NOAAFSYB-A 72-1 ,*^'''°"^o^ Fishery Bull National Oceanic and Atmospheric Administration • National Mar Vol. 72, No. 1 January 1974 KITTREDGE, J. S., FRANCIS T. TAKAHASHI, JAMES LINDSEY. and REUBEN LASKER. Chemical signals in the sea: Marine allelochemics and evolution 1 FULLENBAUM, RICHARD F., and FREDERICK W. BELL. A simple bioeconomic fisheiT management model: A case study of the American lobster fishery 13 OLLA, BORI L., ALLEN J. BEJDA, and A. DALE MARTIN. Daily activity, move- ments, feeding, and seasonal occurrence in the tautog, Tautoga onitis 27 LENARZ, W. H., W. W. FOX, JR., G. T. SAKAGAWA, and B. J. ROTHSCHILD. An examination of the yield per recmit basis for a minimum size regulation for Atlantic yellowfin tuna. Thniiiius albacares 37 FLEMINGER, A., and K. HULSEMANN. Systematics and distribution of the four sibling species comprising the genus Pontellina Dana (Copepoda. Calanoida) 63 HUGHES, STEVEN E. Stock composition, growth, mortality, and availability of Pacific saury, Cololabis saira, of the northeastern Pacific Ocean 121 ANAS, RAYMOND E. Hea\y metals in the northern fur seal, Callorhiinis ursinus, and harbor seal, Phoca vituUita ricliardi 133 WAHLE, ROY J., ROBERT R. VREELAND, and ROBERT H. LANDER. Bio- economic contribution of Columbia River hatchery coho salmon. 1965 and 1966 broods, to the Pacific salmon fisheries 139 POWELL, GUY C, KENNETH E. JAMES, and CHARLES L. HURD. Ability of male king crab. Paralithodes camtschatica, to mate repeatedly, Kodiak, Alaska, 1973. 171 WICKHAM, DONALD A., and GARY M. RUSSELL. An evaluation of mid-water artificial structures for attracting coastal pelagic fishes 181 GRANT, GEORGE C. The age composition of striped bass catches in Virginia Rivers, 1967-1971, and a description of the fishery 193 PEARCY, WILLIAM G., and SHARON S. MYERS. Larval fishes of Yaquina Bay. Oregon: A nurser>' ground for marine fishes? . 201 PARK, TAISOO. Calanoid copepods of the genus Aetideus from the Gulf of Mexico . . 215 LIGHTNER. DONALD V. Normal postmortem changes in the brown shrimp, Pe)iaeus aztecHH 223 STRUHSAKER, PAUL, and ROBERT M. MONCRIEF. Bothii^ thonip.s(>,ii (Fowler) 1923. a valid species of flatfish (Pisces; Bothidae) from the Hawaiian Islands 237 Note CABLE, WAYNE D., and WARREN S. LANDERS. Development of eggs and em- biyos of the surf clam, Spisula Holidissinia, in synthetic seawater 247 Seattle, Wash. U.S. DEPARTMENTOFCOMMERCE Frederick B. Dent, Secretary NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION Robert M. White, Adminisfrator NATIONALMARINE FISHERIES SERVICE Robert W. Schoning, Director Fishery Bulletin The Fishery Bulleiin 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, the Fishery 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, D.C. 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. Reuben Lasker Scientific Editor, Fishery Bulletin National Marine Fisheries Service Southwest Fisheries Center , La Jolla, California 92037 Editorial Committee Dr. Elbert H. Ahlstrom National Marine Fisheries Service Dr. William H. Bayliff Inter-American Tropical Tuna Commission Dr. Daniel M. Cohen National Marine Fisheries Service Dr. Howard M. Feder University of Alaska Mr. John E. Fitch California Department of Fish and Game Dr. Marvin D. Grosslein National Marine Fisheries Service Dr. J. Frank Hebard National Marine Fisheries Service Dr. John R. Hunter National Marine Fisheries Service Dr. Arthur S. Merrill National Marine Fisheries Service Dr. Virgil J. Norton University of Rhode Island Mr. Alonzo T. Pruter National Marine Fisheries Service Dr. Theodore R. Rice National Marine Fisheries Service Dr. Brian J. Rothschild National Marine Fisheries Service Mr. Maurice E. Stansby National Marine Fisheries Service Dr. Maynard A. Steinberg National Marine Fisheries Service Dr. Roland L. Wigley National Marine Fisheries Service Kiyoshi G. Fukano, Managing Editor The Secretary of Commerce has determined that the publication of 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 Management and Budget through May 31, 1974. Fishery Bx^^ LIBRARY CONTEN'l^y 2 0 1974 Vol. 72, No. 1 I Woods Hole, M^'^ j^^^^^.^ ^^._^ KITTREDGE, J. S., FRANCIS T. TAKAHASHI, JAMES LINDSEY, and REUBEN LASKER. Chemical signals in the sea: Marine allelochemics and evolution 1 FULLENBAUM, RICHARD F.. and FREDERICK W. BELL. A simple bioeconomic fishery management model: A case study of the American lobster fishery 13 OLLA, BORI L., ALLEN J. BEJDA, and A. DALE MARTIN. Daily activity, move- ments, feeding, and seasonal occurrence in the tautog, Tautoga ojiitis 27 LENARZ, W. H., W. W. FOX, JR., G. T. SAKAGAWA. and B. J. ROTHSCHILD. An examination of the yield per recruit basis for a minimum size regulation for Atlantic yellowfin tuna. Tliuinuis albacares 37 FLEMINGER, A., and K. HULSEMANN. Systematics and distribution of the four sibling species comprising the genus Pontellina Dana (Copepoda. Calanoida) 63 HUGHES, STEVEN E. Stock composition, growth, mortality, and availability of Pacific saury, Cololabis saira, of the northeastern Pacific Ocean 121 ANAS, RAYMOND E. Heavy metals in the northern fur seal, CaU(i)-hi)tus ursi)iHs, and harbor seal, Pltoca rituliiia richardi 133 WAHLE, ROY J., ROBERT R. VREELAND, and ROBERT H. LANDER. Bio- economic contribution of Columbia River hatchery coho salmon, 1965 and 1966 broods, to the Pacific salmon fisheries 139 POWELL, GUY C, KENNETH E. JAMES, and CHARLES L. HURD. Ability of male king crab, Paralithudes ca nitschatica , to mate repeatedly, Kodiak, Alaska, 1973. 171 WICKHAM, DONALD A., and GARY M. RUSSELL. An evaluation of mid-water artificial structures for attracting coastal pelagic fishes 181 GRANT, GEORGE C. The age composition of striped bass catches in Virginia Rivers, 1967-1971. and a description of the fishery 193 PEARCY, WILLIAM G., and SHARON S. MYERS. Larval fishes of Yaquina Bay, Oregon: A nursery ground for marine fishes? 201 PARK, TAISOO. Calanoid copepods of the genus Aetideus from the Gulf of Mexico . . 215 LIGHTNER, DONALD V. Normal postmortem changes in the brown shrimp, Peiiaei(s aztt'cn!< 223 STRUHSAKER, PAUL, and ROBERT M. MONCRIEF. Bofluis thompsmn (Fowler) 1923, a valid species of flatfish (Pisces; Bothidae) from the Hawaiian Islands 237 Note CABLE, WAYNE D., and WARREN S. LANDERS. Development of eggs and em- bryos of the surf clam, Spisida solidissima, in synthetic seawater 247 For sale bv the Superintendent of Documents. U.S. Government Printing Office. Wasliington. DC. 20402 - Subscription price: $10.85 per year (S2.75 additional for foreign mailing). Cost per single issue - $2.75. CHEMICAL SIGNALS IN THE SEA: MARINE ALLELOCHEMICS AND EVOLUTIO J. S. KiTTREDGE,'- FRANCIS T. TaKAHASHI,^ James Lindsey,^ and Reuben Lasker'^ ABSTRACT Observations in chemical ecology suggest the coevolution of "natural products" of plants and the chemoreceptors of herbivorous insects. We have reviewed evidence which suggests that this coevolution extends back to the primordial protistans. Thus, the evolutionary pressure for the development of a chemosensory capability probably derived from the presence of metabolic products in the milieu. These products are considered to have been both cues to the location of prey and "membrane irritants" evolved in the initial phase of chemical protection. Sometime later this chemosensory capability provided several functions in the evolution of metazoans, i.e. the precursors of developmental signals, hormone function, and synaptic transmission. We consider that most of the extant "natural products" of plants and marine invertebrates are protective allomones. A feature of allomone function that has been termed "antifeedant" or "feeding inhibitor" may represent the "cryptic odors" of Haldane. We provide evidence that the naphthoquinones with a juglone or naphthazarin structure have this activity. Octo- pus ink has a "cryptic odor" effect on moray eels. Marine Crustacea have, however, evolved an ability to perceive the orthoquinone precursors of the ink, a warning signal. Evidence for an array of sex pheromones in a crab and a cycloid swimming pattern in a copepod that may enable it to follow a chemical gradient indicate the complexity of behavioral responses to chemical cues. The earliest form of interaction between organ- isms was probably by means of chemical agents. This interaction involved both conflict and cooperation and its existence implies detec- tion of these agents. Haldane (1955) first suggested that chemical communication is the' most primitive form of communication, orgin- ating with primordial unicellular organisms. He reasons that this primordial protistan com- munication was a necessary prelude to the evo- lution of metazoans and thus is a lineal pre- decessor of synaptic transmission and hormone reception. This early chemical communication may have evolved as an accessory to the active transport mechanism of the cell membrane or as a "membrane sensitivity" to metabolic by-products (Wynne-Edwards, 1962). That a ' This work was supported by NSF grant GB-27703; ONR Contract N00014-7I-C-0103; NOAA Institutional Sea Grant 2-35 187; PHS NB 08599. - Marine Biomedical Institute, University of Texas Medical Branch, Galveston, TX 77550. 3 Zoology Department, Oregon State University, Corvallis, OR 97331. * Department of Biological Sciences, University of California at Santa Barbara, Santa Barbara, CA 93106. 5 Southwest Fisheries Center, National Marine Fisheries Service, NOAA, La Jolla, CA 92037. more detailed understanding of transducer physiology is central to further advances in neurobiology has been emphasized by Delbriick (1970). He considers the stimulus-response system represented by chemoreception or synaptic transmission to be homologous. We wish to examine some of the recent con- cepts of chemical ecology and to present examples from the marine environment. Studies of chemoreception are providing evidence for the pervasive function of chemical signals in the environment. The "membrane sensitivity" concept of Wynne-Edwards may provide a clue to both the initial evolution of a transducer function and the continuing evolution of receptor sites of greater diversity and specificity. It is evident that this diversity has resulted from a continual interplay of chemical counter- measures and the development of neurosensory and behavioral adaptations to these agents. ALLELOCHEMICS At all levels of life we are finding examples of attack, defense, and behavioral response Manuscript accepted July 1973. FISHERY BULLETIN: VOL. 72, NO. 1, 1974 1 FISHERY BULLETIN: VOL. 72, NO. 1 based on chemical agents. These interactions and the characterization of the chemical agents involved are the subject of the newly developing field of chemical ecology (Sondheimer and Simeone, 1970). Chemicals that are syntheized and released by one individual of a species to alter the behavior of other members of the species are termed pheromones. These signals range in their function from trail markers and territorial markers through alarm and defense signals to those which control caste structure in social insects and the sex pheromones that are calling signals and aphrodisiacs. Chemicals also have a wide range of interspecific interactions. A substance produced by one organism may influence the behavior of members of other species. A flower scent that enhances pollina- tion is a well-known example. This field of chemical ecology has been termed allelo- chemics, and the chemical agents have been subdivided on the basis of function into allo- mones, which give adaptive advantage to the producing organism, and kairomones, which give adaptive advantage to the receiving organism (Whittaker and Feeny, 1971). The allomones include the repellents produced by many plants and animals, suppressants which inhibit competitors (e.g., fungal antibiotics), venoms, inductants (e.g., gall producing agents), and attractants (e.g., chemical lures). The kairo- mones include attractants (e.g., the scent of a prey), inductants (e.g., the factor that stimulates hyphal loop development in nematode-trapping fungi), danger signals (e.g., predator scents, secondary plant substances indicating toxicity), and stimulants (e.g., hormones that induce growth in the receiving organism). The diverse natural products, coumarins, quinones, flavonoids, acetylenes, terpenoids, saponins, cardiac glycosides, alkaloids, thiols, and cyanogenic glycosides, which were long considered metabolic waste products, are now recognized to be allelochemic agents. Examina- tion of the function of these natural products provides some insight into their evolution. Some of these compounds are toxic, some are chemical lures, others inhibit the growth of competitive plant species, but the bulk of these compounds probably function as "feeding inhi- bitors" of herbivores (Gilbert, Baker, and Norris, 1967; Munakata, 1970). The coevolution of butterflies and plants is considered by Ehrlich and Raven (1964). They emphasize the role of reciprocal selective responses during this evolution and conclude that "the plant-her- bivore interface may be the major zone of inter- action responsible for generating terrestrial organic diversity." The "accidental" evolution of a metabolic sequence resulting in the produc- tion of a noxious substance by a plant provided a selective survival advantage in the clone carrying this capability. Decreased predation by herbivores on those individuals containing the highest concentrations of the new sub- stance resulted in genetic selection for increased synthesis and storage of the noxious substance. Such "protected" species experience an explosive increase because of their protection from contemporary phytophagous organisms. The first evolutionary response of the her- bivores must have been the development of the capability to detect the compound, i.e. sensitive external chemoreceptors. Later evolutionary events led to the development in some indi- viduals of a tolerance for the noxious substance. The herbivores which developed this tolerance then had access to a large food supply for which there was no competition. The ability to detect the substance then had an altered function, the feeding inhibitor was now a feeding stimulant. The present evidence of the repeated occur- rence of this cycle is the existence of tightly coupled herbivorous insects and their host plants, presumably arising through coad- aptation. In 1955 Haldane, in a consideration of chemical communication and visual signals, wondered if cryptic odors had ever evolved. While most of the feeding inhibitors that have evolved are probably irritants, many may be cryptic odors. It is likely that the two activities may only differ in the membrane affected. The term irritant implies membranic sensitivity and, of those membranes of an organism in immediate contact with the environment, the chemosensory membranes are likely the most sensitive to chemical irritation. In an environ- ment in which a major fraction of the informa- tion flow is chemical, any agent capable of disrupting the chemosensory organs of a preda- tor would provide an ideal mechanism for "hid- ing" from that predator. Cryptic odors may be either "negative odors" altering, for protracted periods, the membrane potential of the dendrites and blocking their normal generator potential, or they may be the chemical equivalent of a KITTREDGE ET AL.: CHEMICAL SIGNALS IN THE SEA "white noise," producing an "uncoded" array of spikes in the chemosensory neurons. The best description of behavior suggesting a "cryptic odor" in the marine environment is that given by MacGinitie and MacGinitie (1968). The ink of an octopus is considered a "smoke screen"; however, it can also affect the olfactory sense. The MacGinities observed that after a moray eel swam through the ink cloud of an octopus it could no longer "recognize" an octopus. The moray eel apparently requires both visual and olfactory input for this recogni- tion. They state, "We were surprised to find that the real effect of the ink of an octopus is to paralyze the olfactory sense of its enemies." The melanin of the ink is a polymer of oxidized L-DOPA. The polymerization proceeds through three orthoquinones, dopaquinone (6, Figure 1), dopachrome (7), and indole-5, 6-quinone (8). In the biosynthesis of melanin, this oxidation is catalyzed by polypheny 1 oxidases; however, heavy metal ions can also catalyze the oxidation, and it can be readily demonstrated that the trace of heavy metal ions in seawater will rapidly convert L-DOPA to melanin. The octopus ink loses its potency with time, a factor that would indicate that the biological activity of the ink is due to the presence of the unstable monomer orthoquinones in the fresh ink (Kittredge, Takahashi, and Lindsey, unpublished data). The observation of Gilbert et al. (1967) that juglone (5-hydroxy-l,4-naphthoquinone) (1. Figure 1) is a deterrent to feeding by the bark beetle, Scolytus multistriatus, suggested a similar function for the polyhydroxynaphtho- quinones occurring in the echinoderms. These spinochromes are all derivatives of juglone (1) or naphthazarin (2). They occur as soluble salts in the tissues and may be present in considerable amounts in the larvae. They also occur as insoluble calcium salts in the spines and tests (Thompson, 1971). The echinoids have received the closest attention, but P. J. Scheuer and his group have demonstrated the presence of these compounds in the other four classes of this phylum — the holothurians, asteroids, ophiuroids, and crinoids (Singh, Moore, and Scheuer, 1967). They also demonstrated the presence of a substituted 2,5-benzoquinone (3) in the genus Echinothnx (Moore, Singh, and Scheuer, 1966). The crinoids are interesting in that they contain primarily a series of poly- hydroxyanthroquinones (e.g., rhodocomatulin, OH 0 I II 0 I II OH 0 (1) I II OH 0 (2) HO- O 'Sr^cH; .CH 0 (3) HO\.^,^^0^/Ar H 0 •^^^'-^^-•^^^^O H nu II II UM 0 COfCHglgCHj (4) 00' I II OH 0 (5) 0^, 0 .CH2-CH-COOH NHo (6) 0< 0' to- H (7) COOH (8) Figure 1. — Structures of compounds typical of those which may function as "cryptic odors." (1) juglone. (2) naphthazarin, (3) 2, 5-dihydroxy-3- ethylbenzoquinone, (4) rhodocomatulin, (5) fiavone, (6) dopaquinone, (7) dopachrome. (8) indole-5, 6-quinone. 4) (Sutherland and Wells, 1967; Powell, Suther- land, and Wells, 1967; Powell and Sutherland, 1967; Matsuno et al.. 1972; Erdman and Thomson, 1972). Utilizing the "feeding response" of the lined shore crab, Pachygmpsus crassipes, which consists of a rapid lateral movement of the mouthparts when presented with a feeding stimulus, we have bioassayed the "feeding inhibitor" activity of juglone and eight repre- sentative spinochromes. The "feeding stimulus" was a 20-iul aliquot of a 3-mM solution of taurine in seawater administered from a repeat- ing syringe close to one of the antennules of the crab. Initially the crabs were immersed in a l-/uM solution of the naphthoquinone and tested for a feeding response. Five experimental and FISHERY BULLETIN: VOL. 11. NO. 1 one control crab were utilized for each compound. No feeding responses were observed in any of the test crabs while all of the controls were positive. A second series of bioassays was designed to determine the onset of inhibition. The crabs were placed in seawater and stimu- lated with 20 fji\ aliquots of a solution of 3 mM taurine and 1 jliM quinone. The stimulus was administered at 2 sec intervals to alternate antennules. Inhibition of the "feeding response" was observed at approximately 10 sec. The naphthazarin derivatives were apparently more potent than the juglone derivatives. We interpret these results as indicative of a "cryptic odor" function; the crabs cannot detect the feeding stimulant after a brief exposure to the quinone. Many higher plants contain juglone or other hydroxynaphthoquinones or benzoquinones. These compounds also occur in fungi, lichens, pholangids, millipedes, and insects. 1,4-benzo- quinones are the most common ingredient of insect defensive secretions and the 2,5-sub- stituted 1,4-benzoquinones are characteristic of fungi. A similar "cryptic odor" function may be predicted for these compounds. Norris (1969) compared the feeding deterrent activity of a number of substituted naphthoquin- ones. Juglone (1) and naphthazarin (2) were the most potent inhibitors. The apparent effective- ness of the hydroxy groups in the 5- or 5,8- positions in these naphthoquinones suggests an examination of the function of the major group of secondary plant metabolites, the flavones (5) (Harborne, 1972) which have a marked structural similarity. Whittaker and Feeny (1971) predict "that research into the relations of multicellular marine algae and their consumers will reveal chemical defenses and responses paralleling those of higher plants and animals on land." The most likely candidates to fulfill this predic- tion are the highly halogenated hydrocarbons that are synthesized by algae and stored in the tissues of the herbivorous gastropod, Aplysia caHfornica (Faulkner and Stallard, 1973; Faulkner et al., 1973). We would add to the prediction of Whittaker and Feeny that research- into the relations of many marine inverte- brates and their predators may reveal allomones. Some of the "natural products" of marine invertebrates that have been recently character- ized and that may have this function are the halogenated antibiotics that have been isolated from, sponges (Sharma, Vig, and Burkholder, 1970; Fattorusso, Minale, and Sodano, 1972; Moody et al., 1972; Anderson and Faulkner, 1973). Steroid saponins that are toxicants or irritants have been characterized from holo- thuroids and starfish (Yasumoto, Nakamura, and Hashimoto. 1967; Tursch et al., 1967; Roller et al., 1969; Tursch, Cloetens, and Djerassi, 1970; Turner, Smith, and Mackie, 1971). We recall a simple demonstration by the late C. F. A. Pantin of the sensitive chemo- sensory capability of sea anemones for saponin. The nematocysts of sea anemones require both a mechanical and a chemical stimulus for discharge. One can brush the surface of a sea anemone's tentacles with a clean glass rod without effecting any discharges. If, however the glass rod is first dipped into a dilute saponin solution, a massive discharge is effected. An observation by Clark (1921) suggests the existence of allomones in crinoids. He discusses the avoidance of comatulid crinoids by fish and suggests the activity of glands at the base of the tentacles. The comatulids are unique in containing both polyhydroxyanthro- quinones and aromatic polyketides (Kent, Smith, and Sutherland, 1970; Smith and Sutherland, 1971). MARINE KAIROMONES As in the terrestrial environment, in- vertebrates utilize chemical cues to locate hosts or to warn of predators. Davenport (1966) demonstrated the response of commensal poly- noid polychaetes to a "host factor" in the water draining from tanks containing the host species of starfish. In an electrophysiological analysis of the antennular chemoreceptors of two com- mensal shrimps. Ache and Case (1969) demon- strated the specificity of the response to "host water" from the specific hosts, Haliotis spp. and Stro)igyloceiitrotus spp. Predatory starfish induce an escape response in a variety of molluscs (Feder, 1967), and these behavioral responses probably effectively reduce the predation on these species that can detect the predator (Feder, 1963). The active materials in extracts of the starfish Marthasteria glaciali.s and Asten'a.s nibcHs which induce the escape response have been shown to be steroid saponins (Mackie, Lasker, and Grant, 1968). KITTREDGE ET AL: CHEMICAL SIGNALS IN THE SEA The threshold for response by the snail, Biicc'nium uudatiim is 0.2-0.4 X lO"-' M (Mackie, 1970). and the structure of these steroid glycosides has been determined (Turner et al., 1971). A behavioral bioassay of one of the ortho- quinones derived from L-DOPA, dopachrome, utilizing the feeding response of the lined shore crab PachygmpsHS crassipes indicated that this quinone might also be a "cryptic odor." Electro- physiological studies, however, demonstrated that these results were misleading. Utilizing a preparation of the dactyl chemoreceptors of the spiny lobster Pa)udinis interruptus, we detected chemoreceptors for this quinone that were about a hundred times as sensitive as the general amino acid receptors in this prepara- tion (Figure 2). While we have not explored the range of specificity of these receptors, the results suggest that these crustaceans, the natural prey of the octopus, have evolved a mechanism for detecting the presence of the predator. Our results with the bioassay likely reflect a priority of responses to the two chem- ical stimuli (Kittredge, Takahashi, and Lindsey, unpublished data). PHEROMONES Unicellular chemical communication, analogous to Haldane's primordial protistan communication, is evident in the conjugation of ciliates. The microconjugant of a peritrichous ciliate, which is free swimming, can identify the macroconjugant, which is sessile, by chemicals released by the latter. Although evidence for I ,VW#MWM 2. <#«i^A/^M'^V'^iVi!,*)/i^SJ<^^ 3. 4. 1 1- i • 1 * 5. 50jj, Volts Figure 2. — Electrophysiological recordings from the dactyl chemoreceptors of a spiny lobster, Panulims interruptus. (1) Seawater blank, (2) IQ-'i M dopachrome in seawater, (3) Persisting spikes in dopachrome receptors (continuation of 2), (4) 10-3 M taurine in seawater, (5) 10"3 M taurine after dopachrome and a seawater wash. FISHERY BULLETIN: VOL. 72. NO. 1 the presence of a large number of agents chemo- tropic for male gametes exists (Machlis and Rawitscher-Kunkel, 1963). only two have been chemically characterized. Sirenin. the active compound produced by the female gametes of the water mold Allomyces, has been isolated and characterized as an oxygenated sesquiterpene (Machlis et al., 1966), and its structure has been uniquely established (Machlis, Nutting, and Rapoport, 1968). It is active in attracting male gametes at 10"'"M. The corresponding work from the marine field resulted in the characterization of the active substance released by the female gametes of the brown alga Ectocarptis siUckIosk.'^ as allo- cis-l-(cycloheptadien -2', 5'-yl)-butene-l (Miiller et al.. 1971). The receptor sites on the male algal gametes evidence a low level of specificity. Many lower hydrocarbons, esters, alcohols, and aldehydes, at higher concentrations, will mimic the natural compounds in attracting male gametes (Cook, Elvidge, and Bentley, 1951; Miiller, 1968; Hlubucek et al., 1970). Though many efforts to demonstrate a chemo- tactic response by mammalian sperm to sub- stances from eggs have yielded negative results, such attraction does occur in marine forms. Sperm of the thecate hydroids Cai)ipanularia flexuosa and C. calceolifera respond to a sub- stance issuing from the aperture of the female gonangium. The response is species specific (Miller, 1966). Observations by Dan (1950) suggest the activity of a similar substance from the eggs of the medusa Spirocodan saltatrix on the sperm of this species. The first examples of sperm chemotaxis in vertebrates are described in pai)ers on fertilization in the herring Clnpea by Yanagimachi (1957) and in the bitterling Acheilognathus by Suzuki (1961). The attraction of the amoeboid form of the slime mold Dictyostelium discoideum during the aggregation phase which results in the formation of a multicellular "slug" represents the best studied protistan communication. The attractant is cyclic adenosine monophosphate (Konijn et al., 1968; Barkley, 1969). Pulses of cyclic AMP radiate out through the soil moisture at 5 min intervals from the center of a growing aggregation. The gradient and the pulse nature of the signal are maintained by each inward streaming amoeba. Each amoeba secretes a phosphodiesterase to break down the cyclic AMP and, on sensing a pulse of cyclic AMP, emits its own pulse of cyclic AMP about 15 sec after receiving a signal (Cohen and Robertson, 1971; Robertson, Drage, and Cohen, 1972). Bonner (1969) has indicated the likely course of the evolution of this communication in the social slime molds. Soil bacteria, the food of the solitary predecessors of the slime mold amoeba, secrete cyclic AMP. It is reasonable to assume that a mechanism which initially increased the feeding success of these amoebas developed, due to selective pressure, the requi- site high sensitivity of response to a chemical signal necessary for aggregation. This capacity then facilitated the evolution of the social species. This is very close to Haldane's premise of the evolution of chemical communication prior to the evolution of metazoans. In further support of Haldane's premise of the lineage of hormones, after aggregation is complete the "metazoan" slug phase migrates to the soil surface and then certain cells differentiate into stalk cells which will eventually support the spore head. Cyclic AMP is apparently the chemical signal for the developmental differ- entiation of some cells into stalk cells (Bonner, 1970). The recent rapid growth of our understanding of pheromone communication in insects was founded on half a century of acute biological observations which implicated the existence of chemical messengers. The isolation and chemical characterizations of a growing number of pheromones, and the concomitant behavioral studies, have provided the basis for our appreciation of the role of chemical communica- tion in the life cycle of many species. Among the many recent reviews are those of Beroza (1970) and Jacobson (1972). Electrophysiological investigations of chemoreception in insects have demonstrated that the receptor cells may be divided into two groups, either "specialists" or "generalists" (Yamada, 1970). Among the "specialists" are the pheromone receptors and the receptors for specific secondary plant sub- stances that act as phagostimulants (Schoon- aoven, 1968). While remarkable success has been achieved in recording the response of single receptor cells as well as the summed receptor potential of all the antennal chemore- ceptors (electroantennogram) these workers have had to contend with a technical problem inherent in studies with this material. Evalua- tion of the response of a chemosensory organ KITTREDGE ET AL: CHEMICAL SIGNALS IN THE SEA or a single cell is difficult when the stimulant must be presented in the gas phase. Each species of stimulant molecule must partition between the gas phase and an aqueous film. The active concentration at the receptor membrane is unknown. A study of the physi- ology of pheromone reception by aquatic organ- isms would avoid this limitation. A survey of the literature reveals that, as in the field of entomology, there exists a broad basis of behavioral observations suggesting the role of chemical communication in the aquatic environment. These studies suggest that marine invertebrates are primarily dependent on chemo- reception for information from their environ- ment. The input is composed of a broad spectrum of chemical messages ranging from species specific pheromones eliciting stereospecific responses, e.g., mating behavior, epidemic spawning, aggregation, or alarm behavior, through those kairomones triggering metamor- phosis or migration to the cues indicating the proximity of predators or prey. The closest parallel to insect pheromone communication observed in marine organisms are the sex pheromones of marine Crustacea. The first experimental demonstration of "chemical recognition" by marine Crustacea is the description of the behavior of male copepods (Labidocem aestiva) by Parker (1902). In a series of elegantly simple experiments he demonstrated that "they [the females] probably give rise to some substance that serves as a scent for the males; in other words, the males are probably positively chemotropic toward the females." Moreover Parker noted that "they [the males] seldom pass near the tube without some characteristic reaction. Usually they made one or two quick circles as they swam by, or even a somersault-like motion; these were observed fifteen times when the females were in the tube, never when they were not." Lillelund and Lasker (1971) observed similar swimming behavior in male Labidocera joUae. Although L. joUae females swim in a seemingly random pattern with only occasionally looped excursions, the males frequently vary their random course of a few seconds duration by swimming in circles, covering a small area intensively. Of greater interest was the observation that rather than circles, the path of the males often resembled a curtate cycloid. The males occasionally pro- gressed for several centimeters in this curtate cycloid path (Figure 3). These observations, although obtained during feeding studies, suggest an important aspect of the physiology of pheromone response in small Crustacea — the mechanism of sensing a chemical gradient. Crisp and Meadows (1962) have stated that, because of the small distance between the chemosensory organs of barnacle cyprid larvae, these larvae cannot detect a chemical gradient and thus 1 cm I 1 Figure 3. — Swimming behavior of a male copepod Lahidoceru jollae. A' and B' mark the termini of the tracings. The upper trace shows both an occasional circu- lar swimming course, progression in a curtate cycloid course and "doubling back." The lower trace is an extreme example of the "doubling back" behavior. FISHERY BULLETIN: VOL 72. NO 1 cannot exhibit chemotactic behavior. This reasoning has been applied to all small marine Crustacea including copepods. From the above observations it is apparent that the reasoning of Crisp and Meadows is invalid for Labidocera and probably for other small Crustacea. The critical dimension is the diameter of the circular course, not the dimensions of the organism. A circular swimming i)attern in a concentration gradient of a stimulant would result in a sinus- oidal variation in the signal intensity. Altera- tion of the radius of curvature of the swimming course in response to this sinusoidal input would result in cycloidal progression in the gradient. It appears from the observations of the behavior of male L. jollae in the feeding experiment that a threshold level of stimulant will trigger a circular swimming pattern, if this circular course results in the detection of a gradient, the circular course will become a curtate cycloid with the ratio of the major to the minor radius being a function of the intensity of the gradient. A frequent observation is a doubling back. If several progressions of the cycloid result in loss of the gradient signal (as must frequently occur in a medium in which the dimensions of the turbulent flow are of the same scale as the swimming pattern), the swimming plots indicate that the male Labido- cera can effectively loop back through the area where the signal was initially detected (Figure 3). These observations indicate some power of spatial orientation and short term memory in Labidocera. In crabs the male is attracted to the premolt female. During this attraction phase he may display a stance characterized by standing on the tips of his dactyls and elevating his body. He will seize the premolt female and place her below his body. He will protect her during the vulnerable molting period and they copulate immediately after molting. Ryan (1966) demon- strated pheromone communication in this inter- action. Water from a tank containing a premolt female Portunus sanguinolentus, when added to a tank containing a male of this species, elicited the premolt stance. Evidence that the pheromone is released from the antennule glands was provided by sealing these glands and noting the absence of the stimulating factor. We have examined this pheromone com- munication in the lined shore crab, Pachygrap- sus crassipes. We isolated an active substance and found that it behaved chromatographically like the molting hormone, crustecdysone. Pure crustecdysone is active in stimulating all of the precopulatory behavior of male lined shore crabs from an early search behavior through the display stance to seizing the female. The thresh- old for stimulating the stance is 10''^ M (Kittredge, Terry, and Takahashi, 1971). Con- firmation of the identification has been obtained by injecting tritiated crustecdysone into inter- molt female Dungeness crabs (Cancer niagister) and detecting its release as the females entered premolt. Recently we have detected the presence of two additional pheromones released by the female lined shore crabs. Compound A is released in addition to crustecdysone prior to molt. After molting compound A is no longer released into the water, but, if the female is held in isolation from male crabs, a second compound, B, is re- leased. It is likely that the postmolt female has a different message to transmit. Evolutionary biologists concerned with the inception of pheromone communication have long been puzzled by a dilemma. This chemical communication implies two new capabilities, that to synthesize a messenger compound and the ability to receive the message and trans- late it into a behavioral response. The improb- ability of the simultaneous occurrence of these two de novo events suggests a stepwise sequence. The observation that the molting hormone of Crustacea can function as a sex pheromone indicates that the primordial Arthropoda, through an evolutionary sequence that resulted in structuring the receptor site for the hormones on chemosensory membranes, were able to initiate pheromonal communication (Kittredge and Takahashi, 1972). SUMMARY Evidence from the literature supports Haldane's premise that chemical communica- tion is the most primitive form of communica- tion and thus the lineal predecessor of synaptic transmission and hormone function. Trans- ducers of environmental chemical information have likely evolved in response to the metabolic products released by their prey and by competi- tive organisms. This coevolution of "natural products" and the respective transducers has existed from the earliest metabolic product that happened to be a membrane irritant to the 8 KITTREDGE ET AL: CHEMICAL SIGNALS IN THE SEA present. We thus consider it likely that most of the "natural products." not only of terrestrial plants, but also of marine plants and inverte- brates, function as allomones, kairomones, or pheromones. Faulkner and Anderson (In press) have provided a review of the chemistry of the "natural products" of marine organisms. Conceptually, in such a "chemical environ- ment" the most effective protection from a predator would be a "cryptic odor," an irritant that disrupts chemoreception. These cryptic odors may be released into the environment, as is the active component of octopus ink, they may exist in the epidermal tissues or glands where they would function at the inception of attack, or they may be contained in the eggs or larvae. Most sessile marine invertebrates re- produce by epidemic spawning, the simultan- eous release of the gonadal products of an entire local population of a species. Most sessile marine invertebrates are also filter feeders. The prime advantage of epidemic spawning is the enhancement of fertilization. However, in the densely populated benthic environment, a heavy loss of eggs or larvae to filter feeders may occur. The presence of a "feeding inhibitor" in the eggs or larvae would reduce such losses. Reiswig (1970) reported that they observed epidemic spawning of the sponge Neofibiilana iiolitaiigere on a Jamaican reef. At the time they were measuring the water pumping rate of other sponges. When the epidemic spawning of A^ nolitangere started, the pumping rate of the. species under study, Vero)igia sp, abruptly decreased and remained negligible for 2 days. A', nolitangere is known to contain toxic sub- stances. The evidence for chemical cooperation, from gamones to sex pheromones, suggests a pattern of increasing complexity in the function of chemical cues. The behavioral response of even a "simple" crustacean to a chemical gradient appears to involve at least some short term "memory" or a type of "chemical-spatial" sense that we have not observed in such clear- cut form in any other organism. The study of the chemical ecology of the marine environment is scarcely in its infancy. The chemical characterization of some of the intraspecific and interspecific messages in the sea and the physiology of their perception are challenges. Solutions to these paired problems will provide insights into the evolution of chemical transduction and perhaps expose a hierarchy of perception from membrane irritation to synaptic transmission. ACKNOWLEDGMENTS We wish to acknowledge the contribution of Paul J. 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Silverstein, and M. Nakajima (editors). Control of insect behavior by natural products, p. 317-330. Academic Press, N.Y. Yanagimachi, R. 1957. Some properties of the sperm activating factor in the micropyle area of the herring egg. Annot. Zool. Jap. 30:114-119. Yasumoto, T., K. Nakamura, and Y. Hashimoto 1967. A new saponin, holothurin B, isolated from sea-cucumber, Holothuria vagahiindci and Holo- iliuria liihiicci. Agric. Biol. Chem. 31:7-10. 11 A SIMPLE BIOECONOMIC FISHERY MANAGEMENT MODEL: A CASE STUDY OF THE AMERICAN LOBSTER FISHERYi Richard F. Fullenbaum^ and Frederick W. Bell-* ABSTRACT The pressures of world economic expansion have led to more intensive exploitation of living marine resources as a source of protein. The exploitation of these common property resources leads, in many cases, to overfishing and depletion. This paper attempts to develop a simplified management tool to prevent overexploitation and depletion of a fishery resource. A general resource model is postulated embracing both biological and economic relationships. This bioeconomic model approximates the operation of a fishery under free access to the resource. A Schaefer type yield function is combined with a linear demand function, and other standard economic relationships and simulations are performed to evaluate the model. Using computer simulation, we imposed five management strategies on the case example, the American lobster fishery. These strategies include (1) freezing fishing effort by raising license fees: (2) reducing fishing effort to that necessary to harvest at the maximum sustainable yield by raising license fees: (3) reducing fishing effort to an "economic optimum"" where marginal cost of doing business is equal to marginal revenue from sales by raising license fees: (4) instituting a "stock certificate plan"" where individual fishermen would own portions of the resource and trade catch certificates on the open market: however, the total number of catch certificates would not exceed the maximum sustainable yield: and (5) doing nothing. The economic impact in terms of catch, fishing effort, number of fishermen, ex-vessel prices, license revenues, and returns per boat and fishermen were computed for each management strategy so that policymakers and industry leaders could see the alternative consequences of these management positions. The simplified model also is available for use in evaluation of other management schemes that might be suggested. In the past few years the world community has become increasingly aware of the sea and its resources. The pressures of world economic expansion have led to more intensive exploita- tion and, at the same time, to increasing con- cern over the marine environment. Many man- agement strategies used to protect these re- sources from overexploitation have resulted in inefficient use of gear and equipment as shown by Crutchfield and Pontecorvo (1969). The purpose of this paper is to develop a bioeconom- ic model of living marine resource exploitation which can be used to assess the economic im- pact of alternative management strategies for the U.S. inshore American lobster fishery. The U.S. American lobster fishery is a classic case of rapid increases in consumer demand impinging upon a limited resource (Bell. 1972). It should be made quite clear that this analysis is intended to predict the effects of alternative actions without recommending any specific policy. SPECIFICATION OF THE GENERAL RESOURCE USE MODEL Before we are able to evaluate the economic impact of various management strategies, it is necessary to develop a general bioeconomic model of how a fishery functions. The following general model has been developed by Fullen- baum, Carlson, and Bell (1971): ' This article was first submitted for publication 7 August 1972. At that time, all data were as current as could be obtained for purposes of the analysis. The views of the authors do not necessarily represent the official position of the U.S. Department of Commerce. 2 Executive Office of the President, Office of Manage- ment and Budget, Washington, DC 20503. 3 Formerly of Economic Research Division, National Marine Fisheries Service, NOAA: present address, Florida State University, Tallahassee, FL 32306. or X = f{X, Kx) Kx = Kg{X, K) X =giX,K) C =Kn (1) (2) (3) 13 Manuscript accepted June 1973. FISHERY BULLETIN: VOL. 72. NO. 1. 1974. FISHERY BULLETIN VOL. 72, NO. 1 TT = pKx -C = pKgiX,K) -Kn (4) 5 277', 7r<0 (5) In the above system, X is the biomass; K equals the number of homogeneous operating units or vessels; x is the catch rate per vessel; C is total industry cost (in constant dollars) or total annual cost per vessel multiplied by the number of vessels; ^ is equal to total annual cost per vessel (in constant dollars) or opportunity cost;' 77 is industry profit in excess of oppor- tunity cost; p is the real ex-vessel price; and 5 J , 5 2 represent the rates of entry and exit of vessels, respectively. Equation (1) represents the biological growth function in which the natural yield or net change in the biomass {X) is dependent upon the size of the biomass, X, and the harvest rate, Kx. X reflects the influence of environmental factors such as available space or food, which constrain the growth in the biomass as the latter increases. The harvest rate or annual catch, Kx, summarizes all growth factors induced by fishing activity. Equations (2) present the industry and firm production function for which it is normally assumed that dg dX = g,>0 and f^=g^<0:^ dg bK In other words, catch per vessel increases when the biomass increases and declines when the number of vessels increases. Equations (3) and (4) are the industry total cost and total profit function, respectively. Equation (5) is a very important equation since it indicates that vessels will enter the industry when excess industrial profits are greater than zero (i.e., greater than that rate of return necessary to hold vessels in the fishery, or the opportunity cost) and will leave the fishery when excess industrial profits are less than zero (i.e., below opportunity cost). ■* Opportunity cost is defined as the necessary payment to fishermen and owners of capital to keep them employed in the industry or fishery compared to alternative employ- ment or uses of capital. ■'•In some developing fisheries, it is possible that .i;2>0. For example, in the Japanese Pacific tuna fishery, inter- communication between vessels may increase the catch rate as more vessels enter the fishing grounds. The equilibrium condition for the industry (n = 0) may be formulated as shown below: P = 77 g{X,K) (6) Equation (6) merely stipulates that ex-vessel price is equal to average cost per pound of fish landed (i.e., no excess profits). There are two important properties of the system outlined in (1) - (5). First, the optimum size of the firm is given and may be indexed by 77. Thus, the firm is predefined as a bundle of inputs." Second, the long-run catch rate per ves- sel per unit of time is beyond the individual firm's control." It is, in effect, determined by stock or technological externalities.** Finally, we are assuming that the number of homo- geneous vessels is a good proxy for fishing effort. Alternatively, we may employ fishing effort directly in our system by determining the number of units of fishing effort applied to the resource per vessel. This will be discussed below. A QUADRATIC EXAMPLE OF THE RESOURCE USE MODEL By combining the more traditional theories depicting the dynamics of a living marine re- source with some commonly used economic relations, we may derive a quadratic example of the general model specified above. This example effectively abstracts from complications such as ecological interdependence and age- distribution-dependent growth of the biomass on the biological side and, furthermore, assumes the absence of crowding externalities (i.e., ^2 ~ 0) in the production function on the economic side. '' In other words, because we are dealing with a long-run theory of the industry, we are assuming that variations in output result from the entry or exit of optimum-sized homogeneous vessels. ^ We have implicitly assumed that such short-run changes as longer fishing seasons, etc., are all subsumed in a long-run context. Normally longer fishing seasons, for example, do not change catch rates per unit of time fished; nor do they change costs per unit of time fished. They do, however, change the effective level of K. * A technological externality exists when the input into the productive process of one firm affects the output of another firm. In the context of fishing, an additional firm or vessel entering the fishery will utilize the biomass (as an input) and, as a result, in the long run will reduce the level of output for other vessels in the fleet. (See Worcester (1969)). 14 FULLENBAUM and BELL: AMERICAN LOBSTER FISHERY The dynamics of a fish stock may be depicted by the logistic growth function (Lotka, 1956).^ X(t) = 1 + Ce -KLt where L>0,O0,/e>0, (7) Kx = rKX (11) where r is a technological parameter.'- Finally, the total revenue function for the industry may take the following form: where L, C, and K are assumed to be environ- mental constants. Differentiating (7) and sub- stituting we obtain, X = ^ = kLX - /v'X2 = aX - 6X2 (g) at where a = kL, b = k. If (8) is set equal to zero, we may solve for the nonzero steady-state biomass, alb (i.e., L). Alternatively, the limit of X{t) as f ^ °° yields identical results. The maximum of (8) occurs when X is equal to al2b. Thus max 3^ = a^l4b (9) The introduction of fishing (i.e., harvest or Kx) is assumed to have no interactive effects, so that the instataneous growth rate is reduced by the amount harvested:'" ^ = gX - 6X2 - Kx. at (10) The economic component of the model re- quires the exact specification of an industry production function and an industry revenue relationship. One hypothesis regarding the fish catch is that the proportion of the biomass caught is a direct function of the number of vessels (or equivalent fishing effort) exploiting a given ground." Thus, the total harvest rate is given as. "Graham (1935) was the first biologist to apply the logistic growth model to exploited fish populations. '" Schaefer, (1954) was the first population dynamicist to develop the function specified in equation ( 10). '• Alternatively, one could assume that the proportion of the biomass caught declines as the number of vessels increases: Kx = [\ - (\ - nf^]X. 0- Figure 3. — Extinction. 17 FISHERY BULLETIN VOL. 72. NO. 1 and 7r.'»* The first three can be developed by combining statistical estimation and indepen- dently derived data. Assume that the biomass is instantaneouslv in equilibrium (i.e., dX_^ q) dt Then, taking the inverse of (14) and substituting it for X in (11), we obtain: (il2b, it follows that the following parameters may be estimated (designated by *): Kx = cK- dK^ (16) r = C/2X b = [d/p2] -1 a = cblr. (18) (19) (20) where and C = J,d If b X = c - dK. (17) Equation (16) is the familiar parabolic yield function postulated by Schaefer (1954).'^ Notice that both the harvest rate, Kx, and output per vessel, X, may be specified solely in terms of the number of vessels or fishing effort. Similarly, the common property resource externality, as given in (17), is a function only of the level of K. Over a longer period of time the basic assump- tion underlying equations (16) and (17) may reflect a valid representation; i.e., effort or K is the only instrumental variable affecting out- put. There are three different parameters em- bedded in estimates of c and (/. The only way that 0, b, and r can be derived is if some inde- pendent biological information is given. More specifically, suppose that we have an estimate of the biomass consistent with maximum sus- tainable yield, call it X° . Since X° is equal to Thus, (17) will be estimated subject to one modification concerning the introduction of an environmental variable. Several biologists, including Dow et al. (1961),-" have argued that a long-term trend of declining seawater tem- perature is partially responsible for the decline in U.S. coastal catches. -• It will be assumed in this study that seawater temperature (°F) affects the a term in the growth function so that, ^ = aCF)X-bX^, (21) where °F is equal to the mean annual sea- water temperature, in degrees Fahrenheit Boothbay Harbor, Maine, with . 9a a( F) a'>0. Seawater temperature can easily be incorporat- ed into (17) in the following way: c -dK + z( F), (22) "* An alternative approach suggested by Thomas (1970) uses the Beverton-Holt model in developing a yield/ recruit relationship. However, because a stock-recruit- ment equation is not specified, it cannot be incorporated •nl'> our bioeconomic model at this time. "* The reader should recognize that it does not follow that (17) can be derived from a generalized growth equa- tion [X = F(X) - K\ = 0] and production function Kx = l\X,K). Only under certain specifications of the previous two functions will it follow that .v can be defined as a unique function of K (or X) only. In addition, this production function could have been more generally speci- fied as Kx - rK^XP. However, two compelling factors make it desirable to employ this function. First, there are no observations on the biomass, X, so that empirical tests cannot be made to estimate B. Second, the equation Kx = rKX combined with the logistic gives an excellent empirical fit to past behavior in the fishery (i.e., R- = 0.962 for yield function equation 23). In addition, Schaefer makes the same assumption as we did, and this assump- tion is generally accepted as plausible for most fisheries. In conclusion it is difficult for us to imagine how a differ- ent assumption could lead to superior predictive results (i.e., goodness of fit). where z represents the change in output per boat as a result of a one-degree change in water temperature. -- Data on the number of traps fished per year for the entire inshore American lobster fishery '-" Dow, R., D. Harriman, G. Ponlecorvo, and J. Storer. 1961. The Maine lobster fishery. Unpublished manuscript submitted to the U.S. Fish and Wildlife Service, Washing- ton, D.C. 71 p. (May be obtained from Sea and Shore Fisheries, Maine.) -• Higher seawater temperature can affect the natural yield of lobsters by providing a climate in which molting is facilitated. A larger number of molts will tend, ccwris paribus, to increase the yield associated with any given level of the biomass. -- Implicit in the way the effect of seawater temperature is measured is the relationship: [a = <;o + d(°¥)]. 18 FULLENBAUM and BELL: AMERICAN LOBSTER FISHERY are available for the 1950-69 period (see Appen- dix Table).-^ Output per trap was regressed against the number of traps and seawater tem- perature on the assumption that the number of traps per boat was constant. The regression estimates yielded the following results: X = -31.82 - 0.00002807(T) + 1.846(°F) (23) (6.55) (4.99) R2 = 0.962 D-W = 2.38 where T = 562. 8( A'): d = 0.0156; c = - 31.82 + 1.846(°F). In (23). T is equal to the number of traps fished per year, and f-ratios are in parentheses.-^ Both T and °F are statistically significant at the 5% level and exhibit the cor- rect sign; the Durbin-Watson statistic indicates no significant autocorrelation. The only step required to obtain the biotech- nological parameters is an estimate of the bio- mass consistent with ma.ximum sustainable yield. It has been calculated that (assuming a temperature of 46°F) the fishable stock of U.S. inshore American lobsters consistent with maximum sustainable yield is equal to 31 mil- lion pounds.'--^ For the Gulf of Maine (where most of the resource is located), estimates of the biomass were made through sampling experi- ments.'-*' Finally, on the basis of recent cost studies, we have derived an estimate of n for 1966 equal 23 The assumption of a constant number of traps per boat is necessary in order to solve for a coefficient on "K". and thereby, to obtain the biotechnological paramet- ers embedded in the yield-effort relationship. The rela- tionship for 1966, derived on the basis of cost data ob- tained from the National Marine Fisheries Service's Divi- sion of Financial Assistance was 562.8 traps per full-time equivalent northern lobster boat. However, it should be pointed out that when the stock is large and the catch high, it may pay to increase the number of traps per boat: therefore, this might bias the number of "standard- ized boats", but not total amount of effort. -'' However, the reader should note that the empirical estimates themselves (1950-69) make no assumption with respect to the relation between K and T. \ was regressed on T and °F. Only in the simulation was a relationship assumed (T = 562.SK). -•^ U.S. Department of the Interior. 1970. Joint master plan for the northern lobster fishery. Unpublished man- uscript. 130 p. (May be obtained from the National Marine Fisheries Service, Washington. D.C.) -6 No attempts were made to run the simulation model with varying sizes of the MSY biomass as this would un- necessarily complicate this paper which is intended to be simplistic as possible. to $12,070.27,28 Therefore, on the supply side, the estimated parameters for 1969 are the fol- lowing: a b r 1.85379 2.9899 X 10-^ 5.1562 X 10-4 $13,191 (see footnote 27). The Demand Function for American Lobsters Only knowledge of d and /j is needed in order to complete the empirical component of the study. The estimation procedure is rather straightforward. We may specify the following demand function for all lobsters: C N = F-m(P'/CPI) + g(y/AO (24) where C is equal to consumption of all lobsters, P' is the money ex -vessel price of American lob- sters, Y is aggregate U.S. personal income (1967 prices), A' is U.S. population, and CPI is the consumer price index. Since there are no exports of lobster, the following identity holds: C = 1+ Q + Q. (25) where /, Q^, and Q^^ are the level of imported lobsters, U.S. production of all other lobsters, and U.S. production of inshore American lob- sters, respectively. Given (25), equation (24) may be solved in terms of P, or, P = CPI If Qq, /, Y, CPI. and N are held constant, equa- tion (26) gives a unique relationship between the ex-vessel price of American lobsters and quantity landed. Using data over the 1950-69 period (see Appendix Table), the parameters of equation (24) were estimated using least squares: -' Cost data from the National Marine Fisheries Serv- ice's Division of Financial Assistance (1966) reveal the following cost breakdown for a representative lobster boat: operating expenses, $4,965.16: fixed expenses, $1,180.20: returns to capital and labor, $5,825.48. This gives a total of $12,070.84. The latter figure was updated to 1969 by income increases in Maine to obtain $13,191. 28 We will assume that rf remains constant in real terms. This is equivalent to keeping our estimate of it". Tf constant, while deflating all nominal variables on the demand side. 19 FISHERY BULLETIN VOL. 72. NO. 1 ^= -0.0632 -0.005029(^j (2.06) 0.00051^ (27) (5.38) «2 = 0.816 D-W = 0.619 All of the independent variables are significant at the 0.05 level. However, the Durbin-Watson statistic indicates the strong possibility of posi- tive autocorrelation. Nonetheless, we will use these estimates as rough approximations to obtain the price-dependent relationship as shown in (26). Given 1969 values of exogenous variables (A^ - 199.100,000; Y - $567,635 million; CPI = 109.8 with a base of 1967 = 100; Q + I = 158.8 million pounds), we have. P= 1.179 - (0.99853 X 10-^)Q.^. (28) Thus initial values for a (1.179) and ^ (0.99853 X IQ-^) have been obtained.-" -9 For purposes of simplification, the parameters of the model are all assumed constant. Certainly, one could argue that the parameters, so tacitly assumed to be constants, are at best random variables. Therefore, a stochastic treatment might be used with criteria like maximal expected present value or minimal maximum expected loss for evaluating the management alternatives rather than simple deterministic computations. Possibly, the parameters are random variables and conditional on some of the suggested management alternatives. For example, freezing effort might accelerate /■, leading to shifts in season or age structure harvested, hence a change in ulh. HOW THE MODEL WORKS: THE IMPACT OF CRITICAL VARIABLES To illustrate the power of the model in ex- plaining the impact of changes in critical variables, we may derive initial quantitative estimates of the ecological equilibrium and economic steady-state functions. In this section we will illustrate the power of the model in explaining the impact of changes in critical variables. The year 1969 is selected for initial quantitative estimates of the ecological equi- librium and economic steady-state functions. Table 1 shows what happens to the value of {X*, K*) as well as the equilibrium harvest level. {Kx)*, when the following changes take place: a) A 25% increase in opportunity costs of labor caused by the development of greater regional industrial activity; b) A 25% increase in the supply of other lobsters traceable to the discovery of a new lobster ground; c) A 5% increase in personal per capita income; and d) A decrease in water temperature from 48° to47°F. Notice that these changes are for illustrative pur- poses; however they do come about on a routine basis in the real world. Perhaps 25% changes in selected variables do not come about in one year so the reader can view the new equilibrium Table 1. — The impact of exogenous shocks to the inshore American lobster fishery on the effort, catch, and biomass. Vessels, Traps Catch Biomass full-time equivalent K* £* Kx* X* Nuinhcr Niiiiibcr Million poiiiuls Initial equilibrium (1969) 1,936 1 ,089,000 28.56 28.62 (computed by model) New equilibrium: (a) Increase (25°o) in opportunity 1,531 861,718 28.1 35.6 cost of labor (b) Increase (25°o) in exogenous 947 533,000 22.3 45.7 supply of lobsters (c) Increase (5°o) in personal per 2,182 1,228,310 27.4 28.0 capita income (d) Decline in water temperature by 1° 1,851 1,041,710 26.8 29.0 (e) Changes (a)-(d) simultaneously 905 509,356 20.7 45.9 20 FULLENBAUM and BELL: AMERICAN LOBSTER FISHERY positions shown in Table 1 to result over a period of years from the 1969 initial e(iuilibrium. We may incorporate all of the four changes given separately in (a) - (d) to ascertain their net impact. The strength of the simulation model is that we can study the separate and combined influences on the fishery of important variables. Because we have both positive and negative influences on fishing effort, it is likely to be such that complete extinction of a particu- lar species would be somewhat difficult.-'" ECONOMIC IMPACT OF SELECTED MANAGEMENT ALTERNATIVES Up to this point, we have been concerned largely with building a bioeconomic model that considers all important variables. The model is based upon the fact that open access to the American lobster fishery is permitted. However, all States restrict gear to pots and traps. Each State (Maine, Massachusetts, New Hampshire, and Rhode Island) has a minimum length re- quirement; permitted minimum lengths vary from S'/h to S-'/ie inches. We are taking the array of existing regulations as given. We shall consider the economic impact of five alternative policies that could be adopted to manage or to limit entry to the entire American lobster fish- ery. These management strategies assume that some central authority such as a regional com- mission could impose these regulations. •'! The specific objectives of these management strate- gies will be discussed below. All strategies have two objectives in common which are (1) to protect the resource from overex])loitation and (2) to allow maximum freedom for operators to function in a free enterprise fashion. Further, the following strategies are meant to be illustra- tive and do not exhaust all possible alternatives. Also, two other management strategies sug- gested by Reeves (1969) and Sinclair (1960) will 30 This is subject to two qualifications. First, since we are plotting only equilibrium relationships, extinction is a possible dynamic outcome (as was mentioned previously). Second, we have implicitly assumed that in the case of American lobster, the rate of technological advance is minimal. This is a fairly realistic assumption for the in- shore trap fishery. However, in general. / = r(i), with ^'>0. 31 With the steady-state assumption, the management policies would in fact maximize the present value of the stream of net benefits over time. be reviewed. As other management strategies are suggested both inside and outside govern- ment, the model formulated above may be used to predict their impact. Some Possible Alternative Management Strategies for Inshore American Lobsters 1. Freeze on existing (1969) fishing effort by placing a lice)ise fee on traps: Under this scheme, the regulatory authority would calcu- late a license fee on traps which would keep the level of fishing effort constant despite an increase in the demand for lob.sters.-'- A license fee could not be levied on the individual vessel because this would not control the number of traps fished per vessel. The increased cost of operations due to the license fee would make it uneconomical for vessels to enter the fishery even though ex-vessel prices have increased. In essence, the license fee would siphon off increased revenue (or profits) from an increase in ex-vessel prices assuming the latter increases faster than cost of operations. For purposes of illustration, let us assume that we desire to manage the inshore American lobster fishery commencing in 1974. Given the estimated trend in important variables in the fishery (i.e., n, I, Qq, Y, N, CPI) to the year 1974, it would be necessary to place an estimated annual license 32 The model can derive the "correct tax" (or license fee) in a number of ways. Suppose, the regulatory author- ity wishes to freeze effort at some specified level K^. We can derive the equilibrium yield consistent with K'\ call it (A^.v)", from the yield-effort relationship. The total tax and the tax per vessel are then respectively given by: 7'^. -(a-/i(/..Y)0)(A-.v)0-AOf K In similar fashion, if the regulatory authority wishes to freeze effort at a level consistent with maximum sustain- able yield, we can obtain the tax that will insure this level of exploitation. The only other taxing scheme that requires further ex- planation is a tax that will insure marginal cost pricing. Long-run industry marginal cost can be defined as: ff/ J^\ where dK.\ is the first derivative of (16). Total industry cost can then be redefined as, ydKx/bK/ This expression can be substituted into the total revenue function and solution for K, Kx can be found by iteration. The tax consistent with these solutions can then be derived by using the formulas given above, i.e., Tx, TxIK. 21 FISHERY BULLETIN VOL. 72, NO. 1 fee of $3.34 (in 1972 dollars) on each lobster trap fished. This is shown in Table 2. The reg- ulatory authority would collect over $3.5 mil- lion in license fee revenue which could be used to finance resource research, enforcement, and surveillance. It should be emi)hasized that these calculations are merely rough estimates and only serve to give the reader some idea of the magnitude of such license fee. The illustra- tive license fee is also based upon an extra- polation of trends 5 yr ahead of 1969. If we did nothing, it is estimated that the catch would be lower and more fishermen and traps would be employed in the fishery by 1974. Obviously, the situation would worsen as demand for lob- sters expanded and the fishery became increas- ingly overfished. The license fee plan does have many disadvantages. First, a license fee on traps fished does not really get at the utilization rate. One might expect that a license fee on an individual trap might induce fishermen to fish each trap more intensively and thereby reduce their number of traps. At this point, we do not have any information on utilization rates whereby the tax could be adjusted upward if utilization increased. Second, enforcement and surveillance might be difficult along the coast- line from Maine to North Carolina. Third, and most important, the quantitative tools and projected figures needed to calculate a license fee are at best crude and would have to be used for calculations each year. 2. Reduce the existing level of fishing effort to that necessary to liarvest MSY by placing a Hcoise fee on traps: With this scheme, the regulatory authority would calculate a license fee on traps which would reduce the level of existing effort to that necessary to harvest maxi- mum sustainable yield (i.e., estimated to be about 1,011,910 traps) despite an increase in demand for lobsters.-''^ Because we are actually reducing fishing effort as opposed to freezing it at the 1969 level, the estimated 1974 license fee per trap must be higher or $5.58 (in 1972 dollars). Actual catch will not be significantly higher. The regulatory authority would receive approximately $5.6 million in license fee reven- nue. However, this plan has the same disadvan- tages of a general license fee plan indicated under alternative one. 3. Reduce the existi)ig level of fishing effort to that )iecessarjj to make the marginal cost of 33 The fishing effort needed to harvest MSY was ob- tained from equation (23) with the 1950-69 average water temperature. Table 2. — The impact of various management schemes imposed on the inshore American lobster fishery in 1974. Impact after the imposition of selected mane igement strategies for 1974 (1) (2) (3) (4) (5) Estimated Issue "stock values before Freeze at Reduce Reduce certificate" Economic imposition of 1969 level fishing fishing to vessel Do variables management of fishing effort effort owner while nothing strategies effort to £max %o MC = P freezing effort ( 1 969) at 1969 level Catch (million lb) 28.6 28.6 28.7 23.9 28.6 28.1 Value of catch 28.0 36.8 36.9 31.9 36.8 36.4 (million $) Vessels (full-time 1,900 1,900 1,798 1,060 1,900 2,070 equivalent) Traps (million) 1.069 1.069 1.011 0.597 1.069 1.165 Ex -vessel price 0,98 1.29 1.29 1.33 1.29 1.30 Total license fees 0 3.56 5.58 13.3 0 0 collected (million $) License fee/vessel ($)'- 0 1,877 3,119 12,622 0 0 License fee /trap ($) 0 3.34 5.54 22.43 0 0 Return per vessel 6,365 8,400 8,400 8,400 10,278 8,400 and fisherman ' Projection of 1974 impact of selected management strategies. Assumes that F° = 48°; Y = $677.9 billion, (1969 prices); POP = 212.4 million; Qo + / = 183.6 million pounds and fi = $15,292. All prices and dollar values projected for 1974 ore expressed in 1972 dollars. ^ The license fee per vessel was obtained by multiplying the tax per trap by the average number of traps (562.8) fished per full-time vessel. 22 FULLENBAUM and BELL; AMERICAN LOBSTER FISHERY knidiiigs equal to ex-ves.sel price by placitig a license fee on traps: The idea hei'e is to obtain the greatest "net economic benefit" and has been suggested by such economists as Crutch- field and Pontecorvo (1969).''^ If a regulatory authority were to try this for 1974, it would have a drastic impact on the fishery as the number of full-time equivalent vessels and traps would be reduced by approximately 47%. To accomplish this objective an estimated 1974 license fee of $22.43 (in 1972 dollars) per trap would be needed. This would yield the regulatory author- ity appro.ximately $13.3 million in revenue. From an economic point of view, it is argued that this management strategy will result in the most efficient operation of the fishery if fisher- men and vessels can easily move to other fish- eries or industries. However, this strategy may be particularly unwise in rural areas such as Maine where labor mobility is low. A drastic cutback in the number of fishermen may create social problems where the cost would greatly exceed any benefits derived from this manage- ment strategy. Therefore this management strategy is difficult, if not impossible, to justify on economic grounds for many rural areas where the fishing industry is located and also has the same disadvantages of a general license fee plan on traps as discussed above. 4. Issue "stock certificates" to each vessel ou'iier based upon average catcJt over last 5 ijr while freezing the existi)ig level of fishing effort: Under this scheme, the historic rights of each fishing firm would be recognized. In a similar manner to a private land grant procedure, the regulatory authority would simply grant each fisherman a "private" share of an existing resource or catch. The stock certificate would be evidence of private ownership. Individual fishermen would be free to catch up to their allotted share through the use of pots or other biologically permissible technology or, if they desired, trade their stock certificates to others for cash. Suppose the regulatory authority were to freeze the level of fishing effort at the 1969 level and distribute the estimated catch via a stock certificate to the existing fishermen. It should be pointed out that the regulatory author- s'* When price is constant, maximization of net economic benefit becomes identical to the goal of maximization of rent to the fishery. This, however, is not the case when the normally downward sloping demand curve is specified. ity fixes effort when it selects a given catch. The selected catch could be either MSY or any other level of catch deemed by the regulatory author- ity not injurious to the viability of the .stock. The expansion in demand for lobsters by 1974 would generate excess profits for those individual fish- ermen who were initially endowed with the property right. By 1974, it is estimated that a full-time lobsterman would be earning $10,278 (in 1972 dollars) a year of which $1,878 would be excess profits (i.e., above opportunity cost). If iirofits become excessive a license fee would be levied on the fishermen holding stock certif- icates to insure against increased abnormal returns and provide the regulatory authority with funding to conduct scientific investigations and enforcement. It should be noted that this plan is identical to the license fee scheme which freezes effort at its 1969 level. However, in the latter case, excess profits are taken by the regulatory authority while for this strategy, fishermen are allowed to hold onto the profits generated in the fishery. Since many fisheries are located in rural areas where earnings are traditionally low, this strategy might be justified on the basis that it will raise income levels and thereby help improve living standards to com- parable levels to those received in urban areas. This management strategy would, of course, be popular with those already in the fishery. How- ever, new entrants would have to buy .stock certificates from those initially in the fishery. This would bring up certain questions of equity and legal precedent which are beyond the scope of this article. 5. No manage Die nt strategy: When consider- ing the economic consequences of alternative management strategies (1-4), it is aJways wise to assess the results of doing nothing. This gives policymakers a better ])erspective in evaluating the benefits from taking action. The consequence of doing nothing would be overcapitalization by 1974 with an expansion in the number of full- time equivalent fishermen and traps fished. Approximately 96,000 excess traps (i.e., above that necessary to take MSY) would be in the fishery, and the catch would fall to 28.1 million pounds. The fishery would grow increasingly over- capitalized, and the resource would be greatly overexploited as demand increased for lobsters during the 1970"s. On economic grounds, these 23 FISHERY BULLETIN VOL. 72, NO. 1 results are hardly ac-ceptable because more fish- ermen and vessels will probably be catching less. 6. Other suggested ma)iageme)it sti'ategies: Reeves (1969) has proposed a hike in license fees to eliminate the marginal or part-time fishermen. He suggests that the present $10 yearly fee in Maine be raised $10 a year over the next 9 yr to a top of $100. In 1969, a little less than one-half of the lobster fishermen were part-time. A part-time lobster fisherman is defined as one who gains less than one-half of his aniRial income from lobstering. The first step in most suggested limited entry schemes is usually to restrict the fishery to full-time utilization of cai)ital and labor. Two problems occur with this policy. First, the part-time fish- ermen may represent the most efficient way of taking the catch. If so, the full-time fishermen may be eliminated by increased license fees. Second, license fees do not directly control fish- ing effort since fishermen may fish more tra})s. However, Reeves also goes on to argue strongly for limiting the number of traps each fisherman is allowed to set. It is not quite clear whether anyone knows the optimum number of tra])s per vessel. Rutherford. Wilder, and Frick (1967) in their study of the Canadian inshore lobster fishery endorse the system suggested by Sinclair (1960). They state: "An alternative management system is that suggested by Sinclair (1960) for the salmon fisheries of the Pacific Coast. This would use the licensing of fishermen to limit entry into the fishery. In the first stage, lasting about five years, licenses would be reissued at a fee but no new entries would be licensed, and it would be hoped that during the period there would take place a reduction in the labour and capital input, to take the maximum sustainable catch of salmon at a considerably lower cost. After the end of the first stage, licenses would be issued by the government under competitive bidding and only in sufficient numbers to appro.ximate the most efficient scale of effort; the more competent fishermen would be able to offer the highest bids and it would be expected that the auction would recapture for the public purse a large portion of the rent from the fisheries that would otherwise accrue to the fishing enterprises under the more efficient production condi- tions in the fishery. "An arbitrary reduction in the number of fishermen by restriction of licenses to a specified number would entail injustice and inequity as well as grave administra- tive problems in determining who should be allowed to continue fishing. The auctioning of licenses to exploit a public property resource is justifiable in a private enterprise system of production, particularly when the state is incurring heavy expense to administer and con- serve the resource: the recovery by the state of some part of the net economic yield by means of a tax on fisher- men (or on the catch) would recoup at least part of such public expenditures, or could be used to assist former fishermen (see strategies discussed above) for instance, by buying their redundant equipment. A tax on fishermen through the auctioning of licenses has, at least, the merit of using economic means instead of arbitrary regulations to achieve a desired economic objective — the limitation of fishing effort to increase the net economic yield from the fishery. Regulations have to be enforced, usually at considerable cost, but economic sanctions tend to be, if not impartial, at least impersonal and automatic in their operation." Actually, this latter management scheme is similar to the taxing scheme, but uses an auction rather than a direct tax. Conclusions The purpose of this article is to explain the use of bioeconomic models in assessing alter- native management strategies. For this purpose the data are less than optimal. However, this does not mean that we cannot take steps in the direction of fishery management. In fact, these steps must be taken to protect the resource from destruction and to achieve a better use of vessels and fishermen. It is hoped that the following conclusions will provide a helpful framework in which to consider the merits of limited entry: 1. For the inshore American lobster resource, there is every indication that the fishery has achieved maximum sustainable yield and is fully capitalized. This has been brought about by a rapid expansion in effort (i.e.. traps fished) produced by (1) free access to the resource, (2) a rising market for lobsters of all species, and (3) a secular decline in seawater temperature. 2. We have presented the bioeconomic im- pact of alternative management strategies to both conserve the resource and use it efficiently. The choice of which strategy to pursue is in the public domain and beyond the scope of this paper. However, the economic alternatives are pointed out. LITERATURE CITED Bell, F. W. 1972. Technological externalities and common proper- ty resources: an empirical study of the U.S. northern lobster fishery. J. Polit. Econ. 80:148-158. 24 FULLENBAUM and BELL: AMERICAN LOBSTER FISHERY CrUTCHFIELD, J. A,, AND G. PONTECORVO. 1969. Pacific salmon fisheries: A study of irrational conservation. Johns Hopkins Press. Baltimore. Md., 220 p. FULLENBAUM, R. F., E. W. CaRLSON, AND F. W. BeLL. 1971. Economics of production from natural re- sources: comment. Am. Econ. Rev. 61:483-487. Graham, M. 1935. Modern theory of exploiting a fishery and application to North Sea trawling. J. Cons. 10:264- 274. GULLAND, J. A. 1961. Fishing and the stocks of fish at Iceland. Fish Invest. Minist. Agric. Fish Food (G.B.) Ser. II, 23(4): 1-32. LOTKA. A. J. 1956. Elements of mathematical biology. Dover Publ., N.Y., 465 p. PeLLA, J. J., AND P. K. TOMLINSON. 1969. A generalized stock production model. [In Engl, and Span.] Inter-Am. Trop. Tuna Comm. Bull. 13:421-496. Reeves, J. 1969. The lobster industry: Its operation, financing. and economics. Master's dissertation. Stonier Grad. Sch. Banking, Rutgers Univ., New Brunswick, N.J., 170 p. Rutherford, J. B., D. G. Wilder, and H. C. Frick. 1967. An economic appraisal of the Canadian lob- ster fishery. Fish. Res. Board Can., Bull. 157, 126 p. SCHAEFER, M. B. 1954. Some aspects of the dynamics of populations important to the management of commercial marine fisheries. Inter-Am. Trop. Tuna Comm., Bull. 1:27-56. Sinclair, S. 1960. License limitation — British Columbia: A method of economic fisheries management. Chap- ter III, p. 98. Can. Dep. Fish. 256 p. Thomas, J. C. 1970. An analysis of the commercial lobster (Homants americanus) fishery along the coast of Maine, August 1966 through December 1970. Final Rep., Lobster Res. Prog. State Maine, Dep. Sea Shore Fish., 73 p. Worcester, D. A., Jr. 1969. Pecuniary and technological externality, factor rents, and social costs. Am. Econ. Rev. 59:873-885. Appendix Table — Economic variables associated with the U.S. inshore American lobster fishery, 1950-69. Per capita disposable Mean annual Ex-vessel personal income seawater temp- price divided Per capita divided by Consumer erature ot Catch Traps Catch Ex -vessel by consumer consumption consumer price price index Boothboy Year by traps Value fished per trap price price index Year of lobsters index (1967= 100) Harbor, Maine Thousand Tlunisand Nmnher Pounds Cems per Cents per Pounds Dollars Dei^rees pounds dollar \ pound pound (live weiKhrl Fahrenheit 1950 22,914 8,283 578,930 39.6 36.1 50.1 1950 0.585 1,892 72.1 49.3 1951 25,749 9,328 512,812 50.2 36.2 46.6 1951 .651 1,888 77.8 51.4 1952 24,681 10,469 544,730 45.3 42.4 53.4 1952 .638 1,909 79.5 50.2 1953 27,509 10,687 569,081 48.3 38.8 48.5 1953 .710 1,976 80.1 52.0 1954 26,628 10,250 628,209 42.4 38.5 47.8 1954 .690 1,969 80.5 50.3 1955 27,886 11,003 669,229 41.7 39.5 49.2 1955 .734 2,077 80.2 50.0 1956 25,386 11,584 666,887 38.1 45.6 56.1 1956 .704 2,141 81.4 48.6 1957 29,358 11,263 688,815 42.6 38.4 45.6 1957 .806 2,136 84.3 48.8 1958 26,143 12,890 753,503 34.7 49.3 56.9 1958 .736 2,114 86.6 47.4 1959 27,752 14,043 856,794 32.4 50.6 58.0 1959 .763 2,182 87.3 47.0 1960 29,345 13,657 844,110 34.8 46.5 52.5 1960 .830 2,185 88.7 47.9 1961 25,621 13,662 895,098 28.6 53.3 59.5 1961 .810 2,214 89.6 47.3 1962 26,728 13,770 909,318 29.4 51.5 56.9 1962 .855 2,280 90.6 46.6 1963 27,210 15,299 866,900 31.4 56.2 61.3 1963 .938 2,333 91.7 47.9 1964 26,844 17,689 904,233 29.7 65.9 70.9 1964 .935 2,459 92.9 46.9 1965 24,737 18,764 949,045 26.1 75.9 80.3 1965 .884 2,578 94.5 45.8 1966 25,606 19,517 947,113 27.0 76.2 78.4 1966 .873 2,680 97.2 45.7 1967 22,098 18,162 907,956 24.3 82.2 82.2 1967 .882 2,751 100.0 45.1 1968 26,918 20,648 966,335 27.9 76.7 73.6 1968 .960 2,827 104.2 46.6 1969 26,930 22,997 1,061,807 25.4 85.4 77.8 1969 .999 2,851 109.8 48.0 Source Fishery Statistics ol the Uni ed States , various years, U.S. Department of Commerce, Bureau 3f Labor Statistics, and Robert Dow. 25 DAILY ACTIVITY, MOVEMENTS, FEEDING, AND SEASONAL OCCURRENCE IN THE TAUTOG, TAUIOGA ONITIS^ BoRi L. Olla, Allen J. Bejda, and A. Dale Martin- ABSTRACT Observations were made on the activity and movements of adult tautog, Taiitogu oniiis, in their natural habitat using scuba and by monitoring the movements of individual fish by ultrasonic tracking. Results showed tautog to be active during the day and inactive at night. Fish larger than 30 cm moved out from the night resting place (home site) each day to feed, while younger fish (^25 cm) remained and fed in close proximity to the home site. Examination of digestive tracts from various-sized fish showed the blue mussel, Mytiliis editlis, to be the principal food for this population. While older fish appeared to move offshore for the winter, the younger fish remained inshore, wintering over in a torpid state. The significance of the tautog's differential responsiveness, food habits, and daily and seasonal movements are discussed. The tautog, Tautoga o)iitis (L.), an inhabitant of the western Atlantic, ranges from Nova Scotia to South Carolina, being most abundant between Cape Cod and the Delaware Capes (Bigelow and Schroeder, 1953:478-484). Its distribution is limited primarily to inshore regions with individual populations being highly localized (Cooper, 1966). This fish lives in close associa- tion with rocky places, wrecks, pilings, jetties, or almost any bottom discontinuity and for part of its range, is a prominent member of inshore benthic communities. Unlike the majority of labrids, this species is valued as a game fish and is an excellent table fish. Our aim in this work was to observe and describe the behavior of adult tautog in situ and to relate our findings to the animal's life habits and history. Our queries primarily con- cerned daily activity and movements, feeding, and seasonal occurrence. The study was carried out on a population residing in Great South Bay, N.Y., using scuba and ultrasonic tracking. MATERIALS AND METHODS The study area was along the south shore of Great South Bay, Long Island, N.Y., extending ' This work was supported in part by a grant from the U.S. Atomic Energy Commission, number AT(49-7)3045. - Sandy Hook Laboratory, Middle Atlantic Coastal Fisheries Center, National Marine Fisheries Service, NOAA, Highlands, NJ 07732. east from the Fire Island Inlet Bridge to 2 km east of the Fire Island Light (Figure 1). Water depth in the study area ranged from 2.4 to 8.8 m with the bottom composed primarily of sand, gravel, and shell. Two methods were employed to observe the activity and movements of the fish: (1) ultra- sonic tracking of a single fish and (2) direct underwater observations while using scuba. Twelve fish were tracked at different times from August through September 1971 and June through October 1972 (Table 1). Fish were captured at night within the Fire Island Coast Guard basin by a scuba diver using a hand-held net, and each fish was held in a floating cage for periods ranging from. 10 to 108 h before a transmitter was attached. ATLANTIC OCEAN tOOO METERS Manuscript accepted June 1973. FISHERY BULLETIN: VOL. 72. NO, 1, 1974. Figure 1. — Study area and areas (A-H) of tautog move- ment as presented in Table 1. 27 FISHERY BULLETIN: VOL. 72, NO. 1 Table 1. — Locations and duration of stay (h) of individual tautog during their daily movements as determined by ultra- sonic tracking. Tautog no. Day Night 1 TL (cm) Age'/sex Release (dote/time) Track duration (h) Mean temperature 2 TL (cm) Age/sex Release (date/time) Track duration (h) Mean temperature 3 TL (cm) Age/sex Release (date/time) Track duration (h) Mean temperature 4 TL (cm) Age/sex Release (dote/time) Track duration (h) Mean temperature 5 TL (cm) Age/sex Release (date/time) Track duration (h) ■ Mean temperature 6 TL (cm) Age/sex Release (date/time) Track duration (h) Mean temperature 7 TL (cm) Age/sex Release (date/time) Track duration (h) Mean temperature 45 12/9 7-25-72/1310 67.5 19.2°C 42 10/9 8- 1 -72/0940 68.3 21.2°C 42 10/9 8-8-72/1215 66.5 20.4°C 43 916 9-15-71/0830 47.5 22.0°C 38 7/9 9-27-71/1400 41.5 18.1°C 47 11/d 8-16-71/1830 41.5 21.7°C 20 3/9 10-4-72/0930 34.0 16.8°C A3'( 5.0)- Al( 2.2) A4( 9.8) A4( 2.6) Al(11.4) Al(lO.O) Al(14.1) A3(10.2) A4( 1.9) Al( 0.8) A4(11.5) A3( 3.1) A4( 0.5) Al( 9.6) Al( 9.8) Al( 9.6) A4( 0.4) A5( 2.3) A4( 9.2) C ( 8.4) A5( 1.8) Al( 3.0) A4( 0.9) A5( 6.2) A5(0.3) Al(11.3) Al(11.6) Al(10.8) A4( 3.0) A9(10.3) A9( 7.0) Al( 1.0) A3( 2.5) A4( 0.5) A4( 5.7) A5( 0.8) A6( 0.6) A6( 4.5) A7( 2.3) A7( 0.8) Al( 0.3) A5( 2.7) A5( 1.0) A4( 0.2) A6( 1.4) A7( 4.0) A8( 0.1) Al( 1.4) A2(10.9) F ( 4.1) A5( 0,3) Al( 9.4) Al(12.5) Al(12,8) Al(15.6) Al(16.6) Al(15.1) Al(10.3) G (12.2) Al(11.5) Al( 0.6) The transmitter emitted pulsed signals at 70 kHz (kilohertz). Those used for small fish (20- 25 cm) measured 30 x 9 mm (manufactured by Chipman Instruments''). Larger transmitters, 65 X 14 mm (SR-69B, Smith-Root Inc.) were used for the remaining fish (38-50 cm). The pharyngeal mill apparatus of the fish precluded internal insertion of the transmitter. This necessitated external attachment through the dorsal musculature, with nylon monofila- ment line just below the midpoint of the dorsal fin. On each side of the body, rubber disks (25- mm diameter) were used to prevent the flesh from tearing. Tags were made neutrally buoy- ant by the addition of a styrofoam collar coated with silicone sealant. Following attachment of the transmitter, fish were held in a 50-liter •' Reference to trade names in this publication docs not imply endorsement of commercial products by the Na- tional Marine Fisheries Service. tank for 15 to 30 min to insure that the fish were responsive and that the transmitter was operating normally. Fish were released within the basin and tracked from a 5.2-m skiff. The signal was moni- tored with hydrophone and sonic receiver (Model SR-70-H and TA-60 respectively, Smith- Root Inc.) in a manner similar to that described by McCleave and Horrall (1970). The location of each fish was recorded in relation to local landmarks. We considered a fish active whenever a change in transmitter signal was detected. Direct underwater obser- vations confirmed that we were able to detect abrui)t changes in the fish's orientation and straight line movement over 1 m. The data were subse(iuently condensed to indicate the i)res- ence of a fish for a i)eriod of time at a specific location (Table 1). For each track, we recorded current velocity, 28 OLLA, BEJDA, and MARTIN: ACTIVITY OF TAVTOGA ONITIS Table 1. — Locations and diiralit)n of stay (h) of individual tautog during their daily movements as determined by ultra- sonic tracking, continued. Tautog Uay no. 1 2 3 4 8 TL (cm) 25 Al( 7.7) Al(12.5) Al(12.5) Al( 0.6) Age/sex 4/9 Release (date/time) 10-3-72/1 115 Track duration (h) 67.7 Mean temperature 16.8°C 9 TL (cm) 50 D ( 0.5) D (10.1) D ( 4.9) Age/sex 14/(5 E (10.9) E ( 3.0) Release (date/time) 6-14-72/0855 F ( 0.6) Track duration (h) 48.8 Mean temperature 14.1°C Renewed track D { 3.9) D (16.8) D (10.2) Dote/time 6-19-72/1750 E ( 3.1) Trock duration (h) 49.9 Mean temperature 15.5°C 10 TL (cm) 43 A5( 8.6) A5( 9.8) Age/sex 9/c5 A6( 5.6) Release (date/time) 6-27-72/1025 Track duration (h) 42.5 Mean tempera'ure 17.3°C n TL (cm) 44 Al( 1.1) Age/sex 11/9 A2( 1.8) Release (date/time) 6-5-72/1345 B ( 0.6) Track duration (h) 3.5 Mean temperature 13.4°C 12 TL (cm) 45 Al( 0.3) Age/sex 12/9 A5( 3.2) Release (date/time) 6-12-72/1145 A6( 2.7) Track duration (h) 8.3 A8( 0.3) Mean temperature 13.8°C B ( 1.1) C ( 0.7) Night G ( 8.0) D ( 7.9) D ( 7.9) D ( 7.9) A5(10.2) A5( 8.3) ' Location as presented in Figures 1 and 2. - Hours given in parentheses. ^ Age estimated from calculated total lengths by Cooper ( 1967) . stage of tide, cloud cover, water temperature, and water transparency. Current velocity was measured either with a Beauvert midget cur- rent meter or by the float method. The current velocity ranged from 0.65 to 1.75 m/s. Temper- ature was measured with a thermistor and transparency with a secchi disk. Cloud cover was visually estimated. In conjunction with our tracking, we directly observed tautog in the study area with scuba for a total of 135 h (90 h daytime and 45 h nighttime). To identify periods of feeding as well as the types and amounts of food ingested, we ex- amined the digestive tracts of fish collected at different times of the day and night. We mea- sured the relative dige.stive tract fullness of each volumetrically with the fullness index being the quotient of displacement volume of empty tract/displacement volume of tract with con- tents. Determination of the maximum size of mussel that the tautog could ingest and of the maximum size it could crush was made by inserting dif- ferent size mussels into the mouth and into the anterior opening of the pharyngeal mill. The maximum ingestable size was defined as the largest mussel that could be completely enclosed in the mouth. The maximum crushable size was the largest mussel that could be partially grasped by the pharyngeal teeth. To aid in describing the method of feeding on mussels, at infrequent intervals over a 16-mo period, we directly observed and used cine anal- ysis of three individuals 25 to 38 cm, held in a 2,200-liter aquarium. RESULTS Activity and Movements The fish which we tracked were active during the day and inactive at night. There was some 29 FISHERY BULLETIN: VOL. 72. NO. 1 degree of variation in tlie precise time that activ- ity began or ceased relative to morning and evening civil twilight (Table 2). Activity began from 10 min before to 69 min after the start of morning twilight. Cessation of activity, however, was more variable, ranging from 222 min before to 69 min after the end of evening twilight. Al- though we were unable to arrive at the cause for this variation, there were indications that cloud cover and water transparency, both affecting light penetration, might play a role. Our direct scuba observations (135 h of observation) on untagged tautog showed that the fish were active during the day and inactive at night. Activity as well as responsiveness at night were at such a low level that we were able to touch individual fish or catch them easily with a hand-held net. Five fish (No. 1-5, Table 1), tracked at dif- ferent times from July through September 1971 and 1972, exhibited similar j^atterns in their daily movements. Each morning at the onset of activity or soon after, the fish moved out and usually remained within 500 m of the basin. They spent most of each day at locations in which there were large concentrations of blue mussel {Mijfihis cdnlis) (areas A2-A9, Figure 2; Table 1). Towards late afternoon or early evening, the fish returned to the basin and with- in 1 to 198 min (x= 55.7), settled in one location and remained throughout the night in an inac- tive state. Another fish (No. 6, Table 1) tracked during this period returned to the basin the first night after being released, following the same i)attern as fishes 1 to 5. However, after s})ending most of the second day in close proximity to the basin, it did not return but rather, at 172 min prior to the end of evening twilight, swam 6.2 km in a direct easterly course to an artificial reef (consisting of sunken barges and tires) where it si)ent the night (area G, Figure 1). Underwater observations made during July through mid-October showed that the number of fish, measuring about 30 to 50 cm, in close prox- imity to the basin increased just prior to and immediately after the beginning of evening twilight in comparison to the number that were present during the day. Comparing these obser- Table 2. — Onset and end of the daily activity of individual tautog relative to morning and evening civil twilight (MCT and ECT'). Mean time and range (min) to Onset of activity End of activity Tautog no. Prior to MCT Following MCT Prior to ECT Following ECT 1 27.0 (21.0 to 35.0) 122.0 (43.0 to 222.0) 2 20.0 (t0.0to30.0) 14.7 ( 8.0 to 26.0) 3 26.0 (12.0 to 43.0) 71.0 (39.0 to 116.0) 4 7.0 (4.0 to 10.0) 78.5 (72.0 to 85.0) 5 23.0 (18.0 to 28.0) 47.5 (12.0 to 83.0) 6 54.5 (52.0 to 57.0) 28.0 ( 4.0 to 52.0) 7 35.0 68.0 (54.0 to 82.0) 8 27.0 (13.0 to 45.0) 75.3 (51.0 to 88.0) 9 62.0 (49.0 to 69.0) 131.0 (26.0 to 158.0) 69.0 10 14.0 51.0 (28.0 to 74.0) ' MCT: start of morning civil twilight. ECT: end of evening civil twilight. 30 OLLA, BEJDA, and.MARTIN: ACTIVITY OF TAUTOGA ONITIS 100 METERS N / Figure 2. — Areas demarcating the locations of tautog during their daily movements as presented in Table 1 (an enlargement of area A, Figure 1). vations with our tracks of similar-sized fish, we were led to conclude that this increase was the result of the normal nightly return to the basin. However the number of smaller fish (^25 cm) appeared to remain the same throughout the day and during evening twilight, i.e., there was no discernible increase at evening twilight. To affirm whether the smaller, younger fish did in fact remain closer to the basin during the day than the larger, older ones, we tagged two fish 20 and 25 cm (No. 7 and 8, Table 1), tracking one for 34 and the other for 66.8 h. These fish exhibited the typical habit of the larger fish of being active during the day and inactive at night (Table 2). However, in contrast to the larger fish, these smaller fish remained within the basin and never ventured farther than 2 m from the walls. Examination of the digestive tract of one of these smaller fish, recaptured after track- ing had been terminated, showed the presence of mussels throughout the tract, indicating that this fish had been feeding on mussels at- tached to the basin walls or other substrate within the basin. These data indicate that tautog occur as an essentially localized population at least from July through mid-October. The basin acts as a focal point for the population, providing a suit- able night habitat for all fish and a forage area for smaller fish. Four fish (No. 9-12, Table 1) tracked during June 1972 exhibited quite different patterns of daily movements. Two of these (No. 9 and 10) ranged farther during the day and spent the night at various locations other than the basin. Tracking was discontinued on the other two fish of this group (No. 11 and 12) during the first day due to inclement weather. However, a search the night following tracking termina- tion and on three successive nights failed to detect the presence of either fish in or around the basin. They, too, evidently spent the night at other locations. The major difference in fish tracked during June from all other fish tracked was that all June fish were in spawning condition, readily extruding sperm or ova during the tagging pro- cedure. Further, if this population bears any similarities to the Narragansett Bay popula- tion (Cooper, 1966), we surmise that during June, fish are still arriving inshore from their offshore wintering area and have not yet be- come localized (at least fish of the size we were tracking). On 26 September 1972, during the day, we sighted just outside the basin (Area 3, Figure 2) a tautog with a transmitter attached. Although we could not ascertain when this fish was tagged, it had been 49 days since the last tagging. The fish, which appeared normally responsive, had either remained localized within this area for at least 49 days or possibly was one of the four fish tagged during June that had not returned to the basin at that time. Feeding There were varying amounts of food through- out the digestive tracts of fish sampled at vari- ous times of the day and just after evening twi- light (Table 3). The tracts of fish sampled just prior to morning twilight (23-83 min), while still in an inactive night condition, were empty. Thus it appears that the fish feed throughout the day, beginning soon after morning twilight and continuing up to evening twilight. Assum- ing that the fish sampled just before morning 31 twilight had fed up to the previous evening twilight, passage through the digestive tract while the animals were quiescent took 8 h or less. Examination of the matter ingested showed that 70% of the fish sampled contained 78.4 to 100% mussels, by volume, in various stages of digestion (Table 3). Next in abundance were remains of various decapod and cirriped crus- taceans, followed by an assortment of other in- vertebrates and debris (vegetable matter, sand, and gravel), with some of the latter probably being ingested incidentally with the mussels. All but two of the fish examined contained over 50% mussels, by volume, indicating that mus- sels are the principal food for this population. Observations on the tautog's method of feed- ing on mussels, in both the field and laboratory, revealed that after approaching a clump of mussels, the fish would grasp one or several at a time with the anterior canine teeth and then tear them from the substrate with an intense lateral or shaking movement of the head. In no case, in either the field or laboratory, did the initial ingestion process involve crushing with FISHERY BULLETIN: VOL 11. NO. 1 the canines. After initial ingestion, muscular contractions in the bucco-pharyngeal area were clearly seen, evidentally resulting from the shells being crushed by the pharyngeal teeth. When a clump of mussels attached by byssal threads was too large to be processed by the pharyngeal teeth, the fish would alternately ingest and egest the clump until it was sepa- rated into a smaller crushable size. The mussels in the digestive tracts consisted primarily of specimens averaging 11.9 mm in length and estimated to be 1 to 2 yr old (Table 3). There was an obvious selection of young, small mussels by all-sized fish. While factors such as ease of crushing and a greater digestive efficiency may be involved in the tautog's preference for small, young mus- sels, we found another possible cause related to the limitations imposed by the dimensions of the pharyngeal area where the mussels are crushed. The mouth can accommodate much larger mussels than the crushing apparatus is able to process. For example in the laboratory on 20 occasions, we saw fish that were starved for more than a day attempting to eat mussels Table 3. — Relative fullness and contents of tautog digestive tracts. °o of total gut content! Median % of Time of Fish Decapod length of mussels capture length Fullness and cirriped mussels less than (EDT) (cm) index ' Mussels crustaceans Other (mm) 30 mm 0400-0500 . 23.5 23.5 45.0 37.0 46.0 1.0 1.0 1.0 1.0 1.0 0800-0830 24.0 0.8 85.7 5.8 8.5 14 100.0 27.5 0.7 100.0 12 100.0 26.5 0.7 99.5 0.5 14 100.0 34.0 0.8 62.5 37.5 16 100.0 1200-1300 31.0 0.6 89.6 4.5 5.9 15 100.0 36.5 0.5 65.3 27.0 7.7 8 100.0 37.5 0.6 78.5 16.1 5.4 16 100.0 21.0 0.7 98.6 1.4 11 100.0 24.5 0.7 100.0 5 100.0 32.0 0.4 95.2 4.8 15 100.0 29.0 0.4 54.5 36.4 9.1 10 100.0 1600-1700 40.0 0.7 99.1 0.6 0.3 8 100.0 32.0 0.4 92.2 6.0 1.8 8 100.0 32.5 0.6 31.3 68.1 0.6 8 100.0 1930-2000 44.0 0.4 90.4 9.6 14 88.1 36.0 0.6 45.9 41.3 12.8 12 87.5 46.0 0.6 65.7 32.9 1.4 10 53.8 37.0 0.6 92.3 7.7 15 100.0 42.5 0.4 94.0 6.0 16 72.7 -20.0 0.6 78.4 21.6 11 100.0 ' Fullness index — volume empty tract/volume of tract with contents. - Fish no. 7 (Table 1) captured at end of track. 32 OLLA. BEJDA, and MARTIN: ACTIVITY OF TAUTOGA ONITIS larger than could be crushed by the pharyngeal teeth. The fish would ingest the mussel, unsuc- cessfully attempt to crush it, and then egest it, the process being repeated 20 to 30 times. We also found in a preliminary determination of the maximum crushable size that fish, 34 to 53 cm, could crush mussels that were only 0.47 times the maximum size they could ingest. Seasonal Movements Direct observations made during the day with scuba from October 1971 through May 1972 and from October 1972 through January 1973 indicated that there was a difference in the seasonal movement between small fish (^25 cm, 2-3 yr old) and large fish (>25 cm, >4 yr old). The ages of fish were estimated from calculated total lengths by Cooper (1967). Tautog of vary- ing sizes were observed in close proximity to the basin on 12 October 1971, at an average water temperature of 17.0°C (range: 15.2°- 19.5 °C). On 1 November with the water temper- ature averaging 10.0°C (range: 8.9°-10.6°C), no large tautog were sighted, but about 25 small ones were seen swimming within 1 m of the basin walls. Small fish were still active on 18 November (water temperature 10.0° C: 9.7°-10.1°C). On 9 December 1971, and 5 January 1972, with temperatures ranging from 4.0° to 5.5°C, a total of approximately 40 small tautog was sighted within the basin. These fish appeared lethargic and rested against the basin walls. When prodded by a diver, they moved only a few feet before settling to the bottom once again. Both large and small fish were sighted on 10 May 1972 with an average temperature of 10.6°C (range: 8.5°-11.5°C) and appeared nor- mally active. Diving observations the following fall and winter substantially supported the fact that small fish wintered inshore. On 2 October 1972, we sighted normally active large and small tautog (water temperature 16.8°C: 16.2°- 17.7° C). On 26 October with the temperature averaging 10.0°C (range: 9.6°-10.5°C), we found no large fish but sighted at least 30 small fish which appeared normally active. During dives on 27 November and 29 December 1972, and 9 January 1973, with the temperature rang- ing 2.0° to 4.8°C, we sighted approximately 35 small fish (^ 25 cm) lying in a torpid state on the bottom between pilings and the basin walls or in bottom depressions within 10 cm of the wall. Some of these fish were partially covered with silt. Opercular movements were so shallow as to be almost undiscernible. Examination of the digestive tracts of five fish captured during this period showed that the fish had not eaten for some time as indicated by the empty and flaccid condition of the tracts. We concluded from these observations that fish at least larger than 25 cm moved offshore to winter, agreeing with the conclusions of Cooper (1966) for a population residing in Nar- ragansett Bay, Rhode Island. However, small fish (approximately ^25 cm) remained inshore throughout the year in close proximity to the home site. DISCUSSION The tautog's pattern of being active during the day and inactive at night is a typical labrid trait having been observed in a number of spe- cies. For example, field observations in the Pa- cific by Hobson (1965, 1968, 1972) showed this pattern to be present in five species (Bodiaiius diplotaeiiia, Halichoeres )iicholsi, Labroides phthirophagus, Thalassoma duperrey, and T. lucasanum). Th* pattern was presumed to be present in Hali^oeres dispilus, Hemipteronotus mundiceps, and H. pavoninus since the fish were observed in the active state during the day but not sighted at night, having apparently buried under sand or rested in crevices. Field obser- vations in the Atlantic by'^arck and Davis (1966) on Bodianus rufus, Clepticus parrai, Lachitolaimus ma.vimus, and Thalassoma bi- fasciatum also show the typical labrid day ac- tive/night inactive pattern. Whether a labrid species spends the night buried under sand or lying in cracks or crevices, all appear to be in a state of low responsiveness. Tauber and Weitzman (1969) investigated the level of responsiveness of the slippery dick, Irideo bivittata, at night. They found the fish to be in a state that resembled the mammalian sleep phase characterized by decreased respon- siveness to altering stimuli, diminished or ir- regular respiration, and eye movement activity. The low level of responsiveness present at night in labrids and other species with a similar habit has wide ramifications with regard to 33 FISHERY BULLETIN: VOL. 72. NO. 1 susceptibility to environmental stress. The prob- ability that fish would be able to respond and escape potentially lethal environmental pertur- bations during the inactive night phase would be less than if the same stress were applied dur- ing the day. Physiological responses would also differ. Differential susceptibility to stresses as related to the daily rhythm has been clearly established (for discussion and review, see Reinberg. 1967). During most of the summer and into early fall, fish of the colony we studied had a fairly well defined home range (Gerking, 1959) with the basin acting as a focal point or home site, providing a suitable night habitat for all-sized fish. While larger fish (^30 cm) moved out each day to feed, the smaller fish (^25 cm) foraged along or in close proximity to the basin walls. The adaptation of young fish re- maining close to the home site may relate to effectively protecting them against predators. On one occasion while diving in early July 1972, we observed three striped bass {Moroue .sa.r- atilis, 80-90 cm) actively pursuing and attempt- ing to capture young tautog (^25 cm) from a group of 30 to 40. The tautog were within 1 m of the basin wall at the onset of the attack. They escaped from the predators by swimming directly to the wall where they remained in crevices. The older fish, not as susceptible to predation, moves out to feed, resulting in a fuller utilization of the potential energy re- sources of the area and in the probable reduc- tion of feeding competition among individuals. The reduction in the probability of feeding com- petition seemed especially critical since all sizes studied preferred, to a large extent, simi- lar-sized mussels. This daily movement of the larger fish out of the basin also seemed to make the home site a nursery for young fish. Our obsen^ations that tautog larger than 30 cm (approximately 5 yr or older) were not present in the vicinity of the basin after the end of October circumstantially agree with the finding of Cooper (1966) that Narragansett Bay fish of similar size wintered offshore. In contrast, our results showed that younger fish remained inshore throughout the year, winter- ing at the home site in a torpid, nonfeeding state. It is apparent that the younger fish are highly dependent on the home site throughout the year for at least the first 3 to 4 and perhaps 5 yr of their life. The habit of remaining inshore over. the winter is not unknown in labrids. Green and Farwell (1971) found various-sized cunner, Tautogolabrus adspersus, lying in a torpid state inshore when temperatures fell below 5°C. Although tautog feed readily on other types of food, the most abundant food available and found most frequently in the digestive tract was mussels. Mussels were predominantly less than 30 mm long, indicating an average age of 1 to 2 yr (Savage, 1956). The next most abun- dant food found in the digestive tract was vari- ous crustaceans, with only negligible amounts of other items. It seemed that, on the basis of our diving observations, the crustacean popula- tion, in terms of a potential alternate food source for the tautog in this area, did not ap- proach the abundance of mussels in the 1 to 2 yr class. We surmise that the equilibrium of the population, in terms of food resources, is highly dependent on a single food item, with no alter- nate potentially serving as a sustaining element. Environmental perturbations that would directly affect 1- to 2-yr-old mussels or any of the pre-adult stages, would lead to a high prob- ability of stress in the tautog population. This would be especially true for young fish (3 yr or less) since they seem especially dependent upon the home site. This dependence on the home site raises the question of whether or not it is within their capability to move out and seek new feeding areas and if so, how successful would they be. Another obvious limiting element of the population is a suitable physical structure which all-sized tautog require during their night inactive phase and upon which young tautog seem totally dependent. In areas where food resources are in relative abundance to support a population, the introduction of a suitable physical habitat could lead to the es- tablishment of new discrete colonies. ACKNOWLEDGMENTS We wish to thank the U.S. Coast Guard, Fire Island, New York, and Charles Entenmann for their assistance and cooperation. Our apprecia- tion is extended to James Johnson, National Marine Fisheries Service, and Case Groot, Fisheries Research Board of Canada, for their advice and encouragement concerning the ultra- sonic tracking portion of the study. In addition, 34 OLLA, BEJDA. and MARTIN: ACTIVITY OF TAUTOGA OMTIS we wish to thank Ralph Sheprow for his tech- nical assistance during the study. LITERATURE CITED BiGELOW, H. B.. AND W. C. SCHROEDER. 1953. Fishes of the Gulf of Maine. U.S. Fish Wildl. Serv., Fish. Bull. 53, 577 p. Cooper, R. A. 1966. Migration and population estimation of the tautog, Taiitoga onitis (Linnaeus), from Rhode Island. Trans. Am. Fish. Soc. 95:239-247. 1967. Age and growth of the tautog. Tautoga onitis (Linnaeus), from Rhode Island. Trans. Am. Fish. Soc. 96: 134-142. Gerking, S. D. 1959. The restricted movement of fish populations. Biol. Rev. (Camb.) 34:221-242. Green, J. M., and M. Farwell. 1971. Winter habits of the cunner, Taiitogolabrus adspersus (Walbaum 1792), in Newfoundland. Can. J. Zool.49:1497-1499. HOBSON, E. S. 1965. Diurnal-nocturnal activity of some inshore fishes in the Gulf of California. Copeia 1965:291- 302. 1968. Predatory behavior of some shore fishes in the Gulf of California. U.S. Fish Wildl. Serv., Res. Rep. 73, 92 p. 1972. Activity of Hawaiian reef fishes during the evening and morning transitions between daylight and darkness. Fish. Bull., U.S. 70:715-740. McCleave, J. D., AND R. M. Horrall. 1970. Ultrasonic tracking of homing cutthroat trout (Salmo clarki) in Yellowstone Lake. J. Fish. Res. Board Can. 27:715-730. Reinberg, a. 1967. The hours of changing responsiveness or sus- ceptibility. Perspect. Biol. Med. 11:111-128. Savage, R. E. 1956. The great spatfall of mussels (Mytilus edulis L.) in the River Conway estuary in spring 1940. G. B. Minist. Agric. Fish. Food., Fish. Invest. Ser. II. 20(7): 1-22. Starck, W. a., II, AND W. p. Davis. 1966. Night habits of fishes of Alligator Reef, Florida. Ichthyol. Aquarium J. 38:3 13-356. Tauber, E. S., AND E. D. Weitzman. 1969. Eye movements during behavioral inactivity in certain Bermuda reef fish. Commun. Behav. Biol. Part A 3:131-135. 35 AN EXAMINATION OF THE YIELD PER RECRUIT BASIS FOR A MINIMUM SIZE REGULATION FOR ATLANTIC YELLOWFIN TUNA, IHUNNUS ALBACARES W. H. Lenarz. W. W. Fox, Jr., G. T. Sakagawa, AND B. J. Rothschild' ABSTRACT Some of the conceptual foundations of yield-per-recruit analysis as a management tool and as applied to the Atlantic yellowfin tuna fishery were critically explored. Problems examined include: (1) estimating the current state of the fishery in terms of a knife-edged recruitment approximation, (2) inferring consequences of management action from the yield-per-recruit isopleth, (3) the difficulty in achieving a maximum yield per recruit when there exist several gear types exploiting different size ranges, (4) the difficulty in obtaining projected increases in yield per recruit when the killing and discarding (dumping) of fish smaller than the optimum size occurs, and (5) the possible interaction between a size limit and the projection of the maximum sustainable yield. In employing yield-per-recruit analysis to the Atlantic yellowfin tuna fishery, two ap- proaches were taken — one approach makes use of a wide range of parameter estimates and a number of simplifying assumptions, but little data, and the other approach makes use of considerably more data, but is more confined in the parameter estimates and uses fewer of the simplifying assumptions. The general results of both approaches, assuming no dump- ing occurs, indicate that only minor increases in yield per recruit would occur if the size at recruitment is increased from our estimate of the present size at recruitment and fishing effort remains constant; an increase in fishing effort without changing other aspects of the fishery would not appreciably increase yield per recruit; and an increase in size at recruit- ment and in fishing effort would result in modest gains in yield per recruit. Specifically meeting the request of the International Commission for the Conservation of Atlantic Tunas, we recommended that a minimum size limit regulation in the vicinity of 55 cm (3.2 kg) be enacted. The second regular meeting, in Madrid, Spain, on 2-7 December 1971, of the commission of ICCAT (International Commission for the Con- servation of Atlantic Tunas) authorized the "Council to recommend to the Contracting Par- ties that they prohibit landing of yellowfin weighing less than a minimum weight some- where between 3.2 and 10 kg." This recommen- dation was based on studies by members of the Subcommittee on Stock Assessment that showed that theoretically the size at first capture which maximizes the yield per recruit of yellow- fin is between 10 and 25 kg. A special ICCAT working group on stock assessment of yellowfin tuna met in Abidjan, Ivory Coast, 12-16 June 1972, to consider fur- ther scientific aspects of size regulation and other matters pertaining to the Atlantic yellow- fin fishery (ICCAT, 1972).- Studies on yield per recruit were presented by Hayasi, Honma, and Suzuki (1972) ;■' Joseph and Tomlinson (1972);^ and Lenarz and Sakagawa (1972)." A similar study was published by Wise (1972) ' Southwest Fisheries Center, National Marine Fisheries Service, NOAA, LaJolla, CA 92037. - ICCAT. 1972. Report of the meeting of the special working group on stock assessment of yellowfin tuna (Abidjan, June 12-16, 1972). Manuscript on file at ICCAT General Mola 17, Madrid, 1 Spain. •^ Hayasi, S., M. Honma, and Z! Suzuki. 1972. A com- ment to rational utilization of yellowfin tuna and albacore stocks in the Atlantic Ocean. Far Seas Fisheries Research Laboratory, Orido 1000, Shimizu, Japan. Unpublished manuscript. -* Joseph, J., and P. K. Tomlinson. 1972. An evaluation of minimum size limits for Atlantic yellowfin. Inter- American Tropical Tuna Commission, La JoUa, Calif. Unpublished manuscript. 5 Lenarz, W., and G. Sakagawa. 1972. A review of the yellowfin fishery of the Atlantic Ocean. Southwest Fish- eries Center, National Marine Fisheries Service, La Jolla, Calif. Unpublished manuscript. Manuscript accepted June 1973. FISHERY BULLETIN: VOL. 72. NO. 1. 1974. 37 FISHERY BULLETIN, VOL. 72. No. 1 before the meeting. The report of the meeting may be considered as a summary of these pa- pers, which indicated that increases in size at recruitment would probably increase yield per recruit but not by more than about 10% . The special ICCAT working group also ex- amined available evidence on the practicability of minimum size regulations. Scientists of the group were concerned that since the gears that fish for yellowfin in the Atlantic supposedly kill most fish that are captured, a minimum size regulation would reduce the number of small yellowfin that are landed but would not have the desired effect of reducing mortality rates of small yellowfin. This, of course, as- sumes that schools of yellowfin containing yel- lowfin less than any minimum size would actual- ly be set upon. In this connection the group noted that the conditions which must be met before minimum size regulations can be effec- tive are: (1) the fishermen must be able to estimate the size of yellowfin in a school, and (2) there must be little or no mixing of small yellowfin with large yellowfin within schools. Very little evidence is available from the At- lantic on these subjects. Ten sami)les were pre- sented at the Abidjan meeting that indicated considerable mixing of small yellowfin (<5 kg) with large yellowfin (>5 kg) within schools. The working group also took note of a study on the subject by Calkins (1965) when size regula- tions were being considered by the lATTC (Inter-American Tropical Tuna Commission) for the yellowfin fishery in the eastei'n tropical Pacific. Calkins, working with only one hypo- thetical minimum size out of a range of 12.7 to 25.0 kg, concluded that a 12.7-kg size regulation would be seriously complicated by size varia- tion within sets. He also noted that a consid- erable amount of small yellowfin are often cap- tured in sets that include skipjack. Thus it ap- pears that it would not be possible to fish for skii)jack without killing some small yellowfin. Evidence based on the few samples from the Atlantic indicated that sets would include yellowfin tuna larger and smaller than 5 kg; thus even if a minimum size regulation were set at this value it would be difficult to prevent the capture offish smaller than 5 kg. The working group recommended that more data should be collected on the subject from the Atlantic. The working group also noted that a reduction in the size at first recruitment should be prevented and that minimum size regulations of 3.2 kg that have been passed by several African nations should help prevent a reduction in size at recruitment. The population dynamics of Atlantic yellow- fin tuna are complex because the fishery is prosecuted by several types of gear: bait boats, small purse seiners, large purse seiners, and longliners. These gears tend to capture differ- ent sizes of fish and thus affect the population in different ways. FAO (1968) noted that long- line gear tends to capture large yellowfin while the other gears capture small yellowfin. Lenarz (1970).'' with more recent data, showed that American" purse seine gear tends to capture relatively more large yellowfin — in significant quantities — than was indicated for the earlier surface fishery. Joseph and Tomlinson (1972, see footnote 4) presented data that indicated small purse seiners of France-Ivory Coast- Senegal (FIS) tend to capture relatively more small yellowfin than the large FIS and Ameri- can purse seiners. The differences among size selectivity of the four gears necessitates con- sideration of the physical makeup of the fleet when e.xamining size regulations. Therefore, considerable attention was paid to this aspect of the problem during the study. The above paragraph might be taken to imply that adequate data are available respecting the relative quantities and size distributions of fish caught by the various gears. It is our feeling that the adequacy of the data needs to be dem- onstrated. We cannot place much faith in the details of the relative size distributions per unit effort among the various fishing units, but we do feel that the general orders of magnitude are essentially correct. We should also point out that with the improvement in data over the last several years, the interpretations which accrue from the data and our appreciation of the considerable complexity of the fishery are more evident. Definitions of Minimum Size Because this paper discusses minimum size, it is necessary to define the term explicitly to " Lenarz, W. 1970. Estimates of yield per recruit of Atlantic yellowfin tuna. Southwest Fisheries Center, National Marine Fisheries Service, La Jolla, Calif. Un- published manuscript. " Refers to vessels registered in Canada, Panama, and the U.S.A. 38 LENARZ ET AL.: YIELD PER RECRUIT OF ATLANTIC YELLOWFIN TUNA avoid ambiguity and to prevent possible mis- applications of the results of this study. "Mini- mum size" may be viewed from two aspects: absolute minimum size and effective minimum size. Absolute minimum size is defined as the smallest fish in the catch and is related to the concept of knife-edged recruitment in defining the size at recruitment to the fishery. Recruit- ment is defined as the act of becoming vulner- able to fishing. In the case of knife-edged re- cruitment, no fish are vulnerable to fishing prior to the size at recruitment. Fish that are larger than the size at recruitment are full}^ vulner- able to fishing. Since most recruitment is size specific, hence sequential, the term effective minimum size is also needed. Effective mini- mum size is that size whose corresponding age is used as the lower bound for integration of the yield equation as if recruitment were knife- edged, and which gives the same yield per re- cruit as the sequential recruitment case. Approaches to Yield - Per-Recruit Analysis This paper examined several of the concepts involved in yield-per-recruit analyses because the question of what is the optimum minimum size for a given rate of exploitation is usually interpreted through such analyses. Both the classical approach, in which fishing mortality is constant with knife-edged reciiiitment. and the more complex approach, in which fishing mortality is size specific, are explored. Throughout the paper we have intentionally kept mathematical notation to a bare minimum. We believe that most of the equations used are well known to readers actively involved in stock assessment. Readers who are not familiar with the equations can find excellent descrip- tions in the cited literature. Employing the classical approach to yield- per-recruit analysis involves: (1) estimating the age or size at recruitment which represents an approximation of the current state of the fishery in terms of knife-edged recruitment; (2) finding the age or size at recruitment which maximizes the yield per recruit at a given level of fishing mortality; (3) imposing some regula- tion on the fishery such to achieve as its effec- tive minimum size, the age or size at reci-uit- , ment which maximizes the yield per recruit. The advice from the yield-per-recruit isopleth (in terms of the optimal age or size at recioiit- ment) may be interpreted as either a knife- edged absolute minimum size or as an effective minimum size. Since for the fishery under con- sideration (and for many other fisheries as well) recruitment is not knife-edged, then we are talking about an effective minimum size. Now, on the other hand, if we assume that the abso- lute minimum size, the regulated size, and the effective minimum size are all the same, then we will have an inappropriate estimate of the yield per recruit, and the optimum may not be achieved. Somehow we need to determine the relationship between the effective minimum size and the regulated size; in some instances they can roughly be the same; but this equality will usually not obtain if the regulated size is chosen to be the absolute minimum size in the catch. The more complex approach, which estimates size-specific fishing mortality, circumvents the first difficulty encountered in the classical ap- proach, i.e., determining a knife-edged approxi- mation to the current state of the fishery. The problem still remains, however, as to interpre- tation of the advice from the yield-per-recruit isopleth in terms of an effective minimum size. Joseph and Tomlinson (1972, see footnote 4) used the more complex approach in a recent study on minimum size regulations for the At- lantic yellowfin fishery. We have updated their analysis by using data made available at the Abidjan meeting and have also examined the sensitivity of the methodology to various sources of errors in the data. DATA, PARAMETERS, AND COMPUTER PROGRAMS Data Catch- and length-frequency data for each type of gear for the 1967-71 period were ob- tained from the report of the meeting of the special ICC AT working group (Tables 10, 11, and 12 of ICCAT, 1972, see footnote 2) with the exception of length-frequency data of the 1967-68 FIS fishery and 1971 Japanese long- line fishery. Length frequencies for the 1967-68 FIS fishery were compiled from various ORSTOM (Office de la Recherche Scientique et Technique Outre-Mer) publications (Lenarz and Sakagawa, 1972, see footnote 5). Length 39 FISHERY BULLETIN, VOL. 12. NO. 1 frequencies from the 1971 Japanese longline fishery are assumed to be the same as those of the 1970 Japanese longline fishery; this as- sumi)tion appears justifiable because year to year changes in length frequencies from long- line fisheries tend to be less than differences in length frequencies between longline fisheries and surface fisheries. Length-frequency data were available only from the Jai)anese longline fishery, FIS surface fisheries, and American large purse seine fishery. Thus it was necessary to make several assump- tions before estimating the length frequencies of the total catch of yellowfin in the Atlantic. Length frequencies for longline fisheries other than Japan are assumed to be the same as Japan's. Length frequencies for the bait boat and small purse seine fisheries other than FIS were assumed to be the same as the FIS fish- ery. Length frequencies for the large purse seine fisheries other than FIS and American were assumed to be the same as those two fisheries. Parameters The growth equation [L = 194.8 X (1 - g-0.42 (< - o.62))j presented in LeGuen and Sakagawa (1973) and length-weight relation- ship {W = 0.0000214L2-9736) given by Lenarz (19713)*^ were used, where L is fork length in cm, t is age in years, and W is weight in kg. The annual instantaneous coefficient of nat- ural mortality (M) is a difficult parameter to estimate and due to a lack of data only pre- liminary estimates have been made for the pa- rameter in the Atlantic. We assume as most authors have that M is constant over the ex- ploited phase. Estimates of M = 2.61 and 1.50 for the Atlantic were made by Pianet and LeHir (1971) based on data from bait boats and seiners, respectively. These estimates seem unreason- ably high perhaps because their data were only from the Pointe Noire region which is a small area compared to the total region in the Atlan- tic where yellowfin tuna are found. Hennemuth (1961) estimated that M is 0.8 in the Pacific while Davidoff (1969) chose the upper bound of Hennemuth's estimate, 1.0. Hennemuth's work was based on estimates of instantaneous coefficient of total mortality (Z) made from age compositions of catches by primarily bait boats and an estimate of instantaneous coefficient of fishing mortality (F) from Schaefer (1957). Since bait boats appear to be selective for small yellowfin, F and Z are not constant, and meth- ods of ageing yellowfin have not been proven correct, Hennemuth's estimate must be con- sidered a first approximation. However, his estimate seems reasonably consistent with what is thought to be the life span of yellowfin. We assumed for the purposes of our calculations here that M is 0.8 as is conventional (based on Hennemuth's work in the Pacific); we also used values of 0.6 and 1.0 to encompass what we believe is the range of reasonable values. Pianet and LeHir (1971) also estimated an average F of 0.88 for the segment of the At- lantic yellowfin tuna population that is exploit- ed in the Pointe Noire region. As we have indi- cated, their estimate is not representative for the population as a whole. Our range of estimates of Z for 1967-71 is 0.91 to 1.82 (Lenarz and Sakagawa, 1972, see footnote 5). If we assume that M = 0.8 for the Atlantic population, then F is 0.11 to 1.02. We believe that F is about 0.6 for recent years. However, we used a range of F values in our study. Computer Programs Most of the calculations were performed on the Burroughs 6700-' computer at the Univer- sity of California at San Diego. Programs used in the analysis, except for FRG708 (Paulik and Bayliff, 1967), were written by the authors; they are as follows: 1. Simplified Beverton and Holt yields per recuit— YPER. 2. Accuracy of knife-edged approximations of age at entry and interactions between mini- mum size and catch quota regulations — GXPOPS. 3. Yield-per-recruit isopleths under knife- edged recruitment — FRG708. ** Lenarz, W. 1971a. Length-weight relations for five Atlantic scombrids. Southwest Fisheries Center, National Marine Fisheries Service, La Jolla, Calif. Unpublished manuscript. " Reference to trade names does not imply endorsement by the National Marine Fisheries Service, NOAA. 40 LENARZ ET AL.: YIELD PER RECRUIT OF ATLANTIC YELLOWFIN TUNA 4. Size-specific rates of fishing mortality — COHORT. 5. Yield-per-recruit isopleths for multigear fisheries with size-specific F — MGEAR. 6. Optimum size at recruitment under differ- ent levels of effort by two gears — OPSIZE. ANALYSIS As previously mentioned in the introduction, we use two approaches in analyzing the data, the knife-edged recruitment approach and the size-specific F approach. Knife-Edged Recruitment Approach Introduction Two commonly used models for computing yield per recruit and determining the size at recruitment which maximizes yield per recruit are those of Beverton and Holt (1957) and Kicker (1958). We employed both models for knife-edged approximation analyses — the sim- plified Beverton and Holt model, making use of a wide range of parameter estimates or extra- polations from fisheries for similar species, and the Ricker model, making use of the best param- eter estimates and giving a more detailed an- alysis of yield per recruit. We used the Ricker model instead of the Beverton and Holt model for calculating yield-per-recruit isopleths be- cause the Ricker model allows the use of expo- nents in the length-weight relationship with values other than 3. It is important to stress that the material in the simplified Beverton and Holt model involves fewer assumptions than the material in subsequent sections. This is important because as our approach becomes more complex the data requirements become more rigorous. It can be argued that we have sufficient data for this simplified approach. In the more complex approaches this assertion be- comes more tenuous; because we use more as- sumptions in the more complex approaches we do not necessarily obtain more information, even though it may appear that way. However, it should be noted that the assumption of a constant rate of mortality over the fishable life span contained in the simplified approach may be important, and we believe that it is not ful- filled. These analyses are followed by sections discussing the problems of determining the proper parameters which represent the cur- rent situation of the fishery. Simplified Beverton and Holt Model The Beverton and Holt yield-per-recruit model may be simplified such that relative yield per recruit, Y\ is a function of three ratios: C = i,:iL^ Q = MIK E = FI(F + M) Y'= YI(RW^) and where // is the size (length) at recruit- ment, W^ , L^ , and K are parameters of the von Bertalanffy growth equation, Y is yield in weight, and R is recruitment. Y' is tabulated in Beverton and Holt (1966), but more extensive calculations were performed with program YPER.i" Beverton and Holt (1959) concluded that, within reason, there exists a common ratio between M and K within related species groups. Therefore, a range of estimates for the various parameters is utilized along with other information obtained by examining parameter estimates for M and K for yellowfin tuna from areas other than the Atlantic. The range of values for the various parameters is as follows: K = 0.28 to 0.53 and L^ = 175.2 to 223.0 cm from LeGuen and Sakagawa (1973), Z = 0.91 to 1.82 from Lenarz and Sakagawa (1972, see footnote 5), and M = 0.6 to 1.0. From these ranges of e.stimates, a maximum range for E is 0.0 to 0.67 and for Q is 1.13 to 3.57. Using our most reasonable parameter estimates of K = 0.42, M = 0.8, and Z = 1.4, however, a rea- sonable range for E and Q was established by allowing either the numerator or denominator of the ratio to be one of our most reasonable estimates — the reasonable ranges are E = 0.12 to 0.56 and Q = 1.42 to 2.86. With K = 0.42, M = 0.8, and Z = 1.4, our most reasonable es- timates of £■ and Q are 0.43 and 1.9. respectively. Table 1 contains optimal values of size (cm) at recruitment, /*/, for the maximum range of estimates of E and Q (deleting the impossible E = 0.0) for the range and most reasonable es- timates of L^. The dashed lines enclose the ,1 f.^n.A"'"^ ^^'"^^ °f '•• Table lib of Beverton and Holt (1966) was slightly higher than computed by YPER- this may be due to differing methods of rounding 41 FISHERY BULLETIN. VOL 72. NO. 1 Table \. — Optimal values of .size at recruitment (cm) as a function of the rate of exploitation (E) and the ratio of M to K (Q) for three estimates of L^..' E Q 0.1 0.2 0.3 0.4 0.5 0.6 0.7 = 175.2 cm 1.0 56.6 1.5 49.4 2.0 43.8 2.5 39.4 3.0 35.9 3.5 32.9 1.0 62.9 1.5 54.9 2.0 48.7 2.5 43.8 3.0 39.9 3.5 36.6 1.0 72.0 1.5 62.9 2.0 55.8 2.5 50.2 3.0 45.7 3.5 41.9 73.1 84.4 94.3 102.3 109.5 64.1 74.8 83.4 90.8 97.1 57.1 66.9 74.8 81.5 87.2 51.7 60.4 67.8 73.9 79.4 47.1 55.4 62.0 67.6 72.7 ""43.3 "■ 51.0 57.1 62.4 66.9 = 194.8 cm 81.2 94.3 104.8 113.8 121.8 r"7r3~ ■ 83.2 92.7 100.9 107.9 1 1 63.5 74.4 83.2 90.6 97.0 1 j 57.5 67.2 75.4 82,2 88,2 j 1 52.4 61.6 69.0 75.2 80.8 1 —js--- 56.7 63.5 69.4 74,4 = 223.0 cm 115.8 102.8 92,5 84.1 77,1 71.1 128.8 114,4 102,8 93.5 85.7 79.1 147,4 130,9 117,7 107,0 98,1 90.5 ' Dashed lines encompass our reasonable range of values; our most reasonable estimate. underlined value is reasonable range of estimates (deleting the un- reasonably low E — 0.12), and the underlined value in the center of Table 1 is our most reason- able estimate. One can see in Table 1 that the values are all greater than the approximate absolute minimum size of 32.5 cm'^ for the At- lantic yellowfin tuna fishery over the range of the estimates of L^ . For the moment let us assume that recruit- ment is knife-edged at 32.5 cm (0.67 kg) and that the fishery can be regulated such to obtain a knife-edged recinaitment at any desired size. Therefore, the maximum possible increases in yield per recruit may be computed. Our smallest reasonable values for optimal size at recruit- ment are 47.1 cm (2.0 kg), 52.4 cm (2.8 kg), or 60.0 cm (4.1 kg) depending on L^. The respec- tive predicted values of yield per recruit are 2.0% , 3.1% , and 4.3% higher than when size at recruitment is 32.5 cm. Our largest reasonable estimates of optimal size at recruitment are 97.1 cm (17 kg), 107.9 cm (24 kg), or 123.5 cm (36 kg). The respective predicted increases in yield " The value of 32.5 cm represents our selection for an approximate absolute minimum size for the Atlantic yellowfin tuna fishery, which also agrees with that chosen by Joseph and Tomlinson ( 1972, see footnote 4). per recruit are 65% , 73% , and 82% . The predict- ed increase in yield per recruit using all of our most reasonable parameter estimates, i.e., rais- ing 32.5 cm to 83.2 cm (11 kg), is 23%. The bounds on an increase in yield per recruit, 2% to 82% , and the most likely value of 23% , are estimated under the assumptions of knife-edged recruitment, and that size at recruitment rep- resents an absolute minimum size. The Atlantic yellowfin tuna fishery, however, does not have knife-edged recruitment. We used equation lb of this paper to obtain our most reasonable estimate of the 1967-71 average effective minimum size for the Atlantic yellowfin tuna fishery from average lengths given in Table 15 of Lenarz and Sakagawa (1972, see footnote 5). The estimate of average effective minimum size is about 55 cm (3.2 kg). Nearly all the values within the dashed lines in Table 1, however, are greater than 55. The only smallest reasonable estimate of optimal effective minimum size greater than 55 cm is 60.0 cm with Lqo — 223.0 cm. An increase from 55 to 60.0 cm would give an increase in yield per re- cruit < 0.2% . The large.st reasonable estimates of optimal effective minimum size predict increases in yield per recruit of 28% , 36% , or 45% with in- 42 LENARZ ET AL.: YIELD PER RECRUIT OF ATLANTIC YELLOWFIN TUNA creases from 55 cm to 97.1, 107.9, and 123.5 cm, respectively depending on L^ . The increase in yield per recruit by increasing the effective minimum size from 55 to 83.2 cm, our most reasonable estimate, is only 7.9% . From the above analysis using a wide range of parameter estimates, we can conclude with reasonable assurance that virtually any increase in the effective minimum size will cause an in- crease in yield per recruit. Our most likely estimate of this increase in yield per recruit is only 7.9% which is bounded, with reasonable parameter estimates, by 0% and 45% . Ricker Model Ricker model yield-per-recruit isopleths were calculated using values of M of 0.6, 0.8. and 1.0 to illustrate our estimates of actual (rather than relative) yield per recruit (Figures 1, 2, and 3). As will be mentioned in the next section it is difficult to estimate the location of the fishery on the graphs, i.e., when fishing mortality is size specific it is not a trivial matter to make reasonable estimates of age at recruitment, t^, and a constant total mortality coefficient, Z. Our most reasonable estimates, taken from Lenarz and Sakagawa (1972, see footnote 5), of these parameters are: t '. is 1.41 yr and Z is 1.4. 0.5 10 1.5 2.0 2.5 30 INSTANTANEOUS FISHING MORTALITY (F) 35 5 10 15 2,0 2 5 INSTANTANEOUS RATE OF FISHING MORTALITY (F) Figure 2. — Yield-per-recruit isopleths as functions of fish- ing mortality and age (and weight) at recruitment when M = 0.8. -60.5 48.0 229 Figure 1. — Yield-per-recruit isopleths as functions of fish- ing mortality and age (and weight) at recruitment when M = 0.6. 5 10 1.5 20 25 INSTANTANEOUS RATE OF FISHING MORTALITY (F) Figure 3. — Yield-per-recruit isopleths as functions of fish- ing mortality and age (and weight) at recruitment when M = 1.0. The results (Figures 1, 2, and 3) show, for example, that with M = 0.6 and Z remaining constant (1.4), an increase in age at recruitment from 1.41 to 1.83 yr (or 77.5 cm) raises the yield per recruit about 20% ; if iV/ = 0.8, the same change raises the yield per recruit on the order of 10% ; and if M = 1.0, the same change does 43 FISHERY BULLETIN, VOL. 72. NO. 1 not change yield per reci*uit. If age at reciniit- ment is held constant and fishing mortality is doubled, when M = 0.6 yield per reci-uit de- creases by some 20% ; when M = 0.8 yield per recruit increases on the order of 5% ; and when M = 1.0 yield per recruit increases about 30%. If effort is doubled and age at recruitment is raised to 1.83 yr, when M = 0.6 or M = 0.8 yield per recruit increases on the order of 20% ; and when M = 1.0 yield per recruit increases by about 40% . Estimation of t r In employing a knife-edged approximation to size-specific recruitment protracted over some time period, the first problem is to determine the proper age at recruitment {t^') such that the integration reflects the same yield per re- cruit as the size-specific recruitment case. There are two problems in doing so. First, there are two values for t^.' that will give the same yield per recruit as the size-specific recruitment case, unless eumetric fishing obtains. Often, however, this may be of little consequence, since one of the two values for t ' could be obviously infea- sible. Second, t ' will depend on the fishing mortality. Two estimators of t ' are provided, at least implicitly, by Beverton and Holt (1957): (1) the age corresponding to the mean selection length, and (2) the resultant of a formula depending on Z and the average age, T (or average length. /). in the catch. The mean selection length is the 50% selection length if the selection curve is symmetrical, and it is not dependent on the magnitude of the fishing mortality coefficient, F. The second estimator of t ' is r t; - 1 -HZ or, in terms of length i; = J-K{L^-J)jZ. (la) (lb) These two equations were obtained from manip- ulations of the Beverton and Holt yield equation. Several computations of yield per recruit with the program GXPOPS were made utilizing F = 0.1 and F - 2.0. M = 0.8, the von Bert- alanffy equation for Atlantic yellowfin tuna, and an arbitrary age-specific selection curve (Figure 4) in order to demonstrate the two 1.0,- 0.8 06 04 0.2 50% SELECTION AT 21 mo. |<— F = 20 tr' = 24 mo F = 0 I tr = 19 mo. 10 20 30 40 AGE (mo) 50 60 70 Figure 4. — Arbitrary age-specific recruitment curve. problems and to evaluate the two estimators of t ', . At F — 0.1, the values of t ! giving the same yields per recruit as the selection curve are <8 mo (^q of the von Bertalanffy growth curve is 7.48 mo) or 24 mo, and 19 or 45 mo for F = 2.0. Since the state of the simulated fishery is not eumetric for either value of F, there are two knife-edged approximation locations. The effect of the magnitude of F on the true t ' is obvious, with the lower value increasing from <8 to 19 mo and the upper value increasing from 24 to 45 mo as F is changed from 0.1 to 2.0. The reasonable values for t ' to approx- imate the selection curve, however, are 24 mo for F = 0.1 and 19 mo for F = 2.0, a change of 5 mo. Estimator 1, the mean selection age, is 21 mo and is shown along with the reasonable values in Figure 4. Using 21 mo for t^' would result in yields per recruit that are 4% and 15% too high for F = 0. 1 and F = 2.0 respectively. Estimator 1 does not change with F, of course, but in this case it lies intermediate between the true t^' values. Estimator 2 gives 19 mo for F = 0.1 and 18 mo for F = 2.0. We emphasize that this estimator does depend on the magni- tude of F. Neither estimator is exact in this examj^le where the catches, their ages, and the selection curve are known without error. This places doubt on their estimates from the usual catch at age data where considerable random error would be involved. Encouraging, though, is that both estimators indicate the proper direction that the fishery's selectivity should proceed to approach the optimal yield per recruit — about 44 LENARZ ET AL.: YIELD PER RECRUIT OF ATLANTIC YELLOWFIN TUNA 15 mo for F = 0.1 and 30 mo for F = 2.0. Since estimator 1 requires size-selective data not fre- quently available and does not respond to changes in F, estimator 2 appears to be the most attractive for knife-edged approximations. The Atlantic yellowfin tuna fishery, however, has a much more complex recruitment pattern and size-specific F than this simple example owing to the diverse gear types. The mix of relative F among the various gear types makes the determination of the appropriate current t ' somewhat tenuous. r Estimation of Constant Z The yield-per-recruit isopleths shown in Fig- ures 1, 2, and 3 were calculated under the assumption that fishing mortality and Z are constant after the fish are recruited. The value of Z was also estimated under the same assump- tion. The section on size-specific fishing mortal- ity will indicate that F is not a constant, but is related to size. Thus our estimate of a constant Z may not be realistic but may be a more reasonable approach to estimating yield per recruit than the size-specific F approach given the quality of the data. It is the average of values of Z estimated for the FIS bait boat and purse seine fisheries (Lenarz and Sakagawa, 1972, see footnote 5). The size-specific F section indi- cates that F decreases with size for bait boats and increases with size for purse seiners. Bever- ton and Holt (1956) gave examples that indi- cated that when F decreases with age, constant Z will be overestimated and when F increases with age, constant Z will be underestimated. Hopefully we have obtained a reasonable esti- mate by taking the average of Z's for the two gears. Size-Specific I Approach Estimates of Length Frequencies Length frequencies, numbers of yellowfin caught by 5-cm intervals starting at 35 cm (32.5 cm ^ fork length <37.5 cm), were estimated for each gear and the total fishery for two overlap- ping periods, 1967-71 and 1969-71 (Figure 5). The first period was used with the hope that the effect caused by unequal strength of year classes would be minimized by averaging. The second period was used because it was felt that 700r o 1969-71 • 1967 - 71 40 60 80 100 120 FORK LENGTH (cm.) 140 160 180 Figure 5. — Average length frequencies for the Atlantic yellowfin tuna fisheries for two periods, 1967-71 and 1969-71. 300 Q 250 UJ o z < -• 200 z li. 3 150 _) UJ >- \k 100 o o o 50 OL o BAITBOAT • SMALL PURSE SEINE A LARGE PURSE SEINE A LONGLINE 40 60 140 80 100 120 FORK LENGTH (cm) Figure 6. — Average length frequencies (1967-71) tic yellowfin tuna caught by four gear types. 160 180 of Atlan- the data are more accurate. Length frequencies of the two periods are quite similar and produce similar estimates of size-specific fishing mortal- ity and estimates of yield per recruit. Thus, to avoid redundancy, only the data for the 1967-71 period are used. Figure 6 and Table 2 show the length frequencies for each gear. The curves are as described earlier (see introductory section.) Estimates of Size-Specific Fishing Mortality Size-specific instantaneous coefficients of fish- ing mortality were estimated with the method of Gulland (1965) and Murphy (1965) as suggested 45 FISHERY BULLETIN, VOL. 72. NO. 1 Table 2. — Basic data on size (age) composition of catch of yellowfin tuna from the tropical Atlantic Ocean. Weight Age 1967-71 average > number of yell Dwfin landed Midpoint of at beginning ot beginning size interval of interval of interval Small purse Large purse (cm) (kg) (yr) Bait boats seiners seiners Longliners Total 35 0.67 1 .0579 1,886 372 100 2,358 40 1.03 1.1325 14,551 5,445 9,057 29,053 45 1.49 1 .2093 72,972 21,782 28,372 123,126 50 2.08 1.2888 246,924 89,614 36,684 7 373,229 55 2.79 1.3710 245,206 146,883 83,153 22 475,264 60 3.66 1.4562 251,017 110,755 59,648 451 421,871 65 4.69 1.5445 165,328 42,427 35,891 647 244,293 70 5.90 1 .6363 197,855 49,929 26,992 2,151 276,927 75 7.30 1.7317 143,885 36,942 23,263 5,435 209,525 80 8.90 1.8310 128,810 37,082 15,528 5,694 187,114 85 10.72 1.9348 89,637 31,143 13,338 12,025 146,143 90 12.77 2.0432 64,128 31,135 9,818 13,049 118,130 95 15.06 2.1568 70,422 22,248 10,062 1 1 ,665 114,397 100 17.61 2.2761 63,619 36,483 13,323 15,074 128,499 105 20.43 2.4017 45,582 48,274 11,647 34,071 139,574 110 23.54 2.5343 36,414 42,283 24,296 40,209 143,202 115 26.95 2.6748 29,227 21,268 21,466 44,034 115,995 120 30.67 2.8240 18,877 18,311 15,144 42,859 95,191 125 34.72 2.9832 22,228 23,711 15,018 57,358 118,915 130 39.10 3.1538 15,152 20,612 16,238 58,544 1 10,546 135 43.84 3.3376 7,142 18,304 18,504 44,690 88,640 140 48.95 3.5368 4,137 15,790 13,569 52,070 85,566 145 54.43 3.7542 3,393 17,301 17,886 55,582 94,162 150 60.31 3.9935 3,459 20,222 16,711 45,648 86,040 155 66.60 4.2595 1,511 12,057 14,926 39,108 67,602 160 • 73.30 4.5590 793 8,754 10,678 24,489 44,714 165 80,44 4.9017 634 7,803 6,633 13,659 28,729 170 88.03 5.3021 327 2,470 2,918 6,265 1 1 ,980 175 96.07 5.7838 209 2,132 1,383 241 3,965 180 104.59 113.60 6.3883 7.2004 49 1,429 361 55 1 ,894 Total 1,945,374 942,961 573,207 625,102 4,086,645 by Lenarz ( 1971b). '^ We followed the modifica- tion of Joseph and Tomlinson (1972, see foot- note 4) by using the inverse of the von Bertalanffy growth equation to convert size distributions to age distributions. This method assumes that there is a reasonably accurate relationship be- tween length and age of yellowfin tuna. This assumption has not been verified. Ageing by modal progression would probably be more satis- factory, if more complete length composition data were available on a monthly or quarterly basis. The reverse iterative i)rocedure with com- puter program COHORT and M = 0.8 was used to estimate size-specific values of fishing mortal- ity (F) starting at the 180-cm interval. Four initial values of F were tried: 0.2, 0.4, 0.6, and 0.8 (Figure 7). Estimates of F tend to converge as size of the yellowfin tuna decreases with the range of initial values tried as is characteristic '2 Lenarz, W. 1971b. Yield per recruit of Atlantic yellowfin tuna for multigear fisheries. Southwest Fisheries Center, National Marine Fisheries Service, La Jolla. Calif. Unpublished manuscript. >| ' I I I I I I Ill 40 60 80 100 120 140 160 180 FORK LENGTH (cm.) Figure 7. — Estimates of size-specific instantaneous fishing mortality coefficients (F) with several initial F values. 46 LENARZ ET AL.: YIELD PER RECRUIT OF ATLANTIC YELLOWFIN TUNA of the methodology (Tomlinson, 1970). Calcula- tions of yield per reciniit using initial values of F of 0.2 and 0.8 are shown in Figures 8 and 9 as functions of initial values of F, effort, and size at recioiitment. The values of yield per recruit do not vary significantly (<10%) with changes in the initial values of F, and the rela- tive values are quite similar. Values of size speci- fic F are shown for each gear in Figure 10 when initial values of F are 0.2 and 0.8. When the initial value of F is 0.8. values of F for small purse seiners increase sharply with size from 170 to 180 cm. This does not occur when the initial value of F is 0.2. Intuitively we do not expect an increase in F with size past 170 cm and thus choose to use the results when the initial value of F is 0.2 in the remainder of the 0.5- 7i- O INITIAL F = 0.8 • INITIAL F = 0,2 I I I I J I 10 15 20 2 5 MULTIPLIER OF EFFORT 30 35 Figure 8. — Yield-per-recruil (kg) of Atlantic yellowfin tuna, when size at recruitment is 32.5 cm, as a function of the multipUer of fishing effort. 32.5 52.5 72.5 92.5 112.5 1325 FORK LENGTH AT RECRUITMENT (cm.) Figure 9. — Yield-per-recruit (kg) of Atlantic yellowfin tuna, with the current level of fishing effort, as a function of length at recruitment. >- _l < I- cr o to 3 o < < O BAITBOAT • SMALL PURSE SEINE A LARGE PURSE SEINE A LONGLINE 80 100 120 140 FORK LENGTH (cm) Figure 10. — Estimates of size-specific instantaneous fish- ing mortality coefficients (F) by gear type when initial values of F are ( A) F = 0.2. ( B) F = 0.8. paper. Validity of the estimates of F depends on the validity of the assumption that recruitment has been fairly constant for the cohorts included in the analysis. The special ICCAT working group noted that the cohort which entered the surface fisheries in 1969 appears to be weaker than the following two cohorts (ICCAT, 1972. see footnote 2). Although inclusion of 5 yr of data in the analysis may minimize the source of error, future studies should examine the sensi- tivity of the results to errors of this type. Estimates of Yield Per Recruit Results of the yield-per-recruit calculations using the estimates of size-specific F when the initial value of F is 0.2 and with M = 0.8 are shown by gear in Table 3. Yield-per-recruit isopleths and the line of eumetric fishing (size at recruitment, / ^, which maximizes yield per recruit at a given effort) for the entire fishery 47 Table 3. — Estimates of yield per recruit (kg) when M = 0.8, initial F Sakagawa (1973) is used. FISHERY BULLETIN, VOL. 72, NO. 1 0.2, and growth curve of LeGuen and BAIT ROATS MINIMUM t;i7E MULTJOLIFO OF FFrOPT CM KG 0.? 0.4 O.A 1.0 1.4 1.8 2.0 a.s 3.0 3.5 12?. S 34.6 117. S 30.6 U2.5 26.9 107. S 23. S 10?. 5 20.4 97.5 17.6 9?. 5 15.0 87.5 12.7 S?.5 10.7 77.5 •3.9 7'. 5 7.3 67.5 5.9 62.5 4.7 57.5 3.7 52.5 2.8 47.5 2.1 42.5 1.5 37.5 1.0 32.5 0.7 O.OR 0.09 o.n 0.13 O.IS 0.17 0.19 0.20 0.22 0.24 0.26 0.27 29 30 31 31 0.31 0.31 0.31 0.15 0.17 0.21 0.24 0.27 0.31 ,35 ,38 ,41 ,45 ,48 O.Sl 0.53 0.56 57 5ft 5ft 21 24 29 33 38 0.58 0.58 0.44 0.50 0.54 0.58 0.63 0.68 0.72 0.75 0.78 0.79 O.ftO O.ftO 0.80 0.80 0.31 0.36 ,43 ,50 ,57 ,66 ,75 ,81 ,88 0.95 .02 .08 .12 .15 .15 1.15 1.15 1.15 1.15 0.39 0.46 0.55 0.64 0.73 0.85 0.96 1.04 1.12 1.22 30 38 1.41 1.43 1.42 1.42 1.41 1.41 1.41 0.46 0.54 0.65 0.75 0.86 1.01 1.15 1.24 1.34 1.45 1.54' 1.62 1.65 1.66 1.63 1.61 1.60 1 .60 1 .60 0.49 0.5ft 0.69 0.80 0.92 1.08 1.23 1.32 1.43 1.55 1.64 1.73 1.76 1.76 1.72 1.69 1.6ft 1.67 1.67 0.56 0.66 0.80 0.92 1.06 1.24 1.41 1.52 1.64 1.78 1.87 1.96 1.98 l."36 1.R8 1.84 1.82 1.81 1.81 0.62 0.71 o.8q 1.0? 1.17 1.38 1.58 1.69 1.8? 1.97 2.07 2.14 2.16 2.11 2.00 1.94 1.91 1.90 1.90 0.68 0.80 0.96 l.U 1.27 1.50 1.72 1.84 1.98 2.13 2.?3 30 30 22 08 00 1.97 1.96 1.95 SMALL PU9SF 5FINJEWS MINIMUM SI7E MULTIPLIFP OF FFFORT CM KG 127.5 34.6 117.5 30.6 112.5 26.9 107.5 2 3.5 102.5 20.4 Q7.5 17.6 o='.5 15.0 87.5 12.7 82.5 10.7 77.5 8.9 72.5 7.3 67.5 5.9 6?. 5 4.7 57. S J. 7 5?. 5 2. ft 47.5 2.1 42.5 1.5 37.5 1.0 32.5 0.7 0.2 0.34 0.35 0.36 0.3fl 0.40 0.41 0.41 0.42 0.42 0.43 0.43 0.43 0.43 0.43 0.44 0.44 0,44 0.44 0.4 0.58 0.60 0.61 0.64 0.67 0.69 0.70 0.71 0.71 0.71 0.71 0.72 0.71 ,71 ,72 ,71 ,71 ,71 ,71 0.6 0.75 0.77 0.79 0.83 0.87 0.89 0.90 0.91 0.91 0.91 0.91 0.91 0.90 0.90 0.89 0.89 0.«8 0.88 0.88 1.0 0.97 0.99 1.01 1.06 1.1? 1.14 1.15 1.16 1.16 1.15 1.14 1.13 1.11 1.10 1.08 1.06 1.06 1.06 1.06 1.4 1.09 1.11 1.13 1.20 1.27 1.30 1.30 1.31 1.30 1.29 1.27 1.24 1.22 1.19 1.16 1.13 1.12 1.12 1.12 1.8 1.16 1.18 1.20 1.28 1.37 1.40 1.39 1.40 1.39 1.37 1.34 1.30 1.27 1.23 1.19 1.15 1.14 1.13 1 . 13 2.0 1.19 1.71 1.73 1.32 1.41 1.44 1.43 1.44 1.43 1.40 1 .36 1.32 1 .78 1.74 1 .20 I.IS 1.14 1.13 1.13 2.5 1.24 1.27 1.28 1.38 1.49 1.52 1.50 1.51 1 .49 1.45 1.41 1.35 1 .30 1.24 1.19 1.14 I. 11 1.11 1.11 3.0 1 .28 1. 30 1.31 1.43 1.55 1.59 1.56 1.56 1.53 1.49 1.43 1.36 1.29 1.23 1.17 l.U 1.08 1.08 1.0« 3.5 1.31 1.33 1.34 1.47 1.60 1.64 1.61 1.60 1.57 1.51 1.44 1.35 1.28 1.21 1.14 1.07 1.05 1.04 1.04 MINIMUM SI7E CM KG 0.4 L4RGF PURSE SEINERS MULTTPLIEP OF EFFORT 0.6 1.0 1.4 1.8 2.5 3.0 3.5 122.5 34.6 0.31 0.54 0.69 0.89 0.99 1.05 1.07 1.10 1.1? 1.12 117.5 30.6 0.32 0.55 0.71 0.90 1.01 1.06 1 .08 1.11 1.1? 1.13 112.5 ?6.9 0.33 0.56 0.73 0.92 1.03 1.09 1.11 1.14 1.16 1.17 107.5 23.5 0.34 0.58 0.74 0.94 1.04 1.10 1.12 1.15 1.17 1.18 102.5 20.4 0.14 0.58 0.74 0.93 1.0? 1.06 1.08 I.IO 1.10 1.10 97.5 17.6 0.35 0.58 0.74 0.9? 1.00 1.04 1.05 1.06 1.06 1.06 92.5 15.0 0.35 0.58 0.73 0.91 0.99 1.02 1.03 1.03 1.03 1.02 ft7.5 12.7 0.35 0.58 0.73 0.90 0.97 1 .00 1 .00 1.00 0.99 0.97 82.5 10.7 0.35 0.5ft 0.73 0.89 0.96 0.98 0.9B 0.97 0.95 0.93 77.5 8.9 0.35 0.58 0.72 0.88 0.93 0.45 0.95 0.^3 0.91 0.88 ?2.5 7,3 0.35 0.57 n.7? 0.86 o.q? 0.92 0.92 0.90 0.87 0.84 67.5 5.9 0.35 0.57 0.71 0.85 0.89 0.89 0.88 0.86 0.87 0.79 6 7. S 4.7 0.35 0.57 0.71 0.84 0.87 0.87 0.86 0.83 0.80 0.76 57.5 3.7 0.35 0.57 0.70 0.8? O.ftS 0.84 0.82 0.79 0.75 0.71 57.5 2.8 0.35 0.57 0.69 0.80 O.ft? 0.80 0. 79 0.75 0.71 0.67 47.5 2.1 0.35 0.56 0.68 0.78 0.79 0.77 0.75 0.71 0.66 0.62 47.5 1.5 0.35 0.56 0.68 0.78 0.79 0.76 0.7S 0.70 0.65 0.61 37.5 1.0 0.35 0.56 0.68 0.78 0.79 0.76 0.75 0,70 0.6S 0.61 37.5 0.7 0.35 0.56 0.68 0.78 0.79 0.76 0.74 0.70 0.65 0.61 48 LENARZ ET AL.: YIELD PER RECRUIT OF ATLANTIC YELLOWFIN TUNA Table 3. — Estimates of yield per recruit (kg) when M = 0.8. initial F = 0.2, and growth curve of LeGuen and Sakagawa ( 1973) is used. — Continued. LONG LINFRS MINIMUM SIZE MUl TIPLIEC OF FFFOPT CM KG 0.? 0.4 0.6 l.O 1.4 1.8 2.0 2.5 3.0 3.5 1??.5 ^'..f. 0.80 1.40 1.8*. 2.49 2.87 3.12 3.21 3.38 3.49 3.57 117.5 30.6 0.82 1.44 1.90 2.53 2.90 3.14 3.23 3.38 3.47 3.54 11?. S ?6.<5 0.84 1.46 1.93 ?.54 2.90 3.12 3.19 3.32 3.39 3.43 107.5 ?3.5 0.85 1.48 1.93 2.52 2.84 3.02 3.08 3.17 3.20 3.21 10?. s ?0.4 0.86 1.48 1.93 2.49 2.78 2.93 2.97 3.03 3.03 3.01 97.5 1 7.6 0.86 1.47 1.90 2.43 2.69 2.81 2.83 2.85 2.8? 2.76 9?. 5 15.0 0.86 1.46 1.89 2.38 2.62 2.71 2.72 2.71 2.66 2.58 87. S 12.7 0.86 1.46 1.87 2.34 2.55 2.62 2.63 ?.<9 2.5? 2.43 8?. 5 10.7 0.86 1.45 1.85 2.?9 2.48 2.52 2.52 2.46 ?.36 2.25 77.5 8.9 0.85 1.43 1.82 2.23 2.38 2.40 2.38 2.29 ?.17 2.04 7?. 5 7.3 0.85 1.41 1.79 ?.17 2.29 2.28 2.24 2.13 1.99 1 .85 67.5 5.9 0.84 1.39 1.75 2.09 2.18 2.13 2.09 1.95 1.70 1.63 6?. 5 4.7 n,84 1.38 1.72 2.03 2.09 2.03 1.98 1.82 1.64 1.48 57.5 3.7 0.83 1.35 1.67 1.95 1.97 1.88 1.81 1.63 1.44 1.27 5?. 5 2.8 0.82 1.33 1.63 1.86 1.85 1.73 1.66 1.46 1.2^ 1.09 i.7.5 2.1 0.82 1.31 1.60 1.81 1.77 1.64 1.56 1.35 1.15 0.98 ^?.S 1.5 0.8? 1.31 1.59 1.79 1.75 1.61 1.53 1.32 1.1? 0.94 37.5 1.0 0.82 1.31 1.59 1.78 1.74 1.60 1.52 1.31 i.n 0.94 3?. 5 0.7 0.82 1.31 1.59 1.78 1.74 1.60 1.52 1.31 i.n 0.94 are shown in Figure 11. Table 3 and Figures 8, 9, and 11 indicate that if size at recruitment remains constant at 32.5 cm, very little increase in yield per recruit ('^5%) can be expected if effort is increased, and if effort remains constant, very little (~10% ) increase in yield per recruit can be expected by increasing size at reciiiit- ment. However, if fishing effort is doubled (i.e., multiplier = 2.0) and size at recruitment in- creased to 55 cm (3.2 kg), yield per recruit would increase 15% , or if size at recruitment is increased to 77.5 cm (~10 kg), yield per re- cruit would increase about 30% (Table 3). Since the line of eumetric fishing shows that optimum size at recruitment changes with fishing effort, any "minimum size" regulation must be geared to fishing effort. If fishermen are unable to distinguish the size of yellowfin before capturing them and a mini- mum size regulation prevents their landing, then the discarding of dead yellowfin will occur. Table 4 presents landings per recruit by gear and Figure 12 the landings per recruit for the total fishery when killing and discarding ("dumping") of all yellowfin smaller than the size limit occurs. If the minimum size limit is 55 cm and effort remains the same, then a 2.7% decrease in landings per recruit would occur; and a 13% decrease in landings per recruit would occur if the minimum size is set at 77.5 cm. If effort is doubled and the minimum size is 55 cm, then a 1% increase in landings per recniit would occur; with a minimum size of 77.5 cm, a 16% decline in landings per recruit would 30 4.0 4 5 50 5 5 1,0 1.5 2.0 2.5 MULTIPLIER OF EFFORT 3.0 3.5 Figure 11. — Yield-per-recruit (kg) isopleths for the entire Atlantic yellowfin tuna fishery. Dotted curve is the line of eumetric fishing. 00 0.5 1.0 1.5 2.0 25 3.0 MULTIPLIER OF FISHING EFFORT Figure 12. — Landings-per-recruit (kg) isopleths for Atlan- tic yellowfin tuna when all fish less than the minimum size that are caught are discarded dead. 49 FISHERY BULLETIN, VOL. 72. NO. 1 Table 4. — Landings per recruit (kg) when M = 0.8, initial F- = 0.2, growth curve of LeGuen and Sakagawa (1973) is used, and yellowfin less than the minimum size are caught and discarded dead. Riir R04TS MIMIMIJM <:I7E MULTIPLIEO OF FFFORT CM KG 0.? 0.4 0.6 1.0 1.4 1.8 2.0 ?.5 3,0 3,5 laa.s Ju.h 0.07 0.1? 0.15 0.18 0.18 0.17 0.16 0.14 0,12 0.10 117.5 30.6 0.08 0.14 0.18 0.2? 0.2? 0.22 0.21 0.19 0,16 0.14 11?. s ?6.9 0.10 0.17 0.2? 0.27 0.29 0.28 0.?8 0.?5 0,22 0.19 107.5 ?J.5 0.12 o.?o 0.26 0..33 0.36 0.36 0.16 0.33 0,3(1 0.?7 10?. 5 ?0.i. 0.14 0.24 0.31 0.40 0.44 0.45 0.44 0.42 0,39 0.35 97.5 W.6 0.16 0.27 0.36 0.48 0.53 0.56 0.56 0.54 0,51 0.47 9?. 5 15.0 0,18 0.31 0.41 0.S5 0.63 0.66 0.67 0.66 0,63 0.59 87.5 12.7 0. 19 0.34 0.45 0.61 0.70 0.74 0.75 0.75 0,7-) 0.69 8?. 5 10.7 0.21 0.37 O.SO 0.68 0.79 0.84 O.Sh 0.87 0,85 0,81 77.5 d.'J 0.23 0.41 0.55 0.76 0.89 0.97 0.99 1.01 1 ,00 0.97 7?. 5 7.3 o.?s 0.44 0.60 0.84 0.99 1.08 l.U 1.15 1,1=; 1,12 67.5 5.9 0.27 0.48 0.66 0.9? 1.10 1.22 1.25 1.31 1.33 1.32 ft?. 5 '..7 0.?8 0.51 0.70 0.98 1.18 1.31 1.35 1.41 1 ,46 1.46 57. S 3.7 0.?9 0.54 0.74 1.05 1.27 1.42 1,48 1.57 1.6? 1.64 5?. 5 ^.8 0.30 0.56 0.77 1.10 1.34 1.51 1.57 1.69 1,7*^ 1,79 A7.5 ^.\ 0.31 0.57 0.79 1.14 1.39 1.58 1.65 1.79 1,87 1.92 A?. 5 1.5 0.31 0.58 0.80 1.15 1.41 1.59 1.67 1.81 1 ,90 1.95 37.5 1.0 0.31 0.58 0.80 1.15 1.41 1.60 1.67 1,81 1 ,9n 1.95 3?. 5 0.7 0.31 0.58 0.80 1.15 1.41 1.60 1.67 1.81 1 ,90 1.95 SM4I L PH3SF SEINERS MIMIMIIM SI?F r^^ KG 122.5 34.6 117.5 30.6 112.5 26.9 107.5 23.5 102.5 20.4 97.5 17.6 92.5 15.0 87.5 12.7 82.5 1U.7 77.5 8,9 72.5 7.3 67.5 5,9 62.5 4,7 57.5 J, 7 5?. 5 2.8 47.5 2.1 4?. 5 1.5 37.5 1.0 32.5 0.7 0.? 0,31 0.32 33 35 0.37 0.38 0.39 0.40 0.40 0.41 0.41 0.4? 0.4? 0.43 0.43 0.44 0.44 0.44 0.44 0.4 0.47 0.49 0.51 0.55 0.58 0.61 0.62 0.63 0.64 0.65 0.66 0.67 0,68 0.69 0.70 0.71 0.71 0.71 0.71 MULTTPL lEP OF EFFORT 0.6 1,0 1.4 0,54 0,57 0,60 0.65 0.70 0.73 0.75 0.76 0.78 0.80 0.31 0.82 0.83 0.85 0.87 0.88 0.88 0,88 0,88 56 60 0,64 0,71 78 82 84 0.87 0.90 0.92 0.94 0.96 0.98 1.01 1.04 1.05 05 06 06 0.50 0.55 0.59 0.68 0.76 0.81 0.84 0.88 0,91 0,94 0.96 0.99 1.01 1.05 1.10 1.11 1.12 1,1? 1,12 1,8 0,43 0,48 0.53 0,6? 0,71 0,77 0.80 0.84 0.88 0.91 0.94 0.98 1.00 1.05 1.10 1.13 1.13 1.13 1.13 2,0 0.40 0,44 0.49 0.58 0.68 0.74 0,78 0.8? 0.85 0.89 0.9? 0.96 0.98 04 10 13 13 13 13 2.5 0.31 0.36 0.41 0.50 0.60 0.66 0.70 0.75 0.79 0.83 0.86 0.90 0.93 1.00 1.07 1.10 1.11 1.11 l.U 3,0 0,25 0.29 0.33 0.42 0.52 0.59 0.6? ,67 ,71 0,76 0,79 0,84 0,87 0,95 03 07 08 08 l.OH 3.5 0.19 0.23 0.27 0.35 0.45 0.51 0.55 0,60 0.64 0.69 0.7 3 0.77 0.81 0,89 0,98 1.03 1.04 1.04 1.04 MiMlMijM SIZF LAPGF PUSSE SEINERS MULTIPLIER OF EFFORT CM KG 122.5 34.6 117.5 30.6 112.5 26.9 107.5 23.5 102.5 20.4 97.5 17.6 92.5 15.0 87.5 12.7 82.5 10.7 77.5 8.9 7?. 5 7.3 67.5 5.9 6?. 5 4.7 57.5 3.7 5?. 5 2.8 47.5 2.1 4?. 5 1.5 37.5 1.0 3?. 5 0.7 0.? 0.?a 0.?9 0.3O 0.31 0.3? 0.32 0.33 0.33 0.33 0.33 0,34 0,34 0,34 0,35 0,35 0.35 0.35 0.35 0.35 0.4 0.43 0.45 0.47 0,49 0.50 0.51 0.51 0.52 0.52 0.53 0.53 0.54 0.54 0.55 0.56 0.56 0.56 0.56 0.56 0.6 0.50 0.52 0.55 0.58 0.59 0.60 0.61 0.62 0.62 0.63 0.64 0.65 0.65 0.66 0.68 0.68 0.68 0,68 0,68 1,0 0.51 0.54 0.59 0.63 0.64 0.66 0.67 0.68 0.69 0,70 0.71 0.72 0.74 0.75 0.77 0.77 0.78 0.78 0,78 1,4 0.46 0.50 0.54 0.59 0.61 0.63 0.64 0.65 0.67 O.^n 0,70 0,71 0.73 0.75 0.77 0.78 0.79 0.79 0.79 1.8 0.39 0.43 0.48 0.53 0.55 0.57 0.59 0.60 0.62 0,63 0,65 0,67 0,69 71 74 75 0,7b 0,76 0, 76 2.0 0.36 0.39 0,44 0,50 0,5? 0,54 0,56 0,57 0,59 0,60 0,6? 0,64 0,66 0.69 0.73 0.74 0.74 0.74 0.74 2.5 0.28 0.31 0,36 0.42 0.44 0.46 0.48 0.50 0.51 0.53 0.55 0.57 0.60 0.63 0.67 0.69 0.70 0.70 0.70 3.0 0.21 0.25 0.29 0.35 0,37 0, 39 0,41 0,4? 0.44 0.46 0,49 0.51 0.54 0.58 0.6? 0.64 0.65 0.65 0.65 3.5 0,16 0,19 0.24 0.28 0.31 0,33 0.35 0.36 0.39 0.40 0,43 0.45 0.48 0.53 0.58 0.60 0.61 0.61 0.61 50 LENARZ ET AL.: YIELD PER RECRUIT OF ATLANTIC YELLOWFIN TUNA Table 4. — Landings per recruit (kg) when M = 0.8, initial F = 0.2, growth curve of LeGuen and Sakagawa ( 1973) is used, and yellowfin less than the minimum size are caught and discarded dead. — Continued. LONG LINFRS MINIMUM SI7F MULTIPLIER OF FFFORT CM KG 0.? 0.4 0.6 1.0 1,4 1.8 ?.0 ?.5 3.n 3.5 12?. =5 34.6 0.7? i.n 1.34 1.43 1.33 1.16 1.07 0.85 0.67 0.5? 117. S 30.6 0.74 1.18 1.41 1.53 1.43 l.?7 1.18 0.96 0.76 0.60 11?. "5 ?6.9 0.77 1.?? 1.47 1 .61 1.53 1.37 l.?8 1.06 0.86 0.69 107.5 ?3.S 0.79 l.?5 1.51 1.68 1.61 1.45 1.37 1.15 0.94 0.77 10?. S ?0.4 O.RO l.?8 1.55 1.7? 1.67 1.5? 1.43 l.?l 1.01 0.84 97. S 17.6 0.81 l.?9 1.56 1.74 1.69 1.54 1.46 l.?4 1.04 0.86 9?. 5 IS.O 0.81 l.?9 1.57 1.76 1.70 1.56 1.48 l.?6 1.06 0.88 87. S 1?.7 0.81 1.30 1.58 1.77 1.7? 1.58 1.49 l.?8 1.08 0.90 8?.S 10.7 0.81 1.30 1.58 1.78 1.73 1.59 1.51 1.30 1.10 0.9? 77.5 ^^.9 0.8? 1.31 1.59 1.78 1.74 1.60 1.51 1.30 1,10 0.93 7?. 5 7.3 0.8? 1.11 1.59 1.78 1.74 1.60 1.5? 1.31 0.93 67. S 5.9 0.8? 1.31 1.59 1.78 1.74 1.60 1.5? 1.31 0.94 6?.S 4.7 n.ft? 1.31 1.59 1.7H 1.74 1.60 1.5? 1.31 0.94 57.5 3.7 0.8? 1.31 1.59 1.7B 1.74 1.60 1.5? 1.31 0.94 5?. 5 ?.8 0.8? 1.31 1.59 1.78 1.74 1.60 1.5? 1.31 0.94 ^7.5 ?.l 0.8? 1.31 1.59 1.78 1.74 1.60 1.5? 1.31 0.94 '.P. 5 1.5 0.8? 1.31 1.59 1.78 1.74 1.60 1.5? 1.31 0.94 37.5 l.P 0.8? 1.31 1.59 1.78 1.74 1.60 1.5? 1.31 0.94 3?. 5 0,7 0.8? 1,31 1.59 1.78 1,74 1.60 1.5? 1.31 0.94 occur. Therefore, if effoi't is constant the pre- dicted gain with no dumping is greater than the possible loss through dumping if the minimum size were 55 cm. but at 77.5 cm the opposite is true. At both size limits we predict a greater gain with no dumping than possible loss through dumping if effort is doubled. Assuming constant recruitment, yield per recruit per unit effort is a measure of fishing success. Table 5 presents the estimated yield per recruit per effort by gear assuming no dump- ing. Increasing the size at recruitment to 77.5 cm at the current level of effort would result in a 17% decrease for bait boats, a 9% increase for small purse seiners, a 12% increase for large- purse seiners, and a 25% increase for longliners. Yield per recruit per effort would drop by about 35% for each of the gears if effort doubled and size at recruitment increased to 77.5 cm. If effort doubled and size at recioiitment re- mained 32.5 cm, yield per recruit per effort would decrease by 30% for bait boats, 50% for purse seiners, and 60% for longliners. Changes in the average weight of landings should be considered because average weight affects the values of landings particularly in light of size-specific changes in the value of yellowfin tuna. Table 6 presents estimates of the average weight of catches by gear. Figure 13 shows average weight isopleths for the en- tire fishery. If effort remained constant and size at recruitment increased to 77.5 cm, the average weight of the catch of the total fishery would increase from 17.7 kg to 30.3 kg. If effort doubled and size at recruitment increased to 77.5 cm, the average weight would increase to 24.2 kg. Sensitivity of Results to Errors when Ageing Large Yellowfin The growth curve used in this study was based on the use of modal progressions to age yellowfin. Unfortunately while this method is probably reasonably accurate for ageing yellow- fin less than about 130 cm long, beyond this size it becomes increasingly difficult to separate modes, and there is a reasonable probability that ages are increasingly underestimated with increases in size. In addition, because tuna apparently spawn over a large portion of the year, the exact meaning of age is not always clear. Alternative methods, such as ageing by 0,0 Q5 LO 1.5 aO 2.5 MULTIPLIER OF EFFORT 30 35 Figure 13. — Average weight (kg) isopleths for the entire Atlantic vellowfin tuna fishery. 51 FISHERY BULLETIN, VOL. 72, NO. 1 Table 5. — Estimates of yield per recruit per effort (kg) when M = 0.8, initial F LeGuen and Sakagawa (1973) is used. 0.2, and growth curve of BAIT RnaTS MINIMUM SIZF MULTIPLIf^R OF FFFORT CM KG 0.? 0.4 0.6 \ .0 1 .'. 1.8 ?.0 2.5 "t.O l.S \??.s 34.6 117. 5 30.6 11?. 5 26.9 107.5 23.5 10?. S 20.4 97.5 17.6 9?. 5 15.0 87.5 12.7 8?. 5 10.7 77.5 8.9 7?. 5 7.3 67.5 5.9 6?. 5 4.7 57.5 3.7 52.5 2.8 47.5 2.1 42.5 1.5 37.5 1.0 3?. 5 0.7 0.40 0.47 0.55 0.64 0.73 0.84 0.94 1.01 1.09 1.19 1.28 1.37 1.43 1.49 1.54 1 .57 1.57 1.57 1.57 0.37 0.43 0.51 0.60 0.68 n.78 0.88 0.95 1.03 1.12 1 .?0 1.28 1.34 1.39 1.42 1 .44 1 .44 1.44 I .44 35 40 0.48 0.56 64 74 0.83 0.90 97 06 13 21 25 30 1.32 33 33 33 33 31 36 0.43 0.50 0.57 66 75 81 88 0.95 1.02 1.08 1.12 ,15 ,15 1.15 1,15 1.15 1.15 2« 33 0.39 0.45 ,5? ,61 0.69 0.74 o.an 0.S7 93 98 01 02 02 01 01 1.01 1.01 25 30 36 42 48 56 64 0.69 0.74 0.81 0.85 0.90 0.92 0.92 0.91 0.90 0.89 0.89 0.89 0.24 0.29 0.35 0.40 0.46 0.54 0.61 0.66 0.72 0 78 82 86 88 0.88 0.86 0.84 0.84 84 84 0.22 0.26 0.3? 0.37 0.42 0.50 0.57 0.61 66 71 75 0.78 0.79 78 75 74 73 0.72 0.72 0.21 0.24 0.30 0.34 0.39 0.46 0.53 0.56 0.61 0.66 0.69 0.71 0.72 0.70 0.67 0.65 0.64 0.63 0.63 0.19 0.23 0.28 0.3? 0.36 0.43 0.49 0.53 0.57 0.61 0.64 0.66 0.66 0.64 0.60 0.57 0.56 0.56 0.56 MINIMUM SIZE SMALL PU'SF SEINERS MULTIPLIEP OF FFFORT CM KG 0.? 0.6 1.0 1.4 1.8 2.0 2.5 3.0 3.5 122.5 34.6 1.72 .46 .26 0.97 0.78 0.65 0.60 0.50 0.43 0.38 117.5 30.6 1.77 ,50 .29 0.99 0.79 0.66 0.61 0.51 0.43 0.38 112.5 ?0.9 1.8? .54 ,31 1,01 0.80 0.67 0.61 0.51 0 .44 0.38 107.5 23.5 1,91 .61 ,38 1,06 0.85 o.ri 0.66 0.55 0.48 0.42 102.5 20,4 1 .9Q .69 ,45 1.12 0.90 0.76 0.70 0.59 0.5? 0.46 97.5 17.6 2.05 .73 .48 1.14 0.93 0,78 0.72 0.61 0.53 0.47 92.5 15.0 2.07 .74 .49 1.15 0.93 0,77 0.72 0.60 0.52 0.46 87,5 12.7 2.10 .76 ,51 1.16 0.93 0,78 0.72 0.60 0,52 0.46 82.5 10.7 2.12 .78 .52 1.16 0.93 0.77 0.71 0.60 0,51 0.45 77.5 8.9 2,13 .78 .52 1.15 0,92 0.76 0.70 0.58 0.50 0.43 72.5 7.3 2.14 ,79 .52 1.14 0.91 0.74 0.68 0.56 0.48 0.41 67.5 5.9 2,16 ,79 .51 1.13 0,80 0.72 0.66 0.54 0.45 0.39 62.5 4.7 2.16 ,78 .50 1.11 0.87 0.70 0.64 0.52 0.43 0.37 57.5 3.7 2.17 .79 .50 1.10 0,85 0,68 0.62 0.50 0.41 0.35 52.5 2.8 2.19 .79 .49 1.08 0.83 0.66 0.60 0.48 0. 39 0.33 '•7.5 2.1 2.19 .78 .48 1.06 0.81 0.64 0.58 0.45 0.37 0.31 42.5 1.5 2.19 .78 .47 1.06 0.80 0.63 0.57 0.45 0.36 0. 10 37.5 1.0 2.19 , ?8 .47 I .06 0.80 0.63 0.57 0 .44 0,36 0.30 32.5 0.7 2.19 ,78 .47 1.06 0.80 0.63 0.57 0.44 0, lf> 0.30 LAPOF PUPSF SEI^JFPS MINIMUM SIZE MULTIPLIER OF FFFORT CM KG 0.2 0.4 0.6 1.0 1.4 1 ,8 2.0 2.5 3.0 3.5 122.5 34.6 117.5 30.6 112.5 2b. 9 107.5 23.5 102.5 20.4 97.5 17.6 92.5 15.0 87.5 12.7 82.5 10.7 77.5 8.9 72.5 7.3 67.5 S.9 62.5 4.7 57.5 3.7 52.5 2.8 47.5 2.1 42.5 1.5 37,5 1.0 32,5 0.7 1.57 1.61 1 .66 1.71 1.72 1.73 1.74 1.74 1.74 1.75 1.75 1.75 1.76 1.76 1.76 1.76 1 .76 1 .76 I .76 1.34 1.37 1,41 1 .44 1 ,44 1.45 1.45 1.45 1 .44 1 .44 1 .44 1,43 1,43 1 ,42 1,42 1 .40 1 .40 1 .40 1 .40 1.16 1.18 1.21 1.24 1.23 1.23 1.22 1.22 1.21 1,20 1,20 1.19 1.18 1.17 1.15 I .14 1.14 1,14 1 . 14 0.89 0.90 0.92 0.94 0.93 0.92 0.91 0.90 0.89 0.88 0.86 0.85 0.84 0.82 0.80 0.78 78 78 78 0.71 0.72 0.74 75 73 72 0.71 0.69 68 67 65 64 0.62 0.60 0.59 0.57 0.56 0.56 0.56 0.58 0,59 0.60 0.61 0.59 0.58 0.57 0,56 0.54 0.53 0.51 0.44 0.48 0.46 0.45 0.43 0.42 0.42 0.42 0.53 0.54 55 56 54 0.53 0.51 0.50 0.49 0.47 0.46 0.44 0.43 0.41 0.40 38 37 0.44 0.44 0.46 0.46 0.44 0.43 0.41 0.40 0.39 0.37 0.36 0.34 0.33 0.32 0. 30 0.28 0.37 0.37 28 28 ?8 0.37 0.37 0.39 0.39 0.37 0,35 0.34 0.33 0.32 0.30 0.29 0.27 0.27 0.25 0.24 0.22 0.2? 0.2? 0.22 0.32 3? 33 34 0.32 0.30 0.29 0.28 0.27 0.25 0.24 0.?3 0.22 0,20 0.19 0.18 0.18 0.17 0.17 52 LENARZ ET AL.: YIELD PER RECRUIT OF ATLANTIC YELLOWFIN TUNA Table 5. — Estimates of yield per recruit per effort (kg) when M = LeGuen and Sakagawa ( 1973) is used. 0.8, initial F -Continued. = 0.2, and growth curve of LONG LINFW5 MINIMUM S17E MULTIPLIED OF FFFORT fM Kb 0.? 0.4 0.6 1.0 1.4 1.8 2.0 2.5 3.0 3.5 1??.S 34. fc 4.00 3.51 3.10 2.49 2.05 1.74 1.61 1.35 1.16 1.02 117. S 30.6 4.1? 3.60 3.17 2.53 2.07 1.75 1.61 1.35 1.16 1.01 11?. 5 ?b.9 4.?1 3.66 3.21 ?.54 2.07 1.73 1.60 1.3 3 1.13 0.98 107. S ?J.5 4.?7 3.69 3.?? 2.5? 2.03 1 .68 1.54 1.27 1.07 0.92 10?. s ?0.4 4.31 3.70 3.21 2.49 1.99 1.63 1.4Q 1.21 1.01 0.86 97. =5 17.6 4.31 3.68 3.17 2.43 1.92 1.56 1.4? 1.14 0.94 0.79 "JP.S 15.0 4.30 3.66 3.14 2.38 1.87 1.50 1.36 1 .08 0.89 0.74 «7.5 1?.7 4.30 3.64 3.11 2.34 1.8? 1.46 1.31 1.04 0.84 0.69 8?. 5 10.7 4.?9 3.6] 3.08 2.29 1.77 1.40 l.?6 0.98 0.79 0.64 77. S tt.y 4.?7 3.57 3.03 ?.?3 1.70 1.33 1.19 0.9? 0.7? 0.58 7?.S 7.3 4.?4 3.5 3 2.98 2.17 1.63 1.26 1.12 0.85 0.66 0,53 67.5 5.9 4.2! 3.49 2.91 ?.09 1.55 1.19 1.05 0.78 0.60 0.47 6?. 5 4.7 4.19 3.45 2.86 2.03 1.49 1.13 0.9^ 0.73 0.55 0.42 57.5 3.7 4.15 3.39 2.79 1.95 1.40 1.04 0.91 0.65 0.48 0.36 5?. 5 2.B 4.1? 3.33 2.72 1.86 1.3^ 0.96 0.83 0.58 0.42 0.31 47.5 d.\ 4.09 3.29 2.67 1.81 1.26 0.91 0.78 0.54 0.38 0.28 42.5 1.5 4.0» 3.?7 2.65 1.79 1.25 0.89 0.76 0.53 0.37 0.27 37.5 1.0 i. .08 3.?7 2.65 1.78 1.24 0.89 0.76 0.5? 0.37 0.27 3?. 5 0.7 4.0A 3.?7 2.65 1.78 1.24 0.89 0.76 0.5? 0.37 0.27 FMTI3F FI5HFSY MINIMUM 5I7F MULTIPLIfo OF FFF09T CM KG 0.? 0.4 0.6 1.0 1.4 1.8 7.0 2.5 3.0 3.5 1??.5 34.6 7.7(1 6.68 5.86 4.65 3.82 3.22 2.98 2.51 2.17 1.91 117.5 30.6 7.97 6.90 6.04 4.78 3.91 3.29 3.05 2.57 ?.21 1.94 11?. 5 ?b.9 8.25 7.1? 6.7? 4.90 4.00 3.36 3.11 2.61 ?.?'^ 1.97 107.5 ?3.5 8.53 7.34 6.40 5.0? 4.08 3.42 3.16 2.65 2.27 1.99 10?. 5 ?0.4 8.75 7.51 6.53 5.10 4. 14 3.46 3.19 2.67 2.28 2.00 97.5 17.6 8.9? 7.64 6.62 5.16 4.17 3.48 3.?0 2.67 2.28 1.99 9?. 5 15.0 9.04 7.73 6.69 5.19 4.19 3.48 3.21 2.67 2.27 1.96 fi7.5 1?.7 9.14 7.80 6.74 5.21 4.19 3.48 3.20 2.65 2.26 1.96 a?. 5 10.7 9.24 7.86 6.78 5.2? 4.18 3.46 3.18 2.62 2.?2 1.92 77.5 e,9 9.34 7.9? 6.81 5.2? 4.16 3.42 3.14 2.58 2.18 1.88 7?. 5 7.3 9.4? 7.96 6.82 5.19 4.1? 3.38 3.09 2.52 2.1? 1.82 67.5 5.9 9.49 7.99 6.8? 5.15 4.06 3.30 3.01 2.44 2.04 1.74 6?. 5 4.7 9.54 7.99 6.80 5.10 4.00 3.?3 2.94 2.37 1.97 1.66 57.5 3.7 9.58 7.98 6.75 5.01 3.88 3.11 2.81 2.25 1.84 1.55 5?. 5 2.R 9.60 7.95 6.68 4.90 3.75 2.98 2.68 2.11 1.71 1.42 47.5 2.1 9.61 7.91 6.61 4. 81 3.65 2.87 2.58 2.01 1.67 1.33 4?. 5 1.5 9.60 7.90 6.59 4.78 3.6? 2.84 2.54 1.98 1.59 1.31 37.5 1.0 9.60 7.89 6.59 '♦.77 3.61 2.83 2.53 1.97 1.5P 1 .30 3?. 5 0.7 9.60 7.89 6.59 4.77 3.61 2.83 2.53 1.97 1.58 1.30 the examination of hard parts, are extremely difficult and not easily interpreted for tropical species such as the yellowfin tuna. The marked increase in estimates of size-speci- fic F beyond 130 cm for the purse seine gears is a possible result of underestimating ages of older yellowfin. To examine this possibility, the growth curve of LeGuen and Sakagawa (1973) was modified. It was hypothetically assumed that the percentage of underestimation of the time interval within a size interval increased linearly from 0% at 135 cm to 100% at 180 cm. The resulting growth curve is compared to the original in Figure 14. Values of size-specific F were then estimated as before with initial values of 0.2 and 0.8. The value of 0.2 gave the most reasonable results for reasons similar to those given before. Values of size specific F for each gear are shown in o LE GUEN a SAKAOAWA • HYPOTHETICAL 5 6 AGE (YEARS) Figure 14. — Growth curves of Atlantic yellowfin tuna. Upper curve is from LeGuen and Sakagawa (1973). Lower curve is a modification of the upper curve (see text). 53 FISHERY BULLETIN, VOL. 72. NO. 1 Table 6. — Estimates of average weight of catch (kg) when M = 0.8, initial F = 0.2, and growth curve of LeGuen and Sakagawa (1973) is used. MINI"UM <;I7F C" <& RAIT ROATS MULTTPLIFTR OF F^FOPT 0.6 1.0 I.'. 1.8 ?.n ?.5 1.0 3.5 133. S 3'*. 6 ^8,87 47.71 46.73 45.1ft 44.0 3 43.14 42.78 42.01 41.41 40,91 117. S 30.6 45.55 44.i.7 43.56 4?. 12 41.06 40.24 39.90 39.19 38.61 38.14 11?. S ?6.)itel- lina has been universally regarded as monotypic since Giesbrecht's (1892) monumental review of planktonic marine copepods. Mori (1937) presented evidence of polytypy in Pontellina ' Scripps Institution of Oceanography, University of California at San Diego, P.O. Box 1529, La Jolla, CA 92037. Manuscript accepted July 1973. FISHERY BULLETIN: VOL. 72, NO. 1, 1974. with his description of a unique male distin- guished by an unusual chela. Apparently in- fluenced by Sewell's views on copepod ontogeny (1929, 1932), Mori ascribed the specimen taken off Japan to pliunata, suggesting that it represented the fully mature state and that previous descriptions of the plumata male were based on incompletely mature specimens. Our study was prompted by the appearance of other seemingly minor morphological features dis- tinguishing adult individuals of both sexes that correlated with indications of distinctive geo- graphical distributions among the observed forms. In this paper we redefine the genus and describe its four species. The distribution of each species is considered in the context of our geographical records. Distribution is also dis- cussed with respect to morphological similarities among the species and relationships to general oceanic circulation. Detailed considerations and views regarding environmental conditions that shape these distributions and the circum- stances yielding the contemporary Pontellina speciation pattern will be presented separately elsewhere. 63 FISHERY BULLETIN: VOL. 72. NO. 1 MATERIALS AND METHODS Materials Plankton samples examined for the genus Pnntdlitta in the course of this study were ob- tained from three major sources: the zooplankton collections of Scripps Institution of Oceanog- raphy. R. Scheltema's collection of Atlantic zooplankton maintained at the Woods Hole Oceanographic Institution, and quantitative sortings of Pontelliiia from the International Indian Ocean Expedition plankton collections, processed and furnished by the Indian Ocean Biological Centre, Cochin, India. Additional collections or specimens were obtained with the kind cooperation of the National Marine Fisheries Service; the U.S. Naval Oceanographic Office; T. K. S. Bjornberg, University of Sao Paulo, Brazil; A. DeDecker, Division of Sea Fisheries, Cape Town, Republic of South Africa; B. Kimor, Israel Oceanographic and Limnological Research Ltd., Haifa, Israel; J. E. H. Legare, Instituto Oceanografico, Cu- mana, Venezuela; D. J. Tranter, CSIRO, Cron- ulla, Australia. Geographical distribution of the samples is shown in Figure la, and the localities yielding Pontellina are listed by species in Table 1. These collections broadly outline most major sectors of the Pacific, Indian, and Atlantic Oceans, the South Atlantic being the notable omission. Most of the samples were taken with open con- ical plankton nets V2 to 1 m in diameter at the mouth. Nets were towed obliquely, vertically, or horizontally between the surface and 200 m of depth. Stations were occupied irrespective of time of day or cloud cover. Sample Analysis Plankton samples were examined in rect- angular plastic trays (5 X 7.5 X 1 cm) at 16 X magnification with the aid of a stereomicro- scope. The entire sample was scanned if the settling volume did not exceed 20 cc. Otherwise volumetric subsamples were drawn, generally with the aid of a 10-cc piston pipette, after stan- dardizing the total volume and stirring vigorous- ly. Usually more than 2% of the total sample was examined, the actual percentage varying inversely with the size of the original sample. Estimates of abundance and frequency of occurrence were obtained from particular sets of quantitative samples (Figure lb) selected for homogeneity of sampling. In the case of Pacific zooplankton samples collecting proce- dures followed standard CalCOFI (California Cooperative Oceanic Fisheries Investigations) sampling practices (cf. Smith, 1971). The Indian Ocean samples (Figure lb) are a composite of quantitative Indian Ocean Standard Net tows (Currie, 1963) obtained by various participants in the International Indian Ocean Expedition. Preliminary quantitative processing of these samples was carried out by the Indian Ocean Biological Centre, Cochin, India (Tranter, 1969). The Centre provided us with specimens of PontelUua sorted from known fractions of the original samples. Standard quantitative sampling from the Atlantic Ocean was unavail- able to us. Specimen Analysis For routine examinations specimens were mounted loosely in a drop of glycerol. To en- hance examination of fine denticles and spines, soft tissue was removed by warming specimens in a 10% aqueous solution of KOH at about 90 °C for 1 to 2 h. After a brief rinse in distilled water the cuticle was transferred to 35% ethanol, then to 70% ethanol for 1 min and then stained in a solution of 1% Chlorazol Black E dissolved in 70% ethanol. Intensive staining usually re- quires not more than V2 min and should be fol- lowed immediately by a 1-min rinse in distilled water. Examinations and dissections were carried out under stereomicroscopes at 12 X to 100 X magnification and under compound micro- scopes at various magnifications up to 600 X . All drawings were made with the aid of a compound microscope equipped with a drawing attachment. Several females and males of each species were studied under a scanning electron micro- scope after preparation by the critical point drying method (Cohen, Marlow, and Garner, 1968). Measurements For each species intact specimens with a reasonably straight urosome were chosen at random from localities scattered over the entire 64 FLEMINGER and HULSEMANN: FOUR SIBLING SPECIES OF PONTELLINA Figure la. — Geographical distribution of sampling stations. Each open circle represents one or more samples. Over- lapping stations and replicate sampling are omitted for the purpose of clarity. Areas intensively surveyed are shown symbolically as evenly spaced grid. 40° N 20° N 0° 20° S — '40°S 92° W Figure lb. — Distribution and identification of sets of quantitative zooplankton samples used to estimate the frequency of Poniellina in the Pacific Ocean. Sets were selected for similarity of sampling; i.e., each set obtained by the same procedures and stations occupied in a closely ordered sequence during the same cruise. Dots indicate the sampling localities. Indian Ocean localities represent Indian Ocean Standard Net samples collected during the International Indian Ocean Expedition that were examined quantitatively for Pontellina in the course of this study. See Table 14 for summary of sampling data and Materials and Methods for analytical details. 