increase exposure. The data also indicate that small prey aire more readily ingested in cod ends than large prey. Accordingly, the bias im- parted to stomach content analyses by net feeding would be toward the smaller prey items. Postcapture ingestion is a complex problem and no clear-cut conclusions can be drawn from the available data except that it occurs to a varying degree and that the extent of its occurrence is subject to fish survival, fish size, and exposure. To gain a predictive capability it will be necessary to investigate these factors further. Acknowledgments We thank J. L. Cox, J. J. Childress, L. B. Quetin, J. J. Torres, and D. K. Vaughan for tlieir help at sea and in the laboratory. We are grateful to T. L. Hopkins and R. C. Baird for their reviews of the manuscript. The research was supported in part by NSF grants OCE76-02251. OCE78-09018, and OCE76-10407-1. Preliminary and experimental studies were conducted aboard the research ves- sels A/p/jo Helix. VeleroIV, andEllen B. Scripps. Literature Cited Baker. A. Dec. m. r. Clarke, and M, J. H.arris 1973. The N.I.O. combination net (RMT 1 + 8) and further developments of rectangular midwater trawls. J, Mar, Biol, Assoc. U.K, 53:167-184, Childress, J, J,, A, T, Barnes, L. B. Quentin. and B, H, ROBISON, 1978, Thermally protecting cod ends for the recovery of living deep-sea animals, Deep-Sea Res. 25:419-422, Hopkins, T, L,, and R, C, Baird, 1975, Net feeding in mesopelagic fishes. Fish Bull,, U,S, 73:908-914, 1977, Aspects of the feeding ecology of oceanic midwater fishes. In N, R. Anderson and B, J, Zahuranec (editors). Oceanic sound scattering prediction, p, 325-360, Plenum Press. N.Y, Thomas M, Lancraft Bruce H. Robison Marine Science Institute Uniuersity ofCalifornia Santa Barbara. CA 93106 INHIBITORY EFFECT OF THE ALGA PAVLOVA LVTHERIl ON GROWTH OF MUSSEL, MYTILVS EDVLIS. LARVAE The culture of bivalve larvae sometimes appears to be more of an art than a science. Many factors can influence the growth and survival of larvae and it is usually difficult to assign a cause to the failure of a particular culture. In one instance we had set up a large experiment with mussel, Mytilus edulis. lai-vae and noticed after 5-8 days that the larvae had ceased to grow in all of our treatments but that they remained alive and ac- tive. During this experiment one factor was known to have been changed: Previously we had been feeding the larvae a mixture of the algae Isochrysis galbana and Pavlova lutherii. while in this experiment only P. lutherii was available. There has been one account in the literature (Fretter and Montgomery 1968) of P. lutherii being toxic; yet Bayne (1965) found P. lutherii to support normal growth in A/, edulis larvae. Davis and Guillard ( 1958) found P. lutherii to be as good as I. galbana (and about as good as a mixture of the two) when fed to larvae of Crassostrea vir- giiiiea and Mercenaria mercenaria . The results of Wilson (1978) show thatP, lutherii is as satisfac- tory as other algae as food forOstrea edulis larvae. In order to determine whether our P. lutherii cul- tures were to blame for the lack of growth we observed, we set up an experiment to compare the growth of mussel larvae when fed several diets of algae. fishery bulletin, vol, 77. NO. 3, 1980. 715 While testing the species of algae, we decided to include different food levels. If P. lutherii were toxic, then its effects may increase with concentra- tion of the algae given to the larvae. Another source of toxic substances could be the algal metabolites which accumulate in the algal cul- tures. In order to test this, we used two different sources of P. lutherii, a young culture and an old one. Bayne (1965) had observed a slightly better growth of M, edulis larvae when fed P. lutherii from a 4-day-old culture compared with those fed a 13-day-old culture. Methods Adult mussels were stimulated to spawn by raising the water temperature from an ambient of 15° C to 22°-24° C. The eggs and sperm from five females and seven males were pooled to give a heterogeneous population of larvae. After 2 days the larvae were placed in the various treatment combinations. In the experiment there were five combinations of algae: a) Isochrysis galbana alone; b) /. galbana plus Thalassiosira pseudo- nana (added after 1 wk); c) /. galbana and P. lutherii throughout, plus T. pseudonana after 1 wk; d) a young culture of P. lutherii harvested 4-7 days after innoculation, and e) an old cul- ture of P. lutherii harvested 14-20 days after in- noculation. In the mixed algae treatments the two or three species were added in equal pro- portion by cell number. There were three feeding protocols used. Cell concentrations were increased gradually over the first week of growth, and although the cell con- centrations changed in each protocol they will be referred to as "levels" here for simplicity. The food levels used were: 1 ) 10,000 cells/ml throughout the experiment; 2) 10.000 cells/ml from day 2 today 4, 15,000 cells/ml from day 4 to day 6, and 20,000 cells/ml for the rest of the experiment; and 3) .50,000 cells/ml from day 2 to day 4, 100,000 cells/ ml from day 4 to day 6, and 500,000 cells/ml for the rest of the experiment. Table L — Analysis of variance on size of My til us I'diilis larvae as related to food treatment. Analysis performed on mean larval length for 6 replicates per treatment combination Source of variation Mean square Food level Food type Food level ■ food type Residual 2,477 2 5,952 9 307 1 100-3 24 7-- 59.35-' 3 06-- There were 6 replications in 1 1 beakers at each of the food type-food level combinations. All beak- ers were held at 15° C. The initial density of the larvae at day 2 was 20 larvae/ml. All beakers were sampled when the larvae were 16 days old and up to 10 larvae were measured from each beaker. Results The main source of variation in the larval lengths at day 16 was due to the food type, with a smaller but significant portion attributable to the food level and the interaction of these two effects (Table 1). The largest source of variation among the types of food was the difference between the larvae fed only P. lutherii and those fed the other food types (Figure 1). There was slightly better growth with the young P. lutherii as food at the 200- z o u u i z o z 180 1 60 140 120 I I I FOOD LEVEL ■•P-0 01, FlOURE 1,— Mean size of mussel larvae at 16 days when grown at three different algal food levels and on five combinations of algal types: a) Isochrysis galbana only; b)/, galbana and Thalassiosira pseudonana; c) /, galbana, T. pseudonana, and Pavlova lutheni; d) young P, /u(/i(?ni:ande)old P lulheni. Means are based on 10 animals from each of 6 replicates at each of the treatment combi- nations. See text for description of food levels used. 716 lowest food level compared with the old culture. The interaction of food level and food type was probably in large part due to food type b (/. gal- bana and T. pseudonana), which gave the best grow^th at food level 1 but poor growth at food level 3. The effect of the food level was to produce higher growth rates at the lower food concentrations. This occurred for all fivefood types (Figure 1). Discussion Contrary to published reports on various bivalve larvae (Guillard 1959; Bayne 1965; Wil- son 1978), we have observed poor growth of M. edulis larvae when fed only P. lutherii. This was true at all three food levels tested and whether the P. lutherii culture was young or old. There was no apparent inhibitory effect by the P. lutherii on larval growth when fed in combination with the other two algal species. It would appear that the suppression of growth of the larvae when fed only P. lutherii was the result of a dietary deficiency. If it were due to toxins in the algal cells, one would expect to see a greater suppression of the growth rate in the larvae at food level 3 when P. lutherii was combined with the other algal species. If the inhibitory effect of P. lutherii were pri- marily due to the accumulation of metabolites in the medium, there should be a more consistent difference between the P. lutherii cultures of dif- ferent age. In fact, there was only a small differ- ence at food level 1. This may indicate that there is some effect of metabolites which were in low enough concentration in the young culture to be diluted at food level 1 but not at the other food levels. Nevertheless, it appears that the main ef- fect of P. lutherii is or is equivalent to a dietary deficiency. This could be due to the biochemical compostion of the algal cells such that they are not digested, lack of some essential nutrient, or are not even ingested. The cells are not much bigger thanl.galbana, especially when fast growing, and there was no evidence of clumping of the cells into large aggregates. There is some evidence in the data presented by Davis and Guillard (1958) and Bayne (1965) of a suppression of larval growth at high concentration ofP. lutherii. But to our knowledge there are no reports of suppression of growth in bivalve larvae at lower concentration of P. lutherii. This algae has been reported as producing substances toxic to four species of prosobranch larvae (Fretter and Montgomery 1968). Apparently, a toxic substance is emitted by the algae, which accumulates in the algal culture. The results of the different food levels are not new (Davis and Guillard 1958; Bayne 1965; Rhodes and Landers 1973). The purpose of using different food levels in this experiment was to look for interaction with food type. At this point we can only speculate as to the reasons for the lack of growth of larvae fed P. lutherii. We would not want to generalize and say that all P. lutherii could produce the same results. Obviously others have obtained good results with their cultures. (All our algal cultures are grown in the f/2 medium of Guillard (McLachlan 1973), which is commonly used in growing algae for shellfish culture.) One explanation would be that we have inadvertently developed through genetic change a strain of P. lutherii which is of inferior quality. Fretter and Montgomery (1968) have suggested that bacteria can metabolize the toxic substance produced by P. lutherii and render the algae culture harmless to bivalve larvae. Perhaps the absence of bacteria in our P. lutherii cultures, or at least the appropriate bacteria, would explain the discrepancy between our results and others. Unfortunately, we did not check the algal cultures for the presence of bacteria. The importance of our observations with P. lutherii need to be assessed by other workers. The culture conditions of algae will vary from lab to lab and could easily have an influence on the growth of bivalve larvae. Literature Cited B.^YNE, B. L. 1965. Growth and the delay of metamorphosis of the lar- vae of Mytilus eduhs (L.). Ophelia 2:1-47. Davis, H. C, and r. r. guillard 1958. Relative value of ten genera of micro-organisms as food for oyster and clam larvae. U.S. Fish. Wildl. Serv., Fish. Bull. 58:293-304. Fretter. v., and M. C. Mo.ntgo.mery. 1968. The treatment of food by prosobranch veligers. J. Mar. Biol. Assoc. U.K. 48:499-520. Guillard. R. R. L. 1959. Further evidence of the destruction of bivalve larvae by bacteria. Biol. Bull. (Woods Hole) 117:258-266. McLachlan, J. 1973. Growth media — marine. In J. R. .Stein leditor), Handbook of phycological methods, culture methods and grovrth measurements, p. 24-51. Camb. Univ. Press, N.Y. Rhodes, E. W., and W. S. Landers. 1973, Growth of oyster larvae, Crassostrea virginica, of various sizes in different concentrations of the chry- 717 aophyte. Isuihrysisgiilhaiu: Proc. Natl Shellfish. Assoc. 63:53-59. WILSON, J. H. 1978. The food value of Phaeodactylum tricornutum Bohlin to the larvae ofOsIrm edulis L. and Crtissiislreu gtgas Thunberg. Aquaculture 13:313-323. G. F. NEWKIKK D. L. WAI'CH Bliilogy Department Dalhousif I'nirersity Halifax. N.S., Canada B3H 4J1 718 NOTICES NOAA Technical Reports NMFS published during the first 6 mo of 1979. Circulars 419. Marine flora and fauna of the northeastern United States. Protozoa: Sarcodina: Amoebea. By Eugene C. Bovee and Thomas K. Sawyer. January 1979, iii + 56 p., 77 fig. For sale by the Superintendent of Docu- ments, U.S. Government Printing Office, Washington, DC 20402 - Stock No. 003-017-00433-3. 420. Preliminary keys to otoliths of some adult fishes of the Gulf of Alaska, Bering Sea, and Beaufort Sea. By James E. Morrow. February 1979, iii -i- 32 p., 11 plates. 421. Larval development of shallow water barnacles of the Carolinas iCirripedia: Thoracica) with keys to naupliar stages. By William H. Lang. February 1979, iv + 39 p.. 36 fig., 17 tables. 422. A revision of the catsharks, family Scyliorhinidae. By Stewart Springer. April 1979, v + 152 p., 97 fig., 4 tables. For sale by the Superintendent of Documents, U.S. Government Printing Office, Washington, DC 20402 - Stock No. 003-020-00147-5. 423. Marine flora and fauna of the northeastern United States. Crustacea: Cumacea. By Les Watling. April 1979, iii -F 23 p., 35 fig., 1 table. For sale by the Superintendent of Documents, U.S. Government Printing Office, Washington. DC 20402 - Stock No. 003-017-00446-5. Sptci.il Scientific Report — Fisheries 727. Expendable bathythermograph observations from the NMFS/MARAD Ship of Opportunity Pro- gram for 1975. By Steven K. Cook, Barclay P. Collins, and Christine S. Carty. January 1979, v + 93 p., 2 fig., 13 tables, 82 app. fig. 728. Vertical sections of semimonthly mean tempera- ture on the San Francisco-Honolulu route: from ex- pendable bathythermograph observations, June 1966-December 1974. By J. F. T. Saur, L. E. Eber, D. R. McLain, and C. E. Dorman. January 1979, iii -(- 35 p., 4 fig., 1 table, 2 app. For sale by the Superintendent of Documents, U.S. Government Printing Office, Washington, DC 20402 - Stock No. 003-017-00438-4. 729. References for the identification of marine inver- tebrates on the southern Atlantic coast of the United States. By Richard E. Dowds. April 1979, iv + 37 p. For sale by the Superintendent of Documents, U.S. Government Printing Office, Washington, DC 20402 - Stock No. 003-017-00454-6. 730. Surface circulation in the northwestern Gulf of Mexico as deduced from drift bottles. By Robert F. Temple and John A. Martin. May 1979. iii + 13 p., 8 fig., 4 tables. For sale by the Superintendent of Docu- ments, U.S. Government Printing Office, Washington, DC 20402 - Stock No. 003-017-00456-2. 731. Annotated bibliography and subject index on the shortnose sturgeon, Acipenser brevirostrum. By James G. Hoff. April 1979, iii -i- 16 p. For sale by the Superintendent of Documents, U.S. Government Printing Office, Washington, DC 20402 - Stock No. 003-017-00452-0. 732. Assessement of the Northwest Atlantic mackerel. Scomber scombrus. stock. By Emory D. Anderson. April 1979, iv + 13 p., 9 fig., 15 tables. For sale by the Superintendent of Documents, U.S. Government Printing Office, Washington, DC 20402 - Stock No. 003-017-00450-3. 733. Possible management procedures for increasing production of sockeye salmon smolts in the Naknek River system, Bristol Bay, Alaska. By Robert J. Ellis and William J. McNeil. April 1979, iii + 9 p., 4 fig., 11 tables. For sale by the Superintendent of Documents, U.S. Government Printing Office, Washington, DC 20402 - Stock No. 003-017-00451-1. 734. Escape of king crab, Paralithodes camtschatica, from derelict pots. By William L. High and Donald D. Worlund. May 1979, iii -i- 11 p.. 5 fig., 6 tables. Most NOAA publications are available by purchase from the Superintendent of Documents, U.S. Government Printing Office, Washington. DC 20402. Individual copies of NOAA Technical Reports (in limited numbers) are available free to Federal and State government agencies and may be obtained by writing to User Services Branch lirs not shown). Scales = 1 mm. the tip of the ventral costa, and the latter ends distally in a spine similar to, but shorter than, that of P. eduardoi. The proximal process of the rib of the dorsolateral lobule is subcircular in P. challengeri like that in P. eduardoi and P. rec- tacuta, but different from the transversely oval one in P. balssi. In females of P. challengeri the plate of stemite XIV is produced in paired, broad anterior lobes, is raised ventrally in a pair of lon- gitudinal, submesial elevations, and bears a sub- rectangular posteromedian protuberance some- times continuing anteriorly as a weak, depressed ridge. In the other species the plate, if produced, forms only small anterior lobes, is flat or (in P. balssi) raised in lateral, rather than submesial. 732 PEREZ FARE ANTE; REVISION OF PENAEID SHRIMP GENUS PENAEOPSIS elevations, and the posteromedian protuberance is caudally pedunculate in P. eduardoi (in the other species a strong median ridge instead of a protuberance is usually present). Finally, in P. challengeri the median plate of sternite XIII is subpentagonal instead of semicircular or cor- diform and exhibits a central depression which continues anteriorly as a median groove. Remarks. -As Perez Farfante {1977b) pointed out. Bate (1888) illustrated the petasma of a male of his Penaeus serratus (= Penaeopsis challengeri] that actually belongs to a different species, Penaeopsis eduardoi. This male together with nine females and at least one other male were taken of Matuku, Fiji Islands, at Challenger stn 173. Five of these females were identified by Bate as Penaeus rectacutus [they are actually, at least the three that are now in the BMNH, Penaeopsis eduardoi ], the other four females are syntypes of his Penaeus serratus. and the male must be as- sumed to be a member of the syntypic series. It is beyond question that the male depicted by Bate as P. serratus is a specimen of Penaeopsis eduar- doi: the dorsomedian projections of the petasma are obsolete and each ventral costa is produced in a long spine extending considerably farther dis- todorsally than that in Penaeus serratus. The probability that Bate also examined the syntypic second male (which is P. serratus, 65 mm tl) is indicated by his statement "Length ... of the largest male 76 mm"; this clearly indicates that he had at least one other male in addition to the "largest" one. The smaller male was in the jar with the three females of "Penaeus rectacutus" [= Penaeopsis eduardoi], but Bate mentioned no male of this species whereas he referred to males o{ Penaeus serratus; consequently, it seems most likely that the small male P. serratus was mistak- ingly placed with the three females of the former species. In regard to the number of male speci- mens recognized by Bate as "Penaeus serratus," it should be mentioned that Alcock and Anderson (1899) stated that "there are two Challenger specimens [of P. serratus] from Fiji in the Indian Museum" and it is possible that one of them is a male that was examined by Bate. Inasmuch as the type-material of P. serratus Bate included a second species, Penaeopsis eduardoi, and a holotype was not designated, it is desirable to select one specimen as the lectotype to associate the name with the species to which it is applied. Although Bate (1888:269) mentioned the "type" oi Penaeus serratus, there is no indica- tion as to which specimen he was referring; how- ever, he stated that some specimens taken off the Fiji Islands "were placed under Penaeus rec- tacutus because the thelycum corresponds with that species rather than with the type of this [Penaeus serratus]." His statement leaves no doubt that it was a female to which he was refer- ring. Because the first specimen specifically cited by him (p. 268) was the "largest female, 114 mm" [24 mm cl], I have selected it as the lectotype of Penaeus serratus Bate 1881. This specimen has been assigned BMNH 1978.323. The very young specimen (a female) taken in the Torres Strait, at Challenger stn 184, which Bate (1888) recorded as "Penaeus serratus," is ac- tually a member of the genus Metapenaeopsis, M. sinuosa Dall 1957, or a closely related species. In the last 45 yr various authors (Burkenroad 1934a; Kubo 1949; Ivanov and Hassan 1976) have pointed out the difficulty in defining the specific characters oi"Penaeus serratus." The uncertainty was due to Bate's (1881) imprecise original diag- nosis and the inadequate, although rather elabo- rate, description, accompanied by figures lacking detail (e.g., a sketchy one of the thelycum and in- complete representations of the telson which is depicted as lacking movable spines), that was subsequently presented by him (1888). I have studied part of the type-series and offer a new description and illustrations of those specimens, including the only available description of the petasma. Penaeopsis challengeri, like all of its congeners except P. rectacuta and P. jerryi, possesses only two pairs of movable spines on the telson. This character was noted by Bate (1888); however, in discussing the relationships of P. eduardoi with other members of Penaeopsis, I (1977b) errone- ously stated that P. challengeri exhibits three pairs of movable telsonic spines. The specimens examined by me at the time were the four female syntypes in only one of which the telson is entire, but it had been bent and torn in such a way that its sharp edge projected laterally in what ap- peared to be a pair of minute movable spines. My confirmation of Bate's observation on the spina- tion of the telson has been based on a reexamina- tion of the just mentioned female, and a study of the male which, although caught together with the four female syntypes of "Penaeus serratus," was not explicitly cited by him. Alcock and Anderson (1899) concluded that "P. 733 FISHERY BULLETIN: VOL. 77, NO. 4 serratus" [= P. challengeri] lacks an epipod on so- mite XII (third pereopod), whereas P. rectacuta has one. This observation is in error; not only both of these species possess such an epipod, but also its presence is typical of all members of the genus. Penaeopsts eduardoi Perez Farfante 1977 Figures 6, 11-14 Penaeus rectacutus. Bate 1888:266 [part], pi. 36, fig. 2z. ? Villaluz and Arriola 1938:38, pi. 3, fig. 3. Penaeus serratus. Bate 1888:268 [part], pi. 37, fig. 1", Iq. Parapenaeus rectacutus. De Man 1911:82; 1913, pi. 8, fig. 26a-c. Yokoya 1933:9. Penaeopsis rectactus. Kubo 1949:322. fig. IH; 8J; 19C; 23A-B; 36K-L; 47J; 58P; 76A, F; 78K; 118 A-E, [?F], G; 119. Penaeopsis challengeri. De Man 1911:76 [part, 9 from Siboga-Expedition stn 253]. Ivanov and Hassan 1976:4. Penaeopsis rectacutus. Burukovsky 1974:31, fig. 37a-c. Penaeopsis eduardoi Perez Farfante 1977b: 172, fig. 1-4 [holotype, V, USNM 168298; type- locality, Balayan Bay, Luzon I., Philippines, 13°41 '00" N, 120°47 '05" E, 366 m. Albatross stn 5116]. Perez Farfante 1979:208. Not Penaeus rectacutus Bate 1881, or Penaeus serratus Bate 1881, or Penaeopsis challengeri DeMan 1911. Material. — For list of records see Perez Farfante 1977b. Additional records are: PHILIPPINES— 1^ .USNM, WofCaboEngano, N Luzon, 410 m, 12 November 1908, Albatross stn 5325. 3$, USNM, W of San Fernando Pt, Luzon, 315 m, 10 May 1909, Albatross stn 5440. 9.5 8 V , USNM, Balayan Bay, Luzon, 366 m, 20 January 1908, Albatross stn 5116. 19, VNIRO, Burias Pass, Sibuyan Sea, 400 m, 1 June 1973, Lira haul 71. Ic5, USNM, off Calapan, Mindoro I, 198 m, 2 February 1908, Albatross stn 5121. 26 19, USNM, Macajalar Bay, Mindanao, 479 m, 5 August 1909, Albatross stn 5506. INDONESIA— 19, USNM, off Tanakeke I, Flores Sea, 386 m, 21 December 1909, Albatross stn 5662. 1 9 , VNIRO, S of Roti I, Timor Sea, 400 m, 1 June 1973, Lira, O. A. Petrov. Ic5 29, VNIRO, S of Timor I, Timor Sea, 320-355 m, 5 May 1973, Lira, 0. A. Petrov. Diagnosis. — Rostrum straight or sinuous, and long, reaching or overreaching third antennular article. Anteroventral angle of carapace broadly obtuse. Telson with two pairs of movable spines. Petasma with proximal plate of dorsomedian lobule lacking mesial crest; proximal process of rib of dorsolateral lobule subcircular; ventral costa lacking distolateral projection and ending distally in long spine extending beyond level of row of cincinnuli. Thelycal plate of sternite XIV with anterior border weakly to distinctly arched on each side of posteromedian projection of ster- nite XIII and strongly sloping posterolaterally; lateral borders turning mesially behind mid- length, then posteriorly; short posteromedian protuberance caudally pedunculate. Description. — Rostrum (Figure 11) horizontal or somewhat upturned, straight or slightly sinuous (strongly arched in young), and long, reaching at least midlength of third antennular article and often overreaching peduncle, its length ranging from about 0.7 to 0.9 that of carapace. Rostral FIGURE 1 1 .—Penaeopsis eduardoi. holotype J 27 mm cl . Balayan Bay. Luzon, Philippines. Cephalothorax, lateral view. Scale - 5 mm. 734 PEREZ FARFANTE: REVISION OF PENAEID SHRIMP GENUS PEN AEOPSIS plus epigastric teeth 8-15, basal rostral teeth close together, ultimate 3 or 4 usually relatively widely spaced; first rostral tooth situated in line with orbital margin. Postrostral carina low, al- though well defined, behind epigastric tooth, end- ing at about posterior 0.4 length of carapace, beyond level of dorsal extremity of cervical sul- cus; small dorsal tubercle located near posterior margin of carapace. Antennal and hepatic spines subequal in size, latter situated distinctly ventral to antennal spine. Anteroventral angle of carapace broadly obtuse (Figure 12A). Antennal carina short; cervical carina sharp, accompany- ing sulcus well marked; hepatic carina sigmoid anteriorly (from below hepatic spine to apex of ptergostomian spine), hepatic sulcus well marked along carina, very shallow posteriorly. Bran- chiocardiac carina, extending well behind hepatic sulcus posterodorsally to near margin of carapace, indistinct in many large individuals. Antennular peduncle with length equivalent to about 0.65 that of carapace, third article stouter and longer in male than in female, about 1.50 as long as second in former and 1.25 in latter; pro- sartema not quite reaching distal margin of first article; distolateral spine long, slender, and sharp, reaching between basal 0.65 and distal margin of second article; stylocerite ending in small spine, length about 0.4 that of first article. Flagella similar to those of P. rectacuta, but ven- tral flagellum in male with less conspicuous knob at junction between semicircular proximal part and straight distal part. Scaphocerite extending to, or barely surpass- ing, antennular peduncle; lateral rib ending in sharp spine ending slightly short of distal margin of lamella. Antennal flagellum broken in speci- mens examined, but not <2.5 as long as body. Third maxilliped of male extending as far as distal 0.35 of third antennular article, that of female to distal margin; ratio of dactyl/propodus about 0.70 in male and 0.75 in female. First pereopod extending to about distal end of carpocerite. Second pereopod overreaching car- pocerite by length of dactyl or by almost entire propodus (i.e., reaching at least distal 0.4, at most 0.1, of first antennular article). Third pereopod of male reaching between proximal 0.35 and distal end of second article, that of female, between mid- length and distal end of third article. Fourth pereopod extending to distal end of carpocerite or surpassing it by length of dactyl. Fifth pereopod reaching at least midlength of second article or B FIGURE 12— Penaeopsis eduardoi. holotype. A, Anteroventral part of carapace. B, Telson and right uropod, dorsal view. Scales = 5 mm. slightly overreaching third. Order of pereopods in terms of their maximum anterior extensions: first, fourth, second, third, and fifth (or fifth, and third). Third maxilliped reaching about as far as fifth pereopod. Abdomen with sixth somite elongate, about 1.7 times maximum height, bearing rather strong, usually interrupted cicatrix on lateral surface. Telson (Figure 12B) with lateral margins armed with two pairs of small, movable spines; pair of fixed spines very long, in young reaching level of apex of telson; terminal portion hastate, its length 6-7 times basal width. Mesial ramus of uropod reaching, or slightly overreaching, apex of telson; lateral ramus surpassing mesial one by almost 0.2 of its own length. Petasma (Figure 13A,Bl with distomedian pro- jection virtually obsolete, distal plate relatively broad, and proximal plate flush with surrounding membranous portion, lacking mesial crest. Rib of dorsolateral lobule terminating proximally in subcircular process. Ventral costa with distolat- eral portion situated marginally (where bent in- ward), curving rather gently at about 120° and continuing in long spine distodorsally beyond row of cincinnuli. Appendix masculina (Figure 13C) transversely oval, broader than long, width 1.35-1.60 length, strongly convex dorsally, and bearing short setae around entire margin. Thelycum (Figure 14) with anterior border of 735 FISHERY BULLETIN: VOL 77, NO 4 FIGURE 13.— Pe/iaeopsis eduardoi, 6 16.5 mm cl, off Matuku, Fiji Islands. A. Petasma, lateral view of left half B, Ventral view. C, Right appendix masculina. dorsal view. Scales = 1 mm. Figure 14. — Penaeopsis eduardoi, holotype. Thelycum, ventral view. Scale = 1 mm. plate of sternite XIV faintly to distinctly convex on each side of posteromedian projection of ster- nite XIII, and conspicuously sloping posterolat- erally; lateral borders sharply turning mesially behind midlength then posteriorly before joining posterior thoracic ridge; plate densely setose an- teriorly, strongly slanting dorsomesially toward deep anteromedian portion, and armed with short, caudally pedunculate posteromedian protuber- ance. Median plate of sternite XIII semicircular to subcordiform (with blunt apex), flat, covered with setae; posteromedian projection caudally bifurcate. Sternite XII bearing posteromedian, semiconical, broad (rather than compressed) tooth; oblique pair of strong, sharp ridges ex- tending posterolaterally from base of tooth. Maximum lengths. — Males 26 mm cl, about 114 mm tl; females 34 mm cl, about 130 mm tl. Geographic and bathymetric ranges. — Penaeopsis eduardoi has been found off the Fiji Islands and from Japan through the Philippines and In- donesia to the Timor Sea (Figure 6), in depths between 289 and 570 m. Previously, Perez Farfante (1977b) noted that the range of this species extends to the "south- western part of the Bay of Bengal." In their treatment of "Metapenaeus rectacutus" [= P.jer- 736 PEREZ FARFANTE: REVISION OF PEN AEID SHRIMP GENUS PENAEOPSIS Maximum lengths. — 160 mm tl (Crosnier and Jouannic 1973). Largest specimens examined by me: males 23 mm cl, about 107 mm tl; females 33 mm cl, about 138 mm tl. Geographic and bathymetric ranges. — Indian Ocean (Figure 6), from the Bay of Bengal (Anda- man Sea; off Madras) through the Arabian Sea (off Cochin) to the Gulf Aden (off Berbera) and south to off Mozambique and Madagascar. It has been found at depths between 183 and 677 m. Affinities. — Penaeopsis jerryi differs from the closely related P. rectacuta, from the South China Sea, Philippines, and Indonesia, mainly by the position of the hepatic spine, the length of the branchiocardiac carina, and features of the thelycum. In P. rectacuta the hepatic spine is located at a level distinctly ventral to, instead of about the same level as, that of the antennal spine, and the branchiocardiac carina ends farther from the hepatic sulcus than it does in P. jerryi. The petasmata of the two species, although similar, differ in that the rib of the dorsolateral lobule in P. rectacuta is straight distally and ter- minates proximally in a subcircular process, whereas in P. jerryi the rib sometimes turns lat- erally and often ends in a semicircular process. In P. rectacuta the thelycal plate of sternite XIV is usually roughly trapezoidal, with the an- terior border almost straight on each side of the posteromedian projection of sternite XIII, and the anterolateral corners forming angles, whereas in P. jerryi this plate is roughly elliptical with the anterior border arcuate and the anterolateral and posterolateral comers arched. Finally, in P. jerryi the median plate of sternite XIII is subsemicircu- lar [e.g., in females illustrated by Alcock (1906, pi. 6: fig. 19a) and by Ivanov and Hassan (1976, fig. 3) as well as in most of those examined by me], or occasionally weakly trilobed as in the specimen figured by Ramadan (1938, fig. 12b). In a few females I have studied, the plate, although almost semicircular, is produced into a minute anteromedian spine, its general shape thus being quite different from the cordiform median plate of P. rectacuta. In occasional specimens of P. jerryi, the basis of the second pair of pereopods is armed with a dis- tomesial spine (Alcock 1901a), a feature that has not been observed in the other species. Also, as pointed out by Ramadan (1938) and confirmed by my observation, some individuals bear less than the tree typical pairs of movable spines on the telson (one or two pairs) and I found one with the spination asymmetrical. Remarks. — On the basis of the scant information provided by Balss ( 1925) it has not been possible for me to determine the identity of the two females he recorded as "Parapenaeus rectacutus" from the Nicobar Islands, Bay of Bengal. Accord- ing to him, the telson bears two pairs of movable spines, a characteristic of three of the five Indo- West Pacific members of the genus — Penaeopsis balssi, P. challengeri, and P. eduardoi. In the same work, however, he identified specimens be- longing to P. balssi, which were taken off east Africa, as "Wenaeopsis challengeri"; con- sequently, it seems very unlikely that the two females belong to P. balssi. It also seems improba- ble that they are members of P. challengeri or P. eduardoi because these species are not known to occur in the Indian Ocean. Balss added that in his specimens the second pair of pereopods is armed with spines; such have been observed only in oc- casional individuals of P. jerryi; but three, not two pairs of movable telsonic spines are charac- teristic of this shrimp typically. Balss' specimens, however, may prove to be atypical P. jerryi be- cause this shrimp is the only species of the genus that has been recorded from the area. Commercial importance. — Survey fishing off the west coast of India at depths between 175 and 375 m (George 1966, 1969; Jones 1967; Longhurst 1971) demonstrated the presence of P. jerryi in sufficient numbers for possible commercial exploitation of this shrimp. Crosnier and Jouan- nic (1973) noted that this species eventually will become commercially fished off Madagascar. Penaeopsis rectacuta (Bate 1881) Figures 6, 20-27 Penaeus rectacutus Bate 1881:180 [V holotype, BNMH; type-locality, between Bohol and Cebu, Philippines, 10°14' N, 123°54' E, 95 fathoms ( \1 Am), Challenger stn 209]; 1888:266 [part], pi. 36, fig. 2, 2", 2 p [fig. 2z = P. eduardoi]. Estam- pador 1937:493. Domantay 1956:363. Perez Farfante 1977b:172. Parapeneus rectacutus. Alcock 1905:520 [part, references only]. 741 nSHERY BULLETIN: VOL, 77. NO 4 Penaeopsis (Penaeopsis) rectacutus. Burkenroad 1934a:5 Anderson and Lindner 1945:309. Penaeopsis rectacuta. Hall 1962:18, fig. 89, 89a, 89b. Holthuis and Rosa 1965:3 [part]. Starobogatov 1972, pi. 5, fig. 39a-b (figures, but not key). Perez Farfante 1977b: 180; 1979:208. Common names: needle shrimp; camaron aguja; crevette aiguille. Material. PHILIPPINES— Luzon: 5 .5 10 9 , USNM, SW of Nasugbu, 247 m, 15 January \90%, Albatross stn 5110. 19, USNM, Balayan Bay, 324 m, 17 January 1908, Albatross stn 5112. 1<5, USNM, Balayan Bay, 366 m, 20 January 190S , Albatross stn 5116. IV, USNM, off Malabrigo Pt., 198 m 2 February 1908, Albatross stn 5121. 26 19 USNM, Tabayas Bay, 274 m, 24 February 1909 Albatross stn 5372. 3 9, USNM, Tabayas Bay 348 m, 2 March 1909, Albatross stn 5374. 2 9 USNM, Albay Gulf, 368 m, 8 June 1909 Albatross stn 5459. Leyte: 2 9, USNM, off Palompon, 344 m, 16 March 1909, Albatross stn 5402. 10<5 13 9, USNM, off Palompon, 333 m, 16 March 1909, Al- batross stn 5403. Camotes Is: 2d 1 9, USNM, Off Pacijan, 291 m, 18 March 1909, Albatross stn 5408. 19, USNM, off Pacijan, 346 m, 18 March 1909 Alba- tross stn 5409. Between Bohol and Cebu (Bohol Strait): Holotype. Id, USNM, 274 m, 15 March 1909, Albatross stn 5416. 4(5 39, USNM, 265 m, 23 March 1909, Albatross stn 5411. 3d 99, USNM, 296 m, 23 March 1909, Albatross stn 5412. 2 9 , USNM, 291 m, 25 March 1909, Alba- tross stn 5418. 3 9, USNM, 320 m, 25 March 1909, Albatross stn 5419. Id 15 9, USNM, 318 m, 9 April 1908, Albatross stn 5197. Mindanao: 1 d 19, USNM, off Tagolo Pt, 401 m, 20 August 1909, A /6a16), basal rostral teeth close together, those to- ward apex variously spaced; second or first (latter usually in young) rostral tooth situated in line with orbital margin. Postrostral carina low, al- though well defined, behind epigastric tooth end- ing at about level of dorsal extremity of cervical sulcus; small dorsal tubercle located near pos- terior margin of carapace. Antennal and hepatic spines subequal in size, latter situated distinctly ventral to antennal spine. Anteroventral angle of carapace broadly obtuse (Figure 3L4). Antennal carina short; cervical carina sharp, accompanying sulcus well marked; hepatic carina sigmoid an- teriorly (from below hepatic spine to apex of pterygostomian spine), hepatic sulcus well marked along carina, shallow posteriorly. Bran- chiocardiac carina very weak, extending pos- terodorsally to near margin of carapace. Antennular peduncle with length equivalent to about 0.70 that of carapace, third article sexually dimorphic, slightly longer and considerably stout- er in males than in females, about 1.4 times as long as second in former and 1.2 times in latter; prosartema reaching, or almost reaching, disto- mesial margin of eye; distolateral spine long, slender, and sharp, reaching between midlength 752 and distal fourth of second article; stylocerite end- ing in small spine, about 0.4 as long as first article. In male, ventral flagellum shorter (even when for- cibly straightened) than dorsal, with inconspicu- ous knob at junction between proximal and distal parts; dorsal flagellum 1.5-1.8 times as long as carapace. In female, ventral flagellum (tapering to filiform distal part) longer than dorsal, 1.5-1.7 times as long as carapace; dorsal flagellum 0.8-1.0 times as long. Scaphocerite falling slightly short of to some- what overreaching antennular peduncle; lateral rib ending in slender spine, falling short of distal margin of lamella. Antennal flagellum long, about 3 times tl of shrimp ( based on measurements made by me on freshly collected specimens during a Caribbean Sea cruise of Oregon II in 1969). Third maxilliped extending at least to basal 0.4 of second antennular article and at most to distal end of third; ratio of dactyl/propodus about 0.75 in males and 0.85 in females. First pereopod reaching distal end of carpocer- ite or overreaching it by as much as 0.8 length of propodus. Second pereopod surpassing carpocerite by at least length of propodus and by as much as that of propodus and half length of carpus (i.e., reaching between base of second antennular arti- cle and midlength of third). Third pereopod PEREZ FARFANTE: REVISION OF PENAEID SHRIMP GENUS PENAEOPSIS FIGURE 23— Penaeopsis rectacuta, holotype 9 24 mm cl, Bohol Strait. Philippines. Thelycum, ventral view. Scale = 1 mm. ered with setae. Posterior thoracic ridge fringed anteriorly with closely set setae. Median plate of sternite XIII cordiform (with acute apex), covered with setae except for central depression (occasion- ally prolonged across entire width of plate); posteromedian projection subrectangular or subelliptical, with posterior margin entire or, occasionally, shallowly emarginate. Sternite XII bearing posteromedian, often laterally com- pressed tooth of variable size, sometimes pro- duced in apical spine; oblique pair of sharp ridges extending posterolaterally from base of tooth. Thelycum in young females (9-11 mm cl) with median plate of sternite XIII produced anteriorly in long, slender spine, and posteromedian projec- tion consisting of only minute knob; plate of ster- nite XIV bearing short median ridge also produced anteriorly in long, slender spine, latter indistinct in females 13 mm cl. The female holotype, 26 mm cl, is in poor condi- tion, with many parts missing; however, except for the rostrum, which is almost entirely lost, the carapace is well preserved as are the antennular peduncle, most of the abdomen, and the thelycum. The following characters of the carapace may be readily observed: the second rostral tooth is situated opposite the orbital margin, while the Figure 24.— Penaeopsis rectacuta. A. ? 25.5 mm cl, offTagolo Point. Mindanao. Philippines. B. J 24 mm cl. Tabayas Bay vicinity of Marinduque Island, Philippines. Thelyca, ventral view (setae omitted on the legs). Scale = 2 mm. 745 FISHERY BULLETIN: VOL. 77, NO 4 epigastric tooth is found at the anterior 0.35 of the carapace, and the hepatic spine lies conspicuously ventral to the antennal spine; the postrostral carina extends along anterior 0.55 of the carapace, ending just posterior to the cervical sulcus; and the anteroventral corner forms an angle of about 90°. The antennular peduncle is 0.75 as long as the carapace, the third article is 1.35 times the length of the second, and the stylocerite is 0.4 that of the first article. The scaphocerite falls slightly short of the end of the antennular peduncle, and the ter- minal spine of the lateral rib does not reach the distal margin of the lamella. The low, sharp mid- dorsal keel of the abdomen extends from the fourth to the sixth somites, and the length of the latter is 1.7 times its maximum height. The thelycum is depicted in Figure 23. In this species each spermatophore bears a con- spicuous, somewhat rigid element which in im- pregnated females lies over the plate of sternite XIV (Figure 25). The paired elements, which pro- ject from the mesial extremity of the sperm sacs enclosed in the seminal receptacles, are joined along their mesial margins and form a roughly circular scale covering a large part of the plate. A similar spermatophore is also found in P. balssi, P. eduardoi, and P.jerryi, the other three Indo- West Pacific species in which I have observed impregnated females. Maximum lengths. — Males 25 mm cl, about 110 mm tl; females 31 mm cl, about 135 mm tl. Figure 25. — Penaeopsis rectacuta. i 25.5 mm cl, vicinity of western Bohol. Philippines. Compound spermatophore attached to female. Scale = 1 mm. and forms an angle with the lateral border, whereas in P.jerryi it is strongly convex and con- tinuous through a broad arc with the lateral bor- der. Furthermore, the median plate of sternite XIII is cordiform and rather elongate in P. rec- tacuta and subsemicircular, or occasionally trilobed in P. jerryi. Geographic and bathymetric ranges. — Indo-West Pacific (Figure 6) from the Philippines (Bate 1881) and Timor Sea to the south China Sea (north of Borneo, Hall 1962). It has been found at depths between 174 and 401 m. Affinities. — Two features of the carapace distin- guish P. rectacuta from the closely allied, western Indo-West Pacific P. jerry;: 1) the position of the hepatic spine, which in the former is situated dis- tinctly ventral to the antennal spine whereas it occurs at about the same level in P.jerryi, and 2) the length of the branchiocardiac carina which is relatively short in P. rectacuta (its anterior ex- tremity situated well behind the posterior end of the hepatic sulcus) and is long in P. jerryi (its anterior extremity located quite near the posteri- or end of the sulcus). In addition, the thelycum of P. rectacuta has the anterior border of the plate of sternite XIV almost straight or slightly sinuous Variation. — This shrimp exhibits a rather large number of morphological variations. In the adult the rostrum may be straight, slightly convex or sinuous, and the number of rostral teeth ranges from 10 to 17. The scaphocerite falls short of, reaches as far as or extends beyond, the antennu- lar peduncle. In the females, the anterior border of the plate of sternite XIV (Figure 24A , B ) varies from transverse to slightly inclined posterolater- ally, the median ridge may be short or extend to the posteromedian projection of sternite XIII, and the submedian depressions that flank the ridge, although most often narrow, may be broad. Fur- thermore, the setation of the plate, usually ex- tending over the lateral portions, sometimes is absent anteriorly and lacking posteriorly or vice versa. The median plate of sternite XIII usually bears a central depression, but occasionally the latter extends across the entire width of the plate, and the caudal margin of the posteromedian pro- 746 PEREZ FARFANTE: REVISION OF PENAEID SHRIMP GENUS PENAEOPSIS jection, which is straight in most specimens, some- times exhibits a shallow emargination. Finally, the tooth on sternite XII may vary considerably in size and shape; although usually compressed, it may be subconical or infrequently strongly pro- duced in an apical spine. Sometimes the entire range of variation of certain characters is rep- resented within a single lot. Among the 16 speci- mens collected at Albatross stn 5197, off western Bohol, Philippines, the number of rostral teeth ranges from 11 to 17 and in several lots females, in which the posteromedian projection of sternite XIII is straight caudally were found together with others bearing a slightly emarginate one. These variations, thus, are intraspecific, not even as- sociated with local populations. A discussion of the features that separate this species from P. eduardoi was presented by Perez Farfante ( 1977b). As noted by Hall ( 1962), typical P. rectacuta possesses longer pereopods than do specimens reported by De Man (1911) as "Parapenaeus rectacutus," which actually are Penaeopsis eduardoi. In P. rectacuta, however, the third maxilliped is slightly shorter than that of P. eduardoi. Remarks. — The specimens from off Borneo re- corded by Hall (1962) as P. rectacuta were in my opinion, correctly identified. The suggestion by Ivanov and Hassan ( 1976) that they might belong to P. balssi — under the synonymy of which the au- thors, "with some hesitation," included the record preceded by a question mark — is not justified. I have found that the petasmata of these specimens are typical and the thelyca vary but slightly from that of the holotype. The only obvious difference is that in the females, the median ridge of the plate of sternite XIV, although broadest posteriorly, is not flasklike. Also, this plate is rather densely setose laterally, as indicated by Ivanov and Hassan, and the transverse thoracic ridge bears a row of setae across the anterior border which is lacking in the holotype; it is probable that in the latter the setae have been lost, as have almost the entire rostrum, telson, and at least part of the appendages during or after capture. Perez Farfante (1978) described three speci- mens found in the waters of the Philippines hav- ing gonopores on the coxae of the fifth pair of pereopods and both male and female genitalia. The petasma, appendix masculina, and thelycum of the three exhibit unique features, but in most respects these shrimp are markedly similar to members of P. rectacuta. It was concluded that they are probably anomalus intersexes of this species. Recently, Boris G. Ivanov of VNIRO, kindly made available to me three specimens (two males and one female; Figures 26A-C; 27) FIGURE 26. -Penaeopsis rectacuta. ? 21 mm cl, S of Timor Island. Timor Sea. A. Petasma, dorsa) view. B, Ventral view. C, Right appendix masculina, dorsal view. Scales: A,B =2 mm; C = 1 mm. 747 Figure 27 .—?Penaeopsis rectacuta. . 31 mm cl, S of Timor Island, Timor Sea. Thelycum, ventral view. Scale = 2 mm. collected in the Timor Sea by O. A. Petrov during a cruise of the RV Lira. There is little doubt in my mind that the males are members of P. recta- cuta. The female, except for the thelycum, also possesses features typical of P. rectacuta. In the thelycum the anterior border of the plate of ster- nite XIV is considerably more inclined posterolat- erally than in typical females. The anterior part of the median ridge is uniquely divided by a groove, and the bulbous posterior part is larger and over- laps the thoracic ridge. Finally, the posteromedian projection of sternite XIII is considerably larger than in any specimen of P. rectacuta examined by me. A bopyrid isopod was found in the branchial chamber of this specimen; it might have been re- sponsible for these peculiar features of the female genitalia. Commercial importance. — Although no estimates of the economic importance of this species have been recorded, it has been cited among the com- mercially exploited shrimps of the Philippines by Domantay (1956), and as of economic value throughout its range by Holthuis and Rosa (1965). FISHERY BULLETIN: VOL. 77. NO. 4 Penaeopsis serrata Bate 1881 Figures 28-38 Penaeopsis serratus Bate 1881:183 [ssmtypes by implication, 16 15, MCZ 7200, 19, MP; type- locality, off Barbados, "Gulf of Mexico," Blake stn 275, 218 fathoms (399 m)]. Bouvier 1905a:981; 1908:5. A. Milne Edwards and Bouvier 1909:221, pi. 4, fig. 1-4. De Man 1911:53. Balss 1925:229. Schmitt 1926:320. Boone 1927:80 [part]. Maurin 1952:91; 1961:530; 1962:210; 1963:1. Burkenroad 1963:172. Maurin 1965:116; 1968a:33; 1968b:479, fig. 3 P. s. Lagardere 1971:33, fig. 39-42. [Placed on the Official List of Specific Names in Zoology as Name No. 2276, Interna- tional Commission on Zoological Nomenclature 1969, Opinion 864:141]. Parapenaeus megalops Smith 1885:172 [syntypes, 2 9, USNM 7262, S of Curacao, ir43' N, 69°09'30" W, 208 fathoms (380 m). Albatross stn 2125. 5d 19, USNM 7263, Golfo de Uraba, 9°30'45" N, 76°25'30' W, 155 fathoms (283 m). Albatross stn 2143J. Rathbun 1901:102. Bouvier 1908:7. A. Milne Edwards and Bouvier 1909:225, Hay and Shore 1918:379, pi. 25, fig. 8. Schmitt 1926:319. Parapeneus megalops. Faxon 1896:163. Alcock 1905:520; 1906:52, Artemesia talismani Bouvier 1905a:982 [syn- types, 2 d 2 9 , MP 304, off Guerguerat, Western Sahara, 25°41' N, 15°56' W (of Greenwich; 18°16' W of Paris on label accompanying speci- mens), 410 m, 9 July 1883, Talisman stn 72; type-locality, "cotes du Maroc et du Sahara"]; 1908:7, A, Milne Edwards and Bouvier 1909:225, Penaeopsis serratus var, antillensis A. Milne Ed- wards and Bouvier 1909:226, pi, 3, fig, 10, pi, 4, fig, 5 [holotype, d , MCZ 7201; type-locality, off St, Kitts, 208 fathoms (380 m) 1978-79, Blake stn 148], De Man 1911:53, Penaeopsis megalops. De Man 1911:53, Schmitt 1926:320, Burkenroad 1936:139. Kubo 1949:321. Voss 1955:8, fig, 19, Burkenroad 1963:172, Bullis and Thompson 1965:5, Joyce and Eldred 1966:26, Anderson and Bullis 1970:116, Roberts and Pequegnat 1970:49, Pequegnat and Roberts 1971:8, Longhurst 1971:237, Perez Farfante 1971:4, Crosnier and Forest 1973:305, Burukovsky 1974:31. 748 PEREZ FARFANTE REVISION OF PENAEID SHRIMP GENUS PENAEOPSIS Figure 31. — Penaeopsis serrata, V 29.5 mm cl, Dry Tortugas Islemds, Fla. A, Anteroventral part of carapace. B, Telson and left uropod. C. Tip of telson. Scales: A,C = 2 mm; B = 5 mm. attaining distal end of antennular peduncle or overreaching it by as much as length of propodus. Fourth pereopod surpassing carpocerite by tip of dactyl or by maximum of dactyl plus about one- half length of propodus. Fifth pereopod extending at least to midlength of second antennular article and at most to distal end of third. Order of pereopods in terms of their maximum anterior extensions: first, fourth, second, fifth, and third; fourth pereopod extending almost as far as second. Third maxilliped reaching about as far as fifth pereopod. Abdomen with sixth somite elongate, about 1.8 times maximum height, bearing faint, inter- rupted cicatrix on lateral surface. Telson (Figure 3LS ) with lateral margins armed with two (rarely three) pairs of short, slender movable spines; fixed spines moderately long, extending at most as far as base of distal third of terminal portion; terminal portion (Figure 31C) with length 6-9 times basal width, spear shaped and with dorsal surface con- vex. Mesial ramus of uropod almost reaching or surpassing apex of telson by as much as 0.15 of its own length; lateral ramus overreaching mesial ramus by 0.25-0.30 of its own length. Petasma (Figure 32A, B) with dorsomedian lobule produced in well-defined distomedian pro- jection, bearing narrow distal plate and broader proximal plate thickened mesially, but not form- Figure 32.— Penaeopsis serrata, 6 22 mm cl. Golfo de los Mosquitos, Panama. A, Petasma, dorsal view. B, Ventral view. C, Right appendix masculina, dorsal view. D. Mesial view. Scales = 1 mm. 753 FISHERY BULLETIN; VOL. 77. NO. 4 ing crest; rib of dorsolateral lobule terminating proximally in flattened subrectangular process. Ventrolateral lobule with distolateral portion broadly rounded, its rather flexible marginal part narrow and turned inwardly; ventral costa curving abruptly dorsomesially and ending in relatively broad process (with interior surface excavate) reaching approximately to level of cin- cinnuli; costa bearing ventral (inner) row of setae along attached margin. Appendix masculina (Figure 32C,D) consider- ably broader tham long (width 1.7 to almost twice length), subelliptical, convex mesially, flat later- ally, and bearing mesial patch of setae. Petasmal endopods becoming joined in male 12 mm cl. Armature of sternites XIII and XIV in very small juvenile male (discussed on p. 723) illus- trated in Figure 33. Thelycum (Figure 34) with anterior border of plate of stemite XIV slightly to strongly inclined posterolaterally, broadly arched on each side of posteromedian projection of sternite XIII; plate of stemite XIV with anterolateral extremities pro- duced laterally into lobules of variable lengths, and lateral portions setose and raised (ventrally), slanting dorsomesially toward corresponding, narrow, submedian depression; median ridge usu- ally ovoid or tear-shaped, sometimes subtriangu- FIGURE 34.— Penaeopsis serrata, 9 29.5 mm cl, Dry Tortugas Islands, Florida. Thelycum, ventral view. Scale = 1 mm. Figure 33.— Penaeopsis serrata, 3 10 mm cl, NE of Puerto Rico. Somites XII-XTV, ventral view. Scale = 1 mm. lar, greatly raised except for short, low, anterior part abutting projection of sternite XIII, and naked posteriorly; posterior thoracic ridge also lacking setae. Median plate of stemite XIII broad, subsemicircular, cordiform or roughly pentag- onal, with transverse depression across its entire width, bearing or lacking minute anteromedian spine, and covered with densely set setae an- teriorly; posteromedian projection strongly de- veloped, broad, with posterior margin slightly emarginate to deeply bifid and studded with numerous posteriorly pointed setae. Sternite XII bearing posteromedian subconical tooth, its apex pointed ventrally or anteroventrally; oblique pair of ridges extending posterolaterally from base of tooth. Seminal receptacles (Figure 35A, B) consisting of paired bilobed membranous sacs, derived from invaginations of sternite XIV. Submedian sac large, extending posteriorly to rather near caudal margin of sternite XIV, other smaller one extend- ing laterally; both diverging from broad an- 754 PEREZ FARFANTE: REVISION OF PENAEID SHRIMP GENUS PENAEOPSIS Figure 35— Penaeopsis sermta, 9 30 mm cl, N ofThunder Knoll, off Honduras. Sperm receptacles. A, Ventral view. B, Dorsal view (specimen stained). Scale = 2 mm. teromedian sinus. Receptacles opening through long, paired slits located between sternites XIII and XIV, and separated by narrow, shallow, an- teromedian portion of sternite XIV. Stages in development of thelycum: in female 8 mm cl (Figure 36A), plate of sternite XIV bearing median ridge produced anteriorly in long, sharp spine not quite reaching sternite XIII; anterolat- eral portions ventrally convex, covering invagina- tions (seminal receptacles) from slitlike openings along anterior margin of plate. Sternite XIII with small triangular median plate produced in long, sharp anteromedian spine reaching margin of sternite XII. Sternite XII bearing minute, sharp posteromedian tooth and pair of ridges extending posterolaterally from base of tooth (tooth and ridges changing little except increasing in size to facies in adult). In female 9.5 mm cl (Figure 36B), plate of ster- nite XIV with spine proportionately smaller than that in few preceding instars, farther removed from sternite XIII; anterolateral portions with openings of seminal receptacles enlarged and still exposed. Sternite XIII with spine on median plate distinctly overreaching sternite XII. In female 10.5 mm cl (Figure 36C), plate of ster- nite XIV with median ridge virtually reaching sternite XIII and bearing no more than rudiment of spine; anterolateral portions overlapping sternite XIII mesially, obscuring openings of sperm recep- tacles, and frequently produced laterally in short lobules, continuous with well-defined, exposed hoods. Median plate of sternite XIII with spine still slightly overreaching sternite XII. In female 12.5 mm cl ( Figure 36D), plate of ster- nite XIV with elongate trapezoidal (usually be- coming tear -shaped with increasing size) median ridge, reaching sternite XIII; basal part of ridge with strong median elevation; anterolateral por- tions broadly overlapping sternite XIII and bear- ing prominent lobules partly obscuring hoods. Median plate of sternite XIII considerably broadened, its anteromedian spine minute and far removed from sternite XII; plate produced in 755 FISHERY BULLETIN: VOL. 77, NO, 4 Figure 36. — Penaeopsis serrata. Stages of development of thelycum injuvenile females. A, 8mmcl;S, 9.5mmcl;C, 10.5mmcl;D, 12.5 mm cl. All from W of Cartagena, Columbia. Scale = 1 mm. broad posteromedian projection markedly over- lapping sternite XIV. In P. serrata the spermatophore does not bear the mesially attached element which in impreg- nated females of P. balssi, P. eduardoi, P. jerryi, and P. rectacuta (i.e., all the Indo-West Pacific species except P. challengeri of which I have not examined females carrying spermatophores) lies exposed on the thelycum. Because of the absence of this element, impregnated females of the former species are not readily recognized. The presence of a certain accessory structure in the sper- 756 PEREZ FARFANTE: REVISION OF PENAEID SHRIMP GENUS PENAEOPSIS matophore of one species of a genus and its absence in others is not unique in Penaeopsis; for in the family Penaeidae a similar phenomenon occurs even within the species of a subgenus. In the genus Penaeus, for instance, of the eight species of the American sxihgexwisFarfantepenaeus Burukovsky 1972, only one, Penaeus (F.) brevirostris Kingsley 1878, exhibits a large, fleshy structure attached to the sperm sac which in impregnated females en- tirely covers the plate of sternite XIV, much like the comparable accessory element of the sper- matophores of P. rectacuta and P. eduardoi. The spermatophores of the remaining seven species of Farfantepenaeus lack such a membranous struc- ture. Color. — This is one of the most beautifully colored shrimp I have seen. The following description is based on observations of a large number of freshly collected specimens obtained during the 1969 cruise of the Oregon 11 in the Caribbean (from Puerto Rico to Antigua). Body varying from translucent light pink (sometimes with salmon hue) to deep reddish pink, interrupted by an iridescent violet to purple subel- liptical patch on gastric region and various other white, deep red, violet or purple markings (lines, bands, patches, dots) on other areas. In many indi- viduals, rostrum with numerous red chromato- phores and red tip. Carapace bearing small patch of red chromatophores at base of antennal spine; anterior cardiac region with narrow, deep violet arc or transverse band running ventrally and fol- lowed by median, reddish purple subrectangular area. Some coloration continuing laterally in short posterior band, then broadening abruptly on branchiostegites, extending ventrally to margin of carapace and anteriorly to hepatic sulcus; subrec- tangular area flanked by white band running an- teriorly to hepatic region; posterior portion of carapace white. In other individuals entire bran- chiostegites of highly iridescent, deep reddish pink or reddish purple. Abdominal somites with transverse reddish to purple band along posterior margin of terga; band often divided by narrow white stripe extending along dorsal midline; an- terodorsal extremities of pleura bearing brilliant red or purple spot forming striking paired rows; pleura of first five somites marked by reddish to purple marginal line; bearing larger median spot and, occasionally, narrow angular stripe extend- ing from anterodorsal spot on pleuron to median spot of same color as line; sixth somite bordered only posteriorly by line of same color as that on margin of pleura of preceding somites. Telson with paired ribs and lateral margins reddish to purple, sometimes also fixed spines and line joining their bases similarly colored. Ocular peduncle white with red stripe along margin of cornea; basal arti- cle bearing large, brilliant red or deep purple cir- cle. Antennular peduncle highly iridescent pink proximally becoming increasingly reddish dis- tally; distal and sometimes lateral margins of ar- ticles red or purple; flagella pink or reddish, fading distally; frequently ventral flagellum white and dorsal reddish. Antennal flagella pink. Pereopods of lighter shade than body, but lateral surfaces usually darker and strongly iridescent. Bases of pleopods white, light pink, or violet with pos- terolateral surfaces iridescent with deep pink or violet hues; endopods and exopods translucent, and bearing reddish or purplish spot proximally. Uropods with lateral portion of protopod of darker shade than mesial; rami usually of same or lighter color than body but deeper proximally. Maximum lengths. — Males 120 mm tl; female 150 mm tl (Maurin 1952). Largest specimens examined by me: males 24 mm cl, 112 mm tl; females 34.5 mm cl, 135 mm tl. Geographic and bathymetric ranges (Figure 37). — Western Atlantic: from east of Barnegat, N.J., south of Martha's Vineyard, Mass. (lat. 40'00' N, long. 70'47' W, coordinates from Haed- rich et al. 1975, Gosnold cruise 197, stn 111), through the Gulf of Mexico and the Caribbean south to French Guiana (lat. 7°11' N, long. 52°58' W). Also found at a disjunct locality, off Rio GrandedoSul(lat.32°45'24"S,long.50°24'00"W). The record from off Barnegat, which represents the most northerly point at which this shrimp has been found, and that off Rio Grande do Sul, mark- ing the southernmost record of the occurrence of the species, were both reported by Perez Farfante and Ivanov (1979). Eastern Atlantic: from south of Cabo San Vi- cente, Portugal, to off Cadiz, Spain (Maurin 1961, 1965) and off the northwest coast of Africa to Tamzak("Tamxat")(lat. 17=26' N, long. 16''03'W), Mauritania (Maurin 1968b). In the western Atlantic, Pe/iaeopsts serrata fre- quents depths between 183 and about 750 m (re- cords of its presence in shallower water are almost certainly erroneous), with maximum concentra- tions occurring from 300 to 450 m. In the eastern 757 FISHERY BULLETIN: VOL. 77, NO. 4 40' 20° FIGURE 37.— Range of Penaeopsis serrata based on published records and specimens personally exam- ined. 90° 60° 30° 20' 40' ~^^ ^ ■. • ■' 40" 20' 20' 60° 30° 40 Atlantic it has been reported between 120 (Lagar- dere 1971) and 700 m (Maurin 1961). The temperature-depth relationship for P. ser- rata is presented in Figure 38. In three areas, two in the Gulf of Mexico and one in the southern part of the Caribbean (off Venezuela), this shrimp shows similar ranges of temperature and depth. In the northeast Gulf, however, the range is appar- ently more extensive, the animals having pene- trated shallower and warmer as well as deeper and colder waters. According to the available data, the population off the southeast coast of the United States occurs within the shallower range depths occupied by other populations, but at lower tem- peratures. Actually, in that area the shrimp is not restricted to the depths presented in the graph. FIGURE 38.— Depth-temperature re- lationships for Penaeopsis serrata in four western Atlantic areas (data ob- tained from Oregon and Oregon II Station Lists). li' SE COASI Of U S (N=I2l U- ~ NE GULF OF MEXICO IN = 137I 13- ^ DRY TORTUGAS IS ( N = 60 ) 12" - ,' VENEZUELA (N=17) ir ^ 1 \ /^ "^^v^^^ in' V ' >s,^ 9" - i ~^-,_ ""'"') 8' : / " \ i .^ """--:. 6- - ^./-^ " ^^^v 5' 1 1 1 1 1 400 500 DEPTH IM 1 758 PEREZ FARFANTE: REVISION OF PENAEID SHRIMP GENUS PENAEOPSIS because in at least one locality (for which tempera- ture data are lacking) it has been found at about 550 m (see "Material" herein), i.e., only 150 m above the maximum depth at which it has been taken in the northeast Gulf. Because the tempera- ture-depth distribution of the population off the southeast coast of the United States is based on only 12 records, one may only point out the un- usual conditions existing in this segment of the range of P. serrata. According to my observations, the specimens of that population exhibit no mor- phological differences from those of other localities throughout the broad range of the species, but Harvey R. Bullis Jr." stated that the specimens, observed by him immediately after capture, had a different coloration from those caught elsewhere. Furthermore, Bullis and Rathjen ( 1959) found that off the southeast coast of the United States P. serrata was most abundant at slightly greater depths than Pleoticus robustus (Smith 1885), whereas in all other areas megalops was not abundant where it occurs with, or at shal- lower depths than, P. robustus. Variation. — This species, like most members of the genus, exhibits a large number of characters that are highly variable. Among them, the ros- trum, strongly arched in the young, may be straight, arcuate only basally or sinuous in the adult, and horizontal or upturned; the number of rostral teeth ranges from 10 to 19. The scapho- cerite may fall short of or surpass the distal end of the antennular peduncle, and the mesial ramus of the uropod may not reach the apex of telson or may extend beyond it by as much as 0.15 of its own length. The thelycal features, especially, show a wide range of variation: the anterior bor- der of the plate of sternite XIV, usually strongly arched on each side of the posteromedian projec- tion of sternite XIII, sometimes is moderately or only slightly so; and the anterolateral lobules of that plate although generally strongly developed are sometimes quite short. The median plate of sternite XIII varies in shape (from subsemicircu- lar to roughly pentagonal), while the posterome- dian projection, although always broad, may range from slightly emarginate to deeply bifid. The entire range of variations in some of the characters cited have been observed in animals from the same locality. ■•Harvey R. Bullis, Jr., formerly Southeast Fisheries Center. National Marine Fisheries Service, NOAA, 75 Virginia Beach Drive, Miami, FL 33149, pers. commun. December 1978. At least in the western Atlantic populations, there are also differences in the relative extension of the third maxilliped and pereopods. I have noticed that in the populations of the Caribbean and Atlantic coast of South America they extend distally slightly farther than they do in northern populations. In the former populations the range extension of these appendages falls within the upper half of the limits cited herein and in the northern ones within the lower half Because most of the few specimens available to me from the eastern Atlantic are poorly preserved, I have been unable to arrive at definite conclusions as to the relative length of the appendages in the popula- tions occurring in that region. Affinities. — Penaeopsis serrata, the only Atlantic member of the genus, differs from its congeners in that the branchiocardiac carina and interrupted cicatrix on the sixth abdominal somite are very weak, and the knob at the distal end of the semicircular part of the ventral antennular flagel- lum in the male is rather inconspicuous. More strikingly, it differs from its allies in a number of features of the external genitalia, as pointed out below. It appears to be closer to P. rectacuta than to any of the other species. They share long rostra which tend to possess a large number of teeth (up to 18 in P. serrata and 17 in P. rectacuta), and the second tooth is located at the level of the orbital margin. In both, the hepatic spine is situated ven- tral to the level of the antennal spine, and the branchiocardiac carina does not approach closely the hepatic sulcus. The petasmata are also rather similar and the telson of P. serrata is sometimes, although rarely, armed with three pairs of mov- able spines as is typical of that of P. rectacuta. The thelyca exhibit the most obvious differences between the two species. In P. serrata the plate of sternite XIV is uniquely produced into laterally directed lobules, beairs an entirely naked and much stronger median ridge (usually subovoid in- stead of flasklike as it is generally in P. rectacuta), and the posterior thoracic ridge lacks setae across its anterior border. Furthermore, in P. serrata the median plate of sternite XIII, although variable in shape, is generally semicircular or roughly pen- tagonal, whereas in P. rectacuta it is cordiform. The posteromedian projection of sternite XIII is also broader and emarginate (often deeply) rather than entire as it usually is in P. rectacuta. The males of these species can also be distinguished by the proximal plate of the dorsomedian lobule of the 759 FISHERY BULLETIN: VOL. 77, NO. 4 petasma which in P. serrata, although thickened mesially, does not form a sharp crest as it does in P. rectacuta; by the proximal plate of the dorsolat- eral lobule subrectangular in the former and nearly circular in the latter; and by the apical process of the ventral costa which is conspicuously broader in P. serrata than in P. rectacuta. Remarks. — With reference to the types of this species, both Bate (1881) and A. Milne Edwards considered the account of P. serratus included in the A. Milne Edwards' manuscript — later pub- lished jointly by A. Milne Edwards and Bouvier (1909) — to constitute the original description; therefore, it seems reasonable to me that the syn- types of this species, from Barbados, designated by A. Milne Edwards and BouVier are, by implica- tion, also those of Bate. Furthermore, Bate (1881:180) stated that "I have not had an oppor- tunity of examining the branchial apparatus to feel quite certain that the genus [Penaeopsis] is a good determination," thereby indicating that he had not examined any specimens of P. serrata. Commercial importance. — Extensive explorations in the Gulf of Mexico, the Caribbean, and along the northern coast of South America by the U.S. Government vessels Oregon and Oregon II dem- onstrated the occurrence of megalops in many areas on the upper slope of the continental and insular shelves. It is common in many localities, and, on the basis of collections made by the RV Alaminos, Roberts and Pequegnat (1970) stated that this shrimp "is the most abundant penaeid caught by \he Alaminos in the Gulf, and it appears to be most abundant in the De Soto Canyon around 200 fathoms [366 m] and, secondarily, off the Rio Grande in 150 fathoms [274 m]." Even though it is frequently taken while trawling for the royal red shrimp, Pleoticus robustus (Smith 1885), Harvey R. Bullis, Jr. (see footnote 4) has informed me that no serious effort was made during the cruises of the Oregon and Oregon II to assess the commercial potential of P. serrata. The reason for lack of in- terest in investigating possibilities for commercial exploitations was the small size of this shrimp — according to Bullis, the average count of megalops tails would have been in the range of 60-100/lb (132-220/kg). In the eastern Atlantic this species constitutes a pairt of the commercial catches: Maurin ( 1952) cited it as one of the shrimps com- mercially fished off Morocco at depths >200 m; I have examined two females sorted by L. B. Hol- thuis from commercial catches made by a Cadiz trawler off Rabat, Morocco; and Holthuis and Rosa ( 1965) listed it among the shrimps of economic value in the "Southeast Atlantic Area." ACKNOWLEDGMENTS This study has been made possible through the generous cooperation of many colleagues on four continents who made available to me invaluable collections. In addition, some of them provided facilities for me to work at their respective institu- tions. I am deeply indebted to Anthony A. Fin- cham and Raymond W. Ingle (BMNH), Jacques Forest (MP), and Lipke B. Holthuis (RMNH) for placing at my disposal critical specimens and pro- viding working space and encouragement. I am also grateful to the following individuals for mak- ing additional material available to me: Alan Crosnier, Office de la Recherche Scientifique et Technique Outre Mer , Paris; Antonio J. de Freitas (ORI); Richard L. Haedrich, Woods Hole Oceano- graphic Institution, Woods Hole, Mass.; Willard D. Hartman (YPM); Boris G. Ivanov (VNIRO): Brian Kensley (formerly SAM); Herbert W. Levi (MCZ); Patsy A. McLaughlin (FIU); G. Ramak- rishna(ZSI);P. Subramanian, Center of Advanced Study in Marine Biology, Parangipettai; Krishna Kant Tiwari (ZSI); and Gilbert L. Voss (UMML). Thanks are due Harvey R. Bullis, Jr., formerly of the Southeast Fisheries Center, National Marine Fisheries Service, NOAA, Miami, Fla., for the graph of the depth-temperature relationship and for his cooperation through the many years during which he, in charge of the Oregon and Ore- gon II, preserved and made available to me exten- sive collections of penaeoids from catches of those U.S. Gtovernment vessels. I am also indebted to my colleagues Horton H. Hobbs, Jr. of the Smithsonian Institution for his invaluable advice and critical comments during the preparation of this work, and Fenner A. Chace, Jr. and Raymond B. Manning, both of the Smith- sonian Institution, for the review of the manu- script and helpful suggestions. An important contribution to this study was the cooperation of Maria M. Dieguez, who rendered the detailed illustrations and assisted me in the preparation of the lists of material. Finally, I am grateful to Arleen S. McClain and Virginia R. Thomas for typing the manuscript. 760 PEREZ FARFANTE REVISION OF PENAEID SHRIMP GENUS PENAEOPSIS LITERATURE CITED ALCOCK, A. W. 1898. A summary of the deep-sea zoological work of the Royal Indian Mfirine Survey ship Investigator from 1884 to 1897. Sci. Mem. Med. Off. Army India 11:45-93. 1901a. A descriptive catalogue of the Indian deep-sea Crustacea Decapoda Macrura and Anomala. in the Indian Museum. Being a revised account of the deep-sea species collected by the Royal Indian Marine Survey ship Inves- tigator. Indian Mus., Calcutta, 286 p. 1901b. Zoological gleanings from the Royal Indian Marine Survey ship Investigator. Sci. Mem. Off. Army India 12:35-76. 1902. A naturalist in Indian Seas or, four years with the Royal Indian Marine Survey ship 'Investigator'. John Murray, Lond., 328 p. 1905. A revision of the "genus" Peneus. with diagnoses of some new species and varieties Ann. Mag. Nat. Hist, Ser. 7, 16:508-532. 1906. Fasciculus I. The prawns of the Peneus group. Catalogue of the Indian decapod Crustacea in the collec- tion of the Indian Museum Part III. Macrura. Indian Mus., Calcutta, 55 p. ALCOCK, A. W., AND A. R. ANDERSON. 1894. Natural history notes from H. M. Indian Marine Survey steamer Investigator, Commander, C. F. Oldham, R.N., commanding. Series II, No. 14. An account of a recent collection of deep sea Crustacea from the Bay of Bengal and Laccadive Sea. J. Asiat. Soc. Bengal 63( Part 11,31:141-185. 1899. Natural history notes from H. M. Royal Indian Marine Survey ship Investigator, Commander T. H. Hom- ing, R.N., commanding. Series III, No. 2. An account of the deep-sea Crustacea dredged during the surveying-season of 1897-98 Ann. Mag. Nat. Hist, Ser. 7, 3:1-27, 278-292. ALCOCK, A. W., .\ND A. F. MCARDLE. 1901. Illustrations of the zoology of the Royal Indian Marine Survey ship Investigator, under the command of Commander T. H. Heming, R.N., Crustacea. Part IX, plates 49-55. Off. Supt. Gov. Print. India, Calcutta. ANDERSON, W. W., AND H. R. BULLIS. JR . 1970. Searching the shrimp beds by sub. Sea Front. 16:112-119. ANDERSON, W. W., AND M. J. LINDNER. 1945 A provisional key to the shrimps of the family Penaeidae with especial reference to American forms. Trans. Am. Fish. Soc. 73:284-319. BALSS. H. 1925. Macrura der Deutschen Tiefsee-Expedition, 2. Natantia, A. Wiss. Ergeb. Dtsch. Tiefsee-Exped. Vatdivia 20:217-315. 1957 Decapoda. Vni. Systematik. /n H. G. Bronn.Klas- sen and Ordnungen des Tierreichs. 5, sect. 1, book 7:1505-1672. Barnard, K. H. 1950. Descriptive catalogue of South African decapod Crustacea. Ann. S. Afr. Mus. 38:1-837. Bate, C. S. 1881. On the Penaeidea. Ann. Mag. Nat. Hist., Ser. 5, 8:169-196. 1888. Report on the Crustacea Macrura collected by H.M.S. Challenger during the years 1873-76. Rep. Sci. Res. Voy. H.M.S. Challenger 1873-76, Zool. 24, 942 p. BOONE, L. 1927. Scientific results of the first oceanographic expedi- tion of the "Pawnee " 1925. Crustacea from tropical east American seas. Bull. Bingham Oceanogr. Collect., Yale Univ. 1(2), 147 p. BOUVIER, E. L. 1905a. Sur les Peneides et les Stenopides recueillis par les expeditions fran^aises et monegasques dans I'Atlantique oriental. C. R. Acad. Sci., Paris 140:980-983. 1905b. Sur les macroures nageurs (abstraction faite des Carides), recueillis par les expeditions americaines du Hassler et duS/a*e. C. R. Acad. Sci., Paris 141:746-749. 1908. Quelques observations systematiques sur la sous- famille des Penaeinae Alcock. Bull. Inst. Oceanogr. (Monaco) 119, 10 p. BULUS, H. R., JR. 1956. Preliminary results of deep-water exploration for shrimp in the Gulf of Mexico by the MJV Oregon (1950-1956). Commer. Fish. Rev. 18(12):1-12. BULLIS, H. R., jR , AND W. F. RATHJEN. 1959. Shrimp explorations off southeastern coast of the United States (1956-1958). Commer. Fish. Rev. 21(6):l-20. BULLIS, H. R., Jr., and J. R. THOMPSON. 1965. Collections by the exploratory fishing vessels Ore- gon,Silver Bay, Combat, and Pelican made during 1956- 1960 in the southwestern North Atlantic. U.S. Fish Wildl. Serv., Spec. Sci. Rep. Fish. 510, 130 p. BURKENROAD, M. D. 1934a. Littoral Penaeidea chiefly from the Bingham Oceanographic Collection, with a revision of Penaeopsis and descriptions of two new genera and eleven new American species. Bull. Bingham Oceanogr. Collect., Yale Univ. 4(7), 109 p. 1934b. The Penaeidea of Louisiana with a discussion of their world relationships. Bull. Am. Mus. Nat. Hist. 68:61-143. 1936. The Aristeinae. Solenocerinae and pelagic Penaeinae of the Bingham Oceanographic Collec- tion. Bull. Bingham Oceanogr. Collect., Yale Univ. 5(2), 151 p. 1959. Addenda et Corrigenda au Memoire XXV. Penaeidae par Martin D. Burkenroad (pages 67-92). In Mission Robert Ph. DoUfus en Egypte (decembre 1927 - mars 1929), S. S. "Al Sayad" Resultats scientifiques, 3' Partie Icontributionsl (XXHI-XXXIV), p. 285. Centre Na- tional de la Recherche Scientifique, Paris. 1963. Comments on the petition concerning peneid names (Crustacea Decapoda) (Z. N. (S.) 962). Bull. Zool. Nomencl. 20:169-174. BURUKOVSKY, R. N. 1972. Some problems of the systematics and distribution of the shrimps of the genus Penaeus. [In Russ. I Fisheries Research in the Atlantic Ocean. Tr. Atl. Nauch.-Issled. Inst. Rybn. Khoz. Okeanogr. 42:3-21. (Translated by Is- rael Program Sci. Transl., 'rT72-50101.) 1974. Keys to the shrimps, spiny lobsters and homarids. [In Russ.] Moscow: Pishchevaia promyshlennost, "Food Industry," 126 p. CROSNIER, a., AND J. FOREST. 1973. Les crevettes profondes de I'Atlantique oriental tropical. Faune Tropicale Tome XIX. O.R.S.T.O.M. (Off. Rech. Sci. Tech. Outre-Mer), Paris, 409 p. CROSNIER, A., AND C. JOUANNIC. 1973. Note d'information sur les prospections de la pente 761 FISHERY BULLETIN: VOL. 77. NO 4 continentale malgache effectuees par le N. O. Vauban - Bathymetrie - Sedimentologie ■ Peche au chalut OR S.T.O.M. Centre Nosy-Be Doc. Sci. 42, 18 p. DOMANTAY, J. S. 1956. Prawn fisheries of the Philippines. Indo-Pac Fish. Counc. Proc. 6:362-366. ESTAMPADOR, E. P. 1937. A check list of Philippine crustacean decapods. Philipp. J Sci. 62:465-559. Fabricius.J.C. 1798. Supplementum entomologiae systematicae. Haf- niae, 572 p. Faxon, w 1895. Reports on an exploration off the west coasts of Mexico, Central and South America, and off the Galapa- gos Islands, in charge of Alexander Agassiz, by the U.S. Fish Commission steamer "Albatross", during 1891, Lieut. Commander Z. L. Tanner, U.S.N. , commanding. XV. The stalk-eyed Crustacea. Mem. Mus. Comp. Zool. Harv. Coll. 18, 292 p 1896. Reports on the results 6f dredging, under the super- vision of Alexander Agassiz, in the Gulf of Mexico and the Caribbean Sea, and on the east coast of the United States, 1877 to 1880, by the U.S. Coast Survey steamer "Blake," Lieut Commander CD. Sigsbee.U.S.N, and Commander JR. Bartlett, U.S.N. , commanding. XXXVII. Supplemen- tary notes on the Crustacea. Bull. Mus. Comp Zool. Harv. Coll. 30:153-166. George, M. J. 1966. On a collection of penaeid prawns from the offshore watersofthesouth-westcoastoflndia. In Symposiumon Crustacea, p. 337-346 Mar. Biol. Assoc. India, Symp. Ser. 2. 1969. Prawn fisheries of India. II Systematics-taxonomic considerations and general distribution. Cent. Mar, Fish. Res. Inst., BuU. 14:5-48. Haedrich, R. L., G. T. Rowe, and p. T. POLLONI 1975. Zonation and faunal composition of epibenthic popu- lations on the continental slope south of New Eng- land. J. Mar. Res. 33:191-212. Hall, D. N. F. 1962. Observations on the taxonomy and biology of some Indo-West-Pacific Penaeidae (Crustacea, Decapo- da). Colon. Off., Lond. Fish. Publ. 17, 229 p. Hay, W. p., and C. a. Shore 1918. The decapod crustaceans of Beaufort, N.C., and the surrounding region. Bull. tU.S.) Bur. Fish. 35:369-475. Holthuis, L B., and H. Rosa, Jr. 1965. List of species of shrimps and prawns of economic value. FAO Fish. Tech. Pap. 52, 21 p. International Commission on Zoological Nomencla- ture. 1969. Penaeid generic names (Crustacea, Decapoda): addi- tion of twenty-eight to the Official List. Opinion 864. Bull. Zool. Nomencl. 25:138-147. IVANOV, B. G., AND A. M. Hassan. 1976. Penaeid shrimps (Decapoda, Penaeidae) collected off east Africa by the fishing vessel "Van Gogh", 2. Deep- water shrimps of the genera Penaeopsis and Parapenaeus with description of Penaeopsis balssi sp. nov. Crus- taceana 31:1-10. Jones, S. 1967 . The crustacean fishery resources of India. In Sym- posium on Crustacea, p. 1328-1340. Mar. Biol. Assoc. In- dia, Symp. Ser. 2. 1969. The prawn fishery resources of India. FAO Fish, Rep. 57:735-747. Joyce, E. a., Jr., and B. Eldred. 1966. The Florida shrimping industry. Fla. State Board Conserv., Educ. Ser 15, 47 p Kemp, S., and R. B. S. sewell. 1912. II. Notes on Decapoda in the Indian Museum. Ill, The species obtained by R.I.M.S.S. 'Investigator' during the survey season 1910-11. Rec. Indian Mus. 7:15-32. KENSLEY, B. F. 1969. Decapod Crustacea from the south-west Indian Ocean. Ann. S. Afr. Mus. 52:149-181. 1972. Shrimps and prawns of southern Africa. South Afr. Mus., Cape Town, 65 p. KINGSLEY, J. S. 1878. Notes on the North American Caridea in the museum of Peabody Academy of Science at Salem, Mass. Proc. Acad. Nat. Sci Phila. 30:89-98. KUBO, I. 1949. Studies on penaeids of Japanese and its a4jacent waters. J. Tokyo Coll. Fish. 36(1), 467 p. KURIAN, C. V. 1964. On the occurrence of the deep-water prawnPenaeop- sis rectacutus (Spence Bate) off the Kerla coast. Curr. Sci. (Bangalore) 33:216-217. Lagarderre,J. p. 1971. Les crevettes des cotes du Maroc. Trav. Inst. Sci. Cherifien Fac. Sci., Ser. Zool. 36:1-140. LONGHURST, A. R. 1971. Crustacean resources. In J. A. Gulland (editor). The fish resources of the ocean, p. 206-255. FAO, Rome. LUCAS, H. 1846. Crustaces, Arachnides, Myriapodes et Hexapodes. Exploration scientifique de I'Algerie pendant les annees 1840, 1841, 1842. Sciences physiques. Zoologie I. Hist. Nat. Anim. Articules Part 1:1-403. MaN.J. G. DE. 1911. The Decapoda of the Siboga Expedition. Part 1 Fam- ily Penaeidae. Siboga-Exped. Monogr. 39a, 131 p. 1913. 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Les crevettes profondes de la region atlantique ibero-marocaine: repartition bathymetrique et geo- 762 PEREZ FARFANTE: REVISION OF PENAEID SHRIMP GENUS PENAEOPSIS graphique. importance economique. Comm. Int. Explor. Sd. Mer Medit. Rapp. P.-V. Reun. 156:116-119. 1968a. Ecologie ichthylogique des fonds chalutables at- lantiques (de la bale ibero-marocaine a la Mauritanie) et de la Mediterranee ocddentale. Rev. Trav. Inst. Peches Marit. 32:1-147. 1968b. Les Crustaces captures par la "Thalassa" au large des cotes nord-ouest africaines. Rev. Roum. Biol., Ser. Zool. 13:479-493. MILNE Edwards, a., and E. L. Bouvier. 1909. Reports on the results of dredging, under the super- vision of Alexander Agassiz, in the Gulf of Mexico (1877- 78), in the Caribbean Sea (1878-79), and along the Atlan- tic coast of the United States (1880), by the U.S. Coast Survey steamer "Blake," Lieut. Com. C. D. Sigsbee, U.S.N. , and Commander JR. Bartlett, U.S.N. , command- ing. XLFV. Les Peneides et Stenopides. Mem. 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Report on the Crustacea Macrura (families Peneidae, Campylonotidae and Pandalidae) obtained by the F.I.S. "Endeavour" in Australian seas. With notes on the species of "Penaeus" described by Haswell and con- tained, in part, in the collections of the Macleay Museum, at the University of Sidney. Biological results of the Fish- ing Experiments carried on by the F.I.S. "Endeavour" 1909-14. Commonw. Aust. Dep. Trade Customs 5, Part 6:311-381. SEWELL, R. B. S. 1935. Introduction and list of stations. Br. Mus. Nat. Hist, John Murray Exped., 1933-34. Sci. Rep. 1(1):1-41. 1955. A study of the sea coast of southern Arabia. Proc. Linn. Soc. Lond. 165:188-210. Smith, S. I. 1885. On some genera and species of Penaeidae, mostly from recent dredgings of the United States Fish Commis- sion. Proc. U.S. Natl. Mus. b. 170-190. Springer, S., and H. R. Bulus, Jr. 1956. Collectionsby the Onegon in the Gulf Mexico. U.S. Fish Wildl. Serv., ^c. Sci. Rep. Fish. 196, 134 p. STAROBOGATOV, Y. I. 1972. 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Hist, Ser. 6, 8:269-286 YOKOYA, Y. 1933. On the distribution of decapod crustaceans inhabit- ing the continental shelf around Japan, chiefly based upon the materials collected by S. S Soyo-Maru, during the year 1923-30. J. Coll Agric, Tokyo Imp. Univ. 12: 1-226. 1941. On the classification of penaeid shrimps by the structural features of the appendix masculina. J. Coll. Agric, Tokyo Imp. Univ. 15:45-68. 763 LIKELIHOOD METHODS FOR THE VON BERTALANFFY GROWTH CURVE Daniel K. Kimura' ABSTRACT Likelihood methods for the von Bertalanffy growth curve are examined under the assumption of independent, normally distributed errors. The following are examined; determining the best method of estimation, relationships between methods of estimation, failure of assumptions, constructing con- fidence regions, and applying likelihood ratio tests. An example is presented illustrating many of the methods discussed in theory. The paper may be viewed as an application of classic nonlinear least squares methods to the von Bertalanffy curve. As such, the concepts discussed are generally applicable and the paper may serve as an introduction to nonlinear least squares. Since the application of the von Bertalanffy ( 1938) growth curve by Beverton and Holt (1957) to the yield per recruit problem, this curve has been widely used in fisheries biology. The original curve has been generalized (Richards 1959; Chapman 1961). However, this paper will not deal with the more general Chapman-Richards growth curve. Nor will it deal with the biological motiva- tion for these curves which have been discussed by the cited authors. Instead, I confine my study to the classic von Bertalanffy curve and examine what appears to be reasonable methods for the statistical treatment of data. THE MODEL AND ITS MAXIMUM LIKELIHOOD ESTIMATES I assume that age-length data are available on some species, and that the relationship between age Eind length can be adequately described by the von Bertalanffy growth curve. Using the usual notation, the length of the uth individual of age t^ is assumed to be /„ = /Jl-exp(-A'(/,-^o))) + e. where I, is asymptotic length, K a constant de- scribing how rapidly this length is achieved, )^ the likelihood function can be written as = (2710^)-'^'^ exp(-S{l^,K.to)l2a^) (1) where N is the number of observations. Since for any given value of cj^, say a-g^, 2(.l^,K,tg,(T^^) is maximized when S(/,,A',2 = N-I degrees of freedom. While recognizing that the von Bertalanffy curve is not a linear model, this statistic may still serve as a tentative examination for lack of fit. Even if the data show significant lack of fit, the von Bertalanffy curve may still provide the most useful growth analysis. Rejection of the von Ber- talanffy curve must ultimately be based on supe- rior alternative curves or methods of analysis. Failure of Error Assumptions When a number of length specimens are avail- able at each age, parameter estimates should be robust against violations of the normality as- sumption. As was previously shown, estimates can be viewed as solutions to a LS problem with obser- vations y = (\ n, )7, which are always approxi- mately normally distributed due to the central limit theorem. The most likely form of heteroscedasticity is the varying of variance with age. Method (c) provides an appropriate analysis for this case. If observations are correlated, there will be no practical remedy. Efficient estimates will general- ly depend on the N >i N correlation matrix of er- rors. This matrix will generally not be estimable. CONSTRUCTING CONFIDENCE REGIONS For method (a), confidence regions of approxi- mate size 1-q around ML estimates (l.^,k,ig) can be constructed using the relationship S(L,K,to) = S(/„,K-,fo)[l + N-3 Fi3,N-3,l-q)] c„ (Draper and Smith 1966) whereF(3,Af-3,l-9) is the (l-glth percentile of the F-distribution with i'^ = 3 and i'^ = N-3 de- grees of freedom. That is, values of (/,;,/f,/„(l-e.xp(-A'(<„-/o))) + lJ(l-expi-Kit^-to))f c^ = S(L.KjQ){\+^^^F(3,N-3,l-q)\. Therefore, S(/„,K,^o)-fg = AlJ-^Bl^-^C where A = I, (\-exp(-K(t^-t o))f U B = -2^lJl-exp(-K(t,-to))) U and C = S/„2_c^ u Solutions exist for the three-dimensional contour problem whenever B^-4AC»0. 