pUJFGRN]^ FISH«»GAME III CONSERVATION OF WILDLIFE THROUGH EDUCATION" California Fish and Game is a journal devoted to the conservation of wild- life, if its contents are reproduced elsewhere, the authors and the California Deportment of Fish and Game would appreciate being acknowledged. Subscriptions may be obtained at the rate of $5 per year by placing an order with the California Department of Fish and Gome, 1416 Ninth Street, Sacramento, California 95814. Money orders and checks should be made out to California Department of Fish and Gome. Inquiries regarding paid sub- scriptions should be directed to the Editor. Complimentary subscriptions are granted, on a limited basis, to libraries, scientific and educational institutions, conservation agencies, and on exchange. Complimentary subscriptions must be renewed annually by returning the post- card enclosed with each October issue. Please direct correspondence to: Robson A. Collins, Editor California Fish and Game 350 Golden Shore Long Beach, California 90802 u 0 VOLUME 62 OCTOBER 1976 NUMBER 4 Published Quarterly by STATE OF CALIFORNIA THE RESOURCES AGENCY DEPARTMENT OF FISH AND GAME STATE OF CALIFORNIA EDMUND G. BROWN JR., Governor THE RESOURCES AGENCY CLAIRE T. DEDRICK, Secretary for Resources FISH AND GAME COMMISSION JOSEPH RUSS III, President Ferndale BERGER C. BENSON, Vice Presidenf SHERMAN CHICKERING, Member San Mateo Son Francisco TIMOTHY M. DOHENY, Member ELIZABETH L. VENRICK, Member Los Angeles CardifF-by-the-Sea DEPARTMENT OF FISH AND GAME E. C. FULLERTON, Director 1416 9th Street Sacramento 95814 CALIFORNIA FISH AND GAME Editorial Staff ROBSON A. COLLINS, Editor-in-Chief _. Long Beach KENNETH A. HASHAGEN, Editor for Inland Fisheries - Sacramento CAROL M. FERREL, Editor for Wildlife Sacramento ROBERT N. TASTO, Editor for Marine Resources — Menio Park STEVEN N. TAYLOR, Editor for Salmon and Steelhead _ Sacramento HAROLD K. CHADWICK, Editor for Striped Bass, Sturgeon, and Shad ..Stockton 231 CONTENTS Page A Limnological Comparison of the Three Basins of Eagle Lake, California K. R. Huntsinger and Paul E. Maslin 232 Distribution and Status of the Sacramento Perch, Archoplites interruptus (Girard), in California Michael E. Aceituno and Stephen J. Nicola 246 Assessment of Ocean Shrimp Management in California Resulting from Widely Fluctuating Recruitment John J. Geibel and Richard F.* G. Heimann 255 Food of the Copper Rockfish, Sebastes caurinus Richardson, Associated witn an Artificial Reef in South Humboldt Bay, CaHfornia Eric D. Prince and Daniel W. Gotshall 274 Food Habits of the Leopard Shark, Triakis semifasciata, in Elkhorn Slough, Monterey Bay, California Larry G. Talent 286 Notes Addition of Citharichthys fragilis Gilbert to the California Fauna M. James Allen 299 First Records of Notacanth Fish, Notacanthus chemnitzi Bloch, from the Northeastern Pacific Alex E. Peden 304 Simple Container for the Collection and Storage of Otoliths Steven E. Hughes 306 Book Reviews 308 Index to Volume 62 321 232 CaJif. Fish and Game 62 (4) :232-245. 1976. A LIMNOLOGICAL COMPARISON OF THE THREE BASINS OF EAGLE LAKE, CALIFORNIA^ K. R. (GINA) HUNTSINGER Department of Geological and Physical Sciences California State University, Chico Chico, California 95929 and PAUL E. MASLIN Department of Biological Sciences California State University, Chico Chico, California 95929 A comparison of the limnologicol characteristics of the three basins of Eagle Lake, California was conducted during 1971-1972. Light extinction, dissolved oxygen, electri- cal conductivity, chlorophyll a concentration, primary productivity, and plankton were investigated in each basin. On the basis of morphometry, the north and central basins were expected to be more eutrophic than the south basin. They are shallow, do not stratify, and hove smooth, regular shorelines. However, the deeper south basin was less clear, more productive, and hod greater populations of plankton. The discrepancy between expected and ob- served trophic state can best be explained by the additional availability of nutrients in the south basin. INTRODUCTION Studies of multi-basin lakes have indicated that separate basins behave like individual lakes due to differences in morphology, geology, land use, etc. (Thomas 1957; Potash, Sundberg, and Henson 1969; Beeton 1969) and may undergo eutrophication at different rates. Rawson (1955) empha- sized the importance of morphometric factors, particularly mean depth, in determining the productivity of lakes. More recently Schindler (1971) has suggested that the ratio of catchment area of the lake watershed to lake volume is a good prediction of productivity. Eagle Lake, California, a large (12,150 ha, 30,010 acre) but Httle-known lake at 1,557 m (5,100 ft) elevation in the northern Sierra Nevada (Figure 1), is located on a climatic gradient reflected by the neighboring terres- trial vegetation. Although its three basins are at the same elevation, the south basin is surrounded by coniferous forest and the north basin by juniper-sagebrush desert; the central basin straddles the ecotone. The three basins are also quite different in morphometry (Figure 1) ; the south is irregular in outline, relatively deep f mean depth 13.7 m, max. depth 30.5 m) (44.9 ft and 100 ft) with steeply sloping banks and a generally rocky or sandy bottom down to depths of about 10 m (33 ft). The central and north basins, by contrast, are shallow (mean depth 3.4 m and 3.9 m; max. depth 9.0 m and 5.3 m, respectively) (11.2 ft and 12.8 ft; 29.5 ft and 17.4 ft) with gently sloping banks forming regular, saucer-like depressions. In general, the morphometry of the central and north basins is characteristic of older, eutrophic lakes (Hooper 1969) . However, the geology of the area is quite complex; the lake appears to have been modified many times by faulting and vulcanism (Gester 1962) and an accurate description of its history would require deep cores from all three basins. ' Accepted for publication March 1976 LIMNOLOGICAL COMPARISON OF EAGLE LAKE 233 CLEGMOHN CREEK FIGURE 1. Location ond morphometry of Eagle Lake, California. Depth contours in feet. The present study was undertaken to determine if limnological charac- teristics of the three basins reflect these differences in microclimate and/ or morphometry. 234 CALIFORNIA FISH AND GAME METHODS Vertical profiles for light, dissolved oxygen, temperature, and specific conductance were measured potcntiometricalK' at 12 stations during the period of 10-15 August 1971. Vertical light extinction coefficients uere calculated for each station as the slope of the best fitting line to a graph of In light intensity vs. depth (Hutchinson 1957) , excluding measurements within 1 m (3.3 ft) of surface or bottom. During the summer of 1972, weekly measurements of light extinction were made at the 12 sample sites in the lake. Water from the 12 sites was also analyzed weekly for chlorphyll. Chlor- phyll a was determined by the trichromatic method (Strickland and Par- sons 1968) with the correction for degradation products. Water samples were filtered through glass fiber filters (Whatman GF/C) and the filters ground in a teflon tissue grinder to ensure complete extraction of chloro- phyll from the algal cells. Measurements of phytoplankton production were made at the 12 sta- tions within the lake during the period of 28 July to 17 August 1971. The oxygen light and dark bottle method was used with 24-hour in situ incuba- tion of six pairs of bottles at even intervals from top to bottom of the lake. During the summer 1972, weekly net plankton samples were taken at the 12 sites. Diagonal tows were made from bottom to surface using a number 10 net on a Clark-Bumpus plankton sampler. The sampler was pulled vertically at a constant rate from a slowly moving boat to get a uniformly integrated sample from all depths. a. Q FIGURE 2. Distribution of temperature with depth and time in Eagle Lake's south basin. LIMNOLOGICAL COMPARISON OF EAGLE LAKE 235 FIGURE 3. Variation in vertical light extinction and conductivity in Eagle Lake during mid-August 1971. 236 CALIFORNIA FISH AND GAME RESULTS Seasonal isotherms for the south basin show formation of a primary thermocline at 10 to 15 m (33 to 50 ft) about 1 July 1971 (Figure 2) . A weak secondary thermocline formed at 4 to 7 m (13 to 23 ft) during a warm, calm period from 17 to 25 July, but disappeared with the return of winds. The basin started to cool in September and the thermocline moved down until the whole basin was isothermal at 6 C (43 F) on 20 November. The basin then continued to cool uniformly. The shallow north and central basins did not thermally stratify. Temper- ature gradually increased throughout the water column to 26 C (79 F) by 12 August and cooled to 2 C (36 F) by 20 November 1971. The north and central basins had a complete ice cover by mid-December, while the south basin was only partially covered. By mid-February 1972, ice thickness was 32 cm (12.6 inches) in the north and 25 cm (9.8 inches) in the south basin. Temperature measurements in 1972 showed essentially the same heating and cooling patterns as in 1971. Variation in electrical conductivity on 12 to 16 August 1971 ranged from 720 to 839 ja Mhos (Figure 3). The central basin, which receives inflow from the major surface tributary. Pine Creek, is the most dilute and shows a strong gradient along the narrow arm leading toward Pine Creek. The other two basins have uniform values of conductivity throughout, with the north basin being most concentrated. Conductivity measurements taken by the California Department of Water Resources during 1971-72 showed the same pattern. In the summer of 1971 and 1972, the CaHfornia Department of Water Resources (Bryte Laboratory) analyzed water samples from several sta- tions in the three basin for nitrate-, ammonia- and organic nitrogen and ortho- and total phosphate. All chemical determinations were performed according to approved methods. Concentrations were slightly higher in the south basin in 1971 and 1972 (Table 1). The predominance of organic nitrogen in all basins was similar to conditions generally found in Clear Lake, California during the summer (Calif. Dept. Water Resour. 1972). Nitrates occur in Clear Lake in large quantity only during the colder months when algal activity is low. TABLE 1. Average Summer Nutrient Concentrations (ppm) in Eagle Lake, California, 1971-72. NO3-N NH3-N Organic N Ortlio PO<-P Total P-P North Basin.. . . 0.01 0.01 0.01 0.00 0.02 0.07 0.8.5 0.92 0.91 0.01 0.00 0.02 0.0.3 Central Basin 0.04 South Basin 0.06 Dissolved oxygen profiles for the south and north basins in mid-August 1971 and mid-July 1972 (Figure 4) indicate that the shallow north basin remained essentially in equilibrium with air. In the hypolimnion of the south basin, oxygen declined to near zero in midsummer, while areas in the lower epilimnion were often supersaturated due to photosynthetic production. Measurement of primary productivity during late July and early August 1971 (Figure 5) showed that productivity in the south basin was generally higher than that of the north and central basins. The mean productivity per unit volume or per unit area in the south basin was significantly {P = 0.05) higher than either north or central basins, which did not differ significantly from each other. Q. Q •o II • O 20 LIMNOLOGICAL COMPARISON OF EAGLE LAKE GBD- 237 D North basin, 1971 ■ North basin, 1972 O South basin, 197! • South basin, 1972 3 4 5 6 Oxygen/ liter 8 FIGURE 4. Typical dissolved oxygen profiles for Eagle Lake in mid-Augusf 1971 and mid-July 1972. The mean Secchi disk visibility in the south basin was 4.6 ± 0.5 m (15.1 ± 1.6 ft) in 1971 and 4.3 ± 0.5 m (14.1 ± 1.6 ft) in 1972. (In the north and central basins the disk can be seen on the bottom in 5+ m (16.4 ft) of water.) Light extinction coefficients measured at various points in the lake on 14 to 16 August 1971 (Figure 3) shows that the north basin was significantly {F = 0.05) clearer than the south but not enough data were available during this time period to evaluate the central basin. The mean (and 95% Confidence Interval) for extinction coefficients and chlorophyll a at 12 sampling stations during the summer 1972 (Figure 6) shows all stations in the north basin were significantly clearer than stations in the central and south basins. Other variations in clarity were 238 CALIFORNIA FISH AND GAME 0.68 (0.09) FIGURE 5. Distribution of phytoplankton production in Eagle Lake during mid-July through mid-August 1971. LIMNOLOGICAL COMPARISON OF EAGLE LAKE 239 0 68 tO^I6 013 *0 02 0 X 0 64* 048- 0 0 18*^004 07 i 0 34 X 0 ''2 0 * 0 0 5 0 X Chlorophyll a (mg/m ) 0 Extinction Coefficient X lis* 0-32 0 0-214 0- 09 i X 1-24* 0 29 0 0-214 0 06 X I 0"^i03l 0 0 19*003 139 4 0^6 X 0 I 9 40 04 0 084 0-23 0 0 r94 004 FIGURE 6. Distribution of values for light extinction and chlorophyll a in Eagle Loke during the summer of 1972. 240 CALIFORNIA FISH AND GAME \ o Chlorophyceae Myxophyceae - Bacillariophyceae 3000 Phytoplankton / liter FIGURE 7. Mean distribution of the major groups of phytoplankton in Eagle Lake during the summer of 1972. LIMNOLOGICAL COMPARISON OF EAGLE LAKE 241 Zooplankton / liter FIGURE 8. Mean distribution of the major groups of zooplankton in Eagle Lake during the summer of 1972. 242 CALIFORNIA FISH AND GAME not significant although the water seemed to be least clear in the north part of the south basin with a gradual trend toward clearer water in any direction from this center. Chlorophyll was considerably more xariable than clarity but showed a similar trend: the south basin had more chloro- phyll than either of the other basins. While the central basin appeared to have more chlorophyll than the north, the difference was not statistically significant. A statistically significant correlation (r = 0.8455, P = 0.01) ex- ists between phytoplankton biomass and extinction coefficient. Net plankton was collected weekly with a Clark-Bumpus sampler at 12 stations throughout the summer of 1972. Although this sampling proce- dure would not be adequate for nannoplankton, several microscopic anal- yses of water samples failed to show many nannoplankton. The a\erage distribution of the major groups of net plankton (Figures 7 and 8) show greatest populations were in the south basin. Myxophyceae consisted pri- marily of one species, Anabaena flos-aquae. Also present were Microcystis spp., Oscillatoria sp., and Merismopedia tenuissima. Chlorophyceae in- cluded Spirogyra sp., Pediastrum duplex, Staurastrum sp., and Planktos- phaeha gelatinosa. The dominant Bacillariophycean was Fragilaria crotenensis. Gomphonema sp. was present infrequently. Myxophyceae were dominant throughout the lake, although more nu- merous in the south basin than in the north and central basins. In the north basin the predominant bluegreen was M. tenuissima, which appeared late in the summer. Mean density of phytoplankton decreased from the south basin to the north. Zooplankton consisted of two species of Copepoda: Diaptomus sicilis and Cyclops vernalis; four species of Cladocera: Daphnia galeata men- dotae, D. sch0leri, Diaphanosoma leuchtenbergianum, and Leptodora kindtii; and five species of Rotifera: Keratella cochlearis, K. quadrata, Filinia terminalis, Trichocerca sp., and Hexarthra sp. Copepods, primarily D. sicilis, were the dominant zooplankters in all basins. Rotifers were more numerous in the warmer north and central basins than in the south. Cladocerans were never very numerous and were generally restricted to the south basin. The central basin had a slightly greater average number of zooplankton per liter than the south basin. However, zooplankton biomass was greater in the south basin since the high percentage of rotifers in the central basin contributed a small amount to the biomass. Also, since the south basin is much deeper than the other basins, both biomass and number of organisms per unit surface area would be considerably greater there. DISCUSSION Frequent strong winds, predominantly parallel to the long axis of the lake, insure that thermocline formation will be late and at a relatixely great depth, thus preventing the central and north basins from stratifying. These winds might be expected to circulate water from one basin to another but this effect is minimal, due perhaps to the orientation of the straits between basins at a sharp angle relative to the lake's long axis. The variation in conductivity between the three basins and the relatively sharp gradients at basin confluences suggest that the basins are well isolated by circulatory patterns and act effectively as three separate lakes. Volume and surface: volume ratios dominate the physical limnology of the basins. The northern basins warm and cool more rapidly than the deeper south basin. The relatively warm, shallow north basin has a high LIMNOLOGICAL COMPARISON OF EAGLE LAKE 243 evaporation rate but no significant dilution from tributaries, thus it devel- ops a greater salt concentration. Horizontal differences in concentrations of plankton have been attributed to wind action (Langford and Jermolajev 1966) . Wind concentration will not explain the greater abundance of both phytoplankton and zooplankton in Eagle Lake's south basin since prevail- ing winds are primarily from the southwest and observed variations in conductivity indicate that the separate basins do not mix significantly. Schindler (1971) hypothesized that the quantity of nutrients entering a lake are directly proportional to the catchment area (terrestrial portion of the drainage basin + surface area of the lake — A) and inversely proportional to the volume (V) . Thus the level of biological productivity should be proportional to the ratio A/V. A change in morphometry, such as the natural filling of the lake with sediment, would reduce lake volume and increase A/V and the nutrients per unit volume. The ratio A/V calculated for the three basins of Eagle Lake are: north = 0.802, central = 1.976, and south = 0.010. On this basis the north and central basins of Eagle Lake would be expected to be more eutrophic than the south basin. Shallowness, higher summer temperatures, lack of stratification, and deep organic sediments should all contribute to a higher production and more eutrophic characteristics (Rawson 1960). However, the south basin was significantly less clear, more productive of algae, and had higher densities of plankton, all of which indicate more eutrophic conditions (Edmondson 1970). The marked discrepancy between expected and observed trophic status can best be explained by the additional availability of nutrients in the south basin. A number of possible nutrient sources exits. A prehminary hydrologic budget indicates that approximately 40% of inflow enters as groundwater. Chemical analyses show that groundwater in the area has three times the concentration of phosphorus found in surface streams. However, at present the volume of groundwater inflow to the three basins has not been determined and its importance as a nutrient source has not been quantified. Increased human activity may be contributing nutrients to the south basin. Eagle Lake has just recently been "discovered" in terms of recrea- tional use. Visitor use at Lassen National Forest recreational sites has increased each year except 1969 (Table 2) . All campsites are located at the south end of the lake and have pit latrines or septic tank waste disposal. One additional campsite (Bureau of Land Management) at the north end is some distance from the water and relatively unpopular. Boating use has nearly tripled since 1967. Most of the fishing pressure is on the south basin because of the concentration of Eagle Lake's game fish. TABLE 2. Use of Recreational Facilities at Eagle Lake, California. campgrounds 1967 Use 1968 in Visitor Days 1969 1970 1971 Lassen National Forest Eagle Lake marina .. 101,900 4,700 113,000 8,000 104,.30O 7,100 139,100 8,300 141,000 11,400 Historically there may have been a greater inflow of nutrients from the more mesic terrestrial communities surrounding the south basin. Logging activities and two large forest fires in the past 50 years have probably increased the amount of nutrient inflow. Also, drainage from the conifer- 244 CALIFORNIA FISH AND GAME ous forests may contribute organic complexes which serve as chelators and thus increase nutrient availabiHty. Studies at the Hubbard Brook Ecosys- tem have quantified the great effects of deforestation on the export of particulate and dissolved masterials (Bormann et al. 1974). Another possibility is that more efficient nutrient cycling occurs in the south basin. Oxygen depletion in the hypolimnion during thermal stratifi- cation may enhance the release of nutrients from sediments. In lakes with long basins and frequent wind disturbance, nutrient enrichment of the illuminated layer may result from incorporation of hvpolimnetic water into surface wind drift (Mortimer 1969) . Fish and zooplankton may aid in recycling nutrients. During the summer increased water temperature concentrates fish in the hypolimnion, but movement across the thermo- cHne surely occurs. Many genera of planktonic Crustacea and larvae of Chaoborus, a common inhabitant of bottom muds, exhibit vertical diurnal migration (Hutchinson 1967). A similar discrepancy between observed and expected trophic state exists in Clear Lake, California, where the two deeper, semistratified basins are more eutrophic than the shallow one (Home et al. 1972, Home and Goldman 1972, Calif. Dept. Water Resour. 