65 FISHERY BULLETIN: VOL. 72, NO. 1 Table 1. — Localities yielding Pontellina listed by species. Location and station Source of collecting data' Location and station Source of collecting data' PONTELLINA PLATYCHELA Atlantic Ocean: RV Alaska 4: Amazon Exp.: RV AtUintis 11-20: -31: Circe II Exp.: RV David Starr Jordan 57: -32: B 12 14 15 16, 24, 25, 26, F 31, 34, 35, 38, 39, 42, 49, 41, 43, 47, 48, 49, 50, 54, 85, 86, 88, 89, 90, 94A, 98, Cato 6 Exp.: RV Chain 35: RV Chain 60: La Creuse Exp.: Lusiod VII Exp. RV Oregon: RV Thomas Washington: 10°29'N 64°12'W 29, 46. 17, 19. 2, 6, 9, 10, 27, 28, 29, 50, 56, 60. 25, 38, 40, 55, 56, 57. 60, 61, 84, 108, 110, 112. 34 (26° 1 rS 38°46'W), 46 (34°37'S 47°58'W). 19,29,33,39,43. 13, 16. 4, 5, 7, 10. 69H-4, 73 H-5, 79(00°56'N 11°29'W), 80 H-12, 81 H-13. 1289(17°10'N 74°20'W), 1291 {17°50'N 72°00'W), 1292 (18°08'N 74°35'W), 1293 (19°55'N 74°10'W), 1294 (19°45'N 74°45'W). Cumand, Venezuela). PONTELLINA PLUM ATA Atlantic Ocean RV Alaska 1 2 4 5 Amazon Exp RV Atlantis IIU ■20 -31 -32: Bjornberg: Cato 6 Exp. RV Chain 49: 60: Cyprus: RV Delaware: la Creuse Exp.: Lusiad VI I Exp. N-3 Cruise: RV Oregon: RV Theodore N. Gill 2: 5: 7: 8: Pacific Ocean: Aries I Exp.: Bonacca Exp.: CaiCOFI Cruise 5804: 5810; 5901: Capricorn Exp.: Circe I Exp.: 29. 46, 56. 10, 29, 40, 42, 46. 42. 19, 20. 9, 35, 44, 48. 2, 22. 2, 5, 6, 7, 8, 9, 11, 13, 15, 17, 18, 21, 23, 24, 25, 26, 28, 29, 38, 44, 57. 61, 62, 63, 64, 66, 67, 68, 72, 73, 74, 87, 118D, 119. M 242 (11°24'S 33°19'W). 33 (25°16'S 49°01'W), 34 (36°11'S 38°46'W), 36 (30°06'S 39°2rW), 39 {30°26'S 35°20'W), 40 {30°56'S 3r21'W), 41 (32°28'S 28°17'V\/), 48 (30°10'S 39°23'W), 49 (25°50'S 39°24'W), 50 (24°33'S 41°02'W). 3, 5, 8, 9, 10, 11, 14, 15, 16, 17, 19, 20, 21, 22, 23, 26, 27. 17. 10-20 (off coast of Israel). 7, 19, 20, 25. 3, 4, 5, 7, 10. 21 (30°23'S 02°47'W), 24 (30°09'S 04°42'W), 52 (19°13'S 13°44'W). 4 (30°55'N 79°21'W). 1291 (17°50'N 72°00'W), 1292 (18°08'N 74°35'W), 1294(19°45'N 74°45'W). 41. 3, 4. 4, 5. 5, 9. 30(09°20'S 127°05'W). 22. A 80.110, 60.110, 100.80. E 100.70, 120.90. 100.70. 1,2,3,28,29,30,31,32,33,35. A 3, 4. B 9, 11, 12, 13, 14. 025(10°30'N 119°43.5'W), 076 (03°20'N 119°42'W), 116(7°30'N 119°43.5'W), 123(07°00'N 120°40'W), 130(09°3rN 120°39'W), 132 (09°45'N 120°12'W). 60: 071 (02°00'N 117°17'W), 122 (04°00'N 116°41'W), 134 (07°05'N 116°58'W). EASTROPAC Exp.: RV Argo 1 1 : 197, 215, 234, 242, 250, 266, 282, 287, 291, 299, 303, 308, 320, 328. D RV David Starr F Jordan 12: 053, 059, 063. D RV Rockawav 13: 056. D B EQUAPAC Exp.: A RV Horizon: 19, 20, 21, 22, 23, 24, 25, 26, 27, 29, 30, 31, 32, 34, 35, 36, 37, 38, 39, 40, 41. A RV Stranger: 3, 5, 11, 15, 17, 19, 21, 23. A Monsoon Exp.: 1,2, 3, 4, 5, 7, 35, 37, 38, 39, 40. A Muddouber Exp.: TDS-86. B Naga Exp. SI lA: 160, 164, 169, 169A. B B SUB: 5, 10, 16, 17, 20, 24, 27, 29, 31, 36, 38, 41, 50, 58, 62, 66, 78, 86. NAVOCEANO RV H itnt 1968: 12, 14. B 1969 (Apr.): 8, 31-6. 1969 (May): 9. H 1969 (Oct.): 3. 1969 (A-14): 6, 16. NAVOCEANO RV Silas Bcni: 1-10, 1-11, 1-12, 1-16, 1-20. B B Piquero IV Exp.: 12, 16, 17. B F V Exp.: 40D, 43D, 44, 45D, 46, 47N, 47D, 48, 49, 50D. Scon IV Exp.: 1, 2, 35D, 6. B V Exp.: 5. Scorpio 1 1 Exp.: 92, 96, 98, 112, 114, 118, 120, 122, 138, 140, 144, 146, 148, 152, 154, 160, 164, 166, 168, 170, 172, 174, 176, 180, 182. B Shellback Exp.: 47, 51, 103. A TO-58-1 Cruise (Scot): 27, 29, 37, 56B. B TO-60-2 Cruise (Step 1): 62. B RV Townsend Cromwell 51: 064 (03°30'S 120°45'W), 085 (02°29'N 120°49'W). TRANSPAC Exp.: 85A, 87A, 87B, 89A, 92A, 92B, 94A, 96A, 98A, 98B, lOOA, 102A, 106A, 108A, llOA, 112A, 1 18A, 118B, 122A, 126A, 126B, 132A, 134A, 142A, 143A. 24, 24A, 25, 25A, 27, 27A, 28, 28A, 31A, 32, 32A, 33, 35. Troll Exp.: 29, 30A, 31 32°15'N 117°16'W (15-VIII-1962). Indian Ocean: Circe II Exp.: Camera 3. Ill Exp.: 22, 25, 27, 28, 29, 38. RV Diamantina: 3/93/63 (27°30'S 110°00'E). Dodo VI Exp.: 13, 65, 70, 74, 81. RV Gascovne: Gl/5/63 (27°30'S 1 10°00'E), G 1/32/63 (28°55'S 110°00'E). International Indian Ocean Exp. RV Anton Brimn A: 6, 8, 9A, 11. 1: 30, 33, 51, 53, 57, 58, 60, 67, 70, 78. 2: 106, 108, 110, 111, 112, 116, 117, 118, 120, 121, 127, 134, 135, 137, 141, 142, 143. 3: 149. 66 FLEMINGER and HULSEMANN: FOUR SIBLING SPECIES OF PONTELLINA Table 1. — Continued Location Source of Location Sc urce of and collecting and CO Meet ng station data station data 1 4A: 189. NAVOCEANO RV H lint 5: 283, 284, 295, 302, 312, 315, 318, 320, 322, 324, 326A, 327B. 1968 1969 (May): 14. 9. B 6: 328, 333. 1969 (Oct.): 2, 3. 7: 370, 371. 1969 (A. 14): 7, 9. 8: 404, 413, 415. NAVOCEANO RV RV Argo Silas Bent: Ml, 1-12, 116, 1-17, 1-18, 1-20. B (Lusiad Exp.): 3, 8, 9, 10, 12, 15, 17, 18, 20, 34, 40, C Piquero V Exp.: 40D, 45D, 48. B 41, 44, 45, 46, 49, 55, 61, 65, 71,81, Scan IV Exp.: 1,2, 3, 35D, HF 18, DSDP 17, 48D. B 86, 96. V Exp.: 4,5. RV Diamuniina Scorpio 1 1 Exp.: 156, B 2 0962): 61, 100. C Shellback Exp.: 100, 105. A ) (1963): 4, 47. TO-58-1 Cruise 3(1963): 113. (Scot): 14. B 2 ( 1 964) : lOOA. TRANSPAC Exp.: 87B, 92A, 96A, 98B. A 5 ( 1 964) : 212. Troll Exp.: 24A, 25, 25A, 26, 27A, 28, 30, 30A, A 1 (1965): 60. 31A, 32, 32A. RV Dncovery 1: 5031, 5038. c Indion Ocean: RV Discovery 3: 5267A, 5269A, 5275, 5371A, 5387, Circe III Exp.: 22, 23, 25, 26, 27, 29. B 5400B, 5412A, 5437A, 5548. Dodo VI Exp.: 12, 70, 81, Mombasa Harbor. A RV Kagoshimu Mam International Indian Ocean Exp. 3: 7, 15, 16, 24, 30. c RV Anton BriiHU RV Kistnu 13: 296, 301. c A: 6, 7, lOA, 11. C RV Kayo Mani 1: 25, 28, 29, 30, 32, 33, 34, 35, 36, 43 14: 19. c 51, 52, 53, 55, 56, 57, 58, 68, 69, 70 16: 20. 71, 72, 73, 75, 76, 79. RV Meieur: 90, 93B, 95B, 114, 1 16A, 116B, 126A, 130A, 137, 138, 144, 151, 157, 168, 173, 181. c 2: 4A: 106, 108, 109, 110, 111, 112, 113, 120, 121, 123, 142. 189, 198. 114, RV Oshoro Marii 5: 283, 284, 323, 287A, 323A, 327B, 327C. 1: 3, 17, 44, 45, 50. c 6: 328, 333, 336 7: 7, 8. 7: 358, 367, 371. 11: 3, 10, 19, 23. 8: 413, 414. RV Vmitaka Mam RV Argo 23: 1-7. c (Lusiad Exp.): 3, 12, 41, 46, 49, 55, 65, 71, 81, 85. C 24: 6303. RV Diamautina RV Vciruna 30: 1775. c 2 ( 1 962) : 61. RV Vitiaz 35: 5198A, 5198B, 5200, 5205, 5207, 5208, 5217, 5221, 5224, 5278. c 1 (1963): RV Discovery 47. C 36: 5336. 1: 5031,5038. C Lusiad 1 Exp.: 2, 4. A 3: 5267, 5269A,5385,5412A. II Exp.: 5, 8, 9, 10, 11, 12, 13, 15, 19, 20, 29, RV Kistna: 296, 298, 301, 304, 514, 515. C 39, 45, 51, 61, 62, 66, 76, 88, 96. RV Meteor: 90, 91, 93A, 93B, 95B, 96, 106, 114, c V Exp.: VI Exp. Monsoon Exp.: Pacific Ocean: Aries I Exp.: CalCOFI Cruise 5810: Capricorn Exp.: Circe 1 1 Exp.: 40, 42, 43, 45, 46, 47, 50, 59, 60, 64, 68, 73, 76, 78, 84, 92, 96, 100, 104. 1, 8. 7, 10, 11, 12, 18, 19. PONTELLINA MORII 30 (09°20'S 127°05'W). 153.70. 2, 4,5, 35. 9, 11, 12, 14. E A B RV David Starr Jordan 57: 60: 116 (07^30'N 119°43.3'W), 123 (07°00'N 120°40'W). 122 (04°00'N 116°4rW), 134(07°05'N 116°58'W). 197, 211, 234, 320, 328. RV Natal 6. RV Oshoro Man, 11: RV Pioneer 442: RV Uniitaka Maru 23 RV Varitna 30: 104: 106: RV Vitiaz 35: Lusiad I Exp.: II Exp.: V Exp.: VI Exp.: Monsoon Exp.: 116A, 130A, 137, 138, 145, 151, 154, 157, 161B, 168, 186, 198. 163, 174. C 3, 13, 19. C 1,35. C 1-7. C 1775. C 2007, 2009. 2041. 5224. C 2. A 1, 10, 11, 13, 14, 16, 27, 55, 62, 66, 90. 43, 45, 58, 60, 66, 68, 76, 78. 1, 8. 7, 11, 14. A EASTROPAC Exp. RV Argo II: RV Rockawav 13: 071, 095, 099, 103. EQUAPAC Exp.: RV Horizon: 20, 21, 25, 30, 31, 32, 35. RV Stranger: 11, 17, 19. RV Islander VI (CSIRO): 2/50/70 (15°47'S 137°28'E), 1/9/71 (12°24'S 138°11'E). La Pared Exp.: 17F. Monsoon Exp.: 1, 3, 6, Noga Exp. SUA: 83, 127A, 164, 169, 169A. SUB: 5, 10, 16, 17, 20, 24, 27, 31, 36, 41, 46, 66, 78, 86. B A B Pacific Ocean: Bonacco Exp.: CalCOFI Cruise 5801: 5804: 5807: 5901: 6108: Capricorn Exp.: PONTELLINA SOBRINA 27, 31, 32, 33, 34, 35, 36, 37, 39, 41, 42, 43, .44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58. 153.50. Gulf of Panama. Gulf of Panama. 157.10. BPT 14. 2, 4, 6, 35. 67 Table 1. — Continued FISHERY BULLETIN: VOL. 72. NO. 1 Lcxation ond station Source of collecting data' Location and station Source of collecting data' Circe II Exp.: 9, 11, 12, 14. R'^ Davtcl Siarr Jordan B 57: 60: 65: Dragon Exp.: EASTROPAC Exp.: RV Argo 11: RV David Slarr 002 {13°42'N 120°I3'W), 012 (13°16'N 119°23'W), 025 (10°30'N 119°43.5'W), 064 (04°00'N 120°43'W), 076 (03°20'N 119°42'W), 108 (06°32'N 119°50'W), 132 (09°45'N 120°12'W). 056 (03°22'S 119°30'W), 067 (01°36'N 117°22'W), 071 (02°00'N 117°17'W), 122 (04°00'N 116°41'W), 132 (06°34"N 116°22.3'W), 134(07°05'N 116°58'W), 148 (09°27.7'N 117°49'W), 156 (10°36'N n7°17'W). 170 (00°28'N 96°58'W). N-1. 234, 291, 299. Jordan 12: RV Roikawav 13 El Golfo II Exp.: Harpoon Exp.: La Creuse Exp.: Muddauber Exp.: Piquero V Exp.: Shellback Exp.: RV Townsend Cr 51: TO-58-1 Cruise (Scot): TO-58-2 Cruise: 033, 037, 041, 059, 063, 077, 100. 048, 056, 060, 064, 071, 075, 083. XVIII Bl-Dl, B2-D1, A6-D1, Bl-Nl. B 13 (16°00'N 95°12'W). 15, 16, 17, 18, 21, OT-1, OT-6, OT-12 B OT-14. 125-4, 126-1, TDS-86. B 40D, 43D, 44. B 47, 51, 63, 67, 185. A oniWL'll 051 (03°15'S 118°23'W), 061 (02°30'S 119°47'W), 064 (03°30'S 120°45'W), 076 (02°28'S 121°42'W), 079 (02°42'N 121°49'W). 16, 17, 27, 29, 31, 32, 33, 35, 36, 37, B 38, 42, 45, 46, 48, 56. 9, 16. B ' A Snyder and Fleminger, 1965 B Snyder and Fleminger, 1972 C Anonymous, 1969 D Love, 1972 E Fleminger, 1967a F Scheltemo, 1971 (only chart) G Anderson, Gehringer, and Cohen, 1956; Anderson and Gehringer, H Collier, Drummond and Austin, 1958 area of its geographical distribution. Total length (TL), prosome, i.e., cephalosome and thorax combined (P), and urosome (U) were measured with an ocular micrometer at 50 X magnification under a stereoscopic microscope; smaller structures were measured under a com- pound microscope at 100 X to 400 X magnifica- tion. The morphological terms and abbreviations in general follow those of Fleminger (1967b). Measurements, drawings, and descriptions refer to the right side or to appendages from the right side unless stated otherwise. TL and the length of U were measured (Figure 2a) to the distal end of the right furcal ramus, without allowance for any telescoping of segments. The length and width of the furcal rami were mea- sured in dorsal view. In the adult female, the right ramus is fused to the anal segment; the length was obtained from the distance between the medial notch indicating the place of fusion with the anal segment and the insertion of the second innermost furcal seta (Figure 2d). The length of the left furcal ramus was also measured from the medial junction with the anal seg- ment to the insertion of the second innermost furcal seta from the median. In both males and immature females the lengths of the right and left furcal rami were measured from the lateral margin at the proximal end to the insertion of the second innermost seta at the distal end 1958, 1959a, 1959b (Figure 2c). For all stages the right furcal ramus was measured across its maximum width (Figure 2c). The segments of the fifth legs (P5) of the female were measured from the anterior side (Figure 2f). The length of the exopod (Re) was taken as extending from the junction with the second basal segment (B2) to the base of the longest distal seta; the endopod (Ri) was mea- sured from the junction with B2 to the tip of the medial spine. The length of the point on the fifth thoracic segment (ThV) is taken in lateral view as the distance between its tip and its base where the point is delineated by a distinct step or turn to the posterior (Figure 2g). The length of the spermatophore sac was measured as the distance from the distal end to the outer margin of the proximal convolution taking care to position the spermatophore to avoid diminu- tion by an oblique angle of view (Figure 2b). Measurements of segments 13-17 and the suc- ceeding three free segments of the male right antennule (Al) were taken from intact specimens positioned in lateral view (Figure 2e). P5 of the male was measured from the posterior side: the length of the second free segment of the left leg extends from the junction with B2 to the distal margin near the seta (Figure 2h); the length and width of the proximal segment of the chela are, respectively, the shortest distance 68 FLEMINGER and HULSEMANN: FOUR SIBLING SPECIES OF PONTELLINA u TL c 1 4 LfL 00 RtW RtL LfL RtL RtW 19-21 f Re LfRel tRelW RtRelL Figure 2. — Measurements taken from Poniellina specimens, a. dorsal view, female; b. abdomen with spermato- phore, ThIV-V, lateral view, female; c. anal segment and furcal rami, dorsal view, male; d. urosome, dorsal view, female; e. right Al, segments 13-25 male; f. right P5, anterior view, female; g. spine on right ThIV-V, lateral view, female; h. left P5, posterior view, male; i. chela of right P5, posterior view, male. L = length; Lf = left; P = prosome length; Pt = spine; Re = exopod; Rel = first exopodal segment; Ri = endopod; Rt = right; Sp = spermatophore; TL = total length; U = urosome length; W = prosome width. 69 FISHERY BULLETIN: VOL. 72, NO. 1 between the shallow swelling in the proximal lateral corner and the distal margin, and the distance between the proximal medial corner and the tip of the large lateral prong (Figure 2i). Types and reference specimeins have been deposited with the Smithsonian Institution, U.S. National Museum, Washington, D.C. GENUS PONT ELLIN A DANA Pontella Dana, 1846 (in part), p. 184, type not designated; Dana, 1849, p. 26. type not designated. Pontellina Dana, 1853 (in part), p. 1135, type not designated; Giesbrecht, 1889, j). 29, type by monotypy, PoiitelUiia plumata (Dana); Giesbrecht, 1892, p. 73, 497; Giesbrecht and Schmeil, 1898, p. 149. Calanops Claus, 1863, p. 211, type by mono- iy^y, CahiHopsi messineyisis C\a.\x% = Pontel- lina plumata (Dana), Giesbrecht, 1889, p. 29. Pseudopo)itia Claus, 1892, p. 861, 864, type by monotypy, Psendopoutia plumata (Dana) = Pseudopontella plumata (Dana), Claus, 1893, p. 278. Pseudopo)itella Claus, 1893, p. 278, type by monotypy, Pseadopoiitilla plumata (Dana) = Pontellina plumata (Dana), Giesbrecht and Schmeil, 1898. p. 149. Not Pontellina Claus, 1892. p. 851; 1893. p. 272. Diagnosis Relatively small pontellids, less than 2 mm in TL. Prosome in dorsal view broadly oval, less than twice as long as maximum width; forehead lacking headhooks; ThIV-V corners symmetrical; rostrum proximally protuberant, bifurcate at base, and extending ventrad as slender, elongate, flexible filaments; in lateral view, filaments more than 10 times longer than wide at maximum width; ventral eye present but inconspicuous, scarcely produced, and lack- ing a distinctive lens. In Al (except sexually modified right Al of male) segments 13. 14, and 15 separate and about equal in length. A2 with Re about as long as Ril, length of Ril less than 4 times maximum width. Female lacking distinctive dorsal lenses in forehead. Furcal rami weakly asymmetrical, right ramus fused to anal segment. P5 with monomerous Re bearing 1 lateral and 3 terminal setae, in addition to one medial setiform process fused to Re and serrated along medial margin; Ri monomerous and terminating in one or two apical spines. A2 and mandible (Mnd) with elongate setae reaching beyond thorax when extended i)osteriad. Male with one j^air of dorsal lenses in fore- head. Additional Description Both sexes with cephalic groove and agree- ing in meristic features of all ai:)pendages except for those modified by sexual maturation. Non- sexually modified appendages agree with those of Pontellina plumata as shown by Giesbrecht (1892, pi. 25, fig. 1, 6, 7, 9, 12-14, 18, 20, 21, 23- 25). Segmentation, setation, and spination of nonsexually influenced appendages are virtually identical among the four species and, except for Al, closely resemble those of Pontellopsis. They are as follows: Al: 17 free segments; segments 2-5, 6-8, 24-25 fused, 9-11 partly fused. A2: 2 basal segments; Re: 3 segments with 1. 4, 3 setae, respectively; Ri: 2 segments; Le: 6, Li: 6 + 2 setae. Mnd: palpus 1 seta; Re: 5 segments with a total of 6 setae; Ri: 2 segments with 4 and 6 setae, respectively. Mxl: Lil: 14 spines; Li2: 3 spinelike setae; Li3: small, 3 setae; B2: 3 + 2 setae; Ri: 4 + 1 setae; Re: 8 setae; Le: 1-1-8 setae. Mx2: lobe 1:3 + 1 setae; lobes 2-5: 2 + 1 setae each; Ri: 6 -H 1 setae. Mxp: 5-segmented, fingered lobe on Bl with 2, 2. 3 setae. PI: trimerous Re: 1. 1. 4 Si; 1 St; 1, 1, 2 Se; trimerous Ri: 1, 2. 4 Se; 1 St; 0, 0, 1 Se. P2 and P3: trimerous Re: 1, 1, 5 Si; 1 St; 1, 1, 3 Se; bimerous Ri: 3, 5, Si; ISt; 0. 2Se. P4: trimerous Re: 1, 1, 5 Si; 1 St; 1, 1, 3 Se; bimerous Ri: 3, 4 Si; 1 St; 0, 2Se. Se of PI smooth; Se of Rel and Re2 of P2 with toothed medial margin; Se of Re3 with toothed medial and lateral margins; in Se of P3 and P4 also both margins toothed. St of Re 3 of PI to 4 with toothed lateral margin. Bl of PI to 4 with 1 Si; B2 ususally without setae. 70 FLEMINGER and HULSEMANN: FOUR SIBLING SPECIES OF PONTELLINA Right Al in male with segments 13-17 swol- len, 13-14 and 16-17 fused; length of swollen section varies considerably due to either tele- scoping of segments or expansion of articula- tions. Distal three free segments slender and consisting of segment 18 followed by a com- pound segment formed by fusion of segments 19-21, and ending in a compound segment fusing segments 22-25. Mandibular blade (Giesbrecht 1892. pi. 25, fig. 14) bearing a one-pointed apical (ventral) tooth, a two-pointed subapical tooth, two deeply cut two-pointed medial teeth, and three basal (dorsal) teeth; basal seta lacking; dorsal acces- sory bristles exceed teeth in length; patches of spinules appear on anterior side of blade. P5 segmentation in both sexes typically pontellid; B2 of male bearing a large plumose seta on posterior surface, Ri lacking. Re bi- merous; right leg with elongate Bl, cheliform Re; left leg with reduced Bl fused to precoxa, distal segment of Re armed with four short seti- form processes. Spermatophore with relatively long neck bearing one full counterclockwise turn relative to proximal end, helix occurring between sper- matophore sac and place of attachment located in a cement mass overlying genital pore of female. Elongate spermatophore neck may also be connected secondarily to right side of genital segment proximal to helix, thereby orienting sac dorsad or anterodorsad with helix and sac flanking right side of genital segment. When secondary lateral cementation absent, neck, helix, and sac hang free from ventral side of genital segment. PONTELLINA PLUMATA (DANA) (Figures 3 and 4) Pontella plumata Dana, 1849, p. 27 (type local- ity not designated); Brady (in part), 1883, p. 92, pi. 37, fig. 1-10 only." Pontella turgida Dana, 1849, p. 28 (type local- ity not designated). Pontelli)ia plumata: Dana, 1853, p. 1135; Dana, 1855, pi. 79, fig. 10; Giesbrecht, 1889, p. 29; Giesbrecht, 1892, p. 497, pi. 4, fig. 1, pi. 25, fig. 1, 4, 6, 7, 9, 12-14, 18, 20, 21, 23-26, 36, pi. 40, fig. 49-53; Mori (in part), 1937, p. 99, pi. 47, fig. 7-11 only; Grice, 1962, p. 240, pi. 34, fig. 11-15; Brodsky, 1962, p. 147, fig. 47; Park, 1968, p. 569, pi. 13, fig. 15-16. Poiitclliiia turgida: Dana, 1853, p. 1136; Dana, 1855, pi. 79, fig. 11, 12. Calaiiops mesMnensis Glaus, 1863, p. 212, pi. 2, fig. 11, pi. 36, fig. 13-16, pi. 37, fig. 10 (Messina). Pontellopsis speciosus Brady, 1915, p. 138, pi. 10, fig. 1-8 (Durban Bay). NEW SYNONY- MY. Pontellopsis aequalis Mori, 1932, p. 172, 175, pi. 4, fig. 7-13 (25°20'50"N, 124°7'30"E). not Pontella plumata: Brady (in part), 1883, p. 93, pi. 37, fig. 11 only, not Po)itelli)ia navalium Oliveira, 1947, p. 472, fig. 12; Vervoort, 1965, p. 191. Specimens seen: 1,259 adult females, 917 adult males. Standard measurements: specimens randomly selected from localities spanning the observed geographical area of distribution. Total length (TL), mm: Standard Mean error Speci- (x) Range Sx mens Female 1.69 1.44-1.94 0.0126 75 Male 1.51 1.34-1.92 0.0130 67 Prosome- ■urosome length ratio (PUR): Median Range Specimens Female 3.28:1 2.92-3.72 1 75 Male 3.07: 1 2.84-3.93 1 52 Diagnosis Female Posterior corner of ThIV-V in lateral view produced into conspicuous spiniform process of characteristic shape (Figure 3 a, b, d-g). Ventral margin of spine more or less continuous with ventral margin of ThIV-V, transition with dor- sal margin abrupt and stepped; junction of distal end of spine and thicker basal portion usually set off by weak shoulder, spine extending posteriad, sometimes tilted weakly ventrad or dorsad. In dorsal view spine more or less con- tinuous with posterior tapering of corner, shoulder or constriction sometimes present; spine usually directed posteriad and slightly laterad, sometimes straight or turned slightly mediad. 71 FISHERY BULLETIN: VOL. 72, NO. 1 0.2 mm b.g 0.2 mm a.d.e.f 0.2mm c,h C lc=J Figure 3. — Pontellma plumata s.str., adult female: a. ThIV-V, genital segment, lateral view (TRANSPAC 96A); b. habitus, lateral view, swimming legs incomplete (same station as a, different specimen); c. rostral filaments, lateral view { Atlantis //-31-2); d. range of variation observed in ThIV-V, lateral view (left to right: Lusiad VI-8; Chain 49-11; Lusiad 11-66; Cham 49-11, different specimen; Atlantis //-31-73; same station, different specimen); e. ThIV-V, urosome, dorsal view (same specimen as a); f. range of variation observed in ThIV-V, dorsal view (top to bottom: Scorpio 11-118; Chain 49-11; same station, different animal; Chain 49-20); g. habitus, dorsal view (same specimen as b); h. lateral margin of right furcal ramus of various specimens, dorsal view (left to right: Atlantis //-31-2; Troll 28A; Atlantis //-20-22; Dodo VI-65; Troll 25; Scorpio 11-182). 72 FLEMINGER and HULSEMANN: FOUR SIBLING SPECIES OF PONTELLINA Genital segment bearing anterolateral and posterolateral clusters of hairs on both sides of segment (Figure 3 a, e); anterior cluster larger, best seen in dorsal view. Posterior cluster less prominent, of similar or coarser hairs. A row of relatively long, fine hairs encircling segment near distal margin. Male In lateral view posterior corner of ThIV-V somewhat angular, apex usually bearing one minute denticle (Figure 4e-h). Chela of right P5 with proximal segment extending disto- laterad as a relatively slender digitiform pro- cess opposing apex of distal falcate segment (Figure 4i); base of distolateral digitiform process flanked by small anterior process, triangular in lateral view, and small angular posterior process bearing a sensoriiform seta (Figure 4j); in lateral view posterior basal process and digitiform process with relatively straight margins intersecting at an angle great- er than 70° (Figure 4j); in posterior view two basal processes overlapping, both extending toward center of lumen of chela; additional sensoriiform setae on proximal segment of chela: one anteromedial near articulation with distal segment; on distal segment: one proximo- medial, one mediosubapical, and three lateral. Left P5 (Figure 4i) with proximal segment of Re (Rel) short relative to other three species below. Length of right furcal ramus exceeds left Rel by 1.55-1.85 times, 46 specimens (see Figure 30). Additional Description Female Right furcal ramus fused to anal segment, varying directly with prosome length, relatively longer than that in Indian and Pacific congeners described below (Figure 25); ratio of length to width highest in genus, usually 1.5 times longer than wide (median 1.56:1, range 1.28-1.74:1, 134 specimens), showing apparent overlap only with the equatorial Atlantic congener (see Figure 27); lateral margin of right furcal ramus with small pointed projection somewhat vari- able in shape and size just anterior to base of outermost seta (Figure 3e, h). Glandlike tissue within right furcal ramus with associated duct- like structure extending toward lateral point. Left furcal ramus not fused and appreciably longer than right ramus (see Figure 19). P5 (Figui-e 4a, c, d) with inner margin of Re lacking hair. Ri polymorphic with one or two apical spines fused to segment, spines on left and right Ri may differ in number in same specimen (Figure 4b, Table 7); Re 2 to 3 times longer than Ri, median 2.37:1, range 1.97- 3.08:1, 59 specimens, differing strongly from Indian and Pacific congeners (see Figure 29). Attached spermatophore observed on four specimens (see Figure 33 a, b; Table 5), hanging free from single place of attachment in vicinity of genital pore, neck with small helical turn near place of attachment and larger helical turn at origin of sac. Male Right furcal ramus not fused to anal segment, about equal in length to left ramus (see Figure 19), varying directly with prosome length (see Figure 26); ratio of length to width relatively high (median 2.30:1, range 2.0-2.53:1, 44 speci- mens), but showing more overlap with congeners than found among females (see Figure 28). Types Unknown, presumed to be lost. Reference specimens from the Atlantic, Pacific, and Indian Oceans have been deposited in the U.S. National Museum, Smithsonian Institution. Reference Specimens 4d. 49, Atlantis //-31-5, lat. 39°13.0'N, long. 63°26.5'W, 14 Jan. 1967, ¥4-m net, oblique tow, maximum cable out 200 m. 2c5, 29, Capricorn 31, lat. 06°31'N, long. 124° 41'W, 13 Feb. 1953, 1-m net, oblique tow, maximum cable out 200 m. 2(5,2 9, TRANSPAC 134A, lat. 23°26.3'N, long. 161°49.6'W, 17 Nov. 1953, 1-m net, oblique tow between surface and 129 m est. 2 d, 4 9, Lusiad V-76, lat. 02°01'S, long. 91°58'E, 24 Apr. 1963, 1-m net, oblique tow, maximum cable out 280 m. 2d Lusiad V-104, lat. 03°01'S, long. 52°58'E, 10 May 1963, 1-m net. oblique tow, maximum cable out 280 m. 73 FISHERY BULLETIN: VOL. 72, NO. 1 0.2 mm I 1 e,h 0.2 mm I 1 0.2 mm a,b,i,j,k 0.1 mm cd Figure 4. — Poniellina pluinuta, s.str. Adult female: a. P5 anterior view (TRANSPAC 96A); b. P5 Ri of other specimens, right side above, left side below (left to right: Scorpio 11-146; Lusiad 11-66; La Creuse 3; same station, different specimen; Atlantis //-31-6; Lusiad V-45); c. enlargement of P5 apex; d. enlargement of P5 Re distal process (TRANSPAC 96A). Adult male: e. habitus, lateral view (Atlantis //-31-28); f. ThIV-V, part of urosome, P5. lateral view (TRANSPAC 92B); g. variation observed in ThIV-V, lateral view (left to right: Dodo VI-70; Gill 8-9; La Creuse 7; Gascoync G 1/5/63; Circe NT-38; Monsoon 18). h. habitus, dorsal view (same as e); i. P5, posterior view (same as f); j. P5 chela, lateral view (same as f); k. mandible, gnathobase, lateral view. 74 FLEMINGER and HULSEMANN: FOUR SIBLING SPECIES OF PONTELLINA Remarks on Synonymy and Variability Dana (1849, 1853, 1855) described the male and female of P. plumata as separate species based on specimens obtained from several equatorial localities (in the Atlantic Ocean: lat. 08°30'N to 00°, long. 23° to 18°W; 00°15'N, 31°00'W; 01°00' to 04°30'S, 17°30' to 21°30'W; 04°30'S, 25°00'W). Our efforts to use his descriptions and illustrations to sepa- rate the two species in our Atlantic collections were fruitless. Moreover, Dana's specimens of Pontellina are apparently lost (T. E. Bowman, in litt.). The present concept of P. plumata originates from Giesbrecht's (1892) redescription and synonymy which have been generally accepted. Hence we regard his description of the species as the basis for the type species of the genus. Several authors have noted morphological variation in jo/« /»afo, observations that may indi- cate that they had examined specimens of two or more of the four species we recognize in the genus. Thus, Dana (1853) reported that the furcal rami were relatively longer in males from the Cape of Good Hope region than in males from the Pacific Ocean. Giesbrecht (1892) found that the posterolateral corners of ThIV-V were longer in males from the Pacific than in those from waters off Naples. Tanaka (1964) mentions differences in the posterolateral cor- ners of ThIV-V in both sexes of plumata. Mori (1937) believed the differences he encountered in specimens of Pontelliua were a function of ontogeny. On the other hand, a number of authors have published illustrations which appear to be based solely on plu))iata specimens (e.g., Giesbrecht, 1892; Brodsky, 1962; Grice, 1962; Park, 1968). Distribution dance estimates ranged from 0.002 to 0.4 adults per m-' water strained, the median being 0.02. In the sets of samples selected for quantitative analysis (Figure lb) the species appeared in- frequently and in minimal numbers in the eastern tropical Pacific. In the remainder of the equatorial Pacific and in the Indian Ocean plumata was found in about half of the samples examined. Values of mean abundance in temporally and geographically related sets of samples usual- ly exceeded 0.02 per m-' of water strained (see Figure 35, Table 14). With regard to the Atlan- tic Ocean our impressions from the available nonquantitative collections is that the abundance of plumata is not appreciably different from that in the Indian and Pacific Oceans. The widespread co-occurrence of three sibling species (described below) imposes serious reser- vations on the use of previously published records of plumata. It would be best to consider earlier records primarily as evidence of the occurrence of the genus, a useful attribute con- sidering the virtual absence of the genus at latitudes above 40°. PONTELLINA PLATYCHELA SP.N. (Figures 6 and 7) Specimens seen: 168 adult females, 466 adult males. Standard measurements: specimens randomly selected from localities spanning the observed geographical area of distribution. Total length (TL), mm: Standard Mean error Speci- (x) Range Female Male 1.70 1.56 error 1.54-1.96 0.0173 1.41-1.74 0.0089 mens 30 57 Prosome-urosome length ratio (PUR): P. plujuata exhibits a warm-water circum- global distribution bounded in the north and south roughly by the subtropical convergence zones of each hemisphere (Figure 5). Adults were frequent in occurrence but relatively low in abundance. For example, in 131 zooplankton samples containing the species from the Indian and Pacific Oceans (Indian Ocean Standard Net and CalCOFI Standard Net zooplankton sam- ples; tows through the epipelagic layer) abun- Median Range Specimens Female 3.44:1 3.19-3.89:1 30 Male 3.22:1 2.86-3.55:1 49 Diagnosis Female Posterolateral corner of ThIV-V ending in a relatively minute dentiform process extending posteriad or weakly medioposteriad (Figure 75 FISHERY BULLETIN: VOL. 72. NO. 1 20° ■-'•--'' ■■'• 60' 100° 140° 180° 140° 100° 60° 20° 0° 20° Figure 5. — Poniellina plitniaia s.str. Geographical distribution of captures recorded during the present study. 6a-c, f-h); in dorsal view denticle not sharply set off from tapering lateral margin of ThIV-V. Genital segment (Figure 6f, g) with several isolated lateral sensory hairs and line of slender hairs along distal margin, lacking lateral clus- ters of coarse hairs. Male Posterolateral corners of ThIV-V in lateral view tending to be rounded and lacking denticle (Figure 7c, d). Chela of P5 differing markedly from that in pluniata due to strong antero- posterior expansion of both segments (Figure 7a, b); distal segment spatulate: in proximal segment base of laterodistal digitiform process greatly expanded; in posterior view posterior basal process barely differentiated but sensori- iform seta present, anterior basal process rel- atively small, and extending toward center of lumen of chela. Left P5 (Figure 7a) with proxi- mal segment of Re (Rel) somewhat longer than that in phonata, length of right furcal ramus exceeds Rel by 1.3-1.5 times, 21 specimens (see Figure 30). Etymology The name platychela is derived from the Greek words platys ( = broad) and chela ( — crab's claw) and refers to the relatively large chela of the adult male. Types Holotype: Adult male, TL 1.52 mm, PUR 3.22:1; sorted from plankton sample taken at Atlantis 77-31 stn. 48, lat. 00°56'N, long. 25°20'W, 12 Feb. 1967, %-m net, oblique tow, maximum cable out 200 m. USNM No. 141613. AUotype: Adult female, TL 1.72 mm, PUR 76 FLEMINGER and HULSEMANN: FOUR SIBLING SPECIES OF PONTELLINA 0.2mnn I 1 b.f 0.2 mm I \ a,c,d,g,h 0.2mm e, d Figure 6. — Pontellina platychela, sp.n., adult female: a. ThIV-V, genital segment, lateral view (Atlantis //-20-28); b. habitus, lateral view (Atlantis //-20-2); c. range of variation in ThIV-V, lateral view (left to right: Lusiad VII-81 H13; Atlantis //-31-40; Lusiad VII-81 H13, different specimen; Atlantis 11-20-31; same station, different specimen); d. rostrum, lateral view (same as a); e. P5, anterior view (same as a); f. habitus, dorsal view (same as b); g. ThIV-V, urosome, dorsal view (same as a); h. ThIV-V, dorsal view, another specimen (Atlantis //-20-31); i. P5 Ri of other specimens, right side above, left side below (all four specimens Lusiad VII-69 H4). 77 FISHERY BULLETIN: VOL. 72, NO. 1 0.2 mm I 1 c,d 0.2mm a,b Figure 7. — PontelUna platychela sp.n., adult male: a. P5, posterior view (Atlantis //-20-24); b. P5 chela, lateral view (same as a): c. ThIV-V and P5, lateral view (Atlantis 11-20-27); d. range of variation in ThIV-V (left to right: 3 specimens Amazon 17; La Creuse 7; Oregon 1293). 3.52:1; right furcal ramus length 0.110 mm, width 0.075 mm; from same sample as male. USNM No. 141614. Paratypes: 3c5 , 89 from same sample. USNM No. 141615. Reference specimeji.s: 56, 5 (^ , Oregon stn. 1293. lat. 19°55'N, long. 74° lO'W, 23 Apr. 1955, G III net towed between surface and 2m. USNM No. 141616. Distribution P. platychela was found only in epipelagic tows taken in equatorial latitudes of the Atlantic Ocean (Figure 8). The species appeared regular- ly in samples collected between lat. 10° S and 10° N. The more extensive sampling available to us from north of the equator indicates that few platychela extend as far as lat. 21° or 22°N and that the species disappears abruptly at high- er latitudes. We anticipate that in the vicinity of the Gulf Stream its northward occurrence may be extended somewhat by examination of additional samples, paralleling occurrences to the south in the Brazil Current. Additional Description Female Right furcal ramus somewhat shorter than in plumata (see Figure 27), typically 1.4 times 78 longer than wide (median 1.44:1, range 1.28- 1.55:1, 35 specimens), lateral process anterior to proximal seta lacking, but interior of ramus with glandlike tissue and ductiike structure leading to lateral margin as in plumata. P5 (Figure 6e) essentially as in plumata including proportional length relationship of Re and Ri, median 2.27:1, range 1.69-2.91:1, 49 specimens (see Figure 29); Ri polymorphic with one or two apical spines fused to segment, in same specimen spines on left and right Ri may differ in number as in plumata (Figure 6i, Table 7). Attached spermatophore observed in one specimen (see Figure 33c-e, Table 5); neck cemented to ventral side of genital segment in vicinity of genital pore and buried within large irregular mound of cement extending across entire length of genital segment and right ventral side of anal segment, neck extending to right anterolateral side of anal segment along with continuation of cement fixing it to anal segment, large helical counterclockwise turn following emergence of neck from cement orienting succeeding sac anterodorsad. Male Right furcal ramus as in plu mata (see Figures 19, 26), but relatively wider (see Figure 28), ratio of length to width typically 2:1 (median 2.06: 1, range 1.91-2.34: 1, 37 specimens). Our impression from the available Atlantic FLEMINGER and HULSEMANN: FOUR SIBLING SPECIES OF POSTELLINA 20° -... -i :-..- .-., 60° 10'^° 140° 180° '40° 100° 60° 20° 0° 20° Figure 8. — PontelUna platychela sp.n. Geographical distribution of captures recorded during the present study. collections is that the abundance of platychela is generally similar to the numbers of Pt>)itel- li)m in the Indian and Pacific Oceans (cf. Tables 14, 18), i.e., typically less than 0.2 adults per m^ of water strained. PONTELUNA MORII SP.N. (Figures 9 and 1 1) PontelUna plumata: Mori (in part), 1937, p. 99, pi. 48, fig. 1-12 only; Dakin and Colefax, 1940, p. 99, fig. 139. NEW SYNONYMY. Specimens seen: 433 adult females, 284 adult males. Standard measurements: specimens randomly selected from localities spanning the ob- served geographical area of distribution. Total length (TL), mm: Standard Mean error Speci- (x) Range sx mens Female 1.61 1.38-1.88 0.0145 54 Male 1.44 1.26-1.68 0.0 100 58 Prosome-urosome length ratio (PUR): Median Range Specimens Female 3.64:1 3.39-4.10:1 35 Male 3.34:1 2.87-3.73:1 50 Diagnosis Female Posterolateral corner of ThIV-V ending in a short spiniform process extending posteriad or somewhat medioposteriad; in contrast to pluma- ta junction of spine and ThIV-V corner relatively 79 FISHERY BULLETIN: VOL. 72, NO. 1 0.2 mm I 1 b.d 0.2 mm I a,c,e,f 0.2 mm g,h,i H Figure 9. — PonwIUnu luarii sp.n., adult female: a. ThIV-V and genital segment, lateral view (Lusiad V-66); b. habitus, lateral view (Circe III NT-27); c. variation in ThIV-V, lateral view (left to right: Troll 31A, 2 specimens Lusiad 11-66); d. habitus, dorsal view (Circe III NT-26); e. ThIV-V and urosome, dorsal view (same as a); f. variation in ThlV-V, dorsal view (top: Troll 31A; bottom: Lusiad 11-66); g. P5, anterior view (Lusiad V-66); h. variation observed in lateral margin of right furcal ramus, dorsal view [left to right: Scan IV-3; TO-58-1 (Scot) 14; Lusiad 11-13; Lusiad 11-10; Lusiad V-4?]; i. P3 Ri in other specimens, right side above, left side below (left: Troll 30; right: Silas Bent 1-12). 80 FLEMINGER and HULSEMANN: FOUR SIBLING SPECIES OF PONTELLINA abrupt in both dorsal and lateral views (Fig- ure 9a-f), right and left sides symmetrical (Table 2), spine small, not exceeding 0.035 mm irrespective of TL (Figure 10), spine roughly one-half as long as that in its congener from the eastern equatorial Pacific described below. Genital segment with posterolateral cluster of coarse hairs on both sides, lacking antero- lateral cluster found in pin mata although several fine hairs may occur at this site (Figure 9a, e): posterior margin of segment bordered by fine, long hairs as in plumata. Male ThIV-V typically ending posteriorly in a small spiniform process (Figure lib, c) similar to female. P5 with chela of plumata-type but both segments showing distinctive features; distal segment short, not reaching opposing disto-lateral digitiform process on proximal segment (Figure lid), apex of distal segment with prominent triangular spur on posterior side (Figure lld-f); proximal segment in lateral view with basal process posterior to digiti- form process acuminate, intersection of posterior basal process and digitiform process usually in form of a deep angular notch; in posterior view proximal segment with axis of posterior basal process extending somewhat parallel to digitiform process and not overlap- ping anterior basal process, latter angled to- ward articulation between proximal and distal segments. Left P5 with Rel longer than that in plumata (see Figure 30). Additional Description Female Right furcal ramus considerably shorter than in plumata relative to prosome (see Figui'e 25), right furcal ramus with median ratio of 1.5 1.4 - E 1,3 e o CO o q: Q. 1,2 o LJ -11,1- 10 I 9 s €9 % a c ^^ 9 e 9€ 2 » c €>9 9 9 ^ mom €) left » right sobrina A left Aright 2-A A-2 4v A i^ 9 ^ i^ t\ t. 2 .02 03 ,04 ,05 LENGTH OF Th E-I SPINE, mm .06 Figure 10. — Length of prosome (ordinate) plotted against length of ThIV-V spine (abscissa) for females of PonteUina morii and P. sobrina. length to width 1.25:1, range 1.12-1.44:1, 46 specimens; lateral edge of right ramus with small point variable in shape just anterior to base of outermost seta (Figure 9e, h), glandular tissue within ramus as in plumata. P5 with Re bearing hairs along median mar- gin (Figure 9g); Ri relatively longer than that Table 2. — Length of posterior spine on thoracic segment IV-V in adult females of Poiiicllina iiiorii and P. sobrina. Species ,v ( m m ) Range (mm) \ N P. morii left side 0.0263 0.018-0.035 0.00 to 38 right side 0.0275 0.020-0.035 0.0032 40 combined 0.0269 0.018-0.035 0.0037 78 P. sohniui left side 0.0409 0.033-0.050 0.0032 33 right side 0.0404 0.028-0.049 0.0032 32 combined 0.0407 0.028-0.050 0.0045 65 81 FISHERY BULLETIN: VOL. 72, NO. 1 0.2 mm a.b.c 0.2 mm cl,e,f,g,h 'I^CV Figure 11. — PoiUelUna morii sp.n., adult male: a. right Al, dorsal view (Lusiad 11-66); b. variation in ThIV-V spine, lateral view (left to right: Shellback 105; Troll 25; Lusiad 11-55; Troll 32A; 2 specimens Monsoon 6); c. ThIV-V, P5 and first two segments of urosome, lateral view (Lusiad V-78); d. P5, posterior view (same as a); e. P5 chela, lateral view (same as c); f. apex of distal segment of P5 enlarged (same as c); g. aberrant chela showing a weakened subapical spur on distal segment, posterior view {Anion Britnn /-58); h. aberrant chela, lateral view (same as g). in plinnata, Re being less than 1.8 times longer than Ri, median 1.45:1, range 1.22-1.76:1, 55 specimens (see Figure 29); Ri typically with two relatively equal apical spines (Figure 9g, i; Table?). Attached spermatophore observed in four specimens (see Figure 33f-h, Table 5), appear- ance and orientation similar to that in platy- chela except for less cement on ventral side of urosome, especially on anal segment. Male Right furcal ramus differing from that in plumata in having a relatively shorter length (see Figure 26), median length-to-width ratio 1.93:1, range 1.80-2.07:1, 39 specimens, but overlapping extensively with its congener from the eastern equatorial Pacific (described below). Left P5 with Rel considerably longer than that in plumata: in morii length of left P5 Rel to length of right furcal ramus ranges from 1.08 to 1.26:1, 20 specimens (see Figure 30). Etymology This patronym commemorates the late 82 FLEMINGER and HULSEMANN: FOUR SIBLING SPECIES OF PONTELLINA Takamochi Mori who first called attention to the distinctiveness of this species and for his pioneering contributions to our knowledge of Pacific Calanoida. Types Holotype: Adult male, TL 1.36 mm, PUR 3.25:1; sorted from plankton sample taken at Lusiad II stn. 66, lat. 01°54'N, long. 79°0rE, 30 Aug. 1962, 1-m net. oblique tow. maximum cable out 280 m, USNM No. 141621. Allotype: Adult female, TL 1.56 mm, PUR 3.87:1, right furcal ramus length 0.090 mm, width 0.080 mm, from same sample as male. USNM NO. 141622. Paratypes: 56, 59 from same sample. USNM No. 141623. Reference specimens: 2d, 29, Lusiad V stn. 76, lat. 02°01'S, long. 91°58'E, 24 Apr. 1963, 1-m net, oblique tow, maximum cable out 280 m. USNM No. 141625. 2d 29. Capricorn stn. 2, lat. 02°54'N, long. 168°40'E, 28 Nov. 1952, 1-m net, oblique tow, maximum cable out 200 m. USNM No. 141624. Distribution P. mcmi was found primarily at Indian and Pacific Ocean localities distributed in a zonal band lying roughly between lat. 20 °N and 20° S (Figure 12). Occurrences at higher latitudes are few and mostly in the vicinity of western boundary currents; e.g., in the Kuroshio Current region just east of Japan and east of southern Africa in the region of the Mozam- bique and Agulhas Currents. In the eastern 20° 0° 20° 20° .=....„., 60° . 100° 140° 180° 140° 100° 60° 20° 0° 20° Figure 12. — Puntellina morii sp.n. Geographical distribution of captures recorded during the present study. 83 FISHERY BULLETIN: VOL. 72, NO. 1 Pacific niorii approached the Americas in the vicinity of Baja California and also at the latitudes of the Gulf of Guayaquil. Among the 72 quantitatively analyzed sam- ples containing niorii estimates of abundance ranged from 0.003 to 0.5 individuals per m-*, the median being 0.01. In the sets of samples selected for quantitative analysis (Figure lb) mean abundance in the Indian Ocean exceeded 0.04 individuals per m'*, 5 or more times higher than that found in sets of samples from the Pacific Ocean (Figure 35, Table 14); frequency of occurrence in the Indian Ocean (~30%) was also higher than in the Pacific Ocean (^20%). PONTELLINA SOBRINA SP.N. (Figures 13 and 14) Specimens seen: 421 adult females, 364 adult males. Standard measurements: specimens randomly selected from locations spanning the observed geographical distribution. Total length (TL). mm: Standard Mean error Speci- f^j Range ■iX mens Female 1.57 1.42-1.78 0.0134 50 Male 1.41 1.18-1.64 0.0118 56 Prosome-urosome length ratio (PUR): Median Range Specimens 3.73:1 3.17-4.16:1 33 3.43:1 3.06-3.75:1 51 Diagnosis Female Most similar in appearance to morii. Spini- form process strongly demarcated from ThlV- V corner and typically symmetrical as in morii, but spine almost twice as long (Figure 10, Table 2); in dorsal view weakly curved spines extending posterolaterad (Figure 13g). Genital segment with two lateral clusters of hairs on both sides, anterior cluster consisting of fine hairs, posterior cluster consisting of coarse hairs (Figure 13 a, g); posterior margin of seg- ment with border of long fine hairs as in all preceding species. Male ThIV-V (Figure 14a. b) as in female. P5 (Figure 14c, d) most similar to that in morii with notable differences present in chela. Distal segment of chela relatively long, apex extending beyond apex of laterodistal digitiform process of proximal segment. Moreover, distal segment lacking subapical spur (Figure 14c, d); in lateral view posterior basal process and digiti- form process of i)roximal segment separated by rounded notch (Figure 14d); proximal segment in posterior view as in morii. Left P5 with Rel longer than that in plumata (see Figure 30). Additional Description Female Right furcal ramus somewhat shorter relative to its width as well as to length of prosome (see Figures 25, 27), median ratio of right furcal ramus length to width 1.12:1, range 1.02-1.31:1, 66 specimens; lateral edge of right ramus usual- ly with broad point immediately anterior to base of outermost seta (Figure 13h), glandular tissue within ramus as in plumata. P5 (Figure 13i) similar to that in morii except that ratio of lengths of exopod to endopod tends to be smaller, median 1.29:1, range 1.07-1.50:1. 52 specimens (see Figure 29); Ri typically with two relatively equal apical spines (see Table 7). Attached spermatophore observed in 27 speci- mens (see Table 5), not differing appreciably in general features from those observed in morii. Male Right furcal ramus similar to that in morii in both relative length (see Figure 26) and in proportion of length to width, median 1.88:1. range 1.71-2.07: 1, 40 specimens (see Figure 28); Rel of left P5, compared to length of right furcal ramus, relatively longer than that in morii (see Figure 30), this ratio in .'«)briiia ranging from 0.96-1.17:1,21 specimens. Etymology The name sobri)ia, Latin for cousin, was chosen to acknowledge the close morphological relation- ship to Diorii. 84 FLEMINGER and HULSEMANN: FOUR SIBLING SPECIES OF PONTELLINA 0.2nnm I 1 b,f 0.2mm I 1 a,c,cl,e,g 0.2mm h,i d h Figure 13. — Pontellimi sobrina sp.n., adult female: a. ThIV-V, urosome, lateral view (Bonacca 35); b. habitus, lateral view (same as a); c. variation in ThIV-V spine, lateral view (left to right: EASTROPAC Jordan 037; 2 specimens Bonacca 31, Shellback 51): d. variation in left ThIV-V, lateral view, specimen with two spines (Bonacca 50); e. variation in left ThIV-V, dorsal view (La Creuse OT-6); f. habitus, dorsal view (same as a): g. ThIV-V and urosome, dorsal view (same as a); h. variation in lateral margin of right furcal ramus, dorsal view (left to right: La Creuse OT-6; La Creuse 18; La Creuse OT-14; La Creuse 17; La Creuse OT-14, different specimen; 2 specimens La Creuse 18; Bonacca 33); i. P5, anterior view (same as a). 85 FISHERY BULLETIN: VOL. 72, NO. 1 0.2 mm 0.2mm a,b Figure 14. — Poniellina sobrina sp.n., adult male: a. ThIV-V, part of urosome and P5, lateral view [TO-58-1 (Scot) 33] ; b. variation observed in ThlV-V spine, lateral view (left to right: Bonacca 55; Bonacca 43; 2 specimens Bonacca 51); c. P5, posterior view (La Creuse 21); d. chela P5, lateral view (Shellback 5 1). Types Holotype: Adult male. TL 1.42 mm, PUR 3.44:1, sorted from plankton sample taken at Bonacca stn. 51, lat. 13°44'N, long. 90°51'W, 19 Aug. 1963, Vz-m net, oblique tow, maximum cable out 200 m. USNM No. 141617. Allotype: Adult female, TL 1.52 mm, PUR 3.75:1, right furcal ramus length 0.080 mm, width 0.075 mm, from same sample as male. USNM No. 141618. Paratypes: 56, 59 from same sample. USNM No. 141619. Reference specimens: 56, 59, La Creuse stn. 15, lat. 08°41.2'N, long. 79°31.2'W, 4 May 1962, GV net towed between 0 and 4 m. USNM No. 141620. Distribution P. sobrina is obviously indigenous to the eastern tropical Pacific Ocean (Figure 15). The species was found only at Pacific stations east of long. 130°W. Occurrences at latitudes higher than 20° were restricted to a few samples taken near the mouth of the Gulf of California. Thus, the apparent boundaries coincide in general with the North and South Equatorial Currents, and its westernmost limits lie in the path of the Equatorial Countercurrent. In 31 quantitative samples containing sobrina abundance varied from 0.01 to 0.66 individuals per m•■^ the median being 0.04. In the sets of samples selected for quantitative analysis (Figure lb) sobritia showed mean abundance values (ranging from 0.02 to 0.09 individuals per m^) similar to those of morii in the Indian Ocean and to plionata outside of the eastern tropical Pacific (see Figure 35, Table 18). DEVELOPMENTAL STAGES AND BREEDING Immature specimens of Pontellina were sort- ed routinely together with adults. They were neither as abundant nor as frequent as the adults, a difference that is at least partially attributable to escapement of younger stages through the relatively coarse mesh (~0.5 mm) of most of the nets used to obtain our samples. General Pontelli)ia habitus characteristics such as appearance of the prosome in dorsal view, rostrum, strong Mx2, and relatively long setae on A2 and Mnd served to distinguish the specimens. The number of swimming legs and body segments as well as total body length were used to determine their ontogenetic stage. Identification to species was reasonably certain only for stage V copepodids; details are present- ed below. Specimens of stages III and IV were tentatively assigned to species on the basis of their geographical origin. The following 86 FLEMINGER and HULSEMANN: FOUR SIBLING SPECIES OF PONTELLINA 20° 0° 20° ■?0° -.... ...;..., ,., 60° lOO" 140° 180° 140° 100° 60° 20° 0° Figure 15. — Pontellina sobrina sp.n. Geographical distribution of captures recorded during the present study. 20° notes and Table 3 summarize ontogenetic characteristics of stages II through V prevailing in the genus. Stage II TL 0.72-0.76 mm (5 specimens). Rostral fila- ments and dorsal ocelli-like structures present; prosome with 4 free segments, urosome with 2 segments. Re of PI and P2 bimerous, Ri of PI and P2 and both rami of P3 unimerous, P4 consisting of a pad with folds, short setae and an incipient Ri; P5 lacking. Stage III (Figure l6c) TL 0.82-0.88 mm (20 specimens). Neither sexes nor species distinguishable. Prosome with 5 segments, urosome with 2 segments. Re of P3 bimerous, Ri of P3 as well as both rami of P4 unimerous. P5 lobiform, bearing one apical seta. Stage IV Female (Figure l6a) TL 0.90-1.10 mm (22 specimens, probably including all four species). Urosome with 3 segments. Re of P3 and P4 bimerous, Ri uni- merous. Re of Po unimerous; right Re and elon- gate seta on mediodistal corner of Re slightly larger than those of left P5; Ri lobiform, in- completely separated from B2. Stage IV Male (Figure l6b) TL 0.95-1.10 mm (22 specimens, probably including all four species). Male resembles 87 FISHERY BULLETIN: VOL. 72, NO. I Table 3. — Ontogenetic development in copepodite stages of Pontellina. Ill IV : IV, V • Thoracic segments Free abdominal segments Rostrol filaments Dorsal ocelli Right Al PI Re segments Ri segments P2 Re segments Ri segments P3 Re segments Ri segments P4 Re segments Ri segments P5 Re segments Ri segments 4 5 5 5 5 5 2 2 3 3 4 3 present present present present present present present present present present present segments 13-16 swollen present 2 2 2 2 3 3 1 1 1 1 2 2 2 2 2 2 3 3 1 1 1 1 2 2 1 2 2 2 3 3 1 1 1 1 2 2 lobe, 1 2 2 3 3 1 seta lobe. 1 1 1 2 2 1 seta absent lobe, 1 1 2 1 1 seta right leg right leg right leg right leg slightly slightly larger with 5 larger larger than left setae. than left than left left leg with 6 setae absent absent rudimen- tary 1 absent 1 corresponding stage of female, but P5 with Ri absent or appearing as a small distal swelling on B2. Right Re also slightly larger than left. Stage V Female (Figure 17a-l) TL 1.18-1.48 mm (40 specimens, all species represented). ThIV and V almost completely separated. Urosome with 3 segments, genital segment largest and with weak ventral swelling. Furcal rami incompletely separated from anal segment. Lateral margin of right furcal ramus proximal to first seta lacking protrusion. Left and right Al symmetrical. Re of P3 and P4 trimerous, Ri bimerous. P5 with proportions of Re and Ri showing similarity to those of adult. Re unimerous with 5 setae on right leg, 6 setae on left leg; proximal Si of left side notable for its size and curved shape, an asymmetry lacking in the adult. Stage V Male (Figure 18a-q) TL 1.20-1.44 mm (40 specimens, all species represented). ThIV and V almost completely separated. Urosome with 4 segments. Furcal rami incompletely separated from anal segment. 0.2 mm a -c Figure 16. — Pontellina sp. copepodite stages: a. stage IV female, P5, anterior view; b. stage IV male, P5, posterior view; c. stage III copepodid, P5. Right Al with segments 13-16 slightly swollen, segments distal to swelling partly fused. P5 trimerous, slightly curved medially; right leg longer than left leg, Ri not developed. In other genera of Pontellidae, as well as in a number of other heterarthrandrid families (Diaptomidae, Temoridae, Centropagidae, Pseu- dodiaptomidae) we note that fusion of urosomal segments I and II in the female first appears in the stage V copepodid (Gurney, 1931; Johnson, 1935; Crisafi, 1960; Lawson and Grice, 1970; Grice, 1971). Morphological features of the geni- tal plate, antrum, and internal structures such as the seminal receptacles (Fahrenbach, 1962; Frost and Fleminger, 1968) are lacking in the stage V female. We also note that in most amphascandrid families (e.g., Calanidae, Para- 88 FLEMINGER and HULSEMANN: FOUR SIBLING SPECIES OF PONTELLINA 0.2 mm a-h 0.2mm I - d Figure 17. — Copepodite stage V, females: a-d. ThIV-V, right P5 and urosome, lateral view; e-h. anal segment,. furcal rami, dorsal view; i-1. P5, anterior view. Poniellina pliiinaia: a, e {Atlantis //-31-1); i (Lusiad V-60). P. platychela: b, f,j (Atlantis //-20-42). P. niorii: c, g, k (Dodo VI, near Mombasa Harbor). P. sobrina: d, h, I [TO-58-1 (Scot) 56] . calanidae, Pseud ocalanidae, Aetideidae, Euchaetidae. Phaennidae, Scolecithricidae) but not in Eucalanidae (Johnson, 1937; Sewell. 1929; Bjornberg, 1967; and our unpublished observations of all species) fusion of urosomal segments I and II seems to be delayed until the appearance of the sexually mature female. This pattern has been documented by a number of ontogenetic studies on individual species (With, 1915; Nicholls. 1934; Campbell, 1934; Marshall and Orr, 1955; Matthews, 1964; and our un- published observations). Notes on Individual Species PoiitelliiiJ pliiiiiata (Figures 17a, e, i; 18a, e, i, m, p) Copepodite stage V female: TL x 1.38 mm. range 1.26-1.48 mm, 10 specimens. Postero- lateral corner of ThV (Figure 17a) produced into a strong point similar to the adult. Furcal rami symmetrical (Figures 17e, 19), length of right ramus relative to width greater than that in morii (Figure 20). P5 Ri shorter than in niorii 89 FISHERY BULLETIN: VOL. 72. NO. 1 0.2 mm I 1 a-q Figure 18. — -Copepodite stage V, males: a-d. ThIV-V, right P5 and urosome, lateral view; e-h. anal segment, furcal rami, dorsal view; i-m. P5, posterior view; n-q. range of variation in ThIV-V, lateral view. Puntellinu phimata: a, e, i (Lusiad V-43): m (Monsoon 2, atypical P5 with Ri); p (left to right: Atlantis 11-31-74: Atlantis II-H-l; Atlantis //-31-28; Atlantis //-31-23; Gascoyne Gl/32/63; Troll 25A). P. platychelu: b (Atlantis //-31-60); f , j (Atlantis ll-}\- 15); n (left to right: Oregon 1289; Atlantis //-31-50; Atlantis //-20-42; Atlantis //-31-57). P. morii: c, g, k (Lusiad V-43); q (left to right: EQUAPAC Horizon 31; Lusiad V-68; Anion Britun II-5S: Anton Bniun /-60). P. sobrina: d, h, I: La Creuse 18); o [left to right: EASTROPAC Rockaway 064; TO-58-1 (Scot) 29; TO-58-1 (Scot) 38; EASTROPAC Rockaway 071; TO-58-1 (Scot) 36; EASTROPAC Rockaway 056]. [ 90 FLEMINGER and HULSEMANN: FOUR SIBLING SPECIES OF PONTELLINA platychela 30 20 S lOf 3 0 o UJ L^ 20 10 0 20 10 - — Y-,. plumata 1 1 r-r+wto??:^ - — morii - ^^^^^ c ^i 1 _ — :V^^\XN>>^ sobrina - ~^~ 1 ..u 0.15 0.10 0.05 <-)H 0 005 0.10 015 020 + ) Figure 19. — Frequency distribution of differences in length of left furcal ramus and right furcal ramus for the four species of Poniellina. Gray with heavy outline = adult females; left-diagonal hatch with light outline = adult males; right-diagonal hatch with dotted outline = stage V females. ,09 E 08 E t- Q 07 4 plumata o morii ♦ ♦♦ O O O O O ♦-S 4-2 o 3-4 4 3-4 ♦ ♦ O 0-7 O f-2 f-3 ^ o o .13 14 .15 LENGTH, mm 16 17 Figure 20. — Width of right furca (ordinate) plotted against length (abscissa) for female stage V copepodids of Pont el- Una pi II mala and P. morii. relative to length of right furcal ramus (Figure 21). Re to Ri length ratio, median 3.0:1. range 2.3-3.5:1, 19 specimens (Figure 22); left P5 with medialmost seta on Re small and gently curved (Figure 17i) relative to that in morii (Figure 17k). Copepodite stage V male: TL x 1.30 mm, range 1.20-1.44 mm, 10 specimens. Postero- lateral corner of ThV ending in a broad point (Figure 18a, p). Terminal segment of right P5 about 3.1 times longer than wide (Figure 18i), endopod rarely pre.sent (Figure 18m). Furcal rami (Figure 18e) similar in relative length and width to those of female. 07 06 I 05 in 0. 04 O I o UJ 03 O O OO O 2-0 O O O O 0-2 0-2 O O O ♦ plumata o morii ♦ ♦ 2-^ 4 ♦ 2-4 ♦♦ 2-4 ♦ ♦ ♦ 13 14 15 .16 LENGTH OF RIGHT FURCAL RAMUS, mm .17 Figure 21. — Length of P3 Ri (ordinate) plotted against length of right furcal ramus (abscissa) for female stage V copepodids of Poniellina plumaia and P. morii. go o UJ q: plumata I — T -rn n-n I \ I I I L 1.5 111 20 2.5 3.0 Re P5-H^, St.S: Females Ri Figure 22. — Frequency distribution of P5 Re:Ri ratio for female stage V copepodids of Poniellina plumaia and P. morii. 91 FISHERY BULLETIN: VOL. 72, NO. 1 Poiitc'lliiiii pUttychela (Figures 17b, f, j; 18b, f, j, n) Copepodite stage V female: Th x 1.37 mm, range 1.18-1.46 mm. 10 specimens. ThV postero- lateral corners rounded and ending in a small denticle (Figure 17b) as in adult. Furcal rami (Figure 170 and P5 (Figure 17j) resembling those of p/«»mfa. _ Copepodite stage V male: TL x 1.30 mm, range 1.24-1.36 mm, 10 specimens. Margin of posterolateral corner of ThV with weak denticle (Figure 18b, n). P5 with distinctive right leg (Figure 18j). Re considerably broader than in the other three species, about 1.6 times as long as wide. Furcal rami (Figure 18f) as in plianata. Poiitelliiui niorii (Figures 17c, g, k; 18c, g, k, q) (Notes based on specimens from localities in the Indian Ocean.) Copepodite stage V female: TL x 1.28 mm, range 1.18-1.36 mm, 10 specimens. ThV corner typically with a small spiniform point (Figure 17c) resembling that in the adult. Ri of P5 (Figure 17k) longer than in plumata (Figure 21), typically with 2 spines; Re:Ri length ratio considerably less (median 2.1:1, range 1.7- 2.6:1, 20 specimens) than in plumata (Figure 22). Furcal rami symmetrical (Figure 19), shorter than those in plumata (Figure 20), as in sexually mature stages. Medial setalike pro- cess of Re of left P5 (Figure 17k) more abruptly bent (~90°) than that of the other three species (Figure 17i). Copepodite stage V male: TL x 1.21 mm, range 1.12-1.32 mm, 10 specimens. Postero- lateral corner of ThV ending in a relatively short spiniform point (Figure 18c, q) about one- half the length of that in sobrina (Figure 18d, o) and much less robust than that in plumata (Figure 18a, p). Di.stal segment of right P5 distinctly bent mediad (Figure 18k). Furcal rami (Figure 18g) similar in relative length and width to those in female. Pontell/ua sohr/i/ii (Figures 17d, h, 1; 18d, h, 1, o) (Notes based on juvtMiilc specimens from eastern- most Pacific localities which were accompanied by large numl)ers of adults; the localities are rela- tively distant from those yielding worii.) Copepodite stage V female: TL x 1.25 mm, range 1.18-1.34 mm, 10 specimens. Differences between sexually immature sobrina and morii females are relatively weak, e.g., greater length of the ThV point (Figure 17d) and the weaker bend of the medial setalike i)rocess on the left Re of P5 (Figure 171), appear to be useful, but lack confirmation by measurements from a geographically representative series of specimens. Copepodite stage V male: TL F 1.25 mm. range 1.12-1.38 mm, 10 specimens. Postero- lateral corner of ThV produced into a relatively long slender point (Figure 18d, o). Right P5 with .straight distal segment resembling that in plumata, but all segments in P5 of sobnjui appear slightly wider. Sex Ratios In laboratory-reared populations sex ratios among adult copepods of several families have been found to vary widely (for recent comments see Heinle, 1970; Katona, 1970; Paffenhdfer, 1970). In natural populations, however, late immature copepodids have been found to pro- duce males and females in about equal numbers (Marshall. 1949). Among randomly sorted, sexually mature adults of the four species of Poutelliiia females consistently outnumbered males by roughly 1.3: 1 (Table 4). Assuming that the sexes are genetically one to one, the observed male-to-female ratios in Poutelliua could be readily accounted for if females live longer than males, a likelihood suggested by many authors for various ampha- scandrid copepod genera. In a small series of rearing experiments on Labidocera trispi)iosa, A. Barnett (pers. comm., 1972) has found that following the adult moult females live 2 to 3 wk and males about 1 wk. Table 4. — Frequency of sexually mature individuals and sex ratios in Pontcllina. 9 6 No. Species N O 0 N % 9:0 samples plane hcla M59 54 '137 46 1.16 72 pliiniiini 1,259 58 917 42 1.37 531 iiioni 433 60 284 40 1.52 240 sDhniui 421 54 364 46 1.16 113 1 One sample, i.e., Allanlis II 20-42, was omitted because it provided the extremely disproportionate capture of 327 moles and 10 females. 92 FLEMINGER and HULSEMANN: FOUR SIBLING SPECIES OF PONTELLINA REMARKS ON SEASONAL OCCURRENCE AND BREEDING Captui'e records alone do not necessarily dis- close the distribution of the optimal habitat of a planktonic species (Fleminger, 1972), i.e., the region in which reproduction is usual, typically successful, and from which the progeny is likely to become entrained in a circulation system that ultimately provides new breeding stocks with suitable conditions for their off- spring. Our sampling of PoiiteUiua is incomplete for critical assessment of the impact of seasonal change on occurrence, geographical distribu- tion, or reproduction. Moreover, as a conse- quence of the relatively large mesh sizes of the nets (see Table 15) sampling of most juvenile stages was not representative. Thus spermato- phore occurrence on females is the only source of breeding information available to us. In C«/o»».s\ spermatophores constitute evi- dence of mating within the past 48 h (Marshall and Orr, 1955). In other copepods, spermato- phores are lost or shed soon after attachment; in Labidocera trispiitosa discarding of the spermatophore has been observed to occur just prior to egg laying (G. Theilacker, pers. comm., 1970). Few spermatophores were observed in Poiitel- Uiia (Table 5) suggesting that as in Calanus they are not retained for an appreciable time after attachment. The 27 records of s(>b)i)ia females bearing a spermatophore afford a glimpse of breeding patterns in that species. Spermatophore-bearing females appeared in Febi-uary, May, and August samples. The local- ities span most of the latitudinal extent of sobrina captures on record, but all lie to the east of long. 98°W, and most are relatively close to the mid-American coast. In contrast, the few records of morii and plionata bearing spermato- phores are widespread, suggesting that both species breed over a more extensive range in accordance with their more extensive geographi- cal distributions. PHYLOGENETIC RELATIONSHIPS AMONG THE PONTELLINA SIBLINGS Dobzhansky (1972) stressed the heuristic value of sibling species when he pointed out "... sibling species permit the dissection of the process of speciation into studiable com- ponents." PoiitelUna appears especially well suited to explore the question of speciation in the planktonic biotope. Restriction to shallow tropical and subtropical oceanic waters apparent- ly limits opportunities for complex diversity in i)lanktonic calanoids (Fleminger and Hulse- mann, 1973). The four species of Po)itelli)ia satisfy the number of suitable ranges that appear to be available within these biogeographical limits. Three of these ranges reflect the geographical- ly limited and relatively shallow lenses of Tropical Surface Water (Wyrtki, 1966, 1967) described from the eastern equatorial Pacific but also known on the basis of similar general features to prevail in the equatorial Atlantic Ocean (Muromtsev, 1963) and in the equatorial Indian Ocean (Wyrtki, 1971). The fourth range consists of the series of deeper lenses of warm water beyond Tropical Surface Waters and lying between the subtropical convergences in the Atlantic, Indian, and Pacific Oceans. PonteUiiia's position as a distinctive genus is unchallenged, being strongly separated from its closest relative, P(>)tteUopsis, in both morphology and habitat. Compelling evidence favoring consideration of the four populations of P(>)iteUi)ia as separate species is furnished by the morphological distinctions of each, their independent geographical distributions, and the morphological integrity of their diagnostic features. That is, despite widespread regions of geographical overlap where two or three of the species may be captured in the same net tow, no evidence of intergradation or hybridization has been observed. Evidence of strongly regionalized habitat adaptation may be inferred from the apparent failure of each species to colonize areas occupied by its adjacent congener. Failure to colonize must be regarded as significant. All four species occur in surface layers (Wilson, 1942; Heinrich, 1961; Vinogradov and Voronina, 1964; Flemin- ger and Hulsemann, unpublished data) where air-sea interactions provide opportunity for dispersal and advection with neighboring cir- culation systems, but the distribution of each species overlaps at most only a portion of the range of its neighboring congeners. 93 FISHERY BULLETIN: VOL. 72. NO. 1 Table 5 . — Adult female specimens of Pontellina bearing a spermatophore. Total Sac Sampling length length Species date Latitude Longitude Station (mm) (mm) P. phuychela III -8-66 00°08'S 18°31'W Atlanli\ //-20-42 1.66 0.490 P. plumaui VI-15-69 33°49'N 139°10'E Scan IV-1 1.66 1.76 0.460 0.460 VI ■6-52 01°00'S 112°24'W Shellback 47 1.50 0.425 111-30-69 21°54'S 110°02'W Piquero V-49 1.56 0.365 P. n}i>iii IV-19-68 05°irN 123^58'E Circe ll-NT 11 1.58 0.420 VII-2-52 05°18'S 85°04'W Shellback 105 1.86 0.440 P. sohrina 11-12-67 00°28'N 92°02'W EASTROPAC Riickaway 060 1.68 0.390 V-12-58 07°22'N 92°47'W Scot 46 1.56 1.70 0.360 0.395 V-4-62 08°4rN 79°31'W La Creuse 15 1.40 1.44 1.46 1.42 0.340 0.385 0.370 0.355 V-7-58 09°45'N 96°04'W Scot 35 1.62 0.410 VIII-16-63 09°5rN 85°43'W Bonacca 42 1.48 1.46 0.385 0.320 V-17-62 13°07'N 91°34'W La Creuse OT-6 1.48 1.50 0.330 0.355 VIII-18-63 13°29'N 90°09'W Bonacca 50 1.50 1.62 1.52 1.48 0.320 0.360 0.340 0.340 Vlll-19-63 13°44'N 90°51'W Bonacca 51 1.50 1.52 0.390 0.340 VII 1-20-63 13°57'N 92°02'W Bonacca 58' 1.54 1.56 1.48 1.56 1.50 1.50 1.52 1.50 0.390 0.415 0.355 0.365 0.375 0.380 0.395 0.385 * One additional specimen was observed in this sample with a damaged spermatophore. Morphology and distribution also support our conclusion that the four species are phylo- genetically close and, in fact, comprise a mono- phyletic unit — or holophyletic in Ashlock's (1971) terminology — appearing to have been recently derived from a single tropical-sub- tropical epiplanktonic precursor (in prepara- tion). Our objective in this section is to examine the degree of similarity among the siblings as a basis for determining phy logenetic relationships. In the absence of a fossil record, inferences drawn from comparative morphology, geograph- ical distribution, and essential habitat adap- tation may provide a relative historical per- spective for judging phylogeny within a taxon. Phylogenetic relationships within P(>)iteUi)io were judged both intuitively and objectively on the basis of characters that showed a cohesive pattern of similarity or dissimilarity. We con- cur with the rebuttals of Throckmorton (1965, 1968) and Voris (1971) to the views of orthodox numerical taxonomy in defense of the weighting of taxonomic characters: i.e., characters differ in their taxonomic usefulness, and the adaptive significance of these differences is not beyond logic and comprehension. 94 FLEMINGER and HULSEMANN: FOUR SIBLING SPECIES OF PONTELLINA Throckmorton and Voris show empirically that characters are decidedly not equal in their content of phylogenetic information. Their operational method for character selection rests upon the direct and assumption-free advantages of a posteriori weighting of correlated sets of derived characters. Judging from the numerous articles in Systematic Zoology, numerical taxonomic phylogenies derived from large numbers of unweighted characters do not vary from phylo- genies implicitly or explicitly arranged by experienced workers employing sets of corre- lated adaptive characters. Body Dimensions and Proportions Total Length (TL) Intraspecific sexual differences in TL are greater than interspecific differences; males are about 10% shorter than females (Table 6, Figure 23). In both sexes morii and .so6?'/»fl are smaller than platychela and plumata. The diffei'ence between the mean TL of males or females of species belonging to the same pair is not signifi- cant. However, the difference between the mean TL of either species of one pair with that of either species in the other pair is highly signifi- cant in both sexes (Student's f-test). The over- all difference is produced largely by the dis- tance between the rostrum and the cephalic groove and the length of the furca (see below). Prosome-Urosome Length Ratio (PUR) In both sexes niorii and sobrina occur at the high end of the PUR distribution (Table 6. Figure 24). In males, morii and sobri)m have similar distributions at the high end of the 25% > o -z. uj 0 o UJ "^ 25% U- 75% 25% -25% 25% - 25% 25% -25% 12 14 1.6 18 TOTAL LENGTH, mm O^ N = 57 platychela % N -30 O^N = 67 plumata N = 75 ¥ (T^N = 58 morii % N = 54 O^N = 56 sobrina % N= 50 2.0 Figure 23. — Frequency distribution of total length for both sexes of the four species of Pontellina. Table 6. — Total length (TL) and prosome-urosome length ratio (PUR) of Pontellina spp. adults; data from various geographical localities combined. Species TL (mm) PUR X Range ' X N X Range 'x N 1.699 1.54-1.96 0.0173 30 3.438:1 3.19-3.89:1 0.0362 30 1.692 1.44-1.94 0.0126 75 3.282:1 2.92-3.72:1 0.0179 75 1.608 1.38-1.88 0.0145 54 3.643:1 3.39-4.10:1 0.0360 35 1.570 1.42-1.78 0.0134 50 3.732:1 3.17-4.16:1 0.0417 33 1.556 1.41-1.74 0.0089 57 3.223:1 2.86-3.55:1 0.0228 49 1.511 1.34-1.92 0.0130 67 3.066:1 2.84-3.93:1 0.0243 52 1.435 1.26-1.68 0.0100 58 3.339:1 2.87-3.73:1 0.0245 50 1.406 1.18-1.64 0.0118 56 3.426:1 3.06-3.75:1 0.0235 51 Moles: P. platychela P. plumata P. morii P. sobrina Females: P. platychela P. plumata P. morii P. sobrina 95 FISHERY BULLETIN: VOL. 72, NO. 1 range, platychela being intermediate and plnnia- ta occupj'ing the low end. Females follow the same general i)attern, but iiiorii and sob7i)ia show considerably less overlap. . Length of Furcal Rami The length of both rami is directly related to prosome length as well as TL. Shortening and fusion of the right ramus in adult females in- troduces asymmetry but the change does not alter the essential relationship to body length. Ill the female sex (Figure 25) niorii and sobrnua occupy one side of the overall distribution of length of the right ramus, platychela and plumata the other with virtually no overlap between the two pairs of species. Males show more scatter (Figure 26) and apparent differ- ences in allometry; sohrina and niorii tend to diverge with respect to furcal length while plumata and platychela tend to diverge with respect to prosome length. Examination of furcal length relative to furcal width increases separation of the three equatorial species. It also enhances separation of platychela and the Atlantic samples of plu ma- -25% ...... -25% _M i^ cr^ N = 49 platychela % N = 30 o ID o UJ CE 25% 25% 25% 25% plumata 2 N=75 cr^N=50 morii % N = 35 O^N = 5l sobrina % N = 33 2 8 I 3.0 I 32 I 3,4 1 3,6 I 3,8 I 4 0 I Prosome Urosome Figure 24. — Frequency distribution of P:U ratio for both sexes of the four species of Ponwllina. - - D 1.5 ~ ♦ ♦ - t. • ♦ 2 - A • • D ♦ - A D ♦ 3 E '4 - • •q» ♦ ^-2 E - A A • D D D ♦ D o ~ • ^^^ A 4-A A • A ♦-2 2-» 3 ♦-□ ♦ ♦ D ♦-2 o g 1.3 Ll O X H • a2 a 2-A^2A-^ •-< • ^^ • > ♦ ♦-s* 4-4 ♦ -z. y ,2 A A 2 D -^ , ; -v,^ A • A A •-2 A ^ A V2 ♦ ♦ ♦ ♦ ♦ ♦ 2-A A • ♦ L 3-^ A I.I • A ♦ ♦ plumata • morn 1 n 1- • 1 1 1 1 1 1 1 A sobrina D platychela 1 1 1 08 10 12 14 16 LENGTH OF RIGHT FURCAL RAMUS, mm Figure 25. — Length of P (ordinate) plotted against length of right furcal ramus (abscissa) for females of the four species of Ponicllina. ta as well as separation of morii and the Indo- Pacific samples of plumata (Figure 27). A generally similar pattern is seen in the males (Figure 28) except that morii and sobrina over- lap freely with respect to the furcal length: width ratio. ThIV-V Posterior Spine Strong sexual dimorphism appears in adults. Among the females, plum,ata is unique; the base of the posteriorly directed spine rises roughly at the level of the proximal margin of the genital segment, the spine is robust and broadly trian- gular in both dorsal and lateral views (Figure 3a, d-f). The spines in the three equatorial species are similar to each other in being dimin- utive and needlelike or dentiform. They differ primarily with respect to relative length of the spine (Figures 6a, c, g, h; 9a, c, e, f; 11; 13a, c, g). The ThIV-V spine in males appears in three states: plumata exhibits a minute denticle that 96 FLEMINGER and HULSEMANN: FOUR SIBLING SPECIES OF PONTELLINA l-5r 1.4 E 13 E o IS) o tr CL ♦ p/umafa • morii A sobrina □ platychela .2 o X I- UJ I.I 1.0 09 A ^ A J L 12 14 16 18 .20 LENGTH OF RIGHT FURCAL RAMUS, mm Figure 26. — Length of P (ordinate) plotted against length of right furcal ramus (abscissa) for males of the four species of Pontellina. may be borne on a weakly produced boss; morii and sobrina bear a small spine resembling that found in the female of the species; platychela has no outgrowth whatsoever. r 0 p/umata Pacific- Ind an <> plumata Atlantic 1.60 - • morn F A sobrina E UJ n 140 - u platychela -A • 8„H 0^ °*yoD. CO o q: Q- o X 120 A A A A • '. • •• \ a5 "^ ,• A 0 1- A A A 0 C»0^0*0 UJ - • 0 _i 1 10 \ • 1 1 1 1 1 1 1.00 1.20 1.40 1.60 1.80 LENGTH RinuT Fl IPr Al DAK 1 IC WIDTH ---".- .^-......o Figure 27. — Length of P (ordinate) plotted against length: width ratio of right furcal ramus (abscissa) for females of the four species of Pontellina. o CO o tr a. 1.40 120 0 plunnata Pacific - Indian 'i plumata Atlantic - • morii A sobrina ^ - a platyctiela O 1.00 ^ D D n A 2- . AAjg *" • -^ 2 •-a . D A ^^^ 0 A A 1.60 180 2.00 LENGTH 220 240 RIGHT FURCAL RAMUS 260 WIDTH Figure 28. — Length of P (ordinate) plotted against length: width ratio of right furcal ramus (abscissa) for males of the four species of Pontellina. Female Genital Segment The distribution of lateral clusters of spinules provides the basis for distinguishing the different character states. Two species, sobrina and plumata, are similar in having two clusters on each side; morii has one cluster and platychela has none. There is preliminary evidence from examination with the scanning electron micro- scope (SEM), however, that the similarity of plumata with sobrina may in fact be superficial. Cluster size and spinule size differ even under the light microscope, and the SEM indicates the presence of fine sensoriiform filaments in sobrina and morii, but not in plumata or platy- chela. The SEM also revealed a second cluster consisting of minute denticles in morii anterior to the one visible with the aid of a light micro- scope (in preparation). Female Fifth Pair of Swimming Legs The two characters found in P5 that provide diagnostic information, i.e., the Re:Ri length ratio (Figure 29) and the distribution of spines on the endopod (Table 7) agree in showing strong similarity between morii and sobrina on the one hand and between platychela and plumata (all geographical sectors combined) on the other. It should be noted, however, that the similarity between platychela and plumata is weakened when the comparison is restricted to Atlantic Ocean samples of plumata (in preparation). The distribution of the spines on the endopod is also noteworthy by virtue of the compelling 97 FISHERY BULLETIN: VOL. 72. NO. 1 10- 0 20- 10- 0 >20 ■z. UJ O 10 UJ 0^ 4oL 20 10 0 J L platychela x= 2.3100 s=.30l8 N = 49 J I 1 1 1 1 1 plumata x = 2.3858 s = .2677 — I N = 59 — 1 1 J I morn x= 1.4555 s = .l5ll N = 55 \ \ I \ ^ I I I I I sobrina x = l.2827 s=.0904 N = 52 I I I I 1.0 14 P5 1.8 2.2 Re Ri 2.6 3.0 .9 Figure 29. — Frequency distribution of P5 Re:Ri ratio for females of the four species of Pontellina. evidence it ))rovides in support of our judgment that the four siblings are valid species recently derived from the same parent species. The frequencies and vv^idespread geographical occurrence of phenotypes are evidence of simple Mendelian inheritance and indicative of balanced polymorphism. Another pontellid, Labklocera diandra, has also been shown to be polymorphic (Fleminger, 1967b). In both Pontellina and Labidocem the apparent polymorphism affects a sexually modified appendage before the onset of maturity, the phenotypes being distinguish- able in copepodite stage V. However, within its species group, only L. diandra displays the polymorphism which is visible in the male sex. Male Fifth Legs and Right First Antenna Segment lengths of sexually modified appen- dages that we examined tend to vary directly with prosome length. We chose the length of the right furcal ramus (Figure 25) instead of the prosome as our standard body length reference for comparing morphometry of sexual appendages because the furcal ramus length yielded graphic presentations with con- siderably less scatter within each sample. .20 E e < < O 3 1- X ^ .14 o o .10 ♦ ♦ ♦ 2-* #-2 a 4 i-s^-z 2-n n-3 2-* ^^♦f ♦-S ♦ ♦ ♦ D D ^-2 ''i no D /2 /2 n D D A • • ♦ plumata • morii A sobrina D platychela Va • -^'^A •' A A A^ A-3 A- 4 _L J 08 ,10 .12 -14 .16 LENGTH OF LEFT P5 Re1, mm Figure 30. — Length of right furcal ramus (ordinate) plot- ted against length of left P5 Rel (abscissa) for males of the four species of Pontellina. Table 7. — Frequencies (%) of phenotypes varying in the number of spines on the endopod of the fifth pair of swimming legs in Pontellina spp. females. Species (/V) Left leg: Right leg: I spine 1 spine 1 spine 2 spines 2 spines 1 spine 2 spines 2 spines plulychela (100) pluinuia (300) morii (200) sobrina (100) 34 16 12 38 37 12 16 34 1 2 1 96 0 1 0 99 98 FLEMINGER and HULSEMANN: FOUR SIBLING SPECIES OF PONTELLINA Table 8. — Dimensions of selected segments of sexually modified appendages of Pontt'lliiui spp. adult males. Segments and species .v(mm) s N Range (mm) Left P5 Rel length; plalychela 0.1193 0.0048 21 0.110-0.130 plurnuta 0.0988 0.0067 48 0.085-0.120 morii 0.1221 0.0079 19 0.110-0.130 sohrina 0.1269 0.0060 21 0.120-0.140 Right P5 Rel width: plalychela 0.1895 0.0109 20 0.170-0.210 plumata 0.1647 0.0112 47 0.140-0.195 morii 0.1960 0.0091 20 0.180-0.215 sohrina 0.1814 0.0098 21 0.165-0.200 Al segment 18 length: plalychela 0.3417 0.0152 26 0.300-0.365 plumala 0.3364 0.0220 32 0.285-0.400 morii 0.3063 0.0159 31 0.280-0.340 sobrina 0.3014 0.0137 29 0.280-0.335 Length of Left First Exopodal Segment This segment is much shorter in plumata than in the other three species (Figure 30, Table 8). Small differences appear among the three equatorial species but they are inconspic- uous in comparison to their distribution as a group relative to that of phi niata. Width of Right First Exopodal Segment As in the section above on the left, Rel, the .20 r E en o cc : I! 16 O ,14 O X o ♦ ♦ ♦ t ♦ ♦ ^U-2 ♦-2 D 2-D D n-2 D £-♦ ♦ ♦ f^f ♦ * 2-0 D'^n a . . .,3 .,3 ♦ 3-4 ♦ ♦ ♦ n-2 n D ♦ ♦ a • • • % 2s^ A ^ • ^-4 2-« • ♦ plumata • morii A sobrina D platycliela A A-2 '^ A-3 A A A-2 A _L _L _J_ .14 16 18 .20 WIDTH OF RIGHT P5 Rel, mm 22 Figure 31. — Length of right furcal ramus (ordinate) plot- ted against width of right P5 Rel (abscissa) for males of the four species of Poniellinu. distributions of the three equatorial species broadly overlap, but plumata tends to be ap- preciably smaller (Figure 31, Table 8). Morphology of Right First Exopodal Segment The proximal segment of the chela appears in three essential states: the swollen condition of platycliela (Figure 7a, b), the slender condi- tion of plumata (Figure 4i, j) and the slender condition characterized by a more distal position of the posterolateral outgrowth shared by morii and sobrina (Figures lid, e; 14c, d). Morphology of Right Second and Third Exopodal Segments The distal segment of the chela appears in three states: the swollen condition of plalychela (Figure 7b), the shortened, spurred condition of morii (Figure lid, f) and the simple attenuated condition shared by plumata and sobrina (Fig- ures 4j, 14d). Length of Segment 18, Right First Antenna Two siblings, plumata and plalychela, broadly overlap and occupy the upper half of the overall distribution; the other two, morii and sobrina, broadly overlap in the lower half of the distri- bution (Figure 32, Table- 8). Spermatophore Attachment (Figures 33, 34) The three equatorial species agree in having 99 FISHERY BULLETIN: VOL. 72, NO. 1 20 3 < ; 18 < 16 o cr 3 X O 14 cr Ll_ o I UJ JO ♦ plumata ^ sobrina D platychela ♦ ^ ♦ ♦ D D 2-D D ♦ "^ ♦ D-2 ♦ ♦ D t^,j»^~D ^-uX • •"♦ • •2 2-»^» '^ A-2 A A • 2-» •-2 ^ A-2 A^~^ A A A A A 'ii A A A 28 30 32 34 36 LENGTH OF RIGHT A1 SEGMENT 18, mm Figure 32. — Length of right furcal ramus (ordinate) plotted against length of segment 18 of right Al (abscissa) for males of the four species of Puiitellina. the proximal end of the sac cemented to the right side of the genital segment, morii and sobrina in a virtually identical fashion, differing somewhat from the condition found in platychela. In plumata, however, attachment is restricted to the proximal end of the neck, the remainder of the neck and the entire sac hanging free from the body but showing helical convolutions similar to those present in the other congeners. Geographical Occurrence Three of the species, morii, sobrina, and platy- chela, were found primarily in low latitudes between 20°N and 20°S (Figures 8, 12, 15). The three species are essentially allopatric to one another, each predominating in a geograph- ically different segment of equatorial circulation in the world's oceans (see Table 20). Relatively high frequencies of abundance or occurrence coincided with eutrophic equatorial regions characterized by a shallow O2 minimum layer (^1 ml/liter) lying at or near the permanent thermocline. The three species tend to concen- trate in the uppermost 20 to 30 m of depth and virtually disappear below 50 m (in preparation). The fourth sibling, plumata, is widespread in subtropical latitudes (Figure 5) and may be locally abundant in tropical regions downstream from areas of persistent upwelling. It is the only species of the genus with a circumglobal range but tends to be infrequent to absent in tropical areas dominated by its equatorial cognates (see Table 20). Its vertical distribution appears to encompass the surface to 200-m depth in subtropical latitudes, the lower limit shoaling to about 100 m in tropical latitudes (in preparation). Summation of Ph> logenetic Similarities Thus within the framework of the 17 charac- ters considered above, morii and sobrina show the highest frequency of similar character states. In practice their overall morphological similarity is sufficient to require routinely close inspection at appreciable magnifications for reliable separation. Though the next most frequently linked pairing, plumata and platy- chela, show similarity in about 60% of the features in Table 9, at low magnifications under a stereomicroscope they are almost as distinct from one another as each is from motii or sobriiia. As noted in the calanoid genera, Labidocera and Clausocalaiius (Fleminger 1967b; Frost and Fleminger, 1968), the distinguishing features of the sibling species in Pontellina are limited to sexually modified characters, i.e., the fifth legs, the genital segment, the posterior corner of ThIV-V, the male right Al, and the caudal furca. There is reason to regard plumata as re- taining the strongest similarity to the Pontellina ancestral stock. This view rests upon two fea- tures: the slightly stronger resemblance of sexually modified structures in plu //m^o, especial- ly the ThIV-V spine in the female, to those of Poiitellopsis and of the more eurytopic circum- global distribution of plumata in comparison to the restricted distributions of its equatorial congeners. To examine the statistical significance of the phylogenetic relationships inferred from the characters given in Table 9 we have utilized a computer program that detects significant levels of co-occurrence among sets of overlapping functions. The program has been informative in the detection of communities as well as in systematic classifications of flexibacteria (Fager, 1969). 100 FLEMINGER and HULSEMANN: FOUR SIBLING SPECIES OF POS'TELLINA 0.2 mm a-h g h Figure 33. — ThIV-V and urosome of female with attached spermatophore. a, b. Poniellina plumata. c-e. P. platychela. f-h. P. morii. a, c, f dorsal view; b, d, g lateral view; e, h ventral view. 101 FISHERY BULLETIN: VOL. 72. NO. 1 Table 9. — Shared character states among species of Pontellina. Character No. of states Species sharing same state Species with unique character state Remarks 1 . .vTL 9 2. PUR 9 3. Furcai ramus length 9 4. Furcai ramus lengthiwidth ratio 9 5. Th IV-V 9 6. Th IV-Vd 7. Genital segment 9 8. P5 9, Re:Ri ratio 9. P5 9, Ri spines 10, P5 •, left Rel length 1 1. P5i, right Rel width 12. P5:;, right Ret morphology 13. P5^, right Re 2-3 morphology 14. Al ' right seg. 18 length 15. Spermatophore attachment 16. Geographical distribution 17. Latitude and depth distribution 2 morii and sohrina; phimaia and plaiychela 2 iiiorii and sobrina; pliimaui and plaiychela 2 morn and sobrina; phtmala and plaiychela 2 niorii and sobrina: plunutia and plaiychela 2 inoni and sobrina: pluiuala and plaiychela 2 morn and sobrina: plumala and plaiychela 2 morii and sobrina: plumala and plaiychela 2 morii and sobrina: plumala and plaiychela 2 morii, sobrina. and plaiychela 2 morii and sobrina: plumala and plaiychela 3 plumala and sobrina 2 morii and sobrina: plumala and plaiychela 4 morii and sobrina: plumala and plaiychela 2 morii, sobrina, and plaiychela 2 morii, sobrina. and plaiychela 3 morii and sobrina 3 plumala and sobrina 2 morn and sobrina: plumala and plaiychela 3 morii and sobrina 2 morii, sobrina, and plaiychela plumala plaiychela: morii plumala plumala plumala: plaiychela morii: plaiychela plumala: plaiychela plumala: plaiychela: morii: sobrina plumala Significant differences produced by furcai ramus length Significant differences produced by furcai ramus length Minor differences between plumala and plaiychela ignored SEM results ignored Frequency of similarities in 17 chorocters: morii and sobrina linked in 15 instances or 82%. plaiychela linked with morii and sobrina in 4 instances or 24%. plumala and plaiychela linked in 10 instances or 59%. plumala and sobrina linked in 1 instance or 6%. plumala unique in 7 instances or 4l°o. plaiychela unique in 5 instances or 29%. morii unique in 3 instances or 18%. sobrina unique in 1 instance or 6%. 102 FLEMINGER and HULSEMANN: FOUR SIBLING SPECIES OF PONTELLINA 0 2 mm I 1 a -c Figure 34. — ThIV-V and urosome of female PonielUna sohrina with attached spermatophore: a. dorsal view; b. lateral view; c. ventral view. The program calculates an index of affinity for all possible pairs of species as the geometric mean of the proportion of common character states corrected for the number of characters used in the analysis: i.e., Jl\/A X B — Viy/W , where A and B are the total number of charac- ters recorded for the two species, B ^ A, and J is the number of shared character states. Values of the index above 0.5 have been found empirically to provide objective repeatable groupings of related sets of values. A nuniber of characters listed in Table 9 were omitted from the recurrent group analysis to avoid biasing the computations with redundant information. Characters 1, 2, and 4 were not scored since their morphometric states are determined largely by the value of character 3. Characters 11 and 14 were deleted since they parallel character 10 in showing a direct re- lationship to TL and to furcal length. In the absence of a fossil record the distributional characters 16 and 17 were not scored on the intuitive grounds that they are complex deriv- atives of both 1) overall genetic adaptation and 2) fortuitous abiotic historical events that might obscure essential phylogenetic patterns. All of the scored characters were weighted equally and disregard the preliminary results from SEM observations. The recurrent group analysis reveals only one grouping with an index higher than 0.5, that of morix and sobnna (Table 10). Similar- ity between phonata and platychela falls well below the acceptable level of significance. The other possible pairings are dissimilar in most to virtuallv all of the 10 characters used in the analysis. Assuming equal rates of evolution the results indicate that the divergence of pliimata, platychela, and the morii-fiobiiua lineage are likely to be divisions of greater age than that of morii and sohrina. GEOGRAPHICAL VARIATION AND SYMPATRY In the course of this study two conspicuous and parallel instances of geographical varia- tion were encountered in the fifth legs of phauata females. This variation was expressed in the number of spines at the distal end of the endopod and the length of the exopod relative to that of the endopod. As noted above the number of spines on the ' endopod of the female's fifth leg is polymorphic throughout Pontellina. The bilateral two-spined morph is overwhelmingly dominant in morii and sobri)ia. However, four morphs are common in platychela and plumata. Comparison of ran- domly selected samples of Atlantic specimens of pluniata with specimens from the Indian and Pacific Oceans indicate significant differences Table 10. — Values of the recurrent group affinity index (Fager, 1969) and the probability of obtaining this or high- er values by chance for all possible pairs of Pontellina spp. Further discussion in text. Species pair Affinity index morii and sobrina 0.642 <0.001 platychela and pliimaia 0.242 >.4 platvchela and morii 0.042 >.8 platychela and sobrina 0.042 >.8 plumata and sobrina 0.042 >.8 plumala and morii 0 103 FISHERY BULLETIN: VOL. 72. NO. 1 in the frequency of the four morphs (Table 11). The bilateral one-spined morph is much more frequent than the bilateral two-spined morph in the Atlantic Ocean whereas in the Indian and Pacific Oceans the frequencies of the two morphs are more alike and the differences are not signi- ficant. Notably, the frequencies of the morphs in platyckela differ significantly from those of the pluniata sample from the Atlantic but not from those of the Indian and Pacific samples of phtiii- ata. Of the j^airs of species sharing common boundaries only niorii and sobrina do not appear to have appreciably different morph frequencies (Table 11). In the ratio exopod to endopod length for the fifth legs in females, the distribution of the Atlantic sample of plumata differed significantly from those of the Indian and Pacific Oceans (Table 12). As in the case of the endopodal spines, pairs of species with common boundaries show- ed significantly different distributions of the exopod-endopod ratios. Extrapolating from the similarity of Indian and Pacific Ocean samples, differences between Atlantic and Indian-Pacific populations of plumata appear to be geographically abioipt. Thus they may be viewed as refiecting 1) local pressures on phi mat a within each geographical population, 2) restricted gene flow between the Indian and Atlantic Ocean populations, 3) or both. P. plumata showed the highest frequency of unique character states in PontelUna (Table 9). Furthermore it tends to occupy a conspicuous- ly peripheral position relative to the other three species in its dimensions of sexually modified appendages in both sexes (e.g., Figures 27, 28, 30, 31). It is also the only species of the genus sharing common boundaries with the other three species of Poitt('lUna. Therefore, the geo- graphical differences between Atlantic and Indian-Pacific populations of plumata parallel the extensive character divergence (Mayr, 1970: 51-53) otherwise distinguishing the species. Con- sidering the fact that all morphological structures involved are sexually modified it would appear that we are witnessing reinforcement of pre- mating barriers (Dobzhansky, 1970:376-382). Similar disjunct morphological differences distinguishing Atlantic from Indian and Pacific populations of epipelagic calanoids have been reviewed (Fleminger and Hulseraann, 1973) and the number of examples increased (Flemin- ger and Hulsemann, 1973; Fleminger, 1973). Similar patterns in the strength of divergence in secondary sexual characters relative to Table 11. — X^ test of homogeneity in the distribution spines on the endopod of the fifth legs in adult females. of Number of spines on endopod (left leg-right leg): 2-2 1-2 2-1 1-1 Population Number of specimens Total platychela. Atlantic Ocean plumata, Atlantic Ocean plumata. Pacific Ocean plumata, Indian Ocean morii, Indian Ocean morii. Pacific Ocean sobrina, eastern tropical Pacific Ocean plumata Atl. vs. pliiinata Pac. plumata Atl. vs. plumata Ind. plumata Pac. vs. plumata Ind. platychela vs. plumata Atl. platychela vs. plumata Pac. platychela vs. plumata Ind. morii Pac. vs. sobrina morii Ind. and Pac. vs. plumata Ind. and Pac. sobrina vs. plumata Pac. 38 16 12 34 100 22 11 16 51 100 39 14 15 32 100 41 11 18 30 100 94 2 1 3 100 98 0 2 0 100 99 1 0 0 100 X2 d.f. 9.48 3 <0.025 p >0.01 11.3 3 0.01 0.76 3 <0.9p >0.75 9.14 3 <0.05p >0.025 3.61 3 <0.5p >0.25 2.5 3 <0.75p >0.5 3.01 3 <0.5p >0.25 146.84 3 <0.001 84.34 < 0.001 104 FLEMINGER and HULSEMANN: FOUR SIBLING SPECIES OF PONTELLINA Table 12. — Comparison by rank test (Tate and Clelland, 1957:89) of the ratio exopod length to endopod length in the fifth legs of adult females. Samples tested Median Range N robs. 1. phiinara, Atlantic Ocean 2.54:1 2.10-3.08:1 21 plumala, Indian and Pacific Oceans 2.29:1 1.97-2.71:1 38 2. pliiniulu, Indian Ocean 2.27:1 2.01-2.71:1 9 phimala. Pacific Ocean 2.31:1 1.97-2.64:1 29 3. pliimata, Atlantic Ocean 2.54:1 2.10-3.08:1 21 ptatychehi, Atlantic Ocean 2.27:1 1.69-2.91:1 49 4. plumata, Indian and Pacific Oceans 2.29:1 1.97-2.71:1 38 plalychela. Atlantic Ocean 2.27:1 1.69-2.91:1 49 5. sobrina, eastern tropical Pacific Ocean 1.29:1 1.07-1.50:1 52 morii, Indian and Pacific Oceans 1.45:1 1.22-1.76:1 55 856.5 373 967.5 1655.5 1911.5 3.58 0.38 2.85 0.14 5.58 <0.01 0.7 <0.01 0.88 <0.001 sympatry have been discussed in recent studies on the calanoid genera Lahidocera and Clauso- calanus (Fleminger, 1967b, in press; Frost and Fleminger, 1968). The similarity of the plumata case to the character displacement found in North American chorus frogs (Pseudacris). reviewed by Littlejohn (1969, Figure 3), is especially noteworthy. Differing only in geo- graphical scale, both cases support the view of a growing number of workers that premating isolating mechanisms tend to be a product of sympatry resulting from expansion of the range of daughter populations that have diverg- ed in geographical isolation (Alexander, 1969). REMARKS ON HABITAT BIOGEOGRAPHY Vertical Distribution Essentially similar results from a number of independent sets of published observations de- lineate general features of the vertical distribu- tion of P<>)itelUiia. The genus has been found commonly between the surface and 200 m. Un- fortunately differences between the congeners were not noticed, and all specimens were re- garded as representing a single species. Though individuals may on occasion appear below 200 m, the largest numbers have been taken regular- ly between the surface and 100 m (Vinogradov, 1968). Diurnal migrations seem to be neither consistent nor extensive in vertical distance (Wilson, 1942; Heinrich, 1961; Vinogradov and Voronina, 1964; Roehr and Moore, 1965). Vinogradov and Voronina's report of a pattern of latitudinal variation in the depth range of Pontellina is particularly interesting in the light of differences in the latitudinal distribu- tion of plumata and the equatorial species. In central waters the daytime 80% level (i.e.. the depth above which 80% of the population occurs) was found at 200 m, and the highest concentra- tions appeared between 50 and 100 m. In equatorial waters of the eastern Pacific the daytime 80% level was found between 100 and 150 m, and the highest concentrations varied between the 0 to 25 m and the 25 to 50 m sam- pling sti'ata. Wilson's (1942) records of Pontellina during Cruise VII of the CaDiegie were based on sam- ples collected with open nets routinely deployed at 0830 h local time at three depths (0, 50, and 100 m) and towed horizontally. As in Vinogradov and Voronina's (1964) results, Wilson's data also show variation in frequency of captures and aoundance at the three depths relative to the geographical origin of the samples (Table 13). Vinogradov and Voronina (1963) and Voro- nina (1964) found the largest number of Pontel- li)ia in equatorial surface waters of the eastern Pacific Ocean. They noted that the genus tends to concentrate in upwelling regions along zones of divergence and in the vicinity of the tropical convergence. Previous observations that the genus Pontel- lina occurs chieflv above 100 m in the more 105 FISHERY BULLETIN: VOL. 72. NO. 1 eutrophic equatorial latitudes but may typically extend through 200 m or more in the oligo- trophic subtropics must now be viewed within the comi)lexity of thi-ee tropical and one tropical- subtropical species. In this context, vertical dis- tribution api^ears to differ among the species: i.e., phiniata probably has a deeper range than its three tropical congeners. Confirmation re- quires analysis of vertically stratified sampling from regions supporting pUintata and one or more of its cognates. Abundance Interest in patterns of geographical distribu- tion relative to phylogenetic affinities among the species prompted us to make preliminary comparisons of abundance among the species of PontelUua. For the analysis we selected sets of similarly collected, quasi-synoptic, quantita- tive samples that represented the epijjelagic layer between 150 m or 200 m and the surface. The sets of samples comprise transects crossing the equator at different longitudes in the Pacific Ocean (Figure lb. Table 14). Only adults were tabulated, the mesh width of the i)lankton nets usually being too large (~0.5 mm) to retain younger copepodids (Table 15). The hour of sami)ling was ignored in the absence of appre- ciable differences in either frequency of occur- rence or mean abundance of PontelUua between samples collected at day or night (Tables 16, 17). The mean abundance of species of PonteUina ranged from 0.01 to 0.9 per m^ (Figure 35). Abundance in the Pacific followed a generally familiar pattern. Higher values api:)ear in the eastern third of the Pacific as well as in the Austral-Asian seas and the Indian Ocean while lower values predominate in the middle and western Pacific (Figure 35). The three species, P. plumafa, morii, and .so6r///fl, tend to vary independently in abundance. Mean abundance and frequency of occurrence values from the Indian Ocean and Austral- Asian seas are similar for morii and plumata, though evidence of finer-scale geographical differences sejiarating the two si)ecies within the Indian Ocean have been noted (Figure 38). Eastward across the Pacific the abundance and occurrence of plnmafa persist or even increase \x\) to but not beyond the boundary of the eastern tropical Pacific where sobriiia predominates. P. morii differs from plumata by showing a sharp decrease in abundance across the entire Pacific Ocean. However, high numbers of morii were found between 10 m and the surface south of the equator along long. 92 ''W. This is too distant for direct transport from the main area of abundance in the Indian Ocean and Austral-Asian seas; the unusually high values for morii, 1.96 per m'' at lat. 4°16'S and 0.16 per m-' at lat. 12°19'S, suggest recruitment by local reproduction. Table 13. — Occurrence of Ponicllinu by sampling depths at selected stations of the Carnegie cruise VII (Wilson, 1942). Analysis limited to Carnegie stations providing abundance estimates from all three sampling depths. Grouping of the stations under a particular species or combination of species determined by its geographical origin relative to the distribution of species of PonteUina determined by the present study. Values are the sums of numerical equivalents of Wilson's index for PonteUina abundance divided by the number of stations in the geograph- ical group. Index equivalents are: 1 = 1-5 specimens (trace); 2 = 6-10 specimens (rare); 3 = 11-24 specimens (frequent); 4 = 25-50 specimens (common); 5 = >50 specimens (abundant). Probable dominanf species Sum of obundonce No. stations 0 m 50 m 1 00 Carnegie station numbers sohrina morii plumaia-morii pliimata-platy chela plumalu 2.66 0.33 1.33 35,37,38 L83 0.0 0.50 40,41,43-45,48 1.05 1.11 0.83 98, 99, 101, 103-108, 151, 153-160. LOO 1.33 0.67 22,23,27,31,32,34 0.50 0.67 0.50 16, 18, 49-52, 56, 57, 67, 79, 94, 96, 97, 109,112,132,133,135,136,139,140,142, 145, 149 106 FLEMINGER and HULSEMANN: FOUR SIBLING SPECIES OF PONTELLINA BS 3 O" UJ u j= «-• so c '^ c« O ,^ Ua yl 'J ;/: 'J L. K -' tfl c c =3 o *-* 6 ^— o C3 C I ,o Jo ^^ 1> OJ z E ■o Di 73 C T3 E c CO i^ £ t?5 an 1) Ph "a o S u cd 13 tzl U f, ? c S o 3 ^ 5u •" ^ XI 0 O Q, * ^ * 3 ^ ■a C3 S I*, o o D o O n c ) ?-* k. \i 'J 7L *J -o ^ "o 73 •a >> c 'J C3 c o (^ 3 C 3- 73 OJ \) .u. U '^" '^ •o v-^ c C 73 73 . — , -a "■ c C u 3 'a 73 aj a * 1) en u o Z > o Csl CN — CN O O o Csl O o o o o o o n O o +1 + 1 +1 +1 +1 +1 00 IX CN o 8 CN o 8 o o o o o o o o o o o o o o o o o o o o +1 +1 CO o o o 8 rx IX o 00 CN P p P 8 o CO p Px CO p o p o o p -0 o p IX O p +1 +1 +1 +1 +1 +1 +1 +1 +1 +1 IX O 00 CO o CO o CN CO p CO CO o o IX o 00 CO p 00 00 s o IX IX 8 CD CD d 6 o 6 6 6 6 6 : CN u q •O CN > D d o d 00 0 IX -o -d CO > D 5 00 d IX -O 1- ~'-.§<0.9 Austral -Asian Seas 0.0483 0.1488 12 0,0413 0.0784 7 0.6000 >0.9 Pacific Ocean 0.0770 1.2224 43 0.0405 0.1720 41 0.1986 >0.8 Atlantic Ocean 0.0857 2.7429 7 0.0133 0.0033 3 1.0251 >0.3 niorii Indian Ocean 0.1504 3.7540 56 0.1550 5.1996 41 0.0107 >0.9 Austral-Asian Seas 0.0300 0.0400 12 0.0400 0.1040 6 0.0081 >0.9 Pacific Ocean 0.0332 0.0804 22 0.0462 0.4721 24 0.0881 >0.9 sohrina Pacific Ocean 0.0307 0.0858 16 0.0914 2.8169 35 0.1423 >0.8 Table 17. — Occurrence of Pontellina spp. in day (0601 to 1800 h local time) and night (1801 to 0600 h local lime) samples. + present, - absent. Day Night + X2 Atlantic Ocean: pliinuua plutychela Eastern Pacific Ocean: phiinata niurii sobrinu Indian -Western Pacific Ocean: pliimata morii 25 16 13 22 3.389 23 18 23 12 0.383 15 19 13 49 4.360 6 28 13 49 0.015 9 25 26 36 1.648 08 30 87 31 0.491 80 58 66 52 0.040 0.1 > p > 0.05 0.75 > p > 0.5 0.05 > p > 0.025 0.9 > p > 0.75 0.25 > p > 0.1 0.5 > p > 0.25 0.9 > p > 0.75 108 FLEMINGER and HULSEMANN: FOUR SIBLING SPECIES OF PONTELLINA ' 40°E-' 80°E- 'I20°E- 156°E - JI74°W- ■ I26°W 'I24°W-'II3°W-' 95° W ' 92°W 80°E IIO°E ' IBCE ' I64'>E ISCW II2°W ' 86°W ' I ^1 ^1 1 INDIAN OCEAN AUSTRAL- ASIAN SEAS PACIFIC OCEAN Figure 35. — Mean abundance (No. adults/m^) and per- centage frequency of occurrence in sets of samples shown in Figures lb and 38 and listed in Table 14. Confidence limits of the means shown in Table 14. Further discussion in text. The appearance of sobrina is restricted to the eastern tropical Pacific where its abundance and occurrence resemble the values for »i(>rii and plaiitata in their regions of dominance, respectively. Quantitative data on Poiitellhto in the Atlantic Ocean are few. In six quantitative samples from the western Atlantic phiniata abundance ranged from 0.01 to 0.46 adults per m-'. Two samples containing platycliela provided estimates of 0.001 and 0.08 adults per m''. Extremely high values of phunato s.l., how- ever, have been reported from the Atlantic. Judging from their geographical origin, the northeastern Gulf of Guinea, these abundance estimates (Mahnken, Jossi. and McCabe, 1968) are probably referrable to platychela. Mahnken and his co-workers record the species at 18 of 63 sampled localities scattered offshore from the Bight of Benin west to Cape Palmas. They indicate areal abundance of the species by contouring selected class intervals of number per 1.000 m-' water strained. In lieu of the actual estimates per sample we used midpoints of each contoured interval to calculate the mean abun- dance. The yield is a surprisingly high mean of 1.01 individuals per m^, an order of magni- tude higher than our highest mean values from the Pacific and Indian Oceans. Aside from possible bias introduced by our extrapolations several factors may be responsible for these unusually high values: e.g., count of immature as well as adult specimens, use of nets with smaller mesh width (0.281 mm), use of surface tows in a region relatively rich in zooplankton presumably concentrated in the very shallow layer of tropical surface water above the permanent thermocline, etc. Summing our mean values of pin )nata, niorii, and sob7'iiia in each meridional set of samples, we find remarkably good agreement between our abundance estimates and those derived by previous studies of pluniata s.l. in the Pacific Ocean (Table 18). We normalized the published data to conform to the units employed in the present study. Normalization was simplified by the following assumptions: a. we assumed 100% filtration efficiency; b. we assumed that PonteUina occurs only above 200 m and, in calculating volume of water strained by the net, omitted segments extending below 200 m; c. in sets of vertically stratified tows we con- sidered the overall estimate of abun- dance as if it were from a continuous tow sampling between 200 m and the surface ; d. we assumed that previous studies on PaiitelUna failed to discriminate among the different species; the published values were regarded as representing a combined estimate of the abundance of all species of the genus found in the region. Estimates obtained from Heinrich (1968) and Vinogradov and Voronina (1963) are about one order of magnitude higher than other middle and west Pacific estimates. These higher values may be accounted for by two factors, namely that the counts include immature copepodids and that the samples were taken with nets of 0.18-mm mesh, small enough to retain Pontel- U)ia copepodids of stage II and possibly of stage I as well (Table 15). Sherman's (1963, 1964) counts appear to have been derived from adult specimens, partly by inference from his text and partly from the relatively wide mesh comprising most of the filtering cone in the POFI (Pacific Oceanic Fisheries Investigation) Standard Net (0.66 mm). 109 FISHERY BULLETIN: VOL. 72. NO. 1 Table 18. — Mean abundance (No. /m^) of Pontellina spp. in meridional transects crossing the Equator. Region Longitude Latitude Source of data .V no. adults V no. adults and juveniles Number of samples Sampling months Depth, tow, net Indian Ocean 40°E-80°E 35°S-25°N present study (west) Indian Oceon 80°E-nO°E 27°S-18°N present study (east) Austral-Asian 125°E135°E 12°S-12°N present study Seas Pacific Ocean 156°E-164°E )2°S-12°N present study 160°E 04°S-16°30'N Vinogradov and Voronina, 1963 176°W 14°S-13°N Vinogradov and Voronina, 1963 0.1419 0.0863 0.0596 0.0230 120°E-175°W 04°S-30°N Heinrich, 1968 95°W 10°S15°N present study 0.0952 0.1023 0.3790 0.1910 168°E-155°W 20°S-20°N Sherman, 1964 0.1379 — 174°W-160°W 06°S-21°N present study 0.0346 158°W 07°S-21°N Sherman, 1963 0.0438 154°W 13°S-13°N Vinogradov and — Voronino, 1963 140°W 18°S-17°30'N Vinogradov and — Voronina, 1963 126°W 12°S-20°N present study 0.0744 0.1172 0.1600 233 107 23 23 17 21 91 92°W 20°S-10°N present study 0.0358 59 15 13 18 29 22 19 22 Jon. -Dec. (1962-65) Jon. -Dec. (1962-64) Mar .-May (1961) Aug. -Sept. (1956) Sep. -Dec. (1961) Sep. -Dec. (1961) W of 160°E Jul. -Aug. (1957) Eof 160°E Nov. -Feb. (1957-58) Jan. -Apr. (1962) Aug. -Sep. (1956) June-July (1961) Sep. -Dec. (1961) Sep. -Dec. (1961) Feb. -Mar. (1967) Feb. -Mar. (1967) Feb. -Mar. (1967) 200-0 m, vert., lOSN' 200-0 m, vert., lOSN' 150-0 m, obi., CalCOFI SN2 (silk) 150-0 m, obi., CalCOFI SN2 (silk) 500-0 m, vert., Juday 80 cm 500-0 m, vert., Juday 80 cm 500-0 m, vert., Juday 80 cm Surface, POFI SN3 150-0 m, obi., CalCOFI SN2 (silk) Surface, POFI SN3 500-0 m, vert., Juday 80 cm 500-0 m, vert., Juday 80 cm 150-0 m, obi., CalCOFI SN2 (nylon) 150-0 m, obi., CalCOFI SN2 (nylon) 150-0 m, obi., CalCOFI SN2 (nylon) ' lOSN = Indian Oceon Standard Net. * CalCOFI SN = California Cooperative Oceanic Fisheries Investigations Standard Net. ^ POFI SN = Pacific Oceanic Fisheries Investigation Standard Net. Disregarding collecting and sample enumer- ating procedures as well as differences among the individual species, estimates of mean abun- dance of Pontellina across the Pacific (Table 18) vary from 0.023 to 0.379 with a median of 0.1 individuals i)er m-'. For einpelagic copepods this appears to be a rather low and remarkably uni- form set of values that varies within the unusually narrow range of one order of magni- tude. Summing the abundance of the three species produces a notable lack of any pro- nounced geographical trend though the mean abundance shows moderate, irregular undula- tions along the equatorial belt crossing the Indian and Pacific Oceans. Low abundance and relatively uniform dis- persion throughout the geographical region occupied by each species suggests that the spe- cies of PoiiteUina are high-order predators. This impression is supported for adults at least by the exclusive presence of animal remains in their stomach and the predominance of copepod 110 FLEMINGER and HULSEMANN: FOUR SIBLING SPECIES OF PONTELLINA fragments (Table 19). Though all of the species appear to be similarly predaceous within their respective epiplanktonic communities, we must conclude that appreciable differences in the abundance and occurrence of the sibling species are indicative of real changes in habitat con- ditions and real differences in the adaptive optima for each species. Remarks on Geographical Distribution This discussion hinges upon inferences drawn from the evidence presented in the preceding sections. Chief among them are the validity of the four sibling species of Po)itelUua as separate noninterbreeding populations. Based on mor- phological homogeneity each population appears to be closely adapted genetically to prevailing environmental conditions in the geographically limited hydrographic systems comprising its particular habitat. Except for differences be- tween Atlantic and Indian-Pacific populations of pluniata morphological indications are that panmixis prevails in each species. The three tropical species, moiii, sobrina, and platychela, occupy eutrophic waters characterized by equatorial upwelling and a shallow, steeply graded, permanent thermo- cline. The mixed layer overlying the thermocline is relatively homogeneous in temperature and has been referred to as Tropical Surface Waters (Wyrtki, 1966, 1967). In our use of this term, Tropical Surface Waters are restricted to the surface layer in regions where the permanent thermocline has a temperature gradient of ^0.1°C per m and encompasses an overall de- crease in temperature from about 24° ± 1°C at the top to about 15° ± 1°C at the bottom. These pools of warm water are subjected to seasonally repetitive changes in the strength of the equatorial Trade Winds (Wyrtki, 1966, 1967; Taft, 1971). The seasonal changes pro- duce monsoonlike reverses in the circulation of the equatorial segment inhabited by each species. This phenomenon apparently provides a suf- ficiently closed hydrographic circulation to maintain breeding stocks in proximity to suit- able nursery grounds and thus ensures contin- ual success of each species. The equatorial distributions of the tropical species of PoiiteUina are not without prece- dence. The tropical Atlantic has previously been characterized in faunistic terms, for example, by a number of mesopelagic fishes (Backus et al., 1970) as well as by a sergestid shrimp Table 19. — List of identified particles from microscopic analysis of stomach con- tents in adult female Pontellimi. Species Speci- Cope- "Para- Crust- men pod "Oncaea"calanus" ocean Algol number ports ports ports parts ports Source of specimen: Oceon Station plumatii 1 X X 2 X 3 X X Pocific 4 X X Indian 5 X X Pocific Percentoge no. with ingested particles in midgut: 71 °o Atlantic la Creuse 5 Indion DodoVI-81 Scorpio II -146 Lusiad V-45 Jordan 57-076 platychela 1 X X Atlantic Atlantis II 20-28 2 X X Aflontic La Creuse 5 3 X Atlontic Atlantis // 31-40 4 X Atlantic Atlantis // 31-54 5 X Atlantic Oregon 1289 Percentage no. with ingested porticles in midgut 63°o morii 1 X X Pocific Troll 30 2 X Pacific TRANSPAC 98B 3 X X Pocifrc EQUAPAC H-31 4 X Indion Lusiad V-45 5 X Indion Lusiod 11-14 Percentoge no. with ingested particles in midgut 63°o sobrina 1 X X Pocific Bonocco 35 2 X Pacific ColCOFI 5801: 153.50 3 X X Pacific Scot 45 4 X X Pacific Jordan 60-056 5 X X Pacific Bonocco 31 Percentage no with ingested particles in midgut 83° o 111 FISHERY BULLETIN: VOL. 72. NO. I (Judkins, 1972). Among the Atlantic Foramin- ifera listed by Be and Tolderlund (1971) as tropical species only Candeina )iitida shows a geographical distribution similar to that of P. platijchcla. In general species characterizing the eastern tropical Pacific, unlike sobriiia, tend to follow the coastline of the Americas from about lat. 30° N to 20° S and extend westward to long. 160° to 180°W: e.g., Euphausia distinguenda, (Johnson and Brinton, 1963), Eucalanus inermis, (Lang, 1967), Melamphaes spiuifer, (Ebeling, 1962), Stomiafi colubrhins, (Gibbs, 1969). These distributions are meridionally and zonally more extensive than the limited disper- sion observed in P. sobriiia and others like Pontella danae, P. agasnizi, and Pontellopsis lubbockii (Heinrich, 1964; Fleminger, 1967b; and unpubli.shed records). The dissimilarities probably relate to differences in depth range, the more widespread forms having access to subsurface currents flowing northward (Woos- ter and Jones, 1970) and southward (Wooster and Gilmartin, 1961) under the eastern boun- dary currents as well as westward in the tongue of low oxygen water accompanying the North Equatorial Current which is traceable to the Philippines (Reid, 1965; Wyrtki, 1966; Tsuchi- ya, 1968). Distributions of epipelagic species in the equatorial Indian and Pacific Oceans resem- bling that of moiii include a number of other copepods, e.g., several species of Eiicctkunts, (Fleminger and Hulsemann, 1973; Fleminger, 1973); Claunucakuni^ ))iiii(>)\ (Frost and Fleminger, 1968); several euphausiids such as Euphausia diomediae, E. paragibba, and Sty- locheiron microphthalina, (Brinton. 1962); and fishes such as Scopeloyadiis iinispiinis, (Ebeling and Weed, 1963) and Stomias o//7»/,s, (Gibbs, 1969) though the lattermost is also considered to inhabit the tropical Atlantic. Although the ubiquitous plumata overlaps geographically with each of the tropical species, plumata s overall range lies mostly in the enor- mous basin of oligotrophic waters spreading across the tropics and subtropics of each ocean, waters markedly different in vertical thermal structure from those of its tropical congeners. The almost mutually exclusive distributions of plumata and its more localized congeners, platychela in the equatorial Atlantic and aobriua in the eastern tropical Pacific, are evidence of relatively intensive environmental gradients and the adaptive response to appreciably differ- ent environmental optima, which separate the distributions of these pairs of species. For example, morii has been found at the edge of the south Atlantic as well as the edge of the eastern tropical Pacific; concomitantly sobriiia occurs in the North Equatorial Current, but successfully extends only a few degrees of longitude to the west of its habitat; platychela is adjacent to but fails to establish itself in the Sargasso Sea; finally plumata, despite apparent circumglobal distribution, does not appear in large numbers where its equatorial congeners abound. Thus, the optimum habitats appear to be regionally distributed and those that are contiguous are sufficiently different to prevent colonization by expatriated congeners trans- ported to the margin of the habitat. The possi- bility of interference among the species is open but in the light of available knowledge of calanoids it seems intuitively to be most unlikely. Thus, the two classes of epipelagic warm- water distributions found in Po)itelliHa suggest a fundamental dichotomy in the circumglobal warm-water belt. The three tropical species correlate with geographically separated shallow lenses of eutrophic water. Each lens is known to overlie regions of intense temperature and oxygen gradients and to be partially bounded by the similarly intense tropical convergences (Neumann and Pierson, 1966). P. plumata, however, correlates with the circumglobal warm-water pool that is largely oligotrophic. The oligotrophic pool tends to be deep, the permanent thermocline often exceed- ing 200 m in depth. Temperature gradients in the thermocline and along its margins at the subtropical convergence are relatively weak, and oxygen is generally at or near saturation (Neumann and Pierson, 1966). Evidence that the Atlantic pool may be at least partially iso- lated with respect to Pontelliiia whereas the Indian and Pacific pools are confluent is sug- gested by morphological differences in the plumata populations rejioited above. The circulation systems and physical condi- tions known to maintain these lenses of eutro- phic tropical water and the pools of oligotrophic tropical -subtropical waters are the obvious mechanisms sustaining the geographical dis- 112 FLEMINGER and HULSEMANN: FOUR SIBLING SPECIES OF POSTELLINA tribution of the four species of Pontellina. This is apparent in the relationship between the distribution of each species and the location of prevailing near-surface isotherms that locate the hydrographic limits of these bodies of water. The localities for the tropical species are largely enveloped by the mean winter season position of the 24 °C isotherm at 10 m (Figure 36), the lower thermal limit of Tropical Surface Water. The 10-m depth was chosen to reduce the influence of diurnal fluctuations. The local- ities for plumata, however, vary broadly be- tween the position of the 20° and 15° C mean winter season isotherms (Figure 37). Factors confining the distributions to the observed lim- its, however, are not obvious; more data on depth range^ vertical migratory behavior, and depth of food organisms would probably be enlightening. Notably, more than three-quarters of the samples (77.5% ) containing Pontellina yielded specimens of only one species. To examine joint occurrences of Po)itelli)ia congeners more close- ly, all capture records of a species were tallied by ocean and grouped with respect to the pres- ence or absence of other congeners in the same sample (Table 20). Comparison of singular and joint occurrences for all possible pairings indi- cates that the latter are relatively infrequent. In no case of joint occurrences did the index of affinity (Fager and McGowan, 1963) reach a positive value. No two species within the genus would appear to occupy the same spatial habi- tat or, in other words, be members of the same community. Thus, the extensive overlapping of morii and plumata in the equatorial Indian and Pacific Oceans may be viewed as a function of intermingling due to the spatial proximity of the two habitats and perhaps also due to a greater number of similarities shared by these two habitats than between those of the other possible pairings within the genus. 60° Figure 36. — Comparison of geographical area enveloping all capture records of tropical species of Pontellina with select- ed mean isotherms at 10 ni for winter season of each hemisphere. Data from Muromtsev (1958, 1963) and Wyrtki (1971). Dotted shading outlines capture records of P. platychela shown in Figure 8; horizontal shading outlines capture records of P. sobrina shown in Figure 15; vertical shading encloses the capture records of P. morii shown in Figure 12. 113 FISHERY BULLETIN: VOL. 72, NO. 1 40° 100" 60° 20° 0° 23' 60° 100° 140° 180° 140° 100° 60° Figure 37. — Comparison of shaded area enveloping all capture records of Pontellina phiinata, shown in Figure 5 with selected mean isotherms at 10 m for winter season of each hemisphere. Data from Muromtsev (1958, 1963) and Wvrtki ( 1971). Further discussion in te,\t. Table 20. — Separate and joint occurrences among species of Pontellina. Values in parentheses are the index of affinity; a value greater than 0.5 suggests joint mem- bership in the same communal assemblage of species. phimaia morii \ohrina plalyc hela Total Indian Ocean and Austra asian Seas: phimala 129 96 (-7.01) 0 0 225 mom 78 0 0 78 sohrinu 0 0 0 platychela 0 0 Total 129 174 0 0 303 Pacifrc Ocean: pluinata 136 46 (-3.77) 23 (-5.20) 0 205 morn 23 6 (-2.69) 0 29 sohrinu 85 0 85 platychela 0 0 Totol 136 69 114 0 319 Atlantic Ocean phimata 80 0 0 14 (-3.93) 94 morn 0 0 0 0 sohrina 0 0 0 platychela 58 58 Total 80 0 0 72 152 All records com bined: pluniaia 345 137 18 4 514 morn 101 1 0 102 sohrina 85 0 85 platychela 58 58 Totals 345 238 104 72 759 114 FLEMINGER and HULSEMANN: FOUR SIBLING SPECIES OF PONTELLINA SOUTHWEST MONSOON (APR- SEPT) No./m' a 0.01 -0.1 D 0.1 1 - I ■ I.OI - 10 40°E NORTHEAST MONSOON (OCT -MAR) 4(yE 120° 120° I.O.S.N. SAMPLES Figure 38. — Abundance of Pontellina morii and P. plumata in Indian Ocean Standard Net (lOSN) collections. Samples collected during southwest and northeast monsoon seasons. Dots represent localities sampled. Abundance values are estimated number of adults per m^ water strained. P. morii and plumata exhibit distinctive dis- tributions in both monsoon seasons (Figure 38) as well as general zonal separation (Figure 39), differences that are blurred in charts prepared without regard for seasonal variation (e.g., Figures 5, 12). During the southwest monsoon, plumata appeared in large numbers off the Somali coast and near the Seychelles whereas morii was much more frequent in the eastern Arabian Sea and the eastern Bay of Bengal. In the northeast monsoon both species were abundant in the Somali Current. However, only morii appeared to be common in and about the Andaman Sea whereas an indication of large numbers of plumata appeared just south of Java. Morphological relationships analyzed above indicate the species have common ancestry that produced three main lines of descent represented respectively by plumata, platychela, and the Indian-Pacific tropical pair of siblings, morii and sobrina. Ample evidence of co-occurrence tvy plumata [\] SOUTHWEST MONSOON ^ NORTHEAST MONSOON [V ^1 Figure 39. — Frequency of occurrence of Pontellina plumata and P. morii in the Indian Ocean north of selected latitudes compared to that south of the same latitudes. 115 FISHERY BULLETIN: VOL. 72. NO. 1 without intergradation between morii and so- biiiia support the conclusion that both are valid species that have evolved relatively recently. Morphological-geographical patterns provide inferential evidence that sympatry among sub- sets of the four species have led to modifications of secondary sexual features, presumably in the course of developing premating barriers to hybridization. Obvious examples of this emerge from comparison of pairs of species which have extensive contiguous boundaries: e.g., plumata and plat y chela in the Atlantic and pliimata and moni in the Indian and Pacific Oceans. In each pair of species the chela on the male fifth leg in the tropical congener is broad- ened in contrast to the slender chela found in plumata. In the females of each pair the hair patches on the genital segment are either miss- ing or reduced to one pair in the tropical species while pluynata maintains two prominent pairs. Another source of evidence lies in the geograph- ical variations in the female fifth legs of plumata which follows a pattern indicative of character displacement. Geographical variation in the frequency of morphs in plumata distinguishes Atlantic from Indian and Pacific populations; relationships with platychela in the Atlantic and morii and sobri)ia elsewhere suggest the variation is the result of character displacement. Three of the four morphs in morii and sobriiia appear to be extremely rare. 7. Each species exhibits a distinctive geo- graphic range independent of the other three. Absence of conspicuous geographical variation indicates sufficient transport and advection to maintain panmixis within each species except the Atlantic and Indian-Pacific populations of plumata. 8. Abundance of all four species is low de- spite relatively frequent occurrence within the limits of the distribution. These indications of high-order predation are supported by examina- tion of gut contents in sexually mature adults in which the remains consisted primarily of particles from small copepods. ACKNOWLEDGMENTS CONCLUSIONS 1. The genus Pontelliua represented by four species is epipelagic and occupies oceanic sec- tors of the circumglobal warm-water belt. 2. Three of the species occur chiefly in eutrophic sectors of equatorial latitudes where the layer above the thermocline is relatively homogeneous; the distinctiveness of this layer was noted by Wyrtki who refers to it as Tropical Surface Water. One species, platychela, occupies the tropical Atlantic; .^obriua is in the eastern tropical Pacific; and morii is found in the tropi- cal Indian and tropical Pacific Oceans. 3. The fourth species, plumata s.str., occurs most frequently in oceanic, oligotrophic regions in tropical and subtropical latitudes. 4. Morphological differences among the spe- cies are subtle and restricted to secondary sexual structures. 5. The four species comprise a monophyletic complex showing three basic derivatives, plu- mata, platychela, and a third that underwent a subsequent episode of speciation to produce morii and sobrina. 6. The female fifth leg is polymorphic and represented by four phenotypes or morphs. 116 This research was supported by the National Science Foundation Grants GB12412, GA31092, GB32076 and by the Marine Life Research Group of Scripps Institution of Oceanography. We express our thanks to R. Scheltema of Woods Hole Oceanographic Institution, Woods Hole, Mass.. and to the Indian Ocean Biological Centre at Cochin, India, who have provided significant quantities of material from the At- lantic and Indian Oceans, respectively. We owe special debts of gratitude to E. W. Eager for his advice on data analysis and to Gillian Mag- gert who carried out much of the preliminary sorting of samples and whose faithful camera lucida renditions of various specimens of Pon- telliua first called our attention to the existence of the problem. LITERATURE CITED Alexander, R. D. 1969. Comparative animal behavior and systematics. In Systematic biology. Publ. No. 16^2. Natl. Acad. Sci.. Wash.. D.C.p. 494-517. 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Found., Wash., D.C., 531 p. 120 STOCK COMPOSITION, GROWTH, MORTALITY, AND AVAILABILITY OF PACIFIC SAURY, COLOLABIS SAIRA, OF THE NORTHEASTERN PACIFIC OCEAN Steven E. Hughes^ ABSTRACT Recent international interest in the Pacific saury (Cololahis saint) resource of the north- eastern Pacific Ocean prompted studies to determine the stock's composition, structure, growth, mortaUty, and availability. During August-September 1969-71, data were obtained from more than 5,000 fish sampled from 19 individual schools captured between southern California and Vancouver Island, B.C. Length and age frequency distributions indicate fish grow to 340 mm in length during their 6-year lifespan. Larger fish apparently migrate farthest north and consequently age at full recruitment off Washington is III or IV, and II off Oregon. Spawning is e.xtended over most of the year and the stock is believed homogeneous. First maturity appears to be reached during the second year. Numbers of males and females were nearly equal until age IV when females began to predominate. Length-weight regressions are presented by sex. Berlalanffy growth parameters were calculated: K = 0.42, Lx = 342 mm, and lo = -0.72 years. The total instantaneous mortality coefficient was estimated at 1.25-2.20. Data on distribution and availability suggest a viable domestic fishery on this species is unlikely. In 1969, an investigation of the distribution, availability, and biology of Pacific saury, Cololabis saira, in the northeastern Pacific Ocean was begun by our laboratory. This study was a direct result of a tenfold decrease in combined Japanese and Soviet landings of the species in the northwestern Pacific Ocean since 1958. Unusually high market demand ci'eated international interest in the unexploited stock in the eatern Pacific Ocean. Initial studies were concerned primarily with the development of sampling and harvesting gears (Ellis and Hughes, 1971). This paper contains results of research on the biology and availability of saury, except for parasite studies which were treated separately (Hughes, 1973). The purpose of the paper is to provide initial information on stock composition, growth, and mortality and to supplement previous studies of distribution and abundance. Data were ob- tained during research vessel surveys, conduct- ed primarily during August and September 1969 off the California coast, and during August ' Northwest Fisheries Center. National Marine Fisheries Service. NOAA, 2725 Montlake Blvd. £., Seattle, WA 98112. Manuscript accepted July 1973. FISHERY BULLETIN:' VOL. 72. NO. 1. 1974. and September 1970 and 1971 off the Washing- ton and Oregon coasts. STATUS OF KNOWLEDGE Parin (1960) reported that the Pacific saury inhabits the northern Pacific pelagic zone and has a continuous range from Asia to North America. Sokolovskii (1969) inferred from studies of parasites and biological and mor- phometric characteristics of the species that there exist within its total range, stocks dis- tinguishable from one another — western (Asian), central (Aleutian), and eastern (American) — that there is no clear boundary between these stocks, and that there are rather wide zones of mixture of the stocks. The eastern stock ranges from Baja California to the Gulf of Alaska (Ahlstrom and Casey, 1956; Clemens and Wilby, 1961). Novikov and Kulikov (1966) found that in the eastern Pacific Ocean, saury occupied an extensive coastal region 50-70 miles wide between lat. 41° and 48°N during August-October, but that major concentrations were irregularly distributed. Their survey indicated the most dense aggregations occurred off southern Oregon during August, October, 121 FISHERY BULLETIN: VOL. 72. NO. 1 and November in water temperatures of 12.5 to 13.5 °C. Data obtained from night-light station observations off California indicated that in the California Cooperative Oceanic Fisheries Investigations area saury occurred most frequently in waters north of San Fran- cisco in a band 40-120 miles offshore (Smith, Ahlstrom. and Casey. 1970). Peak availability occurred during November. Results of egg surveys suggested peak spawning activity occurs off California during April, May. and June and that the standing stock in the eastern North Pacific Ocean was at least 450,000 to 500.000 tons (Ahlstrom, 1968; Smith et al.. 1970). METHODS The method of finding schools of Pacific sauiy was similar to procedures employed by commercial Japanese saury vessels. The Japa- nese technique has been reviewed by Inoue and Hughes (1971). The Japanese use artificial lights during hours of darkness to visually locate schools near the surface and to attract the fish alongside the vessel for eventual capture. Sonar was also used to assist in detecting concentrations during 1970 and 1971. Our surveys were generally restricted to areas where surface water temperatures were between 13° and 17 °C. Typically, they were conducted along a zig-zag track designed to cross boundaries between warm and cold water masses. Once detected and concentrated under the vessel's alluring lights, the total weight of each school was derived by estimating the percentage of the school captured, weighing our catch, and then computing the weight of the remaining fish. During 1969. surveying was confined to waters off California and fishing was conducted with a Japanese-style boke-ami (Andreev, 1962). Operations were conducted off the Washington and Oregon coasts in 1970 and extended to include waters off Vancouver Island, B.C., during 1971. During those periods fishing was conducted with a small purse seine designed for capturing saury (Ellis and Hughes, 1971). Table 1 summarizes times and locations where fishing was conducted and samples retained for biological studies. Catches were randomly subsampled aboard ship. All samples collected were returned to the laboratory for Table 1 . — Fishing areas and number of Pacific saury collected, 1969-1971. Coastal area Location Sample Date W Long N Lot size Aug 1969 Calif. I24°03' 37°49' 220 Aug 1969 Calif. 124°03' 37°5r 222 Aug 1969 Calif. 124°03' 37°53' 143 Aug 1969 Calif. 123°59' 37°55' 52 Aug 1969 Colif. 123°48' 37°58' 31 Sept 1969 Calif. 122°23' 36° 10' 160 Sept 1970 Greg. 125°50' 45°03' 299 Sept 1970 Greg. 125°11' 44°33' 300 Sept 1970 Greg. 125°08' 44°30' 300 Sept 1970 Wash. 126°02' 47°43' 284 Sept 1970 Wash. 125°58' 47°4r 192 Sept 1970 Wash. 126°00' 47°39' 191 *Julv 1971 Calif. 120°00' 33°00' 98 Aug 1971 Van. Isl. 127°06' 49° 16' 105 Aug 1971 Wash. 126°04' 48°2r 512 Sept 1971 Greg. 125°0r 44°01' 506 Sept 1971 Greg. 124°59' 43°55' 508 Sept 1971 Greg. 125°00' 43°54' 508 Sept 1971 Greg. 125°02' 44°02' 268 Sept 1971 Greg. 125°04' 43°58' Total 419 5,248 * Sample captured with variable mesh gillnet. This sample used only in the growth analysis. processing. Samples taken in 1969 were iced, whereas those collected in 1970 and 1971 were frozen. Only length frequency data were taken from the 1969 samples. Biological data from individual fish obtained during 1970 and 1971 included knob length- measured to the nearest millimeter, body weight to the nearest gram, sex, and maturity. Scales were removed for later examination. Sex determination of fish measuring less than 230 mm was generally difficult. When gross examination of gonads proved inadequate, samples were further subsampled — the gonads cross-sectioned and examined for the presence of a lumen under 10 X binocular microscopes. Age was determined from plastic impressions of scales (Clutter and Whitesel, 1956) examined with a microprojector device (Mosher, 1950). Age determination of Pacific saury has long been a point of contention between Soviet and Japanese scientists working in the western Pacific (Kotova, 1958; Hotta, 1960). Details of assessment criteria by which ages were determined for this report have been documented bv Mosher.^ - Knob length (Kiniura, 1956) — the distance between the tip of the lower jaw and the posterior end of the muscular knob on the caudal base — has been accepted internationally as the unit of length measurement for saury. 3 K. H. Mosher. Age determination of eastern Pacific saury using scales. Natl. Oceanic Atmos. Admin., Natl. Mar. Fish. Serv., Northwest Fish. Center, Seattle, Wash. Unpubl. inanuscr. 122 HUGHES: PACIFIC SAURY OF NORTHEASTERN PACIFIC Preliminary scale studies indicated that the samples might be of two races of fish with different growth patterns — those with a wide zone of initial growth (distance between the focus and first annulus) and those with a much narrower zone of initial growth. Similar growth patterns have been detected by Japanese sci- entists on scales of fish of the western stock of Pacific saury and interpreted as distinct spring- and autumn-born "subpopulations" (Hotta, 1960). Accordingly, fish were classified as being either spring-born, autumn-born, or intermediate type by examining the initial growth zone of the scale. Length-weight regressions and von Bertalanffy growth in length parameters were determined for fish of the spring- and autumn-born scale types and compared statistically. In addition, electro- phoretic techniques (Utter, Hodgins, and Johnson, 1972) were emploj'ed to test for significant inter-area heterogeneity as well as heterogeneity of fish with spring- and autumn- born scale features. STOCK COMPOSITION Temporal and spacial variations in length, age, sex, and maturity are treated in this section. In analyzing the sex ratio and age frequency data, fish of the spring- and autumn-born scale types were treated separately. Size and Age Composition There was a trend toward increasing length and average age with increasing latitude. Mean lengths in the California, Oregon, and Washing- ton-Vancouver Island areas were 201 mm, 238 mm, and 277 mm, respectively (Figure 1). Length frequency histograms (Figure 2) show there was an absence of fish < 160 mm off Washington-Vancouver Island which were represented off Oregon and relatively abundant off California. Conversely, fish > 300 mm were absent off California, represented off Oregon, and relatively abundant off Washington- Vancouver Island. Samples taken off California exhibited an unusual quadra-modal length -frequency distri- bution believed to be a sampling artifact rather than fluctuation in year-class strength. [Three of six schools sampled were schooled by size (Figure 1) which produced the minimum length mode at 165 mm and the maximum length mode at 270 mm.] More symmetrical length distributions were produced from the three schools sampled in 1970 and five schools sampled in 1971 off Oregon. Lengths ranged from 159 mm to 293 mm in 1970 and 158 to 330 mm in 1971. Length distributions for both years are similar, being moderately skewed to the right with a mode at 210 mm in 1970 and 235 mm in 1971. The three schools sampled off Washington in 1970 and two schools off Washington-Vancouver Island in 1971 showed more variation between years than the Oregon samples. A bimodal distribution was more apparent in 1971, modes at 245 and 305 mm, than the moderately asymmetrical distribution in 1970 with mode at 260 mm. Lengths ranged from 160 to 334 mm in 1970, and 161 to 340 mm in 1971. The upper limit of this latter range may exceed the previously known maximum length of the species in the eastern North Pacific Ocean. Clemens and Wilby (1961) reported lengths to 14 inches (356 mm); however, it is unclear whether this is standard or total length. The two saury measuring 340 mm knob length were ripe females measuring 363 and 364 mm in total length and weighing 180 and 190 grams respectively. 50° 48" 38° z o X X -j 1512 I J h284 i|9l _,31 rzt -<5Z -1222 -1220 100 150 200 KNOB LENGTH (mm) 300 Figure 1. — Lengths (mean, range and S.D. of mean) of eastern Pacific saury plotted against latitude of capture. Numbers indicate sample size per school. 123 FISHERY BULLETIN: VOL. 72. NO. 1 A WASHINGTON 1970 N ■ 650 llTTk WASHINGTON OREGON COMBINED 1970 Jl Ilk, WASHINGTON- VANCOUVER ISLAND 1971 N • 619 ,^.^rfltb^ WASHINGTON-VANCOUVER ISLAND OREGON COMBINED 1971 ^ ■^^ni}h ITO I9C ZIO 230 250 270 290 310 220 240 260 280 300 320 340 160 200 220 240 260 280 300 320 340 IQ KNOB LENGTH (mm) CALIfOflNIA 1969 N. 823 Mll^l^ 140 150 (70 190 210 2)0 !50 270 290 KNCB LENGTH (mn) Figure 2. — Length frequency distributions of eastern Pacific saury captured off the Pacific coast of North America during August-September 1970-71. Figure 2 also shows length-frequency dis- tributions for combined Washington-Oregon samples in 1970 and Washington-Vancouver Island samples in 1971. A bimodal distribution is not apparent in 1970 but is distinct in 1971. Little variation in modes is noted between years. Age frequency was determined from the 13 saury schools samjjled off the Oregon-Washing- ton-Vancouver Island coasts during 1970-71. Figure 3 histograms indicate the percentage of age groups by area, year, and areas combined within year. Variations in age comi)osition by latitude followed the expected trend established by size composition. Oregon fish were predomi- nantly 1- and 2-year-olds while Washington- Vancouver Island fish were predominantly 2-, 3-, 4-, and 5-year-olds. Age composition of Oregon samples indicated little variation be- tween 1970 and 1971 with age groups 1 and 2 representing 89% of the 1970 fish and 92% of the 1971 fish. In contrast, Washington fish showed considerable variation between years. In 1970, 93% of the fish were 2- and 3-year-olds while 54% were 4-year-olds in 1971. Sampling deficiencies probably account for the decline in the I'elative abundance of the 1968 year class between 1970 (2-year-old fish) and 1971 (3-year- olds). Fish aged as 6-year-olds were represented in 1970 and 1971 Washington samples, but it appears few fish survive beyond the age of 5. Fish of the spring-born scale type consistently dominated all schools sampled (Figure 4) and also dominated most age groups. The greatest variation occurred at Oregon latitudes where fish of the autumn-born scale type comprised 27% of the 1970 samples and 12% in 1971. Washington sami)les were comprised of 21% autumn-born type in 1970 and 22% in 1971. Sex Ratio and Maturity The sex ratio was examined by age group for variation between area, year, and scale type. Area differences in age composition and difficulties in determining sex of young fish hampered some comparisons; however, numbers of males and females were about equal through age 3 with females becoming predominant at age 4 and beyond. For more meaningful anal- ysis, ages 1-3 and 4-6 were pooled for each area- year category. The sex ratio of saury of autumn- and spring-born scale types were next examined and found so similar that statistical treatment was unnecessary. Sex ratios of area-year-age group categories are presented in Table 2. While the sex ratio was age-dependent, sex composi- tion differences in 1-3 year-olds of Washington vs Oregon catches in both 1970 and 1971 and 4-6 year-olds of Washington vs Oregon catches in 1971 were nonsignificant (0.05 level). Size and age at first maturity could not be 124 HUGHES: PACIFIC SAURY OF NORTHEASTERN PACIFIC 60- 50- ^^ Oregon 1970 40 ^m N = 7I3 > O ^^^ z ^^^ ^ 30' ^^^ 3 O ^^^ u ^^§{ J 20- m S5 ^B 10' 0-' P 2 3 4 5 6 Washington 1970 N = 608 12 3 4 5 6 AGE IN YEARS Washington- Oregon Combined 19 70 N=I32I 2 3 4 5 6 Oregon 1971 N=|450 3 4 5 6 Woshington- Vancouver Island 1971 522 Woshington- Voncouver Island, Oregon Combined 1971 N = 1905 I 2 3 4 5 6 AGE IN YEARS 12 3 4 5 6 Figure 3. — Age frequency distributions of eastern Pacific saury captured off the Pacific coast of North American during August-September 1970-71. 50- Oregon 1970 Woshington 1970 Woshington -Oregon pS5 N = 7I3 1^- N = 606 Combined 1970 FREQUENCY ^ i ■ N = I3I9 1 "1 i ::¥: J 1^ ss mM m ■ II :■!■: 10- 0- m PU , , J fcM^^ ^ ■1 Ji ^^^^'>i 1 50-1 ^ Ore gon 1971 :|:S N = 1450 > 40- m o M :•:■:• ^ m ;•:•:■ UJ 3 30 4 ^ o m ::: LlJ m :W e 20 ss 10- II ■^ 0^ 1 1 > 3 4 5 6 I 2 3 4 5 6 AGE IN YEARS Washington- Vancouver Island 1971 Spring Born [ Fish [ Autumn Born I Fish I Washington-Vancouver Island, Oregon Combined 1971 N= 962 12 3 4 5 6 AGE IN YEARS Figure 4. — Age frequency distributions of eastern Pacific saury showing age groups separated into spring- and autumn-born fish. 125 FISHERY BULLETIN: VOL. 72. NO. 1 Table 2.— -Sex ratios of age groups sampled in areas off the Pacific coast. 1970- 197 L Total No. fish Year-area Age no. fish used for Sex ratio category group examined sex ratio (°o males) 1970 Wash. 1-3 578 253 49.4 Greg. 1-3 702 143 43.4 Wash. 4-6 28 26 30.8 Greg. 4-6 10 10 0.0 )971 Wash. -B.C. 1-3 179 100 54.0 Greg. 1-3 1,365 1,024 56.1 Wash. -B.C. 4-6 391 388 37.6 Greg. 4-6 8 6 33.3 directly determined from my samples since all but the very large fish were sexually inactive or immature upon collection. However, egg measurements obtained for ten 300-330 mm females collected off Washington in 1971 showed there were three distinct size groujis of eggs: 0.1 — 0.4 mm, 0.8 — 1.5 mm, and the mature mode of 1.7 — 2.0 mm. Eleven smaller specimens collected off California by Mac- Gregor^ in March 1951 and 1954 ranged from 196 to 204 mm and contained eggs with a similar range (0.84 — 1.9 mm) indicating that saury are capable of reaching first maturity at lengths near 200 mm. Such fish would probably range from 1.1 to 1.4 yrs. old (Table 3). Eighteen of the 19 schools sampled were composed principally of apparently mature fish in a resting state. The remaining school was predominantly 4-year-olds with females out- numbering males 1 to 0.73, and 96% of these were in spawning condition. Fish displaying both spring-born and fall-born growth patterns of scales were found in this school. LENGTH-WEIGHT RELATION The length-weight relation of saury captured in 1970 and 1971 was determined by fitting the logarithmic form of the equation W = qL^ , where W is weight in grams and L is knob length in millimeters, to mean emperical weights in each 5-mm length interval. Separate relationships were determined for each hypothesized race and area-year category by sex. Using an analysis of covariance (Dixon and Massey, 1969), no significant difference in the L-W relation was detected between years, areas, or scale type, but there was a significant difference (0.05 level) between males and females. A total of 1,170 males and 1,642 females representing immature, mature resting, and ripe saury were included in the length-weight regressions presented in Figure 5. The equation for males was W = 3.293 X IQ-^L^oso ^nd for females W = 2.077 X 10"^ L3132 pemales were slightly lighter than males at lengths <225 mm and heavier than males at lengths >280 mm. GROWTH Interpretation of growth was complicated because of the possible racial aspect and extended spawning season. Growth was deter- mined for sexes combined because of the high probability of error in determining the sex of young fish. It was assumed that growth in length is asymj)totic and that the von Berta- lanffy (1938) growth equation adequately rei)resents such growth. Following methods of Stevens (1951), average lengths (observed and calculated from weight at age) were fitted to the equation It = L^ [1 -e-^<'-'o)]. 140- 130 i y 90 60' 50 Molls W- 3,293 X 10"^ L^^^ Ftmol** W=2.077 X lO'^L^ •* J. MacGregor, Fishery Biologist, Natl. Oceanic Atmos. Admin., Natl. Mar. Fish. Serv., Southwest Fish. Center, La Jolla, Calif., personal commun. 180 200 220 240 260 280 300 320 340 200 220 240 260 280 300 320 340 360 KNOB LENGTH (mm) Figure 5. — Length-weight relation of male and female saury. The curve is fitted to mean-observed weight per .■^-mm length interval. 126 HUGHES: PACIFIC SAURY OF NORTHEASTERN PACIFIC Table 3 Average observed length at age, lengths calculated from weight at age and estimated von BertalantTy growth parameters of hypothesized spring- and autumn-born fish. Spring born fish Autumn born fish Age Average observed Length calculated Age Average observed Length calculated (years) len gth at age { mm) from weight at age ' (mm) (years) length at age (mm) from weight at age- (mm) 1.10 183.9 182.5 0.75 142.8 151.2 1.40 219.0 223.6 1.00 178.7 182.1 2.40 245.5 249.3 2.00 232.1 235.8 3.40 268.8 272.7 3.00 256.8 260.6 4.40 308.6 312.5 4.00 297.0 303.0 5.40 319.8 321.4 5.00 314.5 316.8 6.40 319.9 323.0 L„= 351.43 L„ = 360,23 L^ = 353.45 L„= 348.50 K = 0.34 K = 0.36 K = 0.38 K = 0.38 'o = - 1.19 'o = -0-83 'o = -0-72 'o= -l-°2 1 HZ = 1.497 X 10-«Z.3 .iMa 2 K/ = 1.809 X 10-BZ.3 .155 Growth was first compared between fish of the autumn- and spring-born scale type. Table 3 summarizes the respective sets of length at age data and jn-esents growth parameters. Little difference is noted between respective sets of length at age data for the two groups of fish. Although there is no consistent advantage in using lengths derived from weights at age. it should be noted that estimated t^ values are sensitive to the method chosen. Regardless of method, no significant differences in growth parameters L^ and e~^ existed between fish of spring- and autumn-born scale types. Their graphic similarity is shown in Figure 6 where observed lengths at age and fitted curves are presented. Lack of significant differences in growth patterns between fish of spring- and autumn-born type suggested that respective data sets be pooled and that a single growth curve be presented (Figure 7). The resulting estimated parameters were L^ = 342.36, K = 0.41, and t^ = -0.72. The calculated Lqo is close to the maximum observed length of 340 mm. The estimated age at 95% growth completion was 6.5 years. 2 3 AGE lYEARSI Figure 6. — Average observed length at age and fitted growth curves of spring- and autumn-born saury captured in offshore waters from southern California north to Vancouver, British Columbia 1970-71. Figure 7. — Average observed length at age and fitted growth curve of eastern Pacific saury after pooling data from spring- and autumn-born fish. 127 FISHERY BULLETIN: VOL. 72, NO, 1 MORTALITY There are several limitations to the data used for estimating natural mortality: (1) Sampling was conducted during a period of apparent migration which caused the stock along the Pacific coast to become stratified in size and age composition. (2) sampling was limited and not conducted throughout the stock's entire geographical range, and (3) age frequency data indicate possible variations in annual recruitment and/or survival rate. Thus, one or more basic assumptions underlying tradition- al mortality models are violated to some degree. Realizing the above limitations and considering this an initial study of the adult stock, I have generated a- range of estimates using several independent techniques. A catch curve analysis (Robson and Chapman. 1961) was applied to the 1970 data since equal sampling occurred off Washington and Oregon, the only areas sampled, during that period. Coded No. offish Age age in catch II 0 A'o = 644 III 1 A^ = 313 IV 2 A^ = 32 V 3 A^3 = 7 VI 4 A^ = 1 = 997 Annual survival rate estimate: S Var (.s) SE (.s) 95% CI (.s) .2876 0.00017 0.013 .2876+ 2(0.013) = (.2616, .3136) When the above data were converted to a total annual in.stantaneous mortality rate, Z = 1.25 and 95% CI, Z = (1.16, 1.34). The raw age data were also converted to natural log form and treated by simple linear regression. The result was a significant linear relationship with Z = 1.67 and 95% CI, Z = (1.41, 1.93). Beverton and Holt's (1956) formula using length frequency data was also applied to the 1970 data. While this technique was designed primarily for exploited pojjulations, its use generated another independent estimate and enabled the use of substantial numbers of fish which could not be aged. The Beverton and Holt formula Z = KiL^-L) where L is the average length of (L - L,) the fish in the catch that are as large as, or larger than, the first fully recruited length Lf, estimated Z = 1.41 when L^ = 342 mm, K = 0.41, L = 248 mm, and L^ = 220 mm. Survival rates were generated for each of the four area-year categories by subjecting resijective sets of age frequency data to Jackson's (1939) technique: S = N^^N,^ + N„ A^i + A^2 + + N-1 The analysis yielded the following estimates: Oregon, 1970; Z = 1.58, Oregon, 1971; Z = 1.80, Washington, 1970; Z = 2.20. Washington-Vancouver Island, 1971; Z = 1.27. The seven individual estimates obtained indicate a possible range of Z from 1.25 to 2.20 and an overall average Z of 1.60. AVAILABILITY OF FISHABLE CONCENTRATIONS Fishable concentrations of saury (>% ton) were usually located in waters of 15°-17°C near areas of upwelling. Surface temperatures strongly influence distribution and migration patterns of western Pacific saury (Fukushima, 1956 and 1962) as they appear to in the eastern Pacific (Ellis and Hughes, 1971). All studies indicate sharp thermal fronts affect and often dictate patterns of migration and areas where temporary concentrations may form. Throughout the surveys, high density areas capable of sustaining productive fishing opera- tions were rarely encountered. Most encounters were single schools (1-3 tons) or loose aggrega- tions offish dispersed over large areas of surface waters. The average probability of locating at lea.st one fishable concentration during a night's oi)eration (averaging 8 hr of searching- effort and 70 miles of tracklines) was about 0.3. The relative densities decreased slightly with increasing latitudes, but large saury, which are currently in greatest commercial demand, were 128 HUGHES: PACIFIC SAURY OF NORTHEASTERN PACIFIC more available in the northern portion of the study area. Low availability has evidently hampered Japanese attempts to establish new fishing grounds in the eastern Pacific. Operations by about 15 Japanese saury vessels in 1970 and 19 vessels in 1971 met financial failure. Conse- quently, major fishery firms such as Nihon Sui-san, Hoko Suisan, and Nichiro have reportedly abandoned attempts to exploit the eastern Pacific saury resource."' DISCUSSION It seems pertinent to propose some general hypotheses about the life history of the eastern Pacific saury based on information presented here and in papers by Ahlstrom and Casey (1956). Ahlstrom (1968), and Smith et al. (1970). The coastal stratification of saury by size and age composition during at least August- September is probably due to a northerly migration by many adults from California waters. Sea surface temperatures and position of warm-cold fronts strongly influence migra- tion patterns and rates of movement of saury in the western North Pacific Ocean (Fukushima. 1956, 1962). Several factors indicate a similar situation exists in the eastern Pacific Ocean. Our surveys indicated eastern Pacific saury display narrow limits of thermal preference and are found most often near areas of up- welling. Furthermore, there is an excellent correlation between the apparent spacial and temporal distribution of saury and average month-by-month sea-surface temperature data. Using Johnson's (1961) 12-year monthly means andathermal preference range of 14.0° to 17.0°C, it is a]:)parent that large quantities of saury would not begin a northerly migration from California waters before June. Migration into northern Oi'egon and Washington waters would not be expected to occur before July. Rapid warming during July and August produces a favorable temperature regime along the coasts of Washington, Vancouver Island, and into Queen Charlotte Sound. While temperature conditions remain favorable in September, ' J. H. Shohara (Compiler). 1972. 12 Japanese vessels licensed for distant-water saury fishing [Excerpted from Shin Suisan Shimbun Sttkuho. July 18 and July 29, 1972]. U.S. Dep. Commer.. Natl. Oceanic Atmos. Admin., Natl. Mar. Fish. Serv., Foreign Fish. Inf. Release 72-27, p. 3. (Processed.) seasonal cooling occurs off Vancouver Island and Washington during October and continues through Oregon and northern California waters in November. Thus, it appears that in addition to influencing the time and patterns of saury migration, temperature conditions could also restrict the bulk of the stock to oceanic areas between Baja California and Queen Charlotte Sound or the southern Gulf of Alaska. From the data presented, the degree of migration appears to be dependent on size and age of fish, and many young adults and juveniles apparently remain in California waters throughout the year. Fish exceeding 300 mm in length (primarily ages 4, 5, and 6) reach maturity during the migration in August and release their mature mode of eggs (1.8-2.0 mm) in late August or September. Since Hatanaka's (1956) work on maturity in the western North Pacific Ocean (three modes of eggs, 0.6, 1.1, and 1.9 mm) is in close agreement with this study, it seems reasonable that eastern Pacific saury release modes of eggs at about the same intervals — 2 months between the first and middle mode. Thus, the second spawning of large fish would probably take place in October or November and the third spawning during the winter while off California. Younger adults, sexually inactive during August-September, probably mature and spawn during the following winter and spring while in more southerly waters, primarily off California. It is not known whether 2- and 3-year-old fish spawn more than one mode of eggs per year. The above hypothesis would account for the reported low abundance of eggs in California waters during August-September (Smith et al., 1970) when most spawning saury occupy a northerly regime. The spawning of younger age groups coincides with peak egg abundance in California during April, May, and June. Such an extended spawning season would account for spring-born, autumn-born, and some intermediate growth patterns detected from scale samples, as well as the fact that three-quarters of the samples displayed the spring-born growth characteristic. There seems to be little likelihood that spring- and fall-born fish constitute different races, since both types were observed spawning to- gether in the same school. Furthermore, statistical comparisons of length-weight and 129 FISHERY BULLETIN: VOL. 72, NO. 1 growth parameters failed to disclose any significant differences between these groups. These results are in line with unpublished results of Utter whose biochemical gene fre- quency studies gave no indication of hetero- geneity between spring-born and fall-born saury.*' Biochemical techniques also indicated intra-area homogeneity of fish in waters be- tween southern California and Vancouver Island. Additional samples would have been desirable for a more complete racial study; however, results of this initial study strongly suggest the eastern Pacific saury stock is basi- cally represented by a single gene pool. Growth, maturity, and mortality studies indicate that saury (1) display rapid growth during the first year of life, (2) are capable of attaining maturity during the second year, and (3) probably do not survive beyond 6 years of age. Results indicate the total mortality co- efficient (Z) is between 1.25 and 2.20. Since fishing mortality has remained insignificant, Z would be a result of natural mortality {M), assuming migration during the sampling period has not significantly confounded the situation. Intuitively, it seems Z is a reasonable approxi- mation of M since sampling was conducted over a wide geographical area during the middle of the migratory period. No previous estimates of natural mortality have been published for the eastern Pacific saury stock; however, Novikov (1969) reports natural mortality in the western Pacific to be about 50% . Con- verting to instantaneous mortality for direct comparison, his e.stimate would be about 0.70. ACKNOWLEDGMENTS Robert Larsen, Ma.ster of the research vessel J(>h)i N. Cohh, and his entire crew rendered exceptional service and helpful suggestions during the field operations in 1970-71. I also thank George Hirschhorn of the Northwest Fisheries Center for valuable assistance in the growth studies. LITERATURE CITED Ahlstrom, E. H. 1968. An evaluation ot" the fishery resources available '• F. Utter, Biochemical Geneticist, Natl. Oceanic Atmos. Admin., Natl. Mar. Fish. Serv., Northwest Fish. Center, Seattle, Wash., personal commun. to California fishermen. Univ. Wash., Publ. Fish., New Ser. 4:65-80. Ahlstrom, E. H., and H. D. Casey. 1956. Saury distribution and abundance, Pacific Coast, 1950-55. U.S. Fish Wildl. Serv., Spec. Sci. Rep. Fish. 190, 69 p. Andreev, N. N. 1962. Stick-held dip net for saury fishing. In N. N. Andreev, Spravochnik po orudiyam leva, setesna- stnym materialam i proniyslovomu snarya- zheniyu (Handbook of fishing gear and its rigging). Pishchepromizdat, Moscow, p. 459-462. (Translated by Israel Program Sci. Transl., 1966, p. 418-420; available U.S. Dep. Commer., Natl. Tech. Inf. Serv., Springfield, Va. as TT 66-5 1046.) Bertalanffy, L. Von 1938. A quantitative theory of organic growth (Inquiries on growth laws. II.) Hum. Biol. 10:181- 213. 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, Part 1:67-83. Clemens, W. A., and G. V. Wilby. 1961. Fishes of the Pacific coast of Canada. 2d ed. Fish. Res. Board Can. Bull. 68, 443 p. Clutter, R. I., and L. E. Whitesel. 1956. Collection and interpretation of sockeye salmon scales. Int. Pac. Salmon Fish. Comm., Bull. 9, 159 p. Dixon, W. J., and F. J. Massey, Jr. 1969. Introduction to statistical analysis. 3d ed. McGraw-Hill, N.Y., 638 p. Ellis, I., and S. E. Hughes. 1971. Pacific saury — A progress report. Natl. Fisher- man Yearb. Issue 1971 5 1( 13):67-70, 75, 77, 84-85, 92. FUKUSHIMA, S. 1956. On the size-composition of the Pacific saury, Calolahis saira, caught in the North-eastern Sea area of Japan. [In Jap., Engl, summ.] Bull. Tohoku Reg. Fish.Res. Lab. 7:12-36. 1962. On the relation between the pattern of the Kuroshio Current in spring and summer and the saury fishing conditions in fall. [In Jap., Engl, summ.] Bull. Tohoku Reg. Fish. Res. Lab. 21:21-37. Hatanaka, M. 1956. Biological studies on the population of the saury, Cololahis saini (Brevoort). Part I. Reproduc- tion and growth. Tohoku J. Agric. Res. 6:227-269. HOTTA, H. 1960. On the analysis of the population of the saury (Cololahis sciiru) based on the scale and otolith characters, and their growth. [In Jap., Engl, summ.] Bull. Tohoku Reg. Fish. Res. Lab. 16:41-64. Hughes, S. E. 1973. Some metazoan parasites of the eastern Pacific saury, Cololahis saira. Fish. Bull., U.S. 71:943-953. Inoue, M.S., and S. Hughes. 1971. Pacific saury {Cololahis saira): A review of stocks, harvesting techniques, processing methods and markets. Oreg. State Univ., Corvallis, Eng. Exp. Stn. Bull. 43, 102p. 130 HUGHES: PACIFIC SAURY OF NORTHEASTERN PACIFIC Jackson, C. H. N. 1939. The analysis of an animal population. J. Anim. Ecol. 8:238-246. Johnson, J. H. 1961. Sea surface temperature monthly average and anomaly charts northeastern Pacific Ocean, 1947-58. U.S. Fish Wildl. Serv., Spec. Sci. Rep. Fish. 385, 56 p. KiMURA, K. 1956. The standard length of the Pacific saury, Cololahis saini (Brevoort). [In Jap., Engl, summ.] Bull. Tohoku Reg. Fish. Res. Lab. 7:1-1 1. KOTOVA, L. I. 1958. O biologii razmnozheniya sairy v Yaponskom more (The biology of reproduction of the saury in the Sea of Japan). Rybn. Khoz. 34(10):6-10. (Transl. Natl. Mar. Fish. Serv., Foreign Fish (Transl.), Wash., D.C.) MOSHER, K. H. 1950. Description of a projection device for use in age determination from fish scales. U.S. Fish Wildl. Serv., Fish. Bull. 51:405-407. NOVIKOV, N. P., AND M. Yu. KULIKOV. 1966. Perspektivnyi raion promysla sairy (Prospec- tive region for saury fishing). Rybn. Khoz. 42(7):20-21. (Transl. Natl. Mar. Fish. Serv., Foreign Fish. (Transl.). Wash., D.C.) NoviKOV, Yu. V. 1969. Zapasy sairy i regulirovanie ee promysla (Conditions of the saury stocks and the regulation of their fisherv.) Tr. Vses. Nauchn.-issled. Inst. Morsk. Rybn (Transl., Natl. (Transl.), Wash., D.C.) Parin,N. V. 1960. Areal sairy socidae. Pices) Khoz. Okeanogr. 67: 190-200. Mar. Fish. Serv., Foreign Fish. (Cololahis sairu Brev. — Scombre- i znachenie okeanograficheskikh faktorov dlya ee rasprostraneniya (The range of the saury (Cololahis saira Brev. — Scombresocidac, Pisces) and effects of oceanographic features on its distribution). Dokl. Akad. Nauk SSSR New Ser. 130(3):649-652. RoBSON, D. S., AND D. G. Chapman. 1961. Catch curves and mortality rates. Trans. Am. Fish. Soc. 90: 181-189. Smith, P. E., E. H. Ahlstrom, and H. D. Casey. 1970. The saury as a latent resource of the California Current. Calif. Coop. Oceanic Fish. Invest. Rep. 14:88-130. SOKOLOVSKII, A. S. 1969. K voprosu o stadakh sairy v Tikhom okeane (Populations of saira in the Pacific Ocean). Izv. Tikhookean. Nauchn.-issled. Inst. Rybn. Khoz. Okeanogr. 68:203-208. (Transl., 1971, Fish Res. Board Can. Transl. Serv. 1614.) Stevens, W. L. 1951. Asymptotic regression. Biometrics 7:247- 267. Utter, F. M., H. O. Hodgins, and A. G. Johnson. 1972. Biochemical studies of genetic differences among species and stocks of fish. Int. North Pac. Fish. Comm., Annu. Rep. 1970:98-101. 131 HEAVY METALS IN THE NORTHERN FUR SEAL, CALLORHINUS URSINUS, AND HARBOR SEAL, PHOCA VITULINA RICHARDI Raymond E. Anas' ABSTRACT Samples of liver, muscle, and kidney from fur seal, Callurhimts iirsimis, and liver from harbor seal, Pliocu viiiilina ricliarcli, were analyzed for lotal mercury. Liver and kidney of fur seals were analyzed for lead, cadmium, and arsenic. Fur seals were from the Pribilof Islands, Alaska, and from off the Washington coast. Harbor seals were from the waters of southern California, Oregon, Washington, and the Bering Sea. All of the samples, including a fetus taken 3 mo before birth, contained mercury, lead, and cadmium. Arsenic was not detected. Mercury was highest in liver, followed by kidney, then muscle. The maximum concentration of mercury in liver was about 700 ppm in a southern California harbor seal and 170 ppm in a fur seal taken off the Washington coast. Concentrations of cadmium and lead were highest in the kidney (maximums of 1.8 ppm lead and 15.6 ppm cadmium) of fur seals. Concentra- tions of mercury did not correlate with age in muscle or kidney (P> 0.05) but did correlate significantly with age in liver iP < O.OI). Concentrations of cadmium and lead in liver and kidney did not correlate with age (P > 0.05). In samples of liver collected from harbor seals, the highest concentrations of mercury were from southern California seals. Heavy metals are persistent contaminants that ultimately end up in the oceans. Little is known of the sublethal effects of these contaminants on living marine resources, but some heavy metals are known to be harmful. One ppb (part per billion) of four commonly used organo- mercurial fungicides reduced the photosynthetic rate of a marine diatom (Harriss, White, and MacFarlane, 1970). Skerfving, Hansson, and Lindsten (1970) reported chromosome break- age in humans who ate fish containing 1-7 i)pm (parts per million) methylmercury. Heavy metals are added to the sea by land erosion, volcanic activity, and man. A committee of experts selected mercury, lead, cadmium, and arsenic as the four inorganic jjollutants most threatening to the marine environment (Food and Agriculture Organization of the United Nations, 1971). The same elements were selected for this study. Average levels of the four most critical heavy metals in the ocean are about 0.00003 ppm (mg/1) mercury, 0.08 ppm cadmium, 0.00003 ppm lead, and 0.003 ppm arsenic (U.S. Senate, 1970). Williams and Weiss (1973) found 0.00027 ppm mercury at 10-m depth and 0.000029-0.000096 ppm from 100- to 4,080-m depth in water samples taken 430 km southeast of San Diego, Calif. Amounts of contaminants in seals provide us with data at this time in a marine species near the top of the food web in the ocean. Up to 172 ppm mercury in liver of northern fur seals, CaU(>)-}uinis in-si))t(i^ (Anas, 1970a); 66 ppm in liver of gray seals, Hallchoerus gnjpi(s (Jones, Jones, and Stewart, 1972); and 24 ppm mercury in liver of short-finned pilot whales, Globi- cephala scammo)n (Hall, Gilmailin, and Mattsson, 1971) have been reported. Buhler- repoited 60 ppm cadmium in the kidney, 6 ppm cadmium in the liver, and 225 p])m mercury in the liver of California sea lions, Zalophus califnniiaHu.s. This report documents the amounts of mercury, lead, cadmium, and arsenic in northern fur seals and of mercury in harbor seals, PJioca vitulhia richardi. Northern fur seals are a migratory species that breed each summer mainly on the Pribilof Islands, Alaska, and on the Commander Islands ' Northwest Fisheries Fisheries Service, NOAA, Seattle, WA 98 112. Center, National Marine 2725 Monllake Blvd. E., Manuscript accepted June. 1973 FISHERY BULLETIN: VOL. 72. NO. 1, 1974 - D. R. Buhler. Environmental Health Sciences Center, Oregon State University, Corvallis. Oregon 97331, per- sonal communication. 133 FISHERY BULLETIN: VOL. 72. NO. 1 and Robben Island, USSR. Small breeding colonies are found in the Kurile Islands, Japan, and on San Miguel Island, Calif. During winter and sjiring, fur seals are pelagic and migrate as far south as southern California and Japan. Fur seals feed principally on fishes and squids in offshore areas. Harboi- seals are a nonmigratory species found in the northern hemisphere in both the Pacific and Atlantic Oceans. Those collected for this study (subspecies )-icli(irdi) are found from Mexico to the Bering Sea. Harbor seals feed principally on fishes, s(iuids, and octoi)uses near coastlines. METHODS The liver and kidneys were selected as the principal tissues for this study because heavy metals tend to accumulate in these organs (DuBois and Ceiling, 1959; Curry, 1969). Sami)les of muscle were collected from fur seals but not from harbor seals. Collection of Samples In general, the sampling was conducted as follows: From a seal liver weighing about 1.8 kg. a kidney weighing about 0.5 kg, or muscle from the shoulder area, a sample of about 75 g was placed in a new unwashed glass bottle or l)olyethylene bag and stored at — 23°C. Analyses were made about 5 mo after initial sami)ling. Samples included liver and muscle from 3-mo- old pups and 2- and 3-yr-old male fur seals from the Pribilof Islands; liver, muscle, and kidney from fur seals (mostly adult females) from Washington; and liver from harbor seals from California, Oregon, Washington, and the Bering Sea. Tissues from fur seals taken on the Pribilof Islands were kept in jjolyethylene bags; all other tissues were kei)t in new glass bottles. Analyses of Samples For the analysis of mercury, four rei)licate 20-mg samples were taken from a piece of tissue in the sam])le bottle and analyzed. The mean of these four replicates was taken as representative of the i)articular tissue for that analysis. The analytical procedure for mercury involves introduction of the weighed sample into a tubular furnace from which the products of combustion and vaporized mercury are drawn. After scrubbing and filtering to remove interfering components, the mercury vapor is passed through a cell and read by atomic absorption spectrophotometry.'' For lead, cadmium, and arsenic analyses, a separate 2-g sami)le was taken for each metal. The lead analysis was carried out by digesting the sample in a 5:2 nitric-sulfuric acid mixture followed by dry ashing in a muffie furnace at 550° C until all organic material was removed. Following dissolution in 5 ml of hydrochloric acid, lead content was determined by the double extraction, mixed color dithizone method (Committee on Chemical Procedures of the Occupational Health Section, American Public Health Association, 1955). For cadmium, the .sample was wet ashed in a 2:1 nitric-perchloric acid mixture, and the re.sultant solution diluted to a known volume with water. The cadmium was extracted into methyl isobutyl ketone (MIBK) by means of chelation with sodium diethyldithiocarbamate (NDDC) and measured by atomic absorption (Berman, 1967). For arsenic, the sami)le was wet ashed in an 8:4:1 nitric-perchloric-sulfuric acid mixture to oxidize organic matter and release organically bound arsenic. Following digestion, the sample was diluted to 25 ml volume with water and arsenic determined by the silver diethyldithio- carbamate method (American Public Health Association, 1971). Detection limits of the analyses were 1 i)pb for mercury, 0.1 ppm for lead, 0.01 ppm for cadmium, and 0.2 i)i)m for arsenic. Recoveries were over 90% for mercury and cadmium where mercury was added as elemental mercury dissolved in nitric acid and cadmium was added as cadmium sulfate. Lead and arsenic recoveries wei"e over 95% with lead added as lead nitrate and arsenic added as arsenic trioxide. All of the tissue samples were analyzed by Environmental Health Laboratories Inc., ! Hermann, W. J., Jr., J. W. Butler, and R. G. Smith. 1468. A dynamic system for the rapid microdetermination of mercury in undigested biological materials. Presented at Applied Seminar on Laboratory Diagnosis of Diseases Caused bv Toxic Agents, Washington. D.C., Nov. 8-9, 1968. Wayne State Univ.. Detroit. Mich., Dep. Med., 14 p., 1 fig. (Processed.) 134 ANAS: HEAVY METALS IN SEALS Farmington, Mich.^ A sample of paper lid liners from the glass bottles was analyzed by the use of neutron activation by Battelle Pacific North- west Laboratories, Richland, Wash., to deter- mine amounts of mercury, lead, cadmium, and arsenic. Age Determinations Ages were assigned to fiir seals by counting layers of dentine in sectioned upper canine teeth (Scheffer, 1950; Fiscus, Baines, and Wilke, 1964). Errors in assigning ages to fur seals are small in young seals but increase sharply in animals older than 7 yr (Anas, 1970b). Most errors in older animals, however, are only of a magnitude of ± 2 yr. Although canine teeth of harbor seals have layers of den- tine, it is not known if these layers accurately portray age. Ages were not assigned to harbor seals, but body lengths were taken. RESULTS Heavy Metals in Fur Seal Tissues Amounts of total mercury were higher in liver than in muscle or kidney of fur seals (Table 1). Mercury in liver ranged from 0.4 ppm in a fetus taken 3 mo before birth (the liver of the 11-yr-old mother had 86 ppm), to 0.1-0.3 ppm in 10 pups, 3-19 ppm in 30 young males, 7-78 ^ Reference to trade names does not imply endorse- ment by the National Marine Fisheries Service, NOAA. ppm in two young females, and 19-172 ppm in 36 adult females. For muscle, 0.1 ppm was found in five pups, 0.1-0.4 ppm in 29 young males, and 0.2-0.4 ppm in 10 adult females. Mercury in kidney ranged from 0.2 ppm in a fetus (the mother had 1 ppm), to 0.7 ppm in a young male, and 0.6-1.6 ppm in eight females, 1 to 20 yr old. A wide range of mercury was found only in the liver, so variability due to sampling is more important for liver than for muscle or kidney. The 95% confidence limits of within-sample variability for the 20-mg samples of liver were ± 11% of the mean values. The average variabil- ity between seals within ages was 55 times greater than the variability within the 20-mg samples. Thus, to increase accuracy, larger samples of seals are more important than addi- tional 20-mg samples from each piece of liver. Methylmercury was not determined in this study. However, in samples of liver from Cal- ifornia sea lions, about 2% of the total mercury was methylmercury (Buhler, see Footnote 2). On the average, amounts of lead and cadmium were higher in kidney than in liver (Table 2). Arsenic was not detected in any of the samples. Lead in liver ranged from 0.8 ppm in a fetus (the mother also had 0.8 ppm), to 0.2 ppm in a young male, and 0.4-0.8 ppm in eight females. Lead in kidney ranged from 0.3 ppm in a fetus (0.8 ppm in the mother), to 1.8 ppm in a young male, and 0.8-1.2 ppm in eight females. Cad- mium in liver ranged from 0.5 ppm in a fetus (4.6 ppm in the mother), to 0.6 ppm in a young Table 1. — Parts per million mercury on a wet weight basis in liver, muscle, and kidney of fur seals taken off Washington and on the Pribilof Islands, 1970-71. Age Year N jmber (years) Sex Area collected of seals Tissue Mercury 0.3 (Pups) Mixed Pribilof 1970 10 Liver 0.1- 0.3 Islands 1970 5 Muscle 0.1 2-3 Male Pribilof 1970 29 Liver 3.0- 19.0 Islands 1970 29 Muscle 0.1— 0.4 5-19 Female Washington 1970 29 Liver 19.0-'72.0 Coast 1970 10 Muscle 0.2- 0.4 Fetus Male Washington 1971 1 Liver 0.4 Coast 1971 1 Kidney 0.2 1 Male Washington 1971 1 Liver 3.7 Coast 1971 1 Kidney 0.7 1-20 Female Washington 1971 8 Liver 7.1—132.0 Coast 1971 8 Kidney 0.6- 1.6 135 FISHERY BULLETIN: VOL. 72. NO. 1 Table 2. — Parts per million cadmium and lead on a wet weight basis in kidney and liver of fur seals taken off Washington, 1971.' Age (years) Sex Kid ney Liver of of specimens specimens Cadmium Lead Cadmium Lead Fetus M 0.1 0.3 0.5 0.8 1 M 1.7 1.8 0.6 0.2 1 6.9 0.8 0.9 0.6 3 4.3 0.8 2.2 0.6 6 15.6 1.2 2.6 0.6 8 0.2 0.9 1.2 0.5 11 6.2 0.8 4.6 0.8 15 9.6 0.9 1.1 0.4 16 1.0 1.0 1.7 0.5 20 6.8 0.8 1.7 0.7 ' Arsenic was not found obove the limit of detection of 0.2 ppm (mg/kg) in either kidney or liver in any of the samples. male, and 0.9-4.6 ppm in eight females. Cad- mium in kidney ranged from 0.1 ppm in a fetus (6.2 ppm in the mother), to 1.7 ppm in a young male, and 0.2-15.6 ppm in eight females. Lid liners from new glass bottles had 1.1 i)pm mercury and 0.4 ppm arsenic. Lead and cad- mium were not detected. The tissues and lid liners were never in direct contact, but some transfer of mercury from the lid liners and glass bottles could have occurred. However, the maximum contribution from the lid liners would have been 0.004 ppm mercury, so the data were not adjusted. Heavy Metal — Age Comparisons in Fur Seals Regression equations were computed for samples from fur seals collected in 1970 and 1971 to determine if mercury in liver, muscle, and kidney and if lead and cadmium in liver and kidney were correlated with age. Signifi- cant correlations for mercury have been reported for fur seal liver (Anas, 1970a) and whole fishes (Bache, Gutenmann, and Lisk, 1971). Untransformed data were used here because log transformations did not significantly improve the correlations. Fetuses and pups were not included in the calculations. Only liver tissues were collected both in 1970 and 1971. The correlation coefficients in the two years for mercury in liver were common (P>0.05), so the dataware pooled. Mercury in liver had a signi- ficant positive correlation with age (P< 0.001, r — -1-0.84). The data indicate that mercury accumulates in liver. Mercury in muscle and kidney did not correlate with age (P>0.05, r = -h 0.05 and +0.51, respectively). Also, lead and cadmium in liver and kidney did not correlate with age (P>0.05. r = +0.19 and -0.45 for lead and r — +0.17 and + 0.04 for cadmium in liver and kidney, respectively). Sample sizes were 67 for mercury in liver, 39 for mercury in muscle, and 9 for cadmium and lead in liver and kidney. Mercury in Harbor Seal Livers Harbor seals are nonmigratory, so levels of contaminants in this species are useful for locating geographical concentrations of con- taminants, provided that the food species do not migrate long distances. Studies suggest that the principal food species of harbor seals do not migrate far (Scheffer and Sperry, 1931; Spalding, 1964; Kenyon, 1965). The highest levels of mercury were found in harbor seals from San Miguel Island (Table 3). One harbor seal from San Miguel Island had 700 ppm mercury in the liver. The amount of mercury in this sample is so much higher than the amounts found in the other seals that the possibility of contamination of the sample should be considered. However, as far as is known, this sample was treated no differently than the other samples. The sample size is small and the ages are not known, but the concentrations of Table 3. — Parts per million mercury on a wet weight basis in liver of harbor seals taken in the eastern Pacific Ocean, 1970-71. Date Length Location collected Sex (cm) Mercury San Miguel 2 June 1971 F 161 700 Is., Calif. 2 June 1971 F 153 81 4 June 1971 M 176 124 5 June 1971 F 156 171 Columbia R., May 1971 M 0.3 Oregon do M 112 3.2 do F 126 68 Washington 2 Sept. 1971 F 84 1.3 Coast - Puget Sound, 24 Nov. 1970 M 60 Washington 21 June 1971 M 95 12 Pribilof Is., 17 Aug. 1971 M 135 0.6 Alaska do F 140 3.2 do M 175 8.9 136 ANAS: HEAVY METALS IN SEALS mercury in San Miguel Island seals appear to differ significantly from those from the Pribilof Islands. Except for the one seal with 700 ppm mercury, the amounts of mercury found in harbor seals from all areas studied are within the range of those found in livers of fur seals. ACKNOWLEDGMENTS The staff of the Division of Marine Mammals, Northwest Fisheries Center, National Marine Fisheries Service. NOAA, collected the fur seal samples for this study. T. C. Newby, College of Fisheries, University of Washington, Seattle, Wash., helped collect the harbor seals. C. H. Fiscus, H. Kajimura, and A. Y. Roppel, Division of Marine Mammals, assigned ages to the fur seals. LITERATURE CITED American Public Health Association. 1971. Standard methods for the examination of water and wastewater. 13th ed. Am. Public Health Assoc, Wash., D.C., 874 p. Anas, R. E. 1970a. Mercury found in fur seals. Commer. Fish. Rev. 32(12): 3. 1970b. Accuracy in assigning ages to fur seals. J. Wildl. Manage. 34:844-852. Bache, C. a., W. H. Gutenmann, and D. J. Lisk. 1971. Residues of total mercury and methylmercuric salts in lake trout as a function of age. Science (Wash., D.C.) 172:951-952. Berman, E. 1967. Determination of cadmium, thallium and mercury in biological materials by atomic absorption. At. Absorpt. Newsl. 6:57-60. Committee on Chemical Procedures of the Occupa- tional Health Section, American Public Health Association. 