769 FISHERY BULLETIN: VOL 77. NO 4 Points on the three-dimensional contour are easily calculated by conditioning on a value for <„, and calculating the two-dimensional cross section {l^,K) by stepping through plausible values for K, and when B'^-AAC^O, calculating /, = ( -fi±VB2-4AC)/(2A). By varying tg also, this al- gorithm will generate the entire three-dimen- sional confidence region. Although points on the contour surface are eas- ily calculated, the fact that three parameters are involved in the von Bertalanffy curve greatly limits the usefulness of confidence regions. This is due to the simple fact that three-dimensional re- gions are difficult to display. The simplest solution to this problem is to condition on i^, and graph the resulting two- dimensional cross section 11,, K). It must be re- membered that this region is not a true con- fidence region since more extreme values of (/, ,K) may occur at a different value of t^,. Thus this procedure will give only a rough idea of our confidence in the estimates (K,k). A more time consuming solution is to graph a series of cross sections, or possibly a three-dimensional graph. If method (b) is used to estimate parameters, the analysis follows as in method (a), by simply replac- ing /^ with \ and N with /. If weighted methods (c) or (d) is used to estimate parameters, confidence regions are defined by the relationship •Su,(/oo,^,'o) = SjL,kJo)ll+~F(3,I-3,l-q)\ = c^ . Computations proceed as in the unweighted case, but with A^ = ywJl-exp{-K(t,-to))f, method for the statistical comparison of growth curves. It is a well-known and often exploited fact that once a general probability model has been specified (O), hypothesis tests of linear constraints on parameters in this model can be derived using the LR criterion. Alternatively viewed, linear con- straints on parameters in H imply a simplified model to. Tests of linear constraints on 11 are thus equivalent to testing w against il. The LR criterion can be used on the single sam- ple problem, when it is desired to test whether a sample came from a population with some "known" values for any or all of the parameters U„,K,t^); or for the multisample problem compar- ing von Bertalanffy curves in different popula- tions. The first problem will be solved by the simplest application of theory derived mainly in the context of the second problem. When a single parameter is being tested in the one or two sample problem, it makes good sense to simply use a Z-statistic (since ML estimates are asymptotically normal) and forego the more extensive calcula- tions required for LR tests. One advantage that the Z test has over the LR test for the two sample problem is that o^ does not need to be equal in the two populations. Consider / different populations each following the von Bertalanffy curve with parameters (/,, ,/f, ,29,000 larval iden- tifications) and a list of adult central gyre meso- pelagic fish species and their relative abundances (Barnett 1975). For analyses of abundance distributions with depth, the larval fish catches from each sample were converted to numbers per 1,000 m^. These were averaged for each depth interval and then summed to provide estimated water column abun- dance. Individual species distributions are ex- pressed as percent of their estimated water col- umn abundance caught within each of the main depth intervals sampled. The 100-225 m catches were used in calculations only if they contained species not present in 100-350 m or 350-600 m samples. The 100-225 m and 100-350 m samples were compared to assess whether larval abun- dance was concentrated in the upper portion of the larger depth range. Significance of differences in size composition with depth were determined, where sample sizes permitted, using the Kolmogorov-Smirnov test (Conover 1971) on cumulative size-frequency dis- tributions of 0.5 mm (SL) categories of the total larvae taken (all samples combined) within each depth interval. A one-tailed probability of the maximum difference between cumulative size- frequency distributions in two depth strata s0.05 was deemed "significant." Rejection of the null hypothesis of no difference indicates that one of the size distributions being compared is sig- nificantly larger than the other. The results of these tests are in no case altered by the exclusion of larvae from the "day" samples in their calcula- tion. Descriptions of the developmental stages of myctophid larvae in the plankton include addi- tional information obtained from six other central gyre cruises in the vicinity of lat. 28° N, long. 155° W. These cruises utilized Isaacs-Kidd plankton trawls (IKPT) fished obliquely from the surface to about 300 m (Loeb 1979b). Those data (24,500 identified larvae) provide a broader range of larval sizes and developmental stages, and development from eairly larvae to metamorphosis (transforma- tion) has been traced for many species. I used this information as an aid for estimating levels of de- velopment reached while larvae are still in the upper water column, prior to descent to deeper juvenile-adult depths. RESULTS I identified a total of 5,448 larvae (Table 2). These included 94 generic and species identifica- tions from 36 families, and one ordinal grouping. Three families (Gonostomatidae, Sternop- tychidae, and Myctophidae) together contributed 91% of the individuals and 50% of the species. Larvae were taken throughout the 600 m depth range (Figure la); however, over 97% of the esti- mated water column abundance was in the upper 100 m. Only 13 of the 95 kinds of larvae appeared to have maximum abundance below 100 m. Maximum larval abundance (and diversity, or number of species) occurred within the 25-50 m interval (Figure la); the bottom of the summer mixed layer (ca. 40 m) is within this interval (Fig- ure lb). Total larval abundance (Figure la) as well as individual species abundances were highly var- iable from tow to tow within each interval. Despite this variability, most species demonstrated a definite peak of abundance (generally >60% of their estimated water column abundance) and MEAN AND RANGE LARVAE PER l.OOOm^ 0 25 50 75 100. 500 1000 ^225 Q 350- 600 J •(10) '(10) -(10) "(10) (6) (8) (a) FIGURE 1.— Vertical distribution of ichthyoplankton in relation to lat« summer thermal structure in the North Pacific central gyre, (a) Mean and range of total numbers of larvae per 1,000 m^ caught in replicate samples within each depth interval (bracket- ed values are numbers of replicate samples), (b) Temperature profile of upper water column during Climax I, based on average values fi-om 10 day and 7 night STD lowerings. 779 FISHERY BULLETIN: VOL. 77, NO. 4 Table 2 . — Total numbers of individuals (N ) and rank of numerical abundance ( R I of larval fish species caught {n samples combined) within each of seven depth intervals in the North Pacific central gyre during late summer. 0-25 m n =10 25-50 m n = 10 50-75 m n- 10 75-100 m n - 70 100-225 m n =6 100-350 m 350-600 m n = 6 n = Q Species Gonostomatidae: Cyclothone alba C sp- A (prob. pseudopalhda) C. atrana C spp Diplophos taenia Gonostoma atlanticum G elongatum ichthyococcus ovatus Margrethia obtusirostra Valenciennelk/s tnpunctulatus Vinciguerna nimbaria V. powenae V spp Woodsia sp. Sternoptychidae Argyropelecus spp. Sternoptyx diaphana S pseudobscura S spp Myctophtdae Lampanyctinae Bolinichthys distofax B longipes B spp Ceratoscopelus warmingi Diaphus anderseni D "slender B ' (D mollis B'>) D 'slender C" (D mollis A"?) D brachycephalus D. slender spp D. elucens (= perspicillatus) D. rolfbolini ( = phillipsi) D "stubby C " (D schmidti?) D stubby spp ' Lampadena anomala L. luminosa Lampanyctus "big snout" L. "lacks pectorals" L nobilis L. steinbecki L spp. Lobianchia gemellari Notolychnus valdiviae Tnphoturus nigrescens Myctophinae Benthosema suborbitale Centrobranchus andrae C brevirostris C. choerocephalus Diogenichthys atlanticus Hygophum proximum H reinhardtt Myctophum brachygnathum M. lychnobium M. niDdulum M selenops M spp. Symbolophorus evermanni Other Larvae: Congridae: Ariosoma sp Neniichthyidae Nemichthys scolopaceus Bathylagtdae Bathylagus bencoides B longirostris Stomialoid fishes' Idiacanthidae: Idiacanthus fasciola Paralepididae Type A (prob Lestidium nudum) Type B (like L interpacificum) Type D (prob Gen nov sp nov ) Paralepis atlantica Stemonosudis macrura 580 49 1 76 13 (1) (5) (38) (4) (11) 687 (1) (26V2) (10) (54) 171 2 (1) (37) 17 (12) (18) 376 (2) (25V2) 90 (9) 28 (11) 99 (2) 2 (37) 61 (5) 30 10 7 25 60 34 4 (271/2) (6) (14) (IB) (8) (2) (5) (27V2) (46V!) 2 (28V2) 22 (20) 16 1 (14) (46) 2 7 (35) (18) 2 7 (28V!) (16) 1 7 (54) (29'/!) 2 2 4 (37) (37) (28) 1 (38) 4 (33'/!) 4 (28) (13V4) (3) (levi) (8V2) (10'/!) (6) (4) (8'/!) (13'/!) (26'/!) 14 (1) 4 (10'/!) 6 (6) 27 (17) 177 (2) 47 (11) 1 (46) 30 (6) 21 (21) 15 (8) 235 (3) 47 (6) 2 (35) 1 (26'/2) 84 (3) 40 (13) 5 (25) 2 (44'/2) 7 (21) 2 (35) 12 (12) 95 (8) 9 (17'/2) 2 (35) 6 (18) 30 (16) 14 (15) 1 (46'/2) 10 (14'/!) 6 (23) 2 (35) 1 (26'/!) 18 (7) 164 (4) 46 (7) 2 (35) 2 (28'/2) 97 (7) 27 (12) 5 (24) 2 (18'/!) 5 (21) 11 (24'/!) 7 (21) 1 (46'/!) 5 (21) 3 (39) 11 (13) 11 16 (24'/2) (23) 2 (37) 1 (46'/2) 4 {33'/!) 33 (9) 7 (18) 1 (26'/2) 1 (38) 23 (19) 2 (37) 3 (25'/!) 123 7 (6) (29'/!) 12 (16) 29 (10) 26 (7) 2 (18'/2) 2 (37) 40 (4) 6 (18) 128 (5) 8 (19) 4 48 1 1 5 8 (27'/!) (3) 11 (46'/!) (46'/!) (24) (15'/2) 2 (2) (18'/!) 26 (18) 95 (3) 11 (13) 45 (8) 19 (11) 1 (26'/2) 17 (22) 3 (30'/2) 1 (46'/2) 32 (15) 18 1 5 (13) (46) (25) 8 6 (15',4) (21) 2 (18'/!) 9 (26'/!) 76 (4) 22 (9) 1 (26'/2) 1 (38) 1 (38) 1 (54) (13'/2) (11) (") (11) (1) 3 (7'^) 1 (19) 4 (5) 13 (1) (19) (3) (5) (19) (19) (2) (11) 6 (2) 2 (11) 1 (19) .458 60 1 ( 193 14 41 14 12 4 9 514 71 204 5 5 19 (4) 6 10 27 225 51 300 130 11 119 51 19 230 134 23 1 ( 8 23 18 45 26 138 8 57 44 146 (4) (4) (19) (19) 65 1 ( 1 ( 5 12 132 65 21 58 7 5 3 108 1 ( 2 1 ( 4 42 (18'/!) 5 16 780 LOEB: VERTICAL DISTRIBUTION OF LARVAL FISHES Table 2.— Continued. 0-25 m n = 10 25-50 m 50-75 m 75-100 m 100-225 m 100-350 m n = 10 n^lO n = 10 n = 6 n = S Species N N R N R N R 2 (44'/!) 2 (37) 2 (35) 1 (54) 2 (37) 5 (24) 1 (54) 2 (37) 350-600 m n =8 Total N R N R 6 (61) 8 (55'/!) 3 (78'/!) 5 (67) 5 (67) 53 (22) 2 (84'/!) 1 1 (48) 11 (48) 25 (32) 2 (84'/!) 1 (100) 5 (67) 1 (100) 3 (78'/!) 1 (100) 3 (78'/!) 5 1 (100) 9 (52) 1 (100) 7 (58',^) 88 (15) 1 (100) 1 (100) 4 (73'/2) 6 (61) 2 (84'/!) 1 (100) 24 (33) 2 (84'/!) 1 (100) 1 (100) 1 (100) 1 (100) 1 (100) 49 (25) 3 (78'/!) 1 1100) 1 (100) 21 (36'/!) 12 (45) 1 (100) 1 (100) 1 (100) 3 (78'/2) Sudis atrox Uncisudis advena Unidentified Paralepidids Alepisaundae Alepisaurus ferox Evermannellidae Evermannella indica Odontostomops normalops Unidenttfied evermannellids Scopelarchidae Scopelarchus spp Notosudidae Ahtiesaurus brevis Scopelosaurus smithi Neoscopelidae Scopelengys SQ {prob. clarkei) Gigantundae Bathyleptus lisae MelanocetKJae Melanocefus /ohnsoni M sp- Oneirodidae Dolopichthys longicornis OneircxJid A (poss Lasiognathus sp Unidentified oneirodids Gigantactinidae: Gigantactis sp (prob vanhoeffeni) Ceratiidae Ceratias hotboetli Cryptopsaras couesi Caulophrynidae Caulophryne lordani Unidentified ceratioids Bregmacerotidae Bregmaceros spp Ophidiidae Brotulid (poss Lamprogrammus niger) Macroundae Mesobius berryi Exocoetidae Unidentiified exocoetids Melamphaeidae: Melamphaes simus M sp A (prib indicus) M spp Scopeloberyx spp Scopelogadus mizolepis mizolepis Unidentified melamphaeids Anoplogastendae Anoplogaster cornuta Zeidae Unidentified zeid Trachipteridae Trachiplerus sp Stylephondae Stylephorus chordatus Apogonidae Howella sp 1 Bramidae: Brama laponica 1 Coryphaenidae Coryphaena sp, (prob equiselis) 1 Chiasmodontidae Unidentified chiasmodontid l Gempylidae Gempylus serpens 14 Tnchiundae Diplospinus multistnatus Type A (poss Aphanopus carbo) Unidenttfied trichiurid Scombridae Acanthocybium sp 1 Katsuwonus pelamis i Nometdae Cubiceps caeruleus i 3 (30V2) (33V2) 1 (46) 2 (28'/i) 44 2 (12) 7 (44'/2) (21) 4 10 14 (14'/!) (9'/2) 1 8 2 1 (54) (28) (44'/2) (54) 3 4 1 (23'/2) (38) 1 (46) )1 (38) 3 3 (39) (39) 1 (38) 4 (33'/2) 5 (21) 1 4 (54) (33'/2) 4 (23'/2) 3 1 (39) (46) 5 (25) 76 1 (54) 3 (39) 1 (54) 1 (54) 1 (54) (46) (35) (27'/2) 3 (30) (1) 6 (21) 1 (46'/2) 1 (46'/2) 20 (10) 2 (35) 1 (46'/!) (13'/!) (6) (26'/!) (26'/2) (38) 39 ,(14) 9 (17'/2) (38) 2 (44'/!) (38) (38) (9'/!) 4 (33'/!) 2 (37) 1 (46'/2) 1 (54) 4 (28) 5 (21) 1 1 1 (46'/!) (26'/2) (26'/2) (38) (38) 2 (44'/!) (5) (19) (19) (7'/2) (19) (38) 1 (100) 781 FISHERY BULLETIN; VOL. 77. NO. 4 Table 2.— Continued. 0-25 n - N m 10 R 25-50 m n = 10 N R 50-75 m n = 10 N R 75-100 m n = 10 N R 100-225 m n =6 100-350 m n =6 350-600 n = 8 m Total Species N R N R N R N R Total larvae identified Unidentified larvae Tola! larvae Number of rankings 1.190 143 1.333 41 2.583 347 2.930 60 932 89 1,021 49 557 106 663 50 111 22 133 31 63 11 74 24 12 8 20 7 5.448 726 6.174 112 'Stomialoid fishes include Astronesttiidae. f^alacosteidae. Melanostomiatidae. and Stomiatidae. frequency of occurrence within one of the 25 m depth intervals. For many of the more abundant species, the catches in replicate tows within this interval were significantly greater (Mann-Whit- ney U test, P sO.05) than those in adjacent inter- vals (Table 3). Table 3. — Gonostomatidae. Stemoptychidae, and Myctophidae: Total estimated water column abundance of larval species during late summer in the North Pacific central gyre, based on summation of mean estimated abundances I numbers/1, 000 m^) from each depth Total 0-25 m 25-50 m 50-75 m Median Median Median no per F length Range F length Range F length Range Species 1 .000 m^ (10) % (mm) (mm) (10) % (mm) (mm) (10) % (mm) (mm) Gonostomatidae Cyclothone alba 3650 10 39 7 56 3 2-12 6 10 47 0 45 25-12,2 10 117 79 22-124 C sp A 150 9 '817 59 3.2-138 6 150 76 49-13.9 2 33 9.4 5.0-13.7 C. atraria 02 1 100,0 4,6 Diplophos taenia 35 7 '92,9 11.0 5.2-26.8 1 7.1 12.6 Gonostoma atlanticum 83 G elongatum 33 Ichihyococcus ovaws 38 Margrethia obtusirostra 17 Valenaennettus tnpunctutatus 12 Vinciguerna nimbaria 127 0 5 1,2 90 6.8-11.9 10 '74.1 72 3.7-14.5 10 19,5 14 0 37-17.5 V power lae 172 2 29 88 7 2-10.3 Woodsia sp 1 4 Stemoptychidae: Argyropelecus spp 17 Sternoptyx spp 43 f^yctophidae Lampanyctinae Bolinichthys distofax 68 5 100.0 5.7 32-8.8 B longipes 56 2 10 '78 7 46 3.1-84 8 20,9 5,1 34-82 1 04 87 Ceratoscopelus warmingi 75 2 4 50 40 3.2-4 7 10 '782 50 2.7-77 10 156 63 48-8,3 Diaphus anderseni 32 7 10 '643 42 2 7-6 5 7 30,6 4,5 3 2-7 1 2 3,8 7.0 5,3-11,6 D slender B" 28 2 18,2 36 25-46 2 636 5.6 3. 5-6.3 0 "slender C 29 8 3 10 1 38 26-50 9 '79 7 45 2.3-65 4 76 4.9 45-63 D. brachycephatus 128 3 11 8 40 3.7-4.6 6 588 42 2.6-5.9 5 27,4 5.4 4.3-8.7 D elucens 57 5 8 78 35 2.8-48 10 '713 40 2 6-8 7 6 20.0 55 2.6-86 D rollbolini 33,2 1 15 3.4 3.3-3.5 10 '73.1 40 27-66 8 204 4 7 29-7,7 0 ■stubby C ■ 58 2 21 7 3.5 32-3.8 2 47 8 37 3 0-4 2 2 304 36 3 3-3,8 Lampadena anomala 20 5 62 5 51 3.4-5.8 3 37.5 3,7 29-62 L luminosa 58 4 47 8 5.0 3 7-5 9 4 47.8 6,8 34-8.6 Lampanyctus "big snout'" 45 7 '88-9 4,0 2.8-7.1 2 11.1 56 3,9-74 L. "lacks pectorals" 114 3 88 4,0 3.5-5.9 9 '72 2 44 26-6.2 L. nobilis 65 1 38 54 5 885 48 29-105 2 7 7 78 5,4-10.2 L. steinbecki 345 3 22 32 32-42 10 '891 34 2 1-5 5 4 87 44 29-69 Lobianchia gemellari 146 8 497 4,4 28-58 Notolychnus valdiviae 113 2 44 40 3 1-10.5 Triphoturus nigrescens 36 5 4 4 1 5.0 2.3-74 10 '877 4,4 2.7-8 1 4 5.5 67 5.2-7.9 Myctophinae Benihosema suborbilale 14,5 Centrobranchus andrae 02 C brevimslris 02 C choerocephalus 1,2 Diogenichthys atianticus 28 Hygophum proximum 33 0 9 197 38 2 8-5 9 10 '72 0 45 23-87 H reinhafdti 164 9 '68 5 6,5 3 8-9.4 Myctophum brachygnathum 52 6 81 0 29 2 3-4 1 2 14.3 39 25-4.8 M lychnobium 14 5 7 55 2 37 2 8-5 6 5 310 36 25-46 M- nitidulum 18 1 143 39 M selenops 1,2 2 100 47 3.4-54 Symbolophorus evermanni 272 3 8.3 5,5 39-62 9 '69.9 4,5 2.8-5 6 'Designates abundances which, based on abundances within replicate tows, are significantly greater (Mann- Whitney U-test. P =^0.05) than in any other depth interval ^Denotes use of 100-225 m instead of 100-350 m samples 782 LOEB: VERTICAL DISTRIBUTION OF LARVAL FISHES Gonostomatid and myctophid larvae made up most of the ichthyoplankton in the upper 100 m (Figure 2). The "other larvae" were a low, constant percent of the total from the surface to 75 m, but their percent contribution was markedly in- creased between 75 and 350 m. Below 350 m most of the larvae were sternoptychids and gono- stomatids. Family Gonostomatidae The gonostomatids (8 genera, 12 species) com- posed 48% of the identified larvae. The family was an important fraction of the total larvae in all strata (Figure 3a); 97% of the estimated family abundance occurred above 100 m. Maximum abundance was at 25-50 m due to concentrations of the two most abundant species Cyclothone alba interval; and frequency of occurrence (F) in (n) samples, percent of tx)tal estimated water column abundance, median length, and size range (mm standard length) within each depth interval. Species Gonostomatidae: Cyclothone alba C. sp A C. atraria Diplophos taenia Gonostoma atlanticum G. elongatum Ichthyococcus ovatus Margrethia obtusirostra Valenciennellus tripunctulatus Vinciguerna nimbafia V. powenae Woods ia sp Stern op tychidae Argyropelecus spp Sternoptyx spp Myctophidae Lampanyctinae Bolinichthys distofax B longipes Ceratoscopelus warmingi Diaphus anderseni D 'slender B" D "slender C" D brachycephalus D elucens D rolfbolini D ■stubby C " Lampadena anomala L luminosa Lampanyctus "big snout" L 'lacks pectorals' L nobilis L Steinbeck) Lobianchia gemellan Notolychnus valdiviae Tnphoturus nigrescens Myctophinae: Benthosema suborbitals Centrobranchus andrae C brevirostns C choerocephalus Diogenichthys atlanticus Hygophum proximum H reinhardti Myctophum brachygnathum M lychnobium M nitidulum M selenops Symbolophorus evermanni 75-100 m 100-350 m 350-600 m F (10) Median length % (mm) Range (mm) F (6) Median length % (mm) Range (mm) Median F length (8) % (mm) 5 1 2 92 3 7-14 7 '2 0 3 4 1 3.8-47 7 5 3 90.0 6 1 75 1 5 4 45.7 8.0 2.7-16.3 3 7-12 2 5.8-13,2 1 2 ^3 10.0 65 249 65 54 3 110 27-129 4 3-8.2 4 0-16 3 '3 100 2 100 86 7 t-99 9 49 142 3 9-17 8 1 0.3 45 3 7-7 1 9 87 4 108 6 5-19 2 2 97 12 1 68-197 2 1 70 4 5.8 59 3 7-6.2 1 4 296 252 87.0 32 2 758 t 72 2 182 88 62-in.O 2 17 66 4 3-8 9 1 2.0 61 2 0.9 68 4 8-8 9 3 3.8 69 4 9-9 9 1 44 127 4 153 5.7 3 2-6 8 9 44.6 38 3 2-7 9 8 '883 52 3 3-8 0 2 2 7 76 6 2-118 4 82 8 36 2 5-7 8 1 100 59 1 100 53 3 100 62 3 4-7 1 4 707 49 4 3-5 8 5 8.3 55 2,2-10.8 7 28.9 65 24-131 1 4.7 75 3 13.8 36 22-42 3 857 37 2 7-4 9 05 1.3 11 8 105 1.3 47 29-7.f 21 3 7 4 3 '2 5 7 4 0 3 7-4 2 2 7.3 6 2 6 1-6.4 3 17 2 3 9 18-8 0 2 29.3 4 2 3 8-4 6 '1 2 6 4 6 21 16 4 7 783 FISHERY BULLETIN: VOL, 77, NO. 4 PERCENT 25 50 MEAN NO PER 1,000m' 100 200 300 400 50 100 150 200 — Gonostomatidae Sternoptychidae Mycfophidae . Other larvae Figure 2. — Percent contribution of major families and "other larvae" to the total ichthyoplankton caught within each depth interval of the North Pacific central gyre during summer. and Vinciguerria nimbaria (Figure 3b). Maximum diversity occurred at 75-225 m. Gonostomatidae ■ Cyclothone alba - Vinciguerria nimbaria (b) Figure 3.— Vertical distributions of larval gonostomatids in the North Pacific central gyre during summer. Concentrations of (a) gonostomatid larvae (12 species combined) and of (bl Cyclothone alba and Vinciguerria nimbaria larvae by depth interval. increase in standard length with depth; smaller sizes dominated at 25-50 m, larger lengths at 50-75 m, and intermediate sizes at 0-25 m. Al- though median standard length was largest in the 75-100 m interval, the cumulative size-frequency curve was not significantly different from that at 50-75 m, possibly because of the paucity of larvae captured at 75-100 m. The three largest larvae present in 75-100 m samples (11.6-14.7 mm) were in the prometamorphic (white photophore) stage ( Ahlstrom and Counts 19581 of development. Only three small larvae were caught between 100 and 350 m, and 57 metamorphosed individuals were caught at 350-600 m. CYCLOTHONE SPP.— Cyclothone alba is a numerous larval fish species in the central gyre throughout the year, ranking second in abun- dance only to Vinciguerria nimbaria (Loeb 1979b). It was the most abundant species taken during this cruise (27% of all larvae), and was present in all samples from 0 to 75 m; below 75 m it was rare (Table 2). Eighty-seven percent of the estimated water column abundance was from the upper 50 m, with highest concentrations at 25-50 m (Figure 3b). Abundances in replicate tows within the 0-25 m and 25-50 m intervals were not significantly different from each other; they were, however, significantly greater (Mann-Whitney U test, P <0.01) than those in deeper intervals. A wide range of larval lengths was found within each depth interval from 0 to 75 m and the cumu- lative size-frequency curves differed significantly (Kolmogorov-Smirnov test, P<0.05) between all three intervals (Figure 4). There was no simple 100 UJ (J cc UJ Cl ^ 50 3 O 1 <^ ' / / ^75- J 25- 50 i r / / / / / / r lOOm 1 '50- -75 m J •b- -25 rr 1 1 ' 1 ' 1 1 -^ 2 0 4 0 6,0 8,0 10.0 12.0 STANDARD LENGTH (mm) 14,0 Figure 4. — Cumulative size-frequency curves for Cyclothone alba larvae by 25 m depth interval (10 samples per interval) within the upper 100 m of the North Pacific central gyre during summer. 784 LOEB: VERTICAL DISTRIBUTION OF LARVAL FISHES Most of the smallest C. alba larvae apparently occur near the bottom of the mixed layer, and move first up and then downward with increasing size and development; the most advanced stage attained in 0-100 m is prometamorphic. A rapid descent may then occur, indicated by the neair absence of any individuals in 100-225 m and 100- 350 m samples. Photophore completion and metamorphosis probably occur at depths >350 m, in agreement with Ahlstrom's (1974) report that only the white photophore stage oiCyclothone spp. is found above 200 m, and that more advanced stages occur deeper in the water column. Kobayashi (1973) gives a 300-1,000 m depth range for adult Pacific C. alba. He found that the individuals occurring in the range of maximum abundance (400-600 m) were smaller than those occurring shallower or deeper; intermediate-sized adults were shallower and largest adults were deeper. This size distribution of the adults paral- lels that found herein for the larvae, although shifted well downwards in the water column. Cyclothone sp. A is probably the larval form of C. pseudopallida, and is the only other larval Cyclo- thone species found in abundance in the central gyre (Loeb 1979b). Fifty-nine of the sixty larvae caught were from the upper 50 m, and maximum abundance was at 0-25 m (Table 3). Median stan- dard lengths increased with depth but, due to the small sample sizes, significance of differences in size-frequency distributions could not be tested. No metamorphic stages were taken either in the stratified tows or among the 365 Cyclothone sp. A larvae taken in 0-300 m IKPT samples during other gyre cruises. Most of esirly larval develop- ment may occur at 0-50 m, with a subsequent rapid descent to the juvenile-adult depth ranges (500-900 m; Kobayashi 1973). VINCIGUERRIA SPP. —Vinciguerria nimbaria was the second most abundant species caught {9% of all larvae). On a year-round basis it is the most abundant larval fish species taken in the gyre (Loeb 1979b). The larvae occurred in samples from 0 to 350 m (Figure 3b), but were consistently present ( 29 out of 30 samples ) only between 25 and 75 m. Ninety percent of the estimated water col- umn abundance was between 25 and 75 m ( 74% at 25-50 m). Abundances in replicate tows within the 25-50 m depth interval were significantly greater (P<0.01) than in any other interval (Table 3). Samples from 25 to 100 m contained a wide remge of larval sizes. However, median standard length increased with depth (Table 3 ) and cumula- tive size-frequency curves from 25-50 m and 50-75 m (Figure 5) were significantly different from each other. The proportion of metamorphosing indi- viduals increased below 50 m (Table 4). These included the prometamorphic (white photophore), midmetamorphic (rapid body shape change), and postmetamorphic (photophore completion and body pigmentation) stages described by Ahlstrom and Counts (1958). All V. nimbaria present in 0-25 m samples were early larvae, as were most in the 25-50 m samples (only 3% from 25-50 m were pro- or midmetamorphic). In contrast, 75% from 50-75 m were in metamorphic stages. Size dis- tribution at 75-100 m was essentially bimodal: 40% of the larvae were very small (3.5-6.0 mm) and 50% were metamorphic (10.5-17.5 mm). No juveniles or adults were taken. Vinciguerria poweriae was much less abundant, and had a deeper distribution than did its con- gener; it occurred from 50 to 350 m (Table 3), with maximum abundance at 75-100 m. There was a trend for increased size with depth (Table 3). Only four metamorphosing individuals were caught. 100 60 80 100 120 140 STANDARD LENGTH (mm) Figure 5. — Cumulative size-frequency curves for Vinciguerria nimbaria larvae by 25 m depth interval ( 10 samples per interval ) within the upper 100 m of the North Pacific central gyre during summer. Table 4. — Abundance of metamorphic stages of Vinciguerna nimbaria by depth during late summer in the North Pacific central gyre. Depth interval Total indivi- Pro- Mid- Post- Percent (m) duals metamorphic stages metamorphic 0-25 6 25-50 376 5 6 2.9 50-76 99 25 15 34 74.7 75-100 25 2 4 7 52.0 100-350 1 785 FISHERY BULLETIN: VOL, 77, NO, 4 OTHER GONOSTOMATIDS.— The eight other gonostomatid species caught were rare; together <4% of the family total (Tables 2, 3). Diplophos taenia had the shallowest distribution of any gonostomatid species, occurring mostly at 0-25 m. Gonostoma atlanticum, G. elongatum, Ichthyococ- cus ovatus, and Woodsia sp. were present in the 75-350 m range, with maxima at 75-100 m. Mar- grethia obtusirostra and Valenciennellus tripunctulatus were caught only at 100-225 m and 100-350 m. Family Sternoptychidae The Sternoptychidae is the third most abundant family in the central gyre in terms of total larval abundance on a year-round basis (Loeb 1979b). Peak abundances occur during winter months, when this family makes up more than 6% of the total larvae. Minimal catches occur in late sum- mer, so the 40 individuals taken during the pres- ent (late summer) cruise can provide only a very sketchy description of the vertical distributions of this otherwise abundant family. The two genera (Sternoptyx and Argyropelecus) almost always occurred deeper than 100 m ( Figure 2) and were abundant relative to other larvae in the 100-600 m depth range. Sternoptyx spp. ap- peared to have a shallower distribution than Ar- gyropelecus spp. (Table 2). All but 2 of the 35 Sternoptyx larvae were taken between 100 and 350 m, with largest catches at 100-225 m (24 larvae distributed among all six samples). Four of the five Argyropelecus larvae were caught at 350-600 m. This is in contrast with the depth distributions MEAN NO PER 1,000m' 100 200 300 PERCENT 25 50 Lomponyctinoe Myctophinae (b) 600 J Figure 6. — Vertical distributions of larval myctophids m the North Pacific central gyre during sununer. (a) Concentrations of myctophid larvae (31 species combined) by depth interval, (b) Percent of estimated water column abundances of Lampanyc- tinae and Myctophinae larvae in each depth interval. found in the eastern Atlantic (Badcock and Mer- rett 1976) where Argyrope/ecus larvae were found from 100 to 500 m and Sternoptyx from 500 to 1,000 m. A variety of developmental stages of both gen- era were found in the stratified samples. Sternop- tyx diaphana from 100 to 225 m ranged from early larvae (3.8 mm) to larvae with abdominal and isthmal photophores (7.7 mm). The four Argyro- pelecus spp. from 350-600 m ranged from very small undeveloped larvae to one individual with an almost complete photophore complement. Family Myctophidae The myctophids ( 14 genera, 31 species) contrib- uted over 42% of the total larvae. Over 98% of the estimated water column abundance was in the upper 100 m with maximum abundance at 25-50 m (Figure 6a). Diversity was highest (21 to 23 species) between 25 and 100 m (Table 2). The lar- val depth distributions of the two subfamilies dif- fered (Figure 6b). Ninety-four percent of the Lam- panyctinae estimated water column abundance was in the upper 75 m, with peak abundance at 25-50 m; only two (Lobianchia gemellari and Notolychnus valdiviae) of the 19 species were not taken in the 25-50 m interval (Table 3). This sub- family contributed 78% of the myctophid indi- viduals and therefore greatly influenced the shape of the family distribution curve (Figure 6a). Myc- tophinae larvae were never caught in the upper 25 m, and contributed only 7% of the total myctophid larvae in the 25-50 m interval. The subfamily was most abundant from 50-225 m, contributing 49%, 58%, and 71% of the total myctophid larvae in the 50-75 m, 75-100 m, and 100-225 m intervals, re- spectively; peak abundance occurred at 50-75 m (Figure 6b). Only 4 of the 12 myctophine species taken were found at 25-50 m, while 7 were taken at 50-75 m and 11 at 75-100 m (Table 3). Sig- nificant differences were found between the cumu- lative frequency versus depth distributions of the two subfamilies (Kolmogorov-Smirnov test, P<<0.01). Aspects of abundance, size distributions, and development of the more abundant species are considered below. For some species a variety of developmental stages was found. Because of the diverse patterns of photophore development ex- hibited by myctophid larvae (Moser and Ahlstrom 1970) only very general terminology is used to denote these stages. These include: early larvae ( = 786 LOEB. VERTICAL DISTRIBUTION OF LARVAL FISHES no photophore development); early photophore development larvae ( = photophores developing); late photophore development larvae ( = lacking full photophore complement and still having lar- val morphology); transforming, or meta- morphosing, individuals (= those completing photophore development and undergoing changes in pigmentation and morphology); and trans- formed, or early juvenile, stages ( = adult mor- phology and photophore patterns, but still lightly pigmented). Additional information from other gyre cruises on developmental stages is included here. Subfamily Lampanyctinae BOLINICHTHYS SPP. —Bolinichthys longipes was the fifth-ranked species taken, occurring primarily in the upper 50 m, with peak abundance at 0-25 m; abundances in replicate tows within the 0-25 m interval were significantly greater (Mann-Whitney U test, P<0.01) than in other depth intervals (Table 3). Median standard lengths increased with depth (Table 3) and 0-25 m and 25-50 m cumulative size-frequency curves were significantly different from each other. The largest specimen (8.7 mm, from 50-75 m) was still in early photophore development. The largest B. longipes larva (10.8 mm) of the 670 taken from IKPT samples was also in early photophore development. No transforming individuals were taken, although juveniles s 12.8 mm were caught. Bolinichthys distofax had a narrower distribu- tion than did B. longipes; all individuals came from 25-50 m (Table 3). Larval size ranges and developmental stages found in bongo and IKPT samples were comparable with those of B. lon- gipes. CERATOSCOPELUS WARMINGI.-Cerato- scopelus warmingi was the third-ranked species, >5% of total larvae, and is also third-ranked species on a year-round basis (Loeb 1979b). Al- though present at 0-225 m (Figure 7), 94% of the estimated water column abundance was at 25-75 m. Abundances in replicate samples within the 25-50 m interval were significantly greater (P<0.01) than in other intervals; the species made up 9% of the total larvae in this interval. Median standard lengths increased with depth and cumu- lative size-frequency curves for 0-25 m, 25-50 m, 50-75 m, and 75-225 m (Figure 8) were all sig- nificantly different from each other. The three largest larvae (8.6-12.8 mm), taken at 75-225 m, were still in early photophore development stages. No later photophore development stages or trans- forming specimens of C. warmingi were found among the 1,806 larvae (to 16.7 mm) examined from 0-300 m IKPT samples; a few early juveniles (S18.0 mm) were taken. DIAPHUS SPP. — Seven Diaphus species were taken on this cruise. They fell into the two morphological categories described by Moser and Ahlstrom (1974): the "slender" form (which as adults possess a suborbital photophore) and the MEAN NO. PER I.OOOm^ 0 20 30 40 600 -Diaphus anderseni - D elucens -D "slender B" -D rolfbolini D brachycephalus ■ D "slencjer C" — Hygophum proximum -- H. reinhardti Figure 7. — Vertical distributions of various myctophid species m the North Pacific central gyre during summer. Concentrations of (a) Ceratoscopelus warmingi and Notolychnus valdiviae. ibl Diaphus spp., and (c) Hygophum spp. larvae by depth interval. 787 FISHERY BULLETIN: VOL, 77, NO 4 100- UJ O CC bJ Q. LU > < _J O 50 0-25 75- 225m/ 50-75m / / I J 2.0 4,0 ' 1 I 60 80 ' I ' I I I ' I 10,0 12,0 STANDARD LENGTH (mm) Figure 8. — Cumulative size-frequency curves for Cerato- scopetus warmingi larvae taken in 10 samples each from 0-25 m, 25-50 m, 50-75 m, and in combined samples from 75-100 m (10) and 100-225 m (6) of the North Pacific central gyre during sum- mer. "stubby" form (without this photophore). The presence of transforming specimens of most of these species in planitton samples facilitated their probable identifications. The "slender" species were D. anderseni, D. brachycephalus, and the D. mollis complex. The "stubby" species were D. elu- cens, D. rolfbolini, and the possible larvae of D. schmidti. Diaphus anderseni had the shallowest distri- bution among Diaphus species, with 96% of the abundance from the upper 50 m and significant (P<0.05) peak abundance at 0-25 m (Figure 7b; Table 3). Median standard lengths increased slightly from 0-25 m to 25-50 m, with a much greater increase between 25-50 m and 50-75 m (Table 3); cumulative size-frequency curves were significantly different for all three intervals. The largest individuals (11.3 and 11.6 mm), caught at 50-75 m, were transforming. One recently trans- formed ( 10.5 mm) individual was taken at 100-350 m. The entire developmental sequence of D. an- derseni was found in 0-300 m IKPT samples; transforming individuals were 11.3-11.8 mm. Diaphus "slender C" (probably the "B" form of D. mollis; Clarke 1973), D. brachycephalus, D. elu- cens, and D. roZ/bo/jn;' all had similar distributions centered around maximum abundances at 25-50 m (Figure 7b); for all but D. brachycephalus the abundances in replicate tows within this interval were significantly greater than in other depth intervals (Table 3). Within the 25-50 m interval. D. elucens, D. rolfbolini, and D. "slender C" ranked 4, 7, and 8, respectively, in total larval abundance; D. elucens was the fourth-ranked species taken overall during this cruise (Table 2). For each species, median standard lengths in- creased with depth (Table 3) and 25-50 m and 50-75 m cumulative size-frequency curves were significantly different from each other. No transforming individuals of these species were taken in tows considered here, although a transforming D . "slender C" ( 10 .5 mm) was caught in a 0-100 m sample, and one recently transformed D. elucens (11.8 mm) was caught at 0-25 m. Oblique IKPT hauls (ranging in depth from 0-180 m to 0-360 m) on other central gyre cruises have caught late larval, transformational, and early juvenile stages of all four species. Transforming individuals of D. brachycephalus were 9.8-10.5 mm; D. elucens, 10.3-11.7 mm; D. "slender C," 11.2-12.7 mm; and D. rolfbolini, 11.7-12.5 mm. The two other Diaphus species taken were both rare in stratified tows (Table 2). Most of D. "slen- der B" (probably the "A" form of D. mollis; Clarke 1973) occurred at 50-75 m, the deepest distri- bution of the genus (Figure 7b). Transforming specimens (10.0-11.3 mm) have been caught in 0-300 m IKPT hauls. Diaphus "stubby C" may be the larval form of D. schmidti; the larvae have been taken in the central gyre only in small num- bers and sizes. Most were caught at 25-50 m dur- ing this cruise. LAMPADENA SPP. — Lampadena anomala and L. luminosa were caught in low numbers within the upper 50 m. Eleven L. luminosa larvae oc- curred in four tows from both 0-25 m and 25-50 m; one large larva (12.7 mm) was also taken at 75-100 m (Table 3). There was a trend for increased size with depth. Lampadena anomala was taken (one per sample) in five 0-25 m and three 25-50 m sam- ples (Table 3). All Lampadena spp. individuals were in early stages of photophore development. No late-stage specimens of these relatively rare central gyre species have been taken in any of the samples examined. LAMPANYCTUS SPP. -Lampanyctus stein- becki, most abundant of the larval Lampanyctus species taken, ranked ninth for this cruise (Table 2). It was caught at 0-75 m, but 89% of the esti- mated water column abundance was at 25-50 m; abundances in replicate samples within this interval were significantly higher (P<0.01) than 788 LOEB; VERTICAL DISTRIBUTION OF LARVAL FISHES in other intervals (Table 3). Only early-stage lar- vae (2.1-6.9 mm) were taken. Median standard length increased only slightly with depth (Table 3). The three other Lampanyctus species caught in stratified tows were rare. These included: L. "big snout," probably of the L. niger complex; L. "lacks pectorals," a larval stage of an undescribed Lam- panyctus species IE. H. Ahlstrom''); andL. nobilis. The larvae of L. "big snout" and L. nobilis were most abundant at 25-50 m, while L. "lacks pecto- rals" was taken mostly at 50-75 m (Table 3). All three species showed a trend for increased size with depth (Table 3); only early photophore development stages were taken. No late larval or transformational stages of any Lampanyctus species were found in 0-300 m IKPT samples (1,477 specimens examined). LOBIANCHIA GEMELLARI— The larvae of L. gemellari occurred deeper than most lampanyc- tine species, only at depths >50 m (Table 3). Over 94% of the estimated water column abundance was between 50 and 100 m; larvae were similar in frequency of occurrence in samples and in abun- dance at 50-75 m and 75-100 m. Cumulative size- frequency curves for 50-75 m and 75-100 m were significantly different from each other and indi- cated more small and fewer large individuals in the deeper interval. The largest larvae taken in stratified tows (6.7 and 7.9 mm) were in early photophore development. Stages from early larvae through transformation (10.8-12.7 mm) were caught in 0-180 m IKPT hauls. NOTOLYCHNUS VALDIVIAE.— Both the adult and larval N. valdiviae differ from other 1am- panyctine species in several respects, and Moser and Ahlstrom (1974) suggested placement of the species in a separate subfamily. The larvae are also unusual in their depth distributions as com- pared with other lampanyctine species (Figure 7a). Notolychnus valdiviae was absent at 0-50 m and rare at 50-75 m; maximum abundance (40 of the 44 larvae caught) occurred at 75-100 m where the species ranked fourth (Table 2). All stages of development of N. valdiviae were found between 50 and 100 m. The largest pretrans- formation specimen (8.0 mm) was from 75-100 m. 'E. H. Ahlstrom, Southwest Fisheries Center, National Marine Fisheries Service, NOAA, La JoUa, CA 92037, pers. commun. 1977. A 10.5 mm transforming specimen plus nine other individuals ranging from recently transformed to adult (10.8-21.8 mm) were caught at 50-75 m. Three other metamorphosed individuals were found in other intervals: a recently transformed individual ( 1 1.3 mm) at 25-50 m; and twojuveniles (15.7 and 17.3 mm) at 75-100 m. TRIPHOTURUS NIGRESCENS.—Triphoturus nigrescens was the fourth-ranked myctophid (eighth ranked species overall) taken. The larvae were distributed from 0 to 100 m, with 88% of the estimated water column abundance at 25-50 m; abundances in replicate samples within this in- terval were significantly greater (P<0.01) than in other intervals (Table 3). Median standard lengths increased below 50 m (Table 3) and 25-50 m and 50-75 m cumulative size-frequency curves were significantly different from each other. The 1 1.8 mm larva, from 75-100 m (Table 3), was one of the largest T. nigrescens larvae taken in any cen- tral gyre plankton sample; it still lacked photo- phore development. Nine metamorphosed indi- viduals were also caught in stratified tows: six ( 14.7-17.0 mm) at 25-50 m; one (17.9 mm) at 50-75 m; and two (17.0 and 21.3 mm) at 75-100 m. No late-stage larvae have been found among the 612 specimens collected from central gyre IKPT sam- ples. Subfamily Myctophinae BENTHOSEMA SUBORBITALE .—Benthosema suborbitale occurred at 75-350 m, and was an im- portant component of the deeper ichthyoplankton, ranking third in 75-100 m samples and second in 100-225 m and 100-350 m samples (Table 2). Largest numbers occurred at 75-100 m, but 46 of the 48 larvae from this interval came from only 2 of 10 samples; frequency of positive samples was highest at 100-225 m (five of six samples). Size ranges, median lengths, and cumulative size-fre- quency curves were similar for all depth intervals. The largest larva (8.0 mm) was in early photo- phore development. Seven recently transformed juveniles were caught: five (11.1-12.1 mm) at 25-50 m and two ( 10.8 and 12.7 mm) at 50-75 m. Developmental stages to early transformation (10.8-11.3 mm) were found in 0-300 m IKPT sam- ples. CENTROBRANCHUS SPP.— Three species of Centrobranchus were caught at 75-100 m (Table 789 FISHERY BULLETIN: VOL. 77, NO 4 3). Centrobranchus andrae and C. brevirostris were represented by single specimens. The five C. choerocephalus individuals (3.4-7.1 mm) occurred in three samples. All specimens were early photo- phore stage larvae. DIOGENICHTHYS ATLANTICUS. —The 12 D. atlanticus larvae (all early photophore stage lar- vae) were caught between 75 and 350 m; 8 came from 75-100 m (Table 2). During other central gyre cruises, D. atlanticus was abundant in IKPT sam- ples, and developmental stages from early larvae to transformation (11.3-12.8 mm) were found. HYGOPHUM SPP. —Hygophum proximum was the most numerous larval myctophine (Table 2). It occurred from 25 to 100 m, with maximum abun- dance and significantly larger catches in replicate tows (P<0.01) at 50-75 m (Table 3). Median stan- dard length increased with depth (Table 3) and 25-50 m and 50-100 m size-frequency curves were significantly different from each other. The largest larva (10.0 mm, from 75-100 m) was in early photophore development. No late-stage H. proximum larvae have been found among the 490 examined from 0-300 m IKPT samples. Hygophum reinhardti larvae were more deeply distributed than those off/, proximum, occurring from 50 to 225 m. As with its congener, maximum estimated water column abundance and signi- ficantly larger catches (Ps0.05) were at 50-75 m, but the larvae were also frequently taken (7 of 10 samples) at 75-100 m (Figure 7c). There were no apparent trends in size with depth (Table 3). No late photophore development larvae were caught, but two recently transformed individuals (12.3- 13.3 mm) were found in 0-300 m IKPT samples from other cruises. MYCTOPHUM SPP.— Four Myctophum species were caught (Table 2). The 58 M. lychnobium lar- vae occurred between 25 and 100 m, with maximum abundance at 25-50 m; M. brachy- gnathum had a similar distribution. All five M. selenops were caught at 50-75 m, and six of the seven M. nitidulum at 75-100 m. All of the larvae were small (<8.0 mm) and in early photophore development; only those of M. brachygnathum ap- peared to have increased size with depth (Table 3). A total of 393 Myctophum larvae, of all four species, have been examined from central gyre IKPT samples; none exceeded 10.0 mm or were in advanced stages of photophore development. SYMBOLOPHORUS EVERMANNl.—Symbolo- phorus evermanni occurred from 25 to 225 m; over 90% of the estimated water column abundance was between 50 and 100 m; abundances in repli- cate samples within the 50-75 m interval were significantly greater (P<0. 05) than in other inter- vals (Table 3). Although the largest larva (10.5 mm) was from 75-100 m, the median standard length was smaller there than at shallower depths (Table 3). The 25-50 m and 50-75 m cumulative size-frequency curves were significantly different from each other, indicating decreased size with increased depth. Only early photophore develop- ment stages were caught by stratified tows. This was also the case for all 0-300 m IKPT samples examined, where the largest prejuvenile (15.5 mm) of 369 individuals was in the earliest stages of photophore development. Other Larvae Other families contributed only 9% of the iden- tified larvae and included a wide assortment of mesopelagic fishes; only 3 of the 33 families iden- tified were epipelagic. These "other larvae" were found in samples taken from 0 to 350 m ( Figure 2), Total abundance was low in the upper 75 m, but increased greatly below 75 m (due primarily to peak abundances of two families), and made up 25% and 19% of the ichthyoplankton in 75-100 m and 100-350 m samples, respectively. Maximum diversity occurred at 25-50 m. None of these "other" species was abundant. Of the 49 kinds of larvae represented only 3 were caught in even moderate numbers: Bregmaceros spp. (Bregmacerotidae), Odontostomops nor- malops (Evermannellidae), and Howella sp. (Aponogonidae). Only Bregmaceros spp. is abun- dant in the central gyre ichthyoplankton on a year-round basis (Loeb 1979bl. Together these three kinds made up 39% of the other larvae; the remaining 61% was contributed by 1 order and 30 families (42 species). Catch information on the other larvae is presented in Table 2; more detailed distributional data is provided in Loeb (1979a). DISCUSSION AND CONCLUSIONS The overall vertical distribution pattern of cen- tral gyre ichthyoplankton conforms to that de- scribed by Ahlstrom (1959) for the California Cur- rent. Most species and individuals were in the upper 100 m, with maximum abundance and di- 790 LOEB: VERTICAL DISTRIBUTION OF LARVAL FISHES versity at 25-50 m, possibly related to the bottom of the mixed layer. A distinct change in species composition and relative abundances occurred below 75 m. This involved a shift from dominance by Cyclothone alba, Vinciguerria nimbaria, and lampanyctine myctophids to other gonostomatid species, myctophine myctophids, and other families. Ahlstrom (1959) previously had found groups of species (in the California Current) to be either predominantly within the mixed layer and upper thermocline or mostly within or below the thermocline. None of the abundant larvae were taken only in one 25 m interval, and most were found over at least a 75 m depth range. However, almost all species taken in the upper 100 m had distinct maxima of catch frequency and abundance within one of the 25 m depth intervals sampled; for many species, despite high catch variability due to patchiness, the abundances in replicate tows within this interval were significantly higher than in any other interval. Almost twice as many larvae and half again as many kinds were found in 100-225 m samples as in 100-350 m samples, indi- cating that most deeper species may be distributed above 225 m. Significant changes were found in cumulative size-frequency distributions with depth for many of the abundant species. There was a general trend for those species with peak abundance in the upper 50 m to have significant increases in larval size with depth. Species with maximum abundance below 50 m tended to exhibit no size-depth changes, or had significant decreases in size with depth. With these deeper larvae, the apparent lack of size change with depth may be the product of small sample sizes outside the depth of maximum abundance and the broader depth ranges sampled below 100 m. The gonostomatids exhibited two different dis- tributional patterns. Cyclothone spp., V. nim- baria, and Diplophos taenia occupied the topmost 50 m. The other seven species were distributed below 75 m, with maximum abundances in the 75-225 m range. The nighttime depth distribution patterns of juveniles and adults (from Clarke 1974) of the migratory gonostomatid species rela- tive to each other are, with the exception of Gono- stoma elongatum, generally the same as for the larvae (Figure 9). Both larval and adult Dip/op/ios taenia had the shallowest distribution and Valen- ciennellus tripunctulatus the deepest distribution within the family. Also, except for G. elongatum , DEPTH (m) 0 50 100 150 200 250 Diplophos i'-\ larvae foenio Vinciguerria nimbaria Vinciguerria poweriae Ichthyococcus ovafus Valenciennellus tripunctulatus Gonostoma atlanticum Gonostoma elongatum Figure 9. — Larval (upper bar) and adult (lower bar) nighttime depth distributions for migratory gonostomatid species taken in late summer near lat. 28° N, long. 155° W (North Pacific central gyre). Hatched larval depth range indicates intervals where >90% of the estimated water column abundance occurred. Adult depth distributions from Clarke (1974). the upper depth distributions of the adults (usu- ally small adults; Clarke 1974 ) tend to overlap the lower ranges of peak larval abundance. Although Clarke's (1974) adult information is from a differ- ent oceanic regime (offshore Hawaiian waters), his general patterns of depth distribution may still be valid for the central gyre adults. The night depth patterns of larval and adult myctophid species are more complex than those of the gonostomatids. The larvae of subfamily Lam- panyctinae generally occupy shallower depths than do those of subfamily Myctophinae (Figure 6b). The opposite is generally true of the night distributions of the adults from the two sub- families. Clarke ( 1973) presented adult depth dis- tributions for 46 myctophid species taken near Hawaii. Of the 15 myctophine species he listed, 8 had upper night distribution limits at 0-25 m (5 of these were taken in substantial numbers by dip nets); 2 others occurred at 25-50 m. In contrast, only 10 of the 31 lampanyctine species listed by Clarke (1973) were caught in the upper 50 m. Ahlstrom and Stevens (1976) also found that neus- ton (surface) samples taken in the California Cur- rent caught only myctophine juveniles and adults and lampanyctine larvae. Different night adult and larval depth patterns are apparent for the two subfamilies (Figure 10). Lampanyctine adults, generally overlap, or are distributed below, their depths of maximum larval abundance. The shallowest lampanyctine indi- viduals (which share the larval depth range) are usually small adults or juveniles (Clarke 1973). This contrasts strongly with myctophine adults 791 FISHERY BULLETIN: VOL. 77, NO, 4 Subfomily Lamponyclinae Bolinichthys disfofOJr Bolinichthys longipes Cerafoscopelus vvarnmgi Dtaphus onderseni Diaphus tyachycepholus Oaphus e/ucens D'ophus roffboltni Lompadena tummosa Lampanycrus nobihs LdmpanycTus sfeinbecki Lobionchia gsmelldn Nofofychnus valdivide Tnpho/urus nigrescens Subfomily Myclophmae Benthosemo suborbitale Diogenichthys oflonlicus Hygophum proximt/m Hygophum remhardti Myctophum nifidulum Symbolcphorus evermonn: DEPTH (m) 100 200 O Ijrvoe Figure 10. — Larval (upper bar) and juvenile eind adult (lower bar) nighttime depth distributions for the more abundant 1am- panyctine and myctophine (Myctophidae) species taken in late summer near lat. 28° N, long. 155° W (North Pacific central gyre). Hatched larval depth range indicates depth intervals where ^90% of the estimated water column abundance occurred. Adult depth distributions from Clarke (1973). {except for Hygophum spp.), wherein all sizes tend to be distributed above the depths of maximum larval abundance. In most cases the largest adults of both subfamilies are vertically separated from the larvae, and, where overlap occurs, the smallest juveniles are in similar depth ranges with the largest larvae. A variety of patterns of early developmental stages were found. Among the gonostomatids, metamorphic stages of Cyclothone alba and Vin- ciguerria spp. were found in stratified samples. Apparently C. alba leaves the larval depth range once it has reached the prometamorphic stage of development. Vinciguerria spp. go through all early metamorphic stages while in the larval depth range and presumably descend to greater depths once the postmetamorphic stage is com- pleted. For both C. alba and V. nimbaria the ad- vanced stages of larval development were found in the lower portion of the larval depth range. Gradual downward migration with development, as seen in V. nimbaria, may also occur in Valen- ciennellus tripunctulatus and Gonostoma spp. (Badcock and Merrett 1976). The myctophid species exhibited different levels of photophore development before descending to juvenile depths. Developmental series from early larvae to transforming individuals were found from 5=350 m for 11 of the 31 myctophid species 792 taken in Climax I. These include: six of the seven Diaphus species (all but D. schmidti), Lobianchia gemellari, Notolychnus valdiviae, Benthosema suborbitale, Diogenichthys atlanticus, and Hygophum reinhardti . At least some individuals of Diaphus spp., L. gemellari, N. valdiviae, andD. atlanticus complete transformation before descent to juvenile depths or else begin extensive migra- tions before transformation. The presence of lightly pigmented juveniles of D. anderseni, D. elucens, N. valdiviae, B. suborbitale, and H. rein- hardti in the upper 100 m at night indicated that, if these are not predescent individuals, some members of these species may undergo early juvenile migration. No late photophore stage larvae were found for Bolinichthys spp., Ceratoscopelus warmingi, Lampadena spp., Lampanyctus spp., Triphoturus nigrescens, H. proximum. Myctophum spp., or Symbolophorus evermanni in either the Climax I samples or 0-300 m IKPT samples taken on other gyre cruises. These larvae appear to leave the upper 300 m of the water column at varying levels of early photophore development prior to trans- formation. The late stages of photophore develop- ment probably occur at the juvenile day depth range for each species. The developmental state at descent appears to be a generic characteristic within both subfamilies. Except for Hygophum spp., congeners achieved similar levels of photo- phore development while in the upper 300 m. Due to small numbers of other larvae captured, little can be ascertained about their distributional patterns. Most species occurred in the upper 100 m, with greatest numbers of species at 25-50 m. Basic trends in depth distribution appeared to exist on a familial or ordinal level: Notosudidae were most abundant at 0-25 m; five families of ceratioid fishes occurred in the upper 50 m; four families of stomiatoid fishes and the Ever- mannellidae occurred most frequently at 25-75 m; Bregmacerotidae and Melamphaeidae were most abundant at 75-100 m; and Scopelarchidae, Bathylagidae, and Sternoptychidae occurred below 100 m. The paralepidids (much like the myctophids) exhibited a variety of depth distribu- tions through the upper 225 m. The depth distributions described are for the late summer central gyre ichthyoplankton as- semblage. Surface temperature is 6°-7° C lower in winter and the mixed layer depth increases from ca. 40 m in late summer to 110-140 m in winter (McGowan and Williams 1973). There are also LOEB: VERTICAL DISTRIBUTION OF LARVAL FISHES definite seasonal changes in larval fish species composition and abundance relations. As larval depth distributions are apparently affected by temperature distribution and mixed layer depth (Ahlstrom 1959) spatial patterns in winter gyre waters may be different from those portrayed here. ACKNOWLEDGMENTS This work was supported by grants from the Institute of Marine Resources of Scripps Institu- tion of Oceanography and the Oceanic Biology Program (Code 484) of the Office of Naval Re- search. Ship time was in part supported by the U.S. National Science Foundation and the Marine Life Research Program of the State of California. I greatly appreciate the assistance in larval fish identification provided by E. H. Ahlstrom and Betsy Stevens of the Southwest Fisheries Center, National Marine Fisheries Service, NOAA, La JoUa, Calif Special thanks go to Eric Shulen- berger of the Office of Naval Research for his excel- lent editorial advice. Thanks also to John A. McGowan and R. H. Rosenblatt of Scripps Institu- tion of Oceanography for their editorial sugges- tions. LITERATURE CITED Ahlstrom. E. H. 1959. Vertical distribution of pelagic fis)i eggs and larvae off California and Baja California. U.S. Fish Wildl. Serv , Fish. Bull. 60:107-146. 1969. Mesopelagic and bathypelagic fishes in the Califor- nia Current region Calif. Coop. Oceanic Fish. Invest. Rep. 13:39-44. 1974. The diverse patterns of metamorphosis in gonosto- matid fishes — an aid to classification. In J H. S. Blaxter (editor). The early life history of fish, p. 659-674. Springer-Verlag, N.Y. AHLSTROM, E. H., AND R. C. COUNTS. 1958. Development and distribution oWinciguerria lucetia and related species in the eastern Pacific. U.S. Fish Wildl. Serv., Fish. Bull. 58:363-416. AHLSTROM, E. H., AND E. STEVENS. 1976. Report of neuston (surface) collections made on an extended CalCOFI cruise during May 1972. Calif. Coop. Oceanic Fish Invest. Rep. 18:167-188. BADCOCK, J., AND N. R. MERRETT. 1976. Midwater fishes in the eastern North Atlantic. I. Vertical distribution and associated biology in 30°N, 23°W, with developmental notes on certain mycto- phids. Prog. Oceanogr. 7:3-58. Harnett, m. a. 1975. Studies on the patterns of distribution of mesopela- gic fish faunal assemblages in the central Pacific and their temporal persistence in the gyres. Ph.D. Thesis, Scripps Institution of Oceanogpraphy, Univ. California, San Diego. 145 p. Bridger, J. P. 1956. On day and night variation in catches of fish lar- vae. J. Cons. 22:42-57. Clarke, T. a. 1973. Some aspects of the ecology of lantemfishes (Mycto- phidae) in the Pacific Ocean near Hawaii. Fish. Bull., U.S. 71:401-434. 1974. Some aspects of the ecology of sUimiatoid fishes in the Pacific Ocean near Hawaii. Fish Bull., U.S. 72:337- 351. CONOVER, W. J. 1971. Practical nonparametric statistics. John Wiley and Sons, N.Y., 462 p. Gregg, M. C, C. S. Cox, and P. W. Hacker. 1973. Vertical microstructure measurements in the cen- tral North Pacific. J. Phys. Oceanogr 3:458-469. Kobayashi, B. N. 1973. Systematics, zoogeography, and aspects of the biol- ogy of the bathypelagic fish genus Cyclothone in the Pacific Ocean. Ph.D. Thesis, Scripps Institution of Oceanography, Univ. California, San Diego, 487 p. LEGAND. M., and J. RIVATON. 1969. Cycles biologiques des poissons mesopelagiques de Test de I'Ocean Indien, Trosieme note: action predatrice des poissons micronectoniques. Cah. O.R.S.T.O.M. Ser. Oceanogr. 7:29-45. LOEB, V. J. 1979a. The icthyoplankton assemblage of the North Pacific central gyre: spatial and temporal patterns. Ph.D. Thesis, Scripps Institntion of Oceanography, Univ. California, San Diego. 220 p. 1979b, Larval fishes in the zooplankton communtiy of the North Pacific central gyre. Mar. Biol. (Berl.) 53:173-191. MCGOWAN, J. A., AND T. L. HAYWARD. 1978. Mixing and oceanic productivity. Deep-Sea Res. 25:771-793. McGowAN, J. A.. AND P. W. Walker. In press. Structure in the copepod community of the central North Pacific gyre. Ecol. Monogr. MCGOWAN, J. A., AND P. M. WILLIAMS. 1973. Oceanic habitat differences in the North Pacific. J. Exp. Mar. Biol. Ecol. 12:187-217. MERRETT, N. R,, AND H. S. J. ROE. 1974. Patterns and selectivity in the feeding of certain mesopelagic fishes. Mar. Biol. (Berl) 28:115-126. MOSER. H. G., AND E. H. AHLSTROM. 1970. Development of lantemfishes (family Myctophidae) in the California Current. Part I. Species with narroweyed larvae. Bull. Los Ang. Cty. Mus. Nat. Hist. Sci. 7, 145 p. 1974. Role of larval stages in systematic investigations of marine teleosts: The Myctophidae, a case study. Fish. Bull., U.S. 72:391-413 PEARCY, W. G.. AND R. M. LAURS. 1966. Vertical migration and distribution of mesopelagic fishes off Oregon. Deep-Sea Res. 13:153-165. SCRIPPS Institution of oceanography. 1966. A new opening - closing paired zooplankton net. Scripps Inst. Oceanogr., SIO Ref 66-23. 56 p. 1974. Physical, chemical and biological data. Climax I Ex- pedition, 19 September - 28 September 1968 Scripps. Inst, Oceanogr.. SIO Ref 74-20, 41 p. 793 RESISTANCE OF DIFFERENT STOCKS AND TRANSFERRIN GENOTYPES OF COHO SALMON, ONCORHYNCHUS KISUTCH, AND STEELHEAD TROUT, SALMO GAIRDNERI, TO BACTERIAL KIDNEY DISEASE AND VIBRIOSIS^ Gary W. Winter,^ Carl B. Schreck,^ and John D. McIntyre^' ABSTRACT Juvenile coho salmon and steelhead trout of different stocks and three transferrin genotypes (AA, AC, and CO, all reared in identical or similar environments, were experimentally infected with Corynebacterium sp, the causative agent of bacterial kidney disease, or with Vibrio anguillarum, the causative agent of vibriosis. Mortality due to the pathogens was compared among stocks within a species and among transferrin genotypes within a stock to determine whether there was a genetic basis for resistance to disease. Differences in resistance to bacterial kidney disease among coho salmon stocks had a genetic basis. Stock susceptibility to vibriosis was strongly influenced by environmental factors. Coho salmon or steelhead trout of one stock may be resistant to one disease but susceptible to another. The importance of transferrin genotype of coho salmon in resistance to bacterial kidney disease was stock specific; in stocks that showed differential resistance of genotypes, the AA was the most susceptible. No differences in resistance to vibriosis were observed among transferrin genotypes. Bacterial kidney disease (BKD) caused by Corynebacterium sp. is a major cause of serious losses among salmon reared in freshwater hatcheries of the Pacific Northwest (Leitritz and Lewis 1976), and epizootics caused by Vibrio anguillarum in the marine environment are particularly devastating to salmonids maintained in saltwater impoundments (Fryer et al. 1972). Externally applied antibiotics are relatively ineffective in the treatment of these diseases. Immunization with bacterins for the control of vibriosis has been shown to be feasible (Fryer et al. 1976), but attempts to produce a bacterin for BKD have been unsuccessful (Evelyn 1977). The use of disease resistant populations offish may conceiv- ably reduce the incidence and severity of these diseases. Fish that inherit natural resistance to a disease normally maintain that resistance throughout their lives (Snieszko et al. 1959). In addition, information on the resistance of donor stocks, for use in transplants to infected waters, would be valuable. 'Oregon Agricultural Experimental Station Technical Paper No. 4862. 'Oregon Cooperative Fishery Research Unit, Oregon State University, Corvallis, OR 97331. Cooperators are Oregon State University, Oregon Department of Fish £uid Wildlife, and U.S. Fish and Wildlife Service. ^Oregon Cooperative Fishery Research Unit; present address: U.S. Fish and Wildlife Service, Box 1050, Tyler Road, Red Bluff, CA 96080 The existence of disease resistant strains within a species has been demonstrated. Stock or strain refers to a population of fish of one species which shares both a common environment (a particular stream) and common gene pool (discrete breeding group) and, as such, can be considered as a self-perpetuating system (Larkin 1972). Differences in susceptibility to ulcer disease and furunculosis have been observed among different strains of brook trout, Sa/i;e/jnus/bra<(>ja/!s (Wales and Berrian 1937; Wolf 1954; Snieszko 1957; Snieszko et al. 1959), and Gjedrem and Aulstad (1974) noted significant differences in resistance to vibriosis, which they showed to be slightly heritable, between different strains of Atlantic salmon, Salmo salar , parr in Norway. Unfortunately, in most previous studies of disease resistance, fish of the different stocks were not reared in a common environment. Since phenotypic expression is a combination of genotype, environment, and interactions between these two variables, different stocks must be reared under identical conditions if one is to be certain that differences in resistsmce to disease are genetic in origin and not due, for example, to previous exposure of a particular stock to the disease in question or some other factor such as nutritional history. One objective of the present study was to determine whether there are differences in resistance to BKD and vibriosis Manuscnpt accepted May 1979. FISHERY BULLETIN: VOL, 77, NO 4, 1980. 795 FISHERY BULLETIN: VOL 77, NO 4 among stocks of echo salmon, Oncorhynchus kisutch , and steelhead trout, Salmo gairdneri , and whether these differences have a genetic basis. Suzumoto et al. (1977) reported differences in resistance to BKD among three genotypes of transferrin (an iron-binding plasma protein) in coho salmon. In mammals, iron is known to increase the growth and virulence of some pathogens. Transferrin may reduce infection by binding the metal, thereby reducing its availability to invading bacteria, a process known as nutritional immunity (Weinberg 1974). No iron requirement has been demonstrated for BKD bacteria, although it is likely that one exists, judging by the fastidiousness of the organisms. Hershberger (1970) observed differences in iron binding capacity among transferrin genotypes in brook trout and suggested that individuals more efficient in the uptake and release of iron might fare better under "adverse conditions" such as disease. A second objective of this study was to compare resistance to BKD and vibriosis among transferrin genotypes, to evaluate earlier results with BKD, and to determine whether transferrin increases the tolerance of bacterial diseases of salmonids in general. We also sought to determine whether differences in resistance of transferrin genotypes exist among different stocks of coho salmon and steelhead trout. MATERIALS AND METHODS Juvenile coho salmon were obtained as eyed eggs from the Fall Creek (Alsea) and Big Creek salmon hatcheries, Oreg. The Big Creek hatchery was also the source of two crosses. Big Creek x Sol Due (B X S) and Big Creek x Umpqua (B x U). All stocks were reared at Corvallis, Oreg. — the Big Creek stock at Oregon State University's Smith Farm; the Alsea stock at the Oregon Department of Fish and Wildlife's Research Section; and the two crosses at Oregon State University's Fish Disease Laboratory. These rearing facilities presented similar, though not identical, environments for the fish. Because we lacked sufficient fish of the two crosses to include them in all studies, we used them only in the BKD study. Steelhead trout were obtained as green eggs from the following Oregon State hatcheries: Alsea (winter run), Roaring River (Siletz summer run). Cole Rivers (Rogue summer run), and Marion Forks (North Santiam winter run). All four stocks were reared under identical conditions at Smith Farm. For determination of the transferrin genotypes of the experimental fish, we withdrew about 0. 1 ml of blood from the caudal vein of anesthetized fish with a 1 ml tuberculin syringe and ejected it into heparinized hematocrit tubes, which were then centrifuged. The plasma from the salmon was frozen until the time of analysis. Blood samples from steelhead trout were placed on ice and processed within 4 h after collection because we found that frozen storage reduces the stability of transferrin in this species. Fish were individually identified by dangler tags applied immediately behind the dorsal fin. We used starch-gel electrophoresis, adapting the discontinuous buffer system described by Ridgeway et al. (1970), to determine transferrin genotypes. Only the AA, AC, and CC genotypes were considered, and in some stocks only two of these were used. The transferrins of Siletz and North Santiam steelhead trout stocks were not included in this study because resolution on the electrophoretic gels was poor. After the fish were bled, they were given a recovery period of at least 2 wk before they were tremsferred to experimental tanks. Bacterial Kidney Disease All experimental fish were held indoors in 70 1 fiber glass tanks supplied with flowing, aerated, chilled (12°±2° C), dechlorinated water. The fish were allowed to acclimate in these tanks for 2 wk. Fish were fed once daily with Oregon Moist Pellet. ' Each stock of coho salmon and steelhead trout consisted of 125 fish divided into two test replicates of 50 each plus 25 control fish. Included in the steelhead trout experiment was one group of 34 fish of hatchery-reared (Cole Rivers) Rogue River stock, without a replicate. The respective transferrin genotypes were distributed randomly among all tanks. The BKD (Corynebacterium sp.) strain (RB-1-73) used was isolated on cysteine serum agar from a spring chinook salmon, O. tshawytscha, at the Round Butte Oregon State Hatchery by J. E. Sanders, fish pathologist, Oregon Department of Fish and Wildlife. A stock culture was maintained on Mueller-Hinton agar (Difco Laboratories,'' Detroit, Mich.) enriched 'Reference to trade names does not imply endorsement by the National Marine Fisheries Service, NOAA. 796 WINTER ET AL,; RESISTANCE OF COHO SALMON AND STEELHEAD TROUT with cysteine (0.1%) and calf serum (20%). Before each experiment, cells were passed once in the species being tested to produce a fresh isolate, and this isolate was further cultured until sufficient cells were available for an inoculum. All test fish received an intraperitoneal injection of 0.1 ml of a suspension of kidney disease bacteria in phosphate-buffered saline (PBS), and all control fish received a 0.1 ml intraperitoneal injection of only PBS. The approximate inocula were 9 x 10' cells for the coho salmon (mean weight, 23 g), and 3 x 10* cells for the steelhead trout (mean weight, 36 g). The coho salmon were injected on 17 March 1977 and the steelhead trout on 12 September 1977. We examined all fish that died and identified BKD as the causative agent on the basis of presumptive diagnosis, using gram stains of kidney smears. In addition, kidney smears from 10% of the fish that died were cultured on Mueller-Hinton media. Experiments were terminated at the, end of 4 mo or earlier, depending on the progress of infection. One week after the coho salmon had been injected, an accidental exposure of the fish, including the controls, to chlorine resulted in mortalities as high as 50% in some stocks. The study was nevertheless continued, but a second, abbreviated test was begun on 24 August 1977. Only Alsea and Big Creek stocks (mean weight, 33.2 g) were used; the Big Creek fish were obtained directly from the hatchery. The inoculum for this second experiment was increased to 3 x 10* cells. Vibriosis The V. anguillarum strain (LS-174) used in these experiments was isolated on brain heart infusion agar from a coho salmon at Lint Slough, Waldport, Oreg., by J. S. Rohovec. The inocula were either prepared from lyophilized cells or recent passage isolates. Experimental fish were exposed to the pathogen in 93 1 stainless steel tanks at Oregon State University's Fish Disease Laboratory. Two experiments were undertaken with the coho salmon. In the first (8 October 1976), 225 fish (mean weights for Big Creek and Alsea stocks were 10.4 g and 14.5 g, respectively) from each stock were divided equally among two test replicates and an untreated control. The three tanks contained fish from each stock to insure identical treatment. The fish in this experiment, having not been bled and tagged for transferrin genotype identification, were freeze branded to differentiate the stocks in each tank. In the second experiment (10 June 1977) the number offish per tank was reduced to about 25 (mean weight, 36.6 g) because larger numbers were not available, but transferrin genotypes had been determined. In the steelhead trout phase of the study (21 October 1977), 75 fish from each stock (mean weight, 36 g) were divided equally among three test replicates and 15 from each stock were placed in a fourth tank for controls. A hatchery-reared Rogue stock was also used in this steelhead trout experiment. In a second experiment (27 December 1977) in which we used steelhead trout from the Cole Rivers (Rogue), Alsea, and Marion Forks (North Santiam) hatcheries, 50 fish (mean weight, 42.2 g) were divided equally between two replicates. Transferrin genotypes were distributed randomly among the tanks. The initial temperature in all experimental tanks was 12.2° C, to which all fish had been acclimated. The temperature was then raised to 17.7° C over a period of 1.5 h, and at this temperature water flow was discontinued in all tanks for 15 min. The bacteria suspended in brain heart infusion broth (Difco Laboratories) were then introduced into the test tanks (other than those of the controls). The inocula were 5 x 10'' cells/ml for the first coho salmon exposure and 8.6 X 10^ cells/ml for the second; the steelhead trout received concentrations of 8.8 x 10" cells/ml in the first experiment and 7.2 x 10" cells/ml in the second. All fish that died were necropsied and kidney smears were cultured on brain heart infusion agar. Positive diagnosis of V. anguillarum was confirmed by slide agglutination with specific antiserum. The experiments were terminated at the end of 1 wk. Statistical comparison of three or more stocks involved a one-way analysis of variance based on arcsin transformations of percentages and least significant difference, and comparisons of transferrin genotypes of two stocks were based on X^ test employing a 2 x /t contingency table (Snedecor and Cochran 1967). RESULTS AND DISCUSSION Bacterial Kidney Disease In the first experiment in which coho salmon were infected with BKD, the Alsea stock and B x U cross were about twice as resistant to the disease 797 FISHERY BULLETIN; VOL 77, NO. 4 as were fish of the Big Creek stock and B x S cross (see totals, Figure 1 A). The difference in mortality between the B x U and each of the two more susceptible groups (Big Creek and B x S), was significant (P<0.05), but the Alsea mortality was significantly lower than that of only the B x S, cross (P<0.06). A comparison of mean times to death (days) revealed a similar pattern: B x S, 79.5; B X U, 99.9; Big Creek, 88.4; and Alsea, 95.4. The mean times to death for the B x U and Alsea coho salmon were significantly greater than the B x S (P<0.05). The differential resistance of coho salmon stocks to BKD probably has a genetic basis because the stocks were reared in similar environments. Among transferrin genotypes, only the B x S cross and Alsea stock showed any important differences in resistance to BKD (Figure lA). In both groups the AA genotype was the most susceptible, and the AC and CC both showed lower, similar mortalities. The difference in resistance was significant (P<0.07) between the AA and AC genotypes within the B x S cross. The Alsea transferrin results, though not significant due to small sample size, are substantiated by a previous study in which Suzumoto et al. (1977) 100 n I- z u a. GENOTYPE AA AC CC T AA AC T AA AC T AA AC CC T STOCK BxS BxU BIG CR AISEA c BKD- -Steel head GENOTYPE AAAC T AC CC T STOCK BIG CR (HI ALSEA 100 Q < 50 101 34 26 Figure l. — Percentages offish of different stocks and transferrin genotypes that died of bacterial kidney disease iBKD) A and B, coho salmon experi- ments 1 and 2; C, steelhead trout experiment. T indicates total mortality for the stock which sometimes includes fish with unknown genotypes; AA, AC, and CC indicate mortality for individual genotypes; B x S = Big Creek x Sol Due cross and B x U = Big Creek x Umpqua cross; (H) indicates hatchery- reared fish. Numbers above bars show sample sizes; the vertical line above each bar represents the upper limit of the 95% confidence interval. GENOTYPE T I AC CC I T 1 STOCK ROGUE ROGUE (HI ALSEA N SAN SILETZ 798 WINTER ET AL.. RESISTANCE OF COHO SALMON AND STEELHEAD TROUT used Alsea coho salmon in which the AA genotype was also the most susceptible to BKD. Because of similar transferrin results in the B x S cross and Alsea stock, the data were combined. For the combined data, the AC (28% mortality) and CC (24% mortality) genotypes were significantly (P<0.01) more resistant to BKD than was the AA genotype (62% mortality). Within both the stocks and transferrin genotypes, differences between replicates were not significant. The second BKD experiment with coho salmon gave results similar to those of the first on the basis of transferrin genotypes (Figure IB). Unfor- tunately, the AA genotype was not included in the Alsea comparison because we lacked sufficient fish. No stock comparison was made because the Big Creek stock came directly from the hatchery, at a time when 91.5% of the mortalities in produc- tion fish at Big Creek were due to BKD (J. Con- rad^). The probability that the Big Creek coho salmon used in the experiment had previously been exposed to BKD was therefore very high. In the third BKD study, which involved the four steelhead stocks and a second Rogue stock reared at the hatchery (Figure IC), mortalities in all the test groups began to increase at a high rate 3 wk after the study began because of a secondary infec- tion with Aeromonas hydrophila. This trend con- tinued for another 4 wk, at which time mortalities leveled off, and the study was terminated. A com- parison of the resistance of the different stocks is not fully valid because the fish in the different test tanks were obviously not challenged equally with a secondary infection of A. hydrophila. However, there were no significant differences (P>0.10) be- tween replicates, and the mortality of the Siletz steelhead trout (72%) was significantly lower (P<0.05) than that of all other stocks except the Alsea. Because mortality in the Rogue stock was extremely high (96%), a transferrin genotype comparison was not considered. The AC and CC genotypes within the Alsea stock were equally susceptible to the double infection of BKD and A. hydrophila. Although percentage mortality is a better measure of an organism's ability to tolerate disease, mean time to death is also an indication of resistance to diseases, especially chronic ones such as BKD. There were no differences in mean time to death (days) among either the Rogue or Alsea steelhead transferrin genotypes (numbers of fish 'J. Conrad, Oregon Department of Fish and Wildlife, Clatskanie, OR 97015, pers. conunun. February 1978. in parentheses): Rogue— AA, 28.5 (30); AC, 30.0 (41); and CC, 29.7 (19); Alsea— AC, 30.4 (21); and CC, 30.0 (62). The importance of transferrin was probably reduced by the double infection. Vibriosis In the first experiment in which coho salmon were exposed to V. anguillarum (Figure 2A), the Big Creek stock (38 % mortality) was significantly more resistant (P<0.005) than the Alsea stock (62% mortality) (transferrin was not considered in this comparison). There was a significant differ- ence (P<0.005) in mean weight (<'-test, Snedecor and Cochran 1967: 1 14 ) between the Alsea and Big Creek fish. However, there were no significant differences (P>0.10) in resistance to vibriosis among four weight classes (5.1-10.0, 10.1-15.0, 15.1-20.0, and 20.1-25.0 g) within either stock. The difference in resistance between the two stocks appears to be genetic. In a second test, the resistance trend between the Alsea and Big Creek stocks was reversed (Figure 2B), though at a lower level of significance (P<0.07) than the previous experiment. However, the Alsea coho salmon used in this second test came directly from the hatch- ery. Though it is unlikely that any of these fish would have been previously exposed to V. anguil- larum in freshwater, a difference in susceptibility to vibriosis still existed. These conflicting results thus demonstrate that the environment has a strong effect in determining resistance to vib- riosis. In both the Alsea and Big Creek stocks, no differential resistance was shown by the transfer- rin genotypes, although the AA genotype was not included in the Alsea transferrins (Figure 2B). In the first of the two vibriosis experiments with steelhead trout (Figure 2C), the North Santiam steelhead trout were the least susceptible to vib- riosis of all the stocks (P<0.05). The Alsea steelhead trout, though exhibiting a higher mor- tality (87%) than the North Santiam fish, were still significantly more resistant than the remain- ing two stocks (P<0.05). Because mortality was high in the Smith Farm- and hatchery-reared Rogue stocks (96%), transferrin genotype differ- ences and the effects of rearing environment on resistance were not considered. However, no dif- ferences in resistance were observed among genotypes within the Alsea stock. These results using steelhead trout are similar to those observed in the coho salmon exposed to vibriosis. The second vibriosis experiment (Figure 2D), 799 FISHERY BULLETIN: VOL, 77, NO. 4 A VlBRlO-coho VIBRIO-steelhead 100 -\ < 50 100 n i^o < SO- BS 34 *- B VIBRIO coho GENOTYPE T t AC CC T T T STOCK ROGUE ROGUEIHI alSEA N SAN SILETZ D VIBRIO-steelhead 100-1 < 50 (J 100 n Q < 50- z LU o 9 « 39 50 T FIGURE 2— Percentages offish of different stocks and transferrin genotypes that died of vibriosis. A and B, coho salmon experi- ments 1 and 2; C and D, steelhead trout experiments 1 and 2 For interpretation of other features see Figure 1 . GENOTYPE AA AC T STOCK BIG CR AC CC I ALSEA(H) GENOTYPE AA AC CC T STOCK ROGUE (H) AC CC 1 I ALSEA(H1 NSANIHI involving hatchery-reared steelhead trout from the Rogue, Alsea, and North Santiam, revealed the same results as did the first, with respect to transferrin genotypes. No differential resistance was shovTO among genotypes, including the AA's, within either the Alsea or Rogue stocks. Although resistance to vibriosis among the three stocks was similar, the North Santiam stock showed the highest mortalities this time — which again em- phasizes the importance of environmental factors in the determination of resistance and the need for eliminating environmental differences in making genetic comparisons. There was a significant dif- ference in vertebral number between North San- tiam steelhead trout reared at the hatchery and at Smith Farm, indicating an environmental differ- ence (our unpubl. data). The Rogue replicates in this experiment were significantly different (P<0.025) with respect to stock mortality; con- sequently a genetic comparison was invalid. Ex- cept for the hatchery-reared Rogue replicates in the last vibriosis experiment using steelhead trout, there were no significant differences between rep- licates for stocks or genotypes in all four vibriosis tests; consequently we combined replicates in the data analysis. 800 WINTER ET AL,: RESISTANCE OF COHO SALMON AND STEELHEAD TROUT Perhaps stock resistance to acute diseases such as vibriosis depends more on which stock has an environmental advantage at the time of in- fection, rather than on genetic make-up. Also, when mortalities in experiments are high, resis- tance comparisons are difficult to make because any immunity that was present may have been overwhelmed. Genetic factors are probably more important in chronic diseases such as BKD. For example, Zinn et al. (1977) observed appairent genetic resistance to infection by Ceratomyxa shasta, normally not an acute condition, among hatchery strains of chinook salmon. It is also evident that a stock may be resistant to one disease and not to another. Although the Siletz steelhead trout were most resistant to the double infection of BKD and A. hydrophila, they showed the greatest susceptibility to V. anguil- larum. Ehlinger (1977) observed that certain selected brook trout strains, though resistant to furunculosis, were more susceptible to gill disease than was the native stock. Consequently selection of stocks for resistance to several diseases would be difficult (Mclntyre 1977), except possibly when the pathogens are closely related (Hutt 1970). Judging by the present results, it appears that the importance of transferrin genotypes in resis- tance to disease is stock specific. Differences among genotypes were only observed in the Alsea and B X S coho salmon infected with BKD. Wein- berg (1974) noted that different host species may vary in the extent to which they rely on iron- specific nutritional immunity. Although only the most common genotypes were compared within each stock, it is unlikely that other genotypes would have shown greater resistance to BKD; their frequencies within the stocks would have been increased by natural selection if the disease plays an important role as a selective agent. How- ever, it is apparent that factors other than disease may select for different transferrin genotypes. In Ukranian carp, Cyprinus carpio, general survival rates were highest among individuals with the AC genotype (Balakhnin and Galagan 1972). There is also an association of transferrin phenotype with weight gain in juvenile rainbow trout that may be due to the linkage of the transferrin locus with a gene or gene complex affecting growth (Reinitz 1977). The association of resistance to BKD with transferrin genotype may also be due to a gene linkage; if so, transferrin serves only as a marker. Mclntyre and Johnson (1977) observed higher growth rates and better survival in AA than in AC transferrin genotypes of Big Creek coho salmon. While the frequency of the C allele is high in the Alsea stock , that frequency is depressed in a mixed population at Big Creek where Alsea coho salmon have been used to supplement the broodstock (J. D. Mclntyre unpubl. data). Although BKD selects for the C allele in the Alsea coho salmon, the advantage of this allele is offset by some other more important selective factor, such as growth rate, within the Big Creek stock. It is also conceivable that transferrin genotypes provide resistance to different diseases, or not at all — as with vibriosis. The ability to synthesize iron chelators — compounds necessary to remove iron from transferrin — is considered a virulence factor for certain pathogens (Arnold et al. 1977). Perhaps the iron chelators of V. anguillarum re- move iron from transferrin more efficiently than do those of BKD bacteria. This more efficient re- moval would explain to some extent the lack of differential resistance to vibriosis among genotypes within both coho salmon and steelhead trout stocks. Pratschner ( 1978) observed differen- tial resistance among transferrin phenotypes to vibriosis and several other diseEises in coho salmon from the Skagit River, Wash. The AA phenotype exhibited greater susceptibility to vibriosis and cytophagosis but greater resistance to furun- culosis while the CC phenotype was most resistant to vibriosis and very susceptible to furunculosis and cytophagosis. The disparity between Pratschner's and our results with respect to vib- riosis may be due to the stock-specific nature of transferrin. Possibly differences among transfer- rin genotypes are more significant in a chronic disease such as BKD, and less so in an acute dis- ease such as vibriosis — or perhaps the rapid death rate following exposure to V. anguillarum com- pressed the results too much to allow differences to be observed. Because of the short time span in- volved to vibriosis infections, the benefit of such differences to individual fish would be negligible. Keeping in mind such considerations as selec- tion for transferrin genotypes by different factors such as growth or disease, it becomes clear ( as with stocks) that selectively breeding for certain trans- ferrin genotypes would not be advisable. Though selection for one particular genotype might pro- vide resistance to BKD, it might also entail lower growth rates or even greater susceptibility to other diseases. Mclntyre (1977) cautiously rec- ommended selective breeding for disease resis- tance only in propagated fish being held under 801 FISHERY BULLETIN: VOL 77, NO. 4 carefully controlled conditions or when one par- ticular pathogen is a recurrent problem. Other- wise, it seems advisable to maintain variability in a stock to meet the demands of a variable envi- ronment. LITERATURE CITED ARNOLD. R. R.. M. F. COLE. AND J. R. MCGHEE. 1977. A bactericidal effect for human lactoferrin. Sci- ence (Wash., D.C.) 197:263-265. BALAKHNIN, I. A., AND N. P. GALAGAN. 1972. Distribution and survival rate of individuals with different transferrin types among carp offspring from var- ious combinations of parents. Hydrobiol J. 8l3):41-45. Ehlinger, N. F. 1977. Selective breeding of trout for resistance to fu- runculosis. N.Y. Fish Game J. 24:25-36. Evelyn, T. P. T. 1977. Immunization of salmonids. /n Proceedings from the International Symposium of Diseases of Cultured Salmonids. April 4-6. 1977. p 161-176. Tavolek, Inc.. Seattle, Wash. FRYER, J. L., J. S. Nelson, and R. L. Garrison. 1972. Vibriosis in fish, /n R. W. Moore (editor). Progress in fishery and food science, p. 129-133. Univ. Wash. Publ. Fish., New Ser. 5. Fryer, J. L., J. S. Rohovec, G. L. Tebbit, j. s. Mcmichael, and K. S. pilcher. 1976. Vaccination for control of infectious diseases m Pacific salmon. Fish Pathol. 10:155-164. Gjedrem, T., and D. Aulstad. 1974. Selection experiments with salmon. I. Differences in resistance to vibrio disease of salmon parr ^Salmo salar). Aquaculture 3:51-59. HERSHBERGER, W. K. 1970. Some physicochemical properties of transferrins in brook trout. Trans. Am. Fish. Soc 99:207-218. HUTT, F B 1970. (Genetic resistance to infection. In R. H. Dunlop andH. W. Moon (editors). Resistance to infectious disease, p. 1-11. Saskatoon Modem Press, Sask. Larkin, p. a. 1972. The stock concept and management of Pacific salm- on. In R.C. Simon and P. A. Larkin (editors). The stock concept in Pacific salmon, p. 11-15. H. R. MacMillan Lec- tures in Fisheries, Univ. B.C., Vancouver. LEITRITZ, E., AND R. C. LEWIS. 1976. Trout and salmon culture (hatchery methods). Calif. Dep. Fish Game, Fish Bull. 164, 197 p. MclNTYRE, J. D. 1977. Heritable tolerance of disease in salmonids. In Proceedings from the International Symposium on Dis- eases of Cultured Salmonids, April 4-6, 1977, p. 87-90. Tavolek, Tnc, Seattle, Wash. MclNTYRE, J. D., AND A. K. JOHNSON. 1977. Relative yield of two transferrin phenotypes in coho salmon. Prog. Fish-Cult. 39:175-177. Pratschner, G. a. 1978. The relative resistance of six transferrin phenotypes of coho salmon iOncorhynchus kisutch) to cytophagosis, furunculosis, and vibriosis. M.S. Thesis, Univ. Washington, Seattle, 71 p REINITZ, G. L. 1977. Tests for association of transferrin and lactate de- hydrogenase phenotypes with weight gain in rainbow trout iSalmo gairdnen)- J. Fish. Res. Board Can. 34:2333-2337. RIDGWAY, G. J., S. W. SHERBURNE, AND R. D. LEWIS. 1970. Polymorphism in the esterases of Atlantic her- ring. Trans. Am. Fish. Soc. 99:147-151. Snedecor, G. W., and W. G. Cochran. 1967. Statistical methods, 6th ed. Iowa State Univ. Press, Ames, 593 p. Snieszko, S. F. 1957. Disease resistant and susceptible populations of brook trout tSalvelinus fontmalts). In J C Marr (coordinator). Contributions to the study of subpopula- tions of fishes, p. 126-128. U.S. Fish Wildl. Serv., Spec. Sci. Rep. Fish. 208. SNIESZKO, S. F., C. E. Dunbar, and G. L. Bullock. 1959. Resistance to ulcer disease and furunculosis in east- em brook trout, Salvelinus fontinalis. Prog. Fish-Cult. 21:111-116. SUZUMOTO, B. K., C. B. SCHRECK, AND J. D. MClNTYRE. 1977 Relative resistance of three transferrin genotypes of coho salmon iOnchorhynchus kisutch^ and their hematological responses to bacterial kidney disease. J. Fish. Res. Board. Can 34:1-8 Wales, J. H., and W. Berrian. 1937. The relative susceptibility ofvarious strains of trout to fumnculosis. Calif. Fish Game 23:147-148. Weinberg, E. D. 1974. Iron and susceptibility to infectious disease. Sci- ence (Wash., D.C.) 184:952-956. Wolf, L. E. 1954. Development of disease-resistant strains of fish. Trans. Am. Fish. Soc. 83:342-349. ZiNN, J. L., K. A. Johnson, J. E. Sanders, and J. L. Fryer. 1977. Susceptibility of salmonid species and hatchery strains of chinook salmon tOncorhynchufi tshawytscha ) to infections by Cvratomyxa shasta. J. Fish. Res. Board Can. 34:933-936. 