CALIFORNIA Flffl-GAME "CONSERVATION OF WILDLIFE THROUGH EDUCATION' VOLUME 66 OCTOBER 1980 NUMBER 4 \ JSht MM ^^^L ^af^^^l^^ 1 ■ ^^W^HI i mK^ Ov^ ^^^fe r^ ^cT^^wo^— ^^~~ ■ r ji^^^ 1 ^B^^a "^ p^^o^^^ m^^^^Bj^^Bf it ^1 B&eSoS -209 EVIDENCE OF WHITE SHARK, CARCHARODON CARCHARIAS, ATTACKS ON SEA OTTERS, EN HYDRA LUTRIS^ JACK A. AMES Marine Research Branch California Department of Fish and Game 2201 Garden Road Monterey, California 93940 and G. VICTOR MOREJOHN ^ Department of Biology San Jose State University San Jose, California 95192 From 1968 through 1979 all verified dead sea otters, Enhydra lutris, reported to the California Department of Fish and Game have been recorded and often collected. Approximately 15% of the carcasses exhibited lacerations. Although previous inves- tigators had implicated the white shark, Carcharodon carcharias, as a potential predator of sea otters, absolute evidence was meager, and it was believed that most lacerated specimens had been hit by boat propellers. However, since 1974, white shark tooth fragments have been removed from 13 dead sea otters in California (a 14th in the State of Washington) and other indisputable evidence of white shark bites has been found in several additional carcasses. A re-evaluation of previous cause of death determinations ascribed to boat propeller wounds revealed that none of these designations was certain, hence many were changed. Using criteria derived from confirmed shark bitten carcasses, we now speculate that a minimum of 9%, and perhaps 15% or more, of the 657 dead sea otters recorded in California through this period were killed by white shark bites. This mortality has an undetermined effect on California's sea otter population. INTRODUCTION Since 1 968 the California Department of Fish and Game ( DFG ) has coordinat- ed and participated in a program of dead sea otter verification and examination, and has kept a file of all such records. Some carcasses were given a fairly complete laboratory necropsy; some received only a casual examination in the field. Other badly rotted carcasses or those that were never recovered were not examined. Although a white shark tooth fragment had previously been removed from a lacerated sea otter carcass in California (Orr 1959), a number of inves- tigators initially viewed most of these lacerations to be boat propeller wounds ( Morejohn, Ames, and Lewis 1 975 ) . By the end of 1 976, after white shark tooth fragments had been found in several lacerated sea otter carcasses, we began looking for and finding additional fragments with much greater frequency. At this time we were also able to develop criteria which permitted us to assign with certainty shark bite as the cause of death even when tooth fragments could not be found. These findings prompted a re-evaluation of all previous dead sea otter records particularly to check the evidence of boat propeller wounds. REVIEW OF WHITE SHARK ATTACK EVIDENCE Snow (1910) described hunting of sea otters mainly in the Kurile Islands of ' Accepted for publication )une 1980 ^Current address; R.R. 1, Box 14, Day Creek, Oregon 97429 WHITE SHARK ATTACKS ON SEA OTTERS 197 Russia in the late 1800's and reported that sea otters were bitten by sharks because he had often seen tooth fragments in wounds; he did not specifically mention white sharks. Orr (1959) removed the first verified white shark tooth fragment from a lacerated sea otter found near Carmel, California, in 1958 and speculated that other otters may have died of shark bites. Mattison and Hubbard ( 1 969 ) necropsied 1 3 sea otter carcasses but found no lacerating wounds of the type described by Orr. Wild and Ames (1974) reported on 88 carcasses necrop- sied between January 1968 and July 1973; only one had a laceration pattern which was suspected to have been the result of a shark bite while 22 were thought to have been hit by boat propellers. Morejohn et al. ( 1 975 ) summarized data gathered on all 286 dead sea otters recorded in California between January 1968 and July 1974. They found a white shark tooth fragment in one sea otter carcass (DFG SO-381-73) and indicated that a few other carcasses contained laceration patterns similar to those made by the white shark. The same report attributed 47 deaths to boat propellers; however, an addendum pointed out that the importance of boat propellers had probably been overstated and the impor- tance of shark bites had probably been understated. In August 1974, a dead sea otter, presumably from a group transplanted from Alaska in 1969-70, was found on a beach on the central coast of Washington. The carcass contained numerous lacerations and a tooth fragment was found (Keyes 1975) which was later identified as that from a white shark. In January 1975, a sea otter carcass (DFG SO-438-75) was found on a beach at Point Lobos State Reserve, California. The animal was initially thought to have been hit by a boat. Later, B. J. Davis (California State University, San Francisco) found a fragment in a wound which was subsequently identified as an apical portion of a white shark tooth (Figure 1 ). FIGURE 1 . Apical fragment of a white shark's tooth recovered from dead sea otter ( DEC SO-438- 75). Photo by W. I. Fallen. On 23 July 1976, a lacerated sea otter was captured alive in the kelp off Monterey, California, by researchers from the University of Minnesota. Some of 198 CALIFORNIA FISH AND GAME the lacerations were sutured by T. D. Williams, consulting veterinarian to DFG. The wounds were suspected to have been inflicted by a knife or boat propeller. Three days later the animal died (DFG SO-509-76) and during the necropsy a white shark tooth fragment was removed from one of the sutured lacerations. In November 1976, a white shark tooth fragment was removed from a sea otter carcass (DFG SO-529-76) found on the beach near Moss Landing, Califor- nia, by B. Green Ross (Moss Landing Marine Laboratories). In May 1977, a sea otter carcass (DFG SO-569-77) exhibiting numerous puncture wounds was found near Pismo Beach, California. This animal was later examined by C. D. Woodhouse, Jr. and P. Collins (Santa Barbara Museum of Natural History), who found, only after careful scrutiny, five white shark tooth fragments. In August 1977, two lacerated sea otter carcasses were recovered, one (DFG SO-592-77) near Moss Landing (Figure 2) and the other (DFG SO-590-77) near Cambria, California. Many white shark tooth fragments were recovered from both carcasses ( Figure 3 ) . One carcass also exhibited a variety of bone scratches and penetrations (Figure 4) and a fragment embedded in the femur near the knee (Figure 5). FIGURE 2. Lacerated sea otter carcass (DFG SO-592-77) from which several white shark tooth fragments were recovered. Photo by senior author. Also, in August 1977, a white shark tooth fragment was found embedded in the skull of a sea otter (DFG SO-467-75) that had been found (badly decom- posed) near Monterey in June 1975 (Figure 6). The cleaned skeleton had been in a museum collection since that time with the shark tooth fragment undetected. This animal is of additional interest in that it was not listed as a carcass suspected of being shark bitten or even as having lacerations. WHITE SHARK ATTACKS ON SEA OTTERS 199 FIGURE 3. Above. White shark tooth fragments removed from dead sea otters. Note how well these fragments might resemble the chips missing from teeth in the photo below. Below. Teeth in the jaw of a white shark caught in Monterey Bay by a fisherman in 1955. Photo above by senior author. Photo below by J. B. Phillips. In November 1977, three small shark tooth fragments v^ere removed from a sea otter carcass (DFG SO-606-77) found on the beach in Monterey. In 1 978 and 1 979, shark tooth fragments were removed from four different sea otter carcasses, two from near Carmel (DFG SO-621-78, SO-623-78), one from near San Simeon, California (DFG SO-694-79), and one from near Morro Bay 200 CALIFORNIA FISH AND GAME (DFG SO-718-79). The fragments from two of these carcasses were easily identified as white shark. Fragments from the remaining two were very small (no larger than 3 mm x 3 mm). Although one face of these fragments possessed the pearly sheen typical of shark tooth enamel, they did not possess any or enough of the species diagnostic serrated edge. The fragments were decalcified, sec- FICURE 4. (A) Scratched humerus and (B) penetrated scapula from specimen DFG SO-592-77. Scratches or nicks made by white shark tooth serrae are apparent in both. Photos by senior author. WHITE SHARK ATTACKS ON SEA OTTERS 201 tioned and microscopically compared to mammalian bone and tooth enamel, and to white shark tooth enamel by L. T. Pulley (veterinary pathologist). The microscopic appearance was identical to the white shark tooth enamel, however tooth enamel from other shark species was not compared. FIGURE 5. white shark tooth fragment embedded in the femur near the knee of specimen DFC SO-592-77. Photo by senior author. FIGURE 6. White shark tooth fragment embedded in the skull of specimen DFG SO-467-75. Photo by senior author. 