1955. Methods for determining lead in air and in biological materials. Am. Public Health Assoc. Inc., N.Y., p. 38-39. Curry, A. 1969. Poison detection in human organs. 2d ed. Thomas, Springfield. 111., 280 p. DuBois, K. P., and E. M. K. Ceiling. 1959. Textbook of toxicology. Oxford Univ. Press, N.Y., 302 p. Fiscus, C. H., G. A. Baines, and F. Wilke. 1964. Pelagic fur seal investigations, Alaska Waters, 1962. U.S. Fish Wildl. Serv., Spec. Sci. Rep. Fish. 475. 59 p. Food and Agriculture Organization of the United Nations. 1971. Report of the seminar on methods of detection, measurement and monitoring of pollutants in the marine environment: Supplement to the Report of the Technical Conference on Marine Pollution and its Effects on Living Resources and Fishing. FAO, Fish. Rep. 99, Suppl. 1, 123 p. Hall, J. D., W. G. Gilmartin, and J. L. Mattsson. 1971. Investigation of a Pacific pilot whale stranding on San Clemente Island. J. Wildl. Dis. 7:324-327. Harriss, R. C, D. B. White, and R. B. MacFarlane. 1970. Mercury compounds reduce photosynthesis by plankton. Science (Wash.. D.C.) 170:736-737. Jones, A. M., Y. Jones, and W. D. P. Stewart. 1972. Mercury in marine organisms of the Tay region. Nature (Lond.) 238: 164-165. Kenyon, K. W. 1965. Food of harbor seals at Amchitka Island, Alaska. J. Mammal. 46: 103-104. SCHEFFER, T. H., and C. C. SpERRY. 1931. Food habits of the Pacific harbor seal, Phoca richardii. J. Mammal. 12:214-226. ScHEFFER, V. B. 1950. Growth layers on the teeth of Pinnipedia as an indication of age. Science (Wash., D.C.,) 112:309- 311. Skerfving, S., K.. Hansson, and J. Lindsten. 1970. Chromosome breakage in humans exposed to methyl mercury through fish consumption. Arch. Environ. Health 21:133-139. Spalding, D. J. 1964. Comparative feeding habits of the fur seal, sea lion and harbour seal on the British Columbia coast. Fish. Res. Board Can.. Bull. 146, 52 p. U.S. Senate. 1970. The National Estuarine Pollution Study: Report of the Secretary of the Interior to the United States Congress Pursuant to Public Law 89-753, the Clean Water Restoration Act of 1966. 91st Congress, 2d Sess., Doc. 91-58, 633 p. U.S. Gov. Prim. Off., Wash., D.C. Williams, P. M., and H. V. Weiss. 1973. Mercury in the marine environment: concen- tration in sea water and in a pelagic food chain. J. Fish. Res. Board. Can. 30:293-295. 137 BIOECONOMIC CONTRIBUTION OF COLUMBIA RIVER HATCHERY COHO SALMON, 1965 AND 1966 BROODS, TO THE PACIFIC SALMON FISHERIES Roy J. Wahle,' Robert R. Vreeland.' and Robert H. Lander^ ABSTRACT Marked coho salmon, Oncorhyiuhus kisiiuh, smolts of the 1965 and 1966 broods were re- leased from 20 hatcheries on four sections of the Columbia River and tributaries. Com- mercial and sport fisheries in marine waters from Pelican, Alaska, to Avila Beach, Calif., and on the Columbia River were sampled during 1967-69 for marks. The net value of the estimated total catch of hatchery fish was calculated after adjust- ing for the effects of marking. Also estimated for each brood were the total costs of rearing including amortized capital outlay. Total benefits of $8.58 million for the 1965 brood and $9.11 million for the 1966 brood were estimated as applicable to normal production years when no marking takes place. Corresponding costs were estimated as $1.29 million for the 1965 brood and $1.23 million for the 1966 brood. Estimated benefit/cost ratios for the 20 Columbia River coho salmon hatcheries, as operated under production regimes prevailing during the study, may prove useful in decisions affecting management policies. The ratios are 6.6/1 for the 1965 brood, 7.4/1 for the 1966 brood, and 7.0/1 for both broods combined. Use of the Columbia River has expanded tre- mendously in the past 30 years through Federal- ly financed and/or licensed water use projects. This expansion has depleted valuable stocks of Pacific salmon, 0)icorhyuchus spp., and steel- head trout, Salmo gairdneri, through the loss and deterioration of natural stream habitat. Therefore, mitigative measures — hatcheries, fish ladders, and spawning channels — to sup- plement the declining natural production of Columbia River salmon and steelhead trout have been Federally funded. To counteract the severe loss of salmon and steelhead trout environment in the Columbia River basin, the U.S. Government began financ- ing the Columbia River Develojjment Program in 1949. The Program is a cooperative effort of the fish management agencies of the states of Oregon. Washington, and Idaho and the Federal ' Columbia River Fisheries Program Office, National Marine Fisheries Service, NOAA, 811 Northeast Oregon St., Portland, OR 97208. - Northwest Fisheries Center, National Marine Fish- eries Service, NOAA. 2725 Montlake Blvd. E., Seattle, WA 98102. Government. The Columbia Fisheries Program Office, National Marine Fisheries Service, Port- land, Oreg., administers the Program, which is designed to increase production of salmon and steelhead in the Columbia River. The Program's major thrust has been to improve the runs of salmon and steelhead by protecting and improv- ing stream environment and by production of fish in hatcheries. The main accomplishment is the con.struction or modernization of 21 salmon and steelhead hatcheries on the lower Columbia River and tributaries. There are two major reasons for the concen- tration of effort on salmon and steelhead trout. First, their life histories allow successful hatch- ery i^roj^agation. Second, these sjiecies are his- torically and economically important to the United States. Annual catches of Pacific salmon have ranked first or second for the past 3 decades in landed value of commercial finfishes to United States fishermen. Chinook salmon, O. fsliaivytscha, and coho salmon, O. kisKtch, land- ings have accounted for 35% of the 6-yr average (1966-71) commercial value ($70 million) for salmon — $12.5 million for chinook and $11.9 Manuscript accepted June 1973 FISHERY BULLETIN: VOL. 72. NO. 1, 1974 139 FISHERY BULLETIN: VOL. 72. NO. 1 for coho (Lyles, 1968, 1969; National Marine Fisheries Service. 1971; Riley, 1970, 1971; Wheeland, 1972). In addition, the net economic value of marine and freshwater sport fishing for salmon in the U.S. in 1970 was estimated at $77.7 million. This fishery was made up of 64% coho and 32% chinook.^ In 1950 five salmon hatcheries, representing the entire Columbia River production of hatch- ery coho salmon, released about 1 millicjn juve- niles typified by a short rearing period, poor nu- trition, and low survival. In contrast, the num- ber of hatcheries rearing coho increased to 20 by 1966-67, and annual releases averaged 20 mil- lion smolts. These salmon benefited from ad- vances in fish culture, especially nutrition, applied during the early 1960's and were char- acteristically large and healthy with a high sur- vival potential (Cleaver, 1969a). In 1962 the Columbia Fisheries Program Office started a marking study to estimate the contribution of Columbia River hatchery-reared fall Chinook salrnon to the Pacific coast fisheries. In 1965 this study was exj^anded to include coho salmon. Accordingly, representative (10% ) sam- ples from all Columbia River hatcheries rearing 1965- and 1966-brood coho salmon were marked. Sampling for these marked coho took place from 1967 through 1969 in the sport and commercial fisheries from Alaska to California. A contribu- tion study of this magnitude had never before been undertaken. The information to be gained from this study was critically needed to deter- mine if increa.sed Federal funding for Columbia River hatcheries was economically justified. The objectives of this report are to (1) describe the design and operations of marking and release procedures, (2) estimate the contri- bution (catch) to Pacific salmon fisheries during 1967, 1968, and 1969 for the 1965-66 brood coho salmon hatchery releases, and (3) develop bene- fit/cost ratios for these two broods. BIOLOGICAL EVALUATION Experimental Design Procedures were basically the same as 3 George K. Tanonaka. 1972. A general comparison of the commercial and sport salmon fisheries of the United States, 1940-70. Natl. Mar. Fish. Serv., Northwest Fish. Center, Seattle, Wash. (Unpubl. manuscr.) 15 p., 7 tables, 4 fig., App. A-B. described by Worlund, Wahle, and Zimmer (1969) for the fall chinook salmon study but will be summarized here. The Columbia River was divided into four sections. These sections will be defined later. Releases of marked fish were intended to identify and estimate the catches from each section. Execution of the plan dejiended. as for the evaluation of fall chinook salmon hatcheries, on the cooperation of many l)eople in the following agencies: Alaska Department of Fish and Game Fisheries Research Board of Canada Washington Department of Fisheries Fish Commission of Oregon Oregon State Game Commission California Department of Fish and Game National Marine Fisheries Service Bureau of Sjwrt Fisheries and Wildlife The basic plan was to mark the same propor- tion of juvenile coho salmon released at each hatchery and to sample for marks in commercial and sport fisheries. Total catches of fish from all hatcheries then could be estimated from (1) fractions of marked fish in each release, (2) numbers of each type of mark actually recovered, (3) fractions of the total catches sampled for marks by time and area in each fishery, and (4) information on any bias associated with appli- cation or detection of marks. Allocation of Marks The 20 hatcheries involved in this study are distributed over much of the mainstem Columbia River accessible to anadromous fish (Figure 1). Klaskanine River Salmon Hatchery, the lower- most station, and Leavenworth National Fish Hatchery, the uppermost, are on tributaries about 25 km and 800 km (15 and 500 miles), respectively, above the Columbia River mouth. Some hatcheries (Bonneville, Cascade, OxBow, and Little White Salmon) are adjacent to the main Columbia River and release their fish al- most directly into it. In contrast, fish released at the Toutle River station must travel 65 km (40 miles) to reach the Columbia River. Four different marks were available (from the Pacific Marine Fisheries Commission) for the 1965 brood of coho salmon. The Columbia River was therefore divided into four sections — Lower River, Middle River, Upper River, and Upper- most River — and one mark was assigned to each (Table 1). The adipose-right maxillary 140 WAHLE, VREELAND, and LANDER: BIOECONOMIC CONTRIBUTION 90 KILOHCTERt 14 Coscode 15 OiBow* 16 Corson* 17 Little Wliite Solmon 18 Willocd 19 KhcKitol 20 Leovenworth 1 Kloskonine 5 Toulle 2 Groys River 6 Loxer Kolomo 3 Biq Creek 7 Kolomo Foils 4 EloKomin 8 Lewis River 9 Speelyoi 10 Eoqle Creek I 1 Sondy 12 Wosliougol 1 3 Bonneville * Did not porticipote in 1966 brood study mark (Ad-RM) was used for hatcheries in the Lower River section — Columbia River mouth to Cowlitz River. The adipose-only finclip (Ad) was allotted to hatcheries in the Middle River section — the Cowlitz River to Bonneville Dam. Hatcheries in the Upper River section — Bonne- ville Dam to The Dalles Dam — were issued the adii)ose-left maxillary mark (Ad-LM). Leaven- worth National Fish Hatchery, the only study hatchery in the Uppermost River section — above The Dalles Dam — was assigned the dorsal-adi- pose finclip (D-Ad). The same marks were used for the 1966 brood with one exception; at Leavenworth National Fish Hatchery, maxillary marks were added to the D-Ad finclip. Juveniles with D-Ad- RM marks were released at the hatchery and those with D-Ad-LM were trucked downstream and released below Bonneville Dam. The pur- pose of the two marks and release sites was to examine differential mortality due to passage through dams; results will be treated in a sub- sequent report. Sources of Variation and Error To evaluate variations between broods and river sections, two broods (1965-66) of coho HCNARTDAH Figure 1. — Location and grouping by river section of Columbia River hatch- eries participating in this study. salmon were included in the study, and each river section was allotted a specific mark. Mor- tality due to marking, the most important source of error, was evaluated by comparing marked/unmarked ratios in hatchery releases and returns. To evaluate the dilution effect of returning wild fish on the marked/unmarked ratio at study hatcheries, oxytetracycline (TM- 50) was added to the diet of both broods of coho salmon reared at Big Creek (Ad-RM mark) and Eagle Creek (Ad finclip) hatcheries. Tetracycline deposits a permanent mark on the bone structure of feeding juvenile salmon and, at spawning, this mark is readily detected on coho vertebrae under ultraviolet light (Weber and Ridgway, 1967). Thus, wild coho were identifiable and were subtracted from the total unmarked returns to Big Creek and Eagle Creek hatcheries. Marked fish were held at Klickitat State Salmon Hatchery to evaluate the degree of mark regeneration. Markers at all participating hatcheries were asked to record naturally miss- ing fins and maxillary bones. Catch samplers were alerted to possible regeneration so they could look for malformed fins. Rearing techniques at different hatcheries varied within as well as between river sections. 141 The limited number of marks available pre- cluded individual hatchery comparisons as made from data of the fall chinook salmon study (Cleaver. 1969b; Worlund. Wahle, and Zimmer. 1969; Lander, 1970; Henry, 1971). The size of fish at release reflects partially the differences in rearing techniques. In both wild and hatchery salmon stocks, it is well known that large smolts survive better and contribute more to catches, other factors being reasonably equal, than do small smolts (Ricker, 1962; Fredin, 1964; Johnson, 1970). The average size of fish in releases varied considerably between hatcheries, somewhat between river sections, and slightly between broods. Again, the limited number of marks prevented evaluation of the effect of size at release on contribution, but average weights are included to complete the data record (Appendix Tables la and lb). FISHERY BULLETIN: VOL. 72. NO. 1 Estimating Procedures Simple numerical examples explain the basic estimating procedures. A more formal account was reported in the chinook salmon study (Worlund, Wahle, and Zimmer, 1969). The first quantities to be estimated were the numbers of marked and unmarked fish in hatch- ery releases. This was done with data from a 10-part sampler (see "Marking and Release Procedures"). The device was precalibrated from a number of trials with known numbers of fish to find the average number and percentage retained by a single closed pocket. The follow- ing example illustrates the fish enumeration procedure. Suppose a precalibrated pocket is found to remove a 10.1% sample. Also, suppose after passing all the fish in a pond through the sampler, the number of fish retained by the Table 1.^ — Grouping of Columbia River hatcheries participating in study and type of mark assigned to each group. River section and hatchery- .1/ Hatchery location KLaskanine (FCO) Grays River (WDF) Big Creek (FCO) Elokomin (WDF) Klaskanine River Grays River Big Creek, Columbia River Elokomin River Middle River (Cowlitz River to Bonneville Dam) Toutle (WDF) Lower Kalama ( WDF ) Kalama Falls (WDF) Lewis River (WDF) Speelyai (WDF) Sandy (FCO) Eagle Creek (FCO) Washougal (WDF) Bonneville (FCO) Green River, Toutle River Hatchery Creek, Kalama River Kalama River Lewis River Speelyai Creek, Lewis River Cedar Creek, Sandy River Eagle Creek, Clackamas River Washougal River Tanner Creek, Columbia River Upper River (Bonneville Dam to The Dalles Dam) Cascade (FCO) OxBow (FCO) Carson (BSFW) Little White Salmon (BSFW) Willard (BSFW) Klickitat (WDF) Eagle Creek, Columbia River Herman Creek, Columbia River Tyee Springs, Wind River Little White Salmon River Little White Salmon River Klickitat River Uppermost River' (above The Dalles Dam) Leavenworth (BSFW) Icicle Creek, Wenatchee River Mark 2/ Lower River (Columbia River mouth to Cowlitz River) Ad-RM Ad only Ad-LM D-Ad D-Ad-LM D -Ad-RM 1/ Acronyms designate the following agencies: FCO = Fish Commission of Oregon, WDF - Washington Department of Fisheries, and BSFW = Bureau of Sport Fisheries and Wildlife. 2/ Ad = adipose fincllp, D = dorsal flnclip, LM = left maxillary bone clip, and RM = right maxillary clip. 142 WAHLE, VREELAND, and LANDER: BIOECONOMIC CONTRIBUTION closed pocket is found to be 6.060. The total number of fish in that pond is then estimated as 6.060/0.101 = 60.000. Suppose further that of the 6.060 fish retained by the pocket. 606 fish are found to be marked. Then 606/6.060 = 10% of the estimated 60.000 fish in the pond, or 6,000 fish are estimated to be marked and 54.000 un- marked. The total release, numbers marked and unmarked, and proportion marked were esti- mated for a hatchery by summing data from all ponds. Finally, estimates of the foregoing quan- tities for all fish released into a given river sec- tion were obtained by summing the estimates for appropriate hatcheries. To estimate actual recoveries with a certain mark during a specific sampling period in a given fishery, the total catch (of marked and unmarked fish) during that period was multi- plied by the fraction of sampled fish observed with that mark during the same period. For example. 16 Ad-RM marks were detected dur- ing June 1-30, 1968, from 9,827 coho salmon examined at Crescent City, Calif., in a catch of 31,082 from the commercial troll fishery. Thus. 16/9.827 (approximately 0.2%) of the sample had Ad-RM marks. The total marked catch for that period and landing port was estimated to be about 0.2% of the 31.082 fish caught or 62 Ad-RM marks (actual calculations were carried to eight places to avoid rounding errors). Simi- lar calculations were made for each period. The results then were summed for all periods and appropriate landing locations to estimate the seasonal recovery of a certain mark in the given fishery (e.g.. Ad-RM marks in the California troll fishery during 1968). The catch of unmarked hatchery fish for each ocean sport and commercial fishery, and the Columbia River fisheries, was estimated for each year and brood by dividing the estimated catch of fish having a specific mark by the expected marked/unmarked ratio. The latter was calculated from the ratio at release and the estimated relative survival of marked fish. Suppose an estimated 2,000 1965-brood Ad-RM marks were recovered in 1968 in the California ocean sport fishery, the marked/unmarked ratio was 0.1 for all hatcheries where Ad-RM marks were released, and the survival of marked fish was estimated to be 80% that of unmarked fish; then the estimated catch of unmarked fish would be (2,000)/(0.1 X 0.80) = 25,000 fish. The catch of hatchery fish released from a given river section was estimated by summing estimates for marked and unmarked hatchery fish from each type of fishery. Nondetection of certain marks in ocean fisheries complicated the estimation of the hatchery contribution. The relative survival of marked fish was estimated by comparing marked/unmarked ratios at release and return, as noted earlier for tetracycline (internal) and finclip (external) marking at the Big Creek and Eagle Creek sta- tions. At the Big Creek station for the 1965 brood, for example, the pond sampling pro- cedures just described gave an estimated marked/unmarked ratio at release of 0.12083 (for the Ad-RM finclip). Enumeration at the hatchery of all internally- and externally- marked returns ("jacks" or age 2 males in 1967 plus age 3 males and females in 1968) gave a marked/unmarked ratio of 0.09885. The sur- vival of marked fish between the time of release and at return to the hatchery was there- fore estimated to be 0.09885/0.12083 = 0.8181 that of unmarked fish. With estimates of all these quantities at hand, it remained only to estimate the average weight and unit value of fish caught to calculate their total economic value. Weight data were collected from a predetermined number of fish through- out the season at different landing locations from which a given fishery operated. Resulting means were assumed to be representative. Assumptions The foregoing method of estimating catches of hatchery fish requires certain assumptions. These are considered after presentation of the data (see "Bias Associated with Marks" and "SUMMARY"). The main assumptions are: 1. A marked fish is identifiable as a marked fish throughout life. 2. All fish detected and reported with the kind of mark applied are hatchery fish. 3. All coho salmon sampled in ocean fish- eries are in their third and final year of life. 4. Marked and unmarked fish have the same maturity schedules. 5. The same proportion of releases is marked at each hatcherj' in a given river section. 6. Marked and unmarked fish from a given river section are equally vulnerable to capture 143 FISHERY BULLETIN: VOL. 72. NO. 1 (i.e., have the same distribution by time and area) . Field Operations Marking and Release Procedures Artificial propagation procedures were simi- lar at all coho salmon hatcheries during the study period. Adults normally returned to the hatcheries during September-November and were spawned during October-November. Fry generally reach the free-swimming stage in March. The fish were released as smolts 13 mo later at an average length of 12-15 cm (4.5-6 inches) and were available during the following year to the fisheries from central British Colum- bia to central California. The marking phase of this study began in May 1966 and ended in June 1967. About 10% of the 1965- and 1966-brood coho salmon were marked. A modified sampling tool (Worlund, Wahle, and Zimmer, 1969) was used to obtain a random sample for marking. The "10-part sampler" consisted of a cylindrical liner con- taining a circular metal frame divided into 10 equal pie-shaped sections with a zipper-bot- tomed net pocket hung from each section. When a 10% sample was to be taken, the zippers on all but one of the pockets were opened, the frame and liner were placed in a water-filled tub. and about 18 kg (40 pounds) of fish were placed into the liner. The closed net pocket retained the desired sample when the line and frame were lifted. The fish that passed through the open net pockets remained in the tub and were placed into another pond. This procedure was followed until all the coho in each pond were processed. Fish to be marked were anesthetized with MS-222' (tricaine methanesulfonate). The fins and maxillary bones were clipped with bent- nosed scissors. Marked fish were held in hatch- ery troughs until they recovered from the anes- thetic, then returned to the group from which they came. To insure that fins and maxillary bones were actually removed, quality control of marking was maintained by periodic random sampling of the marked fish throughout the marking operation. ■* Reference to trade names in this publication does not imply endorsement of commercial products by the National Marine Fisheries Service. The entire coho salmon production of each hatchery was sampled to estimate the propor- tion and numbers of marked fish released. The "10%" samples removed initially by the cali- brated pocket were set aside then resampled to obtain a "1%" sample which was sorted into marked and unmarked groups, counted, and weighed. The counts together with an estimate of the proportion removed by the particular pocket of the sampler were used to estimate the numbers of marked and unmarked fish released. In Table 2, the estimated numbers of marked and unmarked fish released and the percentages marked are summarized for each mark type and brood year. Detailed data for each hatchery are given in Appendix Tables la and lb. Over 40 million coho salmon of both broods were released from the study hatcheries. The number of marked fish released by section for the 1965- and 1966-brood years combined were Lower River, 0.9 million; Middle River, 1.7 million; Upper River, 1.3 million; and Uppermost River, 0.2 million. A total of 39.1 million coho from both broods was released from the study hatch- eries in the Lower, Middle, and Upper River sections. Of these, 9.8% were marked. About 0.9 million coho were released from the Upper- most River section, of which 21.1% were marked. Recovery of Marks in Fisheries The mark-sampling phase of this study was designed in 1963 for fall chinook salmon and was expanded to include coho in 1967, 1 year before the 1965-brood coho were expected to appear in great numbers in the fishery. This advanced sampling was done for two reasons: (1) to locate the sampling problem areas and correct any deficiencies before the major appearance of the 1965-brood coho in the fish- eries and (2) to assist the Washington Depart- ment of Fisheries in recovering their marked 1964-brood Puget Sound coho. This phase of the investigation ended in 1969. Catch sampling covered major ocean fisheries from Pelican, Alaska, southward to Avila Beach, Calif., and Columbia River fisheries. Sampling for marks in each area consisted of recording numbers of fish examined for marks and the recoveries of each type of mark detected. Lengths and weights of marked coho salmon from both broods were recorded also. The sampling sea- 144 WAHLE. VREELAND, and LANDER: BIOECONOMIC CONTRIBUTION Table 2. — Estimated numbers, percentage marked, and marked to unmarked ratios of 1965- and 1966- brood coho salmon released from evaluation hatcheries by river sections. Brood year River section and (In parentheses) mark Marked released Unmarked released Total released Proportion marked Marked/ unmarked 1965 Lower River (Ad-RM) ■yC6,29h 4,670,794 5,179,088 0.09SI 0.1088 Middle River (Ad) 845,674 7,895,360 8,741,034 0.0967 0.1071 Upper River (Ad-LM) 837,829 7,670,539 8,506,368 0.0985 0.1092 Uppermost River (D-Ad) Subtotal 1965 brood 101,73^ 402,272 504,006 0.2018 0.2529 2,293,531 20,638,965 22,932,496 0.1000 0.1111 1966 Lower River (Ad-RM) 385,630 3,569,807 3,955,437 0.0975 0.1080 Middle River (Ad) 764,262 6,965,703 7,729,965 0.0989 0.1097 Upper River (Ad-LM) 493,110 4,544,676 5,037,786 0.0979 0.1085 Uppermost River {Ti-AA-IM}-' 96,643 466 97,109 0.9952 207.3884 Uppermost River (D-Ad-RM) Subtotal 1966 brood 78,092 269,355 3h7,kk7 0.2248 0.2899 1,817,737 15,350,007 n,l67,7kk 0.1059 0.1184 TOTAL BOTH BROODS 4,111,268 35,988,972 40,100,240 0.1025 0.1142 1/ Released below Bonneville Dam. sons were stratified into relatively small time units (usually 2-\vk periods). The main fisheries sampled were ocean sport and commercial, Columbia River sport and commercial, and Puget Sound fisheries. The ocean fisheries were stratified further by port of landing. The Alaska and British Columbia troll, purse seine, and gillnet fisheries; Columbia River commercial and sport fisheries; and Puget Sound sport and commercial fisheries were stratified by area of catch. The specific fisheries sampled are listed in Table 3 and shown in Figure 2. Catch data for each time-location stratum were provided by management agencies. The catch of coho salmon in numbers of fish was an estimate for most fisheries. Commercial catches were estimated either from (1) the total weight of landings and an estimate of average fish size or (2) total salmon landings (numbers) and an estimate of species composition. Estimates of sport catches were from measures of total effort and catch per unit of effort or from salm- on punch cards together with independent sampling by the management agency. About 20% of each time-location stratum was sampled for marks. Table 4 gives the annual total catch of both broods of coho salmon by year and number sampled for marks each year. During the 3 years of sampling, 15.4% of the total catch of 21.1 million coho were examined for marks. The actual mark sampling percent- ages were 18.3, 13.5, and 14.3% for 1967, 1968, and 1969, respectively. Enumeration of Returns to Hatcheries An estimate of the numbers returning to hatcheries was required to measure the total hatchery output and marking mortality. All returns to most hatcheries were e.xamined for marks; at some hatcheries, the numbers marked and unmarked were calculated after a known percentage of the total return was sampled for marks. A breakdown of the returns to each of the study hatcheries is in Appendix Tables 2a and 2b. Estimation of Total Catch from Hatcheries Actual Recoveries Tables 5a and 5b summarize marked recov- eries by brood year, mark, year of recovery, 145 FISHERY BULLETIN: VOL. 72. NO. I Table 3. — Areas where catches were examined for marked coho salmon of Columbia River origin by port or zone of landing and type of fishery. Type of fishery- Area sampled Sport Commercial Rod and reel Troll Gill net Dip net Purse seine British Columbia Alaska area. Zones 29, 40-'t3, Zones 29, UO-i+3 Zones U0-U3. and Area C.i/ Washington ocean Sekiu Seattle Grays Harbor. Heah Bay Neah Bay Willapa Bay. LaPush LaPush . Westport Westport . Ilwaco Ilwaco. Puget Sound and Juan de Fuca Strait Zones 6-12 Zones 1-15 Zones 1-12. Oregon ocean Warrenton Astoria. Tillamook Tillamook. Pacific City Pacific City. Depoe Bay Depoe Bay. Newport Newport . Florence Florence . Winchester Bay.... Winchester Bay. Coos Bay Coos Bay. Gold Beach Bandon. Brookings Port Orford. Gold Beach. Brookings . California ocean Crescent City Crescent City. ■ Trinidad Trinidad. Eureka Eureka . Shelter Cove. ..... Fort Bragg. Fort Bragg Albion. Albion Point Arena. Bodega Bay Bodega Bay. San Francisco Point Reyes. Half Moon Bay San Francisco. Santa Cruz Half Moon Bay. Monterey Moss Landing. Morro Bay Monterey. Avlla Morro Bay. Avlla. Columbia River and tributaries Zones 1-6 Zones 1-7 Klickitat River. Cowlitz River. Kalama River. Lewis River. Toutle River. Washougal River. 1/ Canadian catch 3-12 miles off Washington, Oregon, and California. river section of origin, and fishery. All marks from the Uppermost River section (Leaven- worth Hatcheiy in Appendix Table 4) are com- bined as D-Ad marks in Table 5b. During the 3 years of sampling, 37,632 marked coho salm- on were recovered. More marked 1965- than 1966-brood coho were caught, but more were released from the 1965 brood. Carson National F^ish Hatchery and OxBow Salmon Hatchery, while participating in the study for the 1965 brood, did not do so for the 1966 brood (Table 2). The fraction of marked releases actually recovered for the 1965 brood. 0.0089, was slightly less than for the 1966 brood. 0.0093 (Tables 2, 5a, and 5b). 146 Estimated Recoveries As explained under "Estimating Procedures," the total catch offish with a particular mark was estimated for each stratum (fishery, port of land- ing or area of capture, and time period) from actual mark recoveries and the sampling frac- tion. It was assumed that a random sample of coho salmon was examined in each stratum and , that in each sample all the marked fish were in- spected. The total catch for each mark in each fishery was estimated by summing over the time periods and appropriate ports of landing or areas of capture. The estimated catches and hatchery returns WAHLE, VREELAND. and LANDER: BIOECONOMIC CONTRIBUTION 140" 1350 130" 125° Figure 2. — Ports and zones sampled for marked coho salmon of Columbia River origin. 147 FISHERY BULLETIN: VOL. 72. NO. 1 of marked fish are summarized in Tables 6a and 6b by region of recovery, fishery, brood year, and mark. The marks from the Uppermost River section (Appendix Table 5a) are com- bined in Table 6b. The total estimated catch of marked fish from both broods was 179,096. A total of 33,910 marked coho salmon returned to the study hatcheries during the 3 yr of sam- pling. Bias Associated with Marks To proceed from the estimated catch of marked fish to the total catch of hatchery fish, we must be sure that our assumptions (see "EXPERIMENTAL DESIGN") are satisfied. Some elements (e.g., loss of maxillary bones due to hooking, loss of fins due to injury) cannot be evaluated; others (e.g., mark regeneration, natural marks, relative survival of marked fish) can be appraised more adequately. Mark Regeneration (Assumption 1) and Quality of Marking We have three indications of the permanence of fin and maxillary marks. First, about 550 marked coho salmon of the 1966 brood were held for 2 yr at the Klickitat station for fin regeneration studies. We examined these fish periodically throughout the retention period and observed no adipose regeneration. However, we noted a 4.5% complete maxillary regenei'ation. Second, the appearance of D-Ad marks in the releases of the 1966-brood coho from Leaven- worth National Fish Hatchery indicated maxil- lary regeneration; the maxillary bone was clipped from all 1966-brood Leavenworth coho marked, vet 5% of the marked coho released had only a D-Ad finclip. During marking of the Leavenworth coho, 100 marked fish per marker were examined at irregular periods each day to check mark quality. No undipped maxillaries were observed. This caused us to disregard fail- ure to clip maxillaries as a reason for the appearance of the D-Ad marks. Therefore, we believe the D-Ad marks occurred mainly be- cause of maxillary regeneration. Finally, the percentage of D-Ad-only marks in the 1969 lower Columbia River commercial catch of 1966-brood Leavenworth Hatchery marked fish was 6.5% . This is very close to the percen- tage of D-Ad-only marks in the release. Because of these indications, we are assuming that mark regeneration caused little bias in this study. Natural Marks (Assumption 2) The catch of hatchery fish would be over- estimated if marks identical to those used in this study occurred naturally. To ensure that no natural marks existed in hatchery stocks, coho salmon returns at most Columbia River and some Puget Sound hatcheries were examined for 2 yr before the study. Approximately 35,000 returns were examined and no marks identical to those we planned to use were observed. Also, fish markers at all participating hatcheries ex- amined approximately 3.5 million coho for naturally missing fins and maxillary bones. Only 26 were found to have naturally missing adipose fins and none had naturally missing dorsal fins or maxillary bones. The possible occurrence of natural marks from other river systems is more difficult to evaluate. Comparisons of the percentage of each mark caught in the lower Columbia River Table 4. — Estimated catches of coho sahnon and number ot fish examined for marks, 1967-69.1 Gate ;h of coho salmor 1 Sampled 1965 brood 1966 brood All ages for marks 1967 1968 1969 22,91+6 8,587,969 0 0 20,1+57 h,933,706 7,539,255 8,608,1+26 1+, 966, 589 1,381,255 1,158,932 710,753 Total 8,610,915 i+,95't,l63 21,lll+,270 3,250,91+0 1/ From all areas sampled (Table 3)» 148 WAHLE, VREELAND, and LANDER: BIOECONOMIC CONTRIBUTION Table 5a. — Number of marked 1965-brood Columbia River coho salmon by release section recovered in the fisheries by year, region of capture, and type of fishery, 1967-68. Washington nriti<;h c- y California Oregon (without Puget Sound " , ^, ., ' , Columbia River ■D, 4. o J \ Columbia Alaska Puget Sound; River section and (In parentheses) mark Year Sport Com- Com- Com- Com- Com- Com- Sport Commercial TOTALS clal Sport mer- cial Sport mer- cial Sport mer- cial mer- cial mer- cial Main Trlb. Gill net Dip net Lower River (Ad-RM) 1967 0 0 0 0 0 0 0 0 0 0 1 0 15 0 16 1968 101 1+91 135 1,049 212 1+01 0 5 72 ♦ 0 3 107 5 2,581 Middle River (Ad) 1967 0 0 0 0 0 0 0 0 0 0 4 20 1 0 25 1968 156 968 1,822 5,106 2,187 3,339 0 67 790 « 2 41 778 1 15,257 Upper River (Ad-LM) 1967 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1968 16 131 77 697 321+ 489 0 1 65 ♦ 0 0 180 65 2,045 Uppermost River (D-Ad) 1967 0 0 0 0 0 0 0 0 0 0 0 0 2 0 2 1968 6 23 52 194 119 144 0 0 9 * 0 0 67 0 614 TOTALS 1967 1968 0 279 0 1,613 0 2,086 0 7,046 0 2,842 0 4,373 0 0 0 73 0 936 0 * 5 2 20 44 18 1,132 0 71 43 20,497 *No sampling . Table 5b. — Number of marked 1966-brood Columbia River coho salmon by release section recovered in the fisheries by year, region of capture, and type of fishery, 1968-69. River section and (in parentheses) mark British S. E. Washington California Oregon (without Puget Sound Puget Sound) Columbia Alaska Columbia River Year Com- Com- Com- Com- Com- Sport mer- Sport mer- Sport mer- Sport mer- mer- clal cial cial cial cial Com- TOTALS Sport Commercial cial Main Trlb. Gill Dip net net Lower River (Ad-RM) Middle River (Ad) Upper River (Ad-LM) Uppermost River (D-Ad) 1968 1969 0 22 1968 0 1969 191 1968 1969 1968 1969 0 14 0 158 0 0 107 911 0 432 0 432 0 0 0 0 0 905 1,578 4,479 2,120 1,865 0 102 0 1+0 0 0 86 662 0 31 0 118 0 525 0 52 0 356 0 67 0 0 0 15 0 32 0 312 0 9 0 1 1 0 2 1 6 158 0 3 5 2,307 17 1 34 33 12 759 0 18 63 12,278 2 0 1 1 6 233 16 53 25 2,042 0 0 0 0 3 50 0 0 365 TOTALS 1968 0 000000 0 0 1969 233 1,205 1,802 6,170 3,179 2,720 2 17 354 *No sampling. 20 37 27 16 IOC 1 35 1,200 74 16,992 commercial fishery with the percentage of each mark caught in each ocean fishery give an indi- cation of the occurrence of natural marks. After making these comparisons, we noted a prepon- derance of Ad-only marks especially in the Oregon sport fishery for the 1965 brood and the California sport and commercial fisheries for the 1966 brood. In these fisheries, we observed 149 FISHERY BULLETIN: VOL. 72. NO. 1 Table 6a. — Estimated number of marked 1965-brood coho salmon in catches and hatchery returns by type of mark, region of recovery, type of fishery, and year of capture, 1967-68. Region Fishery type D-Ad Ad-LM Ad Ad-RM Total 1967 1968 I96T 1968 1967 1968 1967 1968 1967 1968 Ocean fisheries: British Columbia Washington Oregon C£Llif ornia Subtotail Freshwater fisheries: Columbia River Total Columbia River escapement: Study hatcheries Commercial. . . Sport Commercial. . . Sport Commercial. . . Sport Commercial. . • Sport Commercial. . . Sport Commercial. . . All fisheries U6 677 636 226 736 18 109 0 921 0 1,527 0 238 7 2,686 k59 1,809 2,051 265 2,530 30 789 6,339 ii,i+90 14,382 7,9'+'+ 17,821 299 5,55^+ 581 1,206 1,716 i+20 3,564 331 2,617 2,104 5,829 0 846 19,733 44,096 0 1,957 0 8,478 344 290 2 4,907 25 130 16 825 7,425 15,182 18,785 8,855 24,651 678 9,069 0 24,715 0 59,930 369 306 139 6,816 0 8,779 346 69,026 155 11,276 508 91,767 38 138 1,125 1,882 4,391 9,399 1,568 1,864 7,122 13,283 Table 6b. — Estimated number of marked 1966-brood coho salmon in catches and hatchery returns by type of mark, region of recovery, type of fishery, and year of capture, 1968-69. Region Fishery type D-Ad Ad-LM Ad Ad-RM Total 1968 1969 1968 1969 1968 1969 1968 1969 1968 1969 Ocean fisheries: British Columbia Washington Oregon California Subtotal Freshwater fisheries: Columbia River Total Columbia River escapement: Study hatcheries Commercial. . , Sport Commercial. . . Sport Commercial. . . Sport Commercial. . . Sport Commercial. . . Sport Commercial. . . All fisheries 7 242 281 148 645 23 224 0 413 0 1,157 0 283 77 2,333 1,456 392 2,930 38 465 2,970 9,324 7,782 7,304 19,952 611 6,024 278 2,178 1,807 492 4,261 58 728 45 58 2,763 4,928 35 2,470 0 17,239 0 36,728 541 125 397 3,104 31 57 2,728 7,074 20 1,619 6 1,853 103 10,196 666 62,468 3,332 14,077 11,326 8,336 27,788 730 7,441 0 23,143 0 49,887 617 452 246 12,476 11,441 863 85,958 624 1,075 2,191 5,769 2,067 1,771 4,890 8,615 samplers recording partially regenerated Ad-LM and Ad-RM as Ad-only marks. We attribute the preponderance of Ad-only marks in the above mentioned fisheries to the reluctance of samplers to distinguish between partially regen- erated maxillaries and maxillaries lost through injury. Age and Maturity Schedules (Assumptions 3 and 4) Godfrey (1965) noted that ocean catches of coho salmon in the regions sampled in this study are all, or nearly all, age 3 adults. Johnson (1970) estimated that the ocean catch of 150 WAHLE. VREELAND. and LANDER: BIOECONOMIC CONTRIBUTION marked 1964-brood coho from Big Creek Hatchery (Figure 1) contained only 3% age 2 coho. This available evidence indicates that Assumption 3 (all coho in ocean fisheries are in their third and final year of life) is reasonably satisfied. A comparison was made of marked and un- marked returns (Appendix Tables 2a and 2b) to hatcheries in the same river section where released to test Assumption 4 (marked and un- marked fish have the same maturity schedules). Appendix Table 3 shows the percent of 2-yr-old coho salmon in the marked and unmarked re- turns by river section and brood year. Un- marked strays to other river sections could not be identified by origin, so it was necessary to assume that straying was the same for marked and unmarked returns. The D-Ad comparison (Leavenworth Hatchery) was not made because passage difficulties at John Day Dam in 1969 led to no returns of adults to Leavenworth Hatchery. The nearly equal percentages of 2-yr- olds in the marked and unmarked returns by river section and brood year indicate that Assumption 4 is satisfied. Marked Proportions at Release and Capture (Assumptions 5 and 6) Inspection of mark proportion data in Appendix Tables la and lb shows the variabil- ity between hatcheries to be small enough to consider Assumption 5 (same proportion of releases marked at each hatchery in a given river section) reasonably well satisfied. At pre- sent, no data exist to support Assumption 6 (equal vulnerability to capture for marked and unmarked fish from a given river section), but it is intuitively satisfied. Fish marked by clip- ping maxillary bones and/or the adipose fin would not seem to be more vulnerable to cap- ture by fishing gear than unmarked fish. Relative Survival of Marked Fish Worlund, Wahle, and Zimmer (1969) found that marked fall chinook salmon did not survive as well as unmarked chinook. We also found this for coho salmon. To determine the un- marked catch of hatchery fish, we must account 'for the lower survival of marked fish. The rela- tive survival values for both broods and each mark type of coho were calculated as explained under "Estimating Procedures." Oxytetracy- cline (TM-50) was used to mark both broods of coho at Eagle Creek and Big Creek hatcheries to obtain survival values for Ad and Ad-RM marked coho, respectively. Returns to three hatcheries. Little White Salmon, Cascade, and Klaskanine, on streams having no wild spawn- ing populations were used to obtain relative survival values for both broods of Ad-LM and Ad-RM marked coho. Finally, the marked to unmarked ratios at release and return for each river section were combined to obtain survival values for each mark type in both brood years. The relative survival estimates are in Appen- dix Table 6. Marked coho salmon that strayed to sections other than where they were released (Appendix Tables 2a and 2b) were excluded from the marked returns in computing relative sur- vival (see "Bias Associated with Marks"). There- fore, the median value for each of the mark types for both brood years combined was arbi- trarily used to obtain reasonable approxima- tions for relative survival. The same value was used for Ad-LM and Ad-RM marked coho. The median va'ues for the Ad-only and Ad-maxillary marked coho were 89 and 72%, respectively. The relative survival of D-Ad marked 1965- brood coho salmon from Leavenworth National Fish Hatchery (Uppermost section) was obtained from TM-50 marking data. In 1967 and 1968, a total of 174 D-Ad-TM-50 marked and 1,305 TM-50-only marked 1965-brood coho returned to Leavenworth. From these values, the marked to unmarked relative survival of 1965-bi-ood D-Ad marked coho was calculated to be 53% . Few hatchery returns of 1966-brood Leaven- worth coho were obtained because of passage difficulties at John Day Dam due to construc- tion of fish ladders and mortalities caused by trapping at Priest Rapids Dam. Hence, a rela- tive survival estimate for the D-Ad-RM and D- Ad-LM marks could not be calculated. The value for the D-Ad marked 1965-brood coho (53%) was therefore used to estimate the 1966-brood Leavenworth catch of unmarked fish. Final Estimates Corrected for Marking One marked fish represented about 9 un- marked ones at release but about 11-20 (depend- ing on the mark) at return (Tables 2, 6a, and 6b). The foregoing estimates of relative survival for unmarked fish were applied (see "Estimating 151 Procedures") to estimate the catch of unmarked hatchery fish, then marked fish were added to estimate the total catch. An additional calculation was required before estimating the unmarked catch associated with the marked 1966-brood Leavenworth Hatchery fish because of the recovery of 1966 brood D-Ad- only marks. The recovery was due to either regeneration or nondetection of D-Ad-maxillary marks (see "Bias Associated with Marks"). Therefore the estimated catch of 1966 brood D-Ad marks had to be apportioned between the estimated catches of D-Ad-RM and D-Ad-LM marks before calculating the catch of unmarked 1966-brood fish. The D-Ad marks were appor- tioned by the ratio of their occurrence at the time of release. At Leavenworth Hatchery, 5,081 D-Ad marks were estimated to have been re- leased with the D-Ad-RM marks. Below Bonne- ville Dam, 4,393 D-Ad marks were estimated to have been released with the D-Ad-LM marks. This is a total release of 9,474 D-Ad mai'ks of which 54% (5,081/9,474) came from D-Ad-RM marks and 46% (4,393/9,474) came from D-Ad- LM marks. These ratios were used to apportion the estimated catch of 6G6 D-Ad marks (Appen- dix Table 5a) between the D-Ad-RM and D-Ad- LM marked fish in each of the fisheries. For example, 88 D-Ad marked coho (Appendix Table 5a) were estimated to have been caught in the Washington sport fisheries in 1969. Using the occurrence percentages of the D-Ad marks at release, 88 X 0.54 = 48 were calculated to be from D-Ad-RM marks and 88X0.46 = 40 were calculated to be from D-Ad-LM marks. This apportioning was done for each fishery and re- sults are in Appendix Table 4b. The estimated catches of marked fish used to calculate the catches of unmarked hatchery fish are in (1) Table 6a for the estimated 1965 brood D-Ad, Ad-LM, Ad. and Ad-RM marks captured in the ocean and Columbia River fisheries; (2) Table 6b for the estimated ocean and Columbia River catches of 1966 brood Ad-LM, Ad, and Ad- RM marked fish; and (3) Appendix Table 5b for the catches of marked 1966-brood Leavenworth coho salmon. Appendix Table 7 presents the resulting estimated catches of unmarked hatch- ery fish. The estimated total catch of Columbia River hatchery fish (Appendix Table 8) was obtained by adding the estimated catch of marked fish FISHERY BULLETIN: VOL. 72. NO. 1 (Tables 6a and 6b) to the estimated unmarked catches (Appendix Table 7). The resulting catch estimates may affect management decisions in years when no marking studies take place. Therefore, as a final step, we divided the esti- mated catch of each mark in each fishery (Tables 6a and 6b) by the estimated relative survival for that mark (see "Relative Survival of Marked Fish") to obtain a theoretical catch of marked fish assuming no marking mortality. The results were then added to the estimated unmarked catch (Appendix Table 7) to obtain a theoretical total catch of Columbia River hatchery coho salmon. The results are in Table 7 by region of recovery, type of fishery, and year of capture. The table includes the estimated sport catches of hatchery fish in Columbia River tributaries where no creel census took place. This is broken down in detail by year of capture, brood, and stream in Appendix Table 9. An estimated total of 2,188,172 Columbia River hatchery coho would have been caught during the 3 years of sampling had no marking taken place. This is about 16% of the total catch in areas sampled (Table 3) of 1965- and 1966- brood coho caught during 1967-69 (Table 4) — 13% for the 1965 brood and 21% for the 1966 brood. Another useful statistic is the catch/1,000 fish released. For the combined 1965 and 1966 broods, this was 55/1,000—50/1.000 for the 1965 brood and 61/1,000 for the 1966 brood (Tables 2 and 7). ECONOMIC EVALUATION A main purpose of this paper is to develop benefit/cost ratios for the 1965 and 1966 broods of coho salmon from Columbia River hatcheries. To develop these ratios, estimates must be made of (1) the costs of rearing the 40.1 million smolts released (Table 2) and (2) the value of the theo- retical catch of 2,188,172 coho (Table 7). The rearing costs will be presented first. Cost Accounting Production costs are broken down into two categories: (1) amortized construction costs or capital costs and (2) operational costs. Capital The "annual imputed capital charge" for each hatchery was computed by amortizing the capi- tal expenditures at each hatchery into 30 equal I 152 WAHLE, VREELAND, and LANDER: BIOECONOMIC CONTRIBUTION Table 7. — Theoretical catch of 1965- and 1966-brood hatchery coho salmon by region of recovery, type of fishery, and year of capture, 1967-1969.' Region Fishery type 1967 1965 brood 1968 Total 1968 1966 brood 1969 Total Ocean fisheries: British Coliimbla. . . . Washington Oregon California Subtotal Freshwater fisheries: Columbia River Total Commercial. . . 0 Sport 0 Commercial. . . 0 Sport 0 Commercial. . . 0 Sport 0 Commercial... 0 Sport 0 Commercial... 0 Sport 18,739 Commercial... 1,929 All fisheries 20,668 88,755 182,372 226,212 10i^,063 300, 004 8,750 113,700 88,755 182,372 226,212 104,063 300, 004 8,750 113,700 0 0 0 0 0 0 0 38,821+ 171,035 136,016 96,371 332,075 8,393 86,573 38,824 171,035 136,016 96,371 332,075 8,393 86,573 295,185 728,671 10,627 82,831 295,185 728,671 29,366 15,584 84,760 3,087 275,799 593,488 10,855 151,377 275,799 593, J^8 26,439 154,464 1,117, 31** 1,137,982 18,671 1,031,519 1,050,190 1/ Corrected for differential fincllp mortality and assuming no marking had taken place. annual payments using an interest rate of 3.5% .^ This rate was the average 3- to 5-yr government bond interest rate weighted by the total annual capital outlay at all hatcheries from 1949 (incep- tion of Columbia River Development Program) through 1970. All outlays prior to this period are assumed to be depreciated out completely. The imputed capital charge for each study hatch- ery was apportioned among the broods and species present by using the percentage of time spent caring for each group of fish. The total annual imputed capital charges for the 1965- and 1966-brood coho salmon are $271,600 and $235,600, respectively. Operation The operation and maintenance costs at each hatchery are divided into two categories. They are fish food and drugs and other operational costs. The cost of fish food and drugs is appor- tioned between each brood and species according to the pounds of each brood and species pro- duced. The operational costs other than food and drugs include costs for labor, personal services, travel, transportation of items, communication services, equipment, supplies and materials, and administration. These costs are allocated to each brood and species in the same manner as the capital costs. The operational costs appor- ^ The "annual imputed capital charge" is the estimated cost of government funds over the life of the project. tioned to the 1965- and 1966-brood coho are $1,020,700 and $991,000, respectively. The total costs applicable to rearing the 1965- and 1966- brood coho are then $1,292,300 and $1,226,600, respectively. Benefits To determine the benefit provided by hatchery releases of 1965- and 1966-brood coho salmon to the commercial and sport fisheries, an estimate of the net economic value to these fisheries must be made. Additional information is critically needed to improve the basis for estimating values for fishery resources; however, the values used in this report are based on the best information now available and the limitations of these values are discussed. Commercial Ex-vessel market prices have been used to represent estimated net values for commercially caught fish. There are two quite different rea- sons why this method can provide satisfactory estimates. The Columbia River salmon production from hatcheries included in this study provide only a portion of the total salmon production. Use of the ex-vessel price in the standard benefit-cost technique would require the deduction of all associated costs. However, excess capacity typically exists in the fishing sector, so little or 153 FISHERY BULLETIN; VOL. 72. NO. 1 no additional fishing effort would be needed to land the production from these hatcheries. While this provides an adequate reason to omit fishing costs for hatchery fish, this would not be true for total salmon production. A stronger basis for omitting costs necessary to land fish and using the ex-vessel price, results from current fishery management policies. Regu- lated inefficiency has been used in salmon fish- eries to prevent overharvest thus excluding effi- cient fishing methods. This process probably results in dissipation of at least 75% of potential net benefits and may be as high as 95% (Richards, 1969).'* Since the market prices used result from normal market activities and thus represent the market value of the fish resource to users, this potential benefit could be realized if society elects to change management methods and reduce fishing costs. Several inadequacies exist in the use of the ex- vessel price as a representation of the net value for commercially caught fish. The first inade- quacy is that the ex-vessel market price fails to completely measure market value. Gear or sup- plies furnished by processors and bonuses paid are examples of values that are not included in estimated market values. A second inadequacy exists since ex -vessel values fail to completely measure potential production. For example, a large share of the catch is now taken on troll gear and many sublegal size fish are caught. In the removal from the gear and release of these sublegal fish, many sustain injuries that result in death or reduced growth. This wa.stage sig- nificantly reduces the total production from the resource to society. Also, estimated market values do not include other ty])es of benefits. For example, ex-vessel prices may not always be determined in markets with adequate com- petition to indicate total benefits, resulting in a producer surplus (i.e., additional profits to fish buyers). Benefits due to employment and income generated for coastal communities and the regional and national economy are not included. Consumer surj^lus or benefits to con- sumers that are not included in market prices are also omitted. These factors indicate that using the ex-vessel price for commercially caught fish is a reason- able estimate of benefits that could be realized. If all factors were included, this could prove to be a quite conservative estimate of total benefits. Tables 8a and 8b present the net value of com- mercially caught 1965- and 1966-brood coho salmon by ocean regions and Columbia River commercial fisheries. Two calculations were required to obtain the net value. The theoretical commercial catch was multiplied by the average Ad marked coho weight to obtain the total pounds of Columbia River coho caught by region. The total pounds were then multiplied by the average ex-vessel price paid in each region to obtain the net value of the coho catch to that region. Sport The net value for salmon and .steelhead sport fishing is estimated to be $20 per day of fishing. This value results from reconciling the existing research that is closely related to estimated net economic values of Columbia River sport caught salmon. The maximum potential benefits from sport fishing at a single market price is predicted at $20 per fishing day by Brown, Singh, and Richards (1972).' A single market price is in- tended to be comparable with typical conditions that underlie normal market price determina- tion. The original data for this report were from a 1962 survey in Oregon with results published in 1964. The net value that resulted in maximum benefits was estimated at $8 per day of fishing in the original analysis (Brown. Singh, and Castle, 1964). However, Brown and Nawas (in press) developed research techniques that more efficiently utilize available information. When these techniques were used in an analysis of the 1962 survey data, an estimated value of $20 per day was derived. This is the estimated value used in this report. Two other reports support the revised Oregon results. The estimated net economic value for the 1967 sport salmon fisheries of Washington resulted in a recommended value of $28 per day of fishing (Mathews and Brown, 1970). An eval- uation of the net economic values for the Idaho sport fisheries, based on a 1968 survey, resulted ** Jack A. Richards. 1969. An economic evaluation of Columbia River anadromous fish programs. U.S. Dep. Int.. Fish Wildl. Serv.. Bur. C ommer. Fish., Working paper 17, 274 p. (Processed.) ' William G. Brown, Ashok K. Singh, and Jack A. Richards. 1972. Influence of improved estimating tech- niques on predicted net economic values for salmon and steelhead. (Oreg. State Univ., Corvallis), Agric. Exp. Stn. unpubl. manuscr.. 26 p. (Typescript.) 154 WAHLE, VREELAND, and LANDER: BIOECONOMIC CONTRIBUTION M 0) 0) 3 •P H o a) EH > §rnl P( 3 H +J ifl aJ > ^ Oj -H CO m ^ VO rHCO J- O ro O % C) ir\ ON CO LTN 03 L/N V£) ^ \0 OJ rnir\ VO OJ a J- CO.* O J- o u^ o O O C\J ON O VO PO t— On CO CO c- t~- co u^ rH 00 CO CO CO OJ i C\l vn l/N VI) rH H •^ •% 00 --f QD -=t -^ C\J J3 (D -H 3 im s o l/N LTV o o L/N oJ ^ o OJ OJ o CO VO VO LTN VO CO LfN OJ CU «8 O O l^ H U\ t— H ITN O CO t^ f- o-lOJ t- t^ rH VO •\ •» -^ »\ 1 ■N •» 1 "s 03 OJ VO J- o CO r^ LP, CO CO CO OJ o o rH CT\ OJ H OJ H tv-i H OJ I^ u +J (D u a o a Ph o w o -p QJ o s P^ O u h a o a p, o w o u o c •H •H l<-l cc ti 01 (I) •H P P JTl u 3 J-: rH (0 <) ^ Sh o a 0) cd O > +J ^K H cS OJ CO H 0) CO -H O U 0) a j3 O CO <« V-i T3 rH 5 0) CO CQ a o 60 '^ 0) •d >H (3 O 3 o -d ft ti (0 u O CO - CO OJ ft -H ■ tl T) ft -H C O c ^ O o cd to a -rl • u 0) ft ^H 0) O ■d ' o I eg -p i-ee- CO CO -P o 3 m rH cO u a o o G a) T) d CO CO a CO O (D ^ •H J3 Cm +J -p a H O -d -d o J2 o j:: -d 60 a 3 CO CO o -P o o o J3 CO •H ■3 CO a. a o u ■d a) c •H OS O ■p 60 0) 60 cd > 60 •H 0) a cd 0) s a • CO a 0) o o 0) o -p ft ■P •H o 60 Ifl cd u u (11 (I) > > O -H 3 CO H -H CO /2 > a H o o m1 oTl otUPI^ ^ ^ 155 FISHERY BULLETIN: VOL. 72, NO. 1 rH (D a) 3 +^ H o a B^ > SvTl p. 3 O 05 a) > o to ■H 01 w as 11 J3 ^ In cd CO w ^ J3 s ON o" o OJ C\J s o o o •H H O a a) o o J3 +j w JS ^ •H m a ferked Unmarked Total Lower River (Ad-RM) Elokomin Big Creek Grays River Klaskanine Total Ad-RM 85,319 122,552 60,852 116,907 385,630 761,349 1,159,780 530,173 1,118,505 3,569,807 846,668 1,282,332 591,025 1,235,1+12 3,955,437 0.1008 0.0956 0.1030 0.0946 0.0975 28 23 27 28 2E Middle River (Ad) Bonneville Washougal Sandy , Eagle Creek^ Lewis^Z Kalama Falls Lower Kalama Toutle Total Ad 146,457 85,741 98,702 130,384 85,442 85,022 38,792 93,722 764,262 1,361,388 769,789 920,106 1,028,499 882,958 789,515 357,123 856,325 6,965,703 1,507,845 855,530 1,018,808 1,158,883 968,400 871+, 537 395,915 950,047 7,729,965 0.0971 0.1002 0.0969 0.1125 0.0882 0.0972 0.0980 0.0986 0.0989 24 25 22 20 27 28 27 24 2H Upper River (Ad-LM) Klickitat , , Little White Salmon-^ Willard 79,864 369,935 770,023 3,339,807 849,887 3,709,742 0.0940 0.0997 28 20 17 Carson?/ -- ~ — — ~ OxBow2/ Cascade Total Ad-LM 43,311 493,110 434,846 i+78,157 5,037,786 0.0905 0.0979 23 20 Uppermost River (D-Ad-RM, D-Ad-LM^ ) Leavenworth LeavenworthE/ 78,092 96,643 269,355 466 347,447 97,109 0.2248 0.9952 23 23 TOTAL ALL HATCHERIES 1,817,737 15,350,007 17,167,7'+'+ 0.1059 — 1/ I Mean weights in grams per fish. Values in total lines are averages weighted by total release at each hatchery in that river section. Additional 126,323 fish released with LM mark, 87,733 released with An mark, and 127,514 released with RM mark. Includes release from Speelyal hatchery. Includes releases from Willard hatchery. Honpartlclpating for I966 brood. Released below Bonneville Dam. 161 FISHERY BULLETIN: VOL. 72. NO. 1 Appendix Table 2a. — Number of marked and unmarked 1965-brood coho salmon recovered at hatcheries in each section ot the Columbia River in 1967 and 1968. Recovery location, by hatchery Marked and unmarked Origin Middle River- -Continued Lewis River Kalama Falls Lower Kalama Toutle Unmarked -- Ad-LM Upper river Ad Lewis Ad-RM Lower river Unmarked __ Ad-LM Upper river Ad Kalama Falls Ad-RM Lower river Unmarked -_ Ad-LM Upper river Ad Lower Kalama Ad-RM Lower river Unmarked Ad-LM Upper river Ad Toutle Ad-RM Lower river Upper River Year of return 1,072 0 88 0 1,891+ 0 235 0 1,176 0 107 0 10,1+51 0 865 0 521+ 0 89 0 1,915 0 227 0 l+,i+17 0 1+16 0 2l+,931 0 2,030 0 Klickitat Unmarked — 916 1,398 Ad-LM Klickitat 1+1 117 Ad Mid river 6 27 Ad-RM Lower river 0 0 Little White Salmon Unmarked __ 1,0U1+ 5,1+03 Ad-LM Little White Salmon 1+6 1+19 Ad Mid river 8 58 Ad-RM Lower river 0 0 OxBow ■ Unmarked __ ■(♦) 103 Ad-LM OxBow (») 3 Ad Mid river (*) 2 Cascade Unmarked „_ 7,21+7 7,227 Ad-LM Cascade 5I+9 576 Ad Mid river 1+1+ IOI+ Ad-RM Lower river 5 21 roermost River Leavenworth Unmarked __ 310 1,81+9 D-Ad Leavenworth 38 138 ♦Returns not examined. 162 WAHLE. VREELAND. and LANDER: BIOECONOMIC CONTRIBUTION Appendix Table 2a. — Continued. Recovery location, by hatchery Marked and unmarked Origin Year of ret ur n "I96B 1969" Middle Rlver--Contlnued Lewis River Kalama Falls Lower Kalama Toutle Upper River Klickitat Little White Salmon Cascade Uppermost River Leavenworth Unmarked -- Ad-LM Upper river Ad Lewis River Ad-RM Lower river Unmarked __ Ad-LM Upper river Ad Kalama Falls Ad-RM Lower river Unmarked __ Ad-LM Upper river Ad Lower Kalama Ad-RM Lower river Unmarked -_ Ad-LM Upper river Ad Toutle Ad-RM Lower river Unmarked -- Ad-LM Klickitat Ad Mid river Ad-RM Lower river Unmarked __ Ad-LM Little White Salmon Ad Mid river Ad-RM Lower river Unmarked Ad-LM Cascade Ad Mid river Ad-RM Lower river Unmarked D-Ad D-Ad-LM D -Ad-RM 1,911 0 233 0 1,592 0 148 0 1,887 0 192 0 0 200 0 2,91+5 0 302 0 10,696 0 888 1 2,739 1 263 1 23,664 0 2,093 0 Leavenworth Leavenworth Leavenworth 181 1,347 15 163 2 13 0 0 5,036 8,131 341 666 kh 105 1 2 2,144 1,374 146 83 41 22 3 14 69 32 1 0 7 0 0 0 163 FISHERY BULLETIN: VOL 72. NO. 1 Appendix Table 2b. — Number of marked and unmarked 1966-brood coho salmon recovered at hatcheries in each section of the Columbia River in 1968 and 1969. Recovery location, by hatchery Marked and unmarked Origin Year of return 1968 1969 )wer River Elokomln Unmarked -- Ad-LM Upper river Ad Mid river Ad-RM Elokomin Big Creek Unmarked __ Ad-LM Upper river Ad Mid river Ad-RM Big Creek Grays River Unmarked .. Ad-LM Upper river Ad Mid river Ad-RM Grays River KLaskanine Unmarked __ Ad-LM Upper river Ad Mid river Ad-RM Klaskanlne ddle River Bonneville Washougal Sandy Eagle Creek Unmarked -- Ad-LM OxBow Ad Bonneville Ad-RM Lower river Unmarked __ Ad-LM Upper river Ad Washougal Ad-RM Lower river Unmarked __ Ad-LM Upper river Ad Sandy Ad-RM Lower river Unmarked __ Ad-LM Upper river Ad Eagle Creek Ad-RM Lower river LM Eagle Creek 4,527 3 2 280 6,316 1 10 532 5,682 0 0 430 7,719 0 5 489 5,375 0 0 518 5,310 2 10 516 0,473 0 0 788 2,623 0 0 172 7,034 90 585 26 3,115 148 567 24 2,204 0 237 0 9,060 0 1,033 7 4,134 27 422 20 3,079 11 267 13 929 2 85 1 77 1,799 0 191 0 221 164 WAHLE, VREELAND, and LANDER: BIOECONOMIC CONTRIBUTION Appendix Table 2b. — Coniiiuicd Recovery location, by hatchery Marked and unmarked Origin Year of return TgEi 19SB" ower River Elokomin Unmarked -- Ad-LM Upper river Ad Mid river Ad-RM Elokomin Big Creek Unmarked __ Ad-LM Upper river Ad Mid river Ad-RM Big Creek Grays River Unmarked ._ Ad-LM Upper river Ad Mid river Ad-RM Grays River ICLaskanine Unmarked -_ Ad-LM Upper river Ad Mid river Ad-RM Klaskanlne Iddle River Bonneville Washougal Sandy Eagle Creek Unmarked — Ad-LM OxBow Ad Bonneville Ad-RM Lower river Unmarked Ad-LM Upper river Ad Washougal Ad-RM Lower river Unmarked __ Ad-LM Upper river Ad Sandy Ad-RM Lower river Unmarked __ Ad-LM Upper river Ad Eagle Creek Ad-RM Lower river LM Eagle Creek 533 0 0 1+1 1,616 0 3 105 10,51+0 0 26 936 10,573 0 5 1,079 1,363 3 1+1 1+0 2,651 0 0 213 7,201 0 0 527 l+,l5l 0 1 365 7,1+01 1+68 188 5 16,602 735 787 1+1+ 22,098 0 2,651 0 1+3,261+ 3 '+,316 3 6,021 18 661+ 11+ 5,222 21+ 517 32 593 0 63 0 2,371 5 222 2 58 215 165 FISHERY BULLETIN: VOL. 72, NO. 1 Appendix Table 3. — Percentage of iwo-year-old coho salmon in the marked and unmarked returns to Columbia River hatcheries by river section and brood vear, 1965-66. River section and Percent of 2-year-olds (in parentheses) mark Brood Marked Unmarked Lower (Ad-RM) 1965 hi 51 1966 3h 3h Middle (Ad) 1965 32 29 1966 27 28 Upper (Ad-LM) 1965 36 ko 1966 36 1^0 Appendix Table 4. — Actual number of marked coho salmon of the 1966 brood from Leavenworth National Fish Hatchery recovered — by type of mark, year of recovery, region of capture, and type of fishery, 1968-69. Region Fishery type D-Ad D-Ad-RM D-Ad ■U^ Total 1968 1969 1968 1969 1968 1969 1968 1969 British Columbia. Washington Oregon California Columbia River... Total . . . Commercial. . . . Sport Commercial. . . . Sport Commercial . . . . Sport Commercial. . . . Sport Commercial. . . . All fisheries. 0 0 0 0 0 0 0 3 18 30 20 3^+ 2 19 0 2 0 0 0 0 0 0 0 0 5 7 5 32 0 15 0 0 0 0 0 0 0 0 29 30 6 52 3 13 0 33 0 0 0 0 0 0 0 3 52 67 31 118 6 1+0 0 50 125 73 167 365 1/ Released below Bonneville Dam. 166 WAHLE, VREELAND, and LANDER: BIOECONOMIC CONTRIBUTION Appendix Table 5a. — Estimated number of marked coho salmon of the 1966 brood from Leavenworth National Fish Hatchery recovered — by type of mark, year of recovery, region of capture, and type of fishery, 1968-69. Region Fishery type D-Ad D-Ad-RM D-Ad ■U^ Total 1968 1969 1968 1969 1968 1969 1968 1969 British Columbia. Washington Oregon California Columbia River... Total . . . Commercial. . . . Sport Commercial. . . . Sport Commercial. . . . Sport Commercial. . . . Sport Commercial. . . . All fisheries. 0 0 0 0 0 0 0 6 123 lilt 184 7 137 0 7 0 0 0 0 0 0 0 0 23 30 15 176 2 35 0 90 0 0 0 0 0 0 0 0 131 128 19 285 Ik 52 0 186 0 0 0 0 0 0 0 6 242 281 lk8 645 23 224 0 283 660 371 822 1,853 1/ Released below Bonneville Dam. Appendix Table 5b. — Estimated recovery of D-Ad-RM and D-Ad-LM marked 1966-brood coho salmon from Leavenworth National Fish Hatchery after redistribution of the D-Ad-only marks. i^^ Region Fishery type D-Ad-RM D-Ad' Total 1968 1969 1968 1969 1968 1969 British Colvunbia. Washington Oregon California Columbia River. . . Total . . . Commercial Sport Commercial Sport Commercial Sport Commercial Sport Commerc ial All fisheries. . 71 96 77 275 6 109 0 94 0 0 0 0 0 0 0 3 171 185 0 0 71 370 0 0 17 115 0 0 0 189 0 6 242 281 148 645 23 224 0 283 728 1,125 1,853 1/ Released below Bonneville Dam. 167 FISHERY BULLETIN: VOL. 72. NO. 1 Appendix Table 6. — Relative survival of marked 1965- and 1966-brood coho salmon by mark type and hatchery groups. Cascade, Tetracycline Little White, All Brood Mark group Klaskanine hatcheries 1965 Ad-LM Ad Ad-RM 1966 Ad-LM Ad Ad-RM - .69^ .69^ ^ — .9^ ^ .79^ • 79 _ .683/ • 72 3^/ .89^ ^ .1^ .72 1/ Eagle Creek National Fish Hatchery. 2/ Big Creek Salmon Hatchery. 3/ Cascade Salmon Hatchery, Little White Salmon National Fish Hatchery. \J Klaskanine River Salmon Hatchery. 5/ Klickitat State Salmon Hatchery, Cascade Salmon Hatchery, Little White Salmon National Fish Hatchery. 6/ Bonneville Salmon Hatchery returns not included in calculations . Appendix Table 7. — Estimated catch of unmarked 1965- and 1966-brood hatchery coho salmon by region, fishery type, brood year, and year of capture. Region Fishery type 1967 1965 brood 1968 Total 1968 1966 brood 1969 Total Ocean fisheries: British Columbia... Washington Oregon California Subtotal Freshwater fisheries: Columbia River Total Commercial Sport Commercial Sport Commercial Sport Commercial Sport Commercial Sport Commercial. . . 3,928 1,733 80,101 163,997 203,620 93,759 270,127 7,878 102,523 0 265,634 0 656,371 3,21+6 7't,5't8 80,101 163,997 203,620 93,759 270,127 7,878 102,523 265,634 656,371 7,174 76,281 0 0 0 0 0 0 0 34,981 153,837 122,210 86,658 298,453 7,529 77,724 0 248,024 0 533,368 6,516 4,771 2,775 136,057 34,981 153,837 122,210 86,658 298,453 7,529 77,724 248,024 533,368 11,287 138,832 All fisheries 5,66l 999,799 1,005,460 9,291 922,220 931,511 168 WAHLE, VREELAND, and LANDER: BIOECONOMIC CONTRIBUTION Appendix Table 8. — Estimated total catch of 1965- and 1966-brood hatchery echo salmon by region, fishery type, brood year, and year oF capture. Region Fishery type 1967 1965 brood 1968 Total 1968 1966 brood 1969 Total Ocean fisheries: British Columbia. . . . Washington , Oregon California Subtotal Freshwater fisheries: Columhia River Total Commercial Sport Coramerc ial Sport Commercial Sport Commercial Sport Commercial Sport Commercial. . 4,297 1,872 87,526 179,179 222,405 102,614 294,778 8,556 111,592 290,349 716,301 3,552 81,364 87,526 179,179 222,405 102,614 294,778 8,556 111,592 290, 349 716,301 7,849 83,236 38,313 167,91^+ 133,536 94,994 326,241 8,259 85,165 7,133 3,021 271,167 583,255 5,223 148,533 38,313 l67,91i^ 133,536 94,99^ 326,241 8,259 85,165 271,167 583,255 12,356 151, 55^+ All fisheries 6,169 1,091,566 1,097,735 10,154 1,008,178 1,018,332 Appendix Table 9. — Estimated 1967-69 sport catch in Columbia River tributaries (where no creel census was made) of 1965- and 1966-brood hatchery coho salmon. 1965 brood 1966 brood Estimation stream 1967 1968 Total 1968 1969 Total method Icicle River 50 15 65 10 10 20 1/ Klickitat River 5 6 11 5 0 5 2/ 3/y Little White Salmon R. m 8 119 7 2 9 2/3/5/ Wind River 2 0 2 — — -- 2/ 3/y Washougal River (upper) (lower ) 10,382 1,385 2,048 273 12,430 1,658 2,493 332 872 116 3,365 448 i/ 3/ 5/ i/3/1/ Elokomln River 59 75 134 92 115 207 2/3/4/ Grays River 10 218 228 265 213 478 2/3/v Sandy River 513 944 l,i*57 l,i+57 1,198 2,655 3/i±/6/ Eagle Creek (Clackamas) 928 1,709 2,637 \,lkk 1,1+33 3,177 3/4/6/ Big Creek 4lO l^h 1,164 603 496 1,099 3/V6/ KLaskanine River 53it 983 1,517 1,31+6 1,106 2,452 3/5/6/ TOTAL l'+,389 7,033 21,422 8,35lt 5,561 13,915 1/ Estimates from discussions with Gene Nye, Washington Department of Fisheries, and local fishery personnel. 2/ Catches from Washington Department of Fisheries punch card returns 1967-1969- 3/ Age groups broken down by using jack to adult ratios obtained in creel census on Lewis, Kalama, Cowlitz, and Toutle Rivers. 4/ 70?^ of catch apportioned to hatchery production. 5/ Entire catch assumed hatchery. 5/ Catches from Oregon State Game Commission punch card returns I967-I969. 169 ABILITY OF MALE KING CRAB, PARALITHODES CAMTSCHATICA, TO MATE REPEATEDLY, KODIAK, ALASKA, 1973 Guy C. Powell.' Kenneth E. James.- and Charles L. Hurd'' ABSTRACT An experiment lo test abilities of male king crab to mate repeatedly in an environment approximating natural conditions was conducted during the spring of 1970. Twenty-four males of varying size and shell age were placed into separate undersea compartments for intervals up to 56 days with 222 females. The ability of males to mate repeatedly was determined by introducing females in mating condition to males at the rate of one every 5 days. No difference in mating capabilities of males of different types was evident until after expo- sure to seven females. At this point egg fertility and relative fullness of brood chamber of the females mated to the small old-shell males decreased significantly. Large new-shell males showed a marked decline in mating ability after the ninth mating. One small new-shell male mated with 13 females. Owing to declining stocks within the Kodiak Island fishery, commercial harvest of king crab has declined from 96 to 11 million pounds over the past seven years. 1965-1971. To determine the level of king crab brood stocks necessary for perpetuation of a maximum sustained yield fish- ery, the reproductive capabilities of the king crab are being studied in detail. In 1964, biologists of the Alaska Department of Fish & Game determined experimentally that recently-molted sublegal (smaller than 146 mm carapace length) male king crabs were capable of mating. Eleven males ranging from 120 to 144 mm carapace length mated 51 females in 16 days (Powell and Nickerson. 1965). Observa- tions on individual males were not obtained. In 1971. males as small as 85 mm carapace length were found to be capable of mating (Powell. Shafford. and Jones, 1972). Of 3.402 males ob- served mating in nature from 1963 to 1971. how- ever, only two were smaller than 100 mm (Powell. Rothschild, and Buss^). ' Alaska Dept. of Fish & Game, Commercial Fisheries Div., Box 686, Kodiak, AK 99615. - Bio-Statistics Div., Dept. of Preventive Medicine, Stanford University Medical Center, Stanford. CA 94305. ■' Alaska Dept. of Fish & Game. Commercial Fisheries Div.. Box 234. Homer, AK. 99603. * Powell, Guy C. Brian J. Rothschild, and James A. Buss. 1972. A study of king, ParaUthodcs canushaiica (Tilesius) brook stocks, Kodiak Island, Alaska, 1963-1971. 30 p. (Processed) Several authors have reported old-shell males congregated with adult females during the mat- ing season and indicated they may be capable breeders because new-shell males were separate from the females at the time (Gray and Powell, 1966; Miyahara and Shippen, 1965). Currently the reproductive success or failure of any particular brood year is not readily appar- ent until approximately 8 yr later when males are entering the fishery. At this late date, it is doubtful that we can, with any precision, eval- uate the degree to which each of the limiting factors contributes to the success or failure; con- sequently we are unable to determine if resul- tant abundance levels are attributable to initial magnitude of egg production, environment, or effects of commercial fishing. Prior to 1970, managers assumed that any level of harvest of males was acceptable as long as the 7-inch size limit (carapace width outside spines) was observed. In recent years, we observed that the propor- tion of adult females without eggs and with partial broods had increased and that some of the female population was not being serviced (unpublished Alaska Department of Fish & Game data). Large adult females have approxi- mately nine times more eggs than small ones (Haynes. 1968) and initial examination of un- published Department of Fish & Game data reveals that the incidence of adults without eggs and with partial broods is greater among the Accepted tor publication June 1973. FISHERY BULLETIN: VOL. 72. NO. 1. 1974 171 FISHERY BULLETIN: VOL. 72. NO. 1 larger individuals. In order to place more males on the mating grounds and to stabilize annual harvests, a quota system was initiated in 1970. It is important to know whether that segment of the male population harvested by the commer- cial fishery, i.e., large males and old-shell males (Nickerson, Ossiander, and Powell. 1966) pos- sess greater mating capabilities than smaller protected males which molt during the mating season. Also of significance is the question of whether undersized males would be adequate in numbers and ability to mate all females if larger males were removed by the fishery. Recent in- creases in the numbers of adult females with broods of reduced size appear related to simul- taneous increased exploitation rates and may result from matings with males which had mated several times previously. Our experiment was designed to gain insight into these phenom- ena and to obtain more complete data for individual males, especially comparative data on mating ability for old-shell males and recently molted new-shell males. In this paper, mating refers to the actual fer- tilization of the eggs. Hence, the term "mating capability" refers to the ability of the male to fertilize the eggs of the females to which he is exposed. METHODS AND MATERIALS Experimental Equipment and Location The experiment was conducted in undersea l^ens, the sides and top of which were covered with nylon mesh; the bottoms were open to allow crabs to dig in the substrate as they would do in nature. Each pen was 8' X 8' X 4' and each divided into four equal sized compartments. Compartments were numbered 1 through 28 and situated in 40 ft of water on a level stretch of muddy-sand bottom east of Near Island adjacent to an area where king crabs normally mate. The study location is one mile from the city of Kodiak, Alaska. Pens were designed and located to simulate natural conditions. Environmental factors such as daily tidal currents, pressures, light intensities, temperatures, and salinities were considered important in that they might in- fluence mating. For this reason, undersea pens were considered superior to aquaria. The mating study was conducted in compart- ments 1 through 24 while 25 through 28 were used to store crabs. Females were held in storage prior to and after the completion of mating. Fishery biologists and trained technicians utilizing scuba observed the crabs underwater every day. Individual crabs were identified by tagging with permanent "isthmus" loop tags (Gray, 1965) prior to being placed in the pens. Experimental Procedures The experiment was designed to compare mating capabilities of four size shell-age classes of male king crabs (small new-shell, small old- shell, large new-shell, and large old-shell) by studying the effects of repeated matings on the ability of these males to mate successfully with additional females. A 5-mm range, 145-149, was used as a dividing ])oint between small and large males at the juncture of legal and under- size crabs. Those 144 mm or less (commercially undersize males) were classified as small while those 150 mm or larger were classified as large (Table 1). Small males averaged 140 mm, large males 167. Most males used in the experiment were captured by scuba divers. A few of the males of required size, however, were not available by diving (the preferred method of collecting) and therefore were taken from the catches of com- mercial pots and trawls. All females used in the study were in premolt condition and were in the pre-copulatory em- brace (Powell and Nickerson, 1965): i.e., they had already been selected for mating by males in the natural environment. The use of these females (called "graspees") was our method of insuring that females were ready to mate with males when introduced into the ])ens. Females from natural mating areas near the pens were captured by scuba divers a day or two before they were needed and ranged in length from 104 to 181 mm, with an average size of 134 mm. Table 1. — Size relationships of experimental crabs. No. of Coropoce length (mm) Mole king crabs female partners Range Meon Class Number Male Female Male Female Small old-shell 4 29 136-144 107-181 142 133 Large old -shell 9 82 156-193 1 14-175 178 134 Small new-shell 4 35 136-142 1 15-150 139 135 Large new -shell 10 76 150-168 104-160 158 134 Total 27' 222 Three extra males replaced three original males which died. 172 POWELL. JAMES, and HURD: MATING ABILITY OF MALE KING CRAB Females were separated from the males which held them and placed in storage ready for use in the experiment. The average length of females increased as the study progressed because older females mate later in the season. ^ Females cap- tured 15 March through 15 April averaged 128 mm. while those captured 20 April to 20 May averaged 140. Twenty-four females were paired randomly with the 24 males in the pens at the beginning of each of the 14 separate 5-day periods begin- ning 16 March and continuing through 24 May. On days when a complete set of 24 females could not be captured, those which had been were in- troduced to males which previously had had the largest number of female partners. Incomplete sets of females exist for early and late spawning periods — 1, 2, 3, 12, 13, and 14 — when mating crabs were relatively scarce. In addition, 12 fe- males escaped from six compartments on 9 May when two pens were accidentally lifted; as many as three females were lost from a single com- partment. During the middle of the mating sea- son, 31 March through 5 May, females were abundant; consequently each male received a female for each of the eight consecutive periods within this interval. Females were introduced to males as soon after capture as possible; none were held more than two days and many were introduced the same day. Females were left with males until mating was completed and eggs were known to be fer- tilized; consequently males commonly shared their compartments with several females at a time. Approximately 10 days after eggs were deposited on the pleopods, a sample of approxi- mately 1,000 was obtained from each female to determine success of fertilization. Each sample consisted of several separate groups of eggs taken from scattered locations within the egg mass. Samples were preserved in Bouin's solu- tion. Fertilized eggs developing for 7 to 10 days at approximately 37 °F showed cleavage when viewed microscopically. When eggs were known to be fertilized (i.e., advanced cleavage stages observed), females were separated from their experimental male partners and placed in stor- age compartments 25-28. Divers made observations at daily intervals recording data on underwater slates. Observa- tions included collecting and measuring shed exoskeletons to determine day of molting, exam- ining recently-molted females to determine rela- tive fullness of the brood chamber, and recording activities of mating and feeding. RESULTS Relative success of male copulation was measured in two ways. First, relative fullness of brood chamber was determined subjectively by visually deciding what proportion of the brood chamber was filled with eggs and record- ing same on a scale of zero to one hundred (Table 2). The second, percent of eggs fertilized, was determined in two steps; (1) a prompt micro- scopic viewing of several hundred eggs to obtain quick estimates, followed later by (2) a careful microscopic examination of 100 eggs (Table 3). Both measures of mating success provided compatible results and revealed that infertile eggs are scattered throughout the egg mass rather than being grouped separately from fer- tile eggs. The raw data, ij, for each of the two measure- ment variables were transformed so that they would be more normally distributed, using the formula:'' z = y/n + 1/2 sin -1/v + 3/8* n + 3/4 In this case, n is equal to 100, since both methods of measurement are based on a scale of 100. A covariance analysis was performed relating z to X. the number of females mated. This analysis fits a least squares regression line z — 0/ -I- b,- X for each of the four groups, where a,-, bj represent the intercept and slope respectively for the ith. group. The results of this analysis are presented in Table 4. Slopes for each group appear to be significantly different from zero, except for percent of eggs fertilized in large old- shell and small new-shell males. The more nega- tive the slope of the regression line, the less the '" Determined from 3,402 observations of grasping pairs of king crabs captured over a 9-year period, 1963-1971. See page 257 National Geographic Magazine. Vol. 139, No. 2, Feb. 1971 for photograph of grasping pairs. •> Thoni, H. Transformation of variables used in the analysis of experimental and observational data, a review. Technical Report No. 7. Statistical Laboratory, Iowa State University. Ames. Iowa, July 1967. 173 FISHERY BULLETIN: VOL. 72. NO 1 sz -3 c a 01 c o c £ o — < o o o U-) -O O O lO o 00 00 o O O U-) 00 CO 00 o o o o o o ^ o o o o o o o o- o o o o o o o o o o o o o o o o q q CO O 01 IT) 00 "Mill I r' M I I I 5^ I I I I I § I I i o , lo o o CO CO o 00 o O o o o o o -o U-) o o o o o o o o o t> o o CN ^ o ^ o o OOOOOOOOLTi oooooooor^ ooooooooo QOOOOOUIOOO ooooooooo ooooooooo- '_)OOOOiOOOO OOOOC^OOOO OOOOOOiTiOO OOOOOOCOOO OOOOOOOOO OOOOOOOOOO- -^'OCOO'^CO'— OO OlDOOOOOCOOOOO - - m - S - o 00 in ^ o U-) o o r\ (N u-i CO CN 00 o o irt 1 I o £ 1/5 2 o 01 o- cc o- o- O- u-1 o S 1 i o o u-1 O- o z o z — o ^ o -o in 00 CO >o o o o o o -o o o- o m m o o t^ r^ o o o o o CO o t> o o o o o o 00 ~o o o m o o O Pv 00 o o o o o -o o o o ■^ CO -^T n 00 ^ CN 00 O -7 (> M I I M M °§ II I O o r^ o o o o o O O ~0 00 o o o o o i\ m •— o o o o o o CO o o o o o m o o lo o rv o o r>. I I o o -o o m o 00 I I T o o o o o m _^ O O O O O- CO o o o o o o o o t^ — o o o 00 o o o o o o o o o o o o- o o- o o o o o o o o o o o o o o o o- , o o o o o in tv CO tOOOOOOOOOO P^O — OOOOOOO ooincooo — oco — ^ ino^o>o<}<3minin CO -o CN q in -G m <3 CO 00 o r^ b CO ~o OD O CN o o c^ o- O 00 — 00 O 00 — m 174 POWELL. JAMES, and HURD: MATING ABILITY OF MALE KING CRAB Qtl at X; T3 3 t/5 ffi < u _f- a 01 t 0 c £ o — 1 1 1 - 1 1 1 1 i 6 1 o ' ' 1 - 1 1 ' 1 ! o ' 1 ' o o , o r\ rv o [ 1 o 1 1 1 1 o o 1 o- 1 1 1 1 1 1 1 " 1 1 1 1 1 1 o , o o o o o . o o 1 1 1 1 1 o o t 1 o u-1 1 1 1 1 CM o o o , n CO ic in o un b o- ^ o 1 o 1 hv o 1 o o o- CO ' t O 1 o o tN c o o o o o O ; o o 1 o o lO o o ■o 00 o CN 00 o o o o o o o o ' ii : o '6~ CM ■^ t> — go o o o r^ CO o o- CN o o r^ 00 m o- t> -^ o o- O o o ' o o o o ' o o~ 1 2 o o o- ' 1 t> c^ ■^ o o CN CO cr o o CO o o o o o CO o' o o b CO o rv rx O 1^ o , . o , o o 00 o o o~ o o- o o o o r^ o o o o CD o- 00 o o- o 1 1 o 1 o o o o o o o o r^ O o o o o o- o o o o o ^ CO o o c> o ^ 00 o 1^ o- o a fv o o o O- o o o o o o CO 00 o o IT) o o o o o o l\ o o n (^ o o o o o o o o o o- o o CO o o ^ o o o 00 o 00 O- u-1 , o o o o o- o o o o o o o o o o o o o o o~ o o o~ o o c^ o 1 o m CN o r^ o o '^ o- o o o o o o o o o o o o "J o o ^ 00 o o o o o o o o o 00 o o -0 o o o o o o o o o o o o t> o c- o o o o o o o j o o o CN o o o o ^ o O lO o S o r^ o o o o 00 o ^ 00 o ^ tv o o o o CO o o o o o o o o c o o o o o o o o o o o o o o c> o o o o CO o o 1 o o ~o o o o o ^ o o o o o o 00 o o- o o c> o o o o ^ o o o o o Q o o O 00 o o o o o o o o- o o o o o- o o o o o o o o o o o o o o ; o o -o L.O o o o o n o o o o o o o 00 o- o o- o o 00 o o ^ o o o o o o o o o o o o o o o o o o o o o o- o o o o- o o- o o o o o o o o o o o o o in oo o -O CN -^ 'J T .— ^ -o n b ^ n — o o o N o -o CN 00 ■^ o- o o m CO CO ^ o CO ^ — n ^ ■^ TT c 0 -7 -o m -o O 00 o 00 00 00 c 0 N ■T CO t C^' c 0 co iT) -O ■o -o •o •o -o m U1 IT) ~ o ^ o "i o "ci QJ > 0) > ^ > ^ -C -C l/i I/) 0) "o > ^ 'o > 1^ TT CO 00 00 o o o o o o — o O 00 o z I! o '- i? O) CN_0 o E 175 FISHERY BULLETIN: VOL. 72, NO. I Table 4. — Comparison of king crab mating ability, slopes and slope contrasts for relative fullness of brood chamber and percent of eggs fertilized. Relative fullness of brood chamber Percent of eggs fertilized Male class Slope Standard deviation of slope F Value for Test of slope = 0 Slope Standard deviation of slope f Value for Test of slope = 0 Small old-shell Large old-shell Small new-shell Large new-shell /)i = -1.416 /)2 = -0.616 /)3 = -0.328 hi = -0.677 0.234 0.112 0.164 0.116 F F F F = 36.5 P < .0001 = 30.3 P < .0005 = 3.9 P = .05 = 33.9 P < .0001 /'I />2 = -1.171 = -0.087 = -0.036 = -0.637 0.202 0.107 0.142 O.IOO F = 33.5 P < F = .7 P = F= .1 P = F = 40.4 P < 0.0001 .32 .75 .0001 Test for equality of slopes hi = />2 = /'3 = /'4 F = 4.07, P = 0.01 F = 11.74, P = .0001 Slope Contrasts Contrast estimate Standard deviation of estimate f Value for test of contrast = 0 Contrast estimate Standard deviation of contrast F Value for test of contrast = 0 Old-shell vs. new-shell -1.028 b\ + h2 — h^— hi Large vs. small -0.450 hi + hs — b2~ hi 0.329 0.329 9.80 P = O.OOI f = 1.9 P = 0.17 -0.585 -0.482 0.287 0.287 f = 4.1 P = 0.04 F = 2.8 P = 0.10 mating ability of the males in that particular group. A test of the hypothesis of equality of slopes {bi = b2 = b^ = 64) yields an F ratio of 4.1 for relative fullness of brood chamber and 11.7 for percent of eggs fertilized, significant at the 1 and 0.01 percent level respectively. In or- der to determine the significance of the size shell- age classifications, contrasts of old-shell versus new-shell and small versus large were computed as shown in Table 4. These contrasts indicate that the major contribution to the inequality in slopes comes from the difference in shell age. Size did not appear to be a significant factor as is indicated by P values of 0.17 and 0.10 respec- tively for relative fullness of brood chamber and percent of eggs fertilized. Within the shell-age contrast, the small old-shell males contribute the most in the form of a more negative slope, indicating that these males have much less mating ability than the other three groups. The data pre.sented thus far give a comparison of the mating abilities of the four size shell-age groups. A linear approximation was assumed for each group and, although this procedure is not exact, it is sufficiently close for comparative purposes. Graphs of the curves for mating abil- ity versus number of matings indicate that small old-shell and large new-shell males have the least linear relationship of the four groups. The points i)lotted in Figures 1 and 2 are the means of the transformed variables for each successive mating. A point may represent as few as one or as many as ten observations, as shown in Tables 2 and 3. The original 0 to 100 scale is attached to the graphs to make them easier to read; thus after the means are computed, they are trans- formed back to the original scale. The slopes of the functions were approximated by computing the means of the transformed measurement variables for each x and fitting empirical curves to the data points. Figures 1 and 2 show the relationship between percent of eggs fertilized and relative fullness of brood chamber respectively and are presented primar- ily as an aid to fisheries management. The results, however, are quite consistent with those given in Table 4. The graphs show a marked de- cline in the mating ability of small old-shell males after approximately the seventh mating and a decline in the ability of large new-shell males after the tenth mating. Figure 2 indicates that partial clutches result from mating with small old-shell and large new-shell males which had mated several times previously. The least squares regression lines for large old-shell males and small new-shell males are also plotted in Figures 1 and 2. These groups show little decrease in mating ability as the number of matings increases, particularly for the percent of eggs fertilized. The slope of the 176 POWELL. JAMES, and HURD: MATING ABILITY OF MALE KING CRAB 100 90 - = 80 70- 60 50 40 CO 30 o UJ ?0 z UJ o (r UJ 10 a. 00 SMALL OLD SHELLS SMALL NEW SHELLS LARGE OLD SHELLS Pgfg P oints Small Old Shells X Large Old Shells * Small New Shells + Large New Shells • LARGE NEW SHELLS 1 I \ T 3 6 9 12 NUMBER OF SUCCESSIVE FEMALES MATED I 15 Figure I. — Mating ability of male king crabs expressed as percentage of eggs fertilized. 100 z 3 90 >- IT 80 UJ OD z < 70 I o Q 60 <■> O IT m 50 -I 3 40- 30 - 20 UJ 10 < bJ q: 00- J\ SMALL NEW SHELLS LARGE \ NEW SHELLS-^2^ SMALL OLD SHELLS - \ -LARGE OLD SHELLS Data Points Small Old Shells X Large Old Shells * Small New Shells + Large New Shells • I I 6 9 NUMBER OF SUCCESSIVE FEMALES MATED "T" 12 15 Figure 2. — Mating ability of male king crabs expressed as relative fullness of brood chamber of mated females. 177 FISHERY BULLETIN: VOL. 72. NO. 1 regression line for large old-shell males for relative fullness of brood chamber is quite steep (-0.616) and nearly approaches the slope for large new-shell males (-0.677); however, there are no points in the vicinity of zero to indicate that mating ability for large old-shell males drops off suddenly after a certain number of matings. Furthermore, the other measurement variable indicates that the mating ability of large old-shell crabs does not decline at a signif- icant rate when exposed to a maximum of 18 females. DISCUSSION This study indicates that all classes of males tested i)ossessed considerable ability to mate repeatedly at the approximate rate of one female every 5 days. Mating ability of small old-shell and large new-shell male king crabs decreases markedly after approximately the seventh to ninth mating. The decline for large old-shells and small new-shells is not as noticeable. Although the analysis of covariance for this experiment does not indicate significant differ- ences in mating ability attributable to size, one should be hesitant in saying categorically that size is not a relevant factor. By examining the individual slopes in the graphs, it is evident that certain combinations of age and size have a marked effect on mating ability and one must realize that when a given factor is examined, the other factor is averaged out. The knowledge obtained as a result of this investigation represents just a beginning in the understanding of the mating of king crabs. To what extent these findings are applicable to mating in nature remain uncertain. The effects of holding experimental crabs in undersea pens must be understood before realizing full appli- cation of the data to practical management of the fishery. Holding males in pens could adversely affect mating ability of some classes, particularly later matings after prolonged captivity, while simul- taneously enhancing ability of others by forcing partners into constant close association with one another. Larger females used later in the experiment may also have affected results. Even though size does not appear to be a sig- nificant factor in mating ability as far as the number of repeated matings is concerned, and even though small males appear to be capable breeders, it remains a possibility that in some instances in nature small males may not serve adequately as brood stock. Measurements of 6,804 king crabs captured by divers as mating pairs, 1963-1971, reveal that small young fe- males are the first to mate each season followed three months later by large old females (Powell, Rothschild, and Buss. 1972). Further, males mating in nature with "pubescent" females (i.e., those mating for the first time and therefore the smallest found) are older and larger, averaging 42 mm more than females, with grasping ob- served as early as January 9 (Powell, Shafford, and Jones, 1972). Apparently male size and male-female ratios are not the only factors affecting mating in nature. The presence in recent years of high in- cidence of adult females without eggs and with partial clutches within certain locations of the Kodiak fishery seem to be fishery-related because they occur only in areas of intense fishing (Pow- ell, 1969'). Adult female king crabs form mating congre- gations in shallow water from January through April and these congregations are intermittently distributed throughout the thousands of square miles of shallow habitat. For mating to be suc- cessful in each congregation, adequate numbers of capable males must be present during the relatively brief matable period following female ecdysis, otherwise delayed mating may adverse- ly affect the success of ovulation and subsequent fertilization (Kurata, 1961; McMullen. 1969; and Wallace, Pertuit, and Hvatum, 1958). The ratio of males to females necessary for complete mating success in nature appears de- pendent upon factors other than just numbers alone. The rate at which females molt and spa- tial distribution and size differences of adults inhabiting the location are also believed impor- tant. The greater the rate of female molting, the greater the number of males required. Male crabs select partners as early as 16 days prior to mating and continually grasp them until copu- lation occurs soon after female ecdysis (Powell, Rothschild, and Buss, 1972). Because of pre- mating "grasping" behavior, it is possible that females molt without male partners though a ■ Powell Ciuv C. 1969. Some aspects of king crab biol- ogy. Proc. Am.' Fish. Soc. West. Div. Meeting, Jackson Hole, WY, June 1969. (Processed) 178 POWELL, JAMES, and HURD: MATING ABILITY OF MALE KING CRAB favorable male-female ratio exists, because all males are either preoccupied grasping other females or resting between subsequent matings. King crabs segregate to varying degrees according to size, sex. age, and time of year. Com- mercial fishing is concentrated in areas inhabited by large males with total effort varying accord- ing to factors such as accessibility. Thus crop- ping of males may be excessive in one area but not in another. Incidence of nonovigerous adult females is lowest in areas where sublegal sized males are abundant, but is often high in ex- ploited areas with few adult males (unpublished, Alaska Dept. Fish & Game). Size differences between partners, presence of competing males, and time of year also must be considered in evaluating the reproductive potential of mating populations. It is conceivable that even with many young adult males present, a population of large old females may be inadequately serviced partly because the few surviving large males may, through aggressive behavior, keep smaller males away. To what extent competitive be- havior exists is presently unknown but large old males commonly are found mating small young females in nature. Of the 14 matings in this experiment, where females were larger than males, 79 percent produced partial clutches. Small males probably produce less reproduc- tive material (sperm) than large males, and as a result, may be less capable of fertilizing the greater masses of eggs of large females. LITERATURE CITED Gray.G. W., Jr. 1965. Tags for marking king crabs. Prog.-Fish Cult. 27:22 1-227. Gray, G. W., Jr., and G. C. Powell. 1966. Sex ratios and distribution of spawning king crabs in Alitak Bay, Kodiak Island, Alaska (Deca- poda. Anomura. Lithodidae). Crustaceana 10:303- 309. Haynes, E. B. 1968. Relation of fecundity and egg length to carapace length in the king crab. Paralithodcs camtschuticu. Proc. Natl. Shellfish. Assoc. 58:60-62. KURATA, H. 1961. King crab investigations in the eastern Bering Sea in 1961. (Prelim, transl.) I.N.P.F.C. (Int. North Pac. Fish. Comm.) Doc. 48 1, 6 p. McMuLLEN, J. C. 1969. Effects of delayed mating on the reproduction of king crab, Paralithodcs camischatica. J. Fish. Res. Board Can. 26:2737-2740. MiYAHARA, T., AND H. H. ShIPPEN. 1965. Preliminary report of the effect of varying levels of fishing on eastern Bering Sea king crabs, Paralithodcs camischatica (Tilesius). Rapp. P-V. Reun. Cons. Perm. Int. Explor. Mer 156:5 1-58. NiCKERSON, R. B.. F. J. OSSIANDER, AND G. C. PoWELL. 1966. Change in size-class structure of populations of Kodiak Island commercial male king crabs due to fishing. J. Fish. Res. Board Can 23:729-736. Powell, G. C, and R. B. Nickerson. 1965. Reproduction of king crabs. Paralithodcs cuini- schatica (Tilesius). J. Fish. Res. BoardCan. 99: 10 1- 1 1 1 . Powell, G. C, B. Shafford, and M. Jones. 1972. Reproductive biology of young adult king crabs Paralithodcs camtschatica (Tilesius) at Kodiak Alaska. Proc. Natl. Shellfish. Assoc. 63:77-87. Wallace, M. M.. C. J. Pertuit, and A. R. Hvatum. 1949. Contribution to the biology of the king crab, Paralithodcs camtschatica Tilesius. U.S. Fish Wild. Serv., Fish. Leafl. 340, 50 p. 179 I AN EVALUATION OF MID-WATER ARTIFICIAL STRUCTURES FOR ATTRACTING COASTAL PELAGIC FISHESi Donald A. Wickham and Gary M. Russell^ ABSTRACT Mid-water artificial structures positioned off Panama City, Fla. during August 1970 were evaluated to determine their ability to attract coastal pelagic fishes. Quantitative and quali- tative experimental results were obtained using scuba divers and purse seine catches. The feasibility of using artificial structures to facilitate the commercial harvest of coastal pelagic fishes with purse seines was established and the methods described. Average catch values of 398 kg (875 lb) per structure were obtained during a period when coastal pelagic fishes were unavailable to the local fishery. A greater total production was obtained from structures fished daily compared with those allowed to soak for 3 days before being fished. Experi- mental purse seine collections established that fish leave the structures at night with new recruitment occurring daily. No significant differences were obtained from preliminary exper- iments to evaluate the effects of structure size and color on attraction effectiveness. A work- ing hypothesis is presented to describe apparent behavioral mechanisms involved in the attraction of some species of coastal pelagic schooling fish to objects in the sea. This study indicates that artificial-structure fish-attraction has potential for development as a tech- nique to facilitate the harvest of the latent coastal pelagic fishery resources in the Gulf of Mexico. Artificial structures have been shown to be effec- tive for attracting concentrations of pelagic fishes (Hunter and Mitchell, 1968). Klima and Wickham (1971) visually evaluated the species and number of coastal pelagic fishes attracted to experimental artificial structures in the north- eastern Gulf of Mexico. These observations es- tablished the feasibility of attracting large numbers of coastal pelagic fishes with artificial structures; however, many questions concern- ing structure attraction characteristics and dynamics as well as their actual usefulness in augmenting conventional harvesting methods for these species still remained unanswered. Studies were conducted during August 1970, in 5 to 10 fathoms (9 to 18 m) of water offshore of Shell Island, Panama City, Fla. to obtain quantitative samples for evaluating the validity of scuba-diver estimates of structure-attracted fish aggi-egations, to evaluate methods for using a conventional purse seine for capturing struc- ture-attracted fish, and to obtain catch-produc- tion values for single structures. We also evalu- ' Contribution No. 234, Southeast Fisheries Center, Pascagoula Laboratory, National Marine Fisheries Service. - Southeast Fisheries Center, National Marine Fisheries Service, NOAA, Pascagoula, MS 39567. ated effects of structure soak time and size-color differences on attraction effectiveness. Day and night samples, plus scuba-diver observations of fish behavior, provided additional clues to the dynamics of the coastal pelagic fish aggregations attracted to artificial structures. MATERIALS AND METHODS Our fish attraction devices were three-dimen- sional structures. Each structure was construct- ed from vinyl-cloth covered, wood and wire frame panels. Two panels were fastened along one side, permitting the structure to be stored flat, but opened into a three-dimensional right prism when deployed for fish attraction. Two sizes of structures were used. The small struc- ture panels were 0.9x1.5 m (3x5 ft) in size and the large structures, with twice the surface area of the smaller structures, were 1.8 X 1.5 m (6X5 ft). All structures were white except those painted for specific experiments. Structures were positioned 4-6 m (15-20 ft) beneath the surface. The structure design and mooring arrangement are illustrated in Figure 1. Structures were spaced at approximately 0.8-km Manuscript accepted May 1973. FISHERY BULLETIN: VOL. 72. NO. 1. 1974. 181 FISHERY BULLETIN: VOL 72. NO. 1 (0.5-mile) intervals. Their arrangement in the experimental site is shown in Figure 2. The eight structure mooring locations were used with different .structures as required for specific exj)eriments. The 15-m (49-ft) single boat-rig bait purse seiner, Gidf Ranger, was chartered to make quantitative collections at selected artificial structures using a tom-weight type purse seine, 22 m (12 fathoms) deep and 110 m (60 fathoms) in length, with 3.2 cm (lV4-inch) stretched mesh webbing. A 6-m (20-ft) inboard -outdrive power boat was used as a diving platform and for pick- ing up and resetting structures sampled by the purse seine. Daily visual estimates of the number and species of fisti present at each structure were made independently by scuba divers. We ob- tained quantitative data from selected structures by collecting all the fish around these structures with the purse seine. Diver estimates and purse seine catch data are given in Table 1. Scuba divers made visual estimates of the fish aggregation at a structure prior to beginning the purse seine set. The structure anchor was picked Figure 1. — Artificial structure design and mooring arrangement. up by the divers as soon as the seiner began setting its net. When pursing was half completed, the structure counterweight was retrieved to l^revent its being tangled in the jiurse line. After the purse rings were up, the dive boat would take the structure aboard, pass over the cork- line, and reset the structure clear of the net. The captain of the Gulf Ranger estimated the catch weight after each purse seine set and the biologist aboard sanij^led each catch to provide 30'I0' Figure 2. — Map of experimental site with numbered circles illustrating positions where artificial structures were deployed. Stage II is a Navy research platform west of the study area. 182 WICKHAM and RUSSELL: EVALUATION OF MID-WATER ARTIFICIAL STRUCTURES (U 'J C f- £ Q 1 -C 1 5 ^^ " . 0 *- o V ^ V V 0 CO 01 01 01 01 a E o CO 8^ o o Z := -1 o J3 O I I I I I I I I I I I I I M I I o I O O -O lO I o n n -^ in o TT-^TTGorN.oo^rvi^o^LO'Or\^CN inioio — CMOin -^ I ^% •■^ I ^ «^ ^x.1 ^W ^irt >_^ I ^N ^*\ I ^N o o o o ■^r^sj*— fj'MC/^'^t-jrs.ir)'— n-vitr-^ COCOCO'^rvcoio iocN"oioom >0'0Oiocnoo ■^CNCO-OCO'T'^'^COCNCS^fO-^-^TT COCOCO"^CNCOCN o -o O Csl -O CO CO -o o o o o u-1 O o o CO CM CO "^ T CO ^ ^ O CM CM — CM ^ Ohs.^soocoocoo^"^"^oo0'00'0on'r)>or^ — cocNa3ro(>'^cn^oininioinc><>c>cococo(r)u-)C>cocNQO — CM — — — •— nCN-^^TT — — •—•— ^CN — CN-— o o o ■^ CN CO csr-^ocs — o-mm o o o m rv o I^CNIOI^OOOO "^ ^ CS CO CN CM CM CM -O O l\ o CM o o ooorv-^CMcor^oo^^o^m-— oir)>oo>Oioinin>ooco CO — cMinr^ocNOmoooooooocococon'^'^coo* — — COCM"^CNC0CN — NOOI^'OOr^ — — — •— — o o lO o r^-o— •oO'Or^rxr^'^'^'^'^cooo-oco'O-oorv'— -^ CNCOOOCOCOCOCMCMCMIOlOIOin^COOCO — COCOCOCNQOO CM — ■— — — — CMCMCN'^'^'^nCOCO — — — — — CM — CM in — — — -o^of^o^ — o^io-^o*- oh^- oor^oMOO'O COGOCOCOCOCOCNCOOOCOOO^LOOCOCOCNCO — CNf-vCOCOCO 00>0 — — — CM — — MDOr\"^0o CM ^ CM — CO O O O — CO CM >o CO in 00 o CM CO — CM O CO O o o o m m in in o CN CO o CO — o "O -o o CO -o — in '~ •~ '" CM CM — O CM O O r\ o O CN lO oooo-— Tjooin oooooomo-^ o o o O' -o "^ m n ■— CO u^ r^ tv rv in GO -O "^ CM CM CN ■^ O m CN CN CM o o o CM o o m •o m o — o o o 8 O U-) CO CN o n • — ■ — •— ' — *— CM •— OJ — 00 O CM O CO o Tf TT TJ m m m m inunininininin'^ ■^ -^ ^ ■^ -^ -^ -^ -Q O o m o — 2 I n CO o- in -o o ■^ CO n •o o cMoom-^t-vOi^-o- •^■^■^00-^-orv-toivrvr^m — coo CM-0"»incN'^CMcoooinunin — moocMin'^CMCMCM'Tcooo -^CMCOCM — — ■^"^■^CO'^COCM-^COCMCMCM OCO in-ooco-^-^-^cDmrv>0'^'^'^nco ncoo^Oininin-— "^cNcoinininino — CO-^'^'^CO CM — ■^^■^T'^co r^ 00 CM in t^ "^ o CM '- r\ "^ cN in "^ CM CO CM CM n CO o o o CO o O CO o o o o o m o m o rx o o CO CO CM in m o — in CM o -^ CO o m rv CO CO CM ^ m in >» m CO rvcMOor^ — or^- T^r^r^- ■^toorxrxrv^ohv — oocoo CMr^incOCMOOCOCNOOCMCMCMOOin^CNCMCNCOCMOOCOO- o CNCMCM^CM^^CM^CMCMCMO'^inCMCMCM^CM^'- ^- -^r^ocoincN-^ooocoooorN.- o inCM'^ > (U > > Q Q ^ Q 5 m > _ O, CM i-j 01 ~ ' ' P Oi oi P 0) oi 01 > > 01 > > 3q Q 3q h o Ol~ "^ il > > o o 01 0 oi > > 3q b 01 (U u i: 0, n w m > > > 01 S > > 11 S > > 0) 5i Q a < ^'^ Q < Si'^Q 3 0) Q Q <'3! ■O CM -^ O O MD *o CO CM CO O CO CO CO O CO o ■<)■ CO CM "^ " 01 g - '^ 1) ii 2 '5 aJ li > > 1) S > > QQ. O Q Q 3 Q. 183 FISHERY BULLETIN: VOL. 72. NO. 1 01 o o o £ O E to D E LO 0 E 1/3 a o 01 ai 5 ^ J) Q. ^ E § o -^ U1 '5 ->^ a ^ £ .§ o — 5" 01 01 J<: a £ o ■ CO 01 01 ai -1^ gi oi Oj D 0 .? Ol E H O '- lO gi 01 ^2 ooomcNOO ooco o o o lO 00 -^ CO CN in CN — I ,— oiococoron ,-^■^■■^■00 oooo*— 000 inmu^o *oor\ cococo TTTTTrco in o o t^ O CO o o I t 1 , GOO^COCN-— oinco-^O'— ^ — OOt^00OO<3iOO00CX5 OOO-OOCsOO-t^cOtO^'O^ o o CO o t^ o o o -- ^ <3 IT) o o •o lOlOlO^COcsCOI^COCMCO^LOOCOCM TJ-^TTCO^CN^CN^CN^^-^O-OCN uo o — CO o o CO CO -» CO m o o ^ o o CM csir^oc^j-^coocooO'^oco'^'^Trco cncnCncs-^co-^ooco^co^-^"^-^^ O CM O CN CO CO •o — 10 U-) — OJ o o (\coin"^r^cNLOcooooc3or^"^OcN CN>OOinCMCNCN'— OOOOCNlO'^r^ CNCOCM^CN ^—000 CN-^COCM IT) CO CO O IT) o -a- ■^ CM m IT) — -"J UO CO o o •OOOCO-^-rfTTCOO^OOO'^^OO COCOCO^lOiolOOOOOOin'OoO' — ^^ — •^-^Tjcooo-o-^-^'^o o mo o 00 CO CO 10 O CN CO — m CM CN CO jj, 0) CN CO >- >- O .£ ^r ■- Q) Jl 1) CD ^ CO E ■- >- Ji > > Q Q. H Q Q 2 ai Q Q a. 01 ^- .2 l/> 01 £ E o "O 01 D ■- O -x: o;S CO 1) ^- data on species composition. It was not practical to totally weigh each catch as it came aboard or to keep the fish from individual sets separated for later weighing; consequently the captain's catch weight estimates had to serve as our quan- titative standard. The accuracy of the captain's estimates was established by comparing the daily total of his estimates with the daily fish house landing records for the G/iIf Ranger (Table 2). We believed the accuracy of these estimates ()•- = 0.97) justified our utilizing them for eval- uating diver estimates and for quantifying experimental data (Figure 3). RESULTS Diver Estimates The validity of scuba-diver observations was evaluated by comparing the divers' estimates of the total number and species composition of fish present at a structure with data obtained from the purse seine catch at that structure. Numer- ical estimates obtained by the divers for coastal pelagic school fish were converted to weight, utilizing a catch average of approximately 22 fish per kilogram to permit comparison with purse seine catch data. The comparison of diver estimates with the captain's estimates for the corresponding purse seine catches are plotted in Figure 4 for data collected 17-21 August 1970 (Table 1). Data from 24 August to 27 August were not included in this comparison because schools of little tunny {Euthijiunm oUetteratus) began following the purse seiner and were occasionally observed attacking and scattering the structure-attracted fish schools before the purse seine set was com- pleted. A linear regression analysis of the mean for each set of paired diver estimates {Y= 76.5 + 0.56X; ?•- = 0.68) indicates that although con- siderable variation does exist, fish schools less than 182 kg (400 lb) tend to be slightly overesti- mated while the larger schools are increasingly underestimated. A linear regression analysis was also calculated for each diver's individual estimates and these calculations indicated that estimates made by diver 2 tend to be more accurate than the more conservative estimates made by divers 1 and 3. The purse seine catch sample data indicated scuba divers were able to identify the major J 184 WICKHAM and RUSSELL: EVALUATION OF MID-WATER ARTIFICIAL STRUCTURES Table 2. — Diver estimates, purse seiner captain's estimates, and fish house landing totals for daily catches from artificial structures. No. daytime Total average diver estimates for Total purse seiner Fish captain's daily house Fish house landings by species Date 1970 sets structures sampled catch estimates landings Round scad Spanish sardine Aiiiiusi 17 4 1,227 2,227 2,193 830 1,363 18 4 1,057 1,091 909 614 295 19 8 2,568 3,841 4,045 1,830 2,215 20 4 1,227 1,500 1,545 727 818 21 4 830 955 852 432 420 Total 24 6,909 9,614 9,544 4,433 5,111 '21 4 1,136 1,159 1,034 761 273 '25 5 2,034 1,386 1,682 716 966 '26 5 3,182 1 ,068 693 443 250 '27 6 3,523 1,114 1,194 489 705 Total 20 9,875 4,727 4,603 2,409 2,194 9-day total 44 16,784 14,341 14,147 6,842 7,305 Data not used for scuba-diver estimates-purse seiner catch comparisons. species attracted to the structures. They were not, however, able to determine accurately the pei'cent species composition for the schools of mixed coastal pelagic fishes. These mixed schools contributed over 95% of the catch weight taken from each structure. The mixed coastal pelagic school fish consisted of round scad (Decapterns pioictatus) and Spanish sardine (Sardiitella anchovia). The bait fish occurred at each structure in mixed schools of varying per- cent species composition. The difficulty encoun- tered by the divers in obtaining accurate percent species composition data for this group was probably the result of behavioral differences " between the species. Round scad usually approached closer to the divers than Spanish sardine, which tended to concentrate on the side of the school farthest away from the divers. Jacks usually represented less than 5% of the total catch weight and consisted primarily of small 15-cm (6-inch) blue runner {Caranx crysos), crevalle jack (C. hippos), and bar jack (C. ruber). Among the species which comprised the major components of Klima and Wickham's (1971) jack group, amberjack {Seriola sp.) were only occasionally observed and rainbow runner {Elagatis bipi)i)iulata) were notable by their absence in this series of experiments. The jacks are not treated separately' in our paper because of their minor contribution to the total number and weight of the structure-attracted fish aggre- gations. Comparison of diver estimates and purse seine catch data indicates that although purse seine data are quantitatively superior both sampling techniques are complementary and, combined, provide a more complete picture of the experimental environment than either singu- larly. Where diver estimates provided the only available data they are considered sufficient to permit rough evaluation of the experimental results in terms of their commercial significance. FISH HOUSE LANDING (pounds) leOO ZZX 2700 3150 3600 Figure 3. — Relationship between the daily total of the Gulf Ranger captain's estimates of structure-purse seine catches and the daily fish house landing records. Statistical evaluation of this data by linear regression analysis yields Y = 216.4 + O.S16X\ r- = 0.97. N = number of set es- timates in each daily total. 185 FISHERY BULLETIN: VOL. 72, NO. 1 400 800 1200 CATCH (pounds) 1600 2000 2400 1600 1400 1200 :iooo 800 ; 600 400 200 "1 — r 1 — \ — r 2800 3200 3600 — I — I — 1 — 1 — r- 4000 O DIVER 2 X DIVER 3 200 400 600 800 1000 1200 CATCH (kilogroms) 1400 1600 1800 3200 2800 o < 2400 2000 - 1600 -o 1200 800 - 400 Figure 4. — Relationship between divers" estimates of bait fish school size and the captain's estimate of the purse seine catch at each structure. A linear regression analysis of the average paired diver estimates yields Y = 76.5 + 0.56A'; /?- = 0.684. A linear regression analysis of the estimates made by each diver yields Y = 11 .b + 0.?04A',- r- = 0.285 for diver one; Y = 55.3 + 0.683A': r^ = 0.704 for diver two; and Y = 98.4 + 0.501A'; r-^ = 0.42 for diver three. Recruitment Patterns and Production Our observations indicate a rapid reci-uit- ment with fish being observed at structures the day following placement. To obtain estimates of production and recruitment of bait fish to the structures, we made daily diver estimates and purse seine collections at four selected structures. Four other structures, also observed daily by divers, were set on after being in position for 3 days. During this period (17-21 August 1970). our structures produced an average of 398 kg (875 lb) per set. These catch rates are not ex- tremely large, but they were made when bait fish were not seasonally available to the local beach seine fishery. No bait was being landed, excei)t for fish captured around our structures. The total daily diver estimates and purse seine col- lections are plotted in Figure 5, along with the 3-day accumulative totals, to allow comparison of production between the four structures fished daily and the four structures set on once, follow- ing the 3-day soak period. Our day 3 catch results indicate no significant advantage in catch size was realized by allowing the structures to soak for 3 days. The potential total catch, assuming daily sets had been made on the 3-day soak struc- tures, indicated from our consistently conserva- tive diver estimates was three times larger than the actual catch after 3 days' soaking. The total accumulative catch from the four structures set on daily was also approximately three times larger than the actual catch from the four 3-day soak structures even though diver estimates indicated smaller total fish concentrations were present at the .structures set on daily. These results show that a greater total production was obtained by making daily sets. This high rate of daily attraction and the apparent lack offish accumulation provided further indications 186 WICKHAM and RUSSELL: EVALUATION OF MID-WATER ARTIFICIAL STRUCTURES that fish were being attracted to the structures on a daily basis. Comparison of Day and Night Collections A series of day and night sets were conducted to determine whether fish leave the structures at night. Divers estimated the quantities of fish at four selected structures which were then set on during daylight hours. The quantity offish at four other structures was estimated by divers just before dark and fish around these structures were collected after dark. Diver estimates, and day and night catch results, are plotted in Figure 6. The diver estimates were conservative for structures set on during the day, with estimates for both days being less than the actual catch for three of the four structures. The divers frequent- ly estimated that concentrations of fish present at the structures fished at night were larger than at the structures fished in the daylight. Nighttime collections however, consistently pro- duced only 45.5 kg (100 lb) or less of mixed species. These results provided further evidence that bait fish leave the structures at night and that new recruitment was occurring daily. The nighttime sets were made during the new moon and we lack data on whether bait fish also leave the structures at night during the full moon. Size and Color Evaluation The success of bait fish attraction with arti- ficial structures appeared to be dependent upon the visibility of the structure. We evaluated two sizes of structures to determine whether dou- bling the structure size would increase the num- ber of fish attracted. An analysis of variance for purse seine capture data (F — 0.75< Fo.90(i,5) = 4.06) and diver estimates revealed no sig- nificant difference in attraction by structure size. Structure attraction was also evaluated in terms of color visibility. We compared a white structure with ones painted fluorescent green, blue, and yellow since Kinney (1970) reported that fluorescent paints provide greater visibility under water. Structure position was rotated daily so that a structure of each color occupied each of the four positions. An analysis of vari- ance for catch data (F=0.026 7n n ra Ez AGE GROUP Figure 2. — ^^Age composition of sampled pound and fyive net catches in the James, York, and Rappahannock rivers, July 1%7-June 1971. (Tiller, 1950; Vladykov and Wallace, 1952; Murphy, 1960; Shearer, Ritchie, and Frisbie, 1962) and along the migration route in coastal states from Virginia to New England (Merriman, 1941; Schaefer, 1968). Schaefer (1968) concluded that Chesapeake Bay is the primary source of striped bass caught in the surf of Long Island, and that Hudson River stocks may significantly contribute to these populations only when dominant year classes from Chesapeake Bay are unavailable. Yet it is generally believed, although still debatable, that only a small proportion of those striped bass originating in Chesapeake Bay enter the coastal migration (Vladykov and Wallace, 1952; Mansueti, 1961; Massmann and Pacheco, 1961; Grant etal., 1970). Koo (1970) has shown an apparent six-year Table 4. — Summary of the year classes of striped bass ■ that dominated catches in Virginia rivers, 1967-1971. River Samp 1967-68 ing Year 1968-69 (Ju y through J 1969-70 une) 1970-71 James York Rappa ha nnock 1965 1966 1966 1966 1967 1966 1967 1968 1968 1969 1969 1969 Table 5 — Contribution of age groups I-III to pound net and fyke net catches of striped bass in three Virginia rivers, 1967-1971. Sampling Year Perce ntage Age of Samp Groups ed Catch in I-III (July-June) James York Rappahannock 1967-1968 1968-1969 1969-1970 1970-1971 84.7 90.8 90.9 94.3 99.4 96.3 92.7 84.3 92.8 95.3 93.4 85.6 cycle of abundance in Maryland. Such a cycle could result from the appearance of a dominant year class every six years, followed by three years of high catches (Ages I-III), then three of relatively low catches. The younger age groups (I to III) contribute most to Virginia pound net and fyke net catches of striped bass (Table 5), as expected for nonselective fishing gear. Over 90% of sampled individuals were from age gi-oups I to III, except: 1) 84.7% in the James River during the first year of sam- pling due to catches of large numbers of older fish, particularly the 1958 year class; 2) 84.3% in the York River in the 1970-1971 sampling year; and 3) 85.6% in the Rappahannock River in the same year. The last two exceptions occurred because of contributions by the latest dominant year class (1970 — then Age 0). Although the age composition of Virginia catches would seem to conform to Koo's (1970) six-year cycle, no such cycle is apparent in Virginia landings (Figure 1), even though the dominant year classes mentioned by Koo (1970) were also successful ones in Virginia. The difference between Maryland and Virginia landings, relative to this six-year cycle, might stem from local successes of year classes inter- spersed among those appearing at six-year intervals. In addition to the 1958, 1964 and 1970 cyclically dominant year classes, certain Virginia rivers have produced large hatches of striped bass in 1961 and 1966 (Grant and Joseph, 1969; Grant, Burrell, and Kriete, 1971). Catches of these aperiodically strong year clas- 198 GRANT: AGE COMPOSITION OF STRIPED BASS es tend to obscure, or even eliminate, peaks in landings contributed by Koo's Chesapeake- wide dominant year classes. Thus only long- term trends in abundance remain evident (Figui'e 1). ACKNOWLEDGMENTS The author acknowledges with thanks the following colleagues for their helpful dis- cussions and assistance: Edwin B. Joseph, Victor G. Burrell, Jr.. C.E. Richards. William H. Kriete, Jr., George R. Thomas, and James C. Owens. Reviews of the manuscript by Jackson Davis and John V. Merriner were most helpful. Also appreciated are the drafting of figures by Jane Davis, photography by Ken Thornberry and manuscript typing by Louise DeBolt and Linda Jenkins. LITERATURE CITED Grant, B. C, V. G. Burrell, Jr., and W. H. Kriete, Jr. 1971. Age comiiosilion and magnitude of striped bass winter gill-net catches in the Rappahannock River, 1967-1970. Proc. 24th Annu. Conf. South- eastern Assoc. Game Fish. Comm., p. 659-667. Grant, G. C, V. G. Burrell, Jr., C. E. Richards, and E. B. Joseph. 1970. Preliminary results from striped bass tagging in Virginia, 1968-1969. Proc. 23rd Annu. Conf. South- eastern Assoc. Game Fish Comm., p. 558-570. Grant, G. C, and E. B. Joseph. 1969. Comparative strength of the 1966 year class of striped bass, Roccus saxalilis (Walbaum), in three Virginia rivers. Proc. 22nd Annu. Conf. South- eastern Assoc. Game Fish Comm.. p. 501-509. Koo, T. S. Y. 1970. The striped bass fishery in the Atlantic states. Chesapeake Sci. 11:73-93. Lewis, R. M. 1961. Comparison of three tags on striped bass in the Chesapeake Bay area. Chesapeake Sci. 2:3-8. Mansueti, R. J. 1961. Age, growth, and movements of the striped bass, Roccus saxalilis, taken in size selective fishing gear in Maryland. Chesapeake Sci. 2:9-36. Massmann, W. H., and a. L. Pacheco. 1961. Movements of striped bass tagged in Virginia waters of Chesapeake Bay. Chesapeake Sci. 2:37-44. Merriman, D. 1941. Studies on the striped bass {Roccus saxalilis) of the Atlantic coast. U.S. Fish Wild!. Serv.. Fish. Bull. 50; 1-77. Murphy, G. J. 1960. Availability of striped bass during summers of 1958 and 1959 as reflected in commercial haul seine catch. Chesapeake Sci. 1:74-75. Raney, E. C. 1952. The life history of the striped bass. Roccus saxalilis (Walbaum) Bull. Bingham Oceanogr. Collect.. Yale Univ. 14(l):5-97. SCHAEFER, R. H. 1968. Size, age composition and migration of striped bass from the surf waters of Long Island. N.Y. Fish Game J. 15:1-51. SCOFIELD, E. C. 193 1. The striped bass of California (Roccus Imcaius). Calif. Fish Game, Fish Bull. 29, 84 p. Shearer , L. W., D. E. Ritchie, Jr.. and C. M. Frisbie. 1962. Sport fishing survey in 1960 of the lower Patuxent estuary and the 1958 year-class of striped bass. Chesapeake Sci. 3:1-17. Sykes, J. E. 1961. The Chesapeake Bay cooperative striped bass program. Chesapeake Sci. 2: 1-2. Tiller, R. E. 1950. A five-year study of the striped bass fishery of Maryland, based on analyses of the scales. Chesa- peake Biol. Lab. Publ. 85: 1-30. Vladykov, V. D., and D. H. Wallace. 1952. Studies of the striped bass, Roccus saxalilis (Walbaum) with special reference to the Chesapeake Bay region during 1936-1938. Bull. Bingham Oceanogr. Collect., Yale Univ. 14( 1): 132- 177. 199 LARVAL FISHES OF YAQUINA BAY, OREGON: A NURSERY GROUND FOR MARINE FISHES? WiLUAM G. Pearcy and Sharon S. Myers' ABSTRACT Based on a survey of planktonic fish larvae, the Yaquina Bay estuary appears important as a spawning or rearing ground only for Cliipea harengus pallasi (Pacific herring) and a variety of small cottids, gobies, and stichaeids. Other investigators, however, have found an abundance of juvenile Paroplirys vctiihis (English sole), Citharichihys stigiuaeus (sanddab), HyponicsHs pretiosus (surf smelt), Plutichthys siellatiis (starry flounder) and embiotocids (surf perches), indicating that the bay is an important nursery area for these species. Of the 44 types of larval fishes found in the bay, C. h. pallasi and Lepidogobius lepidits (bay goby) were co-dominants each year, 1960-1970, comprising 90% of all larvae collected. There was no evidence of trends in abundances or species composition during the 11-yr study. Maxima of planktonic fish eggs and L. gobiiis larvae occurred in the summer: maxima of all larvae combined and most species of larvae occurred in the winter and spring. High densities of larval herring were found in February and March, and peak numbers appeared earlier in the lower than the upper estuary. Larvae of C. h. pallasi, L. lepidus, and Cotius asper were common at all stations from 0.5 to 8 nautical miles up the estuary, but not in the adjacent open ocean. Larvae of many species that were found in the estuary in small numbers were more abundant in offshore waters. Although English sole and sanddab were rare in the bay as larvae, juveniles were numerous. This is a study of the species composition, relative abundance, seasonal and annual occur- rence and distribution of larval fishes in an Oregon estuary. It was undertaken to increase the extremely limited knowledge of fish larvae in estuaries of the Pacific Northwest and to evaluate the role of these estuaries as spawning and nursery grounds. According to Clark (1967) and McHugh (1966, 1967) the young of up to 70% of the eco- nomically important Atlantic species of fishes inhabit estuaries during part of their early life. Many species spawn offshore and young stages subsequently move into brackish estuaries. Although the Pacific coast is known for its runs of anadromous salmonids which migrate through estuaries, "There is no counterpart on the Pacific coast of the mass inshore movement of larvae and young of offshore-spawning nek- tonic species into brackish nursery grounds that is such a striking feature of the ecology of most Atlantic coast and Gulf of Mexico estuaries." (McHugh, 1967). Thus the number of species that are dependent on estuaries may ' School of Oceanography, Oregon Stale University, Cor- vallis, OR 97.131. not be as great on the Pacific as the Atlantic coast. Oregon's estuaries are few in number and include but a small area. For this reason man's infringement on them for recreation, land development, harbors, agriculture, and waste disposal will be intense. This study evaluates some long-term trends of the relative abundance of larval fishes. Hopefully it will facilitate future comparisons of faunal changes within this estuarine habitat. THE ESTUARY Yaquina Bay (Figure 1) is a small tidal estuary on the central Oregon Coast. It extends inland about 37 km and has an area of about 11.6 km-. A channel is dredged to a depth of 7.9 m to McLean Point and to 3.7 m to the town of Toledo. Tides are mixed, semidiurnal with a mean tidal range of 1.7 m (Kulm and Byrne, 1967). According to Zimmerman (1972) the bay has an exchange ratio of 52% and a flushing time of 13.3 tidal cycles during the summer. The estuary is well-mixed with little vertical strati- fication in the summer when freshwater runoff is low, and is partially mi.xed (4-19"/on salinity Manuscript accepted June. 1973. FISHERY BULLETIN, VOL. 72, NO. 1, W74 201 FISHERY BULLETIN: VOL. 72, NO. 1 I24»00 W. TOLEDO 44' 96' N. CONTOUR INTERVAL 12 FEET DATUM MEAN LOWER LOW WATER Contour! complied from U. S C. AGlS I9S3 •moom tliMt 44" 36 N. 124* 00' W. Figure 1. — Yaquina Bay estuary, showing location of stations: Bridge, Buoy 15, 21, 29, and 39. difference from surface to bottom) during other seasons (Burt and McAlister, 1959; Kulm and Byrne, 1967; Zimmerman, 1972). Salinity is lowest and also most variable during the winter period of high precipitation. Temperatures, however, are most variable during the summer, owing to periodic advection of cold upwelled waters into the bay and to local heating (Fro- lander. 1964; Frolander et al.. 1973). SAMPLING METHODS A 12.5 cm diameter Clarke-Bumpus (CB) Sampler with nylon (Nitex")" net of 0.233 mm mesh aperture was used to collect 393 plankton samples from January 1960 to December 1970 and to provide a long time series for analysis at one station (Buoy 21) located in Yaquina Bay about 4.3 nautical miles from the ocean (Figure 1). In addition, both the CB and a 20.2 cm diameter nonclosing Bongo Sampler were towed together at five stations (Bridge and Buoys 15, 21, 29, and 39) from June 1969 to June 1970 (223 tows). The bongo had nylon 2 Reference to trade names does not imply endorsement by the National Marine Fisheries Service. nets with 0.233 mesh on one side and a 0.571 mesh on the other and was attached 1 m below the CB on the same towing cable. The CB net was 61.6 cm long with the filtering area of the mesh to mouth area ratio of 6.2:1. The bongo nets were cylindrical-conical, 177 and 161 cm long for the 0.233 and 0.571 mesh nets respec- tively. Both bongo nets had a filtering area to mouth area ratio of 10.5: 1. Samples were collected from small boats, generally at weekly intervals during the sam- pling period. Oblique-step tows were made at 2 knots. At the three deep stations (Bridge, Buoys 15 and 21) the net was towed horizontally at each of three depths for 4 min: about 1 m above the bottom, at mid-depth and 1 m below the surface. At the two shallow stations in the upper estuary the nets were towed at each of two depths for 6 min: 1 m above the bottom and 1 m below the surface. Tows were made during day- light, in mid-channel, against tidal currents, and did not coincide with any particular tidal stage. However, several 24-h series of CB tows (123 tows) were made during the 11-yr period to assess diel and tidal variations at single stations. 202 PEARCY and MYERS: LARVAL FISHES OF YAQUINA BAY Samples were also collected with the bongo nets (0,233 and 0.571 mm mesh) in the open ocean off Yaquina Bay from June 1969 to June 1970, often within a day of the bay sampling. A total of 113 step oblique tows was made at four stations 1, 3, 5, and 10 miles from the coast. Volume of water filtered during each tow was estimated by flowmeters in the mouth of the nets. TSK meters were mounted on the inside wall of the bongo frames. Meters were calibrated periodically by towing them over a measured distance. Samples were preserved in the field with Formalin. In the laboratory entire samples were sorted for fish larvae with the aid of 2V4 -power illuminated magnifier. Fish eggs were sorted from the 1960-1968 CB samples. SPECIES COMPOSITION Larval fishes representing 17 families were found in Yaquina Bay during the 11-yr studies. These included 45 distinct types of larvae, 22 of which were identified to species (Table 1). Most families were represented by only one or two species or types. The family Cottidae, however, was represented by 14 different larval types, by far the most for any family. The family with the next largest number of types was Pleuronec- tidae with 6 identified species. THE 11-YR SERIES Relative Abundances Table 2 summarizes the occurrence and average density of different fish larvae collected during the 11-yr CB series at Buoy 21. Two species, Clnpea harengiix pallasi (Pacific her- ring) and Lepidogobius lepidus (bay goby), were clearly the most abundant larvae. Com- bined they accounted for 90% of all the fish larvae collected in the 393 samples. These two species were consistently the co- dominants during all years of the sudy (Table 3). C. h. pallasi ranked first in abundance during 8 yr. L. lepidus ranked first in 3 yr and second in the 8 yr that C. h. palla.^i was dominant. Cottus asper (prickly sculpin) ranked third in abundance. Leptocottus armatus (Pacific stag- horn sculpin), Gobiidae type 1, and Hypomesus pretiosus (surf smelt) alternated in the fourth, fifth, and sixth positions. Average number of Table 1. — Species composition of fish larvae from Yaquina Bay from all samples examined, 1960-1970. Clupeidae Cltipca hurciiKiis pallasi Engraulidae EnKiaitli'' morilax Osmeridae H\ potncsus pii'iiosus Gobiesocidae Gohicsox nwandricus Gadidae Microiiadti^ proxiniWi Gasterosteidae Aiilorhynchus ttavidus Syngnathidae Svni;iHilhm i;iisci>lincan<\ Stichaeidae LumpeiuiS sugilta Annplarchiis sp. ChiroUiphis sp. 2 unknown types Pholidae Pholis (irnara Ammodytidae Ainmodyles hexaptenis Gobiidae LcpuloKohiiis It'dpiitiis 1 unknown type Scorpanenidae SchasU'\ spp. Hexagram mi doe Hi'xaiirainini)^ sp. Ophioddii eU>ui;aiiis Cottidae Leplocollus armalus Conns asper Scarpaenichthys nianuoratus Enophrys bison HeniiU'pidoiiis spp. 9 unknown types Agonidae 2 unknown types Cyclopteridae 3 unknown types Bothidae Cilharichihys sp. Pleuronectidae Psellichthys melanosticiiis Platichlhys stellalus Glyiocephaliis zuchinis Isopsetta isolepis Parophrys vetulus Lyopsetta exilis these larvae per m'' varied from year to year, but no obvious long-term trends in the relative abundance of these species suggested environ- mental changes or species succession. (Similar- ly, Frolander et al. [in press] found no evidence for persistent changes of zooplankton abun- dances in Yaquina Bay over the same time period.) In order to learn if all six of the common species were more abundant in some years than others, rank correlations were calculated from annual abundances in Table 3. Cliipea h. pallasi and L. lepidus were both caught in large numbers in 1967. but the Coefficient of Concordance, W, (Tate and Clelland, 1957) indicated little agreement among ranking of vears (P > 0.2). In other words, there was no 203 FISHERY BULLETIN: VOL. 72, NO. 1 Table 2. — Fish larvae collected in CTarke-Bumpus nets during 1960-1970 at Buoy 2] ranked by abundance. No. of Tows Total No. Total No. larvae — Months of occurred collected total volume of water occurrence item in out of 393 filtered m-'xlO'' Clupeu harentiiis palUiM 76 2,174 510 l-V LepidoKobiiis lepidus 98 1,287 302 IV-X Ci>llu\ a\per 47 129 30 l-V LeptocoUKs armatus 42 53 12 Vlll-lll Gobiidae type 1 27 49 11 Vll-lll, VI H\, pomcsu.s preliosiis 23 39 9.1 VIII-IX, XI-IV Lninpcnus siiaina 8 29 6.8 l-ll Enaphrys his on 12 20 4.7 l-lll AntmodyU's hexapienis 10 15 3.5 l-lll Anopkinhiis sp. 10 12 2.8 ll-lll Cottidae type 1 8 10 2.3 ll-lll, Vi-VII Ennraiilis itiordax 6 7 1.6 VII-IX. Pholis oriuilu 7 7 1.6 l-lll Parophrys venilus 4 6 1.4 ll-lll Plaiichihy^ \ielUmis 3 3 0.7 V-VI Cyclopteridae type 1 3 3 0.7 VI, VII, XII Cottidae type lOA 3 3 0.7 II, XI Cottidae type 5 3 3 0.7 VIM, IX Cilhuncluhys sp. 2 2 0.5 ll-lll Cyclopteridae type 2 2 2 0.5 VI-VII S\Kiitilhus i;risi'i>Unealus 2 2 0.5 VII-VIII Cottidae type lOB 1 1 0.2 1 Cottidae type 1 1 1 1 0.2 III Schasics spp. 1 1 0.2 1 Hexagrammidoe 1 1 0.2 II evidence that "good" or "bad" years occurred simultaneously for different species of larvae. SEASONAL VARIATIONS Total Eggs and Larvae The average monthly catch of pelagic fish eggs at Buoy 21 was highest in the summer, with highest values ( > 2/m^) from July to October (Figure 2). Eggs of the northern anchovy {Engraulis mordax) were sometimes abundant during this season. Numbers of fish larvae, on the other hand, peaked early in the year, from February to June, and few larvae were taken after June. C. h. pallasi and L. lepidus larvae were the main contributors to these large larval catches. These two species, and many others found in the estuary, have demersal eggs. This seasonal maximum of fish larvae in the first half of the year in Yaquina Bay is similar to the seasonality reported in the Straits of Georgia, British Columbia by Parsons, LeBras- seur, and Barraclough (1970). Individual Species The seasonal occurrence of larvae collected at Buoy 21 is summarized in Table 2. The majority of the larval species were most com- mon in the winter or spring, including C. It. pallasi, Coitus asper, Hypomesus pretiosus, Paropltrys retulus, Anintodytes hexapterus, Luinpenus sagitta, Auoplarchus sp., Pholis oruata, and Euophi-ys bisou. L. lepidus was Table 3. — Average abundance of the six most common fish larvae by year, 1960-1970, Clarke-Bumpus samples. Buoy 21. Avera ge number of larvae per lO'^m^ water filtered Item 1960 1961 1962 1963 1964 1965 1966 1967 1968 1969 1970 Clupc'u )iarenHUS 174 542 278 279 1,230 335 273 1,136 961 526 506 pallasi Li'pidoKohiiis 312 230 37 1 14 326 402 161 1,169 471 74 132 lepidus Cdiuis asper 17 35 24 38 41 48 35 68 5 20 14 Gobiidae type 1 11 1 2 50 24 0 0 11 0 34 14 Leplocollits 17 6 12 34 12 7 18 17 5 10 2 armatus Hypomesus 5 7 0 23 4 4 18 3 0 44 7 pretiosus 204 PEARCY and MYERS: LARVAL FISHES OF YAQUINA BAY the only common species with a distinct peak of larval abundance in the summer (April- September). Several species were collected most months of the year: considering all years together, larvae of Hyponiesus pretiosus were found every month but May, June, July and October, L. arniatus every month except April-July, and Gobiidae type 1 every month but April, May and July. Pacific Herring Catches of C. It. pallasi larvae during each January-June period, 1960-1970, are illus- trated for Buoy 21 in Figure 3. Herring larvae were common from. Febi-uary-April, with peak numbers usually in February and March. Though sampling variability and the limited number of samples precluded annual com- parisons of abundance, no obvious long-term trends, such as decreasing catches, are evident during this 11-yr period, nor is there good evidence for large fluctuations in larval num- bers. This suggests a fairly stable population of spawning herring over this time period. The initial occurrence of larval herring varied among years, from January to March, suggesting annual differences in time of spawn- ing or hatching times (e.g., contrast 1969 and 1970 with 1961-1963). This variability may be related to water temperature. The surface temperature of first larval occurrence varied from 7.3°C to 10.5°C (average = 9.0°C). To estimate date of first spawning, incubation time was calculated from a curve of incubation times vs. temperature (Outram, 1955; Taylor, 1971; Steinfeld, 1972). Incubation was estimated to range between 12 and 17 days for the first herring larvae caught during these years using surface water temperatures at Buoy 21. (Because herring spawn in shallow water, often inter- tidally [Steinfield. 1972; Taylor, 1971; Hard- wick, 1973] , surface temperatures were used.) Surface temperatures averaged for the date of first herring larval occurrence and the previous 17 days (2-3 observations) were plotted against time of first larval occurrence after January 1 (Figure 4). This revealed a surprising relation- ship: Years of earliest occurrence of larvae (i.e., 1969 and 1970) had lowest water temperatures (< 8°C) preceding first catches, and most years of latest occurrence (i.e. 1961. 1963, 1965, 1966) had highest temperatures (>9.2°C) during 0 - 2 - _.*_ A I S I 0 I N I D Figure 2. — Average monthly catches offish eggs and larvae in Clarke-Bumpus samples at Buoy 21. Each point rep- resents a monthly average for fish eggs each year, 1960- 1968, and for fish larvae each year, 1969-1970. No samples were available from April-July 1966. incubation of the first hatch. Thus, factors other than water temperature appear to be important in determining the time of the initial spawning of herring in Yaquina Bay. Steinfeld (1972) observed from egg surveys in Yaquina Bay that herring had four major spawnings during February and March 1970. These occurred at about 2-wk intervals starting in early February, the most intensive spawnings coinciding with highest tides. Newly hatched larvae would therefore be expected in most of the catches throughout the larval periods. Measurements of larvae contributing to early and late peaks in 1964 and 1967 showed that recently hatched larvae (6-8 mm) were indeed present in April, but as expected, the percentage of small larvae was lower later in the year. HORIZONTAL VARIATIONS The average number of larvae collected at the different stations in both the estuary and the open ocean are listed in Table 4, permitting comparison of horizontal variations of relative abundance at nine stations from 8 miles up the 205 FISHERY BULLETIN; VOL. 72. NO. 1 cr LlJ CL cc UJ 10- ii- 10 0.1 r I- 0.1 I - l|- "1 r 1 r 1969 1966 1965 1964 1963 1962 •f'l' ^ 1961 I r Figure 3. — Number of Pacific herring larvae per m'* caught in Clarke-Bumpus nets at Buoy 21 during January -June periods, 1960-1970. 10 0) g Q. E 0) 1 1 ,1963 ,1966 ,1965 /968, *I96I — 1964^ ^1967 — . I960, ,1962 - ,/5/c ,1969 - JAN. 1 FEB. 1 MAR. Figure 4. — Average surface temperature at Buoy 21 during and 14-17 days prior to first catches of herring larvae vs. date of first catches of herring larvae, 1960-1970. estuary to 10 miles off the coast. Within the estuary, larvae of C. /;. pallasi, L. lepidus, and CottKs anper usually ranked first, second, and third respectively in the catches at all five stations, from 0.5 to 8 nautical miles up the es- tuary. L. lepidiis was the only common species revStricted to the bay; it was most numerous in the upper estuary. Larvae of C. h. pallasi were abundant in the bay and rare outside the bay. Some of the other species that are considered to be primarily bay forms are Cottus asper, found in greatest numbers in the upper estuary, and Eiiopliiys bison, Leptocottns armatus and Pholis ornata, found mainly in the lower estuary. Many of the larvae found in the bay were found in greater numbers offshore. Larvae of the surf smelt, H. pretiosKs, were sometimes abundant in the lower estuary where juvenile H. pretiosus were also numerous. Osmerids were most abun- dant 1 mile offshore. We assume that these were mainly H. pnfiosKs, a si)ecies known to spawn in the surf zone. Consequently, the surf smelt larvae found in the bay may be carried there by tidal exchange. Larvae of A. hexap- terus, Sebastes spp., pleuronectids, gadids, and cyclopterids were all found in higher numbers offshore than in the bay. Parophryx vetulus was only found offshore. Eiigraulis niordax larvae were found through- out the bay and to 3 miles offshore. They were not found 5 or 10 miles offshore. This larval di.stribution, and the large numbers of anchovy 206 PEARCY and MYERS: LARVAL FISHES OF YAQUINA BAY Table 4, — Average number of larvae per lO-'nv' filtered in bongo nets (mesh 0.233 and 0.571 mm combined) calculated from total number of specimens collected ^ total volume filtered for entire year. Only species represented by five or more larvae are listed. June 1%9-June 1970. BAY OFFSHORE (mi) 39 29 21 15 BR 1 3 5 10 A. BAY ONLY LepiciofiohiHs U-pidiis )06.0 340.5 113.4 92.9 6.4 0 0 0 0 Lumpeniis sa^itui 0 0 0.5 1.1 1.3 0 0 0 0 Anoptarchiis spp. 0 0.6 0.7 1.1 1.0 0 0 0 0 B. PRIMARILY BAY Chipca h. pallasi 509.2 428.2 442.6 556.0 183.3 0.3 0.5 0 0 Gobiidoe type 1 0.5 0.9 13.7 5.3 1.3 0.6 0.3 0 0 Coitus usper 40.7 42.3 21.0 10.1 9.2 0.6 0 0 0 Enophrys bison 0 0 2.3 9.6 18.8 0.3 0 0 0 Leplocoitus arma!u\ 0.7 1.6 10.0 7.2 3.8 0.3 0 0 0 Cottidae Type 1 0 0 0.5 1.3 1.3 0.6 0.5 1.0 0.3 Pholis ornutu 0 0 0.8 1.3 1.3 0.3 0.5 0 0 C, PRIMARILY OFFSHORE Eni;ruulis monlax 0.5 1.0 0.5 0.3 0.2 2.1 1.1 0 0 H} ponu'sus pn'tiosus-Osmeridi 1.0 0.6 3.0 15.7 27.2 100.9 18.6 4.6 0.3 Gadidae 0 0 0.5 0 0.2 0.6 4.5 0.7 1.1 Ammodytes hexapterus 0 0 0 0.5 0.5 1.8 13.0 2.0 2.5 Sebasies spp. 0 0 0 0.5 0.8 6.9 4.2 1.5 19.6 Ophiodon elonf;urus 0 0 0 0.3 0 0.6 0.8 0.7 0 Hemilepidotus 0 0 0 0 0.2 1.5 2.9 0 1.2 Cottidae type 12 0 0 0 0.3 0.5 0.9 0 0 0 Agonidae 0 0 0 0 1.0 0.3 0.5 0.2 0 Cyclopteridae 0 0 0.2 0.3 0.2 0.6 3.2 0.2 0.5 Pseilichthys inelunoslUliis 0.2 0 0.5 0 0.5 5.1 31.1 3.4 0.5 Isopseita isolepis 0 0 0 0 0.2 0.6 36.1 5.1 1.1 Lyopselta extlis 0.2 0 0 0 0 0 9.0 0 0.3 Citharichthys sp. 0 0 0 0.5 0.5 1.0 0 0 0 D. OFFSHORE ONLY Stenobrachius teucopsarus 0 0 0 0 0 0.3 0.5 1.0 1.6 Cottidae type 16 0 0 0 0 0 0 2.4 0 0.3 Cottidae unident, spp. 0 0 0 0 0 1.8 9.6 7.1 0.6 Parophrys veluliis 0 0 0 0 0 1.2 9.0 11.9 8.9 Blennoids 0 0 0 0 0 3.3 4.5 0 0 eggs within the bay, is peculiar since Richard- son (1973) reported that anchovy larvae were abundant well offshore, usually in Columbia River plume waters, and not near the coast. Pacific Herring Abundance Herring larvae were abundant at all five stations during February and March 1970 (Fig- ure 5). A peak in catches occurred in late January at the three stations closest to the ocean, and conversely, higher numbers occurred later (April and May) at the upper estuarine stations. These trends suggest earlier spawning near the mouth and later spawning in the upper estuary. Based on intertidal surveys, Steinfeld (1972) found herring eggs near the mouth from February 5 to 20, 1970, and in the upper estuary above Buoy 21 from March 8 to 24. 1970. The trend for earlier spawning near the mouth of the estuary was therefore found in both larval and egg surveys. However, the fact that Stein- feld did not find any spawn before February 5 while we collected many larvae between January 23 and February 10 indicates that intertidal surveys may miss substantial areas of eggs, perhaps from subtidal spawning. Comparison of Nets Catches of herring larvae in the three types of nets (CB and bongo with 0.233 mm mesh and bongo with 0.571 mm mesh) were usually sim- ilar on a m'^ basis, especially at high densities of larvae (Figure 5). The type of net catching the highest or the lowest number of larvae altei'nated among tows. We had not expected catches by the CB to compare favorably with the bongo in view of the known avoidance capability of Atlantic herring larvae (Bridger, 1956; Tibboetal., 1958). The percentage of herring larvae of different 207 FISHERY BULLETIN: VOL. 72, NO. 1 sizes caught at Buoy 29 in the three nets during the 1970 larval season is shown in Figure 6. Little difference is apparent in the proportion of different sizes of larvae in the different nets. All curves show that the number of larvae caught between 6 and 8 mm was less than be- tween 8 and 10 mm. This is probably explained by hatching of some larvae at lengths over 8 mm, and hence is a true reflection of relative abundance, rather than lack of retention of the smallest larvae by the nets. Larvae larger than 20 mm were not caught at all in the CB samples, presumably because of the capability of large larvae to avoid this gear. TIDAL-DIEL VARIATIONS Figure 7 illustrates the variations in CB catches of fish eggs and larvae during several diel sampling periods at Buoy 21. In Figure 7A, peaks in both egg and larval abundance occurred during periods of low water (Mann-Whitney U test. P <0.01). Similarly, highest catches of herring larvae coincided with times of low water in Figure 7B {P = 0.06). In neither of these figures is a day-night difference evident (P > 0.2). In Figure 7C, however, catches of herring larvae were not correlated with tidal stage (P >0.2), but highest catches coincided with darkness (P <0.01); all but one of the 9 nighttime catches exceeded the 14 daytime catches. Therefore, both tidal and diel factors may influence catches. We believe the high catches associated with low water were caused by tidal excursion of water with high density of eggs or lai-vae. In other words, the center of abun- dance of L. lepidus larvae and fish eggs (Figure 7A) and C. h. pallasi (Figure 7B) was up the estuary from Buoy 21 at high tide. The ability of larger larvae to avoid plankton nets during the daytime (see Figure 6; Tibbo et al., 1958; Bridger, 1956; and Colton, Honey, and Temple, 1961) was thought to explain the high catches after dark in Figure 7C, but this interpretation was not supported by the similar size-frequency distributions of day- and night-caught larvae. Q UJ CE LiJ I E UJ a. (r LJ CO 72 10 0.1 0.01 01 OOI 0[ 10- BUOY 15 0.1- 0.01 0 BUOY 39 • CB 233 ■ BONGO 233 • BONGO 571 BUOY 29 0.1 0.01- Of 1 \ 1 1 1 r BUOY 21 T 1 1 r n 1 1 r "T — ji 1 r T 1 r 1 1 1 r 10 1 1 1 1 1 BRIDGE 1 ' 1' 1 i 'I 1 I OOI 0 hr J ' A ' S ' 0 ' N 1 1 D i J^ 1 1 A M ' 1969 1970 THE ESTUARY AS A NURSERY The results of this study on the i)lanktonic fish larvae tentatively support McHugh's (1966, Figure 5. — Number of Pacific herring per m^ caught in Clarke-Bumpus nets with 0.233 mm mesh, the bongo net with 0.233 mm mesh and the bongo net with 0.571 mm mesh at five stations in Yaquina Bay, June 1969-June 1970. 208 PEARCY and MYERS: LARVAL FISHES OF YAQUINA BAY 1967) contention that estuaries of the Pacific coast may be less important as nursery grounds than eastern seaboard estuaries. But such a conclusion is unwarranted without a comparison of larval abundances within the estuary with those in adjoining open ocean to learn if larvae are restricted to or concentrated in estuaries. High numbers of larvae within the estuary are not necessarily pi-oof of estuarine dependance, as they may be more abundant in the ocean. Conversely, low densities of a species inside the estuary may indicate importance if it is absent elsewhere. A comparison of larval catches in Yaquina Bay with the open ocean is possible since we collected fish larvae at stations 1, 3, 5, and 10 miles off Yaquina Bay, using the same bongo nets during the same sampling period as the bay sampling. The results of this compari- son (Table 4) corroborate our earlier suggestion: with the exception of the Pacific herring the estuary does not appear to be important to the pelagic larvae of commercial fishes. Most of the larvae that were restricted to or were most common in the estuary were of small, non-food species of cottids, stichaeids, and gobies. Larvae of all the pleuronectids collected were more common offshore than inside the estuary. Thus the Pacific herring was the only species of commercial interest that appeared to use the estuary extensively as both a spawning and a nursery ground. In California, herring spawn in bays and estuaries (Hardwick, 1973). Since Pacific herring are known to comprise more or less distinct populations with adults returning to the same bay to spawn (Stevenson, 1955; Rounsefell, 1930), estuaries may be vital to the maintenance of herring along some portions of the west coast. Feeding conditions for herring are undoubt- edly related to their use of estuaries as nurs- eries. Russell (1964) found that Yaquina Bay is used as a feeding ground for 1 to 4 yr-old herring which fed mainly on the copepods Acartia clausii and Pseudocalaiiui< sp., both abundant within the bay. A. clausii, which is thought to maintain indigenous populations in Yaquina Bay, is especially abundant in the upper estuary (Buoys 21 and 29) early in the spring when densities of adults and immatures exceed 30,OOOm-5 (Zimmerman, 1972 Froland- er et al.. 1973). The numbers of copepod eggs, nauplii, and copepodites, important food for Atlantic herring larvae, probably exceed this 100 X 10 o cr UJ Q. CLARKE-BUMPUS 233 -^ BONGO 233 -a BONGO 571 0. o'^ J L 00 O oo ID ^ '^ ?° 9 C\J ^ liJ I , 7 I I f^ c\j c\j (\j ~ 00 C\J (\J LENGTH OF LARVAE (mm) Figure 6. — Catches of different lengths of herring larvi at Buoy 29 expressed as a percentage of the total catc for each of the Clarke-Bumpus and bongo nets with 0.2J mm mesh and the bongo net with 0.571 mm mesl February 10-March 13, 1970. density during the early spring and provid adequate food for larval herring (Blaxter, 196c Bainbridge and Forsyth, 1971; Sherman an Honey, 1971). Our planktonic survey of fish larvae was n( adequate to assess completely the estuary as nursery ground. First, plankton nets are sele( five and only weakly swimming pelagic larv£ were effectively sampled. Other young stag( may not have been fully susceptible to captui because they actively avoid the nets. Secondl; the young of some species may have been preser but simply unavailable for sampling because ( their distributions. These may include youn that migi'ate into the estuary after metamo: phosis, benthic forms, or young that reside i shallow areas of the estuary. For example, viviparous embiotocids (PJiai erudoii furcatus, Rhacochilus vacca, an Embiotoca lateralis) are common species i Yaquina Bay. Mature females of all these specif are numerous in the middle and upper estuar 201 [0) \D) FISHERY BULLETIN: VOL. 72. NO. 1 [O — 10 9 AUG 63 I /O AUG 63 T 12 24 12 21 FEB 64 I 22 FEB 64 1 \ r 12 24 12 ,?(9 /i^/I/? 67 I 21 MAR 67 Figure 7. — Diel variations in the CB catches at Buoy 21: A. 9-10 August 1963; solid line = fish larvae: dashed line = fish eggs. B. 21-22 February 1964: solid line = herring larvae. C. 20-21 March 1967: solid line = herring larvae. The tidal height above mean lower-low water and period of darkness (hatched bar) are shown above each figure. Dates and noon and midnight are indicated below each figure. during the spring when they give birth to young which use the estuary as a nursery (Beardsley, 1969; Wares, 1971). Because of their pelagic nature and swimming abilities, young embiot- ocids are not readily captured in small plankton nets or trawls. Beardsley (1969) and Westr- heim (1955) also found many juvenile starry flounder {Flatichthys stcllufus) in Yaquina Bay, and Haertel and Osterberg (1967) con- cluded that the starry flounder use the upper Columbia River estuary as a nursery ground. A trawl survey of juvenile fishes of Yaquina Bay by Wm. Johnson (pers. comm.), conducted during the same period and at the same stations as our plankton survey, provided useful in- formation on the juvenile fishes caught in mid- channel of the estuary near the bottom. Relative abundances of the young fishes caught are shown in Table 5. Three species were dominant: HypomeHiis pretiosus, Paroplirya vetulus, and Citharichthys stigmaeus. They comprised 79% of the total number of fishes collected. Of these, only the abundant H. pretiosus was also com- mon in plankton collections (Tables 2, 3, and 4). Lepidogobius lepidus, Cottus asper, and Lepto- cottus armatiis, though presumbly benthic as juveniles, were not abundant in the trawl collections despite their abundance as pelagic larve. Johnson (pers. comm.) caught large num- bers of juvenile L. an)iati>>itta Eiigraulis mordax Lepidoi>ohiiis lepidus Cyiuatofiaster aggregata Sehastes nielaiiops Artedius fenestralis P\ettichthys mehmostictus Ophiodon eloitf;atiis Syanathus i;riseolineatus Pallas Ilia barhatu Syinphurus airicauda Artedius harriniitoui Anoplarchus purpurescens Phanerodoii furcatus Einbiotoca lateralis Occella verrucosa G obi e SOX maeandricus 36.2 24.6 18.2 4.1 3,6 2.5 2.3 1.1 1.0 0.7 0.7 0.7 0.7 0.6 0.5 0.5 0.4 0.4 0.4 0.3 0.3 0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 '■'■ Probably C. siifiinaeus, by others in Yaquma Bay. the species usually Found bays (Eldridge, 1970; Misitano, 1970). In our study P. vetulus larvae were common offshore but were absent or rare in Yaquina Bay (Table 4). Therefore young English sole must be trans- ported into the bay from offshore waters as late larval stages or migrate in as juveniles. In Humboldt Bay, Misitano (1970) captured meta- morphosing English sole (average length, 23 mm) by midwater trawling, especially after dark. These larvae were active swimmers in aquaria but usually resided on the bottom. As a result they would be relatively inaccessible to daytime plankton collections. The question remains, however, how these larvae enter estuaries. Currents off the northern Pacific coast during the winter and spring are largely inshore and northerly (Burt and Wyatt, 1964; Wyatt, Burt, and Pattullo, 1972) and would transport buoyant fish eggs such as those of English sole (Budd. 1940; Ketchen, 1956; Alderdice and Forrester, 1968) toward and then along the coast. Retention in estuaries would seem to require active behaviorial re- sponses by the larvae, such as a change in depth distribution to enhance transport into and reduce advection out of estuaries. Since a two-layered transport system prevails in Yaquina Bay dur- ing the winter (Kulm aiid Byrne, 1967; Burt 211 FISHERY BULLETIN: VOL. 72, NO. 1 and McAlister. 1959) and since Kulm and Byrne (1967) found that marine sand was transported by strong currents 6 miles up the Yaquina Bay estuary during the winter, the season when P. vetulus enter the estuary, then descent of larvae into deep water, where net transport exists up the estuary, may result in transport into and re- tention within estuaries of English sole and other species, as found for other larval fish (Pearcy, 1960; Pearcy and Richards. 1962; and Graham, 1972). In conclusion, Yaquina Bay, like many east coast estuaries, is an important nursery for the young of several species of marine fishes. This was not apparent from a survey of plank- tonic larvae, however. Only the larvae of Pacific herring, a species that spawns in bays, were abundant in our plankton collections in Yaquina Bay. Although the pelagic larvae of flatfishes were much more common in offshore than estuarine waters, the juveniles of several species move into the estuary in large numbers. ACKNOWLEDGMENTS We are indebted to H. F. Frolander who has tenaciously conducted the plankton survey of Yaquina Bay since 1960 and provided the 11-yr series of collections and to Joan Flynn who curated these collections. We are also grateful to William Johnson, University of Rhode Island, who generously supplied his data on juvenile fishes, to Peter Rothlisberg, Greg Lough, and Dean Satterlee who were essential for field sampling in 1969 and 1970, to Elbert AhLstrom, Elaine Sandknop, Maxwell Eldridge, and James Blackburn who helped to identify fish larvae and to Sally Richardson, Charles Miller, and William McNeil for their helpful criticisms of the manuscript. This research was supported by NOAA In- stitutional Sea Grant, Contract No. 2-35187. LITERATURE CITED Alderdice, D. F., andC. R. Forrester. 1968. St)me effects of salinity and temperature on early development and survival of the English Sole (Purophrys vciulu.s). J. Fish. Res. Board Can. 25:495-521. Bainbridge, v., and D. C. T. Forsyth. 1971. The feeding of herring larvae in the Clyde. Rapp. P.-V. Reun. Cons. Perm. Int. Explor. Mer 160:104-113. Beardsley, a. J. 1969. Movement and angler use of four foodfishes in Yaquina Bay, Oregon. Ph.D. Thesis, Oregon State Univ., Corvallis, 185 p. Blaxter, J. H. S. 1965. The feeding of herring larvae and their ecology in relation to feeding. Calif. Coop. Oceanic Fish. Invest., Rep. 10:79-88. Bridger. J. P. 1956. On day and night variations in catches of fish larvae. J. Cons. 22:42-57. BUDD, P. L. 1940. Development of the eggs and early larvae of six California fishes. Calif. Dep. Fish Game, Fish. Bull. 56,53 p. Burt, W. V., and W. B. McAlister. 1959. Recent studies in the hydrography of Oregon estuaries. Fish Comm. Oreg. Res. Briefs 7(1): 14-27. Burt, W. V., and B. Wyatt. 1964. Drift bottle observations of the Davidson Current off Oregon. //; K. Yoshida (editor). Studies on oceanography, p. 156-165. Univ. Tokyo Press, Tokyo. Clark, J. 1967. Fish and man. Conflict in the Atlantic estu- aries. Am. Littoral Soc, Spec. Publ. 5, 78 p. CoLTON, J. B., Jr., K. A. Honey, and R. F. Temple. 1961. The effectiveness of sampling methods used to study the distribution of larval herring in the Gulf of Maine. J. Cons. 26: 180-190. Demory, R. L. 1971. Depth distribution of some small flatfishes off the northern Oregon-southern Washington coast. Res. Rep. Fish Comm. Oreg. 3:44-48. Eldridge, M. 1970. Larval fish survey of Humboldt Bay. M.S. Thesis, Humboldt State Coll., Areata, 52 p. Frolander, H. F. 1964. Biological and chemical features of tidal estuaries. J. Water PoUut. Control Fed. 36:1037- 1048. Frolander, H. F., C. B. Miller, M. J. Flynn, S. S. Myers, and S. T. Zimmerman. 1973. Seasonal cycles of abundance in zooplankton populations of Yaquina Bay, Oregon. Mar. Biol. (Berl.) Graham, J. J. 1972. Retention of larval herring within the Sheep- scot estuary of Maine. Fish. Bull., U.S. 70:299-305. Haeriel, L., and C. Osterberg. 1967. Ecology of zooplankton, benthos and fishes in the Columbia River estuary. Ecology 48:459-472. Hardwick, J. E. 1973. Biomass estimates of spawning herring, Clupea harcngiis palhisi, herring eggs, and associated vege- tation in Tomales Bay. Calif. Fish Game 59:36-61. Harry, G. Y., Jr. 1959. Time of spawning, length at maturity, and fecundity of the English, Petrale. and Dover Soles (Parophrys vcliihis, Eopsctta jordani. and Micro- 212 PEARCY and MYERS: LARVAL FISHES OF YAQUINA BAY stunius pacificus, respectively). Fish Comm. Oreg., Res. Briefs 7(1) :5- 13. Jow, T. 1969. Results of English sole tagging off California. Pac. Mar. Fish. Comm., Bull. 7; 15-33. Ketchen, K. S. 1956. Factors influencing the survival of the lemon sole (Parophrys vetulus) in Hecate Strait, British Columbia. J. Fish. Res. Board Can. 13:647-693. KuLM, L. D., AND J. V. Byrne. 1967. Sediments of Yaquina Bay, Oregon. In G. H. Lauff (editor), Estuaries, p. 226-238. Am. Assoc. Adv. Sci. Publ. 83. McHuGH, J. L. 1966. Management of estuarine fisheries. Am. Fish. Soc, Spec. Publ. 3:133-154. 1967. Estuarine nekton. In G. H. Lauff (editor). Estuaries, p. 581-620. .Am. Assoc. Adv. Sci. Publ. 83. MiSITANO, D. A. 1970. Aspects of the early life history of English sole {Parophrys vt'tulus) in Humboldt Bay, Cali- fornia. M. S. Thesis, Humboldt State Coll. Areata, 57 p. Olsen, R. E., and 1. Pratt. 1973 Parasites as indicators of English Sole (Par- ophrys vetulus) nursery grounds. Trans. Am. Fish. Soc. 102:405-411. OUTRAM, D. N. 1955. The development of the Pacific Herring egg and its use in estimating age of spawn. Fish. Res. Board Can. Pac. Biol. Stn., Nanaimo, B. C, Circ. 40, 10 p. Parsons, T. R., R. J. LeBrasseur, and W. E. Barraclough. 1970. Levels of production in the pelagic environ- ment of the Strait of Georgia, British Columbia: A review. J. Fish. Res. Board Can. 27:1251-1264. Pearcy, W. G. 1962. Ecology of an estuarine population of winter flounder Pseudopleuronectes americanus (Wald- baum) Parts I-IV. Bull. Bingham Oceanogr. Collect., Yale Univ. 18(1): 1-78. Pearcy, W. G., and S. W. Richards. 1962. Distribution and ecology of fishes of the Mystic River estuary, Connecticut. Ecology 43: 248-259. Richardson, S. L. 1973. Abundance and distrubition of larval fishes in waters off Oregon, May-October 1969, with special emphasis on the northern anchovy. EngrauUs mordax. Fish. Bull. U.S. 71:697-71 1. ROUNSEFELL, G. A. 1930. Contribution to the biology of the Pacific herring, Clupea pallasii, and the condition of the fishery in Alaska. U.S. Bur. Fish. Bull. 45:227-320. Russell, H. J., Jr. 1964. The endemic zooplankton population as a food supply for young herring in Yaquina Bay. M.S. Thesis, Oregon State Univ., Corvallis, 42 p. Sherman, K., and K. A. Honey. 1971. Seasonal variations in the food of larval herring in coastal waters of central Maine. Rapp. P.-V. Reun. Cons. Perm. Int. Explor. Mer 160: 121-124. Steinfeld, J. D. 1972. Distribution of Pacific herring spawn in Ya- quina Bay, Oregon, and observations on mortality through hatching. M. S. Thesis, Oregon State Univ., Corvallis, 75 p. Stevenson, J. C. 1955. The movement of herring in British Columbia waters as determined by tagging. With a descrip- tion of tagging and tag recovery methods. Rapp. P.-V. Reun. Cons. Perm. Int. Explor. Mer 140:33-34. Tate, M. W., and R. C. Clelland. 1957. Nonparametric and shortcut statistics in the social, biological, and medical sciences. Interstate Printers and Publishers, Inc., Danville, 111., 171 p. Taylor, F. H. C. 1971. Variation in hatching success in Pacific herring (Clupea pallasii) eggs with water depth, tempera- ture, salinity and egg mass thickness. Rapp. P.-V. Reun. Cons. Perm. Int. Explor. Mer 160:34-41. TiBBO, S. N., J. E. H. Legare, L. W. Scattergood, and R. F. Temple. 1958. On the occurrence and distribution of larval herring (Clupea harengus L.) in the Bay of Fundy and the Gulf of Maine. J. Fish. Res. Board Can. 15:1451-1469. Wares, P. G. 1971. Biology of the pile perch (Phacochilus vacca) in Yaquina Bay, Oregon. U.S. Bur. Sport Fish. Wildl. No. 51,21 p. Westrheim, S. J. 1955. Size composition, growth, and seasonal abun- dance of juvenile English sole (Parophrys vetulus) in Yaquina Bay. Res. Briefs Fish Comm. Oreg. 6:4-9. Wyatt, B., W. V. Burt, and J. G. Pattullo. 1972. Surface currents off Oregon as determined from drift bottle returns. J. Phys. Oceanogr. 2:286- 293. Zimmerman, S. T. 1972. Seasonal succession of zooplankton popula- tions in two dissimilar marine embayments on the Oregon coast. Ph.D. Thesis, Oregon State Univ., Corvallis, 207 p. 213 CALANOID COPEPODS OF THE GENUS AETIDEUS FROM THE GULF OF MEXICOi Taisoo Park2 ABSTRACT The copepod population known previously as belonging to Aciidcus annaius (Boeck) in the Gulf of Mexico and Caribbean Sea is recognized as a separate species. The males of Aetideus ciciiius Farran and Aciidciis giesbrechti Cleve are fully redescribed with figures. The genus Aetideus Brady, 1883, comprised four species (A. armatus, A. bmdyi, A. aciitioi, and A. giesbn'chti) when Sars (1925) estab- lished the genus Enaetideus to distinguish the last three species from the first. A new species has since been added to each genus, A. pacificus and E. ausfralis. Bradford (1971) reviewed the genera Aetideus and Euaetideus on the basis of specimens from the Atlantic and Pacific Oceans. Having found a close similarity be- tween the males, she proposed the merging of the two genera. In agreement with her pro- posal, the name Euaetideus is considered here as a junior synonym of Aetideus. In the Gulf of Mexico, three species of Aetideus (A. armatus, A. acutus, and A. gies- brechti) have been recorded (Owre and Foyo, 1967; Park, 1970). During the examination of plankton samples obtained from the Gulf of Mexico by the RV Alamiuos in September 1971. all of these species were found, including the males. A. armatus had been known to have world- wide distribution (Vervoort, 1957) until Brad- ford (1971) recognized a population in the Southern Hemisphere and two in the North Pacific as separate species. Bradford also noted differences between the northern and southern forms of A. armatus in the Atlantic, but the differences were not considered as taxonomical- ly significant. When examined in detail in the light of Bradford's findings, the Gulf of Mexico population of A. armatus, however, was found to be significantly different from either the northern or southern Atlantic form of the spe- ' This study was supported bv National Science Founda- tion Grant GA-27485. - Department of Marine Sciences, Texas A&M Uni- versity, Galveston. TX 77550. cies, or from any other known species of the genus. Therefore, it is described here as a new species. A. acutus and A. giesbrechti found in this study were in agreement with the descriptions by Grice (1962) and Park (1968) for the Pacific forms. The males of these species have not been fully described, except for brief descrip- tions by Giesbrecht (1892) and Bradford (1971). AETIDEUS MEXICAN US, NEW SPECIES Type. — Holotype female, U.S. National Mu- seum No. 143777; allotype male USNM No. 143778; 30 female and 7 male paratypes, USNM No. 143779. Type locality, lat. 25°15'N, long. 89°11'W, in the Gulf of Mexico (sam- pling depth, about 500-0 m). Female. — Body lengths of 31 type specimens, 1.66-1.84 mm. Proportional lengths of pro- some and urosome about 78:22. Viewed dorsal- ly, body slender, with a round, slightly produced forehead (Figure lA). Laterally, dor- sal margin of forehead broadly vaulted at level of mouth (Figures IB, D). Two rostral rami separated by a U-shaped notch (Figure IG). Distance between tips of rostral rami exceed- ing depth of notch (1.07-1.15:1). Metasomal process extending straight backward; although variable in length, generally reaching about distal end of genital segment. Dorsally, genital segment (Figure IH) wider than long, with its widest part close to its proximal end. Shape of spermatheca (Figures IC, F) similar to A. armatus as described by Bradford (1971), with short wide neck connecting proximal and distal sacs; space between two sacs slightly Manuscript accepted July 1973. FISHERY BULLETIN: VOL. 72. NO. I. 1974. 215 FISHERY BULLETIN: VOL. 72, NO. 1 Figure 1. — Actidcus lucxuanus, new species. Female: A, habitus, dorsal; B, habitus, lateral; C, posterior part of body, lateral; D, forehead, lateral; E, posterior part of body, dorsal; F, last metasomal and first two urosomal segments of another specimen, lateral; G, rostrum, anterior; H, urosome, dorsal: I, first pair of legs, anterior; J, second leg, anterior; K, third leg, anterior; L, fourth leg, anterior. wider than connecting neck. Caudal ramus about 2.4 times as long as wide. Antennules extending beyond distal end of caudal ramus by last two segments. Other 216 cephalic appendages as in A. pacificiis as de- scribed by Park (1968). In most of the speci- mens dissected the first pair of legs were asym- metrical, with the external margin of the right PARK: .4£r/D£t'5 0FTHEGULFOF MEXICO basis produced distally into a large tooth-like process (Figure II). Second to foux-th legs (Figures IJ-L) similar to A. pacificu.^, but coxa of fourth leg without spinules at base of inter- nal seta. Terminal exopodal spines of second to fourth legs with 15-17 teeth. Male. — Body lengths of eight type specimens, 1.58-1.68 mm. Proportional lengths of prosome and urosome about 75:25. Body slender, with forehead slightly produced (Figure 2A). Ros- strum reduced. Metasomal process pointing straight backward, reaching about distal end of genital segment (Figures 2D, E). Second to fourth urosomal segments and caudal rami (Figure 2E) with width: length ratios of 1:0.98-1.05, 1:1.08-1.15, 1:1.12-1.19, and 1:1.82- 2.00, respectively. Antennules reaching about distal end of fourth urosomal segment, nine- teenth and longest segment (Figure 2G) with width: length ratio of 1:4.9-5.1. On second leg (Figure 2M), endopod reaching distal end of second exopodal segment. On second and third legs (Figure 2N), terminal exopodal spines longer than third exopodal segments, with about 29 and 23 teeth, respectively. Second to fourth segments of fifth leg (Figure 20) with width: length ratios of 1:3.7-4.2, 1:8.3-8.7, and 1:9.0-9.7, respectively. AETIDEUS ACUTUS FARRAN, 1929 Male. — Body length, 1.22-1.36 mm according to 48 randomly selected specimens. Propor- tional lengths of prosome and urosome about 79:21. Dorsally, forehead (Figure 3B) more produced than in A. ine.vicaitufi. Rostrum re- duced. Metasomal process with wide base, dis- tinctly curved downward when viewed laterally (Figure 3E) and slightly curved inward in dorsal view (Figure 3D). Second to fourth uro- somal segments and caudal rami with width: length ratios of 1:0.83-0.88, 1:0.75-0.81, 1:0.78- 0.81, and 1:1.64-1.83, respectively. Antennules reaching about distal end of third urosomal segment, nineteenth and long- est segment (Figure 3F) with width: length ratio of 1:3.31-3.52. Other cephalic appendages similar to A. nie.vicanus. On second leg (Figure 3L), endopod reaching distal end of second exopodal segment. Terminal exopodal spines of second and third legs (Figure 3M) longer than their third exopodal segments, with about 23 and 18 teeth, respectively. Terminal exopodal spines of fourth legs (Figure 3N) shorter than their third exopodal segments, with about 16 teeth. Second to fourth segments of fifth leg (Figure 30) with width: length ratios of 1:3.41- 3.78, 1:6.72-7.33, and 1:6.00-6.60, respectively. Remark.'^. — The female of A. nie.vicaitus is dis- tinguished from A. annatu.'i by the slender body, long antennules which extend beyond the' caudal rami by two segments and, particularly, the fourth leg which lacks spinules at the base of the coxal seta found in all other species of the genus (Bradford, 1971). The male of A. mexicaiius is very close to that of A. armatu.'i as described by Bradford but seems to differ from it in the proportions of the caudal rami and of the second to fourth segments of the fifth legs. However, the importance of these charac- ters in the distinction between the two species is yet to be determined. Di.'^tribHtio)i. — A. mexicaitH.'< was found in a number of plankton samples taken from the upper 500 m in the Gulf of Mexico by the RV Alantii/os in September 1971. A. arniatus re- corded from the Caribbean Sea by Park (1970) belongs to this new species. Remarks. — The male of A. acutus was first de- scribed very briefly by Bradford (1971). The present specimens seem to be in agreement with her descriptions. The male of A. acutus is easily distinguished from those of A. niexi- caiius and A. gie.sbrechti by its considerably smaller size. In the shape of the forehead, meta- somal process, and antennule, it is closely re- lated to A. gieahrechti, but differs from this species in the relative lengths of the urosomal segments and caudal rami. The female specimens of A. acutus in the present study (1.48-1.62 mm in body length according to 80 randomly selected specimens) are identical with the specimens described by Park (1968) from the Pacific, and can be readily recognized by the shape of the spermatheca (Figure 3A). The appendages are similar to those of A. pacificus as described by Park (1968), except that the maxillule carries 3-1-3 + 6 setae on the endopod. 217 FISHERY BULLETIN: VOL. 72. NO. 1 Figure 2. — Aetidcus incxicuuHs, new species. Male: A, habitus, dorsal: B, habitus, lateral; C, forehead, lateral: D, posterior part of body, lateral; E, posterior part of body, dorsal: F, antennule, setae omitted: G, 19th segment of antennule; H, antenna; I, mandible; J, maxillule; K, maxilliped: L, first leg, anterior: M, second leg, anterior; N, third leg, anterior; (). fifth leg. anterior. (1. and W, length and width of segment.) 218 PARK: /l£r/Det'5 0FTHEGULF0F MEXICO Figure 3. — Aciideus acuiiis. Femnle; A, posterior part of body, lateral. Male: B, habitus, dorsal; C. habitus, lateral; D. posterior part of body, dorsal; E, last metasomal and genital segments, lateral; F, 19th segment of antennule; G, antenna; H, mandible; I, maxillule; J, maxilliped; K, first leg, anterior: L, second leg, anterior; M, third leg, anterior; N. fourth leg. anterior; O. fifth leg. anterior. 219 FISHERY BULLETIN: VOL. 72, NO. 1 Figure 4. — Actidcus tiicshrechii. Female: A, posterior part of body, lateral. Male: B, habitus, dorsal; C, posterior part of body, dorsal; D. posterior part of body, lateral; E, habitus, lateral; F, 19th segment of antennule; G, first leg, anterior; H, second leg, anterior; I, fifth leg, anterior. Dixtrihiition. — A. aciifiis was originally de- scribed from off New Zealand (Farran, 1929). The species has so far been known to occur on the Great Barrier Reef (Farran. 1936), in the Malay Archipelago (Vervoort. 1957), off the Pacific coast of Middle Japan (Tanaka, 1957; Tanaka and Omori, 1970). in the tropical Pa- cific (Grice, 1962). the northwestern Pacific (Brodsky, 1962), the central North Pacific (Park, 1968), the northeast Atlantic (Grice and Hulsemann, 1965), the Caribbean Sea and Gulf of Mexico (Park, 1970), and in the west- ern Indian Ocean (De Decker and Mombeck, 1965; Grice and Hulsemann, 1967). In the Gulf of Mexico, A. acutus is the most common of all three Acfidcus species so far known to occur, and it is mainly found in the upper 500 m. AETIDEUS GIESBRECHTI CLEVE, 1904 Male. — Body length. 1.52-1.60 mm according to 50 randomly selected specimens. Propor- 220 PARK: ^£7/D£f5 0FTHEGULFOF MEXICO tional lengths of prosome and urosome about 77:23. Dorsally, forehead (Figure 4B) produced as in A. acutiis. Rostrum reduced. Metasomal process (Figures 4C, D) as in A. aciitiix. Second to fourth urosomal segments and caudal rami with width: length ratios of 1:0.93-0.95, 1:0.85-0.86. 1:0.88-0.89, and 1:2.27-2.38, re- spectively. Antennules reaching about distal end of third urosomal segment, nineteenth and long- est segment (Figure 4F) with width: length ratio of 1:3.75-3.86. Other cephalic appendages as in A. acutus. On second leg (Figure 4H), endopod extending beyond distal end of second exopodal segment. Terminal expodal spine longer than third exopodal segment, with about 24 teeth. Second to fourth segments of fifth leg (Figure 41) with width: length ratios of 1:3.34-4.00, 1:6.00-6.25, and 1:5.00-6.65, re- spectively. Rei)iark>i. — The male of A. giesbrechti is close to A. niexiccuiKs in size but can be distin- guished from it by the more produced forehead, wide and curved metasomal process, relatively short urosomal segments, wide nineteenth seg- ment of the antennule, and long endopod of the second leg. A. giesbrechti, including the male, was first described with figures by Giesbrecht (1892) under the name of A. armatus. Although the female has been reported by many authors, the male has since been found only by Bradford (1971). The female specimens found in the' present study (1.84-2.08 mm in body length according to 76 randomly selected specimens) are in agreement with the descriptions given by Grice (1962) for the Pacific specimens. The appendages are identical with those of A. acutus, but the females of the two species are different in the form of spermatheca (Figure 4A). Distribution. — As reviewed by Vervoort (1957). A. giesbrechti has been found throughout the world's oceans, except for the high latitudes. In the Gulf of Mexico the species is quite com- mon in the upper 500 m. LITERATURE CITED Bradford, J. M. 1971. Aetideus and Euactidcus (Copepoda: Cala- noida) from the Atlantic and Pacific Oceans. N. Z. J. Mar. Freshwater Res. 5: 12-40. Brodsky. K. a. 1962. On the fauna and distribution of Calanoida in surface waters of the north-western Pacific [In Russ.] Issled. Dal'nevost. Morei SSSR. 8:91-166. De Decker, A., and F. J. Mombeck. 1965. South African contribution to the Interna- tional Indian Ocean Expedition: (4) A Preliminary report on the planktonic Copepoda. S. Afr. Div. Sea Fish. Invest. Rep. 51:10-67. Farran, G. p. 1929. Crustacea. Part X. Copepoda. Brit. Antarctic (Terra Nova) Exped. 1910. Nat. Hist. Rep. Zool. 8(3):203-306. 1936. Copepoda. Great Barrier Reef Exped. 1928- 29. Sci. Rep. 5(3): 73- 142. Giesbrecht, W. 1892. Sytemtik und Faunistik der pelagischen Copepoden des Golfes von Neapel und der angrenzenden Meeres-abschnitte. Fauna Flora Golf. Neapel. Monogr. 19:1-830. Grice, G. D. 1962. Calanoid copepods from equatorial waters of the Pacific Ocean. U.S. Fish Wildl. Serv., Fish. Bull. 61:171-246. Grice, G. D., and K. Hulsemann. 1965. Abundance, vertical distribution and tax- onomy of calanoid copepods at selected stations in the northeast Atlantic. J. Zool. 146:213-262. 1967. Bathypelagic calanoid copepods of the west- ern Indian Ocean. Proc. U.S. Natl. Mus 122(3583): 1-67. Owre, H. B., and M. Foyo. 1967. Copepods of the Florida Current. Fauna Cari- baea; Number 1. Crustacea, Part 1: Copepoda, 137 p. Park,T. 1968. Calanoid copepods from the central North Pacific Ocean. U.S. Fish Wildl. Serv., Fish. Bull. 66:527-572. 1970. Calanoid copepods from the Caribbean Sea and Gulf of Mexico. 2. New species and new rec- ords from plankton samples. Bull. Mar. Sci. 20:472-546. Sars, G. O. 1924. Copepodes particulierement bathypelagiques provenant des campagnes scientifiques du Prince Albert F"" de Monaco. Result. Camp. Sci. Monaco 69, 408 p., 127 plates. Tanaka, O. 1957. The pelagic copepods of the Izu region, Middle Japan. Systematic account III. Family Aetideidae (Part 1). Publ. Seto Mar. Biol. Lab. 6:31-68. Tanaka. O., and M. Omori. 1970. Additional report on calanoid copepods from the Izu region. Part 3-A. Eiiaetideiis, Aetideopsis, CInridius, Gaidnis, and Gaetanus. Publ. Seto Mar. Biol. Lab. 18:109-141. Vervoort, W. 1957. Copepods from Antarctic and sub-Antarctic plankton samples. B.A.N.Z. Antarctic Res. Exped. 1929-1931. Rep., Ser. B (Zool. Bot.) 3, 160 p. 221 NORMAL POSTMORTEM CHANGES IN THE BROWN SHRIMP, PENAEUS AZTECUS^ Donald V. Lightner- ABSTRACT A study was carried out to determine the normal rates and patterns of gross and histologic postmortem changes in the brown shrimp (Penaeus aztecus Ives). Experimental shrimp were held at 10°, 20°. or 30°C in water-saturated air or in seawater at a salinity of 30lysis 1V(mu ehanges liue to disease. MATHRIALS AND Ml- 1 HODS .luxiMiile blow 11 shrimp averaiiing "lO mm in total lenjith (\'\\i of rc^strum to tip of ti'lsoii) were obtained live iVom a eommereial bait ilealei" and were held in 500-liter tiberu'lass tanks for several ilays pritn* to beini; killed. Control shrimp were killed by immersion in tixative. Tlu^ remaininii' shrimp were killed by plaeiiii:' the shrimp between wft towels in an enamel tray for ;>0 min. The slirimji were removed after oO min and plaeed \\\\o 100-ml glass jars. Two groui>s at three temperatures (10'"\ 20 \ ami SOT) were studied: one in air ami the other in seawater. Shrim{) lield in air were introilueed wet into test jars ami tiie jars were sealed. Shrimp held in water were introdueed into the test jars ami enough Instant Oeeaiv' artitieial seawater (at .'U"t "'/(ut salinity') was atldeil to till the jars. ,lars were heUl in wire baskets at midlevel in eonstant temperature baths. Samples for antemortem examination were taken at 0 h while those for postmortem exam- ination were taken at 2. 1. S. 12. 24. 