802 REMARKS ON SYSTEMATICS, DEVELOPMENT, AND DISTRIBUTION OF THE HATCHETFISH GENUS STERNOPTYX (PISCES, STOMIATOIDEI) Julian Badcock' and Ronald C. Baird^ ABSTRACT Sternoptyx pseudodiaphana Borodulina is reported from the eastern North Atlantic in sympatry with S. diaphana, providing conclusive evidence that the former represents a species distinct from S. diaphana. Patterns of geographic variation among various characters are apparent in species of Sternoptyx as is allometric growth. These patterns render species identification difficult in certain allopatric populations, particularly those from the Atlantic and Pacific Oceans. Each species has distinct patterns of horizontal and vertical distribution and where species occur in sympatry, their centers of abundance do not coincide. Members of the genus Sternoptyx inhabit the "lower mesopelagic depth zone" (sensu Baird) from 500 to 1,500 m. Geographic variation in depth of maximum abun- dance for various species can be demonstrated. These appear correlated with variations in tempera- ture and light although competitive mteractions may also contribute to observed depth ranges. Photophore development is similar in the three species described and postlarval individuals of S. diaphana and S. pseudodiaphana are readily distinguishable. Characters useful in distinguishing the various species are presented in relation to patterns of geographic variation. A single ancestral species which gave rise to the four presently recognized species, each exhibiting slight morphological divergence, is advanced as a parsimonious mitial hypothesis of evolutionary relationship. The genus Sternoptyx has, until recently, been thought to contain but a single polymorphic species (Schultz 1961, 1964). However, Baird (1971), and more recently Haruta and Kawaguchi (1976), have demonstrated the validity of three morphologically similar species, S. diaphana Hermann, S. obscura Garman, and S. pseudob- scura Baird, each with broad but distinct geo- graphic ranges. Baird (1971) also noted a mor- phologically distinct population of S. diaphana from the subtropical convergence region of the South Pacific. In view of the degree of character similarity and lack of sympatry with other popula- tions of S. diaphana, he considered his data in- sufficient to substantiate the Southern Ocean form as a distinct species. Borodulina (1977) sub- sequently described the Southern Ocean form as S. pseudodiaphana £md has recently published a synopsis of the hatchetfish genera Argyropelecus and Sternoptyx based on Russian collections (Borodulina 1978). Sternoptyx pseudodiaphana from the eastern tropical Atlantic occurs in sympatry with S. 'Institute of Oceanographic Sciences. Wormley, Godalming, Surrey, U.K. Authorship alphabetical. ^Department of Marine Science, University of South Florida, St. Petersburg, Fla. diaphana. Our new data provide conclusive evi- dence that S. pseudodiaphana represents a species distinct from S. diaphana. Patterns of geographic variation are not well known in deep-sea fishes and patterns occur in the genus Sternoptyx which tend to obscure species distinctions among certain allopatric populations. Characters found useful in distinguishing among various species and popula- tions are presented which complement and expand the treatments of Baird (1971) and Borodulina (1978). We describe metamorphic and postlarval development for various species and include com- parisons among species. Additional data on the geographic and vertical distribution of the genus, including information from discrete-depth trawl- ing studies, are presented which add considerably to our knowledge of the distribution of this wide- spread group of mesopelagic fishes. METHODS All four species of Sternoptyx were examined. The material and its sources are listed in Appen- dix Table 1. The specimens were fixed in Forma- lin^ and preserved either in alcohol (70% ethyl or 'Reference to trade names does not imply endorsement by the National Marine Fisheries Service, NOAA. Manuscript accepted June 1979. nSHERY BULLETIN VOL 77. NO 4. 1980 803 FISHERY BULLETIN: VOL 77. NO 4 40% isopropyl) or in aqueous storage fluid (10% propylene glycol, 1% Formalin, 0.5% phenoxytol, based upon Steedman 1974). Generally, speci- mens were taken by various open midwater nets; however, a number of samples were taken with opening/closing nets of various designs (Clarke 1969; Baker et al. 1973; Hopkins et al. 1973). Photophore Nomenclature The unique pattern of photophore clustering in the family Sternoptychidae (sensu Baird 1971) has resulted in a different system of nomenclature from that used for other stomiatoid families (Fig- ure 1). Weitzman (1974) suggested a revised nomenclature for stomiatoid taxa to include the hatchetfishes and for convenience, both appear in Table 1 (Weitzman's slightly modified). The dis- tinct and unusual specializations in external mor- phology in the hatchetfishes (sensu Baird 1971) make determinations of homology among photo- phore groups difficult. We regard the new terms, therefore, as a convenience rather than as sugges- tions of homologies between similarly named photophore groups throughout the Stomiatoidei. For instance the preorbital photophore (PO) of the genus Sternoptyx differs from that of either Ar- gyropelecus or Polyipnus morphologically, and probably functionally, and is perhaps more aptly termed an oral organ (Herring 1977). Neverthe- less, for convenience, the term PO (ORB of Weitzman) is retained. P'i / /'. tf H ■::. M ...-; , PO / PRO''^ BR' •L IS ^PTO SO./ <•?». '}i18 mm SL) can be distinguished on the basis of vertebral number 29-32 versus 27-29, respectively, Table 2; see also Borodulina 1978), and the placement of the photophore SAN (de- scribed by SAN depth/SL and trunk depth/SAN height, Figures 6, 7) which is appreciably raised in S. pseudodiaphana . Overlap of more than one of these three characters in any given specimen was rarely observed. Other differences, most notice- able in sympatric populations, occur in body shape and pigmentation. Sternoptyx diaphana is gener- ally deeper in body and especially trunk, appreci- ably less pigmented, and lacks streaks on the outer ventral caudal fin margin in larger indi- viduals (Tables 3, 4). Sternoptyx obscura is distinguished from S. 807 FISHERY BULLETIN: VOL. 77. NO. 4 :S ^:^JL -•■'•K-Mt' •-'■-' .'^s-'-X'-iX- : '■■'• ''■■ ^. ■ ' ■"•■■'"^^--. "4- • .y*^ r -'" -''-'/'y ^^^i^ jVA» •■ -. .''fc- ■i»,-' \ I ■■'*■■>-,■. ■ -'--^ -. 4 • .^ ■ ," '. - -. rr'-*' * 4 1^.,* ■%■ '■■^■' ,^:i --^lyj,*!!.- ^-M^' ^lim^^ Z^i m 7%i^ ;a Figure i.—Stemoptyx obscum, 39 mm SL. Table 3. — Proportional measurements of Sternoptyx species for various size classes. 11-16 mm SL^ S. diaphana 17-47 mm SL S diaphana 16-55 mm Mean SL S pseudobscura Hem Mean Range n Mean Range n Range n Body deptti^ 85,2 80 8-900 7 87 1 75 7-96 7 74 87.4 732-96.2 52 AN length' 10 1 8 2-11.4 11 12 0 9 4-13 9 58 8,6 5 5-10 5 45 SC length' 55 4 2-6 4 6 73 59-11 2 55 53 3 8-6 7 41 SAN depth' 298 28 3-31 8 10 332 27 0-39 7 88 208 14 4-30 7 66 Trunk depth' 38.0 34.2.40.8 11 44 1 38 3-49 5 88 39.5 33 7-46 7 56 Trunk length' 36.1 34.2-382 11 36 1 32 0-43 8 86 35.6 27 0-41.5 54 Trunk depth/trunk length 1 05 1,00-1 12 11 1 21 0 94-1 37 86 1.12 0 95-1.33 64 Dorsal base/dorsal blade — — — 0 76 0 56-1 00 72 0 79 056-094 19 Trunk deplh/SAN height 4 4 3 8-6 0 11 38 2 9-6 1 86 2.0 16-2 5 56 Orbit diameter/suborbital length 089 083-0.95 11 103 089-121 57 085 072-104 37 13-17 mm Mean SL' S pseudodiaphana Range n 18-61 mr^ Mean SL S pseudodiaphana Range n 15-40 mm SL S. obscura Item Mean Range n Body depth' 78.6 70 1-89 4 27 80,8 705-92,6 131 74.9 68 4-82 1 18 AN length' 9.8 76-11 8 36 11 4 88-137 120 8.5 6.0-11.1 11 SC length' 63 53-76 19 76 5 0-117 120 5.1 4 0-7.7 11 SAN depth' 24 4 22 3-31.8 36 25 3 21 7-33 2 132 229 20 3-26.2 18 Trunk depth' 358 31 4-41.2 36 38 8 33 5-46 6 132 316 27.5-35 1 18 Trunk length' 37 4 32 9-43 8 36 37 7 33 2-43 4 132 37 7 32 5-42 2 18 Trunk depth/trunk length 095 0.83-1 11 34 1 03 0 86-1 24 131 083 0 75-0 94 26 Dorsal base/dorsal blade — — — 090 065-1 12 51 1.14 1 03-1 43 14 Trunk depth/SAN height 28 23-34 32 27 2 1-3 4 132 36 2 6-5 1 18 Orbit diameter/suborbital length 1 06 0 96-1 21 36 1 07 0 92-1.45 108 105 0 89-130 10 'Subadults 'Percent standard length. pseudobscura (and indeed, all other species of Sternoptyx) by the narrow shape and configuration of the trunk and also the high dorsal fin base/ 808 dorsal blade ratio. The trunk is markedly longer than it is deep, while the dorsal blade height is usually much shorter than dorsal fin base length BADCOCK and BAIRD: SYSTEMATICS OF STERNOPTYX Figure 5. — Sternoptyx pseudobscura . 54 mm SL. (Table 3). Sternoptyx obscura is further distin- guished from S. pseudobscura by its lower place- ment of the photophore SAN and by uniformly dark pigment of body and trunk, as well as the presence of a dark corona along the caudal fin rays, radiating from the fin base. Geographic Variation " The degree of genetic differentiation and nature of geographic variation in populations of midwa- ter fishes have not been thoroughly explored, though evidence is now accumulating that such variation does exist and may be widespread in species with broad geographic ranges (e.g., Naf- paktitis 1968; Baird 1971; Pertseva-Ostroumova 1974; Karnella and Gibbs 1977). Baird (1971) was able to distinguish separate populations in several species of the related hatchetfish genus Ar- gyropelecus . Populations tended to remain distinct over time and differences among populations were generally associated with zoogeographic bound- aries. The present evidence indicates that similar patterns of geographic variation occur in species of Sternoptyx, the extent of which awaits more ex- tensive investigation. Geographic variation is apparent in both S. pseudobscura and S. pseudodiaphana. The sys- tematic problems arising from such variation are illustrated in Figures 6 and 7. In addition to the indicated allometry, the suitability of the two character complexes (trunk depth/SAN photo- phore height and SAN photophore depth) for dis- tinguishing species differs, depending on the populations being compared. Both characters are distinctive among the three species illustrated (S. diaphana, S. pseudodiaphana, and S. pseudob- scura) for sympatric populations in the North Atlantic. However, where southeast Pacific popu- lations of S. pseudodiaphana are compared with 809 FISHERY BULLETIN: VOL. 77. NO. 4 Table 4. — Characters useful in differentiating species of the genus Sternoptyx. S pseudodiaphana S. diaphana S. obscura S. pseudobscura Anal plerygiophore configuration SAN position Ratio dorsal base to dorsal blade Trunk dimensions Trunk pigmentation Caudal fm pigmentation Pectoral fin pigmentation Vertebral number Anal rays Anal photophores Eye size Dorsal rays Maxinnum size (SL) No appreciable pterygio- phore extension posterior to anal photophores {18 mm SL) About 3 or less times in trunk depth; not more than 3''; times in sub- adults Dorsal base normally shorter than blade, occasionally about equal to or slightly longer Trunk depth about equal to trunk length, in sub- adults often less Dark bar above midline, little pigment near midline Light pigment streaks at ventral outermost margin ol caudal rays of larger adults (ca. 40 mm) Absent in adults: present at ray bases in juveniles and subadults 30-32, rarely 29 14-15, rarely 13 In adults longer than peduncle depth, little horizontal extension of ventral body margin above anal fin Orbit diameter greater than suborbital length, rarely less 9-13. usually 11-12 >60 mm Similar to S pseudo- diaphana (>18 mm SL) More than 3 times in trunk depth more than 4 times in subadults (-ca 17 mm) Dorsal base usually less than 0 9 of blade Trunk depth conspicuously greater than trunk length, in subadults can be equal Light in region of midline Little or no pigment on caudal rays Not present 28. occasionally 27 or 29 14-15, occasionally 13 Similar to S pseudo- diaphana, anal photo- phores fill pterygio- phore gap' Orbit diameter about equal to, often less than, suborbital length 9-11, usually -11 <50 mm Extension posterior to anal photophores (see Haruta and Kavi'aguchi 1976) As in S. diaphana Dorsal base longer than dorsal blade Trunk depth conspicuously less than trunk length Uniformly dark over whole trunk region Corona of dark pigment spreading from base of caudal fin rays Not present 30, occasionally 29 12-13 Shorter than peduncle depth, body margin ex- tends posteriorly above anal fin Orbit diameter usually greater than suborbital length 9-11. usually <11 <45 mm Similar to S obscura (see Haruta and Kawaguchi 1976) About IV2 to 2V; times in trunk depth, raised to midtrunk line in Atlan- tic populations As in S pseudodiaphana Trunk width greater than trunk length Nonuniform dark pigment in trunk region Dark pigment restricted to innermost margin of caudal fin rays Not present 29. ocasionally 28 or 30 13-15 Similar to S obscura Orbit diameter less than suborbital length, equal to it 9-11 >55 mm Atlantic forms of S. diaphana the trunk depth character exhibits overlap particularly in smaller individuals. Likewise, while the SAN depth character is distinctive for S. diaphana and S. pseudodiaphana, there is considerable overlap when Pacific populations of S. pseudobscura are compared with S. pseudodiaphana. The lower po- sition of the SAN photophore has been illustrated by Haruta and Kawaguchi (1976, figure 6) for western Pacific forms of S. pseudobscura and can be compared with the Atlantic form illustrated here (Figure 5). Differences in vertebral number between Pacific and tropical Atlantic forms of S. pseudodiaphana are indicated (Table 2) and the character should be useful in distinguishing the Pacific population from S. obscura. Postlarval Development Characters useful in distinguishing later life stages are often less suitable or ineffective for metamorphosing and postlarval stages or indeed small ( <18 mm) subadults. Geographic variation and allometric growth further complicate iden- tification. The present data, while substantiating the presence of both allometry and geographic var- iation {Table 3; Figure 7), cannot be considered comprehensive and intensive studies of collections from numerous geographic regions are yet to be done. The extension of the ventral trunk margin, size of AN photophore group, and elongate pos- terior pterygiophores appear to be neotenic characters established from mid- to late- metamorphic stages (Figures 8, 9) and are con- sequently less useful as species-distinctive characters for early life stages. When present, the location of photophore SAN is diagnostic, though the placement tends to be somewhat lower on the body in postlarvae. SAN is closely associated with photophores AN in S. diaphana and not markedly raised in S. obscura. For S. pseudodiaphana and S. pseudobscura it is vertically separated from the AN group. In Atlan- tic populations of S. pseudobscura the photophore SAN is raised to the midtrunk line, distinguishing it from other congeners. The lower SAN position in Indo- Pacific populations of S. pseudobscura make this character less useful in separating it from S. pseudodiaphana. The smaller eye (noted by GiJnther 18871 in S. pseudobscura (Table 3) is 810 BADCOCK and BAIRD: SYSTEMATTCS OF STERNOPTY'X Figure 6— Scattergram of ratio of SAN photophore depth/SL and SL (mil- limeters) for three species of Stemoptyx . • S. p&eudobscu'o IATl.) n s. p.-.eudodijphono lAiL.*PaC.) AAA ODD 1 D D Figure 7— Scattergram of ratio of trunk depth (TD)/SAN photophore height and SL (millimeters) for three species of Sternoptyx. A S Oiopftono (ATl , • s . paejaoa'Joha^g I fl T L , i O 5, OS&uaodigphQno ( N. PACJ □ S piauOoblCurO fflTL.l (S o D D O O D O O O diagnostic while small individuals of the two species may be separated on the basis of pectoral fin ray pigment present in S. pseudodiaphana . The young of S. obscura are uniformly pigmented and have the characteristically narrow trunk at quite small sizes. The sequence of numbered "stages" in which photophore groups appear and are completed is listed in Table 1 for S. pseudodiaphana and S. diaphana. The sequential pattern is identical in both species, and limited data suggest S. pseudobscura also conforms to this pattern though the early-metamorphic forms of these species are as yet undescribed. For ease of reference a se- quence of stages based on the order of appearance of photophores during development is presented in Table 1. The brief account given below is intended primarily to outline the major anatomical land- marks during metamorphosis and to indicate some of the distinctions among species during postlarval development. Sternoptyx pseudodiaphana The least developed specimen observed of S. pseudodiaphana from the Atlantic (10.2 mm SL) is elongate, with the head about 25% of SL. Dorsal and pelvic fins are undeveloped, while the pectoral fin has six and the anal seven rays developing. The caudal has 19 rays. The postlarva is relatively transparent and pigment is restricted to certain areas: a symphysial pair of spots, two isthmus spots, the pectoral fin, and a caudal peduncle spot. Internally, the swim bladder is pigmented dorsad, as is the posterior part of the stomach. Meningeal pigment is present both as a melanophore in the 811 FISHERY BULLETIN; VOL. 77. NO. 4 Figure 8.— Development o{ Sternoptyx pseudndiaphana: (a) Stage 1, 10.0 mm SL; (b) Stage 4, 8.9 mm SL. pineal region and as scattered melanophores pos- terior to it. In the most advanced Stage 1 specimen (Figure 8a) additional pigment occurs anterior to the stomach. Stomach pigmentation is completed by Stage 3 and during this stage new pigment sites develop along the ventral margin of the orbit, in the opercular region, and along the predorsal crest. Light abdominal pigmentation appears during Stage 4 and the caudal pigment extends anteriorly along the dorsum (Figure 8b), reaching the dorsal fin base later in this stage. As development pro- gresses, pigmentation spreads and intensifies 812 BADCOCK and BAIRD: SYSTEMATICS OF STERNOPTYX Figure 9. — Development of Stemoptyx diaphana. (upper) Stage 2, 7.0 mm SL; (lower) Stage 3, 7.2 mm SL. 813 FISHERY BULLETIN: VOL. 77. NO 4 leading to the adult condition. The rays of the dorsal fin first develop during Stage 3; the rays of the pelvic fin first appear in Stage 4. A series of S. pseudodiaphana taken from the southeastern Pacific (lat. 33°-39° S, long. 80°-120° W) show a similarity in morphology and pattern of development to North Atlantic forms. The data indicate that the sequences of both appearance and completion of the various photophore groups are similar, although the relative timing of com- pletion for certain groups may differ slightly. For example, while the completion of PV in North Atlantic forms apparently occurs prior to the in- itiation of SC, in southeastern Pacific forms it oc- curs afterwards (Table 1). Pigmentation in speci- mens from these two populations is essentially alike, but a small pigment spot located near the posterior end of the dentary in Pacific forms was not noted in the Atlantic material. As in the adults, differences between postlarvae from the two areas, then, does occur. Slight differences in larval characteristics be- tween populations of the same species have been shown for certain lanternfishes (Pertseva- Ostroumova 1974) and do occur in the genus Ster- noptyx, differences which we suspect, based on Argyropelecus, may be more extensive than indi- cated here. They can render species differentiation difficult in certain areas. Early-metamorphic in- dividuals of S. diaphana and S. pseudobscura are superficially similar and in tropical Atlantic col- lections only late-metamorphic stages can be separated with certainty. Metamorphic individu- als of S. pseudodiaphana, on the other hand, are highly distinctive. A series of S. diaphana taken off Bermuda, an area where S. pseudobscura is apparently rare, allowed for some comparison be- tween the midmetamorphic forms of this species and S. pseudodiaphana . The caudal spot so conspicuous in the young of S. pseudodiaphana at Stage 1 (Table 1) is found neither in S. diaphana nor S. pseudobscura prior to completion of photophore development. Pig- mentation of the pectoral fin rays has been found in S. diaphana, although not consistently, up to Stage 3. At any given stage, S. diaphana appears to be in a more advanced state both morphologi- cally and in terms of pigmentation. Thus the configuration of the anal fin pterygiophores at- tains the juvenile appearance during Stage 3, ap- pearing in Stage 4 in S. pseudodiaphana; the pel- vic fins differentiate earlier (Stage 3 versus 4), as does the pigmentation of S. diaphana in general (Figure 9). Even so, the pigmentation of S. pseudodiaphana tends to be denser in the more advanced specimens, which are conspicuous by the dark color of the dorsum. Elbert H. Ahlstrom'* recognizes three forms of postlarval Sternoptyx spp. in his North Pacific collections, none of which bear a caudal melanophore. As populations of S. pseudodiaphana are unknown north of the Equator in the Pacific, then, tentatively, postlar- val S. obscura also lack caudal pigment. Sternop- tyx pseudodiaphana may, therefore, be distin- guished from congeners by this character. General Comments During metamorphosis postlarval Sternoptyx (ca. 6-14 mm) undergo extensive change from an elongate premetamorphic form to a deep-bodied juvenile. In earlier stages, metamorphic individu- als are somewhat shorter than premetamorphic forms, a pattern of apparent loss in length also observed in the related hatchetfish genus Ar- gyropelecus (e.g., Brauer 1906; Jespersen 1915; and others). While the sequential pattern of photophore addition appears identical among the species examined, timetables for the differentia- tion of other external characters do not necessarily coincide. As indicated, S. diaphana appears in a more advanced state of morphological differentia- tion and development than S. pseudodiaphana at comparable photophore stages. A similar pattern has been observed by Baird (unpubl. data) among species of Argyropelecus. Geographic variation both among and within species is apparent. It ap- pears that there can be appreciable flexibility among species in the timing of photophore addi- tion in relation to the development of other mor- phological characters, though the adaptive sig- nificance of these observations is presently unclear. Growth rate, the functional significance of photophore presence at a given size, and broader ecological considerations such as predation or re- I source availability, are likely complexly related to patterns of photophore development. GEOGRAPHIC AND BATHYMETRIC DISTRIBUTION OF STERNOPTYX SPECIES The genus is widespread, occurring in all oceans *E. H. Ahlstrom, Southwest Fisheries Center La JoUa Laboratory, National Marine Fisheries Service, NOAA, La Jolla, CA 92038, pers. commun. November 1975. 814 BADCOCK and BAIRD SYSTEMATICS OF STERNOPTYX and apparently excluded only from polar seas and the Mediterranean ( Jespersen 1915; Geistdoerfer et al. 1970; Baird 1971; Haruta and Kawaguchi 1976; Borodulina 1978). The geographic distribu- tions of the species are presented in Figures 10 and 1 1 and, when coupled with the recent Russian data (Borodulina 1978), exhibit certain distinct pat- terns. The species tend to be limited to areas with hydrographically similar characteristics (sensu Baird 1971) and often exhibit mutually exclusive distributions. The horizontal distributions con- form in general to zoogeographically distinct re- gions in the oceans (e.g., Baird 1971; McGowan 1977; Backus and Craddock 1977), the nature and limits of which are only generally defined. From the limited number of observations of vertical dis- tribution in areas of sympatry, species which share the water column tend to have separate depths of maximum abundance. Sternoptyx obscura is confined to the Indo- Pacific. In the eastern Pacific and Indian equato- rial regions, it is the sole representative of the genus. In the periphery of its distribution, it can be relatively abundant (e.g., basins off southern California) and can occur in sympatry with S. diaphana and S . pseudobscura (Figures 10, 11). In general the geographic distribution resembles that of a number of other species, e.g., Myctophum aurolanternatum, Cyclothone acclinidens. Scopelarchoides signifer, Rosenblattichthys alatus (Nafpaktitis and Nafpaktitis 1969; Parin et al. 1973; Johnson 1974; Mukhacheva 1974; Quero 1974; Becker and Borodulina 1976), that are ap- parent equatorial Indo-Pacific endemics. Sternoptyx diaphana and S. pseudobscura occur in the Atlantic and Indo-Pacific and overlap for much of their ranges (Figures 10, 11). Sternoptyx pseudobscura, however, is apparently uncommon in the western North Atlantic and the Caribbean, where S. diaphana is abundant, yet it is well rep- resented in the Gulf of Mexico. The occurrence of all three species in Indonesian basin regions is indicative of the zoogeographic complexity of the mesopelagic ichthyofauna of that area. Sternoptyx pseudodiaphana is widely distribut- ed in the Southern Ocean (see also Borodulina 1978) and associated boundary currents in the Southern Hemisphere (Figure 11). Evidence from other studies (e.g., Alvarino 1965; Gibbs 1968; Krefft and Parin 1972; Nafpaktitis 1973; Mayer 1975; Bertelsen et al. 1976) has indicated that the subtropical convergence area, at least in the South Pacific, is a distinct zoogeographic region with a number of endemic or characteristic species. The occurrence of S. pseudodiaphana off South Aus- tralia, in the Indian Ocean, and across the South Atlantic between lat. 32°-40° S reinforces the con- cept that many elements of the subtropical con- 60^ 'C) — I — 60* — r 9cr ■60° ■40° 20° 20° •40° — 1 90* —I — 60* — I 30* — t— 0° — I — 30° 120° 150° 180* ISO* 120* Figure 10. — Distribution of Sternoptyx obscura and S, pseudobscura (also from Baird 1971; Haruta and Kawaguchi 1976). 815 0* FISHERY BULLETIN: VOL 77, NO. 4 30" 60° 90° 40°- 20° 20°- 60° 40° 20° -40° 120° 150° 180° 150* 120* 90* 60* 30* 0* 30° 60* 90° FIGURE 11.— Distribution of Sternoptyx diaphana and S. pseudodmphana (also from Baird 1971; Haruta and Kawaguchi 1976). vergence fauna in the Pacific have circum- Southern Ocean distributions (Craddock and Mead 19701. McGinnis (1974) has presented evi- dence in support of counterclockwise circulation in the Pacific subantarctic with observed endemism in mesopelagic fishes resulting from zoogeograph- ic isolation of that region. Sternoptyx pseudo- diaphana from this area can be distinguished from Atlantic forms and the evidence present- ed here is not in conflict with the McGinnis hypothesis. In the tropical eastern North Atlantic S. pseudodiaphana extends as far north as lat. 20° N, long. 21° W (where it exists in sympatry with S. diaphana ) and it is not unlikely that it occurs in the Gulf of Guinea (Figure 11). Although some specimens have been taken in the Benguela Cur- rent area, the general paucity of material at pre- sent available from the South Atlantic precludes judgment as to whether a link exists between the North Atlantic and Subtropical Convergence populations. A potentially disjimct distribution, in a manner less extreme than is expressed by Stomias boa boa (Gibbs 1969), is given some tenta- tive support by the apparent differences observed between postlarvae from the North Atlantic and South Pacific. Thus it is possible that the North Atlantic population of S. pseudodiaphana is a di- verging form of the Subtropical Convergence stock. Finally, mention should be made of the single specimen apparently caught near the Philippines. There is no obvious mistake in the station labelling for this individual (Challenger Stn. 218). The species range extends considerably northward in the Atlantic and future studies may also confirm a more complex distribution pattern in the Pacific than present data would indicate. The species oi Sternoptyx are the deepest dwell- ing of the marine hatchetfishes and do not exhibit marked diel vertical migration. There are few cap- ture records from opening/closing nets but new data are provided from recent comprehensive sur- veys (0-2,000 m) at three locations, in the eastern North Atlantic and Gulf of Mexico, where discrete-depth trawls were taken (Hopkins and Baird 1973; Badcock and Merrett 1976). Sternop- tyx diaphana and S. pseudohscura occur sympatri- cally at all three locations. Sternoptyx pseudodia- phana was found only at the eastern Atlantic stations where it was the least abundant species at lat. 18° N but more common at lat. 11° N. Indi- viduals of all species were taken over a broad depth range (ca. 500-2,000 m) but were only abun- dant over a much more restricted depth zone (Ta- ble 5). Thus, S. diaphana and S. pseudobscura, which have broad areas of sympatry, tend to have distinctly separate zones of maximum abundance while S. pseudodiaphana , at the limits of its dis- tribution, is somewhat intermediate and overlaps 816 BADCOCK and BAIRD: SYSTEMATICS OF STERNOPTYX Table 5. — Range of depths of maximum abundance of species of Sternoptyx in sympatry at three locations (subadults and adults I (Hopkins and Baird 1973; Badcock and Merrett 1976). Species Lat 2r N, long, 86' W Lat. 18° N, long 25° W Lai 11" N. long 20 W S. diaphana S- pseudobscura S. pseudodtaphana 600-750 m 850-1,000 m Not present 600-800 m 800-1.500 m 600-1,500 m 500-700 m 800-1,000 m 600-1.000 m both congeners (Table 5). The shoaling oi Sternop- tyx spp. between lat. 18° N and 11° N is not a function of developmental state and is a feature shown by many species of midwater fishes (Bad- cock and Merrett 1977). In other areas of the eastern North Atlantic and also in the Gulf of Mexico where S. pseudobscura and S. diaphana share the water column, popula- tions of S. pseudobscura are always centered below those of S. diaphana. Data presented by Baird (1971) indicated that S. pseudodiaphana is usually taken in 800-1,200 m depth in the South- ern Ocean. Evidence from recent collections from the South Atlantic imply a similar pattern of ver- tical distribution.^ In general, then, S. pseudodia- phana and S. pseudobscura may be regarded as deeper dwelling species of Sternoptyx while S. diaphana is a shallower living form. In certain areas of the Atlantic, discrete sampling has shown S. diaphana to be centered deeper than indicated above (Badcock 1970; Badcock and Merrett 1976; Roper et al.^). Sternoptyx pseudobscura has been shown to be of low abundance in these areas but the deepening of S. diaphana is likely to be a consequence of the sinking of isotherms relative to other Eireas. The role of competitive interactions among these species is yet undocumented and these may also exert an effect on geographic pat- terns of vertical distribution. Data on S. obscura are not comprehensive, but a preliminary survey of maximum depth of open trawl collections indi- cate a depth range similar to S. diaphana (500- 1,000 m) in basins off southern California. An analysis of the vertical distribution of mid- and late-metamorphic stages in the eastern North Atlantic was possible only for S. pseudodiaphana because of the problems in distinguishing between such individuals of the other two species ex- amined. As with subadults and adults, indi- viduals of like developmental stage lay shallower 'G. Krefft, Instutit fiir Seefischerei, Hamburg, West Germany, pers. commun. 1976. 'Roper, C.F.E.,R.H.Gibbs, Jr., and W.Aron. 1970. Ocean acre: an interim report. Report to the U.S. Navy Underwater Sound Laboratory. Contract No. N00140-69-C-0166. Smithson. Inst., Wash., DC., 22 p. in the water column at lat. 1 1° N, long. 20° W than at lat. 18° N, long. 25° W (400-800 m versus 500-900 m depth). Although the data are sparse, there is evidence for ontogenetic vertical strat- ification among metamorphic stages. At lat. 1 1°N, long. 20° W, Stages 1-3 occurred only in 400-500 m depth; Stage 4 in 400-600 m; Stage 5 in 500-700 m; and Stage 6 in 500-800 m. A similar relationship is implied for metamorphic stages from lat. 18° N, long. 25° W, although stratification occurred deeper in the water column. CONCLUSIONS The evidence presented shows Sternoptyx to contain four closely related species. Morphological distinctions between them are relatively slight, but are consistent among the populations examined. The four species have broad geographic ranges and the limited data indicate the occur- rence of geographic variation in S. pseudobscura and S. pseudodiaphana at adult and postlarval levels. Thus systematic difficulties arise in that certain characters useful in distinguishing species in sympatry may overlap when measurements from other populations are included. Characters subject to allometric growth simi- larly present systematic problems. Nevertheless, most of the morphological criteria used here to separate species are maintained irrespective of population or developmental state. When found in sympatry, distinctions are clear and species con- sistently separable by many characters. While we distinguish two species pairs on the basis of anal fin pterygiophore configuration, no hypothesis of cladistic relationship among the species is advanced. Considering the highly specialized and peculiar morphology of the genus (Baird 1971; Baird and Eckhardt 1972; Weitzman 1974; for discussion of family relationships), the most parsimonious hypothesis advanced is that a single ancestral species evolved which diverged considerably from a more generalized hatchetfish stock. Subsequent speciation in the genus proba- bly involved the isolation of populations which now show very slight morphological divergence, exhibit various degrees of geographic variation, and have distinct horizontal and vertical patterns of distribution. ACKNOWLEDGMENTS Our thanks go to R. H. Gibbs, Jr. (Smithsonian 817 FISHERY BULLETIN: VOL. 77. NO, 4 Institution), A. C. Wheeler (British Museum, Natural History), R. J. Lavenberg (Los Angeles County Museum), M. M. Dick and K. Leim (Museum of Comparative Zoology), R. H. Backus (Woods Hole Oceanographic Institute), J. Nielsen (Zoologiske Museum, Copenhagen), and G. Krefft (Institut fiir Seefischerei, Hamburg) and their in- stitutions for making material available. We are also grateful to P. M. David, N. R. Merrett, R. J. Gibbs, Jr., and R. J. Lavenberg for their valuable comments smd discussions of the manuscript. Fi- nally, our thanks to R. A. Larcombe and Nancy Smith (illustrations). 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APPENDIX Table 1. — Materials and their sources of Sternoptyx spp. No 01 Species specimens Instrtution' Ship (cruise) Station Position Catalog number S pseudodiaphana 1 BMNH H.M.S. Challenger 159 47=25 S. 130-22' E BMNH 87 12 7 151 1 218 02°33 S, 144-04 E BMNH 87 12,7 157 6 RRS Discovery II 81 32°45' S. 08-47' W BMNH 1930 1 12 43035 1 85 33'08' S. 04-30' E BMNH 1930 1 12 441 3 86 33-25 ■ S. 06-39 E BMNH 1930 1 12 552-5 2 256 34°14' S, 06-49' E BMNH 1930 1 12 411-12 4 269 15°55- S. 10-35' E BMNH 1930 1 12413-15 15 RRS Discovery (45) 7824 11°01' N, 20-1 1 ' W BMNH 1977 6 14 1-15 1 IFS Walther Herwig 30/68 36'37' S. 43-30' W 8 427/71 33°00' S. 07-50' E 50 lOS RRS Discover/ (31) 6662 10°58 N, 20-00' W 18 7089 17°50' N. 25-25 W 22 7803 ir50' N, 25-00' W 48 7824 10°50' N, 20-00' W 21 LACM Eltannin 1781 39 42 8. 130 11 W 41 1812 36-38 S. 87-09' W 27 1835 42'23 S. 160-14' E 1 MCZ Anton Bruun (3) 160 40-53 S. 60-01 E 1 (6) 7351 40-51 ' S. 64-49' E 1 (13) 5 34-26- S. 73-28' W 11 6 32-57' S. 74-57' W 3 10 33-32 S. 77-56' W 3 16 33-36' S. 79-32' W 2 20 34-01 ' S. 84-58 W 2 41 33-31' S. 7r29' W 1 Cham (35) 962 05-24' N. 39-55 W 819 FISHERY BULLETIN; VOL. 77. NO. 4 APPENDIX TABLE 1.— Continued. No ol Species specimens Institution' Ship (cruise) Station Position Catalog number 2 USNM Eltannin (21) 3 34-00 ■ S. 80-36 ■ W 207241 19 5 33-06 S, 83°57' W 207243 18 6 33 04 S. 85-49' W 207234:207235 5 8 33-00' S, 89-38' W 207236 7 11 37-12' S. 94-24' W 207233 7 11A 38-35' S. 95-39' W 207227 4 13 39-54' S. 107-36' W 207240 3 15 44-03' S. 120-17' W 207239 S diaphana 2 1 BMNH H.M.S. Challenger 171 214 28-33' S, 17r50' W 04-33' N. 127 06' E BMNH 87 12.7.152-3 BMNH 87.12.7 155 1 CAS Te Vega 548 35-39' N. 131-53' W 13 lOS RRS Discovery (21) 6662 10 58 N. 20-22' W 18 RRS Discovery (45) 7803 ir50'N, 25"00' W 35 7824 10-55' N. 20-00' W 51 RRS Discovery (52) 8281 32- N. 64° W 1 LACM Valero 11360 33'20' N. 118-45' W 1 MCZ Anion Bruun (6) 7247 07-56' S. 65-14- E 2 7298 22-48' S. 64-55' E 2 1 7305 7352 24-22' S. 64-50' E 29-45' S, 64-58' E 5 (19) 824 19"01'N, 79-02' W 2 829 19-21' N. 85-31' W 1 Chain (26) 505 12 "00' N. 65-00' W 4 Delaware (63-4) 31 NW Atlantic 6 MSI Bellows (1) 147 2700' N. 86-00' W 3 Mizar (3) 166 2736' N. 88-40' W S. obscura 1 BMNH H M 8 Challenger 214 04-33 N, 12706' E BMNH 87 12 7 156 1 1 CAS Te Vega 532 620 36 40 N. 122-04' W 32'48 N, 118-16' W 1 lOS Manihine (226) W Equatorial Indian Ocean 3 LACM Eltannin 34 07 47' S, 81-23' W 10203 1 Valero 33-20' N, 118°45' W 11360 10 MCZ Anton Bruun (6) 7194 03-27' N, 65-07' E 10 UANM Eltannin (31) 7A 10-57' N. 149-19' W 20 SIO Monsoon 11-00' N. 163-00' E 11 Tethys 07-00' S. 135-00' W 25 ZMUC Galalhea 10-24 8, 1 14-07' E S pseudobscura 1 1 BMNH H.M.S- Challenger 214 235 04-33' 8, 17r06' E 37-07 N. 138-00' E BMNH 87 12.7 154 BMNH 87.12.7.158 7 lOS RRS Discovery (21) 6662 10-58' N, 20-00' W 5 (45) 7803 ir50' N, 25-00' W 20 7824 10 55' N. 20-00' W 2 Manihine (226) W Equatorial Indian Ocean S- pseudobscura 1 5 1 13 1 MCZ Anton Bruun (6) (13) Cham (35) 7237 7303 24 829 978 05 55' S. 65-10' E 24-03 8. 64-50' E 33-48' S. 90-19' W 21-25- N, 85-30' W 20-00' S. 28-04' W 3 Delaware (63-4) 15 NW Atlantic 17 MSI Bellows (1) 142 2r00 N. 86-00' W 7 SIO Horizon 51375 31 53' N. 152-21' W 6 Monsoon 56133 12-40' N, 165-09' W 'BMNH— Britisti Museum ol Natural History, London; CAS— California Academy ol Sciences, San Francisco. IF8— Institut fur Seefischerei, Hamburg; 108— Institute ol Oceanograptiic Science, Wormley, Surrey; LACM— Los Angeles County Museum, Los Angeles, Calif , MCZ— Museum ol Comparative Zoology, Harvard University, Cambridge, Mass ; MSI— Department of Marine Science, University of South Florida, St Petersburg, Fla , USNM— National Museum of National History, Smithsonian Institution, Washington, D C , SIO— Scnpps Institute of Oceanography, La Jolla. Calil . ZMUC— Zoologiske Museum Copenhagen, University of Copenhagen, Copenhagen. 820 BEHAVIOR OF THE HAWAIIAN SPINNER DOLPHIN, STENELLA LONGIROSTRIS Kenneth S. Norris and Thomas P. Dohl' ABSTRACT The Hawaiian spinner dolphin, Stenella longirostris, was recorded from Kure Atoll to the island of Hawaii. It enters atoll lagoons or specific coves or swims over shallow sandy areas, usually near deep water, to rest. Access to nighttime feeding grounds may regulate the location of these rest areas. Rest areas are generally 50 meters or less in depth. Natural scars and marks allowed study of movements and school structure. Schools are fluid assemblages of variable size and composition. Only small subgroups within schools may have long- term integrity. Spinner dolphins exhibit several aerial patterns including spinning which is mostly associated with sound production upon reentry, and each is typical of a specific school activity level. Sounds may serve as omnidirectional sound sources maintaining school cohesion beyond the limits of vision. The daily cycle of spinner dolphins consists of nighttime feeding, morning approach to shore, morning-midday rest, and travel to feeding grounds near dusk. Feeding is upon scattering layer fishes, squid, and shrimp. Dolphins very commonly show scars from large sharks and from the small squaloid shark, Isistius brasiliensis, which scoops disc-shaped pieces of blubber from them. These wounds heal to form dollar- shaped scars. Most that is known in any depth about the be- havior of dolphins has come from observations of captive animals. Yet the environment of captivity, which is at best a pool a few dozen meters in longest dimension and 5 or 10 m deep, can allow only certain aspects of normal behavior to occur. Intragroup relationships may persist, but are usually distorted because relationships seldom remain intact. At best only hints of normal move- ment and activity patterns can persist where feed- ing schedules are determined by the workdays of trainers. In nature spinner dolphins, at least, travel constantly, even during rest. Dolphins of many species dive and feed in very deep water. Thus, however difficult it might be, the naturalist who would study dolphin behavior feels the need to study them in nature. It is usually no simple task. They are wary and travel many kilometers in a day. The presence of the observer almost inevitably causes bias. Dolphins hear ex- ceedingly well, and dolphin schools may be aware of an approaching ship a kilometer or more away. Our first 2-yr effort ( 1968-69), with a spotted, or "kiko," dolphin, Stenella attenuata, school which we knew to frequent the area within a few 'Center for Coastal Marine Studies, University of California, Santa Cruz, CA 95064. kilometers of Kaena Point, Oahu, Hawaii, was abandoned for the reasons mentioned above. It simply proved too expensive in time, money, and effort to work with the animals. Our work was never free from observer bias. Reports of a school of the spinner dolphin, Stenella longirostris, (Schlegel 1841), living permanently in Kealakekua Bay, on the Kona or lee coast of the island of Hawaii, caused us to visit the area to see if work was feasible. We found an unusual situa- tion in which several vexing observational prob- lems were ameliorated. Spinner dolphins do occur in Kealakekua Bay frequently (our figures indicate occupancy about 74% of the time). The bay itself is remarkably good for observation. The Kona coast is normally quite calm, especially in morning hours. Lateral visabil- ity is usually 20 m or more. The local people sel- dom disturb the dolphins. Only cruise boats, which seek out the schools and run through them, are a predictable disturbance. An abrupt 150 m lava clifT backs the bay. Schools sometimes came close to the cliff base at places where our visibility was blocked and could not be seen from the clifftop. But, most of the time we could watch wholly undis- turbed schools at reasonably close range, although the distance proved too long for individual iden- tification, and the lack of contrast between animal Manuscript accepted June 1979 F1.SHERY BULLETIN VOL. 77. NO, 4. 1980, 821-2''f'7 FISHERY BULLETIN VOL 77. NO 4 and background defeated good photography. Fi- nally, the bay is relatively small, 3.2 km across its mouth and indented about 2.5 km deep. Its entire area was visible from the clifFtop, and usually vis- ibility was good enough that one could see schools well beyond its confines (Figure 1). These unusual circumstances allowed us to gather new information about spinner dolphin be- havior, especially about the diurnal cycle and pat- terns of movement, though some difficult observa- tional problems remain. Spinner dolphins proved exceptionally interest- ing, observational subjects. Not only do they "spin" or leap from the water and revolve rapidly around their longitudinal axis, but they also perform other aerial behavior that can be observed from a considerable distance. These bits of aerial be- havior and the sequence in which they occurred proved to be a key to what one might call the emotional or activity level of the school. This level in turn is closely correlated with a number of fea- tures of dolphin life, especially the regular se- quence of activities during a daily cycle. Aerial Figure l. — Kealakekua Bay, Hawaii. Shown are observation posts on cliif that backs the bay, shallow-water areas (in me- ters), and approximate areas frequented by resting schools of spinner dolphins. Also indicated are arbitrary bay sectors used in analysis of arrival and departure directions. behavior, once understood, becomes a predicator of daily activity patterns. This work, performed in 1970-73, represents a beginning analysis of natural spinner dolphin behavior, a field still in its infancy. Previous re- ports of the behavior of wild dolphin schools have been mostly single or very fragmentary observa- tions (see Norris and Dohl in press for a review). A few detailed studies exist and allow comparison with this work, such as the work performed by Saayman and Tayler (1971); Saayman, Bower, and Tayler (1972); Tayler and Saayman (1972); and Saayman, Tayler, and Bower (1973), and more recently by Wiirsig and Wiirsig (1977); Shane (1977); Wursig (1978); Wells et al. (in press). Saayman and Tayler have analyzed the daily movements of the bottlenose dolphin, Tur- siops aduncus, and the Indopacific humpback dolphin, Sousa teuszii, and their feeding forma- tions and strategies for fish crowding and cap- ture. Wiirsigs' studies concentrated on Argenti- nian populations of Lagenorhynchiis obscurus and T. truncatus, while Wells et al. work dealt with T. truncatus in Florida. There are parallels in these works with the be- havior patterns described here. The recent work by the Wiirsigs on the group size, composition, and stability of bottlenose dolphin schools bears simi- larity. Like ours, much of this work was performed from clifftop observation posts using natural scars and marks to identify individuals. Shane's study, also on bottlenose dolphins, utilized natural scars and marks. Wells et al. carried out extensive tag- ging studies on Florida bottlenose dolphins. All of these studies and that reported here show re- markable fluidity in school composition and size over short periods of time. The dolphin popula- tions that have been studied, it seems, are not composed of discrete schools of modest size but instead of highly fluid groups that may range con- siderable distances and may be found associated in very variable combinations of individual animals. Morphology Hawaiian spinner dolphins are moderate-sized, slim-bodied, and long-beaked odontocete ceta- ceans. Adults reach at least 2 m TL (total length), and about 55-62 kg (Perrin 1975). They are hand- somely marked animals with a dark gray cape over the dorsal surface, a light gray lateral field (using the terminology of Perrin 1972) sharply demarcated from the cape above, and the white 822 NORMS and DOHL: BEHAVIOR OF THE HAWAIIAN SPINNER DOLPHIN belly below. The white of the belly extends up the flanks to about the level of the eye. The beak, or rostrum, is dark gray, tipped prominently with black; the lip margins are dark; and the ventral surface of the beak is white. The pectoral fins are dark gray, and a dark flipper band connects its anterior insertion to the eye, which is surrounded by a black eyepatch. Flukes and dorsal fin are dark gray. These color pattern components have been described in more detail by Perrin (1972), and they have been compared with the patterns of geographical forms of spinner dolphins living in the eastern tropical Pacific. In nature, against the blue or turquoise backdrop of tropical water, the dark pattern components of spinner dolphins ap- pear in shades of brown, but the effect is usually lost when the animals are removed from the wa- ter. The white and other pattern marks are often suffused with pink, from superficial blood flow in the blubber, which may also contribute to the overall brownish cast of pattern components in living spinners. Systematics In recent years a worldwide picture of the dis- tribution and systematics of tropical odontocetes has begun to emerge. Well-documented collec- tions, often with measurements and photographs, have been made from all oceans, especially where dolphins are involved in fishery operations (Kasuya et al. 1974; Perrin 1975). A special bene- ficiau-y of this work has been the once chaotic genus Stenella. It now seems reasonably clear that the genus is composed largely of three major species or species complexes: the spinner dolphins, allied to S. longirostris of the Hawaiian Islands; the striped dolphin, S.coeruZeoo/6a,- and the spotted dolphins, allied toS. attenuata of the Hawaiian Islands. All are tropical or subtropical. All are often found far offshore or near islands. In the eastern and central Pacific, Perrin ( 1975) discerned four geographical forms of spinner dol- phins: 1) a Costa Rican long-snouted form occur- ring close to the Central American coast, 2) an eastern form occupying the open sea from the American coast out to long. 115° W, 3 ) a whitebelly form occupying the open ocean both south and west of the eastern form (and overlapping with it to some extent) to about long. 145° W and nearly to lat. 5° S, and 4) an Hawaiian form localized around the Hawaiian island chain. Perrin ( 1975) stated that Hawaiian spinner dolphins are most closely related to the adjacent whitebelly form, differing from them by being somewhat more robust, by having a larger area of white belly col- oration, and by lacking the speckled margins of the white belly field. He places the complex tenta- tively in the species S. longirostris. Most of the races of spinner dolphins from around the world are quite similar to the Hawaiian form. Only the Costa Rican and eastern forms are strikingly different, being nearly uni- form gray, with faint hints of pattern components found in other races. These aberrant forms also show remarkable sexual dimorphism, which is otherwise rather subtle throughout the species. Fully adult males of these two races often possess a dorsal fin that is canted sharply forward, "like it was stuck on backward," and a very heavy post- anal protuberance. The fin of Hawaiian spinner dolphins is either triangular or very slightly fal- cate, and only a subtle postanal protuberance can be noted in adult males. METHODS A camp was established on the Green well Ranch at the edge of the cliff overlooking Kealakekua Bay (Figure 1). Two observation sites were used for recording and observation by telescopic means. Observer teams kept regular watches during day- light hours. Several vessels were used for observations at sea, or to provide an anchored platform in the bay, including the brigantine Westward and the motor sailers RV Hikino and the RV Imua. A trip through the northwest Hawaiian chain was made on the U.S. Coast Guard buoy tender Buttonwood. Fourteen spotting flights were made through- out the main Hawaiian chain, mostly from small fixed wing aircraft. Underwater observations were made in a spe- cially built underwater observation vehicle or mobile observation chamber (MOC) 6 m long, which looked like a small submarine (Figure 2) but did not submerge. It consisted of a float made from an auxiliary aircraft gasoline tank and a cen- tral observation chamber. The viewer in this chamber below water obtained ventilation from a squirrel cage blower and was surrounded by a band of Plexiglas^ windows at eye height. Controls for turning or tilting the craft were at hand, and a ^Reference to trade names does not imply endorsement by the National Marine Fisheries Service. NOAA. 823 FISHERY BULLETIN: VOL, 77. NO. 4 Figure 2. — Mobile observation chamber (MOO at Kealakekua Bay. The hatch is open to a cylindrical ob- servation chamber that projects 1.5 m below the hull. The observer views through a 360° band of Plexiglas win- dows. The operator steers and operates the engine. tape recorder was connected to a hydrophone^ mounted amidships and oriented forward. The craft was run by an outboard engine set in a well aft. Stability was maintained by 900 kg of lead blocks in a compartment below the observers feet. Other underwater observations were made with scuba, or by putting an observer with snorkle or scuba below the bow of a slowly moving skiff, hold- ing onto a bow painter. In this way the observers could sometimes be towed among the animals and even be jostled by them. A field station was estab- lished at the village of Napoopoo on Kealakekua Bay. Feeding was observed from skiffs and larger vessels. Dip net samples were taken in the region of feeding, and stomach analysis of such specimens as became available to us were collected. The squid and crustaceans in stomach samples were identified by Richard Young of the Department of Oceanography, University of Hawaii. Fish otolith collections were lost through improper preserva- tion. Recordings were made with a hydrophone de- ployed from a stationary skiff located near a school of animals or from the MOC. Monitoring was by use of headphones. During our studies we were fortunate to have William Schevill and William Watkins of the Woods Hole Oceanographic In- ^An Atlantic Research Corporation LC 32 hydrophone, a Hewlett-Packard 466A preamplifier, and a Uher 4000s Vi-in tape recorder composed the recording gear. The upper frequency response of this system was approximately 20 kHz at 7'/i: ips. stitution establish a four-hydrophone array deep in Kealakekua Bay. With this apparatus, three- dimensional tracks of passing dolphins were ob- tained that were of greater range and fidelity than allowed by our simple gear. The experimental ar- rangement of this array and recording charac- teristics are described in Watkins and Schevill (1974). Dolphin radiotracking used dolphin dorsal fin radios (see Evans 1974) and a hand-held direction finder. Dolphins were captured by a standard head net. Throughout this paper we use the term "school" to indicate all animals in a discrete area that move together. Such schools are often composed of rec- ognizable, discrete "groups" of animals clustered together and moving and diving more or less in unison. For instance, while the direction of move- ment of larger schools may be the same for all its parts, diving synchrony for all animals may be quite extended and ragged, being composed of a number of synchronously diving groups. Within such groups one can sometimes recognize small "subgroups" of a few (2 to perhaps 12) animals that are often seen together, regardless of the group or school composition around them. DISTRIBUTION Marine mammal collectors of the Sea Life Park, an Hawaiian oceanarium, suggested that spinner dolphins occur habitually at certain areas along the island shores, while they are largely or wholly 824 NORMS and DOHL: BEHAVIOR OF THE HAWAHAN SPINNER DOLPHIN absent from others. This led us to collect sighting and capture locations for the entire Hawaiian chain. The same collectors reported that after col- lection of animals from a given school, the school as a whole might become shy of the boat for an indefinite period, and suggested that it occupied a given area of coast and the school might have integrity through time. We found that spinner dolphins occur through- out the Hawaiian chain, from its northwest- emmost limit at Kure Atoll (lat. 25°40' N, long. 175°38 ' W) to its southernmost limit at South Point, or Ka Lae, on the island of Hawaii (lat. 18°49' N, long. 155°41' W). Occurrence is not random, but spinner dolphins are gathered in small to moder- ate schools (6 to about 250 animals) near all major islands and shoal areas and can be found with some regularity near certain shoals or coves. Only near small islands that drop abruptly without having significant shoals, such as at Nihoa Island, have we not found spinner dolphins. The following is a synopsis of known spinner distribution. Un- less othervnse specified, all sightings were by the authors. Specific records are shown in Figure 3. Kure Atoll. On 3 September, 1971, Norris vis- ited Kure Atoll. The commanding officer, Lt. (j-g) Joel Greenberg, reported having seen a school of 20-30 spinner dolphins enter a west pass into the atoll lagoon. Without prompting he described their spinning behavior. Midway Island. On the midaft;ernoon of 3 Sep- tember 1971, a school of approximately 35 spinner dolphins was noted in shallow water at the edge of the channel inside of Eastern Island. The regular daytime occurrence of animals in the shallow atoll lagoon was reported to us by residents of Midway. French Frigate Shoals. On 12 September 1971, at 0830 h, 30 animals were noted just off Shark Island, spinning and leaping. I60°W d. Nihau (C^ \ Oahu ^ Oahu I Molokai Lanai\^ ^AMaui j) Kahoolawe ZO^N MoroReet | Wench Fngate Shools Tern Is /, ^ ■ innacle \ ' " , .m,\ , DisoppeorifiQ \z Figure 3. — Sightings of spinner dolphin schools by the authors (triangles) in the Hawaiian Island chain. 825 FISHERY BULLETIN; VOL, 77. NO 4 Pearl and Hermes Reef. Edward Shallen- berger reported seeing a spinner dolphin school at this location in the fall of 1978, entering the cen- tral lagoon during the day. Necker Island. On 13 September 1971, 10.2 mi east-southeast of Necker Island at 1600 h, a school of about 30 spinner dolphins was seen. The following localities in the northwest Hawaiian chain were visited without seeing spin- ner dolphins; Salmon Bank, Lisianski Island, Laysan Island, Gardner Pinnacles, and Nihoa Is- land. Five to 10 animals that may have been spin- ner dolphins were seen 18.5 mi, 134° T from the wreck at Maro Reef, by Ens. Albert Sarra, U.S. Coast Guard, on 9 September 1971. Niihau Island. Spinner dolphins have been sighted at Kaumuhonu Bay (60 + animals) at the southwest tip of the island, between Lehua Island and Kikepa Point (20 + animals); smaller schools (15 -I- each) have been noted along the southeast shore near Pueo Point and on the northwest shore at Nonopapa. The Nonopapa record was of a traveling school that moved close to shore along perhaps half of the northwestern coast. Kauai Island. Spinner dolphin schools were found around Kauai Island at 3-16 km intervals, except along its western coast. The largest schools were estimated at 150 animals on the Napali coast, a 70-80 animal school just north of Kahala Point, and an estimated 60 animal school between Hanapepe and Kaumakani. Smaller schools, scat- tered along the south and east coasts, averaged about 15-30 animals. The only obvious difference between the vacant coast and the occupied areas is that vacant areas have much narrower, shallow water shelves devoid of deep indentations in the coastline. mals seen in this area have been estimated to number from 40 to 250 individuals. Small schools have been seen near Kahana Bay and Waimea Bay. Because this is the windward coast, subject to almost constant tradewinds, little collecting effort has been expended there and dolphins may be more common than our records indicate. A rela- tively narrow shelf (1.6 km) exists along the Waianae coast except at Kaena and Barber's Points where it broadens considerably. The shelf around the remainder of the island is much broader, averaging about 4 km, and is marked on the northwest and northeastern coasts by a fring- ing reef. Molokai-Lanai-Kahoolawe-Maui . Geologically this four-island complex has resulted from one series of volcanic eruptions, producing islands with interconnnecting shallow areas and chan- nels. Spinner schools have been seen at several locations around the margins of this complex, but seem rather seldom to travel to inshore locations over extensive shallow areas such as that at Lahaina Roads (Auau Channel) or over the flats between Molokai and Lanai Islands (Kalohi Channel). Dolphin schools in such areas would have to travel 1 1 km or more from deep water to reach these shorelines. Large spinner schools have been seen over Pen- guin Bank (between western Molokai and Lanai Islands), the south coast of Lanai, especially near Manele Bay (40-100 animals), and along the south shore of Kahoolawe, especially near Halona Point; small schools were seen on the north Molokai shore at Kalaupapa and Cape Halawa, along the Hana coast of Maui, and at Lipoa Point on the northwest end of Maui. Two records of spinner dolphins accompanying humpback whales near Lahaina were reported to us. The bottlenose dol- phin, Tursiops sp., has often been seen with these whales. Oahu Island. Records from the various sources over 14 yr (1962-76) show that two broad areas of the coast are nearly always occupied by spinner dolphin schools during the day. First, along the Waianae coast between Barber's Point and the vicinity of Kaena Point (the west or Kona shore), schools estimated between 30 and 100 animals can nearly always be found close to shore during the day. Second, an apparently larger school or schools is often seen in the coastal area between about Peeirl Harbor and Makapuu Point. Schools of ani- Hawaii Island. Spinner dolphin schools have been found at scattered locations around the en- tire periphery of the island except for the north- east shore, though there are some shorter stretches of coast where we have never seen schools. It is not surprising, in view of the large size of this island, that there are more localities of regular occupancy by porpoise schools than for any other island. We found seven areas of regular oc- cupancy and four localities with more transient occupancy. 826 NORMS and DOHL: BEHAVIOR OF THE HAWAIIAN SPINNER DOLPHIN On the lee side of Hawaii, the largest school was centered at Keahole Point, ranging along about 23 km of coast, from Honokohau Harbor to Kiholo Bay. In all, there are estimated to be about 200- 250 animals generally occurring in this area, and they may be found in a single school at times or fragmented into two or three smaller schools, separated by a few kilometers of coastline. Here, the dolphins do not seem to occupy any of the small coves consistently, but to congregate over the rather extensive area of shallow water, moving back and forth. Not uncommonly, parts of this aggregation moved during the day beyond the limits listed above and may move as far as Kailua-Kona or beyond, though the constant sea traffic in that harbor seems to prevent normal daily quiescence (defined below). We have termed these animals collectively the "North Kona School." Twenty-eight kilometers to the south, at Kealakekua Bay, a school ranging from 2 to 70 animals (average 25 animals over 73 observa- tions) was found. In our observations, dolphins occurred in this bay on 74% of 113 observation days. They most commonly occupied the deeply indented bay but sometimes were found on the shallow area north of the bay to Keauhou or occa- sionally ne£u-ly to Kailua-Kona. Less commonly they were found to the south in or near the very small bays at Honaunau (City of Refuge) or Hookena. The entire 56 km stretch from Hookena to South Point seems not to harbor spinner dolphin schools on a regular basis, though it should be noted that a militau-y air closure zone prevented our flying over the Milolii area regularly. We have a single record of a 20 animal school at Milolii. This precipitous coast drops abruptly into deep water, without shallow areas alongshore. Much of the coast is composed of relatively new lava flows from nearby Mauna Loa volcano. Small schools, estimated generally at about 20 EUiimals, were seen, usually in very rough water, at South Point, between Ka Lae and Honuapo, over the modestly developed shallow area there, or occasionally in the deep cove at Kaalualu. At Keauhou Cove, directly below Kilauea Cra- ter, a small school (20-25 animals) was consis- tently found. The dolphins came into very shallow water there in an area protected by Keaoi Islet and flanking coral heads, which produce a small area of calm water along an otherwise rough water coast. Cape Kumukahi, the easternmost point on the island, hosted a population of about 30 animals. Several small irregular bays along the southern edge of the cape form the "home bay" in this area, with animals being noted at times as far as Opilukao Cove. The largest school on the windward shore (ca. 100 animals) was often found at Kaloli Point, 18 km south of Hilo Bay. This location seemed also to be the northernmost area of occupancy on this side of the island. The dolphins were typically found in the bay protected by the point and fringing coral reefs. The rather shallow bay (maximum depth 20 m) is close to deep water to the south. The 112 km stretch of coast from Kaloli Point to the north end of the island (Upolu Point) seemed devoid of resident spinner dolphin schools. It is also the site of the major sugar cane processing plants on the island. Effluent from these plants seems to produce murky waters along the coast and clearly contributes to the long drift lines of flotsam from processed sugar cane. Whether the absence of animals and this activity are related is unknown. At the north tip of Hawaii we occasionally saw or heard of small schools of spinner dolphins (10-30 animals) in the area between Kawaihae Bay and Honoipu, though more often the entire stretch of coast was found to be without animals from the Kiholo Bay to the north tip at Upolu Point. This circumstance is anomalous, in that well-developed, shallow-water areas occur along this shore, where schools might come during the day, and where the sea is generally calm. REST AREAS Three features of the distribution of spinner dolphins in the Hawaiian chain stand out. First, the distribution is discontinous. Some coasts may have several areas where dolphins congregate, and others may have stretches of many kilometers in extent where no amimals are seen. Second, cer- tain coves or shallow areas are clearly regular aggregation sites, while others seem to be used much more infrequently. Third, some areas con- sistently carry more animals than others. As we will demonstrate, spinner dolphins come inshore during daylight hours to enter a quiescent period of some hours duration, and we think of these congregation sites alongshore as "rest areas." What typifies such rest areas? First, all rest areas are shallow sandy areas with <50 m depth over part of their extent. They are usually com- 827 FISHERY BULLETIN: VOL, 77. NO, 4 posed of a mixture of open sandy bottom dotted with coral formations. Coves may or may not be present. All rest areas are close to deep water. Usually water >500 m depth can be reached within a few kilometers. Some schools, such as those in the Waikiki (Oahu) or Manele Bay (Lanai) areas, have access to considerably shal- lower water than others. Schools living there may be restricted to waters no deeper than about 600 m since our observations on the Kona coast of Hawaii indicate that schools do not move more than a few kilometers from shore at night. Other schools, such as at Keahole Point (Hawaii) regularly move into water >2,000m depth. Ofcourse, the observa- tions we have made on the island of Hawaii may not hold elsewhere. Apparently spinner dolphins only occasionally travel onto extensive shallow areas like that at Lahaina Roads (Auau Channel), which is about 24 km long. Instead they typically congregate along its margins, along the south shore of Lanai Island and Kahoolawe Island, where deep water is nearby. The areas most closely studied here are Kealakakua Bay and Keahole Point, both have deep water accessible within 1.5-2.5 km of shore. The inference is that rest areas are chosen by dolphins not only for physical characteristics such as depth, bottom type, and perhaps calm water but also for their accessibility to nighttime feeding areas. Spinner dolphin schools also rest in atoll la- goons. At Kwajalein Atoll, on 10 September 1973, at 1630, a school of about 40 spinner dolphins was noted about 1 km inside Bigej Pass. The school was moving toward the pass, presumably on its way out to sea. A local resident told us that the school was regularly in this pass and not found in other nearby passes into the central lagoon. Similar ob- servations have been made at Kure Atoll, Midway Atoll, and near Shark Island at French Frigate Shoals. The animals (approximately 35), resting quietly in a shallow channel not far inside Eastern Island at Midway, were sighted from a helicopter. Probably wherever atolls and spinner dolphins occur together the animals use the atoll lagoons for rest. In the eastern tropical Pacific a large spinner dolphin population occupies oceanic areas far from land. In view of the use of shore situations elsewhere in the range of the species, one wonders what, if any, substitution is made. Norris and Dohl (in press) have speculated that the frequently ob- served association between spinner and spotted dolphins in the eastern tropical Pacific (this as- sociation does not occur in Hawaii) may hold the answer. Spinner dolphins may seek the schools of spotted dolphins for refuge during rest in the open sea. We believe this may be true because spotted dolphins feed during the day, while spinners are nocturnal feeders, and spinner dolphin schools have been observed to join spotted dolphin schools in the morning (Norris et al.''). If such rest associa- tion occurs, the spinner dolphins are associating with alert animals in this oceanic area. Related to this the yellowfin tuna seine fishermen chase and encircle dolphins to catch tuna, most fish appar- ently follow the spotted dolphins. Since the asso- ciation between tuna and dolphin is probably food based, the tuna may be following the dolphin species that is actively searching for food. That is, like the tuna, the spinner dolphin may follow ac- tive dolphin schools. Spinner dolphins resting along shores maintain a continuous but slow locomotion, and it seems likely that the searching or feeding activities of spotted dolphins would not greatly change these requirements for rest. MARKED ANIMAL STUDIES Dolphin schools are seen frequently at the same localities while other areas never seem to harbor them. Are these schools of resident animals, or are they composed of transients that for some reason choose certain regions of the coast for rest? The frequent observation of dolphin collectors that a given school will avoid their vessel after animals have been collected from it (Norris and Prescott 1961) indicates possible residency. On the other hand, dolphin schools are not always in these rest localities, and the number of animals using a given cove may vary widely from day to day. This indicates fluidity in school structure and variabil- ity of school movement. Such fluidity has been noted for other porpoise schools by Wiirsig and Wursig (1977) and Saayman and Tayler (1979). Because we were concerned that the spinner dolphins of the Kona coast of Hawaii should not fear our vessel, we sought to recognize individu- als by natural scars and marks rather than by placement of tags. Ultimately we were able to catalog 50 recognizable individuals and resight- "Norris, K. S., W, E. Stuntz, and W. Rogers. 1978, The behavior of porpoises and tuna in the eastern tropical Pacific yellowfin tuna industry-preliminary studies. Natl. Tech. Inf. Serv,. Final Rep, No, MMC76/12 PB 283-970, xi + 86 p. 828 NORMS and DOHL: BEHAVIOR OF THE HAWAIIAN SPINNER DOLPHIN ings provided a partial picture of the school and individual movements. Our shipboard work with dolphin schools was restricted almost wholly to Kealakekua Bay through most of 1970. Only to- ward the end of that year and during 1971 and to a limited extent later, much sea time was spent in other areas. Hence a large proportion of our sight- ings do not bear on the question of dispersal dis- tances or rates by individual dolphins. We gathered no information on possible interisland movements. By far the most useful scars and marks were those of the dorsal fin. Twelve of our animals were in this category (Figure 4). These animals could be resighted from shipboard, and sometimes from considerable distances. It is not surprising that 49, (64%) of our 76 resightings were of these animals. Many marked animals had scars or pattern peculiarities. Such marks could only be sighted on dolphins at the bow of the observation vessel, or from our MOC. The MOC was used sparingly be- cause it was noisy and disturbed dolphin schools and because it was safe only in calm seas. Thus, information on repeated social associations within schools is limited to two sets of sightings and jour- nal notes over 14 days, all within Kealakekua Bay. In any school only a few individuals swam at the bow of a vessel, while others stayed well clear, thus reducing the chances of sighting many ani- mals. Of 38 animals cataloged with body scars or marks, there were 27 resightings. The final marked animal recorded was an individual with a vertical white stripe on its dorsal fin (Figure 4). Our store of recognizable animals built up slowly over the entire period of the study, thus making interpretation of movements difficult; nonetheless, some important ideas emerge: 1) No resident school permanently and regularly uses a given cove or local region of shoreline. In- stead, each cove or resting spot may harbor a given subgroup of dolphins for a matter of days or weeks. 2) Schools are labile mixtures of groups and subgroups. 3) Individual movements may span the entire Kona coast, or even beyond (true ranges of movement remain unknown). A few "marked" individuals have been seen over rather long periods, but other equally recognizable ani- mals have been seen only briefly, or never again .911* '-S^-, FIGURE 4. — Spinner dolphin with vertical white stripe on both sides of its dorsal fin. We suspect that this animal had shed a radio pack after the pin had migrated out of the fin. 829 after an initial sighting, suggesting either rapid population turnover or high levels of intermixing between the various schools of the area. Two pale animals were seen. They were very different visually from their associates. This was especially evident from the air. They were seen along the entire southern Kona coast from Keahole Point to Kamilo Point east of Ka Lae (South Point) and over the longest time span for any "marked" animals (1,220 days out of the total 1,246-day recording period). These pale animals were seen either alone or on occasion together in the same school. These data are suggestive only, because such pale coloration cannot be assigned definitely to a given animal since it is a recurrent condition in the species. For example, such a pale animal was captured near Oahu, and for some years was an exhibit animal at the oceanarium. Sea Life Park. The animal, called "haole" for "white person", gradually grew darker during captivity but always remained slightly pale. Per- rin (1972) described a pale animal from the east- ern tropical Pacific, as "albinistic." Let us examine each of our conclusions in turn. First, is the question of residency. Taking only those animals recognizable from the surface, we find that 7 of 12 animals were seen in both the large Keahole Point schools and in the smaller Kealakekua Bay schools. The pale animals were seen both in Kealakekua Bay and Keahole Point schools amd far to the south at Kamilo Point. There were long periods when a given animal was not seen at one or another locality. This information cannot be usefully quantified because schools were sometimes large and all animals could not be examined and because our records are not the re- sult of concerted attempts to check each animal in a given school. Instead, the records reflect oppor- tunistic sightings during the pursuit of other ac- tivities. Animals clearly moved back and forth between the Keahole Point and Kealakekua Bay as- semblages. Of the 12 animals, 6 were seen at more than one locality and then returned to the first locality of sighting at least once. Three animals were seen at a single locality only, but this may reflect low sighting frequency rather than lack of movement. Finally, three animals were seen at two or more localities but did not return to the locality of first sighting. For these reasons we reject the idea of a given cove having a definable resident school (Ta- ble 1). FISHERY BULLETIN; VOL. 77. NO, 4 Table l. — Movement of Hawaiian spinner dolphins that were identified by natural scars and marks. Dolphin Total time Maximum distance Number of number observed (days) travelled (km) sightings 1 293 18 3 23 183 0 3 24 1.096 36 14 30 342 36 11 32 246 0 3 39 236 36 3 40 275 36 4 44 170 36 6 45 1.220 113 7 46 862 10 3 49 39 36 2 50 1 0 1 Reversals = 6 One location = 3 Two or more sequential locations = 3 Our data are too incomplete to show how long a given animal might spend at a single locality, or how often it switches between rest localities. Only the number of consecutive days during which a given surface-visible marked animal was seen at a single locality vs. the number of days of consecu- tive observation during the sighting period is indi- cative. Considering the animals for which most resightings are available: numbers 24 and 30, during four separate continous periods of obser- vation of 9, 8, 9, and 10 days, animal 24 was seen 2, 2, and 3 days consecutively (Table 2). Animal 30 was seen only once, 2 days in a row, during consecutive observation periods of 7, 10, and 10 observation days. Animal number 13 (a large calf traveling with its mother) was seen three con- secutive days during a 16-day observation period at Kealakekua Bay. During consecutive observa- tion periods in which the observer moved from Kealakekua Bay to Keahole Point, certain ani- mals were noted on consecutive days at the two localities, indicating a switch in a single night from one to the other. These data indicate that movements are frequent, at least between the Kealakekua Bay and Keahole Point rest areas. As for the conclusion that dolphin schools con- sist of labile aggregations of groups and sub- groups, the best information comes from fluctua- tions in school sizes with which a given marked animal was associated. The results reflect almost Table 2. — Occurrence of a single spinner dolphin (No. 24) and the size of schools in which it was seen at Kealakekua Bay, Hawaii, 1970. Dates of observation Estimated school sizes Number of times seen 28 Apr -6 May 23 June-30 June 10 Sept -18 Sepi 28 Oct -6 Nov 15-30 15-40 25-36 7-120 3 days of 9 2 days of 8 3 days of 9 3 days of 10 830 NORMS and DOHL: BEHAVIOR OF THE HAWAIIAN SPINNER DOLPHIN the entire range of school sizes observed. For example, at various times number 24 was found in schools varying from 7-10 to 120 animals, and number 30 covered about the same school size range, from 6 to 150 animals. Observations from the MOC showed that on one occasion the same subgroup, with the same general internal ar- rangement of animals, persisted for at least 3 days. Many times, during three consecutive ob- servation days (25-27 March 1970) the same sub- group of five animals came to the bow of the MOC. This sort of asssociation is well known in captive schools and persists for long periods of time (McBride and Hebb 1948; Tavolga and Es- sapian 1957; and Bateson^). Such groups in cap- tivity may be constructed of related or nonrelated animals or even of animals of different species (Bateson see footnote 5). Thus, while our observa- tions of wild schools do not provide proof, we ex- pect that some subgroup structure may persist over long periods and that familial lineages may be important, as has been observed in captivity (Tavolga and Essapian 1957). The role of subgroups in larger dolphin schools is apparently not simple. Such schools are not simply composed of groups and subgroups that themselves have cohesion. Instead, there are also some assemblages that seem typical only of large schools. For example, in large schools, groups are often segregated. Groups of juvenile animals or of mother-young pairs may be seen. Large schools differ from one another by the presence or absence of such groups. Some schools were composed only of adults, while others had a high proportion of young animals. Subgroups may move between schools. Some social ordering, largely related to growth and reproduction, may take place in schools regardless of the origins of their con- stituent parts. A major force in such ordering within large schools may be the aggression of cer- tain large adults, that may be either male or female, who herd vulnerable gi'oups to central lo- cations within the school (McBride and Hebb 1948). Such patterns have been proposed for S. coeruleoalba by Kasuya ( 1972) and for S. attenuata by Kasuya et al. (1974). AERIAL BEHAVIOR PATTERNS An experienced observer of spinner dolphins can ^Bateson. G. 1965. The cetacean community in Whaler's Ojve-Sea Life Park. quickly judge the activity state of a school by watching its aerial patterns. It is possible to judge the alertness of school members by checking the kind and frequency of aerial patterns. In fact, such analysis soon makes it obvious that the entire sequence of changing behavior patterns through any 24-h cycle is related to the level of activity, or "emotional state," as indicated by aerial patterns. Spinner dolphins not only "spin" but perform several other clearly recognizable aerial patterns. These include leaps, tail-over-head leaps, backslaps, headslaps, noseouts, and tailslaps, or a combination of these patterns — each performed with variable vigor and frequency at various times of day. The spin. The spinner dolphin rushes to the surface as if about to make an arcing leap, and at the last instant, when most of its body is out of water, tips its flukes slightly and flexes its tail stock, causing the airborn animal to spin about its longitudinal axis. As many as four revolutions may be made in the course of such a leap! Hester et al. 1963). The dolphin may literally appear to flicker as flippers, flukes, and the dorsal fin flash by. The animal falls back into the water, usually partly on its side, and its rapidly rotating body scoops out a hollow of water around the sinking animal. The hollow then collapses producing a welter of spray (Figure 5) and a discernible clap of sound. The spin is enhanced in air by postural movements, in addition to the momentum ini- tially imparted when leaving the water. Just as a gymnast flexes his or her body or as a skater moves elbows in a spin, the spinning dolphin flexes its head and tail and moves its flippers toward or away from its body (Figure 6). Spins are usually performed in a series of de- scending intensity (as are other aerial patterns). A given animal may spin as many as a dozen times in succession, each successive spin generally being of somewhat reduced intensity compared with the last. The first leap may reach an apex perhaps 3 m above the surface, while in the last of a series the animal may not clear the water at all. Most spin series are short, being composed of three or four spins. All age-classes spin. It is not uncommon to see small calves spinning repeatedly in moving schools. In one case a young animal leaped into a spin while in a feeding school, landing a dozen meters off our bow. Each successive spin brought the animal closer to us, as it was seemingly oblivi- 831 FISHERY BULLETIN: VOL. 77. NO. 4 ^-: Figure 5. — Spinner dolphin reenter- ing the water after a spin, seen from below. Note the longitudinal hollow of water scooped out by the rotating ani- mal. Photo by Henry Groskinsky, cour- tesy Time, Inc. Figure 6. — Body postures of spinner dolphins during a spin Vertical and horizontal dimensions of leap not to scale. Redrawn from Hester etal. (1963). ous of our presence. The last spin launched the animal nearly at the bow; it fell back into the ship's bow wave, startled, and swam rapidly away below the surface. Spins may be seen in all parts of a school. Lead- ership or dominance do not seem to be the obvious factors in spinning behavior. In fact, the opposite could be true since very young animals spin, and in our observations of captive spinner dolphins a high frequency of spinning was observed in an animal that had not been socially accepted into the resident captive school. The best correlation of frequency of spinning and the condition of a school seem to relate to alertness, or activity level of the animals involved, the greater the alertness the more frequent the spins. The more spread out a 832 NORRIS and DOHL: BEHAVIOR OF THE HAWAUAN SPINNER DOLPHIN school the more frequent spins seem to be. In feed- ing schools, which are the most dispersed of all school formations, spinning and other high energy aerial behavior occur almost continously. The leap. The most common aerial behavior in which spinner dolphins actually leave the water is the leap. Spinner dolphins perform leaps by burst- ing from the water at about a 30° angle, rising a meter or two above the surface, and falling back into the water on the belly or side in a welter of foam. Less frequently, reentry may be made cleanly, snout first. Tail-over-head leap. The most active and perhaps physically demanding aerial behavior pattern is the tail-over-head leap and its variant, the tail-over-head leap with spin. These aerial patterns are seen only when the Spinner dolphin school is most active. In this pattern the animal bursts from the water at a rather high angle, slings its tail over its head in a wide arc, usually trailing a spiral of spray and enters tail first, often slapping its flukes against the water with a loud "thwack" in the process (Figure 7). On occasion this may be accompanied by one or two revolutions of a spin at the same time. Backslap. The emimal leaps about half or a little more of its length out of water at about a 30°-45° angle, upside down. As it falls back, it arches its body sharply, giving the water a sharp slap wrjth the dorsal surface of its head and beak (Figure 8). Backslaps are often performed in slowly moving schools. &-^ FIGURE 8. — A typical backslap of a spinner dolphin. As the school moves slowly the dolphin emerges in the direction of swimming, belly up, and arches its back at the last instant and slaps its back against the water. Headslap. The reverse of the backslap. The animal emerges in the normal position, once again at about 30°-45° angle to the water surface, and then flexes its head sharply downward, slapping its chin and lower beak against the water (Figure 9). It is one of the most common patterns seen in moving schools. FIGURE 7— The tail-over-head leap of a spinner dolphin. This may, at times, be combined with a spin. --=:.^ 833 FISHERY BULLETIN: VOL. 77, NO. 4 Figure 9. — A headslap. The spinner dolphin emerges belly down in the di- rection of swimming and flexes its body forward sharply at reentry. Noseout. The least active aerial behavior. The spinner dolphin simply arches its back as it swims to the surface, raising its snout into the air. It is sometimes seen briefly when a resting school is disturbed, or in schools where other, more active behavior is occuring. It is often the first aerial behavior seen in an awakening school. Tailslap. This pattern may be performed in either the normal or the inverted position. With the dolphin at the surface the tail is arched, bring- ing the flukes above the surface. The flukes are then brought down smartly against the water pro- ducing a clearly audible sound. In the inverted position an animal may sometimes scull along making repeated and rapid tail slaps in a behavior we have called "motorboating," because it not only leaves a continous wake, but makes a "pop pop pop" sound. An animal may slap 10 to 20 or more times in succession in this way (Figure 10). A whaler's term, "lobtailing," describes the same behavior, but seems less descriptive than "tailslap," a term now widely used by porpoise trainers. What are the functions of aerial behavior? A key point, we feel, is that each pattern, with the possi- ble exception of the noseout, clearly makes noise and, in fact, seems primarily structured to make noise. For example, in a headslap the last compo- FlGURE 10. — An inverted tailslap by a spinner dolphin. Tailslaps also may be made in normal body posture. Often a series of a dozen or more slaps may be made at a single time, which has been termed "motorboating" because of the white wake and the sound produced. nent of the pattern is a rapid flexure of the trunk and neck causing the chin and throat to slap against the water. The tail-over-head leap effec- tively slaps the flukes against the water with great force. The spin scoops a cavity from the sea surface whose walls collapse and thus produce a sound we have heard both above and below the water. Other aerial patterns are similarly struc- tured. Such sounds probably radiate in all direc- tions. Dolphin sound generation and beaming ap- paratus, on the other hand, transmits sound in a structured beam, directed forward (Schevill and Watkins 1966; Norris and Evans 1967; Evans 1973). This beaming is better knovvTi for clicks than whistles or burst pulse signals, though ap- parently also true of the latter, at least in the killer whale, Orcinus orca (Schevill and Watkins 1966). The directionality of clicks has been discus- sed for S. longirostris by Watkins and Schevill (1974). Thus, while vocal signals are directed al- most wholly in certain sectors, the sounds of aerial behavior are likely to approach omnidirectional- ity. Our recordings indicate that none of the sig- nals of aerial behavior propagate long distances. Tail slaps may be the loudest. Aerial behavior is most frequent in fully active schools in which the animals are dispersed, some- times rather widely. In tight re.sting schools (see below) sounds of all kinds except for desultory clicking are nearly absent. Conversely, our obser- vations of a captive spinner dolphin school held in a community tank at the Oceanic Institute, Oahu, Hawaii, showed that aerial behavior continued through the night and, in fact, was most frequent in the dark. Thus, high frequencies of aerial be- havior seem correlated with conditions in which many animals in the spread school cannot see each other. Finally, these patterns are stereotyped by species, and a trained observer can often visually identify the genera or species of dolphins by their aerial patterns, sometimes from long distances. 834 NORRIS and DOHL: BEHAVIOR OF THE HAWAIIAN SPINNER DOLPHIN Perhaps the dolphins can make such identifica- tions underwater by sound. What can the use be of such sound signals? The following possibilities seem apparent: 1) If we can gage the activity state of a school by its aerial behavior, it is likely that the dolphins can do so too, and probably in a more refined way than we can; 2) such sound signals may be used where vision is useless; 3) school cohesiveness in the dark, or when animals are spread beyond the limits of vision, may be promoted by repeated short-range omnidirectional sound signals from all parts of a school. The incidence of aerial be- havior is correlated with times when such signals would be most useful. This seems to us to be the most likely function. We considered, and rejected the idea, that the spin might be a pattern relating to dominance or courtship in the school. This seems refuted be- cause animals of all age classes and both sexes spin and because captive observations have shown that even animals that have been rejected from the social structure of a school spin. Another possibility is that spinning is related to removal of ectoparasites such as remoras and copepods. While it might be useful occasionally in detaching such creatures, we have never seen a case in which this seemed to be occurring, and essentially every animal observed to spin was ap- parently without parasites. Captives spin regu- larly even though free of parasites. THE DAILY ACTIVITY CYCLE Obgervations of spinner dolphin schools along the Kona coast of the island of Hawaii, and to a minor extent elsewhere in the Hawaiian chain, show a regular sequence of activities during each 24-h period. Broadly, this consists of nighttime feeding, about which we know little, morning coastward movement that brings the animals into coves and sheltered coastline areas, rest, awaken- ing, zigzag swimming, and then departure to the feeding grounds. Each of these activities will be discussed in turn. Feeding Feeding is upon scattering-layer organisms (Table 3) and seems to be performed during syn- chronous or subsynchronous dives of large and dispersed schools. What we take to be feeding dives start as early as dusk, before most of the scattering laj'er approaches the surface, and such evidence as we have (mainly from a single radio- tracking, from chance encounters with schools at night, and from schools that we have followed to the feeding grounds) suggests that the schools pa- trol along the breaks in the submarine island slope and toward morning gradually make their way into shallow water over the shelf A radiotracked animal, caught over approximately 140 m of water at Keahole Point just before dusk (at 1650 h) on 1 March 1971, moved back and forth along the shore between a point near Kailua-Kona and Kiholo Point. A detailed radiotrack was made dur- ing the night of 1-2 April (Figure 11). The animal stayed with a large school that moved slowly offshore and by 2000 was over the island slope. The group then patrolled back and forth over the slope within a stretch of coast approximately 20 km in length and over water that varied from about 360 Table 3. — Squid and shrimp in the diet of Hawaiian spinner dolphins. Sample and dale Capture locality Squid Shrimp 0170-42 Sepl 24, 1970 0170-35 Mar 25. 1970 0171-1 Jar 8, 0171-2 Jan 8. 