PEREZ and BIGG: DIET OF NORTHERN FUR SEALS 



the energy value of prey. Data from all years of 

 collection were pooled. We assumed that the impor- 

 tance of a prey species to northern fur seals de- 

 pended, at least in part, on its energy content. Table 

 1 lists the estimated caloric values for prey species 

 consumed most often. These estimates are provi- 

 sional because little is known about changes in 

 energy content within each species by season. 

 Energy values for squids tend to be lower than those 

 for fishes, although large variability exists among 

 fish species. 



No attempt was made to describe diet by age, sex, 

 and reproductive condition. In our sample, 88% of 

 the northern fur seals were females aged >3 yr, of 

 which 53% were pregnant and 29% were nonpreg- 

 nant. Thus, the diet described is primarily that 

 for pregnant and nonpregnant females aged >3 



yr. 



The eastern North Pacific Ocean and eastern Ber- 

 ing Sea were divided into 7 regions and 21 sub- 

 regions (Fig. 1). The boundaries for the seven 

 regions were those which have been traditionally 



EASTERN BERING SEA 



SEALASKA 



BEROFF 



^V^ 



62° N 



.- y ( 



UNIMAK 



WESTERN ALASKA 



GULF OF ALASKA 



HECATE 



WASHOFF 

 WASHINGTON 



•BCIMLETS 



WESTVAN . 



PEROUSE 



OREGON 



WASHNO 



CALIFORNIA 



NORTH PACIFIC OCEAN 



NCALOFF 



CCALOFF 



SCALOFF 



CCALIN 



SCALIN 

 \ 



52° 



42° 



32° 



175° W 



155° 



135° 



115° 



Figure 1.— Seven regions (denoted by darker lines) and 21 subregions used in the northern fur seal analyses: 1) California comprised 

 of subregions SCALIN (southern California, inshore), SCALOFF (southern California, offshore), CCALIN (central California, inshore), 

 CCALOFF (central California, offshore), NCALIN (northern California, inshore), and NCALOFF (northern California, offshore); 2) 

 Oregon which includes half of subregion WASHNO (southern Washington and northern Oregon, inshore); 3) Washington which includes 

 subregions PEROUSE (area west of Juan de Fuca Strait from Barkley Sound to Cape Flattery, including La Perouse Bank and Swift- 

 sure Bank; inshore), WASHOFF (Washington, offshore), and half of WASHNO; 4) British Columbia which includes subregions BCINLETS 

 (inside passages and inlets of B.C., inshore), WESTVAN (area west of Vancouver Island and Queen Charlotte Strait, inshore), HECATE 

 (Hecate Strait area, inshore), and BCOFF (British Columbia, offshore); 5) the Gulf of Alaska which includes subregions SEALASKA 

 (southeast Alaska, inshore), NOGULF (northern Gulf of Alaska, including Fairweather Bank; inshore), KODIAK (area around Kodiak 

 Island, including Portlock Bank and Albatross Bank; inshore), and CENGULF (oceanic region of the Gulf of Alaska, offshore); 6) western 

 Alaska which includes part of subregion UNIMAK (Unimak Pass area); and 7) the eastern Bering Sea comprised of subregions BERIN 

 (Bering Sea shelf, inshore) and BEROFF (Bering Sea basin, offshore), and also includes subregions PRIBILOF (area around the Pribilof 

 Islands) and most of UNIMAK. Subregions in which >50% of the area is <100 fathoms are noted as inshore; the remainder are noted 

 as offshore. 



959 



