Abstract.- We studied the food 

 habits of the California sea lion Zalo- 

 phus califoniianus at San Clemente 

 Island, California, from September 

 1981 through September 1986 using 

 fish otoliths, cephalopod beaks, and 

 other prey remains we recovered from 

 1476 fecal samples (i.e., scats). We 

 identified 44 types of prey to species 

 and 8 types of prey to genus. Seven 

 types of prey occurred in at least 

 10% of scats: northern anchovy En- 

 graulis mordax (51.3%); jack mack- 

 erel Tnifhurus symmetriais (24.6%); 

 pelagic red crab Pleuroncodes plani- 

 pes (21.2%); Pacific whiting AfeWwc- 

 cius productus (19.6%); rockfishes, 

 Sehastes spp. (19.0%); market squid 

 Loligo opalescens (16.3%); and black- 

 smith Chromis puwtipinnis (10.7%). 

 We examined trends in the occur- 

 rence of these seven species and of 

 Pacific mackerel Scomber japo7iicus 

 and octopus (Octopus spp.) in scats 

 of California sea lions. We found sig- 

 nificant differences among seasons 

 and years, and season-year differ- 

 ences in the occurrence of northern 

 anchovy, jack mackerel. Pacific whit- 

 ing, and octopus (P< 0.01). Significant 

 effects due to year and season-year 

 interaction were found for pelagic 

 red crab, rockfish, market squid, and 

 blacksmith. Pacific mackerel showed 

 a significant difference only among 

 years. Significant differences in the 

 occurrence of Pacific whiting, north- 

 ern anchovy, jack mackerel. Pacific 

 mackerel, market squid, octopus, and 

 pelagic red crab (P<0.01) were found 

 during pre-El Nifio, El Nifio, and 

 post-El Nino periods. 



Food Habits of California 

 Sea Lions Zaiophus californianus 

 at San Clemente Island, 

 California, 1981-86 



Mark S. Lowry 

 Charles W. Oliver 

 Carolyn Macky 



Southwest Fisheries Science Center, National Marine Fisheries Service. NOAA 

 PO Box 271. La Jolla. California 92038 



Jeannie B. Wexler 



Southwest Fisheries Science Center, National Marine Fisheries Service, NOAA 

 PO Box 271, La Jolla, California 92038 

 Present address: Inter-American Tropical Tuna Commission 

 c/o Scripps Institution of Oceanography, La Jolla, California 92037 



Manuscript accepted 10 April 1990. 

 Fishery Bulletin, U.S. 88:509-521. 



Knowledge of California sea lion Za- 

 lophus californianus food habits in 

 the Southern California Bight (SCB, 

 Fig. 1) has come from stomach con- 

 tent analysis by Scheffer and Neff 

 (1948), and Fiscus and Baines (1966); 

 and from the 1978-79 spring and 

 summer study at San Miguel Island 

 from scat (i.e., fecal) analysis by An- 

 tonelis et al. (1984). These studies 

 identified a wide variety of prey. An- 

 tonelis et al. (1984) reported that 

 Pacific whiting, market squid, juve- 

 nile rockfish, and northern anchovy 

 were the four most important prey at 

 San Miguel Island. A 4-year study at 

 the Farallon Islands in northern Cali- 

 fornia (outside the breeding area) 

 found that sea lions switched be- 

 tween Pacific whiting and juvenile 

 rockfish (Bailey and Ainley 1982). 



From 1981 to 1986, we examined 

 prey consumed by California sea lions 

 using the shoreline located at and 

 south of Mail Point, San Clemente 

 Island (SCI, Fig. 1). San Clemente 

 Island has one of the smallest rook- 

 eries in the SCB (producing approx- 

 imately 666 pups in 1981) as com- 

 pared with San Miguel and San 

 Nicolas islands (producing approx- 

 imately 8255 and 6704 pups, respec- 



tively, in 1981; DeMaster et al. 1982, 

 Stewart and Yochem 1984, Oliver 

 and Lowry 1987). We analyzed fecal 

 samples (scats) to identify prey com- 

 position and temporal changes in the 

 diet. This period was characterized 

 by an abnormal influx of warm water 

 into the SCB during the 1982-83 El 

 Nino/Southern Oscillation (McGowan 

 1984). Effects of this El Nino within 

 the SCB became evident in October 

 1982, when sea-surface temperatures 

 were 1-2°C above normal, and zoo- 

 plankton levels declined (McGowan 

 1984). Water temperatures returned 

 to normal in October-November 1984 

 (F. Miller, Inter-Am. Trop. Tuna 

 Comm., La Jolla, CA 92038, pers. 

 commun., Oct. 1986). This warm- 

 water period off California has been 

 referred to as the California El Nino 

 (McGowan 1984, Fiedler etal. 1986). 



Methods 



Sample collection 



We collected fresh and dry scats dur- 

 ing 40 trips to SCI with between-trip 

 intervals ranging from 2 weeks to 3 

 months. Scats were separated into 

 one of three categories: (1) fresh 



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