1 km oH Ala Wai, Oahu 28 mantles (mantle lengtti 25-52 mm, mean 38 9 mm) 5 Abralia astrosticta 1 4 Abralia tngonura 67 squid beaks, probably of the same species Oft Waikiki, Oahu 200 m off Kailua-Kona Harbor, Hawaii 200 m off Kailua-Kona Harbor. Hawaii 2 Abralia astrosticta 7 Abralia tngonura 1 52 squid beaks of the above species 49 macerated squid 2 Abralia astrostica 6 Abralia trigonura 204 squid beaks, probably of the above species 1 Histioteuthis sp 2 Abralia astrosticta 8 Abralia trigonura 310 squid beaks of the above species 11 pasiphaeids (to 17 8 mm carapace length) 1 small 4 abdominal portions Icandean cephalothorax Probable euphausid fragments No identifiable remains 20Sergia fulgens (12.5-15.5 mm carapace length, mean 14 6 mm) 1 Acanthephyra sp 1 Pasiphaea sp 2 Pasiptiaea sp 1 5 Sergia fulgens (12-14 5 mm mean 1 3 6 mm Some of the above may be of undetermined species) 1 Opiophorus grimaldii (identiftcation probable) 3 Acanthephyra sp (identification probable) 835 FISHERY BULLETIN: VOL. 77, NO. 4 FIGURE 11.— Radiotrack chart of a marked spinner dolphin. 31 March-2 April 1971. Dolphin stayed in moving school of 100 animals presumably feed- ing over the island's submarine slopes. 2200 APRIL 2 A^- ■ ^^*y *[2liO 0300 .,• 2018 ^,.'-':'' ^^""-"-.....^^^^ / / '• \ / START ^ / \« APRIL 1. 1971 '.^ 0100^ 2330«J\ l^ \ ^o^SToo 7 ^"^""'^ ^^0350 •ziooL--^ ,- / V^2030 /' / \Wzo2e ..-' / ^2?« >b400 ^^^ ^-^ tM30 f""^ -^KIMOLO \/ • ^° / s -,•; ■ \ PORPOiSE CAUGHT. f 0500 ^ °"^ \ \ I6S0. MARCH 30. 1971 / ^ \ \^ ', 1 >v^MAKflLaWENA '\^ \ #0540 T? END OF TRACK APRIL 2 .^ ''. HAWAIIAN ISLANDS \ % \ r WEST COAST OF HAWAII \ (keahole pt 6 i 2 , Y nautical miles to 2,600 m deep. By 0300 the school and the radiotagged animal had moved closer to shore and continued to move in ever shallower water until dawn. Feeding schools were observed on three occa- sions at dusk. Each was composed of widely scat- tered groups, covering as much as 3 km in widest dimension, moving together. Diving was subsyn- chronous. Before a dive occurred, groups were evi- dent and there was much aerial behavior across the entire width of the school. Then groups of the school dove individually, all following within ap- proximately a minute or two. Dives were long, averaging 3.5 min according to our records. Sur- facing was approximately as coordinated as div- ing; that is, the various groups straggled to the surface over a minute or two. It was striking to see these very broad diffuse schools reverse their course in relative synchrony (within a minute or two), even at dusk, indicating a communication mechanism, probably acoustic, that could pass information rather quickly across the school. Stomach contents were obtained from four spin- ner dolphins caught early in the day (before noon), while three animals taken in the afternoon had empty stomachs. This same pattern seems to occur in the oceanic spinner dolphins of the tropical Pacific, and a high percentage (65.3%) of empty stomachs (not segregated according to time of day) from 49 spinner dolphins taken from the eastern tropical Pacific were empty (Perrin et al. 1973). A time-stratified sample would probably show some food in the stomachs in the morning before diges- tion of the night's catch is complete, with empty stomachs in the afternoon. If spinner dolphins were diurnal feeders, one would expect few empty stomachs during the day at any time. The ob- served morning defecation period also fits this scheme. We conclude from our own observational data that the spinner dolphin in the open eastern tropical Pacific and around the Hawaiian Islands feeds at night. Our evidence, and that from other studies, suggests that it feeds upon scattering- layer organisms found at considerable depth. Fitch and Brownell ( 1968) reach a similar conclu- sion from otolith studies of stomach contents of five spinner dolphins taken from the yellowfin tuna grounds; they stated: "We feel certain that three of the cetaceans we investigated (Kogia simus, Stenella longirostris, and Lissodephis borealis) had been feeding 800 ft (250 m) or more beneath the surface . . . . " Perrin et al. (1973) similarly concluded that spinner dolphins are feeding mostly on mesopelagic fish and squid, with a small increment of epipelagic squid species in their diet. Our results (Table 3) confirm these ear- lier works, but show a considerable component of sergestid crustaceans in the diet of the Hawaiian spinner dolphin. Epipelagic squid were absent, though common in Hawaiian waters, while such relatively deepwater forms as Abralia astrosticta 836 NORRIS and DOHL: BEHAVIOR OF THE HAWAIIAN SPINNER DOLPHIN and A. trigonura were common in the stomach samples but rare in collections of squid from Hawaiian waters. Richard Young" described A. trigonura as being uncommonly taken in Hawaii, but being a vertical migrant occuring from 500 m depth during the day to the upper 100 m at night. This species made up the majority of our samples. As for A. astrosticta, Young stated that it is known in Hawaii from only a few captures, and that most were taken on the bottom in trawls, while small individuals were sometimes taken in midwater. Our samples were adults. Young commented as follows: "It is a displaced midwater faunal ele- ment, or an animal having the distinctive adapta- tions of a midwater animal but which seems to migrate along the bottom. TheHistioteuthis is also a vertical migrator that stays below about 150 meters." (See Table 3). John Walters (see footnote 6) commented that the shrimp Sergio /u/gens is an enigmatic form known only in the adult form (ours were adults) from night tows. Morning Shoreward Movement After nighttime feeding, spinner dolphin schools turn toward shore, ultimately congregate in certain sheltered locations where the schools subside into the rest pattern. In the case of the radiotracked animal, this movement toward shore seemed to begin at about 0300 and to con- sist of a gradual movement that zigzagged ever closer to shore. The directions from which schools come into Kealakekua Bay suggest that the movement to- ward the coast may be a general one and not neces- sarily pointed precisely at a rest cove. Some enter- ing schools first swim along the coast, round Palemano Point at the south tip of the bay, and enter the bay over the shallows near Keei and Napoopoo (Figure 1), while others enter the bay directly from the open sea, coming in,at various angles to the trend of the coast. Still others enter from the north, once again after a traverse of un- known length along the shore to the north of the bay. More schools enter along the southern limb of the bay than from the north or center. The true figure for south entry may be even higher than the figures indicate (58% for south entry vs. 14.5% for 'Richard Young (Professor of Oceanography, University of Hawaii) examined and identified stomach samples from our Hawaiian spinner porpoise in 1973 and provided notes on the occurrence of squids in the samples, while John Walters (Uni- versity of Hawaii) provided identifications of shrimps. north entry: 27.5% entered in the middle sector), since some first sightings were made close to the cliffs at the back of Kealakekua Bay and, because of their location, were placed in the second sector records. It is likely that some of the schools entered from the south or north prior to the beginning of observation. These congregation patterns suggest that the bays and coves used for rest periods may not neces- sarily be the direct target of daily inshore move- ment. The bays seem simply to collect schools that accumulate along the coast after a night's feeding. The fact that more schools arrive from the south than from the north may reflect the nearby pres- ence of adequate resting areas over the rather extensive shallow- water areas immediately north of the bay between Keikiwaha Point and Keauhou. Waters to the south of Kealakekua Bay are deep close to shore and only very modest sized shallow coves exist at Honaunau and Hookena. Farther south, along the 20 km stretch of coast between Hookena and Milolii, no spinner dolphins were seen although both flights and ship searches were made. Nonetheless, data from marked ani- mals show movement between the populations on each side of this gap. Unless rest areas are encoun- tered, dolphin schools remain transient. This does not preclude the possibility that the animals may be familiar with the various rest coves or actively seek them when nearby. Arrival times (Figure 12) concentrated between 0600 and 0950 h, though some schools arrived much later in the day. The early arrivals typically subsided into rest and spent the majority of the day in the bay. Later arrivals (those entering be- tween 1100 and 1700 h) tended not to form resting schools and often moved out of the bay after a brief stay. The late afternoon arrivals may have com- pleted a rest period elsewhere and then entered the bay as part of a longshore movement prior to going to the feeding grounds. Dolphins engaged in such longshore movements have been followed out to sea. In one such case a school rested, left the bay to the south, traveled slowly very close to shore until the small cove at Honaunau was encoun- tered, and then turned out to sea as dusk ap- proached. Not all dolphin schools encountering Kealakekua Bay enter it. We occasionally saw schools crossing the bay mouth and swimming on in either direction. Our impression is that this occurred when other schools were deep in the bay, but unfortunately, adequate records to document 837 FISHERY BULLETIN: VOL. 77, NO. 4 FIGURE 12 — Cumulative record of time of first sighting, onset of rest, waken- ing, etc. Arrival Rest (First sigtitinq) (beginninq Awa (beg ening nninq) Zig Zag (beginning) Feeding Departure (beqinninq) 0600 -0659 ,. \ 0700- 0759 \ 0800- 0859 16 Z N N 0900- 0959 10 3 \ 1 1000- 1059 4 \ 5 1100- 1159 7 5 ^K 6 1200- 1259 4 5 X 1300- 1359 \' 2 2 ■\ 1400- 1459 '\ ' 2 1 ' N 1500- 1559 3 \ 2 6 2 7 1600- 1659 \ 3 3 4 1700- 1759 1 \ , 9 2 1800- 1859 "^"^ 1 1 3 1900- 1959 \ 5 1 the point were not kept. Our efforts at listening to dolphins in Kealakekua Bay showed that dolphins at the mouth of the bay can easily hear those in its deepest recesses, so the effect may be one of exclu- sion of the passing school by occupants. The point needs further study. Small schools often seemed to coalesce upon ar- rival in the bay. This first became apparent when our estimates of school size during an arrival sequence increased sharply, or even doubled, be- tween the time the animals were at the bay en- trance and when they were deeper in the bay. In other records such obvious increase in school size occurred after the animals were deep in the bay. The arrival of such supplementary schools was occasionally observed and their coalescence into a single school noted. School structure during entry was best observed in those that entered in the central sector, without the visual interference of headlands or the swells and breakers that sometimes obscured sightings close to shore. Such schools were sometimes first seen as far as 4 km beyond the bay and could be watched during the entire entry traverse. These schools typically swam in a ragged rank composed of quite discrete groups. The dolphins were often quite active, and their passage was accompanied by spins and other aerial behavior. Often, by the time the bay mouth was reached aerial behavior had subsided considerably, though it often per- sisted to some degree for as long as 2 h after initial entry. In small schools of approximately 6-15 ani- mals, entry was often quite unobtrusive. In spite of a conscientious watch from the clifftop during early morning hours such small schools were sometimes seen first deep in the bay. Large schools typically exhibited more aerial activity than small ones, and it appeared to persist for a longer period. Arriving dolphin schools often come to the bows of vessels where they engage in assisted locomo- tion or "bowriding" (Norris and Prescott 1961). Even so, if a vessel pursued such schools, re- peatedly making passes through their ranks or changing speeds upon approach, the school usu- ally edged toward deep water, and if the harass- ment continued, the school left the bay. Observers on shipboard usually failed to note the effect on the school as a whole, since their attention was fo- cused on the bowriding animals. But an observer on the cliff above the bay, watching the entire school, could quickly discern this retreat. This ef- fect nearly always occurred, even if the intruding vessel moved very carefully. Later, when the school had subsided into quiescence, it was much 838 NORMS and DOHL: BEHAVIOR OF THE HAWAIIAN SPINNER DOLPHIN more difficult to disturb the animals sufficiently to cause them to flee the bay. Even persistent at- tempts to enter their ranks merely caused avoid- ance and often a transitory flurry of aerial activity (Figure 13). Defecation was a common feature of arriving schools, prior to subsidence into rest. From the underwater viewing vehicle the olive colored trails of semiliquid fecal material were often seen streaming from the dolphins. Three or four ani- mals sometimes defecated simultaneously within the field of view of the vehicle. A rate for one 40-animal school was calculated at one defecation every 15 s. Presumably this rather short defeca- tion period is related to nighttime feeding and early morning digestion. The trailing animals of a school swam through the dispersed clouds of feces with no evident reaction. Subsidence Into Rest Once a spinner dolphin school arrives deep in Kealakekua Bay, it normally subsides slowly into rest, a process sometimes requiring 2 h or more. This process is so gradual and so affected by fea- tures such as school size and the time of day, that its precise onset was difficult to assign (Figure 13), and an arbitrary definition was necessary. Be- cause rest involves the cessation of aerial behavior by all school members, we defined rest as occur- ring when a 10-min observation of the school re- vealed no aerial behavior. Occasionally, even this criterion was confounded because aerial behavior is, to some extent, "infectious," and a school sub- siding into rest may sometimes exhibit 10-min periods without aerial behavior followed by periods in which some aerial activity occurs in several animals. But, generally, once a school was quiet for 10 min, little or no aerial activity oc- curred until arousal. Typically arriving schools were in ranked form, with group structure evi- dent. Such schools often moved quickly (5-8 km/h) and swam resolutely, with considerable aerial be- havior. Little time was spent below the surface. Dives were brief (Figure 14). Once such a school arrived at the back of the bay, under the lava cliffs. k. TJ o O •> w. o 0) SI « w CD 3 '-^ C O '^ b < O V. o (A 9 o c O C a> o i. 3 3 o- O « u t. O u. IKJ • Leaps; including spins, leaps and head- ^ c oT over-tail leaps \ ^1 60 - A Slaps; including backslaps, tailslops. \ o c noseouts, headslops, and \ o undetermined. \ 0.5 !>i^ 50 D Synchronous dives o \ ools 30, hekc n \ 0) o 1 JZ o> o l/t \ o / Sil ' \ 5° 1 1 ?"J 5 ui a; 40 A o c o ? "^ \ O u> / El / 7\ ^ - \ 0» 3 / U. D- O / \ .c CO/ / \ o O 0) \ /\ c >, Q. « 3 II \ E oi/ - / A • 30 - / \ », n T3 - tl ^ » / • lat cu scho rs ne( 11 evi break K ^^ t 20 1 Sal • — > nyi^i^ Wafer skie Though sti diving is l\ • 10 ^^ V 1 1 1 1 0800 0900 1000 1100 1200 1300 1400 Time of Day 1500 1600 1700 1800 Figure 13.— Aerial behavior per 10-min interval for a spinner dolphin school of approximately 40 animals, 30 June 1971, Kealakekua Bay, Hawaii. Synchronous dives define the rest period, broken briefly by the speedboat. See text. 839 nSHERY BULLETIN: VOL. 77, NO. 4 CO LJ I- UJ UJ o a: Z3 CO 4 r 0 CO t^ I Z 1 2 UJ »- 3 UJ > o ■> o c c '5> 0) m M O C i3 O Oi o i >.£ o o > o €^ u> 3 O O o 0) - c >< i; o c in; 1 .27 cm) from which were hung every 2 m, thin poly- 'A hukilau is a Hawaiian "net" made of a cork line with palm fronds woven through it at intervals, which is towed across coral areas, chasing fish in front of it. Because a mesh net is not involved, it does not entangle on the rough bottom but still serves to concentrate the fish, which are then netted from inside the hukilau over sandy bottom. 841 FISHERY BULLETIN: VOL 77. NO 4 prophylene lines ('A in; 0.6 cm) 18 m long (Figure 15). With this insubstantial barrier we were able to encircle whole schools of spinner dolphins in 20-40 m of water and to crowd them severely. In one case when the hukilau was reduced to a sur- face area of 6 x 10 m, a school of 40-60 animals refused to leave through the wide openings but continued to mill inside (Figure 15). Even when two of the thin vertical lines were removed, leav- ing a "door" 6 m wide, the school continued to circle, "eyeing" the opening but not passing through it. Only when the area was further re- duced did the majority of the animals pass through the wide opening. They had been held captive for 3 h 50 min in this fashion. Although large and small schools may become quiescent, sporadic low intensity aerial behavior may continue. The impression given is that very small schools (ca. 6-12 animals) maintain a degree of individual wariness, perhaps related to the un- certain protective effectiveness of their few mem- bers, while very large schools may always contain some alert animals. For instance, based on a small number of observations in the large ( 100-150 ani- mals) schools seen at Keahole Point, we have never noted deep quiescence. It is as if the mem- bers of the small school were afraid, and that some activity always occurred somewhere in the larger schools. Only schools of about 20-40 animals seem to achieve the most complete quiescence. Even though aspects of diurnal behavior se- quences were recorded on 83 days, complete se- quences were recorded on only 13 days. Based on these observations, rest periods ranged from 41 min to 6 h (mean = 3.62 h). Once quiescent, resting schools are rather difficult to disrupt. Several times cruise boats or water skiers went through resting schools during our observations. The usual result was a brief flurry of low-level aerial behavior, for example, a desultory headslap, an imperfect spin, and then the school would subside into complete quiescence again (Figure 13). Arousal Arousal, unlike descent into rest, is abrupt, both in terms of school dispersion and aerial activity. In a completely quiescent spinner dolphin school, arousal was marked by sudden active aerial behavior — a complete spin or headslap, for in- stance. Within 10 min of such initial aerial activ- ity the school was often fully alert, with aerial Figure 15. — An Hawaiian "hukilau" composed of a cork line and hanging vertical weighted lines, showing a school of spin- ner dolphins held inside. Vertical lines are 3 m apart and 20 m long. See text. activity high throughout the school. In fact, the highest levels of aerial activity recorded occurred at arousal, and later, during feeding (Figure 13). Zigzag Swimming At arousal the pace of the spinner school quick- ens. Group structure suddenly becomes obvious again. At arousal the school moved back and forth across the bay, or sometimes in and out from the bay center to the cliff base. In either case the school often began to traverse deep water. Typi- cally, it swam toward the bay mouth beginning with a flurry of activity and speed, often with ani- mals rushing through the water, creating spray and small bow waves as they raced along. As the bay mouth was approached, usually the school gradually slowed and flnally began to mill then turned back into the bay. Sometimes the school then subsided into further rest, or accelerated again, often toward the opposite side of the bay. This entire pattern is what we have termed "zig- zag" swimming. These patterns, we suspect, are, to some extent, influenced by the topography of Kealakekua Bay, and may take somewhat differ- ent expressions elsewhere. Spinner dolphins were observed moving in zig- zag fashion at Kealakekua Bay, in and out and from headland to headland. The longest bout of 842 NORRIS and DOHL: BEHAVIOR OF THE HAWAIIAN SPINNER DOLPHIN this behavior took 2.75 h. Typically zigzag swim- ming ended with fast swimming that took the school beyond the confines of the bay altogether. It was as if one had been rocking a blob of mercury in a bowl, and a final strong motion sent the blob flying, completely free of the bowl. If the animals left the bay early in the day, the school usually traveled close to the shoreline, either to the north or south, and later in the day, turned toward deep water offshore. When a school left the bay near dusk, it usually headed directly out to sea. As exodus from the rest location began, schools traveled either as ranked schools (wider than long) or in straggling lines arranged in more or less linear fashion. As the school moved offshore, it spread. It sometimes coalesced with other schools moving in the same general direction. By the time feeding grounds were reached, usually near dusk, a school that, during rest, had formed a 25 m diameter disc might have expanded until its groups were scattered over a kilometer or more of sea. As noted earlier, we have estimated some feeding schools as 3 km in breadth. Social behavior, including mating, aerial be- havior, sexual play, and aggressive chases, be- comes especially evident in spinner dolphin schools moving toward the feeding grounds. Once there subsynchronus feeding dives begin. Dive Patterns An example of the daily cycle of dive patterns is shown in Figure 14. As animals entered the rest area, the pattern was one of short dives, with most time spent on the surface. Then this pattern gradually shifted as dives became longer and sur- face times shorter. When the school was near or over the shallow area where rest occurs, dives become synchronous, or neairly so. During arrival the groups of a school, especially if it was a large one, often dive out of synchrony with one another. During rest, as shown in Figure 14, the duration of dives continued to increase until the longest dives were approximately 3.5 min duration; surfacings at that time were brief, between 10 and 30 s dura- tion. Throughout the rest period, the school, if it is small or moderate in size, dives in synchrony. Dur- ing the arousal period, surface times gradually increase while dives tend to become much more variable in length than during rest. Finally, as the school travels out to sea, individualism reaches its peak, with animals scattered in pairs or small subgroups, or even alone, within the envelope of the school as a whole. Synchronous diving is lost as movement is at or close to the surface and directed into horizontal travel. Then, on the feeding grounds, when the school is at its most dispersed, the scattered school slows and begins syn- chronized diving again, presumably to feed. Inter- nal factors, such as the return to equilibrium after a dive might play an important role in determin- ing diving patterns. As for mediating signals, the cessation of aerial behavior in an area of the school that has dived could signal adjacent school seg- ments that diving is occurring; or, vocal signals could mediate it, and thus a wave of information about a dive in progress could travel across the school. The high incidence of aerial behavior in feeding schools and the lack of precise synchrony in feeding dives support such a speculation. Social Behavior Social behavior in wild spinner dolphin schools has thus far proved all but impossible to observe in an orderly fashion. Glimpses of individual ani- mals or subgroups are fleeting, and the opportun- ity to identify individuals or their sex is sporadic. Hence, the observations that follow are highly fragmentary. Mother- Young Behavior Very small calves are always seen in the com- pany of adults. However, young spinner dolphins of quite small size (about 1.2-1.7 m TL) may form groups within a school with no evident adults in close attendance. Newborn calves with adults have been seen at all seasons of the year (Figure 16), as have groups of unattended larger calves. • NEWBORN WITH ADULT A INDEPENDENT YOUNG JAN FEB MAR APR MAY JUNE JULY AUG SEPT OCT NOV DEC Figure 16. — Annual occurrence of newborn in spinner dolphin schools off Hawaii (1968-72). Only sightings of newborn with evident fetal folds are included. 843 Nursing has seldom been seen in nature. In one clifflop observation, a 60-animal school swam be- low, containing a group of adult-calf pairs. One of these pairs engaged in nursing. The adult turned slightly on her side as the young dolphin positioned itself obliquely alongside with its beak pressing against her at the mammary slits. The behavior persisted for a few seconds before the animals dove. The posture was like that reported in captive dolphins (Dohl et al. 1974). For 33 days in February-March 1970, a female pair was seen in Kealakekua Bay and nearby Keauhou. Unlike most such pairs, the two often swam near our observation vehicle. The calf had the distal 5-6 cm of its rostrum broken through and bent to the side with some ragged flesh ex- posed. In spited of this apparently grievous wound the calf appeared active and well nourished. Con- tact was very frequent between mother and calf. Both the adult and calf used their flukes, flippers, and dorsal fin to achieve this contact. On two occa- sions the young animal touched its dorsal fin to the adult's flank, laid its flukes up under and touching hers, and held this position as their combined tail beat propelled them both along. The young animal rode both above and below the adult, sometimes directly beneath her midbelly, occasionally slid- ing backward until the moving flukes of the adult tapped against its dorsal fin. In our observations we never noted true assisted locomotion as de- scribed by Norris and Prescott (1961), though FISHERY BULLETIN: VOL. 77. NO. 4 swimming speed was generally so slow that it might not be expected. A common posture was for the baby to swim below and a little to the side of the big female, at which time she placed her flipper against the young animal's back, just anterior to its dorsal fin. Much of the time the pair in this position swam in synchrony, turning and diving together. On occasion the young animal swung away from the adult for a few meters but soon turned, in- creased speed, and rushed back to her. Once, dur- ing a particularly long sortie, the adult pursued the calf, slapped its back with her flukes, and then the pair dove together. Sexual Associations At times, both on a given day and over several days time, specific subgroups of 2-6 spinner dol- phins whose members could be individually rec- ognized, were seen together from the viewing cap- sule. It was possible to determine the sex of some of the animals. Sexually related behavior was exhib- ited between male and male and male and female pairs. It takes several forms. What Bateson (see footnote 5) called "beak propulsion" was noted (Figure 17). In it one animal swam up from below another and inserted the tip of its rostrum into the genital slit of the upper animal, apparently push- ing the passive animal along. Both the dorsal fin and the flippers are commonly used to stroke or gg^ FICURE 17.— Beak propulsion by a captive pair of spinner dolphin.s at Sea Life Park, Hawaii. An adult female is pushing an adult male. 844 NORRIS and DOHL: BEHAVIOR OF THE HAWAUAN SPINNER DOLPHIN probe the genital area of another einimal, and the upper animal sometimes rode along with the dor- sal fin of the lower animal pressed into its genital area. Mating postures were commonly seen, most often in alert schools early in the morning or near dusk. On one occasion (in captivity) we were able to determine that both partners in such a pair were males, even though females were present in the tank. We were able to confirm heterosexual contact in some pairs in nature. Tj^pically, one animal swam in the normal upright orientation while another swam upside down, with the genital areas of the two pressed together. Either sex could be above or below. Intromission was usually difficult to see, but was noted on occasion. Contact was sometimes maintained for several seconds. In some observations the upper partner was rela- tively quiescent and propelled itself with fluke strokes of much reduced amplitude compared with those of normal swimming. One mating chase was noted as a school moved onto the feed- ing grounds off Keauhou, the pair raced by the bow of our vessel as we travelled at an estimated 4 kn. They dove and spiralled swiftly together. The coupling and synchrony of movement of the pair was so perfect that the two animals were not evident until the pair turned on its side. Together they veered away from the bow, diving about 20 m down and remaining in the coupled position for several seconds. We heard whistling with the un- aided ear when such coupled animals were near the ship. A particularly complete observation of mating was made from the MOC on 26 July 1970, at Kealakekua Bay. A male-female pair swam di- rectly in front of the viewing capsule, and the female swung under the male until their ventral surfaces were in contact. The penis of the male was seen to enter the female, though no thrusts were noted as the position was held for 3-5 s, while the smimals glided without fluke strokes, and then the animals parted. Shortly, the female again moved under the male, but no further intromission ap- peared to take place. Instead, the male accelerated with a few fluke strokes, and the pair cruised off, side by side. Competition for partners was occasionally ob- served. On 29 March 1970 at Kealakekua Bay, the MOC entered a school of 12-13 animals, and 2 were noted swimming upside down. Both pursued and came up under a single adult above them. Later, three inverted animals pursued two in the normal swimming posture. At that moment another large adult swam rapidly to the moving group and force- fully inserted itself between one inverted animal and the one above it. The upper animal then dove away from the group, with the intruder following. The two inverted animals moved quietly, main- taining their upside-down orientation, toward another nearby animal swimming in normal orientation. Observations of captive spinner dolphins show that much social interaction is sexually related and that it may occur between animals of all age classes and combinations of both sexes. As has been found in the Atlantic bottlenose dolphin, Tursiops truncatus, sexual behavior and social communication are interwoven to such an extent that it is often impossible to separate true court- ship and mating behavior from communicative behavior of other sorts. For example, Caldwell and Caldwell ( 1967) reported a 2-day-old male Atlan- tic bottlenose dolphin having an erection when brushed by its mother. Sexual maturity is not reached in the spinner dolphin until a minimum of 3.7 yr iPerrin et al.*) and even later in the bottlenose dolphin, and thus one must view this precocious use of sexual patterns as part of the development of communication concerning rela- tionship. Such communicative use of sexual pat- terns has been reported for mixed schools of cap- tive spinner and spotted dolphins (Bateson see footnote 5). Other Social Patterns Contact, not necessarily sexual in context, is common between members of dolphin schools. When groups of animals swam near the viewing capsule, one could often see animals touching one another writh the tips of pectoral fins, the dorsal fins, or fluke tips. Jostling or pushing of animals near the capsule often occurred and was accom- panied by sound emissions. Such jostling can be seen commonly in other bowriding groups. Be- cause a few animals from a given school seem to do most of the riding and some seem to occupy specific places at the bow, one gains the impression that hierarchical relations in the school are involved. The release of air may correlate with social sig- nals in spinner schools. Commonly, long streams 'Perrin.W. F.,D. B. Holts, and R.B.Miller 1976. Growth and reproduction of the eastern spinner dolphin. A geographical form ol Stenella longirostns in the eastern tropical Pacific. U.S. Dep. Commer. NO.AA. Natl. Mar. Fish. Serv., Admin. Rep. LJ- 76-13, 84 p. 845 FISHERY BULLETIN: VOL 77. NO, 4 of air were noted issuing from the blowhole cor- ners in spinners near the capsule. Whistles and chirps could often be heard concurrently. Some- times, during active chases one or more animals would release a large bubble of air underwater, which boiled upward to the surface. Pryor (1973) has correlated such behavior in captive animals with frustration. Spinner dolphins change school swimming pat- terns in relation to weather. In rough seas, groups of dolphins appear to ride the swells and breaking waves that sweep toward the Kona coast. On one such occasion, while we "hove to" in a rough sea, perhaps 100 spinners passed us. They were di- vided into small groups of less than a dozen ani- mals. These groups swam tightly together and often could be seen racing down the foreslope of the waves, sometimes breaking the water together and sometimes staying wholly within the wave. Such behavior is commonly seen in other cetacean species (Norris and Dohl in press). Sound Emmissions A detailed study of spinner dolphin sound emis- sions will be presented in a future paper. A few observations are appropriate here. There is a marked diurnal fluctuation in the kind and amount of spinner dolphin vocalization (Powell 1967). Alert schools produce an array of sound types such as clicks, pure-tone whistles or "squeals," and a variety of burst pulse signals that can be described by such terms as barks, moos, chirps, etc. The clicks are of considerably lower intensity than either the whistles or the burst signals (Watkins and Schevill 1974), and the clicks may be more tightly focused. Resting schools are nearly silent, emitting al- most entirely clicks and even these are sporadic. Simultaneous with arousal, vocalizations rise in variety and abundance. Whistles and burst pulse signals can be heard quite long distances under- water. With WatkinsandSchevill, we wereableto station ourselves outside Kealakekua Bay and hear whistles and various burst pulse signals from a group of spinners swimming close to the cliff", approximately 2 km distant. Thus, a school of dol- phins swimming outside Kealakekua Bay during longshore movement would be able to detect ani- mals deep in the bay without entering it. It is possible that the schools we have seen passing the bay when others occupied it may have been excluded by acoustic signals. 846 No context-specific sound signals have been identified by us, except that it seemed clear that clicks were emitted concurrent with the inspection of the environment. The likelihood of context- specific acoustic signaling in the daily events in the school, however, seemed high. For example, synchronous diving in very widely dispersed schools, or simultaneous turning of an entire school at dusk, are unlikely to be visually cued (though it is not impossible). The sounds produced by aerial behavior have, in a few instances, been picked up by our listening gear. Tailslaps are especially loud, while spins (which we have re- corded in captive situations) produced a lower in- tensity signal quite different in character. Predators Hawaiian spinner dolphins seem to be attacked with some frequency by sharks. Several of the scarred animals we cataloged had obviously been wounded by large sharks. Lunate rows of tooth marks, especially on the tail region, some appar- ently from sharks with a 12-15 in (31-38 cm) gape were noted. In one case it seemed that the entire tailstock had once been in a shark's mouth. Nicked or tattered dorsal fins may also have been pro- duced by shark bite. Subcircular scars somewhat larger than a silver dollar commonly seen on tropical and subtropical cetaceans are common on spinner dolphins. Jones ( 197 1 ) suggested that these scars are produced by the small squaloid shark Isistius brasiliensis. This small shark occurs with scattering layer or- ganisms, is bioluminescent over its entire body, and is thought to be a squid mimic. Feeding dol- phins may be attracted to it, and when close, the shark may swim to the dolphin, attach itself, and then scoop out a disc of blubber and flesh with its peculiar dental and branchiostegal apparatus. The shark has erect cutting teeth only in the lower jaw and a jaw apparatus that allows it to attach and push the teeth through the flesh of its prey like a cookie cutter. The shark may bite while facing the tail of the porpoise and be swTjng around in the current, cutting as it goes. Discs of dolphin blubber have been found in the stomachs of this shark (Jones 1971). We have seen fresh wounds of this shape and size several times, including some com- pletely through the blubber to the flesh beneath. Nearly every adult dolphin bears some scars of this sort, on some part of its body. We have never seen such scars on the appendages or head, though NORMS and DOHL; BEHAVIOR OF THE HAWAIIAN SPINNER DOLPHIN they are common on the throat, flanks, and espe- cially on the belly and the region between the flippers. DISCUSSION Instead of finding tightly knit schools of con- stant size that habitually occupied a given cove, as we had expected we found coves occupied by schools of highly variable numbers and composi- tion. These variable schools often merged with other schools to form large feeding groups offshore, and school members moved back and forth between resting areas many kilometers apart in what seemed a completely free fashion. Rather than finding dolphins occupying a "home cove" the tendency to gather in shallow waters near shore seems to be related to a combination of topographic factors including the presence of adequate areas of shallow water and the proximity to nearby deepwater feeding grounds. Further, the population occupying such a cove during the daily rest period seems limited in some fashion by this same topography. Kealakekua Bay seems able to hold only about 60-70 animals, and even this number seems so large that rest may be inhibited. Deep rest, without aerial behavior, seems only to occur when relatively few animals, about 30-40 or less, are in the cove. In contrast, Keahole Point regularly holds >100 animals during daily rest. Instead of finding schools headed directly for rest areas in the morning, we found schools mov- ing toward the coast in the morning in a much more general fashion, encountering the coast, swimming alongshore, entering coves, sometimes coalescing with schools already in occupancy, or apparently sometimes passing by a cove filled with animals, to move on toward other less occupied rest areas. The entry and exit patterns of schools relative to coves also suggests such opportunistic use. At Kealakekua Bay, schools entered primar- ily from the south perhaps because "rest areas south of this bay are very restricted while much more extensive areas exist to the north and in effect this inhospitable shore "collects" but does not hold incoming schools, Exit, on the other hand, is primarily to the north, as if schools came into the cove rested for a time, and continued on their way toward offshore feeding grounds. The primary feeding grounds seem to be to the north and west of Kealakekua Bay, off the shallows of the island, though our observations are sparse. To the north of Kealakekua Bay are other rest areas, while to the south deep water adjoins the shore. Thus occu- pancy or lack of same of a given rest cove and arrival direction to it may be related to nighttime feeding movements which leave animals offshore at various locations after the scattering layer de- scends with dawn. None of this, of course, indi- cates that dolphins do not know where available rest areas are, or know the features of them. What, then, is the true dolphin school? Are the large offshore aggregations, formed of a coales- cence of smaller resting groups, such a cohesive unit? Or, should we focus our attention on school subgroups of a few animals, which may habitually swim together (though our evidence is inconclu- sive in this respect), in the search for structure, regarding the large groups as opportunistic as- semblages? Or, can both be properly considered as schools? The large offshore feeding assemblages have clear structure in some respects. Such schools often dive and surface more or less together, and much social behavior is evident at times in them. These schools swim in a common direction and sometimes change course in a coordinated fashion. We often noted age-related subgroups within them; mothers and calves, or juveniles swimming together. But, if such schools are followed, they will sometimes split into parts that move in differ- ent directions, and clearly, they fragment during the day when smaller schools enter coves or shal- lows to rest. Smaller schools exhibit most of the same be- havior, though many times not all age classes will be represented in them. Schools of less than about 30 animals are seldom split for long by a vessel. These groupings we call schools, preferring to rec- ognize that such schools change in size from time to time. Clearly, from our marked animal information, individuals utilize a rather extensive area of coast for feeding, moving from group to group, and thus, in aggregate the population of a given portion of coast is a functional unit, in relation to its trophic relations with the immediate environment. The degree of discreteness of such populations from those adjacent remains wholly unknown, as does any possible intermixing between islands. Considering this high degree of fluidity, how is directed movement of a school achieved and how does the structure of schools come about? No leader seems to exist in the standard sense of an animal determining direction of movement by 847 FISHERY BULLETIN: VOL. 77. NO. 4 swimming at the head of a group. Yet directed movement does occur in cetacean schools. Killer whales arrive off sea lion and sea elephant rookeries at the proper time to catch pups (Norris and Prescott 1961), and pilot whales arrive at specific feeding grounds when squid come to spawn or when capelin arrive in large schools (Sergeant and Fisher 1957). Such patterns pre- sumably have a learned component, and similar patterns of dolphins opportunistically using human activities to locate and capture food must be largely or wholly learned. For instance, bottlenose dolphins follow trawlers in the Gulf of Mexico (Leatherwood 1975) and in the Gulf of California (Norris and Prescott 1961) and obtain fish and other food items stirred up by the trawl or cast over the side during sorting of the catch. Tavolga and Essapian (1957) described adult male bottlenose dolphins harassing newborn calves and their mothers, and dominance by adult females is also discussed. We have noted strong aggressive behavior in captive male spinner dol- phins at Sea Life Park oceanarium in Hawaii. In the wild dolphin school, similar actions probably serve to order the structure of the school. Females and newborn young may be herded to their normal position in the interior of the school. We expect that such aggression combined with experience may serve to regulate the direction of school movement from various locations in a school. For instance, adult male killer whales usually occupy a position in travelling schools far out on the wings of the moving group, and from this position direc- tional signals may be communicated to the school as a whole (Norris and Dohl in press). The tendency of spinner dolphins to rest over shallow sandy areas is most probably a protective adaption allowing the quiescent school to place a protective bottom close beneath it and a shore nearby on one flank. The chances of attack from those directions by large deepwater sharks are correspondingly reduced. With much individual behavioral flexibility suppressed in resting schools, collective wariness rises, we presume through sensory integration by the school. Thus, the use by spinner dolphins of alert daytime- feeding spotted dolphin schools in the open eastern tropical Pacific Ocean, we feel, may account for the otherwise unusual daytime association between these two species. We regard this study as preliminary, allowing glimpses into the life of one wild dolphin species and focusing our attention on important problem areas such as acoustic signalling, school structure, energetics, and social relationships. ACKNOWLEDGMENTS The assistance we have been given in this study has been great. We thank our vessel captains, Dan Camacho, Frank Cunningham, Georges Gilbert, Roger Gray, George Hanawahini, and Vern Han- son, and also our observers, Larry Hobbs and David Bryant. We thank also William Arbeit, George Barlow, Marlee Breese, Gregory Bateson, Paul Breese, Robert Eisner, William Evans, Sheri Gish, Sharon Gwinn, Ted Hobson, Ingrid Kang, William McFarland, Fred Munz, Karen Pryor, Scott Rutherford, William Schevill, Robert Shallen- berger, Edward Shallenberger, and William Wat- kins for other field assistance. The discussions we have had with George Bar- low, Gregory Bateson, William Perrin, William Rogers, and Karen Pryor have helped a good deal to clarify our ideas of what these often elusive and hard-to-see animals were doing. Sherwood Greenwell went far out of his way helping with our observation posts on his land. Bob Haws and Don Brandy, especially, helped with the flying. Tap Pryor assisted us many times with ships and support. The MOC grew from the hands and mind of Jimmy Okudara. Richard Young and John Walter of the Univer- sity of Hawaii identified the cephalopod and shrimp remains in stomach contents. Nothing could have been accomplished without patient programmatic support, most of which came from the Biological Branch of the Office of Naval Research, through the continuing interest of Deane Holt, Helen Hayes, Charles Woodhouse, and Ron Tipper. Other support (for the hukilau work) came from the National Marine Fisheries Service and from the Oceanic Institute. Finally, our thanks to Bob Leslie, native of Kealakekua Bay, and some of his fishermen as- sociates, such as "Only LeRoy," we learned much about our animals and the place where they lived. LITERATURE CITED Caldwell, M. C, and D. K. Caldwell 1967. Dolphin community life. Los Ang. Cty. Mus., Q. 5(4>:12-15. DoHL. T. P., K. S. Norris. and I. Kang. 1974. A porpoise hybrid: Tursiops x Steno. J. Mammal. 55:217-221. 848 MORRIS and DOHL BEHAVIOR OF THE HAWAIIAN SPINNER DOLPHIN SVANS. W. E. 1973. Echolocation by marine delphinids and one species of fresh-water dolphin, J. Acoust. Sec. Am. 54:191-199. 1974. Radio-telemetric studies of two species of small odontocete cetaceans. In W. E. Schevill (editor). The whale problem; A status report, p. 385-394. Harv. Univ. Press, Camb. Mass. •"ITCH, J. E., AND R. L. BROWNELL, JR. 1968. Fish otoliths in cetacean stomachs and their impor- tance in interpreting feeding habits. J. Fish. Res. Board Can. 25:2561-2574. Hester, F. J., J. R. Hunter, and R. R. Whitney. 1963. Jumping and spinning behavior in the spinner por- poise. J. Mammal. 44:586-588. Tones, E. C. 1971. Isistms brasiliensis, a squaloid shark, the probable cause of crater wounds on fishes and cetaceans. Fish. Bull., U.S. 69:791-798 Kasuya, T. 1972. Growth and reproduction of Stenella caeruleoalba based on the age determination by means of dentinal growth layers. Sci. Rep. Whales Res. Inst. (Tokyo) 24:57-79. ■{ASUYA, T. , N. MIY.AZAKI, AND W. H. DAW^IN. 1974 . Growth and reproduction oiStenella attenuata in the Pacific coast of Japan. Sci. Rep. Whales Res. Inst. (To- kyo) 26:157-226. LEATHERWOOD, S. 1975. Some observations of feeding behavior of bottle-nosed dolphins iTursiops truncatus) in the north em Gulf of Mexico and (Turstops cf T. gilli) off Southern California, Baja California, and Nayarit, Mexico. Mar. Fish. Rev. 37(9):10-16. McBride, a. f., and d. O. hebb. 1948. Behavior of the captive bottle-nose dolphin, Tur- stops truncatus. J. Comp. Physiol. Psychol. 41:111-123. NORRIS, K. S., and T. p. DOHL. In press. The structure and functions of cetacean schools. In L Herman (editorl, The behavior of marine mammals. Wiley Interscience. NORRIS, K. S., .aiND W. E. EVANS. 1967. Directionality of echolocation clicks in the rough- tooth porpoise Steno bredanensis (Lesson). In W. N. Tavolga (editor). Marine bio-acoustics, p. 305-316. NORRIS, K. S., AND J. H. PRESCOTT 1961 . Observations on Pacific cetaceans of Califomian and Mexican waters. Univ. Calif. Publ. Zool. 63:291-402. PERRIN, W. F. 1972. Color patterns of spinner porpoises tStenella cf. S. longirostris) of the eastern Pacific and Hawaii, with com- ments on delphinid pigmentation. Fish. Bull., U.S. 70:983-1003. 1975. Variation of spotted and spinner porpoise (genus Stenella) in the eastern Pacific and Hawaii. Bull. Scripps Inst. Oceanogr., Univ. Calif. 21. 206 p. PERRIN, W. F., R. R. Warner, C. H. Fiscus, and D. B. Holts. 1973. Stomach contents of porpoise, S(cne//a spp.,andyel- lowfin tuna, Thunnus albacares, in mixed-species aggre- gations. Fish. Bull., U.S. 71:1077-1092. POWELL, B. A. 1976. Periodicity of vocal activity of captive Atlantic bottlenose dolphins: Turstops truncatus. Nav. Ord. Test Stn. Tech. Publ. 4302:237-244. PRYOR, K. W. 1973. Behavior and learning in porpoises and whales. Naturwissenschaften 60:412-420. SAAYMAN, G. S., D. BOWER, AND C. K. TAYLER 1972. Observations on inshore and pelagic dolphins on the south-eastern Cape coast of South Africa. Koedoe 15:1- 24. SAAYMAN, G. S., AND C. K. TAYLER. 1971. Responses of man to captive and free-ranging ceta- ceans. Baralogia; Proc. 1st and 2d South African Sym- posium for Underwater Sciences. Univ. Pretoria, p. 1-9 1979. The socioecology of humpback dolphins ^Sousa sp). In H. E. Winn and B. L. 011a (editors). Behavior of marine animals. Vol. 3: Cetaceans, p. 165-226. Plenum Press, N.Y. SAAYMAN, G. S., C. K. TAYLER. AND D. BOWER. 1973 Diurnal activity cycles in captive and free-ranging Indian Ocean bottlenose dolphins tTursiops aduncus Ehrenburg). Behavior 44:212-233. SCHEVILL, W. E., AND W. A. WATKINS. 1966. Sound structure and directionality in Orcmus (killer whale). Zoologica (N.Y.) 51:71-76. SCHLEGEL, H. 1841. Abhandlungen aus dem Gebiete der Zoologie und vergleichenden Anatomie. 1. Heft. A. Amz and Comp., Leiden, 44 p. SERGEANT, D. E., AND H. D. FISHER. 1957. The smaller cetaceaofeastem Canadian waters. J. Fish. Res. Board Can. 14:83-115. SHANE, S. H. 1977. The population biology of the Atlantic bottlenose dolphin, Turstops truncatus, in the Aransas Pass area of Texas. M.S. Thesis, Texas A&M Univ., College Station, 239 p. Tavolga, M. C, and F. S. Essapian. 1957. The behavior of the bottle-nosed dolphin ^Tursiops truncatus)-. Mating, pregnancy, parturition and mother- infant behavior. Zoologica (N.Y.I 42:11-31. Tay'ler, C. K., and G. S. Saaytvian. 1972. The social organisation and behaviour of dolphins [Turstops aduncus) and baboons iPapto ursmus): some comparisons and assessments. Ann. Cape Prov. Mus. Nat. Hist, 9:11-49. W.ATKINS, W. A., AND W. E. SCHEVILL. 1974. Listening to Hawaiian spinner propoises, Stenella cf Longirostris, with a three-dimensional hydrophone ar- ray. J. Mammal. 55:319-328. Wells, R. S., B. Irvine, and M. D. Scott. In press. The social ecology of inshore odontocetes. In L. Herman (editorl. Cetacean behavior. Wiley Intersci- ence, N.Y. WURSIG, B. 1978. On the behavior and ecology of bottlenose and dusky porpoises in the South Atlantic. Ph.D. Thesis, State Univ. New York, Stony Brook, 334 p. WURSIG B., AND M. WURSIG. 1977. The photographic determination of group size, com- position, and stability of coastal porpoises iTurstops trun- catus). Science (Wash., D.C.I 198:755-756. 849 LARVAL DEVELOPMENT OF HYPOCONCHA SABULOSA (DECAPODA: DROMIIDAE)' William H. Lang' and Alan M. Young' ABSTRACT Larval development of the dromiid crab, Hypoconcha sabutosa, consists of three zoeal stages and one megalopa. The zoea exhibit numerous characteristics normally associated with anomuran larvae. Hypoconcha sabulosa (Herbst) is a relatively un- common inhabitant of coastal waters from North Carolina to the coast of Texas. Another member of the genus,//, arcuata Stimpson, coexists through- out much of the range (Williams 1965). These crabs are frequently overlooked owing to their habit of carrying an empty clam shell on their back. Kircher (1970) described the laboratory- reared larval stages of H. arcuata the larval stages of//, sabulosa are undescribed. The family Dromiidae is an enigmatic group which has remained a point of contention in the phylogeny of the Decapoda. It has often been suggested that the brachyurans are a monophyle- tic group and that the dromiids represent a primi- tive true crab (Balss and Gruner 1961; Glaessner 1969; Stevcic 1974; Warner 1977). However, it is also strongly argued that the brachyurans are polyphyletic and that the dromiids are more closely related to anomuran or thalassinid groups (Gumey 1942; Williamson 1974). METHODS On 14 June 1976, a single gravid H. sabulosa female was collected by dredging in the North Inlet estuary, near Georgetown, S.C. Water tem- perature at the time of collection was 24" C; salin- ity was 27%o. The female was returned to the Baruch Laboratory, Columbia, S.C, and placed in a 9 cm Carolina culture dish containing filtered natural sea water of 25%o salinity and maintained 'Contribution No. 287 from Belle W. Baruch Institute for Marine Biology and Coastal Research, Columbia, SC 29208 ^Belle W. Baruch Institute for Marine Biology and Coastal Research, Columbia, S.C; present address; U.S. Environmental Protection Agency, Environmental Research Laboratory, South Ferry Road, Narragansett, Rl 02882. ^Belle W. Baruch Institute for Marine Biology and Coastal Research, (Columbia. S.C; present address: Biology Department, Nasson College, Springvale, ME 04083. at 25° C under a 14L:10D light schedule. On 21 June, the brood began hatching and 22 active lar- vae were placed individually in 6 cm dishes con- taining 15 ml filtered seawater (25%o) and main- tained as described for the adult. Water was changed daily and freshly hatched brine shrimp nauplii (San Francisco Bay Brand'') were added as food following each water change. Additional lar- vae hatching during the following day were reared in a 1 1 shallow glass dish under similar condi- tions. These larvae were sacrificed during de- velopment to provide replicate material for de- scriptions. Records were kept for each of the 22 larvae indi- vidually cultured to determine the number and duration of larval stages. Exuviae and larvae were preserved in 70% ethyl alcohol. Drawings were made from preserved larvae using a Zeiss drawing tube. Measurements of preserved larvae were made with an ocular micrometer; total length and carapace length are as defined by Pike and Wil- liamson (1960a). Abbreviations and setal types mentioned are as in Johns and Lang (1977). De- scriptions and sizes are based on at least five ap- parently healthy larvae sacrificed at each stage. RESULTS Development Three zoeal stages and a megalopa were ob- tained through laboratory rearing; no variability in the number of larval molts was observed. Lar- vae were easily reared in both mass culture and individual chambers. Of larvae not sacrificed, 72% survived to megalopa and 75% of the megalopae successfully molted to first crab (Table 1). Manuscript accepted June 1979 FISHERY BULLETIN VOL 77, NO, 4. 1980. ^Reference to trade names does not imply endorsement by the National Marine Fisheries Service, NOAA. 851 FISHERY BULLETIN; VOL. 77, NO. 4 Table l, — Survival, development time, and duration of the larval stages oi Hypoconcha sabulosa reared in the laboratory. Item Zoea I Zoea II Zoea III Magalopa 1 St crab Percent survival tram first zoeal stage to successive stages (% based on original 22 minus those sacrificed for figures) Percent survival within each stage (% of stage not sacrificed to reach subsequent stage) Days from hatching to reach each stage mean (range) Duration of each stage in days mean (range) 3 6 (3-6) 86 76 72 53 89 93 75 3 6(3-6) 3 9 (3-4) 7 2 (6-9) 3.4 (3-4) 10 5(9-13) 10 6(8-14) 20 9(17-25) At 25° C, 25%o salinity, development to first crab averageci 21 days (Table 1). Mean duration of each zoeal stage was 3 or 4 days while the megalopa lasted approximately 10 or 11 days. Mean sizes and ranges for five larvae at each stage are given in Table 2. Table 2.- -Size o(Hypoconcha subuhsa larvae stages, based on five larvae at each stage. Carapace length (mm) Mean Range Carapace width (mm) Total length (mm) Stage Mean Range Mean Range Zoea 1 Zoea II Zoea III Megalopa 1.30 120-1.37 149 140-155 1.62 1.51-170 1.60 154-164 0 72 0 66-0.74 0 81 0 73-0 88 0 90 0 85-0.93 1.20 1 11 1.24 239 2.21-2.50 2 51 2 33-2 70 2 90 2,81-2 92 Larval Description LiveH. sabulosa zoeae are strong, active swim- mers which readily capture Artemia salina nau- plii. At first sight they generally look like large, proportionally short and bulky pagurid zoeae. The zoeae have a generally reddish-brown color and are most noted by the distinctive line of chromatophores along the ventral and posterior carapace margin (Figure 1). Figures of the larval stages show the most com- mon arrangement of setal numbers observed. For the most part, the figures should be self- explanatory; the descriptive text is intended to note significant morphological features and out- line setal numbers with observed variations. Zoea I Carapace (Figure 1 A, a) without dorsal and lat- eral spines, rostrum directed anteriorly, ven- trolateral carapace margin smooth. Carapace striated with crisscrossing fine ridges giving a tex- tured "skinlike" appearance. At least one pair of transverse grooves evident, eyes sessile. Abdomen (Figure lA, a) without spines or dis- tinct projections, somite six and telson fused, small pleopod buds may be present. Telson (Figure 2 A) triangular with distinct me- dian notch; setation 1+1 with outer fixed spine, hairlike plumose seta, and five large plumose setae. ANl (Figure 3A) — Single segment; terminal setation of three aesthetascs and two simple setae; subterminal setation of two plumose setae. AN2 (Figure 3E) — With 10 plumose setae on scale and 4 plumose setae on endopodite. MN ( Figure 4 A, a) — With concave median sur- face and lateral serrate rim. Ventroposterior re- gion with asymmetric group of teeth. MAXl (Figure 5A) — With two-segmented en- dopodite, distal segment with six setae, proximal segment with two setae; basal endite with three cuspidate and two plumodenticulate setae; coxal endite with four stout multidenticulate setae, three plumodenticulate setae, and one simple seta. MAX2 (Figure 6A) — With indistinctly seg- mented endopodite, 2 or 3 setae; bilobed basal en- dite, distal lobe with 5 setae, proximal lobe with 5 setae, bilobed coxal endite, distal lobe with 5 setae, proximal lobe with 9 setae, scaphognathite with 17 or 18 marginal plumose setae. All setae plumose, plumodenticulate, or simple. MXPl (Figure 7A) — Exopodite with four plumose setae; endopodite five-segmented with numerous median margin setae and one lateral margin seta on distal segment. MXP2 (Figure 7E) — Exopodite with four plumose setae; endopodite four-segmented with indicated pattern of median margin setae and one lateral margin seta on distal segment. MXP3 — Limited to undeveloped bud. PI (Figure 7L) — Unsegmented biramous ap- pendage with up to two plumose setae. Z..ca II Carapace (Figure IB, b) with same basic fea- tures as stage I but with two distinct pairs of transverse grooves; eyes stalked. Abdominal somites (Figure IB) with pleopod buds; somite six and telson partially fused. 852 LANG and YOUNG; LARVAL DEVELOPMENT OF HYPOCONCHA SABULOSA a !?> O 853 FISHERY BULLETIN: VOL. 77. NO- 4 Figure 2. — Hypoconcha sabulosa: telson of zoeal stages 1 (A), II (B). and III (C), and megalopa (D). Only one disarticiilated uropod is shown for megalopa. Telson (Figure 2B) with reduced median notch; setation 8+8 with small outer fixed spine, hair- like plumose seta, and six large plumose setae. ANl (Figure 3B) — Indistinctly segmented; terminal setation of five aesthetascs and three fine simple processes; subterminal setation of two large plumose setae and two or three short plumose setae; additional one or two short setae may be present along basal margin. AN2 (Figure 3F) — Similar to stage I with 19 plumose setae on scale and 3 plumose setae on endopodite. MN — Similar to stage I; no palp. MAXI (Figure 5B) — With major features as in stage I, basal endite (7 setae) and coxal endite (10 or 11 setael with additional fine setae as indicated. MAX2 (Figure 6B) — With two-segmented en- dopodite, 5 setae distal, 3 setae proximal; bilobed basal endite with 5 or 6 setae distal, 6 setae proxi- mal; bilobed coxal endite with 4 setae distal, 11 setae proximal; and scaphognathite with 21-23 plumose setae. Setal types a mixture of simple, plumose, and plumodenticulate. MXPl (Figure 7B) — Exopodite with six plumose setae; endopodite as in stage I but with two additional plumose setae on lateral margin. MXP2 (Figure 7F) — Exopodite with five plumose setae, endopodite as in stage I but with two additional plumose setae on lateral margin. MXP3 (Figure 71) — Exopodite with five plumose setae; endopodite indistinctly segmented with two to three plumose setae. 854 LANG and YOUNG: LARVAL DEVELOPMENT OF HYPOCONCHA SABULOSA Figure 3: — Hypoconcha sabulosa: antennule of zoeal stages I( A), II (B), III (C). and megalopa (D); antenna of zoeal stages 1(E), II (F), and II (G), and megalopa iH). PI to P5 (Figure IB) — Conspicuous buds, first pereiopod distinctly biramous, four plumose setae on rudimentary exopodite (Figure 7M). Zoea III Carapace (Figure IC, c) similar to stage II, a small blunt lateral spine near ventral carapace margin and posterior to second transverse groove present in some individuals; eyestalk with an- terodorsal papilla. Abdominal somites (Figure Ic) with elongated pleopod buds; sixth somite and telson distinctly segmented. Telson (Figure 2C) normally 6+6 with very small outer spine, hairlike plumose seta, and 4 plumose setae; 2 zoeae 7+7 with 5 plumose setae, uropods with simple endopodite lobe and 13 or 14 setae on exopodite. ANl (Figure 3C) — Two-segmented; inner ramus a simple lobe; outer ramus with three ter- minal stout aesthetascs, three or four terminal fine processes (either simple setae or aesthetascs), three or four subterminal aesthetascs; basal seg- ment with three stout plumose setae and three or four short plumose setae, also two short plumose setae (not figured) or proximal margin. AN2 ( Figure 3G) — With simple two-segmented endopodite and 18-21 plumose setae on scale. MN (Figure 4B) — With simple palp. MAXl (Figure 5C) — With two-segmented en- dopodite, distal segment with two or three termi- 855 FISHERY BULLETIN: VOL, 77, NO. 4 ^o^ FIGURE 4. — Hypoconcha sabulosa: ventral view (A) and outline of biting survace (a) of stage zoea! I mandible: ventral view of zoeal stage in mandible iB); ventral view (C) and dorsal view (c) of megalopa mandible. nal setae and two pairs of subterminal setae, prox- imal segment with two setae; basal endite with four or five stout cuspidate setae and five to seven finer plumose or plumodenticulate setae; coxal endite with six or seven stout multidenticulate setae and seven to nine finer setae. MAX2 (Figure 6C) — With two-segmented en- dopodite, 5 setae on terminal segment, 3 or 4 setae on proximal segment; bilobed basal endite with 6 setae each lobe; bilobed coxal endite with 4 or 5 setae distal lobe, 14-17 setae in three rows proxi- mal lobe (3 subterminal setae on opposite surface not figured); scaphognathite with 25-28 plumose setae. MXPl (Figure 7C) — Same as stage II but with one additional seta on endopodite lateral margin. MXP2 (Figure 7G) — Exopodite with six or seven plumose setae; endopodite as in stage II but with additional seta on lateral margin. MXP3 (Figure 7J) — Exopodite with six or seven plumose setae; endopodite with two distinct segments, four setae on terminal segment, one or two setae on proximal segment. PI to P5 (Figure IC) — With pronounced exten- sion beyond carapace; first pereiopod (Figure 7N) biramus, exopodite with six terminal setae; re- maining pereiopods uniramus with segmentation evident and some simple setae or hairs. Megalopa Carapace (Figure 8A) dorsoventrally flattened with circular anterior margin and concave pos- terior margin; hepatic carapace margin with seven to nine distinct spines on each side, median anterior region depressed leading to short tapered rostrum; ventroposterior margins with short plumose setae; surface generally covered with numerous hairs, spinules, and plumose setae; eyestalk with distinct anterodorsal spine. Abdominal segments with distinct lateral spines on segments two to six; dorsal surface with numerous hairs and spinules. Telson (Figure 2D) nearly square, covered with hairs; anterior margin straight to slightly concave with 8 plumose setae; articulated uropods, en- dopodite with 2 plumose setae, exopodite with 13 or 14 plumose setae. ANl (Figure 3D) — With three basal segments; outer ramus with five segments, setation from tip to base, three simple setae, three or four aesthe- tascs, four aesthetascs, no setae; inner ramus with three segments with 2-3-2 setae. AN2 (Figure 3H) — Basipodite with palp, numerous spines and three or four plumose setae; endopodite with 10 segments. MN (Figure 4C, c) — With outer cutting edge and depressed center; palp three-segmented with five processes on distal segment. MAXl (Figure 5D) — With three-segmented endopodite, setation reduced to 6 setae as shown; basal endite with 7 cuspidate setae, 8 or 9 plumodenticulate setae, and 3 plumose setae on 856 LANG and YOUNG: LARVAL DEVELPOMENT OF HYPOCONCHA SABULOSA Figure 5. — Hypoconcha sabulosa. maxillule of zoeal stages I (A), II (B), and III (C). and megalopa (D). proximal margin; coxal endite with 5 or 6 stout multidenticulate setae and 18-20 finer setae. MAX2 (Figure 6D) — With two-segmented en- dopodite, 5 setae on terminal segment, 1 or 2 setae on proximal segment; bilobed basal endite with 9 setae distal lobe, 8-10 setae proximal lobe, bilobed coxal endite with 7-9 setae distal lobe, 20-22 setae proximal lobe; scaphognathite with 37-40 plumose setae. MXPl (Figure 7D) — Exopodite with 2 or 3 terminal and 2 or 3 subterminal plumose setae; endopodite indistinctly segmented with 8 setae; basipodite with 24-28 setae; coxapodite with about 15 setae. MXP2 (Figure 7H) — Exopodite with 5-7 termi- nal and 2 subterminal plumose setae; endopodite five-segmented, 5 or 6 terminal setae and 8-10 setae subterminal. 857 FISHERY BULLETIN: VOL. 77. NO. 4 Figure 6. — Hypoconcha sabulosa: maxilla of zoeal stages I (A), 11 (B). and III (Cl. and megalopa (D). Setules have been omitted from B-D for graphic clarity 858 LANG and YOUNG: LARVAL DEVELOPMENT OF HYPOCONCHA SABULOSA FlGVRE 1 .—Hypoconcha ,sabu/osa; first maxilliped of zoeal stage I-megalopa I A-Dl; second maxilliped of zoeal stage I-megalopa (E-H); third maxilliped of zoeal stage Il-megalopa (I-Kl; and first pereiopod of zoeal stage I-III (I^N). 859 FISHERY BULLETIN: VOL. 77, NO. 4 Figure 8. — Hypomncha sabulosa: dorsal view of megalopa (A) and details of appendages; cheliped (B>. fourth pereiopod (C), fifth pereiopod (D), and second pleopod (E). MXP3 (Figure 7K) — Exopodite with 6 or 7 plumose setae; endopodite five-segmented, seta- tion tip to base, 6 or 7, 6-8, 6, 10-12, 5-8, numerous spines on two lower segments. PI to P5 (Figure 8A-D) — Uniramous with numerous hairs and short plumose setae. First pereiopod (Figure 8B) with equal-sized claws; sec- ond and third pereiopod similar, dactylpods with simple tapered tip; fourth pereiopod (Figure 8C) shorter, dactylpod hooked; fifth pereiopod (Figure 8D) carried high and over carapace, dactylpod hooked with long stiff simple process. 860 LANG and YOUNG: LARVAL DEVELOPMENT OF HYPOCONCHA SABULOSA DISCUSSION Hypoconcha Species Distinction Both H. arcuata and H. sabulosa have similar ranges and habitats along the southeastern Unit- ed States coast (Hay and Shore 1918; Williams 1965) and adult morphology is quite similar (Rathbun 1937; Williams 1965). The source of lar- vae for this study was a small (carapace 17 x 17 mm) female with characteristics dorsal carapace, color, and marginal spines (Williams 1965). How- ever, the ventral carapace ridges were weakly de- veloped and the three characteristic tubercles (Rathbun 1937) were not evident (one small tuber- cle was present). This may be characteristic of young specimens or it may indicate hybridization of the two species. The distinction of species for these two forms should perhaps be reinvestigated. Not surprisingly, the differences between the larval morphology ofH. arcuata given by Kircher (1970) and//, sabulosa are slight. The differences we observed overlap the ranges of variation re- ported for setation or represent fine points open to interpretation. Based on present published infor- mation, a reliable means to distinguish corres- ponding zoeal stages between the two species is absent. Hypochoncha sabulosa megalopae have spines on the eyestalk and abdominal segments, features not noted for//, arcuata. However, these may be points of omission by Kircher (1970) and represent only tentative differences. A detailed direct comparison of larvae is needed to determine if these species can be identified during ontogeny. Characteristics of Dromiidae Larvae Knowledge of dromiid larvae is limited to five genera within the family Dromiidae (Table 3). The larvae of//, sabulosa demonstrate most general features of dromiid larval development; some fea- tures, however, such as carapace armature are surprisingly diverse. Larval development ranges from six zoeal stages in Dromidia antillensis to two zoeal stages in Conchoecetes artifiosus. Four of ten documented species have abbreviated de- velopment (Table 3). The dromiid zoeal carapace is elongated with a large, anteriorly directed rostrum, transverse grooves, and, in most cases, a textured surface of fine ridges. The carapace may lack armature {Hypoconcha, Conchoecetes), have posterolateral spines (Dromia), have supraorbital spines (Dro- midia), or have a dorsal spine and lateral "wings" (Petalomera). Carapace margins are either smooth or denticulate. All zoeae are richly pig- mented with a general orange-red color. The antennal morphology is unique to the group. The endopodite has 3 or 4 plumose setae in stage I larvae. The exopodite is a flat scale and after stage I has setae on its outer margin. The mandibular palp generally does not develop until the terminal zoeal stage while the maxilla endopodite is well developed and often distinctly segmented. The endopodites of the first and second maxillipeds are five- and four-segmented respec- tively. The third maxilliped is usually biramous and rudimentary in stage I but well developed with a basally situated endopodite by stage II. Table 3.- - Principal studies on the postembryonic development in taxa of the family Dromiidae. Taxon Author Material Dromiidae Gurney (1924) Plankton sample with Gurney(1942) unknown parents Conchoecetes Sankolli and artifiosus Shenoy(1968) Laboratory— all stages Cryptodromia Hale (1925) Abbreviated development octodentata Dromia Cano'(1893) Plankton — 1, IV. megalopa personata Williamson' (1915) Plankton— 1, IV, megalopa Lebour' (1934) Plankton— 1.11,1V. megalopa Pike and Williamson2( 1960b) Plankton— I, ll.lll Riceetal (1970) Laboratory— all stages Dromidia Rice and antillensis Provenzano(1966) Laboratory — all stages Dromidia australis Hale (1927) Abbreviated development Epipedodromia thomsoni Hale (1925) Abbreviated development Hypoconcha arcuata Kircher (1970) Laboratory— all stages Hypoconcha sabulosa Present paper Laboratory- all stages Petalomera Montgomery (1922) Abbreviated development lateralis Hale (1925) Petalomera Wear (1970) Plankton— 1. II wilsoni Wear (1977) Plankton— magalopa ' Desaibed as Dromia vulgaris, ^Described as Dromia personatus The pereiopods may be uniramous (Conchoec- etes, Petalomera) or biramous (Dromidia). Only the first pereiopod is biramous in Dromidia and Hypoconcha. Uropods are well developed in late zoeae oi Dromia, Dromidia, and Hypoconcha but are reduced in Conchoectes and Petalomera. Systematic Position of the Dromiidae The classification and phylogeny of the Dromiidae and other decapod groups rests princi- 861 pally on three lines of evidence: comparative mor- phology, fossil records, and larval development (Stevcic 1971). Based primarily on comparative morphology of adult crabs and sparse fossil re- cords, the family Dromiidae has usually been con- sidered primative but true brachyurans (Balss and Grunner 1961; Burkenroad 1963; Glaessner 1969; Hartnoll 1975; Warner 1977). In contrast to these findings, the larval de- velopment of dromiids is, in many aspects, typi- cally anomuran. Gurney (1924) found all larvae of Dromia to be "definitely Anomuran." Brachyuran and anomuran larvae have since been well charac- terized in several comprehensive studies (Gurney 1942; Pike and Williamson 1960a; Williamson 1974); the findings of Gurney (1924) have been consistently substantiated. The megalopa is not so easily characterized and appears to more closely resemble its parents than both postlarval anomu- rans and nondromiid brachyurans (Wear 1977). A detailed account of the classification of the Brachyura and a proposed new system has re- cently been published by Guinot (1978). The Brachyura are characterized not only by the advanced organizational level of adults but also by a consistant larval form. The evolutionary path should include "brachyurization" to both a crab body (Stevcic 1971) and a "brachygnath zoea" (Williamson 1974). A key to better understanding the dromiids is to find larval types which appear to lead toward a brachygnath form. If, like the Dromiidae, the Dynomenidae and Homolo- dromidae are found to have larvae showing no tendency to develop brachygnath features, the Dromiacea (Guinot 1978) may have progressed toward a crablike form independent of lines lead- ing toward the true brachyurans. The combination of adult and larval charac- teristics exhibited by the Dromiidae has not been satisfactorily explained. In view of obvious con- tradictions and the relative importance of adult morphology in decapod classification, removal of the Dromiidae from the Brachyura based solely on known larval features (Gurney 1924, 1942; Kircher 1970; Williamson 1974) is not warranted. Placement of the Dromiidae within the Brachyura, is by no means "of little doubt" as claimed by Warner (1977) but represents more a matter of convenience (Guinot 1978); their posi- tion is tenuous at best. Hopefully additional mate- rial (larval, morphological, or fossil) will lead to a comprehensive account of the Dromiidae and re- lated families. FISHERY BULLETIN VOL. 77, NO- 4 ACKNOWLEDGMENTS This study was initiated by the authors while at the University of South Carolina. The authors ex- press their appreciation to the Belle W. Baruch Institute for support. Aid for completion of this project was provided by the EPA Environmental Research Laboratory at Narragansett, R.I., par- ticularly through the cooperation of Don C. Miller and Donald K. Phelps. Akella N. Sastry, Graduate School of Oceanography, University of Rhode Is- land, generously allowed use of his microscope. We would also like to thank Daniele Guinot, Richard G. Hartnoll, Anthony L. Rice, and Zdravko Stevcic for providing publications and useful information. LITERATURE CITED BALss. H,. AND H. E. Grunner, 1961. Decapoda. XI. Stammesgeschichte. In Dr. H. G. Bronn's (editor), Klassen und Ordnungen des Tierreichs, Bd. 5. Abt. 1. Buch 7, Lief. 14, p. 1797-1821. Geest and Portig. Leipz. Burkenroad, M. D. 1963. The evolution of the Eucarida, (Crustacea, Eumalacostraca), in relation to the fossil record Tulane Stud. Geol 2:1-21. Cano.G. 1893. Svillupo dei Dromidei. Atti. Accad. Sci. Fis. Nat,, Napoli, Ser. 2, 6:1-23. GLAESSNER, M. F. 1969. Decapoda. /n R. C. Moore(editor),Treatiseoninver- tebrate paleontology, Pt. R, Arthropoda 4,2:R390-R533. Geol. Soc. Am.. Boulder. GUINOT, D. 1978. Principes d'une classification evolutive des Crustaces Decapodes Brachyoures, Bull. Biol. Fr. Belg. 112:211- 292. GURNEY, R. 1924. Crustacea. Part IX. — Decapod larvae. Nat. Hist. Rep. Br. Antarct. "Terra Nova" Exped.. Zool. 8:37-202. 1942. Larvae of decapod Crustacea Ray Soc. (Lond.i Publ. 129, 306 p. Hale, H. M, 1925 The development of two Australian sponge crabs Proc. Lmn. Soc. N. S. W. 4:405-413. 1927 The Crustaceans of South Australia 1. Gov. Print., Adelaide. Aust., 201 p, Hartnoll, R. G. 1975. Copulatory structure and function in the Dromiacea. and their bearing on the evolution of the Brachyu- ra. Publ. Stn. Zool. Napoli 39 (Suppl.):657-676. Hay, W. p., and C. a. Shore 1918. The decapod crustaceans of Beaufort. N.C.. and the surrounding region. Bull. U.S. Bur. Fish 35.369-475. JOHNS. D. M., AND W H. Lang 1977. Larval development of the spider crab.Lifcmia emar- ginata (Majidae). Fish. Bull., U.S. 75:831-841. KIRCHER, A B. 1970 The zoeal stages and glaucothoe of Hypoconcha ar- 862 LANG and YOirNG: LARVAL DEVELOPMENT OF HYPOCONCHA SABULOSA cuata Stimpson (Decapoda:Dromiidae) reared in the laboratory. Bull. Mar. Sci. 20:769-792. LEBOUR. M. V. 1934. The life-history of Dromia nu/gans. Proc Zool. Soc. Lond. 1934:241-249. MONTGOMERY, S. K. 1922. Direct development in a dromiid crab. Proc. Zool. Soc. Lond. 1922:193-196. PIKE. R. B., AND D. I. Williamson, 1960a. Larvae of decapod Crustacea of the families Diogenidae and Paguridae from the Bay of Naples. Publ. Stn. Zool. Napoli 31:493-552. 1960b. Larvae of decapod Crustacea of the families Dromiidae and Homolidae from the Bay of Naples. Publ. Stn. Zool. Napoli 31:553-563. RATHBUN, M, J, 1937. The oxystomatus and allied crabs of America. U.S. Natl. Mus. Bull. 166:1-278. RICE, A. L., R. W. INGLE, AND E. ALLEN 1970, The larval development of the sponge crab, Dromia personata ( L,) (Crustacea, Decapoda, Dromidea), reared in the laboratory. Vie Milieu, Ser, A, Biol, Mar. 21:223-240. RICE, A. L., AND A. J, PROVENZANO, jR. 1966. The larval development of the West Indian sponge crab Dromidra an/iV/efisis (Decapoda:Dromiidae). J. Zool. (Lond.) 149:297-319. SANKOLLI. K. N., AND S. SHENOY 1968. Larval development of a dromiid crab, Conchoecetes artificwsus (Fabr.) (Decapoda. Crustacea) in the labora- tory. J. Mar. Biol. Assoc. India 9:96-110. STEVCIC.Z. 1971. The main features of brachyuran evolution. Syst. Zool. 20:331-340. 1974. La structure cephalique et la classification des de- capodes brachyoures. Biol. Vestn. 22:241-250. Warner, G, F, 1977, The biology of crabs. VanNoatrandReinholdComp., N.Y., 202 p. Wear. R. G. 1970. Some larval stages of Petalomera wilsoni (Fulton & Grant. 1902) (Decapoda, Dromiidae). Crustaceana 18:1- 12. 1977, A large megalopa attributed to Petalomera wilsoni (Fulton and Grant, 1902) (Decapoda, Dromiidae), Bull. Mar, Sci. 27:572-577. Williams. A. B. 1965. Marine decapod crustaceans of the Carolinas. U.S. Fish Wildl. Serv.. Fish. Bull. 65:1-298 Williamson, D, I, 1974. Larval characters and the origin of crabs (Crustacea, Decapoda. Brachyura). Thalassia Jugosl. 10:401-414. Williamson. H. C. 1915. Decapoden.I.TeiKLarven). Nord. Plankton Lief 18, Abt. 6:315-588. 863 BLACK ROCKFISH, SEBASTES MELANOPS: CHANGES IN PHYSICAL, CHEMICAL, AND SENSORY PROPERTIES WHEN HELD IN ICE AND IN CARBON DIOXIDE MODIFIED REFRIGERATED SEAWATER Jeff Collins, Kermit D. Reppond, and Fern A. Bullard' ABSTRACT The purpose of this study was to determine changes in various properties of fillets, minced flesh, and washed minced flesh from black rockfish, Sebastes melanops, as affected by time of holding in ice or carbon dioxide modified refrigerated seawater and frozen storage at ■ 18° C , Fish were held up to 14 days in the holding mediums and removed periodically and analyzed for changes in physical , chemical, and sensory properties. The yield of fillets calculated from the initial whole weight was unaffected by time of holding in either system. Subjective observations made during the holding periods indicated that fillets of good quality could be prepared from rockfish held for 10 days in either system. These observations were confirmed in a later series by sensory evaluation of cooked portions from the frozen blocks of fillets prepared at intervals during an 11-day holding period. The chemical analyses for trimethylamine, total volatile acid, and total volatile base were of no use to measure spoilage. Washing the minced flesh resulted in a reduction of solids, trimethylamine oxide, and salt and a reduction in yield when expressed on a salt-free constant, l&^c solids basis. The extractable protein nitrogen of minced flesh decreased with time of frozen storage at -18° C and was strongly influenced by the length of holding period for the fresh whole fish. Several papers have been published on the fresh or frozen characteristics of fillets or minced flesh from rockfishes. Different species of rockfishes gave products having different fresh acceptability and frozen storage life (Miyauchi and Stansby 1952). Stansby and Dassow (1949) found that the frozen storage quality of fillets from yellowtail rockfish, Sebastes ftavidus, could be improved by removing part of the dark flesh along the lateral line. Barnett et al. (1971) compared yellowtail rockfish held in refrigerated seawater (RSW) and RSW modified with the addition of CO2 (MRSW). The fresh storage life was extended 1 wk in MRSW over RSW. Teeny and Miyauchi (1972) increased the frozen life of minced flesh of yellowtail rockfish and silvergray rockfish, S. brevispinis: by using various additives. Additional improvements in storage life were obtained by washing the minced muscle of black, silvergray, and yellowtail rockfishes (Miyauchi et al. 1975.) The objectives of this study were generally to characterize and compare the changes that occur in black rockfish with time of holding in ice and in MRSW, to determine sensory properties of fillets as affected by fresh holding time, and to determine 'Northwest and Alaska Fisheries Center, National Marine Fisheries Service, NOAA, P 0 Box 1638, Kodiak, AK 99615. Manuscnpt accepted April 1979 FISHERY BULLETIN VOL 77, NO. 4, 1980. the changes in amine content and extractable pro- tein nitrogen with time of frozen storage of washed and unwashed minced flesh. EXPERIMENTAL PROCEDURES Sampling Two groups offish were used in this study. Lot 1 was used to determine physical and chemical properties and Lot 2 was used for formal sensory evaluation. The fish were caught over a 2-h period with hook and line, with or without bait. These fish are found locally on exposed, highly sloped rocky shores with strong currents where trawling gear cannot be used. A sporadic local fishery has employed the same fishing technique. Lot 1 fish (154 fish, 265 kg, 0.2 kg SD) were captured 2 July 1977 at the Triplets, 20 mi northwest of Kodiak, Alaska, and delivered to the laboratory about 2 h later. The fish were individually tagged and weighed before placing in the previously de- scribed ice and MRSW holding systems (Bullard and Collins 1978). The raw fish handling and sam- ple preparation were similar to that previously reported for walleye pollock (Reppond et al. 1979), and are briefly described here. Fish were sampled according to weight classes to give an average of 865 FISHERY BULLETIN; VOL, 77, NO. 4 1.8 kg/fish for an 1 1-fish sample at holding periods of 0, 4, 6, 8, 10, 12, and 14 days. When removed from the holding systems, the fish were washed briefly to remove slime or ice, drained on a rack for 5 min, and individually weighed. The fish were filleted by hand and the fillets were rinsed briefly, drained on an inclined screen for 5 min, and weighed. Notes were made on the appearance of the round fish and the condition of the gills, vis- cera, and fillets. The fillets were ground using the coarse blade of an Oster^ food grinder, and a por- tion was washed with cold water ( 1 part flesh: 2 parts water) for 15 min on a reciprocating shaker. The flesh was drained for 30 min on an inclined 16-mesh plastic screen then weighed. Composite portions of both washed and unwashed meats were frozen at -34" C for chemical tests. Other portions were sealed in polylaminated pouches and stored at -18° C for 2, 4, 6, and 9 mo. Sensory Lot 2 fish ( 184 fish, 258 kg) were used for formal sensory testing and were caught in the same loca- tion 1 mo later, on 26 August. These fish were held in ice and in MRSW in the same manner as Lot 1 and at 0, 3, 6, 8, and 11 days were filleted. The fillets were packed into blocks and held at -34 C for sensory evaluation several months later. The blocks were sawed into portions measuring 80 x 50 X 12 mm and thawed at room temperature. The control sample and samples from fish held in ice were salted by immersion in a 5% solution for 1.5 min to minimize differences in salt content with samples from fish held in MRSW. The portions were cooked in individual sealed aluminum pans at 232° C for 20 min in a commercial oven. Because of the difficulty in equalizing the salt content, samples from the two holding systems were not directly compared. The results of the sensory test were evaluated by analysis of variance. If analysis of variance indicated a change had occurred with time of holding, the Student-Newman-Keuls test was used to determine which samples were differ- ent. Analyses The frozen samples for chemical tests (Lot 1) were tempered overnight in a refrigerator at 3° C ^Reference to trade names here does not i mply endorsement by the National Marine Fisheries Service, NOAA. and ground twice using the fine blade of an Oster food grinder. Analyses were carried out for total nitrogen, total solids, chloride (Horwitz 1975: 15, 309, 310), total volatile acid (TVA, Friedemann and Brook 1938), total volatile base (TVB, Stansby et al. 1944), and extractable pro- tein nitrogen (EPN, Dyer etal. 1950). Analyses for trimethylamine oxide (TMAO, Bystedt et al. 1959), nonprotein nitrogen (NPN, Nikkila and Linko 1954), and trimethylamine (TMA, Tozawa et al. 1971) were carried out on a 5*^ trichloroace- tic acid extract. An aliquot of the extract was neu- tralized and analyzed for dimethylamine (DMA) by Dowden's method ( 1938 ) modified by increasing the time of extraction to 15 min on a mechanical shaker. RESULTS AND DISCUSSION Physical Appearance and Yield At each period of sampling, informal subjective observations were made on the whole fish and their raw fillets. We noted differences in gills, fins, and slime between the two holding systems. In ice, the gills were bright red to day 6 but discolored quickly in MRSW. Cloudiness of the eyes started at day 8 in ice but the eyes were white in a day or two in MRSW. The beginning of off-odors in the fillets, softening of flesh, and gut decompostion was observed in both holding systems at 10 days and worsened thereafter. At day 14, the odor of the fillets was objectionable and mincing intensified the odor. The quality of fillets from the fish held in MRSW were generally judged better than from fish held in ice for the same time. As noted later in this paper, neither formal sensory nor chemical tests detected the changes observed on the 10th day of holding in ice or MRSW. Chemical tests could not confirm the poor raw quality at 1 2 and 14 days which was so obvious that we would not serve these fillets to a taste panel. Consequently, we concluded that experienced observers could sub- jectively judge the various stages of raw quality, namely: good quality (0-8 days), onset of spoilage ( 10 days), and unacceptable quality (12 days). Whole fish gained weight with time of holding in either system ( Table 1 ). Fish held for 14 days in ice gained half as much weight as those held in MRSW, about 3'7f and 6<7f , respectively. The yield of fillets increased slightly with time of holding in ice but was constant with time of holding in MRSW. The average yield of fillets was slightly 866 COLONS ET AL BLACK ROCKFISH: CHANGES IN PROPERTIES higher from fish held in ice than from fish held in MRSW, 31.7% and 30.5%, respectively. When yield data are converted to a salt-free, 18% solids basis however, equal yields of fillets were obtained in both systems (34%). The solids content of the fillets decreased slightly in ice but increased in MRSW because of the increase in salt content (Ta- ble 1 ). The absorption of salt from the MRSW sys- tem is not a problem because rockfish have thick flesh and skin. Sensory Evaluation Table l. — Initial round weight and change in yield, salt, and total solids content of fillets and washed ground flesh from black rockfish (Lot 1) with time of holding in ice and in modified refrigerated seawater. Time of Fillets Washed ground flesh holding wl' inwt Yield Salt Solids Yield^ Salt Solids (days) m (%) (%) (%) (%) (%) (%) (%) Ice 0 18 35 000 30 7 003 20-2 40.5 005 150 4 19 09 1 15 31 0 0 07 192 365 0,04 146 6 18 88 1 51 31 5 009 195 38.5 0,06 138 8 19 48 2 08 31 8 0 10 19.4 389 008 135 10 1951 2 15 31 2 010 19.3 385 0.06 133 12 19 66 274 32.1 0.09 19,1 39,3 0 04 13 1 14 21 49 275 32.7 0.08 19.1 400 007 130 Modified 1 ■efrigerated seawater 0 1835 0 00 30 7 0 03 20 2 40 5 005 150 4 19 90 256 304 020 20 2 36 8 0 08 142 6 19 35 3 89 30 6 0 28 20 6 34 7 0 11 150 8 1926 425 30 0 0 36 20 4 34 0 0 14 14 8 10 18 93 440 30 4 0 48 20 7 34.2 0,20 153 12 19 48 6.27 30.8 057 209 33.5 0.22 161 14 18.81 5.65 30.6 076 20.9 32.9 0.27 168 'Total round weight of fish that composed the sample ^Yield ot washed ground flesh if no portion had been reserved for analysis of fillets Table 2. — Change in mean sensory analysis scores ± standard deviations for baked portions of blocks of fillets from black rockfish (Lot 21 with time of holding in ice and in modified refrigerated seawater (MRSW). Panel had 12 judges. Flavor and texture scores were on the following scale: 5-Very good. 4-Good, 3-Fair, 2-Borderline. and 1-Poor. Preference scores were on a 9-point scale: 9-Like extremely. 8-Like very much, 7-Like moderately, 6-Like slightly, 5-Neither like nor dislike. 4-Dislike slightly, 3-Dislike moderately, 2-Dislike very much, and 1-Dislike extremely. holding (days) Ice MRSW Ice MRSW MRSW 3.5±0.7 3.1 ±0.4 3.8±0.6 34±07 3.6-0.5 36±06 2.9±0.8 3.5±0.8 3.13:0.5 4.1: 3.9±0.7 4 1 ±0.5 4.3±0.5 4.0±0-5 0.6 4.1 ±0.3 4.0±0-4 3.8±0.6 3.8±0-6 6.3 ±1.4 5.8±0.7 6.4±13 6.3±12 63±09 6.5±1.0 5,2±13 6.4±13 5.4±1 2 No significant (P<0.05) change in flavor, tex- ture, or preference was noted between the zero time control and any sample from either holding system (Table 2). No significant differences in sen- sory scores occurred among the ice-held samples but the differences in flavor and preference scores between samples held 3 days and 8 days in MRSW were significant. However, these differences were probably circumstantial since neither the 3- nor 8-day MRSW sample differed from any of the other samples from that holding system. The bland flavor of rockfish flesh was reflected in the preference scores which ranged from "like slightly" to "neither like nor dislike." The sensory data indicate that when held in ice or in MRSW this species of rockfish will maintain its accepta- bility during commercial holding periods of at least 8 to 10 days. Chemical Analyses The protein content of fillets (Table 3) was unaf- fected by time of holding but was slightly lower from fish held in ice than in MRSW. The nonpro- tein nitrogen content decreased slightly with time of holding in both holding systems. Several chemical tests were performed to mea- sure spoilage. TVA values increased from 0.07 at 8 days in ice to 0. 