1972). Nutrient recycling occurs at a slower rate in the shallow basin. While this is partly due to the maintenance of aerobic conditions at the sediment-water interface, a fur- ther explanation (which may have great significance for Eagle Lake) is the pattern of sediment deposition in Clear Lake. The upper shallow basin receives most of the sediment inflow. Only the lighter fine particles of inorganic sediments enter the lower basins and this fraction has the great- est capacity to absorb and store nutrients (Hillel 1971) . The relatively low nitrogen sediment deposited in the upper basin appears to interfere with nitrogen recycling. In Eagle Lake the majority of sediment enters the central basin via Pine Creek. An analysis of bottom sediments in the southern basin (Bendixen 1971) shows deposition of large amounts of sand at the northern end of the basin which may have originated in the Pine Creek drainage. Sediments entering the south basin from other sources are transported north by longshore currents. Because of its larger size, sand offers greater resistance to transport and is deposited in the shallow shelf regions. Wave energy erodes and selectively separates out the finer grained sediments, trans- porting them to the deeper portions of the basin. This silty clay material, which appears as a brownish flocculated ooze, is the predominant textural deposit in the south basin at depths greater than 15 m (50 ft) . This suggests that nutrients entering the south basin with sediments are concentrating at depths where anaerobic conditions develop, allowing their release. Further evidence that morphology is a poor indicator of trophic state has been provided by Brylinsky and Mann (1973) in their analysis of International Biological Program data on 43 lakes and 12 reservoirs. They concluded that variables related to solar energy input were quite impor- tant in governing productivity, but morphological factors had little influ- ence. When data from a restricted range of latitude (which would include multi-basin lakes) were considered, factors related to nutrient availability assumed much greater importance. LIMNOLOGICAl COMPARISON OF EAGLE LAKE 245 Acknowledgments We would like to express our gratitude to the Faculty Research Grants Program at California State University, Chico for providing necessary funds and to the faculty and students at the Eagle Lake Field Station for laboratory facilities, equipment, and field assistance. References Beeton, A. M. 1969. Changes in the environment and biota of the Great Lakes, p. 150-187 In Eutrophication: causes, consequences, correctives. Nat. Acad. Sci. Bendixen, Roald Leroy. 1971. An analysis of the bottom sediments of the southern basin of Eagle Lake, California. Master's Thesis, California State University-Chico. 42 p. Bormann, F. H., G. E. Likens, T. G. Siccama, R. S. Pierce, and J. S. Eaton. 1974. The export of nutrients and recovery of stable conditions following deforestation at Hubbard Brook. Ecol. Monog., 44:255-277. Brylinsky, M., and K. H. Mann. 1973. An analysis of factors governing productivity in lakes and reservoirs. Limnol. Oceanogr., 18:1-14. California Department of Water Resources. 1972. Alternative Eel River projects and conveyance routes. Appendix C. Clear Lake water quality. Calif. Dept. Water Resources, Northern District. Edmondson, W. T. 1970. Phosphorus, nitrogen and algae in Lake Washington after diversion of sewage. Science, 169:690-«91. Gester, G. C. 1962. The geologic history of Eagle Lake, Lassen County, California. Occas. Pap. Calif. Acad. Sci., No. 24, p 1-29. Hillel, Daniel. 1971. Soil and water: physical principles and processes. Academic Press, New York. 288 p. Home, Alexander J., J. E. Dillard, D. K. Fujita, and C. R. Goldman. 1972. Nitrogen fixation in Clear Lake, California. II. Synoptic studies on the autumn Anabaena bloom. Limnol. Oceanogr., 17:693-703. Home, Alexander J., and C. R. Goldman. 1972. Nitrogen fixation in Clear Lake, California. I. Seasonal variation and the role of heterocysts. Limnol. Oceanogr., 17:678-692. Hooper, Frank F. 1969. Eutrophication indices and their relation to other indices of ecosystem change, p. 225-235 In Eutrophication: causes, consequence, correctives. Nat. Acad. Sci. Hutchinson, G. E. 1967. A treatise on limnology, vol. II. Introduction to lake biology and the limnoplankton. John Wiley and Sons, Inc., New York. 1115 p. Langford, R. R., and E. G. Jeromolajev. 1966. Direct effect of wind on plankton distribution. Int. Ver. Theor. Angew. Limnol. Verb., 16:188-193. Mortimer, C. H. 1969. Physical factors with bearing on eutrophication in lakes in general and in large lakes in particular, p. 340-370 In Eutrophication: causes, consequences, correctives. Nat. Acad. Sci. Potash, M., S. E. Sundberg, and E. B. Henson. 1969. Characterization of water masses of Lake Champlain. Int. Ver. Theor. Angew. Limnol. Verb., 17:140-147. Rawson, D. S. 1955. Morphometry as a dominant factor in the productivity of large lakes. Int. Ver. Theor. Angew. Limnol. Verb., 12:164-175. 1960. A limnological comparison of twelve large lakes in northern Saskatchewan. Limnol. Oceanogr., 5:195-211. Schindler, D. W. 1971. A hypothesis to explain differences and similarities among lakes in the Experimental Lakes Area, northwestern Ontario. Canada, Fish. Res. Bd., Jour., 28:295-301. Strickland, J. D. H., and T. R. Parsons. 1968. A practical handbook of seawater analysis. Canada, Fish. Res. Bd., Bull., 167. 311 p. Thomas, E. A. 1957. Der Ziirichsee, sein Wasser und sein Boden. Jahrbuch vom Zurichsee, 17:173-208. 246 Calif. Fish and Came 62 (4) : 246-254. 1976. DISTRIBUTION AND STATUS OF THE SACRAMENTO PERCH, ARCHOPLITES INTERRUPTUS (GIRARD), IN CALIFORNIA ^ MICHAEL E. ACEITUNO ^ California State University Department of Biological Sciences Sacramento, California 95819 and STEPHEN J. NICOLA California Department of Fish and Game Inland Fisheries Branch Sacramento, California 95814 California's only native centrarchid is virtually nonexistent in its native habitat: the waters of the Central Valley, the Clear Lake basin, and the Pajaro and Salinas rivers. However, it has been introduced and successfully established in a number of artificial environments and natural waters outside of its native range; thus, it is in no danger of becoming extinct. The history of its decline and transplanting is traced. INTRODUCTION The Sacramento perch is a unique member of the family Centrarchidae. The only native sunfish west of the Rocky Mountains, it was once abundant in the Sacramento-San Joaquin River system and foimd in the neighboring Pajaro and Salinas Rivers systems (Figure 1). It is believed to be a relict of an ancient fauna, probably attaining its original distribution during Miocene time, before the formation of the Sierra Nevada and Rocky Mountain ranges (Miller 1946, 1959). The occurrence of fossil Archoplites in ancient Lake Idaho, and the fact that the Sacramento perch is the only living member of its genus, suggest a former hydrographic connection between the Snake River, or its antecedent, and the Sacramento River drainage (Miller and Smith 1967). A former connection between the Snake River system and the Mississippi River system is suggested by the occurrence of fossil centrarchids of other living genera in the Lahontan basin (Miller 1959) and elsewhere. The Sacramento perch is regarded as the most primitive member of the centrarchid family on the basis of the morphological, osteological, and histological components of the centrarchid lateral line system. However, it has become highly specialized through long-continued isolation and is no longer in the direct line of centrarchid evolution (Branson and Moore 1962) . Despite its unique status as California's only native sunfish, the history of the Sacramento perch generally was one of neglect. It was ignored by a majority of anglers and biologists who preferred to harvest and manage the more familiar and widespread exotic centrarchids introduced from the ' Accepted for publication November 1975. Based on a thesis submitted in partial fulfillment of the requirements for the degree of Master of Science at California State University, Sacramento. » Present address: Bureau of Land Management, Pacific CCS office, P.O. Box 848, Los Angeles, CA. 90053 SACRAMENTO PERCH STATUS 247 LOS ANGELES FIGURE 1. Probable range of Sacramento perch prior to settlement of California. 248 CALIFORNIA FISH AND GAME midwest and east. Consequently, little is known of its life history, biology, and habitat requirements (see Aceitimo 1974 for summary) . Unfortunate- ly, its native habitat has been so irreparably altered that the original ecological role of this species will never be adequately understood. Most populations, both within and outside its native range, now exist in artificial environments. In recent years there has been a renewed interest in the Sacramento perch both as a game fish and as a candidate for a list of endangered species. In 1973 and 1974, as part of a Master's thesis research project supported in part by the California Department of Fish and Game, the senior author studied several populations of Sacramento perch in order to more fully understand its life history and biology. The results of this inves- tigation have been reported elsewhere (Aceituno and Vanicek 1976). During this period the senior author also attempted to determine the present distribution and status of this species in California. These results are presented here. PAST DISTRIBUTION Sacramento perch were first collected from the Sacramento River by Girard (1854) . The exact collection locality is not known but it is assumed that it was somewhere in the lower river area, probably near Sacramento. In the same year, speciments obtained at a San Francisco fish market were described by another author (Ayres 1854). These presumably also origi- nated in the lower Sacramento River, or perhaps the San Joaquin River. Jordan and Gilbert (1895) were the first to collect Sacamento perch from Clear Lake, Lake County, and Snyder (1913) recorded perch from the Pajaro River, a tributary to Monterey Bay. Although Snyder collected extensively in the nearby Salinas River, none were found there until they were collected by Hubbs (1947) from the lower Salinas River in 1946. Hubbs believed their presence in the Salinas was the result of an introduc- tion. Sacramento perch were apparently native to the Salinas River, however, as Follett (1972) found Sacramento perch remains in an excava- tion at Mission La Soledad (1791-1835) along the Salinas River some 48 km (30 miles) upstream from Monterey Bay. In the late 1800's, the Sacramento perch was described as "abundant along the lower courses of the Sacramento and San Joaquin Rivers and in all branches of these rivers that permeate the lowlands. . ." (Lockington 1879). Neale (1931) reported that "in the year 1890, or before the intro- duced fishes became numerous, Tulare Lake in Kings County, Duck, Pros- pect, and Sycamore sloughs in Yolo County, Butte Creek and many other waters of Sutter County were thickly populated with them." Walford (1931) listed its distribution as "Sacramento-San Joaquin Basin, Clear Lake, Kern Lake." He also noted that it was "esteemed by anglers," and that commercial fishing for it was prohibited. Neale (1931) noted that around 1930, 200 Sacramento perch weighing 2V2 to 4 lb apiece were rescued from Lake Chabot, Solano C^ounty, and transported to two lakes near Sacramento. The names of these lakes were not given. The author also stated that it was his intent and that of W. H. Shebley, in charge of the Bureau of Fish Culture of the then Division of Fish and Game, to "propagate and to endeavor to rehabilitate them by stocking. . ." Records of early collection localities for the Sacramento perch are sum- marized bv Rutter (1908), Evermann and Clark (1931), and Hopkirk (1973). SACRAMENTO PERCH STATUS 249 Despite the apparent abundance of the Sacramento perch in the mid- and late-1800's, by the turn of the century it was considered uncommon, even though it was still collected in "marketable quantities" in the Sacra- mento River near Rio Vista (Rutter 1908). Most publications during the first half of the 20th century indicated that the abundance of perch was declining. By the end of the 1940's it was described as "scarce", except in a few isolated localities, and of "minor" importance as a sport fish (Murphy 1948, Curtis 1949). Apparently sometime during this period it was realized, possibly through the efforts of Mr. Shebley and Mr. Neale, that to save this unique fish it would become necessary to undertake a stocking program. The planting records of the Central Valleys State Hatchery in Elk Grove indi- cate that stocking of Sacramento perch began in 1941. Between 1941 and 1955, Sacramento perch propagated at the hatchery were planted in as many as six waters per year, primarily in farm ponds and reservoirs. Plant- ed fish were occasionally procured from rescue operations. In 1955 the records of the Department of Fish and Game indicated that Sacramento perch were present in only 14 localities (Table 1). Of these, all but three (Brickyard Pond, Washington Lake, Clear Lake) were the result of introductions either into artificial environments within its native range, or into natural waters outside of its native range. In addition. Hop- kirk (1973) listed a record of Sacramento perch collected during chemical treatment operations by the Department of Fish and Game (Pintler and Johnson 1958) from the Russian River near Ukiah in 1953, presumably the result of an introduction. TABLE 1. Known Localities of Sacramento Perch in California in 1955, Based on Records of the California Department of Fish and Game Water Alameda Creek Alamo River Brickyard Pond Calaveras Reservoir Clear Lake Duncan Pond Gravel Pit Ponds near Niles Lake Anza Lassotovich Pond Middle Lake Ramer Lake Tevis Ponds Van Vleck Ponds Washington Lake County Source Alameda Calaveras Reservoir Imperial Introduced Sacramento Native Alameda/Contra Costa Introduced Lake Native Mendocino Introduced .Alameda >■ Introduced Contra Costa Introduced Fresno Introduced San Francisco Introduced Imperial Introduced Marin Introduced Sacramento Introduced Yolo Native At this time there was no known population of Sacramento perch within the Sacramento-San Joaquin Delta; although in 1950, 300 adult Sacramento perch had been rescued from a small pond on the floodplain of the Sacra- mento River about V^-mile above the mouth of Steamboat Slough. It is possible that in the 1950's they were present in the Delta, but in such low numbers that they were rarely encountered. Thus, by 1955 the range of the Sacramento perch had been reduced from one that occupied virtually all waters of the Sacramento and San Joaquin valleys, the Clear Lake basin, and the Pajaro and Salinas rivers (Figure 1), to one that consisted of disjunct populations in two valley floodplain lakes (Brickyard Pond and Washington Lake), Clear Lake, several artificial lakes and farm ponds mostly in the Central Coast area, two waters in the Salton Sea area, and possibly the Sacramento-San Joa- quin Delta and Russian River. Except for some of the waters where it was 250 CALIFORNIA FISH AND GAME introduced, it was probably nowhere abundant. Pintler (1957) presented evidence from the Clear Lake sport fishery that shows the Sacramento perch was no longer abundant there in 1955. PRESENT DISTRIBUTION In 1973, the senior author examined the records of the California De- partment of Fish and Game and determined that the Sacramento perch could be found at that time in 34 waters in the State (Table 2) . Only four of these contained Sacramento perch in 1955: Alameda Creek, Calaveras Reservoir, Clear Lake, and Brickyard Pond, now known as Lake Green- haven. The latter two localities are among the three natural waters within its native range known to contain Sacramento perch in 1955. The third, Washington Lake, Yolo County, was lost as Sacramento perch habitat when it was extensively altered during construction of a port and turning basin for ocean-going ships. However, a recent collection of two Sacra- mento perch in the lower Sacramento River by the Department of Fish and Game, and the collection of one perch by students of the University of Cahfornia at Davis in the Yolo Bypass (Dr. Peter B. Moyle, U.C.D., pers. commun.), indicates a residual population may still exist in the lower Sacramento River and upper Delta area. The Clear Lake population ap- parently has been able to maintain itself despite its small numbers. Puck- ett (1972) noted that it was still taken occasionally by sport fishermen, and Moyle (pers. commun.) saw two perch in the catch of a commercial fisherman at Clear Lake in 1974. TABLE 2. Known Localities of Sacramento Perch in California in 1973, Based on Records of the California Department of Fish and Game Water County Abbots Lagoon Marin Alameda Creek Alameda Alta Sierra Ranch pond - Nevada Bisset Ranch pond - Mariposa Calaveras Reservoir — Santa Clara Clear Lake Lake Clear Lake Reservoir Modoc Crowley Lake Mono Fowler Farm pond .- Madera Hamilton Farm pond. Fresno Hedgpeth Farm pond Fresno Honey Lake Wildlife Management Area - - Lassen Lake Almanor Plumas Lake Greenhaven (Brickyard pond) Sacramento Lester B. Hard Ranch pond Napa Little Lake Inyo Lost Ri ver Modoc Martin Ranch pond - Fresno Merle Collins Reservoir Yuba ^Ioon Lake Reservoir - -. Lassen Oca Tathum Farm pond Fresno Pleasant Valley Reservoir Mono Ruth Lake Merced Sacramento River Sacramento San Joaquin Experimental Range pond Madera San Luis Reservoir Merced Sherwood Lake Ventura Shive Farm pond Fresno Sterling Ranch pond Sonoma Tara Mobil Mstate pond Kings Upper Owens River Mono Visalia City Park ponds Tulare West Valley Reservoir Lassen Woodward Park ponds Fresno SACRAMENTO PERCH STATUS 251 The spread of Sacramento perch to additional waters throughout the State since 1955 has been largely the result of transplant efforts of the Department of Fish and Game. From March 1964 through May 1966 Sacra- mento perch were planted 23 times in 15 different waters. Since 1967 planting has been much less intense. Of the 34 known localities of Sacramento perch populations, 11 (32%) are in lakes and ponds in the San Joaquin Valley, 8 (24%) are in waters of the northern California foothills and mountains, 6 (18%) are in waters of the Central Coast counties, and 4 (12% ) are in waters east of the Sierra Nevada. The only waters where Sacramento perch were not deliberately transplanted by Fish and Game personnel are those on the east side of the Sierra Divide: Crowley Lake, Owens River, Pleasant Valley Reservoir, and Little Lake. These populations are probably the result of unauthorized transplanting by private citizens, the original source possibly being Walk- er Lake, Nevada. As these data show, virtually all of the waters where Sacramento perch now exist in CaHfornia are artificial waters (farm ponds, reservoirs) or natural waters into which they have been introduced by man. Although small populations may persist in Clear Lake and the Sacramento River, the species is virtually nonexistent in its native range. During a 1973 survey of endemic fishes in the Sacramento and San Joaquin valleys, no Sacra- mento perch were found in 196 collections from streams tributary to the Sacramento and San Joaquin rivers, oxbow lakes along the Sacramento River, and waters of the Sacramento-San Joaquin Delta (California De- partment of Fish and Game, unpublished data) . In addition, no Sacramento perch have been found during recent inten- sive collecting by the University of California at Davis in the Pajaro River, nor in a small number of collections from the Salinas River (Moyle, pers. commun.). THE DECLINE OF SACRAMENTO PERCH IN ITS NATIVE HABITAT Predation, habitat alteration, interspecific competition for food and space, as well as a reduction in the abundance of native cyprinids have all been suggested as possible causes for the decline of the Sacramento perch (Jordan and Gilbert 1895; Neale 1931; Dill and Shapovalov 1939; Murphy 1948; Mathews 1962; Hopkirk 1973; Moyle, Matthews, and Bonderson 1974) . That the original habitat of the Sacramento perch has been altered is an inescapable fact. Probably no other natural ecosystem in California, ex- cept the Los Angeles plain, has been more intensively disrupted by man's actions than the Central Valley. The clear Sacramento River of a century- and-a-half ago has been transformed to a permanent murky brown. Floods are now controlled, artificial flow regimes have been created, and flood- plains engineered out of existence. How these changes have affected the Sacramento perch is unknown. Being a sight-feeding predator, it may have been adversely affected by a loss of water clarity. Sight-feeding predators such as the striped bass {Mo- rone saxatilis), largemouth bass {Micropterus salmoides), crappies {Pomoxis spp.), and Sacramento squawfish {Ptychocheilus grandis), however, are able to exist under these conditions. Perhaps channelization and the elimination of flooding deprived the perch of spawning and nurs- ery habitat. However, nonnative centrarchids, with apparently similar spawning habitat requirements, are able to successfully maintain them- selves throughout the Central Valley. 