202 CALIFORNIA FISH AND GAME Other virtually indisputable evidence of white shark bites exists. Two sea otters, one from the Morro Bay area and the other from near Monterey (DFG SO-267-72 and SO-455-75), in addition to having multiple cuts in the pelt, had a costal cartilage completely cut. The cut surfaces of these cartilages contained a pattern of grooves matching the serrae of white shark teeth (Figure 7). Two other sea otter carcasses ( DFG SO-225-71 and SO-360-73 ) , again, one from near Monterey and the other from near Morro Bay, had stab-like puncture wounds through their skulls in addition to multiple pelt lacerations. In one of these there were scratches matching the serrations of white shark teeth leading to one of the skull penetrations (Figure 8). Other indications of shark bite may be found throughout the dead otter records. The commonest example of these is the "bite-like" series of cuts that have been found in several carcasses (Figure 9). BOAT PROPELLER WOUNDS A DFG biologist approaching Monterey harbor in the 6.5-m research vessel OPHIODON in 1970 observed a sea otter grooming itself a short distance directly in the path of the boat. The speed was reduced, but the otter continued to groom and somersault apparently unaware of the vessel's approach. At very close range the boat was taken out of gear, whereupon it drifted into the startled otter who dived, came up about 3 m away, and then swam off rapidly. The propeller did not strike the otter in this instance, but presumably it could have had the boat been traveling at high speed. We have documented only one naturally occurring incident in which a boat propeller actually struck a sea otter. In late July 1970, a small salmon boat owned and operated by N. E. Friddle of Pacific Grove, California, and powered by a 65 hp outboard engine accidentally struck a sea otter at full speed just outside Monterey FHarbor. The impact damaged the propeller beyond repair. Friddle recalls that blood was abundant in the water around what he presumed was a badly lacerated otter, but his immediate attempts to rescue the animal were unsuccessful. A subsequent attempt by Friddle and a DFG employee to locate the otter was unsuccessful. Two days later, in the same general vicinity, a beached otter was located which had a laceration on the left side of the snout. A week later this animal died (DFG SO-1 92-70). At the original necropsy, the neck, shoulder, and hindquarters on the left side were noted to have been severely traumatized but only the snout was lacerated. A recent examination of the cleaned skull of this animal revealed no bone damage underlying the snout laceration. Although the dead otter record still lists this carcass as "Friddle's otter," it is very possible that the sea otter he hit was never recovered. In July 1977, two dead sea otters in fresh condition were intentionally hit by the 7.5-m research vessel ORCA powered by a 250 hp Chrysler marine engine. The boat was traveling at full speed (propeller rotation speed of approximately 1 500 rpm's) . One of the carcasses ( DFG SO-578-77) was totally destroyed and not recovered. The other (DFG SO-577-77) sustained two parallel lacerations both of which were preceded by a distinct shaved area, a condition not previ- ously noted but that could be of diagnostic use (Figure 10). WHITE SHARK ATTACKS ON SEA OTTERS 203 ■ ■■^.'«;?Wijt,MW?"«^^ii£». FIGURE 7. Cut costal cartilage (above) from a dead sea otter (DFG SO-455-75) and the overly- ing piece of pelt ( below) . The grooved cut surface of the cartilage matches the serrate edge of a white shark's tooth. Photos by senior author. CRITERIA TO DETERMINE WHITE SHARK WOUNDS AND BOAT PROPELLER WOUNDS Based upon the wounds found in verified shark bitten sea otter carcasses we 204 CALIFORNIA FISH AND GAME have developed the following criteria which we consider to be diagnostic of white shark bites: 1. Deep stab-like puncture wounds; or very long (superficial or deep) lacera- tions often associated with smaller cuts; or multiple cuts arranged in a line or arc, often occurring on opposite or various aspects of the carcass. 2. Serrated cut or scratch patterns on or through cartilage or bone; usually associated with 1 above. 3. Shark tooth enamel fragments usually associated with 1 and 2 above. Apparently white sharks often lose tooth fragments in animals they bite since their teeth are composed of a relatively thin brittle enamel shell overlying a softer dentin center. Many of these tooth enamel fragments are very small and may not contain part of the diagnostic serrated edge; however, they will have a "pearly" appearance on at least one surface. Careful scrutiny is required to locate some of these fragments. FIGURE 8. Skull from a dead sea otter (DFG SO-360-73) exhibiting stab-like punctures. The two scratches leading to the penetration near the center of the skull are diagnostic of white shark tooth serrae. Photo by Richard McKillop. In practice, we now examine all dead sea otters with lacerations for other evidence of shark bite. Definitive criteria for diagnosing boat propeller wounds do not exist. Our very limited evidence and evidence available from dead manatees, Trichechus mana- tus, suggest that boat propellers make rather large, consecutive, parallel cuts (Figure 11; D. K. Odell, pers. commun.). In heavily furred mammals like sea otters, these cuts may be preceded by a shaved area. Where these cuts extend continuously over hide with and without closely underlying bone, the laceration may appear deeper over the bony area. WHITE SHARK ATTACKS ON SEA OTTERS 205 FIGURE 9. Seriesof cuts across the lower back of a dead sea otter (DFG SO-497-76). The spacing of the cuts is suggestive of shark tooth placement. Numerous other lacerations were present on the back, abdomen, feet, and tail of this animal. Photo by Dan Costa. FIGURE 10. A dead sea otter (DFG SO-577-77) subsequently intentionally run over by a boat. Note the two parallel lacerations which are preceded by a distinct shaved area. Photo by senior author. REEVALUATION OF PREVIOUS CAUSE OF DEATH DIAGNOSES We have reexamined the dead otter records case by case and, using the criteria set forth above, we now cannot assign a single otter death to a boat 206 CALIFORNIA FISH AND GAME propeller wound with any degree of certainty. We know from Norman Friddle's account that these impacts do happen, but none of the cases reexamined fit our proposed criteria at all well. Many cases, however, did fit the criteria for white shark bites and consequently we changed them. Lacerated carcasses fitting no criteria were listed as "lacerated — cause unknown." Some of these may have resulted from boat propeller impacts and some may have been bitten by white sharks. ! FIGURE 11. A dead manatee in Florida with at least ten parallel lacerations on its back, which were probably caused by a boat propeller. Photo by D. K. Odell. WHITE SHARK ATTACKS ON SEA OTTERS 207 FREQUENCY OF WHITE SHARK ATTACKS Based upon the portion of the range which is inaccessible to carcass recovery we believe that less than half of the sea otter mortality in California is recorded and we are therefore unable to comment about total mortalilty. However, we now feel that of the 657 carcasses recorded from 1968 through 1979, roughly three-fourths of which were in good enough condition for at least a cursory post mortem examination, a minimum of 60 (9%) were killed by white shark bites. If all of the lacerated carcasses resulted from white shark bites, the number is 1 00 ( 1 5% ) . If very many of the badly decomposed carcasses ( not receiving any post mortem examination) were shark bitten, the percentage could be higher. Finally, if white sharks eat some sea otters, the percentage for total mortality would be higher yet. DISCUSSION Shark bitten sea otter carcasses are recovered from throughout the otters' present range in California although the relative frequency of bites appears to be greater in the northern portion. Seventy-seven percent of the shark bitten carcasses have come from north of Point Sur, California, and 23% to the south. This compares with 57% of all carcasses recorded being from north of Pt. Sur and 43% south (Figure 12). 80- 70- 60- ^ 50- c i> u 40- 0) Q. 30- 20- 10- South of Point Sur All recorded mortality Mortality due to white shark bites North of Point Sur I Bwra m$mm ■XvX-fe-x-r-x-x n = 14 P^ ■Xs^X-X-MWX :^¥^x^■x■x■x■:^< ^^m n = 46 FIGURE 12. Percent of mortality due to white shark bites (and all recorded mortality) that oc- curred in the southern and northern portions of the sea otters' range in California for the period 1968 through 1979. 