10 meq/100 g at 10 days which may indicate a change in quality at 10 days. No change was noted in fillets from the MRSW system. TVB values were constant and low (about 4 mg N/100 g). As with walleye pollock, TVB data were not useful to indicate spoilage. TMA values increased Table 3. — Change in analytical values of fillets from black rockfish (Lot 1) with time of holding in ice and in modified refrigerated seawater. Time of holding (days) 0 4 6 8 10 12 14 Protein' (%) 18,3 18-5 188 183 184 182 18.4 Ice TVB NPN TVA (mgN: (%) (meg H-'IOOg) lOOg) 0.34 0.33 0 31 0 31 0 31 030 0.30 0 06 006 006 007 0 10 Oil 0.10 3-9 3.6 TMA (mg N: lOOg) 020 041 041 049 0,59 0 62 0.82 DMA (mg N,' lOOg) 020 0 30 0,24 0 27 029 0.30 0.24 Protein' (%) 18.3 18 8 190 19.0 19.2 19 1 19.0 Modified refrigerated seawater ^ ' ' " TVB TMA NPN TVA (mg N; (mg N,' (%) (meqH-'IOOg) 100 g 100 g) 0-34 032 0-31 030 0-30 0-30 0-27 006 0 06 0 07 0 06 0 06 0 07 0-08 39 33 28 29 0 20 0 37 0 43 0 49 0 56 0 67 069 DMA (mg N/ 100 g) 020 023 023 0 29 0 18 037 0 29 867 FISHERY BULLETIN: VOL. 77 NO 4 in an equal, gradual and linear manner with time of holding in both systems. DMA values did not change with time of holding or system (0.3 mg DMA-N/100 g). Effects of Washing Minced Flesh Washing the minced flesh of black rockfish re- sulted in a reduction in salt and solids content (Table 1), in slightly lower EPN values (Table 4), and a big drop in TMAO content (Table 5). Wash- ing increased the apparent yield of minced fillets from 32 to 38% (ice) and from 32 to 33% (MRSW). When yield data of fillets and minced, washed flesh are placed on a comparable basis by convert- ing to a salt-free, constant 18% solids basis how- ever, the washing procedure reduced the yield in both systems from 34 to 28%. Frozen Storage A number of research papers have been pub- lished on the general subject of toughness of fish flesh and the relationship (or not) of free fatty acids, formaldehyde, and EPN (Mills 1975). The tough texture that develops in frozen fish is always accompanied by a decrease in EPN (Castell et al. 1973) but texture and EPN are not necessarily equated. It is generally accepted that reduced EPN occurs with increased fatty acid content and formaldehyde content (sometimes indirectly mea- sured as DMA). The extractable protein nitrogen (Table 4) of minced flesh from ice-held fish de- creased slightly at 2 and 4 mo of frozen storage, decreased to about 50% at 6 mo, and decreased to about 35% at 9 mo. The same general trend was observed with MRSW-held fish except EPN values Table 4. — Change in extractable protein nitrogen content (percent) of minced flesh (unwashed and washed) from black rockfish ( Lot 1 ) with time of holding in ice and in modified refrigerated seawater. Ice filodified 1 efrigerated seawater holding Montus of frozen storage al-18 C fi^onths of frozen storage at -18 C (days) 0 2 4 6 9 0 2 4 6 y Minced flesh M meed flesh 0 85 87 70 60 32 85 87 70 60 32 4 83 83 68 64 42 85 — 73 70 31 6 80 72 78 46 42 80 63 64 59 24 8 87 74 73 54 37 86 53 73 42 26 10 78 70 77 53 34 78 56 65 38 30 12 82 69 72 33 35 73 56 60 49 24 14 86 73 64 48 27 74 48 39 26 22 Washed minced flesh Washed minced flesh 0 90 79 63 56 30 90 79 63 56 30 4 77 79 75 59 33 78 61 58 57 32 6 83 76 74 62 29 75 65 63 42 28 8 81 69 70 38 34 79 71 60 28 26 10 77 75 62 49 34 83 45 54 27 19 12 83 77 66 31 26 67 44 44 23 21 14 74 70 63 42 26 68 40 47 23 15 Tables. — Change in trimethylamineoxidecontentlmilligramsTMAO-N/lOOgI of minced flesh (unwashed eind washed) from black rockfish (lx)t 1) with time of holding in ice and in modified refrigerated seawater. Ice Modified refrigerated seawater holding Months of frozen storage at-18 C Months of frozen storage at -18 C (days) 0 2 4 6 9 0 2 4 6 9 Minced flesh Minced flesh 0 136 100 68 69 74 136 100 68 69 74 4 130 97 56 66 70 145 98 70 67 69 6 128 96 66 65 66 140 93 68 63 66 8 129 92 66 60 64 127 86 63 66 62 10 125 86 64 60 66 126 85 63 58 62 12 143 84 64 60 66 121 83 62 58 59 14 143 86 63 63 61 120 83 59 61 56 Washed minced flesh Washed minced flesh C 36 - 37 36 39 36 — 37 36 39 4 30 — 29 28 29 27 — 30 25 27 6 28 — 26 28 26 24 — 25 23 23 8 25 — 26 25 26 25 — 26 24 26 10 26 — 27 24 26 24 — 25 23 24 12 24 — 26 26 24 22 — 25 26 23 14 22 — 25 25 23 20 — 23 22 22 868 COLLINS ET AL.: BLACK ROCKFISH: CHANGES IN PROPERTIES were slightly lower. Although EPN did not change significantly with time of fresh holding in ice and only slightly in MRSW, the effect of the length of time of fresh holding on EPN became apparent in samples held at -18" C for 6 to 9 mo. If EPN is related to the texture of black rockfish, the data in Table 4 suggest that 6 mo of frozen storage at -18° C was too long for minced flesh at any level of fresh quality and that various periods of frozen storage would give acceptable texture depending on the level of fresh quality when frozen. The TMAO content of the unwashed minced flesh was unaffected by time of holding in ice but decreased slightly in MRSW (Table 5). Although not expected to change with the frozen storage of this non-gadoid fish, amine data were obtained since no data on TMA and DMA and only one value for TMAO (93 mg N/100 g, Dyer 1952) have been reported in the literature for S. melanops. There was a strong reduction in TMAO content of the unwashed minced flesh with time of frozen storage to 4 mo with little change thereafter. TMA and DMA values were not affected by frozen storage (data not included in tables). Con- sequently, the substantial reduction in EPN was not caused by formaldehyde. We cannot explain either the observed loss of TMAO without a con- comitant increase in either TMA or DMA content or the lack of change in TMAO content with time of frozen storage of the unwashed minced flesh. SUMMARY Black rockfish was held in the round in ice or MRSW to 14 days. The yield of fillets was not affected by time of holding but fish held in ice gave slightly higher yields than fish held in MRSW, 32 and 31%, respectively. The usual chemical spoilage tests (TMA, TV A, TVB) were of little or no use as indicators of spoilage. Observations of the begin- ning of off-odors, softness of flesh, and decomposi- tion of viscera at 10 days were not confirmed by sensory evaluation of the cooked portions. For this species, early changes in quality were best judged subjectively on the raw, whole fish and fillets. Formal sensory evaluation was less sensitive than informal evaluation to change in quality, and chemical spoilage tests were not sensitive to obvi- ously advanced spoilage. Washing the minced flesh resulted in a reduction in salt, solids, and TMAO content. The yield increased with washing because of increased water content but when cal- culated on a salt-free, constant 18% solids basis, the yield decreased in both systems to 28% when minced and washed. The EPN values of minced flesh from ice-held fish decreased during frozen storage at -18" C from about 80 to 35% after 9 mo and MRSW-held fish gave similar but slightly lower EPN values. The degree of fresh quality strongly influenced EPN values during frozen storage indicating that the time of holding in ice or MRSW should be considerably less than 10 days to maintain good quality for any reasonable period of frozen storage. LITERATURE CITED Barnett, H. J , R. W. Nelson, P. J. Hunter. S. Bauer, and H. Groninger. 1971. Studies on the use of carbon dioxide dissolved in refrigerated brine for the preservation of whole fish. Fish. Bull.. U.S. 69:433-442. BULLARD, F. A., AND J. COLLINS. 1978. Physical and chemical changes of pink shrimp, Pan- dalus borealis. held in carbon dioxide modified refriger- ated seawater compared with pink shrimp held in ice. Fish. Bull., U.S. 76:73-78. BYSTEDT, J., L. SWENNE, AND H. W. AAS. 1959. Determination of trimethylamine oxide in fish mus- cle. J. Sci. Food Agric 10:301-304. Castell, C. H., B Smith, and W, J. Dyer. 1973. Effects of formaldehyde on salt extractable proteins of gadoid muscle. J. Fish. Res. Board Can. 30: 1205-1213. DOWDEN.H. C. 1938. The determination of small amounts of di- methylamine in biological fluids. Biochem. J. 32:455- 459. Dyer, W.J. 1952. Amines in fish muscle. VI. Trimethylamine oxide content of fish and marine invertebrates. J. Fish. Res. Board Can. 8:314-324. DYER, W. J., H. V. FRENCH, AND J. M. SNOW. 1950. Proteins in fish muscle, I. Extraction of protein frac- tions in fresh fish. J, Fish, Res. Board Can. 7:585-593. Friedemann, T. E.. and T. Brook. 1938. The identification and quantitative determination of volatile alcohols and acids. J. Biol. Chem. 123:161- 184, HORWITZ, W, (editor). 1975, Official methods of analysis of the Association of Official Analytical Chemists, 12th ed. Assoc Off. Anal. Chem., Wash.. DC. 1094 p. Mills, A. 1975. Measuring changes that occur during frozen storage of fi.sh: a review. J. Food Technol. 10:483-496, MIYAUCHI. D,, M. PATASHNIK, AND G. KUDO. 1975. Frozen storage keeping quality of minced black rockfish (Sebastes spp I improved by cold-water washing and use offish binder. J. Food Sci. 40:592-594. MIYAUCHI. D, T,. AND M, E, STANSBY. 1952. Freezing and cold storage of Pacific Northwest fish 869 FISHERY BULLETIN: VOL 77. NO, 4 and shellfish. Part 1 - Storage life of various rockfish fillets. Commer. Fish. Rev. 14( 12al:24-28. NIKKILA.O. E.,ANDR. R, LINKO. 1954. Denaturation of myosin during defrosting of frozen fish. J. Food Res, 19:200-205. REPPOND, K. D., F. A. Bl'LL.ARD, AND J. COLLINS. 1979. Walleye pollock. Theragra chalcogramma: physical, chemical, and sensory changes when held in ice and in carbon dioxide modified refrigerated seawater. Fish. Bull., U.S. 77:481-488. STANSBY, M. E., AND J. DASSOW. 1949. Storage life of whole and split rockfish fillets. Commer. Fish. Rev. ll(7):l-8. STANSBY, M. E., R. W. HARRISON, J. DASSOW, AND M. SATER. 1944, Determining volatile bases in fish Comparison of precision of certain methods. Ind. Eng. Chem., Anal. Ed. 16:593-596. Teeny, F. M., and d. miyauchi. 1972. Preparation and utilization of frozen blocks of minced black rockfish muscle. J. Milk Food Technol. 35:414-417. Tozawa, H., K. Enokihara, and K. Amano. 1971. Proposed modification of Dyer's method for trimethylamine determination in cod fish. In R, Kreuzer (editor), Fish inspection and quality control, p. 187-190. Fishing News (Books) Ltd., Lond. 870 BEHAVIOR AND ECOLOGY OF THE DUSKY DOLPHIN, LAGENORHYNCHUS OBSCURUS, IN THE SOUTH ATLANTIC Bernd Wursig and Melany Wursig' ABSTRACT Dusky dolphins were present in Golfo San Jose. Chubut, Argentina, during most of the year, with a seasonal low in abundance during winter and a high in summer. The presence of the prey species southern anchovy, £ngrau/is anchoita. appeared to affect seasonal movements. Surface feeding was highly visible and birds also fed on fish schools which dolphins herded to the water surface. Surface feeding occurred mainly in spring and summer in the study area, and in late summer and fall m more oceanic waters near the mouth of the bay. This surface feeding pattern corresponded with the presence of southern anchovy. " Dolphins moved in small groups of about 15 individuals while resting in early morning and while looking for food in late morning. Group sizes increased during surface feeding as groups joined existing feeding activity . Because surface feeding occurred mainly around noon and early afternoon, group sizes increased at those times. Dives were longer before and during feeding, and shorter while resting. During spring, summer, and fall nights, dives were shorter, leading to the possibility that dolphins were resting at those times The nonsurface feeding period corresponded with nighttime dispersal of southern anchovy schools. Dolphins moved in shallow water while resting and in deeper water while surface feeding. Near shore resting may be a predator-avoidance mechanism. Most aerial behavior occurred during surface feeding, with behavior before and during surface feeding related to either herding and confining prey or possible communication of neighboring groups. Postfeeding aerial displays were assumed to serve a social function. Calves were bom mainly in the summer. Recently there has been an increase in the number of studies of movements and migration patterns, behavior, and ecology of dolphins. Most of this work has consisted of long-term observations of the bottlenose dolphin, Tursiops sp. (Caldwell et al. 1965; Caldwell and Caldwell 1972; Tayler and Saayman 1972; Irvine and Wells 1972; Saayman et al. 1972, 1973; Saayman and Tayler 1973; Leatherwood 1975; Odell 1975, 1976; Castelloand Pinedo 1977; Shane 1977; Wursig and Wursig 1977, 1979; Wursig 1978; Wells et al. in press; Irvine et al.^), but other odontocete cetaceans have received attention as well (review to 1974 by Nor- ris and Dohl in press; Saayman and Tayler 1979, on Sousa sp.; Evans 1976, on Delphinus delphis, Norris and Dohl 1980, on Stenella longirostris; Gaskinetal. 1915, on Phocoena phocoena.'Wursig in press, on Lagenorhynchus obscunis ). This paper 'State University of New York at Stony Brook, Program for Neurobiology and Behavior; present address: Center for Coastal Marine Studies, University of California, Santa Cruz, CA 95064. ^Irvine, A. B, M. D. Scott, R. S. Wells, J. H. Kaufmann, and W. E. Evans. 1979. A study of the movements and activities of the Atlantic bottlenose dolphin, Tursiops truncatus, including an evaluation of tagging techniques. Final report for US Marine Mammal Commission. Contracts MM4AC004 and MM5AC0018, 53 p. Manuscript accepted July 1979 FISHERY BULLETIN: VOL. 77, NO, 4. 1980. presents data on the yearly and daily occurrence and feeding cycles, movement patterns, general and social behavior, and ecology of the dusky dol- phin, Lagenor/jy'Jc/iz^s obscurus, in a south Atlan- tic bay on the coast of Argentina. Little information on dusky dolphins is avail- able in the published literature. Gaskin (1968) described the distribution of these animals around New Zealand relative to sea-surface temperature, and Gaskin (1972) presented a summary of the literature. Although the genus Lagenorhynchus appears worldwide, populations ofL. obscurus are confined to the Southern Hemisphere, most nota- bly around New Zealand, South Africa, and South America. The exact northern and southern limits of the species are not known. Brownell (19651 states that dusky dolphins are distributed circum- polar to lat. 30' S, but this is disputed by Gaskin (1972). According to Rice (1977), L. fitzroyi is synonymous with L. obscurus. More information is available on the Pacific whitesided dolphin, L. obliquidens. It has been described by Brown and Norris (1956), Norris and Prescott ( 1961), and others. A recent review of the status of this species in the eastern North Pacific 871 -S^C has been presented by Leatherwood and Reeves (1978). MATERIALS AND METHODS Dusky dolphins were observed at Golfo San Jose (Figure 1 ) from September 1973 through January 1974 and from July 1974 through March 1976. We made observations from shore and from a 4.5 m rubber Zodiac^ boat powered by an 18-hp Evinrude outboard motor. Shore observations were made through binocu- lars, and movement patterns of dolphin groups, ranging from six to several hundred individuals, were followed with a Kern Model DKM 1 sur- veyor's theodolite (see Materials and Methods in Wiirsig and Wiirsig 1979). This technique allowed us to describe where and how fast the dolphins moved during different times of day. Observations were made from the boat by mov- ing up to a group of dolphins and then stopping the engine. This allowed us to drift near the dolphins while taking notes on their behavior. We believe that the natural behavior of dolphins was at times affected by the presence of the boat, and therefore made an attempt to confirm all behavior seen from the boat by shore-based observations. To get some idea of group stability over time, we spaghetti-tagged 24 individuals in conjunction with a radio-tagging study. These tags were color-coded plastic streamers lanced into the thick blubber behind the dorsal fin. For a description of the tags and tagging procedures, as well as radio- track data, see Wiirsig (in press). To compare seasonal occurrence data with water temperature, we measured temperature 1 m below the surface 5-10 times per month. For uni- formity, these readings were made 0.5-3 km from shore, and in the afternoon. We used a calibrated laboratory thermometer marked every 0.2° C from 5.0° to 30.0° C. Underwater sounds made by dolphins were re- corded through U.S. Navy Sonabuoy hydrophones suspended 5-10 m below the boat. They were re- corded on a Sony TC800B reel-to-reel tape record- er. A complete analysis of dolphin vocalizations is not presented in this paper. However, mea- surements were made of approximate distance of travel before attenuation (sounds no longer picked up by the hydrophones) of certain splash sounds ^Reference to trade names does not imply endorsement by the National Marine Fisheries Service, NOAA. 872 FISHERY BULLETIN: VOL, 77, NO. 4 related to aerial behavior. During such measure- ments, dolphin and boat position were recorded from shore by surveyor's theodolite, thereby pro- viding the distance from the sound source to the hydrophone. We used standard statistical techniques to test for differences and similarities of observations. These techniques are from Sokal and Rohlf ( 1969) unless stated otherwise. RESULTS Seasonal Occurrence Pattern On days with winds 20 km/h, it was difficult to see dusky dolphins. Of the 433 days with winds <-20km/h, dolphins were seen on 251 days, or 58%. Dolphins were seen from shore during 19 of 21 mo (Figure 2a); June and July 1975 were the only months without sightings. Although the rate of sightings varied from month to month, there was an increase in sightings from late winter ( August) j to summer (February 1975; December 1975), and a ' decrease from fall to midwinter (March through June 1975). During both years, dolphins were pres- ent on over 507c of days during which observa- tions were made from August through February, with the one exception of -50% on the days in January 1976. Could this cycle of dolphin occurrence be related to water temperature? Figure 2b shows average surface temperature per month within 3 km of shore during the same 21-mo period. Although upon superficial examination it appears that dol- phins were less often present during the coldest months, this is not strictly true. Thus, although August was the coldest month in both years, dol- phins in August were present over 70% of sighting days. The rise in temperature in spring-summer 1975-76, however, occurred earlier than in 1974- 75, and temperatures from September to February were 1°-2°C higher per month than in the preced- ing year. Dolphins were more abundant earlier in 1975-76 than in 1974-75. While "the peak" of dol- phin presence occurred in January 1975, it oc- curred in October 1975 in the next season, with a sharp drop-off to January 1976. Where were the dolphins during the period from March through July, when they were rarely sighted in the study area? During 19 of 24 (79%) boat trips made throughout the bay in these months, we found them in the western part of Golfo San Jose, closer to the mouth of the bay and WURSIG and WURSIG: BEHAVIOR AND ECOLOGY OF THE DUSKY DOLPHIN 42' 20 S CAMP 10 km _L. 8000 9000 10000 IIOOO 12000 13000 FIGURE 1— Map of Golfo San Jose on Peninsula Valdes, Argentina (a). The bay is about 750 km^ in area, with a 7 km wide mouth opening to the Atlantic. The lined area in the southeast portion of the bay represents the study area. The crosshatched subsection is shown in detail in b. It is a depth contour map of one-fourth of the study area. Margin numbers represent meter distances relative to a zero location on land. Crosses form 1 km squares. "Cliff Hut" and "Camp" are the locations from which most observations were made. Depth contours are in meters at mean low water ( MLW). The usual distance for good observation of a moving dolphin group was at least 3 km. At a normal tide height of 5 m above MLW, water depth of 40 m was 1 km from Cliff Hut, and thus clearly visible. The map is from a larger area map which was by courtesy of Roger Payne, New York Zoological Society; Oliver Brazier, Woods Hole Oceanographic Institute; and Russ Charif, Harvard University. 873 FISHERY BULLETIN: VOL. 77, NO. 4 OCCURRENCE -1 — 1 — I — I — I I r iJASOND|J FMAMJJASONDiJFM, ii74 1975 19^6 18- 5 16 I I I I I A S 0 N D, rr -TT I I I I I I I A S 0 N D| J F 1974 1975 1976 Figure 2.— Fraction of possible days per month on which dusky dolphins were sighted, and were seen surface feeding (a). The y-axis represents the ratio of number of days on which dolphins were sighted or were seen feeding divided by the number of days each month with winds <20 km/h (sightable days). During all sightable days, observations were made from dawn to dusk Numbers above points represent the number of sightable days per corresponding month. Average surface temperatures within 3 km of shore during the same 21-mo period as in Figure 2a(b). near the open ocean (Figure la). A large oceanic mass of water changes temperature less rapidly than nearshore shallow water, and this may have influenced the dolphin's movement, perhaps by a shift in prey location. Dolphins were found near the mouth of the bay from March through July, when temperatures in the study area dropped from 17° to 11° C (Figure 2), and it is likely that near-mouth temperatures decreased more slowly due to the influence of the open ocean water. Although dolphins were present at the study site most of the year, and were found in Golfo San Jose the entire year, we did not know whether the animals were part of the same population or herd during all seasons. However, four spaghetti tags inserted in December and January were resighted in August, November, December, and January of subsequent years. This indicated that at least some of the animals were present in different sea- sons, and thus did not appear to migrate. Seasonal and Daily Surface Feeding Cycles Surface feeding of dusky dolphins was often highly visible, with birds flocking above the feed- ing site, allowing us to estimate from a distance when and where the dolphins were feeding on schooling fish (Figure 2a). Regardless of season, whenever dolphins were seen they were often feed- ing. However, in August and September 1974 and 1975, dolphins were present much of the time but little surface feeding appeared to take place. Little or no surface feeding took place in low-dolphin months of June and July and in high-dolphin months of August and September. This low in sur- face feeding corresponded with the lowest temper- ature period (about 12= C and below) of the year, possibly because fewer food fish were in the area. When surface feeding bouts occurred, they were observed throughout the day. However, the length of feeding bouts increased as the day advanced. Feeding bouts were longest at 1500 h, then de- clined as evening approached (Figure 3). Although feeding lasted longer during the af- ternoon (to 1500 h), there were nevertheless some long feeding bouts in the morning (Figure 4), with a significant increase in long bouts in the after- noon. Depth of Water and Speed of Movement Are dusky dolphins found at certain water depths and does their swimming speed vary with water depth? To answer these and similar ques- tions, we tracked group movements by surveyor's theodolite. Figure 5a shows that they were most often tracked while in water 5-10 m deep. This peak is probably somewhat biased because obser- vations were possible more often within about 1 km from shore, where depths of 0-30 m were found. Nevertheless, since both 0-5 m and 10-30 m depth areas approximated the area at 5-10 m, dolphins appeared to have a clear preference for traveling in water 5- 10 m deep while near shore. A small but significant secondary peak also occurred at 35-45 m. Although dolphins traveled in water >65 m, this has not been represented in Figure 5a, since no water within sight was >65 m. For radio tracked movement out of sight of land see Wiirsig (in press). The overall average speed was 7.7 km/h. There was a shift in speed depending upon depth of water in which the animals were traveling (Figure 6). 874 WURSIG and WURSIG: BEHAVIOR AND ECOLOGY OF THE DUSKY DOLPHIN 50 — 40- 30- 20- 10 — 10 12 14 HOUR OF DAY 18 32 - b 28 - 24 - 1 1 ' 20 - - - -| - 1 16 - ■ L ■ r 12- -i ^ _ 8^ . ^ ^J 0 —i 1 1 10 12 14 HOUR OF DAY 18 Figure 3. — The number (a) and mean lengths (b) of dusky dol- phin feeding bouts throughout the day, summed for 21 mo from June 1974 to March 1976. Bars above and below mean feeding lengths enclose 95^^ confidence intervals for means. Groups moved at about 5 km/h in water 1-10 m, and faster in deeper water (average speed in water 55-60 m was 16 km/h). Furthermore, there was a general movement from shallow to deeper water as the day advanced (Figure 7a), and dolphins moved more rapidly in the afternoon than in the morning (Figure 7b). Because water depth and dolphin speed were related (Figure 6), it is not surprising that dol- phins, on the average, moved faster in those months in which they were in deeper water (com- pare Figure 8a with b). At the same time there was a strong correlation between depth and speed dur- ing different months and the amount of feeding n 6 7 8 9 10 II 12 13 14 15 16 17 HOUR OF DAY Figure 4. — The number of >50-min surface feeding periods of dusky dolphins during different times of day. Significantly longer surface feeding periods occurred in the afternoon (0600- 1200h = 9or28'7r; 1200-1700h = 23 or 72%; testing equality of percentages, arc sine transformation ofr statistic (5 1. iSOOi 8 z S 1400- < !^ u. 1000- o □: S 600- S 2 200- 10- 8- 6- 4 2- 0 l^tTTTii^ 0 10 20 30 40 50 60 DEPTH (m) FIGURE 5. — Number of theodolite readings of dusky dolphins over depths from 2 to 65 m (a). Although most readings were at 5-10 m, a smaller peak occurred at 35-45 m which appeared to correlate with feeding activity at that depth (see text). Amount of area available in the study region as a function of water depth, at a mean tide height of 5.0 m above mean low water (h). activity during those months (compare Figure 8a with Figure 2a; correlation = 0.77, P = 0.003, Kendall coefficient of rank correlation). Dolphin groups moved into deeper water in the afternoon in each of the 7 mo for which adequate depth versus time of day data exist (Figure 9a). In August and September, when little surface feed- ing occurred, and when water temperatures were lower than in summer, dolphins stayed in rela- 875 FISHERY BULLETIN: VOL, 77, NO, 4 63 14 ^C =0836 _ 50 ^ ' 14 1? - 83 84 .. 76-^0 - 64 ■" 10 " ,'' 8 ^ -107 ^ 6 : ^815 4 - 2 - 15 10 15 20 25 30 35 40 45 50 55 60 DEPTHS ( m) Figure 6. — Average speeds with which dusky dolphins traveled at different depths. The least squares regression, fit to the means shown, is statistically significant (P<0.01). Numbers over bars represent number of observations in that category. 36 32 I ^* I - a 536 40 51 i .. T 318 222 192 90 i 20 o 14 - 81 ! 380 1 J \ .. I 470 8 - 24 i 1 30 1 1 1 1 1 1 6 8 10 12 14 le 18 TIME (hi ~ b 14 - 116 155 107 124 12 — - c --« 10 \r " - 13 136 O 23 ■ w 8 - 168 206 Si 39 216 T 6 - 18 101 21^ 1 4 - 1 1 1 i 1 1 1 1 1 1111 10 12 TIME (h) Figure 7. — Mean depth of water (a) and mean swimming speed (h) of dusky dolphins as a function of time of day. Bars represent 95% confidence intervals for means and numbers above bars represent the number of theodolite readings per hour interval. 50 40 O- W 20 10- 72 IJOpL OVERALL MEAN DEPTH = 27 8 m ir 35 525 1368 n — I — I I ' I I ' I ' 1 ' 1 — r r I — 11' I ' I ' I ' I ' r 1 J ASOND,JFMAM JJA SO NDJ FM, 1974 1975 1976 n — nr 0 N D OVERALL MEAN SPEED = 7 7km/h * 36 n , T — I — I 1 — I T JFMAMJ JASONDJFM 1974 875 1976 Figure 8. — Mean depth of water inhabited by dusky dolphins for different months (a), and mean speed of travel for dolphins for different months (b). Numbers represent number of theodolite readings obtained per month; bars represent 95% confidence intervals for means. tively shallow water compared with the following months (Mann-Whitney [/-test, P<0.001). Dolphins usually moved more rapidly during afternoon than morning (Figure 9b). The increase in rapid movement per month appears related to the amount of surface feeding bouts in that month. Thus, in August 1974 and 1975 few surface feed- ing bouts occurred, and there was no increase in speed during the day. In September, some feeding took place, and there was a small speed increase. In October, November, December, and January much surface feeding took place during one or both years, and the afternoon speed increase was most dramatic. In February, both surface feeding and afternoon speeds were again down to pre-October levels (August, September, and February after- noon speeds are significantly different from Oc- tober, November, December, and January after- noon speeds, Mann-Whitney t/ -test, P<0. 001). From these data we concluded that dolphins traveled faster at surface feeding times. This was confirmed by comparing speed data of dolphins as 876 WURSIG and WUESIG: BEHAVIOR AND ECOLOGY OF THE DUSKY DOLPHIN I h- a. UJ Dam. tJPM, 0500- 1200 1200 - 1900 186 559 •444 82 f^ 326 887 0( 4 A 121 i AUG SEPT OCT NOV DEC JAN FEB MONTHS AM, 0500 - 1200 PM, 1200 - 1900 20 - E — 10 Q UJ LJ CL i A X-sa. i [^ * *■ ID 4 AUG SEPT OCT NOV DEC JAN FEB MONTHS Figure 9. — Mean depth of water (a) and mean speed (b) of dusky dolphin travel in mornings versus afternoons, separated into those months for which adequate data are available. The lines above and below bars represent 95% confidence intervals for means, and numbers represent number of theodolite readings. During August and September, dolphins were -found in sig- nificantly shallower water than during the spring and summer months of October-February I Mann-Whitney {/-test. P< 0.001). During August and September, dolphins also moved sig- nificantly slower than October through January (Mann- Whitney (/-test, P<0.001) Almost all speed increases in these months took place in the afternoon. they moved with no feeding bouts present in the area, and as they moved near feeding bouts (Table 1). The mean speed without feeding bouts was 6.3 km/h, while speeds around feeding bouts averaged about 15 km/h. Dusky dolphins spent more time in deeper water when surface feeding. Furthermore, the depth of water in which surface feeding occurred increased as the summer season advanced (Figure 10). Thus the mean depth of feeding bouts during September was 21m, but by February dolphins were surface feeding in waters 41m deep. Since it is a general rule (and confirmed for Golfo San Jose by Pizzaro ( 1976), and pers. obs. ) that deeper offshore water is cooler than shallow nearshore water in summer, — 1 46 - 34 T 42 64 61 T \ 130 < . 38 34 - - 203 I -- - - 30 - 26 - 9 22 - 18 - 1 1 1 SEPT OCT NCW DEC JAN FEB MONTHS Figure id. — Mean depth of dusky dolphin surface feeding bouts during different months. Bars above and below means represent 95'7c confidence intervals for means. Numbers above bars repre- sent the number of theodolite readings of feeding bouts per month. this change in preferred feeding locations may represent a change in movement patterns of fish upon which the dolphins were feeding. We caught fish from schools on which the dolphins were feed- ing on 15 separate occasions, and identified the species composing such schools in the field about 50 more times. In all cases, the fish were southern anchovy, Engraulis anchoita. These fish are found in deeper water during summer in a nearby coast- al area, where they are netted by fishermen (Mermoz^). and we suspect that they move into deeper water in summer in the present study area as well. *J. Mermoz, research scientist, Museo de Ciencias, Buenos Aires, Argentina, pers. commun. 1975. 877 FISHERY BULLETIN: VOL, 77, NO. 4 Table l .—Average speeds of dusky dolphins not associated with feeding, and associated with feeding activity. The difference in speed between no feeding activity seen (row 1 1 and speed around feeding activity (rows 2, 3. and 4) is significant (P<0.001, r-test of equality of means when variances are assumed to be heteroscedastic). Category No feeding activity seen Dolphins not associated with feeding activity in the area Movement towards feeding activity Movement out of feeding activity Average speed Standard Ttieodolile readings (km/h) deviation (n) 6J 2.35 1,390 15.3 3,46 72 13.7 3.43 88 15.6 352 109 Relationships of Group Sizes, Feeding, and Aerial Behavior For the purposes of this paper, we defined a group as a number of animals that are swimming together and moving as a unit (but not necessarily all pointed in the same direction). Individuals of a group were usually within visual range and cer- tainly within acoustic range of at least some con- specifics. Group sizes varied from 6 to about 300 individuals. There was a seasonal shift in group sizes. From May through September, groups with <20 animals were more common than at other times of the year (Figure 11). As stated earlier, a low in feeding bouts occurred in the southeast part of Golfo San Jose from March to September (Fig- ure 2a), and we gained the impression from boat trips to the middle and western section of the bay that surface feeding there occurred with high fre- quency in March and April , but did not often occur anywhere in the bay from May to September. As a result, it appears that smaller groups were most abundant during the nonsurface feeding months of May to September. There was a direct relationship between size of dolphin group and surface feeding frequency. Thus, groups with 20 individuals were found in feeding bouts only 19% of the times they were spotted, while groups with >20 animals were seen feeding more of the time (Table 2). Because a sur- face feeding-speed relationship was noted, it is not surprising that speed of group travel increased with increasing group size. While small groups O) 0.8 - ) o (T 0.7- o 0.6 r < o 1- U.b' ^ (/) OA- -) \^ 0.3- o o 0.2- a. UJ 0.1 - <20 >20 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec MONTHS Figure 1 1 . — Percentage of dusky dolphin groups with < 20 indi- viduals compared with those with s20 individuals, by month. Dashed lines connect one or both points with < 10 groups sighted that month. October-April percentages are significantly diifer- ent from those of May-September (P- 0.001, equality of percent- age test with arc sine transformation). occurred most often in the morning (and were not surface feeding), larger groups were most often associated with feeding bouts in the afternoon (Table 2). The larger the group size, the longer the feeding activity lasted (Table 3). The number of birds also increased with dolphin group size, and with length of feeding (Table 3). Species of birds, in approxi- mate order of decreasing numbers, were the black-headed gull, Larus dominicanus; cormor- ants, Phalacrocorax brasilianus and P. magel- lanicus;tems, Sterna spp.;diff"erent species of Pro- TaBLE 2.— Average speed and time of day related to group size estimates, and percentage of times dusky dolphins of three different group sizes were associated with feeding activity. Groups with <20 individuals were seen feeding less frequently than larger groups (P- 0.001. testing quality of percentages, arc sine transformation of (-statistic). Dolphin group size (estimate) Item Number of theodolite readings used for speed data Average speed (l39 m. There was, however, some overlap in area covered by both species. On only eight occasions were both species found within 0.5 km of each other. When they were relatively close, each species continued on its previous course, and no interactions ap- peared to take place ( although they may ha ve been interacting by sound). This appEU-ent lack of in- teraction was especially striking because both dolphin types associated with right whales and sea lions. Dusky dolphins were more abundant when bottlenose dolphins were not, and vice versa (Fig- ure 12). DISCUSSION Dusky dolphins were present in Golfo San Jose during most or all of the year, but were located in the southeast portion, in the study area, mainly during spring and early summer. They did not yen and Des Bartlett, wildlife photographers, P.O. Box 17323, Tucson, AZ 85731. pers. commun. November 1974. 882 WURSIG and WURSIG: BEHAVIOR AND ECOLOGY OF THE DUSKY DOLPHIN \.0 0.8 0.6 0.4 0.2 Loatnorhyrnhut ob: JAS0NDJFMAMJJASOND,JFM 1974 1975 1976 FIGURE 12. — Occurrence data from Figure 2a in conjunction with comparable data on bottlenose dolphins during the same period. The two species occurred in the study area with approxi- mately opposite frequency, i.e., when one species was abundant, the other one was less often seen. appear to avoid low ( = 10° C) temperatures, but may have been avoiding higher ( > 1 8° C ) tempera- tures near shore in mid- and late summer. At those times, they were found most often in cooler waters near the mouth of the bay. In Wiirsig (in press), it was shown that during that time they moved outside of the bay as well. Yet they did not show a well-defined seasonal migration pattern, and marked individuals were resighted in the same location during different seasons. Studies of groups of Tursiops sp. have indicated that degree of migration may be different for different popula- tions. For example, bottlenose dolphins off Cape Hatteras, N. C, migrate (Mead 1975), while those of our study site did not ( Wiirsig and Wiirsig 1979). Shane (1977) and Irvine et al. (see footnote 2) reported localized seasonal movements of bottlenose dolphins in the Gulf of Mexico, with differences between their East Texas and West Florida study sites. Degree of seasonally related movement probably hinges on several environ- mental and ecological variables, but an important factor for dolphins in temperate waters may be food availability (suggested by Norris 1967 , Evans 1971, and others). Thus it seems likely that dusky dolphins moved with the food supply most of the year. The main prey item appears to be southern anchovy and we have some evidence that it is found in deeper offshore waters in spring and summer (Ciechomski 19651 and in large concen- trations near the mouth of Golfo San Jose in late summer (Brandhorst and Castello 1971), at the same time dusky dolphins were feeding there. Gaskin (1968) stated that dusky dolphins are present around the Hawke Bay area of New Zea- land generally only in winter and spring. He re- lated this to the presence of the cold Canterbury Current which comes close to Hawke Bay in winter and spring. Clarke (1957) and Sergeant (1962) described the seasonal migration by pilot whales as being regulated mainly by seasonal abundance of squid and certain schooling fish. Wilke et al. (1953) also found seasonal movement patterns for the Dall porpoise, Phocoenoides dalli; the northern right whale dolphin, Lissodelphis borealis; and the Pacific whitesided dolphin, Lagenorhynchus obliquidens. Norris and Prescott ( 196 1) and Evans ( 1 97 1 ) reported that the common dolphin, Delphinus delphis, moved closer to the shore of California in fall and winter, and moved farther offshore in spring and summer. They suggested that this movement was food related. Brown and Norris (1956) stated that whitesided dolphins off California were most often found near shore in winter and spring, and offshore in sum- mer and fall. They also reported that the move- ments of the northern anchovy, Engraulis mor- dax, corresponded with the seasonal dolphin movements. Their observations of L. obliquidens thus agree with those of L. obscurus of the present study. Frequency of feeding in the highly visible man- ner described, with birds flocking overhead, was seasonal. It occurred less often in winter than at other times. In winter, anchovy are found in water > 100 m (which is deeper than Golfo San Jose), and farther north, around lat. 36°-37° S (Brandhorst et al. 1971). Thus it is probable that dolphins were not feeding on southern anchovy in winter in the atudy area. Yet it is not possible that mammals as small and as constantly active as dusky dolphins stopped feeding completely for several months. We can only guess that other feeding was done on prey below and not at the surface, and possibly more individually instead of as a concerted group effort. At any rate, in winter we observed very little aeri- al behavior euid rapid movement usually atten- dant on surface feeding. Instead, dolphin groups consistently moved slowly and in small groups near shore. Stomach content samples would be helpful in solving this ambiguity. Dolphins exhibited a daily feeding cycle as well. Morning surface feeding activity lasted for shorter times than in the afternoon, so that dolphins were more often seen feeding in the afternoon. They moved in shallow water (5-10 m) in the morning, but most afternoon surface feeding occurred in 35-45 m. We gained the impression that im- 883 FISHERY BULLETIN; VOL. 77, NO. 4 mediately before feeding, dolphins were diving for longer periods, perhaps going down deep to hunt for food. This impression was not quantified in direct association with feeding because we were unable to identify particular individuals and thus obtain length of dive records. However, we have evidence from radio-tracked dusky dolphins indi- cating that there is a length of dive-surface feed- ing time association ( Wiirsig in press). Dive times from six dusky dolphins radio-tracked in summer showed a consistent increase in length during af- ternoon, with average night and morning dives about 14 s. Noon and afternoon dives rose to as high as 32 s in average duration. One animal radio-tracked in the austral winter (July-August 1974) showed no such length of dive increase in the daytime and actually surfaced more frequently in the afternoon than at other times of the day and night. This is an indication that feeding in the winter was different from feeding in the summer- time. Since we believe that long dives in summer are associated with surface feeding in deeper wa- ter, it is likely that the extremely shallow and brief dives which occurred at night (Wiirsig in press) in summer were not associated with feed- ing, and that perhaps the animals were resting near the surface much of the night. This is the reverse of what was found in the common dolphin off California (Evans 1971, 1974), which dives for long periods at night — and is believed to be feed- ing at that time — and dives relatively shallowly during the day. Once again, this difference may be food related . While the common dolphin is thought to feed upon the deep scattering layer which rises out of deeper water enough for the dolphin to dive to it at night, no defined deep scattering layer can exist in the relatively shallow nearshore waters of the present study (Hersey and Backus 1962). In- stead, dolphins feed on anchovy during the day, and move into deeper water as the day advances. Whether or not anchovy move into deeper water and are followed by the dolphin is not known. Perhaps the daily movement into deeper water was simply a consequence of being in shallow, n'earshore water during night and early morning (to be discussed later), and having to go into deeper water in order to feed more efficiently. It is known that individuals of southern anchovy schools dis- perse during nighttime (Brandhorst and Castello 1971 ). This dispersal may make nighttime feeding on anchovy more difficult or impossible, and there- fore dolphins may rest at night while feeding dur- ing the day in summer. As an app£u-ent consequence of feeding, dolphins were also found more often in deep water in spring, summer, and fall than in winter. Norris and Pres- cott (1961) suggested a similar movement trend ior Delphinus delphis in California waters. Group sizes were more often larger during the surface feeding season. The reason for this was a direct relationship between surface feeding activ- ity and group size. Small groups usually engaged in surface feeding for only brief periods. The longer the feeding bout, the larger the number of dolphins present. Dolphins appeared to begin feed- ing in the morning and continued feeding through most of the afternoon; thus, there was a general increase in group size as the day advanced. The many small groups in the morning (and presum- ably night as well) covered a large (up to about 10 km in diameter) area, but nearest neighbors were usually no more than 0.5 km apart. We assume that they were probably within acoustic range of each other. Why did surface feeding activity last longer when dolphin numbers increased as groups joined? Perhaps larger schools offish attract more dolphins and keep them feeding for a longer time. It is also possible that more dolphins are more efficient at herding and maintaining the fish school as a tightly clustered unit against the water surface. As an alternative explanation, it might be assumed that the small groups stopped feeding after brief periods because individuals were satiated. In a larger group, with perhaps more individuals per fish school size and more competi- tion, this would presumably take longer. Since small schools which fed briefly were, however, seen to feed more and more as the day advanced, it seems unlikely that they had fed to satiation pre- viously. Therefore, either larger fish schools sim- ply attract more dolphins, or it is of direct advan- tage to animals to feed in larger groups, and a mechanism for telling nearby groups that herding of foodfish is in progress may have evolved. Wari- ous investigators have reported seasonal varia- tions in group sizes, but none appear to link such variations to a particular feeding mode as in the present study. Gaskin (1972) stated that dusky dolphins off New Zealand are found in smaller schools in winter and larger ones in summer, basi- cally the same as in our study. New Zealand dusky dolphins feed on small squid and on surface fish, but it is not clear whether their relative depen- dence on these prey changes seasonally. How do other groups know about the feeding bout 0.5-1.0 km distant? It is unlikely that at that 884 WURSIG and WURSIG: BEHAVIOR AND ECOLOGY OF THE DUSKY DOLPHIN distEince animals are actively echolocating on the fish school, and thus some behavior of the feeding dolphins is implicated. Perhaps underwater vocal- izations serve as cues. The possibility of different sound emissions by dolphins feeding and not feed- ing has not yet been investigated in the present study, although Tyack ( 1976) found such a varia- tion in wild bottlenose dolphins. The incidence of noisy — omnidirectional sound source — leaps in- creases before and during feeding, and these may provide cues to nearby dolphins. Norris and Dohl (1980) discussed the likelihood of leap sounds serv- ing a communication function. We believe that the likelihood of such a function specifically in dusky dolphin feeding is great. If noisy leaps serve to attract or inform nearby schoolmates, and are at least in part designed to do so, this recruitment behavior may be analogous to the "drumming" recruitment of African chimpanzees, described by Reynolds and Reynolds (1965) and others. Saayman and Tayler (1979) suggested that re- cruitment may occur in Sousa sp. ofT South Africa as well, but they did not link it to the possibility of aerial behavior in their population. How do groups orient towEirds feeding locations from a distance of more than several kilometers? Our underwater recordings of sounds created by leaps suggests that they probably do not propagate much over 1 km. Norris and Dohl ( 1980 ) also found rapid attenuation for underwater Hawaiian spin- ner dolphin leap sounds. But, we observed dol- phins that were leaping towards a large feeding bout from as far as 8 km. One possible explanation is that at least one dolphin swam to the distant group with information about the feeding bout, a feat not unknown in the animal kingdom (von Frisch 1967, on honey bees). We have no evidence that such messenger service may take place, and suggest a possible alternative. (Although Eberhard and Evans 1962, Evans and Dreher 1962, and Dreher and Evans 1964 reported that individuals of the Pacific bottlenose dolphin, Tur- siops gilli, have been seen detaching from a group, moving to "investigate" something, and then going back to the group. Their interpretation of scouting behavior, however, is open to specula- tion.) When we saw dolphins swimming towards a feeding bout from more than a few kilometers, we saw individuals leaping out of the water in high forward leaps, clearing the water by as much as three times their own length, and thus leaping as high as 4-5 m. This leaping became lower and finally subsided altogether as the animals came closer to the activity. It seems possible that dol- phins are using in-air vision to orient to the feed- ing bout, taking the birds flying above the activity and the leaping dolphins of the activity as a cue. We present this as a tentative hypothesis because many investigators do not believe that dolphins have a high degree of long-range in-air visual acuity. Dral (1975), Herman et al. (1975), and Rivamonte ( 1976), however, believe that Tursiops sp. may have good in-air vision at infinity. Perhaps dolphins gain information about the feed- ing bout in some other manner, and are leaping that high and often simply as part of their rapid movement (although such high leaps are not seen during after-feeding rapid movement). The high leaps may decline when the dolphins get near the activity because they are tiring. If it should prove, however, that dolphins are capable of long-range vision, and use it in this manner, it would mean that the birds associated with dolphin feeding — up to now assumed to represent a parasitic or neutral role as they scavenge on the dolphins' herding efforts — may serve as a signal to other dolphins. Dolphin leaps would assume a similar in-air sig- naling function. To observers, the number of birds above an activity was a sign of the feeding activi- ty's "success," and if dolphins can see these birds, there is no reason to assume that they could not as well gage such activity level. Various different types of leaps and aerial dis- plays are associated with different stages of sur- face feeding. What function could these leaps serve? To answer this question we will attempt to reconstruct a typical feeding bout in detail: Before surface feeding, dolphins move rapidly, and dive for long periods, indicating that they are covering a large distance and are looking for fish deeper than a few meters below the surface. Immediately before and during feeding, forward movement stops and long dives continue, interspersed with clean, noiseless leaps. During these leaps, animals reenter the water headfirst and rapidly swim down. We therefore believe that the clean leaps allow dolphins to breathe rapidly, and then force- fully and efficiently return to the depths. The humping variant of this leaping type appears similar to the headfirst surface dive employed by experienced skin divers. As long dives decrease, a tightly bunched fish school, usually numbering several thousand fish in an area 3-5 m in diameter, is first seen at the surface. It thus appears that dolphins actively herd fish towards the surface, probably to use the 885 FISHERY BULLETIN: VOL. 77, NO. 4 surface as a wall through which the prey cannot escape. This function has also been suggested by Norris and Dohl (in press), and shown to be carried out by some large predatory fishes by Major (1976; cited by Norris and Dohl in press). Noisy leaps, which started at some point before the fish school appeared, continue throughout sur- face feeding. We gained the subjective impression that these leaps occurred on the periphery of feed- ing bouts. This may be because breaching directly into the fish school would certainly not be of ad- vantage in keeping it tight against the water sur- face. As well, it may serve to keep fish from escap- ing, and thus may be an acoustic or vibration "netting" effect. We often saw dolphins tailslap- ping rapidly (2-3 slaps/s) while moving in a tight circle around feeding bouts, and this action may further serve to keep fish from escaping (it has been described by Norris and Dohl (1980) and labeled "motorboating"). Besides the function of recruiting nearby groups to the feeding bout either purposefully or inciden- tal to keeping fish from escaping, there is a third possibility. The splashes of noisy leaps create an underwater omnidirectional sound which may ac- tually serve to frighten fish and cause them to school more tightly. Although work has been done on schooling relative to pressure waves (Bobbi Low*^) asfar as weknow, no studies exist on sounds and fright reactions in schooling fish. While the feeding bout continues, clean leaps and humpings continue as well, and dolphins still dive steeply. They also come up at a sharp angle, and individuals move rapidly through the bunched fish school, appearing at the other side of the school with several fish in their mouths. They then dive steeply again, and usually resume "at- tacks" on the fish school from below. The dolphins may stay below the fish much of the time to keep the school from escaping downward, and possibly to herd other fish to the surface to continue or prolong feeding. This is not the first indication of apparent cooperative herding and feeding in dol- phins. It appears that many different species coop- erate in herding, and it has been described for representatives of the genera Orcinus. Tursiops, Sousa, Phocoena, Delphinus, and others (see Nor- ris and Dohl in press). Many terrestrial predators do so as well (Wilson 1975). 'Bobbi Low, professor, University of Michigan, Ann Arbor, MI 48109, pers commun. 1976. Acrobatic noisy leaps are most often seen during and after feeding. These may herd fish and recruit nearby groups, but they appear to require much energy and coordination which seems unneces- sary just to make noise. We believe with Norris and Dohl (1980) that they may serve a "social facilitation" function, signaling a high activity level as individuals reaffirm and strengthen social and possibly sexual bonds. Saayman and Tayler (1973, 1979) describe similar high activity levels in Sousa sp. when two or more groups meet, and provide a similar assessment. We suggest that individual animals have taken care of the basic requirement of feeding and are now prepared to spend time socializing and "playing." After feeding, dusky dolphins are more willing to associate with boats, human swimmers, whales, sea lions, and inanimate objects such as kelp. This may be an outgrowth of the high level of social activity at that time. Although we also saw much apparent mating after feeding, we were not able to compare it with amount of mating in small, nonsurface-feeding groups. When many small groups coalesced to form a large one, did the smaller units remain intact or was movement of dolphins throughout the large group "random"? We saw individuals which had been spaghetti-tagged in a small group traveling together within a feeding bout a few days after tagging (Wiirsig in press), and thus have some indication that the small group remained intact. This agrees with data by Norris and Dohl ( 1980) on Hawaiian spinner dolphins. They found that there is fluidity in schools, but that small groups of 4-10 animals may be the only units with longer term continuity. We have no long-term informa- tion on group stability. However, studies of other dolphins suggest that the small-unit group com- position is constantly changing (Saayman and Tayler in press, humpback dolphins; Shane 1977; Wiirsig 1978; Wells et al. in press, bottlenose dol- phins). This flexibility in small-group composition at least superficially resembles chimpanzee group structure, and Saayman and Tayler (1979) and one of us (Wiirsig 1978) independently speculated that the similarity comes from feeding on unpre- dictable and patchy food distribution (see also Nishida 1968). If a similar group structure is found in dusky dolphins, it might be possible that individuals move randomly throughout the large after-feeding group, and that the entire group of up to 300 animals forms the more stable breeding unit or population. 886 WURSIG and WURSIG: BEHAVIOR AND ECOLOGY OF THE DUSKY DOLPHIN Captured animals were of both sexes (Wiirsig in press). As well, there were usually only 1 or 2 calves or small young within a group of about 15 animals, suggesting that mating is not highly polygynous. Given data from captivity (Evans and Bastian 1969 and Caldwell and Caldwell 1972 provided reviews) suggesting that promiscuity is a prominent feature of most odontocete cetaceans at least in unnatural circumstances, it is likely that the dusky dolphin social system is promiscuous as well. However, Bateson (1974) suggested rather stable relationships between some spotted, Stenella attenuata, and spinner dolphins for play, mating, and sleep. We found that young were bom mainly in the austral summer. If we assume an 11-12 mo gesta- tion period (Sergeant et al. 1973 for bottlenose dolphins), most effective matings took place out- side the winter season. If sexual activity continues throughout the year, then we can assume that there is a physiological change in males or females that allows conception to peak during the spring or summer. Seasonal changes in testis weight have been found for several cetacean species (for exam- ple, Ridgway and Green 1967 for Delphinus del- phis and Lagenorhynchus obliquidens). It is possi- ble that a similar physiological change may exist in dusky dolphins. This might relegate some activ- ity appearing to serve a sexual function to the role of greeting or bond-strengthening ceremonies as has been suggested by Caldwell and Caldwell (1967), Bateson (1974), and others. We suspect, but have no definitive proof, that most mating occurs in large groups after surface feeding. Since this feeding occurs mainly in spring and summer, it correlates well with the summer calving peak. Nevertheless, if this is so, it would not invalidate the possibility of a seasonal physiological cycle, nor of "mating" at times serving a purely social function. Groups which had about 10-20 adults and as many calves occurred at times. We saw these nur- sery groups mainly at the periphery of large feed- ing activities. They did not appear to participate in the high-activity level characteristic of large feed- ing bouts and after-feeding. Perhaps, when small groups feed, females with young feed and then split off as activity increases. This can be of adap- tive value. Young may in this way avoid possible aggression and competition within the large feed- ing aggregation, and they may avoid possible predation by killer whales and sharks attracted to the activity. We saw large (3-5 m) unidentified sharks moving in dolphin feeding activity on four separate occasions, but they did not appear to bother the adult dolphins engaged in feeding. The relationship of dusky dolphins and bottlenose dolphins was in some ways puzzling. Dusky dolphins moved in generally deeper water than bottlenose dolphins, but the two at times probably came into acoustic range of each other. Yet they did not appear to take notice of each other, although both species independently sought contact with southern right whales, sea lions, and the boat. Dusky dolphins were found in shallow water in the morning, but bottlenose dolphins were in even shallower water in the morning, then moved into intermediately deep water around noon, then into shallow water once again. It has been suggested (Wiirsig and Wiirsig 1979) that bottlenose dolphins may have been feeding on southern anchovy, the same food as that of dusky dolphins in these intermediate waters. At any rate, by that time of day, dusky dolphins were more often found in deeper water, and as a result, their food niches did not appear to overlap. As well, the two species were found with approxi- mately opposite frequency within sight of the study area at different times of year. This suggests that one or both species may at times have actively avoided the other, although alternative expfana- tions such as different ecological requirements may be more important. Bottlenose dolphins moved in small groups close to shore, dusky dolphins moved in small groups while not feeding, but in larger groups around feeding time. Bottlenose dolphins appeared to spend most of their nearshore time feeding indi- vidually or perhaps in groups of two and three on large solitary fishes inhabiting nearshore rocks. Large groups £ire possibly not of advantage in exploiting a presumably scattered food resource. On the other hand, dusky dolphins appeared to hunt in small groups spread out over a large area, thus increasing their food-finding efficiency for a patchily distributed food resource. When food was found, they rapidly coalesced, and appeared to herd prey cooperatively, allowing more efficient feeding. Dusky dolphins fed near the surface in deeper water in the afternoon, and moved slowly and with little activity in early morning. We suggested that the surface-feeding pattern may be associated with availability of fish at different times of day and in different areas of water. A similar change in area from nonfeeding to feeding was found for 887 FISHERY BULLETIN; VOL. 77. NO. 4 Hawaiian spinner dolphins (Norris and Dohl 1980) and for Sousa sp. (Saayman and Tayler 1979). But what about the consistently shallow- water movement in the morning (and all day in winter) when dolphins did not appear to be surface feeding much of the time? Their activity level was low and they did not move rapidly. They ignored or avoided boats as well as other marine mammals. They moved in small, tight groups and we there- fore gained the subjective impression that they were schooling in an almost "fishlike" manner. Because level of activity was low, objects in their paths were avoided or ignored, and schooling was tight, we believe that the dolphins were resting at this time. There is some evidence that killer whales may prey on dusky dolphins. On three occasions when killer whales came close to dolphin groups, the dolphins moved into extremely shallow water. At the same time, they moved rapidly along shore, perhaps to avoid nearshore predation, of which killer whales Eire known to be capable on more stationary prey, such as elephant seals and sea lions (Norris and Prescott 1961; Tomilin 1967; pers. obs.). As well, their nearshore movement may serve to hide them from possible Orcinus orca echolocation, which might be confused and in- efficient in very shallow water. These observations make it likely that near- shore movement while resting is a defense against predation. In shallow water, killer whales (and possibly deepwater sharks) cannot come from be- low, nor from the flanking shoreline. When danger comes from the open sea, dolphins can retreat to very shallow waters in which larger predators cannot maneuver as efficiently. Norris and Dohl ( 1980) postulated a similar function for nearshore resting of Hawaiian spinner dolphins, suggesting that these animals possibly avoid large deepwater sharks during morning periods of low activity. Saayman and Tayler (1979) also saw Sousa sp. very close to shore when killer whales were near, and suggested that the dolphins might avoid pre- dation in a similar manner. In the present popula- tion, it is possible that nearshore movement dur- ing low-activity levels may serve other functions as well, but we believe that the predator- avoidance hypothesis may be at least part of the reason. CONCLUSION In the preceding discussion, we attempted to 888 link observed behavior patterns to observed or possible ecological variables. We recognize that this endeavor is highly incomplete, and that many more alternative explanations will be made avail- able in the future. One important factor that may have been somewhat obscured in the results and discussion of behavior should be emphasized. Dol- phin behavior in captivity as well as in the wild appears highly plastic and variable. For example, dusky dolphins feed on southern anchovy. Yet many species are more catholic feeders (for exam- ple, Gunter 1942, Leatherwood 1975, for Tursiops truncatus; and Perrin et al. 1973, for Stenella spp.), and it is certain that dusky dolphins engage in other feeding than surface feeding described here. We hope that future work will shed light on other feeding modes, whether subsurface feeding is done cooperatively as is surface feeding, or whether it is performed more often by single dol- phins on nonaggregated prey. Such an analysis may help us understand the dramatic difference in movement patterns and general activity levels be- tween times when dolphins feed cooperatively on the surface and when they feed in other ways. ACKNOWLEDGMENTS Jen and Des Bartlett, Peter Tyack, Marty Hyatt, and Russ Charif helped gather data. Jan I. Wolitzky wrote the computer program for analyz- ing theodolite track data, and Matt Lamishaw pa- tiently worked at the computer. Roger and Katy Payne provided material and intellectual support. George C. Williams, Kenneth Norris, Randall Wells, J. L. McHugh, Douglas Smith, and an anonymous reviewer for theFts/ieryBu//e0.50) survivorship between clams that had settled into substrates with adult clams ver- sus those that settled into substrates with no adult clams. DISCUSSION Growth There has been a great disparity in the reported size of 1-yr-old Manila clams. Three areas in Japan have reported three different lengths: in Hokkaido, 8 mm (Yamamoto and Iwata 1956); in the Inland Sea, 18 mm (Ohba 1959); smd in Ariake Bay (South Japan), 27 mm (Tanaka 1954). Rodde et al. (1976) grew Manila clams to 34 mm in 1 yr under hatchery conditions with high tempera- tures and nutrient rich water. Nosho and Chew (1972) estimated that Manila clams in Hood Canal, Wash. , were 24 mm at the end of 1 yr. These conflicting reports have created some difficulties for scientists in attempting to determine the age of Msmila clams found in Puget Souhd beaches. The fact that I found two sizes of clams that resulted from settlements only a few months apart makes this understandable. In some cases, others have based growth data on checks in the shell without studying the early stages of growth. However, without the knowledge about the time of year that a clam cohort settled and the period of growth until the formation of the first visible checkmark, the determination of the age of a clam can be difficult. Figure 3. — Survival of Manila clams at each sampling period for Treatments 1-4 expressed as a percentage of the initial levels at settlement. The results of my research showed that growth rings were formed by the end of October. For clams that settled in the summer the first visible check was formed at 3-4 mo, but for those settling in the fall (just 2-3 mo later), the first visible mark was formed in 13 mo. The modal lengths, that I found until the first visible checkmark was formed, of 5-8 mm and 14-16 mm for the summer and fall cohorts should give scientists a more con- cise baseline upon which to judge growth data for the Manila clam. Although there was a difference in the grovrth rates between clams that settled in the summer and those that settled in the fall, the length of newly settled clams that I observed was the same for both periods and the same as those found by Loosanoff et al. (1966) at the Milford Laboratory in Connecticut and by Yoshida (1953) in Japan. The clams from the fall settlement more than doubled in size in 2 mo, but then their growrth almost ceased for a 3 mo period and slowly in- creased until March. This slow winter growth was very similar to Japanese findings on larger Manila clams (Yoshida 1935; Yamamoto and Iwata 1956; Ikematsu 1957; Ohba 1959). In southern Puget Sound, Glock (1978) found no growth during this same period for Manila clams with lengths from 12 to 20 mm. Wilbur and Owen (1964) stated that growth is generally negligible for most molluscan species below 5-10 C, which 895 FISHERY BULLETIN: VOL. 77. NO 4 corresponded to the temperatures found in Little Skookum Inlet during the winter months (Table 1 ). The growth for the summer settling clams was much higher, and other studies with Manila clams of the same settling size have reported similar or higher initial growth. Yoshida (1953) found clams settling in early June reached 0.9 mm by the end of July. Clams raised in 22°-29° C water under hatchery conditions, with an optimal food supply, were 5 mm 90 days after settling (Rodde et al. 1976). The small size at settlement for the Manila clam and the slow initial growth of clams that settled in the fall underscores the necessity to use a small mesh size when sampling for spat so as not to possibly mask a large part of their early life. In addition to a difference in the growth rates between summer and fall settling clams, the lengths of clams that I recovered in June were significantly greater (P<0.001) in treatments without adult clams than in treatments with adult clams. A similar decreased growth with in- creased densities has also been shown for larger Manila clams in other studies. Sagara (1952) found this for clams >30 mm, but indicated that clams <20 mm were not affected by density. Ohba (1956) found decreased growth in 10-12 mm clams and related it to competition for food. In other studies, Hancock (1973) found reduced growth with Cardium edule in areas of overpopu- lation and a marked reduction in size in locally overcrowded areas. Finally, in a hatchery-rearing experiment with 14 mm Manila clams, Langton et al. (1977) found that growth increased with ration size in crowded conditions. A decrease in available food to juveniles was implicated as the controlling factor that caused the decrease in Table l. — The daily average and tlie extreme substrate tem- peratures 1 1 cm below surface) between sampling periods for the Manila clam in Little Skookum Inlet, Wash., at the +0.6 m tide level. N Temperatures (= C) Sampling period Average Extremes 1976: Oct. 24-Nov, 20 30 11.6 10,5-12.5 Nov, 20-Dec, 20 30 97 6,5-10,5 Dec 20- Jan, 16.1977 27 78 40- 90 1977 Jan, 16-Feb, 2 17 86 3 0-90 Mar 11-Apr 8 28 95 55-200 Apr 8- May 6 28 122 11 0-18,5 May 6- June 4 29 12,8 12,0-20,0 June 4-July 4 30 156 14.5-28,0 July 4-6 3 16,7 165-21 6 July 30-Aug 4 6 178 16.5-190 Aug.25-Sepl 21 27 16,7 15.5-23,0 Sept 21-Ocl, 12 21 15,6 10,0-16.5 clam growth observed in treatments with adult clams, as compared with those in treatments without adults. There were not sufficient study plots available to determine whether this differ- ential growth continued during the summer. The results of these experiments indicates that the harvest of adult clams from a beach will allow for a better growth of undersized clams. This result coincides with the general view of commercial Manila clam harvesters in Puget Sound (Taylor"). Survival Approximately 1.2% of the clams that settled in September 1976 survived until June 1977. Japanese studies on Manila clams have reported similar low levels of survivorship 4-9 mo after initial settlements. Ikematsu (1957) found that spat densities of 5,000/m2 in March were only 1.0% of the 500,000/m2 he found the previous November. Ohba (1959) estimated settling den- sities of 25,000/m^ in October, but found only 8.0% of that (2,000/m2) by the following June. In studies on a number of clam species other than Manila clams, Muus (1973) reported that regard- less of clam densities at settling, the number of clams recovered per unit area decreased rapidly until a density of several hundred per square meter was approached. The level of survivorship from the fall settlement was similar to these studies but although it was low, the number of spat that it represented (250-450/m^) was more than 2.5 times greater than the density of adults (approximately 100/m^) considered as an adequate level at which a beach can be dug com- mercially (Taylor see footnote 4). Not only was the survivorship from the fall set- tlement low, but the majority of the clam spat mortality occurred during the first 2 mo after settling (57%) and only about 10% of the clams survived to 0.7 mm long (6 mo). One or more of a number of factors are usually identified as causes of high mortality in biological populations. In the case of benthic marine invertebrates, Hancock (1970) stated that survival after settlement will depend upon: a) environmental conditions, nota- bly temperature; b) food supply, which may be affected by intra- and interspecific competition; c) space competition; d) parasites and disease; e) ac- Mustin Tavlor, Totten Seafood, Route 1. Box 372A, Olympia. WA 98502, pers. commun. June 1977. 896 WILLIAMS: GROWTH AND SURVIVAL OF MANILA CLAM SPAT cidental ingestion of newly settled young (of some molluscs by adults of the same or different species; f) physical damage or disturbance; and g) preda- tion. Most of the above factors did not appear to be significant in this study. a) Yoshida (1953) experimented with 1.0-3.8 mm Manila clams and found a survival of 90% or greater in water temperatures averaging 7° C. The water temperatures at Little Skookum aver- aged 8. 9°-12. 7° C during winter and probably were an insignificant cause of mortality, except during the coldest part of January (Table 1). Low water temperature probably attributed to the slight in- crease in clam spat mortality observed at this time. b) When Cahn (1951) surveyed the Japanese Manila clam fishery, he cited starvation under overcrowded conditions of newly settled spat as a probable cause of death. The survival rate in this study, however, remained fairly equal between treatments with no adult clams and those with high adult clam densities. Thus, the expected cropping of the food supply to spat that settled among the adults did not appear to affect the spat's survival. In addition, almost nothing is known about the food requirements of newly set- tled spat, so adequacy of food supply as a control- ling factor would be difficult to determine. c) Lack of sufficient space for growth between two consecutive year classes was proposed by Hancock ( 1973) as one of the largest factors con- trolling survival of newly settled spat in C. edule. He proposed that space requirements for growth of shells would conflict in two adjacent year class- es, with the smaller cockles being forced from the substrate as they grew. In nonadjacent year classes, 0-group cockles could maintain their po- sition between shells of older adult clams. This hypothesis was based on clams first observed when 10 mm long. Space limitation did affect survival of the spat in this study, because their size was quite small compared with the space available for growth. d) There was no evidence of parasites and/or disease in either the adult stocks or the newly settled spat. e) Under experimental conditions, Kristensen (1957) found that inhalation by adult cockles of newly settled spat could cause death of the small spat, even when the larvae were discharged soon afterward. Hancock (1973), however, did not feel that the presence of adults adversely affected survival of settled young in his studies at Burry Inlet, but he felt that mortalities were related to oyster catcher, Haematopus oachmani , preda- tion. Since he did not look at the spat until 5 mo after they had settled, it would be difficult to de- termine at which stage in their early life history the largest mortality occurred. In the present study, the largest initial settlement occurred in Treatment 1, but by April this treatment had not only the lowest survival but also the lowest abso- lute density of the four treatments. If mortality was caused by ingestion by adults, then a higher density would have been expected for Treatment 1, which contained no adults. f) Shellboume (1957) studied small oysters and found that shifting surface semds subjected newly settled spat and juveniles to increased mortality due to abrasion. Quayle (1952) felt the largest cause of mortality for the spat of Venerupis pul- lastra was the unsuitability of the substrate. Glock (1978) planted small (2-4 mm) hatchery- reared Manila clams on a southern Puget Sound beach and then covered some of the area with protective mesh covering. He had a much higher survival rate under the areas with plastic mesh, and attributed this in part to stabilization of the sediment. He also found predation rates to be low. In this study, the Treatment 1 areas in Plots A, II, and III were readily observable through the third month after settling, due to a slight difference in color of the gravel brought down from the high intertidal area. This observation indicated that any movement of the surface gravel must have been slight in order not to mask the visible differ- ences of this treatment. In the laboratory, I sub- jected the spat to considerable mechanical agita- tion during the process of washing and sieving; however, only a few of the thousands of spat that I observed had damaged shells. I also found some unbroken, empty clam shells that were equal in size to live clams sampled, but never a number of shells equivalent to the mortality observed. I con- cluded that abrasion did not cause substantial mortalities in this study. g) Thorson (1966) felt that the biological factor with the greatest effect on survival of newly set- tled larvae was predation. Muus (1973) came to the conclusion after a very complete study on the early life history of newly settled bivalves in Den- mark. Since the largest mortality in this study occurred when the spat were quite small, it seemed most probable that if predation were the cause, then the majority of the loss would be to 897 FISHERY BULLETIN: VOL. 77. NO, 4 meiofaunal predators (defined as organisms that are retained on sieves 0.04-0.1 mm and passed through sieves 0.5-1.0 mm (Mclntyre 1969; Coull 1973)1, that were nearly the same size. Swedmark (1964) listed turbellarians, coelenterates, and nematodes as interstitial predators. Thorson (1966) cited studies that have shown turbellar- ians, nematodes, and harpacticoid copepods to be predators on newly settled spat. Although only a few turbellarians and no coelenterates were recov- ered during the study period, a large number of nematodes and harpacticoids were included in each core sampled. In spite of the citation by Thorson, the harpacticoids in this study were not likely to have eaten even the smallest clam spat, as these particular species are considered almost exclusively detritus feeders (Sibert et al. 1977; Illg^). The degree to which nematodes may have accounted for loss in clam spat is unknown. Al- though larger predators (shore crabs, drilling snails, sea stars, fish, birds) may account for sig- nificant predation losses on larger clams, their effect on survival of the newly settled spat was probably low. Large, active predators would not likely have expended the energy to forage for the small spat that would have provided little energy in return. Of all the above factors listed, I concluded the major cause for the large loss in spat that I ob- served was due to predation by meiofaunal preda- tors. Since some empty clam shells were found on the beach and vigorous sieving in the laboratory did not damage the shells of the spat, only preda- tion could have accounted for both the high mor- talities and the destruction or removal of shells. I assumed that nematodes were the dominant pred- ator. Movement of Clams on the Beach Two experiments were performed (November 1976 and May 1977) to test for movement of small clams on the beach. In each case, 2 cm of surface gravel was removed from a plot that was 0.25 m^, to insure that no small clams remained. One month aft;er the start of each experiment, core samples were taken and small clams were found in the center of each plot that had been previously clam free. It was not known whether this move- ■■^Paul lUg, Department of Zoology, University of Washington, Seattle, WA 98195, pers. commun. February 1977. ment was active or passive. Active movement im- plies that clams physically moved (probably by foot action) across the beach. Passive movement implies physical transport of clams across the substrate, with or without movement of surface gravel. In the present study, byssus threads were detectable on clams as small as 0.45 mm long. This indicated that they had the ability to attach to the substrate which would decrease their sus- ceptibility to movement by currents. To the con- trary, Sigfurdsson et al. (1976) proposed that some postplanktonic bivalve larvae use their byssus threads as a method for dispersal. The method of transport would be analogous to the gossamer flight by young spiders. Either of these two methods for utilization of byssus threads may have been used by some of the calm spat at the study site. Baggerman (1953), with C. edule, found that transportation of clams over the substrate may have been an important factor in the final dis- tribution of clams. In this study, transportation may have played an important part in the growth and survival of the spat. Growth was shown to be significantly greater in treatments without adult clams than in treatments with adult clams. The adults thus may have directly caused a decrease in growth of juveniles by decreasing the availabil- ity of food, and/or indirectly they may have influenced clam spat to actively seek new sub- strates in which to resettle to avoid competition. Additionally, in the process of resettlement, clam spat may have become susceptible to a larger number of predators. ACKNOWLEDGMENTS Thanks to K. K. Chew, J. L. Congleton, P. A. Jumars, and P. L. Illg for their advice and assist- ance. Daniel B. Qualye helped with the identifica- tion of young Manila spat. Office space and materials for field work were provided by R. R. Whitney, Leader, Washington Cooperative Research Unit at the University of Washington. Michael Shepard, T. Schink, D. Skidmore, and R. Carter provided assistance with the field work. My especial thanks to J. Taylor who allowed me to use his beach for this study. His wisdom gained from years of commercial clam and oyster harvesting provided me with valuable insight into the biology of the Manila clam. 898 WILUAMS: GROWTH AND SURVIVAL OF MANE^A CLAM SPAT LITERATURE CITED Baggerman.b. 1953. Spatfall and transport oi Cardium edule L. Arch. Neerl.Zool. 10;315.342. Cahn.a. R. 1951. Clam culture in Japan. U.S. Fish Wildl. Serv. Leafl. Fl-399, p. 12-24. COULL, B. C. 1973. Estuarine meiofauna: a review; trophic relation- ships and microbial interactions. In L.H. Stevenson and R. R. Colwell (editors). Estuarine microbial ecology, p. 499-511. Belle W. Baruch Library in Mar. Sci. ELLIOTT, J. M. 1971. Some methods for the statistical analysis of sam- ples of benthic invertebrates. Freshwater Biol. Assoc. Sci.Publ. 25, 148p. GLOCK.J. W. 1978. Growth, recovery and movement of Manila clams, V enerupis japonica, planted under protective devices and on open beaches at Squaxin Island, Washington. M.S. Thesis, Univ. Washington, Seattle, 67 p. Hancock, DA. 1970. The role of predators and parasites in the fishery for the mollusc Cardium edule L. In P. J. den Boer and G. R. Gradwell (editors). Dynamic numbers population, p. 419-439. Proc. Adv. Study Inst. Osterbeck. 1973. The relationship between stock and recruitment in exploited invertebrates. Rapp. P -V. Reun Cons. Int. Explor. Mer 164:113-131. HOLLAND, D. A, AND K. K. CHEW. 1974. Reproductive cycle of the Manila clam {Venerupis japonica). from Hood Canal, Washington. Proc. Natl. Shellfish, Assoc. 64:53-58. Hollander, M., and D. a. Wolfe. 1973. Nonparametric statistical methods. John Wiley andSons,N.Y.,503p. IKEMATSU, W. 1957. Ecological studies on the clam, Tapes japonica (Reeve) II. On the setting season and the growth in early young stage. [In Jpn., Engl, summ.] Bull. Jpn. Soc. Sci. Fish. 22:736-741. JONES, C.R., III. 1974. Initial mortality and growth of hatchery-reared Manila clams, Venerupis japonica, planted in Puget Sound, Washington beaches. M.S. Thesis, Univ. Wash- ington, Seattle, 90 p. KRISTENSEN, I. 1957. Differences in density and growth in cockle popula- tion in the Dutch Wadden Sea Arch Neerl Zool. 12:350-453. LANGTON, R. W., J. E. WINTER, AND 0. A. ROELS. 1977. The effect of ration size on the growth and growth efficiency of the bivalve mollusc Tapes japoni- ca. Aquaculture 12:283-292. LOOSANOFF, v., H. DAVIS, AND P. CHANLEY. 1966. Dimensions and shapes of larvae of some marine bivalve moUusks. Malacologia 4.351-435. MCINTYRE, A. D. 1969. Ecology of marine meiobenthos. Biol Rev. (Camb.) 44:245-290. MUUS,K. 1973. Settling, growth and mortality of young bivalves in the Oresund. Ophelia 12:79-116. NOSHO, T., AND K. K. CHEW. 1972. The setting and growth of the Manila clam, Vener- upis japonica (Deshayes), in Hood Canal, Washington. Proc. Natl. Shellfish Assoc. 62:50-58. OHBA, S. 1956. Effects of population density on mortality and growth in an experimental culture of a bivalve. Ve- nerupis semidecussata. Biol. J. Okayama Univ. 2:169- 173. 1959. Ecological studies in the natural population of a clam. Tapes japonica, with special reference to seasonal variations in the size and structure of the population and to individual growth. Biol. J. Okayama Univ. 5:13-42. QUAYLE, D. B. 1952. Structure and biology of the larvae and spat of Ve- nerupis pullastra (Montagu). Trans. R. Soc. Edinb. 62(l):255-297, 1964. Distribution of introduced marine mollusca in British Columbia waters. J. Fish. Res. Board Can. 21:1155-1181. QUAYLE. D. B., AND N. BOURNE. 1972. The clam fisheries of British Columbia. Fish. Res. Board Can, Bull. 179, 71 p. RODDE, K. M., J. B. SUNDERLIN, AND O. A. ROELS. 1976. Experimental cultivation of Tapes japonica (De- shayesXBivalvia) in an artificial upwelling culture sys- tem. Aquaculture 9:203-215. SAGARA,J. 1952. On the relationship between population density and growth of the clams, Venerupis semidecussata and Meretrix meretrix lusoria, with the interactive influence upon their growth. |In Jpn., Engl, summ.] Bull Jpn. Soc. Sci. Fish. 18:249-262. Shellbourne, J. E. 1957. The 1951 oyster stock in the Rivers Crouch and Rouch, Essex, and the influence of water currents and scour on its distribution: with an account of comparative dredging experiments. Fish. Invest. Minist. Agric, Fish. Food (G.B.I. Ser. II, 21(2):l-27, SIBERT, J., T. J. BROWN, M. C. HEALEY, B. A. KaSK, AND R. J. NAIMAN. 1977. Detritus-based food webs: exploitation by juvenile chum salmon [Oncorhynchus keta). Science (Wash., D.C. 1196:649-650. SIGURDSSON, J. B., C. W. TITMAN, AND P. A. DAVIES. 1976. The dispersal of young post-larval bivalve molluscs by byssus threads. Nature(Lond.) 262:386-387. SWEDMARK,B. 1964. The interstitial fauna of marine sand. Biol. Rev. (Camb.) 39:1-42. TAMURA.T. 1966. Marine aquaculture. Suisan Zoshokugaku. Kigen-sha, Shuppan, Tokyo. (Translated from Jpn., Natl. Sci. Found., Wash., D.C.) (NTIS PB194051T.) Tanaka, Y. 1954. Spavraing season of important bivalves in Ariake Bay — III Venerupis semidecussata (Reeve). [In Jpn., Engl, summ.] Bull. Jpn. Soc. Sci. Fish. 19:1165-1167. THORSON.G. 1966. Some factors influencing the recruitment and es- tablishment of marine benthic communities. Neth. J. Sea Res. 3:267-293. Wilbur, K. M., and G. Owen. 1964. Growth. In K. M. Wilbur and C. M. Yonge 899 FISHERY BULLETIN: VOL. 77, NO. 4 (editors), Physiology of mollusca, Vol. I, p. 211-242. YOSMDA, H. Academic Press, N.Y. 1935. On the full-grown velagers and early young-shell stages of Venerupis philippinarum (Adams and YAMAMOTO, K.,ANDF. IWATA. Reeve). |In Jpn., Engl, summ 1 Venus, Jpn. J. 1956. Studies on the bivalve, Venerupis japonica, in Ak- Malacol. 5:264-273. keshi Lake II. Growth rate and biological minimum 1953. Studies on larvae, and young shells of industrial size, lln Jpn, Engl, summ.) Bull. Hokkaido Reg. Fish. bivales in Japan. [In Jpn., Engl, summ.] J. Res. Lab. 14:57-62. Shimonoseki Univ. Fish. 3:1-105. 900 DEVELOPMENT AND OCCURRENCE OF LARVAE AND JUVENILES OF THE ROCKFISHES SEBASTES FLAVIDUS AND SEBASTES MELANOPS (SCORPAENIDAE) OFF OREGON' Wayne A. Lakoche and Sally L. Richardson' ABSTRACT Developmental series of larvae and juveniles of two important and very similar species of northeast Pacific rockfishes iScorpaenidae: Sebastes} are described and illustrated: S. flavidus (10 1-105.0 mm standard length) and S. melanops (10.6-111,6 mm standard length). Descriptions include a literature review, identification, distinguishing features, general development, morphology, fin development, spination. scale formation, pigmentation, and color of fresh specimens. The main differences between S. flavidus and S. melanops within the size range described are pectoral fin ray number ( usually 18 versus 19), lateral line pore number (usually >50 versus <50). and caudal pedimcle depth/caudal peduncle length ratio (mean values 0.73, 0.64. 0.64. 0.80 versus 0.88, 0.78, 0.74, 0.92 in postflexion larvae, transforming, pelagic juvenile, and benthic juvenile specimens, respectively). Occurrence of these two species in waters off Oregon is discussed. Small benthic juveniles of S. flavidus seem to inhabit deeper waters. >20 m depth, than those of S. melanops. Comparisons are made among known larvae and juveniles oiSebastes species. Identification problems within the S. flauidus-S. melanopsiS. entomelas-S. mystinus groups are discussed. Rockfishes, Sebastes spp., represent an important commercial and recreational resource along the west coast of North America. In 1976, landings of rockfishes (all species) were 14,000 t, constituting 24% of the total trawl catch by the United States and Canada, second only to Pacific cod landings (Pacific Marine Fisheries Commission^). Since the decline of Pacific ocean perch, S. alutus. landings in the late 1960"s, more rockfish species have been subjected to increasing fishing pressure (Ver- hoeven 1976). This situation, together with con- cern over managing the resource, has emphasized the need to determine the condition of rockfish stocks particularly in order to avoid overexploita- tion (Gunderson''). Knowledge of the early life stages, especially pelagic juveniles, is important since they provide valuable tools for resource as- sessment, systematics, evolution, and other emerging research areas. This paper contributes new information on the early life history of two important rockfish species: yellowtail rockfish, S. flavidus, and black rockfish, S. melanops. They were among the five principal species in the Oregon trawl landings of "other rockfish" from 1963 to 1971, contributing 33 and 12% of the total landings during those 9 yr (Niska 1976). They are also important in the Ore- gon sport catch but landing data are not available. Larval and juvenile development of these two species is described for the first time and occur- rence of young off Oregon is discussed. Particular attention is given to problems involved with iden- tification due to the extreme similarity of these two species as larvae and juveniles. 'From a final report for NOAA NMFS Contract No. 03-7-208- 35263 submitted 15 September 1978 to NMFS Northwest and Alaska Fisheries Center, 2725 Montlake Boulevard East, Seat- tle, WA 98112. ^School of Oceanography, Oregon State University, Corvallis, Oreg : present address: Gulf Coast Research Laboratory, P O Box AG. Ocean Springs. MS 39564. 'Pacific Marine Fisheries Commission. 1978. Data series. Bottom or trawl fish section. Pac. Mar. Fish. Comm., Portland, Oreg., p. 1-472, 500-509. ••Gunderson, D. 1976 Proceedings of the 1st rockfish sur- vey workshop. Processed rep., 14 p. Northwest Fisheries Center, NMFS. NOAA. 2725 Montlake Boulevard East. Seattle. Wash. METHODS Specimens described in this paper came from collections in the School of Oceanography, Oregon State University. The collections were obtained with 70 cm bongo nets, neuston nets, meter nets, Isaacs-Kidd midwater trawls, beam trawls, otter trawls, beach seines, and dip nets off the Oregon coast and in Oregon tidepools and estuaries since 1961. Samples were taken during all months of the Manu.scnpt accepted June 1979 FISHERY BULLETIN: VOL. 77. No. 4, 1980 901 FISHERY BULLETIN: VOL. 77. NO. 4 year and along the entire Oregon coast, but were concentrated along an east-west transect off New- port, Oreg. (lat. 44°39.1' N). All specimens were preserved in 5 or lOVc Formalin^ and transferred to —40% isopropyl alcohol. Our approach to identification, methods of mak- ing counts and measurements, and terminology for development and spination follow Richardson and Laroche ( 1979). Body parts measured include: Standard length (SL) = snout tip to notochord tip preceding development of caudal fin, then to posterior margin of hypural plate. Snout to anus length = distance along body mid- line from snout tip to vertical through posterior margin of hindgut at anus. Head length (HL) = snout tip to cleithrum until no longer visible, then to posteriormost margin of opercle. Snout length = snout tip to anterior margin of orbit of left eye. Upper jaw length = snout tip to posterior mar- gin of maxillary. Eye diameter = greatest diameter of left orbit. Interorbital distance = distance between dorsal margins of orbits. Body depth at pectoral fin base = vertical dis- tance from dorsal to ventral body margin at base of pectoral fin. Body depth at anus = vertical distance from dorsal to ventral body margin immediately poste- rior to anus. Caudal peduncle depth = shortest vertical dis- tance between dorsal and ventral margins of caudal peduncle. Caudal peduncle length = horizontal distance from base of posteriormost dorsal ray to posterior margin of hypural elements. Pectoral fin length = distance from base to tip of longest ray. Pectoral fin base depth = width of base of pec- toral fin. Pelvic spine length = distance from base to tip of pelvic spine. Pelvic fin length = distance from base to tip of longest ray. Snout to origin of pelvic fin = distance along body midline to vertical through insertion of pel- vic fin. 