252 CALIFORNIA FISH AND GAME We believe a more probable explanation for the demise of the Sacra- mento perch in its native habitat is the establishment of exotic centrar- chids. Murphy (1948) indicated that prcdation on Sacramento perch eggs by introduced species, including centrarchids, was responsible for its de- cline. It is not likely that this factor alone, however, is responsible; many native species, such as sculpins (Cottus spp.) , probably served as efficient predators on Sacramento perch eggs before any exotic species were intro- duced. The inefficient nest constructing and the ineffective guarding behavior of Sacramento perch observed by Murphy (1948) and others is indicative of its general lack of territoriality, aggressiveness, and pugnacity which are characteristic of its eastern cousins. These features must place this species at a serious competitive disadvantage with introduced centrar- chids for food and space in all phases of its life history. Moyle et al. ( 1974) have shown that the food of Sacramento perch is similar to that of blucgill {Lepomis nmcrochirus) and have suggested that bluegill are responsible for the decline of perch in Clear Lake. To test this "competitive interaction" hypothesis, we attempted to cor- relate the abundance of Sacramento perch in 14 waters with that of other species present in the same waters. This included 10 waters listed in Table 2, plus 4 waters where it had been introduced but had not become estab- lished. Ratings of relative abundance of all fish species present were based on field collections by the senior author, and /or on data provided by California Department of Fish and Game. The categories of fish abun- dance were ranked on a scale from 1 to 7 and defined as follows: 1 = Absent: once present but no longer caught, even with great effort. 2 = Rare: caught infrequently and with great effort; only one year class evident. 4 = Common: occurs often in the catch; two or more year classes present. 6 = Abundant: occurs in nearly every sample; several year classes present. 7 = Dominant: occurs in every sample and comprises over 75% of the catch. Ratings of 3 or 5 were assigned to species which were judged to be inter- mediate between rare and common, and common and abundant, respec- tively. Correlation coefficients were calculated for the abundance of Sacra- mento perch compared to that of each of 37 other species. The abundance of 24 species was negatively correlated with Sacramento perch abun- dance. Those species that occurred in at least four locations with Sacra- mento perch are listed in Table 3. Only the black crappie had a significant correlation value (r = -0.5946) at the 95% level of confidence. Other species with high, although not statistically significant, negative correla- tions were the largemouth bass, bluegill, and hitch. Total abundance of Sacramento perch versus all other centrarchids combined was negatively correlated (r = -0.36397). In 5 of 6 waters where Sacramento perch had been stocked at one time, but were now absent or rare, at least one other centrarchid species was now dominant. These data lend support to the hypothesis that the demise of the Sacra- mento perch is the result of the introduction of exotic centrarchids. This is not to say the environmental degradation has not affected the Sacra- mento perch. It is our contention that this has not been the major factor. It should be pointed out that since the arrival of European settlers in California, only one species of fish appears to have become extinct in the SACRAMENTO PERCH STATUS 253 TABLE 3. Correlation Coefficients of Abundance Ratings of Sacramento Perch and Some Select- ed Fishes From 14 Waters in California Species Correlation coefficient Black crappie (Pomoxis nigromaculatus) —0.594551 Largemouth bass (Microptents salmoides) —0.38413 Hitch (Lavinia exilicauda) -0.30959 BlueKiU (Lepomis macrochirus) —0.25781. Rainbow trout (Salmo gairdneri) —0.20177 Brown bullhead (Ictalurus nebulostis) —0.10884 Golden shiner (Notemigonus crysoleucas) —0.05411 Threespine stickleback (daslerosteus aculeatus) —0.04631 Green sunfish (Lepomis cyanellus) 0.01224 Brown trout (Salmo trutta) 0. 13458 Carp (Cijprinus carpio) 0. 13579 Sacramento squawfish (Ptychocheilus grandis) 0. 18887 Tui chub (dila bicolor) . 0.22294 Western sucker (Catostomus occidentalis) 0.30648 Total centrarchid abundance —0.36397 Total fish abundance 0. 35481 ' Significant at p = 0.05. Central Valley. The thicktail chub {Gj'Ja crassicauda) has not been seen since a single specimen was collected in the Sacramento-San Joaquin Delta in 1957.^ Although most native species probably have declined in distribu- tion and abundance from presettlement levels, all indications are that most have remained relatively widespread and abundant. Hopkirk (1973) suggested that the decline of the Sacramento perch may have been due to the decline of the thicktail chub, if the latter were the major prey species of the perch. As he stated, this hypothesis cannot be tested; but given the general lack of diet specialization and characteristic opportunism of most temperate zone piscivorous fishes, this hypothesis would seem to have little merit, particularly in view of the demonstrated ability of this species to adapt to a variety of alien habitats. STATUS Although the Sacramento perch may be near extinction in its native habitat, it has become successfully etablished in a number of waters, not only in California but in other states as well (McCarraher and Gregory 1970) . In California, Sacramento perch are abundant or common in a number of waters (e.g., lakes Greenhaven, Crowley, and Ruth), and are at least maintaining viable populations in others (e.g.. Lake Almanor, Clear Lake Reservoir, and several farm ponds). Thus, this species would not qualify for classification as rare or endangered under California law (California Department of Fish and Game 1973). Although federal law permits a species to be classed as endangered over any significant portion of its range, such as the Central Valley or Clear Lake, it is unlikely that signifi- cant populations of Sacramento perch could ever become reestablished in these habitats. ACKNOWLEDGEMENTS We are grateful to W. I. Follett, R. R. Miller, and P. B. Moyle for helpful comments on an early draft of this paper. ' Another species, the Sacramento tui chub ( Gila bicoior Formosa) , has not been recorded since 1875. There is some question as to its taxonomic validity. 254 CALIFORNIA FISH AND GAME REFERENCES Aceituno, Michael E. 1974. An annotated bibliography of the Sacramento perch, Archoplites interruptus (Girard), in California. Calif. Dep. Fish Game Inland Fish. Admin. Rep., 74-3. 10 p. Aceituno, Michael E., and C. David Vanicek. 1976. Life history studies of the Sacramento perch, Archoplites interruptus (Girard), in California. Calif. Fish Game, 62(1): 5-20. Ayres, Wm. O. 1854. [Descriptions of Sebastes ruber, Sebastcs ruber var. par\us. Sebastes variabilis, and Centrarchus maculosus] The Pacific, 3(46): 182. Branson, Branley A., and George A. Moore. 1962. The lateralis components of the acoustico-lateralis system in the sunfish family Centrarchidae. Copeia, 1962(1): 1-108. Calif. Department of Pish and Game. 1973. Fish and Game Code. State of Calif., Documents Sec, Sacramento, Calif. 339 p. Curtis, Brian. 1949. The warm-water game fishes of California. Calif. Fish Game, 35(4): 255-274. Dill, William A., and Leo Shapovalov. 1939. California fresh-water fishes and their possible use for aquarium purposes. Calif. F'ish Game, 25(4): 313-324. Evermann, Barton Warren, and Howard Walton Clark. 1931. A distributional list of the species of freshwater fishes known to occur in California. Calif. Div. Fish Game Fish Bull., 35. 67 p. Follett, W. I. 1972. Fish remains from Mission La Soledad Cemetery, Mnt-233, Monterey County, California. Monterey Archaeol. Soc. Quart., 1(3): 11. Girard, Charles. 1854. Description of new fishes collected by Dr. A. L. Heermann, naturalist attached to the survey of the Pacific Railroad Route, under Lieut. R. S. Williamson, USA. Proc. Acad. Nat. Sci. Phila., 7: 129-140. Hopkirk, John David. 1973. Endemism in fishes of the Clear Lake region of Central California. Univ. Calif. Press, Berkeley. 135 p. Hubbs, C. 1947. Mixture of marine and freshwater fishes in the lower Salinas River, California. Copeia, 1947(2): 147-149. Jordan, David Starr, and C. H. Gilbert. 1895. List of the fishes inhabitating Clear Lake, California. U. S. Fish Comm. Bull., XIV (1894): 139-140. Lockington, W. N. 1879. Report upon the food fishes of San Francisco. Calif. Dep. Fish Game Biennial Rep., 1878-9. 63 p. Mathews, Stephen B. 1962. The ecology of the Sacramento perch, Archoplites interruptus. from selected areas of California and Nevada. M. A. Thesis, Univ. Calif., Berkeley. 93 p. McCarraher, D. B., and Richard W. Gregory. 1970. Adaptability and current status of introductions of Sacramento perch, Archoplites interruptus, in North America. Amer. Fish Soc. Trans., 99(4) : 700-707. Miller, Robert Rush. 1946. The need for icthyological surveys of the major rivers of Western North America. Science, 104 (2710): 517-519. 1959. Origin and affinities of the freshwater fish fauna of Western North America. Pages 187-222 in Zoogeography. Amer. Assoc. Adv. Sci. Publ., 51 (9158). Miller, Robert Rush, and G. R. Smith. 1967. New fossil fishes from pliopleistocene Lake Idaho. Univ. Mich. Mus. Zool. Occ, Pap. 654. 23 p. Moyle, Peter B., Stephen B. Mathews, and Noel Bonderson. 1974. Feeding habits of the Sacramento perch, Archoplites interruptus. Amer. Fish Soc. Trans., 103(2): 399-402. Murphy, Garth I. 1948. A contribution to the life history of the Sacramento perch (Archoplites interruptus) in Clear Lake, Lake County, California. Calif. Fish Game, 34(3): 93-100. Neale, George. 1931. Sacramento perch. Calif. Fish Game 17(4): 409-411. Pintler, Herbert E. 1957. A summary of the 1955 Clear Lake fishery. Lake Count\ Calif. Dep. P'ish Game Inland Fish. Admin. Rep. 57-27. 14 p. Pintler, Herbert E., and William C. Johnson. 1958. Chemical control of rough fish in the Russian River drainage, California. Calif. Fish Game, 44(2): 91-124. Puckett, Larry K. 1972. Estimated angler use and success at Clear Lake, Lake County, California in 1969. Calif. Dep. Fish Game Envir. Serv. Admin. Rep., 72-1. 27 p. Rutter, Cloudslev. 1908. The fishes of the Sacramento-San Joaquin Basin, with a study of their distribution and variation. U. S. Bur. Fish. Bull., XXVTI (1907): 103-152. Snyder, J. O. 1913. The fishes of the streams tributary to Monterey Bay, California. U. S. Bur. Fish. Bull. XXXII (1912): 47-72. Walford, Lionel A. 1931. Handbook of common commercial and game fishes of California. Calif. Dep. Fish Game, Fish Bull. (28): 1-183 p. 255 Calif. Fish and Game 62 (4) : 255-273. 1976. ASSESSMENT OF OCEAN SHRIMP ^ MANAGEMENT IN CALIFORNIA RESULTING FROM WIDELY FLUCTUATING RECRUITMENT JOHN J. GEIBEL AND RICHARD F.G. HEIMANN Operations Research Branch California Department of Fish and Gome The ocean shrimp fishery off California has experienced large variations in annual landings and catch rates that apparently result from fluctuations in recruitment rather than from changes in availability. These fluctuations occur frequently and with a magni- tude such that the establishment of a constant annual catch quota is undesirable, while fluctuating catch quotas are difficult to determine accurately. However the occurrence of large numbers of 1 -year-old females in most year classes combined with the low exploitation rates on 1 -year-olds should insure an adequate spawning stock, under present conditions in the fishery, should the catch quota be eliminated. INTRODUCTION In the early 1950's, the California Department of Fish and Game discov- ered and explored several ocean shrimp, Pandalus jordani, beds off of central and northern California. In 1952, regulations governing the poten- tial shrimp fishery were established; during the same year, the first com- mercial landings of ocean shrimp were made in California (Dahlstrom 1973). Since then, shrimp landings have been sampled during all fishing seasons yielding an excellent series of catch data. In addition, several research cruises have been made to obtain population estimates (Abram- son 1968; Gotshall 1972) . With this data, the California Department of Fish and Game attempted to manage the ocean shrimp resource on a sustaina- ble yield basis. Present regulations include an annual catch quota, mini- mum mesh size, and a closed season. The California Fish and Game Commission set an annual quota each year since 1952 (Dahlstrom 1961, 1970, 1973). In early years of the fishery, quotas were set for each area at one-fourth of the estimated shrimp bi- omass on each bed. Despite the rather conservative fishery, landings fluc- tuated wildly on all but the Area A bed (Figure 1) . This is the largest bed and consistently produces the bulk of the shrimp landed in California (Dahlstrom 1973). The extreme fluctuations in landings that have occurred in three of the four areas have been attributed to natural variations in shrimp abundance which indicated that equilibrium yields were unrealistic for smaller beds. As a result, quotas have remained at the 1962 levels in all areas except Area A (Dahlstrom 1973). In Area A, considerable effort has been directed at applying the Schaef- er stock production model (Schaefer 1954) to the shrimp fishery. Abram- son and Tomlinson (1972) obtained what appeared to be a satisfactory fit of the model using catch and effort data through 1969, and proposed a management scheme based on this model. However, this management scheme has broken down as data from the last few years has become available. As a consequence, we undertook a detailed review of the Area ' Accepted for publication April 1976. 256 CALIFORNIA FISH AND GAME Shrimp beds OPIGEON POINT Area C I POINT CONCEPTION to Mexican border FIGURE 1. Ocean shrimp regulated areas and location of shrimp beds. OCEAN SHRIMP MANAGEMENT 257 = 4 — o 0. z o < o FIGURE 2. Annual combined California and Oregon landings of shrimp from Area A and annual landings OS estimated by GENPROD. A shrimp population dynamics in 1973. We believe this analysis has pro- duced a new understanding of the Area A shrimp population, and an explanation of the failure of a management scheme based on the stock production model. APPLICATION OF THE YIELD MODEL TO SHRIMP In hopes of finding a reliable, relatively inexpensive way of managing the Area A fishery through an annual quota, Abramson and Tomlinson (1972) fit Pella and Tomlinson's (1970) modificationof the Schaefer model to the catch and effort data for the Area A bed using the program GEN- PROD developed by Pella and Tomlinson (1970) . Although the computer program used is capable of fitting a series of curves, the nature of the data precluded considering anything other than the simple parabola. The program operates by making a patterned search through a wide range of possible parameters. The observed effort and a set of parameters are used to develop an expected catch history. This expected catch history is then compared to the actual catch history using a least squares tech- nique. The program ends when a set of parameters is found that mini- mizes the sum of squares of the deviations. The fit between observed and expected catch has always been reason- able (Figure 2). Even though some large deviations occurred, the model appeared to reflect the fishery rather well. Abramson and Tomlinson's (1972) fit through 1969 depicted a population that was capable of yielding an equilibrium catch of 2.5 million pounds from a stock of 4.8 million pounds (Figure 3) . The stock size at the beginning of the 1970 season was predicted to be 7.1 million pounds. The management strategy proposed by Abramson and Tomlinson was to fish at a rate above that required to take the maximum equilibrium yield until the population was brought down to optimum size. They deemed it advisable to bring the stock down gradually over a period of years to preclude developing undesirable instability in the population. The quota for 1970 was calculated as 3.4 million pounds. 258 CALIFORNIA FISH AND GAME It should be mentioned that the data set was far from ideal. Two assump- tions inherent in the model are that catch per unit of effort accurately reflects population size, and that population size is the only factor in- fluencing the productivity of the stock. However, shrimp do not school in the same way each year or even each week, and a dense school u ill show a higher catch per unit of effort than the same amount of shrimp in a larger, less dense school. In addition, the environment will influence pro- ductivity by affecting growth or recruitment. These factors caused a wide scatter in the data points and, with only 16 data points originally available, caused very unstable estimates of the model parameters. Finally, all obser- vations were from stock sizes calculated by model to be above optimum density on the right side of the production curve. Trying to define the top of a parabola from this kind of data is risky business at best. On the other hand, it was to be expected that estimates would improve as time went on. A new point would be added each year. These points would be from populations closer to the optimum size and provide a better definition of the whole relationship. Adding data for 1970 and 1971 caused no insurmountable problems. The estimate of the maximum equilibrium yield fluctuated somewhat, ending up at 2.9 million pounds after the 1971 data was added. This seemed well within reason, although the data set still lacked stability. Simulations of the 1972 season showed relatively large changes in the parameter estimates could be expected for relatively small deviations of catch per unit of effort from the expected. Adding data for 1972 caused problems, however. The year was charac- terized by a strong year class passing through the fishery as well as above average concentrations of shrimp. This combination produced a high catch per unit of effort and resulted in a much stronger estimate of stock 1 \ ! 1972-73 197 1 1 97 0 \. 