48. and 72 h. Vouv eontrol shrimp were taken for study and tw(i shrimp (one tVom seawater and one from air) were taken from the 10 \ 20 \ and ;UV C" baths at eaeh of the remaining sampling times. General appearance, color, odor, aiul eomli- tion of the hepatopanereas were noted at eaeh sampling period. Tissues for microscopic examination were preserved in lO^'c buffered Formalin, prejiared for microscopy with stan- dard paraftin embedding and sectioning methods, anil stained with liematoxylin ami eosin. RKSl LTS Gross Observ ations The tirst change observed w as the onset of a rigorlike condition of the abdomen which appeared at about 2 h after tieath at oO 'C and at I \ni I 1. liiiu- ot oiiMl ol .1 I igDi like sliUcnini; o{ shninp .iIhIihuiiuiI mustulaiuii' ,il 1(V\ 20'\ aiui 30'\' in an and seawater. Tempera ture {" C) H poslmorletii 10 "C 20 ■■'c r 30 *C Air Water Air Wafe Air Water 0 — — — — — _ 2 — — -1- — + + 4 — — + - + + 8 — — + -1- + + 12 — + — -1- — — 24 -1- + + + — - 48 + + — — — — 72 + + — — — — -I- = stiff — = flaccid t and 2 1 h at 20 and \0'\\ respectively. Tlie abdomen became flaccid at 12 and 48 h after tleath in shiimi^ held at SO'^ and 20^X". but at lO'T the abdomen remained rigid at 72 h after death (Table 1). C'olor change ami the api)earance of spoilage odor were tirst observed at 4 h after death at oOH\ The general appearance of the shrimp changed from the usual semitransparent to a wliitish-opaque at about the same time the first trace of odor was detected (Tables 2 and o). At 20 ' ami lO'X' the first color change and appear- ance of odor were notetl at 12 h and 24 li. respectively. At all three temperatures tlie color of the shrimp changed from opaque to an orange- red and finally to red with some blackened areas (Table 2). The intensity of spoilage odor increased along with the color change (Tables 2 and a). Fluid leakage from the hepatopanereas was tirst observed at 4 h at oO'T and at about 8 and 12 h postmortem at 20' and 10 T. Enzymatic cligestion of hepatopanereas and surrounding- tissues was grossly eviilent at 12 h at oOT as 1 AHi E 2. — Times lit' posUiioi tciii color chaniic of whole shrimp at 10'\ 20'\ and 3lVX" in .m .uid se.iw.iiei. Temperoture C'C) H postmortem 10-^C 20 ^X 30 -X Air Water Water Air Water 0 2 4 8 12 24 48 — — — — 0 0 — — — — 0 0 0 — — 0 LR LR LR 0 LR LR Rb Rb LR LR R Rb Rb R Rb R Rb R Rb Rb ' Rctcrcncc to trade names in liiis pul-ihcalion does not imply endorsement of commercial product. — = normol 0 = opaque LR = orange to light red R = red Rb = red with blackened edges of cuticle or blackened appendages 224 LIGHTNER: POSTMORTEM CHANGES IN BROWN SHRIMP Table 3. — Time ui' appearance of poslmortem spoilage- odor in whole shrimp held at 10", 20", and 30"C in air and Table 4. — Rate of poslmortem histologic change shrimp held in air or seawater at three temperatures. a.H epatop ancrea-s Temperature ("'C) H postmortem Tempera ure (°C) H posfmortem 10 C 20 '-C 30 -c Air Water Air Water Air Water 10 '-C 20 "C 30 "C Air Water Air Water Air Woter 0 - - - - — — 2 0 0' 0 0 0 0 0 — — + — + + 2 2.5' 2,5 2.5 2.5 3 3.5 8 — — + + — + + 4 4 4 4 4 4 4 12 — — + + — + + + + 8 4 3.5 4,5 5 4.5 4 5 24 + + + + + + + + + + 12 3.5 4 5 5 5 5 48 + + + + + + + + + + + + + + + 24 5 4 5 5 72 + + + + + + + + + + + + + + + + 48 72 5 5 5 5 5 5 5 5 5 5 5 5 — = normal + = odor indicated by a loo.sening of the junction of the cephalothorax and abdomen. By 48 h the junc- tion was very loose and Vjy 72 h the tissues of the junction appeared mostly liquified. At IC and 20 'C the same process was observed but at a proportionately slower rate. Histological Observations Since the same patterns of autolysis were seen in .shrimp held at all three temperatures, the differences l>eing a function of time (Table 4), only the histological re.sults from the 30 '-C portion will be presented in the text. The only significant histological differences between groups held in air and water noted were the more rapid tissue decomposition due to increased bacterial action in animals held submerged in seawater. Digestive Tract According to Roberts (1966j, the digestive tract in shrimp is composed of three divisions: flj the foregut, which includes the mouth, esophagus, stomach, and associated glands; (2) the midgut and hepatopancreas; and (3) the hindgut. Of these organs the hepatopancreas, the foregut, and midgut were studied in detail. The hindgut was not .studied. Hepatopancreas The glandular hepatopancreas is the first organ to undergo autolytic change (Figure la). This organ is a compound tubularacinar exocrine gland composed of tubules which end in blind sacs or acini. The tubules and acini are lined with a simple low to high columnar epithelium (Figure Ibj. Autolysis of the epithelium of this b. Midgut epithelium. Temperoture (^•'C) H postmortem 0 2 4 8 12 24 48 72 lO'C 20 ''C 30 -C Air Water Air Water Air Water 0* r 2 4 5 5 5 0 1 1-2 4-5 2 5 5 0 1 1-2 4 5 5 5 0 1-2 3 5 5 c. Abdominal muscle. Temperoture (°C) H postmortem 10 'C 20 'C 30 ■-C Air Water Air Woter Air Water 0 0* 0 0 0 0 0 2 0 0 0 0 0 0 4 1 1 2 1 1.5 1 8 0 1 2 2 2 2 12 1 1 2.5 2.5 3 3 24 3 3 3.5 3 3.5 3.5 48 2.5 3 4 4 3.5 4.5 72 4 3.5 4.5 4 4.5 4 d. Epidermis. Temperature CC) H postmortem 10 °C 20 "C 30 •c Air Water Air Water Air Water 0 0* 0 0 0 0 0 1 0 0 0 0 0 0 2 0 0 0 0 0 0 4 0 1 — — 2 2 8 1 1 — 2 3 3 12 2 2 3 3 4 4 24 3 3 3 3 4 — 48 3 3 4 4 5 5 72 5 5 5 5 5 5 - No observation made. Average assigned values from a scale of 0 to 5 denoting the general histological appearance of the tissue or organ. 0 = 3 = 4 = 5 = appearance, like the control, no post- pyknotic nuclei, slight stoining Normal histologic mortem change. Slight chonge, scattered differences. AAore advanced cellular chonge with increases in nuclear pyknosis, koryrhexis, koryolysis, some cytolysis; loss of normal appearance or structure of the tissue or organ. Further odvonced change with no normal oppeoring areas. Advonced autolytic change, tissue or organ represented by cellular debris or by its fibrous or cuticulor stroma. Complete outolysis, tissue or organ no longer demon- stroble. 225 FISHERY BULLETIN: VOL. 72, NO. 1 VffSSi. :.-^t>^ ■•.> .'^i^ ^^^ ^^^■'- '' _* »^ '^- ^^ I Figure 1. — a. Normal stomach (S) and hcpatopancieas (H). 25 X. b. Normal hepatopancreas. 120 X. c. Hepatopancreas at 2 h postmortem showing edematous swelling between adjacent tubules. Autolysis is more advanced nearer the center of the organ (upper right) than at the periphery (left). IIOX. d. Hepatopancreas at 4 h postmortem showing tubules on lon- gitudinal section. Note the progression of autolylic change in the tubules from the periphery of the organ (bottom) to the autolyzed center (top). 1 10 X . e. Hepatopancreas showing near complete autolysis (4 h postmortem). Note network of con- nective tissue stroma (arrows) remaining after autolysis of tubule epithelium. 120 X. f. Hepatopancreas at 8 h postmortem showing advanced autolysis. Intensely pyknotic nuclei are present in the remaining epithelial cells near the periphery of the organ. Tissue debris and remnants of the connective tissue stroma are present nearer the organ's center (upper right). 120 X. 226 LIGHTNER: POSTMORTEM CHANGES IN BROWN SHRIMP organ proceeds so rapidly that by 2 to 4 h postmortem, the epithelium of tubules near the center of the organ showed advanced autolysis. These tubules showed desquamation and cytoly- sis of the lining epithelium and replacement with eosinophilic debris (Figures Ic and Id). Nearer the periphery of the organ, the condition of the tubules and tubule epithelium appeared progressively more normal, with the most normal appearing tubules and acini at the periphery (Figures Ic and Id). In the band of tissues between the normal appearing periphery and the lysed core, all stages of cell death were observed. A thin band of tissue in this area con- tained tubules whose epithelial cells possessed scattered pyknotic nuclei and had slight cyto- plasmic staining differences (Figure le). Deeper to this layer the epithelial cells of tubules and acini possessed scattered pyknotic nuclei and had slight cytoplasmic staining differences (Figure le). The cytoplasm of these cells was highly vacuolated and stained variably with hematoxylin and eosin but generally much less basophilicily than normal (Figure Ic). At this time the s])aces between adjacent tubules and acini had become swollen (Figures Ic and Id). Slightly deeper to this layer epithelial cell nu- clei had undergone karyoi*rhexis or karyolysis and disappeared. Many of the cells of this area had lysed and the cellular debris stained red with eosin. The supportive stroma of the hepato- pancreatic tubules remained intact in some areas after the epithelium had autolyzed, thereby masking the former site of the hepato- pancreatic tubules (Figure le). By 8-12 h i)ostmortem even the tubules and acini at the peripheiy of the organ showed ad- vanced autolytic change, and the tissue debris and remnants of supportive stroma in the center of the organ were liquified (Figure If). The connective tissue capsule of the organ had be- come ruptured and few recognizable tubules were present. Past 12 h no trace of the hepato- pancreas was present, and surrounding tissues had also been partially or completely digested, presumably by enzymes released from the auto- lyzed hepatopancreas. Foregut and Midgut Autolytic changes in the foregut, particularly the epithelium of the stomach (Figure la), proceeded at approximately the same rate as changes in the hepatopancreas. Nuclear changes within epithelial cells were observed at 2 h postmortem with considerable change by 4 h. By 8 to 12 h the epithelium of the stomach had undergone nearly complete autolysis and had disappeared, leaving only the cuticular elements of the stomach lining intact. The cuticular elements of the esophagus and stomach per- sisted for the duration of the study (72 h). The midgut extends from the pyloric stomach to the sixth abdominal segment where it joins with the hindgut (Roberts, 1966). It is without a lining cuticle. The first autolytic change in the midgut was observed in the lining epithelium at 2 to 4 h, when the epithelial cells began to show changes such as scattered pyknotic nuclei, changes in staining reaction from a pale baso- philic reaction to a more eosinophilic one, and the "blebing" of the apical ends of epithelial cells into the gut lumen (Figure 2a). The epithe- lium usually remained attached to the basement membrane at 2 h. but in some areas portions of the midgut epithelium had been sloughed into the gut lumen (Figures 2b and 2c). Sloughed epithelial cells were rounded and had intensely pyknotic nuclei and a uniform eosinophilic cytoplasm. At this time the gut lumen usually contained a fibrous, eosinophilic coagulum (Figure 2b). The gut wall basal to the lining epithelium showed no appreciable changes by 4h. By 8 to 12 h the midgut epithelium had been sloughed into the gut lumen (Figure 2d). The epithelial cells in the gut lumen were rounded, and some had pyknotic nuclei, but they were mostly anucleate. Many of the epithelial cells had lysed and left behind amorphous masses of eosinophilic debris (Figure 2d). Changes in the cellular elements of the wall of the midgut became apparent by 8-12 h. These changes con- sisted primarily of a decrease in nuclear number in the muscle and connective tissue cells present and pyknosis of those nuclei remaining (Figure 2d). In general, the cytoplasm of the cells present showed increased eosinophilia. No trace of the lining epithelium was present after 24 h (Figure 2e). The coagulum, which was present in the gut lumen of some animals at 2-8 h, was still present. Also present in the gut lumen were large numbers of bacteria (Figure 2e). No nuclei were present in the gut wall, and the cellular elements remaining stained intensely with eosin. 227 FISHERY BULLETIN: VOL 12. NO. 1 ■.& .-^ '^ e*^-;- y j;--^ .*%. J-.*v .A.-*' ** / ..X r'' c ■ •! \~'' •.**^^ :a:t!3 '^ -iH,- "^^f^f^ Figure 2. — a. Cross section of midgut at 2 h postmortem. The appearance is near normal e.xcept for the "blebing" of the apical ends of some of the epithelial cells (arrows) and a few pyknotic nuclei. 250 X. b. Midgut showing more advanced autolytic change at 2 h postmortem. Some epithelial cells have been sloughed into the gut lumen where an eosinophilic coagulum (C) has formed. 240 X. c. Midgut at 4 h postmortem. Most of the epithelial cells possess pyknotic nuclei, and some of the cells have been sloughed into the gut lumen. 210X. d. Midgut at 8 h postmortem. Sloughed epithelial cells are rounded and are either anucleate or have pyknotic nuclei. An eosinophilic coagulum is present. 160 X . e. Midgut at 24 h postmortem. An eosinophilic coagulum is present in the gut lumen as are numerous bacteria. No trace of the gut epithe- lium remains. The muscle and tibrocyle cells of the gut wall are anucleate. 190 X. f. Site of midgut at 48 h postmortem. Bacteria and debris have filled the gut lumen. Only fibrous elements of the gut wall remain. 150 X . 228 LIGHTNER: POSTMORTEM CHANGES IN BROWN SHRIMP By 48 h, the gut wall had become thin and was frequently interrupted. The gut lumen was filled with bacteria and other debris (Figure 2f). By 72 h, all traces of the gut. including the gut wall, had disappeared leaving the former site of the gut marked only by masses of bacteria and amorphous eosinophilic cellular debris. Heart and Major Vessels In shrimp the heart lies immediately dorsal and slightly caudad to the large hepatopancreas. Only the thin connective tissue coverings of the two organs separate them. Hence, autolysis of the hepatopancreas and release of its proteo- lytic enzymes results in a rapid destruction of the rather loose tissues of the shrimp heart (Figure 3a). The hepatopancreas showed con- siderable autolytic change by 4 h postmortem leaving the heart barely recognizable (Figure 3b). By 8 h the heart was not distinguishable from the other tissue debris present at the heart's former location in the cephalothorax. Vessels in the vicinity of the hepatopancreas and heart also disappeared by 4-8 h, but vessels elsewhere, such as in the abdomen, persisted much longer, some still recognizable after 24 h. However, by 48 h vessels were not usually demonstrable anywhere in the body of a shrimp. to that of vertebrate striated muscle (Figure 4a). The muscles of the cephalothorax in the vicinity of the hepatopancreas underwent rapid autolytic change, apparently due to digestion by enzymes released on lysis of the hepatopancreas. Further from the hepatopancreas, the rate of autolytic change in the muscle was much slower. The earliest observed postmortem change in the muscle was at 4 h when some individual muscle fibers had a slightly "frayed" appearance. There was a pronounced swelling, presumably edematous, between adjacent muscle fibers (Figure 4b). By 8-12 h, muscle cell nuclei had become pyknotic. After 24 h muscle cells had become anucleate, highly eosinophilic, and the edematous swelling between adjacent muscle cells had decreased. Cross striations within muscle fibers were especially evident (Figures 4d, 4e, and 4f). In some, but not all, of the shrimp studied, bacterial growth was evident between muscle bundles, especially in the vicinity of the gut. The presence of large numbers of bacteria greatly increased the rate of tissue deterioration (Figure 4c), while muscle not heavily invaded by bacteria remained recognizable as muscle tissue at 72 h (Figure 4f). Integument Musculature Shrimp locomotory muscle is striated and presents a histologic appearance that is similar The integument, consisting of epidermis and an overlying cuticle, underwent rapid degen- eration in the area of the cephalothorax that surrounds the hepatopancreas, leaving only r »^v % J Figure 3. — a. Normal heart. llOx. b. Heart al 4 h postmortem showing considerable autolytic change and loss of struc- tural detail. 100 X . 229 FISHERY BULLETIN: VOL. 72. NO. I 1 KV« \ -~I1i '.. ^^Blr** B '^^mm^ I m D ' f Figure 4. — a. Normal abdominal muscle. 220 x . b. Muscle al 4 h postmortem showing edematous swelling between muscle bers. Sarcoplasmic staining reaction is more eosinophilic than normal and there has been a decrease in the number of nuclei although few pyknotic nuclei are shown. 150 X . c. Muscle showing advanced autolytic change due to the presence of large amounts of bacteria (12 h postmortem). 190 X . d. Muscle at 24 h postmortem. Edematous swelling has decreased, but the muscle fibers have become anucleale. Note the prominence of cross striations. 240X. e. Muscle al 48 h postmortem. 240 X . f. Muscle fibers with prominent cross striations are still recognizable at 72 h postmortem. 250 X . 230 LIGHTNER: POSTMORTEM CHANGES IN BROWN SHRIMP the cuticle remaining by 4 h. Distant from the hepatopancreas, the epidermis showed pyknotic nuclei and cell rounding by 4 to 8 h (Figures 5a and 5b). A slight hemocytic response was present at this time in the subepidermal tissue layers representing the only inflammatory- like response observed in the study. The epidermis had frequently become de- tached from the overlying cuticle by 12 to 24 h postmortem and many of the epidermal cells had lysed, with those remaining having pyknotic nuclei (Figure 5c). By 24 to 48 h nearly all traces of the epidermis had been lost and in some animals examined only cellular debris or clumps of bacteria marked its former location (Figure 5d). Though usually interrupted, the cuticle was the most resistant structure to autolytic change and showed only slight histo- logical change by 72 h. Gills The shrimp respiratory system consists of paired gills in the branchial chambers of the cephalothorax. The structure of the gills is dendrobranchiate (Barnes. 1963). The gills are covered by a thin cuticle underlain by a thin epithelium and other supportive cells (Figure 6a). A peritrichous ciliated protozoan (Figure 6b), presumably a commensal on shrimp (especially common on the gills but also found elsewhere on • -^^^v* 5^ ^ v_ B }Cmm •*#•> V^^S?:* *^ ^^ Figure 5. — a. Integument consisting of epidermis and overlying cuticle at 4 h postmortem. Some of the epidermal cells possess pyknotic nuclei. A few hemocytes are present in the subepidermal tissues (arrows). 480x. b. Integument at 8 h postmortem. Inflammatory cells are present in the subepidermal tissue. There is an increase in nuclear pyknosis in the epidermis and in the subepidermal tissue. 300 X. c. Epidermis and cuticle at 24 h postmortem. All of the epidermal cells have intensely pyknotic nuclei, as does all the subepithelial tissue. 600 X . d. Integument at 48 h postmortem. The cuticle is present, but the epidermis is represented by debris (arrows). 750 X . 231 FISHERY BULLETIN: VOL 72. NO. 1 the body surface), increased rapidly in numbers for 2 to 4 h after death of the shrimp. They were absent by 8 h postmortem. The cellular elements of the gills underwent fairly rapid autolytic change. By 8-12 h scat- tered pyknotic nuclei were present (Figure 6c). By 24 h the cellular elements of the gills were for the most part anucleate, with some portions of the gills having only eosinophilic debris within the lamellar cuticle (Figure 6d). By 48 h the thin cuticle of gill lamellae had begun to deteriorate and hence the gill lamellae sec- tioned transversely began to lose their typical "dumbbell" appearance (Figure 6e). By 72 h the gills were usually no longer demonstrable histologically, but in one of four animals exam- ined portions of the gills were still evident (Figure 60- Nerve Tissue The nervous system of shrimp is composed of a large ventral nerve cord and segmental gang- lia from which smaller nerve branches originate to innervate the tissues. At the anterior end of the ventral nerve tract is the supraesophageal ganglion, which anteriorly receives the large optic nerve tracts. Neuron perikaryons in the ganglia (Figure 7a) underwent the most rapid autolytic change of the various elements of shrimp nerve tissue. After 2 to 4 h, these cells showed considerable rounding, pyknotic or karyolytic nuclei, and a change in cytoplasmic staining from highly basophilic to a lesser basophilic to almost eosin- ophilic (Figure 7b). By 8 h no trace of neuron perikaryons was evident. The nerve tracts of the ventral nerve, its branches, and the optic nerves autolyzed less rapidly than did neuronal perikaryons. How- ever, nerve cell processes (axons and dendrites) within the nerve tract autolyzed more rapidly than did the supportive neurolemmal and glial cells, and were no longer demonstrable histo- logically by 12 to 24 h (Figure 7c). The support- ive glial cells of the nerve tracts persisted with- out noticeable change to 8 to 12 h, but these cells became anucleate or underwent autolysis after 24 h, and their former presence was represented only by debris and an occasional pyknotic nucleus (Figure 7d). After 24 h postmortem, the basic structural arrangement of the nerve tract remained rec- ognizable due to the persistence of neurolemmal fibers (Figures 7d and 7e), which persisted to 72 h at the sites of the optic nerve and ventral nerve tracts. Antennal Gland The antennal gland of crustaceans had been demonstrated to be imi)ortant in ion regulation (Robertson, 1959). The antennal or hemocoelic excretory gland in shrimp is located in the cephalothorax above the supraesophageal gang- lion (Young, 1959). The gland is composed of a collection of tubules and a bladder (Figures 8a and 8b). By 4 h some sloughing of tubule epi- thelium was evident (Figure 8b), but for the most part the histologic appearance of the organ remained normal. At 12 h, however, most of the nuclei of the tubule epithelium were intensely pyknotic (Figure 8c), and by 24 h the organ had disappeared or had become difficult to recognize (Figure 8d). No trace of the gland was found after 48 h postmortem. Gonadal Tissue Since the animals used in this study were immature juvenile shrimp, the gonads were small, poorly differentiated and were located in the cephalothorax lateral and slightly caudad to the hepatopancreas. The terminal ampule of male shrimp was poorly developed and in female shrimp the ovarian lobe, which extends into the abdomen in older shrimp, had not yet develoj^ed. The rate of autolysis in the gonads of the shrimp studied was rapid, due to their close proximity to the hepatopancreas. Gonadal tissue was not recognizable histologically after 4 to 8 h postmortem. DISCUSSION The rigorlike stiffening observed in this study may represent true rigor mortis. Sparks (1972) i)ostulated that rigor mortis or a similar phenomenon may occur in some invertebrates with well organized skeletal systems and as- sociated skeletal muscles. He based his opinion on the observation that many arthropods, which are flaccid after somatic death, subsequently 232 LIGHTNER: POSTMORTEM CHANGES IN BROWN SHRIMP ^ ff ■ r ■ '^ Of *,> i. r w -. "J.'- ,*V ^ -r^ >* -'I ,1J 1- ' ** - •< ^i- •e- !V> D ^,*'- ^ Figure 6. — a. Normal gills. 120 x . b. An unidentitied ciliated protozoan abundant on the gills at 4 h postmortem. 240 X . c. Gills at 12 h postmortem. Note the absence of the protozoan and the presence of pyknotic nuclei in the cellular elements. 130 X. d. Gills at 24 h postmortem. Except for a few pyknotic nuclei only the cuticle and cellular debris remain. 160 X. e. Gills at 48 h postmortem. The tissue is still recognizable as gills: however, the lamellae are losing their usual "dumbbell" appearance and contain only eosinophilic cellular debris. 190 X. f. Gills at 72 h postmortem. GUIs were recognizable his- tologically only from this one of four animals examined. 120 X . 233 FISHERY BULLETIN: VOL. 72. NO. 1 s . B^ ■--^J Figure 7. — a. Cross section of an abdominal segment ganglion on the ventral nerve (0 h control). Neuron perikaryons (N) are present ventral to the large ventral nerve tract (T). 1 10 X . b. Sagittal section of an ahdominal segment ganglion at 4 h postmortem. The neuron perikaryons are rounded and have pyknolic nuclei. Nerve cell processes, neurolemmal and glial cells in the nerve tract show no apparent autolysis. 220 X. c. Cross section of the ventral nerve at 12 h postmor- tem. Nerve cell processes are not evident and neurolemmal and glial cells possess pyknotic nuclei. 200 X . d. Cross section of the ventral nerve at 24 h postmortem. Only supportive fibrous tissue elements and eosinophilic debris remain. 190 X. e. Cross section of ventral nerve at 48 h postmortem. Fibrous elements are still present. 200 X . f. Ventral nerve in cross section at 72 h postmortem. The Hbrous elements of the nerve are still present. 120 X . 234 LIGHTNER: POSTMORTEM CHANGES IN BROWN SHRIMP ^jj^ ^,.:^ ■*#» ■ gi!sr^'^ ■ t. «5*r w .^- ■T^^^-Ay*^: ^ »w .„- .'•■' , '■•*' # - ^ '»-*-'fcilr-* -V. <^wv 4' ^.'H.*'- ' '■>5.1i ■ ^Jl # ,r •^ .^ \ .,t ??/j # 1^ B r ^ • •• * .1%*. . . « 'w '■'*••.' - 't' -**--*'.. » •ft- 'V J ~ . D Figure 8. — a. Normal antenna! gland. 100 X . b. Anlennal gland at 4 h postmortem. A few epithelial cells have been sloughed into the tubule lumens. 100 X. c. The tubule epithelium of the antennal gland at 12 h postmortem showing intense nuclear pyknosis. 150 X. d. Antennal gland at 24 h postmortem. The tubule epithelium has lysed filling the tubule lumens with eosinophilic debris and nuclear remnants. 150 X . become rigid. Whether this was due to desic- cation of the tissues or actual rigor of the mus- cles was not determined. In the present study, freshly killed juvenile shrimp became rigid in sealed glass jars containing water-saturated air and when totally submerged in water. Desic- cation was not possible. The time of onset of rigidity was, as in vertebrates, temperature- dependent, occurring earlier at higher tempera- tures than at lower temperatures. Flick and Lovell (1972) in studying post- mortem biochemical changes in penaeid shrimp reported that shrimp tails remained soft and did not exhibit any of the characteristics com- monly associated with rigor mortis during a storage period of 10 days at 0°C. Perhaps the effect of freezing or near-freezing temperature on shrimp muscle either masks or inhibits the onset of physical rigor. The rate of autolysis of the hepatopancreas is extremely rapid. The organ is a large, multi- functional organ believed to produce the bulk of enzymes used in the digestive process in shrimp and to have some absorptive and storage function. The hepatopancreas connects to the midgut near its origin from the pyloric stomach. The gut is a short, nearly straight tube. and, hence, enzymatic digestion must occur as rapidly as possible if the shrimp is to utilize its food efficiently. Even careful handling of shrimp to avoid stress before fixation, opening of the cuticle over the hepatopancreas, or exci- sion and bisection of the gland to enhance fixa- tion, frequently failed to provide adequate penetration and fixation of the organ when Formalin fixatives were used. The remaining tissues of shrimp are generally adequately fixed for light microscopy with Formalin, provided 235 FISHERY BULLETIN: VOL. 72, NO. 1 that small jiieces of tissue are used or that the cuticle is opened on smaller shrimp that are fixed whole. The relative rates and patterns of postmortem change in shrimp are similar to those described for the oyster (Sparks and Pauley, 1964) and for mammals (Cruickshank. 1912; Smith and Jones, 1966). In mammals, oysters, and shrimp, tissues that ])roduce large amounts of proteoly- tic enzymes such as the mammalian i)ancreas and lining epithelium of the stomach, oyster digestive tubules, and shrimp hepatopancreas and gut ejiithelium autolyze the most rajMdly. Tissues that autolyze nearly as rapidly are high lipid containing tissues such as nerve tissue. In the shrimp and in mammals, muscle, connective, and epidermal tissues undergo the least rapid autolysis. LITERATURE CITED Barnes, R. D. 196.^. Invertebrate zoology. Phila., 632 p. W. B. Saunders Co. Cruickshank, J. 1^12. The histological appearances occurring in organs undergoing autolysis. J. Pathol. Bacteriol. 16:167-184. Flick, G. J., and R. T. Lovell. 1972. Post-mortem biochemical changes in the muscle of Gulf shrimp, Penaeus aztecus. J. Food Sci. 37:609-611. Roberts, N. L. 1966. Morphology and histology of the stomach of the while shrimp, Pciuwus flnviatilis (Say, 1817). Ph.D. Thesis. Univ. South. Mississippi. Hattiesburg, 78 p. Robertson, J. D. 19? 9. Osmotic and ionic regulation. In T. H. Water- man (editor). The physiology of Crustacea, Vol. 1, p. 317-339. Academic Press, N.Y. Smith, H. A., and T. C. Jones. 1966. Veterinary pathology. 3d ed. Lea & Febiger, Phila.. 1192 p. Sparks, A. K. 1972. Death and postmortem change. //( A. K. Sparks, Invertebrate pathology noncommunicable diseases, p. 1-19. Academic Press, N.Y. Sparks, A. K., and G. B. Pauley. 1964. Studies of the normal postmortem changes in the oyster, Cnissosircu ,i,'wv.v (Thunberg). J. Insect Pathol. 6:78-101. Young, J. H. 1959. Morphology of the white shrimp, Penaeus seiiferus (Linnaeus 1758). U.S. Fish. Wildl. Serv., Fish. Bull. 59:1-168. 236 BOTHVS IHOMPSOM (FOWLER) 1923, A VALID SPECIES OF FLATFISH (PISCESiBOTHIDAE) FROM THE HAWAIIAN ISLANDS Paul Struhsaker and Robert M. Moncrief' ABSTRACT Boihiis ihumpsoni (Fowler) 1923 is resurrected from the synonymy of B. hleekeri Steindach- ner and redescribed. B. ihonipsuni differs from all other recognized species of the genus in possessing 11-17 gill rakers on the lower limb of the first gill arch and 115-147 lateral line scales. B. ihumpsoni is endemic to the Hawaiian Islands where it inhabits the outer shelf in depths of 70- 115 m. Fowler (1923) proposed Platophry^ thonipi^oiti on the basis of a single specimen obtained by John W. Thompson. Although no exact locality data were given, we assume the specimen was from the Honolulu market. PlatopJirys is now considered a synonym of BotJiu.s, while Norman (1934), without comment, relegated Bathus thonipsoui to the synonymy of B. hhtkeri Stein- dachner. Gosline and Brock (1960) followed Norman in listing B. bleekeri from the Hawaiian Islands. Previously, only the holotype of B. thompsoni was available for study. Our examina- tion of numerous specimens collected by the National Marine Fisheries Service (NMFS) during recent bottom trawling surveys in the 60-700 m depth range of the Hawaiian Islands demonstrates that B. thoinpsoui should be recognized as a valid species. MATERIAL AND METHODS All specimens were collected with 12.5-m (headrope) shrimp trawls during bottom trawl- ing surveys in the Hawaiian Islands with the NMFS RV Toicnsend Cromwell. Sampling effort and general ichthyological results of these surveys are given by Struhsaker (1973). Most specimens examined (one exception from Maui) were from the north coast of the island of Oahu. The following description is based on a series of 29 male (55.8-114.4 mm SL) and 31 female (39.1-103.7 mm SL) specimens all of which are housed in the National Museum of Natural ' Southwest Fisheries Center. National Marine Fisheries Service, NOAA, Honolulu. HI 968 12. History (USNM) and Bernice P. Bishop Museum (BPBM). Additionally, 33 uncata- logued specimens cleared and stained by the method described by Taylor (1967) were utilized in vertebral and gill raker counts, and more un- catalogued specimens were examined, obtaining supplementary dorsal, anal, and caudal ray counts. Measurements and counts are usually as defined by Norman (1934), Hubbs and Lagler (1958), and Gutherz (1967). Standard length was taken from tip of snout to end of hypural plate on the blind side. Horizontal eye diameter was taken between edges of the bony orbits. Snout to axis of greatest depth was taken from the snout to a vertical line at the greatest body depth. The last two dorsal and anal rays are each associated with pteiygiophores and are counted as two. Lateral line scale rows just above the lateral line and pored lateral line scales were counted. Vertebral counts were taken from radio- graphs and from cleared and stained speci- mens. Gill rakers were counted as discussed below. To evaluate morphometric characters, mea- surements in original units and as percent of standard length were plotted as functions of standard lengths. RESULTS Description Although a figure of B. thompsoui did not accompany the original description, Fowler (1928), in listing the species for Oceania, pro- vided a figure of the type (PI. IV, C) which is Manuscript accepted June 1973. FISHERY BULLETIN: VOL. 72. NO. 1. 1974. 237 FISHERY BULLETIN: VOL. 72. NO. 1 housed in the BPBM (3398). Measurements of the 106.8 mm SL male holotype (Fowler gave an undefined length of 134 mm) expressed as percent of standard length are given in Table 1. We obtained the following counts on this specimen: dorsal rays 86; anal rays 62; caudal rays 16; pectoral rays (both sides) 12; lateral- line scale rows 130; pored lateral-line scales 83; gill rakers 19 (5 + 14). Prowler (1923) gave counts of 132 scale rows and 20 gill rakers (6 -I- 14). Otherwise, our counts agree with his. Photographs of recently collected female (106.4 mm SL) and male (114.4 mm SL) speci- mens (both BPBM 14102) are shown in Figures 1 and 2. Counts Dorsal and anal ray counts, expressed as bivariate relations, for 101 specimens are given in Table 2. Dorsal rays ranged from 84 to 95 {X — 87.9) and anal rays ranged from 64 to 70 (A' = 66.3). Although the dorsal ray counts are skewed to the right, the distribution does not deviate significantly from a normal distribution (P>0.2; Kolomogorov-Smirnov test for good- ness of fit, D = 0.0702). There were considerably fewer pored lateral- line scales (Table 3) {X = 80.9) than the numbe£ of vertical scale rows above the lateral line (X = 131.6). There was a tendency towards more pectoral rays (Table 3) on the ocular side (X = 12.24) than on the blind side {X = 11.49). The upper pectoral ray on the ocular side is reduced and sometimes inconspicuous. The upper pectoral ray on the blind side is also reduced, but easily visible. BotJiKs thompso)ii appears to be unique among si)ecies of BotJius in usually jjossessing 16 caudal rays. Of 163 specimens examined (Table 3), 2 (1.2% ) had 15 rays, 157 (96.3% ) had 16 rays, and 4 (2.5% ) had 17 rays. The caudal rays are usually associated with the four hypural elements. Of 31 cleared and stained specimens having 16 rays, 11 had a caudal ray formula of 4-4-4-4 (dorsal element counted first). Other formulae obtained and number of specimens are as follows (rays articulating between elements are enclosed by parentheses): 4-4-3-(l)-4, (6 specimens); 4-4-3-5, (5 specimens) ; 3-( l)-4-4-4, (4 specimens) ; 3-(l)-4-3-(l)-4, (2 specimens); 3-(l)-4-3-5, (1 specimen); 3-(l)-4-3-5, (1 specimen); 4-4-3-5, (1 specimen). Two specimens with 15 rays had formulae of 4-4-3-4 and 3-(l)-4-4-3. None of the caudal rays of B. thompsoiii was associated with the neural and haemal spines of the penultimate vertebra or articulated in the space between the spines and hypural elements. Thus, B. thompsoni differs from certain other species of Botlius which have rays associated with the neural and haemal spines of the penul- timate vertebra or which occur in the interspace between the spines and hypural elements. Gutherz (1970) gives a formula of 1-4-4-3-4-1 for larval BotliHs (species not determined) from the western North Atlantic. We obtained the same formula for 12 cleared and stained specimens of B. pa)ithe7HHUs (Riippell) from the Hawaiian Islands. In these specimens the first and last rays most often articulated in the interspace between the spines and hypural elements. These Table 1. — Bothiis thompsoiu: Measurements of 13 characters for holotype, 29 males, and 31 females expressed as percent of standard length. Holotype excluded from regression statistics (a = ordinate intercept, h = regression coefficient). Holotype Range percent Range percent BPBM 3398 standard standard percent of length length Characters measured standard length for males a h ;-2 for females (/ b r2 Heed length 28.5 25.7-29.5 0.646 0.270 0.965 26.0-29.6 1.100 0.264 0.983 Snout length: to upper eye 23.9 14.0-21.5 -5.865 0.252 0.961 13.0-16.6 - 1.022 0.162 0.968 to lower eye 6.3 4.4- 6.2 0.315 0.048 0.821 4.8- 6.8 -0.171 0.569 0.857 Orbit diameter: upper 11.6 9.1-12.6 2.255 0.084 0.828 8.2-12.4 1.656 0.087 0.896 lower 9.6 7.6-10.9 2.222 0.071 0.811 8.0-11.5 2.263 0.067 0.874 Interorbitol distance 14.9 7.713.5 -5.856 0.182 0.958 5.1- 8.6 - 1.112 0.088 0.949 Length of upper jaw 10.3 8.0-10.6 1.102 0.081 0.856 8.2-10.4 0.770 0.084 0.943 Greatest body depth 60.8 57.7-66.0 - 1.046 0.629 0.968 57.0-67.3 -0.057 0.632 0.973 Least depth caudal peduncle 11.2 9.7-11.4 0.042 0.107 0.970 9.2-11.6 0.195 0.104 0.981 Length of pectoral fin: ocular side 21.7 19.0-24.7 4.661 0.159 0.912 18.8-24.9 4.925 0.153 0.924 blind side 18.4 15.3-18.7 2.294 0.141 0,928 14.0-18.5 0.826 0.155 0.930 Length of anal fin base 75.2 73.4-77.4 2.373 0.734 0.958 71.9-84.8 -3.634 0.814 0.966 Snout to greatest body depth 46.3 41.6-48.6 -4.156 0.497 0.959 41.4-50.0 0.341 0.452 0.961 238 STRUHSAKER and MONCRIEF: BOTHVS THOMPSOSl Figure 1. — A 106.4 mm SL female Boihu.s ihonipsoni. Figure 2. — A 1 14.4 mm SL male Boihu.s ihompsoni. data indicate that B. thompsoni exhibits a more variable caudal ray formula than B. pant'herinus. The first two and last two caudal rays of B. thompsoni are usually simple. Of a sample of 20 specimens, only 2 ( 10% ) had either the second or penultimate ray divided. The arrangement of gill rakers in B. thomp- soni is shown in Figure 3, and counts are given in Table 3. There are 3-9 reduced gill rakers associated with the epibranchial and 1-4 reduced gill rakers associated with the hypobranchial. A series of 9-14 well-developed gill rakers is principally associated with the ceratobranchial. The reduced gill rakers associated with the epibranchial comprise the counts for the upper limb of the gill arch. The first well-developed 239 FISHERY BULLETIN: VOL. 72. NO. I Table 2. — Dorsal and anal ray counis for 101 specimens ot liolhiis ilioinpsdiii. Number of dorsal rays Total nuin- Number of ■ ber of anal rays 84 85 86 87 88 89 90 91 92 93 94 95 specimens 70 __]_ 1 2 69 ____-l-l---- 2 68 -__-1314l— — — 10 67 --2577531- — - 30 66 -37398 — — — — — — 30 65 2-873------- 20 64 21211------- 7 Total number of specimens 4 4 19 16 21 19 7 8 2 - - 1 101 raker occurs at the angle of the arch and is included in the counts forthe lower limb, although stained material reveals this raker to be more closed associated with the epibranchial. The last one or two well-developed rakers are associated with the hypobranchial. The number of gill rakers in the size range examined is apparently independent of size. A regression coefficient calculated for 28 females was not significant (P> 0.4). Vertebral counts were obtained from 96 specimens. There are usually 10 abdominal vertebra (94 specimens), but two individuals had 11 (28 caudal vertebrae in both cases). Counts of caudal vertebrae (including urostyle) were 27 (7), 28 (69), and 29 (18). while total vertebral counts were 37 (7), 38 (69), and 39 (20). Figure 3. — A typical first gill arch from the ocular side of Bcihus iliiimpsoni. Measurements The measurements obtained from 29 male and 31 female specimens for 13 characters are summarized in Table 1. Linear regressions were calculated in original units of measurement (mm) with standard length as the independent Table 3. — Bailius iliomp.soni: Counts for eight characters. Characters Frequency of occurrence 10 II 12 13 14 15 16 19 20 21 22 23 24 N Caudal rays Pectoral rays {ocular side) Pectoral rays (blind side) Gill rakers (upper limb) Gill rakers (lower limb) Gill rakers (total) 157 5 29 29 21 1 7 32 22 2 29 31 1 3 21 22 27 13 1 13 24 17 - 163 16.0) 63 12.24 63 11.49 91 5.92 91 14.38 5 91 20.30 70- 72- 74- 71 73 75 76 90- 92- 78 80 82 84 86 88 91 93 Pored lateral line scales 31 80.9 114- 116- 118- 120- 122- 146- 115 117 119 121 123 124 126 128 130 132 134 136 138 140 142 144 147 Lateral line scale rows 17 63 131.6 240 STRUHSAKER and MONCRIEF: BOTHUS THOMPSONI variable. Plots of all regressions are linear and exhibit high )^ values. The regressions obtained for the 13 measured characters were subjected to analysis of covariance to test for sexual dimorphism. Highly significant differences (P< 0.001) were found between the regression coefficients for two characters (which are related): interorbital dis- tance (Figure 4) and snout to upper eye. Juvenile and adult male specimens of B. thonipsoni are similar to many Bothus spp. males in possessing a much greater interorbital distance than females of the same species. Male B. fliompsoni exhibit positive allometric growth of the interorbital distance, this measurement being about 7.5% - 9.0% of standard length at a length of 50-60 mm and about 12% -14% ofstandard length at a length of 100-115 mm. In female specimens longer than 50 mm the interorbital distances were 6.0% - 8.6% 'ofstandard length. Interorbital distances of 5.3% and 5.1% ofstandard length were noted in two specimens 39 mm and 48 mm long. As ex- pected, male B. thonipficnii exhibited positive allometric growth of the snout to upper eye distance. Among the remaining 11 characters subjected to analysis of covariance, there were no signifi- cant differences between regression coefficients. There were significant differences (P<0.05) in the elevations of the regressions between sexes for four characters. Both the upper and lower orbit diameters of males tend to be larger than for females; the differences in adjusted means for FEM ILES — ' ■ " • • -— — % • ___^.— -—* • ^^„^— -«- ^^u— ■ , ^^>^ 1 • ^t-' • % .- L<^ , ^ f^ • 60 70 60 90 STANDARD LENGTH (mm) Figure 4. — Plots of the interorbital distance of 29 male and 3 1 female specmiens of Boihiis ihonipsciii. the two characters are 0.35 and 0.40 mm, re- spectively. Females tend to have a greater body dei)th and a greater snout to greatest body depth distance. The differences in adjusted means for these two characters are 1.1 and 1.0 mm, respectively. In both sexes, the pectoral fins of the ocular side tend to be longer than those of the blind side (Table 1). The pectoral fins of both sexes exhibit negative allometric growth. This is most pro- nounced on the ocular size where the pectoral length is about 24% -25% of standard length at 40-60 mm and about 18% -21% ofstandard length at a length of 100-115 mm. There is only slight negative allometric growth of the pectoral fin on the blind side where this structure varies from 14.0% to 18.7% ofstandard length. All other morphometric characters examined exhibited approximately isometric growth. Two of the measurements we obtained for the holotype (Table 1) do not fall within the ranges we obtained from our study series: interorbital distance and snout to upper eye. Other morphological characters Botlius thonipsoiii has cycloid scales on the blind side and on most of the ocular side (Figure 5A). Ctenoid scales occur on the proximal portions of the dorsal and anal rays. There are 2-3 rows of ctenoid scales at the bases of the dor- sal and anal fins (Figure 5B). Fowler (1923) stated that the holotype had ctenoid scales on the cheeks and postorbital region. In addition, we find that there is a patch of about 15 ctenoid scales below the curved portion of the lateral line in the holotype. A scale from this region is shown in Figure 5C. The occurrence of ctenoid scales on the cheek and in the vicinity of the curved portion of the lateral line is a variable character. Of 25 specimens (67.5-106.4 mm SL) from our study series, six had ctenoid cheek scales, three had ctenoid scales on the cheek and near the lateral line, and one had ctenoid scales near the lateral line only. The presence of ctenoid scales in these two regions does not appear to be related to size or sex. The cycloid scales are small and nonimbricated, but the ctenoid scales at the dorsal and anal fin bases overlap to a slight degree. The ctenii of the ctenoid scales generally occur in two rows: a primary row of well-developed ctenii and a secondary row of smaller ctenii basal to the 241 FISHERY BULLETIN: VOL. 72. NO. 1 Figure 5. — Scales of Boihus ilioiiip.soni: A, cycloid scale from above the lateral line; B, ctenoid scale from near the dorsal fin base; and C, ctenoid scale from below the curved portion of the lateral line in the holotype. primary row (Figure 5B and C). The number of ctenii on cheek scales varies from 5 to 8, while scales from the dorsal and anal fin bases at the greatest body depth have 15 to 25 ctenii. The general arrangement of teeth in the upper and lower jaws is shown in Figure 6. There are usually three rows of teeth. The outer row consists of a few, stout conical teeth in the anterior portion of the jaws. The middle row consists of more numerous, but less stout, conical teeth. The inner row consists of depressed, poor- ly ossified conical teeth subequal in number to those in the middle row (except on the blind side of the upper jaw). The inner row of teeth are movable, being held in place by flesh and not inserted in the jaw bones. The number of outer teeth, and, to a lesser extent, the middle teeth, vary according to jaw bone and size of specimen. This is illustrated in Figure 7 where the number of teeth are plotted by standard length for 10 females 49.2-106.4 mm SL and 10 males 55.8-114.5 mm SL. The increase in number of outer teeth with size is ai)parent for all jaw bones except the dentary on the ocular side. There also appear to be more outer teeth in the premaxillary of the ocular side of the males. 242 STRUHSAKER and MONCRIEF: BOTHUS THOMPSON! The teeth in the middle row also exhibit a general, but less well-defined, increase in numbers with size. There are no fleshy papillae along the edges of the eyes such as reported for male B. pcvtther- imis (Norman, 1934). There is a single promi- nent, blunt protuberance on the snout of males greater than 60 mm SL. This stnacture is represented in females by a small knob. The anterior edge of the lower orbit tends to be more developed and rugose in males than in females. Coloration of fresh specimens The blind side of both sexes is white, but tending to dusky white in males greater than about 80 mm SL, especially on the cheek and above the cheek. The ground color of the ocular side is light olive green. There is a single prominent dark spot on the lateral line posteriad about 60% of the standard length. There are two secondary dark ocelli near the pectoral fin. There are 14-15 olive green ocelli broadly distributed along the dorsal and ventral borders of the trunk. There are numerous light blue ocelli and spots dis- tributed over the trunk, head, and dorsal, anal, caudal, and ventral fins. The pectoral fins are almost clear. In males, the light blue spots are more numerous and elongated along the anterior profile and between the eyes. Comparison with Other Species oi Bothns A definitive discussion of the relation of B. th()))tps())ii to other species of Bothus must await further study of the genus on a worldwide basis. B. tJiompsoiii differs from all recognized species of Bothus (Fowler, 1933; Norman, 1934; Chabanaud, 1942; Stauch, 1966; Gutherz. 1967; Amaoka, 1969; Topp and Hoff, 1972) in possess- ing 11-17 gill rakers on the lower limb of the first arch (11 or fewer in other species) and 115-147 scale rows above the lateral line (apparently 100 or fewer in other species: Nor- man, 1934). It may also be unique in that it usually has only 16 caudal rays as opposed to 17 in other species. This character, however, apparently has been examined only rarely by earlier authors and few data on the numbers and arrangements of the caudal rays are avail- able (Chabanaud, 1942; Amaoka, 1969; Gutherz, 1970). The figures given by Norman (1934) for B. leopardinus (Giinther) and B.bleekeri indicate Figure 6. — The arrangement of teeth in Baihiis ihompsoni. caudal ray counts of 16. However, a count of 16 is also indicated for B. ovalis (Regan) which Amaoka (1964) has shown to be the young of B. myriaster (Temminck and Schlegel). B. inyriaster has 17 caudal rays (Amaoka, 1969). Chabanaud (1942) described B. biidkeri from the Red Sea and gave caudal ray counts of 16 for the holotype and 17 for the two paratypes. A sample of 368 adult and lai*val specimens of B. panthcrhiKs from the Hawaiian Islands had the following caudal ray counts: 16 (2.7%), 17 (95.7% ), 18 (1.6% ). Further examination of this character is required. We have not examined specimens of B. bleekeri, and we separate this species from B. thompsniii on the basis of the description given by Norman (1934). In addition to the differences in gill raker and lateral line scale row counts dis- cussed above, B. thompso)n has more pectoral rays on the ocular side (10-14 vs. 8-9). Adult male specimens of B. tho))ipso)u do not have elongated pectoral rays (ocular side), whereas male B. bleekeri have elongated pectoral rays. Two other species of Bothus, B. panthennus and B. mcnicKs (Broussonet), occur in the Hawaiian Islands. Adult specimens of B. thomp- suiii may be separated from similar life history stages of the former two species on the basis of body profile alone. Other useful characters for 243 FISHERY BULLETIN: VOL. 12. NO. I distinguishing B. thompsoiu from B. ptDitheri- nus and B. maiicua (in addition to counts of the lateral line scale rows, lower gill rakers, and caudal rays) are as follows. Cycloid scales are present on the ocular side of B. thonipsoiii (except at the bases of the dorsal and anal fin, and occasionally on the cheeks and in the vicinity of the lateral line) as opposed to ctenoid scales on the ocular side for B. paiither- imis and B. ihuiicks. Adult males of the latter two species have elongated pectoral fin rays on the ocular side, while male specimens of B. thonipsoni do not. Bothus niaiicHs possess more dorsal and anal fin rays than do B. thomp- sdiii and B. paiitJwriinis (97-102 vs. 84-96 and 77-82 vs. 64-74, respectively; Hawaiian Island UJ UJ o ffi Z 60 50 40 30 20 10 0 60 50 40 30 20 10 0 40 30 20 10 0 40 30 20 10 FEMALES k MIDDLE TEETH • OUTER TEETH MALES 1 1 1 I 1 T 1 k A 1 1 1 1 i A PREMAXILLARY- BLIND SIDE • • • • • • • i . 1 1 . J • • • 1 1 1 •—L • • • • • 1 111^. ■■ ■ T I 1 1 I 1 \ 1 -I ■ I 1 1 1 A A i A A k A A A * A A * A A A A • • A • • • PRE^flAXILLARY- OCULAR SIDE • • 1 • • fl • m^^- • • • 1 1 1 1 •_! L- 1 1 1 1 1 A ' A ' A A . 1— ■ ■■ 1 A 1 A I A 1 A A A * A A A A A A A - DENTARY - BLIND SIDE • • •b • • • • • • 1 •"— , — •-I-.- •i 1 1 • ^*- -•^ 1 1 1 1 1 ! I 1 1 1 A ' ' I 1 1 A •' — A • A A * A • ' » A A A A A A A — •-^- A *- *A -•-* A • DENTARY -OCULAR SIDE -J — • — •L §• -L» •!- 40 50 60 70 80 90 100 110 120 40 50 60 70 80 90 100 110 120 STANDARD LENGTH (mm) Figure 7. — Numbers of teeth in the outer and middle tooth rt)ws in Butinis ilioinp.soni 244 STRUHSAKER and MONCRIEF: BOTHUS THOMPSONI specimens). Bothus thonipsoi/i has 10-14 pectoral rays, whereas this count is 9-11 for both B. paiitlieri)tns and B. niaiictts. With regard to other Indo-Pacific species recognized by Norman (1934), B. thompsoni differs from B. nnjriaster in that the pectoral fins of males are not elongated in the former species. The combination of cycloid and ctenoid scales on the ocular side of B. thonipsoni dif- ferentiates it from B. assimilis (Giinther) which has onl}^ cycloid scales and from B. leopardinus (Giinther) which has only ctenoid scales on the ocular side (Norman. 1934). Norman (1934) considers also that B. coiisteUatns (Jordan, ill Jordan and Goss) is very doubtfully distinct from B. leoparduius. Although no illustration was given of B. budkeri (Chabanaud. 1942) from the Red Sea, it differs from B. fhotiipi<(>)ii in having a lesser body depth, fewer dorsal and anal rays, fewer gill rakers on the lower limb of the first arch, and only ctenoid scales on the ocular side. Fowler (1933) described five species of Bothus from the Phili])pines and China Sea. The generic placement of several of these species is questionable. At any rate, none of them could be confused with B. thoinp.^oiii. Ecology With the exception of one specimen caught at a depth of 72 m off Maui, all specimens of B. thompsoiii taken to date have come from depths of 90-113 m off the north coast of Oahu where bottom temperatures ranged from 24.5° to 26.0°C. About 580 specimens (32-107 mm SL) have been obtained at 13 stations where catches ranged up to 275 individuals per haul. An analysis of dispersion for this species (Struhsaker. 1973) shows it to have a highly clumped distribution. The type of bottom in the area of capture is primarily muddy sand interspersed with patches of sponge, broken shell, and rubble. Bothus thompsoni was often taken with 20-30 other species of fishes; it usually comprised less than 8% of the total catch, but occasionally ranged up to 30%. Nu- merically dominant species taken with B. thomp- soni include Tmchiiiocephaliis niyops, Priacaii- thus spp., Aiitigoiiia cos. Parupeneus chyysoiie- mus, and Lagocephalus hypselogeueioii. Struh- saker and Higgins (rnanuscr.-) have shown that B. thompsoni is the third most abundant larval flatfish (after Engyprosopo)i .ve)icuidrus Gilbert and B. paiitlierinus) taken in offshore mid water hauls near Oahu. They also presented evidence that B. thompsoni may spawn through- out the vear. ACKNOWLEDGMENTS We thank John E. Randall for the photo- graphs used in Figures 1 and 2 and for review- ing the manuscript. We are also indebted to Elbert H. Ahlstrom and C. Richard Robins for comments on the manuscript. The NMFS Systematics Laboratory provided the radio- graphs. The illustrations are by Tamotsu Nakata and Robert Bonifacio. MATERIAL EXAMINED USNM 208494: TC-33-52 (R/V Towusend Ci'omwell, cruise 33, station 52); 1 male (109.2 mm SL); lat. 19°58.3' N, long. 156°28.5' W; depth 72 m, 13 Nov. 1967. USNM 208495: TC-36-15; 4 females (93.7-99.1 mm SL); lat. 21°37.7' N, long. 158°08.8' W; depth 113 m. 2 May 1968. USNM 208496: TC-36-20; 7 females (39.5-72.8 mm SL), 12 males (55.8- 81.2 mm SL); lat. 21°36.8' N, long. 158° 12.5' W; depth 110 m, 3 May 1968. USNM 208497: TC-40-115; 10 females (56.9-87.3 mm SL), 5 males (70.0-84.5 mm SL); lat. 21°36.8' N, long. 158° 08.2' W; depth 102 m, 8 Nov. 1968. USNM 208498: TC-40-116; 4 females (56.0- 105.4 mm SL), 3 males (58.6-104.5 mm SL); lat. 21°36.8' N, long. 158° 11.6' W; depth 112 m. 1 Dec. 1968. USNM 208499: TC-40-119; 5 females (78.6-91.2 mm SL), 7 males (86.2- 99.2 mm SL); lat. 2r36.8' N, long. 158° 11.2' W; depth 96 m, 1 Dec. 1968. BPBM 14102; TC-40-125; 1 female (106.4 mm SL), 1 male (114.4 mm SL); lat. 21°36.8' N, long. 158°11.6' W; depth 102 m, 10 Nov. 1968. - Struhsaker. P., and B. E. Higgins. Unpubl. manuscr. Post-larval flatfishes (Pisces:Pleuronectiformes): Observa- tions on the identity and ecology of 11 Hawaiian species. Southwest Fisheries Center. National Marine Fisheries Service. NOAA, Honolulu. Hawaii 968 12. 245 FISHERY BULLETIN: VOL. 12. NO. 1 LITERATURE CITED Amaoka, K. 1964. Development and growth of the sinistral flounder, Bothus inyriaster (Temminck and Schlegel) found in the Indian and Pacific Oceans. Bull. Misaki Mar. Biol. Inst.. Kyoto Univ. ^.W- 29. 1969. Studies on the sinistral flounders found in the waters around Japan — taxonomy, anatomy and phylogeny. J. Shimonoseki Univ. Fish. 18:65-340. Chabanaud, p. 1942. Notules ichthyologiques. Bull. Mus. Natl. Hist. Nat. Paris 14:395-402. Fowler, H. W. 1923. New or little known Hawaiian fishes. Occas. Pap. Bernice Pauahi Bishop Mus. 8(7), 20 p. 1928. Fishes of Oceania. Mem. Bernice P. Bishop Mus. 10, 540 p. 1933. Descriptions of new fishes obtained 1907 to 1910, chiefly in the Philippine Islands and adjacent seas. Proc. Acad. Nat. Sci. Phila. 85:233- 367. GOSLINE, W. A., AND V. E. Brock. 1960. Handbook of Hawaiian fishes. Univ. Hawaii Press, Honolulu, 372 p. GUTHERZ, E. J. 1967. Field guide to the flatfishes of the family Bothidae in the western North Atlantic. U.S. Fish Wildl.Serv., Circ.263,47 p. 1970. Characteristics of some larval bothid flatfish, and development and distribution of larval spot- fin flounder, Cydopsciia Jimhriaici (Bothidae). U.S. Fish Wildl. Serv., Fish. Bull. 68:261-283. HuBBS, C. L., AND K. F. Lagler. 1958. Fishes of the Great Lakes region. Revised ed. Cranbrook Inst. Sci., Bull. 26, 213 p. Norman, J. R. 1934. A systematic monograph of the flatfishes (Heterosomata). Vol. I. Psettodidae, Bothidae, Pleuro- nectidae. Br. Mus. (Nat. Hist.), Lond., 459 p. Stauch, a. 1966. Quelques donnees sur les Bothus de TAtlan- tique et description d'une espece nouvelle Bothus guibei: n. sp. (Pisces Teleostei, Heterosomata). Bull. Mus. Natl. Hist. Nat. Paris 38:118-125. Struhsaker, p. 1973. A contribution to the systematics and ecology of Hawaiian bathyal fishes. Ph.D. Diss., Univ. Hawaii, Honolulu, 482 p. Taylor, W. R. 1967. An enzyme method of clearing and staining small vertebrates. Proc. U.S. Natl. Mus. 122(3596), 17 p. Topp, R. W., and F. H. Hoff, Jr. 1972. Flatfishes (Pleuronectiformes). Mem. Hour- glass Cruises, Fla. Dep. Nat. Resour., Mar. Res. Lab.4(2):l-135. 246 NOTE DEVELOPMENT OF EGGS AND EMBRYOS OF THE SURF CLAM, SPISULA SOLIDISSIMA, IN SYNTHETIC SEAWATER The eggs of the surf clam, Spisula solidissima, have been used extensively for investigations of egg structure and embryonic development of bivalves. Allen (1951) has pointed out the ad- vantages of the use of surf clam eggs for research of this nature. These studies have been limited, however, to areas where natural sea- water was readily available, due to the unsuit- ability of most synthetic seawaters for support- ing the embryonic development of bivalves (David A. Nelson, NMFS, Milford, Connecticut and Gerald Zaroogian, Environmental Protec- tion Agency Laboratory, West Kingston, Rhode Island, pers. comm.). Experimental Observations We recently reared Spisi'.lo solidissima em- bryos in a synthetic seawater formulation de- veloped by Zaroogian, Pesch, and Morrison (1969) as a culture medium in which to rear oyster embryos. Our observations were made in salinities of 25 and 30 'Voo at 10°, 15°, and 20°C water temperatures. Within these ranges we found 20°C to be the optimum temperature for development, allowing us to rear eggs to the 5-day-old stage (early veliger) with almost 100% survival and no signs of larval abnormali- ties. At 20°C polar body formation occurs in about 45 min and the two-cell stage in about 90 min. The early veliger, or straight-hinge stage, is reached in less than 24 h. At 15 °C all stages of development are normal but somewhat delayed, with development to the straight- hinge stage requiring more than 24 h. At 10°C the rate of development of all stages is greatly retarded and many abnormal embryos are present. The majority of fertilized eggs held at 10 °C requires more than 96 h to develop to the straight-hinge stage. At 20° C we found that development of fer- tilized eggs in synthetic seawater was com- parable to the best development observed in natural seawater. This study did not involve testing embry- onic development of S. fiolidissima in synthetic seawater over a wide range of salinities, but was limited to those salinities currently in use in other research programs within this labora- tory. It appeared that there was no difference in survival and development of eggs to the 5-day- old stage at salinities of 25 and 30 "/oo. the only salinities tested. In earlier work, however, Stickney (in Yancey and Welch, 1968) reported that S. solidissima eggs failed to develop under experimental conditions in salinities of less than 23 'Voo in natural seawater. Since the synthetic seawater formulation developed by Zaroogian, Pesch, and Morrison (1969) can be readily prepared, its general acceptance could lead to a wider utilization of surf clam eggs by embryologists and cytologists with standardization of techniques and compar- ability of results not always possible when natural seawaters from different locations are used. LaRoche, Eisler, and Tarzwell (1970), in studies of bioassay procedures for oil and oil dispersant toxicity evaluation, suggested the use of Zaroogian 's seawater as a standard testing medium in place of natural seawater, the com- position of which varies, especially in regard to the presence of trace metals, dissolved organics, and particulate matter. They recommended the use of Zaroogian 's seawater because of its ability to support spawning adults and larvae of the American oyster, Crassostrea virginica, for at least 48 h without visible adverse effects, and adult mummichog, Fundulus heteroclitus, grass shrimp, Palaemonetes vulgaris, and sand- worm, Nereis virens, for extended periods. Thus, when sufficient research has been per- formed in this area, it may be possible not only to hold adult animals but also to rear the eggs and larvae of these animals in the same syn- thetic seawater. This would be an obvious ad- vantage in assessing comparative tolerances to pollutants of different life stages. 247 Collection and Maintenance of Surf Clams in the Laboratory Although some information on the collection and maintenance of surf clams in the labora- tory and their reproductive cycle has been pub- lished (Loosanoff antl Davis, 1963; Ropes, 1968; Yancey and Welch. 1968), we feel it pertinent to this pai)er that it be reviewed and our own observations added. Adult surf clams can be purchased from bio- logical supi)ly houses or collected in their nat- ural habitat. The range of S. soUdissuiia is along the Atlantic Coast of North America, from the Gulf of St. Lawrence to Cape Hatteras (Yancey and Welch, 1968). South of Cape Hat- teras the surf clam is represented by Spi>inla solidissinta raveiieli. similar to S. soUdissima but a smaller species. S. soUdissiiua is found in sandy bottoms from the low-tide line to depths of 500 ft in waters of oceanic salinity. They are present in shallow water beds, at various points along their range, and are easily hand-gathered along the coasts of Delaware, New Jersey, Long Island (New York), Rhode Island, and Massa- chusetts. Our collections have come mainly from Little Narragansett Bay and the area of Point Judith, in Rhode Island. Surf clams can also be obtained from com- mercial clam boats working the beds, but our observations have shown that hand-gathered clams are more suitable for laboratory purposes; those obtained from commercial sources are often damaged by the action of the hydraulic dredge used in harvesting. They suffer high mortalities soon after introduction into the laboratory and long-term survival of those re- maining also seems inferior to that of hand- gathered stocks. We feel that the best working size for labora- tory animals to be used as a source of gametes is 4 to 5 inches. Larger ones require more space and do not survive as well in crowded tanks. Smaller animals are more difficult to spawn, even though we have found some specimens as small as 5 cm to have viable sex products. Ropes (1968), in a study of the rej^roductive cycle of offshore surf clam populations, found a biannual cycle during 3 years of the 4-year period covered by his study. This biannual cycle was characterized by a major mid-year spawn- ing and a minor late-year spawning. He found ripe clams as early as May and as late as Octo- ber during 3 years of the study. This pattern of ripeness may vary between inshore and off- shore populations, depending on local tempera- ture conditions. We found ripe clams only from June to August in inshore Rhode Island waters. Surf clams can be collected prior to their natural spawning period and conditioned to ripeness in the laboratory. Conditioning refers to a procedure of gradually raising the water temperatures at which bivalves are maintained as a means of achieving gonad ripeness prior to the time one would expect to find ripe ani- mals in the field (Loosanoff, 1954). We have collected animals with unripe gametes from early winter through late spring (December to May) and conditioned them at 15 °C. This temperature equals or exceeds that at which gametogenesis takes place in natural populations (Ropes, 1968). Such animals col- lected in early winter and conditioned in the laboratory have been spawned as early as March. Ripe surf clams held in the laboratory at 15 °C have never spawned spontaneously; thus, the spawning threshold of this animal in the labo- ratory would appear to be higher than 15 °C. We do feel, however, even though we, as yet, lack quantitative data to substantiate it, that ripe animals held at 15 °C tend to resorb their gametes more quickly than those held at a lower temperature following conditioning. Ripe animals collected in June and held at 10°C con- tained viable sex products in December. Ropes (1968) reported that offshore popula- tions spawn at lower temperatures than we found in our laboratory populations. He also noted that abrupt rises in water temperature were not clearly a cause of spawning in natural populations. A rapid increase in temperature is certainly an important factor in stimulating spawning in the laboratory. Clams conditioned at 15 °C spawned when the temperature was raised quickly to 18-20 °C. However, these clams were less responsive than those held in damp refrigeration (approximately 2°C, covered with a wet towel to prevent drying) overnight prior to exposure to 18-20 °C. Refrigerated clams nor- mally spawned within an hour after exposure to 1*8-20°C, while those conditioned at 15°C and exposed to water at 18-20°C did not. Eggs and sperm can also be obtained by strip- ping the sex products from the gonads using a 248 method described by Costello et al. (1957). This invalves removing one shell and gill, exposing the visceral mass, and slicing into the gonad which overlays the digestive glands and viscera. Care should be taken to avoid cutting into the underlying intestines and digestive glands, as the presence of body fluids in the cultures of eggs appears to be detrimental to embryonic development. The eggs and sperm are washed into separate collecting containers. Most of the tissue and debris collected along with the gametes can be removed by selective screening. Stripped eggs tend to be more irregular in shape than naturally spawned eggs but soon become spherical. Previous investigators (Loosanoff and Davis, 1963) have reported the diameter of spawned mature eggs to average 56.5 jj. Our measurements of rounded stripped eggs from ripe clams have agreed with this. To fertilize the eggs a small quantity of sperm suspension is added to the egg suspension and mixed by rapid stirring; care must be taken to add only a small quantity of sperm as Spi- siila eggs are quite susceptible to polyspermy at high sperm concentrations (Allen, 1951). Fol- lowing fertilization the germinal vesicle breaks down and a thin membrane forms a short dis- tance above the surface of the egg. In conclusion we would like to point out that this is the first time to our knowledge that Spisiila soUdissinia embryos have been reared in synthetic seawater, although they have been previously reared in the laboratory in natural seawater. Not all synthetic seawaters currently available are suitable for this purpose but that developed by Zaroogian, Pesch, and Morrison has consistently given us good results. We feel that the ability to rear these embryos in syn- thetic seawater will enhance the value of surf clam eggs and embryos in embryological and cytological research by offering a standardized rearing medium and a comparability of results not always possible when natural seawaters from different locations are used, as well as making possible the use of these organisms in bioassay procedures where the composition of the seawater must be known. Literature Cited Allen. R. D. 1951. The use of Spisiila solidissimci eggs in cell re- search. J. Cell. Comp. Physiol. 37:504-505. Costello, D. P., M. E. Davidson, A. Eggers, M. H. Fox, AND C. Henley. 1957. Mollusca (Pelecypoda) Maciru (now Spisula) solidi.ssinui. In D. P. Costello, M. E. Davidson, A. Eggers, M. H. Fox, and C. Henley, Methods for obtaining and handling marine eggs and embryos, p. 113-116. Mar. Biol. Lab., Woods Hole, Mass. LaRoche, C, R. Eisler, and C. M. Tarzwell. 1970. Bioassay procedures for oil and oil dispersant toxicity evaluation. J. Water Pollut. Control Fed. 42:1982-1989. Loosanoff, V. L. 1954. New advances in the study of bivalve larvae. Am. Sci. 42:607-624. Loosanoff, V. L., and H. C. Davis. 1963. Rearing of bivalve mollusks. In .Adv. Mar. Biol. 1:1-136. Ropes, J. W. 1968. Reproductive cycle of the surf clam, Spisula solicli.ssinia, in offshore New Jersey. Biol. Bull. (Woods Hole) 135:349-365. Yancey, R. M., and W. R. Welch. 1968. The Atlantic Coast surf clam — with a partial bibliography. U.S. Fish Wildl. Serv., Circ. 288, 14 p. Zaroogian, G. E., G. Pesch, and G. Morrison. 1969. Formulation of an artificial seawater media suitable for oyster larvae development. Am. Zool. 9:549. Wayne D. Cable Warren S. Landers Middle Ailaiuic Cousud Fisheries Center Milford Laboratory National Marine Fisheries Service, NOAA Milford. CT 06460 249 ERRATUM Fishery Bullethi. Vol. 71, No. 3 Paul, A. J., and Howard M. Feder, "Growth, recruitment, and distribution of the littleneck clam, Protothaca staminea, in Galena Bay, Prince William Sound, Alaska," p. 665-677. 1) Page 665, left column, first paragraph. The last sentence should read: "Feder and Paul (1973) and R. Nickeron (Alaska Department of Fish and Game, pers. comm.) suggested that a small clam fishery is feasible in Prince William Sound since paralytic shellfish poison (P.S.P.) does not seem to be a problem there, and many beaches with sizable populations of P. staminea and the butter clam, Saxidomus giganteus, occur in the area." INFORMATION FOR CONTRIBUTORS TO THE FISHERY BULLETIN Manuscripts submitted to the FisJienj Bulletin will reach print faster if they conform to the following instructions. These are not absolute requirements, of course, but desiderata. CONTENT OF MANUSCRIPT The title page should give only the title of the paper, the author's name, his affiliation, and mailing address, including Zip code. The abstract should not exceed one double- spaced page. In the text, Fishenj Bnlletin style, for the most part, follows that of the Style Manual for Biological Journals. Fish names follow the style of the American Fisheries Society Special Pub- lication No. 6, A List of Common and Scie)itific Names of Fisltes from the U)iited States a)id Canada, Third Edition, 1970. The Memam- Wehster Third New International Dictionary is used as the authority for correct spelling and word division. Text footnotes should be typed separately from the text. Figures and tables, with their legends and headings, should be self-explanatory, not requir- ing reference to the text. Their placement should be indicated in the right-hand margin of the manuscript. 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I •O^UT/O/v ^ /Si % ^'^^e-iQi^ NOAA FSYB-A 72-2 .>^^^'°^^o, '^TES O^ Fishery Bulletin National Oceanic and Atmospheric Administration • National Marine Fisheries Service Vol. 72, No. 2 April 1974 KANWISHER, JOHN, KENNETH LAWSON, and GUNNAR SUNDNES. Acous- tic telemetry from fish 251 SOUTAR, ANDREW, and JOHN D. ISAACS. Abundance of pelagic fish during the 19th and 20th centuries as recorded in anaerobic sediment off the Cali- fornias . '. 257 MacGREGOR, JOHN S. Changes in the amount and proportions of DDT and its metabolites, DDE and DDD, in the marine environment off southern Califor- nia, 1949-72 275 HIROTA, JED. Quantitative natural history of Pleurobrachia bachei in La Jolla Bight 295 CLARKE, THOMAS A. Some aspects of the ecology of stomiatoid fishes in the Pacific Ocean near Hawaii ADRON, J. W., A. BLAIR, and C. B. COWEY. Rearing of plaice (Pleuronectes platessa) larvae to metamorphosis using an artificial diet 353 BEN-YAMI, M., and T. GLASER. The invasion of Saurida undosquamis (Richard- son) into the Levant Basin — An example of biological effect of interoceanic canals . . 359 KEMMERER, ANDREW J., JOSEPH A. BENIGNO, GLADYS B. REESE, and FREDERICK C. MINKLER. A summary of selected early results from the ERTS-1 menhaden experiment 375 MOSER, H. GEOFFREY, and ELBERT H. AHLSTROM. Role of larval stages in systematic investigations of marine teleosts: The Myctophidae, a case study . 391 APRIETO, VIRGINIA L. Early development of five carangid fishes of the Gulf of Mexico and the south Atlantic Coast of the United States 415 KAPLAN, EUGENE H., J. R. WELKER, and M. GAYLE KRAUS. Some effects of dredging on populations of macrobenthic organisms 445 MUSICK, JOHN A. Seasonal distribution of sibling hakes, Urophycis chuss and U. tenuis (Pisces, Gadidae) in Nev^' England 481 MILLER, JOHN M., and BARBARA Y. SUMIDA. Development of eggs and larvae of Caranx mate (Carangidae) 497 STICKNEY, ROBERT R., GARY L. TAYLOR, and RICHARD W. HEARD, III. Food habits of Georgia estuarine fishes. I. Four species of flounders (Pleuro- nectiformes: Bothidae) 515 (Continued on hack cover) Seattle, WA U.S. DEPARTMENTOFCOMMERCE Frederick B. Dent, Secretary NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION Robert M. White, Administrator NATIONAL MARINE FISH ER I ES SERVICE Robert W. Schoning, Director i Fishery Bulletin The Fishery Biilli'tiii 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. the Fishery 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, D.C. 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. Reuben Lasker Scientific Editor, Fishery Bulletin National Marine Fisheries Service Southwest Fisheries Center La Jolla, California 92037 Editorial Committee Dr. Elbert H. Ahlstrom National Marine Fisheries Service Dr. William H. Bayliff Inter-American Tropical Tuna Commission Dr. Daniel M. Cohen National Marine Fisheries Service Dr. Howard M. Fcder University of Alaska Mr. John E. Fitch California Department of Fish and Game Dr. Marvin D. Grosslein National Marine Fisheries Service Dr. J. Frank Hebard National Marine Fisheries Service Dr. John R. Hunter National Marine Fisheries Service Dr. Arthur S. Merrill National Marine Fisheries Service Dr. Virgil J. Norton University of Rhode Island Mr. Alonzo T. Pruter National Marine Fisheries Service Dr. Theodore R. Rice National Marine Fisheries Service Dr. Brian J. Rothschild National Marine Fisheries Service Mr. Maurice E. Stansby National Marine Fisheries Service Dr. Maynard A. Steinberg National Marine Fisheries Service Dr. Roland L. Wigley National Marine Fisheries Service Kiyoshi G. Fukano, Managing Editor The Secretary of Commerce has determined thot the publication of this periodical is necessary in the transaction of the public business required by low 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 May 31, 1974. Fishery Bulletin CONTENTS Vol. 72, No. 2 April 1974 KANWISHER, JOHN, KENNETH LAWSON, and GUNNAR SUNDNES. Acous- tic telemetry from fish 251 SOUTAR, ANDREW, and JOHN D. ISAACS. Abundance of pelagic fish during the 19th and 20th centuries as recorded in anaerobic sediment off the Cali- fornias 257 MacGREGOR, JOHN S. Changes in the amount and proportions of DDT and its metabolites, DDE and DDD, in the marine environment off southern Califor- nia, 1949-72 275 HIROTA, JED. Quantitative natural history of Pleurobrachia bachei in La Jolla Bight 295 CLARKE, THOMAS A. Some aspects of the ecology of stomiatoid fishes in the Pacific Ocean near Hawaii 337 ADRON, J. W., A. BLAIR, and C. B. COWEY. Rearing of plaice (Pleuronectes platessa) larvae to metamorphosis using an artificial diet 353 BEN-YAMI, M., and T. GLASER. The invasion ofSaurida undosquamis (Richard- son) into the Levant Basin — An example of biological effect of interoceanic canals 359 KEMMERER, ANDREW J., JOSEPH A. BENIGNO, GLADYS B. REESE, and FREDERICK C. MINKLER. A summary of selected early results from the ERTS-1 menhaden experiment 375 MOSER, H. GEOFFREY, and ELBERT H. AHLSTROM. Role of larval stages in systematic investigations of marine teleosts: The Myctophidae, a case study . 391 APRIETO, VIRGINIA L. Early development of five carangid fishes of the Gulf of Mexico and the south Atlantic Coast of the United States 415 KAPLAN, EUGENE H., J. R. WELKER, and M. GAYLE KRAUS. Some effects of dredging on populations of macrobenthic organisms 445 MUSICK, JOHN A. Seasonal distribution of sibling hakes, Urophycis chuss and U. tenuis (Pisces, Gadidae) in New England 481 MILLER, JOHN M., and BARBARA Y. SUMIDA. Development of eggs and larvae of Caranx mate (Carangidae) 497 STICKNEY, ROBERT R., GARY L. TAYLOR, and RICHARD W. HEARD, III. Food habits of Georgia estuarine fishes. I. Four species of flounders (Pleuro- nectiformes: Bothidae) 515 (Continued on next page) Seattle, WA For sale by the Superintendent of Documents, U.S. Government Printing Office, Washington, D.C. 20402 — Subscription price: $10.85 peryear ($2.75 additional for foreign mailing). Cost per single issue - $2.75. (Contents-continued) ALVARINO, ANGELES. Distribution of siphonophores in the regions adjacent to the Suez and Panama Canals 527 RAJU, SOLOMON N. Three new species of the genus Monognathus and the lepto- cephali of the order Saccopharyngiformes 547 POTTHOFF, THOMAS. Osteological development and variation in young tunas, genus Thunnus (Pisces, Scombridae), from the Atlantic Ocean 563 FRENCH, ROBERT R., and RICHARD G. BAKKALA. A new model of ocean mi- grations of Bristol Bay sockeye salmon 589 Notes BALDRIDGE, ALAN. Migrant gray whales with calves and sexual behavior of gray whales in the Monterey area of central California, 1967-73 615 BROOKS, A. L., C. L. BROWN, JR., and P. H. SCULLY-POWER. Net filter- ing efficiency of a 3-meter Isaacs-Kidd midwater trawl 618 DOW, ROBERT L. American lobsters tagged by Maine commercial fishermen, 1957-59 622 ACOUSTIC TELEMETRY FROM FISH John Kanwisher,' Kenneth Lawson,' and Gunnar Sundnes^ ABSTRACT Methods are described for monitoring physiological parameters such as temperature and electrocardio- gram from free swimming fish. Information is telemetered as sound radiating from an acoustic transmitter implanted on the fish. Limitations of the technique and construction details of representative devices are covered. Uses in both behavior and physiology are considered. Acoustic telemetry allows an investigator to study the behavior and physiology of fish under conditions which approximate their natural state. Improvements in electronic techniques permit construction of devices the size of one's little finger; these devices can transmit data such as heartbeat and temperature over ranges of sev- eral hundred meters for as long as a month. We describe here the use and constraints on sound as a means of transmitting these data. We then dis- cuss, in detail sufficient for duplication, the con- struction of sample devices for transmitting, re- ceiving, and interpreting the data. Finally, we show how these devices have been applied to specific experimental problems, and discuss the results we have obtained. SOUND AS A TELEMETRY MEDIUM For ranges beyond a few meters through water, sound is the only practical form of energy for telemetry. It travels with little loss, whereas radio waves and light are rapidly absorbed. Sev- eral properties of sound in water are important. For example greater ranges are possible in fresh water than salt (one rarely has a choice in this). Low frequencies transmit further than high. For ranges up to several hundred meters, any fre- quency below 100 kHz is suitable. If a range of several kilometers is needed, the frequency should be less than 20 kHz. Low frequencies, however, involve longer wave lengths which im- plies larger transducers. In the small devices necessary for fish work these are difficult to use. Thus we most frequently employ frequencies be- tween 40 and 80 kHz. Only in large tuna could we use a transmitter big enough to work efficiently at 20 kHz. It had an open sea range of 8 km. The interfering background noise, which tends to obscure the signal, varies greatly at dif- ferent places. In general, the shallow water tropics are noisiest. At Coconut Island in Hawaii the natural acoustic energy may be 100 times greater than that at Friday Harbor in Puget Sound. Most of the noise appears to be from bot- tom animals such as snapping shrimp. Man-made noise, like that from boat motors, can also be troublesome. Relative motion between a sound source and the receiver produces a Doppler shift in the ap- parent frequency such that ^/" relative velocity 'Woods Hole Oceanographic Institution, Woods Hole, MA 02543. Contribution No. 3277 from the Woods Hole Oceanographic Institution. This work was supported by National Science Founda- tion Grant G A 31987X. ^University of Trondheim, Trondheim, Norway. / velocity of sound in water The velocity of sound in water is 1,500 m/s. A relative velocity of 1 knot shifts frequency 0.03%. This is only significant when frequency is inter- preted critically, as in the depth transmitter to be described. Additional complications arise from the inter- ference effects due to multiple sound paths be- tween transmitter and receiver. These are fre- quently troublesome in small enclosures where sound reflects from the walls. Nulls in the sound field are produced which represent momentary loss of signal. The ear has little trouble interpret- ing periodic signals such as electrocardiogram (EKG), but in a transcribed record these effects can be confusing (see Figure 2). These remarks are meant to make one's ambi- tions more modest when considering acoustic Manuscript accept October 1973. FISHERY BULLETIN: VOL. 72, NO. 2, 1974. 251 FISHERY BULLETIN: VOL. 72. NO. 2 telemetry, particularly for work in the open sea. It is not possible to send across oceans with a miniscule device. But almost any small amount of energy will work in laboratory tanks. The low power transmitters described here are useful at distances of at least 100 m. CONSTRUCTION Heartbeat Transmitters The cylindrical form of our devices is dictated by the transducers and batteries, both of which are round. A stainless steel tube is chosen into which the battery fits. The electronics are then packaged to this inside diameter. They are cast in epoxy resin in one end of the tube, with the heartbeat lead or thermistor coming out of the plastic. The tubular transducer is fit either inside or outside the tube, and similarly embedded in plastic to assure electrical insulation. The bat- tery is held in place with a watertight cap on the other end. The metal case forms the indifferent reference electrode to the one placed near the heart. With the exception of the transducers (Penn Engineering & Manufacturing Co. Inc., % Aquadyne, Inc., Falmouth, Mass.) parts used in these devices are routine. Parts for a heartbeat transmitter cost about $15.00. Large Heartbeat Transmitter A vertebrate heart produces an electric field when it beats. A millivolt level signal from an electrode near the heart is amplified by Qi in the schematic of Figure 1. The larger voltage is used to vary the frequency of an oscillator (Q2 and Qs). Another amplifier (Q4 to Q7) after the oscillator drives a transducer at this frequency producing i.z.j.i.s.e. 2N5I38 2N5133 T, — TRANSDUCER, PZT-4 CERAMIC CYLINDER 2.25 cm 0,D. FREQUENCY ^- 50I.HZ ',;|7cmL0NG FREQUENCY DEVIATION = 200hz /mv lSJEK G INPUT Figure 1. — Large heartbeat transmitter. sound in the water. With a carrier frequency of 50 kHz the typical excursions are a few hundred hertz. Thus the EKG voltage is transformed into variations of the sound frequency. Another gain stage before the heartbeat amplifier can make the transmitter sufficiently sensitive to send signals of 100 /uv or less. In this way we have been able to follow the electromyograms in the red and white muscles of fish. Figure 2 is an example of an EKG recorded from free swimming Atlantic cod, Gadus morhua, and Atlantic salmon, Salmo salar. The various sequential details of the heartbeat are clearly shown. The transmitter is 2 cm in diameter and 8 cm long. Small Heartbeat Transmitter Similar performance at the cost of greater ef- fort at miniaturization can be had with the sim- pler and smaller transmitter shown in Figure 3, which is 1.5 cm by 7 cm. Reduced power consump- tion allows the same battery life (3 wk) as the larger transmitter. Be replacing Ra in either transmitter with a thermistor, temperature will control the carrier frequency. The heartbeat can still be transmitted as variations around this changing frequency. Depth Transmitter The depth of a fish has been a difficult variable to transmit because of the lack of practical pres- sure sensors. Some information about depth has been discerned from water temperature. The re- cent appearance of small sensitive silicon pres- sure sensors has made direct measurement of depth feasible. We have built a depth transmitter around such a device (Figure 4). The DC output voltage from the pressure sen- sor is increased by an operational amplifer, A. These larger voltage excursions control the fre- quency of an oscillator in the same way as amp- lified heartbeat signals. The thermistor in Qi compensates the oscillator against frequency var- iations due to temperature. The resistor in paral- lel with this thermistor must be empirically cho- sen to optimize this compensation. This allows the received frequency to be interpreted as pres- sure. The frequency change is 1000 Hz/m of depth. A 20°C change in temperature causes an equiva- lent pressure error equal to 5 cm of water. The circuit is a voltage controlled oscillator, useful with any millivolt-level DC signals. This instru- 252 KANWISHER, LAWSON, and SUNDNES: ACOUSTIC TELEMETRY FROM FISH ATLANTIC COD - GADUS MORHUA C D PR PR T P R T PR T P R 1 SEC ATLANTIC "t^hV-UOV^- SALMO SALAR . 1 SEC . J,.^ i \ 1- j^ _Y-|-- — I — t^/^^l +- "h^^ V^~/-~- ^-ry-^- ^ |~Atj'^v_-^J^j^.^-^'^-^(sJ^,^^,Y — -'1.\\«vA\|\v^-4-,.\- • • • • • • Figure 2.— Examples of electrocardiogram from free swimming Atlantic cod and Atlantic salmon. The experimenter approached the aquarium at A and looked over at B. slowing the heart rate. When he went away the heart started at the maximum rate at C, since the T wave is piled on the next P wave at D. The Atlantic salmon also showed a slowing at E from the same source. It was chased at F, resulting in a quickly accelerating heart rate from exercise. Noise while swimming is an acoustic artifact from reflections in the tank. ment has an operating life of 1 wk. We are using it to study gas pressure in swim bladders. With a less sensitive sensor we can determine pressures at depths equal to 1,000 m. Receiver Much of our work has been done with tunable superheterodyne receivers. These employ a mechanical filter to set bandpass. Nearly equiv- alent results can be had from the simpler circuit of Figure 5. The hydrophone contains a frequency selective preamplifer with a voltage gain of 100. Amplification within the hydrophone is impor- tant to eliminate interference from motor igni- tion and radio stations. Power for this preamp- lifer comes down the same wire that carries sig- nals to the receiver. The preamplified signal is amplified another 100 times in Ai (}h of a 1437 dual operational amplifier). Its output is mixed with a local oscil- lator in Q3 to produce a signal at the audio differ- ence frequency. This is amplified 10 times in A2 and used to drive headphones. A l-fiv signal at the receiving hydrophone is clearly audible. RESULTS General We originally developed our telemetry so it could be used with ease for human cardiac monitoring. Work with fish only required miniaturization. The usual method is to have the receiver output played through a speaker in the laboratory. This allows one to notice occasional events of interest. Such more or less casual monitoring has greatly reduced the need for ob- servational patience. In this way we have ob- tained cues related to feeding and behavioral in- 253 FISHERY BULLETIN: VOL. 72. NO. 2 100 p( lOOpf NPO 150 fBj lOOpf 2.2 mh 1_ 1.4 V MALLORY #RM 450 R BATTERY T,— TRANSDUCER, PZT-4 CERAMIC CYLINDER 1.27cm O.D. 1.02cm ID. FREQUENCY = 50 kHz 1.41 cm LONG FREQUENCY DEVIATIONS 200 h; /mv^' EKG INPUT fatigue can result in an increased heart rate for as long as 10 to 20 h while this debt is being repaid. Thus one gets a substantiation of the already recognized biochemical changes in mus- cle glycogen and lactic acid. When remote monitoring shows a rapid heart rate one cannot tell if the fish is swimming at that moment or is reflecting a previous exhaustion. Behavior Figure 3. — Small heart beat transmitter. teraction. At such times we could direct our at- tention more intently. Generally we have found that heart rate changes are related to specific de- tails of a fish's physiology and also its behavior. The transmitter can usually be carried in the stomach of the fish. It is readily inserted into an animal which has been anaesthetized with MS-222.3 The EKG lead is brought out under the last gill arch. It is pushed under the skin im- mediately over the heart. The receiving hyd- rophone is placed against the fish so the trans- mitter can be monitored. There is no difficulty in interpreting when the lead placement for op- timum EKG signal has been reached. The lead is then sutured in place. The gills can now be flushed with anaesthetic- free water and the fish soon released. The entire operation takes 3 or 4 min. The fish will have been under anaerobic stress because no water has been flowing over the gills. Most specimens ap- pear to fully recover in a few hours. If drag is not important the transmitter can be sutured to the outside of the fish. This method has allowed us to work with plaice, Pleuronectes platessa, whose stomachs were too small. It was also convenient for some Atlantic cod and Atlan- tic salmon that repeatedly threw up a stomach tag. Physiological Response When a fish is swimming we find an expected increase in heart rate, reflecting the increased oxygen transport of the cardiovascular system. In an Atlantic cod this is a measure of both the instantaneous exertion, and also of any previ- ously incurred oxygen debt (Wardle and Kan- wisher, In press). Chasing a fish to maximum We were not prepared for the large component of behavioral response observed in the heart rate of all fish. Cardiac arrest is a well known re- sponse in conditioning. We found it to occur with the subtlest of cues, once the fish had recovered from initial handling. This can best be described by two anecdotes. A plaice, which had not eaten for many months, had settled into the sand on the bottom of a 60-ft circular laboratory aquarium. It was mid-winter with low water temperatures and the fish appeared to be doing the equivalent of hiber- nating. In spite of this outward lethargy it re- sponded to doors opening, relays clicking, and to any other sort of human activity in the vicinity. It was, not unexpectedly, most sensitive to vis- ual cues. We gradually reduced these to smaller objects moved in the visual field of the fish. The most sensitive response came early in the morn- ing before local laboratory activity had started. At this time we could come quietly up to the tank and push a pencil a few centimeters over the edge. The plaice, \V2 m below responded by stop- ping its heart for 8 or 9 s. Another incident concerned a venerable cod of more than a year in captivity. It had been re- S 22K I 22K 2N5813 „N 1200i iZOOie] n Q,' {k\%' ;k( — ° 5| '0.11 ;i4 2 ♦ . 4.05 V MALLORY #TR 133R BATTERY "■1.2 „f 2N3663 J?- 1 V'tL' SEMICONDUCTOR PRESSURE TRANSDUCER KULITE#T0S-360-25 FAIRCHILD OP AMP #110 776 R SELECTED TO NULL OFFSETS IN A 1 THERMISTOR. 2K^25°C T, AS USED IN LARGE HEARTBEAT TRANSMITTER B CMOS BUFFER SOLID STATE SCIENTIFIC jjf SCL4441AF FREQUENCY=«55 kH; 'Reference to trade names does not imply endorsement by the National Marine Fisheries Service, NOAA. Figure 4. — Pressure transmitter. 254 KANWISHER, LAWSON. and SUNDNES: ACOUSTIC TELEMETRY FROM FISH peatedly handled for blood samples and had largely accommodated to the presence of people. Its heart slowed only when the fish was physi- cally touched. At one point we started toward the fish with a dip net. This was one which the fish had never seen. It stopped swimming, faced the approaching strange net, and extended its fins in what we had come to recognize as a fright response. Its heart stopped for 19 s. We detail these because we feel that such acoustic telemetry will be a valuable adjunct to behavior and sensory studies. When we have monitored three fish simultaneously some ele- ments of social interaction showed in their vari- able heart rate. In particular, competition for food was easily discerned after a few simultane- ous observations of feeding and listening to the EKG. In this manner we hope to build up a be- havioral repertoire which will allow us to inter- pret data from a fish swimming free in the ocean where it cannot be observed. The potential effect of behavior on such physiology as oxygen consumption had been pre- viously shown by erratic increases when a fish was confined in a respirometer (Sundnes, 1957a, b). This could be overcome by keeping cod in a laboratory aquarium for many weeks, while it became used to people and capture. Veteran fish were found to increase their O2 consumption and also showed immediate color changes whenever strangers were in the laboratory. We were reluc- tant to accept the respiratory data until substan- tiated by simultaneous observations of cardiac response. Some species are difficult to acclimate to cap- tivity. Atlantic salmon were brought directly from a fish farm and wired for EKG transmitting. They swam for several weeks at the maximum sustainable speed until they died. From this we could only learn the maximum heart rate. A 5-kg salmon showed 60 to 62 beats/min. Later we have had fish which were hand fed in a laboratory tank for over a year. When these fish were tagged they were immediately returned to familiar surroundings. They soon joined in feed- ing frenzy and showed cardiac arrest when frightened. When they were chased the heart rate quickly increased, as shown in Figure 2. Rest- ing rates below 30 beats/min were common. This approach was not successful with skipjack tuna, Katsuwonus pelamis, in Hawaii. These 2.5 K SENSITIVITY Tl 2N5B 5 I— »-»— gl'ZNiaoo 1 i IHYDRO- a ;|,jK PHONE RCA S-^ JPPT* -6. ,25 i 270 100- }22 T — AS USED IN LARGE HEARTBEAT TRANSMITTER 437 < 1 ♦ 4001 #7 FREQUENCY 50 kHi CAPACITORS DECIMAL VALUES IN Mf WHOLE NUMBERS IN of A,* A J MOTOROLA OP AMP #MC1'»37L Figure 5. — Simple beat frequency oscillator receiver. fast, probably warm-blooded fish were able to either get rid of our transmitter, or died in the effort. Their heart rates, however, were from 80 to 240 beats/min. This reflects their near mam- mallike metabolic rate. They recovered from fatigue in less than 1 h, much like man. We have used a new miniature tag (7 mm diameter x 35 mm long) successfully on mackerel, Scomber japonicus. CONCLUSIONS We have tried to outline the possibilities and methods of acoustic telemetry from fish. It is a valuable adjunct in both laboratory and open water studies. In many cases, such as monitoring the body temperatures of a free-swimming tuna, it is the only way to get the desired data (Carey and Lawson, 1973). The burgeoning solid state technology promises a rapid advancement in methodology beyond the relatively simple ele- ments we have presented here. LITERATURE CITED Carey, F. G., and K. D. Lawson. 1973 Temperature regulation in free-swimming bluefin tuna. Comp. Biochem. Physiol. 44A:375-392. Sundnes, G. 1957a. On the transport of live cod and coalfish. J. Cons. 22:191-196. 1957b. Notes on the energy metabolism of the cod (Gadus callarias L.) and the coalfish (Gadus virens L.) in relation to body size. Fiskeridir. Skr. Ser. Havunders. 11(9), 10 p. Wardle, C. S.. and J. W. Kanwisher. In press. The significance of heart rate in free swimming cod. J. Mar. Physiol. Behav. 255 ABUNDANCE OF PELAGIC FISH DURING THE 19TH AND 20TH CENTURIES AS RECORDED IN ANAEROBIC SEDIMENT OFF THE CALIFORNIAS Andrew Soutar and John D. Isaacs^ ABSTRACT Anaerobic sediment preserves a chronographic record of the bioclimatological conditions in coastal seas. Of the myriad elements within this record, the accumulation of pelagic-fish debris is of particular interest. The deposition of scales of the Pacific sardine, the northern anchovy, the Pacific hake, the Pacific saury, and the Pacific mackerel in the sediment of the Santa Barbara Basin, Alta California, and the Soledad Basin, Baja California, is generally in accord with available population estimates. The relation between scale deposition and population, when applied to the sedimentary record over the past 150 yr, suggests that major pelagic-fish productivity between 1925 and 1970 was substantially below pre-1925 levels. Man in his search for an environmental perspec- tive has unearthed a number of natural chrono- graphic records. These include the well-known growth rings of trees (Fritts, 1972), the deposition of annual strata in the snowfields of Greenland and Antarctica (Murozumi et al., 1969), the in- cremental growth of coral and stromatolites (Knutson et al., 1972; Panella et al., 1968), and the formation of annual layers in certain lacustrine and marine sediments (Seibold, 1958). Perhaps no richer records exist than those finely laminated deposits encountered beneath the sea in regions of anaerobic sedimentation. A web of circumstance involving productivity and topog- raphy serves to produce and protect such records, but no factor can be more important than the ex- clusion of burrowing animals from the sediment by a persistently low dissolved oxygen concentra- tion in the bottom water. Here such diverse and informative fragments of the air-sea-land system as the tests of the microplankton, skeletal and integument debris from the nekton, air- and river-borne detritus, natural radioisotopes, and more recently, anthropogenic products fall in se- quential association to a common resting place. Undisturbed, these threads of information ac- cumulate to form a remarkable sedimentary chronicle combining the rhythmic pulse of the seasons with the vagaries, trends, and inconsis- tencies of ocean life, chemistry, and currents. Of the myriad elements within the anaerobic sediment record, the temporal framework and the distribution of pelagic fish scales at depth in the sediment in the Santa Barbara Basin, Alta California (Figure la), and in the Soledad Basin, Baja California (Figure lb), compose a particularly relevant set — relevant not only in relation to the continuing importance of pelagic fish as a resource off the Californias, but also as a potential indi- cator of long-term productivity and change. Such knowledge of ocean conditions within the broader context of the North Pacific gyre and the Northern Hemisphere climate can aid man in his search for a rational interaction with his environment, guide him toward a wise stewardship of marine re- sources, and aid him in discriminating between those changes that he produces by his interven- tions and those that are a part of the natural order. Time in the laminated sediment of the Santa Barbara Basin can be estimated through the se- rial assignment of the year of deposition to each laminae pair (Figure 2a). It was suggested that the regular alternation of sediment density is a direct response to the monsoonal climate affecting southern California (Emery, 1960). Confirmation of this and the laminae pair sequence as a yearly depositional record has come through the correla- tion of regional rainfall and sediment-laminae patterns. 2 As indicated (Figure 3), the essentially random pattern of southern California seasonal 'Scripps Institution of Oceanography, University of California at San Diego, La JoUa, CA 92037. Manuscript accepted June 1973. FISHERY BULLETIN; VOL. 72, NO. 2, 1974. ^Soutar, A., J. D. Isaacs, P. A. Crlll. Recent paleoclimatology and paleoecology of the Santa Barbara Basin. Unpubl. manuscr. 257 FISHERY BULLETIN: VOL. 72, NO. 2 120° 1 5' 34°30' lacoo' 34° 15' II9''45' 1 34°30 CALIFORNIA 34°00 34°I5' I20°00 34°00' Figure la.— Santa Barbara Basin, California. The basin lies under the Santa Barbara Channel and reaches a maximum depth of 589 m (Hulsemann and Emery, 1961). Pertinent box-core locations (230,241,239, and 265) are shown. rainfall can be simply transformed into a clear reflection of the serial pattern of varve thickness. This transformation corresponds to factors such as upstream aggradation (Schumm, 1969) which could cause a considerable delay in basin sedimen- tation. Further development of the anaerobic-sediment chronology has been possible through the close agreement of Pb-210 and Th-228/Th-232 radiometric ages and the varve-sequence year (Koide et al., 1972, 1973; Krishnaswami, 1973) (see Figure 4a, b). These relatively short-term radiochronologic tools can be used to considerable advantage in the Soledad Basin sediment. Though this basin is morphologically and oceanogra- phically similar to the Santa Barbara Basin in that there is virtually no dissolved oxygen in the bottom water, the absence of consistent seasonal rainfall inhibits the formation of distinct sequen- tial varves (Figure 2b). Nevertheless, a reasonable time framework can be estimated for the near- surface sediment of the Soledad Basin from the measurement of Pb-210 and the Th-228/Th-232 ratio at depth (Koide et al., 1973) (see Figure 4c, d). The distribution of pelagic fish-scale debris can be determined within the time-sediment frame- work. Specifically, large (20 x 20 cm) cores were frozen, then cut into longitudinal sections measuring 5 x 15 x~40 cm. X-radiograph rep- resentations were obtained for each of the sec- tions, and by means of recognizable stratigraphic patterns 5-yr block templates were drawn. In the case of the Santa Barbara Basin sediment, specific laminae can be identified within cores and be- tween cores as to the year of deposition; therefore, precise templates can be constructed. This is par- ticularly so for the time period 1860-1970 in which the laminae are well defined. The period from some time before 1810 to 1860 is partly obscured by bioperturbation apparently supported by a marginal increase in bottom-water dissolved ox- ygen. Only general sedimentation rates are avail- able for the Soledad Basin sediment; therefore linear estimates of the 5-yr blocks were made for the core slab from which the radiometric ages were obtained. These estimates were carried out to the 90-yr hmit of the Pb-210 method and were transferred by available stratigraphic markers to the other core sections. Furthermore, these linear estimates were continued to the bottom of the core, an additional 80 estimated years. It should be noted that the Th-228/Th-232 method permits age estimates in the uppermost sediment of the Sol- edad Basin that are comparable in accuracy to those in the Santa Barbara Basin. The templates II4°00' 113°00' 112-00 26°00' 25°00' 26°00 25°00' CONTOURS IN METERS AFTER D'ANGLEJ0N.I965 II4*>00' I13°00 II2»00 Figure lb.— Soledad Basin, Baja California. This basin lies in a trough trending northwest from Cabo San Lazaro. The maxi- mum depth is nearly 520 m and it occurs in the vicinity of core 244. 258 SOUTAR and ISAACS: ABUNDANCE OF PELAGIC FISH Core 239 34*' 14.0'N 120** 01.5'W cm Figure 2a.— Radiograph of core 239, Santa Barbara Basin. The radiograph was obtained from a frozen core slab approximately 2 cm thick. The darker laminae are the more dense (negative print of radiograph transparency). Each pair of laminae are consid- ered to be a single year with the denser sediment representing detritus brought in by winter rains (Soutar et al, in prep.). SO constructed were fitted to the frozen core sec- tions by means of morphologic and stratigraphic markers, and the sections were split into the 5-yr blocks. These sediment blocks were subsequently treated with a buffered dilute H2O2 solution and gently washed on a 500/u screen. The retained coarse fraction was transferred to vials and stored wet with ethanol as a preservative. Identification and enumeration of the material was carried out at low magnification. The presence of fish scales in contemporary laminated sediment should not be unexpected, particularly to those acquainted with the stratified diatomite of the Monterey Formation cropping out along the Coastal Range of Califor- nia (David, 1943). In some instances whole or par- tial skeletons offish are present in these deposits. Core 244 25° 13.8' N 1I2°40.6'W 960 1950 SLUMP [ 1 cm Figure 2b. — Radiography of core 244, Soledad Basin. Although laminae are present there are no consistent patterns that would suggest varves. There is, however, enough information to physi- cally correlate between slabs and to identify irregular sedimen- tation events. 259 FISHERY BULLETIN: VOL. 72. NO. 2 < UJ Ll □ z LU U a: Ld Q. 300.00 . SANTA BARBARA AREA RAINFALL aso-00 n aoo-oo , n -] 150-00 . n rh (In n r. n n n nfT " ' n 41 n 100-00 , -D n_ n " - - n n r 1 50-00 . 0-00 J L. .±. 1 1 1 1 1 - 1 1 1 1 1 1 1 1 — 1 1 1 1 1 1 ' 1 - 1 1 1 1 1 1 1 1 - 1 1 1 1 1 It ^ - ****'*'* . 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 — 1 1 N 1 1 N — 1 1 1 1 1 1 1 M 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 Hi ISO 1370 133D laoo 1B70 < UJ Li_ D Ld U q: Ld Q_ 300-00 J SANTA BARBARA AREA RAINFALL (TAU = 4-0) aso-00 . 300-00 . 150-00 ., 100-00 . ----- TLr' -^j-r' "L^J"f TflTfinT-u-rT It Tkrf Tin 50-00 . 0-00 . f^ ,. 1 1 1 1 1 1 1 1 — 1 1 1 1 1 1 1 1 — 1 1 1 1 1 1 1 1 — 1 1 1 1 1 1 1 1 — 1 1 1 1 1 1 1 1 — 1 1 1 1 1 1 1 1 15B0 1370 ISBO ITVl 1330 icgn 1500 IBBO 1S70 IBEO iaBn < Ll O Ld U 01 bJ DL 300-00 . TOTAL VARVE (CORES 230 » 233 » 241) 250-00 . 500-00 . 150-00 . n n r JTi n nXk nr rf n n "1 1-1 i-i_ -I 100-00 . -1 "1 " T-. ' T 1-1 S ' - - - .. " "- ' I 50-00 . 0-00 ■i H — 1 11 ' N 1 1 1 1 1 1 1 M 1 1 1 1 1 1 1 1 1 1 1 ■ 1 1 1 1 1 1 1 1 ■ 1 1 1 1 1 1 1 1 . 1 1 1 1 1 1 1 1 .1 - -LLLLI — 1 1 i 1 i 1 1 i — i 1 M i 1 1 i — 1 1 1 1 N 1 1 1 1 1 1 1 i 1 1 ' 1 1 1 1 1 1 1 1 1 1 ' 1 1 i3ao lao 1830 laao IBEO Such are likely victims of mass mortality result- ing from an invasion of hydrogen sulfide water or red water situations which, while reported in Walvis Bay, South Africa (Brongersma-Sanders, 1957), do not seem characteristic of the present coastal waters off the Californias. On the other hand, the occurrence of separate scales is likely the incidental result of serious if not fatal trophic interactions. Previous investigation has indicated that, with few exceptions, fish scales are deposited in Santa Barbara Basin as individual events (Soutar, 1967). Interstitial-water measurements (Sholkovitz, 1973) indicate an increase of dissolved phosphate within the anaerobic sediment from 20 m moles POi" near the surface to levels in excess of 100 260 SOUTAR and ISAACS: ABUNDANCE OF PELAGIC FISH Figure 3. — Comparison of Santa Barbara regional rainfall, smoothed Santa Barbara regional rainfall, and total varve thickness. Spearman rank-correlation coefficient between Santa Barbara regional rainfall and total varve thickness is 0.26 (P = 0.02, n = 99). The highly variable pattern of seasonal rainfall is smoothed by the filter: Y,= i"^ a-4)i-,- where Yf = smoothed seasonal rainfall at year t; R/ = actual seasonal rainfall at year i; and r = a time constant (years). Thus Yf is the sum of^ of year t rainfall and exponentially decreasing portions of previous year's rainfall. The function tends to damp- en rapid oscillations and lag slower oscillations at a slightly lower amplitude. The value of ris derived by multiple regression analysis. Varve thickness at year t is the dependent variable and rainfall at year t, year t-l, year t-2, etc. are the independent variables. T is found by fitting a log linear line to the regression coefficients. The Spearman rank-correlation coefficient between the filtered rainfall and the total varve thickness is 0.50 {n = 99). Due to the autocorrelation induced by the filter, no probability is assigned. Mean Santa Barbara regional rainfall is 42.2 cm, and mean varve thickness is 1.74 mm (at 60% water by weight). M moles at depth. Since the composition of fish scales is essentially an intermixture of micro- crystalline apatite and a collagen-ichthylepidin matrix ( Wallin, 1957), a potential for the degrada- tion of the scale record is present. However, ichthylepidin, an albuminoid approaching keratin in composition, is unlikely to be degraded in an anaerobic environment (Kaplan and Rittenberg, 1963). Thus the organic matrix may contribute significantly toward the preservation of scales. The distinctly higher frequencies of scales at core depths in excess of 2 m further suggest a non- degraded record (Soutar and Isaacs, 1969). The record of scale deposition in the Santa Bar- bara Basin (16 subcore-sample mean, 1810-1970) and the Soledad Basin (4 subcore-sample mean, 1780-1970) is in part presented (Figure 5a, b) and statistically summarized (Table 1) for: Sardinops caerulea (Pacific sardine), Engraulis mordax (northern anchovy), Merlucciusproductus (Pacific hake), Colalabis saira (Pacific saury), and Scomber japonicus (Pacific mackerel). Of particular interest are those portions of the scale record covering the past few decades for which population estimates exist. Considerable attention has been directed towards the elucida- tion of the historical population levels of the Pacific sardine. Estimates of the population (fish 2 yr and older) derived from the solution of a fishery catch equation extend from 1930 up to 1959 (Mur- phy, 1966). These biomass estimates presented in single- and 5-yr averages (Figure 6) document the historical decline of the fishery and the popula- tion. Comparison of the 5-yr averages of the biomass and the scale-deposition rate in the Santa Barbara Basin sediment indicates a parallel but offset decline. The derived age frequency of the sedimented scales (Table 2) indicates that most (92%) of the contributing fish were less than 2 yr old, suggesting a relatively fast response on the part of the sediment to particular year-class sizes. Comparison of the 5-yr averages of the year-class size (numbers of 2-yr-old fish entering the fishery) and the scale-deposition rate indicates a direct proportional relationship (Figure 7 and Table 3). Population estimates for the central, southern, and total populations of the northern anchovy for the years 1951 to 1966 have been made (Smith, 1972). The estimates of the total spawning pop- ulation presented in single- and 5-yr averages, and the 5-yr averages for the subpopulations, record the recent ascendancy of the anchovy. Comparison is made of these population estimates with the northern anchovy scale-deposition rate in the Santa Barbara and Soledad Basin sedi- ments (Figure 8 and Table 4). In the three 5-yr intervals having sufficient information, the scale deposition is proportional to the spawning biomass. The direct relation to spawning biomass may be associated with the relatively rapid mat- Table 1. — Statistical summary of scale deposition (numbers/10='cm*/yr) for Santa Barbara Basin sediment, 1810-1970, and Soledad Basin sediment, 1780-1970.^ Sediment Mean Median Variance Maximum Minimum Santa Barbara Basin (N=32) Pacfic sardine 3.6 2.8 13.6 15.2 0 Northern anchovy 10.0 9.8 27.8 19.4 2.0 Pacific hake 24.8 21.8 310.1 73,0 5.5 Pacific saury 0.8 0.3 3.2 8.4 0 Pacific mackerel 0.3 0.2 0.2 1.9 0 Other Total 8.5 48.1 8.1 44.7 24.3 532.6 17.8 108 1 0 21.0 Soledad Basin (N=38) Pacific sardine 0.4 0.2 0.4 3.0 0 Northern anchovy 9.2 7.5 43.5 26.4 0.6 Pacific hake 6.1 6.1 8.3 12.0 1.3 Pacific saury 0.3 0 0.8 3.9 0 Pacific mackerel 0.3 0 0.3 1.6 0 Other 2.9 2.2 4.0 6.8 0 Total 19.2 17.9 52.4 39.0 5.6 'In the case of the Santa Barbara sediment, the statistics are drawn from a 16subcoreset representing a combinedareaof 980 cm^. The statistics for the Soledad Basin are drawn from a 4 subcore set having a combined area of 260 cm2. 261 FISHERY BULLETIN: VOL. 72. NO. 2 SANTA BARBARA BASIN C-2S2-I TH-BES/TH-B3B ACTIVITY 0.70 1 1 1 ♦ 1 1 1 1 ♦ 0-« \ a 1—1 0-10 * \ 1371-1370 \^ 1S7013EB < or -0-ao. \ * 1^TH-13EB 1— 1 s 1- -o-so \ + 19EB-13&4 -0-80 . \ a v. ia&4-ia5 •1-10 ♦\ 13EB-1360 -l-IO \ -1-70 \ -8-00 \ \ Q_ O 1-00. LD D _| O-BO.. SANTA BARBARA BASIN C-^39B2-S PB-210 ACTIVITY iaSB-1300 000 e-oo - s u o o o o in ui _i < u in 17.50 15-00 15.50 , 10-00 7-SO 5-00 S-SO 0-00 PACIFIC 5ARDItv£. SANTA BARBARA BASIN 19B0 1370 19B0 1350 1940 1930 13S0 1910 1300 1S30 ISBO 1B70 IflEO 1B50 1&40 iflSO IBEO IBIO IBOO 35-00 3O-0O SS-00 50-00 , NORTHERN ANCHOVr. SANTA BARBARA BASIN 1980 1970 19E0 19SO 1940 1930 13g0 1910 130O 1B90 laBO 1870 1860 ISSO 1840 1830 1850 1810 PACIFIC HAKE. SANTA BARBARA BASIN 1980 1970 1380 1950 1940 1930 1350 1910 1900 1B30 IflBO 1870 1880 1H50 1B40 1B30 1850 1810 Figure 5a. — Histogram plot of the scale-deposition rate of the Pacific sardine, the northern anchovy, and the Pacific hake in sediment of Santa Barbara Basin, 1810 to 1969. considered an unnatural circumstance. The levels of year-class success between 1865 and 1880 were likely as low as those estimated after 1940. It may be argued that in the previous period the sardine had moved offshore or migrated southward, thereby causing a decline in scale deposition. However, abandonment by a substantial popula- tion of a major spawning ground would seem prob- lematic, and in regard to a southern immigration it can be said that during the apparent year-class failures from 1865 to 1880 no substantial sardine population occupied the southern waters near the Soledad Basin, Baja California. Indeed, the only time the sardine appears even moderately in- fluential in these waters is the period 1920 to 1935, coincidental with the development of the fishery to the north. While the evidence from pre- vious decades makes it impossible to accuse the sardine of avoidance, the coincidence may nevertheless underline the naturally intermittent occurrences of abundant sardine populations in California waters. As in the case of the sardine, one's view of the distribution of the anchovy through time is col- ored by perspective. The sediments in both the Santa Barbara and Soledad Basins have re- sponded to the recent increase in the anchovy population. This response appears as part of a 264 SOUTAR ;ind ISAACS: ABUNDANCE OF PFLAGIC FISH >- u a ui o o o Lfl U _l < u Ul a: 2 U o LTl O O O < u m 17.50 15-00 , 15-50 , 10-00 . 7-50 5-00 8-50 0-00 PACIFIC SARDINE. SDLEDAD BASIN 1^0 1970 laeo 1950 1940 1930 19B0 1910 1900 1B30 IBBO 1870 IBEO 1B50 1B.40 1830 18S0 1810 1800 1790 1780 1770 NORTHERN ANCHOVY, SOLEDAD BASIN SO-00 lS-00 10-00 S-00 0-00 1980 1970 19E0 1950 19-SO 1930 1920 1910 190O 1B90 IBBO 870 1860 1850 18->0 1830 IBeO IBIO IBOO 1790 17B0 PACIFIC HAK.E. SOLEDAD BASIN 19B0 1970 1360 1^0 1900 1330 19SO 1310 1900 1B90 1880 1B70 1860 1B50 IBAO 1830 1880 IfllO 1800 1790 1780 Figure 5b- — Histogram plot of the scale deposition rate of the Pacific sardine, the northern anchovy, and the Pacific hake in sediment of the Soledad Basin from about 1780 to 1969. significant pattern of similarity in scale deposi- tion (Table 8). The recorded increase in the an- chovy population, while substantially above re- cent historical levels, when compared to the in- ferred population reached in most of the 19th and the early part of the 20th centuries, appears mod- erate. Furthermore, in contrast to the sardine, the population of the anchovy has been of comparable density in the waters of the Californias over the past two centuries. This then supports contempor- ary observations that the northern anchovy is re- gionally adapted and is capable of successful popu- lation responses covering at least the southern half of the California Current. The inferred distribution of the Pacific hake. although made tenuous by the lack of clearly sup- portive population information, is, in the case of Santa Barbara Basin, strongly suggestive of the anchovy with an indication of a recent increase from low levels between 1920 and 1965 and with substantially higher levels before 1920 (Table 8, Figure 5). The inferred hake population in the water near Soledad Basin corresponds with the levels inferred for Santa Barbara back to the 1930's and in this regard is consistent with recent observations of essentially equal larval abun- dance in both areas. However, levels of inferred population before 1930 at Santa Barbara are con- siderably above those of Soledad, the latter show- ing a consistent level over the past 200 years. 265 Table 4. FISHERY BULLETIN: VOL. 72, NO. 2 -Comparison of the northern anchovy population (Smith, 1972) and the scale-deposition rate in the Santa Barbara and Soledad Basin sediment.' Central subpopulation Southern subpopulation Total population Scale-deposition Seal e-deposition 5-yr average 5-yr average 5-yr average rate. Santa rate, Year spawning biomass spawning biomass spawnmg biomass Barbara Basin Soledad Basin interval (lO'' metric tons) (10« metric tons) (10^ metric tons) no./10^cm2/yr no /103cm2/yr 1969-1965 2470 20.92 2502 4.9 27.0 1964-1960 2.95 1.18 429 10.0 10.3 1959-1955 1.34 0.37 1 85 5.4 3.6 1954-1950 0.54 0.47 1.04 3.3 0.6 1949-1945 — — — 3.4 1.5 1944-1940 — — 22.37 4.7 3.0 'As defined (Vrooman and Smith, 1971) the central subpopulation area includes southern Alta California inshore, offshore, and seaward and Baja California inshore, offshore, and seaward. The southern subpopulation area includes southern Baja California inshore, offshore, and seaward. Inshore includes 0-80 miles: offshore includes 80-160 miles, and seaward includes 160-280 miles. 2|ncomplete data. Table 5. — Comparison of Pacific hake larval abundance ( Ahlstrom, 1969; Smith, in prep.) and scale-deposition rate in Santa Barbara and Soledad Basin sediment. Scale-deposition Scale-deposition California coastal Southern Baja coastal Total (inshore rate rate Year inshore area inshore area and offshore) Soledad Basin Santa Barbara Basin interval (5-yr average) (5-yr average) (5-yr average) no./103cm2/yr no./103cm2/yr 1969-1965 '3,500 '880 '10.360 '21.3 '2.5 1964-1960 480 590 3,810 7.3 6.9 1959-1955 600 420 11,850 5.8 4.6 1954-1950 540 880 1 2,660 5.5 4.0 'Incomplete data. Consideration of the relationships of the three major species provides further insight into the distribution of pelagic fish through time. Most if not all investigators have found the hypothesis that the Pacific sardine and the northern anchovy are direct competitors unavoidable. This hypothesis is not supported by the less-than- significant positive correlation between the scale deposition of the two species in the Santa Barbara sediment (Table 8). However, fluctuations in rela- tive abundance of even closely competitive species in the marine environment may follow quite dif- ferent rules than mere abundance or autecologic correlation. The abundance of species may be di- rectly related to advantageous conditions. How- ever, whenever an advantageous or disadvan- tageous series of years is of critical duration (de- termined by specific differences in life history) the abundances may be inversely related. In this con- text the apparent decline and subsequent recovery of the sardine population between 1865 and 1890 from levels which appear substantially above his- torical experience, in the presence of what also appears to be substantial anchovy populations, may not be entirely enigmatic. The associations of the anchovy, hake, and sar- dine in the Santa Barbara sediment (Table 8) is further suggestive of periods favorable or unfavor- able to these three species. This is in contrast to the Soledad sediment from which it may be inferred the anchovy alone is able to maintain high population levels. Some idea of the total pelagic-fish productivity off the Californias may be gained by combining the inferred populations of the anchovy, hake, and sardine into a total spawning biomass estimate (Figure 9). This biomass estimate suggests that the central California and presumably the northern Baja California regions can become a dominant center of pelagic fish productivity. Even though signifi- cant densities of northern anchovy have been pre- sent in the water above Soledad Basin, available information (Table 4) suggests these represent a relatively smaller southern subpopulation. The Table 6. — Comparison of the Pacific saury population (Smith et al., 1970) and the scale-deposition rate in the Santa Barbara and Soledad Basin sediments. Total population Total scale- Total scale- spawning biomass deposition rate, deposition rate, Year CalCOFI area Santa Barbara Basin Soledad Basin interval (10* metric tons) no./10^ cm2/yr no./10^ cm2/yr 1969-1965 '0.21 '1.1 '0.0 1964-1960 0.12 0.3 0.0 1959-1955 0.18 1.1 0.0 1954-1950 0.23 2.2 0.6 'Incomplete data. 266 SOUTAR and ISAACS: ABUNDANCE OF PELAGIC FISH u n h- LJ Z a 10.00 . 9-00 , S-OO 7.00 S.OO S.OO 4.00 3-00 S.OO 1.00 . 0.00 PACIFIC SARDINE BIDMASS lO-OO ^ 9.00 e.Qo 1 7.QO B.OO u 5-00 4-00 g l-l 2 3.00 a. 00 1.00 PACIFIC SARDItvE BIDMASS laao 1970 laGO 19S0 1940 1930 19B0 1970 19G0 1350 1940 1330 13S0 SARDINES. 2 YR. OLDS VS- YR. SPAWNED esono-oo 2SS00-00 in a 50000-00 17500-00 > 15000-00 ^ *"• lSSOO-00 b 1 in 10000-00 _i 7500-00 1 5000-00 Jl 1 psno-no ■ 1|. ' ■ 0-00 [ H 01 _l < a D 2 O LO z a 1—1 _i -I 25000-00 22500-00 20000-00 17500-00 15000-00 12500.00 . 10000.00 , 7500.00 . 5000.00 ., 2SOO-0O ., 0-00 SARDINES. 2 YR. DLDS VS- YR. SPAWNED laeo 1970 1360 1350 1340 1330 13E0 13B0 1370 19G0 1550 1340 1530 1320 Figure 6. — Yearly estimates of Pacific sardine biomass 2-yr and older and year class size at 2 yr old (after Murphy, 1966). The yearly population estimates (left) are grouped into 5-yr block averages (right) that correspond to the sampling intervals in the sediment. Table 7. — Comparison of Pacific mackerel larval abundance (Ahlstrom, 1969; Smith, in prep.), fishery landings (Fitch, 1952),* and scale-deposition rate in Santa Barbara and Soledad Basin sediment. Southern California Scale-deposition Seal B-deposition Southe rn California Southern Baja Total (inshore landings rate. rate. Year coastal inshore area coastal inshore area and offshore) (5-yr average) Santa Barbara Basin Soledad Basin interval (5-y average) (5-yr average) (5-yr average) (metric tons) no./IO^cm^/yr no /lO^cm^/yr 1969-1965 2 2 2 1,660 20 20 1964-1960 560 21,000 38,600 17,830 0 0 1959-1955 1.260 3,060 16,100 18,390 0-2 0 1954-1950 650 10,100 19.000 10,780 0.2 0.8 1949-1945 — 21,660 0.6 0 1944-1940 — 35,020 0.4 1.6 1939-1935 — — 45,430 0.2 1.6 1934-1930 — — — 1.6 0.8 'Also subsequent Gal. Dept. Fish and Game landing statistics, ^incomplete data. 267 FISHFRY BULLETIN: VOL. 72. NO. 2 PACIFIC 5ARDI^E SCALE DEP- RATE (S- B- ) V5- BIDMA55 2 YRS- AND OLDER (1930-1959) a. \ u o LD O O O \ LH U _l < U >- \ o o o o vH \ in < u m s-oo^ PACIFIC SARDINE SCALE VS- TWD YR. DLD5 DEP- RATE IS- I 1930-1959 B-) 4-50 4.00 3. so / 3.00 / £-50 2.00 1-50 1. 00 0.5D 0.00 1 • m • • •— O'OO i'OO a. CO 3.00 4.00 s-oo e.oo 7.00 s-oo 9-00 10.00 0*00 1.00 £.00 3.00 1.00 5.00 e.oo 7.00 e.oo 9.00 lo.oo MILLION METRIC TONS BILLIONS Figure 7a, b. — Scatterplot of the 5-yr averages of the Pacific sardine biomass (after Murphy, 1966) and the scale-deposition rate in Santa Barbara sediment, 1930 to 1959. The plot of biomass versus scale deposition though indicating a significant relationship (Spearman rank-correlation coefficient is 0.81, n = 6) shows considerable scatter. If, on the other hand, the year-class size at 2 yr of age is plotted against the scale-deposition rate in the year spawned, the scatter is markedly reduced and a highly significant relationship emerges (Spearman rank-correlation coefficient is 0.99, n= 6). The reduction in scatter can be explained through the observation that most of the scales encountered in the sediment were derived from younger fish. >- \ o m o o o \ < IS-OO NORTHERN ANCHOVY, 5- B- SCALE DEP- VS- CENT- AND TOTAL BIOMASS (1950- RATE 19G4) i3<90 y / l£-00 CENT. X U}-50 / ^ 9-00 / y^ 7.S0 X y^ TOTAL 6-ao / 3^ 4-^ /y^ 3-00 /y^ 1-5D ^ 0-00 q: \ u o ui o o o H \ LD u < u NORTHERN ANCHOVY, VS- SO- AND TOTAL SLO- SCALE DEP- RATE BIDMASS (1950-1964) 13-50 / ie-00 / so- / UJ.SD J / 9-00 / / 7-5D / / 6-00 / / TOTAL 4.ao • / o/ / 3-00 / / 1.50 / / 0-00 / * /^ 0-00 O.SD 1.00 1.50 £.00 £.SD 3.00 3. SO 4.00 4.50 5. 00 MILLION METRIC TONS ).00 0.50 1.00 1.50 £.00 £.50 3-00 3.50 4.0O 4.50 5. 00 MILLION METRIC TONS Figure 7c,d. — Scatterplot of the 5-yr averages of the northern anchovy spawning population estimates (after Smith, 1972) and the scale-deposition rates in Santa Barbara and Soledad Basin sediment, 1950 to 1965. The scale-deposition rates in both the basins vary airectly with increasing population estimates of the northern anchovy. The relatively steep slope of the southern subpopulation (S) relative to the central subpopulation (CNT) reflects the smaller southern population. 268 SOUTAR and ISAACS: ABUNDANCE OF PELAGIC FISH NO- ANCHOVY, TOTAL POPULATION lO-OO , 9-00 a 00 7 no LD LJ 1— e 00 u t— ( a^ 5 00 1— UJ 2 4 00 z □ 3 00 _J 2 2 00 o-oo u k LT) U UJ 2 _l 2 NO- ANCHOVY, TOTAL POPULATION 9-00 8-00 7.00 G.OO , 5.00 4.00 3.00 . 2.00 1.00 0.00 19B0 1970 19G0 1950 19S0 1970 19S0 1950 NO. ANCHOVY, CENT- 5UBP0P- NO- ANCHOVY, 50- 5UBP0P- m z a u a. UJ 2 Z D _J _J n 2 9-00 B-OO 7.00 G.OO 5.00 4.00 3-00 . 2.00 . 1-00 0-00 19B0 1970 19G0 1950 10.00 g.oo e.oo 1- 7.00 6.00 u l-t 1. 5-00 4.00 n _l _l 2 3.00 2-00 1.00 0.00 , -1 1 1980 1970 19G0 1950 Figure 8. — Yearly estimates of the northern anchovy biomass (after Smith, 1972). The yearly total population estimates (upper left) are grouped into 5-yr block averages (upper right). Also given are the central and southern subpopulation 5-yr block averages (lower). Table 8. — Rank-correlation coefficients' between the scale occurrences of the Pacific sardine, the northern anchovy, and the Pacific hake in sediment of Santa Barbara and Soledad Basins in = 32). Pacific sardine Northern anchovy Pacific hake Santa Barbara Soledad Santa Barbara Soledad Santa Barbara Soledad Pacific sardine Santa Barbara -002 0.34 0.05 0.49 0.19 Soledad 0.20 -0.19 -0.09 020 Northern anchovy Santa Barbara 0.37 0.65 -0.08 Soledad 0.26 -0.46 Pacific hake Santa Barbara 0.17 Soledad 'While the correlation coefficients above 0.35 appear significant, nevertheless due to autocorrelation inherent in these time series the probabilities associated with these coefficients are likely to be greater than if the series were internally independent. 269 FISHERY BULLETIN: VOL. 72, NO. 2 Lfl z a u 1—1 Z a 25.00 SS-50 30-00 17.50 15-00 lS-50 10-00 7.50 5-00 2.S0 0-00 SARDINE. ANCHOVY, AND HAKE B I DMA55- -CENTRAL AREA 1980 1970 1960 1950 ISaO 1930 1930 1910 1900 1B90 1B90 1970 igGO 1B50 18-10 1830 1830 1910 1900 1790 35.00 ^ 23.50 30-00 17-50 15-00 13-50 10-00 , 7-50 SARDINE. ANCHOVY, AND HAf<,E BIDMAS5- -SOUTHERN AREA 1980 1970 1960 1950 1940 1930 1930 1910 1900 1890 1880 1970 IGEO 1B5C IS-JO 1830 1830 1810 1800 1790 Figure 9. — Combined biomass estimate for the Pacific sardine, the northern anchovy, and the Pacific hake in Alta California and southern Baja California waters, 1810 to 1969. The biomass estimates are derived directly from the information in Tables 3, 4, and 5. In the case of the hake the average population level for the years 1950-1965 was assumed to be 0.9 x IC^ metric tons (P.E. Smith, pers. comm.). One half of this population has been assigned to the central region; the other half has been assigned to the southern region. The actual relations used in the biomass calculation are as follows: Sardine — Santa Barbara (central population) and Soledad (southern population): sinceN^ = 2.27S^2 + 2.15 andB/= 0.38N; -0.40 (Spearman rank-correlation coefficient is 0.97, n = 6; see also Sette, 1969); then Bt = 0.85S^2 + 0.40 Anchovy— Santa Barbara: Bt = 0.36S^ - 0.64; and Soledad: Bt = 0.08S^ -I- 0.29 Hake— Santa Barbara and Soledad: Bt = 0.08S( where N is number of 2-yr olds, B is annual spawning biomass, S is scale deposition rate, and subscript t refers to year. The mean spawning biomass estimates for the sardine, anchovy, and hake are 3.5, 3.0, and 2.0 million tons for the central population and 0.7, 1.0, and 0.5 for the southern area. importance of the central region would also likely extend to the north through the seasonal migra- tion of these fish. The projected mean biomass level for the three main species off California over the past 30 years is roughly 2 million metric tons and over the past 150 yr is 8 million metric tons. Thus the recent rise of the anchovy population may simply be a return to reasonably productive conditions. It is ironic that most of man's experience in the waters off the Californias appears to be associated with low pelagic-fish productivity. Conceding a significant effect of the fishery on the Pacific sardine does not mitigate the synchronous low population levels of the anchovy and the hake. As a matter of perspec- tive, it should be emphasized that most of the understanding regarding the California Current system and pelagic fish, particularly that from 270 SOUTAR and ISAACS: ABUNDANCE OF PELAGIC FISH a. 5 a 01 o o o Ld _j < u 01 17.50 1S.D0 . 15-50 .. 10-00 ., 7-50 , 5-00 . 5-50 O-OO PACIFIC 5AURY, SANTA BARBARA BASIN ■r>^ laeo 1970 isGo laso is^o 1930 i3so laio laoo isao laeo ie7o ibbo ibso i84o leao laeo laio 17.50 15-00 IS-SO , 10-00 7-50 .. 5-00 S-50 , O-OO PACIFIC MACKEREL, SANTA BARBARA BASIN 1380 1370 1360 1950 13^ 1330 1950 1310 1900 1B90 IBBO 1S70 1360 IBSO 1B40 1B30 1850 IBID ISOO Figure lOa.b.— Histogram plot of the scale-deposition rate of Pacific saury and Pacific mackerel in sediment of the Santa Barbara Basin, 1810 to 1969. ^ u o 01 o o o 01 u _l < u 01 17-50 PACIFIC SAURY . Sni.EDAD BASIN 15-00 12-50 « lO-OO 7-50 5-00 , 2-50 1 . 1 1 L .«. J .1 I ., ..,_. 1 .1 1 M « 13B0 1370 19EO 1950 1940 1330 1320 1310 1300 1B30 IBBO 1S70 IflBO IBSO 1B40 1S30 ISSO ISIO IBOO 1730 1780 17-50 15-00 , 12-50 10-00 7-50 S-OC PACIi^IC MACKEREL, SDLEDAD BASIN I ,1 I .1 13B0 1970 1360 1950 1340 1330 1320 1310 1300 1S90 IBBO lfl70 1S60 IBSO 1840 1830 1820 1810 1900 1790 1780 Figure 10c,d.— Histogram plot of the scale-deposition rate of Pacific saury and Pacific mackerel in sediment of the Soledad Basin from about 1780 to 1969. 271 FISHERY BULLETIN: VOL. 72, NO. 2 ui UJ _i < u in >- > u z < \ LD U _/ < U in u z 3 < 2-50 . 3-S5 S-00 1-75 1-50 1-S5 1-00 0-75 0-SO SARDINE/ANCHOVY RATIO. SANTA BARBARA BASIN laeo 1970 1360 1950 1340 1930 19S0 1910 1900 lfl90 IBBO 1B70 IBGO 1B50 IflJO 1H30 IBSO laiO E-SO SARDINE/ANCHOVY RA t TI( :. SDLEDAD BASIN a-2s 5-00 1-75 1-50 1-25 1-00 0-75 0-SO 0-25 . 0-CC „ n-^ ,1 1 ^-T .1 „ 1— n ^^4 . — ,.— . .,. « 19B0 1970 13E0 1950 19-10 1930 1950 1910 1900 1B90 IBBO 1B7Q IBGO IBSO 1B40 1830 IBSO IBIO IBOO 1790 1760 Figure 11. — The ratio of Pacific sardine scales to northern anchovy scales in the sediments of the Santa Barbara and Soledad Basins. intensive efforts over the past 20 yr, has been gleaned from unproductive times, and there is yet limited appreciation of the capacity of the system. In regard to this point, a level of 15 million metric tons is suggested for the 1890's. The scale records of two other pelagic fish serve to underscore the preceding observations. The record of the Pacific saury (Figure 10a, c) indicates an intrusion by this fish during the 1940's into the coastal waters. It would appear the saury found these waters attractive in the anomalous paucity of the more regular inhabitants. Although the information in the case of the Pacific mackerel is meager, the scale record (Figure 10b, d) resembles that of the saury in that the higher scale occur- rences are near the ends of the record. The records preserved in the sediments display a panorama of pelagic-fish abundance in the California Current over the past 150 yr. Interpre- tations of these records in the limited light of pres- ent knowledge point in both disturbing and excit- ing directions: disturbing, in revealing the mag- nitude and duration of the effort needed to encom- pass such a system; exciting, in the temporal glimmer of its flow and potential. The character of pelagic-fish abundance in California Current waters is perhaps best summarized in graphic form (Figure 11). The records of the two critical species, the Pacific sardine and the northern an- chovy, when treated as a simple ratio exhibit a marked cyclical distribution (Santa Barbara) and a unique-event distribution (Soledad). The basic factors which gave rise to these distributions are most likely interspecific and autecologic. The 272 SOUTAR and ISAACS: ABUNDANCE OF PELAGIC FISH former is susceptible to scrutiny through the analysis of the projected fish populations through time. The latter is no less susceptible, for the sed- ■ iments contain a rich record of fossil microplank- ton which promises to further define oceanic con- ditions off the Californias in relation to pelagic- fish productivity. ACKNOWLEDG MENTS This report is a contribution of the Marine Life Research Group, Scripps Institution of Oceanog- raphy. Gratitude is expressed to Peter A. Grill for his statistical calculations, computer graphics, and patience. The support of the National Science Foundation (GA-27306) is gratefully acknow- ledged. REFERENCES Ahlstrom, E. H. 1969. Distributional atlas of fish larvae in the California Current region: jack mackerel, Trachurus symmetricus, and Pacific hake, Merluccius productus, 1951 through 1966. Calif. Coop. Oceanic Fish. Invest. Atlas 11:88-99. Brongersma-Sanders, M. 1957. Mass mortality in the sea./n J. W. Hedgpeth (editor), Treatise on marine ecology and paleoecology, p. 941-1010. Geol. Soc. Am. Mem. 67, Vol. 1. Clark, F. N., and J. B. Phillips 1952. The northern anchovy (Engraulis mordax mordax) in the Cahfomia fishery. Calif. Fish Game 38:189-207. D'Anglejan-Castillon, B. 1965. Marine phosphorite deposits of Baja California, Mex- ico, present environment and history. Ph.D. Thesis, Univ. Calif., San Diego, Scripps Inst. Oceanogr. David, L. R. 1943. Miocene fishes of southern California. Spec. Pap. Geol. Soc. Am. 43:1-193. Emery, K. O. 1960. The sea off Southern California. A modern habitat of petroleum. John Wiley & Sons, N.Y., 366 p. Fitch, J. E. 1952. The decline of the pacific mackerel fishery. Calif. Fish Game 38:381-403. Fritts, H.C. 1972. Tree rings and climate. Sci. Am. 226(5):92-100. Hulsemann, J., AND K. O. Emery. 1961. Stratification in recent sediments of Santa Barbara Basin as controlled by organisms and water character. J. Geol. 69:279-290. Kaplan, I. R.. and S. C. Rittenberg. 1963. Basin sedimentation and diagenesis. In M. N. Hill (editor), The sea. Vol. 3, p. 583-619. John Wiley and Sons, NT. Knutson, D. W., R. W. Buddemeier, and S. V. Smith. 1972. Coral chronometers: seasonal growth bands in reef corals. Science (Wash., D.C.) 177:270-272. KoiDE, M., A. SouTAR, and E. D. Goldberg. 1972. Marine geochronology with Pb-210. Earth Planet. Sci. Lett. 14:442-446. Koide, M., K. W. Bruland, and E. D. Goldberg. 1973. Th-228/Th-232 and Pb-210 geochronologies in marine and lake sediments. Cjeochim. Cosmochim. Acta 37:1171-1187. Krishnaswami, S., D. Lal, B. S. Amin, and A. Soutar. 1973. Geochronological studies in Santa Barbara Basin: Fe-55 as a unique tracer for particulate settling. Limnol. Oceanogr. 18:763-770. MuROzuMi, M., T. J. Chow, and C. Patterson. 1969. Chemical concentrations of pollutant lead aerosols, terrestrial dusts and sea salts in Greenland and Antarctic snow strata. Geochim. Cosmochim. Acta 33:1247-1294. Murphy, G. I. 1966. Population biology of the Pacific sardine (Sardinops caerulea). Proc. Calif. Acad. Sci. 34:1-84. Panella, G., C. MacClintock, and M. N. Thompson. 1968. Paleontological evidence of variations in length of synodic month since Late Cambrian. Science (Wash., DC.) 162:792-796. SCHUMM, S. A. 1969. Geomorphic implications of climatic changes. /« R. J. Chorley (editor), Water, earth, and man, p. 525-534. Methuen and Co., Ltd., Lond. Seibold, E. 1958. Jahreslagen in sedimenten der mittleren Adria. Geol. Rundsch. 47:100-117. Sette, O. E. 1969. A perspective of a multi-species fishery. Calif. Coop. Oceanic Fish. Invest. Rep. 13:81-87. Sholkovitz, E. R. 1973. Interstitial water chemistry of the Santa Barbara Basin sediments. Geochim. Cosmochim. Acta 37:2043-2073. Smith, P. E. 1972. The increase in spawning biomass of northern an- chovy, Engraulis mordax. Fish. Bull., U.S. 70:849-874. Smith, P. E., E. H. Ahlstrom, and H. D. Casey. 1970. The saury as a latent resource of the California Current. Calif. Coop. Oceanic Fish. Invest. Rep. 14:88-100. Soutar, A. 1967. The accumulation offish debris in certain California coastal sediments. Calif. Coop. Oceanic Fish. Invest. Rep. 11:136-139. Soutar, A., and J. D. Isaacs. 1969. History offish populations inferred from fish scales in anaerobic sediments off California. Calif. Coop. Oceanic Fish. Invest. Rep 13:63-70. Vrooman. a. M., and P. E. Smith. 1971. Biomass of the subpopulations of northern anchovy Engraulis mordax Girard. Calif. Coop. Oceanic Fish. In- vest. Rep. 15:49-51. Wallin, O. 1957. On the growth structure and developmental physiol- ogy of the scale of fishes. Inst. Freshwater Res. Drottning- holm. Rep. 38:385-447. 273 CHANGES IN THE AMOUNT AND PROPORTIONS OF DDT AND ITS METABOLITES, DDE AND DDD, IN THE MARINE ENVIRONMENT OFF SOUTHERN CALIFORNIA, 1949-72 John S. MacGregori ABSTRACT This paper is about the contamination of the ocean and its biota off southern Cahfornia by the pesticide, DDT. The accumulation of DDT and the changes in proportions of DDT and its metabolites in the ocean are described for the years 1949 to 1972 especially as they are reflected in the myctophid fish, Stenobrachius leucopsarus. This time period was characterized by continuous dumping of DDT wastes into the ocean by a large manufacturer of DDT and the cessation of this dumping in 1970. Aspects and implications of the pesticide pollution problem in the marine environment are discussed. In January and May 1970, the Fishery-Ocean- ography Center, La Jolla, Calif., collected samples of fish off southern California and Baja California as their part in a survey of chlorin- ated hydrocarbon (CHC) pesticides in marine fishes by the U.S. fish and Wildlife Service Bureau of Commercial Fisheries (now the Na- tional Marine Fisheries Service). Each sample consisted of the livers of several specimens of a single species from one locality. The samples were sent to the Environmental Protection Agen- cy Laboratory at Gulf Breeze, Fla., for analysis. The results (Duke and Wilson, 1971) showed that off southern Baja California 9 samples (170 fish) contained an average of 0. 14 parts per million (ppm) wet weight of DDT and its metabolites; in Sebastian Vizcaino Bay (central Baja California) 3 samples (29 fish) averaged 1.2 ppm; along the southern California coast south of Oceanside and at two offshore banks 15 samples (179 fish) aver- aged 13 ppm; in Santa Monica Bay 8 samples (65 fish) averaged 370 ppm. Two samples (26 fish) of Pacific hake, Merluccius productus, taken by a Russian trawler off northern California and Oregon averaged 2.7 ppm, and fish sampled farther to the north by the Seattle Laboratory contained less than 1 ppm or no detectable DDT residues in the livers. The highest levels of DDT and its metabolites were found in the Los Angeles area with DDT levels declining greatly in samples 'Southwest Fisheries Center, National Marine Fisheries Ser- vice, NOAA, P. O. Box 271, La Jolla, CA 92037. taken to the north, south, and offshore from Los Angeles. Previous pesticide residue surveys of marine birds and fish (Keith and Hunt, 1966; Risebrough et al., 1967; Risebrough et al., 1968) had been confined primarily to central California and did not reveal the extent of DDT pollution in the ocean* off Los Angeles. Risebrough et al. (1967) reported one sample of northern anchovy, Engraulis mor- dax, taken off Los Angeles that contained 12.7 ppm DDT and its metabolites compared with addi- tional samples of anchovies and three other species offish taken north of Los Angeles to San Francisco that ranged in DDT residue content be- tween 0.2 and 2.8 ppm. In the spring of 1969, Keith, Woods, and Hunt (1970) investigated the breeding pelican, Pelecanus occidentalis, colony on Anacapa Island, about 35 nautical miles west of Santa Monica Bay, and found extensive reproductive failure caused by thin-shelled eggs which broke under the brood- ing pelicans. They found that the contents of a composite sample of many broken eggs contained 1,818 ppm DDT residues (lipid basis) while nine intact eggs averaged 1,215 ppm. They also sam- pled pelican eggs from three breeding colonies in the Gulf of California and found DDT residues averaging 58, 61, and 105 ppm. Jehl (1970) sam- pled pelican eggs from Los Coronados Islands, about 95 nautical miles south of Anacapa. These contained 810 ppm DDT residues. At San Martin Island 250 nautical miles south of Anacapa, egg residues were 192 ppm. Manuscript accepted October 1973. FISHERY BULLETIN: VOL. 72, NO. 2, 1974. 275 FISHERY BULLETIN: VOL. 72, NO. More recent data (Southern California Coastal Water Research Project, 1971)2 for thep,p'DDE content of the mussel, Mytilus calif ornianus , show that two samples taken on the Palos Verdes Peninsula, near Los Angeles, contained 61 and 151 ppm of p.p'DDE while samples taken at a greater distance from Los Angeles declined greatly to between 0.3 and 3 ppm at San Diego, Point Conception, and on the farther outlying is- lands. Burnett (1971) determined DDT residues in samples of the sand crab, Emerita analoga, from 19 locations along the coast between northern Baja California and San Francisco. Only in those crabs from the Los Angeles area did he find values greater than 1 ppm (up to 7.2 ppm). The DDT values fell off rapidly north and south of Los Angeles and averaged about 0.1 ppm at most of these locations. These results of the above studies demonstrate that geographical proximity to Los Angeles was accompanied by greatly elevated levels of DDT and its metabolites in marine organisms. High DDT residues in marine life in the ocean off Los Angeles had an adverse effect on the fishing industry. In June 1970, canned jack mack- erel, Trachurus symmetricus, shipped from Los Angeles was condemned by the U.S. Food and Drug Administration in New York for high DDT content (13 ppm). The FDA had set a maximum tolerance of 5 ppm on fish products. In the follow- ing year jack mackerel was withheld from dis- tribution by the packers, and jack mackerel and Pacific bonito, Sarda chiliensis, were condemned by the FDA in the Los Angeles area. In December 1970, the FDA seized about 8,000 lb of white croaker, also called kingfish, Genyonemus lineatus, that had been caught near Los Angeles. These contained 19 ppm DDT residues. While the fishing industry was unable to pin- point any particular area of heavy DDT contami- nation of pelagic fish off southern California, it seemed to be fairly well defined for the more sedentary bottom dwelling species. Although the total DDT in the flesh of the Santa Monica Bay fish samples taken in May 1970 ranged from 12 to 57 ppm, about 30 nautical miles away at Farnsworth Bank on the west side of Santa Catalina Island, ^Southern California Coastal Water Research Project, 1971. Comments on the policy for water quality control proposed by the State Water Resources Control Board. Presented at the State Water Resources Control Board public hearing, San Diego, Calif., 2 Dec. 1971, 27 p. DDT in the flesh of a sample of sculpin, Scorpaena guttata, and in flesh samples of four species of rockfishes, Sebastes spp., had a range of only 0.23 to 0.49 ppm; and, a sample of white croakers taken off Oceanside, 40 nautical miles south of Los Angeles, contained only 0.61 ppm of DDT residues in the flesh. The pelagic fish were not good indicators of the source of pesticide contamination because they are much more migratory than the bottom dwell- ing species, and the area in which they are caught is not necessarily the area in which they were contaminated. Even though this would also mean that their exposure to heavy contamination would be of shorter duration than for bottom fishes living in these areas, they still built up high concentra- tions of DDT in the flesh because pelagic fish tend to store fat throughout the body rather than in the liver as do bottom dwelling, more sedentary species. The DDT residues are stored in the fats, and the distribution of the total body load of DDT residues in the fish is roughly related to the dis- tribution of fat. Although we have no flesh sample analyses from pelagic fish to illustrate this point, concen- trations of DDT were found to be two to six times higher in the livers of samples of four different species of bottom dwelling fish taken in 1970 along the coast between San Diego and Oceanside than they were in the livers of a sample of jack mackerel from the same area, and seven to 19 times higher than in the livers of a sample of Pacific sardine, Sardinops sagax, taken in San Diego Bay at about the same time. And even among bottom fish taken from the same area at the same time, those that have more oil in the flesh seem to carry relatively more of the total DDT load in the flesh. For five species of bottom dwelling fishes taken from Santa Monica Bay in 1970, there is an inverse relation between the ratio of DDT in the liver to DDT in the flesh and the percent of oil in the flesh as given in. Table 1. Because of the prevalence of winds from the Pacific, and the concentration of agriculture in the inland valleys, we considered it unlikely that the heavy DDT contamination in the ocean off Los Angeles was caused by airborne pesticide resi- dues. Surface runoff was also an unlikely source. Southern California's arid climate, the damming of rivers, the large population and importation of water have resulted in a condition in which the annual discharge by sewers into the ocean is at least twice the average annual surface runoff of 276 MacGREGOR: AMOUNT AND PROPORTIONS OF DDT Table 1.— Relation between ratio of DDT in liver to DDT in flesh and percent of oil in flesh of five species of bottom dwelling fishes from Santa Monica Bay in 1970. Number Total DDT Rat io of DDT Liver Flesh Percent oil Species of fish (ppm) (ppm) Liver:flesh in flesh Bocaccio, Sebastes paucispinis 9 590 12 49:1 1.4 Starry rockfjsh. S. constellatus 5 1,030 57 18:1 1.8 Vermilion rockfish, S. miniatus 10 163 16 10:1 2.2 Dover sole. Microstomus paclficus 13 63 13 5:1 3.6 Sablefish, Anoplopoma fimbria 10 103 23 4:1 6.0 water. The "rivers" of southern California are its sewers, and the two largest of these, in the 400 million gallons (1.51 million m^) per day class, are the outlets of the Hyperion treatment plant that serves the city of Los Angeles and those of the White Point treatment plant that serves Los Angeles County. The Hyperion plant empties into the head of an underwater canyon in the northern half of Santa Monica Bay, and the White Point plant empties into the ocean off Palos Verdes Peninsula. Fish samples that showed very high DDT residues came from southern Santa Monica Bay about midway between the two sewer outfalls. The County Sanitation Districts of Los Angeles County (CSDLAC) began a monitoring program to test for CHC pesticides in its sewerage system in December 1969 (Carry and Redner, 1970). They found that very high concentrations of DDT were present in the sewer system. In March 1970, they began to sample the sewer trunk lines in order to pinpoint the sources of DDT input into the sewer system. They soon discovered that the source of most of the DDT pollution was the Montrose Chemical Corporation, a major manufacturer of DDT, lo- cated in the city of Torrance. Los Angeles Times staff writer, John Dreyfus, reported (7 October 1970), after interviewing a Montrose official, that at that time, Montrose was the only manufacturer of DDT left in the United States, and that it ac- counted for two-thirds of the world's sales of DDT. The CSDLAC found that water samples taken from the sewers immediately upstream from Montrose contained 34 parts per billion (ppb) of DDT and its metaboHtes (DDD and DDE) in a flow of 25.3 million gallons (95.8 thousand m'^) per day or 7.2 lb (3.27 kg) of total DDT per day, while samples taken immediately downstream con- tained 2,950 ppb in a flow of 26.6 million gallons (100.7 m3) per day or 654 lb (297 kg) of total DDT per day (Carry and Redner, 1970). In April 1970, Montrose began hauling most of its processing wastes to a storage area, which caused a considerable drop in CHC entering the CSDLAC disposal plant. However, in May 180 lb (81.6 kg) per day CHC, of which 150 lb (68.0 kg) was DDT and its metabolites, were still found to be entering the White Point plant. The primary source of this was found to be the sewer trunk line serving Montrose Chemical Corporation. Because the composition of the total DDT sampled, 14% DDT, 48% DDD, and 38% DDE, was different from the Montrose effluent previously sampled, 74% DDT, 5% DDD, and 21% DDE, CSDLAC per- sonnel concluded that the primary source of pollu- tion was from old deposits in the sewer lines. Between 11 December 1970, and 1 July 1971, 567,000 lb (257,000 kg) of deposits, of which 7,700 lb (3,500 kg) were total DDT, were removed from the interceptor system that served Montrose (Redner and Payne, 1971). The cleaning of this section of the sewer lines also stirred up old de- posits which were washed down into the sewerage disposal plant, resulting in an increase in total DDT entering the plant. By October 1971, the total CHC entering the disposal plant had de- creased to 60 lb (27 kg) a day of which 28 lb ( 13 kg) was total DDT and the remaining 32 lb (14 kg) polychlorinated biphenyls (PCB). Since March 1971, an average of 22,000 gallons (83.3 m^) a day of alkaline waste from the Mon- trose plant has been trucked to the Sanitation District's landfill on Palos Verdes Peninsula, and another 700 gallons (25.9 m^) of acid waste has been trucked to a quarry. The alkaline waste was found to contain about 3,000 ppm of total DDT (Redner and Payne, 1971) or about 550 lb (250 kg) 277 FISHERY BULLETIN: VOL 72, NO 2 per day. The acid waste was not tested, but if the concentration of DDT was similar to that in the alkaline waste, it would amount to an additional 175 lb (79 kg) of DDT residues per day. The average inflow of DDT into the White Point sewerage plant during December 1969 through March 1970 was estimated at 652 lb (296 kg) per day. The amount measured in the sewers at the Montrose plant was 647 (293 kg) per day. The amount trucked out as alkaline waste only was estimated at 550 ( 250 kg) per day. Considering the difficulties in sampling such large volumes of material and the fact that the samples were taken in different localities at different times, there is remarkable agreement among them. It is difficult to determine just how much DDT finally was pumped into the ocean after treatment at the sewerage plant. Some of it was undoubtedly removed in grit, grease skimming operations, and in dried sludge. At the Hyperion treatment plant (city of Los Angeles), the digested sludge is pumped into the ocean, although some of it, at least in the past, has been used for fertilizer. The DDT input into the Hyperion plant was estimated to be on the order of 0.6 lb (0.27 kg) a day (tests by Hyperion personnel cited in Los Angeles Times, 7 October 1970) so, insofar as the DDT input into the ocean is con- cerned, it has had little impact. The White Point treatment plant has never discharged its sludge into the ocean (Terry Hindrichs, Southern California Coastal Water Research Project, pers. commun.) except during a short period of heavy rains in 1955. Until 1959, digested sludge was spread on nearby fields to air dry. Since 1959 a centrifuge has been used to partially dry sludge. The resulting cakes have been used for fertilizer or landfill. CSDLAC personnel were unable to get reliable estimates of the DDT content of their effluent into the ocean until December 1970 (Carry and Red- ner, 1970), long after Montrose stopped dumping most of their wastes. Nine samples that they took from the effluent into the ocean in December showed that the average total CHC entering the ocean was 130 lb (59 kg) a day. The influent into the sewerage disposal plant in December had a load of 153 lb (69 kg) per day. The influent samples were taken after the grit chambers so any CHC removed in grit would not have been included. If we assume that sludge removal accounted for a 15% loss of CHC in December 1969 through March 1970, between influent (average 652 lb or 296 kg per day) and effluent into the ocean, then, the ocean discharge would have been about 552 lb (250 kg) per day of CHC for these months. This is about 100 short tons (91 metric tons) per year or about 10 times the amount of pesticides estimated to be carried into the Gulf of Mexico each year by the Mississippi River (Butler, 1969). Montrose received a permit to dump its wastes into the CSDLAC sewer system in 1953, but it had been dumping for a few years before that accord- ing to company personnel. The continuous dump- ing of large quantities of DDT wastes into the ocean at a single point over a period of about 20 yr presented an unparalleled opportunity to study the effects of DDT on the ocean environment. Un- fortunately the one-time opportunity to take ad- vantage of the situation was not fully realized until some time after the dumping had stopped, and no large-scale coordinated investigation was undertaken to exploit this ecological windfall. An investigation of pesticide pollution of the marine environment was initiated at the Fishery Oceanography Center (FOC), La Jolla, in 1970. Personnel at FOC have collected samples of bot- tom muds, fishes, and other biological samples primarily from the ocean off Los Angeles in order to study the effects of heavy DDT pollution in the marine environment. Collections of marine organisms taken for other purposes, some dating back to 1949, were avail- able for study. Most of the present paper is based on DDT levels found in specimens from one of these collections of a myctophid fish, Stenob- rachius leucopsarus, found in the ocean off south- ern California in an attempt to trace the historical buildup of DDT and its metabolites in the marine environment as reflected in this species. MATERIALS The California Cooperative Oceanic Fisheries Investigations (CalCOFI) has taken plankton samples over an extensive area off California and Baja California since 1949. These samples were obtained over a predetermined pattern of stations in order to determine the species present, their numbers, and their distribution. The most inten- sive sampling took place during the 1950's; during the 1960's the number of CalCOFI cruises was reduced considerably. All fish and fish eggs are routinely sorted out of the collections for identification. About 600 278 MacGREGOR: AMOUNT AND PROPORTIONS OF DDT specimens of the myctophid fish, S. leucopsarus, that had been sorted from the plankton collec- tions, were selected for this study to give best areal and temporal coverage. Initially a few plankton samples, which were available in much greater quantity, were tested for pesticides. However, the plankton species composition varied in time and with locality, and it was felt that the samples might not be compara- ble. The plankton samples also appeared to con- tain both Aroclor 1242^ and Aroclor 1254 (poly- chlorinated biphenyls (PCB) manufactured by Monsanto Corporation) while the myctophids generally contained only Aroclor 1254 in quan- tity. Plankton samples can include man-produced debris that contains relatively large amounts of CHC or other organic chemicals which interfere ^Reference to trade names does not imply endorsement by the National Marine Fisheries Service, NOAA. with analysis, while individual myctophids are relatively free of such material. Myctophids do not undergo any more horizontal movement than other plankton organisms, and, if they use their motility at all, at least in the coastal waters, it is probably to maintain position over the deeper ba- sins. In addition, they tend to contain more pes- ticide than the invertebrate constituents of the plankton with which they are taken, and they are convenient material to work with. The myctophids tested for pesticide residues ranged in standard length (SL) from 14 to 77 mm. They are apparently short-lived fish. Fish of the year can be followed through their first year and into their second by length-frequency distribu- tions (Figure 1). Most of the myctophids tested appeared to be comparable in DDT content to other fish taken at the same time and place, but the amounts in smaller fish were erratic. Some 10 20 I o LU 60 70 80 :? h f T T r r T 1 :7 ' " ' I ' ' ' ' I ' ' ' ] h 1 1 1 1 1 1 1 1 1 r ] ? 1 1 1 1 1 1 1 ;.v;-; 1 m 1 ? ? ] [ill rj.Ti m J 1 I T ? I 1 1 1 1 J" ] h J % r r 3 ] p — M.I, ] 1 1 1 1 J r 1 1 0 50 50 5 10 0 5 0 50 50 50 50 50 50 50 5 NUMBER OF FISH BY MONTH MAY JUNE JULY AUG. SEPT. OCT NOV. DEC. JAN. FEB. MAR. APR. Figure 1. — Length-frequency distribution of Stenobrachius leucopsarus by month. Shaded area is entering year class. 279 FISHERY BULLETIN: VOL. 72. NO. 2 were comparable to larger fish, while others con- tained less DDT than might be expected in larger fish taken at the same time and in the same local- ity. This variation in pesticide content appeared to be related to the "fat" content (hexane extractable portion of the fish) of the specimens. The fat con- tent of the fishes (Figure 2) increased very rapidly and with considerable variation to 30 mm length, 6.5% fat of the dry weight of the fish in an 18-mm specimen to 42.5% in a 29-mm specimen) where it began to level off. In mature fish the fat is about 49% of dry weight and 16% of wet weight. There is no apparent seasonal fat cycle. For comparison of DDT in time and space, only myctophids 30 mm or longer were used. METHODS The myctophids used in this study were pre- served in Formalin which had no apparent effect on the pesticides to be analyzed. The specimens were measured and weighed and placed in tared disposable pipets that had been plugged with glass wool at the small end, or for larger fish in similarly prepared glass tubing of appropriate size. The fish were dried in an oven at 65^0 to constant weight and reweighed to obtain dry weight. Each fish was 20 ••• ••••"^, •,• w * V A CO cPcP J^ "h J L 20 30 40 50 60 STANDARD LENGTH (mm) Figure 2. — Increase in percent fat with increase in length for Stenobrachius leucopsarus. Dark circles equal fat as a percent of dry weight; open circles, as a percent of wet weight. Fat equals hexane extractable substances. Pesticide values forfish less than 30 mm standard length (SL) were not used because of the greater variation in these values than in larger fish in which fat content was more stabilized. macerated in the tube and extracted into a 15-ml graduated centrifuge tube with 10 ml of hexane. The remains of the fish in the pipet were dried and reweighed to obtain the weight of material ex- tracted. The extract in the centrifuge tube was mixed to uniformity, and an aliquot equal to 20 mg or less of fat removed. This was reduced in volume if neces- sary and passed through an activated alumina column as described by McClure (1972). The cleaned up sample was again reduced in volume if necessary and injected into a model 402 Hewlett Packard gas chromatograph (GLC) with a Ni^^ electron capture detector. The 6-foot glass column contained 1.5% OV-17/1.95%QF-l, on 100/120 mesh Supelcoport. DDT gets its name from its former chemical designation, p,p'-dichlorodiphenyltrichloro- ethane. The current chemical designations for DDT and its metabolic products mentioned in this paper are: p,p -DDT p,p -DDD (TDE) p,p -DDE p,p, -DDMU Kelthane (Dicofol) 1 , l-dichloro-2,2-bis(p-chloro- phenyDethane l,l-dichloro-2,2-bis(p-chloro- phenyDethane l,l-dichloro-2,2-bis(p-chloro- pheny 1 )ethy lene l-chloro-2,2-bis(p-chlorophe- nyl)ethylene l,l-bis(p-chlorophenyl)-2,2, 2-trichloroethanol For the ortho-para isomers of DDT, DDD, DDE, and DDMU substitute 2(o-chlorophenyl)-2-('p- chlorophenyl) for 2,2-bisrp-chlorophenyl). In this paper total DDT includes p,p 'DDT, o,p 'DDT, p,p 'DDD, o,p 'DDD, andp.p'DDE. While o,p'DDE andp,p'DDMU are present, although not as major constituents of the fish samples, both have the same short retention times on the column used and are interfered with by a number of other un- knowns as tends to be true of anything having a shorter retention time than p,p 'DDE in these samples; therefore they were omitted because of the difficulty in identification and quantification. Kelthane was also omitted because it breaks down on this column (Morgan, 1967) to a material that has a low response and an even shorter retention time than DDMU. For the purposes of this paper we assume that DDT is metabolized (O'Brien, 1967; Morgan, 1967; Menzie, 1969) as follows: 280 MacGREGOR: AMOUNT AND PROPORTIONS OF DDT DDT < DDE ^-(little or no metabolism) DDD »-DDMU ►►(continued metabolism) Kelthane—»-Dichlorobenzophenone— ♦-(continued metabolism) Since we have no measurements of Kelthane, the scope of this paper includes only the measurement of the metabolism of DDT to DDE and DDD. As mentioned earlier, the effluent from the Montrose plant was already partly metabolized (Carry and Redner, 1970). In seven samples taken between 14 August and 24 November 1970, the total DDT portion of the effluent contained 74% (range 62-84) of DDT, 5% (3-7) of DDD, and 21% (9-35) of DDE. During this period the effluent contained 2 lb or less of DDT per day. The proportions of DDT, DDD, and DDE at the time when dumping was 650 lb (295 kg) per day were 73:2:25. At the beginning of this investigation some pes- ticides were separated on other columns to con- firm the identification of DDT and its metabolites. Additional confirmation was obtained by dehy- drochlorinating samples with alcoholic KOH which converts DDT and DDD to their respective ethylene derivatives, DDE and DDMU, but does not change the PCB, Aroclor 1254. Because there are so many possible sources of variance to the estimates of pesticide content, we cannot obtain a precise measure of this error. Based on the least accurate measurements made in the course of analysis, the standard error of the amount of pesticide in a sample should be about plus or minus 10% . The error may be increased by shortcomings in methodology and by the presence of other peaks that interfere with those to be quan- tified. At low pesticide values the error increases, and it may be more like plus or minus 100% at values on the order of 10 ppb. However, the abso- lute error is only a few parts per billion also and makes little difference when values that differ by orders of magnitude are being compared. In the myctophid samples, Aroclor 1254 seemed to be the only substance that contributed peaks on the chromatogram of any significance which could interfere with quantification of the DDT series. Six Aroclor 1254 peaks span the retention time range ofp,p'DDE, o,p'DDD, o,p'DDT, p,p'DDD, andp,p'DDT (Figure 3). In all the marine sam- ples examined, o,p 'DDT and o,p 'DDD are present in either very small quantities or not detectable at all unless the samples contain very large quan- tities ofp,p'DDT orp.p'DDD. In the myctophid samples, Aroclor 1254 seems to maintain its in- tegrity very well. There is no apparent selective breakdown of its components, and the pattern of peaks from myctophid samples containing this PCB and very little pesticide closely resemble the Aroclor 1254 standard (Figures 3 and 4). RETENTION TIME IN MINUTES Figure 3. — A. Aroclor 1254 standard; column: 1.5% OV-17/1.95% QF-1, 100/120 mesh Supelcoport.B. Sample of two Stenobrachius leucopsarus each 20 mm standard length (SL) taken in July 195 1 . at CalCOFI station 70. 100. About 0.54 ppm Aroclor 1254 with peak no. 5 increased slightly by 0.2 ppm DDE and peak no. 10 by 0.3 ppm DDT. Less highly chlorinated Aroclor peaks no. 1, 2, and 3 may be breaking down in the environment; more highly chlorinated peaks (no. 4 through 10) tend to maintain their integrity of pattern. Same column as A. C. Standard of six DDT analogs. Same column as A. D. Sample of a 33-mmS. leucopsarus taken in November 1955 at CalCOFI station 83.40. This sample contains 2.3 ppm total DDT. Because of the high DDT content of this sample, it was not concentrated as much as sample B. It probably contains at least half as much Aroclor 1254 as sample B. Same column as sample A. 281 FISHERY BULLETIN: VOL. 72. NO. 2 RETENTION TIME IN MINUTES Figure 4. — A. Aroclor 1254 standard; column; 4% SE-30/6% QF-1, 100/120 mesh Supelcoport. B. Sample of a 28-mmS. leucop- sarus taken in November 1955 at CalCOFI station 83.55. Aroclor 1254, 4.2 ppm; pesticides not measured. Same column as A. C. Standard of six DDT analogs. Same column as A. D. Sample of one 37-mm S. leucopsarus taken in March 1954 at CalCOFI sta- tion 85.45. 1.0 ppm total DDT. Same column as A. It is apparent (Figure 3) that the seventh of the Aroclor peaks is not interfered with by the DDT series. The two ortho-para prime peaks bracket- ing it are generally small or absent. Therefore, it may be used to correct the DDT series for PCB interference and to quantify the Aroclor 1254. An estimate of peak area, peak height times width at one-half peak height, was used in quantification. Increasing chart speed makes it possible to measure the width more accurately. Peak area rather than peak height is a more accu- rate measurement of the combined effects of two CHC when their retention times are about the same. Because GLC operating conditions may thange gradually during a sample run, one pes- ticide standard was injected for every two samples Area of Combined peaks Aroclor p.p'DDE + Aroclor no. 5 0.247 p,p DDD 0 o,p 'DDT + Aroclor no. 8 0.547 p,p 'DDD + Aroclor no.9 0.737 p.p' DDT + Aroclor no. 10 0.957 so that each sample would have an adjacent stan- dard for quantification. To correct the areas of the combined peaks of the DDT series and Aroclor 1254 to the area repre- senting pesticide only, we letX equal the area of each peak at the respective retention time of each of the DDT series and Y equal the area of Aroclor peak no. 7. Then for our operating conditions and Aroclor standard, the areas allotted to the compo- nents were: Area of DDT series X- 0.247 X X- 0.547 X- 0.737 X- 0.957 An estimate of Aroclor 1254 was obtained by mul- tiplying the area of the no. 7 Aroclor peak by 12.3 and quantifying against the area of thep,p'DDE standard, or multiplying by 9.6 and quantifying against the area of the p,p 'DDT standard. The subtractive corrections for the DDT series were confirmed in part for a few samples by calculating values both before and after dehydrochlorination with alcoholic KOH. In a few samples taken far from the sewer out- fall and in the earlier years, Aroclor 1254 was high enough to mask out the DDT residues except for slight increases in some peak areas (Figure 3). In such cases the pesticides were present in such small quantities that it made no appreciable dif- ference in the overall results what small values were assigned to them. The illustrated example is an extreme case of masking. In most of the samples the DDT residues domi- nated the PCB peaks and over the range of the six pesticide standards (Figure 3), only peaks no. 6 and 7 of Aroclor 1254 were evident. If DDT re- sidues were high, peak no. 6 was evident as a widening of the base of thep.p'DDE peak (Figure 3). RESULTS AND DISCUSSION The pattern of CalCOFI stations from which the samples were obtained extends across the north flowing coastal countercurrent out into the south flowing California Current cutting across the counterclockwise eddy or eddies that develop be- tween the two currents. At a depth of 200 m the 282 MacGREGOR: AMOUNT AND PROPORTIONS OF DDT California Current is usually farther offshore than at the surface (Wyllie, 1966). In April and May this current moves inshore eliminating the countercurrent at the surface and sometimes at 200 m. When the California Current is offshore, the surface countercurrent develops; when it moves onshore, the surface countercurrent is ab- sent although the southern California eddy usu- ally persists. The currents, and consequently the distribution of the sewer discharge, are influenced locally by such factors as the configuration of the coast, the presence of islands, the topography of the ocean floor, and the short range effects of winds and tides. The total DDT data for the myctophids were divided into four time periods, and the average DDT value determined for all specimens taken at each station, or combined stations if they were very close together, for each time period (Figures 5-8). The total DDT content of the fish tended to be high near the sewer outlet and decreased away from the outlet. Total DDT values increased with the passage of time. Total DDT for the purpose of this discussion consists of DDT, DDE, and DDD. Although total DDT content in the myctophids increased with time, this did not hold true for each of the three constituents. DDT increased for a few years until metabolism and dispersion equalled input and then leveled off. DDD acted in a similar manner but at a lower level. Most of the increase in total DDT after the first few years was caused by the increase in the persistent metabolite, DDE. The ColCOFI STATION NUMBERS Figure 6. — Average total DDT at CalCOFI stations off southern California for the 4 yr 1953-56. s 3 97.80 .75 70 .65 .60 ,55 50 .45 40 .35 50 CalCOFI STATION NUMBERS CalCOFI STATION NUMBERS Figure 5. — Average total DDT at CalCOFI stations off southern California for the 3 yr 1950-52. Figure 7.— Average total DDT at CalCOFI stations off southern California for the 4 yr 1957-60. 283 FISHERY BULLETIN: VOL. 72, NO. 2 s Z 9780 .75 .70 .65 .60 .55 50 45 10 35 .30 ColCOFI STATION NUMBERS Figure 8. — Average total DDT at CalCOFI stations off southern California for the 6 yrl% 1-66. increase inp,p'DDE relative top,p'DDT for the years 1950-51 through 1965-66 in the myctophids was: Year Ratio of DDE to DDT 1950-51 0.33:1.00 1952-53 0.36:1.00 1954-55 0.69:1.00 1956-57 1.06:1.00 1959-60 1.14:1.00 1961-62 2.02:1.00 1963-64 2.39:1.00 1965-66 3.96:1.00 (1970) (4.74:1.00) (1972) (8.80:1.00) These data show a 12-fold increase in the amount of DDE relative to DDT from 1950-51 to 1965-66. The ratio for the fish taken in 1970, 65-70 nautical miles southeast of the sewer outlet (in La Jolla Canyon) indicates a continuing increase in the ratios, although there were only two fish in the sample. The 1972 sample, consisting of only five myctophids, was taken west of Santa Catalina Island and about 25-30 nautical miles south southwest of the sewer outfall about 2 yr after the dumping of DDT into the sewer system had stopped. The high ratio may reflect in part con- tinued metabolism of DDT without replenish- ment. Because there are no data on the amount of DDT discharged into the ocean through the White Point sewer outfall each year, I have assumed that it was constant and discharged continuously throughout the year. Under these circumstances the amount of DDE (and DDD) entering the marine environment should gradually have in- creased in the earlier years until the input of DDT equalled the amount of DDT metabolized, when the input of DDE (and DDD) would also be con- stant. This is indicated by the initial slower in- crease in ratios of DDE to DDT. If we assume that the same amount of pesticide is released into an environment each year and that it is released continuously throughout the year we may empirically represent the accumula- tion of the pesticide in the environment by the formula Y =Ka -S^) in which Y equals the amount of pesticide accumu- lated at the end ofX years; /^ equals the maximum amount of pesticide that could be accumulated by the organism under the prevailing conditions; and S equals the "survival" rate of the pesticide for 1 yr- In some of the years from 1949 to 1966, Cal- COFI cruises were limited, and fewer samples were taken. Also the fish were not uniformly sam- pled with respect to distance from the sewer out- fall in each of the years. But, by averaging the p,p' DDE content of all fish taken in each year and grouping years by twos, a rough indication of the increase in p,p 'DDE was obtained to compare with theoretical values of the formula, Y = K (1 - SX) (Figure 9). The almost linear increase inp,p'DDE indicates that its metabolism is very low. In fact, metabolism in this case would include p,p' DDE lost by removal from the area under study, and, therefore, the data indicate that very little was lost from this area during the years in which dumping occurred. Because of the apparent lack of metabolism of p,p' DDE, this metabolite of p,p 'DDT should give the best picture of areal and temporal buildup of a CHC in the ocean as a result of the sewer dis- charge. Data on p,p'DDE content of the myctophids, year of capture (with 1949 equal to year 1), and distance in nautical miles from the sewer outlet to the place of capture were fitted to the formula: 284 MacGREGOR: AMOUNT AND PROPORTIONS OF DDT Figure 9. — Increase in p,p' DDE in the ocean off southern California, 1949-70. The points are averages of all stations com- bined in 2-yr groupings. Because the same patterns of stations were not run each year, myctophids were not obtained from the same stations or the same number of stations each year. Also pesticide concentrations were more dependent on distance from the point source of contamination than on year. This makes the coarse group- ing of data necessary when increase in DDE with time only is considered. The two theoretical lines are computed to the formula Yf. = K(\-S^). in which Yc = computed value ofp.p'DDE, K = value at which metabolism, excretion, and dispersal of DDE equals input, S = survival of DDE for 1 yr, and X = year with 1949 considered as year no. 1. The data indicate thatp.p'DDE is very stable. For the 98% survival curve, which more closely fits the data. 90% of the equilibrium value would not be attained for 1 14 yr. log y = log a + 6 log X + c log X' in which Y = calculated value of DDE in parts per billion, X = distance from sewer outfall in nauti- cal miles, andX' = year. The data were grouped for greater ease of computation and to minimize individual variations which tend to distort the actual values transformed from log-log calculated values if not minimized by averaging. The values determined for the above equation are: log a 3.054 6 (distance) -1.062 (SE 0.057) c (year) 1.423 (SE 0.122) The correlation coefficients are: multiple partial (6) partial (c) 0.978 -0.829 0.522 all of which are significant atP of less than 0.001. The computed lines did not fit the data for 1949, 1950, and 1951 very well. These years were left out of the calculations because the input of DDE was rising relatively rapidly at this time and did not begin to stabilize until about 1953. Also in these earlier years, the influence of the sewer dis- charge of pesticide extended out to only about 100 nautical miles from the outfall. In the following years the influence of the sewer discharge in- creased rapidly to between 300 and 400 nautical miles from the outfall before becoming indistin- guishable from the ocean background. Although there are no extensive data for any one station throughout the period under study, we can now calculate values for a theoretical station 20 nauti- cal miles from the sewer outfall from the DDE-time-distance formula and in conjunction with the observed changes in ratios among the various DDT analogs, obtain a description of the metabolism of DDT in the marine environment as reflected in the myctophid fish, S. leucopsarus. Because o,p'DDE was not quantified, we used onlyp,/? 'DDE, p,p 'DDT, and p,p 'DDD in the ratios. In more than 300 myctophids 30 mm or longer in standard length in which the above three con- stituents and o,p 'DDT and o,p 'DDD were measur- able, o,p'DDT and o,p'DDD averaged 22.3% of p,p'DDT and p,p 'DDD. In samples of commercial DDT that were tested o,p 'DDT averaged about 25% of p,p 'DDT. From the calculated values of DDE and ratios of DDE to DDT, we can calculate that at our theoretical 20 mile station DDT accumulates in the fish up to 1.077 ppm when input equals metabolism. From this we may calculate that: Yt = 1.077(1 - 0.708^) in which Y, equals calculated p,p' DDT and X equals the year with 1949 equal to year 1. From the values obtained (Table 1, Figure 10) we may recalculate values for DDE. These values remain essentially the same as those calculated from the DDE-time-distance formula for the later years but make allowances for lower input from DDT for the earlier years if we use the formula: 2.0467^ = 0.368X - 1.077 + 1.077(0.708^) or Ye = 0.18QX - 0.526 + 0.526(0.708^) in which Ye -= calculated p,p 'DDE andX equals the year and in which we assume that there is no further metabolism of DDE. 285 FISHERY BULLETIN: VOL. 72. NO. 2 CC LU Q- t— cr Q. 3.5- 3.0 2.5 2.0 1.5 1.0 0.5 0.0"- DDE DDT -DDD •/ • ^ • • • • .V>- I'll 1950 1955 i-r,- I ' I I I I I ■■■A I I I I I960 YEAR 1965 1970 Figure 10.— Trends of p.p'DDE (squares), p.p'DDT (circles), and p.p'DDD (triangles) in the ocean off southern California, 1949-72, at a theoretical station 20 nautical miles from the point source of pesticide contamination. Computed lines show persistant DDE increasing until dumping of DDT wastes ceased in 1970. Both DDT and DDD increase for several years and then level off when metabolism, excretion, and dispersion equal input. Points are based on calculated total value of the three analogs distributed among them on the basis of the observed ratios of the three analogs to each other for each year. The 1972 ratios were affected by sewer cleaning operations that caused large quantities of DDD to enter the ocean. From the calculated values of DDT and the DDD:DDT ratios we may estimate values for DDD. From these it appears that DDD accumu- lates in the fish up to 0.303 ppm where input equals metabolism. From this we may calculate that Frf = 0.303(1 - 0.525^). However, this for- mula is based on a constant input equivalent to 0.189 ppm. The actual input from metabolism of DDT was only 0.028 ppm the first year and in- creased to 0.181 by the 10th year, and 0.188 by the 20th year. By adjusting for these increasing in- puts we obtain accumulative values for DDD, for DDMU, and other metabolites of DDD (Table 2, Figure 10). The percent distribution of total DDT among p,p'DDT,p,p'DDE, andp,p'DDD did not appear to change in myctophids with distance from the sewer outfall. Therefore the percent distribution which is based on large numbers of fish in most years can be used to prorate the total p.p'DDT obtained from the curves to obtain "observed" val- ues ofp,p'DDT,p,p'DDE, andp.p'DDD (Table 1, Figure 10). Both the curves and their observed values are based on observed percent changes in the composition of total DDT transformed to ppm values of the three constituents at a theoretical station 20 nautical miles from the sewer outfall. It should be emphasized that the above descrip- tion of metabolism is only an indication of what is taking place in the ocean. It neither describes the metabolism of DDT in the myctophid fish nor the metabolism in the marine environment, but rather refiects selective storage of DDT and its environmental metabolites in one species offish. Three factors determine the amount of CHC found in myctophid fishes: 1) The CHC present in the fish's environment during its brief life span; 2) the selective absorption of CHC through the gills and the ingestion of selected food particles; 3) and the selective storage, metabolism and excretion of CHC. Factors 2 and 3, above, should remain con- stant for each generation of fish. Therefore, the changes in composition of total DDT probably reflect changes occurring in the environment. However, the percent composition found in the myctophids may not represent the percent com- position in the environment because of the selec- tive nature of intake and excretion. Some of the DDT was changed to DDE and DDD before entering the ocean. Sixteen samples of sewer discharge from the Montrose Chemical Corporation taken between 14 August 1970, and 12 May 1971, averaged 74%DDT, 209^^ DDE, and 6%DDD (Redner and Payne, 1971). Although these samples represented discharges averaging less than 0.5 lb (0.23 kg) a day, samples taken earlier in 1970 when dumping was estimated at 640 lb (290 kg) per day also had ratios of 73:25:2. These percent ratios are very much like the 74:23:2 distribution in the myctophids in 1949 and the 70:23:7 distribution in 1950. Although some DDT was converted to DDD and DDE before it left Montrose, most of the metabolism took place after it was discharged from the plant. This is indicated by the percent distribution of DDT, DDE, and DDD in the myc- tophids in 1970, 16:75:9, by the bottom fish taken 286 MacGREGOR: AMOUNT AND PROPORTIONS OF DDT *» m « a ej ^ rt «> CO r~ w Ol 3 <— < -C* -C O M P D t n * u o JS e -t^ ^ (Tl C/1 ■^ J5 05 1 O. o 01 ■w JS 7 >t s «2 CS c c c o as -»J O 3 C -4J J3 -4J T1 3 c 0) ta u o 0) C o. « TJ a> o C J3 HI ^ o U >-i G V n 3 ■a c "o CQ O. Q (>-. Q Q u ft. 3 o m o. 73 C C (S o U Q. Q V Q "=5. £= ft. o H i D (1) Q ft. E ft. iM O 9i 3 3 es C > o T3 Vm -S O CO 01 3 c "a C8 1r U ■1-1 nj o -Q S c a. o c O o Q Pl ci UJ Pl Q.Q: d Dp- d a Q_ Q 9 o d LU Q - o d (za — 3Q E p _ Q. T i5 CL ^3 , Qj Q y^ ^ Qj ^^ - — 0 o 5 E OD -C ±:-o w Q. t;P-o£E 5 Q- " ra 13 eP °- 8=^ 0 f§I ? 3 Q.Q- HQ- T3 -53§E - § Q-S ra o d O o ra ra _ — = SE c Q.Q. o o < ra — -o = 3 E c c a < — 00 to "- CO ,- o T- cvj eg c*) r IX) 1- 1- r^ r CO CO '- »- to -^ ts> in CO 0 CD P^ CD h- 00 CO CO .- cocO'-CT^r^ .-inor^ T •- O 00 CO •5 CO J C\J CM fj a> ^ C7) r- C35 CO CO CO ■* ra lO in r^ c\j T- in CO CD CO O) o> CO in t^ ra ra in ra CJ) ra ra r 0 0 in a> 00 C31 r^ in ra ■^ 01 TJ- CD 0 0 >- CT> ra ra ra en ra 0 m I- 0 - r^ CO CO LO 10 en TT 00 CO CO en tt ^ CO 0 z CO CO CO CO C\J CO CNJ CO Tf ^ C\J C\J CO .- -0 0 Z -a 0 Z ■0 in 0 ■- Z ■°cj> 0 Z ■D Z CO 0 t- cji in CJl 1- CM CM '- 0 Oi 00 CD 40 CO ▼- 05 r^ lO r^ 0 CM -^ CD CO 05 1- CO m r^ a> 0 CNJ TT ID in CO CNJ *- 0 1- T- ^ T- CM CM CM CM CM CM CO CO CO CO CO -^ -- CO O) CO CO 0 1- .- '- CM 00 CO CO CO in CM CO Ln CM o ''t h- ^ in tt TT -^ in in O^ CO CM 01 CD CO C\J CD o P'cM^co'^in' cD"p^coaro^ ^CNrco"^in" —'--' ^— —' ^^ -— --^ -—-^ y-^ ^^^T-^^ .^^^.^^f^ CNJCMCMCMCM C7)<5i-cMco Trincor-co C7>Oi-cmco TrmcDr^co o^Oi-cmco ^inminin minminin incDcocoto cocdcocdcd cDr-f^r--p^ O Oi O) O O) 287 FISHERY BULLETIN: VOL. 72. NO. 2 in Santa Monica Bay in 1970, 8:87:6, and by a bottom sediment sample taken near the sewer out- fall in 1971, 6:82: 12. Samples of sewer water taken in 1970 that derived their DDT content from sewer sediments had ratios of 14:38:48 (Redner and Payne, 1971). A few specimens of another myctophid, Triphoturus mexicanus, also showed a change in CHC ratios with time. Twenty-one specimens taken between 1950 and 1959 contained an aver- age of 699'f DDT, 99f DDD, and 22*7^ DDE, while 12 specimens taken between 1961 and 1970 con- tained 23% DDT, 15%DDD, and 62% DDE. These fish were taken between Los Angeles and south- ern Baja California (lat 26°20'N). This species has a more southern distribution than Stenobrachius leucopsarus, and therefore the population was less influenced by the sewer discharge. One might expect that DDE would be more abundant in samples taken farther from the sewer outfall, indicating older deposits, but this is not the case. The proportions are very similar in all samples, even those taken outside of the influence of the sewer. For the fish samples taken in 1969-70 for the survey, the percentages are given in Table 3. Each sample contained several fish of the same species, and only the livers were tested. Where the Table 3.— Distribution of p.p'DDE, p.p'DDD, and p.p'DDT in fish samples by area taken, 1969-70. Number of samples Percent as Location DDE DDD DDT Southern Baja California 8 80.6 8.9 10.5 Sebastian Vizcaino Bay 3 74.2 8.8 17.0 Cortez Bank 4 86.5 4.7 8.8 Southern California coast 6 86.0 5.1 8.9 Farnsworth Bank 6 86.9 5.6 7.5 Santa Monica Bay 8 86.6 5.8 7.6 pesticide levels were very high, the proportions were remarkably similar among samples. For the eight Santa Monica Bay samples, the DDE ranged from 85.2 to 87.7%, DDD from 5.1 to 6.6%, and DDT from 5.7 to 9.1%. The high proportions of DDE relative to DDT and DDD seem to be typical of fishes, porpoises, and crustaceans in the ocean off southern Califor- nia (Tables 4 and 5). In six adult pelicans taken on Anacapa Island in 1969 (Keith et al., 1970), DDE made up 99% of the total DDT found in the fat, and 93% in eggs taken at the same time. Lament, Bagley, and Reichel (1970) tested 10 pelican eggs from the same place and year and found that DDE constituted 96% of the total. Stout (1968) gives data for 17 samples repre- senting seven species of marine fishes taken off Washington and Oregon. In these, DDE averaged Table 4. — Percent distribution of total DDT and ratio of DDD to DDT in rockfishes and sablefish from Santa Monica Bay. Major dumping of DDT wastes into sewer system stopped in April 1970. Samples of May 1970 and August 1971 are averages of five separate samples each for fat, liver, and flesh. In each of these 15 samples the ratio of DDE to DDT was greater than one. Percent Total distributior Ratio Part tested DDT (ppm) Species DDE DDD DDT DDD;DDT May 1970; Sebastes paucispinis Liver 519.0 86.3 5.6 8.1 0.69:1.00 S. paucispinis Flesh 11.6 80.6 8.8 10.6 .82 S. miniatus Liver 162.0 87.0 5.6 7.4 .75 S. miniatus Flesh 16.0 92.3 trace 7.7 .0? S. constellatus Liver 1,026.0 87.7 5.5 6.8 .80 S constellatus Flesh 57.2 88.2 5.5 6.3 .86 S. constellatus Fat 2,588.0 85.0 7.0 8,0 .87 Anoplopoma fimbria Liver 103.0 87.3 5.8 6.9 .85 A. fimbria Flesh 23.4 81.2 10.1 8.7 1.15 August 1971: S. paucispinis and S. mystmus Liver 156.0 84.0 10.3 5.7 1.78 A. fimbna Liver 38.0 84.2 12.9 3.9 4.45 January 1972: S. paucispinis Liver 17.0 78.5 15.5 6.0 2.58 S. paucispinis Flesh .20 81.4 12.7 5.9 2.15 S. paucispinis Fat 115.0 78.8 16.1 5,1 3.15 August 1971: Bottom sample Mud 82.0 72.0 6.0 2.00 288 MacGREGOR: AMOUNT AND PROPORTIONS OF DDT Table 5. — Distribution ofp.p'DDE.p.p'DDD andp.p'DDT in various animals from southern California marine waters. Porpoises found dead on beach north of San Diego, various dates May 1970. Fishes and crustaceans taken in net haul in San Pedro Channel 4 August 1971. Organ tested Standard length (mm) Wet weight (g) Total DDT Percent as Species (ppm) DDE DDD DDT Porpoises: Lagenorhynchus obliquidens flesh 84. 