208 CALIFORNIA FISH AND GAME For the 1 968 through 1 979 period, the frequency of white shark bites apparent- ly peaked in 1971 and 1972 (Table 1). However, the paucity of indisputable evidence (tooth fragments) prior to 1976 makes this speculation somewhat tenuous. It is of interest that LeBoeuf, Reidmann, and Keyes (unpubl. data) have documented an increase since the early 1970's in white shark bites on elephant seals, Mirounga angustirostris, at Afio Nuevo Island and the Farallon Islands. TABLE 1. Annual Sea Otter Mortality Due to White Shark Bites from 1968 Through 1979 Mortality due to All mortality white shark bites * Year recorded No. % 1968 16 1 6 1969 36 3 8 1970 51 2 4 1971 21 7 33 1972 46 9 20 1973 84 6 7 1974 45 6 13 1975 52 5 10 1976 67 3 4 1977 90 7 8 1978 82 6 7 1979 67 5 7 Totals 657 60 9 • Includes probable as well as certain cases. We have recorded shark bitten otters in all months except October, but to date. May and June appear to be the months of highest frequency (Table 2). Sharks appear to attack sea otters of both sexes and all age groups with about the same relative frequency. TABLE 2. Sea Otter Mortality Due to White Shark Bites from 1968 Through 1979 by Month All recorded Month mortality January 58 February 50 March 86 April 73 May 36 June 71 July 70 August 64 September 48 October 42** November 29 December 30 Totals 657 • Includes probable as well as certain cases. •• Includes two specimens recovered in the fall of 1969; the month was uncertain. Mortality due to white shark bites * No. % 5 9 4 8 9 10 6 8 7 19 11 15 6 9 4 6 4 8 0 - 2 7 2 7 60 WHITE SHARK ATTACKS ON SEA OTTERS 209 It is significant that only white shark tooth fragments have been found in dead sea otters. Blue sharks, Prionace glauca, and salmon sharks, Lamna ditropis, occur throughout the California range of the sea otter, but no fragments of their teeth have been found. Studies of blue shark stomachs from Monterey Bay from 1975 to 1978 produced no evidence of predation on sea otters (Morejohn, Harvey, and Krasnow 1978). Evidence that white sharks actually prey on sea otters does not exist; i.e., none has been seen consumed, none has been found in a white shark stomach, and no otter carcass has been found with part of the body bitten off. It is obvious that a sea otter could easily be handled by any medium to large white shark. White sharks are known to have eaten far larger mammals. Basically intact harbor seals, Phoca vitulina, have been found in white shark stomachs, as have sizable pieces of large elephant seals and other pinnipeds (LeBoeuf et al., un- publ. data). It is conceivable that the lacerated carcasses we are finding repre- sent but a low fraction of the total taken by white sharks. It is equally likely that for some reason white sharks do not eat sea otters and merely bite them and then let them go. In either case, the extent to which this white shark caused mortality may be affecting the Californian sea otter population, if at all, remains to be determined. ACKNOWLEDGMENTS Very many people and institutions have contributed to the data in this report. It would be impossible to name them all but most notable are D. P. Costa, J. J. Geibel, R. A. Hardy, R. E. Jameson, D. B. Lewis, J. E. Mason, J. E. Mattison, Jr., B. Green Ross, j. E. Vandevere, F. E. Wendell, P. W. Wild, T. D. Williams, C. D. Woodhouse, Jr., Moss Landing Marine Laboratories, and Santa Barbara Museum of Natural History. The shark tooth fragment from the State of Washington was identified by C H. Fiscus (National Marine Fisheries Service) and A. D. Weland- er (University of Washington ) . Most shark tooth fragments from California were verified by W. I. Follett, (California Academy of Sciences). L. J. V. Compagno (Stanford University) and D.J. Miller and R. N. Lea (DFG) also examined some tooth fragments. Critical comment on the manuscript was provided by C. D. Woodhouse, Jr., J. E. Estes, J. R. R. Ally, R. N. Lea. D. J. Miller provided major encouragement for the study. REFERENCES Keyes, M. C. 1975. Shark attacks sea otter. International Assoc, for Aquatic Animal Medicine News 7(1). 2 p. Mattison, J. A., )r., and R. C. Hubbard. 1969. Autopsy findings on thirteen sea otters (Enhydra lutris nereis) with correlations with captive animal feeding and behavior. Pages 99-101 in Sixth Ann. Conf. on Biol. Sonar and Diving Mammals, Stanford Res. Inst., Menio Park, Calif., Proc: 1-113. Morejohn, G. V., J. A. Ames, and D. B. Lewis. 1975. Post mortem studies of sea otters, Enhydra lutris L., in California. Cal. Fish and Game Mar. Res. Tech. Rept. No. 30. 82 p. Morejohn, G. V., J. T. Harvey, and L. T. Krasnow. 1978. The importance of Lolgo opalescens in the food web of marine vertebrates in Monterey Bay, California. Pages 67-98 in C. W. Recksiek and H. W. Frey, eds. Biological, oceanographic, and acoustic aspects of the market squid, Loligo opalescens Berry. Fish Bulletin 169, Cal. Dept. Fish and Game. Orr, R. T. 1959. Sharks as enemies of sea otters. ). Mamm. 40(4) ;614. Snow, H. J. 1910. In forbidden seas. Edward Arnold, London. 303 p. Wild, P. W., and ). A. Ames. 1974. A report on the sea otter, Enhydra lutris L., in California. Cal. Fish and Game Mar. Res. Tech. Rept. No. 20. 94 p. 2—81059 210 CALIFORNIA FISH AND CAME Ca/if. Fish and Came 66(4): 2^0-2^9 RECENT TRENDS IN THE WHITE STURGEON POPULATION IN CALIFORNIA'S SACRAMENTO- SAN JOAQUIN ESTUARY 1 DAVID W. KOHLHORST California Department of Fish and Game Bay-Delta Fishery Project 4001 North Wilson Way Stockton, CA 95205 Recent trends in the white sturgeon, Acipenser transmontanus, population in the Sacramento-San Joaquin Estuary were evaluated from commercial passenger fishing boat (CPFB) and tagging records. Total catch and catch/angler h on CPFB's declined from 1967 to 1974. Catch/angler h increased from 1974 to 1978, while total catch continued to decrease through 1977. Population estimates suggested that a decrease in abundance occurred between 1967 and 1974 and that abundance increased between 1974 and 1979. Mean size of sturgeon caught on CPFB's increased from 1964 to 1973 or 1974, then decreased through 1978. Annual survival rate changed little over the period examined. The population decline was likely due to poor recruitment from year classes produced after the mid-1950's. Possible causes of low recruitment are discussed. INTRODUCTION This report analyzes trends in the white sturgeon, Acipenser transmontanus, population in the Sacramento-San Joaquin Estuary from 1964 to 1979. This species is a native anadromous fish in the Sacramento-San Joaquin Estuary and is the object of a small but important sport fishery. Another species, the green sturgeon, A. medirostris, is much less common and legal-sized ( > 101 .6 cm total length) fish are seldom caught. Sturgeon are long-lived, late-maturing fish (Roussow 1957; California Depart- ment of Fish and Game, unpublished), some living over 50 yr and most maturing at 10 to 15 yr. Fishes with this type of life history normally exhibit long-term population stability and a slow response to environmental vicissitudes (Good- man 1975). FHence, sturgeon populations are vulnerable to overharvest and subsequent decline (Bajkov 1949; Dees 1961) because they cannot rapidly compensate for unusually high mortality. Historical accounts indicate that a commercial fishery substantially reduced the Sacramento-San Joaquin Estuary white sturgeon population in the late 1800's (Skinner 1962). After a complete fishing closure in 1917, the sport fishery was reopened in 1954. Through 1963 the only catches were generally incidental to the striped bass, Morone saxatilis, fishery. Fishing success improved dramatically in 1964 when shrimps, Crangon spp. and Palaemon macrodactylus, first became popular as bait. Estimated annual harvest rates have been low: at least 2% in 1954 (Chadwick 1959), 7.3% in 1967, 6.5% in 1968 (Miller 1972), and 5.6% in 1974 (Kohlhorst 1979). Changes in abundance, catch, mean size, and survival may provide clues to factors affecting the sturgeon resource and influence management of the fishery. Over-exploitation is normally characterized by decreasing catch/unit effort and ' Accepted for publication May 1980. WHITE STURGEON POPULATION TRENDS 21 1 declining mean size of fish in the catch (Gulland 1971 ). Reduced recruitment also causes decreasing catch per unit effort, but mean size increases. The former would suggest that harvest should be restricted, while the latter requires investi- gation of the causes of poor recruitment. Stable or increasing abundance meas- urements would suggest a healthy population. METHODS White sturgeon