'Reference to trade names does not imply endorsement by the National Marine Fisheries Service. NOAA Parietal spine length = distance along posterior margin of parietal spine from insertion to tip. Nuchal spine length = distance along posterior margin of nuchal spine from insertion to tip. Preopercular spine length (third spine; posteri- or series) = distance from tip to basal insertion if visible, or to a line connecting the points of deepest indentation between preopercular spines 2 and 3 and spines 3 and 4 (posterior series). Length of angle gill raker = distance from tip of gill raker to point of articulation with gill arch. Longest dorsal fin spine = distance from base to tip. Longest dorsal fin ray = distance from base to tip. Longest anal fin spine = distance from base to tip. All body lengths given refer to standard length unless noted otherwise. When the two posteriormost dorsal and anal fin rays arise from the same pterygiophore, they are counted as one. A modified descriptive approach is used to minimize repetition which would result due to the extreme similarity in the development of S. flav- idus and S. melanops. Descriptions are combined for both species and differences are noted as they occur. Reference to tabularized development mor- phology data, including relative body proportions and fin and head spine development, is made wherever practical to condense the description. SEBASTES FLAVIDUS (AYRES) AND SEBASTES MELANOPS GIRARD (Figures 1-6) Literature. — Pigment patterns of preextrusion larvae of S. flavidus were described by Delacy et al. (1964), including a figure, Westrheim (1975), and Moser et al. (1977). Preextrusion larvae (mean total length = 4.5 mm) have a row of usu- ally <16 melanophores (x = 10, range 8-12 on 20 specimens) along the ventral body midline which stops short of the anus by at least four myomeres. The gut is pigmented and melanophore(s) are usu- ally present on the ventral body surface near the notochord tip. Larvae and juveniles of S. melanops have not been described. Identification (Tables 1-3; Appendix Table 1). — Fifty-one specimens of S./Zaufdus (10. 1-105.0 mm i 902 LAROCHE and RICHARDSON. DEVELOPMENT AND OCCURRENCE OF ROCKFISHES 10.1 mm 5.9mm FIGURE 1.— Planktonic larvae UO.l, 12.9, 15.9 mm) of Sebastes flavidus. were selected for the developmental series from 556 specimens identified. Juveniles were iden- tified by the following combination of characters recorded from juvenile and adult specimens: Gill rakers = 33-39 Lateral line pores = 46-57, usually 50-54 Pectoral fin rays = 17-19, usually 18 Anal fin soft rays = 7-9, usually 8 Dorsal fin soft rays = 14-15 Preocular spine = absent Supraocular spine = absent Interorbital space = flat to convex Black blotch at base of spinous dorsal fin = present. Fifty-eight specimens of S. melanops (10.6- 111.6 mm) were selected for the developmental 903 FISHERY BULLETIN; VOL. 77. NO. 4 ■'#Aml Jl:'!'-')'^''^vii^50) of lateral line pores than S. flavidus based on counts made on juveniles and adults collected from Yaquina Bay, Oreg., and the Pacific Ocean nearby (Appendix Table 1). Juvenile specimens were identified by us as S. flavidus and S. melanops using the above characters together with color pattern (intensity of melanistic pigment on caudal fin) and location of capture (S. flavidus from depths >25 m and S. melanops from depths <15 ml. Of 52 S. flavidus 904 LAROCHE and RICHARDSON: DEVELOPMENT AND OCCURRENCE OF ROCKFISHES Figure 3. — Pelagic juvenile (46.8 mm) and benthic juvenile 173 mml of Sebastes flavidus. taken off Yaquina Bay (the area offshore of which most larval and pelagic juvenile S. flavidus were collected), 96% had a pectoral fin ray count of 18 on one or both sides. Of 66 S. melanops taken in Yaquina Bay and adjacent tidepool and shallow subtidal locations (the area offshore of which most larval and pelagic juvenile S. melanops were col- lected), 95% had a pectoral fin ray count of 19 on one or both sides. Mean numbers of lateral line pores were 52.33 ±0.52 (95% confidence) iN = 48) and 49.20 ±0.42 (95% confidence) {N = 66) on the left side of S. flavidus and S. melanops, respec- tively. No significant difference was found be- tween counts made on the left and right sides for either species. Two specimens of S./Za()idus had 19 pectoral fin rays on both sides but lateral line pores numbered -50 on both sides. Three speci- mens of S. melanops had 18 pectoral fin rays on both sides but lateral line pores numbered <51 on both sides. Thus the number of pectoral fin rays and lateral line pores allow positive identification of S. flavidus in most cases. Although diagonal scale rows below the lateral line were not used in making the initial identifications, they are useful when they can be counted and can help verify identifications when other characters are not con- clusive (see Appendix Table 1). Specimens of S. flavidus and S. melanops were selected for the developmental series only if pec- toral fin ray counts on both sides were =sl8 and 55 19, respectively, to minimize possible confusion. The presence of discrete melanophores at the ar- ticulation of dorsal and anal fin soft rays and melanophores along the posterior margin of the hypural plate together with counts helped link the developmental series and distinguish the speci- mens from all other Oregon species. The more slender and longer caudal peduncle of S. flavidus and the deeper, shorter caudal peduncle of S. melanops (Table 2) helped tie each series together, confirm identifications, and eliminate confusion between the two species. 905 FISHERY BULLETIN VOL 77. NO. 4 15.9mm Figure 4.— Planktomc larvae 110.6, 12.8, 15.9 mml of Sebastes melannps. Distinguishing Features. — Characters useful to distinguish the smallest identified larvae (10-11 mm) of S. flavidus and S. melanops from those of other Sebastes species are the moderately pig- mented pectoral and pelvic fins, presence of pig- ment along the dorsal body surface under the dor- sal fin, internal and external melanophores above the notochord at and anterior to the point of notochord flexion, melanophores along the dorsal and ventral margins of the caudal peduncle, and melanophores at the articulation of some dorsal and anal rays. The relatively long and narrow caudal peduncle and presence of 18 pectoral rays distinguishes S. flavidus. and the relatively deep and short caudal peduncle and presence of 19 pec- toral rays distinguish S. melanops. Meristics," lack of preocular and supraocular spines, flat to ®The term "meristics" is used to refer to all countable charac- ters which are usually arranged in series. 906 LAROCHE and MCHARDSON: DEVELOPMENT AND OCCURRENCE OF ROCKFISHES 9.2mm 24.0mm Figure 5.— Pelagic larvae (19.2, 24.0, 33,1 mm) of Sebastes melanops. convex interorbital space, body and fin pigmenta- tion, and body morphometry together serve to dis- tinguish larger larvae and juveniles from those of other Oregon species. General Development . — Notochord flexion is com- plete on the smallest larva of S. flavidus (10.1 mm) and S. melanops (10.6 mm) identified. Transformation from postflexion larvae to pelagic juveniles occurs between 23 and 27 mm in S. flav- idus and between -24 and 33 mm in S. melanops as indicated by the structural change of the "pre- spines" in the dorsal and anal fins to sharp, hard spines. Melanistic pigmentation gradually in- creases over the body through the larval and transformation periods and shows no marked change during transformation. Transition from pelagic to benthic habitat usually occurs when 907 FISHERY BULLETIN VOL 77, NO 4 FiGURiD 6 —Pelagic juvenile (45.3 mm) and benthic juvenile 167 mml ofSebastes melanops. fish are between 40 and 50 mm in both species. The largest pelagic juvenile and the smallest benthic juvenile observed were 45 mm and 42 mm for S. flavidus and 47 mm and 38 mm for S. melanops (see Figures 7-10). Morphology (Tables 2, 4, 5). — Various body parts were measured on 51 selected specimens of S. flavidus (10.1-105.0 mm) and 58 specimens of S. melanops (10.6-111.6 mm). Relative growth trends are summarized in Table 2. The most important morphometric character which will separate most S. flavidus from S. melanops is the caudal peduncle depth/length ratio. While the depth and length of the caudal peduncle change only slightly during develop- ment, their ratio changes notably. In S. flavidus it decreases from 73 to 64 or 65% in pelagic stages, increasing again to 80% in benthic juveniles. In S. melanops it decreases from 88 to 74-77% in pelagic stages and then increases to 89% in benthic juveniles. This ratio is usually smaller in S. flavidus than in S. melanops for all specimens of similar size. Caudal peduncle depth is generally less and caudal peduncle length is generally greater in S. flavidus than in S. melanops. Fin Development (Tables 1-4). — Pectoral fins are formed and have the adult complement of 17-19 (usually 18 in S. flavidus and 19 in S. melanops) fin rays in the smallest specimens (10 or 11 mml in the series. The fins in both species are moder- ate in length, reaching 24 or 25% SL in juveniles. The adult pelvic fin complement (I, 5) is present by 10 or 1 1 mm in both species. The pelvic fins are of moderate length, averaging 13-18% SL during the pelagic period. Pelvic spine length is always less than pelvic fin length. The adult complement of 8 + 7 principal caudal rays is present on the larvae of both species along with six superior and five inferior secondary caudal rays. Counts of superior and inferior sec- ondary rays made on three stained juvenile S. 908 Table l . — Meristics from larvae and juveniles ofSebastes flavidus off Oregon, based on unstained specimens. Counts of left and right pelvic fin rays (I,5;I,5), superior and inferior principal caudal rays (8,7), and left and right branchiostegal rays (7;7) were constant from the smallest to largest specimen listed. Standard length (mm) Dorsal Anal fin spines fin spines and rays and rays Pectoral fin ays Gill rakers (first arch) Lateral line Left pores Right Diagonal scale rows Left R ght Lett Right LeH Right 10,1 (').15 IP.8 18 8 — — — 10.3 XIIIM4 11^8 18 8 — — — — — — 107 Xli|2,14 11^8 18 8 — — — — — — 11.4 XIIP.15 IP, 8 18 8 — — — — — — 11.8 X.W.M \f,B 18 8 — — — — — — 11.8 XIIP.15 11^,8 18 8 — — — — — — 11.9 Xlll=.15 IP. 8 18 8 — — — — — — 12.0 XNI2.15 IP, 8 IB 8 — — — — — — 12.2 Xlll=,15 IP, 8 18 8 — — — — — — 12.7 Xlll=.15 IP, 8 18 8 23+ 8=31 23+ 9=32 — — — — 12.8 Xll|2,15 ll',8 18 8 23+ 9=32 24+ 9=33 — — — — 12.9 XIIIM5 IP, 8 18 8 23+ 9=32 23+ 9=32 — — — — 13.1 XIIIM5 IP,7 17 8 22+ 8 = 30 23+ 9=32 — — — — 13.7 Xll|2,15 IP, 7 18 8 23+ 9=32 23+ 9=32 — — — — 14.4 XIIIM5 IP,8 18 8 24+ 9=33 23+ 9=32 — — — — 14.8 XIIP,14 IP, 8 18 8 24+ 9=33 23+ 9 = 32 — — — — 15.8 XIIP.IS IP,9 18 8 24+ 9=33 24+ 9 = 33 — — — — 15.9 XIIIM4 IP.7 17 8 24 + 10=33 23+ 9=32 — — — — 16.4 XIIP,15 IP, 8 18 8 24 + 10=34 24+10 = 34 — — — — 16.8 XIII2.15 IP,7 18 8 24+10 = 34 25+10=35 — — — — 18.9 XIII2.15 IP,8 18 8 24 + 10=34 24 + 10=34 — — — — 19.5 XIIIM5 IP,8 18 8 25+10=35 24 + 10=34 — — — — 19.8 XIIIM5 IP,8 18 8 25+10=35 25+10=35 — — — — 20.5 XIIIM5 IP, 9 18 8 25+10=35 24 + 11=35 — — — — 21.3 XIIIM5 IP. 8 18 8 25+10=35 25+10=35 — — — — 22.3 XIII'.IS IP.8 18 8 24+10=34 25 + 10=35 — — — — =23.6 XIIIM5 IP. 8 18 8 25 + 11=36 26 + 10 = 36 — — — — =23.7 XIIIM5 II .8 18 8 25 + 11=36 26+11=37 — — — — =24.2 Xll|2,15 II ,8 18 8 26+11=37 26+11=37 — — — — =24.8 XIIIM5 IP, 8 18 8 25+10=35 25 + 11=36 — — — — =25.6 Xlll=.15 II ,8 17 7 25+10=35 25+11=36 — — — — =266 XIV'.IS IP,8 18 8 24+10=34 24+10 = 34 — — — — =26.7 XIIIM5 II .8 18 8 27+10=37 26+11=37 — — — — "28-6 XIII .15 II ,8 18 8 25+10=35 26 + 11 = 37 — — — — "29.2 XIII .15 II .8 18 8 26+10=36 26+10=36 — — — — "29.6 XIII .15 II ,8 18 8 26+10=36 27+11=38 — — — — "30.4 XIII ,15 II ,8 18 8 25 + 11=36 26+11=37 — — — — "33.0 XIII ,14 II ,8 18 8 26+11=37 27+11=38 — — — — "33.1 XIII ,15 II .8 18 8 25+10=35 25+10=35 — — — — "35.2 XIII .14 II .8 18 8 26 + 11=37 26 + 11=37 — — — — "364 XIII ,14 II ,8 18 8 26 + 11=37 27 + 11=38 — — — — "37,6 XIII .15 II ,e 18 8 25 + 11=36 25+10=35 — — — — "41 9 XIII .15 II ,8 18 8 28 + 11=39 28 + 11=39 — — — — "436 XIII .15 II .8 18 8 25+10 = 35 25+11=36 — — — — "45,2 XIII ,15 II .8 18 8 27+11=38 28+11=39 — — — — =67,6 XIII .14 II ,8 18 8 26 + 11 = 37 26 + 11=37 54 54 56 56 =71, 5 XIII ,15 II .8 18 8 27 + 11=38 26 + 11=37 46 53 — 55 S72,5 XIII ,14 II ,8 18 8 26 + 11=37 27+10=37 52 53 54 54 >77 5 XIII ,14 II ,8 18 8 26 + 11=37 25 + 10=35 50 53 55 56 '81 0 XIII ,14 II ,7 18 8 26+11=37 26 + 11=37 52 53 — — M05,0 XIII ,14 II ,8 18 8 27+11=38 26+11=37 55 56 57 — 'Forming. ^Posteriormost dorsal and anal spine appears as a soft ray. =Transforming "Pelagic juvenile. ^Benthic juvenile. flavidus (49, 50, and 52 mm long) were 12/13, 12/13, and 12/12, respectively. Counts on four stained juvenile S. melanops (42, 43, 47, and 48 mm long) were 12/13, 12/12, 12/12, and 12/13, re- spectively. Adult complements of the dorsal and anal fin spines and rays can be counted by =11 or 12 mm. The transition of the 13th dorsal and 3d anal fin "prespines" to spines is complete by =27 mm in S. flavidus and =33 mm in S. melanops. Spination (Tables 2, 4-7). — Spines present on the left side of the head of the smallest (10.1 mm) larval S. flavidus include the parietal; first, sec- ond, third, and fourth posterior preopercular; first and third anterior preopercular; postocular; pterotic; superior opercular; first inferior infraor- bital; first superior infraorbital; inferior posttem- poral; and the developing interopercular (indi- cated by a small blunt projection). The smallest 909 Table 2. — Body proportions of larvae and juveniles ofSebastes flavidus and S. melanops. Values given are percent of standard length (SL) or head length (HLl including mean, standard deviation, and range in parentheses. Number of specimens measured may be derived from measurements listed by developmental stage (as indicated by footnotes) in Tables 4 and 5. Item Sebastes flavidus Setiasfes melanops \ Item Sebastes flavidus Sebastes melanops Body deplh at pectoral tin base/SL: Longest anal spine length'/HL Postflexion 28,2± 1,72(25 3-30,8) 29.6:1.77(26.3-32.8) Postflexion 16 5:4 96(10.8-26.3) 19,2:3 99(113-25,6) Transforming 24 5-0-62(23 6-25 6) 26 1 :0.79(25.2-27 5) Transtorming 26.2:2 25(22 2-28,7) 30,4:2,95(27,1-32 7) Pelagic juvenile 24 8±1 08(23 3-26.9) 25 9:0.72(24.7-26.7) Pelagic juvenile 30,6:2,41(26,2-33,6) 32.3:2.44(28.7-37.7) Benthic juvenile 30 0± 1,00(28 4-31 0) 30 9:1,94(27 0-33,0) Benthic juvenile 33,8:1,36(31 9-35 4) 34.7:1.97(31.2-37 1) Body depth at anus SL Pectoral fin length;SL: Posttlexion 22,3 ±1 01(20,6-24,2) 24,3:1,24(21,8-26 1) Postflexion 20,1:1,91(15 8-22,7) 21 7:1 41(18.5-245) Transtorming 20 0±0 51(19,2-20,7) 21 9:0,89(20,9-23,3) Transforming 22,5:1 01(21 4-24 3) 24.0:108(22 8-25 5) Pelagic juvenile 213:0 99(19 9-23,4) 22,2:0 71(20,9-23,6) Pelagic juvenile 24 6:0 35(24 1-25,1) 24.2:0.90(22 4-25.2) Benthic juvenile 25,6±1 11(235-26,3) 26,4:0 75(25,3-27,4) Benthic juvenile 24 1 : 1 30(21 8-25,7) 24.7:1.57(22 9-27.2) Snout to anus length/SL Pectoral fin base depth/SL Postflexion 57 3:t1,77(53 5-61 2) 58,0:2 15(54 0-622) Postflexion 8 5:0,90(7,2-10,9) 8.8:0.69(7,7-10 1) Transforming 60 0:1,23(57 5-60 5) 58,9:3 02(55 8-62 6) Transforming 7 0:0,22(6,7-7 3) 7.7:0 18(7.5-7.9) Pelagic juvenile 60,3 ±1,02(58 8-62,3) 61.3:1.65(59 4-65.3) Pelagic juvenile 7 0:0 45(6,1-7.6) 7.8:0.12(7 6-8.0) Benttiic juvenile 63.2:1.22(62.2-65.6) 63.0:3.43(59.4-70.7) Benthic juvenile 8.4:0.34(7.8-8.7) 9.4:0.39(8.5-9.8) Snout to pelvic fin origin/SL: Pelvic fin length/SL Postflexion 37 9:1 86(34 4-42 7) 38 8:1 86(35 8-42 9) Postflexion 13.4:1 83(8.9-16 7) 15.4:1 17(126-17 4) Transtorming 35 9:0 49(35 3-36 7) 37 3:1.94(34 8-39.3) Transforming 15.5:0.59(14.6-16 1) 16.4:0 30(16 1-16 7) Pelagic juvenile 36 2:0.73(35 3-37 7) 368:1.63(35.2-40 1) Pelagic juvenile 16.3:0,89(14 8-17 8) 17 5:0 64(16.8-18 8) Benttiic juvenile 39 7:2.37(37.2-43 0) 38.2:2.38(35.4-41.8) Benthic juvenile 19,5:0 51(19,0-20,4) 20.7:1 44(18.2-23,0) Head lengtti'SL Pelvic spine length/SL: Postflexion 38 6:1 78(35 4-42 7) 38 5:195(34 8-42 9) Postflexion 104:246(63-157) 12 6:1 57(9 2-14 9) Transforming 35 0:0 91(33 7-36 0) 35 0:2 19(319-37 8) Transforming 13,7:0,92(12 7-15 3) 11,4:092(108-12 1) Pelagic juvenile 33.4:1.34(31.9-36 0) 33.3:1 45(31 1-35 3) Pelagic juvenile 13 6:0,88(12 6-15 4) 14,0:0.56(12.8-14,5) Benttiic juvenile 35.2*2.52(33.4-40.0) 34.8:1.83(32.3-37.3) Benthic juvenile 12,1:0,72(11 3-13,2) 13.3:2.04(10.7-13.9) Eye diameter/HL Parietal spine length/HL: Postflexion 32 0:2.06(27 1-35 4) 308:1 61(269-34 1) Postflexion 8 8:2 17(4 2-11 8) 7.9:2 00(4 2-11 4) Transforming 28 9:0 72(27 8-29 8) 28 6:1 90(26 0-30 6) Transforming 4,0:0 67(3 4-4 7) 5.6:0 35(5 3-5 8) Pelagic juvenile 272:1 29(25.7-29 1) 26.3:149(24 0-28 9) Pelagic juvenile 1.0:0 45(0 7-1 7) 1.2:0.64(0 7-1 6) Benttiic juvenile 268:1 78(24 1-295) 25 6:1 70(23 4-28.7) Benthic juvenile — — Upper jaw lengtti/HL Nuchal spine length/HL Postflexion 42 6:184(39 0-45 9) 42 1:2,21(37 3-45 7) Postftexion 2.1:1 15(0 1-39) 1.6:0.87(0 4-3.2) Transforming 40 5:2.35(37 5-44 0) 412:2 02(37 6-42 7) Transforming 2.1:0.31(1 8-2 6) 2.6:0 35(2.4-2.9) Pelagic juvenile 42 1 :1 33(39 2-44 4) 41 4:1 71(39 3-442) Pelagic juvenile 1.9:0 72(1 1-2 4) 1,4:024(1,2-1 7) Benttiic juvenile 42 5:2 89(39,3-46 5) 44 2:4 16(35 3-48 4) Benthic juvenile — _ Snout lengtti/HL Preopercular spine lenglh/HL Postflexion 27 4:1 74(23 9-30 6) 27 6:1 65(25 0-31 4) Postflexion 20 1:3 30(12 8-27 0) 19,5:3 31(14 5-26,9) Transforming 26 3:0 38(25 6-26 7) 26 7:1 13(25 8-28 0) Transforming 12.8:2 16(100-160) 13,3:1.11(11.8-14 4) Pelagic juvenile 25 6:1 75(23 1-29 1) 27 0:2 12(23 9-30 0) Pelagic juvenile 102:1 60(7 8-130) 9.6:0.81(8 4-10 9) Benttiic juvenile 28 8:3 56(22 9-32,7) 23 1:1 98(199-26 5) Benthic juvenile 3 2:0.86(2 4-4 8) 2.3:1.15(0.4-4.5) Interorbital distance/HL Caudal peduncle depth/SL Postftexion 28 8:1 78(25 0-31 9) 29 0:2 11(24 0-32 7) Postflexion 11.3:071(100-12.6) 12.8:0.89(11.4-14.3) Transforming 24 8:0 71(24 1-26,2) 25,9:101(24 7-27.0) Transforming 9.7:0,43(9 0-10 2) 11.1:0 54(10 5-11 7) Pelagic juvenile 24 7:1 67(21 6-28 0) 24 2:1 25(22.2-26.2) Pelagic juvenile 9,7:0,29(9 3-104) 10.3:0.27(9 7-10 5) Benthic juvenile 22,2:098(21 4-24.1) 23.6:1 97(21.1-26 2) Benthic juvenile 105:0 38(99-110) 11 3:0.23(11,0-11 6) Angle gill raker length/HL Caudal peduncle length/SL Postflexion 12 1:1 46(90-145) 10 9:1 36(7 3-13.5) Postflexion 15 5:0 89(13 4-16 8) 14 6:0,70(13,0-16 2) Transforming 14 7:084(139-16 1) 122:1 92(106-150) Transforming 15,1:0 54(14 3-15 7) 143:0 17(14 2-14,6) Pelagic juvenile 14 4:1 13(11 7-162) 14 1:1 04(13 1-16 1) Pelagic juvenile 15,1:1 06(14 1-17,8) 139»066(128-149) Benthic juvenile 15.0:0.66(14 4-16.1) 14 9:0 71(14 1-15 8) Benthic juvenile 132:088(120-14 5) 126:0,69(11,6-13,4) Longest dorsal spine length' /HL: Caudal peduncle depth/caudal peduncle length Postflexion 19.4:6 84(5.0-32 4) 240:5 11(152-319) Postflexion 73:0 060(0 65-0 83) 88:0069(0,74-1,06) Transforming 32 8:1 53(31 0-34.5) — Transforming 64:0 029(0 60-0 69) 78:0 042(0 73-0 84) Pelagic juvenile 35 3:1 68(33 7-39 3) 36 9:2 46(33 3-39.5) Pelagic juvenile 64:0 046(0 56-0 74) 74:0 034(0 70-0 81) Benthic juvenile 34 6:1 81(31 7-36.7) 354:1 35(33 9-37 8) Benthic juvenile ,80:0 072(0,70-0,90) 92:0 021(0 91-0,94) Longest dorsal ray length^/HL Postflexion 30 5:4 39(190-38.1) 32 6:3 70(25 0-38 3) Transforming 36 7:1 59(35 2-39 3) 36 9:3 07(34 9-40 4) Pelagic juvenile 40 5:3 00(37 1-45 8) 40 1:162(38 5-43 0) Benthic juvenile 43 4:2 34(40 3-46 1) 46 1:2 34(45 2-48 5) ' Usual^ fourth or fifth in larvae, fifth or sixth in juveniles, ^Usually in anterior one-fourth of fin ^The second spine in larvae and transforming lan/ae, the third spine in juveniles S. melanops (10.6 mm) has a nuchal and supra- cleithral (as blunt bumps) an(i a fourth superior infraorbital in addition to the spines listed above. In both species the parietal spine and ridge are finely serrated on all specimens <34 mm long. Parietal spine length decreases with development becoming overgrown in benthic juveniles. The nuchal spine, always shorter than the parietal, is usually present in larvae and pelagic juveniles and is overgrown by scales and tissue in benthic juveniles. (Table 2 lists the mean nuchal spine/ HL value for pelagic juveniles as greater than the 910 Table 3. — Meristics from larvae and juveniles ofSebastes melanops off Oregon, based on unstained specimens. Counts of left and right pelvic fin rays ll.5;l,5), superior and inferior principal caudal rays (8,7), and left and right branch iostegal rays (7;7) were constant from the smallest to the largest specimen listed. Standard Length (mm) Dorsal fin spines and rays Anal tin spines and rays Pectoral fin rays Left Rigtlt Gill rakers (first arch) Lateral line pores Diagonal scale rows Right Left Right Left Right 10.6 11,7 11,9 119 12,4 12.8 12.8 12.8 13.5 13.6 13.9 14.0 14.9 15.4 15,4 15,7 15.9 16,4 16.5 17.2 17.4 17.4 17.7 17.7 18,5 19.0 19.2 19,2 20.7 20.7 21.0 22.9 223.2 224.0 224.0 224.6 227.9 230.6 333.1 =33.9 =35.2 '35,8 '38.2 '39.2 '40.0 '41.0 '43.8 '45.3 '48.4 «525 ■■62,5 ■•67,0 ••76 1 "89,4 "97 7 "100.9 "111,6 XIII XIII XIII XIII XIII X X XIII xiir XIII xiir X X XIII X XIII XIII XIII XIII XIII XIII XIII XIII XIII XIII XIII XIII X XIII' xiir XIII XIII XIII XIII XIII XIII XIII XIII XIII XIII XIII XIII XIII XIII XIII XIII XIII XIII XIII XIII XIII XIII XIII XIII XIII XIII X 19 19 19 19 19 19 19 19 19 19 19 19 19 19 19 19 19 19 19 19 19 19 19 19 19 19 19 19 19 19 19 19 19 19 19 19 19 19 19 19 19 19 19 19 19 19 19 19 19 19 19 19 19 19 19 19 I I ,0 AIM ,\H Ml .0 ^S ^ Postenormost dorsal or anal spine appears as a soft ray 2Transforming 'Pelagic luvenile "Benlhic juvenile. 19 19 19 19 19 19 19 19 19 19 19 19 19 19 19 19 19 19 19 19 19 19 19 19 19 19 19 19 19 19 19 19 19 19 19 19 19 19 19 19 19 19 19 19 19 19 19 19 19 19 19 19 19 19 19 19 19 21 + 22 + 23 + 23 + 21 + 23 + 22 + 8=29 9=31 9 = 32 8 = 31 8=29 9=32 8 = 30 22+10=32 23+ 9 = 32 23+ 9 = 32 21+ 9=30 23+ 9 = 32 24+ 9 = 33 23+ 9 = 32 23+ 9 = 32 23+10=33 24+ 9 = 33 25 + 10=35 23*10 = 33 24+ 9=33 24+10=34 23 + 10 = 33 24*10 = 34 24tl0 = 34 23 + 10 = 33 25-10=35 23 + 10 = 33 24*10=34 25*10=35 24*10 = 34 26 1 1 1 =37 26+10=36 26+10=36 26+11=37 25+10=35 28*11=39 26*12 = 38 25 1 10 = 35 25*11=36 25*11=36 26*11=37 27+12 = 39 25*10=35 26*12=38 26 + 11=37 25 + 10 = 35 26+11=37 27 + 11=38 26+11=37 25+11=36 26*11=37 25 + 11=36 26+11=37 24+10 = 34 23 + 21 + 24 + 22 + 23 + 23 + 22 + 8 = 31 8=29 8=32 8=30 8=31 22+ 9=31 23+ 9 = 32 9=32 9=31 23 + 10=33 22+ 8=30 23+ 9 = 32 23 + 10=33 24+ 9 = 33 23 + 10 = 33 23+10=33 23+ 9=32 23+10 = 33 25 + 10=35 23+ 9=32 24 + 10 = 34 24 + 11=35 24+ 9=33 23 + 10 = 33 25 + 10 = 35 23+10=33 25+10 = 35 23 + 10=33 24+10 = 34 24*10=34 23+10=33 26+11 = 37 25 + 10=35 26+10 = 36 27+11=38 25 + 10 = 35 27 + 11=38 26+11=37 26+11=37 25 + 11=36 25 + 11=36 26 + 10 = 36 26+11=37 25+10=35 27+12=39 26+11=37 24 + 11=35 26*11=37 28 + 11=39 26+11=37 24+11=35 26+11=37 25+10=35 26 + 11=37 24*10=34 50 48 49 46 51 49 50 49 51 49 46 49 51 51 50 53 54 53 54 57 55 58 49 55 56 56 57 52 53 52 58 55 mean pairietal spine/HL value. This results from many broken parietal spines on pelagic juveniles as indicated in Tables 4, 5.) The five spines of the posterior preopercular series are present on specimens of both species by = 11 or 12 mm. The first spine becomes reduced to a small blunt projection by =70 mm. The third spine is always longest but decreases in length from 20 to 2 or 3% HL during development. The second, third, and fourth posterior preopercular spines and the anterior edge of the first spine of the anterior preopercular series are weakly ser- rated on specimens of S. flavidus <17 mm and S. melanops <16 mm. Serrations persist on the third posterior preopercular spine of both species to =32 mm. The second spine of the anterior series is present occasionally (rarely in S. melanops) on one side of the head, particularly on specimens < 13 mm. The first and third anterior preopercular spines are visible on specimens <27 and 25 mm (S. flavidus and S. melanops , respec- tively), become reduced to small bumps, and are no longer visible on specimens >31 and 29 mm. The inferior opercular spine forms by =11 or 12 mm and is sharp tipped by =15 or 16 mm. (Two inferior opercular spines were observed on one 911 *28 3 t: • f ' \ 26 17 4 • • • • '' . 108 23* 18 29 • •■ 65 6 "' r M 45 24 r ^ • • M^^. 1 -■!■ /r-.i '[ Larvae 3 %.. 16 3 23 6 40 I • • • • • • ; Pelagic Juveniles Benthic Juveniles "■■■'I 'i ^' ^1 Figure 7, — Number of specimens and location of capture of larvae and juveniles of Sebastes flavidus ofTOregon ( 1961-78) described in this paper. side of two specimens of S. melanops, 36 and 39 mm long.) The interopercular spine is present on specimens >10 mm and persists as a sharp spine to =71 mm on S. flavidus and —52 mm on S. melanops. This spine becomes skin covered and appears as a bump on large specimens. The ridge anterior to the postocular spine is usually finely serrated on specimens - 16 mm in S. flavidus and <22 mm in S. melanops. Preocu- lar and supraocular spines never develop on either species. The second inferior infraorbital spine is visible as a bump at 10.3 and 11.7 mm on S. flavidus and S. melanops, respectively, and as a sharp spine by =12 mm on both species. A third inferior infraorbital spine appears on both species between 13.5 and 14.5 mm. The second and third inferior spines are reduced to a pair of rounded bony lobes on S. flavidus =36-67 mm and S. melanops 33-50 mm long. Sebastes flavidus -67 mm and S. melanops >50 mm have a single fleshy lobe which encases the bony lobes. The first superior infraorbital spine is present through the larval periods of both species and becomes re- duced and then absent on S. flavidus >45 mm and S. melanops -38 mm long. The fourth superior infraorbital spine develops by =10 mm, is present to =45-48 mm, and then is absent in both species. The third superior infraorbital spine appears on S. flavidus 15-35 mm and on S. melanops 19-33 mm long. A second superior in- fraorbital spine never develops. The nasal spine appears as a bump between 11 and 12 mm and becomes a sharp spine, between 12 and 13 mm, which persists on all larger specimens of both species. The tympanic spine never becomes well de- veloped, appearing as a small bump on =24-63 mm S. flavidus and 30 to =40 mm S. melanops and as a small spine on larger specimens. The pterotic spine is present on all larvae <24 mm; is usually a bump on specimens 24-41 mm; and is absent on larger specimens. The inferior post- temporal spine is reduced to a bump and then absent on S. flavidus >67 mm and S. melanops ■45 mm. The supracleithral spine and superior posttemporal spine first appear at =11 or 12 and = 19 or 20 mm, respectively, and persist in benthic juveniles. These spines are scale covered on benthic juvenile S. melanops >67 mm. The cleithral spine usually appears as a bump at =24 mm in S. flavidus and at =30 mm in S. melanops. Specimens -33 mm have a sharp spine which is scale covered in larger juvenile and adult S. flav- idus and S. melanops >67 mm long. Scale Formation. — Lateral line organs are visible on transforming specimens 14.8 mm in S. flav- idus and >17.2 mm in S. melanops, indicated by a row of light colored spots on the flesh. Develop- ing scales are first visible on unstained specimens =23 or 24 mm long in the region above the pec- toral fin, near the posttemporal and supracleithral spines, and over the upper two-thirds of the body in the postanal region. The body is scale covered by =28 mm. Pigmentation. — The smallest larvae (10.1 and 10.6 mm) of both S. flavidus and S. melanops have melanistic pigment on the head over the brain. Melanophores are usually present on the 912 LAROCHE and RICHARDSON: DEVELOPMENT AND OCCURRENCE OF ROCKFISHES 20 20r APR -I (( 1- MAY -If ^- JUN -• fl 1- JUL If >- AUG SEP OCT NOV W t^fl 40 60 80 100 Standard Length (nnm) 120 140 200 220 FIGURE 8. — Seasonal occurrence of larvae and juveniles of Sebastes flavidus off Oregon. Data from 1961 to 1978 combined. Solid bars indicate pelagic stages, open bars indicate benthic stages. inside tip of the lower jaw, along the anterior margin of the maxillary, around the pterotic spines, and on the operculum. The 10.6 mm larva of S. melanops also has pigment on the snout, along the posteroventral margin of the orbit, on the cheek, and around the posttemporal spine. An internal melanistic shield covers the gut in both species appearing darkest on the dorsal surface. In S. flavidus melanophores are present dorsally on the nape, beneath the second dorsal fin, and on the caudal peduncle. In addition to these, S. melanops has melanophores beneath the first dorsal fin, possibly due to a more advanced state of development for this specimen. Several melanophores also occur along the posterior por- tion of the anal fin base and the ventral margin of the caudal peduncle in both species. Internal and external melanophores are present near the mid- line of the caudal peduncle and several melanophores are at the margin of the hypural elements. The pectoral and pelvic fin blades are moderately pigmented with expanded, elongated melanophores. The inner side of the pectoral base is also pigmented. A discrete melanophore is pres- 913 FISHERY BULLETIN: VOL. 77, NO 4 1 1 • - ' ■?. hj;" 4 2 • • • •• 14 2 • ^f njal • \ if - I ■ Larvae \ •<4U«»l Mild "■ '1 ^i. ^1 S| V"'"- ?^- 6 3 2 7 18 9 • • • • •• • 55 Pelagic Juveniles ^nn!l ?i,n ?l Tl Benthic Juveniles "' '^1 'i *i ^1 Figure 9. — Number of specimens and location of capture of larvae and juveniles ofSebastes melanops off Oregon (1961-78) described in this paper. lOr lOr 0 lOr 0- ^ 20r a> _E o 0) Q. iT) 0 APR ■ I ■■! 1- np ni rii n* j__ f ■■ f 1- i^ -\ 1 1 1- I 1 1 1— /p) — ff— p> 1 MAY -I 1 1 1 • ' — (f ' ff — ' 1 JUN I 1 1 »— (f I (f I 1 JUL -I 1 1 V- 1 i~~> 1-^ -^ 1 1 1 1 »- -if—^— ff I (( I 1 0 20 40 60 80 100 120 140 290 380 Standard Length (nnnn) Figure lO. — Seasonal occurrence oflarvae and juveniles of Sefcostesme/anopsoffOregon, Data from 1961 to 1978 combined. Solid bars indicate pelagic stages, open bars indicate benthic stages. ent at the articulation of each of several dorsal and anal fin rays (more in the 10.6 mm S. melanops than in the 10.1 mm S. flavidus). As larvae develop, pigment increases over the brain. Melanophores are added on the snout, in- terorbital region, tips of the upper and lower lips. 914 LAROCHE and RICHARDSON: DEVELOPMENT AND OCCURRENCE OF ROCKFISHES Table 4. — Measurements (millimeters) of larvae and juveniles ofSebastes flavidus from waters off Oregon. £ c 3 TO Q. .c > 1) c c c «) o E c Z II 03 cno) < 5S o c fi If to 60 mm, have essentially the same melanistic pigment pattern as the largest pelagic juveniles. Pigmentation at the an- terior tips of the lips and along the ventral edge of the maxillary intensifies and ^ dark bar extends from the posteroventral margin of the eye across the cheek. In S. melanops a second dark bar forms dorsal to the first and extends from the eye across the opercle becoming distinct by 76 mm. Melanophores appear on patches of scales covering the dorsal half of the body in both species. These patches overlie the pigment de- scribed for pelagic juveniles creating darker patches with lighter areas interspersed where pigmentless scales overlie pigmented Eireas. The dorsal half of the body has a mottled appearance as a result of this. Melanophores first appesir on the pectoral fin base of S. flavidus in a patch which extends onto the fin membrane and on the underside of the fin base. Later, additional small melanophores lightly cover the pectoral, anal, and caudal fins while only a few small melanophores appear on the pelvic fin. Benthic juvenile S. melanops have melanophores cover- ing all fins, however, the distal margins of those in smaller specimens are usually pigmentless. Although already covered by melanophores, the pectoral fin in small benthic (<63 mm) S. melanops has a patch of large melanophores which spread over the dorsal half of the pectoral ray bases and adjacent fin base in the same area which first appears pigmented on the pectoral fin of S. flavidus. The spinous dorsal fin, anterior to the black blotch, appears mottled in S. melanops. On the soft dorsal fin a more lightly pigmented bar runs through the proximal third of the fin. This bar becomes faint or indistinguishable on specimens >67 mm long. Previously described pelagic juvenile body pigment along the anal fin base, at the articulation of the anal fin rays, and on the caudal peduncle becomes completely obscured by scales and tissues on both species, and small melanophores on the scales are alone visible. In general benthic juvenile S. flavidus are more lightly pigmented than S. melanops taken over similar substrate, however, the pigment pat- terns are very similar. Color of Fresh Specimens. — Yellow chromato- phores are visible interspersed with melanophores over all body surfaces on pelagic and benthic juveniles of both S. flavidus and S. melanops. In S. melanops they are not numerous enough to give the fish a distinctly yellow cast. The concentration of yellow chromatophores is generally greatest in the areas where melanistic pigment is densest, e.g., the base of the caudal fin, the pigment bar radiating from the posteroventral margin of the eye, darker eireas on fins. Yellow pigment is not concentrated around the dorsal fin black blotch. Juveniles generally appear darkly mottled with faintly yellow fins, yellowish areas on the head and body, and cream colored ventrally. However, considerable variation in the intensity of the melanistic pigment of benthic juveniles may occur seemingly dependent upon bottom substrate. When melanistic pigment is less intense, yellow pigment is more outstanding. The yellow tail, 917 FISHERY BULLETIN: VOL 77. NO. 4 Table 6. — Development of spines in the head region ofSebastes flavidus larvae and juveniles. + denotes spine present and - denotes spine absent. Standard length (mm) Parietal 10.1 + 10.3 + 10.7 + 11.4 + 11.8 + 11.8 + 11.9 + 12.0 + 12.2 + 12.7 + 12.8 + 12.9 + 13.1 + 13.7 + 14.4 + 14.8 + 15.8 + 15.9 + 16.4 + 16.8 + 189 + 19.5 + 19.8 + 20.5 + 21.3 + 22.3 + =23.6 + ^23.7 + =24.2 + =24.8 + '25.6 + '26.6 + '26.7 + ^28.6 + >29i + '29.6 + '30.4 + '33.0 + '33.1 + '35.2 + '36.4 + '37,6 1 4J '41.9 + * '43.6 + " '45.2 + ^ '67.6 =71. 5 »72.5 577.5 581.0 MOSO 1 ., Preopercular (anterior series) Preopercular (posterior series) Opercular 3d Inter- Sut>- oper- oper- Pre- Supra- 5th Superior Inferior cular cular ocular ocular Post- ocular + -I- + + -f + + + V) (') {') + (') {') V) (') + - + + - (') + - + + V) + + V) + + V) + + - + -It (') ■+■ + - + + {') + + + + + - -»■ + (') + -t- (') + + (') (') CI (') 'Bump, indicates beginning ot spine formation or bony overgrowth of spine. 'Transforming. 'Pelagic juvenile ^Parietal and nuchal spines fused. ^Benthic juvenile ''Spine covered by fleshy lobe 'Adjacent spines fused ^Spine has become scale-covered. characteristic of adults of S. flavidus, usually be- comes distinct on juveniles 100 mm long. Occurrence (Figures 7-10). — Adults of S. flavidus occur from San Diego, Calif., to Kodiak Island, Alaska (Miller and Lea 1972). Off Oregon they are most common on the continental shelf be- tween 100 and 200 m (Snytko and Fadeev'). Data from Niska (1976) showed that 92% of the total Oregon trawl catch of S. flavidus from 1963 to 1971, was taken from depths of 54 to 218 m. Con- centrations of adult S. flavidus have been found along Astoria Canyon, between lat. 46°10' N and 46°20' N, and also between lat. 44°30' N and 45° 'Snytko. V. A., and N. S. Fadeev. 1974. Data on distribu- tion of some species of sea perches along the Pacific coast of North America during the summer- autumn seasons. Docu- ment submitted to the Canada-USSR Meeting on Fisheries in Moscow-Batumi, USSR. November 1974, 14 p. (Transl. 3436, Can. Transl. Ser.) 918 Table 6.— Continued. Infraorbital Nasal Coronal Tympanic Pterotic Posttemporal Superior Inferior Supra- cleithral ^\t'.1^' lnfer,or Superior (mm\ 1st 2d 3d 1sl 2d 3d 4th Cleithral 10.1 103 107 11.4 118 118 119 120 122 127 12.8 129 13 1 137 144 148 15 8 15 9 164 168 18,9 19.5 198 20.5 21 3 22.3 223.6 223.7 224.2 224.8 2256 226.6 2267 =23,6 '29.2 =296 »30.4 =33.0 =33 1 =35.2 =36.4 =37.6 =41.9 =43.6 =45.2 567.6 =71.5 5725 S775 581 0 5105.0 (') («) (') (') (') CI (') (') (') (') (') ,6.7, ,6 7, ,6 7, ,6 7, ,6 7, ,6 7, (') (') (') (') (') (') {') (') - + V) - + V) - + + - + V) - (') - - (') + - {') + - + + - (') + - + + V) + V) + + + {') + V) + V) + (') (') (') (') (') (') (') (') + (') N (see footnote 7). Larvae, including transform- ing specimens, of S. flavidus in our collections were captured at stations ranging from 24 to 266 km offshore. Larvae apparently range widely and the limit observed are probably most indicative of sampling effort. Within the size range of iden- tified larvae, there was no apparent distribution pattern relative to specimen size. Pelagic juveniles were similarly distributed. Benthic juveniles were taken close to the coast at depths of 20-37 m. Adult S. melanops reportedly occur from Paradise Cove, Baja California, to Amchitka Is- land, Alaska (Miller and Lea 1972), although Quast and Hall ( 1972) noted that records from the Aleutian Islands may have resulted from mis- identified S. ciliatus. Sebastes melanops is most common on the continental shelf at depths <200 m (Dunn and Hitz 1969; Niska 1976). Data tabu- lated by Niska (1976) for Oregon trawl catches show that 82% of the total S. melanops landings, from 1963 to 1971, were taken in depths <54 m while 93% were taken at depths <109 m. Larvae, including transforming specimens, of S. melanops in our collections were captured at sta- tions ranging from 5 to 266 km offshore. Pelagic juveniles have a similar distribution. Larvae seem to range widely. However, sampling effort was not uniform over the area and relatively lit- tle sampling occurred nearshore, <40 km from 919 Table 7 —Development of spines in the head region of Sedosteme/anops larvae and juveniles. + denotes spine present and spine absent. denotes Standard length (mm) Parietal 10.6 11.7 11.9 11.9 12.4 12.8 12.8 12.8 13.5 13.6 13.9 14.0 14.9 15.4 15.4 15.7 15.9 16.4 16.5 17.2 17.4 17.4 17.7 17.7 18.5 19.0 19.2 19.2 20.7 20.7 21.0 22.9 223.2 224.0 224.0 224.6 227.9 230.6 *33 1 •339 •■352 ■•35.8 "38.2 "39.2 MOO MI.O M3,8 ■•453 "48,4 '52.5 '62,5 '67,0 '76,1 '89,4 '97,7 '100,9 '111,6 Preopercular (anterior series) 1 St 2d 3d Preopercular (posterior series) Opercular 5th Superior Inferior oper- cular Sub- oper- Pre- ocular Supra- ocular Post- ocular (') (') (') (') (') ' ■*) ") ") •') ' ') ") ") (' ') (' ') + V) (') (') CI 'Bump, indicates beginning of spine formation or txiny overgrowth of spine ^Transforming 'Parietal and nuchal spines fused "Pelagic juvenile ^Spine IS bifid ^Spine covered by fleshy lobe 'Benthic juvenile "Spine has become scale-covered ^Adjacent spines fused the coast. Benthic juveniles have been taken in estuaries, tidepools, and near the coast at depths <20m. Parturition times reported for S. flavidus are December to February off California (Phillips 1958) and March off Oregon (Westrheim 1975). Larvae 10-20 mm long were taken April through June, although most were taken in April and May. Larvae and pelagic juveniles 20-40 mm long were taken April through July, indicating some 920 Table 7. — Continued. 10.6 11.7 11.9 11.9 12.4 12.8 12.8 12.8 13.5 13.6 13.9 14.0 14.9 15.4 15.4 15.7 15.9 16.4 16.5 17.2 17.4 17.4 17.7 17,7 18.5 19.0 19.2 19.2 20.7 20.7 21.0 22.9 223.2 224,0 224.0 224.6 227,9 230,6 ••33.1 "33.9 "35.2 '35.8 ■•38.2 ■'39.2 MOO '41.0 '43.8 M5.3 '48.4 '52,5 '62 5 '670 '76.1 '89,4 '97,0 '1009 '111,6 Infraorbital Nasal Posttemporal Coronal Tympanic Pterotic Superior Interior Supra- cleittiral Standard lengthi (mm) Inferior Superior isl 2d 3d 1st 2d 3d 4ttl Cleithrai C) (') (') («) (') {') (') (') + (') (') (') (') (') (') (') (') (') (') (') (') (") ,6,9) ,6 9) ,6 9) ,6 9) ,6 9) ,6 9, (') (') (') (') + + + 4- + (') (') (') (') (') (') + + + (') (') + + + (') (') + + + (') (') + + + (') "*" + + + + (') + + + (') (') + + + (') + + + + + + + (') (') + V) + (1) - + + + (') + + + {') o + + + (') V) variability and protraction of parturition time. Benthic juveniles were taken only in June and October due to limited samples. Parturition times reported for S. melanops are February to April (Hart 1973) and January off Oregon (Westrheim 1975). Larvae 10-20 mm long were taken April through May. Larvae and pelagic juveniles 20-40 mm long were taken April through June, indicating some variability in spawning time and duration. Benthic juveniles first appeared in June samples. Comparisons. — Prior to this paper, developmen- tal series of 10 of the 69 northeast Pacific (includ- ing Gulf of California) species of Sebastes had been described: S. cortezi, S. crameri, S. Gulf Type A, S. helvomaculatus , S.jordani, S. levis, S. macdonaldi, S. melanostomus, S. paucispinis, and S. pinniger (Moser 1967, 1972; Moser et al. 1977; Moser and Ahlstrom 1978; Richardson and Laroche 1979). While exhibiting some similarities to larval and juvenile S. flavidus and S. melanops, the previously described develop- 921 mental series differ in many characters. Most ap- parent is the early lack of pigment and the later development of distinct pigment saddles under the dorsal fins of postflexion and pelagic juvenile S. crameri, S. helvomaculatus , S. levis, S. melanostomus , S. paucispinis, and S. pinniger. The only species described to date which has pig- ment along the dorsal surface under the dorsal fins in postflexion larvae and pelagic juveniles, similar to that of S. flavidus and S. melanops, is S.jordani. However, S.jordani has a very short snout to anus distance/SL ratio, 36 to 53% SL, compared with 57 to 60.3% SL and 58.0 to 61.3% SL for postflexion larvae and pelagic juveniles of S. flavidus and S. melanops, respectively. Sebastes cortezi, S. Gulf Type A, and S. mac- donaldi are all deeper bodied than S. flavidus and S. melanops, and both S. Gulf Type A and S. mac- donaldi have much longer parietal spines. Other Oregon species which are easily confused with S. flavidus and S. melanops during larval and juvenile development are the widow rockfish, S. entomelas, and the blue rockfish, S. mystinus. However, pelagic and benthic juveniles of these species are separable based on the presence of preocular and supraocular spines, usually >15 dorsal soft rays, and usually >8 anal soft rays (see Appendix Table 1). Sebastes mystinus is separable from the other three species at all sizes after fin formation has occurred, =9.0 mm, since it is the only species which usually has 16 dorsal soft rays and 9 anal soft rays. Sebastes entomelas and S. mystinus both usually have 18 pectoral rays which distin- guish them from S. melanops, which usually has 19 rays. Sebastes flavidus and S. entomelas are the only pair of species which are not readily separated by fin counts. However, both S. en- tomelas and S. mystinus develop supraocular spines, which appear on specimens larger than = 17 mm, while S. flavidus and S. melanops rarely develop supraocular spines. In addition to these characters, larvae and pelagic juveniles of S. en- tomelas and S. mystinus either lack or have a reduced number of melanophores at the articula- tions of the anal fin rays and on the ventral surface of the caudal peduncle. We have a description of the development of S. entomelas in preparation. Sebastes ciliatus (from British Columbia and Alaska) and S. serranoides (from California) are other similar species which should be CEirefully considered when identifying specimens from areas where they also occur. We have not had the opportunity to observe specimens of S. ciliatus and cannot assess its potential for causing confu- sion. We have examined 20 benthic juvenile S. serranoides. Although the head spine pattern in S. serranoides is the same as in S. flavidus and S. melanops, S. serranoides usually has <18 pec- toral rays and >8 anal soft rays which will usu- ally separate them from S. flavidus and S. melanops (see Appendix Table 1). All of the species discussed, excluding S. ciliatus for which we have no information, have to some extent a concentration of melanistic pigmentation on the posterior portion of the spinous dorsal fin occur- ring on juveniles. Sebastes flavidus and S. melanops have the most intensely pigmented "black blotch." Sebastes mystinus has a more darkly pigmented spinous dorsal fin which pre- sents little contrast from the pigment in the area of the black blotch. Sebastes entomelas and S. ser- ranoides usually have a less distinct "blotch" with most of the pigment concentrated in a fringe along the posterior distal edge of the spinous dor- sal fin membrane. The most important characters useful in separating larval and juvenile S. flavidus and S. melanops from each other are pectoral ray number (usually 18 versus 19), lateral line pore number (usually >50 versus <50), and caudal peduncle depth/length ratio (mean values 0.73, 0.64, 0.64, 0.80 versus 0.88, 0.78, 0.74, 0.92 in postflexion larvae, transforming, pelagic juvenile, and benthic juvenile specimens, respec- tively). Sebastes flavidus taken at the same loca- tion as S. melanops appear to have less dense melanistic pigment. Benthic juveniles of S. flav- idus seem to inhabit deeper waters, >20 m, while S. melanops inhabits estuaries, tidepools, and offshore waters <20 m. Landing data tabulated by Niska ( 1976) indicates a corresponding differ- ence in "preferred" depth for adults with S. flav- idus taken chiefly between 54 and 218 m and S. melanops taken mainly in water <54 m. ACKNOWLEDGMENTS Special thanks are extended to William G. Pearcy for allowing us to use his extensive mid- water trawl collections from waters off Oregon. Additional specimens were provided by Carol Anderson, Range Bayer, Carl Bond, William Esch- meyer, Wendy Gabriel, Gary Hepman, Gary Hewitt, Michael Hosie, Earl Krygier, Robert Lea, 922 and Kate Myers. H. Geoffrey Moser and Sigurd J. Westrheim reviewed the manuscript and offered helpful suggestions. LITERATURE CITED DELACY, A. C C. R. HITZ, AND R. L. DRYFOOS. 1964. Maturation, gestation and birth of rockfish {.Sebas- todes) from Washington and adjacent waters. Wash. Dep. Fish., Fish. Res. Pap. 2:51-57. Dunn, J. R., and C. R. Hitz. 1969. Oceanic occurrence of black rockfish (Sebastodes melanops) in the central north Pacific. J. Fish. Res. Board Can 26:3094-3097. Hart, J. L. 1973. Pacific fishes of Canada. Fish. Res. Board Can. Bull. 180, 740 p. Miller, D. J., and R. N. Lea. 1972. Guide to the coastal marine fishes of California. Calif. Dep. Fish Game, Fish Bull. 157, 235 p. MOSER, H. G. 1967. Reproduction and development of Sebastodes paucispinis and comparison with other rockfishes off southern California. Copeia 1967:773-797. 1972. Development and geographic distribution of the rockfish, Sebastes macdonaldi (Eigenmann and Beeson, 1893), family Scorpaenidae, off southern California and Baja California. Fish. Bull., U.S. 70:941-958. Moser, H. G.. and E. H. ahlstrom. 1978. Larvae and pelagic juveniles of blackgill rockfish, Sebastes melanostomus, taken in midwater trawls off southern California and Baja California. J. Fish. Res. Board Can. 35:981-996. MOSER, H. G., E. H. AHLSTROM, AND E. M. SANDKNOP. 1977. Guide to the identification of scorpionfish larvae (family Scorpaenidae) in the eastern Pacific with com- parative notes on species of Sebastes and Helicolenus from other oceans. U.S. Dep. Commer., NOAA Tech. Rep. NMFS Circ. 402, 71 p. NISKA, E. L. 1976. Species composition of rockfish in catches by Ore- gon trawlers 1963-71. Oreg. Dep. Fish. Wildl., Inf. Rep. 76-7, 80 p. Phillips, J. B. 1958. "Rockfish review." In The marine fish catch of California for the years 1955 and 1956, p. 7-25. Calif. Dep. Fish Game, Fish Bull. 105. QUAST, J. C, AND E. L. Hall. 1972. List of fishes of Alaska and adjacent waters with a guide to some of their literature. U.S. Dep. Commer., NOAA Tech. Rep, NMFS SSRF-658, 47 p. Richardson, S. L., and W. a. Laroche. 1979. Development and occurrence of larvae and juveniles of the rockfishes Sebastes cramert, Sebastes pinniger, and Sebastes helvomaculatus (family Scor- paenidae) off Oregon. Fish. Bull., U.S. 77:1-46. VERHOEVEN, L. a. (editor). 1976. 28th annual report of the Pacific Marine Fisheries Commission for the year 1975. Pac. Mar. Fish. Comm., Portland, Oreg., 48 p. Westrheim, S. J. 1975. Reproduction, maturation and identification of lar- vae of some Sebastes (Scorpaenidae) species in the north- east Pacific Ocean. J. Fish. Res. Board Can. 32:2399- 2411. 923 £ T3 Si § B Si ^ o CO -u J2 c # ,.^- t; 3 60 S- T1 n £ P ffl ^- 3 ■c I I I 1 ' I I I M I -' ^"^ I I I I I I cn cNj lo n I I I j ■- CM lOCDlDCO"- I ICVjnCM tD"jCiir)'-cna)aoa>oj Tj^l/lCvJ^CMCMCMiOcn '- ■- '-CM iD "- -- 00 ro lO I ■- ^ n i/> tn t£> o •- ID r- (£) Tf PI oi •- j "" I I CM CO I I CM . I I 11"- CM I I CM tD I I ID ■- m r- c^ (D c^ C^ -^ iT) D Ifi CD I j I I I " I iT) [ >- cr> CO I I "^ I I I I I M - I M I I I ~: CT^ 0>^ O^^, CT^ O) _jcc_jtr_icr_jcr_ia: 2 e I I I I M I ^ M ^ , I , CM^ , ^ I I r-inco-^r-oocor- i i i-cMO'-f-r-O)'- I CO CMCMCOCOCMCM'-CM I •^ in to o CO »- ' .- ^ .- T- CM CM ■ I |in'-r-*Dr-a)eoco I I I I I ^c^,c^,^^ -- I I CM CM I I in r-~ T- '- „ I I tD in •- CM TJ (D <£> TJ (M — O 01 ■.- ^ 03 CD Cn CD CM CM rgcD— ^cD'TfM'- co '^ CM ■* r-- n I n CD n ■ *- (ji r- in r~ — CM •- CO I I -III _iQ:_iQ:_jcr_ici:_ici: a 3 ffl r o (A m O 1 I I I I I 1 l-l 1 1 1 o E 1 in in ^ ^ 1 1 cf o ™ CO r- to CD ' 1 i o ».- ^ s" CM CM CVJ <-- Q-in r- 1 *- p s ^ in r-- CO >n in I I I I I I I I ^ - I ■- 7- CD T I I I »- to in '- CM I I I I ^ I CO cy n t^ II I ^ II I I II J cc J (I jj (r . S E in . " ^ c^ „ »-» — S " °5ss O „ «J J3 ■ (TJtD ui Z — ™ c I/I c o r 9S-3 0) O 0) - 7 days were omitted due to excessive variability. The catch of legal lobster 'Skud, B. E. 1976. Soak time and the catch per pot in an offshore fishery for lobsters Qiomarus amencanus). Int. Cons. Explor. Mer, Special meeting on population assessments of shellfish stocks. No. 8, 25 p. ^Morgan, G. R. 1976. Trap response and the measurement of effort in the fishery for the western rock lobster. Int. Cons. Explor. Mer. Special meeting on population assessments of shellfish stocks, Contrib. 16, 18 p. 927 FISHERY BULLETIN: VOL. 77, NO 1 per trap haul (ClTH) tended to increase slightly with increasing soak time in both vented and con- trol traps up to 6 days when a slight decline be- came evident (Figure 1). A different pattern emerged for the catch of sub- legal lobster per trap haul ( C^TH ) where we noted an initial increase in CgTH in nonvented traps followed by a general decline with increasing soak time. In vented traps, CgTH declined initially fol- lowed by a slight increase with time (Figure 1). The decline in CgTH in control traps with immer- sion times in excess of 2 days may be the result of escapement through the trap heads and mortality within the trap (Bennett 1974; Austin 1977). We attributed the immediate decline in CgTH in vented traps to escapement, indicating the effec- tiveness of the vents. It is unclear whether the increase in CgTH for the sixth set over day was due to sampling bias or some other factor. Bennett ascribed catch increases with long soak times to decay of the bait with an associated renewed re- lease of chemical attractants. The catch of legal and sublegal lobster was not proportional to immersion time. This may be due LEGAL LOBSTER to the combined effects of declining local availabil- ity, trap saturation, escapement, and mortality (Bennett 1974; Austin 1977; Skud see footnote 3; Bennett and Brown^). Catch per trap haul/set over day (CTHSOD) declined with time in both vented £md control traps (Figure 2). Similar observations of declining CTHSOD with increasing soak time have been noted in the Maine lobster fishery (Thomas 1973), the spiny lobster fishery (Austin 1977) and the European lobster fishery (Bennett 1974). Our data indicated that CTH approached an asymptote with increasing soak time for both legal and sublegal lobster. Following the approach of Sinoda and Kobayasi (1969) and Munro (1974) this relationship may be modelled as: C, = CJl - exp{-Rs)) 'Bennett, D.B., and C.G.Brown. 1976 The problems of pot immersion time in recording and analysing catch-effort data from a trap fishery. Int. Cons. Explor. Mer, Special meeting on population assessment of shellfish stocks, No. 6, 8 p. LEGAL LOBSTER ~1 I 1 2 O vented • Control r ^» — o ,-J5— — — o \ SUBLEGAL LOBSTER [ 1 I 1 1 1 1 3 4 5 SET OVER DAYS Figure l — Relationship between catch per trap haul of Ameri- can lobster euid trap immersion time in vented and control traps. Legal lobster are s78 mm CL. O Vented • Control SUBLEGAL LOBSTER SET OVER DAYS Figure 2.— The relationship between catch per trap haul/set over day of American lobster and trap immersion time in vented and control traps. 928 FOGARTY and BORDEN: EFFECTS OF TRAP VENTING ON GEAR SELECTIVITY where Cj is the cumulative catch on days, C^is the asymptotic catch, and R is the net retention rate assuming constant availability. The term d is dependent on not only the physical holding capac- ity of the trap but on any behavioral interactions which serve to limit the catch. The asymptotic catch will be reached when ingress is balanced by escapement. Parameters of the model were estimated by non- linear least squares (Hartley 1961). The trend in greater legal catch in vented gear was reflected in the slightly higher estimate of C^ in vented traps (Table 3). The substantially lower asymptotic catch level for sublegal-sized lobster in vented gear clearly demonstrated the effectiveness of these traps. Munro ( 1974) stressed the importance of escapement in determining saturation levels in fish traps. This model may also be used to standardize ef- fort to a common soak time. Adapting the ap- proach of Sinoda and Kobayasi ( 1969) and Caddy,*' weighting coefficients are given by 1 — exp(— ills) u) = ^^ — 1 — exp(—Rs*) Table 3. — Coefficients and associated standard errors for the model Cs = C^i^ — exp( -Rs)] relating catch per trap haul and soak time in vented and control traps for legal- ( ss78 mm CD and sublegal-sized lobster. Item C .^ R Vented Legal 0.9745: -0 0715 09879± 0.3610 Sublegal 1 .3847 : =0 1598 0,8796 = 06289 Control Legal 0.9222 ±0.08 11 074281 0,2664 Sublegal 2,16425 -0 1127 2 5369 ± 1 7001 150 - - 1 r \ i -- - VENTED _ ^/ \, V CONTBOL irtioo- 01 / v. • 2 50- /;'' , I / / ] \/^ "V> J ' V. —.r^ ^-.,'=^-:.^ ,- CARAPACE LENGTH (t FIGURE 3. — Size-frequency distribution of American lobster col- lected in vented and control traps in Narragansett Bay-Rhode Island Sound (1976-77). where s* is the standard soak time. The total effec- tive effort (/,jj,) is then the product of nominal effort (trap hauls) and the weighting coefficient (Caddy see footnote 6) s Aot = ^/"sW and the standardized CPUE is given by the catch divided by /'(„, . Adjustment for variable soak times should greatly improve the precision of catch ef- fort data used in surplus yield modelling. Size Selectivity Carapace length (CL) measurements were ob- tained for a sample catch of 2,943 lobster retained in the experimental traps. The reduction in the sublegal catch retained in vented gear was most pronounced for lobster <75mmCL(Figure3). Size selection for lobster >75 mm CL was virtually identical in vented and control traps. The mean 'Caddy, J. D 1977. Some considerations underlying defini- tions of catchability and fishing effort in shellfish fisheries, and their relevance for stock assessment purposes. Int. Cons. Explor. Mer, Shellfish and Benthos Committee, CM. 1977/K;18, 21 p. ^ y X ^ / / ---VENTED / CONTROL - / / , ! / /' / / ^ ^ y' 60 ,'o b'o 9'o ii CARAPACE FIGURE 4. — Retention curves generated for vented and control traps for American lobster collected in Narragansett Bay-Rhode Island Sound (1976-77). size of lobster caught in non vented traps (75.20 mm) and vented gear (78.99 mm) were sig- nificantly different (t = 12.856; P<0.01). Retention curves (Krouse and Thomas 1975) constructed for vented and control traps clearly reflect the differences in the retention characteris- tics for each trap tjrpe (Figure 4). The cumulative retention points for each curve at the Rhode Island minimum legal size at the time of this study (78 mm CL) were 56.0% and 69.5% for vented and control traps, respectively. 929 FISHERY BULLETIN: VOL. 77, NO, 4 We observed a general relationship between the mean size of lobster caught and fishing location. Comparisons of the mean size of lobster in sample catches (pooled by trap type) for six fishermen, for which adequate data were available, revealed a segregation by fishing location (Table 4). In gen- eral, lobster taken in Narragansett Bay and near- shore Rhode Island Sound samples were sig- nificantly smaller ( <^ = 0.05) than those taken in offshore Rhode Island Sound when compared using Duncan's multiple range procedure (Steel and Torrie 1960), although one offshore sample did not conform to this pattern. We attributed the smaller mean size in Narragansett Bay and near- shore Rhode Island Sound samples to intense fishing pressure in these easily accessible areas. Krouse (1973) noted a similar correspondence be- tween fishing intensity and size composition of the catch. Areas within Narragansett and Rhode Is- land Sound with the smallest mean size of lobster also had the lowest CPUE (Table 4). Characteristics of the habitat may also influence the size composition of the catch. Several authors have observed a correlation between the size of lobster and the size of available shelter sites (Scarratt 1968; Cobb 1971; Stewart 1972). Larger lobsters were found in areas with greater shelter size (Scarratt 1968; Cobb 1971) or in mud areas with a high clay fraction capable of supporting larger burrows (Stewart 1972). Inshore rocky habitats are characterized by ledge and mixed rocky debris which offer smaller shelter sites than offshore mud and rock substrates. Table 4. — Results of Duncsin's multiple range procedure com- paring mean carapace length{rankordered)of American lobster from offshore Rhode Island Sound (R.I.S.), nearshore Rhode Is- land Sound (R.I.S.N) and Narragansett Bay (N.B.). Means with the same letter code are not significantly different ( 50 kHz) during the past 10 yr has progressed to the point where research at frequencies up to 3 .0 MHz is now practical (Holliday and Pieper^). Working with high frequencies has several advan- tages over low frequencies. As the frequency is increased, shorter pulses can be used and the reso- lution is increased. In addition, smaller organisms become better sound scatterers as the frequency is increased. At 102 kHz, for example, shoals of 'Institute for Marine and Coastal Studies, University of Southern California. Los Angeles, CA 90007. ^Holliday, D V , and R. E. Pieper. 1978. Volume scattering strengths and zooplankton distributions at acoustic frequencies between 0.5 and 3 MHz. Program of the 96th Meeting of the Acoustical Society of America. Honolulu, Hawaii. 25 p. euphausiid shrimp can be detected and quantified at ranges up to 300 m (Bary and Pieper 1970; Pieper 1979). The present paper reports on two migrating scattering layers recorded only at 12 kHz and a deeper, third layer recorded at both 12 kHz and 102 kHz. Large numbers of a single size class of juvenile Mexican lampfish, Triphoturus mexi- canus (Gilbert 1890), were collected from the deepest scattering layer. Volume scattering strengths of this layer were measured at 102 kHz and corresponding target strengths of T. mexicanus were calculated. Although no directed sampling was completed in the two, shallower, 12 kHz scattering layers, the possible scatterers re- sponsible for these layers are indicated. We dis- cuss the advantage of using acoustic frequencies above swim bladder resonance for biomass studies and recommend the increased usage of high- frequency acoustics for biological studies in the sea. METHODS Three 12 kHz scattering layers were observed migrating towards the surface near sunset on an acoustic survey at the northwest end of the San Clemente basin off southern California on 25 and 26 January 1977. The deepest of these 12 kHz layers was recorded as a strong scattering layer on a 102 kHz echo sounder being used to study euphausiid distributions (Pieper 1979). Quantita- tive acoustic measurements at 102 kHz and biological sampling were completed in this scat- tering layer on 26 January. Salinity and tempera- ture profiles were taken immediately after the tow Manuscript accepted Mav 1 979 nSHERY BULLETIN: VOL 77, NO 4.1980 935 FISHERY BULLETIN: VOL 77. NO I with a submersible salinity, temperature, and depth (STD) recorder. Acoustic Measurements A Ross Laboratories^ 102 kHz echo sounder with its transducer housed in an Endeco V-fin was used in conjunction with a 12 kHz hull mounted Edo transducer triggered by an Edo model 444 trans- ceiver and model 551 recorder. Information from the 12 kHz sounder was recorded only as qualita- tive echograms. Acoustic data from the 102 kHz echo sounder was recorded qualitatively as echo- grams, and quantitatively over specific 20 m (26.87 ms) intervals where the scattering was ob- served. The returned signal for this interval was electronically squared and integrated for each pulse, and the value displayed on a chart recorder. The average scattering level (RL ) over this 20 m interval was then calculated and the volume scat- tering strength iSj was determined by the follow- ing (Urick 1975): the layer. The samples were preserved in 10% buffered Formalin in the field and transferred to 70% ethanol in the laboratory. All fishes were identified to species and their standard length measured. The density of fishes collected was calculated by dividing the number of animals caught by the product of ship speed (meters per minute) times the length of the tow (minutes) times the mouth area (square meters). The mouth area of the net has been calculated to be 2.36 m^ assuming a 45° fishing angle (Davies and Barham 1969). Swim bladders were measured from 12 T. mexicanus which represented the range of sizes of this species collected by the trawl in the 102 kHz scattering layer (trawl 25660''). Swim bladder measurements were also taken from four Protomyctophum crocken, five Argyropelecus sla- deni, and five Vinciguerria h/cetia collected from two earlier trawls (trawls 25657 and 25658). The volume of the swim bladder was calculated by using the formula for a prolate spheroid (Capen^). S,{dB/m^)=RL-SL -h 401ogr -H 2or - 10 log V Calculations where RL = average received (scattering) level SL = source level r = mean range of the 20 m interval a = absoprtion loss per m^ V = volume insonified = (cT/2)(^r2) where c = speed of sound r = pulse length M' = solid angle of the ideal two-way beam pattern. Volume scattering strengths were determined at various times (and depths) as the layer mi- grated toward the surface. Biological Sampling Biological samples were collected with a 6-ft modified Tucker trawl with an acoustically con- trolled opening-closing sequence and a continuous depth readout on a Giffl recorder. While sampling in the migrating scattering layer, the net depth was regulated to keep pace with the movement of The density of fishes was then used to calculate their average target strength (TS ) by applying the formula: TS = S„ (fishes) - 10 log (fishes m-') where S;, (fishes) 10 log[log 1 0.1 S, (total) - log 1 0.1 S,. (plankton)]. The S,, value for plankton was calculated from an average of the two integration values recorded after the fish scattering layer had migrated out of the integration window. The depth where the swim bladder would reso- nate at 12 kHz was calculated for the range of swim bladder sizes observed assuming constant swim bladder volume with depth. These calcula- tions were determined by solving for z (depth) in the following simplified formula for resonance of an air bubble in water (Clay and Medwin 1977; equation 6.3.10): /po = (3.25 X 10«/a)(l +0.l2)^ 'Reference to trade names does not imply endorsement by the National Marine Fisheries Service. NOAA. 'All trawl numbers mentioned refer to ship's station numbers (Ve/ero/V.University of Southern California I. ^Capen, R. L. 1967. Swimbladder morphology of some mesopelagic fishes in relation to sound scattering. U.S. Navy Electronics Laboratory, San Diego, Calif, Rep 1447. 2.5 p. 936 I'lEPER and BAKGO: ACOUSTIC MEASUREMENTS OF MIGRATING MEXICAN LAMPFISH where fpf^ = resonant frequency (Hz) a = equivalent spherical radius (/xm) z = depth (m). In the above formula, /Vr is 12 kHz. The a is the radius of a sphere equal in volume to that of the swim bladder at the surface. RESULTS The deepest of the three 12 kHz scattering layers (Figure 1) was also recorded at 102 kHz (Figure 2). The calculated volume scattering strengths at 102 kHz and at different times and depths are also shown in Figure 2. The biological sample from this layer was composed almost ex- clusively of juvenile T. rnexicanus (Table 1). The movement of the scattering layer with time showed an increasing rate of migration up to a depth of around 180 m which corresponded to a change in the temperature-salinity characteris- tics of the water (Figure 3). Calculated target strengths for T. rnexicanus (Table 2) were highest at the deepest depth ( -60.6 dB at 284 m) and slowly decreased as the layer migrated upwards ( -71.3 dB at 206 m). The de- crease in calculated target strengths corresponded to the increased migratory rate of the layer (Fig- Table 2.— Volume scattering strengths (S^.) for the 102 kHz scattering layer and calculated target strengths ITS) for Tnphoturus rnexicanus. Data from San Clemente basin, south- em California, 26 January 1977. Time (PST) Type of sea tiering Deplti (m) Sv (dB/m^) Fish Sv Fish rS (dB/m3) (dB) WZ KMz scattering laye 1- ot han Clemente basm, sou them 17190 Plankton 257 -76 86 California, 26 January 1977, 1731- 744 h. 1735 0 Plankton 244 -7731 _ _ Average plankton — -77 08 — Total Number Mean 17160 Plankton and fish 284 -69.13 -70.02 -60.6 Taxon number caught per 1 .000 m^ standard length (mm) BE 1726 0 1726 5 Plankton and fish Plankton and fish 257 257 -71,13 -71 13 -72,40 -72.40 -63.0 -63.0 Tnphoturus rnexicanus 263 114 0 245 02 1730 5 Plankton and fish 244 -72 83 -74 88 -65.4 Stenobrachius leucopsarus 3 1 3 247 14 1731 0 Plankton and fish 244 -73.05 -75.24 -65.8 Lampanyctus ntteri 1 04 68 5 1736 0 Plankton and fish 226 -74 48 -77 94 -68.5 Argyropelecus sladent 2 09 105 30 1736 5 Plankton and fish 226 -74 18 -77 30 -67.9 Sergestids 9 39 287 29 1740 5 Plankton and fish 206 -75 23 -79.83 -70 4 Euphausiids 105 450 174 0.7 1741 0 Plankton and fish 206 -75 53 -80 76 -71 3 Q. UJ Q 50- 100- 150 — 200 — 250- T-- (a) /^ I I Interference- -> (b) (c) — 50 — 100 — 150 — 200 ■250 TIME l-H — I — I — I — I — I — I — I — I — I — I — \ — I — l-H 1714 1722 1730 1738 1746 1754 1802 1810 Figure l. — A 12 kHz echogram from the San Clemente basin, southern California, 26 January 1977. Three scattering layers are shown, first appearing at depths around 150 m, and then migrating towards the surface. The first two scattering layers, (a) and (b), to migrate (starting around 1720 and 1745, respectively) were only recorded at 12 kHz. The third scattering layer (c) (starting around 1750 1 was also recorded on a 102 kHz echo sounder. The echogram also shows scattering from single fish or small fish schools between 50 m and the surface. The interference indicated is from the ship's echo sounder. 937 FISHERY BULLETIN: VOL 77. NO, 4 E_ I I- CL LU Q TIME 1658 1702 1706 1710 1714 1718 1722 1726 1730 1734 1738 1742 1746 1750 1754 1758 1802 1806 DISTANCE [m] < > > . ■■ ■• n Rnn ^'>nr\ ^a^^n OArtn Sy (dB/m3) .-^^ « — TRAWL- r-W •""-^^ ■. 0°. .->. * Plankton only ° Fish layer in center of window Figure 2. — A qualitative 102 kHz echogram showing a migrating scattering layer in San Clemente basin, southern California. 26 January 1977. and calculated volume scattering strengths (Sv I at 102 kHz for selected 20 m depth intervals ( horizontal solid lines on echogram). The volume scattering strengths are shown when the scattering layer is in the center of the integration window (open circle), partially in the window (solid circle), and absent from the window (asterisk). The towing period for trawi 25660 is shown. DC < o Z cr < o 05 (X LU o X I- □. UJ o 1700 1 TIME 1730 1745 SALINITY 33 7 33.4 33.6 33.8 34 34 3 34.4 34.6 19 - la - 17 - •so "1 o 15 H o • 60 UJ 14 H d: -1 \- • 80 < cc n - Vsp IK ^^"^^•lOO Q. 5 11 - 120 UJ V"*© H 10 - >r_ 50% 'OO'* 9 - 0%^ \ /\ / Southern 8 - Northern \ \ 4oJV ^3^^'' 7 - water \ \ soo»\ 6 - \o Figure 3. — Left: Depth of the center of the 102 kHz scattering layer plotted against time. Right: The temperature-salinity diagram for the water column immediately after trawl 25660. 938 PIEPER and BARGO: ACOUSTIC MEASUREMENTS OF MIGRATING MEXICAN LAMPFISH lire 4). Measurements were not taken <206 m due to increased interference from surface scattering. The organisms which were responsible for pro- ducing the two, shallower, 12 kHz scattering layers are not known since no trawls were taken from the depths of these two layers. Before the migratory period, however, two trawls were com- pleted from depths which might correspond to the distributions of the scattering organisms. Trawls 25657 (1350-1432 h; 292-302 m) and 25658 (1514- 1547 h; 267-268 m) were completed before the scat- tering layers became evident on either echo sounder. They were also from shallower depths than the first appearance of the 102 kHz scattering layer (1638; 315-325 m). Data from these trawls consisted of small numbers of Argyropelecus sla- deni, Cyclothone signata, Protomyctophum croc- keri, and Vinciguerria lucetia (Table 3). Of these four species, only C. signata is known not to be a vertical migrator (Rainwater 1975; Pearcy et al. 1977). Swim bladder resonance calculations for the other three species are shown in Table 4. DISCUSSION Lanternfishes (Family Myctophidae) have been implicated as the most important scatterers of scattering layers recorded at frequencies around 12 kHz, especially since many of these fishes have air-filled swim bladders of such a size as to be resonant from 1 to 30 kHz (Hersey and Backus 1962). Triphoturus mexicanus is a known vertical migrator off southern California (Paxton 1967) and its distribution has been previously correlated with scattering layers which showed diel migra- tions. Barham (1966) noted that adult T. mexicanus were associated with a 12 kHz scatter- ing layer in the California Current, and Holton (1969) correlated collections of 8-10 cm long T. mexicanus with a strong scattering layer in the Gulf of California. This paper reports on a scattering layer re- corded at both 12 kHz (Figure 1) and 102 kHz (Figure 2). Triphoturus mexicanus dominated the net collection from this scattering layer (Table 1). 60 -| • "62 • -64 - -0 £ -66 - 9 C • ^ -68 - • • • i-70- • -75 • 1.0 3.0 30 4.0 Rate of oscent of scattering loyer [m/minJ FIGURE 4. — Variations in the calculated target strengths for Triphoturus mexicanus at 102 kHz as a function of the rate of ascent of the 102 kHz scattering layer. Kleckner and Gibbs^ suggested that lanternfishes probably regulate the gas in their swim bladders during migration to maintain constant gas vol- ume. Assuming that calculations of swim bladder resonance can be approximated by using equa- tions based on a free bubble in water (Hawkins 1977; Love 1978), these fish would show 12 kHz resonance only between 28 and 43 m (Table 4). In addition, a frequency of 102 kHz is too high for possible resonance effects. We suggest that the deepest 12 kHz layer and the 102 kHz layer were due to a large number of T. mexicanus rather than a few fishes scattering the sound at resonant fre- quencies. Volume scattering strengths (Figure 2, Table 2) and target strengths (Table 2) were calculated at 102 kHz for T. mexicanus. Target strength values decreased as the layer migrated upwards from a «Kleckner, R. C, and R. H. Gibbs, Jr. 1972. Swimbladder structure of Mediterranean midwater fishes and a method of comparing swimbladder data with acoustic profiles, Mediter- ranean Biological Studies Final Report to the U.S. Office of Naval Research 1(41:230-281. TABLE 3.— Fishes collected from trawls 25657 and 25658, San Clemente basin, southern California, 26 January 1977. Trawl 25657 1350-1432 h 292-302 m Trawl 25658 1514-1547 h 267-268 m Species Total number caught Number per 1.0O0m3 Mean standard length {mm) Total number caught Number per 1 ,000 m3 Mean standard length {mm) Argyropelecus sladeni Cyclothone signata Protomyctoptium crockeri Vinciguerria lucetia 4 10 5 3 0.4 0.9 0,5 0,3 11,2 166 22 9 240 12 5 1 4 160 65 1 3 52 126 165 12,5 232 939 FISHERY BULLETIN: VOL, 77, NO 4 Table 4. — Swim bladder size and calculated depths for 12 kHz resonance, assuming regulation of swim bladder volume for the specimens of Triphoturus mexiLunus, Protomyctophum crockeri, Argyropelecus sladeni, and Vinciguerria lucetia in our collections. Standard length Swim bladder Ivlajor axis Minor axis Volume Equivalent sptierical Depth' Species {mm) (mm) (mm) (mm^) radius (/im) (m) T mexicanus 19 1 92 1.00 1.01 622 43 trawl 25660 21 1.83 92 81 578 36 22 2.08 1.00 ,96 612 41 23 2.09 .95 .99 618 42 24 1.77 .95 .84 585 37 25 1.96 .89 .81 578 36 25 2.03 .82 .71 553 32 27 1.65 .89 .68 546 31 27 1.58 .83 .57 514 26 29 2.08 .75 .61 526 28 33 2.0S .67 49 ^'3 fal invested — 39 1.50 .67 35 Completely lat invested — P crockeri 14 1.60 1.12 1.01 622 43 Irawl 25657 22 1.92 1.28 1.68 738 64 26 2.24 1.28 1.95 775 72 29 2,24 1.44 2.25 813 80 A- sladeni 11 1.12 .64 .24 385 10 trawl 25658 14 1.28 .BO .43 468 20 15 1.28 .80 .43 468 20 24 2.40 1.44 2.60 853 69 29 3.36 1.92 5.83 1.117 160 V lucetia 21 3.16 .85 1.20 659 49 trawl 25657 22 3.54 .92 1.56 719 60 and 25658 24 3.80 .89 1.58 723 61 26 3.86 1.14 2.63 856 90 27 5.38 158 703 1,188 182 'Where swim bladder would resonate at 12 kHz, assuming constant volume at all depths. high value of - 60.6 dB at 284 m to a low value of -71.3dBat206m. The change in calculated target strength with depth could be due to two factors: either the densi- ty of fishes per cubic meter decreased with time or the target strength decreased due to the changing orientation of the migrating fishes. The second explanation is more likely for two reasons. First, the thickness of the scattering layer appears to be constant over the period where target strengths were calculated (1716-1741 h, Figure 2). Second, the increase in the migratory rate of the layer over time (Figures 2, 3) implies a more rapid, upward swimming of the fishes. This would result in a more vertical orientation of the fish in the water column. The calculated target strengths for the juvenile T. mexicanus at 102 kHz (Table 2, Figure 4) can only be compared with theoretical values since no measured values could be found in the literature. Love ( 1977) presented formulas for predicting the target strength of an individual fish at any aspect as a function offish size and insonify ing frequency. His equations are valid for the range 1 sL/\ 'S 100 where L is the fish length and k is the acoustic wavelength. Our data on T. mexicanus for a mean standard length of 24.5 mm (Table 1) and at a frequency of 102 kHz would show aL/K ratio of 1 .7. Using his formulas on our data, calculated target strengths for dorsal aspect vary from -55.6 dB to - 56.6 dB and for anterior aspect from -67.1 dB to -67.7 dB. Thus, the target strength would be de- creased by 10 to 12 dB as the orientation of the fish changed from dorsal aspect to anterior aspect. The change in target strength values from our data ( 10.7 dB) indicates that such a change in the orien- tation of the fish might have occurred. The absolute values of our calculated tsirget strengths are about 4.5 dB less than the predicted values. Since the data used by Love ( 1977) to de- termine his equations did not include myctophids, it is possible that juvenile T. mexicanus (and lanternfishes in general) may be poorer scatterers than the larger, nearshore, and surface fishes used for his study. The migratory pattern shown for this layer is not unique to this study. The increased migratory rate of scattering layers during the middle of the sunset migration has been shown by a number of authors (e.g., Kampa and Boden 1954). Kampa and Boden (1954) also correlated this type of mi- gratory pattern to a similar pattern in the isolume at the scattering layer depths. The interrelation- ship between isolumes, scattering layer mi- grations, and vertical water mass structure is not well understood. Thus, the observed change in mi- 940 PIEPER and BARGO: ACOUSTIC MEASUREMENTS OF MIGRATING MEXICAN LAMPFISH gratory rate with change in water type around 180 m (Figure 3) may or may not reflect the reason for the observed migratory pattern. The scatterers responsible for the two, shal- lower, 12 kHz scattering layers cannot be spe- cifically determined in the present study. Of the fishes collected from two previous tows (Table 3) only Cyclothone signata is known not to migrate into surface waters (Pearcy et al. 1977). Since Vin- ciguerria lucetia has been collected at the surface at night, it is probably a vertical migrator (Grey 1964). The information on the vertical distribu- tion and migration for Argyropelecus sladeni and Protomyctophum crockeri indicates that vertical migration is unlikely, but the data on these two species are sparse and incomplete. Argyropelecus sladeni has been collected both day and night at depths from 0 to 2,000 m (Baird 1971; Rainwater 1975; Pearcy et al. 1977), although the center of their distribution appears to be from 100 to 500 m. The information on P. crockeri shows similar broad distributions (Paxton 1967; Rainwater 1975; Pearcy et al. 1977), although Paxton stated that they only reach depths of 150 m at night and Wisner' stated that they are not caught above 100 m at night. Since the two, shallower, 12 kHz scattering layers were not recorded on the 102 kHz echo sounder, it is likely that swim bladder resonance at 12 kHz from a small number of organisms was responsible for the scattering. Based on swim bladder measurements made at the surface and assuming regulation of swim bladder volume to maintain constant volume during migration, the depths where 12 kHz resonance would occur were calculated (Table 4) for the range of sizes of the fishes collected. These calculations indicate that A. sladeni and V. lucetia would show 12 kHz res- onance at depths from 10 to 160 m and 49 to 182 m, respectively. Thus, we suggest that one or both fishes could be responsible for the shallower, 12 kHz scattering layers. The depth range for 12 kHz resonance for P. crockeri (43-80 m) indicates that it was probably not the source of either of the scattering layers. In addition, both shallow layers reached a depth of 40-50 m during the migration and P. crockeri has not been collected at depths <100 m at night (Paxton 1967; Wisner see foot- note 7). It is also possible, however, that the shal- 'Wisner, R. L. 1976. The taxonomy and distribution of lanternfishes (Family Myctophidae) of the eastern Pacific Ocean. Navy Ocean Research and Development Activity, Bay St. Louis, Miss., Rep. 3. 229 p. lower layers resulted from an organism or organ- isms not collected by the two net tows discussed. The potential use of high-frequency acoustics for studying the distribution, behavior, and abun- dance of scattering organisms is strongly indi- cated. Echo sounders operated at frequencies above 30 kHz are working at frequencies above swim bladder resonance and therefore, reflect the biomass of scatterers more accurately. In addition, they generally have narrow beam angles and utilize short pulse lengths (3.5° beam angle and 1.0 ms pulse length in this study) which produce finer resolution in the scattering patterns. Cali- brated, multifrequency acoustic systems used in conjunction with sophisticated net systems are needed to better define distributional patterns and interactions of these midwater organisms. SUMMARY AND CONCLUSIONS Triphoturus mexicanus is known to migrate vertically in the water column (Paxton 1967). We have shown that juvenile T. mexicanus were the major sound scatterers in a migrating scattering layer recorded at both 102 kHz and 12 kHz. Calcu- lated target strengths for T. mexicanus at 102 kHz varied from -60.6 dB at 284 m to -71.3 dB at 206 m. This decrease in target strength with depth was probably due to a change in the orientation of the fish in the water column. The lowest target strength ( - 71.3 dB) occurred when the scattering layer was migrating towards the surface at its highest rate and, therefore, the fishes should be oriented more vertically in the water column. Two, shallower, scattering layers were recorded at 12 kHz but not 102 kHz. We suggest that these two layers probably resulted from scattering which occurred from fishes with swim bladders which 1) resonated at 12 kHz and 2) were regu- lated to maintain constant swim bladder volume during migration. Vinciguerria lucetia and A. sladeni are both possible scatterers of these layers although A. sladeni is not known to be a vertical migrator. The importance of using acoustics to study mesopelagic organisms is indicated. Echo sound- ers can be used to both qualitatively direct biologi- cal sampling and quantitatively determine dis- tributions and biomass. High-frequency echo sounders (e.g., 102 kHz in this study) have an advantage over low-frequency echo sounders. Target strength measurements on the midwater fishes, however, are needed to better predict the 941 FISHERY BULLETIN; VOL. 77, NO 1 concentration of such fishes by the acoustic technique. ACKNOWLEDGMENTS We wish to thank the many people who helped with this study. Larry Marx completed and checked most of the measurements, made the graphs, and edited the manuscript. John Chap- man calibrated and ran the electronics and acous- tic systems. Heidrun Mumper drafted the illustra- tions and Sally Womack typed the manuscript. Cheryl Chapman introduced us to the use of the computer for editing and final typing of the man- uscript. We also appreciate the helpful discussions with M. Neighbors, C. Rainwater, and B. Nafpak- titis of the University of Southern California and D. V. Holliday of Tracor, Inc., San Diego. Special thanks must go to the officers and crew of the Velero TV and to Comdr. R. Tipper of the Office of Naval Research for their support. This work was supported by the Office of Naval Research contract N00014-75-C-0683. LITERATURE CITED Andersen, N. R., and B. J. Zahuranec (editors). 1977. Oceanic sound scattering prediction. Plenum Press, 859 p. BAIRD,R.C 1971. The systematics, distribution, and zoogeography of the marine hatchetfishes (Family Sternop- tychidae). Bull. Mus. Comp. Zool. 142:1-128. BARHAM, E. G. 1963. Siphonophores and the deep scattering layer. Sci- ence (Wash., D.C.) 140:826-828. 1966 Deep scattering layer migration and composition: observations from a diving saucer. Science (Wash., D.C.) 151:1399-1403. Bary, B. McK., and R. E. PIEPER. 1970. Sonic - scattering studies in Saanich Inlet. British Columbia: a preliminary report. In G. B. Farquhar (editor). Proceedings of an international symposium on biological sound scattering in the ocean, p. 601-611. Maury Center for Ocean Science. Wash., DC Clay, C. S., and h. Medwin, 1977. Acoustical oceanography: Principles and applica- tions. John Wiley & Sons, N.Y., 544 p Da VIES, I. E., AND E. G. BARHAM. 1969. The Tucker opening-closing micronekton net and its performance in a study of the deep scattering layer. Mar. Biol. (Berl.) 2:127-131. Farquhar. G. B (editor). 1970. Proceedings of an international symposium on biological sound scattering in the ocean. Maury Center for Ocean Science, Wash., DC, 629 p. Gilbert, C. H. 1890. A preliminary report on the fishes collected by the steamer ALBATROSS on the Pacific coast of North America during the year 1889, with descriptions of twelve new genera and ninety-two new species. Proc U.S. Natl. Mus. 13:49-126. Grey, M. 1964. Famj/y Gonostomatidae. /n H.B. Bigelow (editor), Fishes of the western North Atlantic, Part four, p. 78-240. Sears Found. Mar. Res., Yale Univ. Mem. 1. Hawkins, A. D. 1977. Fish sizing by means of swimbladder. reso- nance. In A. R. Margetts (editor), Hydroacoustics in fisheries research, p. 122-129. Rapp. P.-V. Reun. Cons. Int.Explor.Merl70. Hersey, J. B., AND R. H. Backus. 1962. Sound scattering by marine organisms. In M. N. Hill (editor), The Sea, Vol 1, p. 498-539. Interscience, N.Y. HOLTON, A. A. 1969. Feeding behavior of a vertically migrating lantern- fish. Pac. Sci. 23:325-331. Kampa, E, M., and B. p. BODEN. 1954. Submarine illumination and the twilight move- ments of a sonic scattering layer. Nature (Lond.) 174:869-871. LOVE, R. H, 1977. Target strength of an individual fish at any as- pect. J. Acoust. Soc. Am. 62:1397-1403. 1978. Resonant acoustic scattering by swimbladder- bearingfish. J. Acoust. Soc. Am. 64:571-580, PAXTON, J. R. 1967, A distributional EuiEilysis for the lantemfishes (fam- ily Myctophidae) of the San Pedro basin, Cali- fornia, Copeia 1967:422-440, Pearcy, W. G., E. E. Krygier, R. Mesecar, and F. Ramsey. 1977. Vertical distribution and migration of oceanic micronekton off Oregon. Deep-Sea Res. 24:223-245. PIEPER, R. E, 1979. Euphausiid distribution and biomass determined acoustically at 102 kHz, Deep-Sea Res, 26A:687-702, Rainwater, C. L. 1975, An ecological study of midwater fishes in Santa Catalina basin, off southern California, using cluster analysis, PhD, Thesis, Univ, Southern California, Los Ang,, 159 p. URICK, R, J, 1975, Principles of underwater sound 2d ed, McGraw Hill, N.Y., 384 p 942 EMBRYONIC DEVELOPMENT OF ATLANTIC MENHADEN, BREVOORTIA TYRANNUS. AND A FISH EMBRYO AGE ESTIMATION METHOD Steven P. P^rraro* ABSTRACT Eggs of Atlantic menhaden, Brevoortia tyrannus, were artificially fertilized and embryos were reared in the laboratory at 12 temperature-salinity combinations (temperature: 10', 15", 20", and 25" C; salinity: 10, 20, 30%o). Salinity between 10 and 30%o had no significant effect on embryonic mortality and no noticeable efTect on rate of development. Temperature had a significant effect on embryonic mortality and rate of development. Embryonic mortality was significantly greater at 10° C than at 15°, 20°, and 25 " C, and significantly greater before than aft«r blastopore closure at 15°, 20°, and 25° C. The temperature coefficient for embryonic development of B. tyrannus from fertilization to hatching at temperatures between 10° and 25° C is 3.89, Age of S. tyrannus embryos can be estimated by the regression of age on developmental stages when incubated at constant temperature. The Atlantic menhaden, Brevoortia tyrannus, is an important commerical and forage fish of the east coast of North America (geographic range: lat. 27°-46° N). Atlantic menhaden spawn in Con- tinental Shelf waters and in bays and estuaries in the northern part of its range during a northward spring and southward fall-winter migration (Reintjes 1961, 1969; Higham and Nicholson 1964; Kendall and Reintjes 1975; Chapoton^). Brevoor- tia tyrannus embryos were first described by Kuntz and Radcliffe ( 1917), and B. tyrannus em- bryos captured at sea have been reared in the laboratory by Reintjes (1968) and Hettler (1970), but rearing conditions were not well controlled and details on development were not published. Rapid growth and low natural survival charac- terize the early life history of many marine fishes. Presented in this paper are results of a laboratory experiment to determine effects of temperatures between 10° and 25" C and salinities between 10 and 30'Kio on survival and development rates of B. tyrannus embryos. Also presented is a useful method for estimating fish embryo age from em- pirical relations between embryo age, stage of de- velopment, and temperature. This fish embryo age estimation method is simple and has broader prac- tical applications than other methods. It was de- 'Department of Ecology and Evolution. State University of New York at Stony Brook, Stony Brook, NY 11794. ^R. B. Chapoton. 1972 On the distribution of Atlantic menhaden eggs, larvae, and adults. Unpubl. manuscr.. 69 p. Atlantic Estuarine Fisheries Center, National Marine Fisheries Service, NOAA, Beaufort, NC 28516. veloped for use in ichthyoplankton research to identify cohorts, construct embryonic stage life tables, and back calculate the time of day of spawning. MATERIALS AND METHODS Adult Atlantic menhaden were captured by gill nets off the Shoreham Power Plant, Long Island, N.Y., at 2300 h on 14 June 1973 (lat. 40°58' N, long. 72°52' W; water temperature 20.5" C; sahn- ity 23.5"/oo). Eggs from a sexually mature female B. tyrannus were artificially fertilized on shipboard with milt from five adult males. Fertilized eggs were carried in four 1 1 glass jars in an insulated box to the laboratory at the Marine Sciences Re- search Center, State University of New York at Stony Brook, N.Y. Laboratory rearing experiments were two- factor, 4x3 (temperature x salinity) factorial designs with two replicates per treatment. Twenty-five embryos were transferred to each cul- ture dish containing 85 ml water with salinities 10, 20, or 30%o, and temperature 20° C. Distilled water or artificial sea salts were added to filtered seawater to produce the desired salinities, and loose fitting plastic covers on the culture dishes reduced evaporation. Culture dishes with embryos were placed in thermostatically controlled con- stant temperature Hotpoint (#535)^ incubators •^Reference to trade names does not imply endorsement by the State University of New York at Stony Brook, or the National Marine Fisheries Service. NOAA. Manuscript accepted Mav 1979. FISHERY BULLETIN VOL 77, NO 4.1980 943 FISHERY BULLETIN: VOL, 77, NO. 4 which maintained temperatures within ±0.5° C of 10°, 15°, 20°, and 25° C. Before the experiments began the embryos had been reared for 5 h at 20.5° C and 23.5%o, and had reached the early blastodisc stage of development. By the time of the next ob- servations, about 5 h later, water temperature in the culture dishes had reached the desired incuba- tion temperatures. Development data were mathematically adjusted for the delay in attain- ing experimental temperatures — see Results. Developing embryos were observed with a stereomicroscope at intervals of about 4-6 h. Dead embryos were counted and removed, and stage of development of most live embryos was recorded. The basic nine-stage staging classification (Table 1 ) used in this research was similar to that used by Farris (1958, 1961). I refined this staging scheme by distinguishing among an early, middle, and two late periods within the nine stages. Early and late periods within a stage of development were quantified by subtracting 0.2 from, and adding 0.3, and 0.5, respectively, to the stage number. Table l.