PEREZ and BIGG: DIET OF NORTHERN FUR SEALS 



4 6 



Number of prey species 



10 



Figure 3.^The cumulative percentage distribution of the number 

 of prey species eaten in the total diet of northern fur seals taken 

 during 1958-74. Data for each of the 21 subregions are plotted, 

 although only the average relationship is graphed. 



cause the prey consumed by month within sub- 

 regions were not presented here, we take these data 

 from Perez and Bigg 5 in our interpretation of sub- 

 regional data. 



California 



Northern anchovy, Engraulis mordax, was the 

 most important food eaten by the northern fur seals 

 off California (Fig. 4A) whether its energy content 

 was considered or not. However, it was more im- 

 portant when its caloric value was taken into ac- 

 count. Northern anchovy was eaten mainly during 

 January to March in inshore and offshore waters of 

 central and southern California (Fig. 4B, C). Pacific 

 whiting, Merluccius productus, was second in im- 

 portance (Fig. 4A) and was preyed upon in all areas 

 of California, although primarily during April and 

 May (Fig. 4B, C). Market squid, Loligo opalescens, 

 was eaten from January to June, but only in neritic 

 locations (Fig. 4B, C). Onychoteuthid squids (Ony- 

 choteuthidae) were eaten offshore and were the 

 more important squid species consumed in the south- 

 ern areas off California (Fig. 4C). Other prey types 

 were of relatively minor importance, although some 

 were locally significant, such as Pacific saury, Colo- 

 labis saira, mainly in oceanic areas off northern and 

 central California (Fig. 4 A, B, C). 



6 Perez, M. A., and M. A. Bigg. 1981. An assessment of the 

 feeding habits of the northern fur seal in the eastern North Pacific 

 Ocean and eastern Bering Sea. Unpubl. draft rep., 146 p. North- 

 west and Alaska Fisheries Center, National Marine Mammal 

 Laboratory, National Marine Fisheries Service, NOAA, 7600 Sand 

 Point Way N.E., Seattle, WA 98115. 



100 



Figure 4.— Composition (percent) of diet of northern fur seals by 

 prey species off California during 1958-74 (A) for pooled January- 

 June samples (N = 1,811), using modified volume (dark bars) and 

 energy-adjusted modified volume; (B) by month using modified 

 volume; and (C) by subregion with pooled January-June samples 

 using modified volume. A dark line separates squid and fish 

 categories in the latter two figures. Key: ANC = northern an- 

 chovy; GON = gonatid squids; JAC = jack mackerel; JCK = 

 jacksmelt; MAR = market squid; MF = miscellaneous fish species; 

 MS = miscellaneous squid species; MYC = myctophiform fishes; 

 ONY = onychoteuthid squids; OP = other prey; SBL = sablefish; 

 SRY = Pacific saury; WHI = Pacific whiting. 



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