92.0 2.3 5.7 Delphinus sp. flesh 208. 86.5 58 7.7 Delphinus sp flesh 31. 85.0 7.2 7.8 Delphinus sp. liver 44. 90.7 4.8 4.5 Delphinus sp. liver 300. 92.0 4.0 4.0 Delphinus sp. head oil 196. 898 2.6 7.6 Delphinus sp. blubber 497. 88.5 3.4 8.1 Fishes: Leuroglossus stilbius whole 84 5.20 .49 75.9 11.6 12.4 Melanostigma pammelas. eelpout whole 89 2.40 5.63 87.9 2.7 9.4 Argyropelecus sp.. hatchetflsh whole 30 .50 .09 49.5 7.6 42.9 Cyclothone acclinidens whole 48 .36 2.01 80.7 4.7 14.6 Cyclothone acclinidens whole 43 .37 .64 76.1 6.9 17.0 Cyclothone acclinidens whole 47 .39 2.46 83.2 5.9 10.9 Cyclothone acclinidens whole 38 .18 3.56 89.5 4.5 6.0 Cyclothone acclinidens whole 34 .15 1.55 84.9 8.5 6.6 Crustaceans: Gnathophausia gigas. pelagic mysid whole .42 .55 76.7 7.2 16.1 Sergestes sp. whole .64 4.38 85.1 6.1 8.8 Sergestes sp. whole .38 4.59 82.9 6.1 11.0 Nematoscelis sp.. euphauslld whole .019 .35 90.3 4.3 5.4 Nematoscelis sp.. euphauslld whole .043 .26 90.2 3.0 4.9 52% (26-81), DDD 20%, and DDT 28% of total DDT. Keith and Hunt (1966) list DDT content for samples of mammals, birds, and freshwater fishes taken throughout California. The proportion of DDE tends to be high in categories that include birds of prey and fish eating birds, but varies con- siderably in their other samples. In their warm- water fish samples and the fish eating birds, white pelican, western grebe, and common egret, DDD is unusually high. This may be because of the former use of DDD as a spray on some California lakes (Murphy and Chandler, 1948; Brydon, 1955; Hunt and Bischoff, 1960). Following the cessation of DDT dumping into the ocean off Los Angeles in 1970, a change oc- curred in the DDD:DDT ratios found in fish sam- ples. The five S. leucopsarus taken in April 1972 contained 79% DDE, 12% DDD, and 9% DDT. Each of the five specimens contained more DDD than DDT. In the period 1949-70, only 8 out of more than 500 S. leucopsarus tested contained more DDD than DDT. The five myctophids taken in April 1972 ranged from 40 to 50 mm SL, indicat- ing that most or all of their growth had taken place since dumping stopped in 1970. The shift in DDD:DDT ratios also appeared in some other species. The ratios in rockfishes and sablefish, Anoplopoma fimbria, taken in Santa Monica Bay in May 1970, indicated that DDT was more abundant than DDD while 15 and 20 mo later the reverse was true (Table 4, Figure 11). The pelagic crustaceans and fish taken in the midwater trawl in August 1971 (Table 5) did not show the increased DDD to DDT ratio as did the bottom fish taken at that time, or the five S. leucopsarus taken in April 1972. A mud sample taken in August 1971 (Table 4, Figure 12) about 3 nautical miles from the White Point sewer outfall contained about twice as much DDD as DDT. The work of Burnett (1971) on DDT residues in the sand crab along coastal California showed that the high ratios of DDD to DDT were a local condi- tion. Twelve samples taken in November 1970 and February 197 1 from eight stations on either side of the White Point sewer outfall between 33°22'N and 34°28'N contained more DDD than DDT in all but two samples. The 11 stations north and south of this area all contained less DDD than DDT. The four samples taken closest to the outfall averaged more than three times as much DDD as DDT. This shift in DDD:DDT ratios was undoubtedly caused by the deposits in the sewer system. CSDLAC cleaning operations started in De- cember 1970, and ended in July 1971. Although large quantities of these deposits were removed directly from the sewers, additional large quan- tities were moved through the system to the White 289 FISHERY BULLETIN; VOL. 72. NO. 2 RETENTION TIME IN MINUTES Figure 1 1. — Chromatogram of DDT analog standard and of a fat sample from Sebastes paucispinis taken in Santa Monica Bay 7 January 1972. p.p'DDE (98 ppm) is off scale. Following cessation of dumping of DDT wastes and flushing out of sewer lines in 1970, p.p'DDD (15 ppm) has exceeded p,p' DDT (6.1 ppm) in most fish specimens tested. Prior to cessation of dumping and flushing of sewer lines, DDT was almost always present in greater quantities than DDD. Point plant and out into the ocean. Sewer water from these deposits contained 48% DDD as op- posed to 2-6% in the original Montrose discharges, and although the total amount of DDT and its metabolites was much less than before April 1970, the total amount of DDD entering the ocean ap- peared to be several times greater than it had been before the dumping stopped in April. This would account for the increase in DDD in the myctophids taken in 1972 rather than the expected decrease indicated by the calculated line (Figure 10, Table 1). A mud sample taken from the ocean floor a few miles from the sewer outfall in July 1971, just after the sewer cleaning operations ceased con- tained 6%DDT, 82% DDE, and 12% DDD (Figure 12). This compares favorably with the myctophids taken in April 1972, 9:79:12, and the S. pauci- spinis fat samples (Figure 11) taken in January 1972, 5:79:16, and indicates that the fish reflect the values of these analogs in the environment fairly well. 8 9 10 RETENTION TIME IN MINUTES Figure 12. — Chromatogram of DDT analog standard and sample of mud from the ocean floor in the Los Angeles area taken in August 1971, 16 mo after most dumping of DDT wastes stopped. DDD greatly exceeds DDT. This may have resulted from the sewer cleaning operations, or it may have been the condition existing before and merely reflect what the biota can excrete more easily. In the Sebastes chromatogram (Figure 11), the o.p'DDE peak is within the limits of the right proportions top.p'DDE for it to be considered o.p'DDE. In the mud sample it is much too high and may be DDMU (a metabolite of DDD) which has the same reten- tion time on this column as o.p'DDE. The most noticeable difference between the pes- ticide metabolites in the fish (Figure 11) and the mud (Figure 12) were the two prominent peaks preceding p.p'DDE. The peak at the locus of o,p'DDE also may contain DDMU, a metabolite of DDD. The other peak could be a metabolite of Kelthane. However, several dozen additional mud samples tested subsequently did not contain these peaks except for expected amounts of o,p 'DDE. The mud sample (Figure 12) was run while we were experimenting with methods of determining pesticide content of the mud samples. The subse- quent samples were run after we had settled on a different method that gave maximum recovery of DDT, DDD, and DDE without special regard to other CHC. These subsequent mud samples yielded chromatograms almost identical with those offish and other biological samples from the same general area. 290 MacGREGOR: AMOUNT AND PROPORTIONS OF DDT There was also a large decrease between May 1970 and January 1972, in total pesticides in the fish taken in Santa Monica Bay (Table 4). The S. paucispinis taken in 1972 were smaller than those taken in 1970 which may account in part for the lower values. The five specimens taken in January 1972, averaged 312 mm total length. Phillips (1964) gives the total length of this species at age 2 as 267 mm and at age 3 as 343 mm. Thus, most of the growth of these specimens had taken place since dumping stopped. On land where soil has been subjected to DDT spraying for long periods of time, the situation is very different. In New York State vineyard soils (Kuhr, Davis and Taschenberg, 1972) the residues consisted of 73% DDT and 27% DDE after 24 yr of spraying with DDT. In Oregon (Kiigemagi and Terriere, 1972) samples of soil from one orchard contained 80%DDT, 17%DDE, and 3%DDD after 25 yr of spraying, while soil samples from another orchard in a different area contained 78% DDT, 14% DDE, and 8% DDD after 24 yr. Forests in New Brunswick, Canada (Yule, 1973) were sprayed heavily from 1956 to 1967 in which year spraying with DDT ceased. Many samples taken of soils in this area in 1968 contained 92% DDT and 8% DDE. Three years later a second sampling of the soils in the same locality contained 90% DDT and 10% DDE. DDD was present only in trace amounts in both sampling years. As a general rule soil samples from land areas that have been sprayed with DDT tend to contain a much higher proportion of DDT than DDE or DDD even after many years. This is not neces- sarily true of the fauna that inhabit the land un- less their contamination is the result of recent spraying. Keith and Hunt (1966) give examples of a number of species of mammals and birds in which the proportions of the three analogs vary greatly. Within some species of birds, which are more wide ranging than mammals, there seems to be remarkable uniformity in the proportions of the three analogs. Martin and Nickerson ( 1972 ) tested 125 10-bird samples of starlings from throughout the (48) United States. These samples averaged 91%DDE, 3% DDD, and 6% DDT. Although the total residues ranged from 0.05 to 15 ppm, in only two samples did the amount of DDD exceed DDT, and in only one did the amount of DDT exceed DDE. The proportions of the three analogs of DDT in the starlings is very similar to the proportions found in the fish taken in Santa Monica Bay in 1970 (Table 4), in the porpoises found dead on the beach in 1970, and the small fishes and inverte- brates taken off Los Angeles in the mid-water trawl in 1971 (Table 5). And, in fact, except in cases of recent contamination by DDT, most fauna have tended to approach these proportions in re- cent years. This is in spite of the fact that soil samples from areas of land that have long his- tories of spraying with DDT almost without excep- tion contain very high proportions of DDT. From this it would appear that the selective storage, metabolism, and excretion of DDT is somewhat similar for all animals. When investigators first became aware of the pesticide problem, methods of measuring residues were considerably less refined than they are at present, and few samples were run. Very little work has been done on preserved specimens from these earlier years. But, in view of the similarity in proportions of DDE and DDT in so many differ- ent species in recent years, it seems probable that the increase in DDE and the change in ratios of DDE and DDT inS. leucopsarus are descriptive of the general change in these analogs that has taken place in the earth's environment. There was no pattern discernible in the dis- tribution of Aroclor 1254. In 472 myctophid sam- ples taken between 1949 and 1966, the median values of Aroclor 1254 fluctuated around 0.17 ppm and showed no trend with time. Sixty-eight per- cent of the samples contained less than 0.25 ppm. The only indication of an areal relationship was that while the three stations closest to the White Point sewer outfall, and the city of Los Angeles (CalCOFI stations 87.35, 90.28, and 90.30) consti- tuted only 8% of the total samples, they accounted for 34% ( 12 out of 35) of the myctophids containing more than Ippm of Aroclor 1254. However, there were some samples taken 175-200 nautical miles offshore that contained more than 1 ppm, and there were others taken near shore in the Los Angeles area that contained none or traces only. These higher values could result from the myc- tophids ingesting nondigestible particles of man-made substances either while feeding or ac- cidentally while in the cod end of the plankton net. In the larger fish taken in the Los Angeles area, the high values of the DDT residues tend to mask the presence of Aroclor 1254. What might be re- corded as a trace amount could actually be a rather significant amount in view of the dilute 291 FISHERY BULLETIN: VOL. 72. NO. 2 solutions of sample used in such cases in order to keep the DDT residue recordings on scale. SUMMARY 1. Between 1949 and 1970, total DDT increased in the ocean off southern California. The major source of this insecticide apparently was wastes discharged into the Los Angeles County sewer system by a major manufacturer of DDT. 2. As measured in the myctophid fish, Steno- hrachius leucopsarus, p,p'DDT andp,p'DDD in- creased for several years until metabolism, excre- tion, and dispersion equalled input, at which point the content of these CHC stabilized in the fish. 3. The more persistent, less easily metabolized p,p'DDE continued to increase in S. leucopsarus throughout the time period under study. The amount ofp,p'DDE decreased with distance from the sewer outfall. 4. During the earlier years the abundance of the other analogs in decreasing order wasp.p'DDT, p,p'DDE, andp,p'DDD. During the later period through 1970, the more persistent p,p' DDE be- came more abundant than p,p 'DDT. Following cessation of dumping, in 1970,p,p'DDD became more abundant than p,p DDT in the myctophids and most of the other fish species tested. ACKNOWLEDGMENTS I am especially indebted to E. H. Ahlstrom for sacrificing part of his collection of the myctophid fish, S. leucopsarus, for the present study. Shirley Imsand donated the five myctophids taken in 1972 on the University of Southern California MV Vel- ero IV. Carol Talkington assisted in some of the analyses. I am indebted also to R. Lasker for his invaluable criticism and guidance in the prepara- tion of the paper and to V. McClure and W. Rommel for technical advice and assistance. This work was supported in part by NOAA, Office of Sea Grant, under grant #UCSD 2-35208 with the Institute of Marine Resources, University of California. LITERATURE CITED Brydon, H. W. 1955. The 1954 control treatment of the Clear Lake gnat Chaoborus astictopus D. & S., in Clear Lake, California. Proc. Pap., 23d Annu. Conf Calif Mosq. Control Assoc, p. 108-110. Burnett, R. 1971. DDT residues: Distribution of concentrations in Emerita analoga (Stimpson) along coastal California. Science (Wash., D.C.) 174:606-608. Butler, P. A. 1969. Pesticides in the sea. In F. E. Firth (editor). The encyclopedia of marine resources, p. 513-516. Van Nos- trand Reinhold Company, N.Y. Carry, C. W., and J. A. Redner. 1970. Pesticides and heavy metals. Progress Report, County Sanitation Districts of Los Angeles County, 51 p. Duke, T. W., and A. J. Wilson, Jr. 1971. Chlorinated hydrocarbons in livers of fishes from the Northeastern Pacific Ocean. Pestic. Monit. J. 5:228-232. Hunt, E. G., and A. I. Bischoff. 1960. Inimical effects on wildlife of periodic DDT applica- tions to Clear Lake. Calif. Fish Game 46:91-106. Jehl, J. R., Jr. 1970. Is thirty million years long enough? Pac. Discovery 23(l):16-23. Keith, J. O., and E. G. Hunt. 1966. Levels of insecticide residues in fish and wildlife in California. Trans. 31st North Am. Wildl. Nat. Resour. Conf., p. 150-177. Keith, J. O., L. A. Woods, Jr., and E. G. Hunt. 1970. Reproductive failure in brown pelicans on the Pacific coast. Trans. 35th North Am. Wildl. Nat. Resour. Conf., p. 56-63. KlIGEMAGI, U., AND L. C. TerRIERE. 1972. Persistence of DDT in orchard soils. Bull. Environ. Contam. Toxicol. 7:348-352. KuHR, R. J., A. C. Davis, and E. F. Taschenberg. 1972. DDT residues in a vineyard soil after 24 years of exposure. Bull. Environ. Contam. Toxicol. 8:329-333. Lamont, T. G., G. E. Bagley, and W. L. Reichel. 1970. Residues of o,p'-DDD and o,p'-DDT in brown pelican eggs and mallard ducks. Bull. Environ. Contam. Toxicol. 5:231-236. Martin, W. E., and P. R. Nickerson. 1972. Organochlorine residues in starlings — 1970. Pestic. Monit. J. 6:33-40. McClure, V. E. 1972. Precisely deactivated adsorbents applied to the sep- aration of chlorinated hydrocarbons. J. Chromatogr. 70:168-170. Menzie, C. M. 1969. Metabolism of pesticides. U.S. Fish Wildl. Serv., Spec. Sci. Rep. Fish. 127, 487 p. Morgan, N. L. 1967. The identification and relative retention times of p,p'-Kelthane and its breakdown product p,p'-Dichlorobenzophenone using GLC. Bull. Environ. Contam. Toxicol. 2:306-313. Murphy, G. I., and H. P. Chandler, 1948. The effects of TDE on fish and on the plankton and literal fauna in lower Blue Lake, Lake County, California. Calif. Fish Game, Inland Fish. Admin. Rep. 48. O'Brien, R. D. 1967. Insecticides. Action and metabolism. Academic Press, N.Y., 332 p. Phillips, J.B. 1964. Life history studies on ten species of rockfish (genus Sebastodes). Calif. Dep. Fish Game, Fish Bull. 126, 70 p. Redner, J. A., and K. Payne. 1971. Chlorinated hydrocarbons. Progress Report, County 292 MacGREGOR: AMOUNT AND PROPORTIONS OF DDT Sanitation Districts of Los Angeles County, 77 p. RiSEBROuGH, R. W., D. B. Menzel, D. J. Martin, and H. S. Olcott. 1967. DDT residues in Pacific sea birds: A persistent insec- ticide in marine food chains. Nature (Lond.) 216:589-590. RisEBROUGH, R. W., P. Reiche, D. B. Peakall, S. G. Herman, AND M. N. KiRVEN. 1968. Polychlorinated biphenyls in the global ecosystem. Nature (Lond.) 220:1098-1102. Stout, V. F. 1968. Pesticide levels in fish of the northeast Pacific. Bull. Environ. Contam. Toxicol. 3:240-246. 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. Yule, W. N. 1973. Intensive studies ofDDT residues in forest soil. Bull. Environ. Contam. Toxicol. 9:57-64. 293 QUANTITATIVE NATURAL HISTORY OF PLEUROBRACHIA BACH EI IN LA JOLLA BIGHT Jed Hirota' ABSTRACT An assessment of the quantitative natural history oi Pleurobrachia bachei A. Agassiz was made by estimating growth rates, metabolic rates, distribution, abundance, occurrence of prey, predators and parasites, population parameters, and net production. These were then integrated to give an indica- tion of the ecological significance of this animal in the plankton. Rates of somatic growth and digestion of prey were observed in laboratory experiments and applied to field data. A comparison of growth curves of P. bachei at 20° and 15°C showed development rates from hatching to the same diameter which were 10-15 days faster at 20°C. In addition, a much higher mortality of the ctenophores was observed at 20°C. Maximum growth rate coefficients on a daily basis were 0.21-0.47 and were for 2.5- to 6.5-mm ctenophores (0.1-2 mg bodily organic weight). Studies on the rates of digestion of six frequently ingested prey species by various sizes of P. bachei showed marked differences between species. Although Labidocera was the largest prey offered, it was di- gested the fastest per unit weight. The horizontal, offshore distribution of P. bachei postlarvae often showed maxima within 5 km from the shore and decreased about tenfold by 10 km. Patterns of water movement in La Jolla Bight were described as a prerequisite to the distributional studies. The near-surface current velocities showed counterclockwise rotational motion over the submarine canyon complex of La Jolla Bay; otherwise the water generally moved onshore and towards the north at speeds of about 5 km/ day. The high abundances of the animal nearshore are believed to be caused in part by these water move- ments. The ctenophores occurred in the upper 50-60 m, living mostly in the upi>er 15 m in the day and at about 30 m at night. The range of average abundances of postlarvae was from 1,000/m^ and 1,000 mg organic matter/m^ in August to being nearly absent in December. Hyperoche mediterranea, a parasitic amphifwd, and Beroe sp., a potential predator, showed pat- terns in seasonal abundance similar to that of P. bachei postlarvae, except that H. mediterranea was absent in winter and spring. The higher frequency of occurrence of endoparasites with larger sized hosts and few multiple infections suggests that the parasites are adapted to prevent overexploitation of hosts. The stomach contents of postlarvae showed a pattern of larger prey in larger ctenophores, and within some prey sp>ecies increasing frequency of occurrence in larger ctenophores was observed, e.g., Acartia tonsa. The diel emd seasonal variations in stomach contents were also considered. Prey selection by P. bachei may be determined by the following attributes of prey: density, size, avoidance and escapement behavior, strength and protective spination. Size-specific instantaneous mortality rates, the mean schedule of live births, and somatic growth rates were used to estimate population parameters and compute rates of net production. The highest rate of population growth was 0.02 on a per day basis, which would enable a population doubling in about 35 days. The first 50-100 eggs laid by young postlarvae are most important to replace the population. The mean and range of annual net production by postlarval P. bachei are 5.24 and 2.32-7.65 g organic matter per square meter; mean values for eggs and larvae are 0.08 and 0. 10 g/m*, respectively. The mean annual net production of all stages is 5.4 g/m^, with 95% confidence limits for the mean being 4.4-6.5 g/m^. The ecological significance and functional role of P. bachei are as: Da seasonally dominant carnivorous zooplankter which preys selectively on small crustaceans and may regulate their abun- dances; 2) a vehicle which provides shelter and nutrition for parasites and; 3) an organism which transfers a substantial amount of organic matter and potential energy in the food web of La Jolla Bight. Ecological studies may be grouped into four species populations, 3) communities, and 4) categories, depending on the level of complexity ecosystems. The long-term objective in ecology is being considered: 1) single individuals, 2) single the description of ecosystems. More specifically, two important objectives in studies of ecosystems are: the elucidation of complex interactions be- 'Scripps Insti^tution of Oceanography Institute of Marine Re- tween species in a food web and the understanding sources. La Jolla, CA 92037; present address University of ^ Hawaii, Institute of Marine Biology, Kaneohe, HI 96744. and prediction of the dynamic processes that OCCUr Manuscript accepted September 1973. FISHERY BULLETIN: VOL. 72. NO. 2. 1974. 295 FISHERY BULLETIN: VOL. 72, NO. 2 in this web. To obtain this information, one ap- proach is the investigation of basic trophic rela- tionships among the various developmental stages of different species in the food web (e.g. for herring, Hardy, 1924) and the quantitative mea- surement of matter or energy transferred along these paths (e.g., for a lake, Lindeman, 1942). From the four categories of complexity I chose to study Pleurobrachia bachei A. Agassiz at the single species population level. I have attempted to integrate three basic aspects of the population ecology oi Pleurobrachia into a study of its quan- titative natural history: 1) the structure of its food web, 2) the population parameters and attributes which most affect the population growth rate, and 3) the trophic-dynamic aspect of the quantitative transfer of organic matter. In previous work (Hirota, 1972) the culture and metabolism of P. bachei have been described. Studies on the trophic-dynamics of marine planktonic food webs have concentrated on the measurement of primary production and the fac- tors which influence its level. MuUin (1969) sug- gested that similar production studies of total zoo- plankton or of single species are few, because no simple, direct methods exist for the measurement of secondary production in situ. He stated that two basic approaches exist for these studies: the laboratory "carbon balance" study and the popula- tion dynamics approach. A somewhat more direct measurement could be made as a modification of the approach used in lakes by Haney (1971). In situ population feeding rates (measured using food particles labeled with isotopes) multiplied by the population gross growth efficiency is the rate of net production. This method has the advantages of being more direct and made in nature, but it is impractical for complex marine plankton com- munities with their numerous and relatively large, mobile species. It also requires detailed knowledge of factors which affect gross growth efficiency. Most marine planktonic species are not amena- ble to culture in the laboratory for entire life cy- cles, and results of laboratory experiments may fail to represent accurately activity in nature. Present field sampling techniques and variability in plankton studies are often such that it is neither possible to obtain sequential samples from the same target population nor calculate the rates of biological activity. In spite of these difficulties and such severe limitations (Hall, 1964), more and better data are needed in different ecosystems from their functionally distinct component species before a clear understanding of the structure and dynamics of food webs is obtained and generaliza- tions of predictive nature concerning the systems can be made. Studies on the population dynamics and produc- tion of marine zooplankton (reviews by Mann, 1969 and Mullin, 1969) almost exclusively pertain to "herbivorous" calanoid copepods. At present lit- tle information exists on the production rates of carnivorous marine zooplankters (McLaren, 1969; Petipa, Pavlova, and Mironov, 1970; Sameoto, 1971), and the study of Sergestes lucens (Omori, 1969) is one with the supportive catch data of a commercial fishery. The lack of data for higher trophic levels is in part the result of an inability to culture and maintain delicate or large, mobile forms. Nearly all laboratory data on the long-term metabolism and life cycles of zooplank- ton species come from successful rearing of one or more generations of facultative herbivorous copepods (see Hirota, 1972 for references). Hamil- ton and Preslan (1970) and Gold (1971) have cul- tured ciliate protozoans. The genus Pleurobrachia (Tentaculata, Cydip- pida) includes about 12 species (see Ralph and Kaberry, 1950 for the most recent summary of the species), some of which may be synonymous. The current taxonomic status of the synonymies in this genus is uncertain, because there are few sets of general characteristics which have been set up as important for the separation of species. In par- ticular, some possibly distinct species have been grouped with the boreal species P. pileus O. Miiller of the North Atlantic. One of these, P. bachei, is the boreal form which inhabits the Pacific coast of North America from Puget Sound to San Diego. This species is believed synonymous with P. pileus, based on the works of Moser (1909) and Mayer (1912). However, I agree with Torrey (1904), Bigelow (1912), and Esterly (1914) thatP. bachei is a distinct and separate species. This dis- tinction is supported by work in progress on the differences between these two forms in both meristic and metric characters (Hirota and Greve, unpubl. data). Studies of spatial distribution, vertical migra- tion, seasonal variations in numerical abun- dance, and natural history in the planktonic ctenophores have provided some data on natural populations, but information on population dynamics and rates of production are especially needed. Patterns of the geographic distribution of 296 HIROTA: NATURAL HISTORY OF PLEUROBRACHIA BACHEI IN LA JOLLA BIGHT Pleurobrachia species and other ctenophores have been described (Moser, 1909; Mayer, 1912), but no attempt was made to relate abundance quantitatively to geographic location. Only a few workers have studied vertical distribution of ctenophores (Esterly, 1914; Russell, 1927; Alvarino, 1967; Rowe, 1971) and only the study of P. pileus in Kaneohe Bay, Oahu (Rowe, 1971) could show that diel vertical migration occurs. Pleurobrachia pileus in Kaneohe Bay follow the "normal" pattern for zooplankton with the ctenophores living at depth during the day and moving up near the surface at night. However, the vertical displacement of the migrants was only on the order of 10 m because the bay is very shallow. More is known about quantitative sea- sonal changes in numerical abundance of P. pileus (Wear, 1965; Eraser, 1970; Greve, 1971) and P. bachei (Esterly, 1914; Parsons, LeBras- seur, and Barraclough, 1970). There are also numerous qualitative reports of ctenophore swarms in coastal waters (Chopra, 1960; Ra- jagopal, 1963; Eraser, 1970). Eraser (1962, 1970) reviewed the role of ctenophores and salps in marine food webs and their natural history. Greve (1970, 1972) provided laboratory studies of the effects of temperature, salinity, and food on growth of P. pileus and a field study (Greve, 1971) of variations in abundance of P. pileus and two of their predators, Bero'e gracilis and B. cucumis. These studies did not relate seasonal variations in abundance to rates of population re- cruitment, growth, mortality, net production, or advection. In order to describe the quantitative natural history of P. bachei as outlined above, it was necessary to sample natural populations and to carry out laboratory experiments. The field work was needed for data on the food web and for de- mographic purposes, and the laboratory data were used to calculate metabolic rates which could not be measured from field samples. Metabolic rates measured or calculated from in- dividuals reared from eggs to adults in the laboratory were applied to field populations. Pre- liminary field studies were then made of the var- iations in abundance of P. bachei as a function of distance from shore. The vertical distribution was determined by sampling with opening-closing bongo nets (McGowan and Brown, 1966^) while ^McGowan, J. A., and D. M. Brown. 1966. A new opening- closing paired zooplankton net. Scripps Inst. Oceanogr. Ref. 66-23. (Unpubl, Manuscr.) tracking parachute drogues in those locations where ctenophores were most abundant. Erom the data on water movement and the horizontal and vertical distributions of P. bachei, sampling stations and sample depths (the maximum depth to which a net sample is taken) were allocated for a study of spatial and seasonal variations in numerical abundance, standing stocks and net production. Size or stage-specific instantaneous mortality rates were calculated from the ob- served size-frequency distribution in field sam- ples and development rates calculated from laboratory growth data. Standing stocks per unit area of sea surface were calculated as the sum- mation of the organic weight (ash-free dry weight) of all individuals in a sample multiplied by the ratio of maximum sample depth to the vol- ume of water filtered. The organic weights were estimated from regression equations of bodily weight on bodily diameter. Rates of net produc- tion per 24-h day were calculated from the esti- mated standing stocks of each stage and the stage-specific instantaneous rates of mortality and growth on a daily basis. Eor a given set of stage-specific instantaneous mortality rates, and using the mean schedule of live births derived from laboratory data, the following population parameters were calculated: T, r, d, b, Cx which are the generation time, instantaneous rate of natural increase, death and birth rates, and sta- ble age distribution, respectively. More than 12,000 specimens of P. bachei were counted and measured during the seasonal study, of which 1,352 postlarvae in 10 size classes contained par- tially digested food organisms and 1,007 postlar- vae contained internal parasites of the hyperiid amphipod, Hyperoche mediterranea. Attempts were made to quantify changes in the absolute numbers and the proportions of various prey categories with changes in bodily size of P. bachei. A study of the seasonal variation in num- bers of parasites, percent hosts parasitized, and the frequency distribution of numbers of para- sites per host and percent hosts parasitized at dif- ferent host sizes is also presented. GROWTH IN CULTURE AND METABOLIC RATES Methods Techniques for the laboratory culture of P. bachei at 15°C have been described previously 297 FISHERY BULLETIN: VOL. 72, NO. 2 (Hirota, 1972); culturing has also been done at 20°C to examine the effect of temperature on growth rates. The rates at which different prey species were digested were measured in the laboratory in order to make corrections for preda- tion by P. bachei on the most abundant crusta- ceans during field sampling with nets (Judkins and Fleminger, 1972, discuss feeding by Sergestes in nets). Six ctenophores were cultured from eggs at 20'^C and about 20 /.(g C/liter as prey for the adult ctenophores in order to evaluate the effect of temperature on growth rate (the surface tempera- ture in summer is about 20°C). The basic tech- niques were the same as described previously (Hirota, 1972, Table 1), except that adult Paracalanus parvus replaced Artemia nauplii as food for 2- to 3-mm ctenophores. In this manner, it was possible to raise ctenophores without "arti- ficial" foods of any kind and instead raise them on prey species which they utilize in nature. In addi- tion, antibiotics (streptomycin sulfate and penicil- lin G each at concentrations of 50 mg/liter) were added after 4 wk of culturing at 20°C when several specimens appeared very weak or moribund. When changes in bodily diameter indicated that the last two specimens might also die, the experi- mental temperature was changed back to 15°C to determine whether or not recovery might occur and whether the mortality effect was due to lethal temperature. In order to determine whether or not a prey spe- cies found in the gut of Pleurobrachia sampled with nets was eaten prior to or during capture, a number of observations were made of the rate at which five prey species were ingested and digested after initial entanglement with the tentacles. The time elapsed to achieve one of four scores was recorded during observations with a dissecting microscope through the transparent bodily wall of the ctenophore. These scores are: (4) the prey en- ters the mouth and is in the distal half of the stomach; (3) the prey is moved into the proximal half of the stomach but no digestion of the prey is indicated; (2) the prey is being digested and as- similated, as indicated by less than 10% of the bodily tissues clearing and the occurrence of prey tissues in the aboral, transverse, and pharyngeal canals; (1) the prey is almost fully digested and assimilated, as indicated by transparent skeletal remains (crustacean exoskeletons are not di- gested) and the presence of digested tissues throughout the canal network. The elapsed time to achieve a given score was then compared to the maximum time period a prey organism was at risk in the net sample with the ctenophores. This time period is the elapsed time from the start of the tow until preservative was added to the sample jar. Those prey found in the ctenophore stomachs whose score required more time than the max- imum period at risk are presumed to have been eaten in nature prior to capture by the net. Results and Discussion The growth curve of bodily diameter up to 6 mm at 20°C indicates similar patterns as is the case for 15°C (Hirota, 1972, Figure 1), except that the de- velopment rates to the same bodily diameter are 10-15 days faster at 20°C (Figure 1). The other important differences are: 1) very much higher mortality rates at 20°C than at 15°C, 2) 60% mor- tality despite the addition of antibiotics on day 29, and 3) the recovery and prolonged growth and sur- vival of two specimens after the temperature was lowered to 15°C from 20°C when growth had ceased at 20°C. Note that there is a lag of over a week before the apparent effect of lowered tem- perature is indicated by a response in bodily diam- eter. The significance of the effect of temperature on growth rate will be discussed below. in relation to the stratification of water temperature in na- ture, the diel vertical distribution of the ctenophores, and the effect of these distributions on seasonality in the standing stocks and net pro- duction of the ctenophores. Using the data for growth in bodily diameter at 15°C (Hirota, 1972, Figure 1), it is possible to cal- culate rates of growth in bodily organic weight from regressions of organic weight on bodily diameter (Figure 2). A curve for the mean growth in organic weight and the ranges for weight at a given age and age at a given weight are shown in Figure 3. The mean growth rates are highest from 0.1 to 2 mg (2.5 and 6.5 mm diameter, respec- tively); the exponential growth rate coefficients on a daily basis are 0.21-0.47. Below 0.1 mg and over 2 mg the exponential growth rates are slower, the values being 0.12-0.17 and 0.04-0.17, respec- tively. The range for weight at a given age is about tenfold and for age at a given weight about 15 days. The rates of digestion of five prey species are shown in Table 1. These data show that undi- gested prey present in ctenophore stomachs (scores 4 and 3) can be ingested during a 0.3- to 298 HIROTA: NATURAL HISTORY OF PLEUROBRACHIA BACHEI IN LA JOLLA BIGHT 10 e E or UJ < 10 20 30 40 50 60 DAYS AFTER HATCHING Figure 1. — Growth in bodily diameter o{ Pleurobrachia bachei at 20°C, expressed as a function of age in days. Each symbol represents measurements of a different individual. The point indicated by AB refers to the starting date with antibiotic addi- tions and the points indicated by 15°C refer to change of the experimental temperature from a constant 20°C to a constant 15°C. All ctenophores died after the last observation shown for each individual, except that one which was still alive after 80 days. 5-min period at risk while both the predator and prey are being sampled by nets. Partial or fully digested states (scores 2 and 1), however, required more than 9 and 15 min, respectively. Prey of scores 2 and 1 in ctenophore stomachs are, there- fore, very likely to have been ingested by ctenophores prior to capture by nets in samples of short duration (i.e., less than 5 min). Only prey of these scores were used in the study of stomach analyses presented below, unless the prey were too small to be retained by the 0.363-mm meshes of the net and, therefore, were not at risk to preda- tion during the sampling. Examples of these smal- ler prey species not at risk are nauplii of Acartia and all stages of Euterpina acutifrons, a copepod of 0.7 mm length. Measurements of the organic weight of six species of "important" planktonic marine crusta- ceans in La Jolla Bight are given in Table 2. The first four species are copepods and the remainder are cladocerans. Note that for adults, Labidocera is tenfold larger than Acartia and Evadne and about twentyfold larger than Paracalanus, Corycaeus, and Penilia. A trend exists in the data for scores 2 and 1 when the respective medians for the elapsed time to achieve these scores are expressed per unit bodily organic weight for each prey species (Table 1). Labidocera trispinosa is the most easily digested prey per unit bodily mass although it is the largest. Acartia is digested slightly faster than e I- X UJ < CI (T O luvj - I Mill III 1 1 1 1 1 iii{ — r 1 M 1 iiri 10 — / 1 w 3.2IID -2.386- -f - oA 0.1 z ^ 9n 0.01 — / / 0.001 '-/ / /L -W = 1,9400 - i.eio - 0.0001 J — I I I 1 1 III 1 I I I 1 1 III I I I I III 0.1 0.5 I 5 10 DIAMETER IN mm 50 100 Figure 2. — The relationship between bodily organic weight and bodily diameter of P. bachei on a double logarithmic scale. The open circles represent data on field-collected ctenophores from La Jolla, Calif; the triangles represent data on laboratory cul- tured ctenophores; and the diamonds and squares represent data on ctenophores grown in the deep tank facility at Scripps Institu- tion during experiments 1 and 2, respectively. The lowest four values are calculated from determinations of organic carbon. In the equations the upper line is for ctenophores larger than 3 mm and the lower line for those smaller than 3 mm. In both equations W = log 10 (bodily organic weight in milligrams) and£> = logio (bodily diameter in millimeters). Paracalanus and each of these faster than either Corycaeus or Penilia. Part of the cause for the delay in digestion of Corycaeus and Penilia relative to the above-mentioned calanoid copepods is the protective spination. In addition to stout furcal spines, caudal rami, and very sharp projecting corners of the last thoracic joint, Corycaeus has a large, smooth cephalothorax which encloses much of the bodily tissues and may retard penetration of digestive enzymes. The spi- 299 FISHERY BULLETIN: VOL. 72. NO. 2 nation causes great difficulty for the movement of this prey into the proximal half of the gut where digestion occurs. For example, the median time for score 3 of Acartia is significantly shorter than the corresponding median ofCorycaeus as determined by a [/-test rP<0.05). Similarly, the rigid bifur- cate rostrum, caudal spines, and denticulate carapace oiPenilia are often hooked into the gut wall of the ctenophore and delay passage of the prey to the site of digestion. Contrary to this delay in the passage ofCorycaeus and Penilia, the rela- tively smooth-bodied calanoids are translocated quite easily by peristalsis of the gut. More detailed studies might indicate differences in the integu- ment to penetration by the digestive enzymes or perhaps differences in the specificity of the en- zymes for protein or lipid components of the sub- strate. FIELD ECOLOGY OF P. BACHEI Study Area and Previous Plankton Work The study location is La Jolla Bight (long. 117'20'W, lat. 33'N), including the coastal waters (hereafter coastal waters refers to that area bounded by the shoreline and a line parallel to it out to a distance of about 8 km) south to Point Loma and north to Oceanside (Figure 4). The major physiographic features of the area are: 1) Point La Jolla, which extends about 2 km west of the shoreline at Scripps Institution and forms the southern boundary of La Jolla Bight; 2) two sub- marine canyons (La Jolla and Scripps Canyons) in La Jolla Bight which bring water over 100 m deep within 2 km of shore; 3) numerous kelp beds lo- cated both north and south of Point La Jolla gen- erally in 10- to 20-m depth and extending out to 1 km from shore. The area is not strongly influenced by precipitation and runoff, so that seasonal and annual variations in salinity are within 32-34 Vco (Fager, 1968). The range of sea-surface tempera- ture is 14-2 IX annually and approximates the temperature difference between the surface and 50 m in July (Mullin and Brooks, 1967). The tides are of a mixed semidiurnal type with a diurnal inequality and total daily range that change twice each month. Within a given month the maximum daily tidal range is about 2 m and the minimum about 1 m. Wind velocities are highly variable; storms with wind speeds greater than about 7 m/s generally come from the southwest to the north- west quadrant. Santa Ana winds blow occasion- en £ X < tr o V 0.01 - Q O CD 0.0001 0.001 - 10 20 30 40 50 60 70 DAYS AFTER HATCHING 80 90 100 Figure 3. — Growth in bodily organic weight of Pleurobrachia bachei at 15°C during the second laboratory generation, expres- sed as a function of age in days. The values for bodily organic weight at different ages were calculated from the observed growth in diameter and a regression of organic weight on diame- ter. The horizontal and vertical bars indicate the ranges for age at weight and weight at age, and the numbers in parentheses are the number of specimens observed in the data. ally from the northeast in fall, and diel variations in wind velocities predominate in the east-west directions. Previous plankton work in the study area in- clude the extensive phytoplankton work of Allen (1928, 1941), the California Cooperative Oceanic Fisheries Investigations programs, and the plank- ton study off La Jolla by the Food Chain Research Group (Strickland, 1970). In general these previ- ous studies provide basic information on species lists and levels of abundance and variability of phytoplankton, microzooplankton, and macrozoo- plankton. In these coastal waters, however, very little information is available on the patterns of water circulation, variations in abundance of or- ganisms in relation to variations in the physical parameters (e.g., tidal motion, wind velocities etc.), or the organization and interaction of the species which inhabit this coastal region. 300 HIROTA: NATURAL HISTORY OF PLEUROBRACHIA BACHEI IN LA JOLLA BIGHT Table 1. — Rate of digestion experiments at 20°C for individual adults of five prey species and various sizes of Pleurobrachia bachei. Medians and ranges are given for the diameters of the ctenophores used in the trials and for the elapsed time in minutes from the prey entanglement with the tentacles until each score of digestion is achieved. The values in parentheses are the medians for the elapsed time to achieve scores 2 and 1 divided by the bodily organic weight of each respective prey. Refer to the Methods for details. Diameter (mm) Md 10.9 W 7.6-12.4 Md 6.4 W 2.0-11.7 Md 7.2 W 2.0-11.7 Md 7.5 W 4.0-10.3 Md 8.0 W 5.4-12.0 Prey Trials Labidocera trispinosa Acartia tonsa Paracalanus parvus Corycaeus anglicus Penilia avirostris 12 Score of digestion 4 3 2 1 1.00 2.67 20 46 0.42-2.84 1.58-8.50 14.5-35 37->60 (0.23) (0.53) 0.50 1 83 15 25 0.25-1.50 0.92-3.00 10-29 18-45 (2.08) (3.47) 1.00 2.29 12 21 0.25-2.00 1.00-6.00 9-27 15-37 (3.16) (5.53) 0.33 3.0 16 30 0.04-1.50 1.0-6.0 9->35 18-37 (5.3) (10.0) 1.83 4.8 >40 0.42-2.84 0.83->9 21->50 — (10.1) — Table 2. — The mean and range of organic weight of six prey species of Pleurobrachia bachei. F, M, A, CV, and J refer to females, males, adults, fifth copepodids and juveniles, respec- tively. Prey category Mean Range (mq) (uq) Number of observations Labidocera trispinosa F M CV 88 85-94 86 83-89 29 - 3 2 1 Acartia tonsa A 7.2 6.2-7.9 8 Paracalanus pan/us A 3.8 3.7-3.8 2 Corycaeus anglicus F M 2.2 — 3.4 3.0-3.5 1 3 Penilia avirostris A J 3.6 3.3-4.0 1.2 1.1-1.2 3 2 Evadne tergestina A 74 6.8-8.2 3 Methods The three main physical parameters considered in the course of the field studies are current veloc- ity, water temperature, and tidal stage. Current velocities in La Jolla Bight were measured on five , occasions between November 1969 and June 1970 by tracking surface floats attached to parachute and "vane" drogues (vane drogues were made of Figure 4. — The study area: La Jolla Bight and ac^jacent waters. Sampling stations 1-5 and 6 are located 1.6 and 10 km offshore, respectively. The juncture of Scripps Canyon with La Jolla Can- yon is near station 5. The depth contours are in fathoms. 301 FISHERY BULLETIN: VOL. 72, NO. 2 parachute silk attached to a wooden frame, creat- ing three intersecting planes normal to each other; each plane covers about 9 m^) set at depths in or near the thermocline (about 15-m depth). During the field studies surface temperatures were measured by bucket thermometer to the nearest 0.1°C, and the vertical distribution of temperature was measured by mechanical bathythermograph (BT) or salinity-temper- ature-depth recorder (STD). Tidal heights for the time of particular events are taken from tide cal- endars for predicted tides by the U.S. Coast and Geodetic Survey for La JoUa. For studies of the offshore and seasonal dis- tributions of P. bachei two types of nets were used. The net to collect postlarval ctenophores (i.e., ctenophores larger than 0.5 mm in diameter) is a ring net of 0.5 m diameter and 0.363-mm mesh apertures. This net was used for oblique sampling. The second net is a 0.17-m diameter ring net of 0.035-mm mesh apertures equipped with a 20-cm metal collar that attaches the net onto the wire. This net was towed vertically, and it was used for sampling the eggs and larvae of Pleurobrachia and the smaller zooplankters which were available as prey but not sampled quantitatively by the 0.363-mesh net. Both nets were equipped with a calibrated TSK (Tsurumi- Seiki Kosakusho) flowmeter^ to measure volumes of water filtered. Two studies of the vertical distribution of P. bachei were made, the first during 3-6 November 1969 and the second during 22 May-1 June 1970. In both cases, 0.7-m diameter paired, opening-closing bongo nets with mesh apertures of 0.053 and 0.153 mm were used. In each vertical profile of abundance, four to six depth intervals were sampled at 10- to 20-m intervals for shal- low depths and at greater intervals below 50 m. Thus, a set of four to six pairs of samples com- prised each vertical profile. The volumes of water filtered were between 5 and 50 m^, as determined from calibrations of numerical settings on the net release gear against the calculated cubic meters of water filtered using a TSK flowmeter. In all cases net samples were preserved with 10 ml of 40% formaldehyde solution, buffered with calcium carbonate, in about 750 ml of seawater. This solution is about 0.5% formaldehyde. Pre- liminary experiments with preservation of Pleurobrachia showed this to be the best concen- tration and type of preservative. Relatively small changes occur in length frequencies of P. bachei after 27 mo in this preservative (Table 3). A preliminary survey of the horizontal, offshore distribution (the distribution of numerical abun- dance of Pleurobrachia in samples taken at in- creasing distances from the shore) was made on 28 August 1969. Samples were taken at 10 stations with closely spaced intervals out to 11 km from shore off Scripps Institution. Results of this study showed that the ctenophores occurred in highest abundances within 3 km of shore. Samples were taken in the following manner during the two field studies of the vertical and offshore distributions of P. bachei mentioned above. In both studies of vertical distributions, about 10 sets of four to six pairs of samples were taken alongside or between parachute and vane drogues. Each sample set permitted the descrip- tion of abundances at various depth intervals for one time of the day. In the study of November 1969 the offshore distribution sampling consisted of six transects of stations perpendicular to shore. The transects were about 3-8 km apart, beginning off Del Mar and ending off Point Loma. Each transect consisted of three or more stations located between 1 and 13 km from shore. In the second study the offshore distribution sampling consisted of two transects of seven and nine stations out to 50 km from shore. In all offshore distribution studies rep- licate samples were taken at each station except in five cases where time prohibited it or second samples were lost. Table 3. — Changes in size-frequency distribution of Pleuro- brachia with duration in 2% Formalin-seawater preservative. Samples A and B were analyzed 16 and 12 days after sampling, respectively, and a second time after 27 months as indicated in columns A' and B'. The variable indicated is the number of occurrences of each size class. One specimen in sample A was lost. 'Reference to trade names does not imply endorsement by the National Marine Fisheries Service. Mean diameter A a' B B' (mm) '/) 0 0 1 0 1 10 10 64 69 2 28 24 28 28 3 23 23 17 15 4 12 11 3 1 5 5 4 1 2 6 11 14 4 3 7 5 6 1 3 8 6 8 2 0 9 2 1 1 1 10 2 2 2 2 11 0 4 0 0 12 5 1 0 0 13 2 2 0 0 302 HIROTA: NATURAL HISTORY OF PLEUROBRACHIA BACHEl IN LA JOLLA BIGHT From 8 March to 1 May 1970 sampling for the seasonal variations in the coastal plankton was done at stations located between Del Mar and Scripps Institution 1-3 km from shore. Results of the study of current velocities during 22 May to 1 June 1970 indicated that the plankton were ad- vected northward on the order of tens of kilome- ters per week. Therefore from 18 June 1970 to 2 June 1971 the sampling stations for seasonal vari- ations in the coastal plankton were changed to those six stations in Figure 4. Five stations are located 1.6 km from shore about 8 km apart be- tween Oceanside and Scripps Institution, and the sixth station is located about 8 km beyond the station off Scripps. Replicate samples were taken at stations 1-5 with each of the two kinds of ring nets described above. Samples with only the 0.363-mm mesh net were taken at station 6. Analysis of the 0.363-mm mesh net samples, as described below, was carried out on samples at all stations from 8 March through 29 August 1970 (this period includes the seasonal maximum in abundance). From 29 August 1970 to 2 June 1971 mainly samples from stations 1, 3, 5, and 6 were analyzed once it became apparent that the varia- tions between the five stations parallel to shore could be about as well accounted for by variations at stations 1, 3, and 5. Samples were taken on two occasions for special studies related to the diel variation in predation by Pleurobrachia, their stomach contents in net tows of short duration and their selectivity of prey species with which they co-occur. During a field study from 23 to 27 July 1971, five sets of tripli- , cate samples were taken with the 0.5-m net of 0.363-mm mesh in the upper 50 m off Del Mar. Three of these sets were taken at midnight and two sets at midday. All samples were sorted and counted as described below. The ctenophores were measured and the stomach contents identified to determine whether diel variations exist in: 1) the proportion of ctenophores which contain prey and 2) the numbers and kinds of prey which occur in stomachs during the day and at night. This study is important because all other information about the stomach contents of P. bachei during the sea- sonal study were derived entirely from samples taken between 0900 and 1600 h. On 25 August 1970 a pair of samples was taken at the surface with the 0.363-mm mesh net on station 5 at 1500 h. The tows were for 60 s duration and the maximum period which prey were at risk is 95 s. Samples were sorted and counted and the stomach contents of ctenophores identified for: 1) compari- son of these prey species to other data from field samples of longer sample durations and periods at risk, and 2) calculations of the electivity indices of prey on a numerical and organic weight basis. Counts were made of all zooplankters in 2.5% sub- samples of each net tow, and the proportions of prey in stomachs and in the net samples were used to calculate electivity indices (Ivlev, 1961). Whole samples of each of two replicates per sta- tion taken with the 0.363-mm mesh net were sorted at 6-12x magnification under a dissecting microscope, and all postlarval ctenophores were counted and measured in polar diameter with an ocular micrometer. These procedures apply to all field samples taken for the offshore distribution, seasonal distribution, and special sets of samples taken for the analysis of diel variations in feeding and prey selectivities. For the sets of samples taken during the seasonal study, postlarvae of one or the other replicate sample selected at random were dissected and the contents of stomachs iden- tified and given one of four scores described above. All specimens were examined if there were less than about 100/sample, but during a few periods of high abundances subsamples of about 50 speci- mens were taken. For each of 30 sampling dates between 8 March 1970 and 2 June 1971, data on stomach contents of about 100 specimens were obtained, except on those dates with very few specimens captured in all samples lumped to- gether. For these same ctenophores which were measured and dissected, counts were also made of the numbers of larval and early juvenile stages of the facultative endoparastic amphipod, H. mediterranea. Also enumerated in these samples of the seasonal study were the numbers of adult and late juvenile//, mediterranea, which were not attached to ctenophores, and the numbers of Bero'e sp. Each replicate sample of the eggs and larvae of P. bachei taken at station 5 with the 0.035 mm mesh net was concentrated to 400 ml by settling overnight, siphoning off the excess water and transferring it to a graduated cylinder. Each of two subsamples of 20 ml was removed by Stempel pipet, examined under 12-25x magnification and the numbers of eggs and lar- vae counted. Numbers per square meter of sea surface were calculated as ten times the total numbers in both subsamples times the ratio of the sample depth in meters to the volume of water filtered in cubic meters. 303 iiT'ig 32"'56 FISHERY BULLETIN: VOL. 72, NO. 2 II7°I7' 15' Date Time Height, cm 3 1630 134 2324 2 1 0606 146 1200 67 1730 137 2354 21 0630 159 1236 46 1818 140 0018 24 0648 175 1306 21 1906 143 32° 52 32° 52 117° 19 32° 56 - 54 52 50 II7°I9 Figure 5. — Trajectories of two drogues during the field study of 3-6 November 1969. Observed positions of the drogues are indicated by the open circles, and the date and time of the triangulation are indicated by the one-four digit sequence of numbers near the circles. The date and predicted times (Pacific standard time) and heights of tides in centimeters are given in the inset. Estimates of the standing stocks of food avail- able to P. bachei were obtained from counts of prey taxa in subsamples of the 0.035-mm mesh net samples at station 3, the centrally located station (Figure 4). These pairs of replicate samples were treated in a manner similar to the counts of ctenophore eggs and larvae, except that counts of all zooplankters were made in a 5-ml subsample of a 500-ml sample. Over 100 specimens were counted in each subsample. The counts of numbers were converted to mass of organic carbon using the data from six species (Table 2) which fre- quently occur in these waters, data in the litera- ture, and approximations by proportions of body volumes relative to the known mass of species for which data exist. Counts of ctenophores in samples for vertical distribution studies were made as follows. First, all large ctenophores which could be seen by the unaided eye were removed with pipets from one of the pair of bongo net samples selected at random. When no further specimens could be found by eye, subsamples of 5-12.5% of the whole sample were taken by Stempel pipet or Folsom splitter and examined under 12-25 x magnification for all sizes of ctenophores, including larvae and eggs. The diameters were measured as described above. Numbers per cubic meter were calculated by ap- propriate corrections for subsample fraction and volume of water filtered. Results Physical Parameters and Distribution of Pleurobrachia Patterns in the currents of La Jolla Bight ap- pear to be affected by: 1) the configuration of the coastline (especially in the Point La Jolla-La Jolla Cove complex, 2) the bottom topography and bathymetry in the La Jolla Canyon-Scripps Can- yon complex, and 3) the surface tides. During the first field study in November 1969 a pair of drogues drifted toward Point La Jolla, paralleling the axis of La Jolla Canyon during an ebb tide (Figure 5). Both changed directions several times over La Jolla Canyon and made a complete coun- terclockwise rotation before moving northward nearly parallel to shore. Note that the rotational motion and major changes in direction occur over 304 HIROTA: NATURAL HISTORY OF PLEUROBRACHIA BACHEI IN LA JOLLA BIGHT II7»20' 1 32" 45' Figure 6. — Trajectories of drogues during studies on 12-15 March and 4-5 April 1970. Observed positions of the drogues are indicated by open circles, triangles and squares, and the date and time of the triangulation are indicated by the one-four or two-four digit sequence of numbers near the symbols. The respective dates and predicted times (Pacific standard time) and heights of tides in centimeters are given in each inset. or near La Jolla Canyon. The surface tides as- sociated with the commencement of the rotational motion were slack ebb tides, and completion of the loops during rotation occurred during flood tides. From 1800 h 3 November until 2300 h 4 November wind speeds were less than 3 m/s with variable direction. From 0240 h 5 November until 0600 h 6 November the winds increased to a steady 3-5 m/s from the south southeast to south southwest. The northward drift of the drogues after 0400 h 5 November may have been a response to changes in the wind velocity. Some changes in direction oc- curred on the northward drift of the drogues once they were beyond the submarine canyon complex, but these were relatively slight. While the drogues were over shallow water, the mean drifts were slightly onshore during flood tides and slightly ofFshore during ebbs. The net eastward drift was about 0.3 km and the westward drift about 1 km relative to a line true north at 0400 h 5 November. During two other drogue studies on 12-15 March and 4—5 April 1970 drogues were tracked for 1 to 2 days. The study of March 1970 provided the best information associating the surface tides with changes in direction (Figure 6). A drogue set in the axis of La Jolla Canyon drifted slowly to- ward the southeast along the canyon axis until flood tides changed its direction to northeasterly. On the following slack flood tide the drogue slowed and then moved off'shore toward the west on the next ebb and smaller flood. The onshore- offshore motions occurred during the following flood-slack-ebb sequences but are not as well as- sociated with the surface tide as in the first cycle. During this drogue study the weather was foggy, especially in the early morning hours, and the winds were less than 3 m/s during the day from the northwest. At night and in the early morning hours offshore winds were about 2-4 m/s. Note that the east- west horizontal translation during a tidal cycle is on the order of 1-2 km. This effect will 305 FISHERY BULLETIN: VOL. 72. NO. 2 Figure 7. — Trajectories of four drogues during the study of 22 May to 1 June 1970. Observed positions of the drogues are indicated by circles and triangles for each pair of drogues, and the date and time of the triangulation are indicated by the one-four or two-four digit sequence of numbers near the symbols. Reset drogues indicated by primes refer to other drogues placed into the water after ones placed earlier either ran a4fe(i4— ' JFMAMJJASONDJ FMAMJ 1970 1971 Figure 13. — Seasonal variation in abundance of Pleurobrachia postlarvae from 8 March 1970 to 2 June 1971 at stations located 1.6 km from shore. The solid line connects the medians of each sample date. Note the break of scale to account for absence data. Each type of symbol represents a different station, except for those sample dates prior to May 1970. Refer to the text for details of the field sampling. 309 FISHERY BULLETIN: VOL. 72. NO. 2 100,000 10,000 cr a! 1,000 (T liJ m s 100 n — I — I — I — I — I — I — I — I — I — I — I — I — I — I — r EGGS Q J F M A M J J 1970 -!••*•* JI ASONDJ FMAMJ 1971 J LLl J FMAMJ 1970 D J F M A M J 1971 Figure 14. — Seasonal variation in abundance of Pleurobrachia eggs and larvae from 8 March 1970 to 2 June 197 1 at station 5 located 1.6 km offshore at Scripps Institution. The solid line connects the mean of the replicate samples for each sampling date. The vertical bar represents the range of values for the replicate samples, and solid symbols indicate that the range is less than the size of the symbol; open symbols without any vertical bar are single observations. represent the offshore movement of the high ctenophore abundance while field sampling was taking place. Note the secondary peak in abun- dance which was 25 km from shore. Deviations from an exponential decay function are perhaps the result of coastal water eddies (Figure 7), which move offshore with their surface-living species and give rise to offshore aggregations in moderate abundance. An important question to resolve is whether or not the expatriated or ad- vected aggregations are able to survive, grow, and reproduce as well in offshore areas as they do in the coastal waters. Seasonal variations in abundance of P. bachei postlarvae, larvae, and eggs on semilogarithmic plot indicated different patterns between these stages in life history (Figures 13 and 14). Recall that egg and larval abundances are based on sam- ples from station 5 only, whereas those of postlar- vae are based on the replicate tows of three to five stations. Note the wide range for the median in abundance of postlarvae (Figure 13), which usu- ally was on the order of one-fifth to five times the overall median. In several instances the values from different stations were closer to each other than they were to their respective replicate sam- ple at the same station. This indicates that spatial heterogeneity within a station on the scale of 100 m was often as large as the spatial plus temporal heterogeneity between stations on the scale of 8 km apart in distance and 1 h apart in time to 32 km apart in distance and 5 h apart in time. The 95% confidence limits for the mean of replicate samples at one station is the mean multiplied and divided by 2.15 (determined by two-way analysis of variance estimate of the mean square error using 90 pairs of replicate samples at five stations from 18 June 1970 to 2 June 1971). The 95% confidence limits for the mean of all stations at one sampling date is the mean multiplied and divided by 6.23 (also determined by the two-way ANOVA referred to above). The ratio of the 95% confidence limits for the mean of all stations at one sampling date to that for the mean of replicate samples at one station is 8.4 (the ratio is equal to 6.23^/2.152). This latter residual variability is comprised of time-dependent physical variations plus spatial variation and is 1.8 times larger than replicate sample error (1.8 = 8.4/2. 15^). The seasonal pat- tern of postlarvae showed high abundances in May to October 1970, low values in Novem- ber-January and moderate densities in Feb- ruary-June 1971. Note that median abundances in March-June 1970 were one or two orders of magnitude higher than the same interval in 1971. The seasonal distribution of larval abun- dance was 180^ out of phase with that of postlar- vae for most of 1970 (Figure 14). In 1970 larval numbers were low during the summer maximum of postlarvae and highest in November when post- 310 HIROTA: NATURAL HISTORY OF PLEUROBRACHIA BACHEI IN LA JOLLA BIGHT larvae were in very low abundance. The abun- dance of eggs was generally the same as that for larvae, except for the absence of eggs in April 1970 and the high abundances of eggs relative to larvae in August-September. There were about 1,000-10,000 eggs/m2 in August-September, which are presumed to be spawned by the high abundance of postlarvae. The hatching time of eggs is about 24 h at 15°C, so that the low densities of larvae during this time were the result of large seasonal changes in hatching success, increased mortality rates of larvae, or both, assuming that the observed abundances were not determined mainly by physical processes. The data on sea- sonal variation in length frequency distributions of postlarvae considered below will provide some information to support the interpretation of in- creased larval mortality. From the abundance of eggs, larvae, and postlarvae at station 5 it was calculated that on 13 March, 1 May, 31 July, 21 August, 5 November, and 27 January the eggs and larvae made up 89-99% of the numbers of indi- viduals per square meter. On 13 August the eggs and larvae constituted 69% of the total population. The sample dates in which the eggs and larvae made up a very low percentage of the population are those in June 1970 and April- June 1971. During the seasonal study 18 pairs of replicate samples were taken between 31 July 1970 and 2 June 1971 at both stations 5 and 6, 1.6 and 10 km off Scripps Institution, respectively. The mean abundance of postlarvae per cubic meter was cal- culated at each respective station on each sam- pling date, and a f/-test was performed on these means to determine whether or not medians of mean abundance over time were significantly dif- ferent at stations 5 and 6. The null hypothesis is no significant difference, with a one-tailed alternate hypothesis that the median of station 5 is greater than that of station 6. Results indicate sig- nificantly greater median abundance at station 5 than at 6 (P<0.025). The median difference is a factor of 4.2 and the mean difference is a factor of 4.8. This result supports the three offshore dis- tribution studies which indicated decreasing abundance with increasing distance from shore. However, the observed decrease in abundance in the first 10 km from shore was about tenfold for the offshore distribution studies and about half this for the seasonal study. The discrepancy of a factor of two is probably real and may be caused by sampling bias in relation to stage of the tide and to seasonal changes in the patterns of currents. The TIDAL HEIGHT, cm Figure 15. — The relationship between abundance of postlarval Pleurobrachia bachei and the tidal height. The abundances are in number per square meter of sea surface (Y), and the heights are in centimeters (X) for samples at all stations located 1.6 km from shore. The data are for all stages of the tide. more accurate measure of variations in abun- dance with distance offshore should be found in the seasonal comparisons, but more carefully planned sampling could now be carried out to bet- ter sort out variations due to small scale tidal motions, larger scale "true" spatial variations offshore, and the effect of other types of motion and the wind on patterns of abundance. When all of the 180 samples for the seasonal study (15 samples on five sampling dates are ex- cluded from the analysis as five or fewer ctenophores occurred in all samples lumped per date) are plotted against predicted tidal height in centimeters for all tidal stages (Figure 15), the resulting least squares regression is Y = 0.89X -I- 88.36. Y is the number of ctenophores per square meter andX is the tidal height in centimeters. The slope of the line is significantly different from zero in a two-tailed ^-test (P<0.01). It is surprising to find a significant positive regression coefficient. The strength of the test is in the many degrees of freedom and the removal of 15 samples which might otherwise tend to pull the line down toward a zero slope because of frequent absence data at any tidal height. This result is unexpected be- cause the tidal currents are probably not the same at different locations along the coast. Variations exist in depth, bottom topography, exposure to wind, strike of the beach, etc. The pattern of circu- lation will also be differentially affected by spatial and temporal variations in the wind field. The results suggest that over an annual average, abundance at any one time and place of sampling could be affected by as much as a factor of four due to tidal variations alone at locations 1.6 km from shore. This average range due to tidal effects is about the same magnitude as the annual average difference between mean abundances of stations 5 311 FISHERY BULLETIN: VOL. 72, NO. 2 ID Q. O < UJ o 50 0 50 0 50 0 50 8 MAR. '70 258 ^L^ 8 OCT. '70 411 *—t — I 1 I f I I \^D^ 12 MAR. '70 \- 27 _j I — I — 1_ [L 13 MAR. '70 353 [n 22 OCT. '70 748 5 NOV '70 74 01=1 50 0 50 0 50 0 50 h 0 50 h 0 50 0 50 0 50 0 50 0 50 - 2 APR. '70 237 „I 1 I I L_ E253 \ \ \ I I 25 NOV. '70 93 I MAY '70 1802 30 MAY '70 915 18 JUNE '70 668 2 DEC. '70 30 LI // JAN. '71 28 Ik= 27 JAN. 71 116 \ I 1 1 I I rh-n — 2 JULY '70 391 14 JULY '70 672 8 FEB. '71 336 12 MAR. 71 40 31 JULY '70 798 I I r X \ K-T—i-L ,J I 1 L_ Jl-r^ ^-^ 7 APR. '71 30 \ ^ • 13 AUG. '70 \ \ 2916 lii- 20 APR. '71 24 d kBri I 1 I I I I I 2/ AUG. '70 L 796 \L. 4 MAY '71 30 29 AUG. '70 1117 16 SEPT '70 652 2 4 6 8 10 12 WHOLE YEAR 12.665 ^ — : — I — J 2 4 6 8 10 12 MEAN DIAMETER, mm Figure 16. — Seasonal variations in the size frequency distribu- tions of Pleurobrachia bachei captured by the 0.363-mm mesh 0.5-m net, expressed as the percentage in each size class of total numbers of all sizes on each sampling date. Each histogram is based on all sample data from each respective sampling date. The date and number of individuals measured are given with each histogram. and 6, whose difference should be less influenced by tidal currents and represents the order of true spatial variation within the first 10 km from shore. The size-frequency distributions of postlarvae for the 8 March 1970-2 June 1971 period indicate that most of the year the 1- to 2-mm size classes made up the highest proportion of all postlarvae (Figure 16). The lower abundance of the 0.25-mm class relative to the 1-mm class is the result of sampling gear mesh selectivity caused by the ina- bility of the 0.363-mm mesh to retain larvae quantitatively. At sporadic intervals the size-frequency distributions show drastic changes, and these are attributed to immigration of individuals in advected water. Between 14 July and 21 August 1971 note the decline in proportion of 1 and 2 mm sizes and a shift in modal class from 1 to 7 mm. During this same period the occur- rences of eggs and larvae showed that while up to 9,000 eggs/m^ were present in the water, seven of eight samples for larvae indicated none present (Figure 14). Assuming that these changes in size-frequency distribution over the 4-wk period are the result of biological activity rather than sampling error and advective change, it is con- en E cr UJ Q. X o < q: o J FMAM JJA SONDJFMAMJ 1970 1971 Figure 17. — Seasonal variations in standing stocks of postlar- vae, larvae, and eggs at station 5. Each type of line connects the respective mean values for the replicate samples at each sam- pling date. The vertical bar represents the range of values for the replicate samples, and solid symbols indicate that the range is less than the size of the symbol; the open symbols without any vertical bar are single observations. 312 HIROTA: NATURAL HISTORY OF PLEUROBRACHIA BACHEI IN LA JOLLA BIGHT eluded that the ctenophore population was releas- ing eggs into the water but that the larvae were eaten or died from other causes as fast as they were hatching from eggs. A feedback control mechanism which can account for the presumed high mortality of -larvae, high abundance of eggs, and rapid growth of postlarvae is discussed below. The calculated development rate from 1.5 to 6.5 mm in 30 days from field sample data is about 10 days slower than the growth rates in laboratory cultures at both 15° and 20°C. Patterns in the seasonal distribution of stand- ing stocks of postlarvae, larvae, and eggs at sta- tion 5 (Figure 17) are similar to the respective seasonal variations in numerical abundance. Postlarval values in 1970 increased from March to a seasonal maximum of 1,500 mg organic matter/m^ in August, then decreased to a minimum in December. The range over the year for standing stock of postlarvae was about four orders of magnitude. Note that the mean standing stock of larvae was high relative to that of postlar- vae in April and November 1970 and the following winter months. Except for a few instances in Au- gust and September, the mean standing stock of larvae was about twofold to tenfold greater than that for eggs. The crops for postlarvae were about equal to those of the larvae, except from May to October when they were much greater. Seasonal Variations in Parasites, Predators, and Prey Coincident with seasonal variations in the abundance and size frequency distribution of post- larval P. bachei are variations in abundance of the hyperiid amphipod, H. mediterranea (Figure 18). The data shown are from station 5 off Scripps Institution, but patterns in the seasonal distribu- tion 16 and 32 km to the north (stations 3 and 1, respectively) are essentially the same. Plots of abundance per square meter on a semilogarithmic scale are for postlarval ctenophores, attached en- doparasitic larvae and early juveniles of H. mediterranea, and unattached free-living late juvenile and adult H. mediterranea. The appear- ance of Hyperoche in the plankton is associated with P. bachei when the abundance of hosts ex- ceeded about 100 ctenophores/m^, which was May-June to November 1970. Prior to June 1970 and after January 1971 H. mediterranea was sparse enough to be absent in 6 to 10 samples of 1000 p-i — r p. bachei '__ o — o Attached Hyperoche _ O — O Unattached Hyperoche- 100 — cr a. or LjJ GD Figure 18. — Seasonal variations in numerical abundance of postlarval Pleurobrachia bachei and attached (endoparasitic) and unattached (free-living) Hyperoche mediterranea at station 5. Values are expressed as number per square meter of sea surface in logarithmic scale, and the lines connect respective means at each sampling date. The vertical bar represents the range of values for the replicate samples, and solid symbols indicate that the range is less than the size of the symbol. Hyperoche was absent after December 1970. 15-20 m^ each. Maximal abundance of Hyperoche occurred about a week after the ctenophore maximum, and may represent an "overshoot" phenomenon in a density-dependent, para- site-host system. Note that the larger am- phipods occurred in highest abundance when most postlarval ctenophores were at 6-8 mm sizes. Lit- tle concerning the dynamic aspect of this parasite-host interaction can be deduced from the data because of uncertainties in immigration and emigration over time. In August and September 1969-72 the occurrence of Hyperoche in and onP. bachei has been noted during plankton sampling. The co-occurrence and relative abundance of these two species is predictable and should follow the same pattern from year to year, with temporal shifts in the maxima and minima, depending on the type of "meterological year" and the sequence of events that occur in the plankton during the increase and decline of the ctenophore summer-fall maximum. The important problems to resolve are where the amphipods occur in the winter-spring months, and whether the observed seasonal pattern of co-occurrence is determined 313 FISHFR^ Bl I I FTIN: \ Ol ':. NO. 2 "T — I — I — r O STA. I 0STA.2 _ D STA. 3 ASTA.4 O STA. 5 • ALL STATIONS"! >k»k V' A M 1971 Figure 19. — Seasonal variation in the percentage of postlarval Pleurvbrachia bachei parasitized hy Hyperoche mediterranea at five stations located 1.6 km from shore. The line connects the mean value at each sampling date, and the various types of ojjen symbols represent different stations. suit is caused hy the seasonal distrihution of para- sites in relation to the seasonal distribution of length frequency of postlarval P/t'j/ro6rac/j;a (see Figures 16 and 18). Note that the 6-8 mm sizes with highest frequency of infection are at the size range for beginning reproduction as adults indi- cated by results from laboratory cultures. Also notice that only about I'l of all postlarvae in the 1- to 2-mm size classes were parasitized. These are the sizes of ctenophores which reproduce at an early age with small numbers of eggs. Secondly, the distribution of percentages of total occur- rences and total numbers of parasites for single infection and multiple infection show a decreasing occurrence of multiple infection, such that over 9(y~c of the occurrences and numbers of parasites are as one. two, or three parasites per host. Seasonal variations in abundance of Bfrot' sp., a known predator of other ctenophores, show a pattern very similar to that of P. bachei (Figure 20). The data plotted are numbers per 2 m^ (the sum of numbers per square meter of each repli- cate sample I at station 5. The distributions show seasonal maximum values in July- October with secondary high abundances in winter months. This pattern of seasonal co-occurrence is similar by a periodic convergence of w-ater types contain- ing//vperoc /it' and Pleurobrachia. Data from all stations during the seasonal study were plotted as the percentage of postlarval Pleurobrachia containing one or move Hyperoche. The mean percentage over time shows that Au- gust w'as the month of highest percentage hosts parasitized (Figure 19); at this time over one in three postlarvae were infected. The rate of in- crease of percentage infection appears to be faster than the decrease, although the range of 3 mo time around the maximum was the same for both. The very large variability on some sample dates was more a result of differences in percentages between stations than an artifact of sample size, since several hundred ctenophores were ex- amined per sample date. The frequency distributions of the percentages of total occurrences and of total numbers of para- sites for single and multiple infection and for dif- ferent sizes of hosts show two interesting results (Table 4). First, there is a central tendency in the percentages of total occurrences of parasites, and in the total number of parasites, with 6-8 mm sizes being the most frequently infected. This re- 10000 E CM q: bJ a. bJ m JJASONDJF 1971 Figure 20. — Seasonal variation in the numerical abundance of p)ostlarvalP/ewro6racAia bachei and postlarval Beroe sp. at sta- tion 5. Values are expressed for simplicity as the numbers per 2 m^ (the sum of numbers i>er square meter in the replicate sam- ples*. The range for the mean of replicate samples has been indicated previously (e.g.. Figures 13 and 18). 314 HIROTA; NATURAL HISTORY OF PLELROBRACHIA BACHEI IN LA JOLLA BIGHT Table 4. — The frequency distribution of the number of parasites per host for 14 size classes of postlarval Pleurobrachia bachei, the percentage of total occurrences At and of total numbers 'B* of parasites for each size class, and the percentages of total occurrences 13 1 0.10 0.14 C 72.29 19.66 5.36 2.09 0.30 0.10 0.10 0.10 0 51 78 28.16 11 52 5.97 1.07 0.43 0.50 0.57 to that of P. bachei and//, mediterranea, except that Beroe persists through the year rather than being absent for the winter and spring months. The patterns in the seasonal distribution of Beroe and P. bachei at station 3 were much the same as at station 5, except that the abundance of Beroe was fourfold lower at station 3, and the secondary- high abundances of Beroe in the winter and spring months at station 5 was not as well de- fined at station 3. The partially digested stomach contents of P. bachei captured at the surface in tows of short duration '60 s duration, 95 s maximum period at risk to feeding in the net) showed that the same species groups occur as in tows of fivefold longer duration. These species are : li copepods — L. tri- spinosa, A. tonsa, P. parvus, C. anglicus, E. acutifrons, and 2 ' cladocerans — Evadne nord- manni, E. spinifera. E. tergestina, and P. avi- rostris. The results provide evidence to support the contention isee results of stomach contents below) that the prey in stomach contents of P. bachei captured in tows of short duration are those which were ingested and digested in nature prior to capture by the net. The same species would probably occur in stomachs of P. bachei if the ctenophores were pipetted from the sea sur- 'face and preser\'ed immediately. Seven species of zooplankton. which were retained quantita- tively in the 0.363-mm mesh net as adults, were considered in calculations of electivity indices. In the Ivlev electivity index. E = r - pj ''r - pj, r and p being the proportions of a food item in the stomach and in the environment respectively. Paracalanus parvus, C. anglicus, and E. acuti- frons, which occurred frequently in the stomachs but passed through the net, were not included in the calculations. The results on the basis of num- bers show moderate positive selection for Acartia, Labidocera, andE. tergestina; high positive selec- tion for E. nordmanni a.ndE. spinifera; and mod- erate and strongly negative selection for Penilia and Sagitta 'Table 5). The indices on the basis of organic weight show the same trends, but the values for both copepods and Evadne are in- creased somewhat, and that for Penilia decreased, due to differences in bodily weights. Penilia has a negative electivity and was a slowly digested prey species (Table 1), whereas Labidocera and Acartia have positive electivity indices and were more rapidly digested. Prey selection by Pleurobrachia is more complex than dependence on prey digestibility alone. Data on the stomach contents of P. bachei during the sea- sonal study and observations in the laboratorv* of avoidance behavior and prey protective mechanisms will be discussed below in the con- text of prey selection. In the study of diel variation in feeding, differ- ences in the percentage of ctenophores with 315 Table 5. — Electivity indices for seven species of zooplankton which are retained by the 0.363-mm mesh net as adults. The range for the mean is calculated from the replicate samples from the proportion of the numbers and the proportion of the calcu- lated organic weight present in the sample and in the stomach of the ctenophores. Refer to the text for further details. On a numbers basis On an o ganic weight basis Prey Species E range E E range E Acartia tonsa 0.191 0.118-0.264 0.464 0.434-0.495 Labidocera trispinosa 0.130 0.099-0.160 0413 0.408-0.419 Evadne tergestina 0.244 0.183-0.305 0 506 0.430-0,582 E. nordmanni 0.806 0.748-0.864 0.953 0.936-0.970 E. spinifera 0.770 0.748-0.792 0.776 0.659-0.893 Penilia avirostris -0.345 -0.300to -0.391 -0.055 -0.143to +0.033 Sagitta euneritica -1.000 -1.000 to -1.000 -1.000 -1.000 to -1.000 Table 6. — Diel variation in the percentage of ctenophores which have empty stomachs. The numbers in parentheses are the numbers of specimens examined per sample. Replicate Midnight station Midday station sample A B c A B 1 70 62 75 69 62 (27) (40) (8) (16) (32) 2 76 76 57 77 64 (38) (41) (46) (13) (14) 3 71 90 62 71 67 (55) (10) (26) (24) (18) empty stomachs at midnight and midday were small, the medians being 71% and 68%, respec- tively (Table 6). These medians are not significantly different as determined by a two- tailed U-test (P>>0.20). It is concluded that no day-night differences exist in the proportion of the postlarval ctenophores feeding, at least at the time of this study. The prey categories most frequently found dur- ing the diel study in both day and night stomach contents were copepods and cladocerans — A. tonsa, unidentified copepods, P. parvus, copepod nauplii, Clausocalanus spp.,E. tergestina, C. ang- licus, Oithona spp.,£J. acutifrons, Oncaea spp., and unidentified material. In these samples A. tonsa was over 50% of all prey by numbers. The species which were present in stomachs of P. bachei captured at night include the same groups cap- tured during the day, the larger and deeper-living FISHERY BUM tTlN: VOl 72. NO. 2 copepods, euphausiids and other crustaceans being absent in the stomachs. If redundancy in the presence of prey species day and night (a qualita- tive aspect) occurs at other times of the year, then the prey species of Pleurobrachia could be ade- quately described by stomach analyses of ctenophores captured during the daytime. How- ever, in quantitative aspect diel variations of per- centages of each species may vary. For two of the species most frequently present, A. tonsa and P. parvus, the results are different. As determined by a two-tailed U-test, there is no significant differ- ence in median percentage Acartia of the total number of prey for day vs. night samples (P>0.20); however, the same test ior Par acalanus indicates significant day-night differences (P<0.05), there being more frequent occurrences at night than during the day. Further investigation of prey selection by Pleurobrachia in relation to time-space distributions of prey and predators is important for understanding the ecology of P. bachei but beyond the scope of the present study. The stomach contents (on the basis of numbers and mass of organic carbon) of postlarval Pleurobrachia in 10 size classes over the period 8 March 1970 to 2 June 1971 indicated some pat- terns in the frequency distribution of prey categories (Table 7). The patterns or trends exist as four types: (I) decreasing frequency with in- creasing ctenophore size, (II) increasing frequency with increasing ctenophore size, (III) little change in frequency with increasing ctenophore size, and (IV) non-systematic change and low frequency of occurrence for all ctenophore sizes. Examples of each pattern type are: (I) E. acutifrons, copepod eggs,^. spinifera; (IDA. tonsa, L. trispinosa; (III) Oithona spp., C. anglicus, P. parvus, copepod nauplii; (IV) Rhincalanus nasutus, euphausiid calyptopis, brachyuran zoea, Sagitta euneritica. These results are subject to several sources of bias, three of which are: 1) the occurrence of the stomach contents of ctenophore prey in the stomachs of ctenophores, 2) the numbers of obser- vations per ctenophore size category and the number of total occurrences per prey category, and 3) seasonal variations in the length- frequency distributions of ctenophores and their co-occurrences with prey. The diatom and dino- flagellate prey categories may be biased toward higher frequencies of occurrence if some of these types of organisms which occur in the stomachs of herbivores are released into the gut of a ctenophore during digestion. Fortunately, these 316 HIROTA: NATURAL HISTORY OF PLEUROBRACHIA BACHEI IN LA JOLLA BIGHT Table 7. — Stomach contents over the period 8 March 1970 to 2 June 1971 for 10 size classes of postlarval Pleurobrachia bachei. Data are the percentage by numbers (upper value) and by carbon mass (lower value) of each prey category in the stomachs for each size class of ctenophore calculated separately. The first 10 prey categories are given in ascending order of body mass; thereafter the order is by taxonomic group (e.g., copepods, cladocerans, crustaceans, chaetognaths, etc.). The numbers indicated in parentheses below each size class are the number of ctenophore stomachs examined per size class. Total numbers and total carbon refer to values of all prey in each ctenophore size class. Carbon mass is not calculated for protozoans. Size class, mean diameter (mm) Prey category 1 (189) 2 (211) 3 (235) 4 (190) 5 (158) 6 (150) 7 (105) 8 (68) 9 (24) >10 (22) Euterpina %N acutifrons %C 20.85 9.15 18.33 5.56 15.36 2.98 15.58 3.05 7.41 0.80 5.54 0.71 4.05 0.40 4.00 0.23 0 7.06 1.00 Oithona spp. 6.81 2.18 3.33 0.47 5.03 0.24 3.43 0.14 4.04 0.27 0.98 0.06 0.40 0.01 4.67 0.12 5.17 0.58 2.35 0.17 Oncaea spp. 0.85 0.50 2.33 0.91 0 0 1.25 0.13 0 0 0.33 0.06 1.21 0.15 1.33 0.06 0 0 Corycaeus anglicus 426 2.58 933 9.76 950 5.25 8.41 4.44 9.76 3.45 4.56 1.80 5.26 1.60 7.33 0.77 3.45 1.43 14.12 4.46 Paracalanus parvus 1.70 2.40 3.00 2.22 4.47 2.01 3.43 1.23 6.40 2.11 3.91 1.16 4.86 1.24 6.00 0.67 5.17 1.07 7.06 2.17 Acartia tonsa 10.64 39.59 21.67 48.04 25.14 36.94 29.91 39.21 36 03 33.66 47.23 43.17 55.87 37.49 49.33 16.80 60.34 53.78 47.06 37.62 Calanus helgolandicus 0 0 0.28 3.18 1.25 7.83 1.01 10.14 0.65 2.85 0.81 4.61 0.67 3.26 0 1.18 6.97 Labidocera trispinosa 0 0 2.51 29.33 2.49 28.44 3.37 30.60 2.93 37.24 4.45 37.50 5.33 21.96 1.72 10.52 2.35 25.08 Metridia pacifica 0 0 0 0 0 0 0 1.33 4.89 0 1.18 13.94 Rhincalanus nasutus 0 0.33 0.05 0 0 0.34 4.78 0 0 0 1.72 23.90 0 Clausocalanus spp 0 0 0.56 0.37 0.62 0.27 0.67 0.36 0.33 0.17 0 0.67 0.06 0 0 Ctenocalanus 0 0 0 0 0 0.33 0 0.67 0 0 vanus 0.09 0.06 Tortanus discaudatus 0 0 0 0.31 0.45 0.34 0.17 0 0 0 0 0 Copepod eggs 14.47 6.12 10.67 3.20 8.38 1.66 4.36 0.70 2.69 0.33 1.30 0.07 0.81 0.05 2.00 0.09 3.45 0.49 0 Copepod nauplii 11.91 0.78 6.67 0.25 335 0.08 4.05 0.08 9.43 0.13 4.89 0.07 5.67 0.06 4.67 0.02 3.45 0.05 0 Unidentified copepods 4.26 5.60 4.00 3.03 2.79 1.27 3.12 1.26 2.02 0.57 2.28 0.64 1.21 0.25 1.33 0.13 3.45 0.96 0 Evadne nordmanni 5.96 16.47 7.00 11.12 6.70 6.42 5.61 4.77 1.01 0.60 4.89 2.90 5.26 2.24 1.33 0.27 8.62 5.02 8.24 4.10 Evadne splnifera 2.13 5.88 1.00 1.59 0.56 0.54 0.31 0.26 0.67 0.40 0.33 0.19 0 0 0 0 Evadne tergestma 0.85 2.35 1.33 2.12 1.96 1.87 2.80 2.39 1.68 1.00 6 84 4.06 4.45 1.90 0.67 0.14 0 1.18 0.58 Evadne spp 0 2.67 4.24 3.91 3.75 3.43 2.92 0 0 0 0 0 0 Pen ilia avirostrls 0.42 0.56 0.67 0.50 2.51 1.15 2.18 0.88 3.03 0.86 2.93 0.83 0.40 0.08 1.33 0.13 1.72 0.48 4.71 1.11 Podon polyphemoides 0 0.67 1.06 0.28 0.27 1.25 1.06 1.35 0.80 0.33 0.19 0 0 0 0 Euphauslld calyptopis 0 0 0 28 0.46 0 0 0.33 0.33 0 0 1.72 1.72 0 Clrriped nauplii 0 0 0 0 0.34 0.02 0 0 0 0 0 Mysids 0 0 0 0 0 0 0.40 12.34 0 0 0 Brachyuran zoea 0 0 0 0 0.34 0.96 0.65 1.84 0 1.33 1.30 0 1.18 2.79 (Continued) 317 FISHERY BULLETIN: VOL. 72. NO. 2 Table 7. — Continued Size class, mean diameter mm) Prey category 1 (189) 2 (211) 3 (235) 4 (190) 5 (158) 6 (150) 7 (105) 8 (68) 9 (24) >10 (22) Unidentified crustaceans 383 2.52 1,67 063 1.12 0.25 1-56 0.32 1,35 0,19 0,98 0,14 040 0 04 2-00 0-10 0 0 Sagitta euneritica 0 0.33 2.14 0 0 0,34 6.10 0 0.40 0-01 0-67 48-88 0 0 Oikopleura spp. 0.42 202 0 1.12 1 83 0 1.01 1 03 1 30 1,32 0 0 0 0 Echinopluteus. doliolids 0 0 0 0 0 0 0 0 0 2.36 Fish eggs 0 0.67 2.77 0 0 0,34 0,53 0 0 0 0 0 Sarcodina 0 0 0 0.31 034 0.65 0 0 0 0 Noctiluca scintillans 0 0 0 0 0 0 0,40 0 0 0 Dinoflagellates 0.85 0 1,12 0,31 0,67 1,95 081 0 0 0 Diatoms 0 0 0 0,62 0 0 1-62 0 0 0 Unidentified material 9.79 1.29 4.33 0.33 3.07 0.14 3.43 0.14 4 04 0,11 3.58 0.10 1-21 002 3.33 0.03 0 0 Total numbers 235 300 358 321 297 307 247 150 58 85 Total carbon, ug 178.47 396.48 78476 791.93 1045,87 1087.39 1215-87 1534.41 209.17 358.80 taxa made up less than 2% of any one category by numbers and less on a mass basis because of their small size. The number of observations per ctenophore size category are similar for classes 1-6, but thereafter they decrease sevenfold. There are few observations in the last two size classes, because these sizes are relatively infrequent and occur in high numbers only during July- August. Some of the larger copepods (e.g., Calanus, Met- ridia, and Rhincalanus) occur relatively infre- quently in stomachs, perhaps because of their rel- ative rarity and spatial separation from the ctenophores. Other infrequent groups such as fish eggs, cirriped nauplii, euphausiids, etc., may not be spatially separated but are perhaps rare, not selected as prey or are unavailable because of temporal separation during different seasons. Whatever the reasons for the infrequent occur- rence of these groups in the stomachs of Pleurobrachia, the data for these prey are much less reliable and many more observations are re- quired to establish patterns of occurrence with size of the ctenophore predator. The potential ef- fect of seasonal variations in size-frequency dis- tribution of ctenophores and co-occurrence of prey on patterns of stomach contents is suggested when the annual data are examined separately by sea- sons. The results indicate that some prey are very seasonal in occurrence, while many are present throughout the year. The seasonal data are given (Table 8) for only those categories which showed strong seasonal variations. The first two prey were most frequent in summer-fall, E. tergestina in summer-winter, the next four in fall and the last one in winter-spring. Note the differences in occurrence of three species of Evadne regarding seasonal separation and predation by different sizes oi Pleurobrachia. When all stomach content data are grouped to include all sizes of postlarval Pleurobrachia and prey categories are ordered by rank of occurrence, the results show that A. tonsa and £. acutifrons account for nearly one-half of all prey items (Table 9). Thereafter, the percentage contribu- tion from each category decreases to less than 1% by the sixteenth category, at which point the cumulative percentage is 94.2%. On a mass basis Calanus, Labidocera, and Sagitta join Acartia as the main large prey items. While these larger items may afford good growth to a few individu- als, most of the ctenophore population is being nourished by A. tonsa, E. acutifrons and sev- eral other species of copepods and cladocerans. Variations in the standing stock of food avail- 318 HIROTA: NATURAL HISTORY OF PLEUROBRACHIA BACHEI IN LA JOLLA BIGHT Table 8. — Seasonal variations in the stomach contents of ctenophores for eight prey categories. All values are expressed as the number of occurrences per 1,000 stomachs. The seasons spring (SP), summer (SU), fall (F) and winter (W) are groups of three months starting with February 1970 and ending in January 1971; the following spring 1971 is also included. The dashed lines indicate absence of data. Size class, mean diameter (mm) Prey category 1 2 3 4 5 6 7 8 9 >10 Paracalanus SP 0 100 154 0 200 0 0 0 parvus SU 46 50 52 44 146 67 91 91 91 300 F 0 22 85 55 79 98 125 26 111 0 W 33 0 0 182 400 0 125 429 — 500 SP 0 0 0 83 0 0 0 3,000 333 250 Labidocera SP 0 0 0 0 0 0 500 0 trispinosa SU 0 0 21 0 49 0 45 318 91 100 F 0 0 66 77 79 88 125 26 0 250 W 0 0 0 91 0 0 0 0 — 0 SP 0 0 0 0 125 0 0 0 0 0 Evadne SP 0 0 0 0 0 0 0 0 tergestina SU 0 0 21 44 0 100 0 0 0 0 F 42 0 47 55 56 167 139 26 0 250 W 0 364 0 91 0 91 125 0 — 0 SP 0 0 0 0 0 0 0 0 0 0 Calanus SP 0 0 0 0 0 0 0 — 0 — helgolandicus SU 0 0 0 0 0 33 0 0 0 100 F 0 0 9 44 34 10 28 26 0 0 w 0 0 0 0 0 0 0 0 — 0 SP 0 0 0 0 0 0 0 0 0 0 Evadne SP 0 0 0 0 0 0 0 0 spinitera SU 0 8 0 0 0 0 0 0 0 0 F 21 43 18 11 22 10 0 0 0 0 w 33 0 0 0 0 0 0 0 — 0 SP 0 0 0 0 0 0 0 0 0 0 Penilia SP 0 0 0 0 0 0 0 — 0 — avlrostris SU 0 8 0 0 49 100 0 45 0 300 F 21 22 85 77 79 59 14 26 111 250 w 0 0 0 0 0 0 0 0 — 0 SP 0 0 0 0 0 0 0 0 0 0 Podon SP 0 0 0 0 0 0 0 0 — polyphemoides SU 0 8 0 0 0 0 0 0 0 0 F 0 22 9 44 45 10 0 0 0 0 w 0 0 0 0 0 0 0 0 — 0 SP 0 0 0 . 0 0 0 0 0 0 0 Evadne SP 0 0 0 0 0 0 0 — 0 — nordmanni SU 0 58 72 59 0 0 0 0 0 0 F 62 22 19 0 0 29 14 0 0 0 w 30 1,000 1 ,333 909 0 364 1,500 286 — 0 SP 111 143 538 333 375 1,600 0 0 1,667 1,750 able to Pleurobrachia from 18 June 1970 to 2 June 1971 showed a twentyfold range, with high val- ues in May to early November and low values from mid-November to mid-March (Table 10). The food concentrations were about 10-30 mg C/m^ during the summer-fall maxima in num- bers and standing stocks of Pleurobrachia postlarvae. The decrease in abundance of Pleurobrachia during November and December (see Figure 13) was associated with a fivefold de- crease in the standing stock of prey. The winter increase of P. bachei occurred while food con- centration doubled from the minimum in De- cember. The higher food concentrations in May and June do not seem to cause increases in ctenophore abundance. DISCUSSION The vertical distribution of P. bachei in La Jolla Bight is related to the diel light-dark cycles, but in reverse to the pattern for most migrating zoo- plankton; the pattern is the result of one or more causes of differing selective advantage to the tem- poral persistence of this species. Four potential 319 FISHERY BULLETIN: VOL. 72. NO. 2 Table 9. — Rank order in frequency of occurrence by numbers of all developmental stages per prey category in all sizes of Pleurobrachia postlarvae and the corresponding estimates of total carbon mass per prey category. Table 10. — Seasonal variations in the calculated standing stocks of prey for Pleurobrachia at station 3. Prey category Frequency Percent ug C Percent Acartia tonsa 815 34.56 2,644.23 34.78 Euterpina acutifrons 270 11.45 114.04 1.50 Corycaeus anglicus 180 7.63 225.73 2.97 Copepod nauplii 139 589 6.95 0.09 Copepod eggs' 129 (1,649) 5.47 49.47 0.65 Evadne nordmanni 122 5.17 256.20 3.37 Paracalanus parvus 101 4.28 108.80 1.43 Unidentified 89 3.77 8.90 0.12 Oithona spp. 83 3.52 15.99 0.21 Unidentified copepods 62 2.63 62.00 0.82 Evadne tergestina 61 2.59 128.10 1.68 Labidocera trispinosa 58 2.46 2,085.54 27.43 Penilia avirostris 45 1.91 45.00 059 Unidentified crustaceans 34 1.44 17.00 022 Evadne spp. 33 1.40 69.30 0.91 Oncaea spp. 19 0.81 8.86 0.12 Dinoflagellates 17 0.72 — — Calanus helgolandicus 14 0.59 355.00 4.67 Evadne spinitera 14 0.59 29.40 0.39 Podon polyphemoides 12 0.51 25.20 0.33 Oikopleura spp. 12 0.51 43.20 0.57 Clausocalanus spp. 8 0.34 11.74 0.15 Brachyuran zoea 6 0.25 60.00 0.79 Diatoms 6 0.25 — — Sagitta euneritica 4 0.17 822.4 10.82 Sarcodina 4 0.17 — — Metridia pacifica 3 0.13 125.0 1.64 Rhincalanus nasutus 3 0.13 100.2 1.32 Euphausiid calyptopis 3 0.13 10.80 0.14 Fish eggs 3 0.13 16.50 0.22 Ctenocalanus vanus 2 0.08 2.00 0.03 Tortanus discaudatus 2 0.08 5.40 0.07 Cirriped nauplii 0.04 0.2 0.003 Mysids 0.04 150.0 1.97 Echinopluteus 0.04 — — Doliolids 0.04 — . — Noctiluca scintillans 0.04 — — Total 2,358 7,603.15 'The frequency value refers to the nunnber of groups of copepod eggs and the value in parenthesis below it refers to the total number of eggs. advantages of migration to P. bachei are the abil- ity to: 1) seek locations and depths with favorable food types and concentrations, 2) seek locations and depths with few predators and parasites, 3) avoid lethal or near-lethal surface temperature after the downward migration at night and in- crease the rate of development by living in warmer water during the day, and 4) maintain the pattern of high abundance close to shore and de- crease the chance of drifting offshore. No data have been collected on quantitative changes in the abundance of prey and predators with P. bachei during vertical migration; such information would enable qualitative evaluation of the effect of these changes on the pattern of vertical dis- tributions. Limited data from the study of diel changes in the species composition of prey in stomachs of ctenophores indicated no major changes between day and night, although Sample date Mean (mg C/m3) Range (mg C/m^) 18 June 1970 14 July 13 August 29 August 22 September 5 November 18 November 16 December 11 January 1971 8 February 12 March 4 May 2 June 10.9 10.8-11.0 10.7 10.4-11.1 15.5 6.0-25.0 17.8 16.4-19.1 27.8 20.2-35.4 15.7 13.4-17.9 5.8 3.4- 8.1 2.7 2.6- 2.8 6.8 3.7- 9.9 6.0 2.2- 9.7 5.2 5.1- 5.3 58.4 52.2-64.6 9.3 9.3- 9.4 Paracalanus occurred more frequently in stomachs of ctenophores captured at night. Another major study would be required to quan- tify changes in the temporal and spatial co-occurrence of Pleurobrachia with their prey and predators. The data on vertical and seasonal distribution of P. bachei and the thermal stratification of water; the failure of laboratory cultures at 20°C; and growth experiments in the deep tank facility at 14.5° and 19.5°C are inter- preted to indicate that vertical migration for this ctenophore is beneficial for survival and would optimize the rates of development and increase of bodily mass. A constant temperature of 20°C was detrimental to survival and growth of bodily weight (Figure 1), relative to conditions at 15°C. It is suspected that in August when the ctenophore abundance is highest and the maximum thermal stratification occurs, vertical migration from the surface to 20-m depth increases the chance of survival by lowering the ambient temperature at night by nearly 10°C. In addition, the detrimental effect of high temperature on somatic growth may be decreased and the ctenophores develop at some rate intermediate to the rate at 12° and 22°C. Growth experiments using the deep tank facility in which stratification of temperature is made to simulate conditions in nature might support some of these speculations. Alternatively, laboratory growth experiments could be made in which temperature is varied with a semidiurnal period. Another complication in these experiments, if they are to simulate conditions in the field, is the co-occurrence of the parasite Hyperoche and its possible temperature-dependent effect on the growth and survival of P. bachei. A consequence of diel vertical migration in the 320 HIROTA: NATURAL HISTORY OF PLEUROBRACHIA BACHEl IN LA JOLLA BIGHT coastal waters off southern California is the po- tential effect on the horizontal, offshore distribu- tion of a species. Stevenson (IGSS)"* summarized some wind data for the Newport Beach to Los Angeles Harbor area, which show that in the sea breeze-land breeze diel variation of wind velocity there is a stronger sea breeze component from the west-northwest quadrant during the afternoons and a more variable and weak wind in the morn- ings. Robert Arthur has suggested that a possible result of the diel variation in wind velocity and the observed pattern of vertical migration in P. hachei may in part account for the maintenance of high ctenophore abundances close to shore. By living in the wind-mixed layer during the day with a westerly-northwesterly sea breeze, ctenophores are moved shoreward. At night through the early morning hours the weaker land breeze moves the surface waters offshore, but by living deeper at night the net offshore movement of ctenophores should be relatively smaller than the shoreward displacement. The frequent strand- ing or grounding of drogues nearshore suggests a net onshore movement of water. One mechanism of horizontal, seaward transport is the rip cur- rents, but these are probably important only a few hundreds of meters seaward of the surf zone and are dependent on the size of sea swells. It is not known how important stranding is as a source of mortality to Pleurobrachia, but in summer months Pelagia (Scyphozoa) are frequently stranded on La Jolla beaches and are broken apart in the surf zone. Other macrozooplankton, such as salps and Velella, periodically occur on the beach and in waters near the shore. It is not clear what cues or mechanisms the ctenophores use to main- tain their distribution to within 1 km of shore without most being washed into the surf and killed. A number of net tows taken near the end of Scripps Institution pier and just seaward of the surf zone indicate absence of P. bachei. The estimates of abundance of P. bachei at fixed stations located alongshore 2-3 km from the shoreline are subject to variability in time and space from several causes. At a single station the abundance will be affected by: 1) spatial heterogeneity and patchiness on the scale of 100-m horizontal distance and 20- to 50-m depth over the course sampled during a tow, 2) the stage ••Stevenson. R. E. 1958. An investigation of nearshore ocean currents at Newport Beach, California. UnpubL Rep. to Orange Cty. Sanit. Dist., 108 p. of the tides and the tidal current velocity (see Figure 15), and 3) the water temperature stratification and near-surface drift due to the wind. The magnitude of replicate sample error is one-half to twice the mean, and the variability in abundance due to the presumed horizontal motion generated by the tides and wind for the annual average is about the same as replicate sample error. For estimates of abundance on a given sampling date at stations 1.6 km from the shore at different locations along the coast, "true spatial" variabil- ity exists in addition to replicate sampling error and aliasing due to physical effects of tides and the wind. It is difficult to sort out quantitatively the separate error components due to physical effects and true spatial effects alone, because the time period for the physical effects to bias sampling (about 6 h) is about the same as that required to move through space and sample different stations. Variability around the mean of all stations at one sampling date includes variations due to replicate sampling error, variations due to physical effects, and variations due to true spatial differences. The relative magnitudes of these components of varia- tion estimated from the 95% confidence limits of the two-way analysis of variance and the regres- sion of abundance on tidal height are: 1) the 95% confidence limits about the mean of all stations at a given time of sampling is the mean multiplied and divided by 6.23, 2) the 95% confidence limits about the mean of replicate samples is the mean multiplied and divided by 2.15, 3) the range of the expected abundance from the regression equation over the observed values of tidal heights is four- fold, or a range of about one-half to twice the overall annual mean, and 4) the residual true spa- tial variation calculated by difference is the mean multiplied and divided by 1.45 (i.e., 6.232 = 2.15^ X 2^ X 1.45^). In terms of the relative contribution of these three components to the total variability, the values are 2.2:1.9:1 for replicate sampling error, physical effects, and true spatial variation, respectively. The relative contribution of replicate sampling error vs. physical plus true spatial vari- ations to the total variability of all stations on one sampling date is 1:1.8. These results from a sam- pling program not designed specifically to sepa- rate each effect suggest that physical effects on sampling bias and the replicate sample error are important relative to real spatial differences of abundance between stations equidistant from shore. A synoptic sampling program with two or 321 FISHERY BULLETIN: VOL. 72, NO. 2 more ships would better enable separation of the total variability into variations from time-dependent physical effects, true spatial dif- ferences, and replicate sample error. It is indeed discouraging that confidence limits for the mean of replicate samples could not be reduced below about one-half to twice the mean, even with a t value based on 90 degrees of freedom. Zooplank- tologists may continue to be plagued with the ina- bility to reduce field sampling variability much below this level, given reasonable time and man- power limitations and no significant changes in sampling methodology. Because of their large size and lack of rapid escapement, postlarvalP. bachei are as easy to sample accurately as any zooplank- ter is likely to be. Seasonal changes in abundance of P. bachei postlarvae observed in La Jolla Bight during my study (Figure 13) agree with the earlier work of Esterly (1914) off San Diego and work by Parsons et al. (1970) in the Strait of Georgia, British Co- lumbia (the values reported in the Strait of Geor- gia work are numbers of Pleurobrachia plus Philidium per cubic meter). These two studies showed that seasonal maxima occurred in July or August; high densities were from June to Sep- tember and lower values and absences were ob- served from October to March. Esterly (1914) noted that P. bachei were more abundant at tem- peratures above 18°C than below; they were espe- cially abundant at about 19°C in August. He also noted that although P. pileus and P. bachei are similar in morphology, their distributional pat- tern and temperature optima are widely different. In the Atlantic P. pileus was abundant at lower temperatures during the year (<15°C); in the Pacific the reverse seemed to be the case. Seasonal studies of P. pileus in Wellington Harbor, New Zealand (Wear, 1965) and the North Sea region (Russell, 1933; Fraser, 1970; Greve, 1971) show that it differs from P. bachei in the season of maximal abundance. In Wellington Harbor P. pileus was dominant in the winter plankton, and it was the most variable plank- tonic species. P. pileus was absent in February- March, rare (1-10/20-min tow) in April-May, and December-January, common (20-100/tow) in June and September- November and abundant (500-1,000/tow) in July- August (note that this is the winter in New Zealand). Critical temperature for the occurrence of P. pileus was between 15° and 16°C. When the temperature fell below this level, P. pileus occurred in great abundance; in early summer at temperatures above 16°C they were rare or absent. In the North Sea off Plymouth, P. pileus occurred in a bimodal sea- sonal distribution with early summer (May-June) and fall (October) maxima (Russell, 1933). In the North Sea near Helgoland P. pileus occurred with a May- June maximum at 10-15°C and a less distinct fall peak (Greve, 1971). Long-term mean seasonal distributions in the Scottish North Sea showed a clear November maximum with a less distinct secondary mode in June (Fraser, 1970); however, the month of the seasonal maximum can be as early as July-August in "abnormal" years compared to the expected fall maximum of normal years. Highest numerical abundance of postlarval P. pileus in the North Sea was on the order of 10-20/m3 (Fraser, 1970; Greve, 1971). This is about the same as the maximum of 40/m^ I found for P. bachei postlarvae, but through most of the year the population of P. bachei was dominated by numbers of larvae and eggs. Contrary to the annual or biannual spawning patterns of P. pileus in the North Atlantic (Fraser, 1970), P. bachei produced eggs throughout the year except for spring and some summer months. Important differences exist between P. pileus and P. bachei in addition to the pattern of sea- sonal distributions and the surface temperature at the season of maximum abundance. Patterns in the seasonal co-occurrence of Bero'e with Pleurobrachia and the parasitism of each Pleurobrachia species are different for P. pileus and P. bachei. In the North Sea, P. pileus occurred in patterns of seasonal abundance which were 180° out of phase with the abundance of Beroe (Russell, 1933; Greve, 1971). In La Jolla Bight abundances of P. bachei and Bero'e sp. gen- erally increased and decreased in phase without time lags. The seasonal patterns for the co- occurrence of Bero'e with P. pileus and P. bachei suggest that Bero'e and other predators may over- exploit P. pileus temporarily to decrease the population abundance seasonally, whereas Bero'e and P. bachei appear to co-occur in a less intense predator-prey association. In the North Sea, P. pileus were parasitized by nematodes (Greve, 1971) and cercaria of Opechona, a trematode (Fraser, 1970). In La Jolla Bight, P. bachei were parasitized by H. mediterranea. Farther to the north Hyperoche mediterranea is replaced by H. medusarum (Bowman, 1953), and P. bachei is parasitized by this species in waters off northern 322 HIROTA: NATURAL HISTORY OF PLEUROBRACHIA BACHEl IN LA JOLLA BIGHT California (Brusca, 1970). Off southern California, the strongest equator- ward surface flow occurs during spring and sum- mer, and south of Point Conception the semiper- manent cyclonic eddy produces a northward in- shore circulation (Wyley, 1966). Beneath the California Current, the undercurrent is a sub- thermocline poleward flow of water of relatively high temperature and salinity; for example in Au- gust 1966 the undercurrent at lat. 31°N, long. 177°W was close to the continental slope, being about 20 km wide and 300 m thick (Wooster and Jones, 1970). This undercurrent below 200 m sur- faces well inshore of the main stream in late fall and early winter when northerly winds are weak or absent (Reid et al., 1958). The seasonal distributions of P. bachei in La Jolla Bight showed some features which are con- sistent with seasonal changes in the vertical movement of the California undercurrent (also called the Davidson Current). Postlarvae de- creased by over two orders of magnitude from the end of October through December, and reappeared at moderate abundance in late January and Feb- ruary. For larvae and eggs, the timing and mag- nitude of the winter decrease were about the same, but the frequency of absences was less than for postlarvae (see Figures 13 and 14). Another vari- able associated with the presumed winter shoal- ing of the undercurrent is the fivefold decrease in prey standing stock from early November to the middle of December (Table 10). A subsurface cur- rent which rises to the surface in winter is ex- pected to contain relatively low crops of animals and plants, and poleward advection of water from the south should cause decreases in abundance of Pleurobrachia. Studies of stomach contents of P. pileus in the Scottish North Sea (Fraser, 1970) and in Kaneohe Bay, Oahu (Rowe, 1971) indicate that this ctenophore is predominantly a crustacean feeder, especially of copepods, cladocerans, and cirriped nauplii. In the Scottish North Sea, P. pileus fed about 809c of the time on Acartia, Calanus, Evadne, invertebrate eggs, Temora longicornis, Oithona, unidentified copepods, cirriped larvae, Spiratella, andPodon. In Kaneohe Bay 75% of the prey were nauplii of barnacles and copepods and the appendicularian Oikopleura longicauda (Rowe, 1971). The evidence indicated that Pleurobrachia very rarely fed on fish eggs and larvae. The North Sea study included seasonal and annual data, the differences between which Fraser attributed to differences in the composition of the plankton rather than prey selectivity by Pleurobrachia. The gut contents of P. bachei in La Jolla Bight generally agree with the results for P. pileus in that they fed: 1) predominantly on crustaceans, especially copepods; 2) very rarely on fish eggs and larvae; and 3) on a broad spectrum of organisms some of which appear seasonally for only limited periods. The major difference between the results from the three study areas is that in Kaneohe Bay Pleurobrachia fed on relatively few prey categories, the number being about one-fifth that in my study and the North Sea study. The three most frequent foods on a numerical basis were: 1) barnacle and copepod nauplii, Oikopleura and other copepods in Kaneohe Bay; 2) Acartia, Calanus, and Evadne in the Scottish North Sea, and 3) Acartia, Euterpina, and Corycaeus in La Jolla Bight. Both studies of P. pileus gut contents considered the postlarvae as a homeogeneous group. I have treated the postlarvae of P. bachei as being made up of 10 separate size classes to show that some changes do occur in prey fre- quency during ontogeny (Table 7). All studies of ctenophore gut contents have been inadequate to describe quantitatively the developmental stages of prey species eaten by different life history stages of ctenophores, including the larvae. Great difficulties and amounts of work would be re- quired for such a study (each copepod species has 13 developmental stages counting the eggs). Many important biological interactions probably occur during different developmental stages during on- togeny, yet we know very little about them. Feeding rate experiments with 9- to 10-mm diameter P. bachei (Bishop, 1968) have shown differences between mean ingestion rates of copepodids of Epilabidocera amphitrites and Pseudocalanus minutus; P. bachei also fed at a faster rate on copepodids and adults of P. minutus than on their nauplii. These results showed that rates of feeding depend on prey size and other differences between the same stages of different prey species and between different developmental stages of one species. The study of feeding be- havior of P. pileus indicated that this ctenophore regulates its feeding rate by changing the average size of the tentacles in response to different con- centrations of Artemia nauplii (Rowe, 1971). During laboratory culturing and rate of diges- tion of prey experiments, differences were ob- served in: 1) the avoidance and escape behavior of 323 prey, 2) the protective spination of various species, 3) the strength and sensory acuity of larger zoo- plankters, and 4) the active search patterns of "setting out" tentacles by the ctenophore. Each of these four factors in addition to other variables, which are determined by the relative abundance and movement of species in nature, have some bearing on the selection of prey by Pleurobrachia. The first consideration is time-space co- occurence of prey with the ctenophore. Since the ctenophores are neritic and mostly live close to shore in the upper 50-60 m, they will occur with surface-living holoplanktonic and meroplank- tonic species, only coexisting with deeper-living, migratory species at night. Secondly, the ctenophores will most frequently encounter the most abundant organisms in numbers per unit volume. Size and swimming activity of the prey are also important to determine the chance of en- counter with the tentacles. Bodily length deter- mines the likelihood of retention of a given or- ganism by the tentacle net, and swimming activ- ity determines how often the prey will encounter a given ctenophore if swimming in a random man- ner. Rowe (1971) has shown, using Artemia nauplii, that the instantaneous feeding rate of P. pileus follows the form for effusion of an ideal gas; this requires the assumption that prey move about randomly. However, I have seen P. bachei make at least three different types of settings of its ten- tacles in apparent attempts to alter the pattern of search for prey: 1) a double helix set like two interwoven corkscrews perpendicular to a level surface with the body at the uppermost end, 2) a pair of spirals parallel to a level surface with the ctenophore body at the outer end of the spiral, and 3) linear and curved sets which are placed at dif- ferent angles with respect to the vertical and with the ctenophore body either heading up or down. The types of tentacle settings may be adaptive responses to the nonrandom swimming patterns of different zooplankton species, some of which move more in a horizonal or a vertical plane. It is at this point that animal behavior becomes very impor- tant. Species which co-occur with Pleurobrachia and are relatively abundant (up to several hundred per cubic meter) are not necessarily eaten by this ctenophore, because these potential prey probably use their sensory acuity and locomotive power to avoid danger. One outstand- ing example is S. euneritica, a species which is very fast and difficult to catch compared to most zooplankton; it had a highly negative electivity FISHERY BULLETIN: VOL. 72. NO. 2 index (Table 9). Assuming that a prey organism has just made contact with the ctenophore tenta- cles, three possible outcomes have been observed in the laboratory for different species: 1) the prey is too strong and breaks away from the tentacle hold; 2) the prey provides a strong escape re- sponse, becomes further entangled and is eaten; and 3) the prey provides little or no escape re- sponse, remains nearly motionless and "plays dead," often being dislodged from the tentacle hold and not eaten. A species which is too powerful for P. bachei to capture is H. mediterranea. The adults of this amphipod can break away from the entanglement and also have the ability to exploit the ctenophores as a predator. Prey which provide a strong, "calanoid escape response" are almost always further entangled by swirls of the tentacle branches and are eaten. The immediate strug- gling and pulling away appears to signal the ctenophore of a successful prey capture, much as I would expect that a spider detects the impact and vibrations of the prey struggling on its web. The copepods such as Acartia, Labidocera, Calanus, etc., exhibit strong escape responses when stimu- lated by contact or approaching danger. Two prey species were observed to exhibit the motionless or "play dead" response. These are C. anglicus and P. auirostria. Penilia is also one of the species which has a negative electivity index or is taken less frequently than in proportion to abundance in the water. Once the prey is brought to the mouth of the ctenophore, the next limitations are the configuration of the prey body and appendages plus the protection from external spination. Bodi- ly shapes such as those ofSagitta and zoea larvae of Porcellanidae (a family of crabs) create difficul- ties for their ingestion by Pleurobrachia. Large Sagitta must be bent in half and ingested at the middle section first (observations are from the laboratory work; gut contents from field sampled ctenophores show that this event is very infre- quent). The long anterior and posterior spines of the porcellanid zoeae prevent full ingestion and digestion entirely, although the prey probably do not survive the capture. Many other decapod lar- vae possess stout spines and very thick exoskele- tons (e.g., Emerita larvae), which prevent inges- tion and would retard digestion as well. Some brachyuran zoeae which have dorsal and lateral spines have been observed to cut open the ctenophore gut wall during ingestion. Recall that brachyuran zoeae only make up 0.25% of the total number of prey in ctenophore guts (Table 7). 324 HIROTA: NATURAL HISTORY OF PLEUROBRACHIA BACHEI IN LA JOLLA BIGHT DEMOGRAPHY AND NET PRODUCTION Methods Computations of stage-specific instantaneous mortality rates (hereafter referred to as mortality rates or mortalities) were made in order to use these values in other calculations to estimate population parameters and rates of net produc- tion. Mortalities were calculated using field data on stage frequencies treated as a composite of all samples taken on each sampling date and labora- tory data on rates of development, with tempera- ture and food concentrations being similar to aver- age values observed in the field study area. The growth or development rate data are from laboratory cultures at 15°C and 35 /jg C/liter food concentration. The mortalities were computed by a computerprogram (Fager, 1973) which solves an equation to fixed level or error by a specified number of iterative calculations. N,+ 1 IN^ = t, (1 - e ~'^^v + 1 )lt, + 1 (e ^'x - 1). (1) The variables ^r and tx^^ i are the duration of development in days for stage x andx+1, respec- tively; variables A^v andA^v+i are the numbers of each stage in the composite divided by the respec- tive duration of development. The mortality rate on a per day basis from stage x to stage x + 1 is M; for an organism with continuous growth, such as a ctenophore, a "stage" is a size category. Positive, mortalities can be calculated only when Nx ex- ceeds A'^;^ + 1 . Implicit in the calculation are the assumptions that: 1) successive stages of the or- ganisms were born during a period of constant recruitment and 2) successive stages have lived together in spatial proximity, or emigration is balanced by immigration in the water parcel. . The life table calculations were based on the estimated mortalities for different time periods of field sampling and the mean schedule of live births from laboratory cultures at IS'^C. The equa- tions used to calculate population parameters and stable age distributions are from Birch (1948). The rate of net production per day of each de- velopmental stage is a function of the numbers and weights of the animals and their instantane- ous rate of tissue growth and of mortality on a per day basis; the rate of net production by a species population of a given age structure is simply the sum of the rates for each stage. These rates are calculated from the equation of Ricker (1958), which relates the rate of net production to the mean daily standing stock and the rates of growth and mortality. NP, = G,B,il - e Gi-M )/(M,-G,) = G,Bi.(2) In this equation 0 , and M, are the mean exponen- tial coefficients or mean instantaneous rates of growth and mortality of the ith stage on a per day basis. The variables Bi and B, are the calculated standing stocks per sample in milligrams organic matter per square meter of the ith stage at the beginning of the day (B, ) and the average over a 24-h period (Bi ). This function equates the rate of net production per day for the ith stage (NP, has units of milligrams organic matter per square meter over a 24-h period) to the instantaneous rate of tissue growth times the standing stock at the beginning of the day (the beginning of the day is the time a field sample is taken) corrected for differential increases due to tissue growth and differential decreases due to mortality. For further details refer to the work of Ricker (1958) and Mullin and Brooks (1970). Note that the rate of net production per day is actually an average value, because it is calculated using means for growth and mortality rates. The rates of net production for postlarvae and larvae of P. bachei were calculated according to Equation (2) above. No values for mortality rates of eggs were calculated, but the hatching time of eggs at 15°C is about 24 h. In calculation of the net production of eggs per day, it is assumed a steady state in the standing stock of eggs with a hatching time of 24 h. This is equivalent to the assumption that the rate of net production of eggs per day is equal to the standing crop at the time of sampling the eggs. From calculations of the net production per day of postlarvae for each replicate sample at each station, the mean value and the variance of the mean are calculated according to standard parametric statistics. At a given station, the total amount of organic matter produced over some in- terval of time, i^, equals the product of the mean rate per day and the time interval in days. For calculations of the annual net production (ANP), it is assumed that the mean rate per day on a given sampling date at one station applies linearly over an interval of time equal to the sum of one-half 325 FISHERY BULLETIN: VOL. 72. NO. 2 the period between the given sampHng date and the previous sampling date plus one-half the period between the given sampling date and the next following sampling date. The ANP equals the sum of all net production increments over the year. tn=n ANP = SUM NP t„ (tn 4 ; -t, - ; )/2. tn — J- (3) In the equation tn refers to the nth sample date, ^Ptn refers to the mean rate of net production per day on the nth sample date, and ANP is the mean value of the annual net production for any life history stage being considered. For the first and last sampling dates of the year, the mean rates per day were applied over one-half the following sampling date interval and one-half the previous sampling date interval, respectively. Calculations using Equation (3) were carried out separately for postlarvae, larvae, and eggs at station 5 off Scripps, and the total for all life history stages is the sum of the annual values for the eggs, larvae, and postlarvae at that station. ANP was also cal- culated at stations 1, 3, and 6 for postlarvae only. The variance of the mean value of the ANP at a given station was calculated as the product of the variance of the mean rate of net production per day and the square of the time interval over which it was applied, summed for all time intervals dur- ing the year. The equation was derived from the variance formula of a dependent variable which equals the product of two independent variables (net production over a time interval, a t, equals the product of the mean net production per day and zi^), by solving for the square of the differen- tial of net production over a time interval a^ The covariance term is zero since the daily net produc- tion and time interval between sampling dates are independent. The term for the square of the mean daily net production multiplied by the variance of A Ms presumed to be small, because sampling dur- ing the year was within a few hours at the same time of the day for all sampling dates. t„=n Var(ANP)=SUM Var(A^P^J(^„4i-^„_im.(4) n ^ 1 The symbols are as given above in Equation (3), and Var (ANP) and Nd,x{NPtn) refer to the var- iance of mean annual net production and the var- iance of mean daily net production on sampling date tn, respectively. Results During the field study from 8 March 1970 to 2 June 1971, 100 mortality values were obtained for postlarvae and larvae. On any one sampling date it was not possible to calculate mortality values for all size classes, especially with small sample sizes in older stages. Therefore, the mortalities from all sample dates were grouped into seven time periods and seven size classes (excluding eggs) in order to obtain an estimate of mortality for each class over time. The mortalities were grouped according to the subjective criterion that medians of a group would differ from any other by at least 50%. The mortalities for size classes were set by the comparisons of mean numbers per class between successive classes. For the time period of 1 May to 18 June 1970 a life table calculation is given in Table 11. The mean hatching success of eggs is 94%. The Ix values are the probability that an individual born will survive to the beginning of each age interval. The instantaneous mortality rates which were used to construct the / ,: schedule are as follows: 1) 0.170 for larvae ofage 1-19 days, 2) 0.021 for stage 1-2 mm postlarvae ofage 19-45 days, 3) 0.150 for stage 3-4 mm postlarvae of age 45-53 days, 4) 1.047 for stage 5 mm postlarvae ofage 53-54 days, 5) 0.572 for stage 6 mm postlarvae ofage 54-55 days, 6) 0.378 for stage 7-8 mm postlarvae ofage 55-63 days, and 7) 0.260 for stage 9-13 mm post- larvae ofage greater than 63 days. These mortal- ity rates were applied equally for each age inter- val over the duration of the respective stages. Note that up to age 53 days (4.5 mm) the first 45 live births give a net reproduction of 1 .0405 (60% of the total), enough to replace the population. The next 53 live births add 23% of the total net reproduc- tion. The enormous potential reproductive capac- ity at age 61-63 days and older is not fully realized because of the miniscule numbers which survive to this age. These results show the great impor- tance of early reproduction in size classes 1-2 mm toward the net reproduction. The population parameters and stable age dis- tributions in May-June and three other time periods, each with its own schedule of survival and the mean schedule of births, are shown in Table 12. For the 1 May to 18 June period, the observed 326 HIROTA: NATURAL HISTORY OF PLEUROBRACHIA BACHEI IN LA JOLLA BIGHT Table 11. — The life table for Pleurobrachia bachei during 1 May- 18 June 1970 based on laboratory growth and reproduction data at 15°C and calculated mean rates of mortality for this period. The symbols dx.lx. bx andx represent the age interval in days, survival to the beginning of the age interval, the numbers of live births during the age interval, and the pivotal age, respec- tively. dx 1x bx 1xbx Ubxx 0-1 1 .0000 1-3 .9400 3-5 .6691 5-7 .4762 7-9 .3390 9-11 .2413 11-13 .1717 13-15 1222 15-17 0870 17-19 .0619 19-21 .0441 21-23 .0423 23-25 .0405 1 0.0405 0,9720 25-27 ,0388 0 27-29 .0372 0 29-31 .0357 1 .0357 1,0710 31-33 0342 0 33-35 0328 0 35-37 .0315 0 37-39 0302 0 39-41 .0290 0 41-43 .0277 6 .1662 69804 43-45 0266 15 .3990 17.5560 45-47 .0256 3 .0768 3.5328 47-49 ,0189 13 .2457 11.7936 49-51 .0140 4 .0560 2.8000 51-53 .0103 2 .0206 1.0712 53-55 .0077 53 .4081 22.0374 55-57 .00152 102 .1550 8.6800 57-59 .00071 8 .0057 .3306 59-61 .000336 53 .0178 1.0680 61-63 .000158 353 .0558 3.4596 63-65 .000074 325 .0240 1.5360 65-67 .000044 302 .0133 .8778 67-69 .000026 204 .0053 .3604 69-71 .000015 557 ,0084 .5880 71-73 000009 298 ,0027 .1944 73-75 .000006 960 ,0058 .4292 75-77 ,000003 1026 ,0031 .2356 77-79 .000002 1319 ,0026 2028 Ro - = 1,7481 85.7768 mean age distribution in field samples was 66.7% eggs, 20.0% larvae, 8.7% 1- to 2-mm postlarvae, and 4.7% all other stages. The field age distribu- tion is unlike the stable age distribution in that the proportions of eggs and larvae are reversed and the proportion of late stages is sevenfold higher than in the stable age distribution. The population growth rates (r) in other time periods predict decreases of population abundance from 8 March to 2 April (r = -0.105) and increases in 14 July to 21 August (r = 0.020) and in October (r = 0.0115). Eggs and larger ctenophores were again more frequent, and larvae less frequent in the field during July- August than calculated for the stable age distribution. For postlarvae the mean rate of net production per day for all stations located 1.6 km from the shore (Table 13) followed the seasonal variation in the standing stocks. The maximum rate of net pro- duction on 13 August, 212 mg organic matter m'^ day , was about 20% of the standing crop. About two-thirds of ANP occurred during August. The variance of the mean ANP is quite large, but since the confidence limits for the mean are determined by standard deviations, the 95% confidence inter- val for the mean ANP is 4,200-6,280 mg organic matter m~^ yr \ Mean ANP of postlarvae at stations 1, 3, and 5 (1.6 km from shore) and at station 6 (10 km from shore) are given in Table 14. Note that "annual" net production at the stations 1, 3, and 5 are for 0.956 yr and at station 6 for 0.84 yr; these values were not corrected to a full year by proportion, because statistical tests based on variances would not be valid. Tests for differences of variances (F-ratio) and means (f-tests) between stations 1, 3, and 5 were made. The variance of station 3 was significantly different from that of stations 1 and 5 rP<0.01), but the variances of stations 1 and 5 were not different from each other (P>0.05). The difference between means of all pairs of contrasts for stations 1, 3, and 5 are significant (P<<0.01). The net production at station 6 located 10 km from shore off Scripps Institution was about Table 12. — Summary of population parameters for P. bachei during four time periods in 1970. The symbols /Jo,'", T,B, b,d andCx refer to net reproduction, instantaneous rate of population growth, generation time, finite birth rate, instantaneous birth rate, instantaneous death rate and stable age distribution respectively. The percentages of eggs (E), larvae (L), 1-2 mm, and s 3 mm stages are given in that order for the stable age distribution. Time period «o r T B b d Cx 8 Mar.-2 Apr. 0.0058 -0.105 49.0 0.2485 0.2617 0.3667 1 May-18 June 1.7481 00115 48.6 0.2348 0.2328 0.2213 23.3 E 69.0 L 7.0 1-2 mm 0.7 3 3 mm 14July-21 Aug. 2.9271 0.020 53.7 0.248 0.248 0.228 24.6 £ 69.3 i. 5.6 7-2 mm 0.5 3 3 mm 8-22 Oct. 1.7565 0.0115 490 0.2348 0.2328 0.2213 Same as 1 May-18 June 327 FISHERY BULLETIN: VOL. 72. NO. 2 Table 13. — Seasonal variation of the mean rate of net produc- tion per day (NPtn is in mg organic matter rii^ day"') for postlar- va\ Pleurobrachia bachei at stations located 1.6 km from shore in La Jolla Bight. The mean annual net production is given as the sum of the mean rate per day multiplied by the appropriate time interval, A <; the variance of the mean annual net production is also given. Note that the sum is for 0.956 yr. Sampling Number of NPtn NPtn(^t) Var(/VPrn)Af2 date samples 18 June 1970 10 5.188 36.316 270.5065 2 July 10 5.356 69.628 216.5228 14 July 10 9.080 131.660 639.0759 31 July 10 38.396 575.940 35.286.5025 13 Aug 10 212.287 2,229.014 102.152 1706 21 Aug- 8 70.454 563,632 11.169.1520 29 Aug. 10 22.712 295.256 2,370,3264 16 Sept. 6 21.416 428.320 2,824,7200 8 Oct. 6 10.843 195.174 7,217,9748 22 Oct. 6 41.882 586.348 91,135,2960 5 Nov. 6 1.775 23.962 141,4260 18 Nov. 6 0.350 4.725 7,4322 2 Dec. 10 0.114 1.596 0.7291 16 Dec. 10 0.0003 0.006 0.0003 11 Jan. 1971 6 0.321 6.741 14.4207 27 Jan. 6 0.962 13.468 87.1612 8 Feb. 8 1.745 25.302 102.6440 25 Feb. 6 0.240 3.840 4.9306 12 Mar. 6 1.148 24.108 221.5584 7 Apr. 6 1.018 20.360 48.4800 20 Apr. 6 0.202 2.727 2.8978 4 May 6 0.061 0.854 0,1764 18 May 6 0.044 0.638 0,1051 2 June 6 0.002 0.015 0 0004 SUM 5.239.63 253,914,2097 sevenfold lower than that at station 5 (1.6 km off Scripps Institution) and fivefold lower than the mean for all stations located 1.6 km from shore. For these comparisons, the production at station 6 was extrapolated to 0.956 yr. The net production of larvae and eggs at station 5 contributed only about 3% of the sum of net production of eggs, larvae, and postlarvae at that station. For stations 1,3, and 5 the annual mean ratio of the net production per day of postlarvae to their mean daily standing stock (B, of Equation (2)) are 0.197, 0.196, and 0.211, respectively. The mean ratios are based on 32, 43, and 54 observations for stations 1, 3, and 5, respectively. There are no significant differences between the variances (F-ratio tests) of all paired contrasts of stations (P>0.05). There are no significant differences be- tween all paired contrasts of station means (P>0.50). The overall annual mean ratio at these three stations is 0.202, with 95% confidence limits for the mean being 0.187-0.217. Thus, the ratio of production to biomass on the day of maximal pro- duction was no greater than the annual mean. In order to estimate the food chain efficiency (defined for any trophic level L as the steady state ratio of yield to predators at level L -I- 1 to the net production of trophic level L-1) of the transfor- mation of materials or energy by trophic levels, the two parameters stated above must be known: 1 ) the net production of potential food at level L-1 and 2) the yield to predators from the level L, which in steady state is the total net production of level L minus losses to decomposers. This concept can be extended to include more than three trophic levels, e.g., the square root of the ratio of ingestion by secondary carnivores to net primary production might be termed the equal transfer efficiency of herbivores and primary carnivores. In practice it is very difficult to accurately "measure" the secondary production of the entire herbivore trophic level in the sea, and such data are not available in my study area. Further, the estimates of net production by P. bachei could not be partitioned into the fractional losses to decom- posers and as yield to predators. Therefore, two simplifying assumptions were made in calculat- ing the transfer efficiency for the macrozooplank- ton of La Jolla Bight: 1 ) all of the net production by P. bachei resulted in yield to predators and none to decomposers and 2) the efficiency was constant and equal from the primary producer level through the first-order carnivore level of P. bachei. Given these limiting assumptions, the efficiency calculated is referred to as the "equal transfer efficiency." Thus, if net production data were not available for trophic levels between primary producers and the trophic level of in- Table 14. — Summary of "annual" net production (ANP) values (in mg organic matter in^ time"') of Pleurobrachia bachei, at four stations in La Jolla Bight. The value at station 6 is for 0.84 yr; all other values are for 0.956 yr. The standard deviation of ANP for each respective value is also given. Values are for postlarvae unless otherwise specified. The mean production for larvae and eggs at stations 1-5 were calculated assuming that the same fraction of production would be as larvae and eggs at all stations as at station 5. Number of Station sample dates ANP SD 1 24 2.320 104 3 24 4,320 377 5 25 7.650 144 Larvae 111 Eggs 125 18 6 6 17 950 85 Mean of 24 5,240 504 station 1-5 Mean of 24 5.240 station 1-5 99 Larvae plus eggs and 76 Eggs larvae 5,415 504 328 HIROTA: NATURAL HISTORY OF PLEUROBRACHIA BACHEI IN LA JOLLA BIGHT terest, a general equation to calculate equal trans- fer efficiency for n transfers is ETE ^(NPL/NPP)^'^ (5) In the equation ETE is the equal transfer efficiency, NPL is the net production of trophic level L (which is equal to ingestion by level L + 1), NPP is the net primary production, and n is the number of transfers from primary producers (the zeroth trophic level) through trophic level L. This equation was derived from the works of Schaefer (1965) and Ryther (1969). The equal transfer efficiency calculated in this manner for n>2 says nothing about the efficiency of a given trophic level, but only the equal efficiency of all trophic levels from primary producers through trophic level L. The equal transfer efficiency from primary pro- ducers through P. bachei was calculated using es- timates of annual net primary production in the coastal waters of southern California, ANP of P. bachei, and the weighted mean number of trans- fers from primary producers through P. bachei. The mean number of transfers was calculated from the percentage contribution from each of 21 prey categories to the total numbers of prey (these 21 categories are 989c of the total numbers of prey in the stomachs of P. bachei over a year) and best guesses as to the number of transfers from prim- ary producers to each of the 21 prey species. The mean and range of ANP by all stages of P. bachei extrapolated to 365 days (5,700 and 8,300-2,500 mg organic matter) were converted from units of organic matter into organic carbon by taking 50% of the organic matter as organic carbon. The mean and range of annual net primary production (400 and600-200gC m yr ) were estimated from the mean and range of the rates per day in southern California coastal waters (Eppley, Reid, and Strickland, 1970; W. Thomas, pers. commun.) and multiplication by 365. The expectation of the number of transfers from primary producers through P. bachei is 2.3 with an upper limit of the estimate equal to 2.5. These fractions occur be- cause species of animals often do not fall into a single trophic level, and this is in fact the case with P. bachei; some of its prey organisms are herbivorous and some are themselves carnivor- ous. The equal transfer efficiency was calculated and presented in a matrix for the means and ranges of the three variables stated above (Table Table 15. — Calculations of the equal transfer efficiency in per- cent for different numbers of transfers from primary producers through Pleurobrachia. given the observed range and mean of annual net production of P. bachei and the estimated range and mean of annual net primary production in g C m^ yr"'. In each group of three values, the first is for the highest value of ctenophore net production (4.1 g C m^ yr '), the second is for the mean (2.8 g C m^ yf ) and the third is for the lowest value ( 1 .2 g C Net primary Number of transfers produ ction 20 2.25 25 200 14.3 17.8 21 1 11.8 15.0 18.1 7.7 10.3 12.9 400 10.1 13.0 16.0 8.4 11.0 13,7 5.5 7.6 9.8 600 8.3 10.9 136 6.8 9.2 11.7 4.5 6.3 8.3 15). Note that the range of equal efficiency is found on the diagonal from the lower left to the upper right of the table. The overall central value is an equal efficiency of 11%. This efficiency of transfer involves phytoplankton, herbivores, and those primary carnivores on which P. bachei feeds, P. bachei, and the predators and parasites of P. bachei. This efficiency equals the nth root of the ratio of ingestion by predators of P. bachei to net primary production. DISCUSSION Life table parameters of P. bachei show adap- tive value in the interdependence of the schedule of births and the rates of development and mortal- ity on population growth. Early reproduction makes a very important contribution to net repro- duction and population growth rate, but only in relation to the rates of development and mortality. The larvae have relatively high rates of mortality and lower rates of growth compared to other stages. The 1- to 2-mm postlarvae have the low- est rate of mortality and grow slowly, but they are able to reproduce at an early age and thereby contribute an important fraction of net reproduc- tion. The 3- to 7-mm stages have very rapid tis- sue growth (instantaneous rates of 0.21-0.47) but do not contribute many young to the population. Instead, these larger stages are important to net production of organic matter because of their rapid growth and high abundance in summer. The stages larger than 8 mm are able to produce enormous numbers of young, but few survive to 329 FISHERY BULLETIN: VOL. 72. NO. 2 this size in nature. Regulation of population growth rate would be very sensitive to changes in mortality rates during production of the first 50-100 young and again during the production of the several hundred young by later stages. The seasonal occurrence of//, mediterranea and the frequency distribution of single and multiple infections and of the percentage of cases for differ- ent stages of hosts show two kinds of patterns that are related to life history episodes: 1 ) the parasites do not often attack the 1- to 2-mm stage postlar- vae which are important to net reproduction as discussed above and 2) the parasites occur mainly as one or two individuals per host and most fre- quently in 6- to 8-mm postlarvae. The early stages of parasites infect the larger hosts more frequently than the smaller hosts because of sea- sonal availability and perhaps also because of the ability of the larger hosts to better accommodate the extra metabolic burden. The "strategy" of the parasites appears to be infection of larger hosts with few young to provide sufficient food and shel- ter during their development, but not overexploit each host with too many parasites. The larger stages of hosts are buffered against local extinc- tion by adult parasites, because suitable hosts be- come more difficult to locate the faster they die. The total ctenophore population has some protec- tion from overexploitation of postlarvae by para- sites and other predators in the presence of rela- tively large numbers of eggs and larvae and the ability of young postlarvae to reproduce soon after development to 1-mm size. The calculated population growth rates of P. bachei indicate that the minimum time for a popu- lation doubling is about 35 days (0.693/0.02). This suggests that rapid increases of Pleurobrachia observed on a time scale less than a month are probably due to gross advective change if refer- ence of a "bloom" is made to total abundance of all stages. However, the growth in bodily size of Pleurobrachia from 2 mm to 6-7 mm diameter may occur in about 2 wk, and this may account for the visual impression of a bloom. Regarding indi- vidual and potential population growth rates the salp Thalia democratica as another macrozoo- plankter, is much faster than P. bachei (Heron, 1972a, b). The statistical treatment of variances for mean net production per day describes precision of the estimates, which probably is not the same as inac- curacy in the estimates. For example, it is ques- tionable whether growth rates in the laboratory under constant temperature, food concentration, and food type are accurate estimates of the rates in nature. Variation during a day in ambient condi- tions appear to be at least as important or more important than the average condition (e.g., temp- erature). The rates of tissue growth and mortality both depend on the duration of development within a stage, and they are not fully independent variables although they are treated as such in Equation (2). Another error ignored in the statis- tical treatment is the variance of the standing stock calculated for each replicate sample. I as- sumed in the calculation of the net production per day for each replicate sample at one station that the variance for the best estimate of the crop is negligible compared to the deviations between the best estimates from the regression equations for each sample. The net production per day for each replicate sample is based on the mean rates of growth and mortality and the best single estimate of the standing crop. The variance for the mean value of the ANP depends on the variance of the mean net produc- tion per day and the square of the time interval over which the rate is linearly applied (Equation (4)). Assuming that the data on net production per day would have a Poisson distribution (variance equals the mean), reasonably small 95% confidence limits for the annual net production (ANR±ANP/10) are obtained with repHcate sam- ples if each of ten sampling dates is spaced evenly during the year. The limits are relatively insensitive to whether the seasonal distribution of production is rectangular and continuous, rectan- gular and discontinuous, or triangular and discon- tinuous. The important considerations to minimize the confidence limits for the mean an- nual production are: 1) the number of observations per sampling date, 2) the number of sampling dates, and 3) the time interval between sampling dates in relation to the seasonal maximum abun- dance and rate of production. The number of ob- servations per sampling date is determined by the number of replicate samples and the number of stations. More stations and replicate samples im- prove the accuracy in estimating the mean and should decrease the variance of the overall mean for a given sampling date. The number of sam- pling dates minus one is the number of degrees of freedom for the ^-statistic which is multiplied by the standard deviation of the mean to give one tail of the confidence limit. The time interval between sampling dates will affect the variance for the net 330 HIROTA: NATURAL HISTORY OF PLEUROBRACHIA BACHEl IN LA JOLLA BIGHT production over a given period as the square of the interval; therefore, sampling should be carried out on a regular basis without long intervals between dates unless previous information is available on the seasonal distribution of production and the relationship between means and variances. Three parameters can influence the magnitude of net production by P. bachei in addition to errors in the estimation of abundance: 1) water tempera- ture, 2) food supply, and 3) parasitism. In the first two cases, it would appear that for the observed range of temperature and food supply in the study area temperature is more important than food supply. A 10°C range of surface temperature over the year or the temperature change experienced during a postulated 20-m vertical migration in August (see Figure 8) should affect the rate of growth in length and weight and survival. Data are not sufficiently good for quantitative state- ments about the effect of vertical migration dur- ing August on rates of tissue growth, net produc- tion, and population growth. The case for the effect of food supply on rates of net production is some- what better than for temperature. Rates of growth in the laboratory at 15°C are essentially the same for ctenophores cultured on Acartia at 35 /ug C/liter and 500 yug C/liter. The rates of growth in length and weight at 14.5'C and 1-2 ^;g C/liter of mixed natural food organisms indicated that the postlarvae grow about as well as at tenfold higher food concentrations. From field samples in which the calculated food concentration was about 10 Mg C/liter growth rates in the laboratory and from the field size frequency distributions agree within ±20% of the mean rate. It appears therefore that P. bachei postlarvae are very efficient at the ex- traction of prey from the water at very low con- centrations. The estimates of gross growth efficiency showed that over one-half of the food ingested was incorporated into somatic tissues. Perhaps the "passive" feeding mode of these car- nivores allows them to have a very low threshold for the commencement of feeding activity, espe- cially since the area of the tentacles is very large in relation to the bodily size of the ctenophore, and relatively low metabolic expenditure is generated while waiting for prey to contact the tentacles. The estimates of ANP by P. bachei are also inaccurate, because no corrections were made for effects of parasitism hy Hyperoche on rates of tis- ' sue growth and duration of development. Since the occurrence of parasitism and high rates of production both were in August (two-thirds of the ANP was in August), correction may not be triv- ial. It is not possible to make a quantitative esti- mate of the error based on any data, but the follow- ing sources of error must be considered: 1) the standing stock, B,, was overestimated by the amount of ctenophore tissue in the volume that the parasites occupy; 2) the instantaneous rate of tissue growth, G,, was overestimated by the dif- ference between the instantaneous growth rates of nonparasitized and parasitized ctenophores; 3) the instantaneous rate of mortality, M, , was overes- timated by the difference between the durations of development of nonparasitized and parasitized ctenophores (see Equations 1 and 4) the total loss of ctenophore tissue (due to mortality of all types and to ingestion of tissue by parasites that does not result in mortality) in one time increment was underestimated by that fractional amount of tis- sue removed from the mean standing crop during the time increment by parasitism. Overestima- tion of the standing stock of ctenophores due to presence of parasites is believed to be negligible, especially since only one or two parasites were present in 927c of all cases (Table 4). For given values of standing stock and rates of growth and m.ortality(e.g.,fi, = 100mg/m2,G, =0.2,andM, = 0.5), the effect of additional tissue loss due to parasitism on the rate of net production is rela- tively small (ca. 107c) for instantaneous rates of parasitism up to 50% of the rate of mortality. The mean net production per time interval was overes- timated. The actual extent of the overestimate can not be evaluated without more information on the effect of parasitism on ctenophore growth. The ratio of net production per day to mean standing crop during the day for all postlarvae is the biomass-weighted mean instantaneous rate of tissue growth (Allen, 1971), assuming that growth and mortality rates are exponential. The similarity of mean values between stations 1, 3, and 5 is due partly to the bias of having used only the growth rates at 15°C throughout the year, but the range between stages of the mean exponential growth rate is at least tenfold. Some of the consis- tency in ratios of production to mean standing stock is due to similarity in the length frequency distributions between stations and relative con- tribution of different stages to the total crop. The overall annual mean production to standing stock value of 0.202 indicates that net production per day is 20% of the mean daily standing stock. This value is within the range of values summarized by MuUin (1969), but is quite high considering the 331 F1SHFR\ BULLETIN: VOL 72, NO. 2 relatively large size of postlarvae (e.g., over 10 mg organic weight). The 11% overall mean in the equal transfer efficiency is surprisingly close to the values of ecological efficiency measured in the laboratory (Silliman, 1968; Slobodkin, 1968); food chain efficiency is the same as ecological efficiency if all food available to a consumer level is ingested (the range for ecological efficiency is generally ac- cepted to be 5-20%). The stability and con- vergence characteristics of these efficiencies must be set by two boundary conditions: 1) the minimum net production and food required to just replace the component species within a trophic level and 2) the age-structure weighted max- imum gross growth efficiency of the component species within a trophic level. The upper limit is set by the physiological maximum gross growth efficiency of each developmental stage weighted over all stages and species in proportion to their relative abundance. In this regard the adults of P. bachei are very efficient (60% ) at converting food ingested into somatic tissues, and this is probably near the upper limit of gross growth efficiency. Low ecological efficiency is found in species popula- tions dominated by older, slowly growing indi- viduals with low growth efficiency and low rates of mortality (Mann, 1965). In nature it would seem unlikely that food chain efficiency through several successive trophic levels could vary widely. For example, a low efficiency through producers to herbivores means that less net herbivore produc- tion would be available to first-order carnivores, all else being equal. Under these circumstances the efficiency through herbivores to first-order carnivores should also be low, because the carni- vores must search a larger volume or area to feed and this decreases growth efficiency. Conversely, a high efficiency through producers to herbivores should perpetuate a high efficiency through her- bivores to carnivores, unless the age or size dis- tributions of herbivores which yields high net pro- duction from producers is not conducive to max- imize the efficiency through herbivores to first-order carnivores (i.e., the herbivores are predominantly younger stages which are not avail- able to those stages of carnivores which possess the highest growth efficiency). There is some evidence from lakes and from theoretical considerations of growth patterns that food chain efficiency is at least in some cases de- termined by growth efficiency of component species in a food chain and their metabolic flexibility in response to size and abundance of prey (Kerr and Martin, 1970; Kerr, 1971). In com- plex marine systems considerable effort must be expended before the predator-prey interactions are described and the metabolic rates and efficiencies are measured. Meanwhile, an expla- nation based on sound theoretical grounds is needed to show why the food chain and ecological efficiencies tend to converge on 10% and have a relatively small range from about 5 to 20%. SIGNIFICANCE OF P. BACHEI IN THE PLANKTON The coastal waters of southern California rep- resent an ecotone which includes the boundary of land and sea. It is influenced strongly by physical processes and the biota in the water from several sources. The relatively shallow depths within the first 2-3 km from shore emphasize the inter- dependence and coupling of the benthic and planktonic communities. The benthic community depends on the planktonic community for some of its food supply and for removal of the least fit individuals of those meroplanktonic larvae re- leased by benthic animals. The plankton commun- ity receives some of its food in the form of mero- planktonic larvae, and the benthic community re- turns the materials removed from the water in the form of regenerated nutrients, detritus, and de- composing tissues. It is not surprising, therefore, that Euterpina andOithona are the prey of young stages of newly settled juvenile garibaldi, Hyp- sypops rubicunda (Clarke, 1970) and also of P. bachei. The pattern of high standing stocks of different trophic levels and intense biological activity within the first 5-10 km from shore is probably associated with the high regeneration rates of nutrients and high productivity in shallow water (Anderson and Banse, 1961) and life history adap- tations of coastal water species to exploit highly productive zones. The short generation times of microcopepods, parthenogenesis in cladocerans and spined eggs o^Acartia are some adaptations to enable rapid exploitation of favorable conditions in the plankton. The coastal waters may be com- pared to a chemostat. The rates of dilution by physical forces vary in time and space, but the specific growth rates of the organisms plus their refugial seed stocks and immigrants enable them to persist over time. The quasi-continuous change 332 HIROTA: NATURAL HISTORY OF PLEVROBRACHIA BACHEI IN LA JOLLA BIGHT in the physical-chemical habitat of the coastal waters prevents the formation of a stable, time-independent assemblage of organisms, al- though the system appears to be basically com- posed of the same recurrent species in seasonally varying proportions. Occasionally expatriates from oceanic, southern waters, and northern wa- ters appear (e.g. , Candacia, Eucalanus attenuatus, Tortanus discaudatus, Velella, etc.). The tran- sients are joined by some organisms which appear seasonally in this area during spawning migra- tions (e.g., gray whale, squid, grunion). The regulation of population size in Pleuro- brachia is postulated to be through density- dependent feedback meahanisms proposed by Greve (1972), in which the prey of larger ctenophores (e.g., adult stages of copepods) are detrimental to survival of the small ctenophore larvae. Balance in the abundance of predators and prey is conferred by selection of larger copepods by the larger ctenophores (Bishop, 1968), but with dependence of ctenophore larvae on copepod naup- lii for food supply and low abundance of adult copepods for their survival. A high density of copepod nauplii and low density of copepod adults would favor occurrence of ctenophore larvae and early postlarvae. As both prey and predators grow the roles of predator and prey become reversed to some extent. The large ctenophores may nearly deplete the water of large copepods to satiate their metabolic demands, but this condition is unstable, because the larger ctenophores will become food limited. The population size will not increase greatly because few adult copepods are available to produce eggs, and the nauplii which are hatched from eggs are needed for food of larval ctenophores. If the abundance of postlarvae should increase and some threshold is exceeded, the ctenophore population also becomes vulnera- ble to density-dependent predation by Bero'e and other predators and infection by parasites. All organisms in nature consume food, recycle materials through excretion (and exuviation), and are themselves consumed. In this regard the func- tional role or ecological significance of a species population is closely related to its relative abun- dance and rates of turnover. Pleurobrachia bachei is a dominant carnivorous zooplankter during summer and fall in the coastal waters off San Diego. Its functional role can be divided into three parts: 1) a predator which regulates the abun- dance of small crustaceans (copepods and cladoce- rans) and removes least fit individuals, 2) a vehi- cle which provides shelter and nutrition for para- sites such asHyperoche, and 3) an organism which transfers and transforms material and potential energy in the planktonic food web. As a predator, the role of selective removal of prey is an impor- tant factor for both the evolution of size, shape, behavior, etc. in the coastal water species and for regulating the abundance and species composition of prey. Pleurobrachia bachei is not unique as a planktonic form in providing shelter and nutrition for co-occuring species; salps are exploited in a similar manner by copepods, except that details of the life histories differ (Heron, 1969). As a season- ally dominant carnivore, P. bachei is also un- doubtedly an important species which transfers organic matter and potential energy to higher trophic levels in the food web of La Jolla Bight. ACKNOWLEDGMENTS I am indebted to Michael M. Mullin for his gui- dance and suggestions throughout my research, especially in laboratory work and critical evalua- tion of data. I received considerable help from E. W. Fager and E. Stewart with computer programs and other help in calculations. E. W. Fager also made many suggestions regarding statistical treatment of abundance and production data. T. E. Bowman kindly identified the amphipod parasite of Pleurobrachia bachei as Hyperoche mediter- ranea. The drogue studies and many other aspects of field work were done jointly with A. M. Barnett and D. Kamykowski. Their help in preparation of equipment and participation in cruises is greatly appreciated. I also thank my wife Gail and parents for their support and encouragement. 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Clarke' ABSTRACT Forty-seven species of eight families of stomiatoid fishes were collected in the upper 1,000 m near Hawaii. Most species appear to undertake diurnal vertical migrations; only two definitely did not. Many of the abundant species showed changes in size composition within both day and night depth ranges, the smaller fish occurring shallower. All sizes of several other species appeared to occur throughout their depth ranges. Seasonal changes in the size composition of several species indicated that they spawn principally in the summer. Several species appear to avoid the Isaacs-Kidd trawl better during the day than at night. Some species appeared to avoid the Isaacs-Kidd more than a larger trawl, but many were sampled as well or better by the former. Absence or rarity of mature individuals of several species indicated that the larger fish avoided both trawls. Relationships between vertical distribution and morphology of some species are proposed, and potential interactions between species are considered relative to the degree of similarity of depth ranges or size-depth patterns. Stomiatoids are a dominant and diverse group of mesopelagic fishes. Most previous work on the group has been of a systematic or zoogeographic nature, and only recently have the systematics of some families come into order. With the exception of a few works such as Kawaguchi and Marumo (1967) and Krueger and Bond (1972), ecologically pertinent information such as depth ranges, mi- gration habits, etc., has been appended to other studies and is usually based on so few specimens or inappropriate sampling programs that it is of dubious value. Consequently, even for the fre- quently collected species, little is known of their ecology — especially in comparison to knowledge of the myctophids, another important group of mesopelagic fishes. This paper considers data on 47 species of stomiatoids collected by a mid-water trawling survey in the central North Pacific near the Hawaiian Islands. (Specimens of the Sternop- tychidae and the gonostomatid genus Cyclothone are being investigated by other workers, and the systematics of three genera of the Melanos- tomiatidae are so confused at present that these genera cannot be considered in detail here.) For many species, sufficient numbers were collected to present reliable estimates of depth ranges, migra- 'Hawaii Institute of Marine Biology and Department of Oceanography, University of Hawaii, Honolulu, HI 96822. tions, and seasonal changes in size composition. The habits of this diverse group are compared with those of other mesopelagic fishes. METHODS All specimens considered here were collected near the island of Oahu, Hawaii (lat. 22°20-30'N, long. 158°20-30'W). Details of the sampling pro- gram are given in Clarke ( 1973), and will be only summarized here. Four series of samples were col- lected with a 10 foot Isaacs-Kidd mid-water trawl (IK). These were taken at approximately quar- terly intervals (September 1970, December 1970, March 1971, and June 1971) and attempted to cover the upper 1,000 m of the water column both day and night for each season. Useful information was also derived from a series of samples collected with a 6-foot IK in the upper 400 m at night and between 400 and 1,000 m during the day in June 1970, from a series of samples with a 10-foot IK in the upper 190 m at night during periods of new and full moon in September-October 1971, and from preliminary samples taken in September- November 1969. Also included are data from a series of tows made by the Southwest Fisheries Center Honolulu Laboratory, National Marine Fisheries Service (NMFS), NOAA in conjunction with the March 1971 IK series; these sampled the Manuscript accepted August 1973. FISHERY BULLETIN: VOL. 72. NO. 2. 1974. 337 upper 200 m at night with a modified Cobb pelagic trawl (CT) described by Higgins (1970). I have also examined specimens of some species taken near Hawaii by R. E. Young with a modified Tucker trawl equipped with an opening-closing device. The IK and CT were fished without opening- closing devices. Winch and ship speed were ad- justed to minimize forward motion of the trawl during descent and ascent. Time-depth recorders were attached to the trawls. A few oblique tows were made, but mostly the trawls were towed for 2-3 h at the same depth. Actually, the trawls often sank or rose gradually during the "horizontal" part of the tow, but the range fished was small relative to spacing of different tows. A single, most frequently fished depth was assigned to each tow. The IK was towed at about 1.75 m/s and the CT at about 1.5 m/s. All "night" samples were taken between 2000 and 0500 h, "day" samples between 0800 and 1700 h. Specimens were identified principally from data given by Grey (1964), Morrow (1964a, b, c), Mor- row and Gibbs (1964), Gibbs (1964), Barnett and Gibbs (1968), Goodyear and Gibbs (1969), and Novikova (1967).^ Standard length of all speci- mens was measured to the nearest millimeter. With a few exceptions, gonads of only larger specimens were examined to determine size at maturity and any seasonal changes in gonad de- velopment in mature females. Size at maturity was taken as that of the smallest female which carried obviously ripened ova. For each species considered, the total number of specimens ex- amined and the length range in millimeters are given in parentheses after the species name. The lower limits of depth ranges of the species are, of course, open to some question since the trawls were fished without opening-closing de- vices. The reliability of estimated depth ranges for the more abundant species (50-100 specimens) is probably fairly high. Catches from tows within the depth range were obviously greater than those of deeper tows which passed through the depth range. The latter were comparable with catches of short oblique tows taken during the program and were considered to be contaminants, i.e., caught during ascent or descent, unless data from the opening-closing Tucker trawl indicated other- wise. Any catches below the "normal" depth range that were unexpectedly high or different in size ^Specimens of all species considered here will be deposited at the U.S. National Museum. FISHERY BULLETIN: VOL. 72, NO. 2 composition, etc., are discussed under the species headings. Many species considered here were, however, so rarely taken that there is considerable doubt about estimates of depth ranges and vertical mi- gration. The chances of being taken in a tow with- in the actual range were not much greater than those of being taken during descent or ascent of a deeper tow. Catches with the opening-closing Tucker trawl were helpful in only a few cases since the species where greatest doubt exists were rare to begin with and many were not captured at all or as frequently by the Tucker trawl. For species which were collected in sufficient numbers (ca. 10/tow or more) in more than one tow during a series, changes in size composition with depth were assessed by comparing the size- frequency curves of individual samples from dif- ferent depths using the Kolmogorov-Smirnov test (Tate and Clelland, 1957). Size composition was considered significantly different if the probabil- ity associated with the difference between curves was 0.05 or less. For rarer species, plots of size vs. depth were made using pooled data for all speci- mens. Trends in size composition with depth were noted, but no statistical significance can be at- tached to these. Only one species, Vinciguerria nimbaria, was caught consistently in high enough numbers to permit a quantitative consideration of abundance and size composition throughout the water col- umn (cf treatment of data on the more abundant myctophids in Clarke, 1973). Thus considerations of day-night or seasonal differences in abundance in the remaining species are subject to some doubt. For these, the data from each series were simply pooled without any attempt to weight the catch of each tow for the relative thickness of the depth stratum it represented. Nevertheless, compari- sons between seasonal series are merited since the total trawling times and depth coverages for each of the series were reasonably similar. In compar- ing data from different seasons, I have assumed that changes were not a result of horizontal advec- tion or migration. RESULTS Gonostomatidae Diplophos taenia (169; 35-153 mm) The day depth range ofD. taenia was 450-610 m and the night range 15-100 m. The smaller fish 338 CLARKE: ECOLOGY OF STOMIATOID FISHES tended to occur shallower during both periods. During the day those over 70 mm long were mostly below 525 m and those over 120 mm were below 575 m. At night none over 90 mm were caught shallower than 50 m and none over 120 mm were above 75 m. Smaller D. taenia (< 70 mm) were more fre- quently taken in June, July and September, and larger fish appeared most abundant in March. This suggests that spawning is seasonal, but the season cannot be estimated since the age of 35-to 70-mm individuals is not known. Size at maturity was about 140 mm. It was not possible to deter- mine the spawning season from gonad state of females since very few mature females were taken. The data from the March 1971 series indi- cated that individuals 100-140 mm long avoided the IK better than the CT, but that neither trawl sampled larger individuals adequately. Vinciguerria nimbaria (2,927; 8-49 mm) For most series, the data indicated that V. nim- baria occurred at 400-560 m during the day and migrated to 20-125 m at night. In December 1970, two night tows in the day depth range caught substantial numbers of V. nimbaria — more than expected on the basis of short oblique tows and other night tows below 150 m. The size composi- tion of these catches was within the range of that of the shallow night catches and close to those of day catches at similar depths. The number of ma- ture fish in the deep night catches was low, but there was no obvious difference in sex ratio or gonad state between these and those of other tows. Thus it appears that a fraction, roughly 607c, of the population did not migrate in December. The larvae ofVinciguerria are restricted to the surface layers and do not apparently undertake substantial migrations until metamorphosis ( Ahlstrom and Counts, 1958). Those collected dur- ing this study (8-14 mm) were taken mostly at 15-50 m at night. (No day tows were taken above 250 m.) Consistent and frequently significant differ- ences in size-frequency curves indicated that smaller V. nimbaria occurred shallower in the water column both day and night (Figure 1). Few fish over 25 mm were captured shallower than 75 m at night and few less than 20 mm were captured below this depth. In the day, the small fish occur- red mostly above 500 m and the large individuals were taken almost exclusively below 500 m. 15 20 25 30 35 STANDARD LENGTH (mm) Figure 1. — Cumulative size-frequency curves for Vinciguerria nimbaria taken at 60 m (A, 35 individuals), 80 m (B, 96), 100 m (C dashed line, 44), and 125 m (C, solid line, 12) at night in September 1971. All pairs were significantly different (P<0.05) from each other except 100 m vs. 125 m. The full-new moon series of night tows in the upper layers during September-October 1971, in- dicated substantial differences in depth distribu- tion related to phase of the moon (Figure 2A), but the picture was complicated by the presence of many more larvae and recently transformed juveniles during the October (full moon) series. Calculated (see Clarke, 1973) total numbers in the NUMBER/TOW 60 90 120 I H O. LlT Q Figure 2. — Catches of Vinciguerria nimbaria per tow (l'/2 h each) at several depths at night at new moon (solid circles and lines) and full moon (open circles, dashed lines) during September-October 1971. Left: total catches including larvae and recently transformed juveniles. Right: catches offish larger than 15 mm. 339 FISHERY BULLETIN: VOL. 72, NO. 2 water column for each series were similar, but the calculated size compositions indicated that during full moon 909?^ of the population were larvae or recently transformed juveniles as opposed to only 50% in the new moon series. Since the tows were taken during the season of highest recruitment to the trawlable population (see below), the differ- ence possibly was due to recruitment during the intervening 2 wk. When only the individuals over 15 mm were considered (Figure 2B), it appeared that most of the larger fish occurred about 50-75 m deeper at full moon. The calculated total number for the new moon series was about twice that for the full moon series, and the calculated size-frequency curves were similar. In addition to moving deeper, V. nimharia also appeared to avoid the net better during full moon. Vinciguerria nimbaria was by far the most abundant of the fishes considered here. Among all the species which occurred in the upper layers at night, V. nimbaria ranked eighth after seven species of myctophids, but because of its small size, contributed little to the total estimated biomass (Clarke, 1973). Calculated total numbers in Sep- tember and December were about twice those for March and June (about 30-35/102m2 vs. 15-18/10^m2). The calculated biomass was about 7-8 g/lO^m^ at all seasons. Vinciguerria nimbaria appears to spawn prin- cipally in the summer and fall and reach maturity (27 mm) within 1 yr. The calculated size composi- tions indicated that about 759i: of the population in June were less than 15 mm, while in March, 759^ of the fish were over 20 mm and about 40^ were mature. The September and December series had substantial percentages of small fish, but about 5(Wr were 15-25 mm. Among the mature females examined, the proportion bearing ripened ova was higher in June and September (15/16 and 7/9, re- spectively) than in December and March (5/10 and 4/11). Vinciguerria poweriae (365; 9-35 mm) Only 35 V. poweriae were caught during the day by IK tows. These were mostly 25- to 30-mm fish caught around 500 m. A daytime CT tow at 300 m caught seven individuals (15-29 mm), sug- gesting that this species occurs rather shallow in the water column during the day and avoids the net due to higher light intensities. At night, V. poweriae occurred at 100-200 m. Few larger than 20 mm were caught above 150 m and practically none under 15 mm were taken below 150 m. Seasonal changes in size composition indicated that V. poweriae spawns in the spring and sum- mer. All caught in March were over 15 mm and over 5(Wc were larger than the size at maturity (27 mm). Ten of 11 mature females from the March series carried ripe ova. In June, few of any size were caught, but these included both juveniles (< 15 mm) and mature fish. Three of the four ma- ture females caught in June were ripe. In July and September, the bulk of the fish were 9-20 mm and very few mature. The few caught in December were all over 15 mm. Of the five mature females taken in September and December, only one was ripe. Ichthijococctis ovatiis (45; 12-55 mm) All but nine /. ovatus were taken during the day between 400 and 500 m. The night catches consisted of two small fish (15 mm) taken near the day depth, two larger ones taken at 350 m, and five others (26-35 mm) taken at 150 m and 260 m. Since it seems unlikely that this species occurs as shallow as 150-260 m during the day, at least some fraction of the population apparently moves into the upper layers at night. /. ovatus matures at about 35 mm. Gonostotna atlanticum (680; 10-66 mm) Gonostoma atlanticum was taken principally at 490-560 m during the day and at 150-300 m at night. In several cases, the size-frequency curves from samples at different depths within the same series differed significantly and indicated that the smaller fish occurred at shallower depths. In De- cember, at night all fish from 170 m were less than 30 mm, most from 190 to 200 m were 30-45 mm, and most from 250 to 300 m were 40-60 mm. Catches from day tows in both March and Sep- tember indicated that few fish less than 50 mm occurred deeper than 500-525 m. Gonostoma atlanticum apparently spawns over most of the year. Between 90 and 100% of the mature females (over 50 mm) in each series car- ried well-developed ova, and there were no evi- dent seasonal changes in size composition of the catch. 