19 6 9 10 POPULATION SIZE FIGURE 3. Equilibrium yield curves generated by GENPROD for the years 1969 through 1973. Yield and population size in millions of pounds. OCEAN SHRIMP MANAGEMENT 259 size than would have been predicted by the model. Because the 1972 data represented a large amount of catch and effort, it had a large effect on the fitting procedure. As a consequence, the estimate of maximum equilib- rium yield more than doubled to 6.5 million pounds (Figure 3). This representation of the stock was inconsistent with what had been learned about the resource from past cruises and observations of the fishery. The model thus provided little information for setting the 1973 quota. Conse- quently the quota was left at the 1972 level. We hoped 1973 data when run through the model might bring the parameters back into line with the pre-1972 data. However, this did not happen. The 1973 fishery was poor, with no large concentrations of shrimp on the Area A bed; while off of central Oregon, good concentrations of shrimp attracted many of the northern California fishermen. As a conse- quence, catch and effort were both low, while catch per effort remained reasonable, producing a weak data point that had little influence on the whole series of data. The parameters thus did not return to pre-1972 levels. GENERALIZED CATCH EQUATION Abramson and Tomlinson (1972) had used the generalized Murphy catch equation to analyze aged catch data and had obtained fair agree- ment between the estimates obtained from the Murphy method and those produced by the Schaefer yield model. We have used the Murphy method to extend the parameter estimations of Abramson and Tomlinson (1972) for the shrimp population in Area A. The generalized Murphy catch equation (Tomlinson 1970) uses age structured catch data and an average instantaneous natural mortality rate to compute population size in numbers, instantaneous fishing mortality rates, and exploitation rates for a single cohort. The age structured catch data (Table 1) were derived from the commercial shrimp landings using methods described by Abramson and Tomlinson (1972) and form a con- tinuation of their Table 2. In fitting this data to the generalized Murphy catch equation, we have also used the methods of Abramson and Tomlinson (1972) so that the fishing mortahty rates (Table 2) , the exploitation rates (Table 3) , and the biomass and catchability coefficient, q, estimates (Table 4) are extensions of Tables 5, 6, anjd 7 in their publication. We have rerun part of the 1967 and 1968 data using the additional fishing seasons available to us on the 1966 and 1967 year classes to improve the estimates made by Abramson and Tomhnson (1972). For this reason, these tables begin with 1967 in- stead of 1969. For brevity we have not included the original tables which go back to 1955, and anyone interested in the early data or in a detailed discussion of the methods used to obtain the parameter estimations should consult Abramson and Tomlinson (1972) . A number of the figures present- ed in this paper include data taken from Abramson and Tomlinson (1972) for years prior to 1967. We have adjusted mortality rates so as to hold q fairly constant through- out the period as did Abramson and Tomlinson (1972) . In maintaining an average q of about 8.5 X 10"^, we are assuming that variations in total catch and catch per effort between different cohorts primarily reflect real changes in abundance and not changes in availability. Several independ- ent sources of data tend to support this assumption. 260 CALIFORNIA FISH AND GAME TABLE 1. Aged Catch and Cateh-Per-Effort (C.P.E.) Statistics for Area A, 1969-1973 (Pounds and Numbers in Thousands). Season Montli Age group Relative frequency Average weight C.P.E. numbers Pounds Numbers 1969 May I II III .527 .4r)2 .021 .0048 .0109 .0155 78.1 07.0 3.1 364.7 716.9 47.4 70,753 65,830 3.058 June I II III .574 .412 .014 .0050 .0117 .0159 35.3 25.3 .9 470.3 790.8 30.5 94.383 07,745 2,302 July I II III .005 ..S21 .014 .0052 .0121 .0108 51.2 24.7 1.1 277.2 315.8 19.0 53.721 25,932 1,131 Aug. I II III .820 .107 .007 .0050 .0120 .0104 62.2 12.6 .5 37.7 16.3 .9 6,724 1.359 57 1970 May I II III .153 .783 .004 .0040 .0080 .0147 9.0 46.0 3.8 51.2 493.6 09.1 11.234 57.490 4,099 June I II III .264 .721 .015 .0053 .0095 .0177 20.5 50.0 1.2 153.8 754.2 29.1 28,973 79.127 1.646 July I II III .220 .771 .008 .0000 .0098 .0159 21.0 73.7 .8 303.2 1577.1 20.7 46,149 161,733 1,678 Aug. I II III .238 .753 .009 .0077 .0099 .0108 20.9 06.1 .8 97.5 394.5 8.0 12,014 39,909 477 Sept. I II III .238 .753 .009 .0080 .0101 .0170 13.0 41.1 .5 6.3 23.3 .5 728 2,304 28 1971_ June I II III .334 .635 .031 .0038 .0107 .0135 14.1 20.9 1.3 71.5 385.0 23.5 18,757 35,022 1,741 July I II III .334 .050 .010 .0044 .0114 .0202 16.7 32.8 .5 162.2 816.8 22.0 30,492 71,576 1,091 Aug. I 11 III .711 .284 .005 .0049 .0130 .0179 47.1 18.8 .3 540.3 596.7 13.8 109,755 43,840 773 Sept. I II III .834 .104 .002 .0002 .0142 .0150 52.7 10.3 .1 421.3 191.0 2.5 68,328 13,436 164 Oct. I II III .870 .124 .0068 .0137 71.1 10.1 299.9 86.1 44,296 6,270 1972. Mar. I II III .010 .880 .110 .0020 .0007 .0120 1.1 94.1 11.8 1.5 343.8 80.0 584 51,358 0,420 Apr. I II III .044 .802 .094 .0027 .0009 .0130 4.1 81.7 8.9 5.0 281.8 57.0 2,064 40.758 4,443 May I II III .055 .800 .085 .0029 .0075 .0155 4.4 70.0 6.9 9.4 377.2 77.4 3,189 50,299 4,983 June I 11 III .072 .850 .072 .0034 .0080 .0155 5.3 62.9 5.3 8.3 234 . 3 38.4 2,469 29,442 2,470 July I II in .140 .822 .038 .0054 .0093 .0153 9.2 54.1 2.4 00.7 014.4 45.9 11,285 06,125 2,995 Aug. I II III .282 .097 .021 .0053 .0097 .0173 18.4 45.4 1.4 112.3 500.9 20.8 21,072 52,101 1,551 OCEAN SHRIMP MANAGEMENT 261 Season Month Age group Relative frequency -Average weight C.P.E. numbers Pounds Numbers Sept. III .308 .010 .007 .0000 .0110 .0170 25.2 42.3 .5 147.2 412.5 7.3 22,206 37,346 430 Oct. III .400 .584 .007 .0009 .0122 .0203 32.2 40.5 .5 128.2 327.4 6.4 18,612 26,818 315 1973 . Apr. III .180 .730 .084 .0053 .0109 .0140 11.0 45.1 5.1 34.8 294.9 44.9 6,603 27.055 3,080 May III .357 .014 .029 .0054 .0107 .0151 21»1 36.3 1.7 58.3 200.8 13.4 10,893 18,736 888 June III .552 .438 .010 .0002 .0120 .0182 42.4 33.0 .8 21.6 35.0 1.2 3.507 2,783 60 July III .484 .509 .007 .0009 .0132 .0185 30.1 31.7 .4 289.9 580.0 9.7 41,872 44,047 523 -Aug. III .459 ..533 .008 .0078 .0144 .0230 13.5 15.7 .2 50.0 121.3 3.1 7,282 8,437 131 Sept. III .459 .533 .008 .0078 .0144 .0230 7.1 8.3 .1 4.3 9.2 .2 553 040 8 Post-season shrimp cruises have been made every year from 1966 through 1972 except for 1970. One of the objectives of these cruises was to assess the incoming year class. In 1966 and again in 1968, large numbers of age 0 shrimp were found on the Area A bed; while in 1967, 1969, 1971 and 1972 lower numbers of age 0 shrimp were observed on the bed (Dahl- strom pers. commun.) . This corresponds quite well with the biomass esti- mates for these year classes as 1-year-old shrimp (Table 4). Another independent estimate of the incoming year class can be ob- tained using an index derived from the number of age 0 shrimp found in hake stomachs (Gotshall 1970) . Although this method is fraught with possi- ble bias and cannot give absolute values of the size of the incoming year class, it does appear to be a fair index to the relative strength of the incoming year class. In the period from 1966 through 1973, the largest year class as indicated from biomass estimates was the 1968 year class which coincides with the largest hake stomach index (Table 5). Likewise the hake stomach index for the two poor year classes of 1971 and 1972 averaged about one-tenth of the 1968 index. Growth is another factor that apparently reflects year class abundance. In most years, the average weight of age I shrimp (Table 1) is inversely related to the number of shrimp in that year class. This relationship is discussed in more detail in another section. SEXUAL DEVELOPMENT Prior to examining certain aspects of the population dynamics of Area A shrimp, a brief review of their unusual sexual development may be useful. Adult ocean shrimp mate in the fall when the males transfer their sperm to the females where it is held until the eggs are spawned and fertilized. The fertilized eggs are carried externally by the female for several months until the larval shrimp hatch in March or early April. The young shrimp 262 CALIFORNIA FISH AND GAME are pelagic in the early stages but begin settling to the bottom by mid- summer or fall when a few individuals show up in the commercial landings as the age 0 shrimp (Dahlstrom 1973). The following spring and summer these shrimp, which are now into their second year (age I shrimp) begin developing into either males or females and most if not all will be sexually mature by the fall or early winter. These age I shrimp will spawn in the fall at about 18 months of age and the females will carry eggs until they hatch in the spring. The males begin to change into females sometime after the fall mating and by the following fall will function as mature females. In California it appears that most, if not all age I males, will become females by the following spawning season. However, in the northern portion of their range where growth rates are slower, shrimp appear to mature at a later age, and age II males can occur (Dahlstrom 1970). Once an ocean shrimp becomes a female, it will continue to function as a female. TABLE 2. Monthly Instantaneous Fishing Mortality Coefficients for Area A, 1967-1973. Month Age Year I II III 1967 Mar. Apr. .0014 .0069 .0041 .0206 .0261 .0676 May .0017 .0056 .0203 June .0462 .1900 .1939 July .1115 .3975 .3468 Aug. .0648 .1622 .2391 Sept. .0148 .0490 .0761 Oct. .0032 .0151 .0270 Mean .0313 .1050 .1246 19G8 May June .0130 .0270 .2409 .5049 .7600 .4384 July .0288 .5272 .2394 Aug. .0096 .4326 .7195 Sept. .0011 . 1466 .1591 Oct. .0002 .0188 .0200 Mean .0133 .3118 .3894 1969 May June .0371 .0536 .3600 .6950 .4054 .5510 July .0302 .5690 .5226 Aug. .0053 .0465 .0401 Mean .0330 .4176 .3798 1970 - May June .0075 .0221 .1402 . 2600 .6590 .4607 July .0407 1.1891 1.1034 Aug. .0130 1.0118 1.0390 Sept. .0008 .1222 .1299 Mean .0168 .5459 .6784 1971 - June July .0093 .0200 .1302 .3767 .3401 .3374 Aug. .0728 .3798 .3862 Sept. .0545 .1741 .1201 Oct. .0417 .1054 Mean .0398 .2332 .2368 1972 Mar. Apr. .0005 .0023 .0945 .0926 .2324 .2284 May .0038 .1451 .3917 June .0034 .1088 .3123 July .0179 .3435 .6914 Aug. .0386 .4521 .8696 Sept. .0478 .6181 .5702 Oct. .0475 1.1678 .9999 Mean .0198 .3778 .5370 1973 Apr. May .0087 .0163 .1561 .1414 .7423 .4454 June .0060 .02.58 .0484 July .0841 .6230 .5800 Aug. .0172 .2080 .2522 Sept. .0014 .0200 .0200 Mean .0223 .1958 .3482 OCEAN SHRIMP MANAGEMENT 263 ESTIMATING THE PERCENTAGE OF AGE I FEMALES In ocean shrimp, the percentage of age I females in a year class can be estimated directly from the sex composition of age I shrimp at the end of the fishing season. However, male shrimp are smaller than female shrimp and undoubtedly have a higher escapement rate than do females; this may result in an overestimation of the percentage of female shrimp. In addi- tion, the timing of the sexual change may vary from season to season. If the change is well under way by the end of fishing season, the estimates will be accurate, but if the change is later or the fishing season closes early, females may be underestimated. The percentage of age I females also can be estimated from the sex composition of these same shrimp at age II early in the following fishing season. These shrimp are larger and almost fully recruited to the fishery; therefore, males will be caught at about the same ratio as females. Howev- er, if some individuals that previously functioned as males change to females before the beginning of the fishing season, the age I females will be overestimated. TABLE 3. Monthly Exploitation Rotes for Area A, 1967-1973. Year 1967. 1968. 1969. 1970. 1971. 1972. 1973. Month Age I II III Mar. .0014 .0022 .0277 Apr. .0064 .0107 .0703 May .0017 .0029 .0219 June .0425 .0895 .1929 July .0996 .1554 .3323 Aug. .0591 .0569 .2622 Sept. .0138 .0166 .0983 Oct. .0029 .0050 .0370 May .0121 .2023 .1767 June .0251 .3755 .0676 July .0267 .3880 .0281 Aug. .0090 .3324 .0552 Sept. .0011 .1287 .0081 Oct. .0001 .0176 .0009 May .0342 .2858 .3152 June .0493 .4753 .4013 July .0333 .4111 .3857 Aug. .0049 .0429 .0370 May .0070 .1235 .4577 June .0205 .2205 .3494 July .0377 .6630 .6366 Aug. .0121 .6058 .6150 Sept. .0008 .1085 .1150 June .0086 .1151 .2727 July .0191 .2969 .2708 Aug. .0662 .2988 .3031 Sept. .0500 .1510 .1067 Oct. .0386 .0945 -- Mar. .0005 .0850 .1900 Apr. .0021 .0836 .1929 May .0037 .1276 .3066 June .0032 .0973 .2535 July .0166 .2748 .4737 Aug. .0356 .3442 .5522 Sept. .0441 .4371 .4118 Oct. .0436 .6567 .6016 Apr. .0081 .1364 .4973 May .0152 .1245 .3402 June .0056 .0240 .0445 July .0760 .4399 .4173 Aug. .0162 .1772 .2106 Sept. .0014 .0187 .0187 264 CALIFORNIA FISH AND GAME TABLE 4. Ocean Shrimp Population Biomass in Thousands of Pounds by Age and Month for Area A Ages Est. Year Month I II III Total q X 10« 1967 Mar. Apr. 7,251 0,710 1,311 1,235 334 315 8.896 8,260 59 66 May 0,404 1,177 274 7.915 59 June 6,417 993 205 7,015 83 July 0,031 090 144 0,805 123 Aug. 5,515 501 104 (i,120 94 Sept. 5.226 420 89 5,735 57 Oct. 4,884 402 92 5,378 60 1968 May 0,002 2,433 131 8,500 107 June 5,702 1,.>14 GO 7.312 235 July 5,418 877 44 0,339 169 Aug. 4,785 479 24 5,288 110 Sept. 3.582 283 10 3,875 151 Oct. 3.515 224 9 3.748 163 1969 -- May 9.900 1,991 117 12.008 95 June 8,796 1,140 00. 10,002 49 July 7.750 552 30 8,344 70 Aug. 7,253 350 22 7,025 62 1970.. May June 0,921 0,970 3,525 2,828 105 03 10,551 9.801 46 07 July 7,402 1,333 24 8,819 98 Aug. 7,514 390 8 7,912 105 Sept. 7,391 190 4 7.585 71 1971 June 7,740 2,931 09 10,740 34 July 7,832 2,1 GO 05 10,003 46 Aug. 7,388 1,570 30 8,994 55 Sept. 7,777 1 ,095 20 8,892 53 Oct. 7,209 813 17 8,039 77 1972 Mar. Apr. 2,717 2,499 3,045 3,032 348 253 0,710 5,784 116 120 May 2,374 2,598 197 5,109 125 June 2.459 2,103 123 4,745 127 July 3,428 1,791 GO 5,285 112 Aug. 2,902 1,118 31 4,051 139 Sept. 3,070 005 13 3,748 171 Oct. 2,714 280 7 3,001 267 1973 Apr. May 4,049 3,614 1,889 1,417 00 30 5,998 5,001 104 104 June 3,039 1,358 25 5,022 139 July 3,437 932 17 4.380 145 Aug. 3.273 584 12 3,809 87 Sept. 2.875 401 9 3.345 53 TABLE 5. Numbers of Age 0 Shrimp Found in Pocific Hake Stomachs by Year from July Through October Year Number of stomachs examined Empty* Number of shrimp per stomach 1965 390 880 435 324 977 370 339 407 280 08 115 82 20 260 03 45 59 50 0.22 1966... 1.29 1907 0.11 1908 1.32 1909 0.09 1970. 0.82 1971 0.17 1972 0.05 1973 1.13 * Empty stomachs not included in calculations. OCEAN SHRIMP MANAGEMENT 265 We have used both the sex ratio of age I shrimp and the sex ratio of the same year class as age II shrimp to estimate percentage of age I females in that year class. The sex composition of the landings for each month of the fishing season was plotted for a year class as age I and age II. A straight line interpolation was made across the closed season and the January value was the value used as the estimate of the percentage of age I females (Table 6). All year classes had a higher percentage of females at the beginning of their 3rd year than at the end of their 2nd year, except for the 1968 year class which went from about 63% females at age I to about 40% females at the beginning of the next fishing season. The 1968 year class exhibited less growth at age I than any other year class on record. This could have lead to the males being much less vulnerable to the fishery than usual, and caused a large overestimate of the age I females. Under the circumstances, it seems better to use the observed percentage at age II rather than the interpolated value for 1968. TABLE 6. Percentage of Age 1 Femal Across the Closed Season es by Year Class Obtained from a Straight L ne Interf >olation Year class 1963 19G4 1905 1966 1967 1968 1909 1970 1971 1972 Percentage - 47 58 37 65 55 48 55 42 42 65 It is likely that the straight line interpolation across the closed season overestimates age I females as do the other methods, but the values pool all the available information and tend to fluctuate less than values derived from only one season. Using this method, estimates of age I females for year classes since 1963 have varied from a low of 37% for the 1965 year class to a high of 65% for the 1966 and 1972 year classes and averaged about 50%. Comparable data for seasons prior to 1963 were not available. The mechanism regulating sexual development is unknown. There are indications that sex change in Pandalus borealis is under hormonal control (Allen 1959) . Similarly, Rasmussen (1953) was able to predict the percent- age of immature, males, and females in Pandalus borealis based on size range of age groups at the beginning of the breeding season. In Pandalus jordani, sex composition appeared to be related to the size of age I shrimp. Consequently, we calculated a least squares regression using the percentage of age I females (Table 6) as the dependent variable and the condition index (Table 7), which is derived from the average weight of age I shrimp in June and July, as the independent variable (Figure 4). TABLE 7. Condition Index (Q) by Year (i) from 1955 Through 1973 Year Ci Year Ci Year Ci Year Ci 1955 1950 .92 .93 1.10 .99 1.17 1900 1901 1902 1903 1904 .96 1.03 .94 .85 1.28 1965 1900 1907 1908 1969 .95 1.05 1.08 1.13 .93 1970 1971 1972 1973 1.09 .75 1957 1958 1959 .78 1.22 266 CALIFORNIA FISH AND GAME The slope of the regression line was positive (.266) showing that year classes with larger age I shrimp tend to have a higher percentage of age I females. However, the correlation coefficient was only .48, indicating that approximately 23% of the difference between year classes in the percentage of age I females can be related to the average size of shrimp in those year classes. Consequently, although the size of age I shrimp may be an indication of the percentage that will function as females in the fall, considerable variation is evident between year classes. Whether this varia- tion reflects the effect of factors other than size of age I shrimp or may actually be an artifact reflecting differences between the sex composition of shrimp landings and that of the population is not known. 40 80 120 CONDITION INDEX (x 100) 160 FIGURE 4. Least squares regression with the condition index as the independent variable and percentage of 1 -year-old female shrimp as the dependent variable. However, the advantage to the population in having the percent of age I females increase as the average size of individuals in the year class increases is readily apparent. Year classes with large numbers of shrimp generally grow more slowly than year classes with lower numbers of shrimp, probably reflecting the effect of intraspecific competition. Be- cause weaker year classes grow more rapidly, a greater percentage will OCEAN SHRIMP MANAGEMENT 267 function as age I females. Consequently, fluctuations in spawning biomass will be of a lower amplitude than variations in recruitment. This may be of considerable significance in Area A when the high natural mortality and the intense fishery result in low numbers of age II and age III shrimp. IMPLICATIONS OF AGE I FEMALES ON SPAWNING STOCK Quantifying the spawning stock is important in the management of a fishery. When the sex ratio of a population is stable, the spawning stock size can be calculated from age structured biomass estimates and age at maturity data. Estimations of spawning stock size for ocean shrimp are more difficult because sex ratios can change with each year class. Usually the ratio of males to females in age I shrimp Has been near 50:50 but has ranged from a low 35:65 to a high 63:37 (Table 6) . During this same period, the fall biomass of age I shrimp has averaged over 85% of the combined fall biomass of age I and older shrimp. At a low value of 37% females, the age I shrimp furnished 68% of the spawning female biomass; while in an average year, age I females have contributed over 74% to the spawning female biomass. In recent years, at these levels, age I females have been the major component of the spawning stocks of shrimp on the Area A bed and must be taken into account in any studies of spawning stock size. SPAWNER-RECRUIT RELATIONSHIP Female spawning biomass consists of age I females and all older shrimp. Abramson and Tomlinson (1972) used a mean value of 33% to predict the biomass of age I shrimp functioning as females. However they could not determine a realistic spawner-recruit relationship. Because the percent- age of age I females varies considerably from season to season, it would seem that any spawner-recruit relationship may be masked by using a constant value. As a result, we examined the spawner-recruit relationship using the estimates of age I females by year class from 1963 through 1970 to compute the total female spawning biomass for the years 1964 through 1971. The six year classes from 1965 to 1970 show a reasonable relationship with spawning biomass (Figure 5). The next 2 years were years of poor recruitment despite a large spawning biomass, and no relationship is dis- cernible for the 8-year period. Consequently, the refinement of the data and the inclusion of 4 new years have still left us without a meaningful spawner-recruit relationship. Despite the lack of a clear spawner-recruit relationship, there is a tend- ency for year class strength to alternate (Figure 6). In the early years of the fishery, the stronger year classes coincided with odd years. However, the 1963 year class was small, while the 1964 year class became the strong- er. From 1964 through 1970, the even years have produced the strong year classes. However, with the poor year class in 1972, we appear to have had another reversal. This alternation of strong and weak year classes is not fully explainable at present but is apparently related to the heavy fishery on older shrimp coupled with the phenomenon of age I females. This alternation of year classes would seem to indicate that the number of older shrimp affects survival of the incoming year class. 268 CALIFORNIA FISH AND GAME a. E 0 rt rt ' ' -I — I 05 -r -H (M lO - I --* o d -r -t* ^ 10 J lO »0 •— • r-« I I I I I I I I '- -^ IM — O »— t t I I I I III Ui ^^ Oi 1 O I !M I t-H I I I a O u _>- c o CD < "O I I 03 t-i I I ^ 1 I Oio it-HcC'— « ' I iro •'— ' • r-H ^H I III I I 00 iM 'cs 1 I I I I I I OS ■£ §-S O g. 2 o ft Q Co CO CQ %> ^ 14) eo 65 to oca cu to u Co CO to JT" « « o c3 ::3 Co to o ft " i: Q =3i: a to O O to ^ -^ r= to « ft -c -c B.