ANTONELIS ET AL.: SPRING AND SUMMER PREY OF CALIFORNIA SEA LIONS 



1978 



1979 



Northern anchovy 



Juvenile Rockfish 



Market squid 



Pacific whiting 



Spring 

 Summer 



n = 39 



n = 18 



n = 26 



-i i i l i i i i l i i    i   '    



10 20 30 40 50 60 70 80 90 100 10 20 30 40 50 60 70 80 90 100 



Occurrence (percent) 



Occurrence (percent) 



FIGURE 2. — Spring and summer occurrence (percentage) of the four major prey species identified in California sea 



lions scats collected on San Miguel Island, Calif., 1978-79. 



Spring, n = 67 

 Summer, n = 128 



c 

 u 



v- 

 <D 

 _Q. 



0) 



o 



c 

 a> 



k_ 



L. 



D 

 U 

 O 



O 



2 3 4 5 



Number of different species 



FIGURE 3. — Occurrence of single and multiple prey species in in- 

 dividual sea lion scats collected on San Miguel Island, Calif., 1978- 

 79. 



shown in Figure 4. The seasonal changes in the per- 

 cent of weight for Pacific whiting showed a decrease 

 from spring to summer in 1978 and 1979, while an 

 increase occurred from spring to summer for market 

 squid in 1978 and rockfish in 1979. There was 

 relatively little change in the percentage of weight 

 between the two seasons for market squid in 1979 

 and rockfish in 1978. The northern anchovy also 

 showed little difference between the two seasons 

 during both years. Additionally, the results from this 

 analysis show that market squid made the greatest 

 contribution to the total estimated weight of prey in 

 the summer of 1978 (71.2%) and for both spring 

 (53.9%) and summer (48.7%) of 1979, while Pacific 

 whiting made the greatest contribution to the total 

 estimated weight only in the spring of 1978 

 (87.3%). 



DISCUSSION 



Pacific whiting, market squid, juvenile rockfish, and 

 northern anchovy were the four most important prey 

 of California sea lions at San Miguel Island during the 

 spring and summer of 1978 and 1979. These four 

 prey species have also been reported as common 

 prey of California sea lions in areas north of Point 

 Conception (Morejohn et al. 1978; Everitt et al. 

 1981; Jones 1981; Ainley etal. 1982) and exemplify 



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