population trends were interpreted from catch, effort, and size data reported by commercial passenger fishing boat (CPFB) operators and from catch/effort, size, and absolute abundance estimated from tagging studies. Since variations in annual survival might have caused fluctuations in abundance, I evaluated survival rates from the only data available. These data provided esti- mates of survival in 1967 from tag returns and average annual survival over several years from a catch curve. The CPFB reports were compiled annually from 1964 to 1978 for trips when sturgeon were caught to determine trends in total catch and catch/angler h. Operators of CPFB's are required to furnish the Department with daily logs listing species, number, and sizes of fishes caught, number of anglers, and time spent fishing. Catch /net h during tagging in San Pablo Bay was available for fall 1967, 1968, 1974, and 1979. This catch/effort index was based on trammel netting in similar areas and months in all 4 yr. Trends in size of sturgeon were determined from: ( i ) annual mean lengths and weights calculated from information on logs submitted by the CPFB operators (operators chose to report either length or weight; they seldom reported both), and (ii) mean lengths of white sturgeon tagged in 1967, 1968, 1974, and 1979. Mark-recapture estimates of legal-size white sturgeon abundance were avail- able from tagging studies in 1 954 ( Pycha 1 956) and 1 967 ( Miller 1 972 ) . Pycha's estimate was derived from a multiple census technique and Miller's was a Petersen estimate. For comparison, I estimated abundance from tagging studies in San Pablo Bay in 1967, 1968, 1974, and 1979 (Miller 1972; Kohlhorst 1979) using the multiple census technique of Shumacher and Eschmeyer (Ricker 1975), where: S (QM^) N = 2 (M,R,) and: N = estimated population M, = total tagged fish at large at the start of the t* day C, = total fish caught on day t R, = number of recaptures in the sample C,. All the multiple census abundance estimates likely are biased downward as tagged fish probably did not mix randomly with the untagged population during the 2-month tagging season. Sturgeon not in San Pablo Bay were neither subject to tagging nor recapture. Hence, overall, tagged fish would have been more vulnerable to recapture than untagged fish to initial capture. This differential vulnerability, plus effects of immigration to and emigration from San Pablo Bay, make determining the proportion of the entire sturgeon population represented by the abundance estimates impossible. Despite the bias, the abundance esti- 212 CALIFORNIA FISH AND CAME mates probably reflect major trends. However, due to their imprecision, my intent is to present them as supplementary to the other data. I estimated average annual survival rate from a catch curve (Ricker 1975) using age frequencies of sturgeon collected mostly during tagging in 1974 and on CPFB's in 1973-1976. Aging was as described by Kohlhorst, Miller, and Orsi ( 1 980) . The slope of the descending right limb of the curve was estimated using a least squares fit of the linear regression equation: log^o (number of fish) — a + b (age). The antilogio of the slope (b) is an estimate of survival. Miller (1972) estimated first year survival of sturgeon using 2 yr of returns from tagging in 1 967 and 1 968. 1 re-estimated this survival rate and its confidence interval with 6 yr of returns using a bias-adjusted maximum likelihood equation (Model 1 of Brownie et al. 1978): S, = r^(Tt-Ci)(N2 + 1) NJt(R2 + 1) where: Si = survival rate in T' yr after 1967 tagging Ri = total returns from 1967 tagging R2 = total returns from 1968 tagging 1, = R, Ci = returns in 1** recovery year Ni = number of fish tagged in T' yr N2 = number of fish tagged in 2"** yr Confidence limits for Si were calculated as Si ± 1.96SE(Si), where: SE(Si) =\i sii- — L + L -L + — ] 1 ^' ^ * " Ni R, N, T2 - R2 Ti and T2 = R2 +Ti — Ci. The other elements are the same as above. RESULTS Catch Data Fishing success declined during much of the period examined. Sturgeon catch reported by CPFB's declined from a peak of 2,272 fish in 1967 to a low of 327 fish in 1977 (Figure 1 ). Catch/angler h on CPFB's decreased from 0.052 in 1964 to 0.028 in 1974 and then increased to 0.039 in 1978 (Figure 1 ). Negative linear trend lines for both catch (1967-1978) and catch /angler h (1964-1974) were significantly different from zero (p< 0.0005). The positive trend in catch/angler h from 1974 to 1978 was not significantly different from zero (p s 0.10). Legal-sized white sturgeon also were more difficult to catch with trammel nets in San Pablo Bay in 1974 than in 1967, 1968, or 1979. Catch/net h during tagging was 15.3 in 1967, 19.5 in 1968, 3.7 in 1974, and 8.4 in 1979. Hence, catch rate in 1974 was 79% lower than the 1967-1968 mean and 56% lower than in 1979. Mean length of sturgeon reported by CPFB's increased from 124 cm in 1964 to 134 cm in 1974 (Figure 2). Sample sizes were too small from 1975 to 1978 (only 1 to 11 fish) to calculate reliable mean lengths. Mean weight increased from 13.8 kg in 1964 to 19.0 kg in 1973 and then decreased to 14.9 kg in 1978. Positive linear regression slopes of trends in both mean length from 1964 to 1974 and mean weight from 1964 to 1973 were significantly different from zero WHITE STURGEON POPULATION TRENDS 213 (p< 0.0005). The negative trend in mean weight from 1973 to 1978 was also statistically significant (p< 0.0005). The mean length of sturgeon captured for tagging also increased from the late 1960's to 1974, then declined substantially between 1974 and 1979 (Figure 2). Catch 8 c c < 2500 -I 2000 • 1500 ■ 1000 500 0.06 0.05 0.04 0.03 0.02 - 0.01 o Si < ¥ 0 1964 1966 1976 1978 FIGURE 1. Annual reported sturgeon catch and catch/angler h by commercial passenger fishing boats in the Sacramento-San Joaquin Estuary. Mark-Recapture Estimates From 1967 to 1974, trends in the mark-recapture abundance estimates (Table 1 ) were about the same as those demonstrated by the CPFB and netting data. Specifically, the estimate for 1974 was lower than those for 1967 and 1968 and the estimate for 1979 suggested abundance increased after 1974. My 1967 esti- mate was similar to Miller's ( 1 972 ) for the same year, but a major inconsistency is that the estimate for 1968 is lower relative to 1967 and 1979 than would be expected from the other data. Presumably, this reflects the previously mentioned imprecision in the multiple census data. The 1954 estimate is lower than any of the more recent estimates suggesting abundance was relatively low then. Survival Estimates The slope of the righthand limb (age 9-20) of the catch curve for white sturgeon collected in 1973-1976 was —0.0569 (Figure 3). Estimated mean annu- al survival (antilogio -0.0569) was 0.878 (95% CI = 0.818, 0.941 ). The scatter and moderate nonlinearity of points in the righthand limb suggest that survival and/or recruitment were variable over the 12-yr period represented by those ages. 214 CALIFORNIA FISH AND GAME r 25 n ° E C Of c o CI (- "• _ a. r E 01 o 5 U 150 -1 140 130 120 J (642) a o m If £ IT « £ 20 il ?> 01 i <" J; ■ 2 a. ^ * 15 a E o c |i o u *- 10 (47) (581 c is o H c n 01 S 140 n 130 120 110 (1370) 11617) -T — r- 1963 1965 T — i— T — r 1967 1969 — r- 1971 —I — r 1973 I I 1975 — 1— 1977 1 1979 Year FIGURE 2. Annual mean weight and total length reported by commercial passenger fishing boats and mean total length during tagging of sturgeon in the Sacramento-San Joaquin Estu- ary. Bars are 95% confidence intervals and numbers in parentheses are sample sizes. Six years of returns from tagging in 1967-1968 (Table 2) yielded an estimated survival rate of 0.841 (95% CI = 0.648, 1.03) for the first year after tagging in 1967. The similarity of these two estimates suggests that changes in survival rate were not large enough to cause the observed fluctuations in abundance. WHITE STURGEON POPULATION TRENDS 215 200 •* 100 50 c o w S" a 20 ■ 0) E 3 z 10 ■ 5 ■ 10 15 20 —I 25 FIGURE 3. Age (Years) Catch curve of white sturgeon collected from 1973 to 1976 in the Sacramento-San Joaquin Estuary. Annual survival of 0.878 for age 9-20 fish w/as estimated from the antilog,o of the slope (-0.0569) of the line. 216 CALIFORNIA FISH AND GAME TABLE 1. Population Estimates for Legal-Sized ( > 101.6 cm tl) White Sturgeon in the Sacra- mento-San Joaquin Estuary. Numbers in Parentheses Are the Number of Recap- tures on Which the Estimates Are Based. Population Year estimate 1954 11,154 (45) ' 1967 114,667 (14) ^ 110,500 (10) 1968 40,000 (12) 1974 20,700 (12) 1979 74,500 (13) ' Pycha 1956 » Miller 1972 TABLE 2. Six Years of Tag Return Data from 1967 and 1968 White Sturgeon Tagging in the Sacramento-San Joaquin Estuary Used to Estimate Survival in the First Year After 