^ o COPPER ROCKFISH FOOD 277 g O) >, 3 o O C k X 3 01 ^ K U, O- c o (u o • ■••I • • I •• ooo>-i t^t^o —'OM'-'co .-iorooc;ot-it-o)-*o '-'OOMO c^rooo oc-i (N i-i CO --I i-i C-l 3 I 1-1 lO (M O CM a; a o (N 1^ M Tf Ca lO o ) . ^loO'-'OOOOCMOCsCCO .4 CM o do 1 I o d lTt<.-l do 1^ .-H ,-H ,-. o6 ddd f-, t-, Ui l-i Im t^OOCMO»0005»Ot^»— 'CO ^O ^^t^iO ^ ^ ^-»-H ^ ^ t-c^iuo *-• -it^i-i-i CM t* Tjl .-t Tj* I-H OO CO CO CO 0) OS bo E o 0 o l^ 0) -Q C - 3 E ^ E 8 3 o at • a & o u o o c o £ o .-li-if-iCOO 00O'-iOii-''-i0;a-. CMa>-*00 0>-iCOCMt~t^r--ii-H t^ rt Tf ic ^«0 CM O CO'-iCM'-' ■ Co c c e o IS e 2 OOf>3 s£ (^ i* K ^ u H ~ W *D ^ 't-- if u o o o tj c: « S C C S S c R O B C C O • '-' ccoooooa. 8^? ^ SS ^ '^ t- e c- ^ ^ ■** cu R. S5. a e c e OOO ■2Sc o._ a; U <" c C 5^ "^ Ot^O .2'S 111 ■ < S S mS o-Sf 33^^ 3 278 CALIFORNIA FISH AND GAME K » D N D o "9 E 3 O 5 « c « J 1 ro — lii < CD < 4) E E o e j< w e 4) Q. a o u ■o o 0 3 cr fa c 03 E D - OO « M (N -H « 1 C5 b- 0 Ot^ OlNOOOro 000->000->U3 — •-■ « C) M —I Tj< IN C^ C<3 3 S < "O w-.'t; 3f_i - . o » ."3 ^ : g' , 3 m = C -c: o5 t- 2 •o »-2i ft : ft ~ a c 3 C> ■S » ° «> 3 ? _ ij -* V 69 o 1^ P eo 0.5 ml) over total copper rockfish sample for that month. The largest mean volumes of stomach contents occurred during mid- summer and the smallest in mid-winter (Figure 2). General observations indicated a few important trends in the seasonal availability of copper rockfish food. The Dungeness crab was found to be more abundant in the copper rockfish diet during summer and fall, while occurring less frequently in winter and early spring. This was not true for grass shrimp and gammarid amphipods, which were found in stomach contents of every monthly sample. Noctural Feeding The percentage of empty stomachs of copper rockfish caught at night was similar to those caught during the day, and the percentage of copper rockfish in the total catch was higher in nocturnal samples (Figures 1 and 3). 282 CALIFORNIA FISH AND GAME CO cr UJ h- LU d 4 - UJ o > UJ o < on UJ 3 - 2 - 6.09 ■132 I 0.38 |_ J_ 050 0 48 -004 I I 1__ 0.77 019 024 M M A S MONTH N M FIGURE 2. Monthly average volume of stomach contents (v/ith 95% confidence limits) of copper rockfish from artificial reef in South Humboldt Bay, March 1971 through March 1972. 100 X o O 80 Oo o^ q: UJ CL Q. o o 60 40 20 - 2 2 8 II • 9 / \ 14 / \ /• \i . / \ b \9^ \^/ 10 V ^ 19 DIURNAL NOCTURNAL J L _L J L MAMJJASONDJF MONTH M FIGURE 3. Percentage of copper rockfish (110-300 mm tl) in total catch from artificial reef in South Humboldt Bay, March 1971 through March 1972. Fractions represent number of copper rockfish in total catch during a particular month. COPPER ROCKFISH FOOD 283 DISCUSSION The food habits of copper rockfish can be best categorized as those of an opportunistic carnivore (i.e., feeding on whatever animal is available) . This type of food habit is substantiated by the data of Patten (1973) , who examined the stomachs of 271 copper rockfish from Puget Sound, Wash- ington. In our study, crustaceans were the most important food group in the diet of copper rockfish. Patten (1973) found a very similar situation with the copper rockfish in Puget Sound, and Rogers (1958), Phillips (1964), and Gotshall, Smith and Holbert (1965) found that crustaceans were very important in the diet of other scorpaenids. Eel grass was observed, on one occasion, trailing from the anus of a copper rockfish and appeared to be undigested in the stomach contents. The plant material was probably ingested incidentally along with some of the other food items. The affinity that many of the copper rockfish food organisms have for eel grass (Light, et. al 1964) could help explain the incidental occurrence of plant material in the diet of copper rockfish and other carnivorous fishes. Gotshall, Smith, and Holbert (1965) found undi- gested plant material in the stomach contents of blue rockfish, S. mystinus, and Patten (1973) found a small amount of plant material in the stomachs of copper rockfish. The predominance of juvenile Dungeness crabs in the diet of the copper rockfish emphasizes the importance of this individual food item and the relative availability of crab in the study area. Underwater observations showed that large influxes of Dungeness crabs inhabited the study area during spring, summer, and fall. Dungeness crabs use Humboldt Bay as a nursery during certain times of the year. The extent of this utilization would seem quite significant because the largest commercial concentrations of Dungeness crabs in California occur off Eureka and Crescent City (Frey 1971). Although the general status of Dungeness crab populations on the west coast is known, no population estimates have ever been published. Be- cause Dungeness crabs are the most important food item to copper rock- fish inhabiting the artificial reef, important managerial implications exist. Gotshall (1969) showed that a selective predator like Pacific hake, Mer- luccius productus, could be used as a biological sampler to estimate the annual mortality rates and population size of the commercially important shrimp, Pandalus jordani. Because of their preference for the Dungeness crab as food, copper rockfish show a similar potential as biological sam- plers in estimating the annual mortality and relative abundance of juve- nile Dungeness crabs in Humboldt Bay. Gotshall, Smith and Holbert (1965) suggest that another scorpaenid, Sebastes mystinus, shows promise as a biological sampler because of its opportunistic feeding habits. Because of their small size, gammarid amphipods would not seem to give copper rockfish a significant amount of nutritional value, yet they were the second most important individual food item (Table 4) . Other authors have also suggested that gammarid amphipods are an important food source for scorpaenids: Rogers (1953), Phillips (1964), and Gotshall, Smith, and Holbert (1965). The change of food habits with size and age of fish is well known (Nikolsky 1963) . Generally, larger fish eat larger sized and a greater vari- ety of food organisms, while smaller fish consume less diverse and smaller sized food items. The food habits of copper rockfish seemed to follow these 284 CALIFORNIA FISH AND GAME trends quite closely. Young of the year exhibited a restricted diet (mono- phagic) , feeding almost exclusively on small crustaceans, while larger fish progresssively ate a greater variety of larger food organisms (stenophagic diet). Thus, fish became a progressively more important food item in the diet of older copper rockfish. Patten (1973) found this trend to hold true for the copper rockfish he examined in Puget Sound, and Gotshall, Smith, and Holbert (1965) found similar results with blue rockfish. Copper rockfish relied less on artificial reef associated food items (sub- strate specific organisms like gammarid amphipods) as their age and size increased. This seems logical in light of the size, strength, and speed that would allow older fish to pursue food outside the perimeter of the reef. DeWees (1970) found offshore upwelling and the resulting increase in food production to be an important factor regulating the growth of copper rockfish on the artificial reef in South Humboldt Bay. When the upwelling was- high during spring and early summer, DeWees found the growth rate of copper rockfish increased sharply. Conversely, when the upwelling factor was low during winter, the growth curve leveled off. Miller, Ode- mar, and Gotshall (1967) also found that rapid growth of blue rockfish in Monterey Bay occurred during and after periods of upwelling, while Got- shall, Smith, and Holbert (1965) determined that the lowest percentage of empty stomachs in blue rockfish occurs after periods of heavy upwell- ing. The low percentage of empty stomachs observed in this study during the summer months (Figure 2) compares favorably with the increase in growth curves observed by DeWees during this period. This may be due to upwelling, as well as seasonal changes in light, water turbidity, and temperature, all of which regulate primary and secondarv production (Oduml971). The average volume of stomach contents was also highest during sum- mer (Figure 3) , along with an increase in growth rate and lowest percent- age of empty stomachs. Conversely, slower growth rates (DeWees 1970), higher percentage of empty stomachs (Figure 2), lower average volumes of stomach contents (Figure 3) corresponded with reduced primary and secondary production in the winter. The findings on nocturnal feeding indicated that copper rockfish fed at least as much at night as they did during the daylight hours. However, this conclusion must be tempered with the fact that nocturnal collection of fishes was restricted to hook and line sampling. Night sampling was con- ducted only once per month from July 1971 through March 1972 and may not be entirely representative of the nocturnal feeding habits of copper rockfish. This is especially relevant when examining the extremely low night catches experienced during sofne months (Figure 3). This data is supported by Patten (1973) who found that the copper rockfish in Puget Sound fed most actively at dawn or during the night SUMMARY The study indicates that: (1) food habits of copper rockfish can be best categorized as those of an opportunistic carnivore; (2) crustaceans were the most important food group followed by fish and molluscs; (3) juvenile Dungeness crabs were the most important food item and thus show poten- tial as a biological sampler for this species of crab; (4) gammarid amphi- pods, despite their small size, were the second most important food item; (5) eel grass and other plant material was consumed incidentally along with the other food items; (6) the change in food habits with size and age COPPER ROCKFISH FOOD 285 of fish follows the well known pattern of other species; copper rockfish relied less on reef associated food items as the age and size increased; (7) the low percentage of empty stomachs and high average volume of stom- ach contents for copper rockfish occurred during summer months. This compares favorably with the increase in growth of copper rockfish on the Humboldt Bay reef (DeWees 1970) , and is due, at least in part, to upwell- ing; and (8) copper rockfish fed at least as much at night as they did during daylight hours. ACKNOWLEDGMENTS Numerous people helped collect data for this study. They are Thomas Lambert, Andre De Georges, Jay Jones, Robert Ericcsen, Henry Penning- ton, and Aron Libow. We would also like to thank Melvin Hull, Timothy Hayes, and other members of the Eureka Kiwanis Club for their help and financial support throughout the project. Timothy C. Farley edited the original manuscript. REFERENCES Blodgett, H. A. 1972. The age of juvenile copper rockfish, Sebastes caurinus, on an artificial reef in South Humboldt Bay, California. Unpublished manuscript for Fisheries 195, Dr. James Welsh. Humboldt State University, Areata, California. 22 p. DeWees, C. M. 1970. Population dynamics and fishing success of an artificial reef in Humboldt Bay, California. M. S. thesis. Humboldt State University, Areata, CaHfornia. 74 p. Frey, H. W. (editor). 1971. Market Crab, p. 16-18. In California living marine resources and their utilization. Calif Dept. Fish and Game. Sacramento, Calif. 148 p. Gotshall, D. W., J. G. Smith and A. H. Holbert. 1965. Food of the blue rockfish, Sebastes mystinus. Calif. Fish Game, 51 (3): 147-162. Gotshall, D. W. 1969. The use of predator food habits in estimating relative abundance of the ocean shrimp, Pandalus jordani, Rathbun. F. A. O. Fish Rep., 3 (57): 667-685. Light, W. R., R. Smith, D. P. Pitelka, Abbot and Frances M. Weisner. 1964. Intertidal invertebrates of the central California coast (4th ed.). Univ. of Calif Press, Berkeley, Calif 446 p. Miller, D. J., M. W. Odemar, and D. W. Gotshall. 1967. Life history and catch analysis of the blue rockfish, Sebastes mvstinus, off central California. 1961-1965. California. Dept. Fish and Game, MRO Ref. 67-14:1-130. Nikolsky, G. W. 1963. The ecology of fishes. Academic Press, New York. 352 p. Odum, E. P. 1971. Fundamentals of ecology (3rd ed.). W. B. Saunders Company, Philadelphia. 574 p. Patten, B. G. 1973. Biological information on copper rockfish in Puget Sound, Washington. Amer. Fish. Soc, Trans., 102(2) :412-416. Phillips, Julius B. 1964. Life history studies often species of rockfish (genus Sebastodes) . Calif. Dept. Fish and Game, Fish Bull., (126):l-70. Pinkas, L. M., M. S. Oliphant, and I. L. K. Iverson. 1971. Food habits of albacore, bluefin tuna, and bonito in California waters. Calif Dept. Fish and Game, Fish Bull., (152): 1-105. Rogers, D. W. 1958. Observations on the food of two rockfish, Sebastodes paucipinis and Sebastodes mystinus. Unpublished manuscript for senior project, Calif. State Polytechnic College, San Luis Obispo, California. 32 p. 286 Calif. Fish and Game 62 (4) : 286-298. 1976. FOOD HABITS OF THE LEOPARD SHARK, TRIAKIS SEMIFASCIATA, IN ELKHORN SLOUGH, MONTEREY BAY, CALIFORNIA ' LARRY G. TALENT' Moss Landing Marine Laboratories of the California State Universities, Moss Landing, California 95039 Four hundred thirty-six leopard sharks, Triakis semifasclata, were collected in Elkhorn Slough, Monterey Bay, California from October, 1971, through November, 1972. Three hundred sixty-seven (84.2%) of the shark's stomachs contained identifiable food items which were analyzed as to frequency of occurrence, percentage of total volume, and numerical importance. The Index of Relative Importance (IRI), which combines the numerical, volumetric, and frequency of occurrence measurements of each prey item into one value, was used to rank the importance of each food item. Leopard sharks from Elkhorn Slough fed largely on crabs, clams, fish, fish eggs, and the echiuroid worm, Urechis caupo. Considerable variation occurred in the diets of different sized sharks. The yellow shore crab, Hemigrapsus oregonensis, was the most important food item for sharks under 90 cm (3 ft) total length but as they approached 90 cm, Urechis caupo and fish eggs became increasingly important. Urechis caupo was the most important species in the diet of sharks over 90 cm but various species of crabs, clams, and fish eggs were also important items. The diet of sharks 120 to 130 cm (3.9 to 4.3 ft) was almost evenly divided between crabs, clams, fish, fish eggs, and Urechis caupo. Fishes were the most important food items in sharks 130 to 140 cm (4.3 to 4.6 ft). There was no significant difference between the diet of male and female leopard sharks of similar size. Leopard sharks were able to utilize a variety of food sources in Elkhorn Slough without being dependent on any one source. INTRODUCTION Virtually no research has been conducted on the ecology or life history, including food habits, of any California shark except the spiny dogfish, Squalus acanthias, and the soupfin, Galeorhiniis zyopterus. These species once were heavily fished due to high level of vitamins in their livers (Bonham et al. 1949; Foerster 1942; Herald and Ripley 1951; Ripley 1946; Templeman 1944; Westrheim 1950). Leopard sharks, Triakis semifasciata, are of minimal economic importance and possibly for this reason have been studied little. Some information is available on leopard shark food in San Francisco Bay and Tomales Bay (Russo 1975). However, the only published information on leopard sharks from Elkhorn Slough is in catch analyses of the annual shark derbies held in Elkhorn Slough usually during the months of May and June (Herald and Dempster 1952; Herald 1953; Herald et al. 1960). This information consists mostly of a tabulation of numbers caught, sex ratios, and total poundage. Information on leopard shark food is presented in the form of casual observations. The leopard shark, the most abundant shark in Elkhorn Slough, ranges from Mazatlan, Mexico, to Oregon (Miller and Lea 1972), and is common inshore around jetties, piers, and bays in central and southern California (Miller et al. 1965). Although leopard sharks have sharply pointed teeth, they are generally considered harmless to man due to their timidity (Lim- baugh 1963). However, there is one recorded attack on a scuba diver ' Accepted for publication .\pril 1976. ' Present address: Dept. of Fisheries & Wildlife, Oregon State Univ., Corvallis, Oregon 97331. LEOPARD SHARK FOOD HABITS 287 (Dewitt 1955) . Leopard sharks are one of the most easily identified sharks because of their distinctive color pattern (Schott 1964). Increasing concern about the future uses of Elkhorn Slough and envi- rons has created a need for knowledge of the life history and ecology of fishes occurring there (Browning 1972) . A knowledge of food habits is vital in assessing the ecological requirements of a species. This paper presents the results of an investigation on the food habits of leopard sharks and the effects of sex, size, and season on overall diet patterns. STUDY AREA This study was carried out in Elkhorn Slough, located on the east side of Monterey Bay midway between Monterey and Santa Cruz (Figure 1) . Elkhorn Slough consists of about 2,500 acres of submerged areas, tidal flats, and salt marsh. The slough proper is characterized by extensive mudflats that are periodically exposed during low tide and inundated during high tide. The slough has a maximum depth of approximately 4 to 5 m (13.1 to 16.4 ft) . Pickle weed, Salicornia sp., is the dominant plant at the high tide level. Originally, Elkhorn Slough was part of the Salinas River drainage system and was largely fresh water during part of the year. In 1908 the Salinas River, during a period of heavy runoff, broke through the sand dunes and began flowing into the ocean at its present location, approximately 8 km (5 miles) south of the slough. To prevent future flooding of agricultural land, the old Salinas River channel was dammed up forcing the river to remain in its new channel (Browning 1972) . In 1946, the present entrance channel to the Moss Landing Harbor was constructed resulting in a much greater tidal flux in the slough. The gradually sloping banks of the slough were subject to considerable erosion in some places with subsequent ex- pansion of some of the mudflats. Factors continuing to influence the slough and the type and abundance of organisms living there are tides, water terperature, and precipitation. The Salinas River continues to affect the slough during periods of heavy rainfall, usually in winter, when the rate of flow increases markedly in the river. The tide gates are opened in the old Salinas River channel causing fresh water to enter the slough in large quantities. In addition, several tributaries from the surrounding hills drain into Elkhorn Slough. This influx of fresh water dilutes the slough water and affects the composition of the fishes found in the slough. MATERIALS AND METHODS Leopard sharks were captured over a 14-month period from October 1971, through November 1972, with 90-m (295-ft) nylon gill nets, divided equally among three mesh sizes: 10.2-, 15.2-, and 22.9-cm (4-, 6-, and 9- inch) stretch mesh. In order to avoid capturing large numbers of bony fishes, no mesh size smaller than 10.2-cm (4-inch) stretch was used, result- ing in selection against small sharks. In addition to gill netting, leopard sharks were obtained from two Elkhorn Slough shark derbies during June 1972, in which specimens were captured during daylight hours by hand- held hook and line. Gill nets were set perpendicular to water flow in the slough (Figure 1) . Nets were set 1 or 2 hr before sunset and picked up the following morning. An attempt was made to set nets every week but weather conditions, equipment failures, and other unavoidable circumstances did not always 288 CALIFORNIA FISH AND GAME allow this. During the month of July a green algae, Enteromorpha sp., grew profusely in the slough, completely clogging the nets each time they were set. All leopard sharks were measured to the nearest mm total length (TL) , weighed, sexed, and labeled. Stomachs were removed, labeled, wrapped in cheese cloth, and placed in 10% formalin solution. Stomach contents were sorted into major taxonomic groups and members of each group placed into a separate container for further study. Identification of stom- ach contents was carried to the lowest possible taxonomic lexel when condition of the material permitted. The number of each species of food organism was recorded and the volume determined by water displace- ment to the nearest ml. The identification of each food group posed a different problem. Whole or slightly digested fish presented little difficulty. Partially or near totally digested fish were often identified by otoliths (sagittae) , using a reference collection from species common to the area. Occasionally, fish were identi- fied by use of skeletal elements