340 CLARKE: ECOLOGY OF STOMIATOID FISHES Gonostoma ebelingi (306; 12-158 mm) Gonostoma ebelingi occurred at 520-700 m dur- ing the day and at 125-300 m at night. The size composition of the catches changed with depth for both day and night series. The largest taken shal- lower than 150 m at night was 45 mm, and most fish taken below 200 m exceeded 60 mm. During the day, few fish over 100 mm were caught above 600 m, and none less than 75 mm were caught deeper. Female G. ebelingi matured at about 120 mm, but males, as far as could be told without histologi- cal studies, appeared to mature at about 100 mm. There was, however, no evidence to suggest that this species is a protandrous hermaphrodite as observed in G. gracile by Kawaguchi and Marumo ( 1967). There were no obvious seasonal differences in the percentages of ripe females among mature females, but differences in size composition of the catches of different series suggested some season- ality in spawning. All G. ebelingi caught in December were over 70 mm. In March, all fish were either less than 50 mm or over 70 mm. In June, AQF/c of the catch was 20-60 mm and the rest about evenly distributed between 61 and 150 mm. In September, the catch was again bimodal with all fish either smaller than 70 mm or over 100 mm. Recently transformed juveniles were taken only in March and September and were most abundant in March. More data would, of course, be helpful, but it seems that G. ebelingi spawns principally in early spring and early fall. Gonostoma elongation (1,346; 10-218 mm) In all series but December 1970, G. elongatum occurred at 560-725 m during the day and moved to 60-265 m at night. In December, no individuals over 115 mm long were caught in the upper layers at night, but larger fish were taken in two night tows within the day depth range (of 22 fish, 9 were 117-200 mm. Figure 3). These deep night catches were not large relative to those expected from contamination, and consequently may have re- sulted from encountering patches in the shallow- layers. However, the difference in size suggests that the large individuals did not migrate. Size-frequency curves from night samples at dif- ferent depths during the same series were fre- quently significantly different and consistently indicated that small fish occurred shallower (Fig- 100 50 75 100 125 150 STANDARD LENGTH(mm) 200 Figure 3. — Cumulative size-frequency curves for Gonostoma elongatum taken at 170 m (A, 25 individuals), 190-200 m (B, two tows, 11), 265 m (C, 13), and 750 m (D, two tows, 22l at night during December 1970. The curves were all significantly differ- ent (P<0.05) from each other. ure 3). Those caught above 100-125 m were less than 35-40 mm, most caught between 175 and 200 m were 60-80 mm, and larger fish were taken mostly in tows below 200 m. It was not clear whether a similar pattern existed at depth during the day. There was considerable sexual difference in size at maturity. Males appeared to reach matur- ity at about 120 mm; the largest male was 161 mm. The smallest mature female was 193 mm. Some small, clearly immature females (120-140 mm) were found, but unfortunately, no fish be- tween 161 and 193 mm was collected. Although histological studies of specimens of all sizes are obviously necessary, the above data suggest that some G. elongatum mature directly as females, while others are protandrous hermaphrodites. Kawaguchi and Marumo (1967) have shown that a congener, G. gracile is a protandrous hermaphro- dite. Butler ( 1964) has shown that in some species of pandalid shrimps, a group within which pro- tandrous hermaphroditism frequently occurs, the degree of hermaphroditism varies throughout the species' ranges. Butler suggests that this is a re- sult of varying ecological factors. Varying degrees of protandry may similarly occur among the Gonostoma spp. Too few mature females were collected to assess any seasonal trends in gonad ripeness, but the pooled size composition data for each series indi- 341 FISHERY BULLETIN: VOL 72, NO. 2 cated that the principal spawning season was in the spring or early summer. A few small (10-30 mm) G. elongatum were taken in March and June, but these were far more abundant in July and Sep- tember. In December, substantial numbers of 35- to 50-mm fish were taken, but none were less than 30 mm. Too few large individuals were taken to indicate any further trends, but it seems probable that G. elongatum requires several years to reach maturity. Krueger and Bond (1972) have sug- gested a 3-yr life cycle for this species in the sub- tropical Atlantic. Danaphos oculatus (229; 19-41 mm) Danaphos oculatus does not appear to migrate vertically. The night depth range was 430-600 m and the day range 480-650 m. The day-night dif- ference is an artifact due to depth spacing of the samples. There were no trends in size composition with depth. Danaphos oculatus matures at about 30 mm. There were no seasonal trends in size composition or reproductive condition. Valenciennellus tripunctulatus (600; 10-32 mm) During the day, V. tripunctulatus was taken principally between 400 and 550 m. The size- frequency curves for tows at 500 and 525 m taken in September 1970 were significantly different; 70% in the shallower tow were 20-25 mm, and 75% in the deeper were over 25 mm. The day depth range and evidence of changes in size composition with depth agree with results reported by Krueger (1972) for V. tripunctulatus in the central North Atlantic. Krueger's data show that V. tripunctulatus remains at the same depths during the night, but near Hawaii this species undertakes a limited, but definite upward migration. The night depth range was 200-330 m. The catches per effort within this range were roughly equivalent to those during the day at 400-500 m. Catches below 330 m at night were lower and probably due to contamination. All sizes were taken within the night depth range. Changes in size composition with depth were evi- dent, but numbers sufficient to make statistical comparisons were taken at more than one depth only in December 1970. In that case, the curve from the 200-m depth sample differed signi- ficantly from those from samples at 270 and 320 m. About 90% of the fish in the shallower sample were 10-16 mm and over 90% in the deeper were over 20 mm. Thus the upward extension of the depth range at night was not due solely to shallow catches of postlarvae or juveniles as Krueger ( 1972) has suggested may be the case for Badcock's (1970) earlier observation of limited diurnal vertical migration by V. tripunctulatus in the eastern Atlantic. Valenciennellus tripunctulatus matures at about 25 mm. Large proportions of the mature females (90-100%) carried well-developed ova at all seasons. There were no obvious seasonal trends in size composition. Other Gonostomatidae Two Woodsia nonsuchae (39 and 106 mm) were taken at 530 and 620 m at night, respectively. A damaged specimen (22 mm) that was probably W. nonsuchae was taken in a day tow to 875 m. Margrethia obtusirostra (18; 8-44 mm) was taken mostly at night between 180 and 200 m. The two day catches were in tows at 350 and 540 m. The two largest specimens, 44 mm, were mature females and the next largest, 34 mm, was a female with ova beginning to develop. Chauliodontidae Chauliodus sloani (147; 21-250 mm) Chauliodus sloani appeared to migrate from a day depth range of 450-825 m to 45-225 m at night. No individual over 65 mm was taken above 100 m at night nor above 500 m during the day. All fish over 120 mm were taken below 175 m at night or below 600 m during the day. The pooled data from each series showed significant differences in size composition (Figure 4A) which indicated that C. sloani spawns princi- pally in the spring or early summer and reaches lengths of 70-100 mm by the following March. Individuals less than 40 mm were present only in June, July, and September and were most abun- dant in the June and July series. These were likely represented by the large numbers of 40- to 70-mm fish present in September and December and 70- to 100-mm fish which dominated the March samples. Too few large fish were collected to assess any further trends in size composition. Chauliodus sloani almost certainly takes several years to reach maturity. Only the two largest specimens (females, 225 and 250 mm) were ma- ture. The next largest was only 185 mm. 342 CLARKE: ECOLOGY OF STOMIATOID FISHES 100 r iJ-tf 80 - -L-''Tn - /. rjj 60 f-j 1! 40 1 (B) 11 I© 1 1 1 1 20 w r 1 A indicus 1 1 t 10 20 30 40 50 60 STANDARD LENGTH(mm) Figure 4. — Left: Cumulative size-frequency curves for the pooled catches of Chauliodus sloani (exclusive of individuals over 120 mm) in June 1971 (A, 21 individuals), September 1970 (B, 42), December 1970 (C, 13), and March 1971 (D, 19). The curve for the catch in July 1970 (not shown) did not differ significantly from and was almost identical with that for June 1971. All other curves differed significantly from each other (P<0.05). Right: Cumulative size-frequency curves for the pooled catches of Astronesthes indicus (exclusive of individuals over 60 mm) in September 1970 (A, dashed line, 20 individuals), December 1970 (A, solid line, 41), March 1971 (B, 128), June 1971 (C, solid line, 18), and July 1970 (C, dashed line, 27). All pairs except June-July and September-December differed significantly (P<0.05). Stomiatidae Four Stomi as danae (55-75 mm) were taken at night. Two were from tows at 100 m and two from a tow at 250 m that extended well past dawn. A larger (154 mm), damaged Stomias sp. was taken in a night tow at 225 m. Three specimens (99-290 mm) of the genus Mac- rostomias were taken, but depth information on the samples was questionable for all three. Fedorov and Melchikova (1971) described a new species of Macrostomias, M. pacificus, which they distinguish from M. longiharbatus mostly on the basis of anal fin ray and photophore counts. Two of the specimens I collected had 14 anal rays, and one had 15. Complete photophore counts were possible on only one specimen with 14 anal rays: PV = 81, OV = 82, VAV and VAL = 64. The other specimen with 14 anal rays had PV = 82, OV = 80. The estimated PV + VAV for the remaining specimen was 148. Thus the photophore counts definitely indicate M. longiharbatus, while the anal ray counts fall between those given for the two forms by Fedorov and Melchikova (1971). I suspect that additional specimens will indicate there is only one valid species, M. longiharbatus. Astronesthidae Astronesthes cyaneus (45; 16-66 mm) Astronesthes cyaneus is used here pending further study of the systematics of this species group in the Pacific. The specimens were closest to A. cyaneus as defined by Goodyear and Gibbs ( 1969), but all had rudimentary barbels. Also, the luminous tissue on the operculum of the few larger specimens was not exactly as described by Goodyear and Gibbs. Only eight specimens were caught during the day, six of these between 600 and 700 m. Three- fourths of the night catches were at 80-100 m; the few collected deeper were scattered throughout the water column and were probably contamin- ants. None of the specimens were near maturity; only eight were over 25 mm. Larger fish undoubt- edly avoid the trawl and may occur deeper than the small individuals. It appears that even the small ones avoid the trawl during the day. Astronesthes indicus (307; 11-117 mm) Astronesthes indicus was taken principally at 500-800 m during the day and at 30-200 m at night except in the December 1970 series. In that series, no A. indicus were taken in the upper layers at night, but 21 were taken in three night tows at 625-750 m, within the day depth range. The numbers collected in these tows were larger than expected if they had been due to contamination and were comparable to catches of day tows at this time. At night, no individual over 50 mm was taken shallower than 125 m, but smaller indi- viduals were taken with roughly equal frequency throughout the night depth range. The small fish also appeared to occur throughout the day depth range, but large fish were taken mostly in tows near the deep end. The size composition of the catch varied consid- erably with season and suggested that spawning occurred principally in the summer and fall and that about 2 yr were required to reach 50-60 mm. A few small individuals (< 20 mm) were taken in July 1970, many in September and December, and none in March or June of 1971 (Figure 4B). The small individuals of the September and December samples appear to be represented by a 21- to 35-mm group in March and a 34- to 45-mm group in June. A similar sized group, 37-49 mm, 343 FISHERY BULLETIN: VOL. 72, NO. 2 was present in the July 1970 samples and appeared to be represented by a 42-to 51-mm group in September and a 46- to 57-mm group in December. The CT series in March collected 99 specimens, 56 of which were 24-36 mm or roughly equivalent to the majority of the IK specimens. Of the remaining CT specimens, 26 were 50-76 mm- perhaps representative of the 46- to 57-mm group in the December IK series. The catch per effort and size composition of IK catches were roughly equal for day and night indi- cating no differential avoidance. However, 22 of the 35 specimens over 60 mm were taken by the CT. The largest taken by the CT was 89 mm and only four larger individuals were taken by scat- tered IK tows. Thus it appears that individuals over 60 mm regularly avoid the IK and that larger ones avoid both trawls. The largest individual (117 mm) was a female that appeared to be near- ing maturity. Judged from the above data, it is likely that this species takes at least 3 or 4 yr to mature. the filament. The lateral filaments on the bulb were much shorter than the bulb itself. The sys- tematic status of this form is presently under study by other workers (Gibbs, pers. commun.). Twenty-four of the specimens were taken at 50-200 m at night and eight were taken at 500-640 m during the day. Only four of the specimens ex- ceeded 60 mm indicating that the large, mature fish consistently avoided both trawls. Astronesthes spp. Three other species of Astronesthes were taken. A. gemmifer (6; 91-138 mm) was taken once at night at 245 m, four times at 580-690 m during the day, and once by a day tow to 1,150 m. As- tronesthes lucifer (10; 26-49 mm) was taken five times at night at 25-195 m, and by day at 250, 550 (3), and 640 m. Astronesthes luetkeni (6; 26-74 mm) was taken in only three tows for which depth information was valid: 125 and 200 m at night and 600 m during the day. Astronesthes splendidus (82; 22-110 mm) About 75% of the A. splendidus collected were taken at 25-130 m at night. There was no obvious trend in size composition with depth. Only 16 specimens were taken during the day, all but 2 of these between 600 and 800 m. Nearly transformed larvae with photophores (< 25 mm) and small juveniles were present only in June, July, and September suggesting summer or early spring spawning. These young may have been rep- resented by 40- to 60 — mm fish which made up 85% of the March catch, but so few fish were caught in December that the connection between the two size groups is tenuous. Only 15 of the 82 specimens were over 60 mm and none were ma- ture. The size composition of IK and CT catches in March was similar. Thus both trawls were avoided by most larger juveniles and consistently by adults. Heterophotus ophistoma (28; 32-245 mm) Of 17 H. ophistoma taken at night, 15 were taken between 50 and 200 m. The other two were nearly transformed larvae taken in a closing net tow at about 630 m. Ten of the 11 day specimens were taken at 625-775 m; one was taken at 1,000 m. Eighteen were larvae or recently transformed juveniles (32-64 mm), and all but two of these were taken in July or September. The two largest specimens, 235 and 245 mm, were males and ap- peared to be mature or nearly so. Neonesthes microcephalus (2; 135-147 mm) One A^. microcephalus was taken at 640 m at night and the other in oblique tow to 1,600 m. Melanostomiatidae Astronesthes sp. (near si tnilis) (37; 21-133 mm) The specimens of this species of Astronesthes agreed with the description of^. similis by Gibbs (1964) except for the barbel tip. Instead of being unornamented, the barbel tip of the Hawaiian specimens had a dark terminal filament about as long as the bulb and often a pale tip at the end of Eustomias bibulbosus (20; 80-145 mm) Fourteen E. bibulbosus were taken at 75-300 m at night; however, only two large (131 and 145 mm) individuals were taken below 125 m. During the day, six were taken between 600 and 960 m. Sixteen of the specimens were small (80-102 mm), and none of the large ones were mature. 344 CLARKE: ECOLOGY OF STOMLATOID FISHES Eustomias bifilis (128; 41-170 mm) All but 5 of the 92 night catches of £:. bifilis (40 by IK, 51 by CT) were at 15-200 m. The day depth range appeared to be 635-800 m; only 5 of the 29 day catches were at greater depths. There was no obvious trend in size composition with depth. Size at maturity was about 140 mm. Eustomias gibbsi (28; 55-131 mm) All but three E. gibbsi were taken at night. The night depth range was about 50-200 m, and the three day catches were at 680-800 m. There was no obvious trend in size composition with depth among the night catches. None of the speci- mens were mature. Eustomias spp. Of the remaining specimens of Eustomias, about 130 were too badly damaged to be identified with certainty. The great majority of these had pectoral ray and photophore counts within the range of the three species considered above (most were probably E. bifilis). Some 150 other speci- mens include about 20 different forms, most of which cannot be reliably identified due to present uncertainties in the systematics of the genus. These along with other specimens from the Cen- tral Pacific will be considered in a later, more systematically oriented report. Thysanactis dentex (340; 39-177 mm) Thysanactis dentex, the most frequently col- lected melanostomiatid, occurred principally at 75-200 m at night. A few individuals were taken as shallow as 40 m, and there were scattered night catches throughout the water column. The princi- pal day depth range was 600-800 m with a few caught between 400 and 600 m or scattered deeper than 800 m. Within both ranges, the larger fish tended to occur deeper and the smaller shallower. At night few over 100 mm occurred above 150 m, and catches of those smaller than 80 mm below 125 m were low and probably due to contamina- tion. During the day those over 100 mm were caught mostly below 700 m and those less than 100 mm mostly between 600 and 700 m. Size at maturity was about 160 mm. Bathophilus spp. Seven species of Bathophilus were taken. Al- though data are incomplete for most, it seems that all occur at about 500-700 m during the day and migrate to the upper 250 m at night. Bathophilus kingi (23; 24-95 mm) was taken most frequently. At night, 18 specimens were taken between 50 and 225 m. Three specimens were taken at 590-725 m during the day and one each at 1,000 and 1,100 m. Bathophilus brevis (3; 12-43 mm) was taken only at night between 200 and 225 m. Bathophilus di- gitatus (9; 23-91 mm) was taken seven times at night at 125-175 m and twice during the day at 520 and 550 m. Bathophilus longipinnis ( 10; 25-97 mm) was taken seven times at night scattered throughout the water column (100-1,175 m) and three times between 520 and 590 m during the day. Bathophilus pawneei (7; 30-90 mm) was taken at night between 40 and 195 m and once at 690 m during the day. Bathophilus cf. altipinnis ? (3; 26-59 mm; pectoral rays 26-28, pelvic rays 15-18) was taken at 170 and 265 m at night and at 640 m during the day. A singleB. schizochirus (76 mm) was taken at 265 m at night. Other Melanostomiatidae Pachystomias microdon (33 mm) was taken once in a day tow at 660 m. Two small (55-56 mm) Flagellostomias boureei were taken at 500 m (day) and 750 m (night). Five juvenile Echiostoma bar- batum (29-89 mm) were taken, four at 30-185 m at night and one in an oblique day tow to 800 m. Four species of Photonectes which were collected could be identified with reasonable certainty. Photo- nectes achirus (9; 43-146 mm) was taken at 125-225 m at night and at 400, 550, 620, and 1,400 m during the day. A single Photonectes caerules- cens (127 mm), which is likely to be proven indis- tinct from Photonectes achirus, was taken in a day tow at 800 m. Photonectes albipennis (8; 22-87 mm) was taken once at 620 m during the day and between 60 and 165 m at night. Photonectes fimbria (34 mm) was taken once at 620 m during the day. The above specimens ofPhotonectes fit the descriptions given in Morrow and Gibbs (1964) reasonably well. In addition, two specimens (208 and 255 mm), taken at 650 m at night and 490 m during the day, were close to, but not identical with, Photonectes margarita. Leptostomias spp. (15; 68-134 mm) were taken predominantly at night between 100 and 250 m; 345 FISHERY BULLETIN: VOL. 72, NO. 2 four were taken during the day at 500-625 m. Melanostomias spp. (23; 48-238) were mostly taken at 50-250 m at night or 520-800 m during the day. Due to either damage to the barbels (mostly Leptostomias) or lack of data on the varia- bility of characters used to separate nominal species in these genera, definite identifications cannot be given. Idiacanthidae Idiacanthus fasciola (341; 13-375 mm) Larval /. fasciola (13-50 mm) were taken mostly at night in the upper 200 m; deeper catches both day and night were scattered and probably contaminants. Males (30-50 mm) were taken prin- cipally between 550 and 800 m during the day. Fourteen of the 20 night captures were also in the day depth range, but 6 were taken at 200-300 m. At night, females (47-375 mm) were taken prin- cipally between 30 and 300 m. All taken below 200 m were over 145 mm, but larger ones did occur shallower. In the December 1970 series seven females were taken, but only one was taken at night in the upper 300 m, the remainder were taken within the day depth range. During the day, females were taken mostly between 600 and 800 m, but one was caught at 250 m and several at 400-600 m. Too few were taken to make detailed comparisons of day and night catch per effort, but the data indicated no gross differences in abun- dance or size frequency. Female /. fasciola mature at about 250 mm, but too few large individuals were taken to assess any seasonal trends in gonad ripeness. There were no clear seasonal trends in size composition of the catches. Larvae and males were taken most fre- quently in December. Few were taken in March, with catches for June, July, and September inter- mediate. In July, September, and December, 84- 91% of the females were shorter than 150 mm, while the percentages for March {597c ) and June (30% ) indicated relatively fewer smaller females. There were, however, no definite size groups which could be traced from season to season. Malacosteidae Fhotostomias guernei (159; 24-158 mm) Photostomias guernei was taken principally at 346 15-300 m at night and at 350-800 m during the day. A few specimens were taken in deep night tows with the opening-closing trawl indicating that the entire population does not regularly mi- grate. Small fish were caught throughout these ranges, but only two fish over 100 mm were caught above 185 m at night and none over 80 mm were taken above 750 m during the day. Mature female P. guernei showed a rather curi- ous size distribution. Of 41 females examined (46-158 mm), 11 bore ripened ova. Nine were 64-85 mm and two were considerably larger — 147 and 158 mm. Of the specimens with undeveloped ova, seven were less than 63 mm, and the remain- der 93-149 mm. Some of the large individuals could possibly have spawned already, but the in- dividuals between 93 and 125 mm were clearly immature. The bimodal size distribution suggests that two populations were present in the samples, but there was considerable overlap or agreement in photophore and fin ray counts of both large and small females. Also there was no indication that one type of female had a different depth distribu- tion or seasonal pattern than the other. Photostomias guernei probably spawns over most of the year. Individuals under 40 mm were most frequently taken in June, but were present in all series. There was no obvious seasonal trend in size composition of the larger fish. Aristostomias spp. Aristostomias lunifer (12; 30-151 mm) was taken only between 120 and 260 m at night. The largest specimen, a 151 mm female, was mature or nearly so. Aristostomias grimaldii (5; 33-117 mm) was taken at 100 and 500 m at night and at 690 and 750 m during the day. The largest specimen, a male, appeared immature. Aristostomias poly dac- tylus (10; 33-140 mm) was taken at 100, 175, 320, and 590 m at night and at 625, 850, 875, and 1,100 m during the day. The largest individual was an immature female. Two specimens similar to A. tittmanni (68 and 75 mm) were taken at 15 and 250 m at night. Malacosteus niger (133; 26-186 mm) Malacosteus niger occurred between 520 and 900 m during the day and 500-850 m at night; the day-night differences were due to sample spacing. Most were taken between 600 and 700 m. The CLARKE: ECOLOGY OF STOMIATOID FISHES depth-size plot indicated a trend for greater size with increasing depth, but since 106 of the 133 specimens were 75-125 mm any trends for smaller or larger fish are of dubious significance. The only mature females collected were the four largest specimens (172-186 mm). There was no seasonal trend in size composition of the the catches. DISCUSSION In spite of the fact that the stomiatoids in the study area were quite diverse and that there have been no really comprehensive studies based on extensive sampling programs in the Pacific, only a few species are either undescribed or of uncertain status (with the exception of the Eustomias spp.). To paraphrase Gibbs (1960), it is indeed a reHef that most specimens fit descriptions based pri- marily on Atlantic material. Eight species were previously unrecorded in the Facific: Astronesthes ge?7imifer, Neonesthes micro- cephalus, Aristostomias grimaldii, A. lunifer, A., polydactylus, Eustomias bibulbosus, Photo- nectes achirus, and Bathophilus altipinnis. Three of the more commonly collected species were pre- viously known only from a few specimens. Gonostoma ebelingi (Grey, 1960) and Eustomias bifilis (Gibbs, 1960) were described on the basis of two and one specimens, respectively, and no other specimens have been reported since. Thysanactis dentex, which was taken regularly by the present study and by King and Iversen ( 1962), is listed by Morrow and Gibbs ( 1964) as known from only five captures in the North Atlantic. Further studies of material from other tropical areas will be nec- essary to determine if these species are for some reason present in high numbers only in the Central Pacific. Inadequate information from other areas of the Pacific does not permit detailed consideration of zoogeographic patterns of these species. Negative records of several studies and reports cannot necessarily be considered conclusive. It is likely that the majority of the species recorded here occur throughout the warm water masses. How- ever, preliminary examination of samples from the central equatorial Pacific indicates that at least Vinciguerria nimbaria and Gonostoma ebelingi do not occur continuously across the equa- torial region and also confirm Gibbs' (1969) state- ment that Stomias danae is replaced by S. affinis ' in equatorial waters. Two species, Vinciguerria lucetia and Idiacanthus antrostomus, which ap- pear to occur in eastern and equatorial waters, were not taken during this study. Vinciguerria lucetia has been recorded near Hawaii (King and Iversen, 1962; Ahlstrom and Counts, 1958) and Idiacanthus antrostomus may also be expected to occur here occasionally, but their absence from the material collected during the study indicates that some warmwater species do not normally occur in the central water mass. It is clear from the absence or extreme rarity of mature fish, that neither of the trawls used were adequately sampling the larger sizes of many species — particularly the Astronesthes spp. Al- though differences in day-night catches have not been rigorously demonstrated, it also appears that many large species and individuals avoid the IK better during the day than at night. For most species, the numbers caught by the paired series of IK and CT tows in March 1971, were not sufficient for detailed analyses, but rough comparison of the catches and size ranges (Table 1) indicates some differential avoidance. The total volume sampled by the CT tows was about 10 times that of the IK tows in the same depth range. In 10 species, the ratio of CT/IK catches was considerably lower than 10 (1.3-6.0) suggesting that the IK's greater towing speed was more of an advantage than the greater size of the CT. In these cases, the CT/IK ratio was httle af- fected by considering only the fish larger than the smallest caught by the CT; i.e., the passage of smaller fish through the coarser CT meshes did not seem to be an important factor. Three species, Diplophos taenia, Gonostoma Table 1.— Total numbers and size ranges of 15 species offish taken in nine tows with the IK and eight tows with the CT in the upper 200 m at night during February-March 1971. The tows with each net were roughly equally distributed between 25 and 200 m. The total volume sampled by the CT tows was about 10 x that of the IK tows. Species Total catch Size ran ge (mm) IK CT IK CT Diplophos taenia 5 62 66-83 61-153 Vinciguerria poweriae 29 122 16-34 15-33 Gonostoma atlanticum 10 40 15-45 20-64 Gonostoma ebelingi 11 100 12-37 16-162 Gonostoma elongatum 97 236 10-139 30-165 Chauliodus sloani 4 13 81-162 68-123 Astronestties cyaneus 4 13 18-19 17-44 Astronesthes indicus 18 83 21-89 24-89 Astronesthes splendidus 10 13 29-58 30-65 Eustomias bibulbosus 0 10 — 81-141 Eustomias bililis 2 49 93-115 52-158 Eustomias gibbsi 1 10 77 70-131 Thysanactis dentex 17 102 58-173 44-165 Idiacanthus fasciola 17 81 58-297 54-301 Photostomias guernei 9 26 30-113 40-133 347 FISHERY BULLETIN: VOL. 72, NO. 2 ebelingi, and Eustomias gibbsi, were taken in roughly the predicted ratios, and the other two species of Eustomias treated here were clearly sampled better by the CT. Size ranges, of course, were greatly influenced by just one large indi- vidual, but in general the CT caught considerably larger individuals of the five species which it ap- peared to sample relatively better in terms of numbers. Although not shown by the figures in Table 1, large Astronesthes indicus were also apparently sampled better by the CT (see above). Of the 47 species considered here, only Danaphos oculatus and Malacosteus niger clearly did not migrate to shallower levels at night. All the other abundant species migrated to the upper layers at night and, in spite of the fact that no opening-closing device was used, even the data on many of the rarer species are consistent with mi- grations of several hundred meters. It is, of course, possible that, as in the case of Photostomias guernei, a small percentage of some species may not migrate at any given time. Diurnal vertical migration has been shown to occur in a few of the species considered here (e.g., Badcock, 1970; Krueger and Bond, 1972), but due to limited data it had been only "suspected" for many others. Pos- sibly because of the deeper mixed layer and ther- mocline and greater transparency of the water, migrations in the tropics are greater in extent and thus more easily detected than elsewhere. As with several species of myctophids (Clarke, 1973), there was evidence that some of the stomiatoids did not regularly migrate during the winter. For Vinciguerria nimbaria, Gonostoma elongatum, Astronesthes indicus, and I diacanthus fasciola, night catches within the day depth range during December 1970 were higher than expected if due to contamination and indicated that a frac- tion of the population remained at depth. Too few of the latter two species were taken to permit consideration of any differences between the mi- grating and nonmigrating fractions. The evidence for nonmigration was weak for G. elongatum but suggested that the large fish did not migrate. There were no obvious differences in the two frac- tions of the population of V. nimbaria. Thus as with the myctophids, there is no explanation for the apparent change in behavior. Many of the species showed trends for increased size with depth both day and night. Similar trends were noted for many species of myctophids (Clarke, 1973), and qualitative reports (e.g.. Bad- cock, 1970) indicate that this trend is shown by a variety of mesopelagic species. The trend was clearest for the abundant vertically-migrating gonostomatids, Diplophos taenia, Vinciguerria spp., Gonostoma spp., and Valenciennellus tripunctulatus, but was also evident for Chauliodus sloani, Astronesthes indicus and Thysanactis dentex. The size-depth patterns at night of 10 species are shown in Figure 5 by straight lines connecting the coordinates for the smallest size, upper limit of depth range with those for the largest size, lower limit of depth range (extremes of size and depth have been ignored). These are only rough approximations of the size-depth patterns; in real- ity the patterns are rather complex polygons. The straight lines serve mainly as a basis for consider- ing the possible interactions of the various species. STANDARD LENGTH (mm) Figure 5. — Depth-size profiles (see text) for 10 species in the upper 300 m at night: Vinciguerria nimbaria (A), Vi. poweriae (B), Valenciennellus tripunctulatus (C), Diplophos taenia (D), Chauliodus sloani (E), Thysanactis dentex (F), Gonostoma elon- gatum (G),G. ebelingi (H), Astronesthes indicus (I), andG. atlan- ticum (J). Two very similar species, Vinciguerria nim- baria and V. poweriae, showed distinctly different size-depth patterns. As with many similar species of myctophids, individuals of similar sizes were well separated in the water column. Where the depth ranges overlapped, at 100-125 m, the larger V. nimbaria co-occurred with the smaller V. pow- eriae. Vinciguerria nimbaria generally co- occurred with similar-sized or slightly larger in- dividuals of several abundant species of myc- tophids in the upper 100 m, while V. poweriae co-occurred with the deeper living myctophids (Clarke, 1973). Although their size-depth patterns were slightly different, similar-sized individuals of Gonostoma elongatum and G. ebelingi, two very similar species, co-occurred over much of their depth ranges. G. atlanticum , in addition to being rather different from its congeners in size range, color, and several morphological aspects, also had 348 CLARKE: ECOLOGY OF STOMIATOID FISHES a quite different size-depth pattern and tended to co-occur with much larger individuals of its con- geners. The former two species co-occurred throughout much of their depth range with similar-sized individuals of three species of the myctophid genus Lampanyctus. Thus in the 100-250 m layer at night similar species of at least two genera of two families co-occur. This is in contrast to the upper 100 m where only rather different or distantly related species co-occur. Other gonostomatids exhibited nighttime pat- terns quite different from any of the other species considered. Danaphos oculatus remained at the day depth and showed no trend in size composition with depth. Valenciennellus tripunctulatus occurred much deeper than similar-sized indi- viduals of any other species. Diplophos taenia occurred much shallower, with respect to size, than any of the species thus far investigated. It is possible that some of the shallow-living myc- tophids, e.g., Myctophum spp., which were not adequately sampled by the trawl also have pat- terns similar to that of Z). taenia. The larger stomiatoids with fanglike teeth, dor- sal or mental "lures," or various adaptions for swallowing large items, are generally thought to be predators on small nekton. Near Hawaii, the dominant "predatory" species exhibited a variety of patterns at night. Astronesthes indicus, Chau- liodus sloani, and Thysanactis dentex showed trends for increased size with depth. In the upper 100 m, these species co-occurred with roughly similar-sized or slightly smaller individuals of the more abundant myctophids and Vinciguerria nimbaria. Although there are, scattered through- out the literature, several records of larger stomiatoids ingesting rather large prey, it seems unlikely that these three species are important predators on the abundant fishes in the upper 100 m or that the latter are important items in the former's diet. All sizes of Idiacanthus fasciola, Eustomias bifilis. and Astronesthes splendidus appeared to occur throughout their night depth ranges. Thus it would seem that, if indeed any of the larger stomiatoids are important predators on the small fishes in the upper 100 m, species such as these are more likely candidates. Malacosteus niger did not migrate, and its depth range was somewhat deeper than the day ranges of most of the vertically migrating species consid- ered here. Malacosteus niger has very poorly de- veloped serial, ventral-lateral photophores in comparison with most other stomiatoids. The only nonmigrating species of myctophid, Taaning- ichthys bathyphilus, occurs in the same depth range and has greatly reduced serial photophores in comparison with the other myctophid species. If, as Clarke (1963) has suggested, ventral-lateral photophores are a counter-shading device, their absence or reduction in these deep-living, non- migrating species is likely related to lower light levels and more nearly spherical radiance dis- tribution at such depths even during the day in comparison to the regime which most of the mi- gi'ating species experience day or night. Three of the species which occurred together at 400-600 m during the day, Danaphos oculatus, Valenciennellus tripunctulatus, and Ichthyococ- cus ovatus, all have dorsally directed eyes and markedly ventrally directed serial photophores. These characteristics are shared by the sternop- tychids of the genus Argyropelecus which also occur in the same depth range (S. S. Amesbury, pers. commun.). The argentinoid, Opisthoproctus soleatus, which shares the same day depth range, also has dorsally directed eyes and a ventrally directed luminescent apparatus. At night, none of these species appear to undertake extensive mig- rations. Danaphos oculatus remains at the same depths, V. tripunctulatus undertakes a limited upward migration, and /. ovatus either migrates or disperses upward. The Argyropelecus spp. either move upward slightly or remain at the same depths (S. S. Amesbury, pers. commun.). Opisthoproctus soleatus was for some reason nearly absent from the night samples; out of the 114 specimens only 4 were taken at night. Several investigators (see review by McAllister, 1967) have suggested that the dorsally directed eyes are an adaptation for better detection of prey or predators above the fish and that the ventrally directed light organs serve to disrupt the silhouette of the fish to predators below. These adaptive values would be realized only under a situation where light levels were low but still sufficient for vision and where the radiance dis- tribution was dominated by the downwelling component. Such conditions probably obtain only during the day for the above species. This would suggest that they feed primarily during the day and that they are exposed to heavier predation then also. At least the former seems likely. These species probably feed on zooplankton, and pre- liminary analyses of zooplankton in the study area indicates that these species encounter higher concentrations during the day owing to vertical 349 FISHERY BULLETIN: VOL. 72, NO. 2 migrations of the zooplankton. The situation is just the opposite for most of the other fishes which share the same day depth range and have neither upwardly directed eyes nor as pronounced a ven- tral orientation of their light organs. The latter fishes undertake more extensive vertical migra- tions at night and encounter higher concentra- tions of zooplankton and probably predators then rather than during the day. The species which showed seasonal trends in size composition or gonad ripeness all appeared to spawn primarily in the spring and summer or summer and fall. These were Vinciguerria spp., Chauliodus sloani, Astronesthes indicus, and prob- ably A. spendidus and Heterophotus ophistoma. Their seasons of peak reproduction were thus similar to those of the abundant myctophids (Clarke, 1973). The data onGonostoma elongatum and Idiacanthus fasciola suggested rather incon- clusively that these species spawn primarily in the summer and winter, respectively. Several fairly abundant species, Gonostoma atlanticum, Danaphos oculatus, Valenciennellus tripunc- tulatus, Eustomias bifilis, Thysanactis dentex, Photostomias guernei, and Malacosteus niger, showed no indication of seasonality in reproduc- tion. Possibly the larvae of those species which exhibit no seasonality either hatch at a larger size or live at greater depths than those of the seasonal species and thus the former's spawning is not timed to any seasonal fluctuations in food concen- tration or size distribution in the upper layers. ACKNOWLEDGMENTS I am indebted to the many people who partici- pated on the cruises and also the captain and crew of the RV Teritu. The Cobb trawl samples were taken during cruise 52 of the NMFS RV Townsend Cromwell. I thank B. E. Higgins, chief scientist, and others at the Southwest Fisheries Center Honolulu Laboratory, NMFS, NOAA, for their cooperation. R. E. Young and S. S. Amesbury of the University of Hawaii provided specimens and data from the opening-closing trawl. Patricia J. Wagner assisted capably in all phas- es of the laboratory analyses. R. H. Gibbs, Jr. and R. H. Goodyear kindly supplied or confirmed identifications of many species. Their assistance in untangling several systematic problems is greatly appreciated. Any errors are my own. This research was supported by NSF GB-23931 to the University of Hawaii and by funds from the University of Hawaii, Hawaii Institute of Marine Biology. LITERATURE CITED Ahlstrom, E. H., and R. C. Counts. 1958. Development and distribution of Vinciguerria lucetia and related species in the Eastern Pacific. U.S. Fish. Wildl. Serv., Fish. Bull. 58:363-416. Badcock, J. 1970. The vertical distribution of mesopelagic fishes col- lected on the Sond cruise. J. Mar. Biol. Assoc. U.K. 50:1001-1044. Barnett, M. a., and R. H. Gibbs, Jr. 1968. Four new stomiatoid fishes of the genus Bathophilus with a revised key to the species of Bathophilus. Copeia 1968:826-832. Butler, T. H. 1964. Growth, reproduction, and distribution of pandalid shrimps in British Columbia. J. Fish. Res. Board Can. 21:1403-1452. Clarke, T. A. 1973. Some aspects of the ecology of laternfishes (Myc- tophidae) in the Pacific Ocean near Hawaii. Fish. Bull., U.S. 71:401-434. Clarke, W. D. 1963. Function of bioluminescence in mesopelagic organisms. Nature (Lond.) 198:1244-1246. Fedorov, V. v., and L. I. Melchikova. 1971. The description of a new species Macrostomias pacificus Fedorov et Melchikova sp. n. (Pisces, Stomiatidae) from the Kuroshio waters. Vopr. Ikhtiol. 11:763-769. Gibbs, R. H., Jr. 1960. The stomiatoid fish genera Eustomias and Melanos- tomias in the Pacific, with descriptions of two new species. Copeia 1960:200-203. 1964. Family Astronesthidae. In Y. H. Olsen (editor), Fishes of the western North Atlantic. Part 4, p. 311-350. Mem. Sears Found. Mar. Res., Yale Univ., 1. 1969. Taxonomy, sexual dimorphism, vertical distribution, and evolutionary zoogeography of the bathypelagic fish genus Stomias (Stomiatidae). Smithson. Contrib. Zool. 31, 25 p. Goodyear, R. H., and R. H. Gibbs, Jr. 1969. Systematics and zoogeography of stomiatoid fishes of the Astronesthes cyaneus species group (family Astrones- thidae), with descriptions of three new species. Arch. Fis- chereiwiss. 20:107-131. Grey, M. 1960. A preliminary review of the family Gonostomatidae, with a key to the genera and the description of a new species from the tropical Pacific. Bull. Mus. Comp. Zool. Harvard College 122:57-125. 1964. Family Gonostomatidae. In Y. H. Olsen (editor), Fishes of the western North Atlantic. Part 4, p. 78-273. Mem. Sears Found. Mar. Res., Yale Univ., 1. Higgins, B. E. 1970. Juvenile tunas collected by midwater trawling in Hawaiian waters, July-September 1967. Trans. Am. Fish. Soc. 99:60-69. Kawaguchi, K., and R. Marumo. 1967. Biology of Gonostoma gracile (Gonostomatidae). I. Morphology, life history and sex reversal. Inf. Bull. 350 CLARKE: ECOLOGY OF STOMIATOID FISHES Planktol. Japan. 1967:53-69. King, J. E., and R. T. B. Iversen. 1962. Midwater trawling for forage organisms in the Cen- tral Pacific 1951-1956. U.S. Fish. Wildl. Serv., Fish. Bull. 62:271-321. Krueger, W. H. 1972. Biological studies of the Bermuda Ocean Acre IV. Life history, vertical distribution and sound scatter- ing in the gonostomatid fish Valenciennellus tripunc- tulatus (Esmark). Rep. to U.S. Navy Underwater Sys- tems Center, Wash., 37 p. Krueger, W. H., and G. W. Bond. 1972. Biological studies of the Bermuda Ocean Acre III. Vertical distribution and ecology of the bristlemouth fishes (family Gonostomatidae). Rep. to U.S. Navy Un- derwater Systems Center, Wash., 50 p. McAllister, D. E. 1967. The significance of ventral bioluminescence in fishes. J. Fish. Res. Board Can. 24:537-554. Morrow, J. E., Jr. 1964a. Family Chauliodontidae. In Y. H. Olsen (editor), Fishes of the western North Atlantic. Part 4, p. 274-289. Mem. Sears Found. Mar. Res., Yale Univ. 1. 1964b. Family Stomiatidae. In Y. H. Olsen (editor), Fishes of the western North Atlantic. Part 4, p. 290-310. Mem. Sears Found. Mar. Res., Yale Univ. 1. 1964c. Family Malacosteidae. In Y. H. Olsen (editor). Fishes of the western North Atlantic. Part 4, p. 523-549. Mem. Sears Found. Mar. Res., Yale Univ. 1. Morrow, J. E., Jr., and R. H. Gibbs, Jr. 1964. Family Melanostomiatidae. In Y. H. Olsen (editor), Fishes of the western North Atlantic. Part 4, p. 351-511. Mem. Sears Found. Mar. Res., Yale Univ. 1. NOVIKOVA, N. S. 1967. Idiacanthids of the Indian and Pacific oceans (Pisces, Idiacanthidae). [In Russ., Engl, summ.] Tr. Inst. Okeanol. Akad. Nauk SSSR 84:159-208. Tate, M. W., and R. C. Clelland. 1957. Nonparametric and shortcut statistics in the social, biological, and medical sciences. Interstate Printers and Publishers, Inc., Danville, 111., 171 p. 351 REARING OF PLAICE {PLEURONECTES PLATESSA) LARVAE TO METAMORPHOSIS USING AN ARTIFICIAL DIET J. W. Adron, a. Blair, and C. B. Cowey» ABSTRACT Newly hatched larval plaice were grown to metamorphosis using an artificial diet. The overall survival rate to metamorphosis was of the order of 20%. This compares with a survival rate of 38% in control larvae fed Artemia in a similar tank system. The preparation of the artificial diet is described. The main protein component was freeze-dried cod muscle and the diet contained 70.7% crude protein, 9.7% lipid, 7.9% ash, and 5% digestible carbohy- drate. This food in particle sizes ranging from 180 to 355 m was introduced automatically into the inflowing water of a cylindrical tank containing 200 yolk sac larvae. Water temperature was 10± 2'C. After about 13-14 days a relatively high larval mortality occurred, leaving approximately 70 established feeding larvae. Unfed larvae in an identical control tank did not survive beyond this time. Once feeding had been established larval mortalities were occasional and sporadic. Thirty-five days after commencement of the experiment some larvae began to metamorphose, and 56 days from the start some 35 metamorphosed fish were transferred to a separate tank. These fish have since continued to feed and grow on the same diet. The rearing of marine flatfish from egg to metamorphosis and subsequently to more adult stages was achieved under laboratory or hatchery conditions using live food {Artemia salina) about 10 yr ago ((Shelbourne, 1964). The experimental animal was plaice, Pleuronectes platessa. Since then other flatfish (lemon sole, Microstomus kitt; Dover sole, Solea solea; and tuvhot, Scop h thai mus maximus) have been similarly reared to metamorphosis, using either the same food or- ganism for sole or a combination of organisms such as rotifers followed hy Artemia for turbot. While such methods have been applied success-' fully on a pilot scale the ability to rear these fish on an artificial diet may confer certain advantages such as: ( 1 ) the ability to change the composition of the food and so. ultimately arrive at a composite ration approaching the optimal requirement of the larva; (2) continuity of a food supply of stand- ard quality (the large scale production of live food other than Artemia involves cultivation of several organisms, e.g. rotifers, and food for rotifers. Thus the whole cultivation program must be carefully synchronized and there must be certainty that production of food will keep pace with the increas- ing demands of the growing larval fish. Moreover, Artemia themselves may vary in nutritional qual- ity and may contain variable amounts of pesticide residues (Bookhout and Costlow, 1970)); (3) elimi- nation of the need to wean metamorphosed larvae from a natural to an artificial food. There can be little doubt that the availability of compounded foods has contributed greatly to the growth offish farming procedures for freshwater fish such as trout, salmon, and channel catfish in several coun- tries. All these species of fish have large eggs which give rise to large fry so that, compared with the early rearing of marine fish larvae, few techni- cal problems arise. The present paper describes a partially success- ful attempt to rear plaice from egg to metamor- phosis using artificial food under small scale laboratory conditions. EXPERIMENTAL The apparatus used is shown in Figure 1 and Figure 2. The larval rearing tank was cylindrical and measured 26 cm in diameter with a depth of 23 cm. It was contained in an outer vessel which was normally full of sea water. The bottom of the tank was formed from a circular piece of rigid polyvinyl chloride pipe (Durapipe^) which fitted closely 'Institute of Marine Biochemistry, St. Fittick's Road, Aber- deen ABl 3RA Scotland. ^Reference to trade names does not imply endorsement by the National Marine Fisheries Service, NOAA. Manuscript accepted September 1973. FISHFRV BULLETIN: VOL. 72. NO. 2. 1974. 353 FISHERY BUI l.ETIN: VOL. 72. NO. 2 food dispensef recess into which a clean tank bottom can be inserted nylon screw secumg tank bottom removable tank bottom nylon mesh 10 cm Figure 1. — Vertical section through the larvae rearing tank. In use the tank is suspended within a larger plastic vessel. Figure 2. — Photograph of one of the larvae rearing units in use. round the cylindrical tank and was firmly clipped onto it by a bayonet attachment. This circular piece of Durapipe was covered with 0.75 mm aper- ture nylon mesh to retain larvae and possibly permit uneaten food to escape. In the event the food tended to swell after being in the water for some time and only a portion of it passed through the screen at the bottom of the tank. To facilitate tank cleaning and hygiene, therefore, an exactly similar cover could be fitted over the top of the cylindrical tank and the tank slowly and carefully inverted in the outer vessel so that the bottom cover was now at the top and could readily be removed together with adhering uneaten food. This cleaning arrangement is not ideal, but by permitting the removal of much of the uneaten food from the bottom of the tank, it allowed posi- tive control over tank hygiene and water quality. These factors have been a major obstacle to culti- vation of larval fish on artificial diets in earlier experiments. As the larvae grew larger it became more and more possible to siphon uneaten food from the bottom of the tank without endangering or losing larvae. Food was dispensed into the tank with the in- flowing water by means of an automatic feeder of the type described by Adron (1972). This feeder was held on a clamp stand adjacent to the tank and could readily be removed when the tank was being cleaned by inversion. Approximately 15 mg dry food was introduced into the water via a mixing chamber at 10 min intervals, the flow rate of water being about 150 ml/min. The experiment was car- ried out at a temperature of 10° ± 2°C with a light intensity at the water surface of 250 lux provided by fluorescent light. The composition of the food used is shown in Table 1. Freeze-dried cod muscle and shrimp meal were prepared as in Cowey, Pope, Adron, and Blair (1972). Freeze-dried whole hen's egg was prepared by drying homogenized hen's egg in a bulk centrifugal freeze drier. The gelatin (pre- Table 1. -Composition of diet used for rearing larval plaice. Component g;100 g dry diet Freeze dried cod muscle 53.4 Freeze dried whole hen's egg 10.0 Shrimp meal 10.0 Cod liver oil 4.0 Encapsulated vitamin mixture 3.3 Vitamin mixture 2.8 Mineral mixture 1.0 Glucose 5.0 a-tocopherol 0.4 Sunset yellovi; F.C F. 0.1 Furanace 0.8 mg Gelatin 10.0 2 Water 150 ml 'Cowey et al. 1972 ^Removed finally by freeze drying 354 ADRON, BLAIR, and COWEY: REARING OF PLAICE LARVAE pared from swine skin 300 bloom) and a -tocopherol (500 mg a -tocopherol per g) were obtained from the Sigma Chemical Co., Ltd. Sun- set yellow was a gift from Imperial Chemical In- dustries; it was included in the diet to simulate the color of Artemia nauplii. Furanace, a broad spec- trum antibiotic developed specifically for fish (Shimizu and Takase, 1967) was obtained from Dainippon Pharmaceutical Co., Ltd. Half of the vitamin supplement was encapsulated in hy- drogenated coconut oil to prevent the leaching out of the vitamins into the sea water. Lest this proce- dure rendered vitamins unavailable to the larvae, the other half of the supplement was added with- out further treatment. To encapsulate the vitamin mixture 28 g were homogenized in 100 ml of di-ethyl ether in which 5 g of hydrogenated coconut oil MP 32-34°C (Loders and Nucoline Ltd., London) had been dissolved. The homogenate was dried in a Bucchi Rotary evaporator. Freeze-dried cod muscle, freeze-dried whole egg, and shrimp meal were finely ground together in a hammer mill. To these ground components were added the vitamin mixture, mineral mix- ture, and glucose. The cod liver oil and Q-tocopherol were mixed together and then thoroughly mixed with the dry components, mix- ing being carried out in a Hobart food mixer. The furanace and sunset yellow were dissolved in % of the allotted water and mixed with the dry compo- nents. The gelatin was dissolved in the remaining water at 50°C before being mixed with the other dietary components. While still warm the moist diet was pressed into slabs 5 mm thick and cooled to room temperature. The slabs of diet were then dried in a bulk freeze-drier, ground with a pestle and mortar and graded with sieves, to give sizes of 250 u-355 Id and 180 iJ-250 fi. For the first 2 days of feeding the larvae were given only diet of 180 /U-250 u ; for the next 8 days increasing quantities of the 250 jU-355 /j'size were mixed with the 180 /u-250 u size until only the 250 a/ -355 ju size was offered. By analysis the diet contained protein (N X 6.25) 70.7%, lipid 9.7%, and ash 7.9%. Two hundred newly hatched larvae were put into each of three tanks on 2 April 1973. These larvae were obtained from eggs kindly supplied by White Fish Authority, Hunterston; the eggs had been artificially fertilized on 12 March. Food was introduced into one of the tanks on 5 April; Artemia nauplii were added to the second tank, while the third tank was kept as an unfed control mainly because unfiltered seawater was being used, and it may have contained enough natural food to maintain a number of the larvae. For the first few days of the experiment rela- tively few mortalities occurred in any of the tanks but then 10-12 days after hatching, a rapid mor- tality occurred in the unfed control, together with relatively high mortalities in the tanks fed artificial and natural {Artemia nauplii) diets. By 15 April no larvae remained alive in the unfed control tank, while the numbers surviving in the two tanks receiving food were about 70 in the tank receiving the compounded artificial diet and about 100 in the tank receiving Artemia nauplii. It seems possible that this high mortality corre- sponds with the complete utilization of the yolk and that the fish surviving in the tanks receiving food correspond to Shelbourne's "established feed- ers." After about 15 April mortality rates fell to a low level in both the remaining tanks; some of the deaths in the tank receiving the artificial food were a direct consequence of tank-cleaning opera- tions. Fish began to metamorphose in both these tanks as early as 6 May and by 28 May some 35 metamorphosed plaice from the tank receiving the artificial compounded diet were transferred to a conventional tank in our recirculated system where they continued to eat the same powdered diet. This represents a 17.5% survival of metamorphosed fish from hatched larvae. Of the larvae which were reared on Artemia some 76 survived to metamorphosis (last day of May), rep- resenting 38% of the original newly-hatched lar- vae. No abnormalities of pigmentation were dis- cernible in the larvae, possibly because of the rela- tively uncrowded conditions in which they were reared. The survival rates with the artificial food were much lower than with larvae fed Artemia; this may be due to the greater acceptability of the live moving diet as compared to the inert artificial food; the higher number of "established feeders" obtained when feeding Ar^emm perhaps supports this view. Both our survival rates are considerably lower than those achieved by Shelbourne (1963) using Artemia, his most successful regime giving about 67% survival to metamorphosis (including mortalities between fertilization and hatching). However, with a temperature regime somewhat similar to that used by us (his water bath 4) Shel- bourne obtained survival rates not greatly differ- ent from our "Artemia" tank, i.e. 55% survival (when egg incubation was carried out in the pres- 355 FlSHfRY BULI FTIN: VOL. 72. NO. 2 ence of antibiotics) and SO^c survival (eggs irri- gated with seawater free of antibiotics during in- cubation). Despite the lower larval survival rate when fed artificial food it is felt that this rate is sufficiently high to demonstrate the technical feasibility of using non-living food for rearing marine fish lar- vae. Moreover, eggs are produced in enormous numbers by marine fish and are extremely cheap so that a 209r survival rate to metamorphosis is an acceptable level. If such a survival rate can be achieved with the more exacting larvae of highly esteemed species (Dover sole, turbot) it would give a considerable impetus to the cultivation of these fish. DISCUSSION Reviewing marine fish larval rearing, May (1970) named the provision of a suitable food (i.e. "one which the larvae will consume and grow on and which can be supplied in sufficiently large quantities") as the prime obstacle. Several at- tempts have been made over the years to rear marine fish larvae on non-living, composite foods but none of these have yet been successful (Fishel- son, 1963; Blaxter, 1962; Ivanchenko and Ivan- chenko, 1969). In practice we have had no great difficulty in getting plaice larvae or at least a relatively high proportion of them to ingest the food and develop on it. The main obstacle has been one of tank hygiene and it remains the overriding problem. This too is recognized by May ( 1970) who comments on the use of non-living food: "un- eaten food accumulates on the bottom of the rear- ing container and decays rapidly, fouling the water". Although the present set-up does permit control of the quantity of uneaten food in the water, any improvements in tank design which release uneaten food completely while retaining the larvae are desirable. Various modifications of tank design to this end are under consideration. The problem is particularly acute in the early stages as the food particles tend to swell in the water and fail to pass the screen at the bottom of tank. As larvae increase in size, and a screen of larger mesh size can be substituted at the bottom of the tank, the problem becomes less acute. Some bacteriological control of water may be attained by sterilizing the incoming water by means of ultraviolet light and such a device should be incorporated into future experiments. Microencapsulation of the food may offer a further means of improving tank hygiene. The microcapsules currently available seem to sink very rapidly through a water column. This mili- tates against their chances of being consumed by larval fish in a rearing tank. The development of neutrally buoyant microcapsules, however, could lead to rapid strides in the controlled cultivation of larval marine fish. The use of an antibiotic in the diet calls for some comment. The relatively free use in animal feeds of those antibiotics which are commonly employed in human medicine has obvious social dangers. Attention has yet again been focused on these dangers by Williams-Smith ( 1973). It must, there- fore, be emphasized that furanace was used in very low concentrations and that it has been de- veloped specifically for use in fish. Thus any resis- tant strains which could result from its use should still be sensitive to antibiotics currently in use in clinical medicine. The diet used was designed empirically with the objects of providing a relatively large intake of high quality protein, marine oil, and a luxus of B vitamins all allied to reasonable water stability. The diet is by no means ideal and there is clearly scope for improvement in this ration in many ways. However, it does provide a basic experimen- tal formula from which more nearly optimal diets may evolve. LITERATURE CITED Adron, J. W. 1972. A design for automatic and demand feeders for ex- perimental fish. J. Cons. 34:300-305. Blaxter, J. H. S. 1962. Herring rearing-IV. Rearing beyond the yolk-sac stage. Mar. Res. Dep. Agric. Fish. Scotl. 1, 18 p. BOOKHOUT, C. G.,AND J. D. COSTLOW, Jr. 1970. Nutritional effects of Artemia from different loca- tions on larval development of crabs. Helgolander Wiss. Meeresunters. 20:435-442. CowEY, C. B., J. A. Pope, J. W. Adron, and A. Blair. 1972. Studies on the nutrition of marine flatfish. The pro- tein requirement of plaice (Pleuronectes platessa). Br. J. Nutr. 28:447-456. FiSHELSON, L. 1963. Observations on littoral fishes of Israel. II. Larval development and metamorphosis oi Blennius pavo Risso (Teleostei, Blenniidae). Isr. J. Zool. 12:81-91. Ivanchenko, L. A., and O. F. Ivanchenko. 1969. Transition to active feeding by larval and juvenile white sea herring (Clupea harengus pallasi NATIO Maris-albi BERG) in artificial conditions. Dokl. Akad. Nauk SSSR 184:1444-1446. 356 ADRON, BLAIR, and COWEY; REARING OF PLAICE LARVAE May, R. C. 1-83. Academic Press, N.Y. 1970. Feeding larval marine fishes in the laboratory: a Shimizu, M., and Y. Takase. review. Calif. Mar. Res. Comm., Calif. Coop. Oceanic 1967. A potent chemotherapeutic agent against fish dis- Fish. Invest. Rep. 14:76-83. eases: 6-hydroxymethyl-2-[2-(5-nitro-2-furyl) vinyl] Shelbourne, J. E. pyridine (p-7138). Bull. Jap. Soc. Sci. Fish. 33:544-554. 1963. A marine fish-rearing experiment using Williams Smith, H. antibiotics. Nature (Lend. I 198:74-75. 1973. Effect of prohibition of the use of tetracyclines in 1964. The artificial propagation of marine fish. In F. S. animal feeds on tetracycline resistance of faecal £. coZi of Russell (editor), Advances in Marine Biology, vol. 2, p. pigs. Nature (Lond.) 243:237-238. 357 THE INVASION OF SAURIDA UNDOSQUAMIS (RICHARDSON) INTO THE LEVANT BASIN - AN EXAMPLE OF BIOLOGICAL EFFECT OF INTEROCEANIC CANALS M. Ben-Yami' and T. Glaser2 ABSTRACT The Red Sea lizardfish, Saurida undosquamis (Richardson), invaded the Levant Basin and established a population of considerable commercial importance. Its expansion came at the expense of other commercial fishes on which it preys and with which it competes. The explosion of the Red Sea lizardfish population in the Levant Basin was made possible by a combination of changes in the environmental conditions (abiotic and biotic), one of these being the retreat of, or the recession in, the native hake population. The dynamic coexistence between the lizardfish and the hake, its main competitor, is affected by fluctuations in the abiotic conditions to which the hake seems to be more sensitive than the lizardfish. A faunistic, zoogeographical approach to the marine animal migration through the Suez Canal is common to most investigators of the canal's influence. Animal species native to one sea and found in the other after the opening of the canal serve as main indicators of its biological influence and of its effectivity as a link to the migrant species and as a barrier to others (Ben-Tuvia, 1966, in press; Kimor, 19703; Por, 1971; Steinitz, H., 1968; Steinitz, W., 1929; Thorson, 1971). Many authors listed and described migrant species (Barash and Danin, 1971-*; Ben-Tuvia, 1953; Col- lette, 1970; Gilat, 1964; Gohar, 1954; Gordin, 19665; Holthuis and Gottlieb, 1958; Kosswig, 1951; Steinitz, H., 1967; Tortonese, 1953). Some authors have discussed the Red Sea- Mediterranean animal migrations in relation to ecological conditions in the canal and in the adja- cent sea areas (Gilat, 1966^ 1969^; Oren, 1969, 'Fisheries Technology Unit, P.O.B. 699, Haifa, Israel. ^Kibbutz Ma'agan Mikhael, D.N.Hof Hacarmel. Israel. ^Kimor, B. 1970. The Suez Canal as a link and a barrier in the migration of planktonic organisms. Submitted to the Ocean World-Joint Oceanographic Assembly, Tokyo, 13-25 Sept. 1970, 20 p. ■'Barash, A., and Z. Danin. 1971. Indo-Pacific species of Mol- lusca in the Mediterranean. Appendix to Progress Report 1970/1971. The Hebrev/ University - Smithsonian Institution Joint Project "Biota of the Red Sea and the Eastern Mediterra- nean," 8 p. [Processed.] *Gordin, H. 1966. Migration of fishes through the Suez Canal Ms. in files of Fish. Technol. Unit, Haifa, Israel. ^Gilat, E. 1966. The animal bottom communities in the Le- vant Basin of the Mediterranean Sea. 9 p. In files of Fish. Tech Unit, Haifa. [Processed.] 'Gilat, E. 1969. The macrobenthic communities of the level bottom in the Eastern Mediterranean. In Interim Report, Joint Research Project "Biota of the Red Sea and the Eastern Mediter- ranean," p. 82-89. The Hebrew University of Jerusalem and the Smithsonian Institution, Washington, D.C. [Processed.] 1970; Por, 1969«, 197P), suggesting that the mechanism of the penetration of some species through the canal and their expansion in the Mediterranean is associated with environmental conditions (salinity, currents, nature of substrate, etc.). In this paper we discuss the ecology of the mi- gration and expansion in the new habitat of an important commercial fish. We examine its dynamic coexistence with its native competitor in view of the changing environmental conditions. The Relative Importance of Species It is a well-known fact that, while some of the migrant species have established themselves in the new environment, creating populations with a significant impact on the ecosystem, other species may just survive under the new and, perhaps, hostile conditions. The relative importance of a species in terms of biomass and its role and weight in the food chain is often neglected when two species are listed as "common" or "abundant." One of them may be an important commercial fish with a biomass of an order of tens of thousands of tons or more, and the 8Por, F. D. 1969. The Canuellidae (Copepoda Harpacticoida) in the waters around the Sinai Peninsula and the problem of Lessepsian migration in this family. In Interim Report, Joint Research Project "Biota of the Red Sea and the Eastern Mediter- ranean," p. 34-40. The Hebrew University of Jerusalem and the Smithsonian Institution, Washington, D.C. [Processed.] ^Por. F. D. 1970. The nature of the Lessepsian migration through the Suez Canal. Paper presented at the XXIIe Congres Assemblee Pleniere de la C.I.E.S.M., Rome. Manuscript accepted September 1973. FISHERY BULLETIN: VOL. 72. NO. 1974. 359 FISHERY BULLETIN: VOL. 72, NO. 2 other is, say, a frequently met small, commer- cially unimportant, Apogon. However, such dis- crimination should be made: the first fish is a wholesale consumer and also a supplier of impor- tant food for other species; the other, although frequently collected, occurs in small numbers, and whatever its importance may be in its immediate biotope, its effect on the whole ecosystem is of little consequence. Therefore, in studying the impact of one sea on the other, number of migrant species should not be overemphasized and more attention should be paid to species of ecological importance. Commercial Fish Populations as Indicators of the Biological Effect The most important aspect of interrelations be- tween two seas, especially where a new canal is planned, are the ecological effects which influence the human ecological conditions and economy. To obtain a meaningful picture of the biological effect of the Suez Canal on both seas, emphasis should be put on changes which have considerably affected the large or the commercial populations of either. Obviously, almost any fish species which occurs in great numbers and biomass becomes sooner or later commercially important, either as a market- able product or as a food to commercial piscivores. Changes in the quantity and composition of im- portant commercial fishes are contained in most fisheries statistics. Of course, this can only be shown where fish landings are reasonably well recorded and where the data obtained may be evaluated to eliminate technological and socioeconomical factors. Commercially Important Red Sea Migrants and Their Mediterranean Competitors A number of immigrant Red Sea species have become commercially important in the Levant Basin and/or provide food for both Red Sea immi- grants and native fish populations. Sufficient data are available to discuss the expansion of the Red Sea lizardfish, Saurida undosquamls (Richard- son), and the dynamics of its coexistence with its main native competitor Merluccius merluccius (Linnaeus), the hake. Unfortunately, other species which could serve perhaps as better examples, the yellow-striped goatfish, Upeneus moluccensis Bleeker, and its Mediterranean counterpart the red mullet, Mul- lus barbatus Linnaeus, or the barracudas, Sphyraena chrysotaenia Kiunzinger (a Red Sea migrant), S. sphyraena (Linnaeus), and S. vir- idensis Cuvier (both Atlantic species), cannot be used for this purpose as the catch statistics do not discriminate between the species of the same fam- ily or genus. From the information available on the Mullidae {Upeneus and Mullus), the following can be sum- marized: Red mullets (Mullidae) represent one of the most important components of the Israeli trawl catches. Their share in the total trawl land- ings varied between 1956 and 1970 from 29 to 46%, (Sarid, 1951-71). The bulk of the red mullets consists of two species: the red mullet and the yellow-striped goatfish. The latter species is a Red Sea migrant. According to Wirszubski (1953) in the late 40's the share of the yellow-striped goat- fish in the Mullidae catch was 10 to 15%. Four years later, Oren (1957) estimated on the basis of Gilat's unpublished data that Upeneus formed over 83% of the total number of red mullets caught in trawls during the first half of 1956. These are two closely related fish species, very similar in their appearance and behavior and ap- parently competing for the same food (E. Gilat, pers. comm.). Although the red mullet evidently prefers cooler and, thus, in periods, deeper waters than the yellow-striped goatfish (Ben-Yami, 1955; Ben-Tuvia, in press), they mostly occupy overlap- ping territories. One of them-the invader- succeeded in becoming a majority during 1955 (Ben-Yami, 1955; Oren, 1957). Since 1956, fluc- tuations continue to occur in the Mullus to Upeneus ratio. Ben-Tuvia (in press) estimates the average share of the latter fish in the catches of red mullets to be approximately 30% . What are the reasons for such fluctuations? What are the factors which determine whether a fish which has crossed the canal will establish itself as a sizeable population? Is it possible that after some years of blooming a migrant population will recede into its previous state, and why? Will an expanding migrant popu- lation contribute to the total fish biomass in the new area, or come at the expense of the other fishes? SOURCES AND RELIABILITY OF DATA Fishery Statistics All fisheries data presented in the graphs and 360 BEN-YAMI and GLASER: INVASION OF SAURIDA UNDOSQUAMIS tables are based on statistics collected by the De- partment of Fisheries (Sarid, 1951-71). These are in general reliable, and the proportion of the hake and the lizardfish in the total trawl catch is well represented. The figures, however, may be biased in some aspects, and the following must be borne in mind: 1. The catch per unit effort for all fish and for each of the two species separately is expressed in kilograms per day at sea of a trawler. The Israeli trawlers operating in the Mediterranean during 1950-70 were powered by 110-to 240-horsepower engines. The average power per trawler varied with time, due to transfer of some to the Red Sea, loss of others, and acquisition of new vessels and engines. It increased steadily in the 50's, de- creased in the early 60's, and started increasing again during the recent years (Table 1 ). Therefore, when examining the data in Figure 5A and B, it should be remembered that the unit of effort var- ied from year to year. 2. The total fishing effort and the total catches fluctuated partly because of the changing socioeconomical and geopolitical conditions, which determined the extent of the fishing grounds on which the Israeli trawlers could oper- ate in the Mediterranean, and its effect on the size of the active trawling fleet. 3. The character and extent of the trawling grounds available to and/or preferred by the fishermen partly affect the data: In deepwater op- erations the hake is one of the main fish caught (Ben-Yami, 1971; Zismann, 1971), while the lizardfish is almost absent. In shallow water, trawling depends on the accessibility of the southern trawling grounds, which fluctuated with the Egypto-Israeli relations. On these grounds good summer catches could be obtained in shallow waters, conditions preferred by some skippers to deepwater trawling. From 1953 to 1960, some of the Israeli trawlers operated during the summer months in the north- eastern area of the Mediterranean, between Cy- prus and Turkey, mostly in the Bay of Tarsus. Their catches were included indiscriminately in the general statistical data. In these catches, the lizardfish greatly outweighed the hake. There- fore, the catch composition data for these years may be slightly biased in favor of the lizardfish and to the disadvantage of the hake as compared with the other years, but by no means to a degree which might change the general picture. Sea Temperature In order to study effects of changes in the en- vironmental factors on the catches of the hake and the lizardfish, the temperatures recorded from the sea between Ashdod and Tel Aviv, an area Table 1. — Changes in the fishing effort, catch and catch-per-effort, 1950-1970, in the Israel Mediter- ranean trawling fishery.* Number of trawlers H orsepow^r Number of days at sea Catch total of the selected boats (tons) Year Total Average per trawler Catch/100 hp per day (kg) 1950 7 840 120 976 312 265 1951 19 2.420 127 3,102 1,031 211 1952 14 2,070 146 2,152 667 221 1953 14 2,070 146 2,728 997 250 1954 17 2.350 139 3,047 1.160 273 1955 22 3,120 142 3.523 1,494 298 1956 16 2,530 158 2,616 1,162 281 1957 16 2.520 158 3,185 1.335 225 1958 20 3.020 151 4,350 1.575 239 1959 23 3,330 145 5,208 1.878 235 1960 17 2,580 152 3,386 1.077 208 1961 15 2,130 142 2,957 874 295 1962 14 1,990 142 2,694 766 284 1963 13 1,760 135 2,505 647 191 1964 10 1,390 139 1,765 530 215 1965 13 1,800 138 2,443 676 200 1966 13 1,840 141 2,579 561 155 1967 14 2,010 143 2,933 720 195 1968 14 2,070 147 2,985 925 210 1969 14 2.140 153 2,967 979 224 1970 14 2,290 163 3.013 886 180 'The data do not include research and training vessels, and vessels which fished less than 100 days per year (E. Grofit, private communication). 361 FISHERY BULLETIN: VOL. 72, NO. 2 situated in the center of the trawl grounds, were examined. The water temperatures at, or closely below, the 75-m depth (Figure 1), and a number of sea surface temperatures were collected during monthly cruises of Israeli research vessels (Oren and Hor- nung, 1972, and pers. comm.). During the 21 yr, many monthly cruises were not carried out, hence the numerous gaps (Figure 2). Additional surface temperature data for the period from 1958 to 1970 are monthly averages of daily monitored temperatures at Ashdod. These were supplied by the Coast Study Division of the Israel Port Authority (pers. comm.). T°c 26 25 24 23 22 21 20 19 18 17 16 15 J I I L. -i I I I I L J I L 50 52 54 56 58 60 62 64 66 68 70 YEAR Figure 1. — Sea temperatures at depths of 75 m or below, collected during monthly cruises in or near the Tel Aviv-Ashdod area between 1950 and 1970 (Oren and Hornung, pers. comm.). Dots - yearly maxima; cross - yearly minima. In this graph each year begins in January. 30 29 28 271- 18 - /N. 17 ■• / 16 ■ 15 \ / 14 i 1 1 1 1 1 1 1 1 1 1 1 I 1 1 1 1 1 1 1 1 ., 50/51 52/53 54/55 56/57 58/59 60/61 62/63 64/65 66/67 68/69 70/71 YEAR Figure 2. — Sea surface temperature. Top - summer maxima; bottom- winter minima. A - Data collected during monthly cruises in the area of Tel Aviv-Ashdod (Oren and Hornung, pers. comm.); B - (dashed line) — monthly means of daily collected data at Ashdod, inshore (Coastal Survey Unit, pers. comm.). Each year starts 1 September. 362 BEN-YAMI and GLASER: INVASION OF SAURIDA UNDOSQUAMIS Meteorology Air temperature (monthly averages) and pre- cipitation data for 1950-70 were published by the Israel Meteorological Service. These data are complete and uninterrupted for the whole period. Only those data which were collected at stations between Tel Aviv and Ashdod (Anonymous, 1950-71) were chosen (Figures 3, 4). Presentation In attempting to find the relationship between climatic phenomena and fish catches, it is simpler to follow a calendar based on seasons with the year beginning in the fall, at the beginning of the rainy season in this area. Thus, for the purpose of this study, the environmental and most of the fisheries data are given according to years which start on 1 September and end on 31 August, i.e., 1 Sep- tember 1950-31 August 1951 forms the year 1950/51. In some instances, extreme values rather than annual averages may be influential factors affect- ing crops or populations. One year may be a rainy year, but most of the rains may not have been timely, etc. For this purpose, some data are pre- sented selectively to emphasize the more critical points. Thus, e.g., the average of the three coldest months, whatever these months may be in each T°C 28 27 26 25 16 15 14 13 50/51 52/53 54/55 56/57 58/59 60/61 62/63 64/65 66/67 68/69 YEAR Figure 3. — Air temperatures, 1950/51-1968/69 (Anonymous, 1950-70). A - Summer maxima, mean of the warmest month; B - average of three coldest months. Each year starts 1 September. MM 900 • 800 1 \ i \ ■ ^ 700 600 / »' V V, / \ / X 1 \ 1 500 400 V > // 300 .; />. / \ / i • « 50/51 52/53 54/55 56/57 58/59 60/61 62/63 64/65 66/67 68/69 YEAR Figure 4.— Precipitation, 1950/51-1968/69 (Anonymous, 1950-70). A - September-January; B - January-April. Each year starts 1 September. 363 year, rather than the annual averages are used. Neither the data presented in this paper nor other available pertinent data have been statistically processed. Therefore we have limited ourselves to seek only most general patterns based on the most obvious dramatic changes and to point out apparent or likely correlations. THE RED SEA LIZARDFISH The Invasion Prior to 1954, two species of lizardfish (Synodon- tidae) occurred rather infrequently in the catches of the Israeli Mediterranean trawlers: Synodus saurus (Linnaeus), a tropical Atlantic and Mediterranean species (Fowler, 1936), and the Red Sea lizardfish, an Indo-Pacific species. The latter was first reported from the Mediterranean as Saurida grandisquamis (Gunther) by Ben- Tuvia (1953, in press), who found it for the first time in December 1952. At that time, neither species was of commercial value, and S. undo- squamis was much rarer than Synodus saurus (Ben-Tuvia, 1953, in press; Oren, 1957). Ben-Tuvia (in press) observed that as early as August 1953 the lizardfish was fairly common in trawl catches taken in the Gaza-El Arish area, with 10 to 20 specimens caught usually in each haul. In the winter of 1954-55, together with other changes in the composition of trawl catches, the proportion of the Red Sea lizardfish increased to such an extent that the fishermen attempted to market them as a food fish (Ben-Yami, 1955). Con- sequently, in 1955 lizardfish appeared for the first time in the statistics of landings (Sarid, 1956). In the summer of 1955, unusual numbers of fingerlings were found in the cod ends of trawl nets. The bulk of them consisted of two Red Sea species, the yellow-striped goatfish and the lizardfish (Ben-Yami, 1955). In 1955-56, the lizardfish became one of the main commercial fishes in Israel; its proportion in the total landings of Israel's marine fishery reached 11% (Sarid, 1956), and in the trawl fishery landings approximated 20% (Figure 5). Catch data collected during 1955 and 1956 (Oren, 1957) indicate that the Red Sea lizardfish made its first significant appearance in the trawl catches in the fishing grounds off the Gaza Strip and North Sinai. By the end of summer and autumn of 1955 FISHERY BULLETIN; VOL. 72, NO. 2 it had expanded all over Israel's fishing grounds. During the period 1952-60, most Israeli trawl- ers fished in the summer months in the north- eastern part of the Mediterranean (Gulf of Tarsus and neighboring waters). The Red Sea lizardfish, however, was not found in those waters in 1952 by Gottlieb and Ben-Tuvia (1953), who produced a detailed list of 52 fish species caught in a trawl catch. By summer 1956, it was common in the trawl catches in the Bay of Tarsus (Ben-Tuvia, pers. comm.), and since then it has become well established and is one of the most important com- mercial fish in that area. The quantity of lizardfish caught by the trawl- ers continued to increase until 1959 when almost 400 tons (20% of the total trawl catch) were landed (Sarid, 1960). This was followed by a 4-yr reces- sion. In 1963, the catches dropped to an approxi- mately 120-ton low, and since then, they appar- ently stabilized near this level with "normal" an- nual fluctuations. Food and Habitat of the Red Sea Lizardfish The lizardfish is a demersal piscivore. Its food in the Levant Basin was studied by Bograd- Zismann (1965) and by Chervinsky (1959). Bograd-Zismann examined some 1,500 stom- achs, of which 859 contained food. Of these, 77.3% contained fish; the rest contained inverte- brates, mostly crustaceans, and digested matter. Chervinsky examined some 500 stomachs, of which 131 contained identifiable food. Large in- vertebrates were found in only 16 stomachs; the rest contained fish. Both authors indicate that the most frequent prey of the Red Sea lizardfish are clupeoid fish-according to Chervinsky (1959) an- chovy, and according to Bograd-Zismann (pers. comm.) mostly anchovy, but also some sardines. The second important group in the food of the lizardfish are fish of the family Mullidae (Bograd-Zismann, 1965; Chervinsky, 1959). Other important groups in the lizardfish food are Gobiidae, Centracanthidae (listed as Maenidae by Bograd-Zismann, 1965, and by Chervinsky, 1959), and Leiognathus klunzingeri (Stein- dachner) (Bograd-Zismann, 1965; Chervinsky, 1959; Ben-Tuvia, 1966). No direct information is available on the diurnal-nocturnal feeding activity of the i lizardfish in the Levant Basin. Nonetheless, the high proportion of anchovy in the food of the ' 364 BEN-YAMI and GLASER: INVASION OF SAURIDA UNDOSQUAMIS 25 20 15 10 5 / \ -»^ 50/51 52/53 54/55 56/57 58/59 60/61 62/63 64/65 66/67 68/69 70/71 YEAR Figure 5. — Changes in the hake — Red Sea lizardfish relationship in catches and the catch-per-unit-effort (cpu) in the Israel trawl fishery in the Mediterranean, 1950-70 (Sarid, 1951-71). A - cpu— all fish, each year starts 1 January; B - cpu — (1) lizardfish, (2) hake; C - proportion in catch, percent: (1) lizardfish, (2) hake. BandC — each year starts 1 September. lizardfish may indicate that either the lizardfish is a demersal feeder, feeding on clupeoids only when it approaches the bottom of the sea during the hours of light, or that it ascends during the night to the upper water layers where it could feed on these pelagic fish. We favor the first hypothesis, for the lizardfish almost never occurs in the night catches of purse seines in light fishing. This hypothesis is corroborated by observations of Hiatt and Strasburg (1960) of two lizardfishes, Saurida gracilis and Synodus variegatus, of the Marshall Islands. The lizardfish lie motionless, on or partly buried in the sand, and are virtu- ally impossible to detect. Only when small fish come within a distance of a few feet, the lizardfish seize them in a rapid dart. They were rarely ob- served to ascend for more than 3 to 4 feet while attacking their prey. Hayashi, Yamaguchi, and Hanaoka (1960) and Toriyama (1958) reported on the basis of stomach examinations that S. undosquamis in Japanese waters feeds during most hours of day and night. According to Toriyama, however, feeding activity is most intensive during the early morning hours. According to Chervinsky (1959), the lizardfish is cannibalistic. Bograd-Zismann (1961-62) ob- served that the occurrence of lizardfish in stomachs may rather be a result of panicky indis- criminate attacking in the trawl cod end. The Red Sea lizardfish in the Levant Basin pre- fers rather shallow waters. It is caught in the cool- er seasons at depths generally not exceeding 45 fm 365 FISHERY BULLETIN: VOL. 72, NO. 2 Figure 6. — The overlapping habitats of the Red Sea lizardfish and the hake over the Israel continental shelf. Top - summer; bottom - winter. Depth in fathoms. (fathoms), but mostly at less than 35 fm (Figure 6). During the warm season the lizardfish may spread over deeper trawling grounds. Occasionally it oc- curs in catches made at 80 to 100 fm. In general, however, the lizardfish is of no commercial signifi- cance over the deepwater trawling grounds (Ben-Yami, 1971; Zismann, 1971). Spawning There is very little biological information on the Red Sea lizardfish in this area. Bograd-Zismann (see footnote 10) and Chervinsky ( 1959) found that ripe, nearly ripe, and partly spent females occur in catches almost all year long, though the former author indicated that the greater proportion of nearly ripe females occurs in the early summer. It has to be borne in mind that a fish may spawn over a prolonged season, while the survival of its fry may be confined to a much shorter period con- trolled by favorable, seasonal conditions. The area of spawning can only be speculated as being offshore and in deep water. This is based on the following information: Neither larvae nor juveniles oiSaurida were taken during an exten- sive survey offish larvae made using neuston nets (Ben-Yami et al., 1970) and Isaacs-Kidd mid- water trawl off the coast of Israel and Sinai during 1967-69. This survey consisted of 25 cruises cover- ing inshore (Haifa Bay, Bardawil Lagoon), shal- low water, and offshore stations. Only once, in December 1968, were S. undosquamis fry taken: nine 11-20 mm specimens were caught in deep water in the Isaacs-Kidd trawl, at a station situated 7 miles west of Cape Carmel, over 200 fm depth (Lourie, Herzberg, and Ben-Yami, 1969^S Lourie, pers. comm.). The very fact that S. undosquamis larvae and juveniles did not occur either among the thousands of fish larvae and juveniles caught in neuston nets during day and night tows (Lourie et al., see footnote 11; Lourie, pers. comm.) or in sam- ples taken by means of a light trap for small photokinetic organisms (Zismann, 1969) seems to indicate that they do not occur in the surface water layer, neither during the day nor by night. On the other hand, the capture of the young in December, over deep water and apparently deep in the mid- water, coincided with the seasonal temperature increase at this level (Oren, 1970) (Figure 1). Growth Chervinsky (1959) has measured the length fre- quency of the lizardfish between June and De- cember 1957, concluding that while the bulk of the lizardfish catch consisted offish between 16 and 24 cm long, they grew fast; 2 cm per month. No males exceeding 24 cm were found, although females exceed 30 cm. Bograd-Zismann (see footnote 10) examined the scales of the lizardfish. Two annuli were found on the scales offish 22 to 30 cm total length (TL). On the scales offish 19 to 22 cm TL, one annulus was seen, but there are indications that the year's growth is not marked by a clear annulus. Thus, it seems that the age of the lizardfish at recruitment is about 2 yr or may be 3 yr, the bulk of the fish in the catch being at least 2 yr old. Relation with Relative Species To complete the ecological picture of the Red Sea lizardfish, its relationship with two of its relatives should be mentioned: one is the Atlantic- Mediterranean lizardfish, Synodus saurus, and '"Bograd-Zismann, L. 1961-62. Interim report on the study of the food of Saurida undosquamis in the Mediterranean Sea. Unpubl. manuscr. In files of the Isr. Sea Fish. Res. Stn., Haifa. "Lourie, A., A. Herzberg, and M. Ben-Yami. 1969. A survey of neustonic fishes off the Mediterranean coast of Israel and Sinai, 1968. In Interim Report, Joint Research Project "Biota of the Red Sea and the Eastern Mediterranean," p. 133-150. The Hebrew University of Jerusalem and the Smithsonian Institu- tion, Washington, D.C. [Processed.] 366 BEN-YAMI and GLASER: INVASION OF SAURIDA UNDOSQUAMIS the other is the Indo-Pacific species greater lizardfish, Saurida tumbil (Bloch). The first is a quantitatively insignificant and hence noncom- mercial demersal predator in the Levant Basin. Although a natural competitor to the latter, the native S. saurus was superseded by the invader, being now as rare as ever. Saurida tumbil is one of the main commercial fishes and dominates in the south Red Sea trawl fishery. Another species, S. undosquamis , is the "underdog" there, though not as rare as Synodus saurus is in the Levant Basin. Saurida undo- squamis holds ground only in deeper and, evi- dently, cooler waters, while S. tumbil dominates over most of the trawling grounds (Ben-Tuvia, 1966). On the other hand, it is S. undosquamis, probably the euryecous of the two, which spread into the northern Red Sea, becoming the only sig- nificant lizardfish in the Gulf of Suez and the Le- vant Basin. Feeding in Israel Waters Shmida (1964)^2 investigated 76 stomachs of which 49 contained food. The fish were from catches taken in summer and spring. While the bulk of the food taken in spring consisted of crus- taceans (mostly Decapoda, Macrura), the food of hake caught in summer was mostly fish. Shmida concludes that, in general, the food in terms of weight was half crustaceans and half fish. All identifiable fish were anchovy. Unfortunately, Shmida had at his disposal only small individuals, less than 27 cm long. Larger, faster, and stronger hake may have a different diet in which the pro- portion offish may be higher. This was indicated by a slight trend of more fish in the stomachs of the larger hake, even within the narrow length range investigated (Shmida, 1964). Habitat HAKE Another important commercial fish whose habitat and food in the Levant Basin indicate that it is the main competitor of the lizardfish is the hake, Merluccius merluccius. This is an eastern Atlantic species which is also native to these wa- ters (Ben-Tuvia, 1953), and whose biology and habits in the Levant Basin still remain to be studied. In the Atlantic Ocean the hake is known as a voracious predator, feeding during the day at the bottom and rising at night into higher water layers. It is known as a deepwater species caught at depths down to 400 fm. Off the British Isles, it seems to prefer water temperatures of around lOT. Spawning and Growth Near the British Isles, the hake spawns mostly at or near areas over the 100-fm isobath. Females spawn up to a million eggs each. The eggs are pelagic, floating on the sea surface. Before hatch- ing, which occurs within a fortnight, the eggs de- scend to midwater, where the larvae hatch and develop. The yolk is absorbed within 3 to 4 wk after which the postlarvae feed on zooplankton. The fry descend to the bottom, where hake 3 to 4 cm long were taken. They reach 10 cm at the year's end and become mature at 20 cm (Marshall, 1965; Travis Jenkins, 1954). The hake prefers cool water. This is evident from its occurring over the shallow trawling grounds only during the cooler season of the year. Its proportion in trawl catches can be consider- able, even at depths less than 20 fm, if the water is cold enough. With the approach of the warm sea- son, the hake retreats to the deepwater regions where it remains available to trawls at depths over 100 fm throughout the season (Ben-Yami, 1971). Figure 6 illustrates the relative distribu- tion of the lizardfish and the hake over the Israeli continental shelf and their overlapping habitats. RED SEA MIGRANTS AS PREY OF THE HAKE AND THE LIZARDFISH As mentioned above, both our predators feed extensively on anchovy. It seems, nevertheless, that the hake competes with the lizardfish also for other fish, some of them Red Sea migrants. Ben- Tuvia (1966) reports that two of them, Leio- gnathus klunzingeri and a Red Sea goatfish, Upe- neus asymmetricus Lachner (reported previously as U. tragula Richardson), are components of the food of both the lizardfish and the hake. Leio- gnathus, a trash fish in trawl catches, has been, undoubtedly, of major importance in the food i^Shmida, A. 1964. T'zunat dagim b'Yam Tikohn uv'Yam Suf (Food of fishes in the Mediterranean and the Red Sea). [In Hebrew.] Unpubl. manuscr. In files of the Isr. Sea Fish. Res. Stn., Haifa. 367 FISHERY BULLETIN: VOL. 72, NO. 2 chain of demersal piscivores (Ben-Tuvia, 1966), and has declined (Ben-Tuvia, in press b) since its peak bloom in the 50's. Ben-Tuvia attributes this decline to the spread of the lizardfish, one of its main predators. The U. asymmetricus, usually small, does not occur in commercial quantities, and in the catches it is classified with the other red mullets. Another Red Sea migrant, the yellow-striped goatfish, Upeneus moluccensis has not yet been identified from the stomachs of the hake. There are good indications that, ecologically, both the Upeneus and the lizardfish are closely related in a prey-predator relationship. They occupy the same habitat, the goatfish being an equally rare visitor at the deepwater trawling grounds (Zismann, in preparation). Both species seem to increase in catches during the same years (Ben-Yami, 1955; Oren, 1957), which may be associated with en- vironmental conditions. It is, thus, very likely that in areas where they are both found, the hake and the Red Sea lizardfish compete for food. THE MECHANISM OF AN INVASION Ecological "Barriers" to Migrating Species A demersal fish expanding from one sea to another through a man-made canal encounters several barriers which it must overcome before a significant population can be established in the other sea (Figure 7). The "height" of an ecological barrier differs for each separate species. Hypersa- linity, e.g., which may be prohibitive to some purely marine species, may not be a barrier or may even possess attractive environmental qualities to euryhaline organisms. The height of an ecological barrier may also change with seasonal, annual, and multiannual fluctuations in the environmen- tal conditions. The first barrier is the canal itself which may represent a less or more hostile environment for the migrating species. Migration through the Suez Canal must have been very difficult for some and impossible for other species, because of the complex hydrological conditions in the canal (the high salinity of the Bitter Lakes, freshening of the water due to influx of fresh water at some places, and the seasonal Nile floods) (Oren, 1970; H. Steinitz, pers. comm.). The nature of the Suez Canal, as a barrier, has changed, however, with NATIVE SEA THE CANAL SEA BOTTOM & FOOD DIFFERENCES BARRIER III ^ f) S;°C« '"' r 1 BARRIER IV 1^ COMPETITORS & PREDATORS I NEW SEA Figure 7. — "Barriers" on the path of a migrating species of demersal fish the last three "barriers" may occur in any order and/or overlap. time. Animal migration through the canal may now become easier (Thorson, 1971). The second barrier, especially for demersal species, is the difference in bottom conditions. The importance in the character of the substrate for the expansion of migrating benthic invertebrates was emphasized by Gilat (see footnote 6) and Por ( 1971). The type of bottom influences the type and quality of food available. Bodenheimer ( 1966) em- phasized the negative effect which lack of food may have on fecundity. De Vlaming (1971) has shown that starvation affected the gametogenesis and gonadal regression in a goby, Gillichthys mirabilis. Undoubtedly, it is not enough for a bot- tom fish just to cross a canal. To survive and repro- duce, it must find in its new habitat either the food to which it is accustomed or a food which can replace the former both quantitatively and qual- itatively at all stages of its life cycle. This condi- tion is, generally, controlled by the character of the sea bottom. A third barrier is the hydrological gradient (if any) between both seas. A species may cross a canal, may even find an apparently suitable habitat, but all its spawn may be killed by extreme winter or summer temperatures. Also, adverse 368 BEN-YAMI and GLASER: INVASION OF SAURIDA UNDOSQUAMIS temperature conditions may affect prespawning, reproductive processes in fish (De Vlaming, 1971 ), while difference or seasonal changes in salinity may affect survival of a stenohaline species. Oren (1970) has noticed, e.g., that after the crit- ical 1954/56 years, the minimum seawater winter temperatures over the Israel continental shelf have never returned to their values of 15°C mea- sured prior to this period. He also found that the salinities in the same area increased since the closure of the Aswan Dam in 1964. It seems, thus, that in the long run, the hydrological gradient between the Gulf of Suez, where the temperatures and salinities are higher than in the Levant Basin (Kosswig, 1951; Oren, 1957; Ben-Tuvia, 1966) and the Mediterranean, is on the decrease. The fourth barrier is the predators and com- petitors. Darwin (1859) emphasized the role of prey, predators, and competitors on the distribu- tion range of species. Obviously, the abundance and distribution of the native predators and com- petitors are affected by fluctuations in the hy- drological conditions. Therefore, changes in the hydrological conditions may affect establishment of the migrant species both directly and, through their competitors, indirectly. Human Interference May Facilitate Invasion An invasion may succeed because of human in- terference in the environment. Elton (1958) has shown that such interference, especially where associated with depletion of native populations, considerably increases the vulnerability of an area to invasions. We consider commercial fisheries to be an example of an extreme interfer- ence. The Explosion of the Red Sea Lizardhsh Population The lizardfish, Saurida undosquamis , is an im- portant component of the Egyptian trawl catches in the Gulf of Suez (Latif, 1971). The early records of lizardfish in the Suez Canal by Gruvel and Chabanaud (1937), asS. sinaitica, S. tumbil, and S. gracilis, may have been S. undosquamis (Ben-Tuvia, pers. comm.). Fifteen years later, and 83 years after the open- ing of the Suez Canal, the Red Sea lizardfish ap- peared in the southeastern Mediterranean in suf- ficient numbers to be described as a "rare" fish (Ben-Tuvia, 1953). But within 2 to 3 yr, it became one of the most important commercial trawl fishes forming 20% of the catch. This recalls the invasion of the sea lamprey, Petromyzon marinus, in the Great Lakes in North America (Elton, 1958). Al- though the Welland Ship Canal was opened as early as 1829, the sea lampreys were observed in Lake Erie 100 yr later. Then, within 10 yr, the lamprey population expanded rapidly and dramatically both in space and in number, caus- ing a collapse of the lake trout fishery in Lake Michigan and Lake Huron. The population explosion of the Red Sea lizardfish was much faster, for its 1959 all-time record landings occurred only 4 yr after its first appearance in the trawl catch as a fraction of a percent. Although the subsequent decline in the lizardfish catch may be associated with decrease of the fishing effort (Tables 1 and 2), particularly in the northeast Mediterranean, its relatively stable proportion in the total catch indicates that an ecological balance was reached within the first 2 yr of its appearance in the commercial catch (Fig- ures 5, 8). Subsequent annual fluctuations seem to be normal to natural populations. Table 2.— Israel trawl fishery, 1948-70. Total Number of trawlers landings Year (act vity %) 1 (tons) 1945 25 (56) 508 1946 11 (73) 333 1947 12 (67) 258 1948 12 (46) 111 1949 14 (57) 430 1950 30 (54) 1,092 1951 27 (43) 929 1952 23 (49) 1,000 1953 23 (56) 1,286 1954 22 (75) 1,480 1955 27 (63) 1,518 1956 26 (60) 1,391 1957 27 (69) 1,550 1958 29 (77) 1,740 1959 27 (92) 1,952 1960 25 (69) 1,274 1961 19 (70) 992 1962 18 (75) 830 1963 17 (74) 706 1964 15 (76) 615 1965 18 (70) 761 1966 18 (77) 638 1967 16 (87) 741 1968 16 (80) 926 1969 16 (91) 1,028 1970 19 (82) 930 'Activity index (100';): below 150 hp - 210 days at sea per trawler, over 150 hip - 230 days at sea per trawler. 369 FISHERY BULLETIN: VOL. 72, NO. 2 YEAR PRECIPITATION SHARE IN TRAWL CATCH HAKE LIZARDFISH /qISIO 5 0 5 10 15 l_-l L 15 10 5 0 5 1015 /ft TEMPERATURE YEAR SEA AIR 50/51- 52/53- 54/55- 56/57- 58/59- 60/61- 62/63- 64/65- 66/67- 68/69- 70/61- RAINY YEAR DRIEST JAN-APR SEASON VERY RAINY YEAR DROUGHT RAINY YEAR DRYISH YEAR V.RAINY YEAR DROUGHT RAINY YEAR DROUGHT RAINY YEAR BELOW 75M. WARM IN AUTUMN & SUMMER AIR EXTRA WARM IN WIN. AIR iXTRA COLD IN WINTER -50/51 AIR EXTRA COLD IN WINTER SURF. EXTRA WARM IN WINTER -52/53 -54/55 -56/57 58/59 -60/61 -62/63 -64/65 -66/67 -68/69 -70/71 Figure 8. — Changes of the proportion of the hake and the Red Sea lizardfish in the Israel trawl landings and their relationship with environmental conditions, 1950-71. Hence, in the case of the lizardfish, the population-growth logistic curve (Bodenheimer, 1966) would have been extremely steep in its cen- tral part with extremely sharp flexes between the first and the central sections and, again, between the central and the third sections of the curve. It can be, therefore, speculated that this invasion and expansion were not only a product of a "nor- mal" population growth but were also aided by additional factors. 370 The Role of Environmental Factors The sudden buildup of the Red Sea lizardfish population which occurred between 1954 and 1956 was accomplished by a series of unusual phenomena: 1) unusually high temperatures, both of air and water (Ben-Yami, 1955; Oren, 1957), especially in winter (Figures 1, 2, 3); 2) the ex- tremely dry January-April season of 1955 (Figure 4), as well as a very pronounced absence of winter BEN-YAMI and GLASER: INVASION OF SAURIDA UNDOSQUAMIS gales of anticyclonic depression origin, during the same winter (Ben- Yami, 1955); 3) the hake made a very poor appearance in the 1955/56 Israel trawl catches (Figures 5, 8), decreasing to approxi- mately 40^c of its 20 yr average (Figures 5, 8) in the catch and to approximately 42% of its 20 yr average (Figure 5) in its catch per fishing day. Since then, such low catches of the hake only oc- curred in 1960/61 and in 1966/67. In all three cases, the drop in the hake catches seems to be associated with drought: it followed the January-April drought in 1955, in 1959/60 and 1966/67 it followed a drought in the preceding winter (Figure 8). Trawl Fishery's Rapid Development The rapid intensification of the Israel trawl fishery 1949-54 (Table 2) was probably another important factor contributing to the expansion of the Red Sea lizardfish. The landings, which before 1940 were 100 to 500 tons, rose to approximately 1,000 tons/year during 1950-52 and to almost 1,500 tons in 1954, when the first commercial catches of the lizardfish were taken. Before 1950, the Israeli trawlers did not fish in waters deeper than 50 to 60 fm. Since 1950, deepwater trawling operations have been carried out, and hence there has been considerable exploi- tation of the hake resources (Ben- Yami, 1971). DISCUSSION AND CONCLUSIONS The set of conditions which prevailed just before and during the explosion of the Red Sea lizardfish population and which, apparently, facilitated this explosion included: 1. "Preparation" of the area due to the intensification of the trawling fishery by the factor of 3-4 (Table 2); 2. Water temperature conditions which contrib- uted to good survival of several strong year classes of lizardfish; 3. A combination of climatic (drought) and water temperature conditions which caused the withdrawal of the hake from most of the trawling grounds, leaving ample space for the spread of the lizardfish. It is possible that the population of the Red Sea lizardfish in the Levant Basin has been and, with- out these conditions, might have remained "dor- mant" and suppressed by its competitors and by unfavorable environmental conditions. It may have been still waiting for its opportunity to ex- pand. The fluctuation in the abiotic conditions, subse- quent to the lizardfish explosion years, seems to be correlated with the fluctuations in the catches of both the lizardfish and the hake, though with an "anomaly" in 1961-63 when, in spite of two con- secutive warm winters, the proportion of hake in- creased in comparison to the lizardfish. Here, e.g., the abundant rains of 1961-62, or other factors might have intervened (Figure 8). The hake is much more sensitive to the fluctua- tions of physical conditions than the lizardfish, as may be seen from the shape of the respective col- umns in Figure 8. The declines in the hake catches indicate either recessions in the population or a geographical retreat from the usual fishing grounds, probably into deeper and cooler waters, or a combination of both. An interesting feature of the fluctuation of the hake proportion in catches is that so far they are in phase with those of the solar activity index (Fig- ure 8), though this correlation may be purely inci- dental. The interrelations discussed in this paper are very complex. Different and, perhaps, even vari- able time lags have to be employed to correlate abiotic, biotic-natural, and man-activated (fisheries) factors. A study for further pursuit along this line will require the application of com- puter technique. Unquestionably, a good oppor- tunity for studying the influence of environmental conditions on the relationship of competing mi- grant and native species was lost when data on the Mullus-Upeneus and Red Sea Barracuda- Atlantic Barracuda proportion in catches were not collected during the past years. Such studies should be undertaken in the future. An examination of the available statistical data (Sarid, 1951-71) could not establish any sig- nificant influence of the appearance of the Red Sea lizardfish in the total trawl catches on the landings, catch per unit effort, or returns of the trawl fishery. Undoubtedly, the lizardfish is not just an additional inhabitant, and its invasion did not enrich the existing ecosystem in terms of biomass. It occurs in the catches at the expense of other fish, partly its competitors, such as the hake, and partly its prey, such as the yellow-striped goatfish, red mullet, etc. The proportion of the lizardfish in the trawl catches has never, after its 1954-56 invasion, been less than 13%, although there have been several 371 FISHERY BULLETIN: VOL. 72, NO. 2 cold winters since (Figures 2, 3, 8). This, besides indicating that the Red Sea lizardfish is fairly eurythermic, may also support Kosswig's ( 1972)^^ suggestion of the role of the modificability of species in new environments. It is quite probable that the Mediterranean stock of the Red Sea lizardfish today is better adapted to the local en- vironmental conditions than it was 20 yr ago. The Red Sea lizardfish proved vigorous enough to establish itself in a niche in a habitat occupied by other species; it is euryecous enough to with- stand fluctuations in environmental conditions; and, barring an ecological disaster, it is here to stay. ACKNOWLEDGMENTS The authors' thanks are extended to all col- leagues who have read this paper and offered many valuable comments and remarks, and par- ticularly to Adam Ben-Tuvia, Eliezer Gilat, Av- raham Herzberg, Oton H. Oren, and Sh'muel Pi- santy. Last, but by no means least, we thank Lyka Bograd-Zismann for her reading, correcting, and editing efforts. Irit Brecher helped with the draw- ings. REFERENCES Anonymous 1950-70. Monthly weather reports. Israel Meteorological Service, Ministry of Transport and Communication, Beit Dagan. Ben-Tuvia, A. 1953. Mediterranean fishes of Israel. Bull. Isr. Sea Fish. Res. Stn., Haifa 8:1-40. 1966. Red Sea fishes recently found in the Mediterranean. Copeia 1966:254-275. 1971. Revised list of the Mediterranean fishes of Israel. Isr. J. Zool. 20:1-39. In press a. Man-made changes in the Eastern Mediterra- nean and their effect on the fishery resources. Rapp. Comm. Int. Mer Medit. In press b. Immigration of fishes through the Suez Canal. XVIIth International Zoological Congress, 1972. Ben-Yami, M. 1955. Shnat Tashtav - dayig yeter o batsoret? (1954-55, Overfishing or bad season?) [In Hebrew.] Fishermen's Bull,, Haifa 1(6):10-14. 1971. Fishing surveys and commercial exploitation of deep-water trawling grounds. In O. H. Oren, M. Ben- Yami, and L. Zismann, Explorations of the possible deep-water trawling grounds in the Levant Basin. Stud. Rev. Gen. Fish. Counc. Mediterr. 49:51-59. Ben-Yami, M., A. Herzberg, S. Pisanty, and A. Lourie. 1970. A side-tracking neuston net. Mar. Biol. 6:312-316. '^Kosswig, C. 1972. Modificability, a neglected principle favouring area expansion in marine fish. Heinz Steinitz Memor- ial Lecture, delivered at the Second Scientific Session and Oceanography Seminar, 6 April 1972, Marine Biology Laborat- ory Elat. Beverton, R. J. H., AND A. J. Lee. 1965. Hydrographic fluctuations in the North Atlantic Ocean and some biological consequences. /n C. G. Johnson and L. p. Smith (editors). The biological significance of climatic changes in Britain, p. 79-107. Academic Press, Lond. Bodenheimer, S. 1966. Ekologia shel ba'aley-khayim (Animal ecology). [In Hebrew.] In The Encyclopedia of Agriculture, Vol. 1:530-547. Haentsiklopedia I'khaklaout, Tel-Aviv. Bograd-Zismann, L. 1965. The food of Saurida undosquamis in the Eastern Mediterranean in comparison with that in Japanese wat- ers. Rapp. P.-V. Reun. Comm. Int. Explor. Sci. Mer Medit. 18:251-252. Chervinsky, J. 1959. Hashva'a sistematit u'viologit byen khardon-hayam (Saurida grandisquamis) ba'Yam Hatikhon uv'Yam Suf (A systematic and biological comparison between the lizardfish (Saurida grandisquamis) from the Mediterra- nean and the Red Sea). [Engl, abstr.] Fishermen's Bull., Haifa 19:10-14. COLLETTE, B. B. 1970. Rastrelliger kanagurta, another Red Sea immigrant into the Mediterranean Sea, with a key to the Mediterra- nean species of Scombridae. Bull. Isr. Sea Fish. Res. Stn., Haifa 54:3-6. Darwin, C. 1859. On the origin of species. Facsimile of the first edi- tion. Harvard Univ. Press, 1964, 502 p. de Vlaming, V. L. 1971. The effects of food deprivation and salinity changes on reproductive function in the estuarine gobiid fish, Gil- lichthys mirabilis. Biol. Bull. (Woods Hole) 141:458-471. Elton, C. S. 1958. The ecology of invasions by animals and plants. Methuen & Co., Ltd., Lond., 181 p. Fowler, H. W. 1936. The Marine fishes of West Africa, based on the collec- tion of the American Museum Congo Expedition, 1909-1915. Bull. Am. Mus. Nat. Hist., 70, Part 1:1-605. Gilat, E. 1964. The macrobenthonic invertebrate communities on the Mediterranean continental shelf of Israel. Bull. Inst. Oceanogr. Monaco 62(1290): 1-46. GoHAR, H.A.F. 1954. The place of the Red Sea between the Indian Ocean and the Mediterranean. Istanbul Univ. Hidrobiol: Aras- tirma Enst., Yayin,, Ser. B, 2:47-82. Gottlieb, E., and A. Ben-Tuvia. 1953. Dayig mikmoret b'meimei Turkiya (Trawling in the area of Turkey). [In Hebrew.] Alon Miktsoyi I'Dayagim 1:4-9. Gruvel, a., and p. Chabanaud. 1937. Missions A. Gruvel dans le Canal de Suez. II. Poissons. Mem. Inst. Egypt (Egypte) 35:1-30. Hayashi, T., Y. Yamaguchi, and T. Hanaoka. 1960. Preliminary report on diurnal feeding activities of genus Saurida. Rec. Oceanogr. Works Jap., Spec. No. 4, D.151-158. HiATT, R. W., and D. W. Strasburg. 1960. Ecological relationships of the fish fauna on coral reefs of the Marshall Islands. Ecol. Monogr. 30:65-127. HoLTHuis, L. B., and E. Gottlieb (Gilat). 1958. An annotated list of the decapod Crustacea of the Mediterranean coast of Israel, with an appendix listing the decapoda of the Eastern Mediterranean. Bull. Res. Counc. Isr. 7B(1-2):1-126. Jensen, A. J. C. 1933. Periodic fluctuations in the size of various stocks of fish and their causes. Medd. Komm. Dan. Fisk. Havun- ders. 9(5):l-70. KosswiG, C. 1951. Contributions to the knowledge of the zoogeographi- cal situation in the Near and Middle East. Experentia 7:401-440. Laevastu, T., and I. Hela. 1970. Fisheries oceanography. New ocean environmental services. Fishing News (Books) Ltd., Lond., 238 p. Latif, a. F. a. 1971. Marine fishes of the Gulf of Suez. (Abstracts.) Sym- posium on Indian Ocean and Adjacent Sea, p. 169-170. Marine Biological Association of India, Cochin, India. 372 BEN-YAMI and GLASER: INVASION OF SAURIDA UNDOSQUAMIS LouRiE, A., AND A. Ben-Tuvia. 1970. Two Red Sea fishes. Relates quadrilineatus (Bloch) and Crenidens crenidens (Forsskal) in the Eastern Mediterranean. Isr. J. Zool. 19:203-207. Marshall, N. B. 1965. The life of fishes. Weidenfeld &Nicolson, Lend., 402 P Oren, O. H. 1957. Changes in temperature of the Eastern Mediterra- nean Sea in relation to the catch of the Israel trawl fishery during the years 1954-55 and 1955-56. Bull. Inst. Oceanogr. Monaco 54(1102):1-15. 1969. Oceanographic and biological influence of the Suez Canal, the Nile and the Aswan Dam on the Levant Basin. Progr. Oceanogr. 5:161-167. 1970a. The Suez Canal and the Aswan High Dam. Their effect on the Mediterranean. Underwater Sci. Technol. J. 2:222-229. 1970b. Seasonal changes in the physical and chemical characteristics and the production in the low trophic level of the Mediterranean waters off Israel. Isr. Sea Fish. Res. Stn., Haifa., Spec. Publ., 240 p. Oren, O. H., and H. Hornung. 1972. Temperatures and salinities off the Israel Mediter- ranean coast. Bull. Isr. Sea Fish. Res. Stn., Haifa (59). For, F. D. 1971. One hundred years of Suez Canal — a century of Les- sepsian migration: Retrospect and viewpoints. Sys. Zool. 20:138-159. Sarid, Z. 1951-71. Fisheries in Israel by numbers. Min. Agric, Dept. Fish., Hakirya, Tel-Aviv. Steinitz, H. 1967. A tentative list of immigrants via the Suez Canal. Isr. J. Zool. 16:166-169. 1968. Remarks on the Suez Canal as pathway and as habitat. Rapp. P.-V. Reun. Comm. Int. Mer Mediterr 19:139-141. Steinitz, W. 1929. Die Wanderung indopazifischer Arten ins Mittel- meer seit Beginn der Quartarperiode. [In German.] Int. Rev. gesamten Hydrobiol. Hydrogr. 22:1-90. Thorson, G. 1971. Animal migrations through the Suez Canal in the past, recent years and the future (A preliminary report). "Vie et Milieu," 3rd European Symposium of Marine Biol- ogy 22:841-846. TORIYAMA, M. 1958. On diurnal rhythm in the feeding activity of Saurida undosquamis (Richardson) and Upeneus bensasi (Temminck et Schlegel). [In Jap., Engl, summ.] Rep. Nankai Fish. Res. Lab. 9:84-91. TORTONESE, E. 1953. Su alcuni pesci Indo-Pacifi immigrati nel Mediter- raneo Orientale (Some Indo-Pacific fishes migrant in the Eastern Mediterranean). Boll. Zool. 20(4-6):73-81. Travis Jenkins, J. 1954. The fishes of the British Isles. Frederick Warne & Co. Ltd., Lond. and New York, 408 p. WiRSZUBSKI, A. 1953. On the biology and biotope of the red mullet Mullus barbatus L. Bull. Isr. Sea Fish. Res. Stn. 7, 20 p. Zismann, L. 1969. A light-trap for sampling aquatic organisms. Isr. J. Zool. 18:343-348. 1971. Deep-water trawl fish. In O. H. Oren, M. Ben-Yami, and L. Zismann, Explorations of the possible deep-water trawling grounds in the Levant Basin. Stud. Rev. Gen. Fish. Counc. Mediterr. 49:61-63. 373 SUMMARY OF SELECTED EARLY RESULTS FROM THE ERTS-1 MENHADEN EXPERIMENT^ Andrew J. Kemmerer,^ Joseph A. Benigno,^ Gladys B. Reese,' and Frederick C. Minkler' ABSTRACT A 15-mo study was initiated in July 1972 to demonstrate the potential of using satellite-acquired environmental data to provide fisheries information. Imagery from ERTS-1 (Earth Resources Tech- nology Satellite) was used in conjunction with aerial photographically sensed menhaden distribution information, sea-truth oceanographic measurements, and commercial fishing information from a 8,670-km^ study area in the north central portion of the Gulf of Mexico. Objectives were to demon- strate relationships between selected oceanographic parameters and menhaden distribution, ERTS-1 imagery and menhaden distribution, and ERTS-1 imagery and oceanographic parameters. ERTS-1, MSS Band 5 imagery density levels correlated with photographically-detected menhaden distribution patterns and could be explained based on sea-truth secchi disc transparency and water-depth mea- surements. These two parameters, together with surface salinity, Forel-Ule color, and chlorophyll a, also were found to correlate significantly with menhaden distribution. Eight empirical models were developed which provided menhaden distribution predictions for the study area based on combinations of secchi disc transparency, water depth, surface salinity, and Forel-Ule color measurements. A need of managers and users alike of living marine resources is timely synoptic information about the distribution and abundance of the re- sources. For users, this need is particularly criti- cal in that daily decisions must be made about where to deploy fishing vessels and less frequent decisions about investment strategies for men and equipment. The increasing pressures placed on living marine resources by domestic and foreign fishing fleets interacting with environmental changes demand that resource managers also be kept fully aware of the current status of the stocks to prevent possible catastrophic fluc- tuations in specific fish populations. Unfortu- nately, the tools required to satisfy this need economically are lacking, forcing users to base decisions on inituition and often biased personal knowledge and resource managers to formulate recommendations based on historical rather than current information. In response to this need, a number of relatively new technologies are being examined by the National Marine Fisheries 'Contribution No. 246, Southeast Fisheries Center, Pascagoula Laboratory, National Marine Fisheries Service. ^Formerly Southeast Fisheries Center, Pascagoula Labo- ratory, National Marine Fisheries Service, NOAA, Pascagoula, MS 39567; present address: Office of Resource Research, Na- tional Marine Fisheries Service, NOAA, Washington, DC 20235. ^Southeast Fisheries Center, Pascagoula Laboratory, Na- tional Marine Fisheries Service, NOAA, Pascagoula, MS 39567. Service and, in particular, the technologies asso- ciated with aerial and satellite remote sensing, to determine if they can be used to provide perti- nent fisheries resource information. A 15-mo study was initiated in July 1972 to demonstrate the potential of using satellite- acquired information to predict the distribution and abundance of a fishery resource. The study represented a combined Federal Government and private industry effort and stressed acquisition of data to: 1. determine the reliability of satellite and high-altitude aircraft-supported sensors to provide information about selected oceano- graphic parameters in coastal waters; 2. demonstrate the feasibility of using remotely-sensed oceanographic information to predict the distribution and abundance of a selected species; 3. demonstrate the potential of using satellite-acquired information for improv- ing the harvest and management of a fishery resource and; 4. identify necessary sensor techniques or de- velopments to satisfy selected needs of re- source users and managers. This paper presents a summary of selected results from the experiment. Earlier publications dealing with- the experiment have stressed its management (Stevenson, Atwell, and Maughan, Manuscript acceped September 1973. FISHERY BULLETIN: VOL. 72, NO. 2, 1974 375 FISHERY BULLETIN: VOL. 72. NO. 2 1972), relationships between selected oceano- graphic parameters and fish distribution and abundance (Kemmerer and Benigno, 1973), and commercial fishing operations (Maughan, Mar- melstein, and Temple, 1973). EXPERIMENTAL RATIONALE With existing technology, fish cannot be de- tected directly with sensors aboard orbiting satel- lites. It may be feasible, however, to use satel- lite sensors to measure selected environmental parameters and then to use these parameters to predict, and in some cases even forecast, the dis- tribution and abundance of a fish species. The quality of these predictions or forecasts would depend on how accurately the parameters are measured with the sensors, how precisely the parameters correlate with the distribution of specific fish populations, and how accurately the values were predicted. The rationale employed in the experiment was to convert data obtained with ERTS- 1 or aircraft- supported sensors into oceanographic parameter information, attempt to derive correlations be- tween these parameters and the distribution and abundance of a selected fishery resource, and then determine if the relationships have meaning for commercial fishing operations and resource man- agement. Data obtained with the satellite were supplemented with data obtained with sensors aboard aircraft to provide a broader spectrum of environmental information. In addition, a mas- sive sea-truth sampling effort was undertaken to provide calibration data for remote sensors and backup information for correlation analyses. STUDY AREA AND FISHERY The study area was a 8,670-km rectangle situated in the north central portion of the Gulf of Mexico (Figure 1). It included coastal areas of Alabama, Mississippi, and Louisiana and encom- passed all of the Mississippi Sound, the southern portion of Mobile Bay, and extended offshore from the Mississippi Sound to approximately the 18-m depth curve. The study area is divided in half lengthwise by five barrier islands which isolate the typically turbid, low-salinity waters of the Mississippi Sound from the relatively much clearer oceanic waters of the offshore portion of B D TEST SITE COORDINATES LATITUDE LONGITUDE SCALE 1:875,000 A) 30O27'N B) 30°27'N C) 30°00'N D) SQOQO'N 89°30'W 87045'W 87045'W 89°30'W N.MI, 10 20 TEST SITE DIMENSIONS LENGTH: 170 KM. WIDTH: 51 KM. AREA: 8670 SQ . KM. KM. _L j_ _L J 10 20 30 AO Figure 1. — ERTS-1 menhaden experiment study area. 376 KEMMERER ET AL.; ERTS-I MENHADEN EXPERIMENT the study area. A comprehensive description of the area is given by Christmas (1973). The target fish species for the study was the small (mean weight about 85 g), herringlike, surface-schooHng Gulf menhaden (Brevoortia patronus). These fish occur along the Gulf of Mexico coast and are considered to be an estua- rine-dependent species. They are used com- mercially as a source of fish meal, oil, and con- densed soluble proteins. In the Mississippi Sound, menhaden are fished from about mid-April to October by twin purse seine boats assisted by spotter pilots flying light aircraft. The spotter pilots direct the purse boats to the menhaden and then through radios notify the boat captains when to encircle a school with their purse seine. Once a school is captured and concentrated in the net, a larger mother or carrier vessel is brought along- side and the fish are pumped into the hold of the ship. Menhaden are plankton feeders using a sieve- like branchial apparatus to strain plants and animals from the water (Reintjes, 1969). Their characteristic schooling behavior, which seems innate from late larval stage to old age, makes them particularly available to commercial fishing. School size varies from about 25 to in excess of 2,000 m^ (surface area) and averages about 125 m^. Although Gulf menhaden have been the subject of many investigations (Christmas and Gunter, 1960; Gunter and Christmas, 1960; Reintjes, Christmas, and Collins, 1960; and Rounsefell, 1954), little is known about their distribution in relation to environmental para- meters. DATA ACQUISITION Data acquisition events were divided into four operations categories: main day, secondary day, special purpose, and commercial fishing oper- ations. Main day activities occurred at or near the time of selected ERTS-1 overpasses (7 August, 25 August, and 28 September 1972) and included an intensive sea-truth sampling effort-up to 144 stations were occupied. Only a few sea-truth stations were occupied during secondary day missions, which were conducted weekly, weather permitting, to record temporal environmental and fishery changes. Special purpose missions were designed to satisfy limited objectives and as such did not follow set schedules. Oceanographic and fisheries data were obtained from one to three commercial fishing vessels, usually on three days of each week, June through September 1972. ERTS-1 and Aircraft Environmental Sensors A number of oceanographic parameter sensors were used during the experiment from NP3A (NASA) and D18 Beechcraft'' (NASA/ERL) air- craft at altitudes ranging from 610 to 7,620 m. The sensors included a RC 8 camera, RS-14 scanner, PRT-5 radiation thermometer. KA 62 multiband camera, Hasselblad EL-500 cameras, RS-18 thermal IR scanner, multifrequency microwave radiometer, and an Exotech spectroradiometer. The sensors were configured to measure sea- surface temperature, water color as a function of wavelength, surface current patterns, surface salinity, and surface turbidity patterns. The ERTS-1 satellite, launched on 23 July 1972, operates in a circular sun-synchronous near polar orbit at an altitude of 915 km. It circles the earth every 103 min, completing 14 orbits per day and providing repetitive coverage of specific areas every 18 d. Two consecutive orbits, 24 h apart, are required for complete coverage of the study area. The only environmental sensor aboard the satel- lite operating during the study was a multispec- tral scanner (MSS) which provided images in four discrete portions of the light spectrum (Freden, 1972): Band 4, 0.5-0.6 micron; Band 5, 0.6-0.7 micron; Band 6, 0.7-0.8 micron; and Band 7, 0.8- 1.1 microns. Sea-Truth Oceanographic Parameter Measurements Sea-truth measurements during main day data acquisition events were taken from 25 research boats. Because two orbits 24 h apart of ERTS-1 were required for complete coverage of the study area, only about half of these measurements coin- cided with the passage of the satellite. On 7 and 25 August 1972, coincidental measurements oc- curred for the western portion of the study area, resulting in a 24-h difference for measurements from the eastern portion. A main day occurred on 28 September 1972, which did not correspond to ^Reference to trade names does not imply endorsement by the National Marine Fisheries Service, NOAA. 377 FISHERY BULLETIN; VOL. 72. NO. 2 either orbit of ERTS-1. Orbits instead occurred on the 29th (eastern portion) and 30th (western portion) of September 1972, representing 24- and 48-h differences, respectively. The 25 research boats generally occupied 95 stations in the Mississippi Sound and 46 stations in the offshore portion of the study area. These stations were spaced to provide a sampling density of about one station per 29 km^ in the Sound and one station per 60 km^ in the offshore waters. Parameters measured included surface tempera- ture, salinity, chlorophyll a, currents, sea state, water color, water depth, and secchi disc trans- parency. Surface water temperature, salinity, and chlorophyll a measurements were obtained from bucket samples. Temperature was deter- mined immediately in the bucket, and poly- propylene bottles were used to store samples for chlorophyll a and salinity measurements in the laboratory. Color was estimated with a Forel- Ule color comparator (Hutchinson, 1957), and current speed and direction were measured by timed drifts of neutrally buoyant floats. Fisheries Data Aerial photography provided most of the fisheries distribution and abundance information augmented periodically with nighttime, low- light-level television sensor missions and com- mercial fish-spotter pilot reports. Menhaden are particularly susceptible to aerial sensing tech- niques because of their characteristic surface or near-surface schooling behavior. Discussions on aerial photography and low-light-level tele- vision sensing of fish schools have been pub- lished by Bullis (1967), Benigno (1970), Drennan (1969), and Roithmayr and Wittman (1972). Photographic fish sensing missions were flown to provide 95% coverage of the study area at a scale of 1:16,200. The camera used was a Zeiss RMK-1523 mapping camera with a 15.24-cm focal length lens and 22.86-cm film format. The camera was supplied with GAF-1000 blue insen- sitive (2575) film, selected for its speed and re- ported ability to penetrate the hydrosphere (Vary, 1969). Photographic missions were divided into morning and afternoon flights corresponding to sun angles of 15 to 50 degrees, with morning flights covering the Mississippi Sound and afternoon flights covering the offshore section of the study area. A Houston-Feerless film viewer. providing magnifications of 3 x to 33 x , was used to aid in the search of processed film for imaged menhaden schools. Fish school locations were recorded according to latitude and longitude with an accuracy of ±0.4 km. Menhaden schools could be subjectively differentiated from other schooling species in the study area on the basis of size, shape, and color. Commercial Fishing Data Fishery and oceanographic parameter measure- ments were obtained June through September 1972 from one to three commercial fishing vessels. These measurements were taken at the time and location of capture or attempted capture of a menhaden school. Data collected included sur- face water temperature and salinity, secchi disc transparency, Forel-Ule color, number of fish captured (visual estimate), date, time, and location. Usually, these observations were made the first three days of each fishing week (Monday through Saturday) except during periods when an ERTS-1 overpass or main day occurred, in which case the sampling period was extended over the entire fishing week. DATA ANALYSIS AND INTERPRETATION General Analytical Rationale and Data Limitations Because the overall success of the experiment depended upon finding relationships between menhaden distribution and abundance and oceanographic parameters, the logical point of departure was with these relationships. Thus, impetus initially was given to finding relation- ships between fish distribution and abundance and selected oceanographic parameters, and then to determine if parameters which had fisheries meaning could be measured remotely with suf- ficient accuracy for precise correlation analysis. The last step in the analytical rationale was to determine what, if any, uses these relationships might have for commercial fishing and resource management. The principal data limitation placed on early analyses was a general lack of remotely acquired synoptic oceanographic parameter measure- ments. The conversion of remotely acquired 378 KEMMERER ET AL : ERTS-1 MENHADEN EXPERIMENT oceanographic data into meaningful information has proceeded slowly because of interpretation dif- ficulties. Thus, reported fisheries oceano- graphiuc-parameter relationship analyses de- pend primarily upon sea-truth measurements. An essential exception was the photographically acquired menhaden distribution and abundance information. Oceanographic Parameter-Fish Distribution Relationships Analysis The distribution and abundance of menhaden in the study area, principally in the Mississippi Sound, can be placed into a simplified systems context (Figure 2). Factors directly affecting the system, i.e., the distribution and abundance of menhaden, include fish input, fish output (includ- ing harvest, death, and emigration), the environ- ment, and the innate behavior of the menhaden not directly or immediately influenced by environ- mental conditions. Examples of this latter factor include fish age and degree of sexual maturity. This systems concept can be modified slightly and expressed as an algebraic argument as: A,.y = f(E,B,P) (1) where: A = number of menhaden schools, X and y = refer to school location coordinates, E = environmental conditions, B = innate fish behavior, and Environmental Parameters Menhaden Input ^ Menhaden Distribution and Abundance Menhaden ^ Output Innate Menhaden Behavior P = instantaneous menhaden school population. The problem with the argument is that the de- pendent variable A^.vis a function of more than just the environment, E, and as such cannot be solved with available information. To simplify the expression, two assumptions were made. First, it was assumed that 5 was constant (i.e., the innate behavior of the menhaden did not vary signifi- cantly) and thus could be ignored in the expres- sion, an assumption which led to the development of a new expression where A^^y became a function of E and P alone. This assumption appeared reasonable because only adult menhaden were considered in the experiment while they were in the Mississippi Sound, a relatively short period of time. The second assumption made was that A^,y could be expressed in relative terms such that: 'x,y = f(E) (2) This assumption permitted the normalizing of Ax,y relative to P and has its roots in many fisheries catch/effort related expressions. In the subsequent analyses, the number of photographically detected menhaden schools at any given point was used as an estimator of Ax,y, and the total number of detected menhaden schools was used as an estimator of P. If there was a constant sensor-caused bias in the photography data, the quotient Ax,y/P should not be affected seriously, as the bias cancels. However, if the bias was not constant but instead was a variable function of the environment, then the bias would affect the quotient. Whether or not the effect would be significant would depend on the magnitude and variability of the bias. Because of a concern about the possibility of bias affecting the relationships, a second approach also was used which should have reduced sensor bias. A new dependent variable, D, was defined which reflected only the distribution of menhaden and was related to the environment as: D = f(E) (3) Figure 2. — Simplified systems view of the Mississippi Sound menhaden population described only in terms of distribution and abundance. Inherent in this expression is the assumption that P does not affect the distribution of menha- den within the extremes of P characteristic of the 379 FISHERY BULLETIN: VOL. 72. NO. 2 menhaden population during the experiment. Neither photographic nor commercial fishing data indicated a major change in P on main days, which lends credibility to this assumption. As defined, D can have two possible outcomes: yes, menha- den are present and no, menhaden are not present. In the analysis, areas where menhaden were detected were assigned a value of 1 and areas where fish were not detected were assigned a value of 0. Although/) is clearly a discontinuous dependent variable, the statistical techniques used in the analyses converted it into a continuous variable ranging from about 0 to 1. The general interpretation applied to predicted values is that as the values approached 1, the chance of finding fish increased proportionately. Regression techniques were used exclusively to define relationships between the abundance and/ or distribution of menhaden and available measurements of oceanographic parameters. Because remotely sensed oceanographic data were not available, environmental conditions where fish were detected had to be interpolated and, in some cases, extrapolated from nearby sea-truth sampling stations. This procedure probably introduced experimental error into the analyses and, as such, may have obscured subtle relationships. Results Photographically sensed menhaden distribution and abundance {A^JP) and distribution (D) in- formation were regressed against available oceanographic parameter measurements (Table 1). These analyses reflect only those data col- lected on 7 August, 25 August, and 28 September 1972 (i.e., main days) from the Mississippi Sound portion of the study area. Forel-Ule color data were not collected on 7 August 1972; consequently, color analysis was limited to 25 August and 28 September. Clouds and cloud shadow obscured portions of the Sound on 25 August and 28 September; these areas were ignored in the analysis. In general, the two approaches, i.e., relative abundance and distribution dependent vari- ables, gave similar results. The type of relation- ship, either positive or negative, was the same in every case. Their precision varied, how- ever, which affected level of significance. Of the two approaches, relationships derived using dis- tribution as the dependent variable probably are the most reliable. Recent work has shown that there may have been a variable bias associated with the photographic sensor system used to obtain the fisheries data (Benigno and Kem- merer, 1973). The bias appeared to relate to school size and atmospheric conditions and ap- parently affected the number of schools detected more than where they were detected. Assignment of biological significance to these correlations is difficult in that the parameters may be serving as indices of unmeasured parameters. In other words, there is a question of concomi- tance. Nevertheless, there does appear to be support for the distribution significant (^ 90% confidence level) correlations presented in Table 1. Menhaden fishermen frequently are frustrated Table 1. — Correlations between menhaden relative abundance (Ax.yIP) and distribution (D) estimates and selected oceanographic parameters (E). Correlation coefficient (r) Mean conditions where menhaden Degrees of Relative Distribu- were detected Parameter freedom abundance tion (±95% confidence limit) Temperature ("C) 195 0.009 0.044 29.75 (0.33) Salinity (ppt) 195 -0.257*" -0.222*" 25.53 (1.85) Chlorophyll a (mg/m^) 195 0.025 0.119- 5.61 (1.95) Current speed (cm/s) 195 -0.062 0.027 13,61 (5,50) Sea state (m) 195 -0.064 -0.103 0,25 (0,08) Forel— Ule color (units) 113 -0.256— -0.150- 13,69 (1.21) Wafer depth (m) 195 -0.216— -0.404"- 1.91 (0.47) Secchi disc trans- 195 -0.093 -0.146" 1.25(0.17) parency (m) ' 90% significance level '■ 95% significance level *• 99% significance level 380 KEMMERER ET AL.: ERTS-1 MENHADEN EXPERIMENT in attempts to capture schools because the schools often inhabit waters too shallow for efficient boat and net operations (negative correlation associated with depth). Spotter pilots tend to concentrate their fish-searching efforts on turbid waters because of a relatively high frequency of fish encounter in these waters (negative correlation associated with secchi disc transparency). The positive correlation associated with chlorophyll a seems reasonable in that menhaden are plankton feeders. Salinity is a questionable concomitant factor although, because these fish are euryhaline organisms and inhabit estuarine waters throughout most of their lives, a preferred association with waters of low salinity seems plausible (negative correlation associated with salinity). Christmas and Gunter (1960) reported that 70% of the catch from 87 sets in the Mississippi Sound came from waters ranging from 5 to 24 ppt salinity, suggesting also a menhaden preference for low salinity waters. No biological significance can be attached directly to Forel-Ule color (negative correlation) yet, although this color may manifest water trans- parency and chlorophyll content. Correlation coefficients between Forel-Ule color and secchi disc transparency and chlorophyll a were -0.404 and 0.369, respectively, significant at the 99% confidence level. The lack of statistical significance for several of the parameters listed in Table 1 should not necessarily be construed as meaning that no such correlations exist. For example, surface water temperature was relatively constant spatially throughout the study period and there- fore its effect, if any, on the distribution and abun- dance of menhaden may not have been sufficient to gain statistical significance. In the long run, however, temperature may be a very important parameter. One also should be reminded that the correlations were developed from linear expres- sions for the sake of statistical tractability. The correlations, therefore, may not factually represent real world situations where most responses probably are nonlinear. The concern over a possible significant sensor bias in the menhaden distribution estimates prompted attempts to substantiate the results through other approaches. The set of commercial fishing data which included measurements of selected oceanographic parameters provided the only avenue through which substantiation could be accomplished. However, these data were notice- ably biased in that environmental measurements were obtained only from areas where catches were made or attempted. In addition, the boats did not fish randomly throughout the study area; rather, they fished according to fish availability, distance from home port (minimized to reduce operating expense), day of the week (tendency to fish farther from home port as the fishing week progressed), and water depth (usually about 2 m for efficient boat operation). Nevertheless, if caution is used in the analysis, the data can be used to substantiate some of the results gained through photographic sensing of the menhaden stocks. In the classical statistical situation, one gener- ally attempts to differentiate between two pre- sumably different populations, e.g., with and without menhaden. As noted previously, the principal problem with the commercial fishing data is that data were not obtained from areas without fish. However, if the assumption is made that all other environmental measurements collected throughout the study period (main and secondary day events) were taken at random in terms of temporal and spatial coverage, then it is logical to assume that these latter measure- ments included areas with and without menhaden. The commercial fishing data can then be handled as a "with fish" subset of the total data population, i.e., with and without fish. The difficulty in this approach is that differences are difficult to demonstrate with a high level of statistical significance because the subset (with fish) is not discrete from the total population (with and without fish). The hypotheses which can be tested are that the means (x) and standard deviations (s) of the subset and total population are different, resulting in the following four general conditions and accompanying conclusions: 1. Means and standard deviation are not significantly different; conclusion: fish dis- tribution is not related to the parameter tested. 2. Means are significantly different but stan- dard deviations are not; conclusion: fish dis- tribution is related to the parameter tested. 3. Means are not significantly different but standard deviations are; conclusion: fish dis- tribution is related to the parameter tested. 4. Means and standard deviations are both significantly different; conclusion: fish dis- tribution is related to the parameter tested. 381 FISHERY BULLETIN: VOL. 72. NO. 2 A note of caution should accompany the conclu- sions, however. They are valid only for the data collected under the conditions of the experiment, and therefore extrapolation to other areas or to the same area under different experimental condi- tions might not be valid. The commercial fishing data demonstrated a Condition 4, i.e., means and standard deviations different with respect to water depth, salinity, Forel-Ule color, and secchi disc transparency (Table 2). Temperature and sea state were not tested, and data were not available for chlorophyll a and currents. The subset of fishing data included measurements from 237 "fish sets" and the total population of oceanographic conditions included measurements from 29 June, 30 June, 6 July, 7 Au- gust, 25 August, and 28 September 1972. For each parameter, a negative correlation is indicated as the mean parameter values for the fishing subsets were significantly less than the mean values for the total parameter populations. The lack of high significance levels for mean salinity and Forel-Ule color value differences was not particu- larly surprising in that the subset approach tends to preclude such significance. In any case, the rela- tionships shown in Table 2 substantiate those shown in Table 1. A second approach was used to substantiate still further the correlations formed between fish dis- tribution and salinity, Forel-Ule color, secchi disc transparency, and water depth. Mean parameter values for conditions where menhaden were photographically detected (Table 1) were com- pared with similar values from the fishing subset (Table 2). None of these values were significantly different at levels down to 80% (^-test). In summary, water depth, secchi disc visibility depth, surface salinity, and Forel-Ule color were found to correlate negatively with the distribution of menhaden. Chlorophyll a correlated positively with fish distribution, although independent data were not available with which to corroborate this relationship as in the case of the other four parameters. ERTS- Imagery and Fish Distribution Relationships Analysis The only complete docket of quality ERTS-1 MSS imagery coincidental with main day acquisi- tion events was from 7 August 1972. Band 5 imag- ery from 25 August 1972 was of poor quality and no imagery was available for 28 September 1972. The four MSS bands from 7 August 1972 were examined to determine if their density levels re- lated to fish distribution. Bands 6 and 7 did not contain any readily apparent useful density de- tail. Band 4, for reasons which are still unclear, seemed to contain too much density detail. Den- sity levels in Band 5, however, appeared to relate to menhaden distribution. Results Figure 3a shows a portion of the ERTS- 1 Band 5 imagery covering the western portion of the Mis- sissippi Sound and adjacent offshore waters as displayed on a I^S DIGICOL video screen. Superimposed on the image are locations of 23 photographically detected menhaden schools. Water imagery densities were divided into two density ranges and color-enhanced (Figure 3b). All menhaden schools were found to lie in the less dense range, enhanced as orange. This density range was further reduced by slicing it to the nar- rowest range possible with the instrument. All of the fish schools can be found to either lie in or immediately adjacent to this range, enhanced as Table 2. — Comparison of total parameter populations (with and without fish) and fish parameter population subsets (with fish). Total population Fishing subset population Level of signi- ficant difference (%)' Parameter n X s n X s X s Water deptfi (m) 354 3.41 1.27 237 2.19 1.17 99 90 Seccfii disc trans- 348 1.45 0.71 237 1.10 032 99 99 parency (m) Salinity (ppt) 357 26.30 4.15 237 2585 2.95 80 99 Forel-Ule color 166 14.16 304 237 13.78 2.44 80 99 (units) 'f-tests for differences between means for populations witti unequal variances and F-tests for differences between standard deviations (Ostle, 1963) 382 KEMMERER ET AL.: ERTS-I MENHADEN EXPERIMENT 383 KEMMERER ET AL : ERTS-I MENHADEN EXPERIMENT orange (Figure 3c). The 10 tightly grouped school location indicators in the middle-left portion of the image overlie a small orange enhanced area making the latter difficult to see. Unfortunately, the lack of additional data to test the persistence of the relationship between menhaden distribution and MSS Band 5 imagery density levels precludes any but the most tenta- tive of conclusions. However, the data are suffi- cient to warrent an observation that the imagery does appear to contain information relating to the distribution of menhaden schools. ERTS-1 Imagery and Oceanographic Parameter Relationships Analysis An analysis was performed on the MSS Band 5 imagery for 7 August 1972 to determine if image densities could be explained based on oceano- graphic parameter measurements. An isodensity tracing was made of that portion of the imagery covering the study area to provide quantitative relative density data. The tracing was not particu- larly satisfactory because of instrument limita- tions which caused more than one density range to be represented by the same color trace, but accurate enough to demonstrate relationships. Results Water depth, secchi depth visibility, and the interaction between the two parameters (formed by their product, Mott, 1967) were regressed against relative image densities. Simple correla- tions (r) between these parameters and image density were 0.56, 0.73, and 0.69, respectively, significant at the 99% confidence level. A slight improvement in precision (r = 0.77) was realized when the parameters were combined through multiple regression (Table 3) into the following equation: Image Density = 0.5776 + 0.0222B + 0.0762T -0.00515T (4) where: B = water depth in meters, T= secchi disc transparency in meters, BT = interaction formed as the product of B and T Of the parameters, secchi disc transparency was Table 3. — Analysis of variance for the relationship between ERTS-1 image density and two oceanographic parameters. Degrees of Mean F- Source of variation freedom square value Total 47 0.0051 Regression (secchi disc trans- 3 00469 21.040*" parency, water depth, and interaction) Error 44 0.0022 the most important one in the equation as indi- cated by the relative magnitude of the coefficients and the simple correlation coefficients. The most meaningful facet of this analysis is that the two parameters correlating significantly with image density levels also correlated significantly with menhaden distribution (Tables 2 and 3). Thus, it appears that the apparent correlation between menhaden distribution and Band 5 density levels (Figure 3) is more than a chance occurrence and can be explained based upon secchi disc transpar- ency and water depth measurements. PREDICTION MODELS FOR RESOURCE MANAGEMENT AND UTILIZATION A potential management and utilization benefit from this experiment is identification of an ap- proach through which remotely sensed environ- mental data could be used to provide distribution information about menhaden stocks in the study area. This information could be used to reduce search time for commercial concentrations of menhaden by fishermen and as a means to develop efficient survey designs by resource managers. Ideally, distribution information should be valid for the entire Gulf Coast menhaden fishery; how- ever, this ideal case cannot be supported with re- sults from this experiment but can be realized only through future experiments specifically designed to test demonstrated relationships in other areas. Model Development Demonstrated menhaden distribution- oceanographic parameter relationships (Table 1) were placed into a context potentially useful to commercial fishermen and resource managers. Multiple regression analysis was used to develop eight empirical models to predict menhaden distribution (D) in the study area based on 385 FISHERY BULLETIN: VOL. 72. NO. 2 four oceanographic parameters: water depth, secchi disc transparency, Forel-Ule color, and salinity (Table 4). The models contain selected 2-factor interactions formed as products between parameters and treated as additional independent variables. Interaction selection was based on whether or not an interaction significantly in- creased the precision of the estimate 0). The models were constructed from data collected on main days (i.e., 7 August, 25 August, and 28 Sep- tember 1972) and are presented separately and in combination and with and without the inclusion of color as an independent variable. Model Testing and Interpretation The models were tested by playing them with oceanographic data collected during commercial fishing operations and main day sea-truth station data stratified to include only those stations where menhaden were not detected photographically (Figure 4). Ideally, model products for fishing data should have grouped close to 1, and products for the "without fish" sea-truth stations should have grouped close to 0; obviously, this type of grouping is not demonstrated in Figure 4, indicating a gen- eral lack of accuracy and precision in the models. Product populations, however, are significantly 1-0 1,0 MODEL I'm: DICTIONS 4 Figure 4. — Histogram plots of "with fish" (shaded) and "with- out fish" (unshaded) model products. Table 4. — Empirical regression models which predict menhaden distribution (D) in the ERTS-1 study area. B = water depth (m) S = salinity (ppt) T = Secchi disc transparency (m) C = Forel-Ule color (units) BT, BS, ST, CT, and CS = interactions formed as the products of the respective parameters. Model Signifi- Inclusive Standard correla- cance dates error tion co- level Model (1972) n Regression model of D efficient (%) D1 7 Aug. 82 D = 1.9959-0 06645+0 7453 7-0.68208- 0.0233S7 - 0.01448 7 + 0 02308S D2 25 Aug 42 D = 5.1537 - 0.1740S - 0.91957 - 0.0371C - 0.43508 + 0.0502S7 - 0.12438 7 + 0.01958S D3 28 Sept. 73 D = 2.3473 - 0 0934C - 0.81178 - 0.0358S 7 - 0.0007CS + 0.0528C7 + 0.05168 7 + 0.02358S D4 7 and 25 124 D = 2.4691 - 0 0855S + 0.3948 7 - 0.64778 - Aug 0.0054S 7 - 0.04418 7 + 0.02238S D5 7 Aug and 155 D = 1.8559-0 05775 + 0,56047-0 69548- 28 Sept. 0.0191S7 - 0.00798 7 + 0,023285 D6 25 Aug and 115 D =2.9396-0.10245 + 0.15227-0 74868- 28 Sept. 0.00265 7 - 0 05478 7 + 0 026885 D7 25 Aug and 115 D = 3.6035 - 0.09875 -0 12497 - 0.0416C - 28 Sept 0.67178 + 0 00875 7 - 0 04418 7 + 0.023485 D8 7 and 25 Aug. 197 D = 2,3759-0 07975+0.3928 7-0.70518- and 28 Sept 0 00865 7 - 0 03268 7 + 0 024285 0.2492 0.3793 0.2443 0.3009 02489 0.596 0.630 0.409 0.584 0480 0 3118 0.488 0 3090 0 508 99 99 90 99 99 99 99 028560,515 99 386 KEMMERER ET AL.: ERTS- 1 MENHADEN EXPERIMENT different for each model even though the distribu- tions overlap without a wide margin of difference between means (Table 5). A number of factors probably contributed to the failure of the models to group fishing data closer to 1. It should be pointed out first, however, that no seasonally caused variation in products was noted, suggesting that the nonparametric group- ing was caused by factors prevalent throughout the June through September commercial fishing sampling period. One of these factors may have been the effect of commercial fishing operations on the distribution offish as evidenced by visual ob- servations made during the photographic surveys of the study area. Menhaden schools frequently were observed being chased by purse boats through waters of varying visual qualities (i.e., turbidity). In addition, oceanographic parameter measurements generally were taken from the mother vessel rather than the purse boats, which often was several kilometers distant from the ac- tual site offish capture. Another of these factors is that there is no biological reason to suspect menhaden distribution to be wholly a determinis- tic function of environmental conditions; rather, there most likely is a probability associated with how and where fish are distributed in response to these conditions. Also, there were errors as- sociated with all of the parameter measurements used to develop and test the models as well as a distinct possibility that other parameters having a direct influence on menhaden distribution might not have been measured (e.g., zooplankton biomass, presence or absence of predators, oxygen tensions, etc.). And finally, there is the linear ad- ditive nature of the models which at best probably only approximates the real world situation. Selection of a best model was difficult in that they all provide similar products. On the basis of sample size, number of parameters (minimum), and difference between means (Table 5), Model D8 would have to be given selection priority, how- ever. A number of interpretations and presentation methods can be applied to model products as long as they recognize the imprecision of the models. An example of one method applied to Model D8, for 7 August 1972 sea-truth data, is presented in Figure 5. The categorization of model products was done by dividing the values shown in Figure 4 for Model D8 into three ranges based upon a direct comparison of fishing and nonfishing histograms: high potential = > 0.2 moderate potential = -1.0 to 0.2 low potential = <-1.0 The interpretation applied to high, moderate, and low potential areas is related to relative probabil- ity. In high potential areas, the probability offish capture is higher than in moderate or low poten- tial areas and higher in moderate than in low potential areas. Incomplete commercial fishing reports from 7 August 1972 indicate that most, if not all, fishing occurred in the high potential areas. An additional analysis was performed on the commercial fishing data to determine if relation- ships could be demonstrated between catch size and the four oceanographic parameters which made up the models. Catch size ranged from 5 to 225 and averaged about 38 thousand fish. Catch Table 5. — Tests of empirical models played with oceanographic data taken near sites of commercial fish capture (with fish) and during main day events, the latter stratified to include only those areas where fish were not detected photographically (without fish). With fish Without fish Sig for niflcance level difference be- Model n D C.V.(%)' n D C.V.(%)' tween means {%f D1 225 0.202 86 165 0071 147 99 D2 225 0.371 78 94 0.100 187 99 D3 225 0.146 184 94 -0.115 132 99 D4 225 0.305 67 165 0.139 80 99 D5 225 0.175 106 165 -0.017 755 99 D6 225 0 288 79 165 0089 165 99 D7 225 0338 70 94 0093 151 99 D8 225 0.145 163 165 -0,111 160 99 'Coefficient of variation. 'r-test for populations with unequal variances (Ostle, 1963). 387 FISHERY BULLETIN; VOL. 72, NO. 2 89°00'W 88°30'W 30°30'N 30°20'N 30°10'N X X a. < < CD < BAY ST. LOUIS ... . BILOXI •■ OCEAN ;"< SPRINGS. .PASCAGOULaJ V HIGH POTENTIAL AREA 30°00'N -^ **»«,>'<« flX) ^ [ I MODERATE POTENTIAL AREA LOW POTENTIAL AREA i Figure 5. — Model D8 predictions for menhaden distribution in the Mississippi Sound on 7 August 1972, between 0900-1500 h (CDT) (based on 95 sea-truth measurements). size was divided into three categories: 0-50, 50-100, and more than 100 thousand fish, and an analysis of variance applied to the categories to test for differences between mean parameter con- ditions. No significant differences were found be- tween catch size and salinity, Forel-Ule color, and depth parameters at significance levels down to 50%. However, a significant difference at 95% was found between the first and third catch size cate- gory for averaged secchi disc transparency values (T 0-50K = 1.09 m and T >100K = 1.32 m). This sig- nificance probably does not have biological mean- ing, however. It probably reflects changes in the ability of fishermen to selectively detect and capture fish schools with respect to water clarity. SUMMARY AND CONCLUSIONS The feasibility of using satellite-supported en- vironmental sensors to predict fish distribution was demonstrated. ERTS-1, MSS Band 5 imagery was shown to contain density levels which corre- lated with menhaden distribution. These density levels were further shown to correlate signifi- cantly with sea-truth measurements of secchi disc transparency and water depth, two pa- rameters which also correlated significantly with menhaden distribution. Additionally, sur- face salinity, Forel-Ule color, and chlorophyll a were found to correlate significantly with menha- den distribution. Independent tests of four oceanographic parameter-menhaden distribu- tion relationships with oceanographic informa- tion taken at or near sites of commercial menha- den captures corroborated these relationships. The correlation between chlorophyll a and menhaden distribution could not be substantiated because of insufficient data. Eight empirical regression models which pre- dict menhaden distribution in the study area were constructed from combinations of four oceano- graphic parameters: water depth, secchi disc trans- parency, surface salinity, and Forel-Ule color. Al- though the models did not provide particularly precise predictions about menhaden distributions, their predictions nevertheless were statistically significant. The importance of the models is that they demonstrate a potential means or direction through which remotely sensed oceanographic in- formation can be used to provide menhaden dis- tribution information on a real-time basis. This information could be used by the commercial in- dustry to reduce spotter-pilot search time by iden- tifying likely areas for concentrations of menha- den and by resource managers as an aid in plan- ning assessment surveys. 388 KEMMERER ET AL.: ERTSI MENHADEN EXPERIMENT ACKNOWLEDGMENTS The authors wish to express their sincere ap- preciation to Kenneth J. Savastano, Fisheries En- gineering Laboratory, Mississippi Test Facihty (MTF), for his programming help in many of the analyses; the Earth Resources Laboratory (NASA), also at MTF, for the use of their painstak- ingly acquired oceanographic data; and Earth Satellite Corporation for the use of their commer- cial fishing data. This research was supported in part through NASA Project 240. LITERATURE CITED Benigno, J. A. 1970. Fish detection through aerial surveillance. Tech. Conf. on Fish Finding, Purse Seining, and Aimed Trawl- ing; Reykjavik, May 1970. FAO (Food Agric. Organ., U.N.), FII:FF 70 78; 13 p. Benigno, J. A., and A. J. Kemmerer. 1973. Aerial photographic sensing of pelagic fish schools: A comparison of two films. Preprint of the American Society of Photogrammetry, American Congress on Surveying and Mapping, and National Convention and Symposium on Remote Sensing and Oceanography, Orlando, Fla., Oct. 2-5, 1973. BuLLis, H. R., Jr. 1967. A program to develop aerial photo-technology for as- sessment of surface fish schools. Proc. Gulf Caribb. Fish. Inst., 20th Annu. Sess., p. 40-43. Christmas, J. Y. 1973. Cooperative Gulf of Mexico estuarine inventory and study, Mississippi. Phase I Area Description. Spec. Rep. to the Mississippi Conservation Commission (Gulf Coast Research Laboratory, Ocean Springs, Miss.), 450 p. Christmas, J. Y., and G. Gunter. 1960. Distribution of menhaden, genus Brevoortia, in the Gulf of Mexico. Trans. Am. Fish. Soc. 89:338-343. Drennan, K. L. 1969. Fishery oceanography from space. Proc. 6th Space Congr. Space Tech. Soc. Canaveral Counc. Tech. Soc, Cocoa Beach, Fla., p. 9.1-9.6. Freden, S. C. 1973. Introduction: Performance of sensors and systems. /n W. A. Finch, Jr. (editor). Earth Resource Technology Satellite-1, Symposium proceedings, p. 1-6. Goddard Space Flight Center, Greenbelt, Md. Gunter, G., and J. Y. Christmas. 1960. A review of literature on menhaden with special re- ference to the Gulf of Mexico menhaden, Brevoortia pa- tronus Goode. U.S. Fish. Wildl. Serv., Spec. Sci. Rep. Fish. 363, 31 p. Hutchinson, G. E. 1957. A treatise on limnology. Vol. I, Geography, physics, and chemistry. John Wiley & Sons, N.Y., 1015 p. Kemmerer, A. J., and J. A. Benigno. 1973. Relationships between remotely sensed fisheries dis- tribution information and selected oceanographic parameters in the Mississippi Sound. Symposium of Significant Results Obtained from ERTS-1, Goddard Space Flight Center, Greenbelt, Md., NASA, Mar. 5-9, 1973. Maughan, p. M., a. D. Marmelstein, and O. R. Temple. 1973. Application of ERTS-1 imagery to the harvest model of the U.S. menhaden fishery. Symposium of Significant Results Obtained from ERTS-1, Goddard Space Flight Center, Greenbelt, Md., NASA, Mar. 5-9, 1973. MoTT, D. G. 1966. The analysis of determination in population systems. In K. E. F. Watt (editor), Systems analyses in ecology, p. 179-194. Academic Press, N.Y. OSTLE, B. 1963. Statistics in research. [2d ed.], Iowa State Univ. Press, Ames. Reintjes, J. W. 1969. Synopsis of biological data on the Atlantic menhaden, Brevoortia tyrannus. FAO (Food Agric. Organ. U.N.) Species Synopsis No. 42. (Available U.S. Fish Wildl. Serv., Circ. 320, 30 p.) Reintjes, J. W., J. Y. Christmas, Jr., and R. A. Collins. 1960. Annotated bibliography on biology of American menhaden. U.S. Fish Wildl. Serv., Fish. Bull. 60:297-322. Roithmayr, C. M., and F. P. Wittman. 1972. Low light level sensor development for marine re- source assessment. Preprints, 8th Annu. Conf Expo., Mar. Tech. Soc, Sept. 11-13, 1972, Wash., D.C., p. 277-288. ROUNSEFELL, G. A. 1954. Biology of the commercial fishes of the Gulf of Mexico. U.S. Fish Wildl. Serv., Fish. Bull. 55:507-512. Stevenson, W. H., B. H. Atwell, and P. M. Maughan. 1972. Application of ERTS-1 for fishery resource assessment and harvest. Eighth International Symposium on Remote Sensing of the Environment. Willow Run Lab., Ann Arbor, Mich., Oct. 2-6, 1972. Vary, W. E. 1969. A new non-blue sensitive aerial color film. Seminar Proceedings— New Horizons in Color Aerial Photography; American Society of Photogrammetry and Society of Photographic Scientists and Engineers, June 9-11, 1969, p. 127-130. 389 ROLE OF LARVAL STAGES IN SYSTEMATIC INVESTIGATIONS OF MARINE TELEOSTS: THE MYCTOPHIDAE, A CASE STUDY^ H. Geoffrey Moser and Elbert H. Ahlstrom^ ABSTRACT The lanternfish family Myctophidae is the most speciose and widespread family of mid- water fishes in the world ocean. As presently recognized it contains about 30 genera and 300 nominal species. Their larvae are highly prominent in the plankton and make up about 50% of all larvae taken in open-ocean plankton tows. Our studies of myctophid larvae, on a worldwide basis, have demonstrated that characters of the larval stages of lanternfishes are of great utility in systematic analysis. The genera and species can be recognized on the basis of eye and body shape, the shape and length of the gut, and pigment pattern and by the sequence of photophore development. In this paper the larvae of 55 species representing 24 genera are illustrated and used to demonstrate the usefulness of larvae in understanding the relation- ships of species within genera. Characters of the larvae provide insight into generic affinities of lanternfish, allowing us to construct an evolutionary scheme of tribes and subfamilies that differs in some aspects from those proposed on the basis of adult characters. The concept of using larval characters in combination with adult characters to delineate phylogenetic lines in myctophids is discussed, as is our view of evolutionary strategy in the family. A major facet of comprehensive systematic inves- tigations is the search for functionally unrelated characters. Whether the independence of these characters is actual or merely apparent, they con- stitute useful elements in the analysis of systema- tic relationships. Ample evidence of this is the higher classification of teleosts (Greenwood et al., 1966) generated by the synthesis of a diverse array of classical taxonomic characters. The re- cent surge of serological and biochemical studies on fish has placed a fresh group of characters in the hands of systematic ichthyologists (De Ligny, 1969). Likewise, recent advances in fish cytogene- tics (e.g., Ohno, 1970; Benirschke and Hsu, 1971; Ebeiing, Atkin, and Setzer, 1971) are providing another group of taxonomic characters. It is likely that behavioral science will be still another source of taxonomic characters, as exemplified by the growing body of information on the acoustic be- havior of fishes (Fish and Mowbray, 1970). One group of well known taxonomic characters, those of the embryonic and larval stages, has re- ceived scant attention from all but a few systema- tic ichthyologists. Characters of the larvae have 'This paper was presented at the International Symposium on the Early Life History of Fish (sponsored by lABO, FAO, ICES, ICNAF, and SCOR) held at Oban, Scotland, 17-23 May 1973. ^Southwest Fisheries Center, National Marine Fisheries Ser- vice, NOAA, La Jolla, CA 92037. Manuscript accepted Agust 1973. FISHERY BULLETIN: VOL. 72, NO. 2, 1974. played a large role in the taxonomy of anguil- liform fishes (Castle, 1969) partly because of the conspicuousness of eel leptocephali and partly be- cause of the unavailability of adults of many of the families. Bertelsen's (1951) treatment of the ceratioid fishes is a superb example of the value of utilizing larval stages in a systematic revision of a large group of teleosts. Apart from these two groups, it is the larvae of myctophiform fishes which have received the most attention from tax- onomists. Ege (1953, 1957) relied heavily on lar- val stages in his extensive works on the Paralepididae. Johnson (1971) employed larval characters in defining species and genera of Scopelarchidae. Bertelsen, Marshall, and Krefft (pers. commun.) have used larval stages exten- sively in their revision of the Scopelosauridae. Our studies on the family Myctophidae itself (Moser and Ahlstrom, 1970, 1972) indicated that larval characters can aid significantly in differen- tiating taxa and defining evolutionary lineages within this family. The lanternfish family Myctophidae is the most speciose and widespread family of mid-water fishes in the world ocean. As presently recognized it contains about 30 genera and 300 nominal species. Their larvae are highly prominent in the plankton and make up about 50% of all larvae taken in open-ocean plankton tows. 391 FISHERY BULLETIN: VOL. 72. NO. 2 Our studies of the larvae of this family have included material from all oceans. We have been able to identify larvae from all recognized genera except Hintonia and Dorsadena. Larval evidence supports giving generic status to Metelectrona and Parvilux. Including these, we have developmental series for 29 myctophid genera and for many gen- era we have series for all known species. This has afforded a more comprehensive view of the range and variability of larval characters, and we are increasingly impressed with the functional inde- pendence of the larval and adult characters. It is apparent that the world of the larvae and the world of the adults are two quite separate evolutionary theaters. Our studies of larval lanternfishes have disclosed a full range of charac- ters, from generalized to specialized and from con- servative to labile, equal in scope to those of the adults. These characters fall into several categories. An important group is the shape of various structures such as the eye, head, trunk, guts, and fins, especially the pectoral fins. Another group is the sequence of appearance and the posi- tion of fins, photophores, and bony elements. Another is the size of the larvae when fins and other features appear and the size of the larvae when they transform into juveniles. Pigmentation provides an important group of characters based on the position, number, and shape of melano- phores. Finally, there are the highly special- ized larval characters such as voluminous fin folds, elongated and modified fin rays, chin bar- bels, preopercular spines, etc. It is our purpose here to point out some of these characters and demonstrate how they can be of advantage in defining taxa and establishing phylogenetic lineages. THE SUBFAMILY MYCTOPHINAE The most trenchant character of larval myc- tophids is eye shape. Our studies show that lanternfish larvae fall naturally into two groups on the basis of eye shape — those with narrow ellip- tical eyes and those with round or nearly round eyes (Moser and Ahlstrom, 1970). The species composition of these two groups agrees closely with that of the two subfamilies, Myctophinae and Lampanyctinae, established by Paxton (1972) on the basis of osteological and photophore charac- ters of adults. Larvae of the Myctophinae have elliptical eyes; some species have ventral pro- longations of choroid tissue and some have the eyes on stalks. Paxton recognized 11 genera in the subfamily Myctophinae and distributed them into two tribes, the Myctophini and the Gonich- thyini. Larvae of the species in each of these genera generally conform to a particular morph based on form, pigment, and developmental pattern and, although these morphs are remark- ably diverse, we can find no character or set of characters that would divide the genera into tribes. Within each genus of the subfamily, how- ever, the larval characters are indispensible in delineating groups of related species or subgenera. This is best illustrated by examining the impor- tant genera of the Myctophinae. Protomyctophum larvae have a slender shape (Figure 1). For all species exceptP. anderssoni, the gut is short during most of the larval period and characteristically there is a marked interspace between the anus and the origin of the anal fin (Figure lA-D). The gut elongates dramatically in late larvae, to fill the interspace. Gut development is completely dissimilar in P. anderssoni, where the gut is long at all larval sizes, in fact longer than in most other lanternfish larvae (Figure IE). Series of ventral tail melanophores are formed in some species of both recognized subgenera (Heirops and Protomyctophum sensu stricto), for example in P. Protomyctophum normani (Figure lA) and P. Heirops thompsoni (Moser and Ahl- strom, 1970). Larvae of the subgenera can be sepa- rated, however, on the basis of eye shape, the eyes of Heirops (Figure IC, D) being characteristically narrower than those of Protomyctophum sensu stricto (Figure lA, B). Choroid tissue is absent from the ventral surface of the eye in all species of the genus except P. anderssoni, which has a well- developed "teardrop" (Figure IE). Larvae of P. anderssoni are so markedly different from those of all other species of Protomyctophum, which otherwise form a rather cohesive group, that this species should be placed in a separate subgenus or perhaps even in a distinct genus. This suggestion is supported by the unique placement of certain photophores and by the structure of the sup- racaudal luminous tissue in adults of this species. Larvae of the genus Electrona are a less homogeneous group but are united by a common- ality of body shape and especially gut shape (Fig- ure 2). A marked interspace is present between the end of the gut and the origin of the anal fin. This space is closed only at the termination of the 392 MOSER and AHLSTROM: ROLE OF LARVAE IN SYSTEMATICS -■n -^i. t^ ^t ^ ^ 9 * ■* * * •v '!:>«"■■''?*?■•■% ^sl^;^ ^^^^$^>^^^K:^- * js:-^ MS5SS?S555* .--■.'*^.,L-— -•" -'fffip^ ^-^.•v^-^* ■ 'C^v--y>^ K^.>>- Figure 1. — Larvae of Protomyctophum. A. P. Protomyctophum normani. 15.2 mm; B.P. Protomyctophum teni- soni, l4.5mm;C. P. Hieropssubparallelum, 15.2mm;D. P. Hieropschilensis. 11.0mm;E.P. anderssoni, 15.7 mm. 393 FISHERY BULLETIN: VOL. 72, NO. 2 /T? i ''■'""?™i*-4i'l ■m:»- - -A Figure 2.— Larvae of Electrona and Metelectrona. A. E. antarctica, 12.7 mm; B. E. carlsbergi, 11.1 mm; C. E. subaspera, 10.5 mm; D. M. ahlstromi, 10.3 mm. 394 MOSER and AHLSTROM: ROLE OF LARVAE IN SYSTEM ATICS larval period. None of the species forms photo- phores during the larval period other than the Br2 pair. The characters that most clearly separate the three developmental lines in Electrona are eye shape and the amount of choroid tissue developed under the eye. Electrona antarctica has an elon- gate choroid mass uniquely divided into two nar- row eyes (Figure 2A). Also, E. antarctica larvae attain a large size (20 mm), are the deepest-bodied oiaWElectrona larvae, and have the heaviest pig- mentation. The two species in the second de- velopmental line transform at a small size (ca. 10 mm in E. rissoi and 12-13 mm in £■. carlsbergi), have a small choroid mass under a moderately narrow eye, and develop scant pigment (Figure 2B). In the third line, consisting of £. subaspera and E. paucirastra, the eye is the least narrow, has no choroid tissue, and the larvae attain a large size (20 mm) (Figure 2C). The larva of the species described as Metelec- trona ahlstromi (Wisner, 1963) is illustrated in Figure 2D. It is more laterally compressed than any species of Electrona and has no interspace between the anus and origin of the anal fin. In some features it resembles the larvae of Hygophum; it has a late-forming dorsal fin and the gut is shaped very similarly to that inH. taaningi and H. macrochir. Its pigment is unique and the eye is distinct, with the ventral edge of the scleral envelope characteristically squared off. Also, in late-stage larvae, in addition to the Br2, a second pair of photophores (PO5) develops, a feature found in neither Hygophum nor Electrona. Paxton (1972) synonymized Metelectrona with Electrona and suggested that M. ahlstromi andE. ventralis are synonyms, however, the uniqueness of the larva strongly suggests the resurrection of Metelectrona as a valid genus. The genus Benthosema is the least cohesive of any genus in the subfamily Myctophinae, from the viewpoint of larval structure (Figure 3). We can find only four types of larvae in the world ocean, although Nafpaktitis (1973) recognizes five species on adult characters. We cannot distin- guish larvae of B. pterota and B. panamense although Nafpaktitis has listed a number of con- vincing characters that distinguish the adults of the two species. We find two highly divergent species pairs. One is composed of B. glaciale and B. suborbitale with a narrow eye subtended by a lunate choroid mass and with a pronounced inter- space between the anus and the anal fin origin, reminiscent of Protomyctophum and Electrona (Figure 3A-C). In the other pair, consisting of B. panamense-pterota and B. fibulatum, the eye is wider, is subtended by a mere sliver of choroid tissue and the gut, of moderate length, lacks a postanal interspace (Figure 3D, E). The one feature held in common by the four species is the development of some photophores in addition to the Bra during the larval period. The only other myctophine genera that develop photo- phores in addition to the ubiquitous Br2 during the larval period are Diogenichthys, Myctophum, and Metelectrona. This feature is much more pre- valent among genera of the Lampanyctinae and is helpful in defining groups of related genera there (Moser and Ahlstrom, 1972). In B. panamense-pterota and B. fibulatum the Dn pair is formed soon after the Br2 at about 5.0-6.0 mm. The PO5 pair is the third to appear in Table 1. — Sequence of photophore formation in larvae of three species oi Benthosema . Size No. of Smallest larva photophore juvenile Species (mm ) Photophores pairs (mm) B. fibulatum ca. 4.0 Br2 1 13.2 5.4 Bra Dn 2 6.0 Bra Dn PO5 3 6.4 Br2 Dn PCs POt 4 7.3 Br2 Dn PO5 POi AOai 5 7.7-8.7 Br2 Dn PO5 PO1 AOai PO2 6 ca. 10.0 Br2 Dn PCs PO1 AOai PO2 Op2 VLO 8 B. pterota (panamense) 40 Br2 1 11.8 5.0 Br2 Dn 2 60 Br2 Dn PO5 3 ca. 7 0 Br2 Dn PO5 PVO1 4 7.1 Br2 Dn PO5 PVO, Op2 5 7.5 Br2 Dn PO5 PVO, Op2 VO1 PVO2 7 8.0 Br2 Dn PO5 PVO, Op2 VO, PVO2 PO1 AOai 9 B. suborbitale 4.1 Br2 1 10.7 8.3-9.2 Br2 PO1 PO2 3 9.4 Br2 PO, PO2 Br, Br3 Op2 6 11.5 Br2 PO1 PO2 Bri Br3 Op2 PO3 PO4 PO- AOai A0a2 11 395 FISHERY BULLETIN: VOL. 72, NO. 2 Figure 3.— Larvae of Benthosema. A. B. glaciale, 7.2 mm; B. B. glaciate. 10.5 mm; C. B. suborbitale, 9.2 mm; D. B. pterota, 8.5 mm; E. B. fibulatuni, 8.7 mm. 396 MOSER and AHLSTROM: ROLE OF LARVAE IN SYSTEMATICS larvae about 6.0 mm long. Thereafter the pattern diverges as shown in Table 1, but both species gradually add about a dozen pairs during the lar- val period. Specimens of B. pterota from the Per- sian Gulf off India, formed photophores at some- what larger sizes than larvae of B. panamense, but in the same sequence. Transformation occurs at a small size, 10-12 mm in B . panamense-pterota and 11-13 mm inB. fibulatum. Photophores appear relatively late in larvae of B. suborbitale and S. glaciale. however, the Bri, Br2, Op2, and PO series appear in late larvae of both species (Table 1). Transformation occurs at about 9-11 mm in both species. The larvae of 5. panamense-pterota and B. fibulatum are close to the larvae of Diogenichthys in several characters including body shape, gut shape, and early ap- pearance of photophores. As in Benthosema, the larval characters of Hygophum suggest some divergence within the genus, although all species have a highly charac- teristic series of isthmal melanophores, form the dorsal fin late in the larval period, and develop no photophores other than the Br2, as larvae (Figure 4). The genus contains three divergent types of larvae. The most unusual of these are the ex- tremely elongate larvae of//, reinhardti and//. atratum, which have very narrow eyes that are underlain by prominent choroid tissue and are borne on short stalks (Figure 4A). The amount of pigmentation along the gut and tail and on the myosepta and fin fold increases throughout the larval period. A second larval type is represented by the largest number of species, H. proximum, H. hygomi, and //. brunni, all illustrated (Figure 4B-D), as well as H. benoiti, H. hanseni, and an undescribed form in our collection. These larvae are only moderately slender and have unstalked eyes of moderate width, subtended by prominent choroid tissue. Melanophores are located chiefly on the head and gut, however some species have pigment on the myosepta and fin fold. The trend in this group of species is for the early larval stages to have the heaviest pigment and for melano- phores to be lost as development proceeds. A third type of larva is exhibited by H. mac- rochir, H. taaningi, and an undescribed form in our collection (Figure 4E, F). These are relatively deep-bodied, have large, relatively wide eyes with little or no choroid tissue, and lack tail pigment. Also, the gut has a highly distinctive form; the anterior half has a very small diameter and opens dorsally into a prominent enlarged posterior sec- tion. In H. macrochir this enlarged section is covered with large melanophores. Larvae of this group occur only in the Atlantic. The genus Hygophum affords an excellent ex- ample of the taxonomic utility of larval stages. The juveniles and adults of some species are notoriously difficult to identify. In contrast, the larvae of these species are highly distinct and can be readily identified. We have 11 such distinct larval types, whereas only 9 species are currently known for the adults. Search for adults of the two remaining larval types has led to the discovery of two undescribed species. In addition, characters of the adults of this genus reveal little about the relationships of the member species (Becker, 1965). A study of the larvae, however, shows that there are three highly distinct subgeneric groups, each containing from two to six closely related species. Such an independent view of the complete species complement of a genus is an invaluable tool in the formal revision of that genus. Larvae of the species of Symbolophorus are perhaps the most cohesive of all myctophine gen- era (Figure 5A). In all species known to us the pectoral fin is large and is supported by an elon- gate aliform base. Also, the pelvic fins are large and develop earlier than in any other lanternfish genus. The narrow eyes have choroid tissue and are borne on short stalks. The amount of pigmen- tation decreases towards the end of the larval period. Most species attain a large size — up to 24 mm. The species differ principally in the size at which various larval structures appear. The closely related genus, Myctophum, has a diversity of larval form unmatched in the family (Figures 5, 6, 7). Before taking up the bulk of the species in this genus we must first examine the most aberrant of all lanternfish larvae, that of M. aurolaternatum (Figure 5B). In this remarkable larva the eyes are borne on long stalks and the free trailing section of the gut is almost as long as the fish itself. The dorsal fin forms at the margin of the fin fold. These characters are so bizarre that it would seem preposterous to identify it as a lanternfish larva, much less that of M. aurolater- natum. Nonetheless, A. Vedel Taning first sug- gested the true identity of this larva (E. Bertelsen, pers. commun.) which we can now confirm since recently receiving the critical transforming specimens through the courtesy of Warren Freihofer (California Academy of Science). The uniqueness of this larva would certainly suggest 397 FISHERY BULLETIN: VOL. 72. NO. 2 ^^"^^ Figure 4.