1967 Tagging. Year Number Year of recovery Total tagged tagged 12 3 4 5 6 recoveries 1967 1968 ,212 87 73 34 18 11 7 230 819 53 22 14 14 11 114 DISCUSSION My analysis of trends in the sturgeon fishery depends greatly on unsupervised reporting by CPFB operators. The long-term reliability of sturgeon CPFB logs is unknown, but striped bass logs do adequately reflect catch trends in that fishery (Grant 1977), and sturgeon size and catch trends developed from the log data agree reasonably well with trends apparent from our own measurements sug- gesting that the log data are adequate for my purpose. Trends in catch/effort during tagging and by CPFBs, total CPFB catch, and population estimates all indicate that white sturgeon abundance declined in the Sacramento-San Joaquin Estuary between 1967 and 1974, and, possibly, since at least 1964. After 1974, CPFB reports and the 1979 population estimate suggest that abundance increased. Mean size increased as abundance decreased, suggesting that the population decline between 1967 and 1974 was not due to overexploitation. Reductions in fish populations due to exploitation are normally accompanied by decreases in mean size of fish in the catch (Gulland 1971), assuming growth does not increase concurrently. The survival rate apparently changed little and exploitation was low during the period examined. Annual survival of 84-88% and harvest rates of 6-7% intui- tively appear adequate to maintain a stable population. Hence, the trends in abundance and size most likely resulted from low recruit- ment from 1967 to 1974. Since white sturgeon reach legal size at age 6-12 (Kohlhorst, Miller, and Orsi 1980), the weak year classes would have to be produced starting as early as the mid-1 950's or as late as the early 1960's. The three most likely causes of poor recruitment are: (i) Degradation of juvenile habitat. Survival of juveniles of other anadromous species in the Sacra- mento-San Joaquin System, such as striped bass, American shad, Alosa sapidis- sima, Chinook salmon, Oncorhynchus tshawytscha, and longfin smelt, WHITE STURGEON POPULATION TRENDS 217 Spirinchus thaleichthys, is reduced by low freshwater flows and high water diversion rates during the spawning and nursery periods (Turner and Chadwick 1972; Chadwick, Stevens, and Miller 1977; Stevens and Miller, unpubl. data). Low freshwater flows apparently innpact juveniles of these species by restricting available habitat or reducing food supplies. Water diversions reduce survival by directly removing fish or by changing flow patterns to disrupt migrations. Freshwater outflow from the Sacramento-San Joaquin Delta in late spring and summer, the period that might be critical for sturgeon, was low from 1959 to 1962 and in alternate years thereafter through 1972. During this period, flows were highest in 1967 and 1969. Also, the percent of inflow diverted from the Delta increased substantially after 1958. For example, the mean percent of May-June inflow diverted was 5.1% from 1951 to 1958 and 19.7% from 1959 to 1968. Since sturgeon are recruited between ages 6 and 12 (Kohlhorst, Miller, and Orsi 1980), flow and/or diversion conditions during a period as brief as 1959-1962 could have depressed recruitment from 1965 to 1974, while high flows in 1967 and 1969 may explain increased abundance since 1974. As partial corroboration of the latter, the 1 969 year class comprised 1 9.1 % of the sturgeon tagged in 1979 and was the most abundant age group in the sample. However, the next most abundant year class was from 1 970 ( 1 7.6% ) , a relatively low flow year. The effect of flow on recruitment also may be reflected in Pycha's (1956) data which suggested that dominant year classes were produced in 1938 and 1948. Late spring and early summer flows were high in both of those years, particularly in 1938. (ii) Environmental contaminants. Polychlorinated biphenyls (PCB's) are of special concern. Samples of legal-sized sturgeon collected in San Pablo and Suisun bays in 1975 contained mean gonadal PCB concentrations of (mean ± SD) 49.3 ± 24.8 ppm in males and 23.7 ± 27.8 ppm in females (California Department of Fish and Game, unpublished). A concentration of 7.0 ppm of PCB in eggs of the sheepshead minnow, Cyprinodon variegatus, caused mortal- ity in the fry (Hansen, Schimmel, and Forester 1974). Hogan and Brauhn (1975) found that 60-70% of rainbow trout, Salmo gairdneri, fry were deformed 30 d after hatching due to PCB levels of 2.7 ppm in the eggs. Mortalities were also increased by PCB's in the first 30 d after hatching. These studies suggest that PCB's may reduce survival of larval sturgeon and subsequent recruitment. They gained wide use in late 1930's and early 1940's (Walker 1976), so sturgeon probably have been accumulating them for many years. Unfortunately, long term information on PCB concentrations in white sturgeon is not available to indicate whether PCB's actually could account for recent changes in sturgeon abundance. ( iii ) Spawning stock size. Declining abundance of sturgeon between 1 967 and 1974 and the apparent increase thereafter may be caused by fluctuations in abundance of mature spawners. Preliminary analysis of age composition data collected in 1 954, 1 965-1 970, and 1 973-1 976 suggests that, since 1 932, there has been about a 14-yr periodicity in year class strength. Fourteen years is approxi- mately the age of first spawning of female white sturgeon (California Depart- ment of Fish and Game, unpublished). Perhaps, strong year classes produce large numbers of young when they mature and weak year classes, few young. 218 CALIFORNIA FISH AND CAME However, all females from a year class do not mature at the same time and many live long enough to spawn more than once. These older fish have higher fecun- dity than first-time spawners. These facts suggest the explanation is more com- plicated than a simple 14-yr cycle. Exploration of factors possibly affecting sturgeon recruitment is continuing. If recruitment is affected by controllable factors, these could be manipulated to increase sturgeon abundance. ACKNOWLEDGMENTS I wish to thank D. Ramczyk for first bringing to my attention t.e decline in catch and increase in size of white sturgeon reported by CPFB's. Many other Department employees assisted me in both the field and laboratory. D. Stevens and H. Chadwick critically reviewed the manuscript. A. Conner drafted the figures. This work was performed as part of Dingell-Johnson Project California F-9-R, "A Study of Sturgeon, Striped Bass, and Resident Fishes", supported by Federal Aid to Fish Restoration funds. REFERENCES Bajkov, A. D. 1949. A preliminary report on the Columbia River sturgeon. Oregon Fish. Comm. Res. Briefs 2:3-10. Brownie, C, D. R. Anderson, K. P. Burnham, and D. S. Robson. 1978. Statistical inference from band recovery data— a handbook. U.S. Dept. Interior, Fish Wildl. Serv. Resource Publ. 131:1-212. Chadwick, H. K. 1959. California sturgeon tagging studies. Calif. Fish Came, 45(4):297-301. Chadwick, H. K., D. E. Stevens, and L. W. Miller. 1977. Some factors regulating the striped bass population in the Sacramento-San )oaquin Estuary, California. Pages 18-35. In: W. Van Winkle, ed. Proceedings of the confer- ence on assessing the effects of power-plant-induced mortality on fish populations. Pergamon Press, New York. 380 p. Dees, L T. 1961. Sturgeons. U.S. Fish Wildl. Serv., Bur. Comm. Fish., Fish. Leaflet 526:1-8. Goodman, D. 1975. The theory of diversity-stability relationships in ecology. Quart. Rev. Biol., 50(3):237-266. Grant, J. J. 1977. Evaluation of striped bass party boat log reporting for the Sacramento-San Joaquin Estuary from 1969 to 1974. Calif. Dept. Fish and Game, Anad. Fish. Br. Admin. Rept. 77-8:1-21. (Mimeo). Gulland, ). A. 1971. Appraisal of a fishery. Pages 259-269. In: W. E. Ricker, ed. Methods for assessment of fish production in fresh waters. Internat. Biol. Programme Handbook No. 3. Blackwell Scientific Publications, Oxford. 348 p. Hansen, D. J., S. C. Schimmel, and J. Forester. 1974. Aroclor 1254 in eggs of sheepshead minnows: effects on fertilization success and survival of embryos and fry. Southeastern Assoc. Game Fish Comm., Proc. 27**" Ann. Conf., p. 420-^26. Hogan, J. W., and ). L. Brauhn. 