in conjunction with a reference collection of cleared and stained fish common to Elkhorn Slough (Clothier 1950). Fish eggs were recorded as the number of egg masses consumed rather than individual eggs because large numbers of eggs were always clumped together. Identification was based on a reference collection taken from common Elkhorn Slough fishes known to be spawning in the slough at the time of capture. Specific identification of intact crustaceans normally presented no prob- lem. In cases where digestion had reached an advanced state, the number of crustaceans recorded was the maximum number of individuals ob- served based on the number of carapaces, paired chelipeds, or thoraxes, whichever were more abundant. Specific identification of clams was not usually possible except in a few cases when part of the shell remained intact. The gaper clam, Tresus nuttallii, is easily identified by an intact siphon with plates, but such intact siphons rarely occurred. Thus, clams were identified only as clams, with the number established by counting either siphons or bodies, whichever represented the greatest number of individuals. The echiuroid worm, Urechis caupo, was easily identified by its posterior setae. Specific identification of polychaete worms was not possible since it normally requires appendages to be attached and intact. Bait consisting almost entirely of market squid, Loligo opalescens, was found in several stomachs of sharks captured during the 1972 shark der- bies. This material was easily identifiable as bait and not part of leopard shark's regular food in Elkhorn Slough. Therefore, bait was excluded as a food item in all tabulations. The Index of Relative Importance (IRI), which combines numerical, volumetric, and frequency of occurrence measurements of each prey item into one value, was used to rank the importance of each food item in the diet. The IRI of each food item was estaolished as a linear combination of its numerical importance, volumetric importance, and frequency of oc- currence (Pinkas et al. 1971). The numerical importance of a particular item was the percentage ratio of its abundance to the total abundance of all items in the contents. The volumetric importance of a food item was the percentage ratio of its volume to the total volume of all items in the contents. The percent frequency of occurrence of a food item was the percentage of fish containing at least one individual. The combination of percentages, (number + volume) X (frequency), equals the Index of Relative Importance. The value of the IRI ranges from zero, when all i LEOPARD SHARK FOOD HABITS 289 FIGURE 1. Map of study area showing location of sampling station. three values are zero, to 20,000, when all three indices are 100%. To facilitate seasonal comparisons of food habits, the year was divided as follows: summer (May,June,July); fall (Aug., Sept., Oct.); winter (Nov., Dec, Jan.); spring (Feb., Mar., Apr.). The data presented in Figure 2 and Tables 1, 2, 3, and 4 relate only to the number of stomachs that contained food. 290 CALIFORNIA FISH AND GAME O CRUSTACEANS □ FISH EGGS A URECHIS CAUPO V CLAMS O FISH 0) 1 CD If) O o O o * in Ol Ol 0) CT) CJ to O O O O (\J lO (10) (30) (37) (33) (32) (37) (51) (67) (22) TOTAL LENGTH IN MM (NO. STOMACHS WITH FOOD) FIGURE 2. Variation in the relative importance of five major food groups in the diets of different length classes of leopard sharks, Trlakis semifasciata, captured in Elkhorn Slough. The number of stomachs containing food in each length class is indicated in parentheses. LEOPARD SHARK FOOD HABITS 291 ■D O O Ik ••- o ^^ oe ^-/ « w C O 0 w r o k a o E •^ ■" o » u > >- 0 0 0) CD ae >> •»- 0) o k « X *- 0) c "O o ^ s ■o c o 0) 3 ^ o o t/) r u. k ^ o 'ta^ ^ « lU u C c 0) '~ k "O 3 0) u w 3 o O. •k 0 O u >« x c 3 c V IL 0 ^ ^ n c h- 0) w E 9) E a. «. Ch /"^ Z Ch ^ k ^ « ^ ^ F (A 3 Z ^ X c -1 ^ O » « E O 3 « O X > c c •^ 0) lA w E » « OL ♦- CO < O W ►J <; H O H C5 I o ooo 00 OS* I o o o ■<*< « o K O ^ K O y. L? f-H lO 00 c r~ f- IM (M 1 O O ' T-H O t-H 1— t 00 W 00 O -^ PI IM .-I OOM 1-1 iccoopooo iio iccccoro CO lo coo CO to "O OO lO 00 --I i-iCOOCO (M (^rti-ii-H ■-1 ■* O -H C<3 !N CD IN — lO —1 c-i n l-H M oo> -*< -^ IN CO —I -t< i(N 1 1 CO-*T)<'* I .... I I .... OO'H N CD CO t^ 00O>O -^0000 ooo a> lO lO o icDooo-* lO) O'-'ira- I . . . . I . ... CD10CD>0 Tf O t^ COOOi-iOO-H t~ CD'l" CO C^t^ (N 05 O CO o CO CO CDC"^ IIN-^CDCO --ID CO CD I 00 (M ■-H O r~ I -I' iiO IN t^O it^— 'COCO -^Tf 1 ■-HIN c^) rt .-I >ooo lor^-i"'^ >-i"-i l-H i-H 0> t^ i-H 05 I G> ' I • I I . I I I I C^ lO O»0n0C^l»0i iOiO CD O 00 (Nl^ COIN -H o O I »0 • I I I I • I I I I 1-1 Tjl O (N coco lOOINCOCN INi-l 1-1 'H CO t^ ^ CD •^T-l OO CMt-. 1-1 1-1 1-iCO CO I N I i 1 1 1 . 1 I I I i-l lO 00 IN CO t^iO iXOJt^O lOl t^ lO O ' CD 1-1 I 00 -H C>I t^ CO IIO lO »0 lO »00i0 0«0 0 i»oii lO I. . . . ..I.... I. II (Nt^N.C^lNO(NiOC^iO IN IN Ol r-1 00 t^ IN I r^ CD r^ 1 i.O OS 00 00 CO 1-1 CO iiom^iN 00 IN CD C^l 00 0-1 CO CD 100 I I lO CO w H Q O o > C3-D J- C3 eg oj (11 ^ C3 O <5 S 60 e3 d in ^ CO "^ c3 " C s g 3 e K 5i S ■2 3 e £ ,Sft. L. ^ ^ t. ^ 3 goomoo C Oi 2 3-T3 J, ^ o r aC 3 ;.C-0 = i o*^ O IS tS C (3 5 c :« fc I e ""2, J "" csS-l ■" a C3 CO ■S 2 t- ca ^-z ex; ft.~ « o 2 f; 2 Q. o 5- <^' .S us in ^ _ 0) J2 C3CC O cj C T3 O O a 'a '3 o CS cS s o 3 P^PL, 292 CALIFORNIA FISH AND GAME TABLE 2. Percent volume (%V), Percent Number (%N), Percent Frequency of Occurrence (%F.O.), and Index of Relative Importance (IRI) of Food Items in the Diet of Leopard Sharks, 1000 to 1399 mm Total Length, Captured in Elkhorn Slough, Monterey Bay, California FOOD ITEM Plant Material Poly chaeta Echiuroidea Urechis caupo Crustacea Decapoda (total) Carides Crangon sp Brachyura Cancer antennarius Cancer gracilis Cancer magister Cancer productus Hemigrnpsus oregonensis. Unidentified crab parts . Anomura Blepharipoda occidentalis MoUusca Bivalvia Clams Cephalopoda Octopus sp Fish eggs Pisces (total) Rhinobatidae Clupeidae Engraulidae Sciaenidae. Embiotocidae Gobiidae Scorpaenidae Cottidae .- Atherinidae Bothidae. Cynoglossidae Batrachoididae Unidentified fish TOTAL LENGTH (mm) %V .4 .3 18.2 24.5 .1 2.5 2.2 ?!? 5.2 .2 4.9 1.7 19.7 2.0 22.5 12.1 .0 2.5 .9 .4 "i .2 .1 4^5 1000-1199 (88)* %N .7 1.4 33.9 20.7 .7 2.5 7.1 4.3 3.2 1.8 1.1 13.9 5.7 10.7 13.1 .4 2.9 1.1 .4 ^4 .7 .4 l'4 5.4 %F.O. 2.3 4.G 38.0 48.9 1.1 5.7 9.1 4.0 7.9 5.7 19.3 2.3 35.2 5.7 34.1 23.9 1.1 4.0 2.3 1.1 i"i 1.1 1.1 4^0 11.4 IRI 3 8 2011 2210 1 29 85 55 00 11 95 1183 47 1132 602 1 5 1 "i 1 1 27 94 %V .7 .1 11.3 18.5 .1 3.3 2.5 .0 9.1 .4 2.5 20.4 20.8 22.7 1.5 1.7 .4 .1 2.8 1.1 .5 1.5 1.8 'i 8.0 3.2 1200-1399 (89)* %N .7 .3 20.0 10.2 .3 2.9 3.3 .3 7.1 2.3 10.2 11.4 28.7 .7 1.3 5.5 .3 2.3 .7 .3 4.0 3.9 "3 2.0 0.8 %F.O. 2.3 1.1 38.2 44.9 1.1 4.5 4.5 1.1 14.0 4.5 20.2 43.8 39.3 44.9 2 . 3 4.5 1.1 1.1 0.8 2.3 1.1 9.0 7.9 Kl 7.9 19.1 IRI 3 <1 1448 1558 <1 28 27 1 237 12 51 1003 1501 2308 5 14 7 <1 35 4 1 50 45 e "5 o E E §: o o o o a. o « o 0) o « E 0) •o o o « w e P k o a E o • E > o ••c rt t"5 O D ■S >- T * t) ^ X c — o ES e ^ o £ O 3 •z o 1^ S £ o uj ** c CO CO < I o o 00 H O W '-I <; O 03 I o o CD lO I o o '>'* c^ C3 02 r-* 55o CO! c* 03 rl CO 03 C) a; CC-l w Q O O lTt< (N o (N 100 IIMIO lOl in ICO 05 o> ■* IM lf~r). lO) ■"^ O OS t^ C<5 lO j-i lO 100 to 100 CO 00 o o CO 1-1 CO CO CO CO CO o ■ (MO lO "O I ,-. in I iM 00 lO CO 10-* ,—1 o O-H CO o c^co M< o 1— ( -^ ICOO(M^ IrH in^f IIO I 05 ^ 00 O I (M r-H I .I O 1-1 i(NCO rfiM ■* i»0 CO t^ COr-l ICO (N o l>0 CO lO o 00 o 00 lO lO o o o o o in CO CO (N 1 1—1 ooio-*t^ 1 1^ CD CO CO lO -iiO ICO 00 o om in 1 00 00 3 gOOCQO PhPuW UQ C3 u Ci P ° s a~ :^ c. -c-o c u •— O 03 ■v S <^ O Co en o , T3 O O (4-1 bH a 'a '3 +j d o c3 a; "' oj R..^ i.S tt) u ^ O O c3 I oJCC t.T3 c3 C c3 J3 3 2: fl^PLl 294 CALIFORNIA FISH AND GAME quency of occurrence was noteworthy. Polychaetes were commonly found in stomachs of sharks 60 to 120 cm (2.0 to 3.9 ft) whereas octopuses occurred most often in sharks 90 to 120 cm (3.0 to 3.9 ft). The species of crabs utilized as food varied with the size of shark. Hemi- grapsus oregonensis, a small-sized crab usually less than 25 mm (1 inch) in diameter, was the most important food item for sharks under 90 cm (3.0 ft). However, as sharks increased in size, larger species of crabs became more important. Cancer gracilis, a medium-sized crab, was the most im- portant crab in the diet of sharks 90 to 120 cm (3.0 to 3.9 ft). Cancer productus replaced Cancer gracilis, and was the most important species of crab in the diet of sharks 120 to 140 cm (3.9 to 4.6 ft) . Cancer productus, Cancer antennarius, and Cancer magister, are large crabs and most adult individuals were in the soft shelled stage when eaten. Most Cancer pro- ductus eaten were juveniles. Clams formed an important part of the diet of sharks over 80 cm (2.6 ft) . Clam siphons made up the bulk of clam material eaten but several large complete specimens were found in stomach contents, all without shells. Several species of clams were probably eaten, but due to the ab- sence of all, but very small shell fragments, specific identification of most TABLE 4. Seasonal Variation in the Index of Relative Importance (IRI) of Food Items in the Diet of Leopard Sharks, 1000 to 1399 mm Total Length, Captured in Elkhorn Slough, Monte- rey Bay, California FOOD ITEM Plant Material Polychaeta Echiuroidea Urechis caupo Crustacea Decapoda (total) Carides Crangon sp Brachyura Cancer antennarius Cancer gracilis Cancer magister Cancer productus Hemigrapsus oregonensis. Unidentified crab parts. Anomura Blepharipoda occidentalis Mollusca Bivalvia Clams Cephalopoda Octopus sp Fish eggs -- Pisces (total) Rhinobatidae Clupeidae Engraulidae Sciaenidae Embiotocidae Gobiidae Scorpaenidae Cottidae Atherinidae Bothidac Cy noglossidae Batrachoididae Unidentified fish TOTAL LENGTH (mm) 1000- -1199 1200 -1399 Summer (21)* Fall (20)* Winter (20)* Spring (27)* Summer (9)* Fall (16)* Winter (,33)* 4G 13 10 G G -- -- -- 1138 370 3494 3079 1G3 576 925 1551 19 42 274 15 GO 3022 907 3346 79 2733 1760 123 190 338 432 1G9 31 112 9G 8G 500 31 36 '3 136 38 126 247 17 209 8 208 4 81 124 -- -- -- -- -- -- 37 50 IG 1518 916 186 5277 954 10 981 2312 22 109 91 14 78 231 1865 442 2130 1.59 17 170 7G93 245 2207 42 2849 1970 10 48 91 -- -- '9 580 72 15 15 5 -- "7 "7 1.33 38 33 236 29 59 122 530 78 135 ii 4 922 482 367 4 227 Spring (31)* 22 "s 2624 1212 3 "7 459 59 15S0 2284 1138 19 '7 6 69 189 32 * Number of shark stomachs containing food. LEOPARD SHARK FOOD HABITS 295 clam parts was not possible. However, several gaper clams, Tresus nuttal- lii, were identified by their siphon plates, and most clam parts appeared to be from this species. Another clam identified from parts was the Wash- ington clam, Saxidomus nuttallii, and rarely, the rough piddock clam, Zirfaea pilsbryi, was found. Fish eggs became increasingly important as a food item as leopard sharks increased in size. Almost all fish eggs found in stomach contents appeared to be either jacksmelt, Atherinopsis californiensis, or topsmelt, Atherinops affinis. Some overlap occurred between the spawning periods of these species and differentiation of the eggs was not always possible. On a few occasions, Pacific herring, Clupea harengus pallasi, eggs were found in stomach contents but were insignificant as food items. Several leopard shark stomachs contained plant material consisting mostly of algae, Gracilaria sp., and some eel grass, Zostera sp. All plant material observed was associated with fish eggs. Usually the eggs were firmly attached to the plant material by long filaments. Apparently the spawning fish attached their eggs to the plants and leopard sharks swal- lowed pieces of plant material incidentally along with the eggs. Several species of fish were eaten by leopard sharks. The northern midshipman, Porichthys notatus, was the most important species of fish eaten, due largely to the considerable volume of each individual con- sumed. Of particular interest was the presence of three yellowfin gobies, Acanthogobius flavimanus, among the fish eaten by leopard sharks. The first record of this introduced species in Elkhorn Slough is July 17, 1970 (Kukowski 1972). These additional specimens indicate that this goby is becoming well established in the slough. Three small specimens of shovel- nose guitarfish, Rhinobatos productus, represented the only elasmo- branchs found in leopard shark stomachs. Other species of fish identified in stomach contents were Citharichthys stigmaeus, Clupea harengus pal- lasi, Cymatogaster aggregata, Embiotoca jacksoni, Engraulis mordax, Genyonemus lineatus, Leptocottus armatus, and Symphurus atricauda. No one species of fish was eaten in large numbers. Leopard sharks thus ap- peared to be opportunistic feeders on fish, feeding on species most abun- dant or easiest to catch. There was no significant difference in diet of male and female leopard sharks of similar size. However, it should be noted that females attain a larger size than males and therefore made up a greater proportion of the largest size class. Although a sufficient number of stomachs could not be collected throughout the entire year to make good monthly comparisons of diets for each size class, some seasonal trends were observed (Tables 3 and 4) . Small sharks, less than 80 cm (2.6 ft) fed mostly on crabs throughout the time they were captured while larger sharks showed some seasonal variation in their diets. Much of the variation was due to almost total absence of fish eggs in their diet during fall. Jacksmelt and topsmelt are reported to spawn from October to April and May through July respectively (Clark 1929; Schultz 1933). Because of the unavailability of fish eggs as a food source, leopard sharks probably fed more heavily on clams and crabs during the fall than at other times. During winter and spring, the yellow shore crab, Hemigrapsus oregonensis, decreased to insignificance as a food item simultaneously with an increase in importance of several species of Cancer crabs, fish eggs, and Urechis caupo. Large sharks ate fish mostly during the summer, at which time clams decreased to their lowest value of the year. 296 CALIFORNIA FISH AND GAME DISCUSSION Leopard sharks of many sizes, except those below 40 cm (1.3 ft), fre- quenting Elkhorn Slough were captured during this study. Most leopard sharks examined appeared to have fed in Elkhorn Slough and not Monte- rey Bay. Food items such as Urechis caupo and Hemigrapsus oregonensis are usually associated with mudflats and rarely occur in strictly sandy substrates such as are generally found in the bay (MacGinitie 1935) . Most other major food items are found in Elkhorn Slough in abundance al- though, many are also common in the bay. However, Blepharipoda occi- dentalis and Cancer magister are usually not found in the slough proper, although they are common in the bay. The presence of these species in the diet of leopard sharks probably indicates that a few sharks fed in the bay shortly before being captured in the slough. Although crabs and fish are presumably taken through a simple pursuit and capture, leopard sharks seem to be capable of utilizing a variety of methods for capturing other types of organisms. Leopard sharks must be very adept at feeding on Urechis caupo, as it was the most important prey species in the diet of sharks over 90 cm (3.0 ft) . This echiuroid worm lives in a U-shaped burrow about 1-ft deep in mud and reportedly never leaves its burrow (MacGinitie and MacGinitie 1968). It seems unlikely that the morphology of leopard sharks would allow them to dig Urechis out of mud. However, Urechis may protrude, on occasion, a few mm from its burrow during maintenance of the burrow or elimination of waste products and then be captured by leopard sharks. Another and more probable possibil- ity is that leopard sharks pull Urechis from their burrows by suction. Some species of sharks are capable of creating enough suction, by rapid expan- sion of their pharyngeal cavity, to obtain food from tubes and may obtain much of their food in this manner (Tanaka 1973) . The fact that most intact Urechis found in stomachs were completely undamaged seems to indicate that teeth probably were not used to pull the worms from their burrows. Leopard sharks probably feed on clams by swimming over the bottom and seizing the extended siphons. Most clam material in stomach contents consisted only of siphons. Leopard sharks apparently unable to pull the entire clam out of mud, pull until the siphon breaks at some point along its length. In several cases, entire gaper clam bodies were found without shells in stomach contents. Apparently these clams were pulled free of the mud or possibly had already been eroded out of the substrate by tidal currents. It is not known how the shells were removed. The small and pointed teeth of leopard sharks appear to be efficient at holding onto prey but unsuited for cutting or crushing clam shells. Food habit data indicate that leopard sharks are primarily opportunistic bottom feeders, fish being the only food item not always taken from the bottom. Sharks in the smallest size groups were most restricted in their diet, feeding primarily on one species of crab, Hemigrapsus oregonensis, but they utilized a much wider variety of food items as they increased in size. Seasonal variation in food item selection may have been a result of increasing abundance of one item or the decrease in abundance of an- other, or both. Changes in the population density of leopard sharks along with intra- and interspecific competition for food also may have been contributing factors to food item selection. Generally, leopard sharks were quite versatile in their feeding habits throughout the year, being able to utilize several major food sources without being dependent on any one. This flexibihty of feeding habits along with the differences in the food LEOPARD SHARK FOOD HABITS 297 habits of leopard sharks in the various size groups undoubtedly permits an efficient utilization of Elkhorn Slough's food resources and probably al- lows a greater density of leopard sharks to live in the slough. Russo (1975) suggested that leopard sharks in San Francisco and Tomales Bay did not feed intertidally and Hemigrapsus oregonensis, a crab usually associated with an intertidal habitat, was absent from exam- ined stomach contents; although it was common in the diet of brown smoothhounds, Mustelus henlei, taken from the same general area. In Elkhorn Slough, leopard sharks do feed intertidally and Hemigrapsus oregonensis is an important food item. It is apparent that the food habits of leopard sharks in any one area may not be representative of the food habits elsewhere within the species' range. Large leopard sharks are op- portunistic feeders and probably can utilize a number of food sources in a variety of habitats. However, shall leopard sharks appear to have a more restricted diet and may require a special environment, such as Elkhorn Slough, where a particular food item is abundant. Further research is needed to determine if leopard sharks have specific nursery grounds and if so, how important these areas are to the survival of the species. ACKNOWLEDGMENTS I thank Arthur Staebler, Mary Silver, Gregor Cailliet, and Peter Moyle for advice and critical review of the manuscript. For assistance in collec- tion of animals, I thank Edgar Yarberry, Joel Cohen, Daniel Varoujean, Dave Lewis, and Jan Cross. Special thanks are due to Gary McDonald for helping set nets and assistance in preparation of the figures. I especially thank my wife, Carline, for her continuous encouragement and assistance in all areas of the study. REFERENCES Bonham, K. S., F. B. Sanford, W. Clegg, and G. C. Bucher. 1949. Biological and vitamin A studies on dogfish landed in the state of Washington (Squalus suckleyi) ■ Wash. Dep. Fish. Biol. Rep., 49A:83-114. Browning, B. M. 1972. The natural resources of Elkhorn Slough their present and future use. Calif. Dept. Fish and Game, Coastal Wetland Series, 4:1-105. Clark, F. N. 1929. The life history of the California jacksmelt, Atherinopsis califomiensis. Calif. Dept. Fish and Game, Fish Bull., (16):l-22. Clothier, C. R. 1950. A key to some Southern California fishes based on vertebral characters. Calif. Dept. Fish and Game, Fish Bull., (79):l-83. Dewitt, J. W. 1955. A record of an attack by a leopard shark, Triakis semifasciata Girard. Calif Fish Game, 41(4):348. Foerster, R. E. 1942. Dogfish tagging — preliminary results. Canada, Fish. Res. Bd. Pacific Coast Sta., Prog. Rep., 53:12-13. Herald, E. S. 1953. The 1952 shark derbies at Elkhorn Slough, Monterey Bay, and at Coyote Point, San Francisco Bay. Calif. Fish Game, 39(2):237-243. Herald, E. S., and R. P. Dempster. 1952. The 1951 shark derby at Elkhorn Slough, California. Calif Fish Game, 38(1) :133-134. Herald, E. S., and W. E. Ripley. 