— Larvae oiHygophum. A. H. reinhardti, 12.8 mm; B. H. proximum, 8.9 mm; C. H. hygomi. 8.1 mm; D. H. brunni, 9.7 mm; E. H. macrochir. 7.3 mm; F. H. taaningi, 6.8 mm. 398 MOSER and AHLSTROM: ROLE OF LARVAE IN SYSTEMATICS r-ni^^^^^^^s >^^/^l^^ Figure 5. — Larvae of Symbolophorus and Myctophum. A. S. calif orniense, 9.6 mm; B. M. aurolater- natum, 26.0 mm; C. M. punctatum, 13.6 mm; D. M. nitidulum, 8.2 mm; E. M. phengodes, 9.8 mm. 399 the creation of a distinct genus for M. aurolater- natum and it is highly probable that corroborative characters will appear after careful reexamina- tion of the adults. With the removal of M. aurolaternatum , the re- maining larvae o^Myctophum form a diverse, yet recognizable, group. All have large broad pectoral fins supported on a highly characteristic fan- shaped base. The species may be divided into two groups, those which form only the Br2 photophores and those which develop additional photophores during the larval period. In the first group the elongate larva of M. punctatum (Figure 5C) has stalked eyes and a slightly aliform pectoral fin base, reminiscent of Symbolophorus larvae, and may be the closest relative of that genus among the species of Myctophum. A closely related species, M. nitidulum, is also stalk-eyed, but is deeper-bodied, more heavily pigmented, and has a more fan-shaped pectoral fin base (Figure 5D). It is obvious from our studies thatM. nitidulum is one member of a complex, that includes M. affine (not illustrated) and several other species. The lightly pigmented larva of M. phengodes has only a sug- gestion of stalked eyes but is similar in body shape toM. nitidulum (Figure 5E). The larval characters substantiate Paxton's (1972) decision to abolish the genus Ctenoscopelus, established for this species by Fraser-Brunner (1949). The other major group of Myctophum is charac- terized by the appearance of the Dn photophore anterior to the eye, usually early in the larval period. These species fall into three rather distinct species groups on the basis of body and eye shape. The first is a group of four rotund broad-headed species, which have large unstalked eyes sub- tended by a short mass of choroid tissue. Of these, the larvae of M. asperum are the most heavily pigmented, particularly on the body (Figure 6A). Pigment is confined to the head in M. obtusirostre, is heavy under the posterior part of the gut in FISHERY BULLETIN; VOL. 72. NO. 2 Myctophum sp. (possibly brachygnathum) and is developed on the jaws, branchistegal membrane and lower part of the pectoral fin base in Myc- tophum sp. (possibly /issKnoui) as seen in Figure 6B-D. The latter three species form the PLO photophores on the pectoral fin base soon after the appearance of the Dn organs (Table 2). Nafpaktitis (1973) has listed a number of characters for distinguishing adult M. ob- tusirostre from M. brachygnathum. He showed that M. pristilepis is a synonym of M. brachyg- nathum. The status of M. imperceptum Bekker and Borodulina has yet to be determined. A second larval type is represented by M. selenops (Figure 7A) and a closely related species restricted to the Indian Ocean and Persian Gulf for which we can find no adult (Figure 7B). In these rotund species, the head is relatively longer and narrower than in the previous group and the slightly stalked eyes are narrower and bear more elongate choroid tissue. The two species differ in that the eyes of the unnamed larva are more definitely stalked than in M. selenops. Also the pigment pattern is markedly different, as is the size at which photophores appear. We have care- fully examined larvae of M. selenops from the At- lantic, Indian, and Pacific Oceans, find them to be identical in all three oceans, and seriously ques- tion Wisner's (1971) allocation of the Hawaiian population as a distinct species, based on slight differences in relative eye size and SAO photo- phore orientation. The third type of larvae that develop the Dn photophores is represented by M. spinosum (Figure 7C) andM. lychnobium (Figure 7D). These are elongate fusiform larvae with moderately nar- row unstalked eyes, underlain by a pronounced choroid mass. M. spinosum is the more slender of the two and is extremely heavily pigmented, espe- cially in older larvae. Pigmentation in M. lych- nobium is confined to that in the illustrated Table 2. — Sequence of photophore formation in species oCMyctophum that form two or more pairs during the larval stage. Size range Size at first to rmation Size at Species (mm) (mm) transformation Br; Dn PLO PO, (mm) M. asperum ca. 3.0-9.8 42 4.6 9.8 _ Early transf. 1 1.4 M. obtusirostre ca. 3.0-8.9 3.8 4.0 ca. 7.1 8.9 Late transf. 12.5 M. sp. (possibly fissunovi) ca. 3.0-7.1 4.1 4.1 7.1 — M. sp. (possibly brachygnathum) 6.0-11.4 6.0 6.0 ca. 9.0 ca. 9.0 Late transf. 13.8 M. lychnobium 3.5-12.1 ca 60 6.3 12.1 — Late transf. 14.2 M. spinosum 3.5-13.7 ca 5.5 7.2 13.7 — Late transf. 14.5 M. selenops 3.5-7.5 5.1 5.1 6.2 7.5 Late transf. 11.4 M. sp. 40-9 1 ca 70 9 1 — — — 400 MOSER and AHLSTROM: ROLE OF LARVAE IN SYSTEMATICS ^=^^^m^-m f.i:i'.-''- ^■-^^ii^^ ^*^i^.: Figure 6.— Larvae of Myctophum. A. M. asperum, 6.8 mm; B. M. obtusirostre , 7.6 mm; C. M. sp. (possibly brachygnathum), 7.5 mm; D. M. sp. ipossihiy fissunovi), 7.4 mm. 401 FISHERY BULLETIN: VOL. 72. NO. 2 ^^^:; ^■^^';n> )) n_) //in) ■! . ; J , ,, -■— J^ ' ■"* ir^zh-L^ Figure 7. — Larvae oi Myctophum. A. M. selenops. 7.8 mm; B. M. sp., 9.1 mm; C. M. spinosum, 9.0 mm; D. M. lychnobium, 9.5 mm. 402 MOSER and AHl.STROM: ROLE OF LARVAE IN SYSTEMATICS specimen. Only larvae of M. lychnobium have been taken in the eastern Pacific, whereas both species have been taken in the central and west- ern Pacific and in the Indian Ocean. Taxonomists dealing with adult characters only, have placed M. lychnobium in synonymy with M. spinosum but the distinctiveness of the larvae suggests that the adult characters should be reexamined. The larvae ofM. spinosum andM. lychnobium, although clearly developing the Dn pair of photo- phores, resemble the larvae of M. punctatum in body shape and pigmentation, a species which does not develop the Dn as larvae. Actually, there are some common characters of pigmentation and eye structure which appear in all of the groups of Myctophum species described above. What we ap- pear to be dealing with is a mosaic of larval characters in a highly complex genus. The tax- onomy of Myctophum presently is confused; our work on the larvae should help define the number of species in the genus and, perhaps, adult charac- ters will emerge that can be combined with larval characters to define the phyletic lines within the genus. Larvae of the four genera known collectively as the slendertailed myctophids are shown in Figure 8. Quite obviously there are two highly divergent generic pairs. Loweina and Tarletonbeania are characterized by large oval eyes, posterior place- ment of median fins to accommodate the immense fin fold, and elongated lower pectoral rays bearing spatulate processes. Gonichthys and Centrobran- chus are characterized by a deep but markedly compressed head and body and small narrow eyes with extremely elongate choroid tissue. As stated earlier, the larval characters suggest strongly that the two generic pairs are not closely related and should not be grouped into a tribe. The Gonichthys-Centrobranchus pair is similar in eye shape and gut shape to some species of Myc- tophum, however no species o{ Myctophum even approaches this pair in body shape. The characters of the other pair are so divergent as to give no clue of their affinities within the subfamily Myctophinae. THE SUBFAMILY LAMPANYCTINAE The subfamily Lampanyctinae is considerably larger than the Myctophinae; it contains about 19 genera and 200-250 species compared with 12 genera and about 75 species in the Myctophinae. Paxton (1972) divided the genera into four tribes on the basis of a combination of osteological fea- tures and characters of the photophores. In a pre- vious paper (Moser and Ahlstrom, 1972) we dis- cussed Paxton's placement of genera in these tribes and indicated that the larval characters suggested a somewhat different distribution of genera among the four tribes. For the purposes of this discussion the tribes referred to here are those suggested by the larval characters. In general, the larvae of the Lampanyctinae are much less diverse in larval characters and specializations than are the larvae of the Myc- tophinae, although exceptions to this may be found in two of the lampanyctine tribes, the Diaphini and the Lampanyctini. The tribe Diaphini is made up of two genera — Diaphus contains about 50 species and Lobian- chia has 3 species. Both genera develop photo- phores, in addition to the Br2, during the larval period; in fact more are developed in Diaphus than in any other lanternfish genus. There are two basic larval types in Diaphus (Figure 9A, B). One has a slender body, small head, and a series of persistent melanophores on the ventral midline of the tail. The other type has a deeper body, bulbous head, and a single persis- tent ventral tail melanophore, or none. It is excep- tional for larvae of either type to develop pigment on the head and it never occurs between the eyes, as is common in Lampanyctus. Both types do form embedded melanophores at the base of the caudal fin rays. The slender type is restricted to the species that develop a suborbital photophore as adults [Diaphus sensu stricto of Fraser-Brunner, 1949) and is represented in Figure 9A by D. theta. The stubby type is represented by D. pacificus (Figure 9B). The specimens illustrated for the two species are rather early larval stages which have not yet formed their larval photophores, other than the Br2. The first additional pair to form in both types is the PO5 and then the POi (Table 3). The large genus Diaphus, except for the Atlantic species ably reviewed by Nafpaktitis (1968), is in a state of taxonomic confusion. Various workers (Fraser- Brunner, 1949; Bolin, 1959) have attempted to split the genus into smaller, more cohesive groups; the larval evidence would suggest that at least two divergent groups are present. The larvae of the three species ofLobianchia are 403 FISHERY BULLETIN: VOL. 72. NO. 2 1 Figure 8.— Larvae of Gonichthyini. A. Loweina rara, 17.6 mm; B. Tarletonbeania crenularis, 18.9 mm; C. Gonichthys tenuiculus. 7.7 mm; D. Centrobranchus choerocephalus, 7.3 mm. 404 MOSER and AHLSTROM: ROLE OF LARVAE IN SYSTEMATICS J*=P^£ Figure 9. — Larvae ofDiaphus and Lobianchia. A. D. theta, 6.9 mm; B. D. pacificus, 5.2 mm; C. L. urolampus, 7.2 mm; D. L. gemellari, 6.7 mm; E. L. dofleini, 8.2 mm. 405 FISHERY BULLETIN: VOL. 72. NO. 2 Table 3. — Sequence of photophore formation in larvae of two species of Diaphus. Species Size larva (mm) Photophores No. of photophore pairs Smallest luvenile (mm) D. theta 6-2 Bra PO5 2 ca. 12.0 7.6 Br2 PO5 PO, 3 8.2 Br2 PO5 PO1 VO1 4 8.6 9.0 Br2 PO5 PO1 VO, PO2 Op2 Br2 PCs PO1 VOi VO, PO2 Op2 PO3 PO4 VO5 6 9 9.2 Br2 PCs PO1 VOi PO2 Op2 PO3 PO4 VO5 VLO 10 D. pacificus 5.7 6.2 6.5 7.5 Br2 PCs PO. Br2 PO5 PO1 PO2 PVO1 Br2 PO5 PO, PO2 PVO, PO3 Br2 PO; PO, PO2 PVO, PO3 VO, 3 5 6 7 9.8 deep-bodied, have large broad heads, and are eas- ily identified by their unique wing-shaped pec- toral fins (Figure 9C-E). The larvae of all three species are heavily pigmented and develop the Br2, POi , and PO5 photophores sequentially. In L. urolampus (Figure 9C) and L. gemellari (Figure 9D) the eyes are large and nearly round and the lower pectoral rays are delayed in developing. In L. dofleini the lower pectoral rays develop along with the produced upper rays and the eye is com- pletely different (Figure 9E). With its narrow el- liptical shape and unique squarish mass of choroid tissue, it is the single obvious exception to the rule of narrow eyes in the subfamily Myctophinae and rounded eyes in the Lampanyctinae. All other lar- val characters identify this species as a Lobian- chia, and we conclude that the narrowing of the eye in this species occurred independently as a secondary adaptation. In our view the tribe Lampanyctini contains the genera Lampanyctus, Triphoturus, Steno- brachius, and Paruilux. As recently as Fraser- Brunner's (1949) review of the family Myc- toi)hidae, Lampanyctus was still a catchall genus with a number of disparate subgenera. Since then the subgenera Stenobrachius, Triphoturus, and Lepidophanes have been removed from Lam- panyctus and afforded generic status. Lepido- phanes has been further split into the genera Lepidophanes and Bolinichthys. All of the separated genera have distinctive larval morphs. With their removal, the species oi Lampanyctus form a more coherent assemblage of 40-50 species, and despite the diversity of larval specializations encountered in the genus, there is a central morph and pattern of larval development. Lampanyctus larvae are deep-bodied and bigheaded. In older larvae characteristic pigment can develop at a variety of locations such as the tip of the lower jaw, between the eyes, the back of the head, the side of the head, the adipose fin, the pectoral fin, internally in the region of the cleithra, and along the myosepta. The pigment patterns are of prime importance in identifying the larvae to species. There are several rather distinct larval types in Lampanyctus. One of these consists of a group of species whose adults are characterized by having the pectoral fins much reduced or even absent, and has been separated recently as a distinct genus Paralampanyctus by Kotthaus (1972) with P. niger as type. Previously, Giinther (1887) had proposed the generic name Nannobrachium for this species and this has priority over Paralam- panyctus (John Paxton, pers. commun.). There is a remarkable trend of jaw specialization in the lar- vae of this group (Figure 10). The larva of L. ritteri has jaws of moderate length and the other species shown have progressively longer jaws with more prominent teeth, particularly anteriorly. This trend culminates in the larva of Lampanyctus sp. (possibly achirus) which somewhat resembles a larval billfish. This species will lack the pectoral fin in juveniles and adults, even though it is well developed in the larvae. The pectoral fins are also large inL. regalis andL. niger larvae, but will be small and weakly developed in adults. This dis- parity is even more apparent in another eastern Pacific species, which lacks pectoral fins as an adult, but whose larvae have the largest pectoral fins with the highest number of rays that we have encountered among Lampanyctus larvae. Other less spectacular specializations appear in the other subgroups 0^ Lampanyctus, but it appears that the larval characters will be helpful in defining the species composition of the several subgenera. Representatives of other genera of Lampanyc- tini, Triphoturus, Stenobrachius, andParvilux are illustrated in Figure llA-C. Small larvae of Triphoturus and Stenobrachius have a row of melanophores along the ventral margin of the tail 406 MOSER and AHLSTROM: ROLE OF LARVAE IN SYSTEMATICS ^/^///;'-^//^^ ^r?". Figure 10. — Larvae of Lampanyctus. A. L. ritteri, 10.1 mm; B. L. regalis, 9.1 mm; C. L. njger, 8.7 mm; D. L. sp. (possibly achirus), 13.4 mm. 407 FISHERY BULLETIN: VOL. 72, NO. 2 Figure 11. — Larvae of Lampanyctini and Gymnoscopelini. A. Triphoturus mexicanus. 10.5 mm; B. Stenobrachius leucopsarus, 10.4 mm; C. Parvilux ingens, 14.4 mm; D. Bolinichthys supralateralis , 9.4 mm; E. Ceratoscopelus townsendi, 16.6 mm. 408 MOSER and AH I STROM: ROLE OF LARVAE IN S't STEMATICS but these coalesce into one or two spots in mid- stage larvae. Triphoturus larvae are character- ized further by their distinctive head shape and by the series of melanophores along the ventral mid- line below the gut. Stenobrachius larvae add con- siderable pigment late in the larval period, par- ticularly along the dorsum and on the myosepta of the trunk. The larvae of Parvilux are distinct in shape and pigmentation. Paxton (1972) placed this genus in Lampanyctus based on osteological characters. In certain photophore arrangements, however, particularly in the posterior placement of the VLO and the nonangulate arrangement of the SAO, the genus appears to us to be more closely related to Stenobrachius than to Lam- panyctus. These characters in addition to the dis- tinctness of the larvae would suggest that the va- lidity of Parvilux should be reconsidered. The tribe Gymnoscopelini judged from larval and/or adult characters contains a dozen genera {Notoscopelus, Lampichthys, Scopelopsis, Cerato- scopelus. Lepidophanes. Bolinichthys, Lampadena, Taaningichthys, Dorsadena, Lampanyctodes, Gymnoscopelus, and Hintonia). The larvae of these genera are united by a group of common characters, including a distinctive, usually slender, body outline, a series of melanophores on the dorsal and ventral midlines of the tail (in most genera), and the development of a group of photophores during the larval period, most notably the PO5, FLO, and Vn. The larvae of this tribe were treated extensively in a previous paper with representative larvae illustrated for 10 of the 12 genera (Moser and Ahlstrom, 1972). Ad- ditional species of Bolinichthys (B. supralateralis, Figure IID), Ceratoscopelus (C. townsendi, Figure HE), Lampadena (L. luminosa. Figure 12B), Lepidophanes (L. gaussi. Figure 12C) are illus- trated herein. Illustrations of Notoscopelus re- splendens (Figure 12 A) and Scopelopsis mul- tipunctatus (Figure 12D) are included for com- parative purposes. It need only be mentioned here that the clusters of closely related genera within this tribe are readily apparent from examining the larval characters, especially the sequence of photophore development, and these groupings agree closely with those established on the basis of adult characters. The species Notolychnus valdiviae has so many unique adult characters that Paxton (1972) as- signed it to the monotypic tribe Notolychnini. Likewise the larva has a number of unusual characters (Figure 12E). The shape of the eye is variable from specimen to specimen; it can be nar- row and elliptical or nearly round, but most typi- cally would be classified as irregular in shape. The shape of the head, body, and gut is unusual and distinctive. The larval characters are of little help in elucidating the affinities of this species within the Myctophidae and, when added to the list of unique adult characters, only magnify the prob- lem. It would seem to make just as much sense to establish a separate subfamily for Notolychnus as to place it in a monotypic tribe in the subfamily Lampanyctinae. The larvae illustrated in this paper comprise 55 species representing 24 genera. Illustrations are included for larvae of 11 of the 12 genera in the subfamily Myctophinae; not included are illustra- tions of Diogenichthys (see Moser and Ahlstrom, 1970 for D. laternatus and D. atlanticus). In the subfamily Lampanyctinae larvae are illustrated for 13 of the 19 genera. The omitted genera {Lam- pichthys, Lampanyctodes, Gymnoscopelus, and Tanningichthys), all from the tribe Gymnoscope- lini, are illustrated in Moser and Ahlstrom (1972). Larvae of Hintonia and Dorsadena have not yet been identified. SOME EVOLUTIONARY CONSIDERATIONS With this brief review of lanternfish larvae completed, let us now turn to an interesting prob- lem of myctophid evolution to which study of the larvae may contribute importantly — the evolu- tion of photophore pattern. With a single excep- tion, all adult myctophids have two conspicuous rows of photophores that extend the length of the body on each side of the ventral midline. The photophores are grouped and positioned in a definite and often diagnostic pattern. Also, lanternfishes have a specific pattern of photo- phores on the sides of the body, below the lateral line, and on the ventral aspect of the head. The exception is Taaningichthys paurolychnus, which appears to lack body photophores entirely. In ad- dition to these photophores, some lanternfish gen- era have photophores positioned in a pattern above the lateral line and some have small "sec- ondary" photophores distributed more generally over regions of the body and head. Another type of luminous structure present on most myctophids are discrete glands located at the caudal peduncle. Typically, these are sexually dimorphic in charac- ter and, doubtless, play some part in courtship 409 FISHERY BULLETIN: VOL. 72. NO. 2 >^^; L^i=^ k ' -f|^^ -sa- '■•^-; ^^=^^Si:j;^f5^i::JL^ Figure 12.— Larvae of Gymnoscopelini and Notolychnini. A. Notoscopelus resplendens, 11.2 mm; B. Lampadena luminosa, 12.8 mm; C. Lepidophanes gaussi, 13.5 mm; D. Scopelopsis multipunctatus, 17.5 mm; E. Notolychnus valdiviae, 9.2 mm. 410 MOSER and AHl STROM: ROLE OF LARVAE IN SYSTEMATICS behavior. Finally, some myctophids have small patches of soft whitish, apparently luminous, tis- sue located at various regions of the body. The most popular speculation as to the possible function of the patterns of photophores and lumin- ous scales is that they function in species recogni- tion (see McAllister, 1967). An explanation for the universality of the two ventral rows was postu- lated by Clarke (1963). His suggestion that these downward directed rows emit a continuous light of ambient wavelength, which conceals the fish from deeper-living predators by countershading, has much appeal. We have long been interested in the mechanism by which such patterns of photophores could have evolved and believe we have gained some insight into this mechanism through our studies of the larval stages. Our proposal, as expressed in an earlier paper (Moser and Ahlstrom, 1972), is that ancestral myctophids had a generalized arrange- ment of unspecialized photophores, one at the posterior margin of each scale pocket, and a group of similar photophores on the head. We further proposed that the specific photophore patterns of contemporary myctophids evolved through pro- gressive enlargement and specialization of certain photophores of the generalized pattern and con- current diminution or loss of the unspecialized photophores. This idea came to us upon discover- ing the remarkable transforming specimens of Scopelopsis multipunctatus, the adults of which have a small photophore at each scale pocket and a group of photophores on the head. In the adults, the "primary" organs can be distinguished only by their modified lens-bearing scales, but in the transforming specimens (Figure IID) the primary photophores stand out clearly as enlarged mem- bers of the meristic series of light organs. It struck us that a similar arrangement of photophores might have existed in the adults of an ancestral species, and led to the development of our ideas on the evolution of photophore pattern. Our theory was further strengthened by neurological findings and by what we feel are inherent weaknesses in Bolin's ( 1939) and Fraser-Brunner's ( 1949) theory that photophore patterns evolved by the upward migration of organs from ventral rows of photo- phores. Viewed from the standpoint of our theory the subfamily Myctophinae would be considered highly specialized, since it is here that diminution of secondary photophores has reached its highest degree; they are totally lacking in the subfamily. The individual "primary" photophores are typi- cally highly developed and concentrated ventrally on the body. The ventral location of photophores in Myctophinae is probably related to their habitat. That is, they are generally shallow-living active fishes that have well-developed gas bladders and it is plausible that concentration of photophores ventrally on the body evolved as an adaptation for countershading and protection from deeper-living predators. This view of the Myctophinae is com- pletely contrary to those previously held for this subfamily. On the basis of the "upward migration" theory of photophore evolution, myctophines were thought to be primitive unspecialized forms. For- merly, we too subscribed to this view, and con- trasting the then supposed primitive features such as low photophore position and short jaws of the adults with the highly specialized and diverse features of the larvae, we proposed that the evolutionary pace had differed in the larval and adult stages of the subfamily. Our altered opinion would view both larvae and adults of the Myc- tophinae as highly advanced and would interpret the low photophores, prominent gas bladders, short jaws, and often narrow caudal peduncles as specialized adaptations of active surface-dwelling fishes. Our view of the Lampanyctinae must also be revamped. Formerly we considered the diverse and often dorsally oriented pattern of photophores and accessary luminous tissue to be highly specialized features. Possibly, the luminous scalelike patches and luminous glands are specialized adaptations, but we feel that the pres- ence of small secondary photophores and the dor- sal positioning of primary photophores in many of the genera, indicate a retention of the ancestral condition. The Lampanyctinae are generally deeper-living than the Myctophinae and many genera are lethargic fishes that rest vertically in the water column (Barham, 1970). In deeper- living fishes with such a behavior pattern there would be little evolutionary advantage in having ventrally concentrated photophores, and the fat- invested swim bladders and long jaws typical of many genera could have evolved in relation to habitat and activity pattern. It is interesting that the most obvious exception in the subfamily, the Diaphini, are active, often surface-dwelling fishes with relatively short jaws and ventrally concen- trated photophores. It is obvious from the present paper that the larvae of Lampanyctinae exhibit much less diversity than the Myctophinae, but we 411 FISHERY BUllFTIN: VOL. 72. NO. 2 no longer view the adult myctophines as being more "primitive" than the adult lampanyctines. We feel that the adults of both subfamilies are equally specialized and that these specializations are basically related to their particular habitat. In summary, thorough study of the larvae of a teleost family such as the Myctophidae can be most helpful in species validation, in analyzing affinities at all taxon levels, and in assessing phylogenetic lineages. Also, the above discussion would indicate that larval studies can provide in- teresting insights into the major directions of evolution within a family offish. ACKNOWLEDGMENTS George Mattson executed 15 of the illustrations (Figures IE, 4A, 5A and D, 8A-D, lOA, B, and D, llA and E, and 12A and E) and we thank him for his efforts. The remaining illustrations were made by one of us (H. G. Moser). Larval specimens came from a variety of sources and we are especially indebted to the following persons for their gener- ous provision of material: E. Bertelsen and J. Nielsen, Zoological Museum, Copenhagen; N. B. Marshall and A. Wheeler, British Museum; W. Nellen, Institute fiir meereskunde, Kiel, Ger- many; R. McGinnis and B. Nafpaktitis, Univer- sity of Southern California (USC); R. J. Laven- berg, Los Angeles County Museum; R. Rosenblatt and R. Wisner, Scripps Institution of Oceanog- raphy (SIO); T. Clarke and J. Miller, University of Hawaii; W. Freihofer, California Academy of Sci- ences. We would like to thank B. Nafpaktitis and R. McGinnis, USC; R. Wisner, SIO; J. Paxton, Australian Museum, Sydney; and G. Krefft, Fisheries Institute, Hamburg, Germany, for shar- ing their vast knowledge of lanternfishes with us in numerous discussions. Discussions with N. B. Marshall, British Museum; B. Robison, Stanford University; and A. Kendall, Middle Atlantic Coastal Fisheries Center, National Marine Fisheries Service (NMFS), Sandy Hook, have been helpful in stimulating some of the ideas put forth herein. We appreciate the able technical assis- tance of Elaine Sandknop, Elizabeth Stevens, and Patricia Lowery, Southwest Fisheries Center La Jolla Laboratory, NMFS. Kenneth Raymond kindly lettered the illustrations. LITERATURE CITED Barham, E. G. 1970. Deep-sea fishes lethargy and vertical orientation. In G. B. Farquhar (editor), Proceedings of an international symposium on biological sound scattering in the ocean, p. 100-118. Maury Center for Ocean Science, Department of the Navy, Wash., D.C. MC Rep. 005. Becker, V. E. 1965. Lanternfishes of the genus Hygop/ijzm (Myctophidae, Pisces). Systematics and distribution. Tr. Inst. Okeanol. Akad. Nauk SSSR 80:62-103. (In Russ., Engl. Transl. No. 45, Natl. Mar. Fish. Serv., Syst. Lab., Wash., D.C.) Benirschke, K., and T. C. Hsu (editors). 1971. An atlas of mammalian chromosomes. Vol. 5 and 6. Springer-Verlag, N.Y., 200 p. Bertelsen, E. 1951. The ceratioid fishes. Ontogeny, taxonomy, distribu- tion and biology. Dana Rep., Carlsberg Found. 39, 276 p. BoLiN, R. L. 1939. A review of the myctophid fishes of the Pacific coast of the United States and of Lower California. Stanford Ichthyol. Bull. 1:89-156. 1959. Iniomi Myctophidae. Rep. Sci. Results "Michael Sars" North Atl. Deep-Sea Exped. 1910. 4, 2(7):l-45. Castle, P. H. J. 1969. An index and bibliography of eel larvae. J. L. B. Smith Inst. Ichthyol., Rhodes Univ., S. Afr. Spec. Publ. 7, 121 p. Clarke, W. D. 1963. Function of bioluminescence in mesopelagic organisms. Nature (Lond.) 198:1244-1246. De Ligny, W. 1969. Serological and biochemical studies on fish populations. Oceanogr. Mar. Biol. Annu. Rev. 7:411-513. Ebeling, a. W., N. B. Atkin, and P. Y. Setzer. 1971. Genome sizes of teleostean fishes: increases in some deep-sea species. Am. Nat. 105:549-561. Ege, V. 1953. Paralepididae I. (Paralepis and Lestidium). Taxonomy, ontogeny, phylogency and distribution. Dana Rep., Carlsberg Found. 40, 184 p. 1957. Paralepididae II. (Macroparalepis). Taxonomy, on- togeny, phylogeny and distribution. Dana Rep., Carlsberg Found. 43, 101 p. Fish, M. P., and W. H. Mowbray. 1970. Sounds of Western North Atlantic fishes. Johns Hopkins Press, Baltimore, 207 p. Fraser-Brunner, a. 1949. A classification of the fishes of the family Myctophidae. Proc. Zool. Soc. Lond. 118:1019-1106. Greenwood, P. H., D. E. Rosen, S. H. Weitzman, and G. S. Myers. 1966. Phyletic studies of teleostean fishes, with a provi- sional classification of living forms. Bull. Am. Mus. Nat. Hist. 131:341-455. GUNTHER, A. 1887. Report on the deep-sea fishes collected by H.M.S. Challenger during the years 1873-76. Rep. Sci. Res. Voy- age H.M.S. Challenger 22:335 p., 73 plates. Johnson, R. K. 1971. A revision of the alepisauroid family Scopelarchidae (Pisces: Myctophiformes). Ph.D. Thesis, Scripps Inst. Oceanogr., La Jolla, 474 p. KOTTHAUS, A. 1972. Die meso-und bathypelagischen Fische der Meteor-Rossbreiten-Expedition 1970 (2. und 3. Fahr- tabschnitt). "Meteor" Forsch.-Ergeb. Dll:l-28. 412 MOSER and AHI STROM: ROLE OF LARVAE IN SYSTEMATICS McAllister, D. E. 1967. The significance of ventral bioluminescence in fishes. J. Fish. Res. Board Can. 24:537-554. MosER, H. G., AND E. H. Ahlstrom. 1970. Development of lanternfishes (family Myctophidae) in the California Current. Part I. Species with narrow- eyed larvae. Bull. Los Ang. Cty. Mus. Nat. Hist. Sci. 7, 145 p. 1972. Development of the lanternfish, Scopelopsis mul- tipunctatus Brauer 1906, with a discussion of its phylogenetic position in the family Myctophidae and its role in a proposed mechanism for the evolution of photo- phore patterns in lanternfishes. Fish. Bull., U.S. 70:541-564. Nafpaktitis. B. G. 1968. Taxonomy and distribution of the lanternfishes, gen- era Lobianchia and Diaphus. in the North Atlantic. Dana Rep., Carlsberg Found. 73, 131 p. 1973. A review of the lanternfishes (family Myctophidae) described by A. Vedel Taning. Dana Rep., Carlsberg Found. 83, 46 p. Ohno, S. 1970. The enormous diversity in genome sizes offish as a reflection of nature's extensive experiments with gene duplication. Trans. Am. Fish. Soc. 99:120-130. Paxton, J. R. 1972. Osteology and relationships of the lanternfishes (Family Myctophidae). Bull. Los Ang. Cty. Mus. Nat. Hist. Sci. 13, 81 p. WiSNER, R. L. 1963. A new genus and species of myctophid fish from the South-Central Pacific Ocean, with notes on related genera and the designation of a new tribe, Electronini. Copeia 1963:24-28. 197 1 . Descriptions of eight new species of myctophid fishes from the eastern Pacific Ocean. Copeia 1971:39-54. 413 4 EARLY DEVELOPMENT OF FIVE CARANGID FISHES OF THE GULF OF MEXICO AND THE SOUTH ATLANTIC COAST OF THE UNITED STATES Virginia L. Aprieto' ABSTRACT Larvae of round scad, Decapterus punctatus; rainbow runner, Elagatis bipinnulata; banded rudderfish, Seriola zonata; lookdown, Selene vomer; and leatherjacket, Oligoplites saurus, collected in the Gulf of Mexico and off the south Atlantic coast of the United States are described and illustrated. Larvae 2 to 3 mm long show general family characteristics but generic and specific characters are differentiated in later stages. Morphological features including supraoccipital crest, thickness of the first interhemal spine, and body indices; meristic characters; mode of development and modification of the dorsal and pelvic fins; and patterns of pigmentation are useful in distinguishing the family, genera, and species. Information on distribution and spawning is included. The family Carangidae consists of about 200 species of fishes which vary widely in form and are distributed in tropical and subtropical waters. Various attempts by authors to divide the family into subfamilies proved unsatisfactory in view of the numerous, weak characters used for this pur- pose and the presence of many transition genera which did not permit delineation of groups which may have been proposed as subfamilies (Gins- burg, 1952). Twenty-eight species of carangids have been found along the Atlantic and Gulf coasts of the United States (Table 1). The larvae of some of these species occurred frequently in plankton and nekton collected in the Gulf of Mexico and off the south Atlantic coast of the United States during the multiship cruises in October to November 1970 and May to October 1971 during continuing surveys of marine biological communities con- ducted by the National Marine Fisheries Service (Southeast Fisheries Center) and cooperating agencies. The larval development of five species is described and illustrated in the present work. Only a few studies dealing with early life his- tory stages of North Atlantic carangids have been carried out by American workers. Hildebrand and Cable (1930) described larvae and early juveniles of Decapterus punctatus and Seriola dumerili. 'College of Fisheries, University of the Philippines, Quezon City, Philippines. Fields (1962) described postlarvae of these species of Trachinotus: T. carolinus, T. falcatus, and T. glaucus; McKenney, Alexander, and Voss (1958) described a rather complete larval series of Caranx crysos; Berry (1959) described late-stage larvae and juveniles of five species of Caranx, including: C. crysos, C. bartholomaei, C. ruber, C. hippos, and C latus. None of the above series in- cluded eggs or yolk-sac larvae and the majority lacked early-stage larvae as well. Over a third of the carangids that occur off the eastern United States are wide-ranging species, and early life history series had been described from other areas for the following: Selar cru- menophthalmus by Delsman (1926) and Devane- san and Chidambaram (1941), Naucrates ductor by Sanzo (1931), Caranx dentex by Schnakenbeck (1931), Seriola dumerili by Sanzo (1933), Trachinotus glaucus by de Gaetani ( 1940), Caranx hippos by Chacko (1950) and Subrahmanyam (1964), Chloroscombrus chrysurus and Alectis crinitus by Aboussouan (1968), and Elagatis bipinnulata by Okiyama (1970). Hence, early life history series — some complete, some fragmen- tary— were known for 16 of 28 species of caran- gids that occur along the Atlantic and Gulf coasts of the United States. A proper understanding of the early life history of fishes, particularly those of species important to man, can never be overemphasized. The presence of larvae is indicative of recent spawning, and Manuscript accepted August 1973. FISHERY BULLETIN; VOL. 72, NO. 2, 1974. 415 FISHERY BULLETIN: VOL. 72. NO. 2 Table 1.— Meristic characters of adult carangids of the Gulf and Atlantic coasts of the United States. Pectoral Verte- Species Dorsal fin An al fin fin GMI rakers brae Source Alectis crinitus (VII)O; 1,18-19 (11)0; 1 , 15-16 18-20 5- 6 + 14-16 _ Ginsburg, 1952 Alectis crinitus - - - - 24 Starks, 1911 Caranx bartholomaei VIM : 1. 25-28 II: 1 , 21-24 1. 19-21 6- 9+18-21 - Berry, 1959 Caranx bartholomaei - - - - 24 Miller and Jorgensen 1973 Caranx crysos VIII ; 1, 22-25 II: 1 , 19-21 1, 19-23 10-14 + 23-28 - Berry. 1959 Caranx crysos - - - - 25 Miller and Jorgensen 1973 Caranx crysos VIII : 1, 23-25 - - - McKenney et aL, 1958 Caranx crysos - - - - 25 Starks. 1911 Caranx hippos VIII ; 1, 19-21 II: 1 16-17 1, 19-20 6- 9 + 22-27 - Berry, 1959 Caranx hippos - - - - 24 Lane, 1965 Caranx latus VIII 1, 19-22 II; 1 16-18 1. 18-20 6- 7+16-18 - Berry, 1959 Caranx latus 20-21 16-18 18-20 16 + 17 24 Lane, 1965 Caranx lugubris VIM 1, 22 11; 1 19 1, 19 6 + 20 - Berry, 1959 Caranx lugubris - - - - 24 Lane. 1965 Caranx lugubris VIM 1,22 II: 1 18 - - - Fowler, 1936 Caranx ruber VIII 1, 26-30 II; 1 23-26 1, 18-21 10-14 + 31-35 - Berry, 1959 Caranx ruber - - - - 24 Miller and Jorgensen, 1973 Caranx dentex VIM 1, 25-26 II: 1 21-23 1, 19-20 11-13 + 26-28 - Berry. 1959 Chloroscombrus chrysurus VIII 1, 26-28 II: 1 25-27 19-20 9-11+31-35 - Ginsburg, 1952 Chloroscombrus chrysurus - - - - 24 Miller and Jorgensen, 1973 Chloroscombrus chrysurus VII-VIII 1. 24-26 II: 1 25-26 - 9-10 + 32-35 - Fowler, 1936 Chloroscombrus chrysurus - - - - 24 Starks, 1911 Decapterus macarellus VIII 1,31-37 II; 1 27-31 1, 21-23 9-13 + 32-39 24 Berry, 1968 Decapterus punctatus VIII 1, 29-34 II; 1 25-30 1, 18-20 11-16 + 32-44 25 Berry. 1968 Decapterus punctatus VIII 1, 28-32 II; 1 25-27 19-21 12-15 + 34-40 - Ginsburg, 1952 Decapterus punctatus VIII 1, 27-31 II; 1 24-27 - 12-15 + 35-40 - Fowler. 1936 Decapterus tabi VIII 1. 29-34 II; 1 24-27 1, 20-22 10-12 + 30-33 24 Berry, 1968 Elagatis bipinnulata V -1. 25-26 O-ll; 1 16-17 20-21 10-11+25-26 - Ginsburg, 1952 Elagatis bipinnulata V-VI 1, 25-30 II 18-22 1, 18-21 9-12 + 25-29 24 Berry, 1969 Hemicaranx amblyrhynchus VII-VIII 1, 27-29 II; 1 23-25 19-22 8-10 + 19-23 - Ginsburg, 1952 Hemicaranx amblyrhynchus - - - - 26 Miller and Jorgensen, 1973 Naucrates ductor lll-IV; 1 -II. 26-28 O-ll; II 15-16 - 6^18-19 - Fowler, 1936 Naucrates ductor - - - - 25 Starks, 1911 Oligoplites saurus V-VI 1, 19-21 11; 1 18-21 15-17 6- 9 + 13-15 - Ginsburg, 1952 Oligoplites saurus - - - - 26 Miller and Jorgensen, 1973 Selar crumenophlhalmus VIII 1, 24-26 II; 1 21-23 20-22 9-11+27-30 - Ginsburg, 1952 Selar crumenophlhalmus - - - - 24 Miller and Jorgensen, 1973 Selar crumenophlhalmus VIM 1, 26 II; 1 22 - 10-12 + 28-31 - Fowler, 1936 Selar crumenophlhalmus - - - - 24 Starks. 1911 Selene vomer VIII 1, 21-23 0-11; 1 18-20 20-21 6- 8 + 23-27 - Ginsburg, 1952 Selene vomer - - - - 24 Miller and Jorgensen, 1973 Selene vomer VII-VIII 1, 21-23 II; 1 18-19 - 7- 8 + 24-28 - Fowler. 1936 Seriola dumerili VII 1, 30-35 II; 1 19-22 19-22 2- 3 + 11-13 - Ginsburg, 1952 Seriola dumerili - - - - 24 Miller and Jorgensen. 1973 Seriola dumerili VII 1, 29-35 - - 11-24 - Mather, 1958 Seriola fasciata VIM 1, 30-32 II; 1 19-20 19-20 7- 8+18-20 - Ginsburg, 1952 Seriola fasciata VII-VIII 1, 29-32 II; 1 18-21 - 6+15 _ Fowler, 1936 Seriola fasciata VIM 1, 28-32 - _ 22-26 _ Mather, 1958 Seriola rivoliana VII-VIII 1. 28-32 I-II: 1 19-22 19-20 7- 8+16-18 - Ginsburg, 1952 Seriola rivoliana - - - - 24 Miller and Jorgensen, 1973 Seriola rivoliana VII 1, 29 II; 1 21 - _ - Fowler, 1936 Seriola rivoliana VII 1, 27-33 - - 18-28 - Mather. 1958 Seriola zonata VII-VIII 1, 33-40 I-II: 1 19-21 16-21 2- 3 + 11-13 - Ginsburg, 1952 Seriola zonata VIII 1, 38-40 - _ 12-13 _ Mather, 1958 Seriola zonata - - - _ 24 Starks, 1911 Trachinotus carolinus V-VI 1, 23-27 II; 1 20-23 17-19 - +7-11 - Ginsburg, 1952 Trachmotus carolinus V-VI 1, 22-27 M: 1 20-23 1. 16-18 4- 7+ 6-13 _ Fields. 1962 Trachinotus carolinus - - - - 24 Starks, 1911 Trachinotus falcatus VI 1, 18-20 II; 1 17-18 18-20 - + 9-13 - Ginsburg, 1952 Trachinotus falcatus - - - - 24 Miller and Jorgensen, 1973 Trachinotus falcatus VI 1, 17-21 II; 1 16-19 1. 17-19 3- 8 + 12-14 - Fields, 1962 Trachinotus glaucus VI 1, 19-20 II: 1 16-18 16-19 - +8-12 - Ginsburg, 1952 Trachinotus glaucus VI 1, 19-20 II; 1 16-18 1, 15-19 3- 8 + 9-14 - Fields, 1962 Trachurus lathami VIII 1. 28-33 II; 1 26-30 21-22 12-14 + 34-39 _ Ginsburg. 1952 Trachurus lathami VIII 1. 30 II: 1. 28 - 15 + 36 24 Merriman. 1943 Uraspis heidi VIII 1, 29 0-1 21 23 6+14 - Ginsburg, 1952 Vomer setapinnis VIII 1. 20-23 O-ll; 1 17-19 17-19 5- 8 + 25-29 - Ginsburg, 1952 Vomer setapinnis VIII 1, 21-22 II: 1 18-20 - 6- 8 + 26-30 - Fowler, 1936 Vomer setapinnis - - - - 24 Starks, 1911 416 APRIETO: EARLY DEVELOPMENT OF FIVE CARANGID FISHES data derived from the study of larvae provide use- ful tools in gaining insight into the abundance and fluctuation of the size of spawning populations (Farris, 1961 ). Patterns of larval development and larval structures, when sufficient groups are studied, are potential keys to possible relations which often are not adequately illustrated in adult morphology and osteology. The present paper aims to contribute to the understanding of the early life stages of members of the family Caran- gidae. MATERIALS, METHODS, AND TERMINOLOGY Larvae, juveniles, and adults were largely in the collections of the Miami Laboratory, South- east Fisheries Center. The larvae and juveniles were collected with 1-m bongo plankton (Posgay, Marak, and Hennemuth, 1968) and nekton nets on board research vessels during oceanographic and biological surveys and during the routine sam- pling for larval fish in the Gulf Stream off Miami. Descriptions of vessels, cruise tracks, and sam- pling methods are available at the Miami Laboratory, Southeast Fisheries Center. Some specimens were contributed from a private collec- tion and from the fish museum of the Center. One species was raised in the marine fish larvae rear- ing system of the Rosenstiel School of Marine and Atmospheric Science, University of Miami. The larval development of the carangids in this work is based on 551 larval and early juvenile specimens ofDecapteruspunctatus, 94 ofElagatis bipinnulata, 86 of Selene vomer, 64 of Seriola zonata, and 31 of Oligoplites saurus. Meristic characters and sequence of ossification data were taken from stained and cleared specimens. The complete sequence of ossification was not ob- served, however, in Selene vomer and Oligoplites saurus on account of the lack of transforming specimens and poorly preserved materials, respec- tively. The embryological and anatomical terms and measurements used in this study follow largely those of Lagler, Bardach, and Miller ( 1962), Man- sueti and Hardy (1967), and Moser and Ahlstrom (1970). Terms for ossification are those of Starks (1911), Suzuki (1962), and Weitzman (1962). Chromatophore terminology is from Fujii (1969). However, for clarity, certain terms are defined as they relate to larvae of carangids. Growth stages beyond the yolk-sac stage are defined according to Moser and Ahlstrom (1970), and the terms prolarva and postlarva of Hubbs (1943) are not used. The larval period lasts from hatching to the attainment of juvenile characters. The transformation or metamorphosis of the lar- vae into juveniles is called the transitional period and the individuals undergoing this process are called transforming, metamorphic, or transitional specimens. The fish is a juvenile when it has the essential features of the adult, particularly the complete fin ray counts. The juvenile period ter- minates with the attainment of sexual maturity when the fish is considered an adult. The dynamic approach of Moser and Ahlstrom (1970) is adapted in the description of larval fish. Here, a complete or fairly complete series of growth stages from the smallest differentiated larvae to the juvenile is assembled, and the de- velopment of each character is traced sequen- tially. The method used for determining apparent relative abundance is based on Ahlstrom (1948). The youngest specimens collected in the plank- ton were past the yolk-sac stage. While eggs were present in the collections, identification is uncer- tain in view of the conspicuous absence of the intervening yolk-sac stages. Perhaps, the yolk sac ruptured or collapsed at capture due to mechani- cal stress. All specimens used in this study are deposited in the larval fish laboratory of the Miami Labora- tory, Southeast Fisheries Center of the National Marine Fisheries Service. DESCRIPTIONS Rainbow runner, Elagatis bipinnulata (Quoy and Gaimard) Figure 1 Literature Larval stages of this species from the Indo-Pacific oceans were illustrated and described by Okiyama (1970) who also traced their de- velopment. Berry (1969) illustrated an 18.5-mm juvenile from the Straits of Florida. Schnaken- beck (1931) illustrated an 11.5-mm larva from the Lesser Antilles under the name of Caranx hel- volus. 417 FISHERY BULLETIN: VOL. 72. NO. 2 S B o M B E o d I— I M J" a s CO CO CO a a lO i?.--. -■■■■■ 424 APRIETO: EARLY DEVELOPMENT OF FIVE CARANGID FISHES o en g S ea CO S G ^ W E M « I 01 g _^ 00 in t^ Q " J 1 3 6 J two spines fuse at the posterior wall of the abdomi- nal cavity which becomes elongated vertically. Consequently, the long and slender gut forms ver- tical loops following the shape of the abdominal cavity. The gut opening is pushed anteriorly and lies adjacent to the base of the pelvic fins. Snout- to-anus distance decreases relative to standard length. It is 56% at 2.5 mm and declines to 40% at the end of the larval period. During the early juvenile stages, snout-to-anus distance had an av- erage of 38%. The length and width of the head increases rela- tive to standard length. Head length is 31.0% in the smallest larva (2.5 mm) and does not increase substantially until the juvenile period when it attains a maximum of 41.9% at 23.9 mm. To ob- tain the true depth of the head and not the body depth at the head region, the measurement is taken from the posterior margin of the preopercle from the dorsal margin of the head to the articula- tion of the mandible and maxillary. Head depth is 100% of the head length at 2.5 to 3.2 mm. There- after, head depth exceeds head length. During the larval period, the head is deepest at 4.6 mm when it is 140% of the head length. This is, however, exceeded by the progressive deepening of the head during the transition and juvenile stages with a maximum of 182% and an average of 158%. The dorsal profile of the snout is slightly concave in the early larval period (2.5-3.8 mm) but becomes straight in older and transforming larvae. The nasal, frontal, and supraoccipital bones become markedly elongated and slope steeply, giving the head an almost vertical anterior profile. The eyes are round and large. Relative orbit diameter increases during the larval and juvenile development; it is 32% at 2.5 mm and attains a maximum of 37% at notochord flexion with an average of 31% during the larval and transition periods. In the juveniles, orbit diameter decreases to a range of 20 to 27%. The orbital and supraoccipital crests are well marked in early larval stages up to 5 mm. The crests are gradually resorbed and are vaguely vis- ible at metamorphosis. Preopercular marginal spines consist of 4 to 7 long and strong spines while the lateral surface spines are smaller and limited to the lower surface. All preopercular spines are resorbed at transformation. Scales are absent. Pigmentation The common larval pattern of pigmentation in 433 FISHERY BULLETIN: VOL. 72, NO. 2 Standard length Table 8. — Measurements (mm) of larvae and juveniles of Selene vomer. (Specimens between dashed lines are undergoing notochord flexion.) Snout-to- anus distance Head length Head depth Body depth at base of pectoral fin Snout length Orbit diameter Snout to fin origin Predorsal Prepelvic Preanal 2.5 1.4 0.78 0.78 0.80 0.25 0.25 1.0 0.7 _ 3.2 1.7 1.0 1.0 1.0 .37 32 1.1 1.2 1.7 3.5 1.8 1.1 1.2 1.3 .37 .35 1.2 1.0 1.8 3.8 1.8 1.2 1.4 1.5 .42 .42 1.2 1.35 2.0 4.0 2.0 1.2 1.5 1.5 .47 .37 1.3 1.2 2.0 4.3 2.2 1.5 1.9 1.9 .52 .50 1.5 1.6 1.9 4,4 2.1 1.5 2.0 2.1 .55 .50 1.4 1.6 1.8 4.5 2.2 1.5 2.0 2.0 .52 .45 1.4 1.5 2.0 4.6 1.8 1.5 2.1 2.1 .55 .42 1.6 1.6 2.1 48 2.6 1.7 2.0 2.1 .55 .45 1.8 1.7 2.8 5.0 2.7 1.7 2.2 2.2 .52 .47 1.8 1.9 3.0 5.3 3.0 1.7 2.1 2.3 .55 .45 1.7 2.0 3.0 5.5 2.7 2.0 2.5 2.9 .62 eo 1,8 1.8 3.1 6.1 2.8 2.0 3.0 3.2 .87 62 2.0 2.0 3.0 7.5 3.6 2.6 3.5 3.9 .90 .85 2.4 2.5 4.0 8.2 4.5 3.0 3.8 4.8 1.2 .87 2.9 3.0 4.6 '9.0 3.6 3.1 5.2 5.8 1.3 1.0 2.9 2.8 5.0 M3.5 6.7 5.2 9.5 6.2 2.2 1.7 5.5 5.5 6.2 ^23. 9 8.7 10.0 14.0 23.0 3.1 2.5 7.0 8.0 11.0 227.5 11.5 10.0 15.0 24.5 3.5 26 11,0 8.0 14.0 ^30.0 12.0 11.0 17.0 27.0 5.0 3,0 14,0 12.0 14.0 ^34.0 12.0 13.5 22.0 31.0 6.5 3.0 14.0 13.0 14.0 ^38.0 14.0 14.5 200 31.0 5.0 3.2 15.5 11.5 16.0 ^42. 5 14.0 17.0 28,0 35.0 5.5 3.9 17.0 15.0 14.0 247.0 16.0 200 30,0 35,0 80 42 16.0 18.0 17.0 'Transfornning ^Juveniles carangids, including melanophores along the bases of the dorsal and anal fins and along the lateral-midline, is present inS. vomer. In the early larvae (2.5-5.0 mm), a few melanophores develop on the tips of the jaws, head, sides of the body, pelvic fin, dorsal fin, and base of the caudal fin. The earliest patch of melanophores is formed on the lower side of the body anterior to the caudal peduncle. In older larvae, the melanophores gradually proliferate all over the body and form discrete patches which develop into broad spots at transformation and in the juvenile stages. The heaviest concentrations of pigment cells comprise those lining the dorsal wall of the peritoneum. Reglarly spaced melanophores similar to those in Elagatis bipinnulata (Figure IB-D) are present along the midventral line in the trunk region. Fin Development The sequence of fin formation and ossification is as follows: 1) pelvic; 2) first dorsal; 3) second dor- sal, caudal, and anal; and 4) pectoral (Table 9). The pectoral finbud is formed at 2.5 mm but the rays are not differentiated until the larvae are 5 to 6 mm. The full complement of 18 to 21 is formed at 9 mm. The pelvic fins are fully formed in the smallest larva (2.5 mm). They steadily increase in length and at metamorphosis extend beyond the origin of the anal fin. The first 3 dorsal spines are ossified at 2.5 mm. The second and third spines progressively in- crease in length throughout the larval period, forming extremely long filaments. At metamor- phosis, they are about twice the length of the body. The full complement of 8 spines in the first dorsal fin and of 1 spine and 20 to 22 soft rays in the second dorsal fin is present at 9 mm. Rudiments of the anal fin are discernible at 3.2 mm and the rays ossify at 4 to 5 mm. The full complement of 3 spines and 16 to 18 soft rays is present at 6 mm. The development and structure of the caudal fin and supporting structures are similar to those of E. bipinnulata. The full complement of 17 princi- pal and 7 to 9 dorsal, and 7-8 ventral secondary caudal rays is present at 9 mm. 434 APRIETO: EARLY DEVELOPMENT OF FIVE CARANGID FISHES Table 9. — Meristic characters of cleared and stained larvae and juveniles of Selene vomer (Linnaeus). Standard length nal fin Left pectoral fin Left pelvic fin Primary caudal fin rays Secondary fin ray caudal s Gill rakers, left first gill arch Left pre- opercular Dorsal fin A Dorsal Ventral Dorsal Ventral margin spines 2.5 III _ 1, 5 _ _ 3.2 V — — 1, 5 — — — — — — 3.4 V — — 1, 5 — — — — — — 3.5 VI — — 1. 5 — — — — — — 4.0 V; 3 II — 1, 5 2 3 — — 0+11 1 4.4 VIII 1, 10 II , 10 — 1, 5 5 6 — — 0+11 2 4.9 VIII 15 II 1. 14 — 1,5 7 7 — — 0 + 16 2 5.2 VIII 18 II , 1. 16 — 1, 5 7 8 — — 3 + 16 2 5.5 VIII 18 II ; 1. 17 6 1. 5 7 8 — — 3 + 18 3 6.1 VIII 19 II ; 1. 17 10 1. 5 8 8 — — 4 + 19 2 6.3 VIII 20 1 ; 1, 16 13 1, 5 8 8 3 4 5 + 20 2 7.6 VIII 21 1 ; 1. 17 17 1, 5 9 8 5 4 6 + 20 2 8.6 VIII 20 1 : 1. 17 17 1, 5 9 8 6 6 6 + 20 2 9.0 VIII 20 1 ; 1. 18 18 1, 5 9 8 7 8 6 + 22 1 13.5 VIII 21 1 ; 1. 18 18 1, 5 9 8 8 7 6 + 23 — 23.9 VIII 21 1 ; 1, 18 20 1, 5 9 8 9 8 6 + 25 — Distribution and Spawning Adults of Selene vomer have been recorded on both coasts of the United States, from Cape Cod to Brazil and from Lower California to Peru (Jordan and Evermann, 1896). They have also been re- ported from the Gulf of Mexico (Ginsburg, 1952), the Bahamas (Bohlke and Chaplin, 1968), and West Africa (Fowler, 1936). Larval and early juveniles of S. vomer were taken in all months except in June, October, and December. The monthly occurrence and distribu- tion of the larvae is a composite of the records of specimens which include those taken from the coastal waters of the eastern tropical Pacific from Baja California to Costa Rica, the Gulf of Mexico, and the tropical Atlantic off Brazil and Liberia (Aprieto, 1973). In the Gulf of Mexico, larvae were abundant mainly in the northeastern offshore waters in August which suggests a short spawn- ing period in that area (Figure 2). The larvae oc- curred in 2.2% of the net stations and constituted 2.6% of the larval carangids collected in the Gulf of Mexico and the south Atlantic coast. Leatherjacket, Oligoplites saurus (Bloch and Schneider) Figure 8 Literature Larvae of this species have not been described previously. Distinguishing Features Larvae of O. saurus resemble those ofElagatis bipinnulata and Seriola zonata. Further, as in E. bipinnulata, the first interhemal spine is thick- ened and, as in-S. zonata, the supraoccipital crest is lacking. Larvae of O. saurus are distinct from those of the two species mentioned in having an orbital crest with fine serrations, 1 to 3 denticles which appear early in the larval period on the dorsal side of the longest preopercular spine, and 26 vertebrae — the highest vertebral count among carangids. The number of dorsal spines and pec- toral fin rays formed is fewer than in most caran- gids, 5 to 6 and 15 to 17 respectively. Larval pig- mentation is moderately profuse and, as in most carangid larvae, conspicuous melanophores are present along the bases of the dorsal and anal fins, on the lateral midhne, and on the dorsal wall of the abdominal cavity. The larvae transform at 7 to 10 mm. The Embryo Two preserved eggs of O. saurus are 0.87 and 0.88 mm in diameter. They have ventral, single oil globules, 0.33 and 0.34 mm in diameter. The oil globule consists of minute oil droplets and is en- closed in a rather tough, pigmented capsule. The pigmented yolk is bright yellow and unseg- mented. The perivitelline space is narrow and the egg case smooth. The embryos are well developed and have stellate melanophores along the back and upper sides of the body. A large melanophore is present at the posteroventral midline (Figure 8A). Morphology The larvae are 1.87 and 1.97 mm at hatching. 435 FISHERY BULLETIN: VOL. 72. NO. 2 436 APRIETO; EARL'l DEVELOPMENT OF FIVE CAR.ANG1D FISHES 0 B CO 05 S "^ E O * J' ^ CO BQ g o 6 <: CO . 6 « 6 a « t. <-< O ^ » 7: :cs CO §■6 q CO d J CO E 00 u Bi D O CO e g o 00 CO g g o d The body is slender but appears robust at the an- terior end in view of the distended yolk sac (Figure 8B). The head is well marked and the eye buds are discernible. The dorsal finfold originates behind the nape and is continuous with the anal finfold at the tail region. At the first day of hatching, the yolk sac is reduced to a spherule, the eyes are formed but unpigmented, and the dorsal and anal finfolds completely surround the larva except at the mouth. More and bigger melanophores are formed along the sides and back, and a large ventral melanophore is located at the opening of the gut (Figure 8C). Early larvae of O. saurus are slender compared to other larval carangids. Body depth increases relative to standard length and ranges from 20 to 26.9^f during the larval period (Table 10). It in- creases to a maximum of 32% at metamorphosis and thereafter declines to 28 to 29%. The slender gut is straight and forms a single loop at 4 mm. A second loop develops at metamorphosis, and a third is added in the early juvenile period. Snout- to-anus distance ranges from 51 to 61% during the larval period and decreases slightly in subsequent 437 FISHERY BULLETIN: VOL. 72, NO. 2 Table 10. — Measurements (mm) of larvae and juveniles of Oligoplites saurus. (Specimens between dashed lines are undergoing notochord flexion; W - wild, L - laboratory reared.) Specimen number Standard length Snout-to- anus distance Head Head Orbit Body depth Snout to fin origin length depth length diameter pectoral fin Predorsal Prepelvic Preanal 1(L) 1.87 _ 2(L) 1.95 — — — — — — _ _ _ 3(L) 2.17 1.25 0.50 0.45 0.05 0.10 0.45 ~ — — 4(L) 2.25 1.3 .51 .50 .07 .10 .50 — - — 5(L) 2.3 1.3 .57 .54 .09 .20 .60 — — — 6(L) 2.5 1.4 .60 .59 .09 .25 .60 — — — 7(L) 2.5 1.5 .60 .60 .12 .25 .50 — — — 8(1) 2.6 1.5 .60 .55 .12 .25 .55 — — — 9(L) 2.8 1.6 .67 .65 .12 .30 .60 — — — 10(L) 4.1 2.4 1.1 .95 .25 .40 .87 — — — 11(W) 4.3 2.2 1.3 1.2 .37 .37 1.0 1.9 — 2.0 12(W) 4.9 2.7 1.4 1,3 .40 .45 1.3 2.1 — 2.8 13(L) 5.2 3.0 15 1.4 .40 .52 1.4 2.1 — 3.0 14(1) 5.9 3.5 1.8 1.5 .45 .62 1.4 2.5 — 3,5 15(L) 7.2 4.4 2.6 2.2 .75 .75 2.2 36 3.2 46 16(W) 8.7 5.1 3.0 2.5 .80 .80 2.4 4.0 3.6 5,4 17(W) 10.4 5.4 3.3 3.0 .75 1.1 3.0 4.7 3.9 5.7 18(L) 10.5 5.8 3.5 2.9 .90 1.0 3.4 4.9 3.7 6,0 19(W) 10.5 5.5 3.5 3.0 1.0 1.0 3.0 4.9 3.7 5.6 20(W) 11.0 5.9 3.6 3.2 1.0 1.0 3.3 5.2 3.8 6,1 21(W) 15.0 6.9 4.4 3.7 1.3 1.3 4.1 60 4.8 7,0 22(W) 16.0 8.0 4.5 4.0 1.2 1.3 4.5 6.5 5.0 8.1 23(L) 18.5 9.5 5.3 4.6 1.3 1.9 5.3 8.0 6.0 9.5 24(L) 21.0 10.5 60 5.3 1.5 2.1 6.1 8,9 6.0 11.0 stages. Hypaxial muscles enclose the gut at 4 mm, and the abdominal cavity is completely covered at 7.2 mm. As in most carangid larvae, the head is long and deep. Relative head length ranges from 23 to 36% of standard length during the larval and juvenile periods. Depth of head ranges from 82 to 100% of the head length. The dorsal profile of the snout is convex except for a slight indentation at the an- terior margin of the forebrain. The eyes are round and large; eye index ranges from 20 to 44% during the larval and early juvenile periods and is high- est in larvae 2 to 3 mm long. Pigmentation de- velops on the second day of hatching. A finely ser- rated orbital crest is present in larvae from 4 mm long and is gradually resorbed following metamorphosis. Preopercular spines are present but only the marginal ones are well developed. One to three denticles occur on the dorsal side of the longest marginal spine. The scales and lateral line are not yet developed in 25-mm juveniles, the oldest of the laboratory- reared specimens. Pigmentation Larval pigmentation is well developed and progressively increases during the larval and juvenile stages. Pigment cells are more abundant in laboratory-reared specimens than in the wild ones. A conspicuous U-shaped, unpigmented area at the caudal peduncle persists from 7.2 mm up to the early juveniles 20 mm long (Figure 8H-J). Throughout the larval and juvenile stages xanth- ophores are present on the sides of the body, but they readily fade on preservation. Melanophores form at the base of the dorsal finfold in the early larvae but disappear when the fin rays are dif- ferentiated. The conspicuous anal pigment spot in the embryo and newly hatched larvae disappear at the third day of hatching. In the early juveniles, pigmentation develops on the membrane of the dorsal and anal fin spines. Fin Development The dorsal, anal, and caudal finfolds are present at hatching, and the sequence of ossification is as follows: 1) dorsal, anal, and caudal; 2) pectoral and pelvic (Table 11). The pectoral finfold is formed a day after hatch- ing. As in other larvae described here, the pectoral fin rays begin to ossify dorsally and the rest are added ventrally. The full complement of 15 to 17 rays is completed at 10 mm. The pelvic fin buds appear 13 days after hatch- ing at 6 mm and the rays soon become differen- tiated. The full complement of 1 spine and 5 soft rays is present at 10 mm. 438 APRIETO; EARLY DEVELOPMENT OF FIVE CARANGID FISHES Table 11. — Meristic characters of cleared and stained larvae and juveniles of OUgoplites saurus. Primary caudal Secondarv caudal Lett pre- Standard Lett pectoral Left pelvic fin rays fin rays Gill rakers, left first opercular margin length Dorsal fin Ana fin fin fin Dorsal Ventral Dorsal Ventral gill arch spines 4,1 — — — 4 4.3 — — — — — — — — 4 4.9 — — — — — — — — 4 5.9 III 8 7 — — 3 3 — — 0+4 6 7.2 V 18 , 16 7 2 9 8 1 2 0+10 8 8.7 V 1, 17 . 17 10 1, 5 9 8 — — 0+9 9 10.4 IV 1, 20 , 19 13 i, 5 9 8 9 9 3 + 12 12 11.0 V 1. 20 , 18 14 1, 5 9 8 9 9 3+11 9 12.2 V 1. 21 . 19 14 1, 5 9 8 10 9 3 + 11 10 13.0 V 1. 19 , 18 14 1, 5 9 8 9 9 3 + 10 9 15.1 V 1,20 , 19 14 1, 5 9 8 9 9 5 + 11 8 15.2 V 1. 21 . 19 15 1, 5 9 8 9 9 5 + 11 6 16 V 1,21 , 18 16 1, 5 7 9 9 9 5 + 11 5 17 V 1,21 , 20 16 1, 5 9 8 9 10 5 + 12 6 18.5 V 1, 20 , 20 16 1, 5 9 8 9 8 5 + 13 4 19 V 1,20 , 18 15 1.5 9 8 10 9 5 + 13 3 21.0 V 1, 21 , 18 16 1, 5 9 8 9 9 5 + 13 3 The dorsal and anal fin rays differentiate simul- taneously in an anteroposterior direction. Unlike previously described species, in which either the middle or anterior spines are longer, the posterior spine of the first dorsal fin is slightly longer than the rest. The full complement of 6 spines and 19 to 21 rays is present at 10 mm. The anal fin rays of 3 spines and 18 to 20 soft rays are also complete at 10 mm. Caudal fin formation is similar to that of the other species described. The full complement of 9 to 10 dorsal and 8 to 10 ventral principal rays and 18 to 20 secondaries is present at 10 mm. Distribution and Spawning Adults of O. saurus are known from both coasts of Central America and in the West Indies (Jordan and Evermann, 1896). They also occur along the Atlantic coast of the United States from Mas- sachusetts to Florida and in the Gulf of Mexico (Ginsburg, 1952). The wild larvae and juveniles in the present work were taken from Escambia Bay, Fla., and at Sapelo and St. Simons Islands, Ga., in May and July by means of channel nets and beach seines. The laboratory-reared larvae were hatched from planktonic eggs collected from Bis- cayne Bay. Larvae and juveniles were not col- lected in any of the net stations in the Gulf of Mexico and the south Atlantic coast. Distribution of the young in these regions is obscure, and abun- dance and frequency of occurrence in relation to the other larval carangids could not be estab- lished. The wild larvae obtained were too few to derive conclusive information, but apparently spawning occurs in summer. Unlike the other carangids which spawn in offshore pelagic waters, O. saurus spawns in inshore and shallow waters. Further investigation is necessary to establish with certainty the spawning period and sites and the distribution of the young. Laboratory Rearing Planktonic eggs of O. saurus were collected in a 1-m, 505-;u mesh plankton net at the pier of the Rosenstiel School of Marine and Atomospheric Science on 15 July 1972, at 9:00 A.M., EDT. A total of 75 eggs was sorted from the plankton and incubated in a 50-liter glass aquarium. The aquarium water was drawn from Biscayne Bay through the School's seawater system. It was oxy- genated and circulated with compressed air added through airstones and lighted continuously by two cool, white, fluorescent bulbs. Temperature ranged from 23.9" to 28'C and salinity from 32 to 36 %o during the experiment. The larvae were fed wild plankton collected from Biscayne Bay as well as nauplii of brine shrimp {Artemia salina). A detailed description of the rearing technique em- ployed is given in Houde and Palko (1970). The eggs began hatching in the afternoon of the day of collection and after 24 h all the eggs were presumed hatched. The larvae averaged 1.92 mm at hatching, were 5.2 mm 8 days after hatching, and about 21 mm at 34 days (Figure 9). Mortality in the first 18 days included 2 eggs and 16 larvae preserved for describing larval development. Six young juveniles averaged 25 mm after 45 days. Thereafter, the juveniles failed to feed and all but one died at 51 days when the rearing experiment was terminated. 439 FISHERY BULLETIN: VOL. 72. NO. 2 Ossification The sequence of ossification of the skull, axial, and appendicular skeleton is generally similar among the four species in which ossification was observed (Table 12). Without exception, the pre- maxillaries, preopercular spines, and cleithra os- sify in the smallest larvae (2.5-3.8 mm). Next to ossify at 4 to 5 mm are the maxillaries, dentaries, parasphenoid, supraoccipital, articulars, frontals, angulars, and the branchial arches. The entire maxillary arch is ossified before the larvae are 6 mm long. Teeth are formed along the entire mar- gin of the premaxillaries and anterior region of the dentaries in the youngest larvae following the ossification of these elements. It is apparent that the bones related to feeding ossify early, and this is consistent with the need of the larvae for food from external sources following the absorption of the yolk. Seven branchiostegal rays on each side are pre- sent in 3-mm larvae. Ossification begins with the posterior and longer rays and proceeds anteriad. The ceratohyal and epihyal to which the bran- chiostegal rays are attached ossify simulta- neously with the rays. The rest of the hyoid arch including the glassohyal, urohyal, and hypohyal ossify at metamorphosis. Aside from the quadrate and hyomandibular which ossify during the larval period, the rest of the palatine arch is not calcified until metamor- phosis. The branchial arches initially ossify in larvae 4 to 5 mm long and all arches are calcified at 6 mm. The first branchial arch is the first to ossify start- ing from the center of the ceratobranchial towards 20.0 18.0- 16.0 ;i2.o c -• 10.0 — I 1 1 1 1 1 1 1 1 1 1 1 I I I I I '" 0 2 4 6 8 10 12 It 16 18 20 22 24 26 28 30 32 34 Dar* Aflar Halchlni Figure 9. — Growth of Oligoplites saurus larvae reared in the laboratory at an average temperature of 26.0°C. both ends. The epibranchial is the next to ossify beginning from near the angle of the arch out- ward. Ossification of the other arches follows in a similar sequence. The gill rakers calcify following the ossification of the elements to which they are attached. The number of gill rakers increase as growth pro- gresses but gill rakers are slow to ossify, and the full complement usually is not completed until the transition and early juvenile stages. The adult count in Seriola zonata is fewer than is formed in the juveniles due to the reduction of the terminal gill rakers into tubercles in the ceratobranchial. Patches of fine teeth are formed on the superior pharyngeals of the third and fourth gill arches while the fifth and shortest gill arch has teeth patches for most of its length. Pharyngeal teeth ossify in larvae 6 to 8 mm long. In the cranium, the parasphenoid, frontals, and supraoccipitals ossify in the youngest larvae (2.5-3.8 mm). Except for the parietals which ossify in the midlarval period, the rest of the cranium is not ossified until the late larval and transition periods. The cleithra, postcleithra, and posttemporals are ossified in the early and midlarval stages, but the rest of the pectoral girdle calcifies in late and transforming larvae. From 2 to 4 posttemporal spines protrude from the myotomes during the early larval period. These are small and hardly visible in most species except in stained speci- mens. These spines are soon overgrown by the developing muscles. The pelvic girdle calcifies following the ossification of the pelvic fins. Ossification occurs at 5 to 8 mm in the vertebral column and proceeds in an anteroposterior direc- tion. The neural and hemal spines ossify ahead of the centra of their respective vertebrae. The centra ossify at their anterior margins and ossification proceeds posteriorly. This pattern of ossification in the vertebrae was noted in Trachurus symmetricus (Ahlstrom and Ball, 1954). Ribs similarly ossify in an anteroposterior di- rection. The pleural ribs are the first to ossify followed by the epipleural ribs. All trunk verte- brae have ossified pleural and epipleural ribs in juveniles 15 to 17 mm long except on the first and second in which pleural ribs are lacking. Teeth are initially uniserial but become multi- serial as tooth formation progresses. Following 440 APRIETO: EARLY DEVELOPMENT OF FIVE CARANGID FISHES 1 09 o u Ji a a 9) U 0) a. CD B m Q) C 01 (U F o 00 ^ w a 3 CD o O c 1) Q Q. ■5 o c Q) 00 N CT3 « w 3 C C to U. 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CD S £ 3 £ CL C/) 3 ro ro ro ro ro .c — -c -= ro CL r-' o ro o ro >- o ro _c: to -^ ^ 0 X O liJ C3 3 i ■ ■ ^ lU CJ ro X ro — ^ ™ ?- JS ro ^ ^ ro — (0 I i ^ I S £L 5 C/) 441 metamorphosis 2 to 3 irregular rows of sharp teeth are present. ACKNOWLEDGMENTS The author wishes to thank the Miami Labora- tory, Southeast Fisheries Center of the National Marine Fisheries Service, which made available the working space, facilities, materials, and funds. She is deeply grateful to William J. Richards for supervision and encouragement and to Thomas W. McKenney for the many helpful discussions and suggestions on larval fish work. She wishes to express her appreciation to Elbert H. Ahlstrom for reviewing the manuscript and for his valuable criticisms and suggestions, and also wishes to acknowledge the helpful comments from Donald P. de Sylva, Hilary B. Moore, Charles E. Lane, and Lowell P. Thomas. She is grateful to Barbara Palko, Edward D. Houde, and George Miller for carangid larvae given to her, and also wishes to thank Thomas Potthoff for information on stain- ing fish larvae, Alexander Dragovich for transla- tion of Russian literature, John Wise and John Stimpson for assistance in computer work, and Elizabeth Leonard for help in securing much needed literature. This research project was completed while the author was on a University of the Philippines Fac- ulty Fellowship and a scholarship grant from the International Women's Fishing Association of Palm Beach, Fla. LITERATURE CITED Aboussouan, a. 1968. Oeufs et larves de Teleosteen de I'Ouest Africain VI. Larves de Chloroscombrus chrysurus (Linne) et de Blepharis crinitus (Mitchill) (Carangidae). Bull. Inst. Fr. Afr. Noire, Ser. A. 30(3):226-237. Ahlstrom, E. H. 1948. A record of pilchard eggs and larvae collected during surveys made in 1939 to 1941. U.S. Fish Wildl. Serv., Spec. Sci. Rep. 54:1-76. Ahlstrom, E. H., and O. P. Ball. 1954. Description of eggs and larvae of jack mackerel (Trachurus symmetricus ) and distribution and abundance of larvae in 1950 and 1951. U.S. Fish Wildl. Serv., Fish. Bull. 56:209-245. Aprieto, V. L. 1973. Early development of carangid fishes of the Gulf of Mexico and the South Atlantic coast of the United States. Ph.D. Thesis, Univ. Miami, Coral Gables, 179 p. Berry, F. H. 1959. Young jack crevalles (Caranx species) off the south eastern Atlantic coast of the United States. U.S. Fish FISHERY BLILLETIN: VOL. 72. NO. 2 Wildl. Serv., Fish. Bull. 59:417-535. 1968. A new species of carangid fish (Decapterus tabl) from the Western Atlantic. Contrib. Mar. Sci. 13:145-167. 1969. Elagatis bipinnulata (Pisces: Carangidae): Morphol- ogy of the fins and other characters. Copeia 1969:454-463. BoHLKE, J. E., and C. C. G. Chaplin. 1968. Fishes of the Bahamas and adjacent tropical waters. Livingston Publishing Co., Wynnwood, Pa.,771p. Briggs, J. C. 1960. Fishes of worldwide (circumtropical) distri- bution. Copeia 1960:171-180. Chacko, p. I. 1950. Marine plankton from waters around the Krusadai Island. Proc. Indian Acad. Sci. 31, Sect. B:162-174. Delsman, H. C. 1926. Fish eggs and larvae from the Java-Sea. 5. Caranx kurra, macrosoma and crumenophthalmus. 6. On a few carangid eggs and larvae. Treubia 8:199-218. Devanesan, D. W., and K. Chidambaram. 1941. On two kinds offish eggs hatched out in the labora- tory of the West Hill Biological Station, Calicut. Curr. Sci. (India) 10(5):259-261. Dooley, J. K. 1972. Fishes associated with the pelagic sargassum com- plex, with a discussion of the sargassum community. Contrib. Mar. Sci. 16:1-32. Farris, D. a. 1961. Abundance and distribution of eggs and larvae and survival of larvae of jack mackerel (Trachurus symmetricus). U.S. Fish Wildl. Serv., Fish. Bull. 61:247-279. Fields, H. A. 1962. Pompanos (Trachinotus spp.) of south Atlantic coast of the United States. U.S. Fish Wildl. Serv., Fish. Bull. 62:189-222. Fowler, H. W. 1936. Marine Fishes of West Africa. Bull. Am. Mus. Nat. Hist. 70(part II):675-724. FuJii, R. 1969. Chromatophores and pigments. /« W. S. Hoar and D. J. Randall (editors), Fish physiology, Vol. 3, p. 307-353. Academic Press, N.Y. Gaetani, D. de. 1940. Stadi larvali e giovanili in Lichia glauca Risso. Mem. R. Com. Talassogr., Ital. 270, 15 p. Ginsburg, I. 1952. Fishes of the family Carangidae of the northern Gulf of Mexico and three related species. Publ. Inst. Mar. Sci., Univ. Texas 2(2):43-117. Gosline, W. a., and V. E. Brock. 1960. Handbook of Hawaiian fishes. University of Hawaii Press, Honolulu, 372 p. Herre, a. W. 1953. Checklist of Philippine fishes. U.S. Fish Wildl. Serv., Res. Rep. 20, 977 p. Hildebrand, S. F., and L. E. Cable. 1930. Development and life history of fourteen teleostean fishes at Beaufort, N.C. Bull. U.S. Bur. Fish. 46:384-488. Houde, E. D., and B. J. Palko. 1970. Laboratory rearing of the clupeid fish Harengula pensacolae from fertilized eggs. Mar. Biol. (Berl.) 5:354-358. 442 APRIETO: EARLY DEVELOPMENT OF FIVE CARANGID FISHES HUBBS, C. L. 1943. Terminology of early stage of fishes. Copeia 1943:260. Jordan, D. S., and B. W. Evermann. 1896. The fishes of North and Middle America: A descrip- tive catalogue of the species offish-like vertebrates found in the waters of North America, north of the Isthmus of Panama. Bull. U.S. Natl. Mus. 47, Part 1:895-945. Lagler, K. F., J. E. Bardach, and R. R. Miller. 1962. Ichthyology. John Wiley & Sons, Inc., N.Y., 545 p. LUTKEN, C. F. 1880. Spolia Atlantica. Bidrag til kundaskab on foraforandringer nos Fiske under deres Vnext og Udvikl- ing, saerlight nos nogle af Atlanterhavets h0h0sfiske. Kgl. Dan. Vidensk. Selsk. Biol. Skr. 5, 12:049-613. Mansueti, a. J., and J. D. Hardy, Jr. 1967. Development of fishes of the Chesapeake Bay region. An atlas of egg, larval, and juvenile stages, Part 1. Natural Resources Institute, Univ. Maryland, 202 p. Marshall, T. C. 1965. Fishes of the Great Barrier Reef and coastal waters of Queensland. Livingston Publ. Co., Narbeth, Pa., 566 p. Mather, F. J. Ill 1952. Three species of fishes, genusSerioZa, in the waters of Cape Cod and vicinity. Copeia 1952:209-210. 1958. A preliminary review of the amberjacks. Genus Seriola, of the western Atlantic. In Proc. Int. Game Fish Conf., p. 1-13. McKenney, T. W., E. C. Alexander, and G. L. Voss. 1958. Early development and larval distribution of the carangid fish, Caranx crysos (Mitchill). ull. Mar. Sci. 8:167-200. Miller, G. L., and S. C. Jorgenson 1973. Meristic characters of some marine fishes of the west- ern Atlantic Ocean. Fish Bull., U.S. 71:301-312. MiTANI, F. 1960. Fishery biology of the yellowtail, Seriola quin- queradiata T.& S., inhabiting the waters around Japan. Mem. Fac. Agric. Kinki Univ. 1:81-300. MiTO, S. 1961. Pelagic fish eggs from Japanese waters - II Lam- prida, Zeida, Mugilina, Scombrina, Carangina and Stromateina. [In Jap., Engl, summ.] Sci. Bull. Fac. Agric. Kyushu Univ. 18(4):451-466. MosER, H. G., and E. H. Ahlstrom. 1970. Development of Lanternfishes (Family Myctophidae) in the California Current. Part I. Species with narrow- eyed larvae. Bull. Los Ang. Cty. Mus. Nat. Hist. Sci. 7,145 p. Nichols, J. T. 1946. On young western Atlantic Seriolas. Copeia 1946:259-260. Okada, Y. 1966. Fishes of Japan. Illustrations and descriptions of fishes of Japan. Uno Shoten Co., Ltd., Tokyo, 458 p. Okiyama, M. 1970. Studies on the early life history of the rainbow run- ner, Elagatis bipinnulata (Quoy and Gaimard) in the Indo-Pacific Oceans. Far East Fish. Res. Lab. (Shimizu) Bull. (3):167-186. PosGAY, J. A., R. R. Marak, and R. C. Hennemuth. 1968. International Commission for the Northwest Atlan- tic Fisheries. Res. Doc. 68/85, 5 p. Sanzo, L. 1931. Uovo, stadi embrionali e post-embrionali di Nauc- rates ductor L. Mem. R. Com. Talassogr. Ital. 185, 14 p. 1933. Uovo larvae e stadi giovanili de Seriola dumerili Risso. Mem. R. Com. Talassogr. Ital. 205, 12 p. Schnakenbeck, W. 1931. Carangidae. Report on the Danish oceanographical expeditions 1908-1910 to the Mediterranean and Adja- cent seas. No. 10, 2(Biol.) A. 14:1-20. Shojima, Y. 1962. On the postlarvae and juveniles of Carangid fishes collected together with the jelly-fishes. [In Jap., Engl, summ.] Bull. Seikai Reg. Fish. Res. Lab. 27:49-58. Starks, K. 1911. The osteology and relationship of fishes belonging to the family Carangidae. Stanford Univ. Publ. Univ. Ser. 5:27-49. Subrahmanyam, C. B. 1964. Eggs and early development of a carangid from Madras. J. Mar. Biol. Assoc. India 6(1): 142-146. Suzuki, K. 1962. Anatomical and taxonomical studies on the carangid fishes of Japan. Rep. Fac. Fish. Prefect. Univ. Mie 4(2):43-232. Uchida, K., Y. Dotu, S. Mito, and K. Nakahara. 1958. The spawning and early life history of "buri" Japanese yellow tail, Seriola quinqueradiata Temminck et Schlegel. [In Jap., Engl, summ.] Sci. Bull. Fac. Agric. Kyushu Univ. 16:329-342. Uchida, K., S. Imai, S. Mito, S. Fujita, M. Ueno, Y. Shojima, T. Senta, M. Tahuku, and Y. Dotu. 1958. Studies on the eggs, larvae and juveniles of Japanese fishes. Kyushu Univ., Fac. Agric, Fish. Dep., Second Lab. Fish. Biol., Ser. 1, 89 p., 86 pi. Vijayaraghavan, p. 1958. Studies on fish eggs and larvae of Madras Coast. Univ. Madras, G. S. Press, 79 p. Weitzman, S. H. 1962. The osteology of Brycon meeki. a generalized characid fish, with an osteological definition of the family. Stanford Ichthyol. Bull. 8:1-77. 443 SOME EFFECTS OF DREDGING ON POPULATIONS OF MACROBENTHIC ORGANISMS Eugene H. Kaplan/ J. R. Welker,^ and M. Gayle Kraus^ ABSTRACT Populations of epi- and infauna were studied from 10 mo before to 11 mo after a navigation channel was dredged through a small, shallow lagoon. A new sampler which jjenetrated 20-30 cm into the substratum was used. Current velocities and sedimentation patterns were changed due to an altered distribution of tidal currents, although flushing time was not appreciably altered. Values of certain particulate and dissolved nutrients changed after dredging, but no correlation was observed between animal populations and fluctuations in nutrients. Significant reductions in standing crop figures and species and specimen numbers occurred in both the bay and the dredged channel. Mercenaria mercenaria populations were reduced, but there was no evidence of mass mortality. Recovery of biomass in the channel was affected by sediment composition, but seasonal and sediment type variations were not significant in the bay as a whole. Goose Creek had a high predredging epi- and infaunal standing crop estimated at 36.83 g/m^, but the number of organisms/m^ was relatively low, indicating a preponderance of large forms. Productivity of Goose Creek was calculated at 89.87 g/m^/yr before dredging and 31.18 g/m*/yr after dredging. Productivity figures for the mixed peripheral marsh were calculated and the annual loss due to replacement of 10.87 ha of marsh by spoil areas was estimated at 49,487 kg. Altered land usage patterns tended to fix this loss on a permanent basis. The unusually profound effects of dredging reported for Goose Creek are attributed to its small size and shallowness. In 1965, Suffolk County, N. Y., obtained the services of a consortium of universities to study the characteristics of a small embayment before and after a channel 22.8 m wide x 2.1 m deep x 1,037 m long was dredged from the narrow inlet through most of the bay. The investigations re- ported in this paper are confined to the population dynamics and ecology of the macrobenthic organisms. Reference will be made to the other areas of investigation only as they affect the macrobenthos. The following phenomena will be considered in relation to their effects on epi- and infaunal population dynamics: 1. Changes in the hydrodynamics of Goose Creek as the result of the introduction of the newly dredged channel. 2. Changes in the morphology of the sediment effected by the dredging process. 'Biology Department, Hofstra University, Hempstead, NY 11550. ^Institute of Marine Sciences, Southampton College, South- ampton, NY 12837. ^Zoology Department, University of Rhode Island, Kingston, RI 02881. 3. Changes in physical and chemical char- acteristics of the water associated with the dredg- ing process. 4. Changes in populations of macrobenthic organisms which occurred during 1966 and 1967. The Study Area Goose Creek is a small, shallow lagoon located on the north fork of Long Island in the town of Southold, N. Y. (lat. 41°03'00"N, long. 72°25'23" W). Its dimensions are 1,464 m east-west by 533 m north-south, a total area of about 0.32 km^. A channel approximately 30.5 m wide at the east- ern end opens into Southold Bay, thence into Shelter Island Sound, an arm of Little Peconic Bay (see Figure 1). The mean high water depth before dredging was 1.7 m, but much of the bay was extremely shallow and at low water it was impossible to navigate even a small boat in the western half of the bay. Mean tidal range was 68.5 cm, and the mean depth at mean low water was 1.0 m. The prevailing wind is from the southwest in Manuscript accepted September 1973. FISHERY BULLETIN: VOL. 72, NO. 2, 1974. 445 FISHERY BULLETIN: VOL. 72, NO. 2 72= 25' GOOSE CREEK, N.Y. 0 100 200 300 A1 e f e r s 41° 03 Figure 1. — Location map of Goose Creek, N.Y. the summer months and from the northwest in winter. There are four "minor" and five "major" islands in Goose Creek, the largest of which is 115.6 m by 42.4 m. They sustain a heavy growth of Spartina alterniflora with dense colonies of Modiolus demissus and Uca pugnax. The entrance of Goose Creek was dredged from a mean low water depth of 0.8 m to a minimum of 2.1 m below mean low water. In cross section the channel was changed from a gentle depres- sion to a steep-sided U. As a consequence of dredg- ing the channel, the main water flow was shifted from one channel to another and current velocities dropped approximately one-half, except in the western half of the bay where previously negli- gible velocities increased. The substratum of the bay consists of coarse gravel and sand in the main channel before it trifurcates into channels A, B, and C, which are characterized by sand grading into fine sand and mud in areas with reduced current velocity. The bottom sediments in the western half of the bay consist of thick silt over gray clay mixed with shell and sand. The surrounding upland consists of Spartina marsh edged by stands ofPhragmites communis. Before dredging, the south shore was almost completely developed, with small summer homes along the shores. The north and west shores were undergoing partial development with year-round homes. Five years after the dredging (1972), the area was almost completely developed, much of the marsh having been replaced by areas filled for homesites. 446 KAPLAN, WELKER, and KRAUS: EFFECTS OF DREDGING In 1966-1967 salinities ranged from a mean low of 26.79 7cc to a mean high of 28.34,^^0. The pH ranged from 7 to 8. The dissolved oxygen levels varied seasonally and from station to station from a low of 4.50 ml 02/liter to a high of 9.95 ml 02/liter. Readings were always at saturation. The mean temperature range was between -1.0°C and 26.18°C over the 2 years; the bay is too shallow to exhibit a pronounced thermocline. Portions of the surface were frozen solid during parts of the months of February and March, 1966, and January, February, and March, 1967. The tidal currents were relatively rapid in the eastern section of the bay, reaching a velocity of 56.7 cm/sec at station 1, at the confluence of the three channels, but they rapidly lost velocity until negligible readings were recorded in most of the western half of the bay. Yearly rainfall (1967) amounted to 126.09 cm. Pollution by effluents from cesspools along the southern periphery of the bay consisted of fecal material, other organic material, and detergents as indicated by coliform bacteria and phosphate levels. Previous Dredging of Goose Creek Goose Creek was chosen for this investigation because of its unspoiled nature. This is a relative term, however, and on Long Island, with its high population density, it is unlikely that any bay or inlet has escaped some form of dredging operation. There have been a number of private drag-line dredgings in Goose Creek reported by local residents. The earliest incident described was a dredging operation along channel A in 1930; a 1904 map of the region reveals, however, that the general contours of the bay remained unchanged. The first officially recorded dredging in the environs of Goose Creek performed by Suffolk County occurred in November, 1959. A channel approximately 500 m long and 30 m wide was dredged from the bridge east by southeast into Southold Bay as an aid to small boat navigation. The depth of the channel was increased from approximately 0.5 m to 3 m mean depth below mean low water, and 35,653 m^ of spoil were placed along the southeast shore of the inlet, covering 20,920 m^ of Spartina marsh. Another area, smaller in size, received some spoil from this dredging. It was contiguous with what was to become spoil area C. The second dredging operation began on 27 June 1967 and ended on 2 August 1967. The effects of that operation are the subject of this investigation. A channel 23 m wide by 825 m long was dredged from the bridge at the inlet to the bay in an easterly direction along Channel B. A total of 57,383 m^ of spoil was removed and placed on spoil areas A, B, and C. Spoil area A covered approximately 6,000 m^ of Spartina and Phrag- mites marsh adjacent to a previously used spoil area of approximately 26,000 m^ covered to a maximum height of 3 m above mean low water. Spoil areas B and C in the southwest corner of Goose Creek covered 44,640 m^ and 23,250 m^ of Spartina marsh respectively. A third dredging took place from 22 December 1967 to 12 April 1968. A 15.25-m wide channel was dredged to extend the previously constructed channel across the bay to the cut opening into the eastern shore. A small extension to an existing channel was also dredged through the center of Thyone Cove. The combined dimensions of these extensions were 427 m x 15.25 m and 8,508 m^ of substratum were removed and placed on spoil area B. During the spring and summer of 1970, drag- line operations in the northwest corner of Goose Creek obliterated 13,950 m^ of Spartina marsh along a frontage of 152 m as site preparation for a housing development. This was part of the largest portion of the original peripheral marsh which remained after the dredging operations of 1967-1968. The only remaining marsh in Goose Creek at the time of this writing was an area approximately 16,000 m^ bordering the north- western edge of the bay (see Figure 2). Estimates of the areas of marsh covered by dredge spoil along the periphery of Goose Creek can be seen on Table 1. An estimate of the remaining marsh in Goose Creek comes to 43,826 m^ (islands) plus 23,715 m^ (peripheral) or a total of 67,541 m^. This is 31.4% of the total acreage covered by marsh in 1959. Excluding the islands, only 10.7% of the 1959 peripheral marsh remains. Examination of a map of the Goose Creek area drawn in 1904 reveals that the entire periphery of the bay was sur- rounded by extensive marshes. Probably less than 447 FISHERY BULLETIN: VOL. 72, NO. 2 Figure 2.— Aerial photograph of Goose Creek, May 1972. Note straight edge of northwest shorehne (light area) caused by 1970 private dredge and landfill operation. Upper embayment is Jockey Creek. Note dredged channels in both bays and virtually complete eradication of marsh around Jockey Creek. 1% of the original Goose Creek marsh is still present. METHODS AND MATERIALS In order to determine what changes occurred in the macrobenthic population in Goose Creek, 23 stations were established in the bay, exclusive of the area to be dredged for the deepened channel. Fifteen additional stations were located at 30 m intervals in the path of the proposed channel. The present study was initiated 1 yr before the scheduled dredging operation. Since a complete characterization of Goose Creek was necessary before the onset of dredging, it was deemed necessary to use a sampling procedure which could cover the whole of Goose Creek once every month. As the western half of the bay is uniform in bottom composition, being composed of deep, gray-black silt over muddy gray sand, there is little need to sample it as extensively as the eastern half of the bay, which is characterized by f'-equent changes in sediment type caused by variegated current flow patterns and topographic variability. Faunistic distribution was found to be dependent on the nature of the sediment, whose characteristics were, in turn, dependent on the erosion and deposition rates of the overlying tidal currents. Consequently, it was decided to divide the bay into zones of high, medium, and low current velocities, sampling each region by 448 KAPLAN, WELKER, and KRAUS: EFFECTS OF DREDGING Table 1. — Dimensions of known dredging operations in Goose Creek. Area Amount Dredged area Spoil area covered of spoil Navigation channel Edge of Southold 20,920m2 35,653m3 in Southold Bay to Bay on either side bridge. of inlet to Goose Creek. June-August 1967 Spoil areas A, B, 73,842m2 57,383m3 dredging of channel and C. through Goose Creek. Dec. 1967-April Spoil area B. Included 8,508m3 1968 dredging of above. spur channel to western shore, plus navigational channel through Thyone Cove. Spring-summer, Northwest edge ca. 13,950m2 Unknown 1970 private drag- line operation in NW corner of Goose Creek. Totals 108,712m2 101,544m3 means of transects across the zone. In addition, a number of intertidal stations were set up, and a "characterization" survey was embarked on which sampled the intertidal area 2 m from shore and the sublittoral 6 m from shore every 30 m around the periphery of the bay. Using data from the preliminary surveys, sampling stations were established as representative of major substratum categories in Goose Creek. The advantages of placing greater sampling emphasis on certain areas rather than randomly sampling or using established as representative of major substratum (1967), Stickney and Stringer (1957), and Lee (1944). Figure 3 indicates the positions of the stations in Goose Creek. Each station was sampled with a "suction- corer" (Kaplan, Welker, and Kraus, In press-a) once a month for 9 mo preceding dredging and 11 mo after dredging terminated. A small shallow- draft vessel was propelled to the stations by an outboard motor. Locations were fixed by tri- angulation. Once the vessel was located over a station, "spuds" consisting of 7.62 cm OD galvanized pipes were lowered fore and aft to keep the barge from swinging with current or wind. The sampler consisted of a chamber 36 cm in diameter by 30 cm high from which extended a hydraulic hose leading to a 3 hp pump on the deck of the barge. The corer was then lowered through a hole in the center of the deck until it reached the bottom. The pump was started and the water was with- drawn from the coring chamber. The evacuated chamber had negative pressure relative to the water column above it; this pushed it into the bottom. In practice depth of penetration varied, but a sample was not considered adequate unless the chamber had penetrated to a mini- mum depth of 20 cm. After maximum penetra- tion the chamber was inverted by means of a winch and the sample was hauled to the deck where it was emptied onto a 60 cm x 90 cm sieve of 1 .4 mm mesh size and washed. The screen- ings were placed in gallon bottles and formalde- hyde was added to a concentration of 10%. GOOSE CREEKN.y. Figure 3. — Location of stations, Goose Creek. Letters in circles represent channel stations; letters in squares repre- sent intertidal stations; letters in triangles represent spoil areas. Shaded extension of channel represents 1968 dredging. 449 Holme (1953) and Reish ( 1959) established that 1.5 mm and 1.4 mm mesh sieves recovered 90% of the biomass from their samples, respectively. In view of the importance of large forms in the Goose Creek species composition, it is likely that the 10% potential error described by Reish and Holme is a conservative estimate. Since the purpose of this investigation required an accurate estimate of total standing crop, with special emphasis on such commercially important species as Mercen- aria and Mya, no attempt was made to separate the "large" and "small" forms by using an arbi- trary cut-off point, as the 0.2 g of Sanders (1956). Thirty-eight stations and the once-a-month sampling schedule produced over 400 separate samples; this large A^ helped compensate for statistical inaccuracies introduced by the pres- ence of large forms. After a minimum of 1 yr of storage the speci- mens were identified, weighed (blotted wet weight), and dried at 40°C until uniform dry weight was obtained. Pelecypods were shelled, but crustaceans did not have their carapaces re- moved, since many were too small for this procedure to be performed with precision. Instead the major weight factor of the shells, the car- bonates, was substantially removed by the acidic action of the unbuffered formaldehyde. The use of an acidic medium to remove carbonates was employed by Sanders (1956), Holme (1953), and others. The data were expressed as number of organ- isms/wet weight/dry weight (biomass) per m^ of substratum, including all animals recovered, according to the recommendation of Lee (1944). RESULTS Hydrography of Goose Creek The hydrographic data recorded below were obtained from the reports of Hair (1968), Fazio (1969), and Black (pers. comm.). Salinity was measured by a portable Beckman salinometer (Model RS 5-3),'* dissolved oxygen and tempera- ture readings were taken with a portable oxygen meter (Electronic Instruments Ltd. Model 15 A) and pH was determined with a portable Orion Instruments Specific Ion Meter (Model 401). Light penetration was measured by a Secchi disc. ••Reference to trade names does not imply endorsement by the National Marine Fisheries Service, NOAA. FISHERY BULLETIN: VOL. 72, NO. 2 Water Temperature Average daily temperatures ranged from 25.5°C to 0.5"C in the bay in 1967-68. The lowest indi- vidual reading was -1.5°C on 11 January 1968 and the highest 29.0°C on 7 July 1967. In January, February, and March, the bay was often covered by ice. Salinity Maximum salinity values occurred in mid- July to mid-October with a 1966-1968 high of 30. 12 /CO. Low salinities occurred from mid- January to mid-April, with the 1966-68 low of 18.38 Vco recorded on 28 March 1968. Mean 1966-67 salinity in the bay proper (ex- cluding the relatively less saline cut extending from, the west shore) was 28.37 /^o . pH Average daily pH in Goose Creek ranged from 7.1 to 8.3 (excluding the somewhat more variable western cut) in 1967 and 7.7-8.2 in 1966. The highest individual value in 1967 was 8.6, occur- ring during a phytoplankton bloom in Thyone Cove, on 27 July 1967. The highest individual value for 1966 was 9.0 during a dinoflagellate bloom. Light Penetration Secchi disc readings were taken at weekly intervals throughout the duration of the study. In the bay itself the photic zone usually reached to the bottom, since the total water column was never more than 3.5 m. Virtually the entire bay could be considered euphotic except during the month in which the dredging took place, July 1967, when the minimum light penetration as recorded by the Secchi disc was 0.4 m (Fazio, 1969). It appears, then, that light penetration values were not substantially affected by the introduction of suspended materials into the water as the result of dredging. This is not surprising in view of the shallow nature and relatively rapid flushing time of the region of the bay most severely affected by the dredging, the eastern half. On the other hand, deposition of a canopy of flocculent material on the leaves of the Ruppia and the thalli of the Enteromorpha was observed during and after the dredging process. 450 KAPLAN, WELKER, and KRAUS: EFFECTS OF DREDGING This factor almost certainly reduced available light to the plants despite the relative clarity of the water. Current Velocity Readings of current velocities were taken on 9 June 1967, before dredging, and on 19 July 1968, after the new channel was completed. Attempts were made to match the tide height and wind direction and velocity on both occasions so as to minimize variables related to natural fluctuations of water level and current velocity. During both readings the wind was from the southwest and differences in wind velocity between the two days were not greater than 10 mph. The wind velocity was slightly higher during the post-dredging series (7 mph vs 15 mph) as was the tidal range (70 cm vs 73 cm). These factors would tend to increase the velocity of the flood tide rather than decrease it. Since current velocities de- creased, this effect cannot be attributed to the influences of wind and/or tide. The bridge readings were made with an Ekman current meter at 20 min intervals, 0.5 m beneath the surface and 0.5 m above the bottom of the channel. The meter was allowed to run for 120 sec and the readings were converted into centi- meters per second according to the standard formula. The readings in the channels were taken with Price meters on hand-held rods. The meters were set at 0.5 m above the bottom. Maximum depth of water at any station was approximately 1 .2 m so that lamination or stratification according to current velocity was minimized. Maximum inter- vals between readings at the same station were less than 30 min. The data consisted of the number of revolu- tions of the wheel during a 70 sec interval con- verted into centimeters per second from a nomo- graph calibrated to each meter. One replication of each measurement was taken as a check on the accuracy of the meters. Table 2 and Figure 4b compare current veloci- ties before and after dredging. Figure 4a indicates the current velocity sampling stations. Maximum current velocity before dredging was through channel A. After dredging, the most westerly portion of channel A still has the maxi- mum current velocity, but approximately 100 m east of the point of trifurcation at stations 4 and Table 2. — A comparison of current velocities at flood tide in Goose Creek, before and after dredging. Before After Difference Station (cm/sec) (cm/sec) (cm/sec) 1 56.7 25.8 -30.9 7 41.4 13.r -28.3 6 40.2 7.2 -33.0 2 55.2 25.2 -30.0 '3 43.9 2.6 -41.3 4 23.2 13.1 -10.1 5 17.2 18.0 + 0.8 ID 28.8 NA NA 2D 38.4 5.5 -32.9 3D 12.1 2.7 - 9.4 4D Neg (0) 5.5 + 5.5 50 Neg (0) 4.8 + 4.8 Bridge 92.0 47.2 2-44.8 Bridge 83.8 39.6 3-44.2 'Station 3 was a sand bar with a thin, rapid flow. The water was never more than 30 cm deep over this bar. It was removed by the dredging operation and replaced by a 2.1 m deep channel. ^f^aximum surface velocity. ^Maximum bottom velocity. GOOSE CREEK, N.y: Figure 4 a. — Map of current velocity sampling stations. Figure 4 b. — Map of current velocity differences before (open arrows) and after (solid arrows) dredging. Each millimeter represents 4 cm/sec current velocity. 451 7, the current velocities in channels A and B were matched at 13.1 cm/sec. Thereafter, the post- dredging velocity in channel B was greater than in channel A, i.e., 18.0 cm/sec at station 5 and 7.2 cm/sec at station 6. Thus, maximum flow was changed from channel A to channel B as a result of the dredging. Channel B was converted from a shallow, wide passage with maximum surface area in contact with the current (hence maximum friction and impedance of water flow) to a deep channel, whose depths at mean low water before and after dredging were 0.4 m and 2.1 m at the entrance. The substratum of channel A was gravel and sand at the most westerly end, changing to sand for most of the length of the channel as it passed islands I and II, after which it gradually became muddy sand. Near Thyone Cove only the shoreline and 3 m of littoral remained muddy sand; below this level the substratum was gray sand covered by 2 cm of silt. As indicated earlier, channel B had a lower velocity before dredging than channel A. The transitional area was compressed in channel B; the area of sand at the westerly end merged rapidly into muddy sand, then silt, a short distance past the easterly end of island I. Channel C, both pre- and postdredging, was characterized by an initial high velocity (55.17 cm/sec at station 2 and 38.40 cm/sec at station 2D), but this rapidly dissipated over the sand flats and eddies north of islands III and IV. Maximum surface and bottom velocity was halved after dredging at the inlet to the bay. This, of course, would have a most profound influence on transport of materials, since it represented a section of water approximately 22 m wide by 2.8 m deep. Since the original mean depth of the channel was approximately 1 m, the cross section of the dredged channel was approximately three times greater than the original channel, increasing its volume commensurately. Isaac (1965) stated that current velocities of 0.6 to 1.3 ft/sec (18.29 to 39.62 cm/sec) are sufficient to resuspend bottom deposits with 1 .0 mm particle diameter. According to changes in current velocity at Goose Creek, the deposition of such particles would have taken place at the following stations after dredging, although not before dredg- ing: station 7 (41.4 to 13.1 cm/sec), station 6 (40.2 to 7.2 cm/sec), station 3 (43.9 to 2.6 cm/sec), station 4 (23.2 to 13.1 cm/sec) and station 2D (38.4 to 5.5 cm/sec). FISHERY BULLETIN: VOL. 72, NO. 2 Mass Movement of Water Hair (1968) calculated the volume of water moving in and out of Goose Creek during each phase of the tidal cycle. Assuming the average depth to be 1.3 m at high tide with a tidal range of0.8mandanareaof2.59 x lO^m^, he calculated the volume of the bay at high tide to be 3.88 x lO^m^. At low tide the corresponding calculation was 1.44 x lO^m^. The volume lost at each falling tide would then represent approxi- mately 60% of the volume at high tide. Fazio (1969) recalculated the tidal exchange on the basis of the increased volume of the bay caused by the construction of the dredged channel. His volumes were 7 x lO^m^ at high tide and 3.1 x lO^m^ at low tide. This represents a loss of 66% at each ebb and is considered by Fazio as a corrobora- tion of Hair's calculations. Of importance in any consideration of the benthos in Goose Creek is the fact that during the 6 h of ebb tide roughly 60% to 66% of the total volume of water in Goose Creek (approxi- mately 2 X lO^m^ before dredging and 4 x lO^m^ after dredging) flowed out of the bay. All of this water passed through channels A, B, and C which, at a maximum value of 23 m wide and 3.0 m deep for channel B and 30 m x 1.5 m for the combined channels A and C, represents a total cross-sectional volume of 114 m^ for the passage of ca. 3.9 X lO^m^ of water. The relatively small volume of channels A, B, and C and the 244 m channel formed by their confluence and flowing eastward into Southold Bay accounts for the rapid current velocity in the eastern half of Goose Creek. On 21 May 1966, an attempt was made to determine the proportion of water exchanged in various parts of the bay. Rhodamine B was released into the easternmost portion of Goose Creek (near the bridge) on an incoming tide, so that the average dilution was approximately 27 ppm after 2 h over the entire surface area of the bay. Six weeks later the readings on the fiuorometer revealed values of the order of 1.7 ppm in most of the eastern half of the bay while Thyone Cove and the western shore of Goose Creek had readings as high as 9.6 ppm and lows rarely below 6.3 ppm. Figure 5 demonstrates that the exchange of water, as revealed by residues of Rhodamine B, was greater in the eastern half of the bay, with areas of Thyone Cove and the west shore having 452 KAPLAN, WELKER. and KRAUS: EFFECTS OF DREDGING maximum values for the dye and, therefore, a comparatively low exchange rate. Dissolved Nutrients Fazio (1969) and Hair (1968) studied the dis- tribution of certain nutrients in Goose Creek before and after the dredging operation. The results of their investigations are summarized in Table 3 and fluctuations in pre- and post- dredging concentrations of chlorophyll a, silicate, dissolved organic phosphate, and nitrite are depicted in Figure 6. Fazio reported that there were significant changes in the values of particulate phosphorus, silicates, and chlorophyll a as a result of the dredging. He demonstrates high correlations between particulate phosphorus and chlorophyll a {r = 0.83), but is unwilling to suggest a direct relationship between this nutrient and phy- toplankton productivity. Instead, he explains the congruent increases in particulate phosphates and chlorophyll a as either a suspension of living benthic organisms intro- duced into the water by the disturbance of the sediment, or resuspension of detrital material and/or land runoff. Analysis of the water near a leaking spoil area revealed great amounts of particulate phosphorus and chlorophyll a were being added to the water column. The distribution of silicates was shown to be related to the dredging process since highest readings were associated with stations in the vicinity of the dredge pipe and spoil areas; these high readings shifted down the bay following the movements of the dredge. There was, however, a low positive correlation between silicates and chlorophyll. Coupling high concentrations of chlorophyll a with extreme turbidity and very low light penetration in the vicinity of the dredge, Fazio (1969) concludes that the chlorophyll is not necessarily an indicator of the presence of phytoplankton, since the opacity of the sediment- laden water would prevent photosynthesis and limit phytoplankton production. Instead, he sug- gests that plant detritus in the spoil runoff is the main source of the high chlorophyll a readings and that phytoplankton populations might be very low. Examination of Figure 6 reveals a second high in chlorophyll a readings in December 1967- GOOSE CREEK, NY. Figure 5. — Rhodamine B residues in ppm on day of adminis- tration and after 6 weeks. Figures in parentheses represent the later readings. (Drawn from data from Black, pers. comm.) January 1968. This corresponds with a second dredging which occurred from 22 December 1967 to 12 April 1968 in the western quarter of the bay. The picture is very much like that of the first dredging. A similar peak chlorophyll a read- ing occurred at the onset of dredging followed by a sustained high yield throughout the late winter and early spring. Mean chlorophyll a readings for the months of December 1967 to June 1968 are consistently two to five times those of the comparable 1966-1967 period. Resolution of the problem of whether the chlorophyll readings represent an increase in phytoplankton or are artifacts resulting from runoff will be decided when Cassin publishes his analysis of the phy- toplankton cycle 1967-1968. Table 3. — The fluctuations in certain dissolved and particulate nutrients in Goose Creek, 1966-1968. Nutrients Mean concentration 1966 (Hair) Mean concentration 1967 (Fazio) Dissolved 0.81 pg at. P/liter 0.86 Aig at. P/llter inorganic phosphorus Nitrates 2.8;i/g at. NOj-N/liter 3.5 /ig at. NOa-N/liter Silicates July-Aug. values July-Aug. dredging betw/een 8 and 16 period values between fig at. Si/liter 30and35/:/gat.Si/liter. Variable from station to station according to proximity to dredge. Particulate Mean of 8 readings Mean of 8 readings phosphorus 6/16-7/18. 1966 7/5-8/7, 1967 4.94 /:ig at. P/liter 18.30 /jg at. P/liter 453 FISHERY BULLETIN: VOL. 72, NO. 2 30 25 O20 10 5 ASONDJ f/MAAIJ ^P Sl.l 40 • * \ 30 V) ^ 0 ^ 20 Mn'^ 10 -^ H r^^Ay-lA^^ A SON OJ FA1AA1J ON OJ f M A M J Figure 6. — Fluctuations of (from top to bottom) chlorophyll a, silicates, dissolved inorganic phosphates, and nitrites in Goose Creek, 1966-1968. (Redrawn from Hair, 1968; Fazio 1969.) Solid line represents 1966-1967 data; dotted line repre- sents 1967-1968 data. In general, the results of the Goose Creek nutrient studies are similar to those carried on in Chesapeake Bay by Flemer (1970) and Biggs (1968). Particulate phosphates, silicates, and chlorophyll a increased significantly. Concentra- tions of nitrates, nitrites, and dissolved organic and inorganic phosphates were not appreciably different before and after dredging. Copeland and Dickens (1969) report that in Maryland, Texas, and South Carolina there was an initial diminution of phytoplankton produc- tivity due to shading and a later enhancement due to resuspension of nutrients from dredge spoil. Flemer (1970) indicates that he found no demon- strable effect of the deposition of fine sediments from dredging on the production of phytoplankton in Chesapeake Bay. There is no evidence that the release of nu- trients from dredging produces an effect similar to that described by Raymont (1947, 1949) where the addition of fertilizer to small, enclosed embayments raised the level of benthic pro- ductivity up to 300% by stimulating production of phytoplankton. Mechanical Analysis of the Sediment Sanders (1956) points out the great variability in establishing criteria for the differentiation of particles constituting the sediment. He ex- pressed the composition of the sediment in terms of the proportion of the particular component which was either most predominant or most rele- vant to the point he was making (e.g., Mulinia lateralis is either absent or present in low num- bers when the proportion of silt-clay in the sample is greater than 40*7^). In the present study the samples were sieved and the lighter fractions analyzed by pipetting. Phi values were calculated and eight fractions recorded, one for sand (up to a maximum phi coefficient of 4.0), six for the various fractions of silt (phi = 4.5-8.0) and one for clay (phi = 9.0 and beyond). Data are recorded in percent sand, silt, and clay to conform with common practice. Three sets of sediment samples were obtained during the course of the study. A preliminary survey was performed in September 1966, using a 1 m Phleger corer at each of the permanent sampling stations. Figure 7 delineates the sedi- ment facies distribution compiled during this survey. Also found on this map are the stations 454 KAPLAN. WELKER, and KRAUS: EFFECTS OF DREDGING for the second survey (triangles) taken just before the dredging in June 1967, and the post- dredging survey (circles) in July 1968, 1 yr after dredging. Table 4 reveals that 1 yr after dredging, sedi- ments in those stations in the path of the dredge (3, 10b, 11, and 11a) contained less sand after dredging in the previously sandy, high current velocity stations (3, 10b) and more sand in the previously silty, low current velocity stations (11, 11a). Station 10a, in channel A, experienced a reduc- tion in its sand proportion and an increase in silt. This conforms to the hypothesis that the lowered current velocity in channel A, resulting from a shift in the main volume of water transport to channel B, would favor the settling of lighter particles in the post-dredging period. Similarly, station 5 in channel C increased in its silt and clay components. Stations 16 and 17 were located in the west- central portion of the bay, south of the channel. Both stations maintained a constant proportion of sand. Station 17 exhibited a marked increase in silt and a decrease in the clay facies. Stations 14 and 24 exhibited an increase in sand and a decrease in silt and clay. Since these stations were near the western shore in an area of negligible current flow, it is difficult to envision pronounced sediment transport brought about by normal tidal flow, even with the slightly enhanced exchange rate brought about by the deepening of channel B. It is possible that spring tides and strong easterly winds could have acted syner- gistically with the deepened channel to bring about this effect. GOOSE CRIEK NY. Figure 7. — Sediment facies and station locations, Goose Creek. Triangles represent pre-dredging stations, circles represent post-dredging stations. The foregoing data must be viewed in con- junction with data on current velocities, wind- driven currents, etc., as further presumptive evidence of what appear to be permanent changes in the sediment transport patterns of Goose Creek brought about by current velocity modifica- tions in the tidal channels. The Effects of Wind-Driven Currents on Sediment Deposition The importance of wind-driven water currents on the deposition of sediment in shallow-water estuarine situations has been emphasized by Table 4.— Comparison of pre- and post-dredging sediment composition at selected stations. Goose Creek. Pre -dredging Post-dredg ng Station %Sand %Silt %Clay Station %Sand %Silt %Clay Comparison F6 F7 F8 97 97 97 97 65 3% silt, 3% silt, 3% silt, clay clay clav 3 78 14 8 Less sand F4 F5 3% silt, 18 clay 17 5 30 41 29 Less sand E8 D5 D6 C5 B7 97 97 97 40 44 3% silt 3% sill, 3% silt. 26 26 clay clay clay 34 30 7 10b 10a 11a 11 70 91 72 75 74 20 8 24 17 13 10 1 4 8 13 Less sand Less sand Less sand More sand More sand B8 B9 48 49 28 18 24 33 16 49 29 22 No change B11 34 24 21 34 24 39 32 1/ 35 54 1 More silt A2 A4 52 40 14 80 17 3 More sand A7 A8 37 55 44 12 19 33 24 62 28 10 More sand 455 FISHERY BULLETIN: VOL. 72, NO. 2 Table 5.- — Wind velocity recordings at or above 15 mph on days when there were two or more such recordings, 1967.' Wind direction Number of 3-hourly recordings NE (10°-80') E (90°) SE (100=- 170°) S (180°) SW (190-260=) W (270=) NW (280-350°) N (360=) 76 2 23 2 77 10 224 29 'Source: Local Cllmatologjcal Data, 1967, John F. Kennedy Airpori. US. Dep. Commer., Environ. Sci. Serv. Adm. -Environ, Data Serv. U.S. Gov. Print. Off., Wash.. D.C. Biggs (1968), Hantzschel (1939), Hellier and Kornicker (1962), and others. In a shallow, almost completely enclosed em- bayment like Goose Creek, with a relatively broad exposure to prevailing winds, the effect of wind on the distribution of fine sediments becomes accen- tuated. Biggs (1968:481) states that "strong and persistent winds may cause high suspended sediment loads . . ." The wind velocity data for Kennedy airport on Long Island were tabulated, and those days with two or more recordings of winds at 15 mph or above were compared. As can be seen from Table 5, the prevailing winds 15 mph and above come from the northwest on Long Island. Indi- vidual recordings from the northwest were more than ten times as common as those coming from the opposite direction, and at least three times more common than winds coming from any other quarter. All other factors being equal, one would expect that the difference in mean wind velocity favoring the northwesterly prevailing winds would result in a net deposition of sediment in the south- eastern region of the bay. Examination of Figure 1 reveals that this is the region where the channel opens to Southold Bay, the area of maximum tidal current velocity. This complex interaction of factors would probably result in an unusually high suspended sediment load in the incoming and outgoing tidal currents and the deposition of light particles carried by incoming tides in the southwestern margins of the bay. This hypothesis is given substance by three sets of data: Hair (1968) and Fazio (1969) demon- strate that the transport of nutrients in Goose Creek was strongly influenced by wind-induced currents both before and after dredging. By draw- ing isopleths of NO3 concentrations and relating them to wind direction and velocity, they were able to show that nitrate concentrations were responsive to both factors, with progressive diminutions of concentration across the bay in the direction of the wind source (see Figures 8 and 9). Minimum wind velocity required to induce clear-cut distribution of particulate constituents was 5 mph according to Fazio. He also showed that a wind increase from 13 to 20 mph caused a resuspension of bottom material affecting con- centrations of particulate phosphorus, chlorophyll a, dissolved inorganic phosphate, and nitrate. Nuzzi (1969) shows a correlation between bac- terial count and wind velocity in Goose Creek. He suggests that a critical wind velocity is GOOSE CREEK NY. WIND DieEC TION Figure 8. — Isopleths of NO3 concentration in;ugat. NOs-N/liter, wind coming from the northern quarter. (Redrawn from Hair, 1968). 456 KAPLAN, WELKER, and KRAUS; EFFECTS OF DREDGING GOOSE CREIKN.Y. Figure 9.— Isopleths of NO3 concentration in ug at. NOg-N/liter, wind coming from the southern quarter. (Redrawn from Hair, 1968). GOOSf CREEK NY. Figure 10. — Depths of sediment below mean low water in meters. Data taken from Suffolk County map dated 4/5/67. necessary to overcome the inertia of the sediment particles as well as associated bacteria. Further substantiation of the hypothesis that sediment distribution in Goose Creek was affected by wind-driven currents can be obtained from an examination of Figure 10. Depth of the sedi- ment increases in a north-south direction, irre- spective of the probable contour of the basin. Table 6 tabulates the number of 3-hourly records of winds at or above 15 mph for 1967. Suspension of fine sediments during dredging occurred during the months of least occurrence of high winds (July- August). The absence of strong winds would tend to minimize the distribution of suspended sediment but it also prevents the re- moval of the canopy of flocculent material observed covering the Enteromorpha and Ruppia stipes and leaves during and after dredging. Flemer et al. (1968) suggest that late fall is the season which would be most desirable for dredging, since benthic animal populations are lowest then. On the other hand, the months of November and December are characterized by frequent windy days and any disturbance of the sediment would be accentuated by wind-driven currents. Saila, Polgar, and Rogers (1968) describe summer surface and bottom current pat- terns which caused maximum harmful effects of dumped dredged sediment. Such factors as water depth, contour of basin, and wind- and water- driven currents must be studied further to deter- mine the optimal season for dredging. Mercenaria Survey Mercenaria mercenaria is exploited commer- cially in Goose Creek and it supports a substantial sport fishery. Both before and after dredging, from two to four commercial clammers regularly visited the creek. In 1968, less than a year after the dredging, two clammers were interviewed regarding changes in the productivity of clams over the interval of the dredging operation. They reported that there was no substantial difference in the size of their catch which, according to the local conservation officer, was 4-5 bushels of clams per day. Apparently there was no mass mortality of clams resulting from the release of flocculent and suspended material into the water as a result of dredging. Four major clam producing areas of the bay were sampled before and after dredging, on 8 July 1967 and 4 July 1968 (dredging was com- pleted on 2 August 1967 (see Figure 11)). Table 6. — Number of days of at least two recordings of winds over 15 mph by months (recordings taken at 3 h intervals), 1967. Number Number Month of days Month of days January 7 July 1 February 13 August 1 March 9 September 13 April 17 October 5 May 18 November 13 June 10 December 11 457 FISHERY BULLETIN; VOL. 72, NO. 2 GOOSF CREEK, N.y. Figure 11. — Map of stations, Mercenaria study. A 3.35 m^ square frame was placed on the sub- stratum and a skin diver sampled the area by hand, removing all clams. These were sorted as to size in the following categories: up to 1.90 cm; 1.90-3.80 cm; 3.81-5.70 cm; 5.71-8.90 +cm. The areas sampled were channel B (destined to be the region of the newly dredged channel) and the three major clamming areas used by local residents. Stations 7c to lie were 30 m apart running east to west down channel B. Stations 12c, 13c, and 14c were located on the north, west, and south shores of the bay respectively. Each station in channel B comprised two sampling areas, one 1.5 m from shore and the other in midchannel or about 9 m from shore. Each station in the clam beds used by local residents (stations 12c, 13c, 14c) comprised four sampling areas beginning 6 m from the shore- line at the east end of the bed and progressing westerly at 6-m intervals. The total area sampled was 33.5 m^ in the channel and 39.25 m^ on the clam beds (total 72.75 m^). The data obtained on the pre- and post-dredging surveys are compared in Table 7. Clams in Goose Creek not directly exposed to mechanical disturbance by the dredge (such as clam beds at stations 12c and 13c) were able to survive the dredging process itself, even though they were located within 400 m of the channel (see Table 7). The considerable reduction in the size of the clam populations at stations 12c and 13c suggests that some mortality-inducing factor was at work. The effects of the mechanical removal of the clams by the dredge are obvious. Whether or not finding a few clams in the post^dredging survey at stations 10c and lie means that there are signs of recovery in the population remains to be seen. No evaluation of the long-term effects of changes in the environment has been attempted. These include processes such as the gradual incur- sion of silt towards the mouth of the bay due to lowered current velocity, factors affecting pro- ductivity such as a reduction of the quantity of organic materials introduced into the water as the Spartina marshes were covered with spoil, and an increase in pollutants as the population density of humans along the periphery of the bay increased. Changes in Land Usage Patterns At the inception of the study (1966) most of the periphery of Goose Creek was composed of Spartina and Phragmites marshes, except for the south shore and a neck of land on the southeastern corner which were developed with summer homes. On a map of the area drawn in 1954, 41 homes are recorded bordering the bay. The total number of houses within 300 m of the bay was 114. At the present writing most of the previously undeveloped north shore of the bay is undergoing intensive development of houses used year round. An aerial photograph taken in 1972 (Figure 2) revealed 223 houses within 300 m of the bay, an increase of 94%. All of the houses along the shore of Goose Creek were built on spoil taken from public or private dredging operations. All homes have cesspools. Smith (pers. comm.) introduced Rhodamine B into a toilet in one of the homes bordering Goose Creek. In four weeks detectable quantities were found in the bay waters. Nuzzi (1969) speculates that human fecal coliform bacteria (as identified by elevated temperature incubation) were re- leased into Goose Creek from the septic tanks of the surrounding homes. Maximum coliform counts in his 1966-1968 study were 918 MPN (most probable number)/100 ml. The maximum federal permissible level for waters from which shellfish are taken is a median of 15 readings not exceeding 70 MPN/100 ml, or 10% of 15 readings above 230 MPN/100 ml (Houser, 1965). Individual readings above 230 MPN/100 ml were recorded throughout the period December-March 1967, at one station, and three 458 KAPLAN, WELKER, and KRAUS: EFFECTS OF DREDGING Table 7. — A comparison ofMercenaria populations in four selected areas of Goose Creek before and after dredging. Num bar of clams Befo re dredging (7/8/67) After dredging (7/4/68) Station Inshore Mid-Chan nel Inshore Mid-Channel 7C 1.9 cm 1.9-3.80 cm 5 8 13 1.9-3,80 cm 9 "9 0 0 8C 1.9 cm 1.9-3.8 cm 3.8-5.7 cm 4 18 16 38 3.8-5.7 cm 17 0 0 9C 1.9-3.8 cm 3.8-5,7 cm 31 3 34 1 9-3.8 cm 14 14 0 0 IOC 1.9-3.8 cm 3.8-5.7 cm 2 _5. 7 to 1.9 cm 3.8-5.7 cm 5,7-8.9 cm 2 9 2 13 1.9-3.8 cm 1 T 0 11C 1.9-3.8 cm 2 0.75-1,50 cm 1.50-2.25 cm 3 -6 9 to 1.9 cm 3 3 to 1.9 cm 1 T 12C Station A Station B Station A Station B 1.9-3.8 cm 29 to 1.9 cm 12 to 1.9 cm 8 to 1.9 cm 8 29 1.9-3.8 cm 11 23 1.9-3.8 cm 7 15 1.9-3.8 cm 3 11 Station C Station D Station C Station D to 1.9 cm 16 to 1.9 cm 7 to 1.9 cm 5 to 1.9 cm 3 1.9-3.8 cm 14 1.9-3.8 cm 12 1.9-3.8 cm 1 1.9-3.8 cm 3 3.8-5.7 cm 30 19 3.8-5 7 cm 1 7 T Average numbe r of clams perm' = 7.5 Average number of clams jerm' = 2.9 13C Station A Station 8 Station A Station B 5.71-8.9 cm 27 "27 3.8-5.7 cm 5.7-8.9 cm 18 10 28 0 "o 0 "o Station C Station D Station C Station D 1.9-3.8 cm 22 3.8-5.7 cm 8 1.9-3.8 cm 3 0 5,7-8.9 cm 9 31 5.7-8.9 cm n 19 3.8-5.7 cm 1 4 0 Average numbe r of clams perm» = 7.8 Average numbe rofclams perm' = 0.3 14C Station A Station B Station A Station B 5,71-8 9 cm 44 "44 3.8-5.7 cm 5.7-8 9 cm 17 20 37 na. na. Station C Station D Station C Station D 1.9-3.8 cm 24 5,7-8.9 cm 47 na. na. 3.8-5.7 cm 6 5 71-8.9 cm 17 47 47 Average numbe rofclamsperm' = 12.1 Average numbe r of clams perm' = na. times at another, with levels of 542, 918, and 348 MPN/100 ml. These readings appear to exceed the 10% limit mentioned above and may be suf- ficient grounds for closing the bay to clamming. The densities of presumptive human fecal coli- forms found by Nuzzi correlated with increases in human population size, suggesting that the increase in number of homes around the periphery of the bay during the 1968-1972 will further increase the contamination of clams beyond acceptable sanitary standards. ANALYSIS OF THE EFFECTS OF DREDGING ON MACROBENTHIC ANIMAL POPULATIONS Dry weights from 263, 0.1 m^ samples collected from the bottom of Goose Creek over 22 mo were compared by means of analysis of variance. In addition, chi-square analyses were performed to determine whether or not significant differences existed between pre- and post-dredging popula- tions in number of individuals and species. All 459 FISHERY BULLETIN: VOL. 72, NO. 2 Table 8. — Analyses of variance of pre- and post-dredging dry weights and between stations, in the bay and dredged channel. Sum Degrees of Mean squares Source of squares freedom (variance) F test Probability Stations before and after dredging 158.387 1 158 387 10.623 0005 Variation between stations 492.212 22 22373 1 501 Less than 0.05 Interaction of pre- and post-dredging and stations 311 698 22 14.168 0.950 Less than 0.05 STATIONS 2-25 PLUS A-J, M (CHANNEL) Stations before and after dredging 491.813 1 491.813 37.211 0001 Variation between stations 691.024 33 20.940 1.584 Lessthan0.05 Interaction of pre- and post-dredging and stations 635.301 33 19252 1.457 Less than 0.05 STATIONS A-J, M (CHANNEL) Stations before and after dredging 341.885 1 341.885 127 426 0.001 Variation between stations 163.579 10 16.358 6.097 0.001 Interaction of pre- and post-dredging and stations 133.872 10 13 387 4990 0001 computations were performed on an RCA SPECTRA 70/46 computer.^ Two-way analyses of variance were performed on dry weights of the samples drawn from sta- tions 2-25; 2-25 plus channel stations A-J, M; and channel stations A-J, M alone. Table 8 reveals that pre- and post-dredging biomass varied significantly among stations 2-25, among all stations, and between each channel station. The variances in biomass between sta- tions were not significant in the bay and combina- tion of bay and channel, even though they represented a substantial spectrum of substrata and current velocities. Biomass variances were, however, significant in the channel alone. There was also no significance in the variances of the interaction between stations and dredging, except in the channel. The macrobenthic biomass in Goose Creek had not returned to its pre-dredged level 11 mo after dredging. In the channel substratum, which had a virtually linear reduction in particle size and current velocity progressing from east to west, there was significance in both station to station 'The authors are grateful for the assistance rendered by the Hofstra University academic computing facility, Eugene In- goglia. Director; John Pizzeriella, Programmer; Claire Gittel- man, Statistician. variance and in the interaction between stations and pre- and post-dredging variances. This demonstrates a systematic difference between stations, as well as a significant difference from station to station in the manner in which the animal populations responded to the dredging process. A second two-way analysis of variance was performed on all three sets of data in an attempt to determine whether or not the variance in bio- mass was a function of sediment type. The sampling stations were classified according to the sediment map (Figure 7), with verification pro- vided by visual analysis of samples from the suction corer. Table 9 lists the stations according to their sediment classification. Table 9. — Classification of the Goose Creek sampling stations according to sediment type. Sediment type stations Sand Muddy sand Sandy mud Mud-silt Intertidal 2, 3, 4. 9, 10 A, B, C. D 6, 7, 8. 24 E, F. G 11, 12, 18 H, I, J 14,15,16,17 22, 23. 25, K 9A, 13,20.21 460 KAPLAN, WELKER, and KRAUS: EFFECTS OF DREDGING Table 10 summarizes an analysis of variance of the biomass at the Goose Creek stations according to sediment type. Separate analyses were per- formed on the data for stations 2-25; 2-25 plus channel stations A-J, M; and channel stations A-J, M alone. Significance was found in all three analyses only among dry weights before and after dredging. There was no significance in the variances among substratum types, nor among the interactions of substrata and pre- and post-dredging bio- mass. There was, then, no systematic effect of particular sediment types alone on the rate of recovery of the in- and epifauna, even in the channel. A four- way analysis of variance was performed to examine the relationship between seasons and variances in biomass at each station, without considering pre- and post-dredging effects. Sta- tions 2-18 were studied. The unrepresented stations are in the less saline western half of Goose Creek which was frozen over during Jan- uary and February of both years. There were no significant differences in the seasonal variances among stations, indicating that seasonal fluctua- tions in biomass were not factors which accounted for the differences in biomass, heretofore attrib- uted to the dredging operation. Table 11 sum- marizes the statistics for the analysis of variance according to seasons. Another four- way analysis of variance was per- formed to examine the relationship between seasonal variances and substratum type for stations 2-25. Again, there was no significance in any of the interactions, indicating that variances in biomass are not a function of season, sediment type, or of an interaction between these factors. This analysis is summarized in Table 12. It was expected that the channel would show substantial effects of the dredging process, since it was from the channel that massive quantities of substratum were removed. The sediment and its inhabitants were physically removed to a depth of 2 m. What is of greater importance is the evidence Table 10. — Analyses of variance of pre- and post-dredging dry weights according to sediment type in the bay and channel. Sum Degrees of Mean squares Source of squares freedom (variance) F test Probability STATIONS 2-25 stations before and after dredging 107.634 1 107.634 6.584 0.025 Sediment types 32.746 4 8.187 0.501 Less than 0.05 Interaction of stations and sediment types 62.912 4 15.728 0.962 STATIONS 2-25 PLUS A-J, M (CHANNEL) Stations before and after dredging 206.841 1 206.841 13.899 0001 Sediment types 42489 4 10.622 0.714 Less tfian 0.05 Interaction of stations and sediment types 81.747 4 20.437 1.373 Less tfian 0.05 STATIONS A-J, M (CHANNEL) stations before and after dredging 160.146 1 160.146 22.043 0.001 Sediment types 17.083 3 5.694 0.784 Lessthan0.05 Interaction of stations and sediment types 22.863 3 7.621 1.049 Less than 0.05 Table 11.- -Four-way analysis of variance of dry weights according to season, stations 2-18. Sum Degrees of Mean squares Source of squares freedom (variance) F test Probability Seasonal variations 10.653 3 3.551 0.250 Less than 0.05 stations 224.442 16 14.028 0.988 Less than 0.05 Interaction between seasons and stations 566.497 48 11.802 0.831 Less than 0.05 461 FISHERY BULLETIN: VOL. 72, NO. 2 Table 12. — Four-way analysis of variance of dry weights according to season and sediment type. Source Sum of squares Degrees of freedom t^ean squares (variance) F test Probability Seasons 17.307 3 5.769 0332 Less than 0 05 Sediments 18.002 4 4.500 0259 Less than 0 05 Interaction between seasons and sediments 119 121 12 9.927 0,572 Lessthan0.05 that the rest of Goose Creek, as represented by stations 2-25, also suffered a reduction in biomass from which recovery was not evident 11 mo after dredging. Further evidence of the reduction in biomass after dredging can be found in Table 13, which is a comparison of dry weights at stations 2-25 in -June 1967 and 1968, 1 mo before and 11 mo after dredging. Only one station of the 13 (station 11) for which comparative data exist had biomass in excess of the 1967 levels. The significance of any individual datum is not great, since the presence of an adult clam or sea cucumber could inor- dinately affect a particular station. The general trend, however, is clear; 12 out of 13 stations have substantial reductions in biomass. This reduction cannot be attributed to mechanical removal of sediment or specimens, and is attrib- uted to the dredging process itself. Chi-Square Analysis of Number of Species and Specimens Chi-square analyses were performed to deter- mine whether or not the number of species and individuals in the post-dredging series differed significantly from the pre-dredging population. Data were further analyzed to determine if sub- stratum and seasonal variations affected species diversity and numbers of individuals. Table 14 represents the chi-square analysis of the number of species before and after dredging for the whole bay (minus the intertidal stations), the bay sta- tions plus the channel stations, and the channel stations alone. In all cases the chi-square was significant, indicating that species number was affected by dredging. Since chi-square analysis is limited by its inability to discriminate between sign (-1- or -), Table 15 tabulates the number of species found at stations 2-25 in June 1967, 1 mo before dredging, and in June 1968. A reduction in species number occurred at 75% of the stations after dredging, with three stations or 18.7% exhibiting small increases in species number. A chi-square analysis was performed on the number of species according to sediment type (e.g., sand, muddy sand, mud-silt). The number of species altered significantly according to sub- stratum after dredging, both in the bay as a whole and in the channel (see Table 16). Table 13. — A comparison of dry weights from stations 2-25, June 1967 and June 1968 (in g). Station 2 3 4 5 6 7 3 9 9A 10 11 12 13 14 15 16 17 18 20 21 22 23 24 25 June 1967 1,37 1,80 1.92 0.63 9.44 4.81 18.25 0.55 1.07 0.30 586 0.00 7.68 8.77 2.70 1,41 June 1968 9,47 16,13 0 00 0.92 0,31 1.04 0.15 0 83 0,07 1,64 1.82 000 0,71 0.41 1.08 0,01 0,005 Table 14.— Chi-square analyses of the number of species before and after dredging for stations 2-12, 14-19, 22, 23; stations 2-12, 14-19, 22, 23 plus channel stations A-J, M, and stations A-J, M alone. Stations Chi-square Degrees of freedom Level of significance 2-23 32,763 18 0.025 2-23, plus A-J, M 55.366 26 0,005 A-J, M 21,557 7 0.005 462 KAPLAN, WELKER, and KRAUS: EFFECTS OF DREDGING Table 15. — Number of species found at stations 2-12, 14-19, 22, 23 on June 1967 and June 1968. Station June 1967 2 22 3 16 5 19 6 11 7 25 8 19 9 21 10 26 11 9 12 3 14 0 15 11 16 10 17 5 18 5 22 9 23 1 June 1968 5 5 17 3 (4/68) 13 13 5 5 6 4 (4/68) 0 3 1 7 3 1 Table 16.— Chi-square analysis of the number of species before and after dredging, as a function of sediment type. Stations 2-25; 2-25 and A-J, M; channel stations A-J, M. Stations Chi-square Degrees of freedom Level of significance 2-25 8.43 3 0.05 2-25; A-J. M 21.41 3 0.005 A-J. M 38.24 3 0005 Table 17.— Chi-square analyses of number of organisms before and after dredging, stations 2-21, 23; 2-21, 23 plus A-J, M; stations A-J, M only. Stations Chi-square Degrees of freedom Level of significance 2-25 6.075,22 20 0.005 2-25. A-J. M 6,364.59 29 0.005 A-J, M 152,84 8 0005 Table 18. — Chi-square analysis of the number of organisms before and after dredging as a function of sediment type, stations 2-25; 2-25 plus A-J, M; stations A-J, M. Degree of Level of Stations Chi-square freedom significance 2-25 2.051.59 3 0,005 2-25. A-J, M 1,679.51 3 0005 A-J. M 21,57 3 0005 Similar chi-square analyses were performed using number of individuals at all stations. Here results were even more positive. For example, the pre-dredging number of specimens at station 2 was 6,682; the post-dredging number was 27. Five out of 30 stations, or 16.6%, showed post- dredging increases in population; the others experienced drastic decreases. Table 17 is a summary of the chi-square analysis of the number of individuals before and after dredging. The difference in specimen num- bers was highly significant in both the bay as a whole and in the channel. Chi-square analyses were made on the number of specimens before and after dredging as a func- tion of sediment type. In both the bay as a whole and the channel the number of specimens was significantly different (0.005) in the post-dredging samples, according to sediment types (Table 18). In summary, the numbers of species and organisms differed significantly before and after dredging, in the bay as a whole, as well as in the channel. Additional data show that this difference was in the direction of a post-dredging reduction in both species diversity and number of individuals found at each station. A few stations showed apparent recovery by June 1968, 11 mo after dredging. These were invariably low-popula- tion stations in the mud-silt region of the bay, where a few influents could appreciably change the population size. Stations 2-11, the sand, muddy sand, sandy mud stations, had drastic reductions in both parameters. Table 19 provides further substantiation for this conclusion. Standing Crop Estimates A total of 137 species was taken from the sedi- ment of Goose Creek during the 22 mo of the study. Maximum wet weight at any one sta- tion was 2,581.4 g/m^, with a corresponding dry weight of 355.6 g/m^. Mean dry weight before dredging (excluding the channel) was 36.8 g/m^ (49.6 g/m^ including the channel) while the cor- responding weight after dredging was 12.7 g/m^ (10.1 g/m^ including the channel), a loss of 63% of dry weight. The loss, including the channel, was 79%. (Pfitzenmeyer, 1970, reported a loss of 64% in his spoil deposition area and 72% in the channel.) The mean number of species per station (sta- tions 2-24 minus the four intertidal stations) was 5.47 (54.7/m2) before dredging and 4.02 (40.20/m2) after dredging, a reduction of 26%. 463 The maximum number of specimens found at any one station was 3,521, of which 3,470 were the gastropod, Crepidula fornicata (station 2, October 1966). The mean number of specimens before dredging for stations 2-24 (minus the inter- tidal stations) was 120.14 (1201.4/m2), ^^lile the after-dredging mean was 25.63 (256.3/m2). This constitutes a 79% reduction in the number of specimens found at the post-dredging stations.^ Comparison With Other Areas Direct comparisons between the standing crop estimates at Goose Creek and other areas is complicated by the diverse methods of obtaining these estimates used by workers in the field. As previously indicated, Holme (1953) and Sanders (1956, 1958) used HCl to remove the carbonates from the carapaces of crustaceans and both removed all specimens greater than 0.2 g dry weight from their samples. For reasons pre- viously mentioned, it is important in this investi- gation to obtain data on the populations of the larger forms which dominate the communities of the shallow, estuarine study area being investi- gated. Variation in sieve mesh size between studies is also an important factor accounting for differences in infaunal biomass estimates, but Sanders (1956) attempted to compare numerical results of several investigations by plotting mesh size against the log of the number of animals per square meter. The lowest estimates were those obtained by Holme (1953) from the English Channel (160/m2) and Miyadi (1940, 1941a, 1941b) from Japanese bays (266-1, 290/m2). Sanders' mean number of animals for Long Island Sound was 16,443/m2, although 63% of his sta- tions had fewer than 8,500 animals/m^. The mean number of animals at Goose Creek (l,201.4/m2) is considerably lower than that obtained by Sanders, but it is unlikely that this parameter is the most useful in comparing areas since his Ampelisca and Nepthys incisa-Yoldia limatula communities contained relatively dense popula- tions of small organisms, while at Goose Creek amphipods and protobranch pelecypods made up a very small proportion of the biomass. FISHERY BULLETIN: VOL. 72, NO. 2 Table 19.— The number of organisms found at each station before and afler dredging, stations 2-25 , A-J M. Station number Before dredging After dredging 2 6.682 27 3 1.499 188 5 466 330 6 266 41 7 566 266 8 342 95 9 153 56 9A 92 80 10 505 239 11 144 49 12 47 117 13 6 5 14 73 92 15 125 100 16 192 121 17 270 79 18 66 241 20 129 809 21 124 21 22 271 38 23 102 1 24 300 325 25 65 4 A 74 35 B 708 43 C 612 208 D 262 33 E 53 23 F 54 11 G 95 26 H 64 5 1 49 1 J 51 7 M 46 0 «The data for the means of the stations (per 0.1 m^ samples) were provided as a more accurate estimate of such quantities as species number, because extrapolations from 0.1 m^ to 1.0 m^ in the case of small numbers like 5.47 specimens/0.1 m^ seem to introduce an inordinate amount of potential error. In a comparison of the dry weights of Long Island Sound with other areas, Sanders gives a figure for the mean total dry weight (including "large animals") of 54.627 g/m^. This corresponds to a dry weight of only "small animals" of 15.88 g/m^, a figure which is roughly twice as great as the highest mean value for the other areas discussed. Pfitzenmeyer (1970) performed a study closer in purpose to the present investigation than those described by Sanders. His pre-dredging mean dry weight (including large forms) was 0.90 g/m^, while the immediate post-dredging mean was 0.67 g/m2. Holme's (1953) mean dry weight was 11.2 g/m^, including "large" animals. The figure obtained by Sanders for total dry weight are in good agreement with those com- puted for the present study, since the pre-dredging dry weight for Goose Creek was 36.83 g/m^, while the Long Island Sound figure was 54.627 g/m^. The substantial variance of these data from those of Holme (11.2 g/m^) and Pfitzenmeyer (0.90 g/m2) has been accounted for, in principle, by Sanders in his 1956 paper. 464 KAPLAN, WELKER, and KRAUS: EFFECTS OF DREDGING For data reported on the basis of the 0.2 g dry weight cut-off point, it is sufficient, in many cases, to add the factor suggested by Holme when he points out that 64.4% of the dry weight of his samples was excluded by the 0.2 g point, in order to bring the data to comparable levels. Factors relevant in an explanation of the relatively high standing crop in Goose Creek are: 1. None of the studies referred to sampled to a depth beyond 22 cm, and most examined only the top 6-10 cm of sediment. Deeper-dwelling, large forms were excluded. 2. Virtually all of the investigations previously referred to examined relatively large, slow cur- rent velocity, deep bodies of water with relatively unvarying bottom sediments, such as Chesapeake Bay. Often the populations described comprise mud-silt or silt-clay communities, such as the Ampelisca community described by Stickney and Stringer (1957). It is well known that this sediment is not highly productive of biomass since most organisms are relegated to the upper few centimeters where gaseous exchange is most rapid (cf Raymont, 1950; Sanders, 1956; Holme, 1953; Pfitzenmeyer, 1970). In Goose Creek the high current velocity over a substantial portion of the bay and the diversity of sediment types sup- ported sizeable populations of large organisms, such as the 3,470 C. fornicata found in one dredge haul at station 2. 3. Phytoplankton production is high. Cassin (1968) studied the phytoplankton cycle in Goose Creek during the year before dredging, and found a mean standing crop of 1.64 x 10^ cells/liter. This was lower than that for Long Island Sound (2.38 X 106 cells/liter; Conover, 1952), but considerably higher than those for Block Island Sound and Vineyard Sound. According to Riley (1955), the mean standing crop of phytoplankton in the English Channel is one-quarter that of Long Island Sound; while Flemer (1970) makes a primary production estimate for Upper Chesa- peake Bay at one-fifth of that estimated by Riley for Long Island Sound. Phytoplankton population size appears to vary with benthic standing crop in the studies mentioned above. Population Dynamics and Distribution of Organisms Most of the dominant and subdominant organ- isms found in the channel before dredging were present in greatly reduced numbers after dredg- ing (Kaplan, Welker, and Kraus, in press-b). Three species of mollusc increased in numbers after dredging. Tellina agilis and Lyonsia hyalina increased in sandy sediments while Mulinia lateralis became more abundant in the finer substrata. Two polychaetes, Notomastus later- iceus and Clymenella torquata, abundant before dredging, virtually disappeared afterwards. O'Connor (1972) noted an increase in popula- tions of Mulinia lateralis and Tellina agilis in his study of Moriches Bay. He suggests that M. lateralis is a fast-growing, short-lived species that is more successful in silt. If this is so, it may be suited as an indicator organism which would rapidly increase in numbers in areas where dredged channels cause decreased current veloc- ity and, consequently, invasion of sandy areas by softer sediments. The channel data were not duplicated in the bay as a whole. The most fundamental difference between the two areas was the fact that the substratum and all its infauna were removed in the channel study, while only stations 2 and 3 in the bay study were directly in the path of the dredge. Consequently, the drastic effects of the removal of the habitat were limited, and the reduced population size throughout the bay must be a concomitant of other long-term variables, such as changes in current velocity and anoxia resulting from siltation. Stations 22, 23, and 5 were particularly susceptible to this latter in- fluence, being near spoil areas. Portions of Thyone Cove were inundated when the spoil gate broke during the dredging operation. In addition, sta- tion 23 was in the path of the 1968 dredging of an extension of the navigation channel through Thyone Cove. Most stations, even those in the farthest reaches of the bay, showed reductions in benthic populations; however, no station was farther than 500 m from the dredge at some time during the operation, except for station 25. Figure 12 depicts the changes in population densities of 13 domi- nant and subdominant benthic organisms before and after dredging. In addition, the abscissa of each histogram represents the sediment type, from the gravel of station 2 to the silt of station 23. Clymenella torquata, the nearly ubiquitous bamboo worm, was the numerical dominant in the sandy substrata, forming dense colonies. Notomastus latericeus shared this habitat, though in reduced numbers. Both species of worm 465 FISHERY BULLETIN: VOL. 72, NO. 2 24 7 7.5 305 1 22 C f y m e n e / /o 20 0 i« I 16 N ,4 r 10 Y 8 6 4 2 1 : .... 1 24 22 Ne e ( J u c c 1 n t a 20 18 16 14 12 10 8 « 4- 2 1 . . ,1 ;.:lir.:|. . 1: 24 22 Notornoitus 20 18 16 14 12 10 ■ 8 • 6 ■ 4 ■ 2 1 M , 2 3 5 » 7 8 9 I0 1I12141S16I7182223 24 . STATIONS is l^ in ' " " 'nu • S4N0 MUOOT i4NDY MUD Sill „ ' ° S«~D " ° SUBS Te A TES 2 3 5 6 7 8 9 101M2I41SI61718222324 STATIONS SANO MUOOr $ANOr MUD S 4 NO SUBS T RAT e S 7 8 9 1011121415161718222324 STATIONS UDOT SANDY MU AND SUBSTRATES 24 22 S CO o p OS 20 0 '« f 16 N,4 1 '» T 10 V 8 ■ 6 4 2 , , ll.. M:li.. . M ■ 1 1 24 22 20 ■ 18 16 ' 14 12 10 8 6 4 2 Spi 24 22 C a p 1 ft lla 20 18 16 14 12 10 8 6 4 2 1 1 . 1. . 1 2 3 5 6 7 8 9 10 11121415161718222324 STATIONS 2 3 5 6 7 8 9 10 11 12 14 15 16 17 18 22 23 24 TATIONS 2 3 5 6 7 9 10 11 12 14 STATIONS 15 16 17 18 2223 24 24 22 Po y d o r a 20 D '« E 16 N,4 1 " T 10 f 8 6 4 2 1 .; .i.. 1 1 . 1 24 22 20 Sc 'erodocty la 18 16 14 12 10 8 6 4 2 1- . 1. 1 1: .: . . . 24 3 8 60 22 20 M Y a 18 16 14 12 10 8 6 4 2 '■ 1- ■Mi : ,! 2 3 5 6 7 8 9 10I11214I516I718222324 STATIONS SUBSTRATES 2 3 5 6 7 8 9 10 11121415161718222324 ^ STATIONS i s I ^ tt I " »»- E D SAND SILT 0 D SUBSTRATES 2 3 5 6 7 8 9 10111214151617182223 24 STATIONS UDDY SANDY MUD AND SUBSTRATES 24 22 Mercenor a 20 0 IS E 16 N 14 T 10 V 8 6 4 2 : 1. i: i: 1: 1. •i 1 1. . I. 24 22 Neoponope 20 IS 16 14 12 10 8 6 4 . 2 1 h ., .; 1 . .. 24 22 3 Shrimp 1 20 18 16 14 12 •lO 8 6 4 2 I. I ,i 1 2 3 5 6 7 8 9 10 11 1 2 14 15 16 1 7 18 2 2 23 24 STATIONS 2 3 5 6 7 8 9 1011121415161718222324 STATIONS 2 3 5 6 7 8 9 10 11 12 14 15 16 17 18 2223 24 STATIONS 24 22 20 H Y d r o b i a 18 16 14 12 10 8 6 ■ 4 ■ 2 ■ . 1 . 1. . 1 . ....... Figure 12. — Population fluctuations before and after dredging, and distribution according to substratum, of 13 dominant and subdominant epi- and infauna of Goose Creek. The solid line represents pre-dredging; the dotted line post-dredging popu- lation sizes. 2 3 S 6 7 8 9 10 11 12 14 15 16 17 18 2223 24 STATIONS SANDY MUD N 0 D 0 SUBSTRATES 466 KAPLAN, WELKER, and KRAUS: EFFECTS OF DREDGING showed substantial reductions in density in the post-dredging samples. Spio setosa, another inhabitant of sandy substrata, seems to have maintained its population size, with 50% of the stations recording increases in the number of specimens.'^ Capitella capitata and Polydora ligni, inhabi- tants of sandy mud, also decreased in number. Nereis areonodacea was found in muddy sand in small numbers, whileNereis succinea was present in densities up to 42/in^ in the sandy mud and silt stations, which were also frequented by Mercenaria mercenaria. Modest reductions in the Nereis and Mercenaria populations occurred after dredging. Mya arenaria was found in sand and muddy sand. Certain areas experienced drastic reduc- tions in the densities of these organisms, but since most of the Mya recorded were juveniles, popula- tion fluctuations independent of dredging may have been an important factor. Factors favorable to larval settling and the growth of juveniles may have been unsuited to their sustenance as adults, resulting in mass mortality of juveniles at critical points in their development. Of the epifauna, Neopanope texana sayi was found in greatest abundance in the high current velocity, stony gravel of station 2. It was also abundant in the muddy sand of station 8 and the silt of stations 16, 18 and 22. It was recovered in five of the samples at station 16 and four at station 18, so it is unlikely that the presence of this crab in the silt regions was accidental. Neopanope texana sayi experienced a reduction in population density after dredging. Crepidulafornicata was found in large numbers (3,470 in one haul) at station 2 before dredging,- but since this station was in the channel, it was decimated by the dredge and no recovery was noted in the 11 mo period after dredging. Crepi- dula broods its young; recovery would be expected to be relatively slow in a decimated area as dispersal is not accomplished by free-swimming larvae. Four species of Caridean shrimp were abundant on the silt substratum of Goose Creek. These were ■'The reader should be cautioned in interpreting the fluctua- tions in population densities on these graphs. Although each column represents six pre-dredging or six post-dredging samples, the distribution of organisms was so patchy that accumulating the data and recording means still does not compensate for possible sampling error as the corer penetrated a worm colony one month and sampled a relatively sterile area 1 m away from it the next. Trends, however, are apparent. Hippolyte pleurancanthus , Crangon septimspino- sus, Palaemonetes vulgaris, and P. pugio. Their numbers fluctuated seasonally and from station to station, possibly reflecting sampling error in- herent in using the cumbersome corers to capture these relatively rapidly moving organisms. There were population decreases at most stations. The snail, Hydrobia totteni, was most common in the sandier sediments, especially at stations 3 and 7 which had substantial current velocities. Its post-dredging density was considerably re- duced from pre-dredging levels. Mulinia lateralis was found to be more abun- dant in the channel after dredging than before. Too few were encountered in the bay study to corroborate this finding. The polychaete Maldanopsis elongata was found only at station 11 in virtually all samples, reaching a density of 60/m2. Its population size was maintained after dredging. The holothurian Sclerodactyla ( = Thyone) hriaerius was common in the silt stations 12-22, reaching a density of QOIva^ in the deep silt of station 22. The mean numbers at station 22 were 33/m2 before dredging and 2lxn^ after dredging, reflecting, perhaps, the close proximity of this station to the spoil gate of spoil area C. Sclerodactyla briaerius experienced declines at five of the six stations at which it was recorded in substantial numbers. The tunicate, Molgula manhattanensis , was common on the Enterornorpha which covered the silt at stations 22, 23, and 24, reaching a con- centration of 590/m2 in December 1966 at station 23 and declining in numbers after dredging at all three stations. An amphipod community, similar to those described by Stickney and Stringer (1957) and Rhoades and Young (1970), occurred in the silt west of station 12. The most abundant species were identified as Ampelisca macrocephala and A. spinipes. Maximum abundance recorded for sta- tions 16, 17, and 18 was 310, 490, and 190/m2, considerably lower than the level of 10,000 m^ mentioned by Stickney and Stringer for Green- wich Bay. The 1.4 mm sieve size used in this study contrasts with the practice used by Stickney and Stringer of examining the fine sediments completely, using no sieve. However, it seems unlikely that population densities would be comparable, since there was no massive concen- tration of amphipod tubes in the Goose Creek 467 FISHERY BULLETIN: VOL. 72, NO. 2 samples. The amphipods found in Goose Creek were limited to the soft sediments, in contrast to Long Island Sound and Buzzards Bay, as reported by Sanders (1956, 1958), making it likely that they are detritus feeders. No pattern was evident between pre- and post-dredging popula- tion densities of amphipods. The Nepthys incisa-Nucula proxima community of Sanders was not found in Goose Creek since both species were not abundant enough at any one station to be considered dominant. Instead, a Nereis succinea-Mercenaria mercenaria-Sclero- dactyla briaerius community was found, with subdominants including Capitella capitata and the caridean shrimp previously mentioned as epifaunal subdominants. Clymenella torquata and Mya arenaria can be considered the dominant sandy sediment assem- blage, with Notomastus latericeus and Hydrobia totteni comprising important subdominant popu- lations. Scoloplos robustus, S. fragilis, and Neopanope texana sayi were distributed throughout the sediment types in Goose Creek, apparently with- out specificity. There was no evidence that the dredging process eradicated any species. There was, however, evidence of two cyclical fluctuations in population density which occurred naturally and were super- imposed on the dredging data. Individual Aequi- pecten irradians were found in only four sampler hauls. Much of the shell in the substratum was contributed to by this species, testifying to its former abundance. In fact, it was commercially harvested from Goose Creek in previous years. Its absence coincided with a cyclical low in its density and had nothing to do with the dredging. Similarly, not one specimen ofCallinectes sapidus was recorded for the 22 mo of the study, yet in July 1970 large numbers of these crabs were observed in Goose Creek. Sanders' mean ratio for all stations in his Long Island Sound survey was 2.44. He estimated the total productivity of "small infauna" in the sedi- ment of Long Island Sound at 21.49 g/m^. In computing his estimate he did not consider epifauna and "large" forms. He also makes the assumption that the substratum of Long Island Sound is comprised of 80% fine sediments and 20% coarse. Goose Creek has a distribution closer to 50% of each type of sediment. Correct- ing for these factors would tend to raise the total value of the estimate, even though the biomass of "short-lived" species is a practically negligible component of the Goose Creek samples, a factor which could lower the figure to 2.1. Because of these considerations, and because of the con- tiguity of the two study areas, Sanders' figure of 2.44 was adopted for Goose Creek. Macrobenthic animal production in Goose Creek before dredging is estimated at 89.87 g/m^/yr, using the factor of 2.44. If Sanders had used his standing crop figure for all epi- and in- fauna from Long Island Sound (54.627 g/m^) in a similar calculation, his estimate would be 54.63 X 2.44= 133.30 g/m^/yr, a figure in essential agreement with the ratios of the standing crop estimates in the two areas. The after-dredging productivity figure is 31.18 g/m^/yr for a loss of 58.69 g/m^/yr. This means that 18,780 kg of animal production were lost from the 0.32 km^ of bottom in Goose Creek during the post-dredging year. This corresponds to ap- proximately 58,700 kg/km^/yr reduction in the productivity of the bay, out of a total productivity of 89,870 kg/km2/yr. Primary productivity of the extensive Ruppia and Enteromorpha beds was not estimated. An Estimate of the Productivity of the Marsh Productivity The mean pre-dredging dry weight for Goose Creek was 36.83 g/m^ before dredging and 12.78 g/m^ after dredging, a decrease of 63%. Sanders (1956) suggests that standing crop figures for in- fauna are a function of productivity by a ratio of 2.1-5.0:1. Taylor and Saloman (1968) used a factor of 4 in their calculations of infaunal productivity in highly productive turtle grass beds. The islands in Goose Creek are represented on a 1904 map with virtually unaltered boundaries. Their natural isolation makes it unlikely that they have ever been exploited by man. The relative abundance of "bank" or "mud" oysters and extensive colonies oi Modiolus and Uca give further evidence of their pristine state. The islands evidently have been created by the deposition of materials at the confluence of chan- nels A, B, and C. They are covered with a uniform growth of Spartina alterniflora, with 468 KAPLAN, WELKER, and KRAUS: EFFECTS OF DREDGING Salsola kali and other plants growing on patches of shghtly higher ground. The dominant animal is Modiolus demissus which was abundant on all four major islands, averaging 19.58 specimens per m^. Colonies of fiddler crabs, predominantly Uca pugnax, were found on islands I and II. The islands are little more than hassocks of Spartina. At low tide they project 0.7 m to 1 m above the water surface; at high tide they are vir- tually inundated. The largest of the islands, island II, was 115.59 m x 42.39 m. The islands represent the most unspoiled aspect of the Goose Creek marsh. For that reason, they were chosen as the site for estimating the productivity of the Spartina alterniflora marsh along the periphery of Goose Creek. The result- ing figure will be higher than other productivity estimates because it does not represent the Spartina patens and Phragmites communis marshes which are both transitory and strongly affected by man in the Goose Creek area. Island II, the most southeasterly of the islands, was sampled by means of seven stations arranged at 15 m intervals and staggered so that both edges and the center of the islands were sampled at least twice (Figure 13). A 1.83 m X 1.83 m frame was placed on the area to be sampled so that 3.34 m^ were delimited. A team of four collectors was stationed, one collector on each of the sides of the sample area, to prevent motile forms from escaping. All surface-dwelling animals were removed by hand. The area was then spaded to a depth of 20 cm to remove burrowing forms. The total area sampled was 23.4 m^. Table 20 represents the animal biomass of the stations on island II. Animals making up the species mix were: 104 Uca pugnax, 6 Uca pugi- lator, 442 Modiolus demissus, 28 Sesarma reticu- latum, 1 Carcinus maenus, 3 Littorina littorea, and one unidentified Nereid. The total wet weight of the macrofauna taken from the seven stations is 2,327.01 g, or 90.94 g/m^. The corresponding calculation for dry weight is 20.21 g/m^. The ratio of dry weight to wet weight is 1:4.9. The computations for estimating primary pro- ductivity of the marsh were taken from Udell et al. (1969) from their study of the Hempstead, Long Island, salt marsh. They calculated a total minimal estimate (harvest method) of annual production of 3.68 tons per acre of tall Spartina Figure 13. — The distribution of stations on island II. Table 20.— Biomass of animals found on island II, Goose Creek. Animals Wet wt. Dry wt. Dry-wet No. No. Station (g) (g) ratio specimens species 1 397.32 78.52 1/5 62 2 2 595.55 108.90 1/5 109 4 3 155.76 28.47 1/6 39 4 4 175.46 34.19 1/5 47 4 5 705.24 156.86 1/5 157 3 6 213.97 41.90 1/4 96 4 7 83.71 16.43 1/5 29 3 Total 2.327 01 475.27 alterniflora and 2.55 tons per acre of the mixed species comprising the typical Long Island marsh (tall and short .S. alterniflora, S. patens, Distichlis spicata, etc.). These weights corresponded to a mean dry weight of 827.2 g/m^ for tall S. alterni- flora and (by extrapolation) 578 g/m^ for the mixed species. Animal production taken from our mid- August study is 20.21 g/m^, dry weight. Sanders (1956) suggests that standing crop figures for infauna are a function of productivity by a ratio of 2.1-5:1. Since the organisms predomi- nating in our samples are predominantly "long- lived," Sanders' factor of 2.1 was applied. Animal productivity of the marsh comes to 42.4 g/m^/yr, by this calculation. This is roughly 5% of the tall S. alterniflora productivity figure or 7% of the overall estimate. The total animal and plant pro- ductivity of the tall S. alterniflora marsh as repre- sented by island II, is 869.64 g/m^/yr. Thus, if the dredged channel had passed through island II instead of skirting it, its 4,900 m^ of marsh or 4,261.2 kg (dry weight) of animal and plant productivity would have been permanently obliterated. The portion of the Goose Creek marsh inun- dated as spoil areas has been estimated at 108,712 m^. Using Udell's estimate of 2.55 tons/acre (4,553.57 kg/ha), the total primary productivity of the marsh which became the spoil areas would 469 be 4,553.57 kg/ha x 10.87 ha or 49,497.31 kg/yr. Animal production of tall S. alterniflora marsh has been estimated to be 5-7'7f of primary pro- ductivity. Since mixed marsh is not as productive of animals as tall S. alterniflora marsh, a figure of 4% of the mixed marsh primary production seems to be a reasonable estimate. Annual animal production on the 10.87 ha of inundated mixed marsh would then be 4% of 49,497.31 kg or 1,979.89 kg. Virtually the entire spoil areas have been turned into homesites. If they had been left to produce aPhragmites communis community, only a relatively small proportion of the original productivity would have been locally available on a trophic level (Johnson, pers. comm.). Since approximately 45% of the net production of a salt marsh (Teal, 1962) is exported outside the area of its source, the loss of this productivity will have repercussions beyond Goose Creek. The estimates given herein should be con- sidered conservative, as E. P. Odum (1959) estimated the primary productivity of tall S. alterniflora in Georgia salt marshes at a high of 14 tons/acre and Ryther (1959) gives a figure for net organic production of Spartina marsh of 9.0 g/m2/day. H. T. Odum (1963) indicates that Thalassia beds in Redfish Bay, Tex., recovered in the areas not directly in the path of the dredge after one year, but his data indicate that the dredged area and an area 0.25 mile east of the channel had no productivity due to removal of the substratum to bedrock in one case and "beds covered with 30 cm of soft silt" in the other. Virtually all of Goose Creek was within 0.25 mile of the dredge. Studies of large embayments tend to deemphasize dredging effects because of the dissipation of the products of the dredging process and dilution factors. Similarly, regions like Chesapeake and Redfish Bays have relatively extensive bottom areas and circumferences and dredge spoil is either deposited back in the basin where it spreads to form a relatively shallow homogeneous layer often virtually indistinguishable from the bottom (Biggs, 1968, 1970), or covers a relatively small portion of the bay edge. The effects of dredging appear to be accentuated as the size of the embayment decreases. FISHERY BULLETIN: VOL. 72, NO. 2 DISCUSSION The Relationship of the Substratum to the Distribution of Organisms Wilson (1938, 1953), Morgans (1956), Sanders (1958), and Sasaki (1967) related larval or adult infaunal population densities to sediment type. McNulty, Work, and Moore (1962) and Harrison, Lynch, and Altschaeffl (1964) fail to corroborate either degree of sorting or median grain size as definitive factors affecting the distribution of deposit or filter feeders. It appears that animal- sediment relationships are variable depending on such factors as sediment type, life cycles of related fauna, and location. In the Goose Creek study the analysis of variance between biomass before and after dredging as a function of sediment type revealed no significant interaction between productivity of animal biomass and sediment type in the bay as a whole. In the channel, however, there was a positive correlation between biomass and sta- tions. Since the stations were arranged in linear fashion virtually in descending order of particle size and in the direction of lowered current velocity, these factors appear to have had an influence on productivity. The recovery rate of the macrobenthic popula- tions varied in different substrata according to a chi-square of the number of species found at the stations representing different sediment types. Similarly, the number of species was sig- nificantly different before and after dredging, as a function of sediment type. It appears, then, that productivity in terms of animal tissue was not independently influenced by substratum in the bay as a whole, but there was a response to the specific conditions in the channel. Recovery of species and specimen num- bers appeared to be affected by sediment type in both channel and bay. These data tend to sub- stantiate those of Sasaki (1967). The Relationship of Current Velocity to the Characteristics of the Sediment and the Distribution of Organisms In a shallow bay with a narrow mouth like Goose Creek, wind-driven currents probably have a disproportionately large effect on the char- acteristics of the sediment. Prevailing winds can 470 KAPLAN. WELKER, and KRAUS: EFFECTS OF DREDGING cause a net transport of materials towards the lee shore. Wind storms can so pile up water at the mouth of the bay that flood tide current veloci- ties would be considerably above the normal range, causing erosion of the banks of tidal channels and exaggerated depositional patterns, or winds can depress the natural flushing action of the ebb tide, increasing the deposition of light particles. A number of the aforementioned factors have not been considered in the literature in detail, perhaps because most investigations are concerned with relatively large and deep bodies of water. However, Biggs (1968) concludes that most of the suspended material in Upper Chesapeake Bay came from the bottom and had been stirred by wind-waves and currents. Inman ( 1949) refers to three basic factors in the transportation and deposition of sediments: degree of bottom roughness, settling velocity, and threshold velocity. He shows that as current velocity drops in a downstream direction, particle size also decreases. The degree of sorting, however, is at a maximum in sediments with a median diameter near the grade of fine sand (0.18 mm). Threshold velocity for grain diameters less than 0. 18 mm increases with decreasing grain size. Since the threshold velocity is much greater than the setting velocity for smaller particles, suspended particles entering a bay will, when deposited, have a tendency to remain a part of the substratum rather than move about by surface creep or resuspension. On the basis of these characteristics of fine sands, Sanders (1958) deduces that they must represent a very stable environment. He also emphasizes the role of clay as an efficient binding agent for organic matter, thus influencing the number of deposit feeders present. The simple clay-silt proportion governing the population size of Sanders' deposit feeders is not apparent in the distribution of filter feeders, where more complex factors are at work. McNulty et al. (1962) related low current veloc- ity to the accumulation of a detritus layer on the sediment surface capable of supporting large populations of detritus feeders. Rhoads and Young (1970) suggest that biogenic reworking lowers critical erosion velocity and increases the instability of the substratum as manifested by a high resuspension rate and in- creased turbidity close to the silt-water interface, placing selective pressure on suspension feeders. In the present investigation, maxima in bio- mass production occurred in areas of coarse and fine sand in the channel (stations B, C, and H) with current velocities of the order of 56 cm/sec and 17 cm/sec, before dredging. In the bay as a whole 14 of 113 individual dredge hauls yielded dry weights above 80 g/m^. Since the distribution of organisms was so patchy, these extraordinarily large standing crop mea- sures are perhaps the best index of the productiv- ity of the various substrata. The highest biomass was recorded for station 2. However, this con- sisted almost exclusively of Crepidula fornicata, an epibenthic gastropod which requires the scouring action of a rapid current to establish a substratum of stones upon which it clings with a broad foot. Stations 7 and 9 had high and medium current velocities (41.5 and 12 cm/sec) and supported extensive colonies of the poly- chaetes Clymenella torquata and Notomastus la- tericeus, as well as large pelecypods (Mya, Ensis, Mercenaria) in the case of station 9. Both C torquata and A'^. later iceus are deposit feeders inhabiting sandy sediments. Stations 16, 17, and 22 were in regions of almost negligible current velocity which were characterized by a substratum of silt over fine gray sand. The major weight contributors at sta- tions 16 and 17 were Sclerodactyla (Thyone) and large Mercenaria, with the polychaetes, Capitella capitata, Polydora ligni, Scoloplos robustus, and S. fragilis making important contributions. Poly- dora is almost exclusively an inhabitant of mud, while the other worms are found in sandy mud. All of the above-mentioned worms are deposit feeders whereas Sanders groups Mercenaria and Sclerodactyla together as suspension feeders. Deposit-detritus feeders were important con- tributors to the biomass in Goose Creek, in both the sandy and muddy habitats. These animals are more or less substratum-specific, as can be seen on their distribution graphs (Figure 12) and in Sanders' data. Changes in current velocity have a profound influence on the nature of the sub- stratum and, consequently, on animal distribu- tion. This is especially true in the regions of the sandier sediments. Stations 2, 7, and 9 had reductions from 50 to 75% of pre-dredging velocities. In the western portion of the bay, wind- driven currents are the predominant means of sediment transport, and, although some changes in the mid-bay region could be expected due to increased current velocities, these would not have a substantial influence on the soft sediment of the western half of the bay. 471 FISHERY BULLETIN: VOL. 72, NO. 2 The most numerous instances of high infaunal standing-crop production were in areas which cor- respond to the general classification proposed by Sanders (1956), of a relatively high silt-clay composition, although the stations with the highest animal biomass were either somewhat above the 13-25'7c silt-clay level reported as most highly productive, or toward the lower end of the spectrum. Suspension feeders, with the excep- tion of station 2, were not the dominant forms in the sandy sediments of Goose Creek, except in the littoral. Instead, deposit feeding polychaetes were numerically dominant and often constituted the major weight factor in the biomass. Further- more, if Mercenaria andSclerodactyla are grouped together (Sanders, 1956), the biomass of suspen- sion feeders predominates in high silt-clay regions. An important Ampelisca community was not found. The Effects of Dredging on the Substratum and Its Fauna Three major categories of environmental dis- turbance brought about by dredging are: 1. Immediate effects, during and directly after the dredging, including suffocation of benthic ani- mals by siltation; flocculation and removal from the water column of planktonic organisms (which affects benthic filter feeders by removing their source of food); and changes in water chemistry, as substances are released from the substratum and dissolved. Large quantities of bottom mater- ials placed in suspension by the dredging process decrease light penetration, change the propor- tion of wavelengths of light reaching the plants and interfere with the food-getting processes of filter feeders by inundating them with wrong size or nonnutritive particles. On the other hand, the release of nutrients into the water profoundly affects the composition of the plankton by favoring the growth of some species. This effect could be beneficial or harmful depending on whether or not the plankton bloom is utilized by the filter feeders. If nannoplankton like Nannochloris and Stichococcus, which have been incriminated in mass mortalities of Mer- cenaria, are the dominant forms in the bloom, selective removal of certain species of filter- feeders could be expected. 2. Transitory or semipermanent effects such as the mechanical removal of the benthos from the dredged area and a change in the nature of the substratum by the deposition of spoil. These changes may be temporary, as the dredged area is recolonized or tidal currents reestablish the original substratum composition by scouring away fine particles and reestablishing old chan- nels, or depositing fine sediment over exposed, sandy areas. Recolonization of areas denuded of organisms has been studied under either artificially induced conditions or as the result of major disturbances such as oil spillage. Reestablishment of the original fauna is estimated to take at least 8 yr in the intertidal zone, as reported by Castenholz (1967) and by North (1967). Clarke and Neushul ( 1967:47) give some insight into the complexity of the recolonization process when they report: "Apparently a barnacle stage had to be established before the surface of the rock was suitable for the larval stages ofMytilus to become established." In their study it took 4 yr for the reestablishment of small Mytilus californianus colonies. In the aforementioned works the environment was not fundamentally changed by the conditions leading to defaunation, namely, storms, oil spil- lage, or artificial removal of the organisms from the substratum. If a rock has been manually denuded of organisms, natural succession can begin imme- diately. In the case of dredging, however, the substratum may remain unstable for a con- siderable time and final recolonization cannot begin until the climax substratum is reestab- lished. 3. Permanent changes in the ecology brought about by dredging occur if the ambient flow of water and current distribution patterns are dis- rupted. One of the results of dredging was the reapportionment of maximum water transport into Goose Creek from channel A to channel B. Furthermore, the current velocity in all three channels dropped because of the enlarged capacity of the dredged channel for containing water, since it was approximately three times deeper than the channel it replaced. A different dis- tribution pattern of silt and other fine particles occurred as the result of lowered current veloci- ties which resulted in sediment changes in a sub- stantial portion of the bay. Spoil deposition on the surrounding marshes has a profound effect on the species composition 472 KAPLAN, WELKER, and KRAUS: EFFECTS OF DREDGING and productivity of an estuarine area. Raising the level of the marsh above the inundation zone will replace the highly productive Spartina community with the less biologically useful Phragmites communis. Much of the food of detritus feeders comes from the disintegrating plant material of the Spartina marsh and, in the ab- sence or depletion of this food source, the species mix and/or proportion of detritus to deposit on filter feeders may be permanently changed. Even the removal of shell from a mud bottom has been suggested as a reason for the exclusion of certain species from a dredged bay. Barnard and Reish (1959) suggest that the amphipod, Metaceradocus occidentalis and the polychaete Scyphoproctus oculatus were in danger of losing their habitat as the upper shell and rock laden layers of the mud substratum were removed by a dredging operation. The distribution or removal of materials during dredging in a body of water with even minimal flushing action results in immediate, temporary, and long-term changes in its ecology. The inter- action of organisms with this rapidly changing environment is poorly understood. Estuarine organisms are noted for their ability to withstand environmental vicissitudes, yet this adaptability may be overstressed by one or another aspect of the dredging process. For example, Postma (1967:226) refers to the difference in the distribu- tion patterns of dissolved and suspended ma- terials. He points out that dissolved materials have a net transport from regions of high con- centration to regions of low concentration, causing a rapid dispersal of the dissolved matter and its consequent removal from the source area: "In the case of suspended matter the reverse often occurs. This material may be trapped and accumu- lated in the nearshore environment." Thus, a benthic organism in the vicinity of a dredging operation can be subjected to a short-term rapid surge of dissolved nutrients in its environment, with all of the concomitant interactions this represents. Superimposed on this relatively fleet- ing enrichment of the water would be the longer- term deposition of suspended sediments. The interaction between the two, such as the adsorp- tion of organic compounds on suspended clay particles (e.g. amino acid complexes binding strongly to clays) (Siegel, 1966), the effects of flocculation, etc., is poorly understood. The pre- sence of the dissolved organic compounds lib- erated by the dredging process also can have beneficial effects on the benthic organisms. Siegel quotes Stephens and Schinske (1961) who found that glucose, glycine, and aspartic acid can serve as energy sources for marine inverte- brates. Organic matter may also supply a growth factor such as vitamin B12 or may inhibit the growth of bacteria by its antibiotic effect (Saz et al., 1963). It may promote growth by solu- bilizing trace metals, thus making them available (Johnston, 1964). Udell et al. (1969) analyzed marsh grasses and found a number of vitamins, including vitamin B12. The destruction of peri- pheral marsh by spoil deposition may eliminate a constant source of vitamins and other nu- trients made available by the disintegration of the Spartina. The effects of the dispersion of light rays in the turbid water of a dredged bay is also in- completely understood. It is unlikely that in- creased turbidity can destroy benthic flora through light deprivation in shallow waters. Clendenning (1958) studied the relationship be- tween photosynthesis and light intensities for Macrocystis pyrifera laminae. Compensation (light intensity where photosynthesis balanced respiration) occurred at 15 foot candles using white light. First evidences of saturation occurred at about 400 foot candles and maximum photo- synthetic rates occurred at 1,600 foot candles. Since the intensity of daylight delivered to the water surface is about 10,000 foot candles, it is unlikely that the light values would so depreciate in shallow water as to seriously impair photo- synthesis. On the other hand, the authors ob- served a colony of Ruppia after dredging and the leaves were covered by a light brown flocculent material which had been deposited from the water. Large areas of Enteromorpha and Aghardiella showed a similar canopy of fine sediment. It is possible that the deposition of opaque material from the water onto leaves and stipes in areas of negligible current velocity might pose a threat to the plants by inhibiting photosynthetic activity even though the turbidity of the overlying water is not high enough to reduce adequate light penetration. The estuarine environment is particularly sus- ceptible to particle deposition. Although it shares the factor of close proximity to the source of the particulate matter with open beaches, the beaches have a longshore drift factor which tends to distribute particulate matter. It is well known that beach sands are well sorted. Estuarine areas, 473 FISHERY BULLETIN: VOL. 72. NO. 2 on the other hand, have a circulation cycle which favors deposition. Postma (1967:229) states: "The estuarine circulation therefore acts as a 'sediment trap' in which water flows freely seaward, but particles heavier than the water are retained." Flemer et al. (1968) list a numher of factors associated with the effects of dredging on animal survival and suggest that suspended sediments probably affect many sites in the energy flow sequence of the benthic community. Several studies have been made on the effects of siltation on the survival of pelecypods. Loosanoff and Tommers (1948), Davis (1960), Davis and Hidu (1969), and Loosanoff (1962) described harmful effects of heavy sediment loads on eggs, larval development, and adult pelecypods, while Lunz (1938), Wilson (1950), Mackin (1956), and Dunnington (1968) showed that adult oysters do not suffer appreciable physiological damage unless subjected to very heavy siltation or buried. Pfltzenmeyer (1970) described the effects of dredging and spoil deposition in Upper Chesa- peake Bay. The dredging process did not cause major topographical or stratigraphical changes since the spoil was fundamentally identical with the substratum upon which it was deposited and it spread out to form a thin layer over the bottom, undisturbed by strong currents. Species mix and biomass were markedly reduced immediately after dredging, but recovered to original levels after 18 mo. Of interest in Pfitzenmeyer's study is the super- imposition of the natural cycles of certain mol- luscs on the data related to dredging. The pele- cypods Macoma phenax and M. balthica were in a period of natural decline during the period of the study, while i?an^ia cuneata experienced a short- lived population explosion, reaching a density of 10,000 clams per m^. One year after the study, the Rangia population had disappeared. These rapid and extreme fluctuations in the population densities of organisms profoundly affected bio- mass calculations because of the relatively large size of the pelecypods, compared with, for example, the three permanent dominants, two of which were an isopod and an amphipod. If the Rangia population increase had not compensated for de- creases in the Macoma populations during the study, it is possible that there might have been significant differences in the results. If the dredg- ing had substantially altered the substratum, e.g., by removing the silt to a depth sufficient to expose the sand underneath, the recovery of the populations might have required a period of substratum stabilization before achievement of normal populations. Pearce (1970) studied a spoil deposition area of the New York Bight known as the "dead sea." He describes the benthic environment as severely affected by the deposition of large quantities of spoil. He found contamination by heavy metals, pesticides, and petroleum derivatives. The central portion of the spoil area contained no living macrofauna; peripheral areas were frequently barren or impoverished; interstitial waters of spoil sediments had extremely high coliform counts. In laboratory experiments where the crusta- ceans Homarus americanus and Cancer irroratus and the xiphosuran Limulus polyphemus were exposed to sludge and spoil sediments, high mortalities, and pathological conditions were described. Pearce concluded, ". . . sewage sludge and dredge spoil deposits are incompatible with most normal biological phenomena," (p. 66). He blames this condition on: 1) adults being killed by toxins, anoxia, or inundation by solid wastes; 2) interference with or destruction of eggs and larvae; and, 3) active avoidance by adult and larval organisms. A number of reasons suggest themselves to explain why the results of Pfitzenmeyer's and Pearce's studies are so diametrically opposed. For one, Pearce's study area was one of constant spoil deposition; Pfitzenmeyer's had only one in- undation. Secondly, Pfitzenmeyer records rela- tively normal concentrations of oxygen while Pearce indicates that oxygen concentrations were frequently 2-3 ppm lower in the water above the spoil. Finally, there seems to be a very high degree of contamination of the dredged sediments with heavy metals, insecticides, and petroleum frac- tions in Pearce's study, which is absent in Pfitzen- meyer's. A number of studies was performed on the effects of dredging on oyster production. Breuer (1962) reported major changes produced by dredg- ing spoil deposition in South Bay, Tex. Water circulation was impaired by reducing the size of the entrance. Water depth decreased, much of the oyster population was silted over and destroyed, and high local turbidity was evident. 