1975. Abnormal rainbow trout fry from eggs containing high residues of PCB (Aroclor 1242). Prog. Fish. Cult., 37(4):229-230. Kohlhorst, D. W. 1979. Effect of first pectoral fin ray removal on survival and estimated harvest rate of white sturgeon in the Sacramento-San Joaquin Estuary. Calif. Fish Came, 65(3):173-177. Kohlhorst, D. W., L. W. Miller, and J. ). Orsi. 1980. Age and growth of white sturgeon collected in the Sacramento- San Joaquin Estuary, California, 1965-1970 and 1973-1976. Calif. Fish Came, 66(2):83-95. Miller, L. W. 1972. White sturgeon population characteristics in the Sacramento-San Joaquin Estuary as measured by tagging. Calif. Fish Game, 58(2):94-101. Pycha, R. L. 1956. Progress report on white sturgeon studies. Calif. Fish Came, 42(1):23-35. Ricker, W. E. 1975. Computation and interpretation of biological statistics of fish populations. Can., Fish. Res. Bd., Bull. 191:1-382. Roussow, G. 1957. Some considerations concerning sturgeon spawning periodicity. Can., Fish. Res. Bd., J., 14(4):553-572. Skinner, J. E. 1962. An historical review of the fish and wildlife resources of the San Francisco Bay area. Calif. Dept. Fish and Came, Water Proj. Br. Rept. 1:1-226. Turner, J. L., and H. K. Chadwick. 1972. Distribution and abundance of young-of-the-year striped bass, Morone saxatilis, in relation to river flow in the Sacramento-San Joaquin Estuary. Am. Fish. Soc, Trans., 101 (3):442- 452. WHITE STURGEON POPULATION TRENDS 219 Walker, C. R. 1976. Polychlorinated biphenyl compounds (RGB's) and fishery resources. Fisheries (Bull. Am. Fish. Soc), 1(4):19-22. 220 CALIFORNIA FISH AND GAME Calif. Fish and Came 66(4) : 220-232 AN ANNOTATED CHECKLIST OF FISHES FROM HUMBOLDT BAY, CALIFORNIA ^ DANIEL W. COTSHALL California Department of Fish and Came P.O. Box 98 Avila Beach, CA 93424 GEORGE H. ALLEN Fisheries Department Humboldt State University Areata, CA 95521 ROGER A. BARNHART California Cooperative Fishery Research Unit Humboldt State University Areata, CA 95521 Records of fishes occurring in Humboldt Bay have been kept since the mid-1950's in order to determine the Bay's importance as a nursery or spawning area, feeding area, or residence for the various sport and commercial fishes of California's north coast. Occurrences were obtained from published and unpublished reports. Various methods were used to collect the fishes, including traps, trawls, hook-and-line, beach seines, and collections at a power plant's intake screens. To date, 110 species have been recorded from the Bay. The study indicates that the Bay plays an important role in the life history of several important sport and commercial fishes including: Clupea harengus, (spawning); Embiotoca lateralis, (resident); Hexagrammos decagrammus, (nursery); Ophiodon elongatus, (nursery); Parophrys vetulus, (nursery); Oncorhynchus kisutch and O. tshawytscha, (feeding); and Sebastes caurinus, (nursery). INTRODUCTION Humboldt Bay is one of the largest natural bays in California, comprising 17,000 acres of open water, tidal flats, and marshes. Bay waters function as habitat, a food source, breeding ground, nursery area, and migratory route for a host of marine animals. Man has used the Bay for over 100 years as a deep- water port, food source, log dump, dumping ground for sewage and other waste, recreational area and for land development. These activities affect the ability of the Bay to continue in its historical biological function. Fishes comprise the major portion of the Bay's fauna, both in number of species and in biomass. Many are important to the Bay's sport fishery and small commercial fisheries; others, which use the Bay as a nursery area, contribute to commercial and sport fisheries outside the Bay. During the 1950's, California Department of Fish and Game (DFG) biologists began compiling species lists to obtain a more complete understanding of the Bay's role in the ecology of north coast fishes. The checklist presented here combines data from sport fishing creel censuses, research trawling, larval fish studies, fish collections from trash racks in water intake screens, and other sources. MATERIALS AND METHODS Species occurrences were obtained from the following sources: Allen, Delacy, ^ Accepted for publication June 1980. FISHES OF HUMBOLDT BAY 221 andCotshall (1960); Miller and Gotshall (1965); Gotshall (1966); Gotshall and Fitch (1968); Allen, Boydstun, and Garcia (1970); Dewees (1970); DeGeorges (1972); Eldridge and Bryan (1972); Prince (1972); Stein (1972); Sannuelson (1973); Sopher (1974); Quirollo and Dinnel (1975); unpublished Department of Fish and Game monthly trawl data; unpublished Humboldt State University trawl data; monthly collection of fishes at trash screens at coolant water intakes at the Pacific Gas and Electric Company (PG&E) Buhne Point Power Plant; beach seining by commercial fishermen; and validated, unpublished records. The designation of the Bay's function in the life history of each species is based on our observations over the years and is subject to future revision. Families are listed alphabetically under each of the two major classes of fishes, the cartilagi- nous fishes and the bony fishes. Lengths are total lengths in centimetres (cm) unless otherwise noted. Maximum size was not available for all Humboldt Bay species. Data from Miller and Lea (1976) were used to determine new size records. RESULTS The list contains 110 species belonging to 43 families (Appendix 1 ). Forty-four species are known or probable residents. At least six species are known to spawn in the Bay, based on the presence of eggs and/or larvae and capture of adults during the spawning season. Probably the most important spawner is the Pacific herring, Clupea harengus. The Bay functions as a nursery area for at least seven species including the English sole, Parophrys vetulus, an important component of the commercial trawl catch outside Humboldt Bay. Our observations also indicate that 16 species enter the Bay to feed, the most important of this group are the coho and chinook salmon, Oncorhynchus kisutch and O. tshawytscha. Thirty-five species are infrequently or rarely captured in the Bay and are consid- ered as occasional or chance visitors. A total of 45 species has been caught by sport fishermen in the Bay and 9 species have been commercially fished. DISCUSSION We realize that the list is not complete. Any fish inhabiting the eastern north Pacific ocean outside the Bay could be expected in the Bay on occasion. Additional species also will be recorded in the future, as different collecting techniques are employed. Many species that we had expected to appear in collection records for the Bay were missing. For example, the gopher rockfish, Sebastes carnatus, and black-and-yellow rockfish, Sebastes chrysomelas, which reportedly range north to Eureka, to our knowledge have not been observed or captured in Humboldt Bay or around the entrance jetties. It is clear that Humboldt Bay is an important habitat for many species of fishes; therefore, any project that would threaten the Bay's ability to function as a nursery, feeding, spawning area, or permanent residence should be very careful- ly considered. ACKNOWLEDGMENTS This checklist is the result of contributions of time and data from a great many individuals. Space limitations force us to list only a few of those who have contributed over the years. Department of Fish and Game biologists E. Best, E. 222 CALIFORNIA FISH AND GAME Gibbs (deceased), and T. Jow were responsible for compiling the original checklist. J. E. Fitch confirmed many of the identifications. T. Sopher provided data from his trawl study in Areata Bay; P. Dinnel supplied the data from the PG&E screens; E. Herald (deceased), R. Stein, L. B. Boydstun, J. Hanlon, J. Turk, and "Jake" Houck provided individual species records; N. Nelson, S. Taylor, M. Willis, R. Hardy, j. Spann, D. Cross, and L. Murakami assisted in the Depart- ment's Humboldt Bay trawl study. R. N. Lea and J. E. Fitch edited the original manuscript. R. N. Lea also provided taxonomic and nomenclatural assistance. To all of these individuals and the host of Humboldt State University students and sport and commercial fishermen who also provided records or participated in individual projects, we offer our sincere thanks. REFERENCES Allen, C. H., L. B. Boydstun, and F. G. Garcia. 1970. Reaction of marine fishes around warmwater discharge from an atomic steam-generating plant. Prog. Fish-Cult., 32(1): 9-16. Allen, G. H., A. C. Delacy, and D. W. Gotshall. 1960. Quantitative sampling of marine fishes— a problem in fish behavior and fishing gear. Pages 448-51 1 in E. A. Pearson, ed. First Int. Conf. Waste Disposal Mar. Environ. Proc. Pergamen Press, New York. Bailey, R. M., J. E. Fitch, E. S. Herald, E. A. Lachner, C. C. Lindsey, C. R. Robins, and W. B. Scott, 1970. A list of common and scientific names of fishes from the United States and Canada. Amer. Fish. Soc. Spec. Publ. No. 6. 