— Fish embryo stages of development used (orBrevoor- tia tymnnus. Stage Description 1 Fertilized eggs prior to cell division to 8-cell stage 2 Eight-cell stage to completion of blastodisc formaton 3 Blastodisc formation to germ ring halfway around egg 4 Germ ring halfway around egg to |usl prior to blastopore closure 5 Blastopore closure to tall bud beginning to separate from the yolk 6 Tail bud free of yolk to caudal one-eighth of body free of the yolk 7 Caudal one-eighth of body free of yolk to caudal one-fourth of body free of yolk 8 Caudal one-fourth of body free of yolk to fin fold moderately wide and tail portion of embryo rotated out of embryonic axis and tail approaching head 9 Tip of tail approaching head to hatching RESULTS Survival to hatching in theB. tyrannus rearing experiments was low, particularly at the 10° C incubation temperature. Temperature but not sa- linity had a significant effect on embryonic mor- tality in these experiments (Table 2). Testing by a posteriori sum of squares simultaneous test proce- dure (SS-STP) (Sokal and Rohlf 1969) revealed that embryonic mortality was significantly great- er {P< 0.05) at the 10° C incubation temperature, and not significantly different tP 0.05) at 15°, 20°, and 25° C. During the experiments it became clear that most embryo deaths occurred during the first half of embryogenesis, and in particular, just prior to blastopore closure (prior to stage 5 in the staging classification used in this research) (Table 3). Table 2. — Data on mortality (upper) and two-way ANOVA (lower) with replication to determine the effect of temperature and salinity onBrevoortia tyrannus embryos. Mortality data are the proportion of dead embryos (p). ANOVA performed on angu- lar transformed (arc sine p"^) data. Temperature Salinity 10° C 15°C 20° C 25° C 10V. 0 96 0.64 0 68 0.56 92 60 92 72 20%.. 1.00 .72 76 64 1.00 .56 .60 80 30'>.» 1.00 .48 56 68 1.00 .48 .52 .68 Source of variation df SS MS Fs Subgroups 11 5.327,935 484 358 Temperature 3 4.640-063 1,546 688 49 6" Salinity 2 106 056 53028 1 7 ns Temp ■ Salinity 6 581 816 96 969 3 1 ns Within subgroups (error) 12 373,950 31 162 Total 23 5,701.885 •• =iP 0.01. ns = P 0.05. Table 3.— Percent (cumulative) mortality o( Brevoortia lyran- nus embryos prior to and after blastopore closure (stage 5 1 reared at four temperatures in the laboratory. Mortality to stage 5 Mortality to stage 9 (%J 94 98 49 58 59 67 63 68 Temperature ( C) 10 15 20 25 When the difference in frequency of embryo deaths prior to stage 5 and from stage 5 to stage 9 was tested at each of the four incubation tempera- tures, mortality was not significantly different throughout development at 10° C, but was sig- nificantly greater prior to stage 5 at the 15°, 20°, and 25° C incubation temperatures (Table 4). Data on embryonic age and stage of develop- ment were virtually identical in replicate culture dishes and for embryos reared at the same tem- perature but different salinity. Therefore, analysis was restricted to temperature effects on development rate. Table 4. — Significance of difference in deaths of Breevortia tyrannus embryos prior to and after blastopore closure (stage 5) at four temperatures. Test is 2 ■ 2 test of independence using the G-statistic with Yates' correction. Temper- Development ature stage Alive Dead Sum % dead l^adi 10 C Prior to stage 5 9 141 150 94.0 stage 5-stage 9 3 6 9 66 7 3 639 ns 15 C Prior to stage 5 77 73 150 48 7 Stage 5-stage 9 63 14 77 182 19.922" 20 C Prior to stage 5 62 88 150 587 stage 5-stage 9 49 13 62 21.0 24684" 25 C Prior to stage 5 55 95 150 63.3 stage 5-stage 9 48 7 55 12.7 42 685" ns = P -0 05: " = P<0 01. 944 FERRARO; EMBRYONIC DEVELOPMENT OF ATLANTIC MENHADEN Brevoortia tyrannus embryos used in the exper- iments were fertilized and reared at 20.5° C and 23.5%o for the first 5 h of embryogenesis. To adjust development data for the delay in attaining ex- perimental temperatures, correction factors were calculated to estimate the age embryos would have been at the beginning of the experiment had the embryos been incubated at experimental temperatures from fertilization. Since at 20°±0.5° C incubation temperature was constant through- out development, the correction factor used was the ratio of development time to stage 9 for em- bryos reared at 10°, 15°, and 25° C relative to development time to stage 9 at 20° C. Correction factors should be approximately proportional to Figure l. — Symbols represent age-stage relations of mostBre- voortia tyrannus embryos in experiments (unadjusted data) at 10° C, 15° C, 20° C, and 25° C. Solid lines are regression lines of embryo age U4 ) on developmental stage (S) with experimental data adjusted for preexperimental time and temperature. Re- gression equation at 10° C is A = 25.476(S - 1); 15° C, A = 9.295(S - 1);20°C.A = 4.948(S - 1);25°C,A = 3.311(S - 1). development rates at different temperatures if the effect of delay in attaining experimental tempera- tures is small relative to incubation time to stage 9, and development rates are linesir, as they ap- pear to be (experimental (unadjusted) data points in Figure 1). When the experiments began, em- bryos had reached the early blastodisc stage of development; the age at that stage, therefore, for each incubation temperature, was estimated by multiplying the appropriate correction factor by 5 h. Development data were adjusted by adding to or subtracting from experimental data the difference between the expected age at the early blastodisc stage at 10°, 15°, and 25° C from the age observed at 20° C. Derivations of correction factors are pre- sented in Table 5, and adjusted data on embryonic development in Table 6. Age was regressed on embryonic stage of de- velopment (S) by least-squares linear regression. Table 6. — Aejjusted data on the embryonic development ofBre- voortia tyrannus incubated at four temperatures. Temper- ature Age Embryonic Temper- (h) stage ature Age (H) 24.0 1.8 28.5 2.0 33.0 2.0 36.5 2.3 41.5 2.5 45.5 2.5 49.5 2.5 53.5 2.8 57.5 2.8 61.5 3,0 68.5 3.3 72.5 4.0 76.5 4.0 80.5 4.3 85.5 4.5 89.5 4.5 94.5 4.5 103.0 48 107 0 5.0 1130 5.0 117 0 50 129.5 6,0 137.5 6,5 151,0 7.0 156 0 75 163,0 7,8 170,5 8,0 181 5 83 194,0 88 2050 9 0 20 C 25" C Embryonic stage 86 18 130 23 175 25 21,5 33 255 40 30.0 4.5 33.0 4,8 385 5,0 420 53 46 0 58 530 6,3 57 0 70 61 0 7,3 650 80 70,0 88 74 0 93 50 18 100 25 140 40 185 50 225 53 270 63 305 7,3 35.0 80 39.0 90 3.5 18 90 3,3 130 50 17.0 6.0 21 0 70 25.0 90 Table 5. — Derivation of correction factors to adjust development data for differences between experi- mental and preexperimental temperatures during the first 5 h of embryogenesis in Brevoortia tyran- nus. Item 10 C 15 C 20' C 25° Hours to stage 9 in experiment (unadiusted data) Ratio of hours to stage 9 relative to 39 ti to stage 9 at 20 C Expected age (h) at early blastodisc stage Line 2 • 5 h Correction factor to unadjusted data Line 3 - 5 ti 186 4 77 24 0 + 190 67 1 72 86 + 3,6 39 1 00 50 0 27 0 69 35 -15 945 FISHERY BULLETIN: VOL. 77, NO. 4 Age =B (S - 1). (1) The results (Table 7; Figure 1) showed that agt stage relations were nearly perfectly linear as a function of incubation temperature, and the re- gressions were highly significant (Table 7). Analysis of variance of the regression coefficients showed that development rates were highly sig- nificantly different among temperatures iFiS, 57) = 1,405.0;P<0.001). (Regression coefficients (fi's) of Table 7 represent the "stage" development rate (units: hours/stage) of embryogensis in B. tyran- nus and are only meaningful when used in context with the embryo staging classification in Table 1 . ) The linear relationship between the logrithm of the stage development rate ofB. tyrannus (B ) and temperature (7' in degrees Celsius) (Figure 2) is expressed by the following: logio B 1.923 - 0.059 T. (2) The temperature coefficient (Qi^) forB. tyran- nus embryonic development from fertilization to hatching at 10° to 25° C determined by Equation Table 7. — Linear regression o{ Brevoortia tyrannus embryo age (A) in hours since fertilization on morphological stage of de- velopment (S). Temper- ature Regression equalion F ratio P r= 10° C A = 25-476 (S - 1) F(1. 29) = 7.110.8 0 996 15 C A = 9.295 (S - 1) f(1. 15) = 6,427 6 998 20° C A = 4.948 (S - 1) F(1.8) =3,386 8 998 25° C A = 3.311 (S - 1) F(1,5) = 1,258 6 ■•* ,996 ■ = P<0.001. 2.0-1 Log B= 1.923-.059 T CD o 1.5- 1.0- 0.5- 5 10 15 TEMPERATURE 20 C ) Figure 2. — Linear regression of the log^^^ of the "stage" de- velopment rate ofBrevoortia tyrannus embryos (B) on tempera- ture (T). Coefficient of determination = 0.96; SE regression coefficient = 0.0084. (2) is 3.89. The relation between the logarithm of the embryonic development rate of fish and tem- perature, though, is not necessarily linear (Kinne and Kinne 1962; Fonds et al. 1974), and, therefore, best predictions of stage development rates of B. tyrannus embryos (fi) incubated at constant tem- perature (T in degrees Celsius) are obtained from the explicit empirical equation: logj„ fi = -0.193 + 17.193 7^ + 34.090 r' - 461.276 T (3) DISCUSSION The B. tyrannus embryo rearing experiments were mainly designed to determine effects of tem- perature and salinity on development rate; how- ever, the results also have a bearing on tempera- ture and salinity effects on embryonic survival. Wide salinity tolerances have been reported for many marine fish embryos (Holliday 1969). Bre- voortia tyrannus embryos have a salinity toler- ance range >10-30%o, and they are, therefore, euryhaline by Kinne's (1964) criteria. Atlantic menhaden embryos have been collected in water with salinity as low as 18.15%" (Wheatland 1956), but according to Reintjes (1967) most spawning occurs ". . . in the ocean or in inshore waters with salinities similar to those of the ocean." It would appear, therefore, that B. tyrannus embryos can tolerate low salinity conditions not normally en- countered in nature. Details of the salinity-development rate rela- tion are species dependent, and they may be com- plicated by the influence of salinity on dissolved oxygen (Kinne and Kinne 1962; Forrester and Al- derdice 1966), and the hatching process (Kinne and Kinne 1962; Alderdice and Velsen 1971); but, within limits, salinity effects on embryonic de- velopment rates tend to be small or insignificant for most marine fishes studied (e.g., McMynn and Hoar 1953; Alderdice and Forrester 1968, 1971a, b). Slight but apparently significant positive relations between embryonic development rate and salinity have been reported in some oceanic species (Forrester and Alderdice 1966; Laurence and Rogers 1976). Embryos of oceanic species are probably more sensitive to low salinity and changes in salinity than estuarine species. In the experiments presented in this paper, salinity be- tween 10 and 30"/cio had no noticeable effect on the embryonic development rate of B. tyrannus. 946 FERRARO: EMBRYONIC DEVELOPMENT OF ATLANTIC MENHADEN Brevoortia tyrannus embryo mortality w£is high at the 10° C incubation temperature. In a prehmi- nary laboratory experiment, naturally fertilized B. tyrannus embryos at the blastodisc stage of development (stage 2) from field plankton collec- tions ( 14.7° C, 24%!)) failed to develop beyond stage 4 when the incubation temperature was lowered to 6°± 1° C. The lowest temperatures at which Atlan- tic menhaden embryos have been collected in the field generally range between 10° and 13° C (Perlmutter 1939; Wheatland 1956; Richards 1959; Herman 1963), but they have been reported in water as low as 7.7° C (Mundy^). The available information, therefore, indicates that while spawning rarely occurs in water <10° C, the low lethal temperature of B. tyrannus embryos is probably about 7° C. The temperature range in the experiments (10°-25° C) was not sufficiently wide to determine the upper temperature tolerance of S. tyrannus embryos, which survived equally well at 15°, 20°, and 25° C . There are no references in the literature of Atlantic menhaden embryos in nature in water >25° C. A number of investigators have noted that high fish embryo mortalities tend to occur during gas- trulation and just prior to or during hatching (McMynn and Hoar 1953; Alderdice and Forrester 1971a; Laurence and Rogers 1976; and others). High mortalities of B. tyrannus embryos occurred only during gastrulation. Generally there is a linear or slightly cur- vilinear relationship between the logarithm of the development rate offish embryos and temperature (see Blaxter 1969, fig. 4; Williams 1975; and others). The embryonic development rate of B. tyrannus followed this general rule (Figure 2). Brevoortia tyrannus embryo age-stage relations at each of the four incubation temperatures were nearly perfectly linear (Figure 1; Table 7). These results imply a) the durations of the stages (Table 1) are approximately equal, b) the effect of the four incubation temperatures on rate of development of B. tyrannus embryos was relatively the same in all stages, and c) the stages of development can be *Mundy,B.C. 1974. Order Clujwiformes Family Clupeidae Brevoortia tyrannus (Latrobel, Atlantic menhaden. In H. M. Austin (editor). Preoperational ecological monitoring program of the marine environs at the Long Island Lighting Company (LILCO) nuclear power generating facility, Shoreham, Long Is- land, N.Y., vol. 2, sect. 5, p. 15-20. Contract SR-72-32. LILCO Community Relations, 250 Old Country Road, Mineola, NY 11501. used to estimate the age of embryos if the incuba- tion temperature is known and constant. A simple method of predicting the age of a B. tyrannus embryo at any stage of development from Table 1, incubated at any constamt temperature (degrees Celsius) is to solve Equations (3) and (1), in succession for B and age. At low temperatures precision of the age estimate decreases because duration of stages increases. At temperatures in which menhaden commonly spawn (15°-20° C), this method yields an estimate of embryo age with an average expected error from stage duration of between 1.3 and 2.3 h (average error = 'A x stage development rate). Kuntz and Radcliffe (1917) and Hettler (1970) gave the incubation time of fi. tyrannus embryos, but Kuntz and Radcliffe did not specify the incuba- tion temperature. Hettler (1970) observed hatch- ing within 66-74 h at an average incubation tem- perature of about 15.5° C (range 11.5°-19.5° C). The embryo age calculated for stage 9 at 15.5° C from the age prediction equations is 68.8 h, which compares well with Hettler's observation. Other methods have been developed which es- timate age of fish embryos. Simpson (1959) and Brown and Hassler (1973) constructed nomo- graphs recording the influence of temperature on durations of embryonic stages of Pleuronectes platessa and Morone saxatilis, respectively. Ahlstrom (1943) and Talbot (1977) used regres- sion analysis to describe the relationship between temperature and durations offish egg stages, but their methods require calculating separate re- gressions for each development stage and temper- ature and does not allow interpolation of develop- ment rates between temperatures. Zweifel and Lasker ( 1976) applied the Laird-Gompertz growth equation to incubation times and embryonic growth (extrapolated from early posthatch growth) offish embryos. The Laird-Gompertz equa- tion appears to give good predictions of fish em- bryo growth, but its computation requires solving a multiparameter equation by iteration for each incubation temperature. The fish embryo age es- timation method described in this paper is simple and has broader practical applications than the methods above. Together Equations (3) and (1) accurately describe the age-stage-temperature re- lations of B. tyrannus embryos at easily identi- fiable stages, during the entire embryonic de- velopment, and over a wide range of temperatures. Embryo age prediction equations can be calcu- lated for other species in the manner described 947 FISHERY BULLETIN VOL, 77. NO 1 here for B. tyrannus, and, if necessary, the preci- sion of embryo age estimates by this method can be improved by increasing the number of develop- ment stages of approximately equal duration in the embryo stage classification scheme. ACKNOWLEDGMENTS I thank the field research team from the New York Ocean Science Laboratory, Montauk, N.Y., for their assistance in the capture of ripe menha- den. I thank John L. McHugh, Marine Sciences Research Center, State University of New York at Stony Brook; and Herbert M. Austin, Virginia In- stitute of Marine Science, for reviewing an earlier draft of the manuscript. Thanks also to Fishery Bulletin reviewers for constructive criticism of the manuscript. Special thanks to George C. Wil- liams, State University of New York at Stony Brook, for reviewing the manuscript and for assistance and support throughout the research. Research for this paper was financially sup- ported in part by NOAA, Sea Grant Project 2-35281 to G. C. Williams, and by Grant-in-Aid emd University Awards from the State University of New York at Stony Brook Research Foundation, and 1977 and 1978 summer Biomedical Research Grants to the author. LITERATURE CITED AHLSTROM, E. H. 1943. Studies on the Pacific pilchard or sardine iSardinops caerulea). 4. Influence of temperature on the rate of de- velopment of pilchard eggs in nature. U.S. Fish Wildl. Serv., Spec. Sci. Rep. 23. 26 p. ALDERICE, D. F., AND C. R. FORRESTER. 1968. Some effects of salinity and temperature on early development and survival of the English sole iParophrys vetulus}. J. Pish. Res. Board Can. 25:495-521. 1971a. Effects of salinity and temperature on embryonic development of the petrale sole tEopsetta jordani). J. Fish Res. Board Can. 28:727-744 1971b. Effects of salinity, temperature, and dissolved oxy- gen on early development of the Pacific cod iGadus niac- rocephalus). J. Fish. Res. Board Can. 28:883-902. ALDERDICE, D. F., AND F. P. J. VEI.SEN. 1971. Some effects of salinity and temperature on early development of Pacific herring (C/upcapaHasi). J. Fish. Res. Board Can. 28:1545-1562. BLAXTER, J. H. S. 1969. Development: Eggs and larvae. In W. S. Hoar and D. J. Randall (editors), Fish physiology. Vol. 3. p. 177-252. Acad. Press., N.Y. BROWN, J. T., AND W. W. HASSLER. 1973. A nomography for age determination of striped bass {Morone saxatilis) eggs. (Abstr.l /n A. L. Pacheco (editor), Proc. of a workshop on egg, larval and juvenile stages of fish in Atlantic Coast estuaries, p. 66. U.S. Dep. Commer., NOAA, NMFS, Sandy Hook Lab. Tech Publ. No. 1. farris, d. a. 1958. Jack mackeral eggs. Pacific coast, 1951-54. U.S. Fish Wildl. Serv., Spec. Sci. Rep Fish. 263, 44 p. 1961. Abundance and distribution of eggs and larvae and survival of larvae of jack mackerel {Trachurus symmel- ricus). U.S. Fish Wildl. Serv., Fish. Bull. 61:247-279. FONDS, M., H. ROSENTHAL, AND D. F. ALDERDICE. 1974. Infiuence of temperature and salinity on embryonic development, larval growth and number of vertebrae of the garfish, Belone belone. In J. H. S. Blemter (editor). The early life history offish, p. 509-525. Springer- Verlag, N.Y. FORRESTER, C. R., AND D. F. ALDERDICE. 1966. Effects of salinity and temperature on embryonic development of the Pacific cod iGadus mac- ■ rocephalus). J. Fish. Res. Board Can. 23:319-340. Herman, S. S. 1963. Planktonic fish eggs and larvae of Narragansett Bay. Limnol. Oceanogr 8:103-109. Hettler, W. F, Jr. 1970. Rearing menhaden. U.S. Fish Wildl. Serv., Circ. 350:24-26. HIGHAM, J. R., JR., AND W. R. NICHOLSON. 1964. Sexual maturation and spawning of Atlantic menhaden. U.S. Fish Wildl. Serv., Fish. Bull. 63:255- 271. HOLUDAY, F. G. T. 1969. The effects of salinity on the eggs and larvae of teleosts In W S. Hoar and D. J. Randall (editors), Fish physiology, Vol. 1, p. 293-311. Acad. Press, N.Y. Kendall, a. W., Jr., and J. W. Reintjes. 1975. Geographic and hydrographic distribution of Atlan- tic menhaden eggs and larvae along the middle Atlantic coast from RV Dolphin cruises, 1965-66. Fish. Bull., U.S. 73:317-335. KINNE, O. 1964. The effects of temperature and salinity on marine and brackish water animals II. Salinity and temperature salinity combinations. Oceanogr. Mar. Biol. Aimu. Rev. 2:281-339. KiNNE, O., AND E. M. KiNNE. 1962. Rates of development in embryos of a cyprinodont fish exposed to different temperature-salinity-oxygen combinations. Can. J. Zool. 40:231-253. KUNTZ, A., AND L. RADCLIFFE. 1917. Notes on the embryology and larval development of twelve teleostean fishes. Bull. lU.S.I Bur. Fish. 35:87- 134. Laurence, G. C, and C. a. Rogers. 1976. Effects of temperature and salinity on comparative embryo development and mortal ity of Atlantic cod iGadus morhua L.) and haddock iMelanogrammus aegleftnus (L.)). J. Cons. 36:220-228. McMYNN, R. G., and W. S. HOAR. 1953. Effects of salinity on the development of the Pacific herring. Can. J. Zool. 31:417-432. Perlmutter, a. 1939 Section I. An ecological survey of young fish and eggs identified from tow-net collections. In A biological sur- vey of the salt waters of Long Island, 1938, Part II, p. 948 FERRARO: EMBRYONIC DEVELOPMENT OF ATLANTIC MENHADEN 11-71. NY. Conserv. Dep., Suppl. 28th Annu. Rep., 1938, Salt- Water Surv. 15. REINTJES, J. W. 1961. Menhaden eggs and larvae from M/V Theodore N. Gill cruises, South Atlantic coast of the United States, 1953-54. U.S. Fish Wildl. Serv., Spec. Sd, Rep. Fish. 393, 7 p. 1967. Classification and distribution of North American menhaden. U.S. Fish Wildl. Serv., Circ. 264:14-15. 1968. Development and oceanic distribution of larval menhaden. U.S. Fish Wildl. Serv., Circ. 287:9-11. 1969. Synopsis of biological data on the Atlantic menha- den, Brevoortm tyrannus. U.S. Fish Wildl. Serv., Circ. 320, 30 p. Richards, S. W. 1959. Pelagic fish eggs and larvae of Long Island Sound In Oceanography of Long Island Sound, p 95- 124. Bull. Bingham Oceanogr. Collect., Yale Univ. 17( 1). SIMPSON, A. C. 1959. The spawning of the plaice {Pleuronectes platessa ) in the Irish Sea. Fish. Invest. Minist. Agric, Fish. Food IG.B,), Ser. 11,22(8), 30 p, SOKAL, R. R., AND F. J. ROHLF. 1969. Biometry. The principles and practice of statistics in biological research. W. H. Freeman and Co., San Franc, 776 p. Talbot, J. W. 1977. The dispersal of plaice eggs and larvae in the South- em Bight of the North Sea. J. Cons. 37:221-248. WHEATLAND, S. B. 1956. Pelagic fish eggs and larvae. In Oceanography of Long Island Sound, 1952-54, p. 234-314. Bull. Bingham Oceanogr. Collect , Yale Univ. 15. Williams, G. C. 1975. Viable embryogensis of the winter flounder Pseudopleuronectes americanus from -1 .S^ to 15° C. Mar. Biol. (Berl.) 33:71-74. ZWEIFEL, J. R., AND R. LASKER. 1976. Prehatch and posthatch growth of fishes — a general model. Fish. Bull., U.S. 74:609-621. 949 DISTRIBUTION AND MOVEMENTS OF RISSO'S DOLPHIN, GRAMPUS GRISEUS, IN THE EASTERN NORTH PACIFIC Stephen Leatherwood,' William F. Perrin,^ Vicky L. Kirby,^ Carl L. Hubbs/ and Marilyn Dahlheim* ABSTRACT Records of occurrence are summarized from 22 strandings/collections and 210 sighting records from miscellaneous soxirces. When available, levels of effort have been identified and utilized to interpret the trends in distribution and movement apparent from the data. Risso's dolphins occur from at least the Equator (southern end of area examined) north to approximately latitude 50° N. with regions of apparently very low density centering at about latitude 20' and 43° N. Records from northern and inshore portions of the range were most numerous during late spring through early fall. Both within and among years, periods of greatest abundance for the species north of latitude 43° N, near Monterey Bay, California, and over the southern California continental borderland appear to correspond with protracted periods of warm water Groups contained from 1 to an estimated 220 animals, about a geometric mean of 10.7. An estimated 76.4% of the groups contained fewer than 20 animals. The Risso's dolphin or gray grampus, Grampus griseus, is widely distributed in tropical and tem- perate waters around the world. It occurs on the western side of the Atlantic Ocean from at least Newfoundland (approximately lat. 50° N, Leath- erwood et al. 1976) south to Cape Horn (approxi- mately lat. 53° S, Norris''), and in the Gulf of Mexico (True 1885; Gunter 1954; Paul 1968) and the Caribbean (Caldwell et al. 1971). On the east- ern side of the Atlantic it occurs from the Shetland Islands, Scotland (Turner 1892), south to the Cape of Good Hope (approximately lat. 34° S, Barnhard 1954), including the North Sea (Schultz 1970), and throughout the Mediterranean Sea complex (Baz- zauti 1910; Tamino 1953; Pilleri and Gihr 1969), including the Adriatic (Trois 1883; Ninni 1901; Carrucio 1906; Riedl 1965; Pilleri and Gihr 1969). It also occurs in the Red Sea (Hershkovitz 1966) and in the Indian Ocean (Ellerman et al. 1953; 'Biomedical Branch, Naval Ocean Systems Center, San Diego, Calif.; present address: Hubbs/Sea World Research Institute, 1700 South Shores Road, San Diego, CA 92109. ^Southwest Fisheries Center La Jolla Laboratory, National Marine Fisheries Service, NOAA, P.O. Box 271, La Jolla, CA 92038. ^Department of Biology, San Diego State University, San Diego, CA 92115. 'Scripps Institution of Oceanography, La Jolla, CA 92037. Deceased. 'Department of Biology, San Diego State University; present address: Northwest and Alaska Fisheries Center, National Marine Fisheries Service, NOAA, 7600 Sand Point Way NE, Seattle, WA 98115. «Norris, K. S. 1968. Cruise report of the R/V Hero. November 12-December 11, Valparaiso-Puntarenas, Chile, 11 p. Coastal Marine Laboratory, University of California, Santa Cruz, CA 95060. Weber 1923), at least to the Indo- Australian Ar- chipelago, and on the west side of the Pacific Ocean from the Commander Islands (approximately lat. 55° N, Sleptsov 1961) south to New Zealand (Hec- tor 1873; Parker 1934; Alpers 1960; Gaskin 1968; Baker 1974), including the South China Sea, the Philippine Sea (Baker 1974), and the waters around the New Hebrides (Maxwell 1952), the Solomon Islands (Dawbin 1966), and New Guinea (Gaskin 1972). On the eastern side of the Pacific it has been reported from the Bering Sea (Clark 1945) and British Columbia (Guiguet and Pike 1965) south to Valparaiso, Chile (Aguayo 1975), and Cape Horn (Norris see footnote 6), including the Gulf of California (Leatherwood et al. 1979). That Risso's dolphins are present in Hawaiian waters as well is indicated by three sightings and a stranding on Maui in 1977 (E. W. Shallenberger'). Davies (1963) remarked on the species' overall distribution that it is basically tropical but ex- tends its ranges poleward to overlap the ranges of temperate forms, though they generally do not penetrate so far into high latitudes. In all areas, the species' distribution is known only from in- frequent stranding records and at-sea sightings, and published accounts continue to restate those records, often without adding substantial new data. Details of the animal's distribution and movements Eire not reported. This paper reviews the information available through 1975 on Risso's Manuscript accepted May 1979 FISHERY bulletin VOL 77. NO. 4. 1980 'E. W. Shallenberger, Curator, Sea Life Park, Waimanalo, HI 96795, pers. commun. to Leatherwood September 1977. 951 FISHERY BULLETIN VOL 77. NO 4 dolphins in the portion of the eastern Pacific from the Equator and long. 145° W north and east re- spectively, from strandings, collections, and sight- ing records, and examines the data for patterns in distribution, movement, and seasonal occurrence. METHODS Inherent in the approach to this paper is the opinion that for this as for other areas, there are numerous scientists and organizations which have small amounts of information of little sig- nificance alone, but when the data are combined, they can yield a better understanding of what is known about a given cetacean species (e.g., see Leatherwood and Walker ( 1979) on Lissodelphis borealis). We reviewed previously published records of at-sea sightings of Risso's dolphins in the study area (Table 1). We then examined over 250 previ- ously unpublished reports of sightings of the species in the area from 1958 to 1975 for reliabil- ity of identification. Interviews with observers and *A summary of verified records of observations of Grampus griseus in the northeast Pacific is available from Leatherwood or Perrin. photos assured us of the accuracy of most records. Descriptions of animals with slate gray to nearly all-white coloration, extensive scarring, a bifur- cated melon, and a prominent dark dorsal fin, all distinctive characteristics of Risso's dolphins (Figure 1), aided in verification of the remainder. We discarded questionable records. Many of the reports included estimates of herd size. Since many of these were stated as ranges (e.g., 30-40 animals), we used the midpoint of each estimate. If the estimate was such that the mid- point was ahalfnumber (e.g.,an estimate of 10-15 animals) we took the lower of the numbers (e.g., 12). Some records also included measurements of sea surface temperature at or near the location of the observation. The few of those most important to interpreting apparent trends in the more northern portions of the study area were used, along with annual summaries of temperature trends. Incidental sighting records alone cannot be used to reliably determine trends in distribution, movements, or abundance. Data on sighting effort are essential. Although a few major marine sur- veys have been conducted in the study area, effort is difficult to quantify for most other sources of Table 1. — Previously published at-sea sightings of Risso's dolphins in the eastern North Pacific. In the few cases where collections were reported, as in Orr (1966), herds from which animals were collected are not included as sight records. Source Dale Location Number in school Hubbs(1960) ' 1960 Isia Guadalupe. Mexico Unreported Fiscus and Niggol (1965) 18 Mar 1958 38 30'N.124 15' W ■'Many aninnals " Guiguet and Pike (1965) 22 July 1958 50 00N, 145 00' W 1 Fiscus and Niggol (1965) 27 Jan 1959 36 45' N, 122 33 W 3 Fiscus and Niggol (1965) 4 Feb 1959 35 12 N, 122 05 W 50* Fiscus and Niggol (1965) 8 Feb 1959 35 44 N, 122 43 W 2 Fiscus and Niggol (1965) 18Mar. 1959 41 42 N, 12553W 10 + Fiscus and Niggol ( 1 965) 28 Mar 1959 40°52 N. 125 19 W 5 Guiguel and Pike (1965) 1 1 Oct 1 959 50"OON.145 00 W 6 Guiguel and Pike (1965) 15 Aug, 1960 50 00N, 145 00 W S Guiguel and Pike (1965) 4Sepl 1960 5000 N, 145 00 W 4 Daugliefty(1972) 7 1971 Midway between San Diego (PI Loma) and San Clemente Island, Calil 50 Leatherwood et al (1972) ? 1971 05 00 N, 87 04 W Unreported Leathenivood et al (1972) ? 1971 ll'OO N, 109"30W Unreported Leathen»ood et al ( 1 979) 13 Feb 1974 24'52N, 108 58 W 5-10 Leatherwood etal,( 1979) 13 Feb 1974 2821N, 112'30W 2 Figure l. — Risso's dolphins off south- em California, 1973. The animal's dis- tinctive whitish head (in adults), scar- ring, and high subtriangular dorsal fin enhance the reliability of "incidental" observational records. ( Photo by G. E. Lingle, courtesy Naval Oceans Systems Center, San Diego, Calif.). LEATHERWOOD ET AL-: DISTRIBUTION AND MOVEMENTS OF GRAMPUS GRISEUS data. The following information on effort, from which we feel reliable trends may be determined, exists for the survey programs in the study area. From San Diego to Equator — National Marine Fisheries Service (NMFS) observers, aboard tunaboats working primarily out of San Diego, Calif, surveyed the area from San Diego south to the Equator from 1966 through 1975. The major- ity of effort was concentrated in January and Feb- ruary, declining rapidly through April to no effort in the Commission Yellowfin Regulatory Area (CYRA) of the Inter-American Tropical Tuna Commission by the third quarter (Figure 2). It is evident that there has been very little effort in the nearshore portion of the tropical CYRA during the third and fourth quarters, although there were six chartered cruises between September and De- cember. Far-offshore fishing and research activity continued throughout the year. Because the ves- sels return north to San Diego, running anywhere from 12 mi offshore to beyond the continental shelf off Baja California, effort appears to have been adequate throughout that area to detect major seasonal changes in composition of marine mam- mal fauna. This is the only program for the area for which extensive and quantified data on effort and sightings were available. Since 1968, cruises of the Naval Ocean Systems Center, San Diego (NOSC, formerly Naval Under- sea Center), have examined the continental shelf area off northwestern Baja California during winter and spring (October-December and February -April I. Vessels of the Scripps Institu- tion of Oceanography with marine mammal ob- servers aboard have cruised extensively among the San Diego-Guadalupe Island-Cedros Island triangle for over 30 yr. Southern California Continental Border- land— Survey effort has been extremely heavy over the continental shelf from Ensenada north to Point Conception. Norris and Prescott (1961) re- ported on activities of Marineland of the Pacific, primarily between Catalina and Santa Barbara Islands and the mainland shore near Los Angeles. Leatherwood (1974), Evans (1975), and Leather- wood and Walker ( 1979) summarized NOSC aerial 40° N FIGURE 2.— Relative numbers of hours io"n of observation by NMFS/SWFC obser- vers aboard tunaboats in the eastern tropical Pacific by quarter of year, 1974-75. and ship survey effort in this area for 1968-75. Norris et al. summarized Bureau of Land Man- agement (BLM) aerial and ship surveys during 1975 and 1976. Although variable by month, we consider this combined effort adequate at all sea- sons to have detected trends in composition of marine mammal fauna for the borderland and ad- jacent continental slope. Coverage was particu- larly thorough for the area in 1975, when NOSC and BLM programs overlapped. Offshore Southern and Central California — During 1967 and 1968, cruises of the Smithsonian Institution's Pacific Ocean Biological Survey program surveyed the outer California Channel Islands and the area from lat. 29° to 37° N and seaward to long. 126° W during all quarters of the year. Marine mammal observations by experi- enced personnel were logged for all cruises (R. L. Brownell, Jr. ). Offshore Baja California North to Washing- ton— More recent coverage of the area from lat. 25° N to Washington State, primarily offshore, has been provided by NMFS observers out of the Southwest Fisheries Center (SWFC) placed on commercial albacore boats. In 1971-75, observers 'Norris, K. S., T. P. Dohl, R, C. Guero, L. J. Hobbs, and M W. Honnig. 1976. Cetaceans; numbers, distribution, and move- ments in the southern California Bight. 192 p Draft report to Bureau of Land Management, OCSEAP. from Coastal Marine Laboratory. University of California, Santa Cruz, CA 95060. '"R. L. Brownell, Jr., U.S. National Museum of Natural His- tory, National Fisheries and Wildlife Laboratory, Wash., DC 20560, pers. commun. to Leatherwood June 1975. Table 2. — Months during 1961-75 in which marine mammal watches were maintained aboard one or more albacore vessels (X) in the eastern Pacific (197 1-75), by 5° increments of latitude. A total of 15 vessels were involved. '^^ Lat, C N) May June July August September 45-50 X X 40-45 X X X X 35-40 X X X 30-35 X X X 25-30 X ^ 'Laurs, R M,, and Associates 1972 Report ol )oint National Marine Fisheries Service - American Fishermans Research Foundation albacore sludiesconducteddunng 197t and 1972 Spec Putil SWFC, NMFS NOAA. La Jolla. Cahl , 78 p ^Laurs, R M , and Associates 1973 Report of joint National Marine Fisheries Service ■ American Fisherman's Research Foundation albacore studies conducted during 1973 Spec, Publ SWFC, NMFS, NOAA, La Jolla, Calif, ^Laurs, R M , and Associates 1974 Report of joint National Marine Fisheries Service ■ American Fishermans Research Foundation albacore studies conducted during 1974 Admin Rep 25-74-47, SWFC. NMFS, NOAA, LaJol^,CaJif 'Laurs, R M,, R J Lynn, and R N Nishimcto 1975 Report of joint National Marine Fisheries Service - American Fishermans Research Founda- tion albacore studies conducted during 1975 Spec, Publ, SWFC, NMFS. NOAA, La Jolla, Calif FISHERYBULLETIN: VOL, 77,NO 4 aboard 15 working albacore boats reported marine mammal observations made between May and September from lat. 25° to 46° N (Table 2). Al- though the time and location of their activities varied annually with the albacore migration, coverage was generally restricted to summer and generally moved north as the season progressed. Nearshore Central California — Recent aircraft and ship surveys by the University of California at Santa Cruz have examined the area from about Point Conception north, with the most extensive sampling effort in Monterey Bay. Coverage near Monterey Bay has been year-round (J. D. Hall"). Infrequent cruises by personnel from Hopkins Marine Station and Moss Landing Marine Laboratory have examined the same area (A. Baldridge'^). Oregon and North — With one important excep- tion, recorded survey effort begins to decline as one moves north from California. NMFS albacore-boat observer programs conducted in the summer have extended north of Point Conception (Table 2), and one NOSC marine mammal cruise was conducted from San Diego to Kodiak, Alaska, in April 1971. The primary effort, however, in- cluding extensive coverage of the area from Seat- tle north through the Gulf of Alaska and north- west to the Aleutian Islands and the Bering Sea, has been that by cruises of the NMFS Northwest and Alaska Fisheries Center (NWAFC) Pelagic Fur Seal Research Program. Over the past 10 yr, these cruises have primarily spanned the fall and winter months (C. H. Fiscus'^). Other research cruises by NWAFC have begun in the Seattle area and worked south to southern California in January, February, and March (Fiscus and Nig- gol 1965), while still others beginning in San Francisco have worked south to the Revillagigedo Islands in winter and spring (Rice 1963a, b). The remainder of the sighting effort for the northeastern Pacific is difficult to assess, though it "J. D. Hall, U.S. Fish and Wildlife Service, Office of Biologi- cal Services, 800 A Street, Suite 110, Anchorage, AK 99501, pers, oommun. to Leatherwood August 1975, '^A. Baldridge, Library, Rosenstiel School of Marine and At- mospheric Sciences, University of Miami, Miami, Fla.; present address: Hopkins Marine Station, Pacific Grove, CA 93950, pers. commun. to Leatherwood 1975. '^CH Fiscus, Northwest and Alaska Fisheries Center Marine Mammal Division, NMFS, NOAA. 7600 Sand Point Way NE Seattle, WA 98115, pers. commun. to Leatherwood June 1976. 954 LE ATHERWOOD ET AL,: DISTRIBUTION AND MOVEMENTS OF GRAMPUS GRISEUS is clearly sporadic and has concentrated on coastal regions near population centers. The areas of coverage of the most important programs considered in this report are sum- marized in Figure 3. (The expanded area cover- age of the SWFC tunaboat-observer program is shown in Figure 2). RESULTS Strandings and Collections As nearly as we can determine, 22 strandings and/or collections of specimens of G. griseus have been recorded in the northeastern Pacific since about 1872 (Figure 4). 1. (Published). In the late 19th century, probably in 1872, although the exact date is undeterminable, Charles M. Scammon obtained two lower jaws from Monterey, Calif (Scammon 1874). Dall (1874) used these two lower jaws as the basis for his description of G. sternsii, later rejected as a species by True (1889) because it was indistinguishable from G. griseus (G. Cuvier 1812). One lower jaw and two teeth were depos- ited in the U.S. National Museum (USNM 13021), though True could not make his mea- surements agree with Ball's and tentatively said that it was "apparently neither the No. 1 nor the No. 2 of Mr. Ball's description" (True 1889). The whereabouts of the second mandible or, if True's 180°w 170°w 160°w 150°W 140^; 130°w 120°w 11.0°w 1Q0°W 9,0°w 8p°W -^ ' T^ ' ^ f^^^. 70 N 60"N 40"N r - 20"n FIGURE 3. The eastern North Pacific north of lat. 15° N, showing areas surveyed by m£gor marine mammal survey programs ( 1958-75). See text for details of documentation. 955 FISHERY BULLETIN: VOL. 77. NO, 4 52 N 1 6.(P)?Mav 1964 20°N- 10 N- 01" S. 11.(P)Apr. 1970 9.(P)Apr. 1967 17.(U)Mar 1975 7. (U)May 1966 \ 12.(U)Dec 1970 / 14.(U)May 1973 5.(P)Jun 1963 1. (P)?? 1872 2.(U)?? 1872 3.(U)?1880,S? 16.(U) Dec 1974. 13.(U)??1972 10.(P)Jan 1969 8. (PJMar 1967 15.(U) Jun 1973 100"W 79° W Figure 4. — Dates and approximate locations of strandings and collections of Risso's dolphins in the eastern North Pacific ( 1972-75) numbered in chronological order. The letters in parentheses indicate whether the record has (P) or has not (U) been previously published. observations are correct, both mandibles de- scribed by Dall, are unknown, as is the identity of USNM 13021. 2. (Unpublished). During the same period, exact date also undeterminable, Scammon col- lected a second specimen which he also forwarded to True at the U.S. National Museum (USNM 21163). Like the first, this specimen was report- ably taken in Monterey Bay, Calif. (C. H. Gil- bert"). "C. H. Hubbs. Gilbert undated letter to W. Dall, in possession of 3. (Unpublished). There are three remain- ing specimens from the Pacific coast of North America in the collection of the U.S. National Museum. One (USNM 28066) was purchased from fishermen in Monterey; one (USNM 49895) was taken from an unidentified locality in California; and the third (USNM 49347) was col- lected by C. H. Gilbert, presumably also in Mon- terey. Interestingly, in referring to this last specimen in his correspondance with Dall, Gil- bert (see footnote 14) wrote "In addition to that, I have the complete skeleton of a calf about 6 months old. The species is abundant in Monterey 956 LE ATHERWOOD ET AL.: DISTRIBUTION AND MOVEMENTS OF GRAMPUS GRISEUS Although the specimen was reportedly deposited in the San Diego Natural History Museum, the Museum has no record of the specimen and its Bay and additional specimens could be secured for you if you desire." 4. (Unpublished). In 1959, a single lower jaw identifiable as that of a Risso's dolphin was brought to Hubbs from Isla de Coco ("Cocos Is- land"), lat. 05°32' N, long. 87°04' W. The location of the specimen is currently unknown. 5. (Published). On llJune 1963, a 325.0 cm male apparently dead from gunshot wounds stranded on the beach 0.9 km from Princeton by the Sea, San Mateo, Calif The account of the stranding and its workup includes a description of the specimen, analysis of stomach contents, mis- cellaneous external measurements and organ weights, and some cranial measurements (Orr 1966). The specimen was deposited in the collec- tion of the California Academy of Sciences, San Francisco (CAS 13461, Orr 1966). This account represents the first continental eastern Pacific record of the species published since the late 19th century. 6. (Published). In May 1964, a single 11-ft (334.0 cm) Risso's dolphin was observed alive in Big Bay on the west side of Stuart Island, British Columbia (approximately lat. 50°20' N, long. 125°00' W). The animal was shot, dissected, and discarded. The caudal peduncle and flukes were later recovered and placed in the collection of the British Columbia Provincial Museum (BCPM 907 7) . The animal was reported by the collectors to have been feeding on squid and to have had a heavy intestinal parasite load (Guiget and Pike 1965). 7. (Unpublished). On 13 May 1966, Robert E. Jones (Museum of Vertebrate Zoology, Berkley, Calif.) found a long dead but complete carcass of a stranded male approximately 10 km south of Cape Mendocino, Humbolt County, Calif. The total length of the specimen was 9 ft 7.5 in (293.9 cm). The skull and left flipper were collected and depos- ited at the Humboldt State University (HSC-66- 4). 8. (Published). On 18 March 1967, an adult male stranded alive at Cantomar (Rosarita Beach), 42 km south of Tijuana, Baja California, Mexico (approximately lat. 32°18' N, long. 117°00' W). It was taken to Sea World in San Diego, Calif., where it survived for a short time. A photo of this animal appeared in the San Diego Union 28 March 1967 on page B-5. This specimen was 307.0 cm long (Harrison et al. 1969) and weighed 850 lb (386 kg) (measured by Hubbs). whereabouts are unknown. 9. (Published). On 20 April 1967, a 258 cm male apparently dead from a gunshot wound in the head was found stranded at Makkaw Bay, Wash. (lat. 48°19'N, long. 124°40'W).Thedolphin had been dead an estimated 1 mo. Its stomach contained squid beaks and fragments. The skull and postcranial skeleton were preserved in the collection of NWAFC, NMFS, NOAA, Seattle, Wash. (Stroud 1968). 10. (Unpublished). On 21 January 1969, a 309 cm adult male stranded alive at Imperial Beach, San Diego County, Calif The animal was taken to Sea World, San Diego, where it died the night of 21-22 January 1969. The complete skele- ton was collected by Raymond M. Gilmore and deposited in the San Diego Natural History Mu- seum (SDNHM 21554) (R. M. Gilmore'^). 11. (Published). On 17 April 1970, a 266 cm male washed ashore on the east side of Vargas Island, British Columbia (lat. 49°10' N, long. 125°58' W). The skull, axial skeleton, and bones from one pectoral appendage were collected and placed along with a complete photo series (Photofile No. 51) in the collection of the Verte- brate Museum, Department of Zoology, Univer- sity of British Columbia ( UBC 9464 ) . The report of the stranding includes external measurements, organ weights, and an analysis of stomach con- tents (Hatler 1971). 12. (Unpublished). On 26 December 1970, a male neonate was collected from the beach in Shelter Cove, Humboldt County, Calif. The entire specimen (Field No. WJH 71-1) was deposited at the Humboldt State University (HSU 1620) (W. J. Houck ). 13. (Unpublished). In August of 1970, re- sponding to a radio call from local fishermen, F. Brocata and B. Falcone of Marineland of the Pacific investigated a call about an "albino" pilot whale which had been harpooned by fishermen between Santa Cruz and Santa Rosa Islands, Calif When Marineland's research boat, the MV Geronimo, approached the whale, which turned out to be a Risso's dolphin, the animal managed to "R. M. Gilmore, Research Associate, San Diego Natural His- tory Museum, San Diego, CA 92112, pers commun. to Leather- wood 1975. '8W. J. Houck, Humboldt State University, Areata, CA 95521, pers. commun. to Leatherwood 1975. 957 FISHERY BULLETIN; VOL. 77. NO. 4 pull out the harpoon and swim away (W. A. Walker''). 14. (UnpubHshed). On 20 May 1973, an im- mature female was found stranded on southeast Farallon Island, off San Francisco, Calif (approx- imately lat. 37°42' N, long. 123"00' W). The avail- able measurements for the specimen are as fol- lows: total length 270 cm, dorsal fin 27.5 cm, axilla-tip of flipper 5 cm, origin of flipper to tip of lower jaw 46.5 cm, anus-tip of lower jaw 178 cm, width of flukes 62 cm. The specimen was not col- lected (R. L. Brownell, Jr. see footnote 10). 15. (Published). On 18-19 June 1973, four females and a fifth animal of undetermined sex, all about 13 ft long (400 cm) and weighing 500-600 lb (73-77 kg) stranded alive at Punta Buffeo, Baja California, about 100 mi (160 km) south of San Felipe on the northwest coast of the Gulf of California (approximately lat. 29°55'20" N, long 114"'26'20"W). All five animals were towed out to sea (dead), and no materials were retrieved (Leatherwood et al. 1979). 16. (Unpublished). On 8 December 1974, a female stranded alive at the Manhattan Beach Pier, Los Angeles, Calif, (approximately lat. 33°55' N, long. 118°25' W). The animal was alive when it was collected by Marineland of the Pacific but died almost immediately after collection. It was photographed, measured, and necropsied at the Los Angeles County Museum of Natural His- tory, where it is currently held as specimen LACM 47145. Detailed findings will be reported elsewhere (W. F. Samaras and D. R. Patten ). 17. (Unpublished). On 10 March 1975, a 348 cm female stranded alive at Port Discovery, Wash., in the Strait of Juan de Fuca (about lat. 48'02' N, long. 122°52' W), perhaps driven ashore by killer whales. The animal was recovered alive and taken to Seattle Marine Aquarium where it died on 11 March. The complete skeleton is in the collection of the NWAFC (No. 1975-1). At-Sea Sightings We found 16 previously published records of at-sea sightings of Risso's dolphins for the study area (Table 1) and 194 additional previously un- published reliable records (see footnote 8) (Figure 5). When examined by latitude (Figure 5), the distribution of sightings falls into three major groups — those from the Equator to approximately lat 20° N (Zone I); those thence north to approxi- mately lat. 43" N (Zone II); and those north of lat. 43° N (Zone III). Zones I and II are separated by a broad region characterized by very few sightings, centering at about lat. 20° N and extending from lat. 14° to 29° N. All except two sightings in that area of low density were within 60 mi of the Mexi- can coast, though seaward of the continental shelf. The separation between Zones II and III is less pronounced, centering at lat. 43° N emd extending from lat. 38° to 45° N. Regarding seasonality, records in Zone I are al- most exclusively limited to first and second quar- ters, and the majority of those from Zone III are from the period July through October. Both of these apparent seasonal fluctuations result from the biases in observation effort discussed above. Those from Zone II are distributed throughout the year. Records from north of Point Conception (lat. 35° N) are most numerous in the third quarter (Figure 6). Off southern California (approximately lat. 31°-35° N), records from 1959 to 1975 were sporadic, reaching a peak of 11 in 1974 (Table 3). Until 1971 the majority of sightings for the area were seaward of the 100-fathom curve; however, beginning in 1971 and increasing in frequency through 1974 (9 of 11) and 1975 (3 of 3), most sightings were over the continental shelf Although surface water temperatures were not reported for most sightings, Risso's dolphins have been sighted in waters ranging from 28° to 10° C. Sightings in Zone I cover the full range of temper- atures reported for the area. Sightings off south- ern California in 1974 and 1975 were associated with water temperatures above 19° C. Of the 22 Table 3. — Summary of sightings of Risso's dolphins off southern California labout lat. 3r-36° Nl. 1959-75, showing the frequency of encounter over and seaward of the continental shelf. "W. A. Walker, 21 Barkentine Road. Rancho Palos Verdes, CA 93704, pers. commun. to Leatherwood 1975. "W. F. Samaras. Research Associate, and D. R. Patten, Curator, Department of Mammals. Los Angeles County Museum of Natural History, Los Angeles, CA 90007, pers. commun. to Leatherwood 1975. Total no Over continental Seaward of Year sightings shell continental shelf 1959 1 1 0 1960 1 1 0 1965 1 0 1 1966 3 0 3 1967 9 0 9 1968 3 1 2 1971 4 4 0 1972 4 4 0 1973 3 2 1 1974 11 10 1 1975 3 3 0 958 \THERWOOD ET AL : DISTRIBUTION AND MOVEMENTS OF GRAMPUS GRISEUS a Z E < I D o laniiivi 959 nSHERY BULLETIN: VOL 77. NO 4 TIME OF YEAR Figure 6. — Frequency of sightings of Risso's dolphins by month in Zone II in the eastern North Pacific (defined in Figure 5). most northern records, the 4 from February to April were associated with water temperatures of 12° and 13° C, unusually high temperatures for the season. Of the records, 12 published and 191 unpub- lished provided usable estimates of herd sizes. Numbers of animals sighted ranged from 1 to 220, about a geometric mean of 10.65. About 75% of the groups contained fewer than 20 animals (Figure 7). No statistically significant differences could be demonstrated among herd sizes from different zones (I, II, III) or different seasons (Mann- Whitney U Test, a = 0.05). SUMMARY AND DISCUSSION Risso's dolphins are clearly abundant and widely distributed year-round in tropical and warm temperate waters of the northeastern Pacific. -I 1 1 r- O z 60 50. 40 DETAIL Geometric Mean 10. 6S rm N= LSI ■'■'"V''"'"i;i'''ti, — y-'-i Ei-iv: 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 Herd Size. No of Animals N = 1R4 jpn. 10(1 120 140 Herd Size, No of Animals 160 ISO 200 220 240 Figure 7.— Distribution of estimated "herd" sizes of Risso's dolphins, in the eastern North Pacific (1958-75). Inset gives detail for herd sizes with ■ 30 animals. 960 I ATHERWOOD ET AL ; DISTRIBUTION AND MOVEMENTS OF GRAMPUS GRISEUS The rather dramatic decrease in the number of sightings north of about lat. 13° N and the very limited number of offshore sightings in the broad belt from about the latitudes of Cedros and Guadalupe Islands south to approximately Acapulco, appear to reflect an £u-ea of apparent very low density in the species' distribution, since survey effort in the area was heavy even where no sightings were reported. Pronounced distribu- tional gaps in portions of the same ocean area have been documented for Delphinus delphis (Evans 1975) and Stenella spp. (Perrin 1975). Risso's dolphins appear to occur year-round in offshore waters from about central Baja California northward to about San Francisco. Movements onto the continental shelf of southern California are seasonal and appear to be related to surface temperatures. For example, records of Risso's dol- phins over the continental shelf were more numerous in 1974 than in previous years since 1968, despite an equal effort, and more numerous than in 1975, despite increased survey effort in that year. In 1974 and 1975, surface temperatures were unusually high (California Cooperative 19 Oceanic Fisheries Investigations ). A poorly defined area of apparent low density in distribution, centering at about lat. 43° N, proba- bly reflects generally poor sampling in the area from about San Francisco north to the latitude of Seattle and not any real change in the species' density there. Records from lat. 45° to 51° N are most abundant during summer and are primarily ofT the conti- nental shelf. Like the movements onto the south- ern California continental borderland and those into more northern latitudes, this change appears to relate to warming of surface waters. The reports of abundance near Monterey in the late 19th century seem inconsistent with modern records of low abundance in the area. It may well be that this indication of the common occurrence of the species in Monterey Bay in the 1870's and 1880's represents a holdover of the occurrence of tropical animals in central California in the 1850's (Hubbs 1948). This being the case, the movement of Risso's dolphins north and inshore in some abundance during that period is consistent with behavior in 1974 and 1975 off southern California. Southward movements of the Ball's porpoise. "California Cooperative Oceanic Fisheries Investigations. Unpublished data in files of CalCOFl at the Southwest Fisheries Center La Jolla Laboratory, National Marine Fisheries Service, NOAA, La Jolla, CA 92038. Phocoenoides dalli. into southern California (Nor- ris and Prescott 1961) and seasonal movements of the right whale dolphin, Lissodelphis borealis (Leatherwood and Walker 1979), and the Pacific whitesided dolphin, Lagenorhynchus obliquidens (Leatherwood and Reeves 1978), in the eastern North Pacific have been similarly linked to sea- sonal changes in water temperature. Despite extensive survey effort in the northern temperate and Arctic eastern Pacific, Risso's dol- phins have not been reported north of lat. 51° N. Therefore, since it provided no new data, the summary report of the species' occurrence in the Bering Sea (Clark 1945) is of doubtful accuracy. Considered together, these records tend to sup- port Davies' (1963) summary of the species' dis- tribution, at least in the northeast Pacific. It ap- pears, as he contended, to be primarily tropical, extending its range poleward to overlap with temperate forms, though not penetrating as far into high latitudes. Perhaps the most important point supported by these records is the dynamic nature of distribution of this (and probably other) marine mammal species. In addition to well- documented short-term and seasonal movements, there appears to have been a long-term fluctuation in the boundries of species' ranges, apparently in responses to long-term environmental changes. ACKNOWLEDGMENTS The authors thank all the following institutions and individuals for contributing unpublished data: Fisheries Research Board of Canada (MaCaskie from Pike's records); University of Southern California (Capt. F. Zeischenhene); Mo- clips Cetological Society (K. C. Balcomb); North- west and Alaska Fisheries Center, NMFS, NOAA (C. H. Fiscus, R. L. DeLong, and D. W. Rice); Uni- versity of California, Santa Cruz (T. P. Dohl, J. D. Hall, and L. J. Hobbs); U.S. Fish and Wildlife Service (R. L. Brownell, Jr.); Museum of Verte- brate Zoology, Berkeley (R. E. Jones); Humboldt State College (W. J. Houck; San Diego Natural History Museum (R. M. Gilmore); Los Angeles County Museum (W. A. Walker, D. R. Pattern, and W. A. Samaras); Hopkins Marine Station (J. E. Vandevere); University of Oregon (T. Wahl); USAAJSSR Marine Mammal Cooperative Pro- gram (D. W. Rice and W. E. Evans); and Hubbs-Sea World Research Institute (W. Evans and J. Jehl, Jr.). J. D. Hall, F. G. Wood, M. Schaeffer, and D. W. Rice critically reviewed the manuscript. 961 FISHERY BULLETIN; VOL 77, NO LITERATURE CITED Aguayo, a. 1975. Progress report of small cetacean research in Chile. J. Fish. Res. Board Can 32:1123-1143. ALPERS, A. 1960. A book of dolphins. J. Murray, Lond., 147 p Baker, A.N. 1974. Risso's dolphin in New Zealand waters, and the identity of "Pelorus Jack." Rec. Dom. Mus. Wellington 8:267-276. Barnard, K.H. 1954. A guidebook to South African whales and dolphins. S. Afr. Mus., Cape Town, Guide 4:1-3. Bazeauti,A. 1910. Grampus griseus (G. Cuv.) Monit. Zool. Ital. 21:85-95. Caldwell, D. K., M. C. 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Fish Game, Sacramento, Calif., 87 p. Davies,J. L. 1963. The antitropical factor in cetacean specia- tion. Evolution 17:107-116. DAWBIN.W. H. 1966. Porpoises and porpoise hunting in Malaita. Aust. Nat. Hist. 15:207-211. ELLERMAN, J. R., T. C. S. MORRISON-SCOTT, AND R. W. Hayman. 1953. Southern African mammals, 1758-1951. Br. Mus. (Nat. Hist.) Lond, 363 p. Evans, W. e. 1975. Distribution, differentiation of populations, and other aspects of the natural history of Delphinus delphis Lmnaeus in the northeastern Pacific Ph D. Thesis, Univ. California, Los Ang., 145 p. FISCUS, C. H., AND K. NIGGOL. 1965. Observations of cetaceans off California, Oregon, and Washington, U.S. Fish Wildl. Serv., Spec. Sci. Rep, Fish. 498, 27 p. Gaskin.de. 1968. The New Zealand cetacea. N.Z Fish. Res Div.. Fish. Res Bull. 1.92 p. 962 1972. Whales dolphins and seals. Heinemann Educ. Books.N.Y., 200p. GUIGUET. C. J., AND G. C. PiKE. 1965. First specimen record of the gray grampus or Risso dolphin. Grampus griseus (Cuvier) from British Colum- bia. Murrelet 46:16. GUNTER, G. 1954. Mammals of the Gulf of Mexico. In P. S. Galtsoff (coordinator), Gulf of Mexico; its origin, waters, and marine life, p, 543-551. U.S. Fish Wildl. Serv., Fish. Bull. 89. HARRISON, R.J. 1969. Reproduction and reproductive organs. In H. T. Andersen (editor). The biology of marine mammals, p. 253-348. Academic Press, N.Y. HATLER, D F. 1971. A Canadian specimen of Risso's dolphin. Can. Field-Nat. 85:188-189. Hector, J. 1873. Notes on the whales and dolphins of the New- Zealand seas. Ann. Mag. Nat. Hist., Ser. 4, 11:104-112. HERSHK0V1TZ,P. 1966. Catalog of living whales. Bull. U.S. Natl. Mus. 246, 259 p. HUBBS.C.L. 1948. Changes in the fish fauna of western North America correlated with changes in ocean tempera- ture. J, Mar. Res. 7:459-482. 1960. The marine vertebrates of the outer coast. In Symposium: The biogeography of Baja California and ad- jacent seas. Part 11, Marine biotas, p 134-147, Syst, Zool. 9. 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Monogr., Bull. 97(58), 38 p. 963 DESCRIPTION OF LARVAL AND JUVENILE RED SNAPPER, LUTJANUS CAMPECHANUS^ L. Alan Collins, John H. Finucane, and Lyman E. Barger* ABSTRACT Identification and description of the red snapper, Lutjanus campechanus, family Lutijanidae, were based upon the general morphology, meristic characters, head spination, and pigmentation of 18 larval and 6 juvenile specimens, 4.0-22.4 mm standard length. These 24 specimens were selected from a total of 226 larval and juvenile L. campechanus which were collected mainly along the Texas coast from 1975 to 1977 . Lutjanids <4.0 mm lacked presently recognizable characters that are diagnostic at the species level. The key to the development of the series was a unique meristic count. Some other useful diagnostic characters were: small serrations on the anterior margin of the pelvic spine in specimens of 4.8-12.4 mm, and a long unbroken soft ray immediately adjacent to the pelvic spine in specimens of 4.8-10.6 mm. A brief comparison was made between L. campechanus and other lutjanid larvae and juveniles. The red snapper, Lutjanus campechanus (Poey), family Lutjanidae, is one of the most important commercial and recreational fish species in the Gulf of Mexico (Bradley and Bryan 1975; Beaumariage and Bullock 1976). Numerous biological and fisheries publications concern the adult of this species. Apparantly only one short publication has dealt with the early life history of L. campechanus however. Arnold et al. (1978) de- scribed the spawning of this species in captivity. The primary purpose of the present paper is to describe the larval and juvenile development of L. campechanus. METHODS A total of 226 larvae and juveniles (4.0-22.4 mm SL, standard length) of the species were captured by four different methods, which are listed in Table 1. The bongo and neuston net sampling was done according to Marine Resources Monitoring, Assessment and Prediction specifications (Jossi et al. 1975) and was made at a vessel speed of 2.8 km/h (1.5 kn). The largest specimen was preserved in 40% isopropyl alcohol. Other larvae and juveniles were preserved in buffered 5% Formalin.^ Some larval 'Contribution No. 79-32PC, Southeast Fisheries Center Panama City Laboratory, National Marine Fisheries Service, NOAA. ^Southeast Fisheries Center Panama City Laboratory, Na- tional Marine Fisheries Service, NOAA, 3500 Delwood Beach Road, Panama City, FL 32407. ^Reference to trade names does not imply endorsement by the National Marine Fisheries Service, NOAA. and juvenile specimens were stained with alizarin-red to aid in measuring £md in counting body parts. A dissecting microscope with an ocular mi- crometer was used to make standard measure- ments (Laroche 1977) on 24 specimens. The level of accuracy for micrometer measurements was 0.01 mm for measurements <1 mm and 0.1 mmfor measurements >1 mm. All measurements of body length refer to standard length unless otherwise noted. Standard length was defined as the distance from the tip of the snout to the posterior tip of the notochord (before hypural formation) and the tip of the snout to the posterior margin of the hypurals (after hypural formation posterior to the notochord tip). Larvae were defined as individuals which had absorbed the yolk sac but which had not completed differentiation of adult fin spine and ray comple- ments. Juveniles were defined as sexually imma- ture individuals having adult fin complements of spines and rays. We used the serial or dynamic method of tracing certain characters back from juvenile to larval specimens (Moser and Ahlstrom 1970). IDENTIFICATION The genus Lutjanus is the most speciose in the family Lutjanidae. Lutjanus campechanus is 1 of 10 species of that genus which occur in U.S. waters <200 m deep (Bailey et al. 1970). Lutjanus cam- pechanus occurs along the continental shelf of the Manuscnpt accepted May 1979- FISHERY BULLETIN VOL 77. NO 965 FISHERY BULLETIN VOL 77, NO. 4 Table l. — Catch data arranged chronologically for larval and juvenile Lutjanus campechanus from the Gulf of Mexico and adjacent waters. Location Depth range (m) Latitude (N) Longitude (W) Period Gear/tow No. col- lected Size (mm SL) Temp. rc) Salinity (V) SI. Andrew Bay, Fla 6 30'09' 85-41 ' July 1973 10.7 headrope otter trawl: 2.5 cm stretched mesh in cod end/bottom tow 1 22.4 27.0 33.7 South Texas continental shelt 42-131 2754 26 57' to to to 961 9' 96 48 Sept 1975 1 m diameter plankton net 0 250 mm mesh; single oblique tow 59 4 0-12 4 19 7-29 2 33 7-36 4 2n7' 96 23' 26 10' 96 24 42-183 27 54' 26' 57' to to to 96 19' 96 48' July-Sept. 1976 61 cm diameter bongo nets 0 505, 0 333 mm mesh/double oblique tow 57 4 1-106 17.4-29.7 34 7375 2ri5' 96 18 26' 10' 96 39 49-131 27 30' 2717' to to 96 44 96 23 May, July-Sept , Nov 1977 As above 17 4.2-5.8 17.3-29.8 33 4-36.5 26' 10 96 24 Buccaneer Oil Field. near Galveston, Tex. 17 28 52' 94 '40' July 1977 As above, also 1 0 ■ 0 5 m, 0 505 mm mesh neuston net 92 4 0-7 3 23 0-26 0 32 8-35.5 Atlantic coast of the United States and in the Gulf of Mexico (Rivas 1966). The taxonomy of this species has undergone several revisions. Three specific names have been used for the Gulf of Mexico red snapper in recent literature: L. cam- pechanus, L. aya, and L. blackfordii (Anderson 1967). We used the American Fisheries Society (Bailey et al. 1970) nomenclature. To date, the only lutjanid that has had its larval stages described in the literature is Rhomboplites aurorubens (Laroche 1977), Identification of lu- tjanid larvae is difficult unless a series of the lar- vae and juveniles is available for study. Juveniles of only three Atlantic species o{ Lu- tjanus and one specimen of Symphysanodon have been illustrated. Illustrations of 10,5, 14,4, 19.9, and 48.5 mm juvenile L. griseus have been pre- sented by Starck (1971). A 17.8 mmL. synagris or L. mahogoni was described and partially sketched by Heemstra (1974). A 14.4 mm fork length juvenile identified as Lutjanus sp. was illustrated by Fahay (1975). A 20 mm juvenile Symphysano- don was partially illustrated in Fourmanoir (1973). Identification of the present series of L. cam- pechanus is based upon the meristic characters of the juveniles. Six juveniles (8.0-22.4 mm) had the meristic complement of adultL.campec/ra^iiis and formed the key to the series. These counts included 24 myomeres; X, 14 dorsal fin spines and rays; III, 9 anal fin spines and rays; 9+8 principal caudal fin rays; 16-18 pectoral fin rays; I, 5 pelvic fin spine and rays. These counts have also been reported for L. analis andL. aya (Miller and Jorgenson 1973). However, Anderson ( 1967) reported thatL. analis has a maximum of 8 anal fin soft rays. Rivas (1966) reviewed the L. campechanus complex of "red snappers" and stated that the species described as Bodianus aya by Bloch in 1790 was probably not a lutjanid. Rivas recognized only two species in the complex commonly referred to as red snappers: L. campechanus, from the Gulf of Mexico and the South Atlantic coast of the United States, and L. purpureus, from the Caribbean Sea and south- eastward along the coast of the Guianas, and probably to Brazil. Rivas (1966) synonymized L. blackfordii with L. campechanus . Therefore, L. campechanus is the only species occurring in the northern Gulf of Mexico which has the meristic complements observed in our specimens. DESCRIPTION Although we collected many lutjanid larvae, only those ^4.0 mm were identifiable as L. cam- pechanus. Lutjanids <4.0 mm lacked presently recognizable characters diagnostic at the species level and, therefore, were not described. This gen- 966 I OLLINS ET AL : LARVAL AND JUVENILE RED SNAPPER eral lack of development has also been observed in laboratory-reared larvae of L. campechanus <4.0 mm (Rabalais'*). Pigmentation Diagnostic melanophores occurred on various regions of the specimens (Table 2). The first melanophore to appear on the head was on the dorsal midline over the midbrain. The dorsal sur- face of the peritoneum was nearly covered by large melanophores in all specimens. The presence and amount of pelvic fin pigment was variable. Fading of the pigment in some specimens was probably due to the preservation and/or handling. When pelvic fin pigment was present in specimens <7.3 mm, it was located only on the fin membrane. Our undamaged specimens s=7.3 mm had pelvic fin melanophores primarily on the most anterior soft ray (Figure ID) and/or in the fin membrane (Fig- ure 2B). The largest juvenile had the most pigmentation (Figure 2C). Four vertical bars made up of small melanophores were located between the head and the caudal section. All fin membranes between the *N. Rabalais, University of Texas Marine Laboratory, Port Aransas, TX 78373, pers. commun. October 1978. 2d and 10th posteriormost spinous dorsal rays had three melanophores between each spionous ray. The soft dorsal fin had five melanophores on the fin membranes between the 7th and 13th pos- teriormost rays. An additional melanophore was present near the distal end of the dorsal principal caudal rays. Unfortunately, specimens were not available to link the development of pigmentation between 12.4 and 22.4. Fin Formation Dorsal and pelvic fins were the first to begin development in L. campechanus (Figure lA), fol- lowed by caudal, anal, and pectoral fins. The adult complement of fin spines and rays was completed in the following order: caudal (principal rays only), pelvic, pectoral, dorsal, and anal (Table 3). Dorsal Fin The smallest illustrated specimen had de- veloped only the five anteriormost dorsal spinous rays (Figure lA). Most dorsal soft rays seemed to develop simultaneously, with the exception of the posteriormost soft rays which developed last. The total adult number of dorsal fin rays ( 24 ) was pres- ent at 4.9 mm, with the 2 posteriormost dorsal Table 2. — Number of melanophores on regions of larval andjuvenileLutjanus campechanus. When available, several larvae of a given size were used in determining the number of melanophores. Head Gut Dorsal and pelvic Caudal On ventral On Fin On On Internal, midline ventral membrane anterior Internal, ventral On lateral to anterior Internal. midline between portion near midline ventral notoctiord Over Over On to ventral over dorsal just 2d and 3d of posterior of principal and anterior SL fore- mid- oper- tip of surfaces of anterior dorsal pelvic base ct myomere caudal to point (mm) brain brain culum cleitfirum peritoneum to anus spines fin anal fin no 22-25 rays of flexion 4.0 0 1 0 5-10 1 1-2 1-2 1 0 4.2 0 1-2 0 5-10 1 1-2 0-2 1 0 4.6 0 1 0 5-10 1 2 0-2 1 0 4.7 0 2 0 5-10 1 2 0-2 1 0 4.8 0 2 0 5-10 1 3-7 1-2 1 0 4.9 0 1-2 0 5-15 0-1 3-6 0-2 1 0 5.4 0 1 0 5-15 0-1 1-8 0-1 1 0 5.5 0 1-2 0 5-15 0 3-5 0-3 1 0 6.1 0 2-3 0 5-15 0 2-8 2-3 1 0-1 6.2 0 3-5 0 5-15 0 3-8 1-2 1 0-1 6.3 0 1-2 0 5-15 0 3-8 1-2 1 0-1 6.4 0 1-6 0 5-15 0 3-8 0-2 1 0-1 6.5 0 1-3 0 5-15 0 3-8 1-3 1 (') 6.6 0 3-4 0 5-15 0 1-8 0-8 1 0-1 7.3 0 2 0 5-15 0 12-20 14 1 7.4 1 6 2 5-15 0 2 (') 1 7.5 3 9 2 5-15 0 1 3 1 7.6 (') (') (') (') 5-15 0 3-8 (') 1 '8.0 1 13 1 5-15 0 3 (') 1 29.0 3 17 2 0 5-15 0 3-8 (') 1 29.5 6 30 2 0 5-15 0 3-8 3-8 1 MO-6 3 34 3 0 5-15 0 3-8 3-8 1 M2.4 7 36 1 0 5-15 0 10 6 1 '22 4 ca 30 ca 100 2 0 ca 20 0 3 (') 1 3 4 2 'Specimen was damaged and no count was taken ^Juvenile 967 FISHERY BULLETIN: VOL. 77. NO 1 spines represented by 2 soft rays (Table 3). At 5.4 mm the anteriormost soft ray became a spine. All specimens s=7.5 mm had X, 14 dorsal fin spines and rays. The second dorsal spine was the longest ray in the dorsal fin in specimens 4.0-12.4 mm. In the 22.4 mm specimen, all dorsal fin rays except the first spine were about equal in length (Figure 2C). Serrations did not appear on the dorsal spines of L. campechanus between 4.0 and 22.4 mm. Pelvic Fin The smallest larva had not yet developed pelvic fin soft rays but had developed the pelvic spine (Figure lA). The pelvic spine was smooth on the anterior margin on 4.0 and 4.7 mm specimens. Between 4.7 and 4.8 mm this spine developed —30 fine serrations along its anterior margin. All lar- vae and juveniles 4.8-12.4 mm had these serra- tions. The number of serrations generally in- 968 COLLINS ET AL. LARVAL AND JUVENILE RED SNAPPER FIGURE 1— Developmental stages of the red snapper,iu(;anus campechanus. larvae drawn using a camera lucida: A, 4.0 mm SL;B,4.2 mm; C, 4.9 mm; D, 7.3 mm. 969 FISHERY BULLETIN VOL. 77, NO, 4 creased with specimen size between 4.8 and 12.4 mm. The 12.4 mm juvenile had ~60 fine serrations on the anterior margin of each of its pelvic spines. Between 12.4 and 22.4 mm these serrations were lost. Three distinct pelvic rays appeared on the 4.2 mm larva in the anterior portion of the previously undifferentiated finfold (Figure IB). Between 4.6 and 5.5 mm the pelvic fin attained the adult com- plement of 1 spine and 5 soft rays (Table 3). The pelvic spine was long. It extended to or beyond the anus in all but the smallest and largest specimens, 4.0 and 22.4 mm, respectively (Figures 1, 2). The pelvic soft ray closest to the pelvic spine was always the longest pelvic fin ray. Apparently this longest ray may be easily broken off during collection and handling. Approximately half of all specimens had this ray broken off. The unbroken, anteriormost pelvic ray in specimens 4.8-10.6 mm extended at least to the center of the anal fin base (Figure IC). Specimens of 6.4, 7.3, and 9.5 mm had an unbroken ray that extended posteriorly beyond the center of the emal fin base (Figures ID, 2A). Caudal Fin Caudal fin formation began at -4.2 mm (Figure IB, Table 3). The most ventral principal rays and those near the tip of the urostyle were the last to develop. Between 4.2 and 4.7 mm the adult com- plement of 17 (9 dorsal and 8 ventral) principal caudal rays developed. Notochord flexure occurred between 4.7 and 4.9 mm (Table 3). Anal Fin At 4.7 mm, 8 anal rays were present as 2 spines and 6 soft rays in the anteriormost part of the fin (Table 3). The posteriormost rays formed last. By 4.9 mm the adult complement of 12 rays was pres- 970 COLLINS ET AL . LARVAL AND JUVENILE RED SNAPPER FIGURE 2.— Developmental stages of the red snapper. Lutj anus campechanus, juveniles drawn using a camera lucida: A, 9.5 mm SL; B, 12.4 mm; C, 22.4 mm. 971 FISHERY BULLETIN; VOL. 77. NO 4 Table 3. — Meristic characters and notochord flexure of larval and juvenile Lutjanus campechanus. Pr ncipal SL (mm) caudal fin rays Dorsal fi n Anal fin Pectoral fin Pelvic lin Upper Lower Spines Rays Spines Rays Rays Spines Rays Notochord 4.0 0 0 V 0 0 0 0 0 Straigfil 42 4 4 VII 0 0 0 (') 3 Straight 46 5 5 VI 0 0 0 (') 3 Straight 4.7 9 8 VII 8 II 6 (') 4 Flexed 4.8 9 8 VIII 11 II 8 (') 4 Straight 4.9 9 8 VIII 16 II 10 (') CI Flexed 5.4 9 8 IX 15 II 10 (") CI Flexed 5.5 9 8 IX 15 II 10 (') 5 Flexed 6.1 9 8 IX 15 II 10 (') 5 Flexed 6.2 9 8 IX 15 II 10 (') 5 Flexed 6.3 9 8 IX 15 II 10 (') 5 Flexed 6.4 9 8 IX 15 II 10 (') 5 Flexed 6.5 9 8 IX 15 II (') (') 5 Flexed 6.6 9 8 IX 15 II 10 14 5 Flexed 7.3 9 8 IX 15 II 10 16 5 Flexed 7.4 9 8 IX 15 II 10 17 5 Flexed 7.5 9 8 X 14 II (') 16 5 Flexed 7.6 9 8 X 14 II 10 17 5 Flexed '8.0 9 8 X 14 III 9 17 5 Flexed '9.0 9 8 X 14 III 9 18 5 Flexed '9.5 9 8 X 14 III ■ 9 18 5 Flexed '10.6 9 8 X 14 III 9 18 5 Flexed '12.4 9 8 X 14 III 9 18 5 Flexed '22.4 9 8 X 14 III 9 17 5 Flexed ^An accurate count was not possible. 'Juvenile ent in the form of 2 spines and 10 soft rays (Figure IC). The transformation of the anteriormost soft ray into the third anal spine occurred between 7.6 and 8.0 mm and marked the end of the larval period. Anal spines were not serrated. Pectoral Fin The 4.0 mm larva had only a pectoral finfold (Figure lA). Between 4.0 and 6.5 mm ray de- velopment began, but ossification was not com- pleted and the exact number of rays was difficult to determine. The 6.6 mm larva had 14 pectoral rays, and 2 more rays were added by 7.3 mm. The 16 rays on the 7.3 mm specimen were within the 16-18 range for adult pectoral rays (Rivas 1966). The number of pectoral rays on specimens 7.3-22.4 mm varied from 16 to 18 (Table 3). Squamation Scales were present on the 22.4 mm specimen only. An accurate lateral line scale count was not possible. Head The head of the larval and juvenile L. cam- pechanus was large, ranging between 32.5 and 44.9^r SL (Table 4). Head size (head length as percent of SL) generally increased in larvae and Table 4. — Measurements and body part proportions for larval and juvenile Lutjanus campechanus. Snout to Eye SL Head length anus length Body depth diameter (mm) (mm) (% SL) (mm) (% SL) (mm) (% SL) (mm) % SL, 40 13 325 19 47 5 1 3 32,5 044 11,0 42 1 6 38,1 23 54 8 1 5 35,7 0 51 12.1 4fi 1 7 370 23 500 15 326 053 115 4 7 19 40,4 26 553 18 38 3 0 59 126 48 18 375 28 58,3 1 9 400 0 66 138 4,9 22 449 30 61 2 20 40.8 056 114 54 2,4 44 4 33 61 1 23 42,6 0.77 143 55 23 41 8 3,4 61 8 21 38,2 0 70 12,7 fi 1 24 393 36 590 23 377 0-78 12,8 62 26 41 9 39 629 2,4 38 7 0,79 127 6 3 2,6 41 3 38 60.3 25 397 079 125 64 24 37,5 38 59-4 26 40,6 0 79 123 65 26 40 0 4 1 63 1 2.7 41 5 083 128 66 28 42,4 43 65 1 29 43,9 087 132 73 2,7 37,0 43 589 28 384 095 13,0 7 4 3 1 41 9 47 63,5 31 41 9 0 93 12 6 75 30 400 4 7 62 7 3 1 413 097 129 76 3 1 40 8 4,7 61 8 3,0 395 098 12-9 'RO 32 40,0 51 638 3,3 41,3 0.99 12.4 '90 3,3 367 58 64 4 33 367 1,2 13 3 '95 3,5 36.8 5,9 62 1 34 358 1,2 126 '10,6 4,0 377 6,7 63,2 40 37 7 1,2 11,3 '1?4 48 387 79 63.7 47 379 1,4 113 '224 78 34.8 15 1 674 8,1 362 27 12,1 decreased in juveniles. The smallest and largest specimens had the smallest head proportions, 32.5% on the 4.0 mm larva and 34.8% on the 22.4 mm juvenile. The head was proportionally largest, 44.9 and 44.4%, on the 4.9 and 5.4 mm larvae, respectively. Head length was about equal to body depth in all specimens. Head length ranged from 32.5 to 44.9% SL and body depth from 32.5 to 43.9% SL. 972 COLUNS ET AL,: LARVAL AND JUVEMLE RED SNAPPER Spines were found on the preopercle, pos- terodorsal margin of the operculum, posttemporal, and supracleithrum. Serrations developed on the supraocular crest. The preopercular spines developed in two rows, one anterior to the preopercular margin and one along the preopercular margin (Figures 1, 2). Both rows had vertical and horizontal segments. The vertical segments were situated approximately perpendicular to the body midline, and the hori- zontal segments were situated approximately parallel to the body midline of the fish. The ante- riormost row had 3-6 spines (1-3 vertically and 2-3 horizontally) in the 4.0-22.4 mm specimens. The number of anterior row spines decreased in the largest specimens. The row along the preopercular margin had 5-27 spines (2-18 vertically and 3-9 horizontally) in the 4.0-22.4 mm specimens. The number of both vertical and horizontal preopercu- lar margin spines increased between 12.4 and 22.4 mm. Vertical spines increased by 16 and horizon- tal spines increased by 4 along the preopercular margin between these two lengths. A small spine was present on the interopercle of all specimens. A larger spine was also present on the posterodorsal margin of the opercle of all specimens. ( Figures 1,2). The spine at the angle of the preopercle was the largest spine on the head. No serrations developed on this or any other preopercular spine. A spine on the posttemporal was first present on the 7.3 mm larva. A second spine developed on this bone by 9.5 mm. These 2 posttemporal spines were greatly reduced in the two largest specimens. A supracleithral spine was present on the smallest larva (4.0 mm). Three spines were present by 4.2 mm, and 5 spines had developed by 9.5 mm (Fig- ures lA, B; 2A). The 2 most ventral supracleith- ral spines were longer in the 12.4 mm specimen than in smaller specimens. The 22.4 mm juvenile had all of the supracleithral spines, but these spines were much smaller (Figure 2C). Two serrations developed on the supraocular crest by 7.3 mm (Figure ID), and two more by 12.4 mm. The 22.4 specimen had no serrations on the supraocular crest (Figure 2C). Eye diameter was 11.0-14.3% SL (Table 4). The eye was almost spherical, and the iris had a ven- tral cleft in all but the largest specimen (Figures 1, 2). Teeth were present in all specimens on the den- tary and premaxillary bones. In addition, the two largest specimens (12.4 and 22.4 mm) had vo- TaBLE 5. — Predictive linear regressions of body measurements on standard length for 24 larval and juvenile Lutjanus cam- pechanus over the size range 4.0-22.4 mm SL. Measurement Slope Intercept Head length Body depth Snout to anus length Eye diameter 0341 0699 0359 0,118 0350 •0 601 0 197 0.050 0 177 0 159 0 181 0054 0991 0998 0,992 0.993 merine and palatine teeth. The vomerine teeth in these two specimens were arranged in a V-shaped pattern with the angle pointed anteriorly. Body Growth Measurements of four body parts are given in Table 4. The growth of these parts in relation to standard length is described by linear regressions (Laroche 1977; Sokal and Rohlf 1969), the statis- tics for which are presented in Table 5. All rela- tionships have high correlation coefficients of S0.991. Comparison With Other Lutjanid Larvae and Juveniles As stated earlier, R. aurorubens is the only lu- tjanid to have previously had its larval and juve- nile stages described. The two snappers are easily separated as follows: In specimens ^4.0 mm, R. aurorubens has serrations on the largest spine at the preopercular angle. Figure lA in Laroche ( 1977) did not show the serrations on this spine, however, the text stated that, "A large, stout, and serrated spine occurs at the preopercular angle in all specimens." Laroche^ confirmed this. In addi- tion, large serrations develop on the anterior and posterior margins of the dorsal and pelvic spines in larval/?, aurorubens &4.7 mm. None of the 4.0-4.7 mm L. campechanus had serrated preopercular, dorsal, or pelvic spines. Both species have serrated pelvic spines in specimens >4.8 mm, but R. au- rorubens has large serrations on the anterior and posterior margins while L. campechanus has small serrations on just the anterior margin. The total number of rays in the dorsal and anal fins also separates these two snappers at sizes s=5.0 mm. Rhomboplites aurorubens has 22 or 23 dorsal and 11 anal rays while L. campechanus has 24 dorsal and 12 anal rays. Rhomboplites aurorubens is the only lutjanid to have an adult complement of 'W. A. Laroche, School of Oceanography, Oregon State Uni- versity, Corvallis, OR 97331, pers. commun. June 1978. 973 12 dorsal spines. All other members of the Lu- tjanidae have 10 spines. Finally, the head length of R. aurorubens is greater than the body depth (Laroche 1977), while in L. campechanus head length is about equal to body depth (Table 4). Identification of the larvae and juveniles of other lutjanid species is more difficult than that of L. campechanus and R. aurorubens, since the meristic characters are very similar in most other species of lutjanids. At the present time, field- collected lutjanid larvae <4.0 mm can be iden- tified only to family. Laboratory rearing presents the most likely solution to the larval and juvenile lutjanid taxonomic problem. ACKNOWLEDGMENTS We thank Suzanne Christoff for making the il- lustrations and Barbara Y. Sumida and William J. Richards for furnishing information on illustrat- ing techniques. We are indebted to Arthur W. Kendall, Jr., both for assistance in the identifica- tion of all but the largest specimen and for the preliminary review of most of our illustrations. We are grateful to Larry H. Ogren who collected and identified the largest specimen. We thank William D. Anderson, Jr., Edward D. Houde, G. David Johnson, Wayne A. Laroche, William J. Richards, and Bruce W. Stender for reviewing the manuscript. LITERATURE CITED ANDERSON, W. D.. Jr. 1967. Field guide to the snappers ( Lutjanidae) of the west- em Atlantic. U.S. Fish Wildl. Sen.. Circ. 252, 14 p. ARNOLD, C. R., J. M. WaKEMAN. T. D. WILUAMS, AND G. D. Treece 1978. Spawning of red snapper (Lu<;anus compeoAanus) in captivity. Aquaculture 15:301-302. BAILEY, R. M., J. E. FTTCH, E. S. HERALD, E. A. LACHNER, C. C. Lindsey, C. R. Robins, and w. b. Scott. 1970, A list of common and scientific names of fishes from the United States and Canada. Am. Fish. See, Spec. Publ 6, 149 p fishery bulletin: vol. 77, no, 4 Beaumariage, D. S., and L. H. Bullock. 1976 Biological research on snappers and groupers as re- lated to fishery management requirements In H. R. Bullis, Jr and A. C. Jones (editors), Proceedings; Col- loquium on snapper-grouper fishery resources of the west- em central Atlantic Ocean, p. 86-94. Fla. Sea Grant Rep, 17. FSUS-76-R-17. Bradley, E., and C. E. Bryan. 1975. Life history and fishery of the red snapper [Lutjanus campechanus^ in the northwestern Gulf of Mexico: 1970- 1974. Gulf Caribb. Fish, Inst., Proc. 27th Annu. Se8s.,p. 77-106. Fahay.M, p. 1975. An annotated list of larval and juvenile fishes cap- tured with surface-towed meter net in the South Atlantic Bight during four RV Dolphin cruises between May 1967 and February 1968. U.S. Dep. Commer , NCAA Tech. Rep. NMFS SSRF-685, 39 p. Fourmanoir, p. 1973. Notes ichthyologiques(V). Cah. O.R.S.T.O.M. Ser. Oceanogr. 11:33-39 HEEMSTRA, P. C. 1974. On the identity of certain eastern Pacific and Carib- bean postlarval fishes (Perciformes) described by Henry Fowler. Proc, Acad, Nat, Sci, Phila. 126:21-26, Jossi, J, W,, R, R, Marak. and H, Peterson, Jr. 1975. At-sea data collection and laboratory procedures. MARMAP survey I manual. National Marine Fisheries Service, Wash., DC, 115 p. Laroche, W. a. 1977. Description of larval and early juvenile vermilion snapper, Rhomboplites aurorubens. Fish. Bull., U.S. 75:547-554. Miller, G. L., and S. C. Jorgenson. 1973. Meristic characters of some marine fishes of the western Atlantic Ocean. Fish. Bull., U.S. 71:301-312. MOSER, H. G., AND E. H. AHLSTROM. 1970. Development of lantemfishes (family Myctophidae) in the California Current. Part I. Species with narrow- eyed larvae. Bull. Los Ang. Cty. Mus. Nat. Hist. Sci. 7, 145 p RIVAS, L. R. 1966. Review of the Lutjanus campechanus complex of red snappers. Q. J. Fla. Acad. Sci. 29:117-136. SOKAL, R. R., AND F. J. ROHLF. 1969. Biometry. The principles and practice of statistics in biological research. W. H. Freemen and Co., San Franc, 776 p. STARCK. W. a., II. 1971. Biology of the gray snapper, Lutjanus gnseus (Lin- naeusl, in the Florida Keys, In W. A. Starck II and R E. Schroeder. Investigations on the gray snapper, Lutjanus griseus, p. 11-150. Stud. Trop. Oceanogr. (Miami) 10. 974 ISOLATION OF OLIVE ROCKFISH, SEBASTES SERRANOIDES, POPULATIONS OFF SOUTHERN CALIFORNIA Milton S. Love' ABSTRACT Movements of the olive rockiish. Sebastes serrancides, off Santa Barbara, California, were investi- gated, using mechanical and parasite tags. The movements were restricted over shallow reefs though somewhat less so around deeper oil platforms. Highly restricted movements may cause greater vulnerability of populations to overfishing — comparisons of olive rockiish size fi'equencies between two reefs indicated that fishing pressure had reduced olive rockiish populations to almost all prereproduc- tive individuals on the more heavily fished site. Rockfishes, genus Sebastes (Family Scor- paenidae), form a most diverse fish group along the California coast. Some 57 species are found in these waters (Miller and Lea 1972), inhabiting virtually every marine habitat from estuarine (oc- casionally) and intertidal waters to depths of more than 610 m (Miller and Lea). Rockfish are very important to both sport and commercial fishing industries; in California waters in 1974, rockfish ranked third in the commercial fishery (poundage landed) and first in the sport fishery (numbers landed) (McAllister 1976). California species can be roughly divided into two bathymetric groups: shallow species that in- habit subtidal areas of reef and kelp, and those that live in relatively deep water (deeper than about 70 m). All species are ovoviviparous, produc- ing pelagic larvae. There is some evidence that the shallow water species may remain within a rela- tively small area of reef or kelp (Miller and Geibel 1973). A species that consists of relatively sedentary, reef-oriented aggregations would present poten- tial problems in management, as certain man- agement strategies presuppose movements of this fish (Harden Jones 1968; Gushing 1968). If the exploited species inhabits reefs, for example, it might soon be decimated at a heavily fished reef if individuals were parochial and did not move from an unexploited site to repopulate the depleted one. Obviously, a management strategy to protect this type of segregated reef species would differ from that for a species whose individuals move between 'Department of Biological Science, University of California, Santa Barbara, Calif.; present address: Department of Biology, Occidental College, 1600 Campus Road, Los Angeles, CA 9004 L sites. Many rockfish species grow very slowly (Phillips 1964; Chen 1971: Westrheim and Har- ling^). Thus, even if a depleted reef were densely settled by a successful year class, it would not harbor adults for a number of years. Before then, the subadults would probably be caught before the age of first maturity, so the reef would effectively be lost as a site of propagation for the species. If this process continued through all available reef sites, the fisheries would be endangered. On the other hand, a rockfish species whose in- dividuals move freely from reef to reef may be less vulnerable to such perturbations. Even a locally depleted reef could be sufficiently repopulated by adults during breeding season because of the tjrpi- cally high fecundity of females (Phillips 1964) and great dispersability of pelagic larvae. Thus the fishery might be effectively managed by conven- tional procedures of establishing catch limits, etc. The olive rockfish, Sebastes serranoides, in- habits reefs and kelp beds from San Benito Island, Baja California, north to Redding Rock, Del Norte County, northern California, and from intertidal waters (juveniles) to 146 m (Miller and Lea 1972). The species is most common in southern and cen- tral California from surface waters to depths of about 75 m. It is a major sport fish throughout much of the state (Miller and Gotshall 1965), par- ticularly in southern and central California. Ob- jectives of the present study were to determine whether individuals move from reef to reef and if average size was smaller at heavily fished reefs. Manuscnpt accepted May 1979 FISHERY BULLETIN VOL 77. NO 4, 1980 ^Westrheim, S. J., and W. R. Hading. 1975. Age-length relationships for 26 scorpaenids in the northeast Pacific Ocean. Fish. Mar. Serv. (Can.), Res. Dev. Dir. Tech. Rep. 565, 12 p. 975 FISHERY BULLETIN: VOL METHODS Artificial Tagging Between 26 October 1973 and 17 October 1976, 1,847 olive rockfish (19-43 cm total length, TL) were tagged and released upon capture at 18 sites off southern California (Figure 1, Table 1). Gener- ally, sites were selected either on the basis that they were reefs regularly fished by partyboats or private vessels, which maximized the opportunity to recapture tagged animals; or that sites had to be within 2 km of another regularly fished reef that harbored olive rockfish, which maximized the op- portunity to recover fish that move short dis- tances. The exception was Naples Reef, which had no other suitable site within 2 km. Naples Reef was included because its fish fauna was being studied intensively by other scientists. Only a few fish were tagged at some sites, such as Anacapa Island, Platform Holly, and Avila, either because olive rockfish were infrequent there or because the sites were relatively remote from Santa Barbara. The tags (yellow Floy^ anchor type FD-67c) con- sisted of a plastic tube 42 mm long with a 15 mm nylon stem and a 10 mm cross b£ir attached to the stem and were inserted with a Floy tagging gun, FDM 68, with a heavy-duty needle 2 cm long. My name. Department of Biology, UCSB, and a number were printed on each tag. The anchor was injected into the dorsal musculature between the second and third dorsal spines, leaving the brightly colored end free. Even though bryozoan growth completely obscured the legend within a few months, this growth was easily rubbed off by a person's finger when the tag was read. Fish were caught by hook and line aboard re- seeu^ch vessels and sportfishing partyboats, then measured, tagged, and returned to the water. Be- cause of expanded gas in their swim bladders, fish taken at depths greater than about 20 m had to be deflated before they could return to depth. Perhaps 10% of all fish tagged required deflation, using a technique modified slightly from Gotshall (1964). A 3.8 cm, 18 gage hypodermic needle was inserted through the body wall into the swim bladder. However, instead of placing both fish and needle underwater, then waiting for the gas bubbles to stop emanating from the needle, gas was sucked Table l. — Descriptions and locations of tagging sites for olive rockfish near Santa Barbara, Calif. For locations of sites see Figure 1 also. Site and description Diablo Canyon, Avila — 1 1 km west of Avila Harbor. 