1951. The relative abundance of sharks and bat stingrays in San Francisco Bay. CaHf. Fish Game, 37{3):315-329. Herald, E. S., W. Schneebeli, N. Green, and K. Innes. 1960. Catch records for seventeen shark derbies held at Elkhorn Slough, Monterey Bay, California. Calif Fish Game, 46(l):59-67. Kukowski, G. E. 1972. Southern range extension for the yellowfin goby Acanthogobius flavimanus (Temminck and Schlegel). Calif. Fish Game, 58(4):326-327. Limbaugh, C. 1963. Field notes on sharks, p. 63-94. In P. W. Gilbert (editor). Sharks and survival. D. C. Heath and Company, Boston. MacGinitie, G. E. 1935. Ecological aspects of a California marine estuary. Amer. Midi. Nat., 16(5):629-765. MacGinitie, G. E., and N. MacGinitie. 1968. Natural history of marine animals. McGraw-Hill, New York, 523 p. 298 CALIFORNIA FISH AND GAME Miller, D.J. , D. Gotshall, and R. Nitsos. 1965. A field guide to some common ocean sport fishes of California Calif. Dept. Fish and Game, Sacramento, 87 p. Miller, D. J., and R. N. Lea. 1972. Guide to the coastal marine fishes of California. Calif. Dept. Fish and Game, Fish Bull., (157): 1-235. Pinkas, L., M. S. Oliphant, and I. L. K. Iverson. 1971. Food habits of albacore, bluefin tuna, and bonito in Cahfornia waters. CaHf. Dept. Fish and Game, Fish Bull., (152): 1-105. Ripley, W. E. 1946. The soupfin shark and the fishery. Calif. Dept. Fish and Game, Fish Bull., (64): 1-37. Russo, R. A. 1975. Observations on the food habits of leopard sharks ( Thakis semifasciata) and brown smoothhounds (Mustelus henlei). Calif. Fish Game, 61 (2) :95-103. Schott, J. VV. 1964. Chromatic patterns of the leopard shark, Triakis semifasciata Girard. Calif. Fish Game, 50(3):207-214. Schultz, L. P. 1933. The age and growth of Atherinops affinis Oregon ia Jordan and Snyder and of other subspecies of baysmelt along the Pacific coast of the United States. Wash. Univ., Publ. Biol., 2(3);45-102. Tanaka, S. K. 1973. Suction feeding by the nurse shark. Copeia 1973:606-608. Templeman, W. 1944. The life history of the spiny dogfish (Sqiuihis ncanthuis) and the \'itamin .\ \alues of dogfish liver oil. Newfoundland Dep. Nat. Resources, Fish. Sect. Bull., (15):1-102. Westrheim, S. J. 1950. The 1949 soupfin shark fishery of Oregon. Oregon Fish. Comm., Res. Briefs, 3(l):39-49. 299 Calif. Fish and Game 62 (4) : 299-303. 1976. NOTES ADDITION OF CITHARICHTHYS FRAGILIS GILBERT TO THE CALIFORNIA FAUNA On May 15, 1974, one specimen of the sanddab, Citharichthys, fragilis Gilbert 1890, was taken near Dana Point, California at 88 m (290 ft) during a quarterly trawl survey conducted by the Southern California Coastal Water Research Project (SCCWRP). This species (Figure 1) is common in the Gulf of California (Jordan and Evermann 1896-1900; Norman 1934) , but the most northerly record was for Punta Cabras, on the west coast of Baja California Norte (Scripps Institution of Oceanography collection, SIO 60-471). Since May 1974, nine more specimens have been taken at two locations near Dana Point at 88 m (290 ft) , and seven specimens have been taken at three locations near Palos Verdes Peninsula at 137 to 143 m (452 to 472 ft) (Table 1). In examining the collection at the University of California, Los Angeles, I found three additional specimens (UCLA W 59-215) taken on May 28, 1959 off Manhattan Beach, California at 54 m (178 ft). FIGURE 1. Gulf sanddab, Citharichthys fragilis. Illustration by Christine Bondante. 300 CALIFORNIA FISH AND GAME ♦ » ^^ + + ^c<:r~'«'t~«raooOh~ots«rao--ooooi^'^t^c-. iOOOOOOOtOOOOOOOOO'CO--;C OT -»; >i a c * » iZ "S + ; + 2 oo«-";Dc>5-root-»'MOf— 'Tr~t;iMC»oo o lOt^i^ooooooooooaoooooooooooooooDooraoc P ei V a oo>oi«ooot»ot~'Ht~«ooot^r~ooooo!0> -f*'*' 0 * -C 2L 03 J- t!< 00 W 00 1^ O c^ lO 0000 00 CO -J" -(- « Q « •Si c 0 < .c Ci ^ ^ •- V ". ^ D O 'O o >o o o o "S "H n r- lo t^ u3 in o M -fcJ Oi tc in o CD 05 o 'S (N -^ -^ -^ •-( ^ C^l C c o o o o o o o,^ 9. t» 00 t~l^ t^ 00 00 00 ,E ^H rH ^^ f-l ^H ^ .-H .— < .— t 1— 1 o-t 1— I .— ■ t-H 'S • a t'S "^ t» t^ t^ 9 ot. - » o> o> > C o "^ ,_( ,-( ^ -c t- ... 02 -f . 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K CC O O 4 ^ d J2 OS T3 1 " 13 m T3 T3 P d "3 d — . w C3 CO 0) C3 cS S »*-< --. o CJ (!> c "a d a o O pL| 02 1-3 o o en r~i O rn 00 d Lj fl r o t^ ri O 2 rt "* o > O c d o t; c •^ (i> r -^ J3 r* -4J ,- o 3 c m o n -0 g e o o 2 F ff) o c d lOO o ffl c c (-■ d d r> U. •*j ^-> ,*^ u u o a t* m ■►J Tl rt a (U 03 ^ >> c3 on m OT •-H O N ^ -*J £ X tfj oj S3 c c « 2 si CL CO 3 O c 3 O V fC e M o t3 c3 o 3 cii o , :2 o 3 Q O IH S o ■3 If ^^ i^ OS 2 >.0 O CO £ « eo rt M aT3 8 o -^ « « a'ls « 1^ M O CD c o ~ o S 1^ 3T3 ,2'o I ^ 3 03 <« -^ c w.s- .^ -^ CO --J •2 £ SCO e.£ S c3 CO O CO IS o O CO Q •- 1 C3 u CO CO :li OJ S 03 :2 as -tJ "^ o C « 13 o a — .£ s o % o >>.2 s a c -71 « £ o CO ri u •^ 312 CALIFORNIA FISH AND GAME ^ 3 es -t^ CO C 0) e] tf >. 03 on pq to m O ■«.3 £ X OJ en 0) ^ « 01 ci ei ci ci ei in m m rn cf if :£ K o t3 X 'r^ >^ y. y. y X y y CO o 73 05 c3 >-> c: O o o y O s* ha y y y y y y y y y y y •S2 >-• C ^ o M >^ X X XX X X X E c3 C C o £ S o O to 'o a g 03 ■-> o 3 o e o ^ ex c« S P. ^ 9 « (u t-i O H r-i c J= o 03 T3 C CO CO S .s s D. 00 -^ -s; cj -:: CO .J- ^ 2 r^'f^ c ,. C CO >, C3 o s c o .- a) a o3 a. V |l CO g -2 ■* 2 H e -Si ■s g 03 a a. •T3 u 03 u "2 CO ^-' u >> < o O 2 is OS S ^ -a o ^ "3 -^ I X X ^ >i X X X y, X X X X X X X X X X X X X X a:2 ^^ O a ^ I I, C « C 0) 8« Ilia O O 03 ^« o " II I' „ OCO C .. c o 3 o I O. -. > 2 0) -a O 3 O 3 (D C d ft o o ^^ in T3 o o) e 0) en g to >« o o -I -a a. '^ I •- & 3 ' '3 *^ O a o t-i c3 ID o 3 13 u O c 3 03 a o o O 3 s C 3 3 3 03 W Sr ft •c; o w O ■c "r "« o S ^ 2,-^ H "^ 0) rt 03 ^ IB o 6 C3 (J «— I c:; 03 ^ 3 2 o ~ > <^ 3 ■^ 3 -1-3 -* ft tj (/} I o <»> o 03 o o O ' s o o w 3 O o — ' -»^ .« 3 «^ o e -^ . <- CO ■'J 3 e XI "^ s Si ^ a, ft to o 314 CALIFORNIA FISH AND GAME ACKNOWLEDGEMENTS I would like to thank the many people who assisted in the field work. Regrettably, they are too numerous to mention by name. I also thank Jules M. Crane, Jr., Camm C. Swift and Michael H. Horn for their encourage- ment and help and Patricia Allen for her valuable assistance. REFERENCES Allen, Larry G. and Michael H. Horn. 1975. Abundance, diversity and seasonality of fishes in Colorado Lagoon, Alamitos Bay, California. Estuarine and Coastal Marine Science., 3(3):371-380. Crane, Jules M, Jr., Larry G. Allen and Connie Eisemann. 1975. Growth rate, distribution and population density of the northern quahog, Mercenaria mercenaria, in Long Beach, California. Calif. Fish Game, 61(l):68-85. Reish, Donald J. 1968. Marine life of Alamitos Bay. Forty-Niner Shops, Inc., Long Beach, Calif. 92 p. — L^rry G. Allen, Department of Biology, California State University, Fullerton, California 92634. Accepted August 1975. 315 BOOK REVIEWS The Fly-Tyer's Almanac by Robert H. Boyle and Dave Whitlock; Crown Publishers, Inc. New York. 1975. xii + 242 p. Profusely illustrated. $12.95. Crown Publishers, Inc., continues to lead the field in top quality fishing books. The Fly-Tyer's Almanac is another fine example. To quote from the blurb on the cover, the Almanac is "a practical, fully illustrated guide to the latest advances and developments in fly tying, including more than 20 proven patterns for fresh- and saltwater, described by their creators — new materials, tools, and techniques . . ." Unless a fly tyer is associated with a really fine fly typing shop or with a truly innovative tyer, his chances of developing the techniques and skills necessary to tie a really first quality fly are really pretty slim. Top quality shops and /or innovative tyers who are willing to share or teach on a one-to-one basis are always few and far between. The Almanacis offered as a forum to present new ideas, techniques, and materials. A second volume designed to update this current volume is already planned. There are new, innovative imitations for taking trout, steelhead, black bass, striped bass, and other saltwater species. Caddis, dragon- and damselflies, midges, leeches, frogs, shrimp, and various fresh- and saltwater minnows are beautifully and artfully imitated. Materials range from the usual fur and feathers to polypropylene, liquid latex, and other synthetics. There are comprehensive chapters on life history aspects of dragonflies and caddis flies. The appendixes include a glossary of ento- mology, a list of basic scientific books and periodicals, names and addresses of the world's top dealers in fly tying materials, and profiles on this vol- ume's contributors, to hit just the major sections. The entire book is profusely illustrated with excellent, step-by-step photographs, and several color plates. This is really a top quality book and the first "how to" book that has sent me running to my fly shop to purchase the necessary materials so I could try some of the patterns. The price is a reasonable $12.95. — K A. Hashagen, Jr. Fisherman's Fall by Roderick L. Haig-Brown; Crown Publishers, Inc., 1975; viii + 279 p. illustrated. $7.50. Like the other three books in Haig-Brown's cycle of the seasons, Fisher- man 's Fall is a combination of excellent writing, personal observations, and fishing experiences. It was originally published in 1964 as the last book of the four-book series. Fall in the northwestern United States and in British Columbia is the time of movement. Haig-Brown talks about the Pacific salmon, their life cycles, and their return to fresh water. His discussions cover all aspects of fishing and fisheries science. He touches on artificial spawning channels and their potential value. There is, as always, a strong plea for habitat protection and warnings of the danger of excessive logging and of dam construction. One entire section of the book is devoted to estuaries — the description of an estuary, patterns and problems, and solutions and surmises. Steel- head, obviously the author's favorite fall species, are covered comprehen- sively. Low water, fast water, dry fly, personal observations, and actual experiences, when described by Haig-Brown, make fascinating and in- formative reading. 316 CALIFORNIA FISH AND GAME The final two sections, "Aquarium Notes" and "Conclusions'", contain a comprehensive discussion of the author's observations of young fish and their forage in aquaria and in situ during snorkeling drifts down the rivers he fishes. He chronicles the arrival of the salmon and steelhead in the rivers in the fall, and his underwater observations of behavior, interac- tions, and holding locations of these fish in the rivers provide valuable information for the fisherman. Excellent writing, combined with accurate facts and interesting experiences, make this Haig-Brown book well worth the asking price of $7.50. — K. A. Hashagen, Jr. Fisherman's Winter by Roderick L. Haig-Brown. Crown Publishers, Inc., New York. 1975. 288 p. illustrated. $7.50. Originally published in 1954, Fisherman 5 Winter vs, once again available, and* like all other Haig-Brown books, this one is well worth the time it takes to read it. Unlike the other three books in the series {Fisherman s Spring, Summer, and Fall), this book is not about the Pacific Northwest and salmon and steelhead. Fisherman 's Winter is about salmonid fishing in South America — Chile and Argentina — and is not about winter fishing but about a "second summer". Today most of the fishing magazines carry ads for fishing tours to South America, but Haig-Brown was there before this type of trip became relatively commonplace. The Tolten, Liucura, and Trancura rivers, Lago Maihue and the Calcurrupe, big water and big fish; the armchair fisherman can really sit back and enjoy this one. — K. A. Hashagen, Jr. Fly Fishing Strategy by Doug Swisher and Carl Richards; Crown Publishers, Inc., N. Y. 1975; 184 p., illustrated. $10.00. The fly leaf of Fly Fishing Strategy indicates the book "presents a new system of practical fly fishing techniques — casts, approaches, patterns, and equipment — that every fly fishing enthusiast can use". After reading the book, I found I was having a little bit of trouble with that introductory sentence, particularly the words "new" and "every". The casts they at- tempt to teach are not new — the roll, the reach, and the curve casts — and the analogies they use to teach their system aren't new. Using the text and its accompanying illustrations, I was unable to "teach" myself how to cast, although I spent several hours casting with various rods out on the lawn. If you know enough about casting to understand the book's explanations, you probably don't need the book! The chapters on hatches and fly tying are good, thought provoking, and clearly are what the authors should be writing about. The concepts of the stillborn dun and the no-wing spinner are interesting; but, with our unso- phisticated California fish, I'm not sure how necessary. The chapters on the midwest salmon and steelhead fisheries, lake fishing, and saltwater fly fishing are weak, based on relatively few trips and a lot of talk and theory. The section on new tying materials and techniques has one major short- coming in that it fails to tell the reader where the new products can be obtained. The book is very handsomely illustrated, with line drawings in the margins by Dave Whitlock, and the few color photographs are superb. All-in-all, it is a fine book, well worth the price; it just doesn't have the "meat" that Selective Trout did. — K. A. Hashagen, Jr. REVIEWS 317 Fly Fishing for Trout By Richard W. Talleur; Winchester Press, N.Y., 1974; 260 p., illustrated with both black and white and color photos. $10.00. The complete title of this book is Fly-Fishing for Trout — A Guide for Adult Beginners. The book is complete. I really think someone who had never fly fished and knew no one who did, could pick up the book and quickly learn to go out and catch trout. The book begins very basically, describing how to put a rod together and string a line on it. Equipment is discussed thoroughly, including construction, care, cost, and quality. Casting — both basic and slightly more advanced — is covered. Leaders, fly tying, stream entomology, how to read water, and conservation are all covered thoroughly and completely. The photos, by Matt Vinciguerra, and the drawings, by Roberta Sullivan, are clear and detailed. If the book has any drawbacks at all, it would be that the author often gets a little too chatty and flowery for my taste. By reading Mr. Talleur's book and talking with competent fly fishermen, any adult can quickly master the delightful hobby of fly fishing. — K. A. flashagen, Jr. Fisherman's Summer By Roderick L. Haig-Brown; Crown Publishers, Inc., New York, 1975; 253 p., illustrated. $7.50. A Haig-Brown book doesn't need a long, detailed review to convince potential buyers that this is the book they should buy. Any fisherman who las read one Haig-Brown fishing book will quickly buy any new offering 3y the author. Fisherman 's Summer is another Crown Publishers, Inc. reprint. It is another of the four book series on the fishing seasons. It was first published in 1959 and quickly became a collector's item (as are original editions of the other three seasons). Fisherman s Summer talks about grayling, early British Columbia explorers, the Campbell River on Vancouver Island, summer steelhead, and salt water fishing. It is another delightful book by an excellent author and fisherman. — K. A. Hashagen, Jr. Culture of Bivalve Molluscs By P. R. Walne: Fishing News (Books Ltd.) 23 Rosemount Avenue, West Byfleet, Surrey, England. 172 p., illustrated. 1975 £5.85 This book evolved from a series of lectures given by the author in 1968 under the auspices of the Buckland Foundation. It is largely a review of the investigations made at the Fisheries Experiment Station, Conway, on the culture of oysters and other bivalve molluscs. The opening chapter describes the structure, physiology and reproduc- tion of bivalves which are particularly relevant to hatchery culture. Other topics in succeeding chapters deal with methods and conditions of rearing larvae of the European flat oyster in outdoor tanks during the summer months and the hatchery rearing of oyster larvae including the handling of the larvae, a description of the seawater supply, provision of adequate amounts of algae for food, and care of the breeding stock. The effect of various factors on growth and survival of oyster spat is discussed and also methods which have been found satisfactory for spat culture at Conway are described. Although the principal work at Conway has been concentrated in the European flat oyster, experience of rearing six other species, five of which are not native to the British isles, are detailed. These species include the Chilean oyster, Ostrea chilenses; the New Zealand oyster, Ostrea lutaria; 318 CALIFORNIA FISH AND GAME the Pacific oyster, Crassostrea gigns; \.\\e Palourde or butterfish, Venerupis decussata; the Chilean mussel, Chromytilies choros; and Quahay, Mer- cenaire Venus mercenaria. A total of 38 figures and 24 plates well illustrate the experiments and activities carried on at Conway. This book, based on Dr Walne's outstanding success in his work at Conway for almost 25 years, should be of great benefit to aquaculturists who are engaged in or are contemplating entering the new and promising industry of shellfish cultivation. — Walter A. Dahlstrom Northern Fishes By Samuel Eddy and James C. Underhill; Univ. of Minn. Press, Minneapolis, 1974. 414 p. $17.50 This is the third edition of Northern Fishes (Fishes of Minnesota would be a more appropriate title) . This edition was written to reflect significant changes in the distribution of Minnesota fishes, to add to the list of species, and to add up-to-date information on current knowledge of fishes and their environment. The last edition was published in 1947. The authors updated and improved chapters on fishing techniques, lake dynamics, population dynamics, and classification and origin of fishes. The chapter on management of waters was changed slightly from the second edition by adding a paragraph on pollution, and the chapter on improvement of lakes and streams was changed slightly by adding a discussion of two- storied lakes and improving lakes by introducing new species. The second edtion chapter on structure of fishes was improved considerably and it is now titled "Anatomy and Physiology of Fish". A new chapter on the diet of fish was added, and a chapter on fish parasites was expanded to include infections of fish. A new chapter was added which describes how the aquatic environment contrasts from the terrestrial environment. The re- mainder of the book is devoted to descriptions of families and species of fish. Species accounts include current information on characteristics, range, habits, spawning, value, and status. Although most of the informa- tion pertains to Minnesota, much of it has broader application. Descrip- tions of ranges, for example, embrace other areas of the continental United States. The first and second editions had several photos of fishes, a few in color; this edition has good line drawings of almost all species. Initially, Northern Fishes was published as a source of basic information for sportsmen and others who were concerned with the welfare of fish. The latest edition would be a worthwhile possession for any angler; it would be quite useful to students, and I believe it is a must for professional biologists and teachers. — Larry K. Puckett Pollution Ecology of Freshwater Invertebrates C. W. Hart, Jr. and Samuel L H. Fuller, eds.; Academic Press, Inc., N.Y., 1974; 389 p., $24.50. Any student of biology knows how tedious a literature search for infor- mation can be. Add to that a gross lack of data and a successful search becomes near impossible. Such is the case in the study of pollution and its effects on freshwater invertebrates. With the amount of interest focused today by government and private business on pollution and ecology, this scarcity of knowledge is incredible but sadly true. Pollution Ecology of Freshwater Invertebrates was written with this REVIEWS 319 problem in mind. It is multi-purpose in design: it presents discussions on both the normal and pollution ecology of freshwater invertebrates, gives the latest systematic interpretations, and compiles extensive reference lists as starting points for data searches. Each chapter covers a major taxonomic group and is written by an accepted authority in that field. Much of the text is tables and graphs. There is much to recommend the book. Each of the authors has written a concise yet clear synopsis of the current knowledge of ecology in his field of interest. A semi-outline organization and a table of contents in each chapter make relocating any specific topic easy. The reference lists alone could save hours of individual labor and are, for that very reason, invalua- ble. Some items deserve special mention. I greatly