474 KAPLAN, WELKER. and KRAUS: EFFECTS OF DREDGING Mackin (1961) reviewed the literature on the biological effects of dredging, with special refer- ence to oyster survival. Most of the authors he cited found that oyster mortality was caused by direct inundation with spoil resulting in suffoca- tion. Beyond the area of deposition, oysters and fishes were unaffected. Mackin found that at low current velocities turbidity is not an important factor in oyster mortality at levels up to 700 ppm. Such levels were higher than those found beyond 250 ft from the outlets of the three types of dredges studied. He also argues that oxygen levels are not appreci- ably decreased under conditions normally found on oyster beds. SUMMARY AND CONCLUSIONS The results of the present study differ from those reported in most other investigations of the effects of dredging in that profound changes are reported in macrobenthic animal populations throughout the bay. Abundant evidence is avail- able concerning long-term depreciation of stand- ing crop in dredged channels (cf. Taylor and Saloman, 1968; Odum, 1963; Murawski, 1969; and O'Connor, 1972), but these reports show limited residual effects beyond the immediate region of the channel and/or spoil areas. This difference in results is attributed to the fact that most previous studies reported on the creation of channels through relatively large bodies of water such as Chesapeake or Boca Ciega Bays. Spoil distribution effects and changes wrought in cur- rent velocity and sediment deposition are mini- mized when the ratio of the dredged area to total bottom area and contained water volume is large. Long flushing time and reduced inlet size of small estuarine bays exaggerates the hydrodynamic effects of channel construction. Wind-induced sediment transport and- the effects of spoil deposi- tion on the surrounding peripheral marshes are factors which complicate the evaluation of the effects of dredging, especially in small bays. In areas of high human population density, combined dredging-landfill operations have be- come common and their effects have been felt primarily in the small shallow bays which could provide (if dredged) good anchorages for pleasure boats and picturesque settings for homes. Yet these small bays, edged with Spartina marshes, are primary trophic energy sources in the economy of the sea. It appears that further long-term investigations of the effects of dredging on these bays is warranted. A summary of the areas of investigation and conclusions follow: 1. The dredging process caused turbidity throughout the bay. Light penetration was re- duced to 0.4 m during dredging, but the particu- late matter released was rapidly dissipated. It is unlikely that turbidity affected light penetration enough to interfere with photosynthesis. How- ever, a canopy of flocculent material deposited on the plants as the result of the deposition of suspended bottom material may have interfered with primary productivity in the low current velocity areas of the bay. 2. Water transport patterns were greatly modi- fied as the result of dredging. Current velocity in the eastern half of the bay was reduced approximately 50%, while small increases were noted for the middle portion of the bay, which previously had negligible velocities. The main mass movement of water shifted from channel A to channel B as the result of deepening the latter channel. Dye studies revealed that flushing time of the bay as a whole was not appreciably changed. 3. Correlations between sediment particle size and changes in current velocity suggested that the distribution of sediment types in Goose Creek would be permanently changed as the result of modified current velocities. 4. Values of particulate phosphorus, silicates, and chlorophyll a increased substantially. Dis- solved organic phosphorus and nitrates increased slightly during the post-dredging year. A number of authors have reported increases in phytoplankton and/or benthic productivity as a result of increased nutrient levels, but no defini- tive correlation could be observed in the course of this study. 5. It was found that wind-driven currents af- fected the distribution of nutrients and bacteria in the bay. In view of the predominance of strong northwesterly winds over the year and the shallow, slowly moving water of the western half of Goose Creek, it was suggested that sedi- ment deposition in this region was primarily a function of wind-driven currents. The assertion by Flemer (1968) that late fall is the best season for dredging is disputed on the basis of a high 475 FISHERY BULLETIN: VOL. 72. NO. 2 level of wind-influenced sediment distribution at that season. 6. Standing crop figures for the commercially important clam, Mercenaria mercenaria, were reduced in the bay as a whole. Some areas, especially those in the path of the dredge, did not recover one year after dredging. 7. Land usage patterns were drastically altered during the study as well as in the previous 15 yr. Homes within 300 m of the bay increased by 94%. Rhodamine B placed in a toilet in a house along the periphery of the bay was detected in the bay water, although all houses have septic tanks. Maximum coliform counts exceeded pres- ent legal standards in 1968. 8. Significant reductions in standing crop figures occurred in the channel and the bay as a whole. Recovery of biomass in the channel was also affected by sediment composition and an interaction between the sediment and the dredg- ing process itself The effect of different sediment types and seasonal variances on the biomass is shown to be not significant, negating two of the most important variables which might confuse the interpretation of the pre-and post-dredging data. Chi-square analyses were done on number of species and number of individuals in the bay and in the channel. There were significant reduc- tions in both parameters. Recovery of species and specimen numbers appeared to be affected by sediment type. Drastic reductions in biomass, species number, and population size occurred in the dredged channel as a function of the removal of the sub- stratum and its in- and epifauna. Recovery had not occurred at the termination of this study, 11 mo after dredging. Of perhaps greater significance are the sub- stantial reductions in all parameters which oc- cured in the bay as a whole, with only a few stations showing recovery to pre-dredging levels. Only one of the stations was more than 500 m from the dredged channel and spoil deposition areas. 9. Goose Creek had a relatively high in- and epifaunal standing crop estimated at 36.83 g/m^ for the bay as a whole, including large forms. This compares to Sanders' (1956) estimate of 54.627 g/m2 for Long Island Sound, but is much higher than the standing crop levels obtained for Upper Chesapeake Bay or the English Channel. The number of organisms per m^ is lower for Goose Creek than for the other areas reported on, indicating a preponderance of large forms. 10. Phytoplankton production in Goose Creek was lower than that of Long Island Sound, but far higher than that of the English Channel or Upper Chesapeake Bay. There were three maxima in phytoplankton production in Goose Creek in 1966-1967. 11. The removal of the substratum in the channel affected the population dynamics of the infauna. The molluscs Tellina agilis, Lyonsia hyalina, and Mulinia lateralis, while insignificant components of the standing crop both before and after dredging, increased in numbers in the post- dredging samples. Two dominant forms, the polychaetes Cly- menella torquata and Notomastus latericeus, virtually disappeared after dredging. In the bay as a whole there appeared to be no substantial change in the species mix, except for the removal of the dense population of Crepidula fornicata (34,000/m2) by the dredge near the confluence of the three channels. No recovery was noted for this species after 11 mo at that station. In general, the bay sediments exhibited an over- all reduction in epi- and infaunal populations, which did not approach recovery levels 11 mo after dredging. The Ampelisca spinipes and Nepthys incisa- Nucula proxima communities described by Stickney and Stringer (1957) and Sanders (1956, 1958) were not found in Goose Creek, being replaced by a Clymenella torquata-Mya arenaria community in the sandy sediments, and a Mer- cenaria mercenaria-Sclerodactyla briaerius- Nereis succinea community in the softer sub- stratum. 12. Animal productivity for Goose Creek was calculated at 89.87 g/m^/yr before dredging and 31.18 g/m^/yr after dredging. During the post- dredging year, 18,780 kg of animal production was lost from the 0.32 km^ bottom of Goose Creek. 13. The productivity of island II was considered representative of unspoiled tall Spartina alterni- flora marsh. Animal productivity was estimated at 42.44 g/m^/yr, composed almost entirely of Uca pugnax, Modiolus demissus, and Sesarma reticulatum. This represented 5-7% of the total productivity figures of 869.64 g/m^/yr. The gross estimate for mixed peripheral marsh came to 4,553.57 kg/ha. Using this figure to calculate the 476 KAPLAN, WELKER, and KRAUS: EFFECTS OF DREDGING loss of productivity represented by the spoil areas which had inundated 10.87 ha of marsh, 49,497.31 kg of plant matter were removed from the trophic cycle of Goose Creek in the post- dredging year. Replacement by houses or Phragmites marsh would tend to fix this loss on a permanent basis. In summary, reductions in the productivity of Goose Creek were induced by the dredging pro- cess. Recovery to pre-dredging levels had not occurred 11 mo after dredging. Arguments were proposed which suggested that changes in current velocity and the concomitant modifications in substratum type represented permanent changes which would affect the future productivity of the bay by changing the nature of the habitat. Spoil disposal and land usage changes brought about an enhanced land value of the disposal areas, stimulating the development of the peri- phery of the bay, removing or depleting the marsh as an energy source available to the aquatic environment. These changes also were of a perma- nent nature. ACKNOWLEDGMENTS This study was supported in part by a grant from Suffolk County, N.Y. The authors are grate- ful to the following persons for assistance in obtaining samples: John Dinaro, Paul Laucher, Ed Wainwright, Pat Langstone, Paul Salomans, and Harry White. Edwin J. Sherrill, Jr., designed the vessel and saw to its construction. John Black supplied data on water chemistry. Walter Smith originated the project. LITERATURE CITED Barnard, J. L., and D. Reish. 1959. Ecology of Amphipoda and Polychaeta of Newport Bay, California. Part I. Introduction. Allan Hancock Found. Occas. Pap. 21:1-12. Biggs, R. B. 1968. Environmental effects of overboard spoil disposal. J. Sanit. Eng. 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Macro- molecular Nature of Antistaphylococcal Factor. Limnol. Oceanogr. 8:63-67. SlEGEL, A. 1966. Equilibrium binding studies of zinc-glycine com- plexes to ion-exchange resins and clays. Geochim. Cosmochim Acta. 30:757-768. 1967. A new approach to the concentration of trace organics in seawater. In T. A. Olson and F. J. Burgess (editors). Pollution and marine ecology, p. 235-256. John Wiley and Sons, N.Y. Stephens, G. C, and R. A. Schinske. 1961. Uptake of amino acids by marine invertebrates. Limnol. Oceanogr. 6:175-181. Stickney, a. p., and L. D. Stringer. 1957. A study of the invertebrate bottom fauna of Green- wich Bay, R.I. Ecology 38:111-122. Taylor, J. L., and C. H. Saloman. 1968. Some effects of hydraulic dredging and coastal development in Boca Ciega Bay, Florida. U.S. Fish Wild]. Serv., Fish. Bull. 67:213-241. Teal, J. M. 1962. Energy flow in the salt marsh ecosystem of Georgia. Ecology 43:614-624. Townes, H. K., Jr. 1939. Ecological studies on the Long Island marine invertebrates of importance as fish food or bait. 28th Annu. Rep., 1938, State N.Y. Conserv. Dep., 14 (Suppl.): 163-176. Udell, H. F., J.Zarudsky,T. E. Doheny, andP.R. Burkholder. 1969. Productivity and nutrient values of plants growing in the salt marshes of the Town of Hempstead, Long Island. Bull. Torrey Bot. Club 96:42-51. Wilson, D. P. 1938. The influence of the substratum on the meta- morphosis of Notomastus larvae. J. Mar. Biol. Assoc. U.K. 22:227-243. 1953. The settlement o{ Ophelia bicornis Savigny larvae. The 1951 experiments. J. Mar. Biol. Assoc. U.K. 31:413-438. Wilson, W. B. 1950. The effects of dredging on oysters in Capano Bay, Texas. Annu. Rep. Mar. Lab. Tex. Game, Fish Oyster Comm. 1948-1949, p. 1-50. Appendix Table I. — Faunal list for Goose Creek. Total number of species = 138. CNIDARIA— ANTHOZOA Haloclava products^ Metndium senile Sagartia modesta'' PLATYHELMINTHES— TURBELLARIA Euplana gracilus'' NEMERTINEA Amphiporus caecus'' Carinoma tremaphoros^ Cerebratulus lacteus Zygeupolia ru bens' ANNELIDA— POLYCHAETA Amphitnte af finis'' A. cirrata' A. ornata' Arabella iricolor Arenicola cristata' Capitella capitata Cirratulus grandis Clymenella mucosa'^ C. torquata Dispio uncinata Dnlonereis longa Eteone heteropoda'' E. /acrea' E. longa' Eumida sanguinea Glycera americana G. dibranchiata Glycinde sotitaria' Harmothoe imbncata Lepidametria commensalis'' Lumbrinens tenuis Maldanopsis elongata' Melinna cristata Nephtys picta Nereis (Neanthes) arenaceondonta' N. (Hediste) diversicolor' N. (Neanthes) succinea N. (Neanthes) virens' Notomastus latericeus' Orbinia omata' Pectinana gouldii Phyllodoce arenae' P. groenlandica' Pista cristata'' P palmata Poly dor a ligni' Prionspio malmgreni'' Sabella microphthalma' Scolecolepides viridis' Scoloplos fragilis S robustus - Spio setosa Sthenelais boa' Tharyx acutus'' SIPUNCULOIDEA Golfingia gouldi ARTHROPODA— CRUSTACEA Cirrjpedia Balanus amphritrite niveus' B. balanoides Isopoda Chiridotea almyra'' C. caeca' Cyathura polita ( = C. carinata)' Amphipoda Ampelisca macrocephala A. abdita {=Ampelisca B.) A. spinipes Gammarus (=Carinogammarus) mucronatus Microdeutopus gryllotalpa Oecapoda Caridea Crangon septemspinosus Hippolyte pleuracanthus Palaemonetes intermedius' P. pugio P. vulgaris Thallassinidea Callianassa atlantica^ Upogebia aftinis' Brachyura Neopanope texana sayi Ovalipes ocellatus Pinnixa chaetopterana' P. cylindrica' P. sayana Sesarma reticulatum' Uca pugilator U. pugnax Anomura Pagurus longicarpus MOLLUSCA Gastropoda Acteon punctostriatus Alexia myosotis' Bittium alternatum Busy con carica^ B. canaliculatum' Columbella lunata' ^ C. translirata' ^ Crepidula fornicata Crepidula plana' Eupleura caudata Epitonium multistriatum' Haminoea solitaria Hydrobia totteni' Littorina littorea L. obtusata L. saxatilis Lunatia heros Melampus bidentatus' Melanella oleacea' Nassarius obsoletus N. vibex' N. trivittatus 479 FISHERY BULLETIN: VOL. 72, NO. 2 Odostomia bisuturalis^ O. seminuda Polinices duplicatus Pyramidella fusca'' ' Tornatina canallculatum^ Triphora nigrocincta'' ^ Urosalpinx cinerea Pelecypoda Aequipecten irradians Aligena elevata^ Anadara transversa' Anomia simplex Clinocardium cilialum (=Cardium islandicay Crassostrea virginica' Cuminga tellenoides'' Ensis directus Gemma gemma Laevicardium mortoni'' Lyonsia hyalma Macoma balthica'' Mercenaria mercenana Modiolus demissus Mulmia lateralis Mya arenaria Nucula proxima Pandora gouldiana Petricola pholadiformis Solemya vellum'' Spisula solidissima' Tagelus plebeius'' Tellma agilis Yoldia limatula ECHINODERMATA— HOLOTHUROIDEA Leptosynapta roseola^ Sclerodactyla ( = Thyone) briareus CHORDATA-UROCHORDATA ASCIDIACEA Dendrodoa ■arnea'' Molgula manhattensis Styela partita^ 'Organisms not heretofore reported in the major faunal lists of Long Island (Sanders. 1956; Hechtel. 1968; Townes. 1938. ^Shells only; no living specimens found 480 SEASONAL DISTRIBUTION OF SIBLING HAKES, UROPHYCISCHUSS AND U. TENUIS (PISCES, GADIDAE) IN NEW ENGLAND 12 John A. Musick^ ABSTRACT The seasonal distribution patterns of sibling hakes, Urophycis chuss and U. tenuis, differ from one another in depth and geographic area and within each species by life history stage. Urophycis chuss spawns off southern New England in depths of less than 60 fm and probably at temperatures between 5° and 10°C. Two major spawning concentrations occur, one east of Block Island, the other on the southwest part of Georges Bank. Spawning in the Gulf of Maine probably occurs inshore at depths shoaler than 30 fm. After spawning, the adult fish disperse and the larger individuals move offshore into water 60 fm or deeper where the mature fish remain until the following spring. Juvenile U. chuss are inquiline within sea scallops, Placopecten magellanicus , until they outgrow their hosts or until water temperatures, colder than about 4°C, either kill the hake or force them to seek out warmer temperatures in deeper water. Immature U. chuss remain in the vicinity of the scallop beds if water temperatures are compatible until the fish are in their second year of life. During that autumn, the fish migrate inshore to within 30 fm and remain until water temperatures drop to about 4°C, at which time they move to warmer, deeper water along the offshore shelf. The following spring, these fish migrate inshore with the older adult fish during April and by summer are mature and attain the typical seasonal behavior of adults. Im- mature U. tenuis in the Gulf of Maine occur at all depths but tend to remain in shallower water than the adults during the winter. Mature U. tenuis migrate inshore in the northern Gulf of Maine in the summer, disperse in the fall, and move into the deepest area of the Gulf in winter. Along the eastern edge of Georges Bank and west of there, both immature and mature U. tenuis are fish of the continental slope. Both stages occur over the shelf in small numbers, but at all seasons the highest concentrations are found deeper than 100 fm. The distribution patterns of these two sibling species are not coincidental, as assumed in the past. Rather, they are complementary. Urophycis chuss is more abundant in the Mid-Atlantic Bight, whereas U. tenuis is more abundant on the Scotian shelf, in the Gulf of St. Lawrence, and on the Grand Banks. They occur together most often in the Gulf of Maine. But even there, U. chuss is more abundant in the southwest sector and U. tenuis predominates in the northern part and in the Bay of Fundy. The geographical ranges and seasonal movements of the red hake, Urophycis chuss (Walbaum), and of the white hake, U. tenuis (Mitchill), have not been defined because previous workers have had difficulty in distinguishing between the two species (Musick, 1973). The purpose of the present paper is to examine the validity of published accounts of the ranges off/, chuss and U. tenuis; to compare the seasonal distribution of the two species with regard to depth, bottom temperature, and substrate in New England waters; and to determine whether the patterns of seasonal dis- tribution vary among juvenile, immature, and adult stages (these stages are defined below). ' Contribution Number 562 of the Virginia Institute of Marine Science. * This paper contains parts of a Ph.D. dissertation submitted to Harvard University. ' Virginia Institute of Marine Science, Gloucester Point, VA 23062. Two recent faunal works treat both species together and give the northern limit of distribu- tion of U. chuss and U. tenuis as Labrador (Leim and Scott, 1966) or the Grand Banks of Newfoundland (Bigelow and Schroeder, 1953). However neither documentation nor voucher specimens are available to establish the presence of U. chuss off Labrador or on the Grand Banks (as there are for U. tenuis). Kendall (1909) re- ported U. tenuis from Labrador, and the New- foundland Fisheries Research Commission (1932, 1933, 1934) captured U. tenuis along the south- western edge of the Grand Banks during warmer months of the year. Templeman (1966) reported that all Urophycis taken commercially on the Grand Banks have been U. tenuis (1966) and that he had never seen a specimen of U. chuss from Newfoundland waters (pers. comm.). Jordan and Evermann (1898) and Breder (1948) gave the Manuscnpt accepted September 1973. FISHERY BULLETIN; VOL. 72. NO. 2. 1974. 481 FISHERY BULLETIN: VOL. 72. NO. 2 northern limit of U. chuss as the Gulf of St. Lawrence, apparently on the basis of reports of U. chuss (under the name of Phycis americanus (Block and Schneider)) from the Gulf of St. Law- rence by H. R. Storer ( 1850), Fortin (1863), Knight (1866), and Gilpin ( 1867). These authors, however, had followed the nomenclatural usage of D. H. Storer (1839, 1846, 1858) whose descriptions of Phycis americanus from Massachusetts obviously referred to U. tenuis because of the large size of his specimens (Musick, 1973). Similarly all other reports off/, chuss from the Gulf of St. Lawrence are based on nomenclatural errors or were made by workers (Cox, 1905, 1921; Cornish, 1907, 1912; Craigie, 1916, 1927; Vladykov and Trem- blay, 1935; Vladykov and McKenzie, 1935; Mc- Kenzie, 1959; and Vladykov and McAllister, 1961) who by their own admission or by the species descriptions they published had shown their in- ability to distinguish between U. chuss and U. tenuis (Musick, 1969). Urophycis chuss is absent from or very rare in the Gulf of St. Lawrence. Several thousand specimens of Urophycis examined at Souris, Prince Edward Island, in August 1966 were all U. tenuis (Musick, 1973). Juvenile and post- larval Urophycis captured in the Gulf of St. Lawrence by Fisheries Research Board of Canada personnel from St. Andrews, New Brunswick, and sent to me for identification were all U. tenuis. Several hundred Urophycis examined on a cruise of the RV Prince in the Northumberland Straits and Magdalen shallows in September 1972 were all U. tenuis (K. Able, pers. comm.). The Newfoundland Fishery Research Commis- sion captured one U. chuss (a pelagic juvenile) and many U. tenuis (benthic adults) on the Scotian shelf between Sable Island and Ban- quereau Banks (Newfoundland Fisheries Re- search Commission, 1932). Similarly, trawl col- lections made from RV Albatross IV on the Scotian shelf in March 1969 and 1970 and Novem- ber 1969 (J. McEachran, pers. comm.) contained few U. chuss and many U. tenuis. Trawl col- lections made from RV Cameron between Canso, Nova Scotia, and Banquereau Bank in August 1970 and 1971 contained very few U. chuss but many U. tenuis (C. Wenner and J. McEachran, pers. comms.). To my knowledge the most north- eastern locality from which voucher specimens of U. chuss are available is lat. 43°39'N, long. 59°26.5'W (Virginia Institute of Marine Science lot No. 01957) collected by otter trawl from RV Cameron, 14 July 1971, at a depth of 197 m. Both U. chuss and U. tenuis have been reported frequently from the Gulf of Maine and the Mid- Atlantic Bight as far south as Cape Hatteras, N.C. (Musick, 1969). Svetovidov (1955) classified Phycis borealis Saemundson 1913, an Icelandic form, as a junior synonym off/, tenuis. Icelandic specimens exam- ined during my study confirm Svetovidov's taxo- nomic judgment and document the range exten- sion of the species to Iceland. Similarly Bullis and Thompson (1965) reported U. tenuis from the continental slope of the east coast of Florida. I examined these specimens and confirm their identification as U. tenuis. Fraser-Brunner (1925) reported two small speci- mens of U. chuss from the Irish Atlantic slope but was not certain of their identity: "Two small specimens [25 and 55 mm standard length] apparently referable to this species (U. chuss) were taken in the tow net near the surface . . . ." Urophycis chuss of this size were considered to be unidentifiable by American workers such as Bigelow and Welsh (1925) who had many oppor- tunities to examine small specimens. It is probable that Fraser-Brunner's postlarvae were a species of Phycis, not Urophycis. The known ranges of the two species can now be summarized: U. chuss occurs on the continental shelf from southern Nova Scotia to North Carolina and may stray to the Gulf of St. Lawrence. Urophycis tenuis occurs on the continental shelf and slope from Iceland, Labrador, and the Grand Banks of Newfoundland to the coast of North Carolina, straying as far south as Florida in deep water. Sampling Procedures Data for a study of the seasonal distribution patterns off/, chuss and U. tenuis were collected during a groundfish survey conducted by the National Marine Fisheries Service at Woods Hole, Mass. The survey consisted of nine seasonal cruises by RV Albatross IV from the mouth of the Bay of Fundy to Hudson Canyon. Approxi- mately 1,800 fishing stations were occupied, and cruises were conducted during the summer and fall in 1963, 1964, and 1965 and during the winter in 1964, 1965, and 1966. The survey area was divided into 42 sampling strata according to depth (Figure 1), and stations were located randomly within strata. A No. 36 482 MUSICK: SEASONAL DISTRIBUTION OF SIBLING HAKES i^ ^/^ ^Hb^ 8' jV^ ij^ ^^5\ ^K/Ny.t,2.S0 ^*^"i.£iu^ i°- 'o. *> Figure 9. — Distribution and abundance of immature Urophy- cis chuss during the summer. Abundance in each sampling stratum is indicated on a log scale. The fall distribution pattern off southern New England (Figure 10) suggests a movement inshore which is further substantiated by an increase of U. chuss in the inshore industrial fisheries land- ings in October and November (Edwards and Lux, 1958; Edwards, 1958a, 1958b; Edwards and Law- day, 1960). Edwards (pers. comm.) has noted that this fall fishery off southern New England landed mostly small hake. Also reports by Smith (1898) for Woods Hole; Latham (1917) for Orient, Long Island; Breder (1922) for Sandy Hook Bay; and Hildebrand and Schroeder (1928) for the New Jersey coast and New York Bay document an immigration of U. chuss in these inshore areas in the fall with an emigration in the winter. In the Gulf of Maine, immature U. chuss were moderately abundant in the fall around the entire perimeter in strata shoaler than 60 fm. The winter distribution of immature U. chuss was essentially limited to those strata deeper than 30 fm off Long Island, 60 fm off Nantucket, and 100 fm along the southern edge of Georges Bank (Figure 11). In the Gulf of Maine immature U. chuss were moderately abundant in strata deeper than 60 fm. Concentrations occurred between 60 and 100 fm along the northern edge of Georges Bank and off Massachusetts Bay and Jeffries Ledge (Stratum 27). The only strata shoaler than 60 fm with moderate values of abundance were 26 and 40, located in the southwestern part of the Gulf where temperatures were warmer than to the north and east. Immature U. chuss were taken during three seasons within the entire temperature range with the exception of the highest intervals (15° to 16°C), which were inadequately sampled (Figure 12). Most immature fish were taken between 5° and 13°C. As with the juveniles, immature U. chuss were absent from the shallow parts of Georges Bank during the winter and they may avoid water colder than 4°C. Edwards (1965) noted that in the late fall most U. chuss had migrated from the inshore industrial fishing grounds when the water temperature dropped to 5°C. Adult U. chuss migrate inshore in the spring of the year. Smith (1898) reported U. chuss to be abundant at Woods Hole in May or June but rare FALL 15-28 cm. Total length Figure 10. — Distribution and abundance of immature Urophy- cis chuss during the fall. Abundance in each sampling stratum is indicated on a log scale. ^r WINTER 15-28 cm Totol length Figure 11. — Distribution and abundance of immature Uro- phychis chuss during the winter. Abundance in each sampling stratum is indicated on a log scale. 487 FISHERY BULLETIN: VOL. 72. NO. 2 in the summer. Latham (1917) reported U. chuss from Orient, Long Island, in the spring but not summer. Breder ( 1922) noted U. chuss from Sandy Hook Bay in the spring; and Hildebrand and Schroeder (1928) reported that off New Jersey and New York U. chuss appeared in April, dis- tended with spawn, that they remained close inshore for a short period, were caught 2 to 6 miles off until late May, and in July were abundant offshore on Cholera Bank. Edwards and Lawday (1960) reported that U. chuss were abundant in the industrial fish landings in April and May from the shallow inshore fishing grounds off No Man's Land, Mass., and Point Judith, R.L The fish dispersed in June and July and were less available to the fishery. After they migrate inshore in the spring, southern New England U. chuss migrate offshore in the summer to spawn. Mature U. chuss were heavily concentrated during the summer (Figure 13) in the strata shoaler than 60 fm off Block Island and on the southwest part of Georges Bank. GULF OF MAINE sxjmmeb 0 = 309 FALL WINTER 78 pj 4 1 I 5 e 7 e 9 to II 12 [3 14 c e 4 5 6 7 a 9 10 II 12 13 14 15 TEMPERATURE (°C ) 25456789 10 I Figure 12. — Seasonal catch per tow of immature Urophycis chuss taken off southern New England and the Gulf of Maine. Abundance data are stratified by temperature intervals of one degree (C). The total number of individuals captured during each season = n. The number of stations occupied at each temperature is indicated above each respective histo- gram bar. 'J. -1°" U chuss SUMMER K?-S-^ > 29 cm Total length '--t>^ V, i^ti. V > "^ WiM^ i-'X 111 ^~- fi- Iffl 0 \\ ^^fe^ s^ 0 n 5-0.24 ^ ^^^)^^^^^ ^ NX yJltttk 7 □ 0.25-0.99 "v^^^H - > ij WitlUk / ■ 1.00-2.49 ^^^5^- __y^ i^-^ ■ >2.S0 ^=^^ —^ •v°° 'o. *?■ Figure 13. — Distribution and abundance of mature Urophycis chuss during the summer. Abundance in each sampling stra- tum is indicated on a log scale. These concentrations were probably spawning aggregations because ripe fish were taken quite frequently during the survey (Musick, 1969). Also Domanevsky and Nozdvin (1963) reported spawning aggregations of U. chuss offshore on Georges Bank in July and August. Although a small number oft/, chuss remain in the southern New England sounds during the summer (Ed- wards and Lawday, 1960), these are probably immature fish because spawning does not occur there. Wheatland (1956) found no U. chuss eggs or larvae in Long Island Sound, and Merriman and Sclar ( 1952) took no eggs but captured larvae in Block Island Sound, an area less land-locked and more adjacent to deep water than the previous one. U. chuss emigration from shallow southern New England waters to offshore spawning grounds is probably correlated with temperature. Figure 14 shows that U. chuss were not abundant within adequately sampled temperature intervals higher than 12°C. Riley ( 1956) noted that temper- atures exceeded 12°C over most of Long Island Sound during June and increased until October when temperatures were in excess of 20°C. Ed- wards, Livingstone, and Hamer (1962) reported that during the summer off southern New Eng- land U. chuss were most abundant at about 9°C, and Edwards (1965) showed that U. chuss mi- grated offshore when the bottom temperature reached about 10°C in the early summer. In the Gulf of Maine U. chuss became avail- able to the shallow water trawl fishery off Gloucester and Ipswich, Mass., in April or May 488 MUSICK: SEASONAL DISTRIBUTION OF SIBLING HAKES GULF OF MAINE SUMMER n- 709 ,^^. WINTER n:976 25 3 4 5 6 7 a 9 '0' I 12 13 14 3 4 5 6 7 8 9 10 M I2 13 14 15 2 J 4 5 6 7 SOUTHERN NEW ENGLAND j t*^ ^ 4 5 6 7 8 9 <0 I) [2 13 14 15 16 4 S 6 7 a 9 O II 12 1314 15 TEMPERATURE (°C) nil S456789I0I Figure 14. — Seasonal catch per tow of mature Urophycis chuss off southern New England and the Gulf of Maine. Abundance data are stratified by temperature intervals of one degree (C). The total number of individuals captured during each season = n. The number of stations occupied at each temperature is indicated above each respective histogram bar. (Edwards, 1958a; Edwards and Lawday, 1960) and increased in abundance until August. Thus mature U. chuss are abundant in the summer at depths less than 30 fm. The Albatross IV survey data (Figure 13) which show highest values of abundance in strata 60 fm and deeper are probably not indicative of the true summer dis- tribution off/, chuss. Both the industrial fishery and region of greatest abundance in the Albatross IV survey are in the southwestern section of the Gulf, but the fishery and survey data were taken at different depths. Additional evidence that U. chuss congregate in the summer at depths less than 30 fm comes from Bigelow and Schroeder (1953). They noted that U. chuss spawns in the Gulf in the summer and that most eggs and larvae have been collected close to shore. Water tem- peratures inshore are comparable to those that occur in known offshore spawning areas of U. chuss off southern New England (5°-10°C). Similar temperatures also occur in deeper waters of the Gulf, but young U. chuss spawned in such areas would have little chance of finding Placopecten for shelter after descending because Placopecten is restricted to shoal areas of the Gulf (Dow and Baird, 1960). Therefore, there may be selection for inshore spawning in the Gulf of Maine. During the fall (Figure 15), mature U. chuss were dispersed over the entire survey area, but the original data (Musick, 1969) show that most individuals longer than 32 cm had moved into water deeper than 60 fm. The winter distribution pattern of mature U. chuss (Figure 16) shows that a very strong offshore movement occurred in water deeper than 60 fm, in the Gulf of Maine, and off southern New England. The fish were most heavily concentrated along the edge of the conti- nental slope from the southwest part of Georges Bank to Hudson Canyon. Edwards et al. (1962) reported U. chuss to be most abundant in winter between 100 and 250 fm in their study area south of Nantucket. In addition, Edwards et al. (1962) found that U. chuss were "most abundant where the water temperature was between 47°F (8.3°C) and 50°F (10.0°C)," values which are within the range which adult hake were most abundant in the present study (5-12°C). Juvenile and immature U. chuss occurred with- in a narrower temperature range than the adults. However, the latter were more concentrated within relatively narrow temperature limits. This implies that although adults may tolerate a wider range, they may prefer a narrower range than young fish do or, at least, are more mobile and can undertake longer and faster seasonal migrations, thus remaining within relatively nar- rower temperature limits throughout the year. Such behavior might allow the fish to maintain an optimal thermal environment for gonadal development, spawning, and feeding during various times of the year. Figure 15. — Distribution and abundance of mature Urophycis chuss during the fall. Abundance in each sampling stratum is indicated on a log scale. 489 FISHERY BULLETIN: VOL. 72. NO. 2 Figure 16. — Distribution and abundance of mature Urophycis chuss during the winter. Abundance in each sampling stratum is indicated on a log scale. U tenuis SUMMER 9-50 cm Total lengtti 0 □ <-0.24 □ 0.25-0.99 ■ 1.00-2.49 Figure 17. — Distribution and abundance of immature Urophy- cis tenuis during the summer. Abundance in each sampling stratum is indicated on a log scale. Seasonal Distribution of U. tenuis During summer (Figure 11 ), immatur ell. tenuis were rare or absent over most of the southern New England area. Moderate numbers were taken in the strata deeper than 100 fm off Nantucket and the southern part of Georges Bank and the strata deeper than 60 fm along the eastern part of Georges Bank. In the Gulf of Maine, immature U. tenuis were taken in mod- erate numbers in the Great South Channel (Stratum 23) and in the northern part of the Gulf. The highest abundance value was in Stratum 39 off the northern Maine coast. In the fall, immature U. tenuis were most abundant in the northern and eastern parts of the Gulf (Figure 18), and moderately abundant in the deep central Gulf, the Great South Chan- nel, and on the middle and northern edge of Georges Bank. Immature U. tenuis were also abundant in the stratum deeper than 100 fm at the eastern edge of Georges Bank and mod- erately abundant in strata deeper than 60 fm to the south and west off southern New England. Only one stratum south of Georges Bank less than 60 fm deep (Stratum 2) had moderate numbers of U. tenuis. This stratum includes the inshore extension of Hudson Canyon. In the Gulf of Maine during the winter (Figure 19), immature U. tenuis were most abundant in the deeper northern strata (Strata 36 and 38) and along the northern edge of Georges Bank. Immature U. tenuis were absent or rare in areas less than 60 fm off southern New England but were fairly abundant in some strata deeper than 100 fm. Indices of abundance of U. tenuis by tempera- ture interval were less reliable than those of U. chuss because U. tenuis was much less abundant, particularly off southern New Eng- land. Single large tows often lowered the preci- sion of mean catch estimates because of the relatively small total number of U. tenuis col- lected. Consequently, for some seasons only tem- perature ranges can be discussed. In the southern New England area, immature U. tenuis were taken from 4° to 14°C in the summer. Only one station was made at 15^C and at 16°C. Although U. tenuis was not taken there, the sampling U tenuis FALL 9-50 cm Total length Figure 18. — Distribution and abundance of immature Urophy- cis tenuis during the fall. Abundance in each sampling stratum is indicated on a log scale. 490 MUSICK: SEASONAL DISTRIBUTION OF SIBLING HAKES intensity does not give a true indication of its presence or absence. During the fall, immature U. tenuis occurred over the entire temperature range, 4° to IS^'C. In the winter, they were taken from 3° to 10°C. In the Gulf of Maine in the sum- mer, immature U. tenuis occurred from 4° to 9°C and the highest mean catch was at 8°C. The fish were absent at 3°C and from 10° to 14°C; how- ever, these temperature intervals were not ade- quately sampled. In the fall, immature U. tenuis occurred from 3° to 11°C and the highest mean abundance was at 9°C. The fish were absent from 12'' to 15°C but the sampling intensity at these temperatures was inadequate. In the winter, only a few fish were taken at 2°C and 3°C and mean catches increased from 4° to 7°C. Im- mature U. tenuis were taken over an annual range of 2° to 15°C but were most abundant be- tween 4° and 10°C (Figure 20). During the summer (Figure 21), mature U. tenuis were rare or absent off southern New Eng- land except in two strata deeper than 100 fm. They were moderately abundant in the Gulf of Maine and heavily concentrated in Stratum 39 along the northern coast of Maine. In the fall (Figure 22), off southern New England, mature U. tenuis were moderately abundant in all strata deeper than 100 fm, in two strata from 60 to 99 fm deep, and in only one stratum from 30 to 59 fm deep. They were rare or absent in all other south- ern New England strata. Mature U. tenuis were mo^lerately abundant in the Gulf of Maine. The highest values of abundance are in Strata 27 and 28, between 60 and 100 fm. SUMMER n: 35r GULF OF MAINE FALL /\ 3 4 5 6 7 8 9 10 II l2 i3 SOUTHERN NEW ENGLAND WINTER n:634 ^^4£r a f^ 5 6 7 a 9 10 II 12 II 14 15 16 kq.^764i& 1 4 5 6 7 8 9 to II t2 13 14 15 2 3 4 5 6 7 8 9 10 II TEMPERATURE l°C) Figure 20. — Seasonal catch per tow of immature Urophycis tenuis off southern New England and the Gulf of Maine. Abundance data are stratified by temperature intervals of one degree (C). The total number of individuals captured during each season = n. The number of stations occupied at each temperature is indicated above each respective histogram bar. During the winter off southern New England (Figure 23), mature U. tenuis were rare or absent in all strata shoaler than 100 fm except Stratum 7, which was 60 to 99 fm deep. Mature U. tenuis were moderately abundant there and in all strata deeper than 100 fm. In the Gulf of Maine, mature U. tenuis were absent from all strata WINTER 9-50 cm Totol length Ho n 5-0.24 n 0.25-0.99 ■ 100-2.49 Figure 19. — Distribution and abundance of immature Uro- phycis tenuis during the winter. Abundance in each sampling stratum is indicated on a log scale. SUMMER >5I cm Totol length 11 0 □ <-0.24 □ 0.25-0.99 ■ >250 Figure 21. — Distribution and abundance of mature Urophycis tenuis during the summer. Abundance in each sampling stratum is indicated on a log scale. 491 FISHERY BULLETIN: VOL. 72. NO. 2 FALL >5( cm-Tolol length '^^-iush.^ 0 □ <-0.24 [~1 025-0.99 ■ 1.00-2.49 Figure 22.— Distribution and abundance of mature Urophycis tenuis during the fall. Abundance in each sampling stratum is indicated on a log scale. shoaler than 60 fm. They were moderately abun- dant in most deeper strata and most abundant in Strata 28 and 36, which were deeper than 100 fm. Catches of adult U. tenuis off southern New England were very small. Consequently, tem- perature-abundance estimates (Figure 24) are not reliable. Adult U. tenuis occurred from 6° to 12°C in the summer, from 4° to 13°C in the fall, and from 4" to 10°C in the winter. Adult U. tenuis were taken in the Gulf of Maine from 4° to 9°C in the summer (Figure 24). The highest mean catch was at 8°C. During the fall, the range of occurrence was 3" to 11°C, the highest mean catch occurring at 9°C, and in the winter the range was 2° to 7°C, the highest mean catch occurring at 7°C. WINTER >5I cm Totol length Figure 23. — Distribution and abundance of mature Urophycis tenuis during the winter. Abundance in each sampling stratum is indicated on a log scale. GULF OF MAINE FALL n=350 n 6l,»478l ^ /^»^ 3 4 ^ G 7 e 9 10 II 12 13 14 3 4 5 6 7 B 9 10 II ■£ l3 14 1% 2 3 4 S G 7 SOUTHERN NEW ENGLAND 32 iir^^23Z^iZ. % 4 5 6 7 8 9 lOII 12 13 14 15 16 4 5 6 7 8 9 lO 1 1 (2 H 14 (5 TEMPERATURE (°C ) Figure 24. — Seasonal catch per tow of mature Urophycis tenuis off southern New England and the Gulf of Maine. Abundance data are stratified by temperature intervals of one degree (C). The total number of individuals captured during each season = n. The number of stations occupied at each temperature is indicated above each respective histogram bar. Annually, adult U. tenuis were taken from 2° to 13°C but were most abundant between 5° and 9°C. Adult U. tenuis appear to occupy a more restricted temperature range than immature U. tenuis. Also, adult U. tenuis occupy a narrower and lower temperature range than adult U. chuss. U. tenuis may be more abundant off southern New England than the survey data indicate. Edwards et al. (1962) and Schroeder (1955) fre- quently captured U. tenuis along the continental slope off southern New England at greater depths than those sampled during the Albatross IV sur- vey and recent research (Musick, unpublished data) indicates that U. tenuis is a common mem- ber of the continental slope fish fauna of Virginia. Distribution of Urophycis chuss and U. tenuis with Substrate U. chuss and U. tennuis are absent or rarely, occur on rock, shell, or gravel bottoms. Both "prefer" sand or mud. Few or no Urophycis oc- curred in Strata 24, 32, and 33 during any season. 492 MUSICK: SEASONAL DISTRIBUTION OF SIBLING HAKES These strata are dominated by rock or gravel bottoms (Fritz, 1965, Plate B). Storer (1858), Goode (1884), Hildebrand and Schroeder (1928), and Bigelow and Schroeder (1939) noted the association of U. chuss, U. tenuis, or both with mud bottoms. Bigelow and Welsh (1925) reported that both species dwelled over soft bottoms (silt, sand, or mud) but that the U. tenuis was more strictly a "mud fish" than the U. chuss. The Alba- tross IV data appear to agree with the last state- ment, because the regions where U. tenuis occurred most commonly are dominated by muddy or silty substrates — the northeastern Gulf of Maine, the central basins of the Gulf, and along the continental slope on Georges Bank and south- west. However, these areas are also cooler during the summer, and the correlation between U. tenuis abundance and mud bottoms (rather than sand) may be an artifact. Urophycis chuss were abundant over mud or sand or both depending on season, because the deeper strata were covered with muddy substrates whereas the shallower strata in the southwest Gulf of Maine and off southern New England were covered with sand (Fritz, 1965, Plate B). ACKNOWLEDGMENTS Thanks are due to R. L. Edwards and M. D. Grosslein of the National Marine Fisheries Ser- vice (NMFS) Laboratory, Woods Hole, Mass., for providing ship time, research space, and scientific direction during the course of my study. A. C. Kohler of the Fisheries Research Board of Canada Laboratory, St. Andrews, New Brunswick, pro- vided me with specimens from the Gulf of St. Lawrence. G. Jonsson of the Hafrannsoknastof- nunin Marine Research Institute, Reykjavik, sent me material from Iceland and D. M. Cohen of the NMFS Systematics Laboratory, Smithsonian In- stitution, allowed me to examine hake from Florida. Also, I wish to thank my students at the Virginia Institute of Marine Science — J. D. McEachran, K. Able, and C. Wenner — for col- lecting data for me on Urophycis while pursuing their own research at sea, and to G. W. Mead formerly of the Museum of Comparative Zoology, Harvard University, for thoroughly editing the early drafts of the dissertation from which parts of the present paper have been extracted. My research was supported in part by National Science Foundation grants G-19727 and GB-3167 to the Harvard Committee on Evolutionary Biology (Principal Investigator, Reed C. Rollins) and a Grant-in-Aid from the Sigma Xi - RESA Committee. LITERATURE CITED Bigelow, H. B. 1927. Physical oceanography of the Gulf of Maine. Bull. U.S. Bur. Fish. 40(2):511-1027. 1933. Studies of the waters on the continental shelf. Cape Cod to Chesapeake Bay. I. The cycle of temperature. Pap. Phys. Oceanogr. Meteorol. 4(1), 135 p. Bigelow, H. B., and W. C. Schroeder. 1939. Notes on the fauna above mud bottoms in deep water in the Gulf of Maine. Biol. Bull. (Woods Hole) 76:305-324. 1953. Fishes of the Gulf of Maine. U.S. Fish Wildl. Serv., Fish. Bull. 53, 576 p. Bigelow, H. B., and W. W. Welsh. 1925. Fishes of Gulf of Maine. Bull. U.S. Bur. Fish. 40, 567 p. Bourne, N. 1964. Scallops and the offshore fishery of the Maritimes. Fish. Res. Board Can., Bull. 145, 60 p. Breder, C. M., Jr. 1922. 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Notes on the total weights of squirrel hake, the pollock, the winter flounder, and the smelt, and on the weights of the liver and gonads in the hake and in the pollock. Trans. R. Soc. Can., Ser. 3, 21:153-173. Dickie, L. M. 1958. Effects of high temperature on survival of the giant scallop. J. Fish. Res. Board Can. 15:1189-1211. Domanevsky, L. N., and Y. P. Nozdvin. 1963. Silver and red hakes. In Reproduction offish stocks. AtlanNIRO, Fish Husbandry 39(5):10-13. (Engl, transl., P.S. Galtsoff, Bur. Commer. Fish, Woods Hole Lab., Ref. 63-8.) 493 FISHERY BULLETIN: VOL. 72. NO. 2 Dow, R. L., AND F. T. Baird, Jr. 1960. Scallop resource of the United States Passama- quoddy area. U.S. Fish Wildl. Serv., Spec. Sci. Rep. Fish. 367, 9 p. Edwards, R. L. 1958a. Gloucester's trawl fishery for industrial fish. Commer. Fish. Rev. 20(8):10-15. 1958b. Species composition of industrial trawl landings in New England, 1957. U.S. Fish Wildl. Serv., Spec. Sci. Rep. Fish. 266, 23 p. 1965. Relation of temperature to fish abundance and distribution in the southern New England area. Int. Comm. Northwest Atl. Fish., Spec. Publ. 6:95-110. Edwards, R. L., and L. Lawday. 1960. Species composition of industrial trawl-fish landings in New England, 1958. U.S. Fish Wildl. Serv., Spec. Sci. Rep. Fish. 346, 20 p. Edwards, R. L., R. Livingstone, Jr., and P. E. Hamer. 1962. Winter water temperatures and an annotated list of fishes— Nantucket shoals to Cape Hatteras. Albatross III Cruise no. 126. U.S. Fish Wildl. Serv., Spec. Sci. Rep Fish. 397, 31 p. Edwards, R. L., and F. E. Lux. 1958. New England's industrial fishery. Commer. Fish. Rev. 20(5): 1-6. FORTIN, P. 1863. List of the cetacea, fishes, Crustacea and mollusca which now inhabit . . . the Canadian shores of the Gulf of St. Lawrence, etc. Annu. Rep. of Pierre Fortin, Esq., Magistrate in command of the Expedition for the Pro- tection of Fisheries in the Gulf of St. Lawrence, during the seasons of 1861 and 1862. Append. 109-124. Quebec. Fraser-Brunner, a. 1925. New or rare fishes from the Irish Atlantic slope. Proc. R. Irish Acad. 43:319-326. Fritz, R. L. 1965. Autumn distribution of groundfish species in the Gulf of Maine and adjacent waters, 1955-1961. Ser. Atlas Mar. Environ. Folio 10, 1 p. Gilpin, B. J. 1867. On the food fishes of Nova Scotia, No. 5, the cod family. Proc. Trans. N. S. Inst. Nat. Sci. 2(1):101-111. Goode, G. B. 1884. Natural history of useful aquatic animals. Part III, The food fishes of the United States. In G. B. Goode, Fisheries and fishery industries of the U.S., Sec. 1:163- 682. Grosslein, M. D. 1969. Groundfish survey program of BCF Woods Hole. Commer. Fish. Rev. 31(8-9):22-30. Hildebrand, S. F., and W. C. Schroeder. 1928. Fishes of Chesapeake Bay. Bull. U.S. Bur. Fish. 43(1), 366 p. Jordan, D. S., and B. W. Evermann. 1898. The fishes of North and Middle America. Part III. U.S. Natl. Mus. Bull. 47:2183-3136. Kendall, W. C. 1909. The fishes of Labrador. Proc. Portland Soc. Nat. Hist. 2:207-243. Knight, T. F. 1866. Descriptive catalogue of the fishes of Nova Scotia. Halifax, 54 p. Latham, R. 1917. Migration notes of fishes, 1916, from Orient, Long Island. Copeia 41:17-23. Leim, a. H., and W. B. Scott. 1966. Fishes of the Atlantic coast of Canada. Fish Res. Board Can., Bull. 155, 485 p. McKenzie, R. a. 1959. Marine and freshwater fishes of the Miramichi River and Estuary, New Brunswick. J. Fish. Res. Board Can. 16:807-833. Merriman, D., and R. C. Sclar. 1952. The pelagic fish eggs and larvae of Block Island Sound. Bull. Bingham Oceanogr. Collect., Yale Univ. 13(3):165-219. Moyle, J. B., and R. Lound. 1960. Confidence limits associated with means and medians of series of net catches. Trans. Am. Fish. Soc. 89:53-58. MusicK, J. A. 1969. The comparative biology of two American Atlantic hakes, Urophycis chuss and U. tenuis (Pisces, Gadidae). Ph.D. thesis. Harvard Univ., Cambridge, Mass., 150 p. 1973. A meristic and morphometric comparison of the hakes, Urophycis chuss and U. tenuis (Pisces, Gadidae). Fish. Bull., U.S. 71:479-488. Newfoundland Fisheries Research Commission. 1932. First list of fishes in the Newfoundland fishing area. Newfoundland Fish. Res. Comm., Annu. Rep. 1(4):107-110. 1933. Second list of fishes in the Newfoundland fishing area. 1932. Newfoundland Fish. Res. Comm., Annu. Rep. 2(1):125-127. 1934. Third list of fishes in the Newfoundland fishing area. 1933. Newfoundland Fish. Res. Comm., Annu. Rep. 2(2):115-117. Pereyra, W. T., H. Heyamoto, and R. R. Simpson. 1967. Relative catching efficiency of a 70-foot semiballoon shrimp trawl and 94-foot eastern fish trawl. U.S. Fish. Wildl. Serv., Fish. Ind. Res. 4(1):49-71. Riley, G. A. 1956. Oceanography of Long Island Sound, 1952-1954. II. Physical oceanography. Bull. Bingham Oceanogr. Collect., Yale Univ. 15:15-46. Roessler, M. 1965. An analysis of the variability of fish populations taken by otter trawl in Biscayne Bay, Florida. Trans. Am. Fish. Soc. 94:311-318. Schroeder, W. C. 1955. Report on the results of exploratory otter-trawling along the continental shelf and slope between Nova Scotia and Virginia during the summers of 1952 and 1953. Pap. Mar. Biol. Oceanogr., Deep-Sea Res., suppl. to Vol. 3, p. 358-372. Smith, H. M. 1898. The fishes found in the vicinity of Woods Hole. Bull. U.S. Fish Comm. 17:85-111. Storer, D. H. 1839. A report on the fishes of Massachusetts. Boston J. Nat. Hist. 2:289-570. 1846. A synopsis of the fishes of North America. Mem. Am. Acad. Arts Sci., New Ser. 2:253-550. 1858. A history of the fishes of Massachusetts. Mem. Am. Acad. Arts Sci., New Ser. 6:309-371. 494 MUSICK: SEASONAL DISTRIBUTION OF SIBLING HAKES Storer, H. R. 1850. Observations on the fishes of Nova Scotia and Labrador, with descriptions of new species. Boston J. Nat. Hist. 6(l):247-270. SVETOVIDOV, A. N. 1955. Notes on Phycis borealis Saemundsson (Pisces, Gadidae). Tr. Zool. Inst. Acad. Nauk. SSRF 17:346-348. (Engl, transl., [U.S.] Bur. Commer. Fish., Ichthyol. Lab., Wash., D.C., 1961, 6 p.) Taylor, C. C. 1953. Nature of variability in trawl catches. U.S. Fish Wildl. Serv., Fish. Bull. 54:145-166. Templeman, W. 1966. Marine resources of Newfoundland. Fish. Res. Board Can., Bull. 154, 170 p. Vladykov, V. D., AND D. E. McAllister. 1961. Preliminary list of marine fishes of Quebec. Nat. Can. 88:53-78. Vladykov, V. D., and R. A. McKenzie. 1935. The marine fishes of Nova Scotia. Proc. N.S. Inst. Sci. 19:17-113. Vladykov, V. D., and J. L. Tremblay. 1935. Liste des poissons recuellis jjendant I'ete 1934 par la Station Biologique due St. Laurent, dans la region de Trois-Pistoles, P.Q. Nat. Can. 62:77-82. Wheatland, 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. 495 DEVELOPMENT OF EGGS AND LARVAE OF CARANX MATE (CARANGIDAE)i John M. Miller and Barbara Y. Sumida^ ABSTRACT The development of eggs and larvae of omaka (Caranx mate) is described from approximately 2 h after fertilization to day 36 after hatching. The pelagic, spherical eggs (700-740 /i diameter) had a single oil droplet and hatched after about 26 h incubation at 24.5°C. The average growth rate in culture was 0.44 mm/day; feeding began four days after hatching. Fin develop- ment and ossification of omaka occurred at smaller sizes, but in the same sequence as jack mackerel (Trachurus symmetricus) off California. Of the body proportions measured, body depth was most useful in separating omaka from at least two other species of carangid larvae. The pigment pattern was also of diagnostic value. Reared larvae were indistinguishable from similar-sized field specimens. Omaka {Caranx mate) is one of the most abundant carangids in the Hawaiian Islands. The species is rather widespread throughout the Indo-Pacific, reaching the eastern coast of Africa. In Hawaii, the preferred habitats are estuaries, bays, and harbors with relatively long water residence times. Kuthalingham ( 1959) described the feeding habits of omaka near Madras, India. The growth rate of captive adult omaka was reported by Watarai (1973). Omaka have a protracted spawning period in Hawaii; the eggs can be taken with fair regu- larity from March through September from the surface waters of Kaneohe Bay, Oahu. Little else is known of the spawning habits. However, a bi- weekly year-round fish-egg survey in Kaneohe Bay indicated three spawning peaks: one in April and May, another in September and October, and a third, smaller, peak in July (Watson and Leis, 1973).^ During these peaks omaka eggs were by far the most abundant of any, occasionally exceeding concentrations of 10/m^ in the surface waters of south Kaneohe Bay. Larval densities, on the other hand, were found to be much lower than these egg densities, rarely reaching 0.1/m^ (Watson and Leis, see footnote 3). As is char- acteristic of many carangids, young are frequently 'Hawaii Institute of Marine Biology Contribution No. 427. ^Hawaii Institute of Marine Biology, University of Hawaii, Coconut Island— P.O. Box 1346, Kaneohe, HI 96744. ^Watson, W., and J. M. Leis. 1973, Ichthyoplankton in Kaneohe Bay: A one-year study of the fish eggs and larvae. Unpubl. manuscr. seen under medusae. Large larvae and juveniles are similarly attracted to floating raffia, and have been collected in this manner. Adult omaka do not appear to make the off'shore spawning move- ments characteristic of many of the resident fish species in Kaneohe Bay. MATERIALS AND METHODS Larvae used for description came from two sources: reared specimens and field specimens. Reared larvae of known age were the primary source of material; field specimens were used mainly to verify observations and conclusions based on the former. Over the past 2 yr omaka larvae have been taken in numerous plankton tows. Each time that comparisons were made between similar-sized field and reared specimens, the larvae were indistinguishable. Larvae were obtained from two cultures (called Series A) begun in February 1971. One of these (Al) supplied larvae through day 5 (Table 1). This culture was terminated on day 6, when high mortality (of unknown cause) was experienced. Although the sizes of these larvae are included in the growth rate curve (Figure 4), they were not used in the description of developmental stages. The second (A2) was maintained for 36 days during which post yolk sac specimens (day 6 and older) were taken for description. Two other cultures (Series B) were begun in May 1972 to provide eggs and yolk-sac larvae. The first, begun 1 May, was to determine the approximate rate of development and design a Manuscript accepted September 1973. FISHERY BULLETIN: VOL. 72, NO. 2. 1974. 497 FISHERY BULLETIN: VOL. 72. NO. 2 Table 1. — Caranx mate- -reared larvae, 22 February-31 March 1971. Age No larvae Date (day) picked standard length(mm) Feb. 22 (eggs tched) mean range collected & ha SERIES A A1 Feb. 23 1 8 1.36 1.16-1.55 Feb. 24 2 10 2.18 1.47-2.50 Feb. 25 3 10 2.46 2 13-2.58 Feb. 26 4 5 2.59 2.55-2.68 Feb. 27 5 5 2.57 2.35-2.84 >42 Feb. 28 6 10 3.05 2.94-3.19 Mar. 1 7 10 3.24 2.77-3.39 Mar. 2 8 10 3.46 3.31-3.75 Mar. 4 10 10 3.97 3.50-4.41 Mar. 6 12 10 4.47 3.48-533 Mar. 8 14 10 5.17 4.28-5.75 Mar. 10 16 10 6.21 5.83-7.00 Mar. 12 18 10 7.43 5.58-842 Mar. 14 20 10 8.27 7.25-8.88 Mar. 16 22 10 9.50 8.13-1063 Mar. 18 24 10 10.41 888-1200 Mar. 20 26 10 10.89 8.63-11.75 Mar. 22 28 10 11.42 9.38-12.75 Mar. 24 30 10 12.46 10.63-14.95 Mar. 27 33 10 13.83 11.50-17.25 Mar. 30 36 5 16.62 14.28-18.00 Mar. 31 (Term nated — no larvae remaining) sampling schedule. The second, begun 5 May, provided most of the specimens used in the description, although certain additional measure- ments (e.g., size at hatching) were made on specimens from the first culture. Series A Cultures One thousand eggs were pipetted from the washed plankton of a surface tow with a 505 /j mesh meter net in south Kaneohe Bay, Oahu, on 22 February 1971. These eggs were placed in a 78-liter fiberglass and glass aquarium which had been filled with triple CUNO^ filtered (5 /J effective pore size) bay water. The water was previously exposed to long-wave ultraviolet light for 1 min. Penicillin (to a concentration of 50 mg/liter) and Polymixin B (to a concentration of 8 mg/liter) were added before introduction of the eggs. These antibiotics have been shown to substantially reduce bacterial counts in cultures and materially increase hatching success of omaka eggs (Struhsaker, Hashimoto, Girard, Prior, and Cooney, 1973). A Chlorella sp. culture was added initially to an approximate cell count of 10 X 10" cells/ml. ■•Reference to trade names does not imply endorsement by the National Marine Fisheries Service, NOAA. Salinity, oxygen, and temperature in the tank were usually measured daily. Salinity remained nearly constant throughout the experiment at 35 /CO, the value in the bay at the time of collection. Oxygen values ranged from 6.1 to 9.5 mg/liter during the subsequent 36 days. The maximum range of temperature in the tank was 21.5 to 25.9°C, with a 36-day mean of 24.5°C. The bay surface temperature at the time of collection was 24.4°C. The tank was continuously illuminated by two 40 watt fluorescent "daylight" bulbs. The light intensity at the surface of the water was approxi- mately 6.5 X 10^ flux. The tank was aerated with a single airstone, with airflow adjusted to produce a slow single stream of bubbles. Food was added daily from the third day after hatching. Through day 11 the food was the 75-150 Ai fraction of wild zooplankton attracted to a night light suspended in the bay. On day 12 the addition of wild plankton was replaced with additions ofArtemia nauplii. Wild plankton and Artemia were added each time to a concen- tration in the tank of 5/ml and 1/ml, respectively. No doubt the culture tank supported other (unknown) populations of plankters and micro- organisms. Usually ten larvae were captured by dipping or pipetting at about two-day intervals from hatch- ing (the day after introduction of the eggs) until 36 days after that time (Table 1). No attempt was made to select particular sized larvae. Series B Cultures Larvae reared for yolk-sac-stage description were hatched from eggs taken from Kaneohe Bay on 5 May 1972. At the time of collection (midafternoon), eggs were found in both late middle stage and early stage, i.e., from two spawnings. Only the latter (in blastodisc stage) were selected for culture. (The exact time of fertilization is unknown; hence the duration of the early stage was estimated.) Extrapolating from the subsequent rate of development, we estimate the eggs had been fertilized for about 2 h before capture. Two hundred eggs were placed in each of four 4-liter beakers of unfiltered seawater obtained about two miles offshore from Kaneohe Bay. This "offshore" water contained less plankton 498 MILLER and SUMIDA: DEVELOPMENT OF CARANX MATE and, in general, was of higher quality than that found in the bay used in the Series A cultures. Salinity was always about 35 Vco . Water temperature in the beakers during the experiment ranged from 23.5 to 24.4°C. Bay surface temperature at the time of collection was 25°C. No food or algae was added to these cultures. Erythromycin gluceptate was added to a concentration of 9 mg/liter before intro- duction of the eggs. The beakers were con- tinuously illuminated with fluorescent lights. Eggs and larvae were pipetted from these cultures, which were terminated on the sixth day after hatching. Larvae were immobilized in a refrigerator (ca. lO^C) before preservation in 2.5% buffered formaldehyde. This practice resulted in fewer distorted and curled larvae than did placing them directly in preservative. All measurements and counts were made with a microscope equipped with an ocular micrometer. At the usual magnification (50 x) the precision of measurement is ± 0.02 mm. Illustrations are camera lucida drawings, subsequently inked, by B. Sumida. Owing to rapid loss of certain pigments after preservation, a size series of larvae was microphotographed with color film for sub- sequent reference. Illustrations of early larvae (day 6 and younger) show pigment patterns observed in live larvae. Pigment patterns retained after preservation are so noted in the text. Pigments stabilized in older larvae so that differences between live and dead larvae became much less pronounced with age. Illustrations of these larger larvae (day 8 and older) were made from preserved specimens. DEFINITIONS, MERISTICS AND MORPHOMETRICS Body depth At insertion of pectoral fin. (Prior to pectoral bud formation, taken through shoulder.) Dorsum Region dorsal to medial horizontal line through body. Eye diameter Horizontal diameter of orbit. Head length Tip of snout to posterior margin of operculum. Larva Larva after yolk absorption completed and prior to metamorphosis when scales and lateral line develop. (All of our specimens were larvae based on this definition.) Lateral line streak Dashed line of pigment along the lateral midline of body. Snout to anus length Tip of snout to vertical from anus. Standard length (SL) Prior to notochord flexion and formation of hypural bones, SL taken from snout to tip of notochord. Thereafter, taken to posterior margin of hypural plate. SL = mean standard length. Deviations from means are standard deviations. All length measure- ments were made on preserved specimens, except where noted. Ventrum Region ventral to medial horizontal line through body exclusive of abdominal area; generally area inclusive of hypomeres. Yolk sac larva Larva from hatching to approxi- mately the third day when yolk absorption was nearly complete. DEVELOPMENT OF THE EGG Because the development of the omaka egg proceeds rapidly in discrete stages, we have chosen to summarize it as follows: Early stage Blastodisc stage to blastopore closure (fertiliza- tion to blastopore closure) (Figure lA). Egg size: (diameter) Live: 722 ± 19 m. Preserved: 722 ± 19 m- Figure 1A.— Ventral view of early stage egg oi Caranx mate. BP = blastopore. 499 FISHERY BULLETIN: VOL. 72. NO. 2 Figure IB. — Early middle stage egg. Ventral view of embryo. The omaka egg is pelagic, clear, and spherical with a single oil droplet at the vegetative pole. At the time of collection the eggs were in the early blastodisc stage. Oil globule: Diameter in live egg: 190-200 ^. Diameter in preserved egg: 176-192 /j. Positioned at the vegetative pole, the oil globule was almost centered on the polar axis of the developing blastodisc (Figure lA) Figure ID. — Dorsal view of advanced middle stage egg. Pigment on oil globule omitted. and later between the head and tail bud of the early embryo. At the time of blastopore closure, the oil globule was situated slightly off-center and closer to the tail end of the developing embryo. The blastopore closed between the oil globule and the tail end of the embryo. Perivitelline space: Size range: 26 ± 4 /j. Figure IC. — Ventro-lateral view of advanced middle stage egg, showing oil globule pigmentation. Figure IE. — Lateral view of early late-stage egg. 500 MILLER and SUMIDA: DEVELOPMENT OF CARANX MATE The perivitelline space was not evident in the early blastoderm stages but developed as the egg advanced. Yolk: (diameter) 660± 23 m. The segmentation of the yolk was apparent in the form of irregular polygons across the egg diameter in the early stage eggs (not illustrated). This pattern was lost with preservation of the eggs in 2.5% formalde- hyde, whereupon the yolk took on a "bubbly" irregular appearance. Embryo development: The optic vesicles were evident on the young embryo before blastopore closure of the egg (not illustrated). Initiation of somite develop- ment in the anterior end of the embryo was also observed before closure of the blasto- pore. Kupffer's vesicle was conspicuous at the tip of the rudimentary tail bud. Pigmentation: No pigmentation was present in the egg or embryo during this stage. Duration of early stage: 11-12 h subsequent to capture. Estimated total time — 14 h. Middle stage Following blastopore closure to separation of the tail bud from the yolk (Figure IB). Noteworthy events: Advanced development of the embryo and pigmentation patterns. Egg size, width of perivitelline space, etc., same as above. Oil globule: The oil globule remained nearly centered between the developing head and tail of the embryo. The underside of the oil globule (closest to the embryo) appeared heavily pigmented during the latter part of the middle stage owing to melanophores which had migrated from the surrounding yolk surface (Figure IC). Yolk pigmentation: In the early middle stage, numerous small melanophores were observed overlying the anterior surface of the yolk surrounding the oil globule (Figure IB). Most of these melano- phores migrated during the middle stage and aggregated on the underside of the oil globule. Embryo pigmentation: Small, faintly pigmented melanophores first appeared along the lines separating the developing somites and spread laterally covering the dorso-lateral region of the body. A conspicuous patch of pigment was notice- able at the anterior and posterior margins of the optic vesicles, and a small cluster of melanophores in the area of the snout. Later in this stage, larger melanophores appeared in an irregular line along the medial dorsal surface of the body (Figure ID). Somite development: By the end of the middle stage, 21 well- defined myomeres could be counted. Kupffer's vesicle was still evident in the middle stage. Duration of the middle stage: 11-12 h at24.5°C. Late stage Tail bud completion to hatching of larva (Figure IE). Oil globule: When the advanced embryo had coiled around the yolk, the oil globule shifted in position and became situated closer to the head rather than maintaining a median position under the embryo. Pigmentation became more abundant, extending over the hemisphere of the underside in contrast to the small, dense cluster in the middle stage. Virtually no pigment remained on the surrounding yolk. Embryo pigmentation: Dense pigmentation remained on the dorso- lateral surfaces of the body. Melanophores appeared over the top of the head in addition to those on the snout and along the anterior and posterior margins of the eye. A band of small melanophores developed around the body near the tail region. There also appeared a ring of melanophores on the yolk surface posterior to the tip of the tail bud. This was subsequently lost in the final span of the late stage when fin fold formation was com- pleted and tail flexure occurred. Kupffer's vesicle was observed in the early part of the late stage but was subsequently lost. Somite development: The adult complement of 24 somites was attained in the late stage embryo. Duration of late stage: 0.5-1 h at 24.5°C. 501 FISHERY BULLETIN: VOL. 72. NO. YOLK SAC LARVAE The newly hatched omaka larvae measured 1.32 mm to 1.70 mm SL live, with a mean of 1.46 ± 0.12 mm for 47 larvae. Following preser- vation in 2.5% formaldehyde, a different group often larvae ranged from 0.87 mm to 1.03 mm with a mean of 0.98 ± 0.05 mm. The difference between means (0.48 mm) indicates a shrinkage of 33%. Pigmentation Live Larvae at Hatching Newly hatched omaka larvae resembled ad- vanced embryos in pigmentation pattern. Melano- phore pigment was heaviest on the dorso-lateral surfaces of the body with melanophores usually forming a loop posterior to the head. Additional small clusters of melanophores were observed on the top of the head and at the anterior and posterior margins of the eye vesicles. A broad band of small melanophores encircled the body about 6 myomeres posterior to the anal papilla. Ventral body pigment was not apparent in the newly hatched larvae but was found in older yolk sac larvae, perhaps due to the migration of some dorso-lateral melanophores and those in the band region (see Orton, 1953). Dendritic melanophores (Figure 2A) lined the posterior margin of the yolk sac. The oil globule displayed heavier pigmenta- tion than in the late egg stage, with melanophores present on both its anterior and posterior surfaces. Preserved Larvae at Hatching The remaining pigmentation following preser- vation in 2.5% formaldehyde for at least 24 h were the melanophores on the head and dorso- lateral region of the body. The band of pigment around the body posterior to the anal papilla was lost except for a few scattered melanophores. The yolk sac and oil globule had contracted and obscured any pigment which may have remained. Live Larvae One to Three Days Old The pigmentation pattern of the yolk sac larvae changed markedly during the first few days after hatching. Owing to the rapid change, larvae (preserved) at any time exhibited various stages of pigment development. Therefore the descrip- tions presented are "average" patterns observed. Had the larvae come from simultaneously fer- tilized eggs, the differences would probably have been less pronounced. As the pigment pattern stabilized with age, variations among larvae were correspondingly reduced. There was a loss of lateral pigmentation coinciding with a coalescense of the small dorsal melanophores to form fewer, large melanophores on the dorsal edge of the body, and also with the appearance of pigment on the ventral edge of the hypomeres. These cjianges were apparent in most of the day-old larvae. By the end of the second day, the larvae pos- sessed discrete melanophores on the dorsal and ventral edges of the body in a single discon- tinuous line. The dorsal body melanophores showed branches or "dendrites" which projected up into the fin fold. These were most pro- nounced in the region of the dorsal fin opposite the divergence of the posterior end of the gut from the body. A network of dendritic melano- phores developed about midway along the dorsal and ventral fin folds (Figure 2B). These networks were gradually lost within the next five days of growth. Also evident on the second day was the cluster of melanophores on the top of the head and over the snout region (present in the advanced embryo). The first indication of eye pigmentation appeared with faintly pigmented melanophores over the iris, but concentrated along its posterior margin. The caudal region usually possessed a single minute melanophore dorsal and two or three ventral to the end of the notochord (Figure 2A). The dorsal melanophore was lost in the older larvae, but the ventral melanophores persisted and were situated over the early caudal actino- trichia at about the sixth day. Three-day-old larvae were similar in pigmen- tation to the two-day-old larvae except in their heavier eye pigmentation and fewer melano- phores on the dorsal body edge. Preserved Larvae One to Three Days Old Following preservation in 2.5% formaldehyde for 48 h, virtually all pigmentation, except for the dorsal and ventral body, eye, and head melanophores, were lost. In a few specimens, 502 MILLER and SUMIDA: DEVELOPMENT OF CARANX MATE Figure 2A. — Yolk sac larva, Caranx mate, just after hatching, 1.62 mm SL. Figure 2B. — Three-day old larva, Caranx mate, 2.26 mm SL. Figure 2C. — Six-day old larva, Caranx mate, 3.06 mm SL. Figure 2D. — Twelve-day old larva, Caranx mate, 3.96 ram SL. 503 FISHERY BULLETIN: VOL. 72. NO. 2 faint traces of the fin fold and oil globule pigment could be distinguished. Morphological Development of Yolk Sac Larvae Omaka larvae hatch in a relatively undif- ferentiated state, the only conspicuous structures being the large yolk sac, the unpigmented eyes, otic vesicles, and heart. The oil globule, positioned forward of the head at the extreme anterior margin of the yolk sac, is characteristic of carangids (Ahlstrom and Ball, 1954). Ten hours after hatching (1.80 mm SL), the larvae had developed a narrow, straight gut tube (it became convoluted on the fifth day) terminating at the anal papilla and urinary bladder (Figure 2B). The gradual yolk resorption resulted in the oil globule's shifting its position posteriad while remaining at the anterior margin of the sac. The oil globule lay just ventral to the head at 10 h. Pectoral buds appeared in the larvae by the end of the second day and the jaw buds by the third day. After three days most of the yolk had been absorbed, and the oil globule had diminished in size to a small, barely noticeable spherical body. The end of the third day was thus selected as the termination of the yolk sac stage of the larvae. By the fourth day, the eyes were completely pigmented, the mouth was open and the broad, membranous pectoral fins were functional. The small collapsed yolk sac containing the now minute oil globule was still evident ventral to the anterior portion of the abdominal cavity. LARVAE Pigmentation Head Pigmentation Following yolk absorption (in three-to four- day-old larvae), head pigmentation was present in the following areas: (1) the median dorsal surface of the midbrain (optic lobes) consisting of one or two small melanophores; (2) the floor of the otic vesicle with two or three expanded melanophores which remained visible until obscured by the overgrowth of tissue in older larvae at about day 10 (Figure 2C); (3) along the dorsal margin of the opercle which exhibited a few faintly pigmented melanophores; (4) on the I lower jaw with a melanophore situated at the tip , of the lower jaw and another at the angular I bone, with most of the larvae having a melano- ' phore midway between these two. As the larvae grew, the density of head pig- j mentation increased — particularly over the mid- and forebrain region and on the jaws. The number of melanophores increased on the postero- lateral half of the midbrain lobe while a ring of melanophores concurrently outlined the mar- gin of the midbrain capsule. Larvae of approximately 3.5 mm (day 8-not illustrated) exhibited a cluster of expanded melanophores over the midbrain which gradually extended antero-ventrally to the forebrain and snout region. Pigmentation on the surface of the head had intensified in the older larvae, with the cap over the midbrain being especially conspicuous. By the tenth day (4.0 mm SL), most larvae possessed a melanophore at the tip of the upper jaw in addition to those on the lower jaw; pigmentation subsequently increased over the premaxillary, maxillary, and dentary region as the larvae advanced. Melanophores located on the jaws were smaller and more punctate than those on the top of the head and along the operculum. Pigmentation on the membrane overlying the branchiostegal rays and along the gular region developed in eight- to ten-day-old larvae (3.5- 4.0 mm SL) (Figure 2D). The most anterior branchiostegal rays were initially pigmented with pigmentation proceeding distad until the full complement of seven rays was pigmented. Pigmentation of each ray also proceeded distad resulting in larvae of 20 to 22 days (8.3-9.5 mm SL) possessing as many as two or three melanophores over the basal end of each branchi- ostegal ray (Figure 3A). This pigmentation was barely discernible in larvae of 26 days (10.9 mm SL) and eventually lost altogether in larvae of 28 days (11.4 mm SL). Melanophores along the median gular region similarly increased in density, forming an almost continuous dotted line of contracted melanophores posterior to the isthmus in larvae of 14 days (5.2 mm SL). Additional melanophores formed along this line but pigmentation in this region gradually dis- appeared, like the branchiostegal pigmentation, in the advanced larvae. 504 MILLER and SUMIDA: DEVELOPMENT OF CARANX MATE Figure 3A. — Eighteen-day old larva, Caranx mate, 7.67 mm SL. Figure 3B. — Thirty-three-day old larva, Caranx mate, 12.60 mm SL. The operculum was never heavily pigmented, although melanophores formed along the region between the preopercular spines of larvae from day 8 to 16 (3.5-6.2 mm SL), as the spines were being resorbed. In addition there were several melanophores scattered over the upper region of the operculum posterior to the eye. Body Pigmentation ABDOMINAL REGION.— The abdominal region of the omaka larvae following yolk absorp- tion as used here refers to the peritoneal cavity with its overlying tissue. At six days (3.0 mm SL) the one or two faintly pigmented melano- phores could be seen immediately ventral to the base of the pectoral fin. These melanophores persisted until the larvae were 14 days old (5.2 mm SL) (Figure 2C, D). A few melanophores were scattered over the abdominal wall in the early larvae with increasing numbers being formed in older larvae. The spherical gas bladder was apparent by the sixth day (3.0 mm SL) with its dorsal cap of embedded pigmentation. The gas bladder was gradually depressed into an elliptical shape by day 10 (4.0 mm SL) and its pigment largely obscured with the increasing growth of muscula- ture dorsally. A line of melanophores developed by day 6 (3.0 mm SL) (Figure 2C) extending along the dorsal wall of the abdominal cavity from the gas bladder to the terminus of the gut where it converged with the ventral line of melanophores along the edge of the hypomeres (see section on ventrum pigmentation). This pigmentation in- creased in density through day 8 (not illustrated) until it was obscured by the growth of overlying tissue by day 12 (Figure 2D). This pigmentation had a diffused appearance owing to its internal, dorsal position, but consisted of discrete melano- phores. Also evident in six-day-old larvae was peri- toneal pigmentation along the ventral edge of the abdominal cavity, including a small precleithral cluster of melanophores, a larger cluster just ventral to the liver (where the pelvic bud sub- sequently appeared), and a row of melanophores extending from the ventral surface of the stomach to the anus. These pigments gradually diminished 505 FISHERY BULLETIN: VOL. 72. NO. 2 and were obscured or lost in larvae of about 26 days (10.9 mm SL). DORSUM. — Dorsum pigmentation of the post yolk sac larvae of four days of age (2.6 mm SL) consisted of a single line of 9 to 13 large, stellate melanophores extending posteriad from the base of the hindbrain to the 17th to 19th myomere along the dorsal edge of the body (Figure 2C). At ten days (4.0 mm SL), numerous small melanophores had formed ventro-laterally, inter- spersed along the prominent line of melanophores of the dorsal edge. The appearance of these lateral melanophores coincided with the appear- ance of dorsal and anal fin anlagen (which were visible as opaque thickenings in the fin fold). By day 12 (Figure 2D) (4.5 mm SL) the dorsal melanophores had become smaller and more numerous, bordering each side of the ventral margin of the dorsal fin anlage. The formerly conspicuous single row of large melanophores on the edge of the dorsum was now lost, having been replaced by these smaller dorsal melano- phores in a double row along the base of the fin anlage and continuing in a single row posteriorly. Larvae of 15 to 16 days of age (5.2-6.2 mm SL) showed increased lateral spreading of pigmen- tation. By 18 days (7.4 mm SL) (Figure 3A), melanophores had formed along the more pos- terior two-thirds epaxial myoseptal lines, which became more pronounced in 20-day-old larvae (8.3 mm SL). This epaxial myoseptal pigmenta- tion pattern was gradually obscured by the increasing density of pigmentation over the entire area of the dorsum beginning in 22-day-old larvae (9.5 mm SL). The caudal peduncle remained sparsely pig- mented both dorsally and ventrally throughout development. (The pigment along the base of the caudal fin is described in the section on fin pigmentation.) VENTRUM. — The pigmentation changes of the ventrum from the four-day-old larvae followed a similar pattern to that of the dorsum with a few exceptions. The larvae of four to eight days of age exhibited a single line of 12 to 26 small melanophores along the ventral edge of the body from the anus to the 23rd or 24th myomere. These ventral melanophores were smaller and extended more posteriad than those aligned along the dorsal edge of the body until fin formation was well initiated. In addition, two to four minute punctate melanophores appeared on the ventral tip of the notochord (which subsequently migrated ventrally to become situated along the proximal edges of the caudal actinotrichia discussed in the section on fin pigmentation). With the first appearance of the anal fin anlage in ten-day-old specimens, faint melano- phores formed dorsolaterally over the ventrum, followed by the appearance of a double line of melanophores along the base of the anal fin anlage in 12-day-old larvae (4.5 mm SL) from the previously single line as it occurred along the base of the dorsal anlage. From day 14 to 16 (5.2-6.2 mm SL), melanophores formed a con- spicuous pattern along the hypaxial myoseptal lines, with others scattered in the surrounding region (Figure 3A, B). These latter were most concentrated over the ventral one-third of the hypomeres. The hypaxial myoseptal pigment pattern remained visible in the largest larvae (18.0 mm) in contrast to that on the dorsum and remained as a major distinguishing char- acteristic. "LATERAL LINE STREAK".— The "lateral line streak" refers to the dashed line of pigmen- tation along the lateral midline of the body as described for several other carangid larvae (see Ahlstrom and Ball, 1954; and Kramer, 1960). It appeared in the six-day (Figure 2C) omaka larvae (3.0 mm SL) with two or three elongate melanophores arising near the vertical of the anterior portion of the hindgut, with as many as 13 melanophores having formed in eight-day-old (3.5 mm SL) larvae. Indeed, body pigmentation of the larvae at this age was characterized by three lines: along the dorsal and ventral edges of the body, and the lateral line streak. Although it was largely obscured by the over- growth of tissue and heavier lateral pigmentation, the streak was still noticeable in the 36-day-old larvae (16.6 mm SL). It provided a sharp line of demarcation between the heavily pigmented dorsum and the more sparsely pigmented ven- trum in the older larvae (Figure 3B). Fin Pigmentation CAUDAL. — Prior to notochord flexion, a few small melanophores were present along the distal margin of the early hypural plate (Figure 2D). In addition, a line of minute melanophores had formed along the ventral margin of the caudal 506 MILLER and SUMIDA: DEVELOPMENT OF CARANX MATE fin fold, but was lost in older larvae (ca. 7.5 mm SL). Following flexion of the notochord (ca. 6.0 mm SL), melanophores were still evident along the posterior margin of the hypural bones and along the dorsal and ventral margins of the fin mem- brane in the caudal peduncle region, with addi- tional caudal fin pigment developing distally between the rays. The density of melanophores increased in the older larvae, generally forming in one or two rows between the rays. PECTORAL.— Larvae of ca. 6.0 mm SL had minute melanophores scattered along the distal margin of the pectoral fin, but pigmentation remained sparse compared to that of the caudal, dorsal, and anal fins. By 8.5 mm, the pigmentation had increased to rows of three to five melano- phores interspersed between the more dorsal rays, with this pigmentation spreading ventrad as the larvae grew. DORSAL AND ANAL.— Pigmentation of the dorsal fin fold was described earlier. In the early larvae up to ca. 3.0 mm, there were dendritic melanophores lining the edge of the preanal fin fold which were lost in larvae by 4.5 mm. The pattern of pigment development was similar for both fins, although that on the anal was formed earlier. This was consistent with the apparent earlier formation of the anal fin. By 6.0 mm, larvae displayed the beginning of a row of melanophores along the distal margin of the anal pterygiophores (Figure 3A). Initially each of these melanophores was situated between ad- jacent pterygiophores in the anterior portion of the fin; more developed posteriad in older larvae. The entire length of the proximal margin of the anal fin had this pigment by 8.0 mm, but the dorsal fin margin showed no evidence of it until ca. 7.0 mm. Approximately three-fourths of the anterior portion of the dorsal fin margin was pigmented at 10.0 mm. Rows of two to four melanophores were evident along the distal region of the fin membrane between the anteriormost anal fin rays at ca. 6.0 mm. The fin pigmentation process proceeded posteriad, with the melanophore number increas- ing to as many as 14 in double rows between rays in larvae of ca. 10.5 mm. Larvae of ca. 8.5 mm showed melanophores forming distally on the fin membrane surrounding the dorsal spines and between the first few dorsal rays. Subsequently, the fin pigment developed posteriad as in the anal fin; and the density of melanophores on the dorsal fin membrane was similar to that of the anal fin by 11.3 mm. PELVIC (VENTRAL).— Like the pectoral fin, each pelvic fin was sparsely pigmented. Two or three melanophores were observed on the small, rayless fin on larvae of ca. 6.0 mm. By ca. 7.6 mm, two or three rows of a few small, incon- spicuous melanophores had formed between the rudimentary fin rays (Figure 3A). Fin Development The omaka larvae hatched with no developed fins but a broad, flat fin fold. The subsequent formation of fins (first development of lepido- trichia) followed a sequential pattern much like that described for Trachurus symmetricus (Ahl- strom and Ball, 1954), viz. caudal, pectoral, anal and soft dorsal, spiny dorsal, and pelvic (ventral) in that order. The stage of omaka fin development par- ticularly, appeared to us to be more dependent on size attained than age. Smaller, older larvae were found to have not yet completed certain stages, while some precocious (larger) larvae had. Owing to rapid development of larvae, larger samples at more frequent time intervals would be required to test a hypothesis of size versus age dependence of developmental events. Caudal Caudal actinotrichia could be observed in larvae as small as 2.2 mm in the form of faint lines projecting distally from the area around the tip of the notochord. True rays (lepidotrichia) were first evident in larvae ca. 3.4 mm (day 7) and became more prominent in 4.0 mm larvae as ventrally projecting incipient rays from the presumptive hypural plate below the tip of the notochord. These rays were well-defined in larvae of ca. 4.5 mm (day 12), when notochord flexion was initiated. At this time as many as 15 rays of the total 17 principal caudal rays could be observed still projecting obliquely from the developing unossified hypural bones lying ventral to the notochordal tip. Notochord flexion and the formation of the 17 principal caudal rays (nine 507 FISHERY BULLETIN: VOL. 72. NO. 2 above the midline of the hypural plate, eight below) were completed in larvae by 6.0 mm (day 16). (Secondary rays were added anteriad along the dorsal and ventral margins of the caudal peduncle with as many as nine formed on each edge in the largest larvae.) The rounded caudal fin fold was confluent with the dorsal and anal fin folds in the young larvae, but an indentation of the fin fold occurred in the region of the future caudal peduncle in the older larvae. The caudal fin was separated from the dorsal and anal fin membranes in larvae between 5.3 mm and 6.0 mm (day 14-16). At this stage of development the caudal fin possessed a straight margin, rather than rounded, along its posterior edge and subsequently attained a bilobate shape in larvae of ca. 10.5 mm (day 24). Pectoral The pectoral fin developed early during the yolk sac stage (see earlier sections). However, rays did not form until the larvae were ca. 5.4 mm (day 14) when six or more rays could be counted in the upper region of the fin. Addition of rays pro- ceeded ventrally with the rays decreasing in length ventrally to give the pectoral fin an obovate shape in the older larvae compared to the earlier, more rounded, membranous larval fin. The adult complement of 21 to 22 rays was attained in larvae of 9.3 mm. A short, inconspicu- ous spine at the extreme dorsal margin of the pectoral was evident upon close examination of our cleared and stained specimens of minimal length 8.4 mm and larger cleared and stained juveniles from our field-collected samples. Anal Formation of the anal fin was first evidenced by the appearance of the anal anlage in larvae as small as 3.75 mm. (See section on ventrum pigmentation.) Following the formation of the dorsal and anal anlagen, it appeared that the separation of the fin fold into dorsal, anal, and caudal sections coincided with the development of incipient rays and first few spines of the dorsal and anal fins in larvae from 5.4 mm to 5.5 mm (day 14). One anal spine formed concurrently with six or more incipient rays in larvae of 5.4 mm or larger; the two remaining spines developed anteriad to the first formed spine in larvae between 7.0 and 9.0 mm which had at least 15 rays formed posteriorly. Generally by 9.0 mm, the two most anterior anal spines had separated from the third which remained associated with the soft rays. However,, a well-defined separation of the fin membrane did not occur until the larvae were 16.0-17.0 mm in length. The adult complement of II-I, 17-19 for the anal fin was completed in larvae by 9.0 mm, although three smaller specimens (8.13, 8.63 and 8.88 mm SL) had complete anal fins. An inconspicuous flap of tissue could be observed developing over the bases of the spines and first few rays of the anal fin in most of the larvae by 11 mm. The flap was not completely formed along the basal margin of the anal fin in our largest larva (18 mm) but had covered only about three-fourths of the length of the fin base. This was the precursor to the flap of tissue which overlies the entire length of the dorsal and anal fin bases in adult omaka. Dorsal The dorsal anlage appeared at approximately the same size as the anal anlage. Development of the soft dorsal occurred prior to formation of the spiny dorsal. There was no clear difference in the rate of development of the soft dorsal fin and anal fin in contrast to the jack mackerel (Ahlstrom and Ball, 1954). Distal pterygiophores of the soft rays were evident in larvae of 5.0 to 5.4 mm, with incipient rays becoming differentiated in 5.55 mm (and larger) larvae. Subsequent fin development was rapid. Four to six spines had developed with as many as 16 rays in larvae of 5.8-6.0 mm. Spines were added anteriad and rays posteriad. Most of the larvae of 7.3 to 8.0 mm length had attained a dorsal fin complement of IX-20 to IX-22. In larvae larger than 9.0 mm, the ninth spine had separated from the preceding eight to separate the two dorsal fins. The fourth dorsal spine remained the longest in the larger larvae, with the others progressively decreasing in length. Larvae from 9.0 to 18.0 mm possessed the adult fin complement of VIII-I, 20-23. By 9.25 mm, only cleared and stained specimens, showed a small, embedded, forwardly projecting spine arising from the pterygiophore of the first external spine. We did not count this spine 508 MILLER and SUMIDA: DEVELOPMENT OF CARANX MATE separately in the fin complement, although some investigators have apparently done so in pre- senting spiny dorsal meristics for C. mate as I+Vm+I (e.g., Smith, 1965; Munro, 1967). The spine is apparent only upon dissection of juveniles and adults of the omaka. A narrow flap of tissue had begun to form over the basal edge margin of the anterior three to four dorsal spines in larvae of 10 mm. It appeared slightly earlier than that for the anal fin. Like the flap over the anal fin base, the dorsal flap had only developed along three-fourths of the length of the dorsal fin base in our largest reared larva (18 mm). Pelvic (Ventral) The inconspicuous pelvic fin bud appeared in larvae of 4.4 to 5.7 mm, except for two specimens of 3.64 and 3.96 mm which had already formed the fin buds. These appeared as small pro- tuberances just ventral to the liver and gradually differentiated into a larval fin in 6.0 mm larvae. Two or three rays had formed in larvae by 6.2 mm, and the adult complement of I, 5 was com- pleted in larvae of 7.7 mm. OSSIFICATION Eighteen larvae, one of each age group sampled and representative of the size range in the sample, were cleared and stained with alizarin following the technique described by Hollister (1934). (Three 7-day-old larvae were cleared and stained to further define the sequence of tooth formation on the upper jaw. ) The specimens were cleared and stained primarily to confirm the meristics taken and developmental descriptions presented earlier on unstained material. In order to determine the limits of precision for our statements derived from these cleared and stained larvae about size of first structural development, length differences among our relatively few specimens were measured. They ranged from 0.1 to 0.2 mm for 2.9-3.5-mm speci- mens, 0.5 mm for specimens 3.5-4.6 mm, and about 1 mm for larger specimens. Ahlstrom and Ball (1954) present a thorough discussion of the ossification sequence for the carangid, T. symmetricus (jack mackerel). Our cleared and stained specimens showed exactly the same sequence, but ossification (defined as taking up alizarin) of each bone began in smaller omaka larvae than jack mackerel (Ahlstrom and Ball, 1954). Likewise, most of these bones had com- pleted ossification at a smaller size in omaka. The cleithrum, upper and lower jaw bones, and preopercular spines were already ossified in our 2.94 mm larva. Minute teeth (ca. 4 on the upper jaw) had begun staining in the larva of 3.35 mm with numerous small teeth filling in the single row in larger larvae. Teeth on the lower jaw first appeared in the 9.25 mm larve. Five branchi- ostegal rays were stained in the larva of 3.50 mm, with all seven branchiostegal rays on each side of the base of the operculum being stained in the 4.58 mm larva. Gill arches were ossified or stained in the 4.09 mm specimen, and gill rakers began staining in the. 5.42 mm larva. Meristics for ossification of fin elements are presented in Table 2. All neural and haemal spines and centra of the 24 vertebrae (10 abdominal vertebrae, 14 caudal vertebrae) had completed ossification in the 6.25 mm larva. The initial vertebral ossification, indicated by the stain in the neural spines of the first few abdominal vertebrae and in the haemal spines of the caudal vertebrae, was present in the 4.09 mm larva. Preopercular spines of the omaka larvae were formed along two rows as in the jack mackerel (Ahlstrom and Ball, 1954), viz. the posterior edge of the preoperculum and the "preopercular crest" just anterior to the preopercular edge (as defined by Ahlstrom and Ball, 1954). Those spines situated along the preopercular crest were fewer and smaller than those along the edge of the preoperculum. During the larval development of omaka, the number of spines along the Table 2. — Meristics of cleared and stained Caranx mate larvae. Larvae smaller than 4.58 mm are omitted owing to lack of ossification of these fin elements. SL Age Caudal Dorsal Dorsal (mm) (days) (principal) Pectoral Anal (second) (first) Ventral 4.58 12 7 + 8 5.42 14 8 + 7 6 1.6 9 6.25 16 9 + 8 11 11,13 17 VII 3 7.67 18 9 + 8 18 111.17 1,21 VIII 1,5 8.38 20 9 + 8 20 1 1-1,18 1,21 VIII 1,5 9.25 22 9 + 8 21 1 1-1,17 1,22 VIII 1,5 9.88 24 9 + 8 22 1 1-1,17 1,21 VIII 1,5 10.88 26 9 + 8 1,20 1 1-1,18 1,22 VIII 1,5 11.63 28 9 + 8 1,20 1 1-1,19 1,22 VIII 1,5 12.38 30 9 + 8 1,20 1 1-1,17 1,21 VIII 1,5 13.50 33 9 + 8 1.21 1 -1,19 1,23 VIII 1,5 17.00 36 9 + 8 1,21 1 -1,18 1,22 VIII 1,5 509 FISHERY BULLETIN: VOL. 72. NO. 2 ascending arm of the preoperculum increased from two (2.9-3.5 mm larvae) to as many as six (7.0-9.0 mm larvae) and from two to seven along the anteriorly projecting descending arm. The apical spine of the preoperculum remained slightly larger and broader-based than the others as in the jack mackerel (Ahlstrom and Ball, 1954), but was still smaller and less prominent than in our other common carangid larva, Gnathanodon speciosus (unpublished data), and provides one characteristic for separating the two species. The omaka larvae showed no serrated dorsal crest at the back of the head which was evident in the jack mackerel (Ahlstrom and Ball, 1954). It is considered to be a rather common feature of carangid larvae (Berry 1959, McKenney, Alexander, and Voss 1958, Okiyama 1970, Sho- jima 1962) and is present in several of our unidentified species of carangid larvae. GROWTH The growth rate and description of changes in body form are based mainly on specimens reared from eggs taken in surface tows from Kaneohe Bay on 22 February 1971 (Table 1). At that time the bay surface temperature was 24.4°C. Rearing tank temperatures ranged from 22.1° to 25.9°C, with a mean of 24.5°C, so the thermal environ- ments were similar. As stated in the methods section, the salinity and oxygen level in the tank remained similar to those in the bay throughout the experiment. Without data on the quantity and quality of food for any given time of the rearing period, however, it is impossible to assess the reality of the growth rate. The general shape of the curve (a nearly straight line) and the absence of any mass mortality suggests that the rearing environment was at least adequate throughout the experiment. The absence of prolonged lags in growth suggest the absence of periods of major stress. The growth curve (Figure 4) is composed of at least three segments of differing slope: from hatching through day 2; day 3 through day 5; and from day 6 onward. The inflection in the curve at day 2-3 coincides with the near final absorp- tion of yolk, and perhaps more important, the development of a functional mouth. No major structural change occurs at day 6 which might be linked to that inflection. Among four rearing o z z Y^-0 3016 ♦0.4362 X r. 0.9929 n.16 16 20 TIME (DAYS) 28 32 Figure 4. — Growth rate oiCaranx mate in culture. Regression based on mean length after day 6. n = 16. trials, the change in length from hatching to day 6 (ca. 2.5 mm) was extremely variable. In two of the trials, larvae increased in length through day 3, then shrank. It appears that the vari- ability in early omaka growth rate might be linked to the success of larvae in obtaining their first exogenous energy (Thomas Cooney, pers. comm. — M.A. thesis research). Owing to this variability, the statistical description of the growth rate of larvae through day 5 is of little value. Interpolation between mean (preserved) size at hatching (1.03 mm) and mean size of day 6 (3.05 mm) yields an estimate growth of 0.35 mm/day. The relationship chosen to express larval growth beyond day 6 was the linear regression: SL (in mm) = -0.3016 + 0.4362 (age in days) (Figure 4), as determined from 153 preserved specimens. A slightly better fit would have been obtained with a more complex function, but the improvement in the curve would be slight. The greatest departures from linear growth occurred at day 14 and day 28 (SL = 5.2 mm and 11.4 mm, respectively). No major morphological developments occurred at these sizes, so the causes (if the departures are real) are not known. The generally poorer fit of the data to the curve at the largest sizes is probably attributable to sampling. As the vagility of larvae increases with size, the probability increases that the smaller 510 MILLER and SUMIDA: DEVELOPMENT OF CARANX MATE larvae in a tank are selected for preservation. This effect is apparent from the larger (than predicted from the curve) mean size of the five fish on day 36, which were the last specimens in the tank when it was emptied. One source of error in relating early growth rates of larvae to those of larger larvae is their shrinkage upon preservation. Five groups of ten live larvae (one to five days old), ranging in mean standard length from 2.46 to 2.85 mm, ranged in length from 2.13 to 2.55 mm 24 h after preserva- tion. Shrinkage was also observed to begin within seconds after death when larvae died while being observed microscopically. This latter observa- tion suggests that shrinkage was not entirely due to the effects of formaldehyde on body proteins. The percent shrinkage was not correlated in a simple way with size. Although, presumably, this percentage decreases with increased size of larvae, the shrinkage values, which ranged from 8 to 22'7f in the five groups, can introduce significant error into estimates of early larval growth. Newly hatched larvae shrank as much as 30% when they died. Farris (1959) described two growth stanzas of the jack mackerel, viz. (A) from hatch to day 3 and (B) from day 3 to 7. If these corres- pond to our first two segments, then the second segment (day 3-7) of growth in omaka is twice that of jack mackerel (0.195 mm/day compared to 0.10 mm/day). Alternatively, comparing growth from hatching to yolk absorption — day 3 in omaka, day 6 in jack mackerel — yields a similar difference, 0.48 and 0.26 mm/day, respectively. The comparisons suggest that effects of starva- tion may occur prior to complete yolk absorption. Farris' growth rates for segment B (on starved fish) may be underestimates. Lasker, Feder, Theilacker, and May (1970) found that larvae may begin to feed before complete yolk absorp- tion. Comparisons need to be made between starved and fed yolk-sac larvae of the same species reared in the same physical environment before a definitive answer can be reached. BODY PROPORTIONS As Marr (1955) pointed out, expression of relationships between body dimensions as ratios contributes nothing more than plots of the original measurements, so the latter were used. Relationships between standard length and 1) head length, 2) eye diameter, 3) snout to anus length, and 4) body depth at pectoral fin were all adequately described by an equation of the form: Y = a + 6(SL). All of the data used in the regressions are from one series of reared omaka larvae (Table 1). The ratios all adequately describe specimens captured in the field. In the following discussions of these relation- ships, comparisons are made between the omaka and jack mackerel (T. symmetricus), described by Ahlstrom and Ball (1954). The latter is the only carangid larva for which these kinds of data are published. With similar data for other carangid species, these may prove useful in a key to carangid larvae. Head Length Head length was related to standard length according to the equation: HL = -0.2796 + 0.3477 (SL in mm) (Figure 5). Unlike T. symmetricus (Ahlstrom and Ball, 1954), there was no inflection in the curve at ca. 4 mm. The slope of the regres- sion line for omaka (0.3477) is not very different than that for the jack mackerel (0.378), so this ratio would not be very useful by itself in dis- tinguishing the two species. Ahlstrom and Ball ( 1954) did find a different slope (0.556) in the jack mackerel larvae smaller than 4.2 mm, but several of our smaller larvae would fit either regression. Eye Diameter The relationship between eye diameter and STANDARD LENGTH (MM) Figure 5. — Relationship between standard length and head length ofCaranx mate larvae. 511 FISHERY BULLETIN: VOL. 72. NO. 2 S 15 Y> -0 1089*0 1366 X '.09928 n.l9l .^■^ STANOASD LENGTH (MM) Snout-to-Anus Length The snout-to-anus length increased 0.5347 mm for each millimeter increment in standard length throughout larval development (Figure 7). As might be expected from the body depth differences between omaka and jack mackerel, the ratio between snout-to-anus length and standard length of omaka is slightly smaller than that for the jack mackerel (0.581), the latter being a more elongate larva. Again, however, the difference is probably too small to be useful in separating the species. Figure 6. — Relationship between standard length and eye diameter ofCarartx mate larvae. standard length was described by a straight line of the equation: ED = -0.1089 + 0.1266 (SL in mm) (Figure 6). Omaka larvae have almost the same (proportional) eye size as T. symmetricus (0.127), reported by Ahlstrom and Ball (1954). Therefore, this ratio is not useful. as a dis- tinguishing characteristic. The omaka eye was somewhat ovoid with the blunt end anterior. The posterior, more acute, end of the eye became more angled up to day 4, then the trend was reversed so the juvenile round eye shape was reached by day 20 (SL = 8.27). The "squarish distortion" reported for T. symmetricus (Ahlstrom and Ball, 1954) did not occur in omaka. Body Depth at Pectoral Insertion The relationship between the body depth and standard length remained constant throughout larval development (Figure 8). No inflection was evident in the omaka, as was reported for T. symmetricus by Ahlstrom and Ball, 1954 (larvae smaller than 4.2 mm). The slopes of the regres- sion lines (0.425 for omaka and 0.278 for jack mackerel larvae) are different enough to be used to distinguish these species over 4 mm; omaka larvae are considerably deeper-bodied. The other common carangid in Kaneohe Bay, G. speciosus, has a still deeper-bodied larva (our unpublished data); so this ratio appears the most useful of the four discussed to distinguish at least these three species. • 0 1223.0 5347 X ■ 09972 _1 1 l_ STANDARD LfNGTH (MM) 6 3 Y. -0 S583 *OA24bx f .0 9953 n.l9) S 10 STANDARD LENGTH (MM) Figure 7. — Relationship between standard length and snout- to-anus length ofCaranx mate larvae. Figure 8. — Relationship between standard length and body depth oCCaranx mate larvae. 512 MILLER and SUMIDA: DEVELOPMENT OF CARANX MATE SUMMARY 1. Omaka eggs were pelagic and spherical with a single oil droplet and segmented yolk. The diameter was about 700-740 fi. 2. Egg development occurred in three distin- guishable stages: early — fertilization to blasto- pore closure; middle — to tail flexure; and late — to hatching. Respective duration times at 24.5°C were 11-12 hours, 11-12 hours, and 0.5-1 hour. 3. Yolk sac larvae hatched at a length of 1.3- 1.7 mm with the oil globule positioned forward in the yolk sac. 4. By the fourth day (SL = 2.6 mm), the eyes were pigmented, the yolk and oil globule absorbed, and the mouth functional. 5. Fin development (first appearance of lepido- trichia) occurred in the order: caudal (3.4 mm); pectoral (5.4 mm); anal and soft dorsal (5.4-5.5 mm); spiny dorsal (5.8 mm); and pelvic (6.2 mm). 6. Unlike many carangid larvae, omaka did not develop a serrated crest behind the head. 7. Values for ratios of body proportions to standard length were: head length, 0.3477; eye diameter, 0.1266; snout-to-anus length, 0.5347; body depth, 0.4246. Only the body depth/SL ratio was useful in separating omaka from jack mackerel and certain other Hawaiian carangid larvae. 8. The growth of our cultured omaka after day 6 was adequately described by a straight line with slope 0.44. Before day 6, growth was ex- tremely variable, averaging about 0.35 mm/day. 9. Of primary use in separating omaka from jack mackerel larvae (the only other similarly described carangid larva) were pigment pattern, the absence of a serrated dorsal ridge behind the head, and the difference in the ratios of body depth to standard length. 10. Significant decreases in size (up to 33%) and pigmentation of larvae occurred upon preser- vation. Both of these effects decreased with age of larvae. 11. Although based on larvae reared in the laboratory, our data relating growth and develop- ment to time would be expected to simulate those from natural tropical habitats, especially the data for fish eggs and early larva. ACKNOWLEDGMENTS Throughout the paper reference is made to the excellent paper by Ahlstrom and Ball (1954), describing the eggs and larvae of the jack mackerel (T. symmetricus). The authors acknowl- edge a debt to Ahlstrom and Ball for their example. Many of their descriptive techniques were used by us, and, in our opinion, should be considered a standard for all larval fish descriptions. Larval fish taxonomy suffers greatly from dissimilarities among descriptive tech- niques. Thanks are also extended to David Hashimoto, Senior Technician at the Hawaii Institute of Marine Biology, for rearing the larvae. This research was, in part, supported by University of Hawaii Sea Grant No. GH-93. (UNIHI-SEAGRANT-JC-74-02.) LITERATURE CITED Ahlstrom, E. H., and O. P. Ball. \ 1954. Description of eggs and larvae of jack mackerel {Trachurus symmetricus) and distribution and abun- dance of larvae in 1950 and 1951. U.S. Fish Wildl. Serv., Fish. Bull. 56:209-245. Berry. F. H. 1959. Young jack crevalles (Caranx species) off the south- eastern Atlantic coast of the United States. U.S. Fish Wildl. Serv., Fish. Bull. 59:417-535. Farris, D. a. 1959. A change in the early growth rates of four larval marine fishes. Limnol. Oceanogr. 4(l):29-36. Hollister, G. 1934. Clearing and dyeing fish for bone study. Zoologica 12:89-101. Kramer, D. 1960. Development of eggs and larvae of Pacific mackerel and distribution and abundance of larvae, 1952-56. U.S. Fish Wildl. Serv., Fish. Bull. 60:393-438. Kuthalingham, M. D. K. 1959. A contribution to the life histories and feeding habits of horse-mackerels, Mega/aspis cordyla (Linn) and Caranx mate (Curv and Val) and notes on the effect of absence of light on the development and feeding habits of larvae and post larvae oiMegalaspis cordyla. J. Madras Univ., B. 29(2):79-96. Lasker, R., H. M. Feder, G. H. Theilacker, and R. C. May. 1970. Feeding, growth, and survival ofEngraulis mordax larvae reared in the laboratory. Mar. Biol. 5:345-353. Marr, J. C. 1955. The use of morphometric data in systematic, racial and relative growth studies in fishes. Copeia 1955:23-31. McKenney, T. W., E. C. Alexander, and G. L. Voss. 1958. Early development and larval distribution of the carangid fish, Caranx crysos (Mitchill). Bull. Mar. Sci. GulfCaribb. 8:167-200. MUNRO, I. S. R. 1967. The fishes of New Guinea. Victor C. N. Blight, Sydney, New South Wales, 650 p., 78 pis. 513 FISHERY BULLETIN: VOL. 72, NO. 2 Okiyama, M. 1970. Studies on the early life history of the rainbow runner, Elagatis hipinnulatus (Quoy & Gaimard) in the Indo-Pacific Ocean. Bull. Far Seas Fish. Res. Lab. (Shimizu) 3:167-186. Orton, G. L. 1953. Development and migration of pigment cells in some teleost fishes. J. Morphol. 93:69-99. Shojima, Y. 1962. On the postlarvae and juveniles of carangid fishes collected together with the jelly-fishes. (In Jap., Engl, summ.] Bull. Seikai Reg. Fish. Res. Lab. 27:47-58. Smith, J. L. B. 1965. The sea fishes of Southern Africa. Cape and Transvaal Printers Ltd., Capetown, 580 p.. Ill pis. Struhsaker, J. W., D. Y. Hashimoto, S. M. Girard, F. T. Prior, and T. D. Cooney. 1973. Effect of antibiotics on survival of carangid fish larvae (Caranx mate), reared in the laboratory. Aqua- culture 2(l):53-88. Watarai, L. T. 1973. Growth rate of a carangid fish, the omaka Caranx mate, in Hawaii. Trans. Am. Fish. See. 102:617-620. 514 FOOD HABITS OF GEORGIA ESTUARINE FISHES I. FOUR SPECIES OF FLOUNDERS (PLEURONECTIFORMES: BOTHIDAE) Robert R. Stickney/ Gary L. Taylor/ and Richard W. Heard III^ ABSTRACT The food habits of four species of bothid flounders from Georgia coastal waters were examined by means of stomach content analyses. Ocellated flounders, Ancylopsetta quadrocellata (Gill); bay whiff, Citharichthys spilopterus (Giinther); and windowpane, Scophthalmus aquosus (Mitchill) fed heavily on the mysid shrimp, Neomysis americana, without regard to season of the year or location within the estuary. The food habits of both A. quadrocellata and C. spilopterus changed to some extent as the fish became larger. Organisms larger than N. americana dominated the stomach contents of A. quadrocellata larger than 150 mm standard length and C. spilopterus larger than 125 mm. S. aquosus, in the size range examined, fed almost exclusively on A^. americana. Fringed flounder, Etropus crossotus (Jordan and Gilbert) primarily consurried the calanoid copepod, Pseudodiaptomus coronatus, during the spring, summer, and fall and diversified their food habits during the winter. P. coronatus dominated the stomach contents both in the rivers and sounds of Georgia estuarine waters and was the dominant organism in fishes of all sizes up to 100 mm when polychaete annelids became important. The food of E. crossotus did not appear to vary with time of day; however, E. crossotus did not actively feed at night. The difference in food habits between E. crossotus and the other three bothid species appears to be associated with the relative size of the mouth. Pleuronectiform fishes of the family Bothidae are common in the estuarine waters of the southeast- ern United States. Otter trawl samples taken within the sounds and rivers of Georgia indicate that fishes of the family Sciaenidae are the most common, with bothids being among the next most common species. Summer flounder, Para- lichthys dentatus and southern flounder, P. letho- stigma, are common, but are not present in com- mercially exploitable quantities. P. albigutta has also been reported from Georgia waters, but appears to be relatively rare (Dahlberg and Odum, 1970). Ocellated flounder, Ancylopsetta quadrocellata, while not commercially valuable, is occasionally caught by sport fishermen. Bothid flounders are generally associated with the bottom, either lying on the surface of the substrate or buried to a greater or lesser extent in the sediments. The feeding behavior of floun- ders under various conditions (both in nature and in culture) has been described (Steven, 1930; ' Skidaway Institute of Oceanography, P.O. Box 13687, Savannah, GA 31406. ^ Gulf Coast Research Laboratory, P.O. Box AG, Ocean Springs, MS 39564. 011a, Wicklund, and Wilk, 1969; de Groot, 1970; 011a, Samet, and Studholme, 1972; Stickney, White, and Miller, 1973), but little information on the selective food habits of bothids is presently available. The food habits of Paralichthys sp. have been examined by Darnell (1958) in the Gulf of Mexico and by Poole (1964) in New England waters. A limited amount of additional information on P. albigutta is also available from samples taken off the southwestern coast of Florida (Topp and Hoff, 1972). Examination of the stomachs from a few specimens of A. quadrocellata and Etropus crossotus, fringed flounder, demonstrated that both feed on crusta- ceans in Florida waters (Topp and Hoflf, 1972) with E. crossotus also utilizing polychaetes and chaetognaths for food (Reid, 1954; Topp and Hoff, 1972). Fourteen species of bothid flounders were examined by de Groot (1971) who found that they divided into three groups by food preference: fish feeders, crustacean feeders, and polychaete-mollusc feeders. The food habits of bothid flounders along the Georgia coast have not been previously elabor- ated. For purposes of the present study, four Manuscript accepted September 1973. FISHERY BULLETIN: VOL. 72, NO. 1974. 515 FISHERY BULLETIN: VOL. 72. NO. 2 species were selected which seasonally account for the majority of bothids captured by otter trawling and were thus judged to be important in the energy flow through the Georgia estuarine ecosystem. The four species chosen were A. quadrocellata; bay whiff, Citharichthys spilop- terus; E. crossotus\ and windowpane, Scophthal- mus aquosus. Other important Pleuronectiform fishes of the Georgia coast include P. dentatus, P. lethostigma, Trinectes maculatus, and Sym- phurus plagiusa. MATERIALS AND METHODS The coastal region of Georgia consists of a system of barrier islands separated by sounds from which a network of rivers and tidal creeks emanate. The tide range (reaching nearly 3 m on spring tides) coupled with the low relief of the barrier islands and coastal plain results in extensive areas of intertidal marshlands. The marshes are dominated by Spartina alterniflora. Flounders were collected by otter trawl and cast net from Wassaw Sound, Ossabaw Sound, St. Catherines Sound, and Sapelo Sound, and from various locations in rivers above the sound limits (Figure 1). Most of the fish utilized in this study were captured during 1971 and 1972 by personnel from the Savannah Science Museum and Skid- away Institute of Oceanography. Others were donated from collections made by workers at the University of Georgia Marine Institute during 1968. Whole fish were preserved in 10% Formalin^ after capture. Location, date of capture, and standard length were recorded for each specimen used in the study. The stomachs were removed, and their contents examined under a dissecting microscope. Or- ganisms found within the stomachs were identi- fied to species when possible and counted. Para- sitic nematodes and trematodes were found in many stomachs but were excluded from the food habit data. In many instances identifications of food or- ganisms were made from pieces of animals found within stomachs. In most cases these pieces pro- vided enough material for specific identification, but in those cases where decomposition made identification to species impossible, the material was identified to the class or family level. Few ^ Reference to trade names does not imply endorsement by the National Marine Fisheries Service, NOAA. cases were found in which the stomachs contained completely unidentifiable organic material. Emphasis was placed on correctly enumerating the organisms found in stomachs. Neither bio- mass nor volumetric displacement data were obtained. Since food items were often identified from parts of an individual (the remainder having been either digested or not actually ingested), it was felt that any estimate of biomass would have little significance. Many stomachs contained pieces of polychaete annelids which had apparently been nipped off by the fish in their feeding activities. Since it was not possible to reconstruct these fragments into whole animals, heads were counted. Counts based on fragments of organisms cannot be con- sidered completely accurate; however, such food organisms often accounted for a relatively small fraction of the total stomach contents. The or- ganisms which made up the numerical bulk of the food were usually in good condition, facilitat- ing exact counting. One of the more important organisms found, Neomysis americana, has not been reported from as far south as Georgia by many previous authors, although it has been reported from the stomachs of two species of Gadidae, Urophycis regius and U. floridanus (Sikora, Heard, and Dahlberg, 1972). The reported range oiN. americana is from the Gulf of St. Lawrence to Virginia (Tattersall, 1951; Wigley and Burns, 1971). This range was extended to near the northern South Carolina border by Williams (1972) who also reported that N. americana was common in North Carolina. The range is presently again being extended by A. B. Williams (pers. commun.) who has examined and verified examples of A^. americana from our collections. RESULTS AND DISCUSSION Overall Evaluation Data summarizing the food of each of the four bothid species are presented in Table 1. Organ- isms are excluded which were not present in at least V7c of the stomachs examined in any of the four species of fish or which did not account for 1% or more of the total food organisms found in the stomachs of one or more of the species of fish. A complete list of food organisms recovered is presented in the Appendix. 516 STICKNEY, TAYLOR, and HEARD: FOOD HABITS OF FOUR FLOUNDERS GEORGIA Location of River Sampling Stations Savannah River Wassaw Sound GEORGIA Ossabaw Sound BRUNSWICK i Catherines Sound Sapelo Sound Doboy Sound '^<^~^AItamaha Sound ATLANTIC OCEAN St. Simons Sound Andrew Sound Cumberland Sound i Figure 1. — Sampling area along the coast of Georgia indicating the sounds and river locations from which fish samples were obtained. 517 FISHERY BULLETIN: VOL. 72, NO. 2 The food habits of E. crossotus are distinct from those of the other three species (Table 1). Pseudodiaptomus coronatus dominated the stom- ach contents of E. crossotus but accounted for only an insignificant fraction of the stomach contents of A. quadrocellata , C. spilopterus, and S. aquosus. The stomach contents of each of the latter three species were dominated by Neomysis americana. Of secondary importance in the stomachs of E. crossotus were polychaete annelids, especially the spionid, Paraprionospio pinnata. The im- portance of Pa. pinnata is extended if the assump- tion is made that most of the animals listed under Spionidae (Table 1) were, in fact. Pa. pinnata in a state of decomposition, making specific identification impossible. No fish remains were found in any of the stomachs ofE. crossotus examined, although they were found in A. quadrocellata, C. spilopterus, andS. aquosus. The difference in primary feeding habits between E. crossotus and the other three species of bothids appears to be a reflection of relative mouth size (Figure 2). E. crossotus has a very small mouth relative to head length (mouth averages about 6 into head), whereas, A. quadro- cellata, C. spilopterus, and S. aquosus all have relatively larger mouths in proportion to head length (mouth averages 3 to 4 into head). The small mouth of E. crossotus correlates with its selectivity for small organisms (such as Ps. coronatus, which range {vom 1 to 1.5 mm in length) and those of small diameter (such asPa. pinnata). While the remaining three fish species appear to favor A^. americana as a primary food organism, the diversity of sizes or organisms available to them appears greater. A'^. americana ranged from 6 to 12 mm in length in our collections. This organism was not completely excluded from the food of £■. crossotus (Figure 3) but was fed upon only to a limited extent. Table 1 presents the food habit data collected for each species without regard to season of the year, location in the estuary, or size of the fish under investigation. In order to more critically evaluate the data collected on each species, a Cithorichthys spilopterus Ancylopsetta quadrocellata Scophthalmus aquosus Etropus crossotus I cm Figure 2. — Line drawings of the four species of Bothidae discussed depicting the differences in mouth size relative to body length. 518 STICKNEY, TAYLOR, and HEARD: FOOD HABITS OF FOUR FLOUNDERS Table 1. — Occurrence of organisms appearing in 1% or more of the stomachs examined, or representing 1% or more of the total number of food organisms recovered from the stomachs of one or more of the four species of Bothidae under investigation.* Etropus crossotus Citharichthys spilopterus Percentage Percentage of Ancylopsetta quadrocellata Scophthain Percentage lus aquosus Percentage Percentage of Percentage Percentage of Percentage of occurrence total number occurrence total number occurrence total number occurrence total number Food organisms in stomachs of organisms in stomachs of organisms in stomachs of organisms in stomachs of organisms Ectoprocta: Bugula nentina 0.2 <0.1 0.0 0,0 0,0 0,0 1.0 0.1 Polychaeta: Diopatra cuprea 1.7 0.3 0.0 0,0 0,0 0,0 1.0 0.1 Nereis succinea 4.0 0.2 0.0 0,0 0,5 0,1 1.0 0.1 Nereidae 1.0 0.1 0,0 0,0 0,0 0.0 0.0 0.0 Parapnonospio pinnata 29.5 2.9 0.5 0.2 00 0.0 0.0 0.0 Spionidae 15.9 2.6 0.5 <0,1 0,9 0.2 0.0 0.0 Asabellides oculata 3.3 0.4 0-0 0.0 0,0 0.0 0.0 0.0 Sabella microphthalma 1.0 0.1 0.0 0.0 0-0 0.0 0.0 0.0 Unidentified remains 1.7 0.1 0.0 00 0,5 0.1 0.0 0.0 Mollusca: Pelecypod siphons 1.9 0.1 0.0 0.0 00 0.0 0.0 0.0 Decapoda — Reptantia Pmnixa sp. 2.4 0.1 0.0 0,0 3,2 0.5 0.0 0.0 Portunid megalops and zoea 2.6 0.2 7,1 0,9 0,0 0.0 0.0 0.0 Portunus spinimanus 0.0 0.0 0,5 <0,1 1.4 0.3 0.0 0.0 Portunus gibbesii 0.0 0.0 0.0 0,0 1.4 0.4 0.0 0.0 Neopanope sayi 0.0 0.0 0.0 0,0 3.7 1.0 0.0 0.0 Hexapanopeus angustifrons 0.0 0.0 0,0 0,0 1,8 0.5 0.0 0.0 Cancer irroratus 0.0 0.0 0,0 0,0 1,4 0.4 0.0 0.0 Portunid postlarvae 0.2 <0.1 1,4 0,1 2.8 0.8 0.0 0.0 Calltnectes sapidus 0.0 0.0 4.3 06 0.5 0.1 0.0 0.0 Decapoda— Natantia: Acetes americanus carolinae 0.2 <0.1 0.0 0,0 0.0 0.0 1.0 0.1 Palaemonetes pugio 1.4 0.1 16.2 28 0.9 0.5 1.0 0.1 Trachypenaeus constrictus 1.0 0.1 35.7 10,4 7,8 5.3 0.0 0.0 Penclimenes longicaudatus 00 0.0 1.4 0,1 0,0 0.0 0.0 0.0 Ogyrides limicola 5.2 0.3 10.5 3,3 0.0 0,0 0.0 0.0 Stomatopoda: Squilla empusa 0.0 0.0 15.2 2,0 5,5 1.0 1.0 0.1 Amphipoda: Ampelisca vadorum 3.8 0.6 1,0 0,1 1,4 0.3 1.0 0.1 Corophium tuberculatum 2.6 0.2 0,0 0,0 0,9 0.1 1.0 0.1 Unciola serrata 0.2 <0.1 0.0 0,0 3.7 4.6 1.9 0.1 Batea cattiarinensis 0.5 <0.1 0.0 0.0 0.5 0.1 2.9 0.2 Monoculodes edwardsl 7.4 0.6 1.0 0,1 0,5 0.1 1.0 0.1 Erichttionius brasiliensis 0.2 0.1 0,0 0,0 0.5 0.1 2.9 0.1 Caprella equilibra 0.0 0.0 0,0 0,0 0,0 0.0 1.0 0.1 Gammarus palustris 0.0 0.0 0,0 0,0 0.0 0.0 1.0 0.1 Microprotopus ranei 0.2 <0.1 0,0 0,0 0.0 0.0 1.0 0.1 Listnella barnardi 2.1 0.1 1.0 0.1 0.9 0.1 0.0 0.0 Copepoda; Pseudodiaptomus coronatus 34.2 84.6 1,4 0.8 0,5 0.8 1.9 0.5 calanoid copepod remains 0.5 0.1 1,0 0.2 0,9 0-1 3.8 1.0 Cumacea: Leucon americanus 6.9 0.5 0.5 <0.1 0,0 0,0 0.0 0.0 Mancocuma altera 2.1 0.2 0,0 00 0,0 0.0 4.8 0.2 Oxyurostylis smith! 7.4 1.4 0.0 0.0 0,5 0.1 3.8 0.3 Mysldacea: Neomysis americana 19.0 3.1 65.7 72.1 51.6 81.0 59.0 96.3 Isopoda: Edotea montosa 5.7 0.4. 00 0-0 0,5 0.1 0.0 0.0 Osteichthyes: Symphurus plagiusa Anchoa mitctiilli Cynoscion sp. Sciaenidae remains Gobiidae remains Unidentified remains 0.0 0.0 4,8 0.5 1,4 0.2 0.0 0.0 0.0 0.0 1,0 0-1 0,9 0.3 0.0 0.0 0.0 0.0 1,9 0,2 00 0.0 0.0 0.0 0.0 0.0 16.7 2,8 0.0 0,0 0.0 0.0 0.0 0.0 4.3 0,5 0,0 0.0 0.0 0.0 0.0 0.0 11.4 1,1 1,8 0,3 1.0 0.1 Others 0.0 0.0 0,0 0,7 0,0 0,5 0.0 0.0 Empty stomachs 26,5 7,6 309 35.2 'The total number of stomachs analyzed for each species were: E. crossotus. 421 : C, spilopterus. 210; A. quadrocellata. 217: and S, aquosus. 105, The total number of organisms obtained from the stomachs of fishes examined were: E. crossotus, 8,734; C, spilopterus. 2,442; A. quadrocellata, 1,490; S aquosus. 2,209, 519 FISHERY BULLETIN: VOL. 72. NO. 2 SPRING SUMMER FALL WINTER RIVERS SOUNDS <4I 41-50 51- 60 61-70 71-80 81-90 91-100 >I00 Pseudodioplomus coronatus Poiychoeto Crustaceo Mdiusca N=I55 z o Pseudodloptomus coronatus P C N =128 < Pseudodioptomus coronatus P, C N = 89 H -I Pseudodioptomus coronatus P c N=7I < o o Pseudodlaptomus coronatus P C SM N = 350 _l Pseudodioptomus coronatus " 'u N = I2 'e F Pseudodioptomus coronotus P, c N = 40 X Pseudodioptomus coronatus pac N = 45 1- (S> Pseudodioptomus coronatus P c N=57 y Pseudodioptomus coronatus N P caM N=87 o IE < Pseudodioptomus coronatus ' a c N «95 Q Z Pseudodioptomus coronotus P cau N=56 1- Pseudodioptomus coronotus Polychoetes c N = 29 1 1 1 1 1 1 1 1 1 0 10 20 30 40 50 60 70 80 90 100 CUMULATIVE PERCENTAGE Figure 3. — Histogram illustrating the feeding habits of Etropus crossotus by season of the year, locality, and standard length. (N = number of stomachs analyzed for each bar, P = Poly- chaetes, C = Crustacea other than those sjjecifically identified in the bar, Ps = Pseudodiaptomus coronatus, M = moUusca, and N = Neomysis americana.) series of figures was prepared which take these parameters into consideration (Figures 3-8). year. This change in food habits does not appear to reflect a reduction in the availability of Ps. coronatus. Plankton samples taken in conjunction with this and other studies have demonstrated thatPs. coronatus is present during the winter in numbers often exceeding those of other seasons of the year. The change in food habits may reflect an increased availability of Pa. pinnata rather than a decrease in the availability of Ps. coronatus. The increased availability of Pa. pinnata may have been a function of an increase in absolute numbers of the polychaetes or may have been due to a change in the behavior patterns of the preda- tor, prey or both. Studies of benthos associated with stations in Ossabaw Sound, from which many of the fishes were collected, indicate that Pa. pinnata is the dominant benthic infaunal form throughout the year on mud substrates and exhib- its widely fluctuating standing crop levels (Stick- ney and Perlmutter, unpubl. data). The possibility that the shift in food habits in winter may have been a function of the size of the fishes occurring in the estuaries during that season was considered. Animals in the larger size ranges did not dominate the winter samples but were generally present during the spring (Figure 4). Fish in the smallest groups were pre- sent most often in the summer when Ps. coronatus were highly dominant in the stomachs. Suitable numbers of £■. crossotus were present throughout Etropus crossotus The food habits ofE. crossotus related to season of the year, locality within the estuary (rivers as opposed to sounds), and standard length are pre- sented in Figure 3 indicating the percentage of total numbers of food organisms contributed by each taxa. E. crossotus was most abundant during the spring and summer months (March through August). Ps. coronatus was the dominant organ- ism in the stomachs of E. crossotus during the spring, summer, and fall. During the winter, Ps. coronatus was displaced to a large extent by the spionid polychaete Pa. pinnata and by N. americana. Whereas Table 1 indicated that Pa. pinnata was of general importance especially in terms of frequency of occurrence in the stomachs. Figure 3 indicates that this organism was more important during the winter (December through February) than during any other season of the 4! 41-50 51-60 61-70 71-80 81- 90 91-100 100 Summer E F Sp Summer Foil X Summer Fall Winter H O Spring Summer Foil Winter LlI _l Spring Su Fall Winter Q Spring Su Fall Winter ir < Sprmg S Fall Winter < Spring Su Fall Winter (n 1 1 1 1 1 1 1 1 1 1 0 10 20 30 40 50 60 70 80 90 100 CUMULATIVE PERCENTAGE Figure 4. — Histogram of percentage of stomachs examined during spring (March through May), summer (June through August), fall (September through November), and winter (December through February) for Etropus crossotus of various standard length groups. 520 STICKNEY, TAYLOR, and HEARD: FOOD HABITS OF FOUR FLOUNDERS each season of the year to provide rehability to the data (Figure 4). The food habits of E. crossotus were similar in both the rivers and sounds of Georgia. There were some alterations in food habits associated with increased standard length, however. While Ps. coronatus was present in a greater percentage in the stomachs ofE. crossotus of all sizes than any other food organism, polychaetes increased in importance in fishes longer than 100 mm. The appearance of polychaetes in stomachs of larger E. crossotus may be a function of the increase in mouth size during growth. Virtually all of the copepods found in the stomachs of E. crossotus were Ps. coronatus. Plankton samples taken by us during the course of this study verified that the copepod population in Georgia coastal waters is dominated by Ps. coronatus. During October 1972, a series of bihourly trawls over a 24-h period was obtained in Ossa- baw Sound. Each trawl was of 10-min duration and covered the same bottom. A total of 121 E. crossotus were captured in the 12 samples, and their stomachs were analyzed. Data from these fish were excluded from Figure 3 but are included in Figure 5. UJ 0800 1000 1200 1400 1600 1800 2000 2 200 2400 0200 0400 0600 Pseudodioptomus coronatus Porapnonospio Neomysis r pinna To amer icana Pseudodiaptomus coronatus Pseudodioptomus coronatus Pseudodioptomus coronatus Pseudodiaptomus coronatus Leucon p r amer. . ' Pseudodioptomus cornotus Pseudodioptomus coronatus pac^ Pseudodiaptomus coronatus Pseudodiaptomus coronotus Pseudodiaptomus coronotus ( 5 of 6 stomachs empty) N = 2 N = 13 N = 8 N = II N =18 N = 7 N = 17 N =12 N = II N = 1 N = 6 N = 15 _L. 0 10 20 30 40 50 60 70 80 90 100 CUMULATIVE PERCENTAGE Figure 5. — Histogram illustrating the feeding habits of Etropus crossotus at 2-h intervals for 24 h. (N = number of stomachs analyzed for each bar, C = Crustacea other than those specifically identified in the bar, P = polychaetes, and Leucon amer. . . = Leucon americanus.) P. coronatus was the numerically dominant organism in the stomachs with the exceptions of samples taken at 0200, 0600, and 0800 h. At 0200 and 0600 h none of the stomachs examined (16) contained food. At 0800 h only two E. crossotus were obtained, and a variety of food organisms were identified, with Ps. coronatus most abundant. The 0400 h sample contained six E. crossotus of which only one contained food (100% Ps. coronatus). Based on this limited information, it appears that£. crossotus feeds mainly during the daylight hours with unchanging food habits throughout the day. This observation correlates with the findings of de Groot (1971) which indicate that bothids are visual feeders. Ancylopsetta quadrocellata The food habits of A. quadrocellata at different seasons of the year, location within the estuary, and standard length are presented in Figure 6. The preponderance of the animals were captured during the spring, reflecting the seasonal avail- ability of this fish in Georgia estuarine waters. N. americana was the dominant food organism throughout the year. Trachypenaeus constrictus became important during the summer and fall. Neopanope sayi was present in significant quan- tities during the winter. While the food habits of A. quadrocellata cap- tured in rivers were nearly identical to those cap- tured in sounds, there were some differences in food habits with size of the fish. A^^. americana exceeded 50% of the total number of organisms found in the stomachs of fishes of less than 150 mm. Fish remains were found in the stomachs of fishes longer than 75 mm, although fish were never the dominant food organism. T. constrictus first became important as food in A. quadrocellata longer than 100 mm and was the dominant or- ganism in fishes from 150 to 174 mm. Fishes longer than 175 mm fed on a variety of organisms. These data indicate that the diversity of foods increases with the size of the predator. The rela- tively large mouth of A. quadrocellata compared to that ofE. crossotus may account for some of this variability in food habits with size (Figure 2). Ps. coronatus, the dominant organism in the stomachs of E. crossotus, was virtually absent from the stomachs of A. quadrocellata longer than 521 FISHERY BULLETIN: VOL. 72. NO. 2 O V) < UJ < u o E E X I- o z UJ _l d I- SPRING SUMMER FALL WINTER RIVERS SOUNDS 25-49 50-74 75-99 100-124 125-149 150-174 175-199 Neomys'S (mericona Neomysis amenc Trochypeneus ccnstrtctus Neomysis amerlcono Trachypeneus consir ictus Nsomysis omthcoKi Neopanope •oyi U P,C, N = I66 N = 7 N =37 7 Squilla •P [] N Neomysis omencana Fa C N = Neomysis americona 27 F, p a c N = 190 Neomysis omencona u| N = Neomysis americona Neomysis am«ricana Neomysis amsncono Neomysis omericono constncrus pugio Trochypeneus constnctus N sayi Neopanope 3 soyi Co Po Fish P a C 3 N = 58 N=88 N=29 N=4 N«I4 N^ll 0 10 20 30 40 50 60 70 80 90 100 CUMULATIVE PERCENTAGE Figure 6.— Histogram illustrating the feeding habits of Ancylopsetta quadrocellata by season of the year, locality, and standard length. (N = number of stomachs analyzed for each bar, U = Unciola serrata, P = polychaetes, C = Crus- tacea other than those specifically identified in the bar, F = fish remains, Ps = Pseudodiaptomus coronatus, and T. constrictus = Trachypenaeus constrictus, P. pugio = Palaemonetes pugio, N = Neomysis americana, S = Squilla sp., H = Hexapanopeus augustifrons, Ca = Cancer ir- roratus, and Po = Portunus gibbesii. 50 mm. This may also relate to mouth size dif- ferences between the species. Studies with Para- lichthys lethostigma and P. dentatus reared in the laboratory on brine shrimp, Artemia salina, indicate that once the flounders reach sufficient size (in this case about 25 mm), they have diffi- culty retaining ingested A. salina nauplii (Stick- ney and White, unpubl. data). The nauplii tend to be flushed through the gills and out the oper- culums. While the fish are still able to hunt the A. salina by sight, they do not seem to ingest a great number of nauplii. The relative mouth sizes of P. lethostigma and P. dentatus are simi- lar to those of A. quadrocellata, C. spilopterus, and S. aquosus. Citharichthys spilopterus The food habits of C. spilopterus in relation to season of the year, location, and size are docu- mented in Figure 7. The majority of the fish examined were captured during the summer (June through August). No fish were captured during the winter months (December through February). N. americana was the dominant species occurring in the stomachs of C. spilopterus during each of the three seasons for which data are available. A greater proportion of T. constrictus occurred in fishes captured in sounds than in those taken from rivers. The percentage of A^. americana and fish remains in the stomachs of C. spilopterus from the two localities were nearly identical. Food habit patterns relative to standard length of C. spilopterus were similar to those observed in A. quadrocellata. N. americana became less impor- tant as food with increasing size in C. spilop- terus. T. constrictus became the dominant organ- ism in C. spilopterus of 125 mm and above. N. americana was absent in the stomachs of fishes longer than 125 mm. Fish less than 50 mm were not obtained in the trawls. It is possible that all sizes of C. spilop- terus do not occur in Georgia estuarine waters but merely that they migrate through the south- eastern Atlantic coast during certain seasons of the year. Specimens longer than 140 mm were not taken. The seasonal distribution observed agrees with that determined by Dahlberg and Odum (1970). o CO < UJ ID < o SPRING SUMMER FALL RIVERS SOUNDS Neomysis omencona Neomysis omencona Neomysis omencona 1 N=4 N=I83 N=23 Neomysis omericono Neomysis omencano D" N=69 141 50-74 75-99 100-124 125-149 Neomysis americana T F CrustGceo X 1- UJ E _J^ Neomysis omencano T F pac Neomysis omencona T constrictus F Ish c d 1- Trachypeneus constrictus "Pp u»o S (/) 1 1 1 1 _i 1 i 1 N=52 N=II7 N=37 N = 4 0 10 20 30 40 50 60 70 80 90 100 CUMULATIVE PERCENTAGE Figure 7.— Histogram illustrating the feeding habits of Citharichthys spilopterus by season of the year, locality, and standard length. (N = number of stomachs analyzed foi" each bar, T = Trachypeneus constrictus, F = fish remains, C = Crustacea other than those specifically identified in the bar, P = Palaemonetes pugio, and S = Squilla empusa.) 522 STICKNEY, TAYLOR, and HEARD: FOOD HABITS OF FOUR FLOUNDERS Scophthalmus aquosus S. aquosus were present in Georiga coastal waters primarily during the spring (March through May). Few specimens were captured dur- ing the remainder of the year (Figure 8). S. aquosus fed nearly exclusively on N. americana during all seasons and in all locations. Several species of Crustacea, fish remains, and an ectoproct made up the remainder of the food organisms found in the stomachs of S. aquosus (Table 1). There was no change in food habits with size as found in A. quadrocellata and C. spilopterus, even though S. aquosus longer than 150 mm were captured. There were few animals in the size ranges above 74 mm, however, and the presumed food habits may reflect a lack of samples. Most of the fish captured were rather small. The relative abundance of small fish compared with the larger sizes is probably a good indication of their relative abundance in nature. CONCLUSIONS The four bothid fish species examined during this study are all relatively small fishes which feed on a variety of organisms. All appear to be totally carnivorous, since no plant material was re- covered from the stomachs. Because of the pre- dominance of certain organisms within the stom- achs and the lack of detritus and sand so common in animals which indiscriminately browse off the sediments, they appear to be selective feeders. This selectivity apparently relates to the ability of bothids to feed by sight (de Groot, 1971). E. crossotus was found to feed heavily on Ps. coronatus , and secondarily on spionid polychaetes, especially Pa. pinnata. The small mouth relative to body size of £■. crossotus may play an impor- tant role in the food habits of this species. By the same token, the larger mouths of the other species may prohibit them from feeding on small food items. A. quadrocellata, C. spilopterus, andS. aquosus fed heavily on A^. americana, however, A. quadro- cellata and C spilopterus adjusted their food habits, becoming more diversified and utilizing T. constrictus as a primary food organism as they grew larger. The food habits of S. aquosus did not change with increasing size within the range of sizes examined. The relatively larger mouths of these three species seem important in SPRING Z O SUMMER ^ FALL WINTER t RIVERS g SOUNDS 25-49 E 50-74 X 75-99 I- 100-124 LlI in 125-149 150 - 174 Neomysis americana Neomysis americana Neomysis omericana Neomysis americana c N=95 N=2 N = 7 N = l Neomysis amencano J[\ N = 24 Neomysis americana Fsc- N=86 Neomysis americana Neomysis americana Neomysis americana C - Neomysis omencano Neomysis americana Neomysis amencano c - N = ll N =75 N= 12 N = 5 N = 3 N = 4 c- 0 10 20 30 40 50 60 70 80 90 100 CUMULATIVE PERCENTAGE Figure 8. — Histogram illustrating the feeding habits of Scophthalmus aquosus by season of the year, locality, and standard length. (N = number of stomachs analyzed for each bar, F = fish remains, and C = Crustacea other than Neomysis americana. ) allowing them to consume food organisms of larger sizes than those eaten by E. crossotus. The three fishes with the larger mouths fed to some extent on other species of fishes, whereas no fish remains were found inthe stomachs ofE. crossotus. ACKNOWLEDGMENTS The authors are grateful to Walter Sikora for providing specimens from the area in the vicinity of Sapelo Island, Ga., and to the Savannah Science Museum for allowing us access to some of their specimens from Wassaw and Ossabaw Sounds. This study was supported in part by the IDOE Office of the National Science Foundation (GX- 33615). Ship support was provided by NSF Grant GD37558 (Office of Oceanographic Facilities and Support). LITERATURE CITED Dahlberg, M. D., and E. P. Odum. 1970. Annual cycles of species occurrence, abundance, and 523 diversity in Georgia estuarine fish populations. Am. Midi. Nat. 83:382-392. Darnell, R. M. 1958. Food habits of fishes and larger invertebrates of Lake Pontchartrain, Louisiana, an estuarine community. Publ. Inst. Mar. Sci., Univ. Tex. 5:343-416. DE GrOOT, S. J. 1970. Some notes on an ambivalent behaviour of the Greenland halibut Reinhardtius hippoglossoides (Walb.) Pisces: Pleuronectiformes. J. Fish Biol. 2:275- 279. 1971. On the interrelationships between morphology of the alimentary tract, food and feeding behaviour in flatfishes (Pisces: Pleuronectiformes). Neth. J. Sea Res. 5:121-196. Olla, B. L., C. E. Samet, and A. L. Studholme. 1972. Activity and feeding behavior of the summer flounder {Paralichthys dentatus) under controlled labora- tory conditions. Fish. Bull., U.S. 70:1127-1136. Olla, B. L., R. Wicklund, and S. Wilk. 1969. Behavior of winter flounder in a natural habitat. Trans. Am. Fish. Soc. 98:717-720. Poole, J. C. 1964. Feeding habits of the summer flounder in Great South Bay. N.Y. Fish Game J. 11:28-34. Reid, G. K., Jr. 1954. An ecological study of the Gulf of Mexico fishes, FISHERY BULLETIN: VOL. 72. NO. 2 in the vicinity of Cedar Key, Florida. Bull. Mar. Sci. Gulf Caribb. 4:1-94. SiKORA, W. B., R. W. Heard, and M. D. Dahlberg. 1972. The occurrence and food habits of two species of hake, Urophycis regius and U. flcridanus in Georgia estuaries. Trans. Am. Fish. Soc. 101:513-525. Steven, G. A. 1930. Bottom fauna and the food of fishes. J. Mar. Biol. Assoc. U.K. 16:677-698. Stickney, R. R., D. B. White, and D. Miller. 1973. Observations of fin use in relation to feeding and resting behavior in flatfishes (Pleuronectiformes). Copeia 1973:154-156. Tattersall, W. M. 1951. A review of the Mysidacea of the United States National Museum. Bull. U.S. Natl. Mus. 201, 292 p. Topp, R. W., and F. H. Hoff, Jr. 1972. Memoirs of the Hourglass Cruises. Flatfishes (Pleuronectiformes). Fla. Dep. Nat. Resour., Mar. Res. Lab. 4(2):1-135. WiGLEY, R. L., AND B. R. BURNS. 1971. Distribution and biology of mysids (Crustacea, Mysidacea) from the Atlantic coast of the United States in the NMFS Woods Hole collection. Fish. Bull., U.S. 69:717-746. Williams, A. B. 1972. A ten-year study of meroplankton in North Carolina estuaries: mysid shrimps. Chesapeake Sci. 13:254-262. 524 STICKNEY, TAYLOR, and HEARD: FOOD HABITS OF FOUR FLOUNDERS APPENDIX List of organisms found in stomachs of Bothidae from Georgia estuarine waters Rhynchocoela Cerebratulus sp. Ectoprocta Bugula neritina (Linnaeus) Polychaeta Diopatra cuprea (Bosc) Paraprionospio pinnata (Ehlers) Nereis succinea (Frey and Leuckart) Sabellaria vulgaris Verrill Sabella microphthalma Verrill Asabellides oculata Webster Clymenella torquata Leidy Spionidae Nereidae Mollusca Gastropod remains Pelecypod siphons Pelecypod postlarvae Crustacea Amphipoda' Ampelisca uadorum Mills Ampelisca sp. Listriella barnardi (Wigley) Corophium tuberculatum Shoemaker Unciola serrata Shoemaker Batea catharinensis Muller Melita appendiculata (Say) Melita nitida Smith Monoculodes edwardsi Holmes Erichthonius brasiliensis Dana Paracaprella tenuis Mayer Microprotopus ranei Wigley Corophium simile Shoemaker Cerapus tubularis Say Lembos websteri Bate Gammarus palustris Bousfield Caprella equilibra Say Corophium lacustre Vanhoffen Copepoda Pseudodiaptomus coronatus Williams Labidocera aestiva Wheeler Calanoid copepoda Cumacea Leucon americanus Zimmer Oxyurostylis smithi Caiman Mancocuma altera Zimmer Mysidacea Neomysis americana (S. I. Smith) Ostracoda (unidentified) Isopoda Edotea montosa Stimpson Stomatopoda Squilla empusa Say Squilla neglecta Gibbes Decapoda (Natantia) Acetes americanus carolinae Hansen Penaeus setiferus (Linnaeus) Trachypenaeus constrictus (Stimpson) Palaemonetes pugio Holthuis Palaemonetes vulgaris (Say) Ogyrides limicola Williams Periclimenes longicaudatus (Stimpson) Latreutes parvulus (Stimpson) Alpheus normanni Kingsley Caridean larvae Decapoda (Reptantia) Pagurus pollicaris Say Pagurus sp. Callinectes sapidus Rathbun Portunus spinimanus Latreille Portunus gibbesii (Stimpson) Callinectes similis Williams Cancer irroratus Say Hexapanopeus angustifrons (Benedict and Rathbun) Neopanope sayi (Smith) Pinnixa sp. Persephona punctata aquilonaris Rathbun Megalops and zoea Portunid postlarvae Osteichthyes Prionotus sp. Symphurus plagiusa (Linnaeus) Synodus foetens (Linnaeus) Bairdiella chrysura (Lacepede) Anchoa mitchilli (Valenciennes) Etropus crossotus Jordan and Gilbert Fundulus heteroclitus (Linnaeus) Menidia sp. Cynoscion sp. Bothid postlarvae Fish remains 525 DISTRIBUTION OF SIPHONOPHORES IN THE REGIONS ADJACENT TO THE SUEZ AND PANAMA CANALS Angeles Alvarino^ ABSTRACT These studies are based on the material collected by Israeli cruises in the eastern Mediterranean and the Red Sea (Gulf of Elat), and by Scripps Institution of Oceanography Expeditions in the Caribbean and the Pacific regions adjacent to the Panama Canal. Published information on the distribution of siphonophores in those areas and in adjacent regions is included. Distributional tables and maps are also included. The eastern Mediterranean collections encompass 21 species of siphonophores. Most of these species have been previously recorded in the western Mediterranean. Eudoxia russelli (eudoxid of Chelophyes appendiculata), Sulculeolaria angusta, and S. chuni have not been previously observed in any Mediterranean region. New records for the eastern Mediterrranean are: Ch. contorta, Diphyes bojani. D. dispar. Lensia campanella, L. meteori, L. subtilis, S. quadrivalvis, S. turgida. Rosacea plicata, Physophora hydrostatica , and Apolemia uvaria. Few sjjecies previously observed in the Mediterranean were not present in the collections here analyzed. Fifteen species of siphonophores appeared in the material from the Gulf of Elat. New records for the Red Sea are Ch. appendiculata, E. russelli, Diphyopsis mitra. The other species present iCh. contorta, Diphyes dispar, L. subtilis, S. chuni, S. quadrivalvis, Abylopsis eschscholtzi, A. tetragona, Enneagonum hyalinum, Cordagalma cordiformis, Agalma elegans, and A. okeni) have been previously observed in the Red Sea. New records at both sides of the Suez Canal which could be considered indicative of migration along this waterway are: Ch. appendiculata (Mediterranean to the Red Sea), and S. chuni (Red Sea to the Mediterranean). However, the species are cosmopolitan in distribution, and the source of the populations in the regions adjacent to the Suez Canal may be in the adjacent oceanic regions. Thirty species of siphonophores were observed in the Caribbean and Pacific regions adjacent to the Panama Canal. Most of the species are new records for those regions. Twenty one more species, not present in the collections here analyzed, had been previously recorded at either or in both the Caribbean, Gulf of Mexico and/or in regions of the Pacific adjacent to the area surveyed. Particular attention is devoted to the distribution of closely related pairs of allopatric species, Muggiaea atlantica-M. kochi, and Ch. appendiculata-Ch. contorta. Muggiaea kochi (neritic species) and Ch. appendiculata inhabit the Caribbean, Gulf of Mexico and adjacent regions of the western tropical Atlantic. Muggiaea atlantica (neritic species) and Ch. contorta inhabit the Pacific regions off Mexico and Central America. However, few specimens of Ch. contorta and M. atlantica were also observed in the Caribbean at locations near the opening of the Panama Canal, and specimens of Ch. appendiculata and M. kochi occurred at locations in the Pacific close to the Panama Canal. This distributional incidence may suggest that migration or artificial transport is taking place via the Panama Canal. It is also indicated that few specimens of L. challengeri (Indo-Pacific species) were observed near the opening of the Panama Canal in the Caribbean, New data have been published on the siphono- phores of the regions adjacent to the Suez Canal (eastern Mediterranean and the Red Sea), as well as for the regions adjacent to the Panama Canal (western Caribbean and the Central American Pacific). Bigelow and Sears (1937) included data on the distribution of the siphonophores in the eastern Mediterranean, and Lakkis ( 1971) on the 'Southwest Fisheries Center, National Marine Fisheries Service, NOAA, P. O. Box 271, La Jolla, CA 92037. Manuscript accepted September 1973. FISHERY BULLETIN: VOL. 72. NO. 2. 1974. Lebanese region. Schneider (1898), Totton (1954), and Halim (1969) presented information on the siphonophores of the Red Sea. Bigelow (1911) analyzed the siphonophores of the eastern tropical Pacific, which included few locations in the regions here surveyed; Alvariho (1968, 1972) studied the siphonophores of the tropico-equa- torial oceanic regions, and Alvarino (1971) covered the Central American Pacific including also a compilation of distributional data for the world oceans. 527 FISHERY BULLETIN: VOL. 72, NO. 2 The present work constitutes a more detailed survey on the siphonophores of the regions ad- jacent to the above mentioned interoceanic canals. These studies are based on the Siphonophorae material (65 plankton samples) collected by Israel in the eastern Mediterranean during 1967, 1968, 1969, and 18 plankton samples (Red Sea, 1969, 1970) corresponding to two locations in the Gulf of Elat; and the 64 plankton samples from Scripps Institution of Oceanography Expeditions (La Creuse 1962, Bonacca 1963, Thomas Washing- ton 1969) in the Caribbean and Pacific regions adjacent to the Panama Canal. The Scripps Institution collections covered larger regions than the area in which the present studies are con- centrated, and the total collections of the mentioned expeditions have been analyzed and the results included in Alvariiio (1968, 1971, 1972). The present studies chiefly concern with the distribution and some ecological aspects of the siphonophores. The subject is treated under two parts: 1) distribution of siphonophores in the eastern Mediterranean and the Red Sea, and 2) the siphonophores of the western part of the Caribbean and the Central American Pacific. The pattern of distribution of the species is presented. Tables with the distribution of the species include also references on previous records for the regions. Maximum density for most of the species off Israel and around Cyprus can be attributed to the high productivity of the region (Lakkis, 1971). The present study also indicates the Red Sea includes fewer species than the Indian Ocean. This factor may be related to the high salinity and temperature of the Red Sea, as well as to the shallowness of the sill at Bab el Mandeb. The incidence of both polygastric and eudoxid forms in most of the samples shows breeding is taking place in those regions, and that repro- duction may be an uninterrupted process along the year. A large number of species of siphonophores are truly cosmopolitan, inhabiting the Arctic, Antarc- tic, Indian, Pacific, and Atlantic Oceans, whereas other species inhabit only the Atlantic, Pacific, and Indian Oceans (Alvariho, 1971), and some others are restricted to the Indian Ocean, adjacent waters and the southeastern Asiatic regions, while few are restricted to either the Atlantic or the Indo-Pacific regions. Owing to the above mentioned biogeographic considerations, particular emphasis in the dis- tribution of the species should be dedicated to the pairs of closely related species allopatric in distribution. The pairs to be considered corres- pond to the Panamanian region: Chelophyes appendiculata-Ch. contorta (respectively related to cold-temperate, and warm waters), Muggiaea atlantica-M. kochi (inhabiting respectively the neritic temperate and neritic warm waters), and Lensia challengeri-L. fowleri (respectively Indo- Pacific and Atlantic species). The evidence of a two way migration "via" the Panama Canal, as shown by the distribution pre- sented by several species at the regions adjacent to the entrance to the Panama Canal, could be active, by progression of the population along the waterway, or passively transported in the ballast waters or the waters used in the cooling system of ships. Therefore, migrations could be also greatly intensified or enhanced by passive transport along the canal. METHODS The plankton samples here analyzed were not collected in uniform manner. The plankton collections from the eastern Mediterranean and the Gulf of Elat were obtained with a standard plankton net of the Villefranche type, as designed and described by Working Party No. 2 (1968). The net has a mouth internal diameter of 57 cm, a total length of 261 cm, and 200-^( mesh. Vertical, oblique, and horizontal tows were taken. The vertical and oblique hauls in the eastern Mediter- ranean and the Gulf of Elat reached from 200 m to the surface, and the horizontal tows were obtained at various depths in the upper 200 m at a speed of 2-3 knots during 10 min. The material from the Scripps Institution col- lections corresponds to 1-m net oblique hauls taken from about 140 m to the surface, and at less than 100 m or less than 50 m in shallow waters; and the V2-m net oblique tows were obtained from about 150 m to the surface and the horizontal hauls at various depths between 50 and 0 m. Each total plankton sample was analyzed for siphonophores, and the number of specimens determined for both polygastric and eudoxid forms. However, owing to the diversity of the collecting methods used, and the time span 528 ALVARINO: DISTRIBUTION OF SIPHONOPHORES covered by the collections, quantitative data are not considered, and only qualitative data are included in the presentation of the results. DISTRIBUTION OF SIPHONOPHORES IN THE EASTERN MEDITERRANEAN AND THE RED SEA Twenty-one species of siphonophores were observed in the eastern Mediterranean collec- tions, and fifteen species in the Gulf of Elat (Red Sea) collections. Eudoxia russelli (eudoxid of Ch. appendicu- lata), Sulculeolaria angusta, and S. chuni are new records for the Mediterranean. Chelophyes contorta, Diphyes bojani, D. dispar, Lensia campanella, L. meteori, L. subtilis, Sulculeolaria quadrivalvis, S. tur- gida. Rosacea plicata, and Apolemia uuaria are first records for the eastern Mediterranean. These species have been previously observed in the western Mediterranean. The only previous records of Ch. contorta for the Mediterranean correspond to the Alboran Sea (Alvarino, 1957). Therefore, the presence of the species in the Levant Mediterranean basin could be considered a tracer of Atlantic waters. All the Mediter- ranean species are also found in the Atlantic. Some of the species have permanently established populations in the Mediterranean, while others may be only remains of the Atlantic flow. Most of the species previously found in the eastern Mediterranean (Bigelow and Sears, 1937; Lakkis, 1971) were also observed in the collec- tions here analyzed. Some species previously found in the western Mediterranean (M. atlantica, L. fowleri, Clau- sophyes ovata, Ceratocymha sagittata, Vogtia pentacantha, V. spinosa, Praya cymbi- formis, Amphicaryon acaule, Anthophysa rosea, Rhizophysa filiformis, Cordagalma cordiformis, Athoribya rosacea, and Nanomia cara) have not been observed in the eastern Mediterranean (Alvariiio, 1971; Lakkis, 1971) (Table 1). The most abundant species in both distribu- tional coverage of the surveyed region and in number of species, Ch. appendiculata, D. dispar, Hippopodius hippopus, Bassia bas- sensis were found along the years, and in December appeared scattered or absent (Figures 1, 2, 6, 8). Eudoxoides spiralis, S. turgida, S. quadrivalvis , and S. angusta followed in decreasing order of abundance in both space covered and number of individuals (Figures 3, 5). These species appeared abundantly off Israel, Lebanon, Syria and around Cyprus. Sulculeolaria angusta and S. turgida were also found in the Cretan region. Species with few scattered records are, E. russelli (north of Cyprus), C/i. contorta (off Israel and between Syria and Cyprus), D. bojani, M. kochi, L. campanella, L. multicristata, L. subtilis, S. chuni, A. tetragona, R. plicata, A. uvaria, Agalma elegans, and Physophora hydrostatica (spread along the Levant basin). (Figures 1-8.) It is worthy of notice that the maximum density for most of the species of siphonophores appeared at the easternmost part of the Mediterranean Sea, off Israel and around Cyprus, which can be attributed to the high productivity of the region (Lakkis, 1971). The species scattered along the eastern Mediter- ranean, not previously observed in this sea, could be considered tracers of Atlantic waters (Oren, 1971). The presence of L. multicristata (a meso- planktonic species) off Tira, Israel, could be an indicator of upwelling. It is well established that the fauna of the eastern Mediterranean is an impoverished fauna from that of the western basin. Many species do not reach the Levant Mediterranean basin, and only appear accidentally there, and few be- come established in the area. Por (1971) con- sidered that "The colder areas of the Aegean Sea probably constitute an environment in which the Atlantic fauna is much better represented and better fitted to withstand the competition of the tropic immigrants." Siphonophorae fauna of the Red Sea is poorer than that of the Indian Ocean, both in number of species and in the density of the respective populations. The Gulf of Elat may also include fewer species than the main Red Sea basin. The Gulf of Elat collections correspond to the winter months. Some of the species observed in the Gulf of Elat constitute new records for the Red Sea (Ch. appendiculata, E. russelli, and Diphyop- sis mitra). Por (1971) stated that siphonophores and other holoplanktonic groups have not been found in the Suez Canal waters. 529 FISHERY BULLETIN: VOL. 72, NO. 2 •TV 29* _ r 30* 35' *^ ^ ^^^^^r * » •M — ^^ ^ .^^^^ + ;;^*S^ r d I0S" ^^ + 38* . « r-^^ + _^^L^ 4- — 4-^y -1- ^ + + ■ + ■ fl + + +• ^™ ^^ 4.^H .+..T'^« 3E 1 39* Ch appendiculata E russelli Ch contorta A,B ^ A,B 13 A,B 1 35* Figure 1. — Distribution of Chelophyes appendiculata, Eudoxia russelli, and Chelophyes contorta in the regions adjacent to the Suez Canal. D. mitra Figure 2. — Distribution of Diphyes bojani, Diphyes dispar, and Diphyopsis mitra in the regions adjacent to the Suez Canal. 530 ALVARINO: DISTRIBUTION OF SIPHONOPHORES zv Figure 3. — Distribution of Muggiaea kochi, Eudoxoides spiralis, and Lensia campanella in the regions adjacent to the Suez Canal. 38* 25* f + "7^ 30* ■r 1' + 39* ^1 + + + k gj 1 4^^^^^| L. meteori m 30* L multicristata L subtilis tiilill A.B 1 1 ^^^H ^^^^^^^^^Ly*^^^^^^^^! L. subtiloides 1 2a« n A,B 30* 1 35* 39* 30* Figure 4. — Distribution of Lensia meteori, Lensia multicristata, Lensia subtilis, and Lensia subtiloides in the regions adjacent to the Suez Canal. 531 FISHERY BULLETIN: VOL. 72, NO. 2 Figure 5. — Distribution of Sulculeolaria angusta, Sulculeolaria chuni, Sulculeolaria quadrival- vis, and Sulculeolaria turgida in the regions adjacent to the Suez Canal. A. eschscholtzi A tetragona B. bassensis E. hyalinum □ A,B 25 Figure 6. — Distribution of Abylopsis eschscholtzi. Abylopsis tetragona, Bassia bassensis, and Enneagonum hyalinum in the regions adjacent to the Suez Canal. 532 ALVARINO: DISTRIBUTION OF SIPHONOPHORES 29* 9»* — 30' 30* 39* f IK + ■r + + ^H + + + k 1 K^^^J^^H R plicata ^ i A. uvaria n ■ 1 K^^Hj^H C. cordiformis □ B ■ 1 K^K^I Ath. rosacea 1 29* n B 1 30* 1 ^ 1 ^B 39* 39* Figure 7. — Distribution of Rosacea plicata, Apolemia uvaria, Cordagalma cordiformis , and Athoribya rosacea in the regions adjacent to the Suez Canal. Figure 8. — Distribution of Hippopodius hippopus, Agalma elegans, Agalma okeni, and Physophora hydrostatica in the regions adjacent to the Suez Canal. 533 FISHERY BULLETIN: VOL. 72, NO. 2 Other new records for the Gulf of Elat are Diphyes dispar, L. subtilis, L. subtiloides, S. chuni, S. quadrivalvis, A. eschscholtzi , A. tetragona, E. hyalinum, C. cordiformis, A. rosacea, A. elegans, and A. okeni. These species, except CA. contorta, were only previously observed in either the central and the southern Red Sea or both (Figures 1, 2, 4-8). Ch. contorta was previously observed in the Gulf of Elat (Furnestin, 1958). The depth of the sill at Bab el Mandeb does not exceed 100 m (Halim, 1969) and consequently meso and bathypelagic species are extensively excluded from the Red Sea. Halim considered the scarcity of species in the Red Sea as due to the "excluding action of the deep outflow over the sill at the southern entrance of the Red Sea on the deep water species; and . . . the effect of the high (21.5°-22°C) minimum tempera- ture of the Red Sea deep water in inhibiting many species. . . ." He also considers excluding features the "high salinity (40.5-41.0''/oo) and the very low oxygen content (below 1 ml/1 in summer and 2 ml/1 at the end of the winter) below sill depth." Similar interpretation could be applied for the paucity of the Mediterranean siphonophores as compared with the Atlantic, because of the sill at Gibraltar. Thorson (1971) stated that "the physical- chemical conditions for the animals to pass the Canal have improved enormously although there are still obstacles for the migration of many species." Seasonal variations in occurrence, abundance and in the distributional pattern presented by the species of siphonophores in both the Levant Mediterranean basin and the Gulf of Elat are to be expected. The various populations may show changes in both location and time of year. These changes may be due to the characteristics of the flow through the Strait of Gibraltar, and Bab el Mandeb respectively, and the characteristics of the circulation in the Mediterranean and the Arabian Sea, as well as the aspects of the vertical migration (Halim, 1969), and the ontogeny of the population. Most of the siphonophores, except for a few species as explained above, present a wide almost cosmopolitan distribution (Alvariho, 1971). However, species abundant in the western Mediterranean and the Atlantic reaching the easternmost Mediterranean region could be con- sidered "indicators" or tracers of the Atlantic waters. This could be similarly applied to some Indo-Pacific or Indian Ocean species reaching the Red Sea. SIPHONOPHORES OF THE WESTERN CARIBBEAN AND THE CENTRAL AMERICAN PACIFIC The pairs of closely related species allopatric in distribution, Ch. appendiculata-Ch. contorta, M. atlantica-M. kochi, and L. challengeri- L. fowleri deserve special attention. Chelophyes appendiculata inhabits the temperate oceanic regions, and appears scattered along the tropico-equatorial realm, while Ch. contorta presents a distribution restricted to the tropico-equatorial regions (Alvariho, 1971). Muggiaea atlantica inhabits the neritic tem- perate eastern Pacific, Transition region (band between the Subarctic and Central Pacific), the Japanese neritic waters and the neritic regions of the temperate Atlantic. Muggiaea kochi occupies the neritic tropico-equatorial Atlantic and the eastern equatorial Pacific (Al- variho, 1971). Lensia challengeri is an Indo-Pacific species, and L. fowleri is most probably restricted to the Atlantic waters (Alvariho, 1971). However, Ch. appendiculata, M. kochi, and L. fowleri appear widely distributed in the Carib- bean region annex to the Panama Canal and in adjacent regions of the Caribbean, Gulf of Mexico, and western tropical Atlantic. Ch. contorta, M. atlantica, and L. challengeri appear in the Central American Pacific region. Few specimens of Ch. appendiculata and M. kochi were observed at locations near the opening of the Panama Canal in the Pacific, and few specimens of Ch. contorta, M. atlantica, and L. chal- lengeri occurred at locations near the opening of the Panama Canal in the Caribbean. These observations suggest the Caribbean and the Pacific populations may be able to migrate or survive artificial transport via the Panama Canal (Figures 9-11, Table 2). The species of siphonophores appearing abun- dantly distributed in the surveyed region in both the Caribbean and the Central American Pacific are Diphyes bojani, D. dispar, Diphyopsis mitra, and A. eschscholtzi. Diphyes bojani occurred at all Caribbean stations, except for the close to 534 ALVARINO: DISTRIBUTION OF SIPHONOPHORES Figure 9. — Distribution of Chelophyes appendiculata and Chelophyes contorta in the regions adjacent to the Panama Canal. 84" 81* 78° ^^■1 R I 1 ^^H %. H^^^^H ^ "" B ^^^^^^^^^^^ 1 ^ ■^^ X ^ » flj^H ^^^§\ X ^H X x^^H ^^ H X X J X X X x" igSW X ^^|| ^^Hm. atlantica ^ 1 1 1 I ^Bm. kochi ■ f^ - - 6* 75* Figure 10. — Distribution of Muggiaea atlantica and Muggiaea kochi in the regions adjacent to the Panama Canal. 535 FISHERY BULLETIN: VOL. 72, NO. 2 75° Figure 11. — Distribution of Lensia challengeri and Lensia fowleri in the regions adjacent to the Panama Canal. shore locations off Huani, Nicaragua, off Puerto Colombia and Cartagena de Indias, and east to the entrance of the Panama Canal. In the Pacific region it was only missing at the northernmost station in the Gulf of Panama, south of Peninsula de Azuero, south of Coiba Island, off Gulf of Nicoya, and ofFPunta Arenas and Punta Guiones (Costa Rica) (Figure 12). Diphyes dispar and Diphyopsis mitra appeared abundantly distributed in the Pacific region, and only in two locations in the Carib- bean. Diphyes dispar was present off Colombia and off Laguna Perlas (Nicaragua), and Diphyop- sis mitra at two locations a few miles north of Panama (Figures 12, 13). Abylopsis eschscholtzi was only absent at a few stations in the Caribbean and in the Central American Pacific (Figure 14). Species scattered distributed in both the Carib- bean and the Pacific regions were Eudoxoides spiralis, A. tetragona, S. chuni, A. okeni, and E. hyalinum. Eudoxides spiralis was present only at five Caribbean locations, which include two stations off Nicaragua and three off the entrance to the Panama Canal, and in the Pacific appeared at two stations southeast of Peninsula de Azuero and at two offshore stations west of Costa Rica (Figure 13). Abylopsis tetragona appeared off Colombia and near the entrance of the Panama Canal in the Caribbean, and south of the Azuero Peninsula, south of Coiba Island, west of Nicoya Peninsula, and at one offshore station west of Costa Rica in the Pacific (Figure 14). Sulculeolaria chuni was observed at three locations over the deepest part of the western Caribbean, and in the Gulf of Panama, south of Nicoya Peninsula, and at two offshore stations west of Costa Rica in the Pacific (Figure 16). Agalma okeni was found once in the Caribbean region (off Costa de Mosquitos, Nicaragua), and in the Pacific regions appeared from the Azuero Peninsula to Coiba Island, south of Costa Rica and west of Nicoya Peninsula (Figure 19). Enneagonum hyalinum was only observed at the western Caribbean, and at several locations in the Pacific extending northwestwards from Coiba Island (Figure 17). Species scattered distributed in the surveyed region of the Central American Pacific were, S. quadrivalvis, S. turgida, B. bassensis, and H. hippopus (Figures 16-18). 536 ALVARINO: DISTRIBUTION OF SIPHONOPHORES Figure 12. — Distribution of Diphyes bojani and Diphyes dispar in the regions adjacent to the Panama Canal. 6* - - 12° - 6* 84* 78* 75* Figure 13. — Distribution of Diphyopsis mitra and Eudoxoides spiralis in the regions adjacent to the Panama Canal. 537 FISHERY BULLETIN: VOL. 72, NO. 2 Figure 14. — Distribution of Abylopsis eschscholtzi and Abylopsis tetragona in the regions adjacent to the Panama CanaL Figure 15. — Distribution of Lens ia cossack, Lensia hotspur, and Lensia subtilis in the regions a4jacent to the Panama CanaL 538 ALVARINO: DISTRIBUTION OF SIPHONOPHORES 6* - Figure 16. — Distribution of Sulculeolaria chuni, Sulculeolaria monoica, Sulculeolaria quadri- valvis, and Sulculeolaria turgida in the regions adjacent to the Panama Canal. Figure 17. — Distribution of Abyla haeckeli, Abyla schmidti, Bassia bassensis, Ceratocymba dentata, and Enneagonum hyalinum in the regions adjacent to the Panama Canal. 539 FISHERY BULLETIN: VOL. 72, NO. 2 75° Figure 18. — Distribution of Hippopodius hippopus, Athoribya rosacea, and Amphicaryon acaule in the regions adjacent to the Panama Canal. Figure 19. — Distribution of Agalma okeni, Stephanomia bijuga, and Melophysa melo in the regions adjacent to the Panama Canal. 540 ALVARINO: DISTRIBUTION OF SIPHONOPHORES Table 1. — Siphonophores of the regions adjacent to the Suez Canal. Species Eastern Mediterranean Red Sea Species Eastern Mediterranean Red Sea Chelophyes appendiculata (Diphyes dispar) Eschscholtz. 1829 32=20'N-34=51'E Gulf of Elat: 32=45'N-34=57'E 29=30'N-34'55'E 33=03'N-34=55'E 29=25'N-34=50'E 35=05'N-35=00'E 33=00'N-35=00E 32=55'N-34=34E 35=35'N-35=26'E 34=50'N-28=55'E 35=55'N-28=37'E 36=30'N-28=13'E 36=31 ■N-27=27'E 35=14'N-26=33'E 33=25'N-30=20'E 33=10'N-33=50'E 31=31 'N-34=28E 32=23'N-34=37'E 34=37'N-32=20E 32=30'N-33=21'E 31=42'N-34=28'E 32=46'N-34=53E 32=50'N-34=50'E 33=25'N-33=14'E 32=01 'N-33=25'E 33'25'N-25=15'E 34=47'N-25=10'E 35=11'N-22=15'E 35=35'N-21=50'E 35=57'N-22=15'E 34=10'N-34=29'E 35=57'N-32=23'E 34=35'N-33=35'E 35=05'N-34=38 E 35=50'N-31 = 15'E 32=43'N-34=38'E 32=10'N-32=50'E 32=07'N-33=24'E 31=42'N-33=00'E 35=55'N-28=33'E Eudoxia russelli Totton, 1932 35=57'N-32=23'E Gulf of Elat: 29=30'N-34=55'E 29=25'N-34=50'E Chelophyes contorts •* * + (Lens & Riemsdijk. 32=45'N-34=57'E Gulf of Elat: 1908) 35=05'N-35=00'E 32=23'N-34=37'E 32=50'N-34=51'E 32=01 ■N-33=25'E 32=43'N-34=38'E 29'25'N-34=50'E Diphyes bojani (Escfischoltz. 1829) 36=31 'N-27=27'E 33=25'N-30=20'E Diphyes chamissonis + Huxley. 1859 Diphyes dispar •* . + Chamisso & 34=50'N-32=47'E Gulf of Elat: Eysenhardt, 1821 35=05'N-35=00'E 33=00' N-35=00'E 32=46'N-34=53'E 32=55'N-34=34'E 35=35'N-35=26'E 35=05'N-34=05'E 34=50 ■N-28= 55 'E 35=55'N-28=37'E 36=30'N-28'13'E 36=31 ■N-27=27'E 35=14'N-26=33'E 33=25'N-30=20E 31=31 ■N-34=28'E 32=23'N-34=37'E 34=37'N-32=20'E 32=30'N-33=21'E 31=42'f^-34=28'E 29=30'N-34=55'E Diphyopsis mitra Huxley, 1859 Muggiaea atlantica Cunningfiam, 1892 Muggiaea kochi Will. 1844 Eudoxoides spiralis Bigelow, 1911 Clausophyes ovata Keferstein & Ehlers. 1861 Sphaeronectes spp. Lensia campanella Moser, 1925 Lensia conoidea Keferstein & Ehlers. 1861 Lensia fowleri Bigelow, 1911 Lensia hotspur Totton, 1954 Lensia meteon Leioup. 1934 Lensia multicristata Moser, 1925 Lensia subtilis Chun, 1886 33=25 32=01 34=47 35=35 35=57' 32=20 31=37 31=44 32'=45 32=50 35=57' 34=35' 35=05' 33=50' 32=43' 32=10' 32=07' 35=00 35=55 N-33' N-33' N-25 N-21' N-22' N-34' N-34' N-34' N-34' N-34' N-32' N-33' N-34= N-3r N-34' N-32' N-33' N-35' N-28' 14'E 25'E 10'E 50 'E 15'E 51'E 32'E 26'E 49'E 50'E 23E 35' 38' 15' 38 'I '50'l 24'l OO'E 33'E 33°03'N-34°55'E 35'=05' 31=31' 34=37' 32=50' 34=35' 34=10' 35=57' 34=35' 35=05' 33=50' 32=43' 32=10' 32=07' 31=42' N-35= N-34= N-32= N-34= N-29= N-34= N-32= N-33= N-34= N-31 = N-34= N-32= N-33= N-33= OO'E 28'E 20'E 51'E 40'E 29'E 23'E 35'E 38 E 15'E 48'E 50'E 24'E OO'E 32=43'N-34=38E 32=10'N-32=50'E 32=07'N-33=27'E 34=35'N-33=35'E 33=50'N-31 = 15'E 32°45'N-34°49'E Gulf of Elat: 29=30'N-34=55'E -I- + + + 34=35'N-29''40'E Gulf of Elat: 32'10'N-32'50'E 29°30'N-34=55'E 32=07 'N-33=24'E 29=25'N-34=50'E Lensia subtiloides • •• -t- Lens & Riemsdijk, 1908 Gulf of Elat: 29°30'N-34°55'E Sulculeolaria angusta Totton. 1954 35=05'N-35=00'E 32=55'N-34=34'E 32=46'N-34=53'E 37=17'N-22=47'E 35=11'N-22=15'E 34=35'N-29=40'E 32°07'N-33=24'E 35=00'N-35=00'E Sulculeolaria biloba Sars. 1846 541 FISHERY BULLETIN; VOL. 72, NO. 2 Table 1 ontinued. Species Eastern Medjterranean Red Sea Species Eastern Mediterranean Red Sea Sulculeolaria chuni Lens & Riemsdijk. 1908 Sulculeolaria quadrivalvis Blainville, 1834 Sulculeolaria turgida (Gegenbauer, 1854) Abylopsis eschscholtzi Huxley, 1859 Abylopsis tetragona Otto, 1823 Bassia bassensis Quoy & Gaimard. 1834 Ceratocymba sagittata Quoy & Gaimard. 1827 Enneagonum hyalinum Quoy & Gaimard. 1827 Hippopodius hippopus Forskal, 1776 32=10N-32'50E 32'07N-33'24'E 32=45'N-34°49'E 32'21N-34=48'E 32=55'N-34'34'E 35'57N-32'23'E 34'35N-33'35'E 35°05N-34 38E 33'50N-3ri5'E 32=45 35'35 34'47 35°35 35=57 34=35 34=10 35=57 34=35' 35=05 33=50' 32=43' 32=10' 35=00 N-34 N-35 N-25 N-21 N-22 N-29 N-34 N-32 N-33' N-34' N-3r N-34' N-32= N-35' 49'E 26 E 10'E 50'E 15'E 40'E 29'E 23'E 35'E 38'E 15'E 38'E 50'E OO'E 33=25'N-30=20'E 35=05'N-34=38'E 32=10'N-32=50'E 33=03 'N• 33=25'N■ 31=31 'N- 32=23'N 32=30 N 35=1 1 N- 35°57'N- 34=35'N- 34=10'N- 32=46'N- 35=57'N- 34=35'N- 35=05'N- 33=50'N- 32=43 N- 32=10'N- 32=07 'N■ 31°42'N■ 3r37'N- 35=55'N- 34=55'E 30=20'E 34=28 E 34=37'E 33=21 'E 22=15'E 22=15'E 29=40'E 34=29 'E 34=53'E 32= 23'E 33=35'E 34= 38'E 31 = 15'E 34=48 'E 32=50'E 33=24'E 33=00'E 34=32'E 28=33 E Gulf of Elat: 29=30 N-34=55'E Gulf of Elat: 29'30'N-34=55'E 29=25'N-34=50'E (Hippopodius hippopus) Gulf of Elat: 29=25'N-34=50'E + Gulf of Elat: 29=30'N-34=55'E 29=25'N-34=50'E + Vogtia glabra Bigelow, 1918 Vogtia pentacantha Kolliker. 1853 Vogtia spinosa Keferstein & Efilers, 1861 Praya cymbilormis Cfiiaje, 1841 Rosacea plicata Quoy & Gaimard. 1827 Amphicaryon acaule Cfiun, 1888 Amphicaryon ernesti Totton, 1954 Anthophysa rosea Brandt, 1835 Apolemia uvaria Lesueur, 1811 Rhizophysa filiformis Forskal, 1775 Cordagalma cordiformis Totton, 1932 Athoribya rosacea (Forskal, 1775) Agalma elegans Sars. 1846 Agalma okeni •• Eschscholtz, 1825 + Gu If of Elat; 'Stephanomia bijuga 29=25'N-34=50'E (Cfiiaje. 1841-42) • •* + Stephanomia rubra 32=21 'N-34=48'E Vogt. 1852 35=39 'N-26'34'E Nanomia cara Agassiz, 1865 35=05'N-35=00'E Physophora hydrostatica 32°23'N-34°37'E Forskal, 1775 32=55'N-34=34'E 35=35'N-35=26'E 35=05'N-34=05'E 34=50'N-28=55'E Forskalia edwardsi 35=55'N-28'37'E Kolliker, 1853 36=31' 32=46' 33=25' 32=01 34=47 33=25 37=17 35=11' 35=35 35=57' 34=35' 34=10' 32=50 32=20 31=37 31=42 31=44 32=45 34=35 35=05 33=50 32=43 32=10 32=07 31=42 35=00 35=55 N-27' N-34' N-33 N-33 N-25 N-25 N-22 N-22= N-21 = N-22= N-29= N-34= N-34' N-34' N-34' N-34' N-34' N-34' N-33' N-34' N-31' N-34' N-32' N-33' N-33 N-35' N-28' 27E 53'E 14'E 25'E 10'E 15'E 47'E 15'E 50'E 15'E 40'E 29'E 50'E 51 E 32'E 28'E 26 'E 49'E 35'E 38'E 15'E 38'E 50'E 24'E OO'E OO'E 33'E 32=10'N-32=50'E 36=31 'N-27=27'E 35=55'N-28=33'E 35°57'N-22°45'E 34=35 'N-29=40'E 35=50'N-3r 15'E 3r42'N-33=00'E + + + 29=25'N-34=50'E + 29=25'N-34=50'E + Gulf of Elat: 29=30'N-34=55'E 29=25'N-34=50'E + Gulf of Elat: 29=30 'N-34=55'E 29=25'N-34=50'E + Previously observed (see Alvarirto. 1971: Lakkis. 1971). • Previously observed in tfie Red Sea (Alvarirto. 1971 compilation of distributional data). 'Previously observed in the western (Mediterranean (see Alvarirto, 1971). 542 ALVARINO: DISTRIBUTION OF SIPHONOPHORES Table 2. — Siphonophores of the regions adjacent to the Panama Canal. Caribbean Sea Central Eastern Species region American Pacific Species Mediterranean Red Sea Chelophyes appendiculata {Diphyopsis mitra) 07=12'N-79'54'W ir07N-74'47'W 08=41 ■N-79=31W 07=02N-79=57W 10M9'N-75=38'W 08=48 'N-79=30W 06'40'N-79=59'W 09^46N-79'20W 08=00N-79=43W 06=55N-80=50W 09'37'N-79^39'W 07=18N-82=25'W 09'27N-7y48W 07=30'N-83=54'W 14'19'N-83 09'W 07=39'N-84=46'W 13=56N-82 59W 07=57'N-85=49'W 13°38N-82'38W 08=48'N-85=57'W 13=12 N-82'25W 09=07N-84=58'W 12'=3rN-8r52'W 09=32N-85=10'W 12=11 N-8138'W 09=51 'N-85=43'W 10=04'N-80 22'W Muggiaea atlantica • • Chelophyes contorta •• 09=28N-84=2rW 09=38 'N-85=44'W 09=27N-79=48W 07=30'N-79=54W 09=46'N-79=20'W 08=41 ■N-79=3rW 09'25N-79=57'W 08 46'N-84=irW 09=13'N-84=45W 09 28N-85=15'W 09=39'N-85=4rW 07=12'N-79=54W 07=02'N-79=57W 06=55'N-80=50'W 07=12'N-81=48W 07=18'N-82=25'W 07=27N-83=04'W 07=30N-83=54W 0739'N-84=46'W 07=51 ■N-85=49'W 08=48'N-85=17W 09=07'N-84=58'W 09=23'N-84=52W 09=27'N-79=48'W 07=30'N-79=54'W 08=10N-82=13W 08=10'N-82=15'W 08=10N-82=16W 09=13N-84=45W 09=28'N-85=15'W 09=39'N-85=4rW 08=48'N-79=30W 07=12'N-79=54'W 07=02'N-79=57'W 06=55N-80=50W 09=07N-84=58'W 09=23N-84=52'W 09=39 ■N-84=44W 09=32N-85=10W 09=51 'N-85=43'W 09=51 ■N-85=43W Muggiaea l