150 p. Behrstock, R. A. 1976. First record of the decorated warbonnet Chirolophis decoratus (Jordan and Snyder 1902), in California waters. Calif. Fish Game, 62(4); 308-309. Best, E. A. 1961. Occurrence of the round stingray, Urolophus ha //eri Cooper, in Humboldt Bay, California. Calif. Fish Game, 47(4): 335-338. Boydstun, L. B. 1967. Northern range extension of the giant sea bass, Stereo/epis gigas Ayres. Calif. Fish Game, 53(4): 296-297. De Georges, A. 1972. Feasibility of artificial reefs in intertidal waters. MS Thesis, Humboldt State Univ. 102 p. Dewees, C. 1970. Population dynamics and fishing success of an artificial reef in Humboldt Bay, California. MS Thesis, Humboldt State Univ. 77 p. Eldridge, M. B., and C. F. Bryan. 1972. Larval fish survey of Humboldt Bay, California. NOAA Tech. Rept. 665: 1-8. Gotshall, D. W. 1966. Marine resources of Humboldt Bay. Center for Community Development, Humboldt State College, Symposium, Areata, CA, p. 23-26. Gotshall, D. W., and J. E. Fitch. 1968. The louvar, Luvarus Imperlalis, in the eastern Pacific with notes on its life history, Copeia 1968(1): 181-183. Miller, D. J., and D. W. Gotshall. 1965. Ocean sportfish catch and effort from Oregon to Point Arguello, California, July 1, 1957 to June 30, 1961. Calif. Dept. Fish and Game, Fish Bull., (130): 1-135. Miller, D. J., and R, N, Lea. 1976, Guide to the coastal marine fishes of California, Calif. Dept. Fish and Game, Fish Bull., (157): 1-249. Quirollo, L, F,, and P. A, Dinnel, 1975, Latitudinal range extensions for yellow and spotted snake eels (genus Ophichthus). Calif, Fish Game, 61 (3): 156-157, Prince, E, D, 1972. The food and behavior of the copper rockf ish, Sebastes caurinus Richardson, associated with an artificial reef in south Humboldt Bay, California, MS Thesis, Humboldt State Univ, 102 p. Samuelson, C, E. 1 973, Fishes of south Humboldt Bay, Humboldt County, California, MS Thesis, Humboldt State Univ,, Areata, CA, 94 p, Sopher, T. R, 1974, A trawl survey of the fishes of Areata Bay, California, MS Thesis, Humboldt State Univ,, Areata, CA, 103 p. Stein, R. 1972, Identification of some larval Pacific cottids. MS Thesis, Humboldt State Univ,, Areata, CA, 41 P- > "c Z3 ^ "oj ffl c c e c 3 rS Q E Qe "E o (J c o * E o u k_ 01 Q. C O 00 c T- ■fl .s C: 'E X .5 k ^ *— o CQ ^ > "55 U ■^ o 1 e ■5 .N o J9 ! > E 3 X E 1 1 0 ^ i« V f^ FISHES OF HUMBOLDT BAY 223 Si t ■% S 8 - ^ E a;~ ^ 3 T o , 1 ^ 1- ^ c o J! fS c DO u E o . fc u m 2 . O i ^ £ a; a; v; _;Enj CfTJuj- -=i: - ^ o . ^ H "^ • ^ Qj 01 z) . S: . ^ : E E o . J^ 2 n3 00 -C ,c t/> tn ^ DC ■o c c (U 3 > o o c u u u u .y £r 3i rd — .2 o c 'I' 5; >; ^ ,§C-SE-5 = -^ ai|9-.?d.o o ^ J5 XI ^ "> c - DO'^ 3 >^ o ? -C -^ _c E T f^f ° U U t/i Q W . ,, -U -W O' T fl I ^ « il il ft |i|t^i^ 224 CALIFORNIA FISH AND GAME _!. Ol 3 C U Q "o u N "^ N . 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Research into techniques to estimate invertebrate biomass in specific vegeta- tive types is needed to evaluate the aspects of preference versus availability in winter foods of Pintails. 100 90 80 70 60 u 50 a. 40 30 20 10 0 i\ A \ i \/\/ .^•* »«^^ MALE N FEMALE F S MONTH N FICURE 1. Monthly aggregate volume percentage of animal and vegetative food items found in the esophagi of male and female Pintails collected at the Los Banos Wildlife Manage- ment Area, California, 1976-77. Solid line — vegetation; Broken line — animal ACKNOWLEDGMENTS Appreciation is extended to the following California Department of Fish and Game personnel: J. Cawthon provided the original impetus for the project; D. Ruegg and C. Wood helped in the collection, preparation, and analysis of sam- ples. We are also indebted to W. Stienecker, formerly with the Food Habits Section of the Department's Field Laboratory, for his assistance and use of laboratory facilities. R. McLandress, University of California, Davis, reviewed the manuscript and provided valuable suggestions for its improvement. REFERENCES Kortright, F. H. 1942. The ducks, geese, and swans of North America. Stackpole Co., Harrisburg, Pennsylvania. 476 pp. Krapu, G. L. 1974. Feeding ecology of Pintail hens during reproduction. Auk, 91 (2); 278-290. Krapu, G. L., and C. A. Swanson. 1977. Foods of juvenile brood hen and post breeding Pintails in North Dakota. Condor, 79(4):504-507. Krull, J. N. 1970. Aquatic plant-macroinvertebrate associations and waterfowl. J. Wild!. Manage., 34(4):707-718. PINTAIL FOOD HABITS 237 Martin, A. C, R. H. Gensch, and C. P. Brown. 1946. Alternate methods in upland gamebird food analysis. J. Wildl. Manage., 10(1):8-12. McCilvrey, F. B. 1966. Fall food habits of ducks near Santee Refuge, South Carolina. J. Wildl. Manage., 30(3) :577- 580. McMahan, C. A. 1970. Food habits of ducks wintering on Laguna Madre, Texas. J. Wildl. Manage., 34(4):946-949. Serie, J. R., and C. A. Swanson. 1976. Feeding ecology of breeding Cadwalls on saline marsh. ). Wildl. Manage., 40(1);69-81. Swanson, G. A., and J. C. Bartonek. 1970. Bias associated with food and analysis in gizzards of Blue-winged Teal. J. Wild!. Manage., 34(4):739-746. Swanson, G. A., M. L. Meyer, and J. R. Serie. 1974. Feeding ecology of breeding Blue-winged Teals. J. Wildl. Manage., 38(3):396-^W7. 238 CALIFORNIA FISH AND GAME NOTES HARBOR SEAL AND FISH POPULATIONS— BEFORE AND AFTER A SEWAGE SPILL IN SOUTH SAN FRANCISCO BAY A sewage spill occurred 4 through 29 September 1979, at the San Jose-Santa Clara Water Pollution Control Plant during which 4,000,000,000 gallons of par- tially treated sewage flowed into Artesian Slough (H. Singer, Senior W.R.C.E., California Regional Water Quality Control Board, pers. commun.). Initial reports by the media indicated massive wildlife die-offs in the Bay south of the Dumbar- ton Bridge. It does not appear that effluent reached Mowry Slough, which is a major harbor seal haul-out area in San Francisco Bay (Fancher 1979; Risebrough et al. 1979) about 8 miles from the spill's origin (Figure 1). Data on fish and seal numbers in the Mowry Slough area are available before, during, and after the spill as part of a year-long harbor seal study on the San Francisco Bay National Wildlife Refuge. Although sample size is small, the results are of interest since the impact of the spill on south Bay macrofauna is still unknown. / SCALE IN MILES FIGURE 1 . Map of San Francisco Bay showing where the sewage spill originated and the Mowry Slough study site. Fish were sampled with a specially designed trap (Wild 1 969 ) of 6-mm square mesh set at high tide to completely block a 5-m wide, 2-m deep tidal gut. Fish present in the gut were trapped as the water drained with the receding tide, a process taking approximately 4 hours. There were no major differences between sampling results 7 days prior to spillage onset, during the spill, and 5 days after the spill ceased (Table 1 ). The increased numbers of northern anchovy, Engrau- NOTES 239 lis mordax, and bay shrimp, Crangon franciscorum, appear minor when com- pared to the monthly fluctuations seen in the south Bay by Alpin (1967) and Wild ( 1 969 ) , respectively. Dead or deformed fish were not observed during this study. TABLE 1. Numbers of Fish and Invertebrates Collected at Mowry Slough Before, During, and After a September 1979 Sewage Spill. Date: August 28 September 6 October 4 Time trap set: 0530 1430 1335 Salinity; 25.5 %o 26.0 %o 26.0 %o Temperature water: 20° C 24° C 21° C Species Number of Individuals Fish Topsmelt Atherinops affinis 235 309 237 Northern anchovy Engraulis mordax 2 38 94 Yellowfin goby Acanthogobius flavimanus 3 7 1 Threespine stickleback Gasterosteus aculeatus 4 4 1 Dwarf perch Micrometrus minimus 0 1 8 Shiner perch Cymatogaster aggregata 1 0 0 Rainwater killifish Lucania parva 0 0 2 Pacific staghorn sculpin Leptocottus armatus 8 0 0 Leopard shark Triakis semifasciata 0 2 3 253 361 346 Invertebrates Mud crab Hemigrapsus oregonensis 0 6 1 Oriental shrimp Palaemon macrodactylus 5 0 20 Bay shrimp Crangon franciscorum 35 50 J7^ 40 56 193 Harbor seals, Phoca vitulina richardii, were counted two to seven times per month at Mowry Slough during 1979. Twenty-five seals were hauled-out on the last census made prior to the spill. The number of seals fluctuated between 17 and 35 during and immediately after the spill (Table 2). Based on past censusing ( Fancher 1 979 ) , a fluctuating seal count of this magnitude is not unusual for the fall and winter months at Mowry Slough. A dead seal found at Mowry Slough on 27 September 1979, 23 days after the spill began, was unusually small, indicating a chronic condition probably not attributable to the recent spill. Although the last known pupping in the area occurred in May, this small seal (8.7 kg, 86.9 cm tl) with adult pelage was similar in size to a newborn pup. It was retained at the Museum of Vertebrate Zoology, U.C. Berkeley, for additional study. 