appreciated John Cairn, Jr.'s tips on how to collect and preserve protozoans during field studies. Also, Samuel Fuller's tables citing references for some freshwater mussels and their glochidial host fish could save a novice researcher much time and energy. After reading this book, I think it would be a valuable addition to any reference library, whether public or private. — E. V. Qleason Best Ways to Catch More Fish (in fresh and salt water) By Vlad Evanoff; Doubleday and Co., Inc., Garden City, N.Y., 1975; 228 p., illustrat- ed. $7.95 This is another in a series of "how to" by this author. At this stage of the game it seems a little superfluous that another general interest fishing book should be published. Indeed, even the author points out this short- coming in his foreword. Recognizing this, the author has tried to ". . . impart to anglers some new and helpful information they can't find in other fishing books." In spite of this, the book /5 another general book; one of a genre that exists in sufficient numbers. The material itself is mostly accurate. Reproduction of photographs is excellent. The format and text is easy to follow and a detailed index is included. For a beginning fisherman, perhaps, this would be a beneficial book. It would be useful as a gift for a young fisherperson just starting out. — Ed Littrell 320 CALIFORNIA FISH AND GAME 321 INDEX TO VOLUME 62 AUTHORS Aceituno, Michael E., Mark L. Caywood, Stephen J. Nicola and W. I. Follett: Occurrence of Native Fishes in Alameda and Coyote Creeks, California, 195-206 Aceituno, Michael E., and Stephen J. Nicola: Distribution and Status of the Sacramento Perch, Archoplites interruptus (Girard), in California, 246-254 Aceituno, Michael E., and C. David Vanicek: Life History Studies of the Sacramento Perch, Archoplites interruptus (Girard), in California, 5-20 Ainley, David G.: see Follett and Ainley, 28-31 Allen, James M.: Addition of Citharichthys fragilis Gilbert to the California Fauna, 299-303 Allen, Larry G.: Additions to the List of Fish Species Known from Alamitos Bay, California, Based on Studies in Colorado Lagoon, 310-314 Behrstock, Robert A.: First Record of the Decorated Warbonnet, Chirolophis decoralus (Jordan and Snyder 1902) in California Waters, 308-309 Bernard, David R.: see Twedt and Bernard, 21-27 Boles, Gerald L.: A Range Extension for the Logperch, Percina macrolepida in California, 154 Bowlus, Donald R.: see Carpenter and Bowlus, 168-178 Carpenter, M. Ralph, and Donald R. Bowlus: Attitudes Toward Fishing and Fisheries Management of Users in Desolation Wilderness, California, 168-178 Carroll, Dennis: see Chesemore and Carroll, 158-159 Caywood, Mark L.: see Aceituno, Caywood, Nicola and Follett, 195-206 Chesemore, David L., and Dennis Carroll: First Record of the Mohave Ground Squirrel {Citellus mohavensis) in Kern County, California, 158-159 Connolly, Guy E., Michael E. Fry and Janet Fammatre: Prey Remains at a Golden Eagle, Aquila chrysaetos. Nest Near Hopland, California, 85-86 DeMartini, John D.: see Wendell, DeMartini, Dinnel and Siecke, 41-64 Dinnel, Paul: see Wendell, DeMartini, Dinnel and Siecke, 41-64 Duncan, Don A.: Frequent Mowing Increases Turkey Mullein on California Foothill Rangeland, 82-84 Eley, Thomas J., Jr.: Helminth Parasites in American Coots from the Lower Colorado River, 156-157; Fall and Winter Foods of American Coots Along the Lower Colorado River, 225-227 Fammatre, Janet: see Connolly, Fry and Fammatre, 85-86 Follett, W, I.: First Record of Albinism in the Leopard Shark ( Triakis semifasciata) , 163-164; see Aceituno, Caywood, Nicola and Follett, 195-206 Follett, W. I. and David G. Ainley: Fishes Collected by Pigeon Guillemots, Ceppbus columba (Pallas), Nesting on Southeast Farallon Island, California, 28-31 Foreman, Larry D.: Nest Site and Activity of an Incubating Common Merganser in Northwestern California, 87-88; Observations of Common Merganser Broods in Northwestern California, 207-212 Fry, Michael E.: see Connolly, Fry and Fammatre, 85-86 Geibel, John J., and Richard F. G. Heimann: Assessment of Ocean Shrimp Management in California Resulting from Widely Fluctuating Recruitment, 255-273 Gill, Robert E., Jr.: On the Foraging Distance and Prey Selection of Nesting Caspian Terns, 155 Gotshall, Daniel W.: see Prince and Gotshall, 274-285 Gregory, Paul A., and Tom Jow: The Validity of Otoliths as Indicators of Age of Petrale Sole from California, 132-140 Heimann, Richard F. G.: see Geibel and Heimann, 255-273 Hobson, Edmund S.: The Rock Wrasse, Halichoeres semicinctus, as a Cleaner Fish, 73-78 Hughes, Steven E.: Simple Container for the Collection and Storage of Otoliths, 306-307 Huntsinger, K. R. (Gina), and Paul E. Maslin: Contribution of Phytoplankton, Periphyton, and Macrophytes to Primary Production in Eagle Lake, California 187-194; A Limnological Comparison of the Three Basins of Eagle Lake, California, 232-245 Jow, Tom: see Gregory and Jow, 132-140 Klingbeil, Richard, and Eric H. Knaggs: Southern Range Extension of the Blue Rockfish, Sebastes mystinus, the Flag Rockfish, S. rubrivinctus, and the Shortbelly Rockfish, S. jordani, 160 Knaggs, Eric H.; see Klingbeil and Knaggs, 160 Kohlorst, David W.; Sturgeon Spawning in the Sacramento River in 1973, as Determined by Distribution of Larvae, 32-40 Maslin, Paul E.: see Huntsinger and Maslin, 187-194; 232-245 322 CALIFORNIA FISH AND GAME May, Robert C; Effects of Salton Sea Water on the Eggs and Larvae of Bajrdiella icistia (Pisces: Sciaenidae), 119^131 Misitano, David A.; Size and Stage of Development of Larval English Sole, Parophrys vetulus. at Time of Entry into Humboldt Bay, 93-98 Moring, John R.: Estimates of Population Size for Tidepool Sculpins, Oligocottus maculosus, and Other Intertidal Fishes, Trinidad Bay, Humboldt County, California, 65-72 Moyle, Peter B.: Some Effects of Channelization on the Fishes and Invertebrates of Rush Creek, Modoc County, California, 179-186 Nicola, Stephen J.: see Aceituno, Caywood, Nicola and Follett, 195-206; Aceituno and Nicola, 246-254 Peden, Alex E.: First Records of the Notacanth Fish, Notacanthus chemnitzi Bloch, from the Northeastern Pacific, 304-305 Prince, Eric D., and Daniel W. Gotshall: Food of the Copper Rockfish, Sebastes caurinus Richardson, Associated with an Artificial Reef in South Humboldt Bay, California, 274-285 Rienecker, Warren D.; Distribution, Harvest and Survival of American Wigeon Banded in California, 141-153 Schuur, Anthonie: see Wickham, Shleser and Schuur, 89-92 Siecke, John: see Wendell, DeMartini, Dinnel and Seicke, 41-64 Shleser, Robert: see Wickham, Shleser and Schuur, 89-92 Sturgess, James A.: Taxonomic Status of Percina in California. 79-81 Sunada, John S.: Age and Length Composition of Northern Anchovies, Engraulis mordax, in the California Anchovy Reduction P'ishery, 1973-74 Season, 213-224 Talent, Larry C: Food Habits of the Leopard Shark, Triakis semifasciata, in Elkhorn Slough, Monterey Bay, California, 286-298 Turner, Jerry L.: Striped Bass Spawning in the Sacramento and San Joaquin Rivers in Central California from 1963 to 1972, 106-118 Twedt, Thomas M., and David R. Bernard: An All- Weather, Two- Way Fish Trap for Small Streams, 21-27 Vanicek, David C: see Aceituno and Vanicek, 5-20 Wendell, Fred, John D. DeMartini, Paul Dinnel and John Siecke: The Ecologj- of the Gaper or Horse Clam, Tresus capax (Gould 1850), (Bivalvia, Mactridae), in Humboldt Ba\', California, 41-64 Wickham, Daniel E., Robert Shleser and Anthonie Schuur: Observations on the Inshore Population of Dungeness Crab in Bodega Bay, 89-92 Work, Jack Q). \ Swimming Crab, Euphvlax doviiSKim.'pson 1860, New to the Marine Fauna of California, 161-162 SCIENTIFIC NAMES Acanthogobius fJavimanus: 295 Acipenser guldenstadti: 37 Acipenser medirostris: 32 Acipenser nudiventris: 37 Acipenser stellatus: 37 Acipenser transmontanus: 32 Aix sponsa: 151 Allosmerus elongatus: 278 AInus rubra: 2ff7 Ameletus: 185 Amidostomum fulicae: 156-157 Ammodytes hexapterus: 278 Anabaena: 190 Anabaena flos-aquae: 242 Anas acuta: 142 Anas americana: 141 Anas clypeata: 143 Anas crecca: 143 Anas platyrhynchos: 142 Anisotremus daxidson: 130 Anser caerulescens hyperborea: 145 Arbutus menziesii: 87, 207 Archoplites: 246 Archoplites interruptus: 5, 198 Armandia bioculata: 277 Artedius Harrington: 29 Atherinops a/finis: 295 Atherinopsis caJiforniensis: 155, 295 Aythya vaslisineria: 142 Bairdiella icistia: 119 Barleeia sp.: 278 filepharipoda occide.>!a/i>: 291-294, 296 I'othragonus suanil: 2'-* dnichionus plicatilis: 129 Brachycentrus: 185 Bromus spp.: 85 Bulbochacta: 190 Callianassa caJiforniensis: 291, 293 Callinectes arcuates: 161 CaJ/inectes bellicosus: 161 Cancer: 91, 277, 295 Cancer sp.: 277, 279-280 Cancer antennarius: 277, 291-294 Cancer gracilis: 92. 291-294 Cancer magister: 41, 60, 89-91. 274-275. 277. 279-280. 291-294, 296 Cancer productus: 277. 280. 291-294 Caprella caJifornica: 2T1, 280 Caprella equilibra: 277 Caprella incisa: 277 Caprella laenuscula: 277. 279-280 Carassius auratus: 6. 155, 198 Cardium edule: 50, 53 Carex sp.: 225-226 Catostomus microps: 179 Catostomus occidentaJis: 7, 181. 198, 253 Ceppbus columba: 28 Cetengraulis mysticetus: 130 Chaoborus: 244 Chirolophis decoratus: 308-309 INDEX 323 Chirolophis nugator: 29, 309 Chirolophis polyactocephalus: 308 Chitonotus pugetensis: 29 Cibicula leana: 226 Citellus beecheyi: 85 Citellus mohavensis: 158 Cithahchtys spp.: 278, 302 Cithahchthys fragilis. 299, 301-302 Citharichthys sordidus: 301-302 Citharichthys stigmaeus: 29, 295, 301-302 Cithahchthys xanthostigma: 301-302 Clinocottus recalvus: 30 Cloacotaenia megalops. 156-157 Clupea harengus pallasi: 295 Coleochaete: 190 Corvus brachyrhynchos: 85 Cot t us asper: 198 Cot t us gulosus: 198 Cottus pintensis: 179 Co«uy spp.: 252 Crangon franciscorum: 277 Crangon nigricauda: 277, 279-280 Crangon nigromaculata: 275, 277, 279-280 Crangon sp.: 277, 279, 291-294 Crangon spp.; 280 Cyc/ocoe/um mutabi/e: 156-157 Cyclops vernalis: 242 Cymatogaster aggregatus: 155, 275, 278, 280, 295 Cynoscion parxipinnis: 130 Cynoscion xanthulus: 130 Cyprinodon maculahous: 129 Cyprinus carpio: 6, 155, 198, 253 Damalichthys vacca: 76 Daphnia galeata mendotae. 242 Daphnia achperi: 242 Diaphanosoma leuchtenbergianum: 242 Diaptomus scilis. 242 DioTchis inflata: 156-157 Distichhs stricta: 226 Dorosoma petenense: 7, 129 Echinostoma chloropodis: 156 Echinostoma revolutum: 156 Eleochahs macrostachya: 226 Embiotoca jacksoni: 74, 295 Embiotoca lateralis: 276 Emerita anaJoga. 291, 293 Engraulis mordax. 130, 213, 275, 278-280, 295, 310 Enophrys bison: 276 Enteromorpha sp : 288 Entosphenus tridentatus: 198 Eopsetta jordani: 132 Ephemerella: 185 Epigeichthys: 30 Eremocarpus setigerus: 82, 84 Eubhanax: 185 Euphylax do\ii: 161 Filrnia terminalis: 242 Fragilaria: 190 Fragilaria crotenensis: 242 Fulica americana: 156 CaJeorhinus zyopterus: 286 Gambusia affinis: 6, 198 Gasterosteus aculeatus: 198, 253, 278 Genyonimus lineatus: 295 Gibbonsia montereyensis: 29 C/7a bicolor:!, 253 C//a crassicauda: 198, 253 Gillichthys mirabilis: 129 Girella nigricans: 74 Gomphonema: 190 Comphonema sp.: 242 Gracilaria sp.: 295 Halichoeres semicinctus: 73 Hemigrapsus oregonensis: 286, 291-297 Hemilepidotus spinosus: 29, 276 Heptagenia: 185 Hesperoleucus symmetricus: 198 Hexagrammos decagrammus: 276 Hexarthra sp.: 242 //u.so /ju5a- 37 Hydrolagus colliei: 29 Hydroprogne Caspia: 155 Hydropsyche: 183, 185 Hypsurus caryi: 76 Hypsypops rudicundus: 74 Hysterocarpus traski: 198 Icelinus oculatus: 29 Icelinus tenuis: 29 Ictalurus catus: 198 Ictalurus nebulosus: 7, 198, 253 Ictalurus punctatus: 6 Idothea resccata: 277, 279 /ro/3. 185 Isoperia: 185 /u/7cu:s. 190-193 Juncus baJticus: 190, 192 Juncus sp.: 225-226 Keratella cochlearis: 2A2 Keratella quadrata: 242 Labroides phthirophagus: 76 Lampetra lethophaga: 181 Lampetra richardsoni: 198 Larrea divaricata: 158 Laxinia exilicauda: 198, 253 Lepomis cyanellus: 6, 198, 253 Lepomis machrochirus: 6, 155, 198, 252-253 Leptocottus armatus: 155, 276, 295 Leptodora Kindtii: 242 Lepus californicus: 85, 86 Limnophilus: 185 Lithocarpus densiflorus: 207 Livoneca vulgaris: 277 Loligo opalescens: 288 Loxorhxnchus crispatus: 277 Macrocystis: 73 Medialuna californiensis: 74 Mercenaria mercinaria: 310 Mergus merganser: 87, 207 Merluccius productus: 283 Merismopedia tenuissima: 242 A//cro Cooddingii: 225-226 Salmo clarki: 22 5ii/mo gairdneri: 7, 22. 155. 179. 198. 253 5ay/no fro«a. 7. 22, 179. 253 SaJvelinus fontinaJis: 22 Saxidomus nuttaJli: 278 Saxidomus nuttallii: 295 Scirpus: 190-193 Scirpus acutus: 190-193 Scirpus californicus: 225-226 Scirpus lacustris: 193 Sciurus griseus: 85-86 Scorpaenichthys marmoratus: 29 Sebastes: 274 Sebastes auriculatus: 276 Sebastes caurinus: 274 Sebastes couhnus: 276 Sebastes fl avid us: 29 Sebastes jordani: 29. 160 Sebastes melanops: 29. 69, 276 Sebastes mystinus: 29. 160, 276. 283 Sebastes pinniger: 29 Sebastes rubrivinctus: 160 Sequoia sempenirens: 207 Siliqua pa tula: 53 Siphonurus sp.: 226 Spirogyra sp.: 242 Spirontocaris brevirostris: 277 Spirontocaris sp.: 277. 279 Staurastrum sp.: 242 Strongyloides: 157 Strongyloides an'uni: 151 Strongyloides sp.: 157 Squalus acanthias: 286 Sylvilagus bachmani: 85 Symphurus atncauda: 295 Tamarix pentandra: 226 Tresus capax: 41. 278 Tresus nuttaJli: 60 7>wui nuttallii: 288. 295 7>;ajt« semi fascia ta: 163. 286. 290 Trichocerca sp.: 242 Tricorythodes: 185 Tritella pilimana: 277 Typha latefolia: 266 Ultricularia vulgaris: 190 Umbellularia californica: 85 Upogebia pugettensis: 291. 293 Urechis: 296 t/recA« caupo: 286, 288. 293-296, 291-292 Vsnea spp.: 85 Xererpes fucorum: 30 Xiphister: 30 Xiphister atropurpureus: 30 Xiphister mucosus: 30 Zirfaea pilsbryi: 295 ZoiYera sp.: 275. 278. 280. 295 SUBJECT Age: of Petrale sole, otoliths as indicators of, 132-140 Age composition; of northern anchovies in the 1972-73 season California anchovy reduction fishery, 213-224 Alameda: occurrence of native fishes in, 195-206 Alamitos Bay: additions to the list of fish species, 310-314 Albinism: in the leopard shark, first record of, 163-164 All-weather, two-way fish trap; for small streams, 21-27 Anchovy, northern: age and length composition in 1972-73 season California anchovy reduction. 213-224 Anchovy reduction fishery; age and length composition of northern anchovies in, 1972-73, 213-224 Attitudes; toward fishing and fisheries management of users in desolation wilderness, 168-178 Bairdiella icistia: effects of salton sea water on the eggs and larvae of, 119-131 Bass, striped; in the Sacramento and San Joaquin Rivers, spawning of, 106-118 Bodega Bay; observations on the inshore population of Dungeness crab of, 89-92 INDEX 325 Broods: of common merganser in northwestern California, observations of, 207-212 California foothill rangeland: frequent mowing increases Turkey mullein, 82-84 Caspian terns: foraging distance and prey selection of, 155 Channelization: on the fishes and invertebrates of Rush Creek, effects of, 179-186 Cleaner fish: Rock wrasse as, 73-78 Colorado River, lower: helminth parasites in American coots from, 156-157; fall and winter foods of American coots along the, 225-227 Coots, american: from the lower Colorado River, helminth parasites in, 156-157; along the lower Colorado River, fall and winter foods of, 225-227 Comparison, limnological: of the three basins of Eagle Lake, 232-245 Container: for the collection and storage of otoliths, 306-307 Contribution: of phytoplankton, periphyton, and macrophytes to primary production in Eagle Lake, 187-194 Coyote Creeks: occurrence of native fishes in, 195-206 Crab, dungeness: observations of inshore population, 89-92 Crab, swimming: new to the marine fauna of California, 161-162 Decorated Warbonnet: in California Waters, first record of, 308-309 Development, state of: of Larval English Sole at time of entry into Humboldt bay, 93-98 Distribution: of American Wigeon banded in California, 141-153; of Sacramento Perch in California, 246-254 Eagle Lake: contribution of phytoplankton, periphyton, and macrophytes to primary production in, 187-194; a limnological comparison of the three basins of, 232-245 Ecology: of Gaper or Horse clam in Humboldt Bay, 41-64 Eggs and Larvae: of Bairdiella icistia, effects of salton sea water on, 119-131 Elkhorn slough: food habits of the leopard shark, 286-298 Farallon Island, southeast: fishes collected by nesting Pigeon Guillemots, 28-31 Fish species: additions to the list of, known from Alamitos Bay, 310-314 Fish trap: all-weather, two-way for small streams, 21-27 Fishes, collected: by Pigeon Guillemots nesting on southeast Farallon Island, California, 28-31 Fishes and invertebrates: of Rush Creek, effects of channelization on, 179-186 Fishing and fisheries management: of users in desolation wilderness, attitudes toward, 168-178 Food: of Copper Rockfish associated with an artificial reef in south Humboldt bay, 274-285 Food habits: of the leopard shark in Elkhorn Slough, 286-298 Foods: of American coots along the lower Colorado River in fall and winter, 225-227 Gaper or Horse clam: ecology of in Humboldt Bay, 41-64 Golden Eagle: nest near Hopland, California, 85-86 Harvest: of American Wigeon banded in California, 141-153 Helminth parasites: in American coots from the lower Colorado River, 156-157 Hopland, California: prey remains at a Golden eagle nest, 85-86 Humboldt bay: ecology of the Gaper or Horse clam in, 41-64; size and stage of development of Larval English Sole at time of entry, 93-98; food of the Copper Rockfish associated with an artificial reef in, 274-285 Intertidal fishes; estimates of population size in Trinidad bay, 65-72 Invertebrates and fishes: of Rush Creek, effects of channelization on, 179-186 Kern County: first record of the mohave ground squirrel in, 158-159 Larvae and eggs: of Bairdiella icistis, effects of salton sea water on, 119-131 Larval English Sole: size and stage of development at time of entry into Humboldt Bay, 93-98 Lenth composition: of northern anchovies in 1972-73 season California anchovy reduction fishery, 213-224 Life history study: of Sacramento Perch in California, 5-20 Logperch: range extension for, 154 Macrophytes: contribution to primary production in Eagle Lake, 187-194 Management: assessment of Ocean shrimp, 225-273 Merganser, common: incubating in nest site and activity of, 87-88; observations of broods in northwestern California, 207-212 Mohave ground squirrel: in Kern County, first record of, 158-159 Native fishes: in Alameda and Coyote Creeks, occurrence of, 195-206 326 CALIFORNIA FISH AND GAME Notacanth fish; from the northeastern Pacific, first records of, 304-305 Observations: of Dungeness crab, inshore population at Bodega Bay, 89-92; of Common merganser broods in northwestern California, 207-212 Occurrence; of native fishes in Alameda and Coyote Creeks, 195-206 Ocean shrimp; assessment of management, 255-273 Otoliths; of Petrale sole, as indicators of age, 132-140; simple container for the collection and storage of, 306-307 Parasites, helminth; in American coots from the lower Colorado River, 156-157 Percina: taxonomic status in California, 79-81 Periphyton; contribution to primary production in Eagle Lake, 187-194 Petrale sole; otoliths as indicators of age of, 132-140 Phytoplankton: contribution to primary production in Eagle Lake, 187-194 Pigeon guillemots; fishes collected while nesting on southeast Farallon Island, California, 28-31 Population, inshore: of Dungeness crab at Bodega Bay, 89-92 Population size; estimates for tidepool sculpins and other intertidal fishes in Trinidad Bay, 65-72 Range extension, southern; of the Blue Rockfish, Flag Rockfish, and Shortbelly Rockfish, 160 Rockfish; Blue, Flag, and Shortbelly; southern range extension of, 160 Rockfish, Copper; food of, 274-285 Rock Wrasse: as a cleaner fish, 73-78 Rush Creek; effects of channelization of the fishes and invertebrates of, 179-186 Sacramento Perch: life history study in California, 5-20; in California distribution and status of, 246-254 Sacramento River; site of spawning sturgeon, 32-40; spawning of striped bass, 106-118 San Joaquin River; spawning of striped bass, 106-11 Shark, leopard: in Elkhorn, food habits of, 286-298 Size; of Larval English Sole, 93-98 Spawning: of sturgeon in the Sacramento River, as determined by distribution of larvae, 32-40 Status: of Sacramento Perch in California, 246-254 Status, taxonomic; of Percina in California, 79-81 Sturgeon: spawning in the Sacramento River, 32-40 Survival; of American Wigeon banded in California, 141-153 Taxonomic status; of Percina in California, 79-81 Tidepool Sculpins; estimates of population size of, 65-72 Trinidad Bay; estimates of population size for tidepool sculpins and other intertidal fishes, 65-72 Turkey Mullein; increases on California foothill rangeland, 82-84 Wigeon, American: distribution, harvest and survival of, 141-153 Photoelectronic composition by CALIFORNIA OFHCE OF STATK PRINTING VC89335— 800 5-76 4,500 LDA ^