9 m reef in 33 m, 0-3 km offshore Naples Reef— 24 km west of Santa Barbara, 16 km offshore, in 8-10 m, surrounded by 16-20 m deep sand flats Oil Platform Holly — 18 km southwest of Santa Barbara, in 60 m, about 3-2 km offshore 1 Mile Reef — 2 km southeast of Santa Barbara, 2-6 m reef in 30-35 m Horseshoe Reef — 10 km east of Santa Barbara, Average depth 8- 10 m, sur- rounded by 12-13 m Oil Platform Hilda — 8 7 km east of Santa Barbara. 3 1 km offshore in 34 m 4 Mile Reef — 6 4 km southeast of Santa Barbara. 6-8 m pinnacle in 40 m Oil Platform Hillhouse — 10 4 km southeastot Santa Barbara, 8 9 km offshore in 58 m Oil Platforms Houchin, Hogan, Hope — About 14 0 km southeast of Santa Barbara, about 7 km offshore in 50 m Talcott Shoals, Santa Rosa Island — 64,0 km southwest of Santa Barbara, 2-15 m pinnacles in 4-45 m Fraser Pt , Santa Cruz Island — 46 km south of Santa Barbara, 2-6 m reefs in 12-15m Smugglers Cove. Santa Cruz Island — 40 km southeast of Santa Barbara Anacapa Island — 43 km southeast of Santa Barbara Rincon Oil Island — 19 km east of Santa Barbara (not figured) Deephole Reef — 68 km east of Santa Barbara, 2-6 m reefs in 24-28 m, about 18 km offshore (not figured) from the bladders to speed the process, and if needed, the fish's everted stomach was pushed back into place. About 20% of the inflated fishes died either before or immediately after being re- turned to the water. Undoubtedly others that swam downward also died; of six fish placed in a tank after deflation, two died within 1 day and the rest survived for 2 wk, to the end of the test. Elimi- nated were all fish whose eyes were everted by gas expansion in the choroid plexa. Experience with S. caurinus, S. paucispinis, and S. serranoides indi- cates that this condition frequently leads to blind- ness and/or death, whether or not pressure is re- leased. Tagging mortality in fish that did not have to be deflated was probably low. Ten of 12 tagged olive rockfish lived for 2 mo in an aquarium, two dying after about 1 mo, apparently of a fungal infection. I saw none of the extensive hemorrhaging previ- ously observed in Floy-tagged Pacific mackerel. Scomber japonicus (Gregory''). Biological Tagging I analyzed the parasite mix of olive rockfish to determine the feasibility of using parasites as "biological tags." Differences in parasite infection ^Reference to trade names does not imply endorsement by the National Marine Fisheries Service, NOAA. 'Gregory, P, A, 1977, Results of tagging mortality experi- ments on Pacific mackerel, Pneumatophorus japonicus . Calif. Dep Fish Game. Mar Res, Tech. Rep. 40. 21 p. 976 LOVE; ISOLATION OF OLIVE ROCKFISH POPULATIONS ^^^^^^^^^^^^^^'^'fLLWOOD PIER NAPLES REEF t^J HASKELS ^ I I I N 2 KM •HOLLY BARBARA SANTA ROSff ISLAND ANACAPA ISLAND ,i^er at large Percentage Site tagged (days) recovered Horseshoe Reef 75 309 34.6 Naples Reel 177 156 237 Platforms Houchin. Hogan. Hope 513 172 15.2 Talcott Shoals. Santa Rosa Island 159 371 9.4 Fraser Pt . Santa Cruz Island 81 302 7.4 Deephole Reef 369 42 65 Rincon Oil Island 17 18 5.8 1 Mile Reel 240 291 5.0 4 Mile Reef 99 112 3.0 Other sites' 117 — 00 Total 1.847 11.2 'Platform Hilda, Platlorm Holly, Anacapa Island. Smugglers Cove 978 LOVE: ISOLATION OF OLIVE ROCKFISH POPULATIONS three oil platforms off Summerland (15.2%), all of which were heavily fished by partyboats. Eighty- one percent of all returns were made by partyboat fishermen. Only the fish tagged around the Summerland oil platforms showed any movements; here nine moved from one platform to another (about 0.8 km). Regarding biological tags, only the incidence of infection of Microcotyle sebastis (Table 3) differed significantly among study sites. Naples Reef and Ellwood Pier differed significantly from the other four sites: a G-test of independence (Sokal and Rohlf 1969) was significant when all six sites were included (G = 186.45, P<0.005), but not sig- nificant when only the oil platforms, 4 Mile Reef, and Horseshoe Reef were included (G = 1.14, 0.9>P>0.5). Naples Reef also differed sig- nificantly from Ellwood Pier (G = 16.8,P<0.005). There was no seasonality in incidence of infec- tion, as G-tests of independence among four sea- sons were not significant for any site (Table 3). To test whether environmental conditions at Ellwood Pier were suitable for the monogenetic trematodes, tagged fish from Horseshoe Reef in- fected with M. sebastis were introduced into the site. Untagged fish were collected 1 and 6 mo later. After 1 mo 2 of 20 untagged fish (10%) were in- fected and after 6 mo 7 of 20 (35%) were infected (not a significant difference, G = 3.6, 0.1>P>0.05). The presence of M. sebastis in the population seems to indicate that conditions were suitable for the trematode. Fish lengths averaged significantly shorter it = 9.3, P<0.001) at the heavily fished Naples Reef than at the lightly fished Haskels site (Figure 2). Most fish taken from Naples Reef were prere- productive, while mature individuals made up about 45% of the Haskels catch. DISCUSSION Kabata (1963) lists five criteria which should ideally be met if a parasite is to be useful as a tag: 1) the parasite should be common in one popula- tion and rare or absent in another; 2) the parasite should have a direct life cycle, infecting only one host species during its life; 3) the parasitic infec- tion should be of fairly long duration; 4) the inci- dence of infection should stay relatively stable; 5) environmental conditions throughout the study site(s) must be within the physiological tolerance of the parasite. Compared with artificial tags, biological tags have both advantages and disadvantages. Arti- ficial tags may alter the normal behavior of the tagged animal, whereas, in most cases, parasites do not. Moreover, the parasite mix of a population is usually the result of long-term processes, and may be a more accurate indicator of movements than short-term tagging studies. On the other hand, parasite tags will not indicate individual movements. Over the past 20 yr, studies using parasites as tags have delineated nursery grounds (Olson and Pratt 1973), spawning grounds (Mar- golis 1963; Hare and Burt 1976), and discrete or semidiscrete populations (Sindermann 1961; Kabata 1963). Results of both artificial and biological tagging indicated that olive rockfish rarely moved be- tween shallow water reefs. A good example of this was the apparent lack of movement between Naples Reef and Ellwood Pier. Though only about 2 km apart, no tagged Naples Reef fish were taken at Ellwood Pier or anyplace else, nor were any of the M. sebastis found to be infecting Ellwood Pier fish before I introduced it, though they infect Naples Reef fish. Like other monogeneans, M. sebastis has a di- rect (one host) life cycle. The maximum distance the infective oncomiricidium larval stage can travel before finding a host is not known, though it is probably limited to a few meters (Llewellyn 1972). Apparently, Ellwood fish were not parasitized because they were sufficiently isolated Table 3.— Incidence of parasite Microcotyle sebastis in 80 olive rockfish sampled 20/mo from each of six sites off Santa Barbara, Calif. P values reflect G-teste of independence (Sokal and Rohlf 1969) for incidence of infections among four seasons. Number infected (1976-77) Total P Site June-Aug Sept -Nov Dec -Feb Mar -May Percent Ellwood Pier 0 0 0 0 0 — 00 Naples Reef 4 3 3 4 14 0 9 -P •0 5 175 Platform Houctiin 12 12 14 15 51 0,5>P: •0,1 63 8 Platform Hilltiouse 10 14 13 15 52 0.9>P: '05 65 0 Horseshoe Reef 14 11 15 15 55 0,9>P: >0,5 68,8 4 me Reef 17 13 15 12 57 09 >P »0,5 71 2 979 FISHERY BULLETIN: VOL. 77, NO 4 from others to escape exposure to infected fish, even pelagic larvae. Yet, neither tagging nor parasite data indicated whether fish move offshore from the Ellwood area to Naples Reef. However, size-frequency data of fish taken on Naples Reef and at Haskels (adjacent to the Ellwood Pier) (Figure 2), are evidence that there was probably little movement from Ellwood to Naples. Naples Reef harbors primarily juvenile and preadult olive rockfish (Love and Ebeling 1978) and adults are rarely observed (Ebeling^). Apparently, fishing pressure removes fish before they can mature. However, adults were abundant at the lightly fished Ellwood Pier, and limited sampling along a 16 km stretch of kelp inshore of Naples Reef indicated that mature fish were com- mon throughout the bed. Apparently, few of these fish move across the sandy stretch between Naples Reef and the inshore bed. Though inshore movements seem to be inhibit- ed by stretches of sandy bottom, movement from one oil platform to another obviously is not: tagged fish must traverse at least 0.8 km over sandy bot- tom with a depth of about 50 m to reach the adja- cent site. Miller and Geibel ( 1973) observed a simi- lar greater mobility in deep waters for blue rockfish, S. mystinus. Olive rockfish off Santa Barbara feed primarily on midwater organisms (nekton and plankton) rather than substrate-oriented prey (Love and Ebeling 1978). It is not known whether these prey are less abundant at the platforms compared with inshore waters. However, if they are less abun- dant, olive rockfish might be more likely to leave the platform to follow prey. I have noted olive rockfish feeding on anchovies as much as 300 m away from the platforms. Perhaps in these in- stances some fish may not return to the original platform. This study emphasized movements of fish that inhabit isolated reefs. Little work was done on fish from the extensive area of continuous kelp forest which grows mostly on sandy bottom and parallels most of the Santa Barbara coast, because sam- pling is more time consuming in such areas of low rockfish densities. Moreover, much of the tagging was done aboard partyboats which rarely fish these extensive beds. It is quite possible that olive rockfish in kelp beds move about considerably more than those on isolated reefs. I suspect that the limited movements observed may be due to the lack of cover on the relatively barren bottom sur- rounding the reeflike study sites. Olive rockfish have been rarely taken over sand, either in otter trawls (Ebeling et al.**), or seen in underwater transects in kelp beds over a sand bottom (Quast 1968), and seem to be strongly attracted to high- relief substrate, such as that of platforms and rocky reefs. Kelp beds may provide "bridges" from one reef to smother. Previous studies (Table 4) indicate that many other shallow water rockfish exhibit limited movements. The two most extensively investi- gated benthic species, S. carnatus and S. chrysomelas, defend small feeding territories and shelter holes (Larson 1977; Hallacher 1977). Also, agonistic displays by S. serriceps (Feder et al. 1974; Haaker 1978) and long-term residence in particular crevices by S. nebulosus (McEl- derry') indicate that these benthic species may also be territorial. Thus, it seems likely that most or all benthic reef rockfish may move relatively little. Similarly, some midwater rockfishes that live over these shallow reefs, seem to stay within a fairly small area. In particular, tagging of S. mys- tinus (Miller and Geibel 1973) indicated re- stricted movements, and tagging of S. flavidus (Carlson and Haight 1972) showed that this species has a strong homing tendency. However, movements of tagged S. melanops (Coombs 1979), along with pelagic capture (Dunn and Hitz 1969) indicate that it probably moves about exten- sively. Relatively parochial midwater rockfish, such as S. mystinus, S. serranoides, and S. flavidus, do not appear to be territorial, in the sense that a territory is a "defended" (Noble 1939) or "exclu- sive" (Schoener 1968) area. Indeed, these species often form single or multispecies aggregations of thousands of individuals, which show little or no agonistic behavior. The sizes of rockfish home ranges have not been estimated, though Miller and Houk* believed that S. mystinus aggrega- 'Ebeling, Alfred W. Department of Biological Sciences, Uni- versity of California, Santa Barbara, CA 93106, pers. commun. February 1978. 'Ebeling, A. W., W Werner, F. A Dewitt, Jr . and G M. Cailliet. 1971. Santa Barbara oil spill: short-term analysis of macroplankton and fish. EPA, Water Qual. Off. Doc. no. 15080EA02/71, 68 p. 'H. McElderry Department of Biology, University of Victoria, Victoria, B.C. pers. commun. January 1978. «D. Miller and J Houk, California Department of Fish and Game, 2201 Garden Road, Monterey, CA 93940, pers. commun. January 1978. 980 LOVE ISOLATION OF OLIVE ROCKFISH POPULATIONS Table 4. — Summary of published observations on rockfish, Sebastes spp., movements m the northeast Pacific. Species Location Method Results Source S alutus Northeast Pacific Analysis of fish catch Seasonal bathymetric movements of many Review in Gunderson (1 977) Ocean data kilometers and 100 m in depth S atrovirens Monterey. Calif Tagging No movement Miller and Geibet (1973) S aunculatus Monterey Tagging No movement Miller and Geibel (1973) Humboldt Bay, Calif Tagging No movement DeWees and Gotshall (1 974) S. carnatus Santa Barbara Underwater observation. Has home range, no evidence of extensive Larson (1977) Channel. Calif tagging movement Monterey region. Underwater observation. No movement Hallacher (1977) Calif tagging S caunnus Monterey Bay. Calif Tagging, underwater observation Limited movement, farthest 2 4 km Miller and Geibel (1973) Monterey region Tagging No movement Hallacher (1977) Humboldt Bay Tagging No movement Deweesand Gotshall (1974) Puget Sound. Underwater observation Fewer individuals seen in shallow water Dewees and Gotshall (1974) Wash during summer Patten (1973) Puget Sound UndenA'ater observation Very limited bathymetric and onshore- offshore movement, a few meters vertical movement between summer and winter Moullon(1977) S chrysomelas Santa Barbara Underwater observation . Species has home range, no evidence of Larson (1977) Channel tagging extensive movement Monterey region Underwater observation, tagging No movement Hallacher (1977) Monterey Bay Tagging No movement ^ Miller and Geibel (1973) S flavidus Puget Sound Underwater observation Very limited bathymetric and onshore- offshore movement, a few meters vertical movement between summer and winter Moullon (1977) Alaska Tagging Homing study, species homed up to 22.5 km Carlson and Haight (1972) S melanops Monterey Tagging No movement Miller and Geibel (1973) Humboldt Bay Tagging No movement DeWees and Gotshall ( 1 974) Oregon Tagging Limited number of recoveries, 2 of the 10 recovered fish moved, one 619 km. other 24 km Coombs (1979) Puget Sound Underwater observation Very limited bathymetric and onshore- offshore movement, a few meters vertical movement between summer and winter Mouiton (1977) Gulf of Alaska Capture Review of pelagic captures Dunn and Hilz (1969) S miniatus Redondo Beach, Tagging Movement of 8-9.6 km Turner et al (1969) (Juv) Calif (Juv.^) Monterey Tagging No movement Miller and Geibel (1973) S mystinus Southern to northern Calif Tagging Generally little or no movement, slight movement in deeper water Miller and Geibel (1973) Monterey Bay Tagging Restricted movement S ptnniger Monterey Bay Tagging No movement Miller and Geibel (1973) S rosaceus Monterey region Underwater observation No movement Hallacher (1977) S rubernmus Oregon Tagging No movement Coombs (1979) S serranoides Santa Monica Bay Calif Tagging No movement Turner et al (1969) Santa Barbara Tagging No movement in shallow water, limited Present paper Channel movement in deeper water tions are quite patchy within a kelp bed and some fish may remain within a very limited area for extended periods. In kelp beds, individuals of S. serranoides may move about more than those of S. mystinus. Miller and Houk noted that S. ser- ranoides individuals were not seen as consis- tently as those of S. mystinus in kelp-bed tran- sects in Monterey Bay. As S. mystinus preys primarily on plankton and animals on plant sur- faces (Gotshall et al. 1965; Hallacher 1977; Love and Ebeling 1978), it seems likely that this species spends much of its time waiting for prey to drift by. Sebastes serranoides feeds somewhat more on moving prey (Love and Ebeling 1978) and so may forage more widely. Some seasonal movement of rockfish may also occur, at least north of Pt. Conception. A number of studies report that rockfish numbers on shal- low water reefs seem to decrease during winter (Miller and Geibel 1973; Mouiton 1977; Burge and Schultz^). Increased turbulence may drive the fish into deeper water or into reef shelters where they are less visible. Ebeling (see footnote 5) observed no winter decrease in rockfish abun- dance at Naples Reef. The waters of the Santa Barbara Channel are considerably less turbulent "Burge, R. T., and S. A, Schultz. 1973. The marine envi- rormient in the vicinity of Diablo Cove with special reference to abalones and bony fishes. Calif. Dep. Fish Game, Mar. Res. Tech. Rep. 19, 433 p. 981 FISHERY BULLETIN: VOL. 77, NO. 4 than those above Pt. Conception; perhaps here fish can remain on the reefs despite winter storms. Miller and Geibel (1973) noted a sharp winter decrease in S. mystinus numbers on a reef in Monterey Bay. Yet despite extensive tagging at this site and intensive sampling and underwa- ter observation of surrounding reefs during winter, no tagged individuals were found at other reefs (Miller and Houk see footnote 8). Factors other than turbulence may account for a winter exodus. Some rockfish species may leave inshore reefs to spawn. If fish do leave the reef, the extent of their movement is, in general, not known. Moulton (1977) found that during winter rockfish on Puget Sound reefs retreated only short dis- tances, into slightly deeper water. The between site difference in mean fish length found between Naples Reef and Haskels probably reflects a difference in fishing pressure. The more heavily fished site averaged smaller fish and fewer mature ones because larger fish were selec- tively angled, or have been subjected to fishing effort for a longer period and are thus more likely to be caught. As heavily fished sites contain primarily pre- reproductive individuals (as, in general, does Naples Reef), reproduction of mature fish at lightly fished sites could account for much of the recruitment for all areas. Based on data from mechanical and parasite tags, olive rockfish off Santa Barbara exhibit very restricted movements on shallow water reefs, but may be somewhat more mobile around deeper water oil platforms. The species' parochialism in shallow water makes it susceptible to overexploi- tation as interchange of individuals from other reefs is rare. ACKNOWLEDGMENTS I thank Alfred W. Ebeling, Alice Alldredge, Bruce Robison, and Elmer Noble for critically reading the manuscript and their suggestions. Norm Lammer provided technical help with boat- ing operations. Fred Benko of Sea Landing Sportfishing graciously allowed me space on par- tyboats for sampling. I particularly thank par- tyboat operators Chet Phelps, Irv Grisbeck, Frank Hampton, George Kelly, and Dick Clift for making sampling possible and pleasurable. Dave Laur, Lew Haldorson, Tony Hampton, Merritt McCrea, Ken Du Mong, and Dennis Evans assisted in specimen collections, and three anonymous reviewers made helpful suggestions. I thank my wife, Regina Paull-Love, for typing the manuscript and for her support and assistance, and Sara Warschaw and Jessica Schulz for typing successive drafts. This work was sponsored by NOAA, Office of Sea Grant, U.S. Department of Commerce, under grant no. 04-7-158-44121 (Project r/f-39) and NSF Grant OCE 76-23301. LITERATURE CITED Carlson H. R., and r. E. Haight. 1972. Evidence for a home site and homing of adult yellow- tail rockfish, Sebasles fktvidus. J. Fish. Res. Board Can. 29:1011-1014. Chen, L.-C. 1971. Systematica, variation, distribution, and biology of rockfishes of the subgenus Sebastomus (Pisces. Scor- paenidae, Sebastes). Bull. Scripps Inst. Oceanogr. Univ. Calif. 18, 115p. Coombs, C. 1979. Reef fishes near Depoe Bay, Oregon: movement and the recreational fishery. M.A. Thesis, Oregon State Univ.,Corvallis.39p. CUSHING, D. H. 1968. Fisheries biology. Univ. Wis. Press, Madison, 200 p. DEWEES. C. M., AND D. W. GOTSHALL. 1974. An experimental artificial reef in Humboldt Bay, California. Calif Fish Game 60:109-127. Dunn, J. R., and C. R. Hitz. 1969. Oceanic occurrence of black rockfish iSebastodes melanops) in the central North Pacific. J. Fish. Res. Board Can. 26:3094-3097. FEDER, H. M., C. H. Turner, and C. Limbaugh. 1974. Observations on fishes associated with kelp beds in southern California. Calif Dep Fish Game, Fish Bull 160, 144 p. GOTSHALL, D. W. 1964. Increasing tagged rockfish (genus Sebastodes) sur- vival by deflating the swim bladder. Calif. Fish Game 50:253-260. GOTSHALL, D. W., J. G. Smith, and a. Holbert. 1965. Food of the blue rockfish Sebastodes mys- tinus. Calif. Fish Game 51:147-162. Gunderson, D. R. 1977. Population biology of Pacific ocean perch, Sebastes alutus. stocks in the Washington-Queen Charlotte Sound region, and their response to fishing Fish Bull., U.S. 75:369-403. Haaker, p. L. 1978. Observations of agonistic behavior in the treefish, Sebastes serriceps (Scorpaenidae). Calif. Fish Game 64:227-228. Hallacher. L. E. 1977. Patterns of space and food use by inshore rockfishes lScorpaenidae:Se6as(es) of Carmel Bay, California. Ph.D. Thesis, Univ. California, Berkeley, 115 p Harden Jones, F. R. 1968. Fish migration. Edward Arnold, Lond , 325 p. Hare. G. M., and M. D. B. Burt. 1976. Parasites as potential biological tags of Atlantic salmon (Salmo salar) smelts in the Miramichi River sys- 982 LOVE: ISOLATION OF OLIVE ROCKFISH POPULATIONS tern. New Brunswick. J. Fish. Res. Board Can. 33;1 139- 1143. Kabata, Z. 1963. Parasites as biological tags. Int. Comm. Northwest Atl. Fish., Spec. Publ. 4:31-37. Larson, R. J. 1977. Habitat selection and territorial competition as the causes of bathymetric segregation of sibling rocklishes {Sebastesl Ph.D. Thesis, Univ. California, Santa Bar- bara, 170 p. Llewellyn, J. 1972. Behaviour of monogeneans. /n E. U. Canning and C. A. Wnght (editors). Behavioural aspects of parasite transmission, p. 19-30. Academic Press, N.Y. Love, M 1978 Aspects of the life history of the olive rockfish, Sebastes serranoides. Ph.D. Thesis, Univ. California, Santa Barbara, 184 p. Love, M. S., and a. w. Ebeling. 1978. Food and habitat of three switch-feeding fishes in the kelp forests off Santa Barbara, California. Fish. Bull., U.S. 76:257-271. Margolis, L. 1963. Parasites as indicators of the geographical origin of sockeye salmon, Orworhynchus nerka (Walbaum), occur- ring in the North Pacific Ocean and adjacent seas. Int. North Pac. Fish. Comm. Bull 11, 156 p. MCALLISTER, R. 1976. California marine fish landings for 1974. Calif. Dep. Fish Game, Fish Bull 166, 53 p. Miller, D. J., and J. J. Geibel. 1973. Summary of blue rockfish and lingcod life histories; a reef ecology study; and giant kelp, Macrocystis pynfera , experiments in Monterey Bay, California. Calif. Dep Fish Game, Fish Bull. 158, 137 p. Miller, D. J., and D. Gotshall. 1965. Ocean sportfish catch and effort from Oregon to Point Arguello, California. Calif. Dep. Fish Game, Fish Bull. 130, 135 p. Miller, D. J., and R. N. Lea. 1972. Guide to the coastal marine fishes of California. Calif. Dep. Fish Game, Fish Bull. 157, 235 p. moulton, l. l. 1977 . An ecological tmalysis of fishes inhabiting the rocky nearshore regions of northern Puget Sound, Washington. Ph.D. Thesis, Univ. Washington, Seattle, 181 p. Noble, G. k. 1939. The role of dominance in the social life of birds. Auk 56:263-273. Olson, r. e., and I. Pratt. 1973. Parasites as indicators of English sole iParophrys vetulus) nursery grounds. Trans. Am. Fish. Soc. 102:405-411. Patten, B. G. 1973. Biological information on copper rockfish in Puget Sound, Washington. Trans. Am. Fish. Soc. 102:412-416. Phillips, J. B. 1964. Life history studies on ten species of rockfish (genus Sebastodes). Calif. Dep, Fish Game, Fish Bull. 126, 70 p. Quast, J. 1968. Estimates of the populations and the standing crop of fishes. In W. J. North and C. L. Hubbs (editors). Utili- zation of kelp-bed resources in southern California, p. 57-79. Calif. Dep Fish Game, Fish Bull. 139. SCHOENER, T. W. 1968. Sizes of feeding territories among birds. Ecology 49:123-141. SINDERMANN, C. J. 1961. Parasite tags for marine fish. J. Wildl. Manage. 25:41-47. SOKAL, R. R., AND F. J. ROHLF. 1969. Biometry. The principles and practice of statistics in biological research. W. H. Freeman and Co., San Franc, 776 p. TURNER, C. H., E. E. EBERT, AND R. R. GIVEN. 1969 Man-made reef ecology Calif. Dep. Fish Game, Fish Bull. 146, 221 p. Westrheim, S. J. 1975. Reproduction, maturation, and identification of lar- vae of some Sebastes ( Scorpaenidae) species in the north- east Pacific Ocean. J. Fish. Res. Board Can. 32:2399- 2411. 983 TRENDS TOWARD DECREASING SIZE OF BROWN SHRIMP, PENAEUS AZTECUS, AND WHITE SHRIMP, PENAEUS SETIFERUS, IN REPORTED ANNUAL CATCHES FROM TEXAS AND LOUISIANA* Charles W. Caillouet. Frank J. Patella, and Wiluam B. Jackson^ ABSTRACT An exponential model adequately characterized the size composition (expressed as a regression of transformed cumulative percentage of weight on size category) of reported annual catches of brown and white shrimp in Texas and Louisiana from 1959 to 1976. Louisiana catches contained considerably greater proportions of small shrimp than did Texas catches. For both species and States, there was a significant trend toward increase m proportion of small shrimp in the catches over the period. The size composition of a stock has long been used as a simple criterion for assessing the status of a fishery (Henderson 1972; Ricker 1975). Decreas- ing average size of individuals can be an indica- tion of increasing mortality (usually equated with increased fishing mortality) or decreasing growth (usually attributed to overcrowding). This paper develops a new and simple approach to as- sessing size composition of catches, and uses it to detect differences and trends in size composition of brown shrimp, Penaeus aztecus, and white shrimp, P. setiferus, catches in Texas and Louisiana. We chose to compare Texas and Louisiana shrimp fisheries because 1) they are regulated by substantially different laws (Christmas and Et- zold 1977), resulting in different size distribu- tions of shrimp harvested within the two States, and 2) they are adjacent States which together produced the bulk (75%) of the reported shrimp catch from inshore and offshore waters of the U.S. coast of the Gulf of Mexico in 1975. Inshore refers to estuarine or bay waters landward of barrier islands, and offshore refers to waters Seaward of barrier islands. Texas shrimp laws provide for licenses, limits on number and size of trawls used per boat in- shore, limits on trawl mesh size, daily limits on inshore catch, and size limits on food shrimp (not 'Contribution No. 79-21G from the Southeast Fisheries Center Galveston Laboratory, National Marine Fisheries Ser- vice, NOAA. ^Southeast Fisheries Center Galveston Laboratory. National Marine Fisheries Service, NOAA, 4700 Avenue U, Galveston, TX 77550. on bait shrimp) during the fall ( 15 August-15 De- cember) open season inshore and during all open seasons offshore. No size limits are imposed on food shrimp during the spring 1 15 May-15 July) open season inshore. All offshore areas are closed to shrimping from 1 June to 15 July, and offshore areas within 7 fathoms are closed from 16 De- cember to 1 February. No nighttime shrimping is allowed inshore. These laws lead to a fishing strategy emphasizing the harvest of larger shrimp offshore, with considerable restriction of harvest of smaller shrimp inshore. Louisiana shrimp laws provide for licenses, limits on number and size of trawls used per boat inshore, limits on trawl mesh size, and size limits during the fall open season (third Monday in Au- gust to 21 December), with the exception that size limits are removed for brown shrimp after 15 November. No size limits are imposed during the spring open season (opened not later than 25 May and extending 50 days thereafter unless closure is warranted to protect young white shrimp). Nighttime shrimping with "butterfly nets" (wing nets) is allowed inshore. These laws encourage a fishing strategy emphasizing harvest of consider- able quantities of small shrimp inshore as well as harvest of larger shrimp offshore. Brown and white shrimp spend the juvenile and subadult phases of their life cycles inshore, and the adult and larval phases offshore (Cail- louet and Patella 1978), thus recruitment to the fishery begins in the juvenile or subadult phases. The entire life cycle is completed within a year, therefore the shrimp crop in a given year depends upon recruitment in that year. Environmental Manuscript accepted April 1979. FISHERY BULLETIN: VOL, 77. NO 4. 1980, 985 FISHERY BULLETIN: VOL 77. NO, 4 factors affecting maturation and spawning of adults and survival of larvae, juveniles, and sub- adults apparently have pronounced influences on recruitment. While some maturation and spawn- ing takes place year around, peaks occur in spring and fall. The size composition of the reported annual catches of brown and white shrimp greatly affects the value of these catches. For the years 1959-75, Caillouet and Patella (1978) estimated that the ex-vessel value (expressed in dollar units based upon 1975) of reported annual catches of brown shrimp in Texas was 1.6 times greater than that in Louisiana, for a given weight of catch. For white shrimp, it was 1.2 times greater in Texas than in Louisiana. They attributed these differ- ences in value of the catches to differences in size composition of the catches because larger shrimp command higher prices than do smaller shrimp on the market. In addition, they were impressed that the size composition of reported catches of brown and white shrimp had remained remarka- bly constant within each State despite wide vari- ations in weight of the annual catch from year to year in response to fluctuations in recruitment. DESCRIPTION OF DATA This paper deals with combined inshore and offshore reported annual catches of brown shrimp and white shrimp from the Texas coast (statistical areas 18-21) and Mississippi River to Texas (statistical areas 13-17), representing the Texas coast and that part of the Louisiana coast west of the Mississippi River, respectively (Figure 1 ), and from 1959-76 (U.S. Fish and Wildlife Service 1960-69; National Marine Fisheries Service 1970-78). The annual catches reported in the Gulf Coast Shrimp Data (U.S. Fish and Wildlife Service 1960-69; National Marine Fisheries Service 1970-78) represent only a portion of the total an- nual catches; those landed by United States craft at U.S. ports along the coast of the Gulf of Mexico. Portions not reported include some of the commer- cial landings (including those of foreign fishing craft), undersized shrimp that are discarded, and landings by domestic sport fishermen. The propor- tion of the total annual catch that is not reported is unknown, and we do not know what effect its in- clusion would have on size composition of the an- nual catch. However, we believe that the reported catch represents the bulk of the total catch and that the reported catch is a reasonably good reflec- tion of the combined effects of shrimp population characteristics (growth and natural mortality) and removals by fishing (or fishing mortality). Size composition of the reported catches was examined in units of pounds (as reported in catch statistics) caught in eight "count" or size categories representing number of shrimp per pound, heads-off ( 5=68, 51-67, 41-50, 31-40, 26-30, 21-25, 15-20, and <15). These categories are ap- proximately equivalent to the following number of shrimp per kilogram (heads-off), respectively: 3=150, 112-148, 90-110, 68-88, 57-66, 46-55, 33-44, and <33. The use of count (number per pound) as a measure of shrimp size amounts to a reciprocal transformation of the weight (W) per shrimp (in pound): Count = Figure l. — Statistical areas used in reporting Gulf Coast Shrimp Data for Mississippi River to Texas and Texas coast. w The same would be true if count and weight per shrimp were expressed in metric units. Kutkuhn (1962) described biases associated with determi- nation of size composition of reported shrimp catches, including those resulting from interview sampling methods, from prevailing practices of catch culling, grading or sorting, and from catch sampling practices. Because the methods used to determine size composition of catches have re- mained essentially unchanged from 1959 to 1976 (Farley^), we believe that the biases would have "Orman Farley, National Marine Fisheries Service, NOAA, Galveston, Tex. pers, commun. December 1978. 986 CAE.LOUET ET AL.; TRENDS TOWARD DECREASING SIZE OF SHRIMP more or less constant effects on comparisons be- tween Texas and Louisiana and over the period from 1959 to 1976, and therefore would have only minor if any effects upon our conclusions. We further recognize that each size category may in- clude representatives of more than one peak of recruitment, since they include catches taken over the period of 1 calendar year. Therefore, it is likely that any differences or trends in the time phasing of peak fishing activity within Texas and Louisiana within a year could contribute to the observed differences and trends in size composi- tion of the respective catches in the two States. ANALYTICAL METHODS Percentage (by weight, heads-off) was deter- mined for each size category in reported annual catches of brown and white shrimp from Texas coast and Mississippi River to Texas for each of the years from 1959 through 1976 (see Caillouet and Patella 1978). Cumulative percentage (F) for each size category was then determined for catches of both species, from Texas coast and Mis- sissippi River to Texas, and for each year. Percen- tages were summed from the smallest shrimp (highest count, ^68) to the largest (lowest count, <15). An exponential model was chosen to represent the relationship between cumulative percentage, F, and size category, C, for brown and white shrimp, for Texas coast and Mississippi River to Texas, emd for the years 1959-76 as follows: F, = ae>>c, where F, = cumulative percentage (by weight, heads-off) of catch in ith size cat- egory C, = lower limit of ith size category (Cj = 15, Ca =21,.. .,C^ =68) i = 1,2,. ..,7 a = constant b = exponent e = base of natural logarithm. The cumulative percentages, F, were trans- formed to natural logarithms, and the log£irithmic form of the model was used to esti- mate parameters by least squares: InF, = ln(a) + bC, = ( where e = residual (deviation from regression). Thus, the logEirithmic form of the model describes the relationship between transformed cumulative percentage and size category, and represents size composition of the reported annual catches. Note that this linear relationship describing size com- position of the reported annual catches is achieved by transforming both the cumulative percentage to In F and the weight per shrimp (in pound, heads-off) to count (number per pound). Midpoints of size categories were not used be- cause the size categories have unequal intervals, an unavoidable result of using data based on size categories developed by the shrimping industry. Upper limits of size categories were not used, be- cause we could not determine the upper limit of the 2=68 category, and this category represented a significant proportion of the catches. Also, we did not use the <15 size category because we could not determine its lower limit (zero was not realis- tic), and this category represented a very small fraction of the catches. Apparently, total mortal- ity (natural and fishing combined) is such that relatively small portions of the shrimp popula- tions survive to be caught at sizes as large as <15/pound. Because lower limits of size categories were used for regression analyses, and because the < 15 size category was not used in the analysis, the magnitude of the ordinate intercept, ln(a), is of no particular use. It is the slope, b ( = exponent of the exponential model) that is of most interest and use as an index showing the rate of change in InF with C. Extrapolation below 15 count is not advised, because the linear relation- ship does not apply beyond this point. In order to determine whether size composition of the reported annual catches changed with time, the slopes, 6, of the regressions of trans- formed cumulative percentage on size category were plotted against years, and straight lines were fitted to points b and x ( = last two digits of each year) by least squares, for brown and white shrimp from the Texas coast and Mississippi River to Texas, 1959-76 (Figures 2, 3). RESULTS AND DISCUSSION Slopes, 6, of the regressions of transformed cumulative percentage versus size category, all differed significantly from zero at the 99.9% level of confidence, showing that the lineeir fit was good (Tables 1, 2). The slopes changed with time as 987 FISHERY BULLETIN: VOL, 77, NO, 4 -0 02 -0 04 ^1 Q. O (/J -0 06 -0 08 -0 10 -0 12 r BROWN SHRIMP MISSISSIPPI RIVER TO TEXAS I 1 [ ] 1 1 1 I 1 I I 1 [ I I 1 1 ' 1959 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 Figure 2. — Trends in slope (fc) of regressions of transformed cumulative percentage (Inf ) on size category (C) for brown shrimp in Mississippi River to Texas (solid line, circles) and Texas coast (dashed line, dots) 1959-76 (data from Tables 1,2). WHITE SHRIMP MISSISSIPPI RIVER 10 TEXAS , -r TEXAS COAST I I I I I I I I I ^ I I I 1 I I I I 1959 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 VEAR. x Figure 3. — Trends in slope (6) of regressions of transformed cumulative percentage (InF) on size category (C) for white shrimp in Mississippi River to Texas (solid line, circles) and Texas coast (dashed line, dots), 1959-76 (data from Tables 1,2). shown by positive trends that were significantly different from zero at the 95% level of confidence (Table 3; Figures 2,3). This change in b with time indicated that the size composition of the reported annual catches of brown and white shrimp shifted during 1959-76 toward greater proportions of shrimp of smaller size in the catches. This shift was more pronounced in Texas, but the Louisiana catches contained considerably greater propor- tions of small shrimp than did those of Texas. Points for 1959 and 1960 may be less reliable than those for later years because the Gulf Coast Shrimp Data reports were released for the first time in 1956, and by 1961 the data collection methods had been greatly refined. Elimination of data points for 1959 and 1960 decreased all the Table l. — Linear regressions of trtinsformed cumulative percentage (Inf) on size category (C) for brown and white shrimp, Mississippi River to Texas (based on U.S. Fish and Wildlife Service 1960-69; National Marine Fisheries Service 1970-78).' Brown shrimp White shrimp Year ln(a) b r' ln(a) b r' 1959 4,881 -001% 0 962 5508 -0.0537 0.992 1960 4 767 -00154 0978 5 468 -00496 0988 1961 4 842 -00180 0976 5 097 -0,0301 0990 1962 4,696 -0,0077 0994 5005 - 0,0222 0968 1963 4 823 -00144 0 980 5273 -0,0336 0.960 1954 4817 -0,0156 0 927 5 101 -0,0318 0.996 1965 4 749 -00126 0992 4 849 -0,0206 0.996 1966 4 795 -00144 0,988 5003 0 0248 0,952 1967 4786 -0 0119 0 992 4 928 -0 0273 0,994 1968 4 730 -00117 0 982 4 849 0 0207 0 986 1969 4654 -00079 0-947 4,922 -0 0207 0.998 1970 4 747 -0,0135 0988 4884 -0,0227 0,986 1971 4 746 -00118 0994 4 936 -0,0230 0.996 1972 4 795 -00152 0 992 4 818 -0,0179 0.992 1973 4 601 -00080 0,872 4 852 0,0184 0.996 1974 4 657 -00101 0,910 4 767 -0,0171 0.980 1975 4,657 -0,0105 0910 4 760 -0,0165 0.968 1976 4712 -00112 0964 4 889 - 0 0232 0.980 'F = Cumulative percentage of weight caught in each of seven size categories; C = lower limit of each ol seven size categories; all b s were signific antly different from zero at the 99 9% level of confidence; r^ ^ coefficient of determination Table 2 — Linear regressions of transformed cumulative per- centage (In Fl on size category (C) for brown and white shrimp, Texas coast (based on U.S. Fish and Wildlife Service 1960-69; National Marine Fisheries Service 1970-78.1.' Brown shrimp White shrimp Year ln(a) £> r' ln(a) b r' 1959 6.651 -0.1039 0.965 6 848 -01042 0895 1960 6%1 -0 1140 0957 6008 -0,0635 0899 1961 6 069 -0 0790 0 972 5448 0,0521 0990 1962 5 525 -0 0558 0977 5 369 -0,0436 0,993 1963 5936 -00771 0986 5,875 -0.0704 0.990 1964 5 743 -0,0669 0 995 5 697 -0.0626 0.994 1965 5626 - 0 0588 0 991 5 268 -00449 0998 1966 5 692 -00655 0984 5 478 -0,0541 0.995 1967 6016 -00764 0 980 5 171 -00455 0.991 1968 6 420 -0 0883 0964 5 462 -0,0440 0.946 1969 5901 -0 0680 0 969 5 808 -0 0643 0983 1970 5 737 -0 0661 0 986 5412 -0 0502 0.994 1971 5 784 0 0629 0 973 5 302 -0 0476 0996 1972 6010 -0 0722 0 979 5 470 -0 0522 0.992 1973 5 427 -0 0437 0 978 5 140 -0 0283 0976 1974 5 690 -00603 0989 5 023 0 0343 0 984 1975 5432 -0-0460 0 991 4 995 -00259 0992 1976 5457 -00478 0990 5032 -0 0278 0.995 ^F = Cumulative percentage of weight caught in each of seven size categories. C = lower limit of each of seven size categories, all b's were significantly differentfromzeroatthe 99 9% level of confidence. r^ - coefficient of determination. trends in b, and the trend for brown shrimp from Mississippi River to Texas was no longer different from zero at the 95% level of confidence (Table 3). However, elimination of points for the first 2 yr from the trends also reduced the degrees of free- dom from 16 to 14 for the test of significance of trends, so the test was less sensitive in this case. Whether or not the apparent trend was real for brown shrimp from Mississippi River to Texas could be determined by examination of data for years beyond 1976, as they become available. 988 CAILLOUET ET AL.: TRENDS TOWABD DECREASING SIZE OF SHRIMP Tables. — Trends in slopes (6) of regressions of transformed cumulative percentage (In Fl on size category (C) for brown and white shrimp, Mississippi River to Texas and Texas coast, 1959-76 vs. 1961-76 (based on data from Tables 1, 2; Figures 2. 3). Brown sfirimp Wtlite shrimp r^ississipp R -Texas Texas coast lulississ ppi R.-Texas Texas coast Item 1959-1976 1961-1976 1959-1976 1961-1976 1959-1976 1961-1976 1959-1976 1961-1976 Trend' Trend coefficient of determination 000036- 0-332 0 00026 0 172 0,00244- 0 492 000141 0289 0.00148- 0574 0.00077- 0.496 0.00255- 0 542 000183- 0448 ' Equals slope of the regression of P on x where x is the last two digits of each year -The change in slope (ft) per year was significantly different from zero at the 95% level of confidence. There was a positive correlation (r = 0.702) be- tween the slopes of regressions of transformed cumulative percentage on size category for brown and white shrimp from Mississippi River to Texas in 1959-76, that was significantly different from zero at the 99% level of confidence. The same was true (r = 0.742) for brown and white shrimp from the Texas coast. This indicated that the direction of the shift in size composition of reported catches within a given year was usually in the same di- rection for both species in a given State (Tables 1, 2). For a given weight of reported annual catch, the ex-vessel value of shrimp harvested in Louisiana is considerably less than that in Texas (Caillouet and Patella 1978), and this is largely a function of the size composition of the respective catches in the two States. Our analysis cannot distinguish whether the observed differences and trends in size composition of the reported catches are due to differences and trends in fishing mor- tality, natural mortality, or growth, but we suggest that the predominant causes of the ob- served differences and trends are differences and trends in fishing mortality. There is no evidence to indicate that separate shrimp stocks exist in these two States, or that natural mortality or growth differ between the two States (see Christmas and Etzold 1977). On the other hand the number and size of shrimp fishing craft and other indices of fishing effort are different in the two States and have increased over time (Christ- mas and Etzold 1977; Caillouet and Patella 1978). Also, differences and trends in time phas- ing of peak fishing activity in Texas and Louisiana within a year could have contributed to the differences and trends in size composition re- ported herein. Regardless of the cause or causes, continued shifts in size composition toward grea- ter proportions of smaller shrimp in the catches can be expected to weaken the ex-vessel value of the catches. LITERATURE CITED Caillouet, C. W., and F. J. Patella. 1978. Relationship between size composition and ex- vessel value of reported shrimp catches from two Gulf Coast States with different harvesting strategies. Mar. Fish. Rev. 40(21:14-18. CHRISTMAS. J. Y., AND D. J. ETZOLD (editors). 1977. The shrimp fishery of the Gulf of Mexico United States: A regional management plan. Gulf Coast Res. Lab., Ocean Springs, Miss., 128 p. HENDERSON, F. 1972. The dynamics of the mean-size statistic in a chang- ing fishery. FAO Fish. Tech. Pap. 116, 16 p. KUTKUHN,J. H. 1963. Gulf of Mexico commercial shrimp populations — trends and characteristics, 1956-59. U.S. Fish. Wildl. Serv., Fish. Bull. 62:343-402. National Marine Fisheries Service. 1970-78. Gulf coast shrimp data, annual summary 1967- annual summary 1976. U.S. Dep. Commer., NOAA, Natl. Mar, Fish. Serv.. Curr. Fish. Stat. 5412, 5721, 5925, 6126, 6425, 6725, 6925, 7225. RICKER.W. E. 1975. Computation and interpretation of biological statis- tics of fish populations. Fish. Res. Board Can.. Bull. 191, 382 p. U.S. FisH AND Wildlife Service. 1960-69. Gulf coast shrimp data, annual summary 1959— annual summary 1966. U.S. Fish. Wildl. Serv., Curr. Fish. Stat. 3 unnumbered publ., 3358, 3515, 3784, 4111,4411,4781,5107. 989 NOTES STAGE 1 ZOEAE OF A CRANGONID SHRIMP, CRANGON FRANCISCORVM ANGVSTIMANA, HATCHED FROM OVIGEROUS FEMALES COLLECTED IN KACHEMAK BAY, ALASKA Information on the larval stages of crangonid shrimp of the North Pacific Ocean is meager. Need- ier (1941) described the first zoeal stage of Cran- gon septemspinosa (as Crago septemspinosus Say) hatched in the laboratory from ovigerous females and the remaining four zoeal stages from plankton collected near Prince Edward Island, Canada. Kurata (1964) described the larval stages of C. affinis de Haan and various larval stages of six unidentified Crangon spp. from Japanese waters. He obtained the first zoeal stage of C. affinis from known parentage, but the remaining stages were collected from plankton. Makarov (1967) briefly described larvae of C. dalli Rathbun and C. sep- temspinosa (Say) which were collected from plankton along the western Kamchatka shelf. He suggested that C. dalli was an analog of C. allmani Kinahan and C. septemspinosa was an analog of C. crangon (Linnaeus). Crangon allmani and C crangon are eastern Atlantic species. He assumed that the C. affinis larvae described by Kurata (1964) were actually larvae of C. sep- temspinosa. Loveland ( 1968) described larvae of C alaskensis Rathbun reared in the laboratory from females collected near Anacortes, Wash. Morphology of Stage I larvae is closely related to Caridean development and can be used to estimate the number of larval stages, classify species, categorize larvae for identification purposes, and identify subsequent larval stages (Needier 1938; Pike and Williamson 1961, 1964; Kurata 1964; Ivanov 1971; and others). In this report I describe and illustrate the first zoeal stage of C. francis- corum angustimana Rathbun from ovigerous females and compare these zoeae with Stage I zoeae of crangonids described by other authors. Also, I show that the criterion of the absence of exopodites on the second pair of pereopods for dis- tinguishing larvae of Crangon from other genera of the Crangonidae is invalid for Crangonidae of the North Pacific Ocean. Methods Ovigerous C. franciscorum angustimana were caught at 30 m (16 fathoms) in shrimp pots in early May 1976 in Kachemak Bay, Alaska. Four females were kept in seawater in a plastic bucket for about Vi h and then each female was put into a 4 1 glass jar containing filtered, aerated seawater. The water was about 35%o salinity, about 6°C, and was changed daily until zoeae were released, about 5 days later. Most zoeae were released at night. I did not determine whether the larvae were hatched as prezoeae. Terms used in the text, nomenclature of gills and appendages, and techniques of measurement and illustration are given by Haynes ( 1976). As an aid to the study of segmentation and setation, some larvae were cleared in 10% KOH and the exoskeleton stained with Turtox' CMC-S (acid fuchsin stain mountant). Only the left number is figured because the paired appendages of the lar- vae are symmetrical; except, the mandibles are drawn as a pair. There was no morphological vari- ation, except variation in total length, among the zoeae used for the description. Stage I Zoea Mean total length of Stage I zoeae (Figure lA) was 3.1 mm (range 2.8-3.3 mm; 10 specimens). Rostrum slender, spiniform, without teeth, about one- third length of carapace. Carapace with small rounded prominence near posterior margin. Two distinct denticles immediately posterior to pterygostomian spine; no supraorbital or antennal spines. Eyes sessile. ANTENNULE (Figure IB).— First antenna, or antennule, an unsegmented peduncle (inner flagellum) bearing a conical projection and a setulose spine. Conical projection bears a simple seta and three aesthetascs of about equal length. ANTENNA (Figure IC).— Consists of inner flagellum (endopodite) and outer antennal scale (exopodite). Flagellum unsegmented, slightly ' Reference to trade names does not imply endorsement by the National Marine Fisheries Service. NOAA. FISHERY BULLETIN: VOL 77, NO 4. 1980. 991 shorter than scale, bears a setulose spine. Anten- nal scale not distally segmented, fringed with nine heavily plumose setae and subterminal plumose seta on outer margin. Protopodite bears spine at base of flagellum but not at base of scale. MANDIBLES (Figure ID).— Without palps; well developed. Incisor process of left mandible bears three teeth in contrast to biserrate incisor process of right mandible. Left mandible bears a movable premolar denticle (lacinia mobilis) adja- cent to incisor process and large subterminal tooth on truncated molar process. MAXILLULE (Figure IE).— First maxilla, or maxillule, bears coxal and basial endites and an 992 0.25 mm 1 .0 mm 0.25 mm Figure l. — Stage I zoeae o{ Crangon fmnciscorum angustimana: A. whole animal, right side; B. antennule. ventral; C. antenna, ventral; D. mandibles, left and right, posterior; E, maxillule, ventral; F, maxilla, dorsal; G, first maxilliped, dorsal; H, second maxilliped, dorsal; I, third maxilliped, dorsal; J, first pereo[>od, right side; K, second pereopod, right side; L, telson, dorsal. Setuleson setae are omitted for clarity; spinulose setae are shown. 993 endopodite. Proximal lobe (coxopodite) bears six spinulose setae. Median lobe (basipodite) bears five spinulose spines terminally. Unsegmented endopodite originates from lateral margin of basipodite and bears three terminal and two sub- terminal spinulose setae. No outer seta on maxil- lule. MAXILLA (Figure IF). — Exopodite (scaphog- nathite) bears four long plumose setae and a prox- imal seta; proximal end not projected posteriorly. Endopodite unsegmented; bears eight setae. Both basipodite and coxopodite bilobed. Basipodite bears eight setae, four on each lobe. Coxopodite bears 10 setae, three on distal lobe and seven on proximal lobe. Most setae on basipodite and coxopodite spinulose. FIRST MAXILLIPED (Figure IG).— Unseg- mented protopodite bilobed; bears 14 setae. En- dopodite four-segmented; setation formula 4, 1, 1, 3. Exopodite bears four natatory setae. No epipo- dite. SECOND MAXILLIPED (Figure IH).— Un- segmented protopodite not lobed; bears five setae. Endopodite four-segmented; setation formula 5, 2, 0, 5. Exopodite bears five natatory setae. THIRD MAXILLIPED (Figure II).— Unseg- mented protopodite not lobed; bears two setae. Endopodite nearly as long as exopodite; five- segmented; setation formula 4, 2,0, 1,2. Exopodite bears five natatory setae. PEREOPODS (Figure IJ, K).— Only pairs one to four present; pairs one and two (Figure IJ, K) biramous, pairs three and four uniramous. All pereopods poorly developed, unsegmented, and compacted tightly under cephalothorax. PLEOPODS.— Absent. ABDOMEN AND TELSON (Figure lA, L).— Abdomen consists of five somites (somite six is fused with telson in Stage I). Third somite bears a dorsal spine on posterior margin; fifth somite bears pair of spines on posterolateral margin that extend posteriorly about one-fourth length of fifth abdominal somite. Telson emarginated distally; bears 7 + 7 pairs of densely plumose setae. Minute spinules at base of each seta, except possibly last pair, and along posterior margin of telson to fourth setal pair and on setae themselves. No anal spine. Comparisons of Zoeal Stage I With Descriptions by Other Authors Of the published descriptions of Stage I zoeae of Crangon spp. from the North Pacific Ocean, Stage I zoeae of C. franciscorum angustimana are most similar to Stage I zoeae of C alaskensis, C. affinis, C. septemspinosa, and Kurata's ( 1964) "Species A" and "Species D." These examples are charac- terized by a median dorsal spine on the posterior margin of the third abdominal somite and by pos- terolateral spines on the fifth abdominal somite. Stage I zoeae of C. alaskensis can be distin- guished from Stage I C. franciscorum angus- timana by the rostrum and pereopods. In Stage I C. alaskensis the rostrum does not extend beyond the eyes and the pereopods are absent (Loveland 1968), but in Stage I C. franciscorum angustimana the rostrum extends beyond the eyes and the lar- vae bear undeveloped pereopods 1-4. Stage I zoeae of C. affinis and "Species A" are distinguished from Stage I zoeae of C. francis- corum angustimana by the presence in Stage I zoeae of C. affinis and "Species A" of a shallow transverse groove in the carapace and two sub- terminal setae along the outer margin of the an- tenna! scale. Also in Stage I C. affinis and "Species A," the endopodite of the third maxilliped is four segmented. In Stage I zoeae of C. franciscorum angustimana, the carapace does not have a shal- low transverse groove; there is only one subtermi- nal seta along the outer margin of the antennal scale; and the endopodite of the third maxilliped is five segmented. Stage I zoeae of Kurata's "Species D" are distin- guished from Stage I zoeae of C. franciscorum an- gustimana by the presence in Stage I zoeae of "Species D" of a five-segmented endopodite on the second maxilliped and pleopods that occur as dis- tinct buds. In Stage I zoeae of C. franciscorum angustimana, the endopodite of the second maxil- liped is four segmented and there are no pleopod buds. Stage I zoeae of C. septemspinosa are like Stage I zoeae of C franciscorum angustimana with some exceptions: the antennal scale of C septemspinosa bears five plumose setae and the endopodite of the first maxilliped is unsegmented (Needier 1941); whereas, the antennal scale of C. franciscorum angustimana bears 10 plumose setae and the en- dopodite of the first maxilliped is four segmented. Tesmer and Broad (1964) described nine zoeal stages of C. septemspinosa reared in the labora- tory from ovigerous females obtained off Beaufort, N.C. They found distinct morphological differ- ences between their zoeae and zoeae of the same species as described by Needier, especially in the later stages. Based on Tesmer and Broad's descrip- 994 tion, Stage I zoeae of C. septemspinosa can be dis- tinguished from Stage I zoeae of C. franciscorum angustimana by the exopodites of the maxilhpeds. The exopodites of the maxillipeds are jointed in Stage I zoeae of C. septemspinosa and are not jointed in Stage I zoeae of C. franciscorum angus- timana. Also, the fifth pair of telson spines are distinctly shorter than the fourth or sixth pair in C. septemspinosa: whereas, in my Stage I zoeae of C. franciscorum angustimana, the fifth pair of tel- son spines are about equal in length to the fourth and sixth pairs. The occurrence in later zoeal stages of func- tional exopodites on the first pair of pereopods but not on pereopodal pairs 2-5 has been used as a criterion for distinguishing larvae of the genus Crangon from larvae of other genera of the family Crangonidae( Williamson 1960). I found buds of exopodites on both the first and second pair of pereopods in Stage I zoeae of C. franciscorum angustimana. Assuming zoeae of C. franciscorum angustimana undergo typical de- velopment for crangonid larvae, these buds will become functional exopodites at Stage III or IV (Needier 1941; Kurata 1964; Makarov 1967). The criterion of the absence of exopodites on the second pair of pereopods for distinguishing larvae of Crangon from other genera of the Crangonidae, therefore, is invalid for the North Pacific Ocean. Unfortunately, larvae are described for only a few species of crangonids from the North Pacific Ocean, including the genus Crangon, and confirmation of the generic characteristics of the larvae is needed. Acknowledgment I thank Terry Butler, Pacific Biological Station, Nanaimo, British Columbia, Canada, for identify- ing the ovigerous females. Literature Cited haynes. e. 1976. Description of zoeae of coonstripe shrimp, Pandalus hypsinotus, reared in the lalMratory. Fish. Bull., U.S. 74:323-342. IVANOV.B. G. 1971. The larvae of some eastern shrimps in relation to their taxonomic status, [in Russ.Engl. summ ] Zool Zh. 50:657-665 Kurata. H. 1964 Larvae of decapod Crustacea of Hokkaido. 4. Cran- gonidae and Glyphocrangonidae. [in Jpn.. Engl, summ.] Bull. Hokkaido Reg. Fish. Res. Lab. 28:35-50. (Translated by Division of Foreign Fisheries, Natl. Mar. Fish. Serv., NOAA.) LOVELAND.H. A..JR, 1968. Larval development under laboratory conditions of Crangon alaskensis Rathbun. (Crustacea:Decapo- da). M.A. Thesis. Walla Walla Coll., Walla Walla, Wash., 22 p. Makarov. R. R. 1967. Larvae of the shrimps and crabs of the west Kamtschatkan shelf and their distribution. (Translated from Russ. by B. Haigh. ) Natl. Lending Libr. Sci. Technol , Boston Spa. Yorkshire, 199 p. NEEDLER.A. B. 1938. The larval development of Pandalus stenolepis. J. Fish. Res. Board Can. 4:88-95. 1941. Larval stages of Crago septemspinosus Say. Trans. R. Can. Inst. 23:193-199. PIKE, R. B., .\ND D. I. Williamson 1961. The larvae of Spirontocaris and related genera (De- capoda, Hippolytidae). Crustaceana 2:187-208. 1964. The larvae of some species of Pandalidae (Decapo- da). Crustaceana 6:265-284. Tesmer, C. a. , and a. C. Broad 1964. The larval development of Crangon septemspinosa (Say) (Crustacea:Decapoda). Ohio J. Sci. 64:239-250. Williamson, D.I. I960. Crustacea, Decapoda: Larvae VII. Caridea, Family Crangonidae, Stenopodidea. Cons, Int. Explor. Mer, Fiches Identification Zooplankton 90. 5 p EvanHaynes Northwest and Alaska Fisheries Center Auke Bay Laboratory National Marine Fisheries Service, NOAA P.O Box 155 Auke Bay. AK 99821 LENGTH-WEIGHT RELATIONSHIPS OF WESTERN ATLANTIC BLUEFIN TUNA, THVNNUS THYNNUS' The Atlantic bluefin tuna, Thunnus thynnus, is seasonally distributed over most of the North At- lantic Ocean from Newfoundland to Brazil and from Norway to the Canary Islands (Gibbs and Collette 1967). There has been a great reduction in the Atlantic-wide catch ( including Mediterranean ) from 38,500 metric tons (t) in 1964 to 12,500 t in 1973 (Miyake et al. 1974). Because of this, a number of studies have been made and are being continued in order to understand the reason for this decline (Parks 1977; Shingu and Hisada 1977). 'Contribution Number SEFC 80-OlM, Southeast Fisheries Center Miami Laboratory, National Marine Fisheries Service, NOAA, Miami. Fla. FISHERY BULLETIN: VOL, 77. NO. 4, 1980, 995 Length-weight, length-to-length, and weight- to-weight relationships are necessary in popula- tion analyses for converting one measurement to another. In this paper I present the relationships o*" the following: round weight-straight fork length, round weight-dressed weight, and straight fork length-curved fork length. During my review of bluefin tuna literature, I found a lack of information on size relationships. Mather and Schuck (1960) used a length-weight curve based on 778 bluefin tuna from Cape Cod to estimate length. They did not indicate, however, when these fish were collected. They did not give a regression formula for the length-weight relation- ship, but they did present a straight length-curved length relationship based on 185 measurements fitted by inspection. Rodriguez-Roda (1964, 1971) collected 793 bluefin tuna and then determined the length-weight relationship. Of these, 467 bluefin tuna (prespawning) were entering the Mediterranean during May and June and 326 bluefin tuna (postspawning) were leaving the Mediterranean during July and August 1956, 1958, 1959, and 1961. Butler (1971) determined the length-weight relationship by the standard least squares regression method for 237 giant bluefin tuna caught during July through Sep- tember 1966 from Conception Bay, Newfound- land. Mather et al. (1974) presented regression equations for converting from weight to length for bluefin tuna from Newfoundland, Libya, and the Bahamas from data supplied by the Fisheries Re- search Board of Canada, the International Council for the Exploration of the Sea, and the Woods Hole Oceanographic Institution. They also presented an equation for converting dressed weight to round weight. The method of determining the equations, the sample sizes, and time period sam- pled were not presented. Coan (1976) gave a length, weight, and age conversion tablefor bluefin tuna of both sexes. He converted length to weight based on a length-weight regression given in Sakagawa and Coan (1974), who had in turn, ob- tained this regression from Frank J. Mather, Woods Hole Oceanographic Institution. Unfortu- nately, there was no mention of sample size, loca- tion, or date. Methods Bluefin tuna length and weight measurements were collected during 1974 through 1977 from var- ious landing points and processing plants along 996 the east coast of the United States from Florida to Maine and from the Bahamas. These fish had been caught by purse seine, rod and reel, handline, and harpoon. Straight fork length (centimeters) was measured by caliper, and curved fork length (cen- timeters) was measured along the body contour by tape. Round weight (total weight of fish when caught) and dressed weight (head, viscera, and tail removed) were recorded in pounds and later con- verted to kilograms. Ricker ( 1973) showed that the geometric mean (GM) regression can be used for a majority of biological situations as a reasonable and consis- tent estimate of the functional slope because most of the variability is natural. The functional (GM) regression was calculated for the. logarithmic transformation of the length- weight relationship for 3,578 bluefin tuna taken from May through October. The GM regression was also calculated for the relationship between round weight and dressed weight for 685 bluefin tuna taken from July through September, and for the straight fork length to curved fork length rela- tionship for 606 bluefin tuna taken from July through October. The general equation for the GM regression as given by Ricker is: Y = u + vX, with variables X and J^, and u is they-axis intercept, where u =Y - vX, V is the slope, and v = [1y^l1x^\^. where y = y, - y and X = Z, - X. The limits on all i are i = \, . . . , n. The standard error of the slope was computed for each regression equation using the following equa- tion from Ricker (1973): S, = [S^^'^I^'^W where Si, is the standard error of the slope and Svj ^ is the mean square or variance of the obser- vations from the regression line in the vertical direction. Results and Discussion Based on the classification system of Rivas and Mather (in press), the fish sampled mainly con- sisted of two size categories, giant bluefin tuna ( >180 cm straight fork length and 130 kg round weight) and small bluefin tuna ( < 130 cm straight fork length or '45 kg round weight). Based on previous growth studies by Mather and Schuck (1960), the giant fish are probably age 9 and older and the small bluefin tuna are most likely age 4 or younger. Very few medium bluefin tuna ( 130-180 cm straight fork length and 45-130 kg round weight) probably ages 5 through 8 were sampled. The functional (GM) regressions for straight fork length-round weight (log transformation), round weight-dressed weight, and straight fork length-curved fork length are presented in Table 1. All of these relationships were characterized by high correlation coefficients. The data points are plotted with regression lines in Figures 1-3. The data points show that the GM regression model fits the data reasonably well for the size ranges studied. Extrapolation beyond the size range of observations may yield erroneous predictions. Re- gression statistics for each relationship are pre- sented in Table 2. The use of logarithmic transformations may lead to bias in data estimates (Pienaar and Thom- son 1969; Beauchamp and Olson 1973; Lenarz 1974). However, since the mean square error for the round weight-straight fork length logarithmic transformation is low (Table 2), the bias in the data estimate was found to be minimal ( 19c ). Previous publications have not included stan- dard errors or confidence limits or statistics neces- sary for their estimation. Therefore, comparisons with my data could not be made. To compare re- sults from my study with studies by other authors, I compared estimates of Y using both their regres- sion equations and mine. Whenever possible, I Table l. — Functional (GM1 regression equation and correlation coefficient for the relationships between round weight (Y) and straight forli length (X), round weight (Yl and dressed weight (X). and straight fork length (Y) and curved fork length (X) for western Atlantic bluefin tuna. Weights in kilograms and lengths in centimeters. Geometric mean regression equation r Log,o round weight - 109,0 straight foric length log,„y= -4 52307 + 2 91920 log, oJ< Round weight - dressed weight Y = -7 92240 + 1 29607 X Straight fork length - curved fork length: y = -2 06971 ^ 0 963300 X 0 997 0.935 0,892 selected X values at each end of their range of values that corresponded with my range of values. I also compared estimates of Y for an X value taken at the middle of their size range. My estimates of round weight from straight fork length using the functional (GM) regression agreed most closely with my estimates obtained using the regression equation of Sakagawa and Coan (1974), with the greatest difference in esti- mates of only 2% occurring for a 270 cm fork length (FL) bluefin tuna. My calculated functional regression estimates next most closely agreed with estimates obtained using the length-weight relationship of Butler ( 1971), with the largest dif- ference of 6% occurring at 250 cm FL. My esti- o Figure l.— Functional (GM) regression of round weight on straight fork length for 3,578 western Atlantic bluefin tuna 1974-77. (Number of fish indicated, star signifies number >9.) 1 ^51 rTT' 12 20 160 1 200 240 1 280 320 STRAIGHT FORK LENGTH (Cm) 997 13 a z s o DRESSED WEIGHT (Kg) FIGURE 2. — Functional (GM) regression of round weight on dressed weight for 685 western Atlantic bluefintuna 1974-77. (Number of fish indicated, star signifies number >9.) Table 2.— Regression statistics for logio round weight (Yi - log,o straight fork length (X). round weight (Y) - dressed weight (XA and straight fork length (Y) - curved fork length (Xj of western Atlantic bluefin tuna. Weights in kilograms and lengths in centimeters. Ix' \~v2 2.xy Syx' Log,o round weight - log,o straight fork length 3,578 2 19254 187739 222 745 1.898 17 648 054 0 00356051 0,00399809 Round weight dressed weight 685 256.993 325 158 832.635 1.398.650 1.009.090 257 261 0 0175776 Straight fork length - curved fork length 606 271.477 259.444 120.979 112.262 103,959 37.9615 0.0177140 mates of weight from length differed most from estimates which I calculated using equations of Rodriguez-Roda (1964, 1971). The largest varia- tion (12%) was found for a prespawning fish measuring 48 cm. No size range was reported by Mather et al. (1974) for estimating length from weight. How- ever, estimated length corresponding to the ex- tremes and middle of the size range in weight I studied agree closely to values I calculated using their regression equation for Newfoundland, with the greatest difference being only 39r for a 5 kg fish. A greater difference (13%) was noted when comparing estimates from my functional (GM) re- gression with estimates obtained using their re- gression equation for the Bahamas for a 5 kg fish. This large difference may have resulted from their not including fish in this size range when calcu- lating their equation because differences at the middle and upper end of my size range were small, 4% or less. There appears to be a typographical error in the equation these authors gave for bluefin tuna from Libya, so no comparison was made. My functional (GM) regression estimates of round weight from dressed weight agree well with the estimates I obtained using the regression equation of Mather et al. (1974). The largest dif- 998 E O MS- X u P 23S O 5 22S- 1 205 1 2 IS 1 22S 1 24S -I — 275 1 305 2SS 26S CURVED FORK LENGTH (Cm) Figure 3. — Functional (GM) regression of straight fork length on curved fork length for 606 western Atlantic bluefin tuna 1974-77. (Number offish indicated, star signifies number >9.) ference I found was SVe for a 130 cm bluefin tuna. Again I used my range of values for dressed weight since the range was not given by these authors. My functional (GM) regression estimates of straight fork length from curved fork length agree very closely over my entire size range with esti- mates I obtained using the regression equation given by Mather and Schuck (1960). The largest difference I found, only 1%, occurred at the lower end of my range of curved fork length values of 200 Acknowledgments I thank Gary Sakagawa of the Southwest Fisheries Center, National Marine Fisheries Ser- vice (NMFS), NOAA; Emma Henderson of the Northeast Fisheries Center, NMFS, NOAA; Fred- erick Berry, Raymon Conser, Mark Farber, Michael Parrack, William Richards, Luis Rivas, James Tyler, and James Zuboy of the Southeast Fisheries Center, NMFS, NOAA; and Arvind Khilnani of Stanford University for their helpful comments on the manuscript. I also thank Tom Chewning of the Southeast Fisheries Center for computer programming assistance. Literature Cited BEAUCHAMP. J. J., AND J. S. OLSON, 1973. Corrections for bias in regression estimates after logarithmic transformation. Ecology 54:1403-1407. BUTLER, M. 197 1 . Biological investigation on aspects of the life history of the bluefin tuna 1970-1971 Newfoundland and Lab- rador Tourist Development Office, St, Johns, 169 p. COAN, A, L. 1976. Length, weight and age conversion tables for Atlan- tic tunas. Int. Comm. Conserv. Atl. Tunas, Collect. Vol. Sci. Pap. 5 (SCRS-1975):64-66. GIBBS, R. H., Jr., and B. B. COLLETTE. 1967. Comparative anatomy and systematica of the tunas, genus Thunnus. U.S. Fish Wildl. Serv., Fish. Bull. 66:65-130. LENARZ, W. H. 1974. Length-weight relations for five eastern tropical At- lantic scombrids. Fish. Bull., U.S. 72:848-851. Mather, F. J., Ill, J. M, Mason, and A. C. Jones. 1974. Distribution, fisheries and life history data relevant 999 to identification of Atlantic bluefin tuna stockB. Int. Coram. Conserv. Atl. TunaB, Collect. Vol. Sci. Pap. 2 (SCRS-1973):234-258. Mather, F. J., m. and H. a. Schuck. I960. Growth of bluefin tuna of the western North Atlan- tic. U.S. Fish WUdl. Serv., Fish. Bull. 61:39-52. Ml YAKE, M. P., A. A. DeBOISSET, AND S. MANNING (compilers). 1974. International Commission for the Conservation of Atlantic Tunas. Stat. Bull. 5, Unnumbered pages. Parks, W. W. 1977. Cohort and equilibrium yield-per-recruit analyses for the Atlantic bluefin tuna fisheries system accounting two system configurations and two natural mortality models. Int. Comm. Conserv. Atl. Tunas, Collect. Vol. Sci. Pap. 6 (SCRS-1976):385-401. PIENAAR, L. v., AND J. A. THOMSON. 1969. AUometric weight-length regression model. J. Fish. Res. Board Can. 26:123-131. RICKER, W. E. 1973. Linear regressions in fishery research. J. Fish. Res. Boatxl. Can. 30:409-434. RivAS, L. R., AND F. J. Mather ni. In press. Proposed terminology for size groups of the north Atlantic bluefin tuna Thunnus thynnus. Int. Comm. Conserv. AU. Tunas, Collect. Vol. Sci. Pap. (SCRS-1978). RODRIGUEZ-RODA, J. 1964. Biologia del Atiin, Thunnus thynnus (L.), de la costa sudatlantica de Espana. Invest. Pesq. 25:33-146. 1971. Investigations of tuna [Thunnus thynnus) in Spain. In Report for biennial period 1970-71, Part II, p. 110-113. Int. Conrna. Conserv. Atl. Tunas. Sakagawa, G. T., and a. L. COAN. 1974. A review of some aspects of the bluefin tuna Thun- nus thynnus thynnus fisheries of the Atlantic Ocean. Int. Comm. Conserv. Atl. Tunas, Collect. Vol. Sd. Pap. 2 (SCRS-1973):259-313. Shingu, C, and K. HISADA. 1977. A review of the Japanese Atlantic longline fishery for bluefin tuna and the consideration of the present status of the stocks. Int. Comm. Conserv. Atl. Tunas, Collect. Vol. Sci. Pap6 (SCRS-1976):366-384. RAYMOND E. BAGLIN, JR. Southeast Fisheries Center Miami Laboratory National Marine Fisheries Service, NOAA 75 Virginia Beach Drive, Miami, Fl 33149 Present adireBa: National Marine Fisheries Service, NOAA do Alaska Department of Fish and Game P.O. Box 686, Kodtak, AK 99615 DEVELOPMENTAL ANATOMY AND INFLATION OF THE GAS BLADDER IN STRIPED BASS, MORONE SAXATILIS In 1974, a percentage of striped bass, Morone saxatilis, fingerlings reared at the Cooperative Fishery Research Laboratory, Southern IlUnois University, lacked an inflated gas bladder. The purpose of this study was to describe the de- velopmental anatomy of the gas bladder and its associated structures in striped bass so that a bet- ter understanding of the inflation mechanism could be obtained. With regard to gas bladder morphology, bony fishes are classified as physostomes or physocUsts. Generally, the more ancient, soft-rayed fishes (Malacopterygii) are physostomous, while the more modern, spiny-rayed fishes (Acanthop- terygii) are physoclistic (Lagler et al. 1962). A physotome possesses a hollow connection, the pneumatic duct, between the gut and the gas blad- der throughout its entire life. Some physotomes gulp surface air through the pneumatic duct to initiate inflation of the gas bladder (Tait 1960). Fish that are physoclistic do not possess this open connection as adults. Some physoclists, however, do possess a pneumatic duct as larvae, but the duct atrophies prior to adulthood. Giinther's (1880) examinations have shown that adult striped bass are physoclistic. Doroshev and Comacchia ( 1979) give a partial description of the development of the gas bladder in striped bass. Several theories have been advanced to explain how the gas bladder is initially inflated in fishes that do not gulp surface air or are physoclistic prior to initial inflation. Some of these theories include: gases produced by the disintegration of organic materials (Powers 1932); production of gasses as a result of digestion (Johnston 1953); vacuolation of the gas bladder epitheUa (McEwen 1940); and functioning of a rete mirabile, or gas gland (Schwarz 1971). Methods Histomorphological Studies Striped bass larvae were obtained from the Hudson River, N.Y., and Lake Charles, La. Upon arrival, the 1- to 4-day-old larvae were transferred into 200 1 aquaria and maintained at 16°-18° C. Brine shrimp, A rfemta salina, were fed regularly to the larvae. Eighty-three striped bass larvae 4.3-24 days old (from the time of hatching) were removed from the aquaria and prepared for his- tological study. The larvae were fixed in either 10% Formalin^ or Bouin's fluid, dehydrated in a series of graded alcohols, cleared in benzene, and embedded in Carbowax. From a representative 'Reference to trade names does not imply endorsement by the National Marine Fisheries Service, NOAA. 1000 FISHERY BULLETIN VOL 77. NO 4. 1980 series of 34 larvae, we prepared transverse and longitudinal series sections 7 and 10 fim thick (Table 1). The mounted specimens were stained with either Harris's hematoxylin and eosin or a modification of Mallory's connective tissue stain (Martan^). Table l. — Number of striped bass larvae sectioned to deter- mine the internal anatomy of the gas bladder and its associated structures. Age With inflated Without inllated (days) gas bladder gas bladder 4,3 1 2 4.8 2 3 5.5 2 2 6.0 5 1 7.0 2 0 8.0 2 2 14.0 0 3 21 0 0 1 24.0 4 2 Results During laboratory aquaria experiments, striped bass larvae were observed with inflated gas bladders as early as day 4. A pestk period of inflation occurred during day 5, closely corre- sponding with the absorption of the yolk sac. Doroshev and Cornacchia (1979) found that striped bass inflated their gas bladder from the 5th to the 7th day. Striped bass larvae with inflated gas bladders were easily distinguished from larvae with un- inflated gas bladders. Morphologically, the newly inflated gas bladder has the general appearance of a small air bubble, located dorsal to the gut. Behaviorly, larvae that had inflated gas bladders oriented horizontally within the water column and maintained their position without continual swimming motion. Larvae without inflated gas bladders assumed a vertical swimming position, sinking when swimming movements ceased. This characteristic swimming behavior of larvae with noninflated gas bladders was defined as "swim- up" behavior. In 4.8-day-old striped bass larvae, the nonin- flated gas bladder primordium was dorsal and slightly posterior to the jimction of the esophagus and the stomach. The stomach was at the right of the dorsomedial gas bladder primordium. The walls of the noninflated gas bladder primordium were much thicker ventrally than either dorsally ^Martan, J. 1968. Laboratory instructions: Histological techniques in zoology. South. 111. Univ., Carbondale, 98 p. or laterally. Columnar epithelium comprised the ventral mass of the gas bladder primordium. The noninflated gas bladder possessed a slight, dor- sally located lumen. An open pneumatic duct connected the foregut with the right side of the posterior wall of the gas bladder primordium. The duct was composed of a single layer of cuboidal epithelium, surrounded by a layer of connective tissue. A network of arterioles and venules, a rudimentary rete mirabile, ran parallel and ven- tral to the noninflated gas bladder primordium. At the posterior end of the gas bladder, the rete ar- terioles and venules turned dorsoanteriorally and entered a layer of loose connective tissue adjacent to the ventral columnar epithelium of the gas bladder. Within this connective tissue, a network of capillaries connected the arterioles and ven- ules. Since the rete mirabile proceeded directly to the secretory epithelium of the gas bladder, the whole structure may properly be called a gas gland (Steen 1970). A gas gland is formed in striped bass before the initial inflation of the gas bladder. In older (8 days) striped bass larvae that still had a noninflated gas bladder, the capillary net- work was more developed and pushed closer to the ventral columnar epithelium of the gas blad- der. This gave the epithelium a festooned appear- ance. In striped bass larvae that were in the process of inflating their gas bladders, the initial infla- tion occurred at the anterior end of the gas blad- der. The columnar epithelium, which previously had dominated the ventral wall of the gas blad- der, became confined to the posterior portion of the gas bladder as inflation progressed. At no time were distinct vacuoles visible within the ventral, columnar epithelium. In 5.5-day-old striped bass larvae that pos- sessed an inflated gas bladder, the ventral epithelium was reduced to cuboidal epithelium and was restricted to the posteriorventrad portion of the gas bladder where it was in close association with the gas gland. The remaining walls of the inflated gas bladder were composed of stretched epithelium. The rete mirabile still ran parallel and ventral to the newly inflated gas bladder. Capillaries of the rete mirabile made contact with secretory epithelium towards the posterior of the gas bladder. In all striped bass larvae which were 4.3-5.5 days old and possessed an inflated gas bladder, a 1001 pneumatic duct with a well-defined lumen still appeared to form a connection between the gut and the gas bladder. However, in the older larvae of this group, the lumen of the pneumatic duct was smaller. In some sections, the openings be- tween the pneumatic duct and the gut and the pneumatic duct and the gas bladder were not plainly visible, indicating that the pneumatic duct was beginning to atrophy. We examined 14- and 21-day-old striped bass larvae without inflated gas bladders, and 24- day-old larvae with and without inflated gas bladders. In 14-, 21-, and 24-day-old larvae that had noninflated gas bladders, a well-developed rete mirabile still ran ventral and parallel to the gas bladder, turning dorsally to make a medial connection. The retail capillary network was de- veloped, distending the overlaying connective tis- sue into a villuslike structure which was bor- dered by the ventral, columnar (secretory) epithelium of the gas bladder. The villuslike pro- jections occupied most of the internal volume of the gas bladder. The pneumatic duct was well defined and continued to connect the gut with the gas bladder. In 24-day-old striped bass larvae that had inflated gas bladders the pneumatic duct was ab- sent. Unfortunately, we did not collect any striped bass larvae with inflated gas bladders be- tween day 8 and day 24. We were thus unable to accurately describe the atrophication of the pneumatic duct, which seemingly occurs after inflation of the gas bladder. The rete mirabile was connected to a narrow band of cuboidal epithelium at the ventromedial wall of the gas bladder. Discussion Striped bass larvae possess an open pneumatic duct. An experiment designed to determine if striped bass have to gulp surface air to initiate gas bladder inflation was inconclusive, as was a similar experiment conducted by Doroshev and Cornacchia (1979). However, allowing striped bass larvae unobstructed access to the surface did not guarantee inflation in either study. In our study, the pneumatic duct had atrophied in 24-day-old larvae which had inflated their gas bladders, but an open pneumatic duct was still present in 24-day-old larvae which had not inflated their gas bladders. This suggests that inflation of the gas bladder stimulates the at- rophication of the pneumatic tube in striped bass. Johnston (1953) observed a similar phenomenon in the largemouth bass, Micropterus salmoides. The rete mirabile, or gas gland, is developed before initial inflation of the gas bladder in larval striped bass. Since the gas gland concentrates gases within the gas bladders of many adult fishes, it is reasonable to assume that the gas gland plays a role in achieving initial inflation of the gas bladder in larval striped bass. The con- tinued presence of a gas gland, and the prolonged retention of an open pneumatic duct in striped bass larvae that had not achieved initial inflation of the gas bladder within 24 days suggests that initial inflation may occur over an extended period of time. Other workers have indicated that failure to initiate inflation of the gas bladder may lead to slower growth rates (Tait 1960), a higher per- centage of morphological abnormalties (Baker^), and an increased susceptibility to stress (Lewis et al.''). Studies designed to define the stimuli re- sponsible for the initiation of gas bladder infla- tion in striped bass, an important sport fish species that is often cultured, would be beneficial. Literature Cited Doroshev, S. I., and J. W. Cornacchia. 1979. Initial swim bladder inflation in the larvae of Tilapia mossambica (Peters) and Morone saxatilis (Wal- baum). Aquaculture 16:57-66. GUNTHER.A. C. L. G. 1880. An introduction to the study of fishes. Adams and Charles Black, Edinb., 720 p. Johnston, p. m. 1953. The embryonic development of the swim bladder of the largemouth black bass Micropterus salmoides sal- moides (Lacepedel. J. Morphol. 93:45-67. Lagler, k. F, J. E. Bardach, and r. r. Miller. 1962 Ichthyology. Wiley,N.Y.,545p. McEWEN.R. S. 1940. The early development of the swim bladder and cer- tain adjacent parts in Hemichromis bimaculata. J. Morphol. 67:1-59. POWERS, E. B. 1932. The relation of respiration of fishes to environ- ment. Ecol.Monogr. 2:385-473. SCHWARZ, A. 1971 , Swimbladder development and function in the had- ^Baker, J. F. 1975. The rearing of Hudson River striped bass at the Edenton National Fish Report prepared for Consolidated Edison Company of New York, Inc.. 30 p. ^Lewis. W. M., R. C Heidinger, and B. L. Tetzlaff. 1977. Striped bass rearing experiments 1976. Report pre- pared for Consolidated Edison Company of New York, Inc., 197 p. 1002 dock, Melanogrammus aegleftnus L. Biol. Bull. (Woods Hole) 141:176-188. STEEN, J. B. 1970. The swimbladder as a hydrostatic organ. In W S. Hoar and D. J. Randall (editors), Fish physiology, Vol. IV, p. 413-443. Acad. Press, N.Y. Tait.J.S. 1960. The first filling of the swim bladder in salmonoids. Can. J. Zool. 38:179-187. Table l. — Collections of age 1 and 2 Atlantic tomcod from Haverstraw Bay, Hudson River, 1973-76. Sample size Total length (mm) Season Mean 95% confidence limits Winter (Jan -Feb.) Spring (Apt -June) Summer (July-Aug.) Fall (Oct -Dec ) 72 165 10 91 130 5 1587 156.3 182 6 1262-1347 155 8-161 6 1422-170.3 178.3-186.8 James S. bulak Fisheries Research Laboratory and Department of Zoology Southern Illinois University, Carbondale, III. Present address: South Carolina Wildlife and Marine Resources Department P.O. Boxl70,Bonneau. SC 29431 RoyC. Heidinger Fisheries Research Laboratory and Department of Zoology Southern Illinois University Carbondale, IL 62901 FOOD OF AGE 1 AND 2 ATLANTIC TOMCOD, MICROGADUS TOMCOD, FROM HAVERSTRAW BAY, HUDSON RIVER, NEW YORK Atlantic tomcod, Microgadus tomcod (Walbaum), are opportunistic fee(iers (Howe 1971; Grabe 1978) with amphipods Gammarus spp. and the decapod Crangon septemspinosa identified as primary prey (Howe 1971; Alexander 1971; Scott and Grossman 1973; Grabe 1978; NittelM. Lim- ited data are available on the biology of year- ling and older Hudson River tomcod due to their low overall abundance and because they are most abundant during winter when ice cover restricts sampling. This note summarizes feeding data of 339 tomcod, ages 1 and 2, from the Haverstraw Bay area of the Hudson River (37.5-41.5 mi north of the Battery, New York City) on 19 dates, January 1973- June 1976, and supplements food preference data on juveniles (Grabe 1978). All fish were collected as part of an ecological monitoring program conducted by Lawler, Matusky & Skelly Engineers for Orange and Rockland Utilities, Inc. Methods Collections (Table 1) were made with a 9.1 m otter trawl (64 mm mesh cod end liner) towed against the tide at 1.5-2.0 m/s during both day and night. The data are likely to be biased to- wards daytime feeding preferences since almost twice as many tows were taken during daytime as at night. Diel differences in feeding could not be evaluated because day and night collections were often combined for other analyses. Fish were pre- served in 10% buffered Formalin.^ In the labora- tory they were measured ( ± 1 mm total length, TL) and weighed (±0.1 g), and the stomachs were removed and preserved in 70% ethanol. Prey were identified and counted, and the contents of 195 stomachs were dried at 103° C. The number of fish per sampling period whose stomach contents were analyzed were limited by contract and were randomly selected from the total catch. Whenever possible, I analyzed additional fish to increase both sample size and temporal coverage. Yearling and older tomcod collected during fall 1973 were separated from young-of-the-year by examination of length-frequency histograms drawn from larger samples (Lawler, Matusky & Skelly En- gineers^); by this method age 1 and 2 fish were those 3^160 mm TL. On other sampling dates young-of-the-year were present only as larvae or as juveniles < 1 10 mm TL. Food preference data were classified seasonally and examined as percentage occurrence (number of fish in which prey item "a" occurred/total number offish), percentage composition (number of prey item "a'Vtotal number of prey), and as im- portance, I, the geometric mean of these two mea- surements (Windell 1971). This approach, how- ever, may overestimate the utilization of smaller prey (e.g., copepods) but should provide a better indication of feeding preference than either per- cent occurrence or percent composition taken singly. An index of fullness (Windell 1971), If, was calculated to evaluate feeding intensity (dry 'Nittel, M. 1976. Food habits of Atlantic tomcod Mi- crogadus tomcod) in the Hudson River. In Hudson River Ecology. Fourth Symposium on Hudson River Ecology. Bear Mountain, NY., March 28-30 1976. Hudson River Environmen- tal Society, Inc. ^Reference to trade names does not imply endorsement by the National Marine Fisheries Service, NOAA. ^Lawler, Matusky & Skelly Engineers. 1976. Environ- mental impact assessment — water quality analysis: Hudson River. Natl Comm on Water Quality. NTIS PB-251099, FISHERY BULLETIN: VOL 77. NO, 4. 1980 1003 weight of stomach contents x 10* as a percentage of wet weight offish). Empty stomachs were in- cluded in seasonal measurements of feeding in- tensity. Statistical tests were from Sokal and Rohlf(1969). Results and Discussion Gammarus spp. were the most important prey during all seasons (Table 2). Secondary prey in- cluded copepods (winter), the oppossum shrimp, Neomysis americana (spring and fall) Monoculodes sp. (Amphipoda) (spring), Cyathura polita (Isopoda) (spring and fall), and sand shrimp, Crangon septemspinosa (fall). Gam- marus spp., N. americana, and Monoculodes sp. are numerically important tychoplankters in this area of the Hudson River (Ginn 1977; Lauer et al.'*). Abundant infaunal species in the Haverstraw Bay area include the polychaete Scolecolepides viridis the amphipod Lep- tocheirus plumulosus, and Cyathura polita (Ris- tich et al. 1977). Tychoplankton appears to be more important as prey of Hudson River tomcod than infauna. In other estuaries, however, in- fauna may be more important; e.g., Alexander (1971) found that polychaetes, even though