240 CALIFORNIA FISH AND CAME TABLE 2. Harbor Seal Numbers at Mowry Slough Before, During, and After the Spill. Counts Were Made 2 to 5 Hours After High Tide Date Number of seals 30 August 25 Spill started: 4 September 14 September 25 25 September 17* 27 September 27 29 September 20 Spill stopped; 30 September 2 October 35 1 1 October 24 16 October 32 30 October 33** 31 October 35 • At low tide. •• Two hours after low tide. Based on the above, obvious short-term effects of the sewage spill on Mowry Slough seal and fish populations appear to be minimal or absent. Long-term effects are possible and monthly monitoring of both seal and fish populations continues. REFERENCES AlpinJ.K. 1967. Biological survey of San Francisco Bay (1963-1966). State of Calif. Dept. Fish and Game, MRO Reference No. 67-4:1-131. Fancher, L.E. 1979. The distribution, population dynamics, and behavior of the harbor seal (Phoca vitulina richardii) in South San Francisco Bay, California. Thesis. Calif. State Univ., Hayward. 109p. Risebrough, R., D. Alcorn, S. Allen, V. Anderlini, L. Booren, R. DeLong, L. Fancher, R. Jones, S. McCinnis, and T. Schmidt. 1979. Population biology of harbor seals in San Francisco Bay, California. Contract MM6AC006, unpub. report to Mar. Mam. Comm., Wash., D.C. 62p. Wild, P.W. 1969. Macrofauna of Plummer Creek of San Francisco Bay collected by a specially designed trap. Thesis. San Jose State Univ. 85p. — Doris J. Alcorn, Lyman £ Fancher, and Jane Gull Moss, U.S. Fish and Wildlife Service, San Francisco Bay National Wildlife Refuge, P.O. Box 524, Newark, CA 94560. Accepted for publication April 1980. STATUS OF REDEYE BASS, MICROPTERUS COOSAE, IN THE SOUTH FORK STANISLAUS RIVER, CALIFORNIA Redeye bass, Micropterus coosae, are native to streams in the lower Appa- lachian regions of Alabama, Tennessee, Florida, Georgia, North Carolina, and South Carolina (MacCrimmon and Robbins 1975). They are most common in small headwater streams (Hurst, Bass, and Hubbs 1975). Ramsey (1975) asserts that redeye bass are similar to smallmouth bass, M. dolomieui, in habitat require- ments. According to Parsons (1954), redeye bass are the brook trout of the warmwater game fish because they are similar in size, habitat preference, feed- ing habits, desirability, and gameness. In an effort to provide more diverse gamefish populations in California's small warmwater streams, the California Department of Fish and Game transplanted redeye bass from Georgia and Tennessee to a total of six California streams from 1962 to 1964 (Goodson 1966). Included was the South Fork Stanislaus River NOTES 241 below Lyons Reservoir in Tuolumne County, which received 510 fingerlings in July 1962. The South Fork Stanislaus River, situated in the Sierra Nevada foothills, has widely varying flows. Flows of 28 m ^/s or greater are common during spring and early summer, but drop sharply to about 0.06-0.14 m ^/s in late summer and fall. Temperatures reach as high as 11 TQ in August. To determine fish species composition in the South Fork Stanislaus River two 30-m sampling stations were electrofished on 25 October, 1 978. One station was established immediately above the confluence of Fivemile Creek; the other was 8 km upstream near Keltz Mine. The stations were at elevations of 450 and 650 m, respectively. The redeye bass was the dominant species captured; of 92 fish collected from both stations, 79 were redeye bass. Other fish included: California roach, Hes- peroleucus symmetricus; hardhead, Mylopharodon conocephalus; Sacramento sucker, Catostomus occidenta/is; and brown trout, Salmo trutta. Identification of the bass as Micropterus coosae was confirmed by T. Mills (Fishery Biologist, Dept. Fish and Game). Ten of the redeye bass were deposited in the Depart- ment's Ichthyological Museum. Redeye bass collected were generally small. Sixty four of the 79 fish examined ranged from 30 to 53 mm fork length (fl); these were presumably young-of-the- year. The remaining 15 ranged from 100 to 191 mm fl (Figure 1 ). 20r 15 - 10 s. 3 — I r- o o o October 25,1978 n=79 S 1 1 r- o o o o o o 2-(A Leptochloa (ascicularis: 234 Leptocottus armatus: 30, 239 Limnodrilus hoffmeisteri: 115, 117 Lithocarpus densi flora: 7 Lucania parva: 29-31, 124-125, 239 Micrometrus minimus: 239 Micropsectra: 1 1 7 Micropterus coosae: 1 25, 240-242 Micropterus dolomieui: ZS-Z'i, 159, 163-172, 240 Micropterus punctulatus: 62 Micropterus salmoides: is, 163-172, 178 Micropterus salmoides floridiar)us: 1 33-1 62 Micropterus salmoides salmoides: 133, 1 89 Mirounga angustirostris: 208 Monadenia churchi: 7, 8, 1 4 Monadenia fidelis: 11, 13, 14, 15 Monadenia setosa: 4-1 6 Morone saxatilis: 210 Mulloidichthys dentatus: 1 23 Mylopharodon conocephalus: 241 Nitella: 118 Notemigonus crysoleucas: 178 Odocoileus hem ion us: 105-111 Odocoileus virginianus: 106 Oncorhynchus Icisutch: 59-62 Oncorhynchus tshawytscha: 59-62, 68-82, 216 Ophiodon elongatus: 187-188 Orthodon microlepidotus: 178 Palaemon macrodactylus: 83, 210, 239 Paspalum distichum: 233 PAoc<3 vitulina: 209 Phoca vitulina richardii: 239 /'/>7t/5 ponderosa: 6 /'/>7(/5 sabiniana: 7 Pisidium: 112, 115, 117 Polinices spp.: 175 Polypedilum: 1 1 7 Pomoxis annularis: 1 78 Pomoxis nigromaculatus: 1 25 Prionace glauca: 209 Procladius: 117 Prosopium williamsoni: 96-104 Prosopium williamsoni cismonatus: 101 Pseudotsuga menziesii: 6 Pseudupeneus grandisquamis: 1 23-1 24 Quercus chrysolepis: 8 Quercus kelloggii: 7 Rana aurora: 184 Randall ia ornata: 175 Rhinichthys cataractae: 97 Richardsonius egregius: 97 Salcornia virginica: 25, 26 Salix spp.: 38, 184 Salmo clarki: 96 Salmo clarki henshawi: 49, 97 Salmo gairdneri: 17-24, 53, 62, 68, 96, 97, 217 Salmo gairdneri aquilarum: 1 9, 22 Salmo gairdneri gilberti: 20 Salmo gairdneri kamloops: 1 9 Salmo gairdneri stonei: 1 9 5a/mo ^/-t/ffa; 62, 97, 241 Salvelinus fontinalis: 96-104 Scirpus sp.: 184 Scirpus robustus: 234 Scorpaenichthys marmoratus: 188 Sphyrna lewini: 121-123 Sphyrna mokarran: 122 Sphyrna zygaena: 1 22 Spirinchus thaleichthys: 217 Stempellini: 1 1 7 Trachurus symmetricus: 121 Tr/aA-tf semifasciata: 239 Trichecus manatus: 204 Trichocorixa reticulata: 26 Trilobopsis: 8 Ty'pAa sp.: 184 TypAa latifolia: 234 Xenopus laevis: 1 24 SUBJECT Bass, redeye: Status of, in South Fork Stanislaus River, California, 240-242 Bass, largemouth: Exploitation, natural mortality, and survival in Shasta Lake, California, 163-171 Bass, largemouth, Florida: Impact on northern California waters and use of meristics to determine introgression and intergradation, 133-162 Bass, smallmouth: Mortality and survival of Tagged, in Merle Collins Reservoir, 35-39; exploitation, natural mortality, and survival in Shasta Lake, California, 163-171 Bluegill: Introduction of southeastern bluegill, with notes on growth of initial year class, 62-64 Catfish, blue: From Sacramento-San Joaquin Delta, 120-121 Condor, California: Estimating size and trend of the population, 1965-1978, 40-48 Deer, mule; Use of road-killed deer to assess reproductive pK)tentlal and winter condition of Devil's Garden interstate herd, 105-111 Ditches, mosquito control recirculation: Effects of, on fish community of a San Francisco Bay salt marsh, 25-34 Eel, wolf: Diet and behavioral aspects of, on sandy bottom in Monterey Bay, 173-178 Fish, distribution: Seasonal benthic, in Pyramid Lake, Nevada, 49-58 Fishes: Checklist of, from Humboldt Bay, 220-232 250 CALIFORNIA FISH AND GAME Goatfish, bigscale: Added to California's marine fauna, 123-124 Killifish, rainwater: Established in California, 124-125 Lakes, high elevation: Bottom fauna of, in Kings Canyon National Park, 112-119 Lamprey, Pacific: Repeat spawning of, 186-187 Lingcod: A diver-operated device for capturing, 187-188 Perch, Sacramento: Decline of Lake Creenhaven population, 178-183: karotype of, 189-191 Pintails: Food habits of, in Northern San Joaquin Valley, California, 233-237 Salamander, Santa Cruz long-toed: A population from Monterey County, California, 184-186 Salmon, chinook: Estimated safe levels of copper and zinc in upper Sacramento River, 68-52; a head-off method of measuring, 59-64 Salmon, coho: A head-off method of measuring, 59-64 Seals, harbor: Populations before and after a sewage spill in South San Francisco Bay, 238-240 Shark, scalloped hammerhead: First record in coastal California waters, 121-123 Shark, white: Attacks on sea otters by, 196-209 Snail, land: Distribution, ecology, and reproductive anatomy of Monadenia setosa Talmadge, 4-16 Sturgeon, white: Age and growth in Sacramento- San Joaquin Estuary, 1965-70 and 1973-76, 83-95; population trends in Sacramento-San Joaquin Estuary, 210-219 Surfperch, redtail: a geographic record for, 242 Trout, brook: Diets in Little Walker River, Mono County, California, 96-104 Trout, rainbow: Ancestry of artificially propagated strains, 17-24 Whitefish, mountain: Diets in Little Walker River, Mono County, California, 96-104 Photoelectronic composition by CAUFORNIA OmCE OF STATE PRINTING 81059—800 8-80 4,600 LDA _ o a Si'. z H I in _-4 Ul > > z m z H O _ s» C4 : (X so g S as -n fj ii m a