FISHERY BULLETIN: VOL. 81, NO. 1 



Kenyon 1957; Fiscus 1979; Kajimura et al. foot- 

 notes 2, 3), and fertility (Abegglen and Roppel 

 1959). 



Bering Sea groundfish and pelagic fisheries 

 data, which give estimates of relative abundance, 

 life history parameters, and migratory patterns 

 of important fish stocks, are contained in a num- 

 ber of Northwest and Alaska Fisheries Center 

 (NWAFC) reports (Pereyra et al. 1976 5 ; Favorite 

 et al. 1979 6 ; Pruter 1973; Bakkala et al. 1979 7 ). 

 These data cover the period of development of the 

 large foreign groundfish fishery in the eastern 

 Bering Sea (1954-78) and include catch, catch 

 per unit effort (CPUE), mortality, seasonal mi- 

 gration patterns, and diets for a number of com- 

 mercially important fish, including walleye pol- 

 lock and Pacific herring, important food sources 

 for the fur seal in the eastern Bering Sea. 



Fur Seal Data Synopsis 

 Seal Data Collected at Sea 



Fur seal migration patterns were deduced 

 from fur seals sampled at sea from 1958 to 1974. 

 Adult males remain year-round in the Bering 

 Sea and Gulf of Alaska, while females migrate 

 south in winter, with smaller (younger) females 

 tending to migrate the farthest south. Many sub- 

 adult males also migrate south, but not nearly so 

 far as the females. Females begin returning to 

 the rookeries of the Pribilof Islands in June, and 

 the rookeries are almost completely established 

 by the end of July (Kajimura et al. footnotes 2, 3). 



Pelagic data were also used to construct a fur 

 seal life table (Lander 1981) which, along with a 

 pup production estimate, gave an overall fur seal 

 biomass estimate for the Pribilof Islands stock of 

 29,000 t or 1.25 million animals. Seasonal pat- 

 terns of growth were also computed from the 



5 Pereyra, W. T., J. E. Reeves, and R. G. Bakkala. 1976. 

 Demersal fish and shellfish resources of the eastern Bering Sea 

 in the baseline year 1975. Proc. Rep., 619 p. Northwest and 

 Alaska Fisheries Center Seattle Laboratory, National Marine 

 Fisheries Service, NOAA, 2725 Montlake Blvd. E., Seattle, 

 WA 98112. 



"Favorite, F., W. J. Ingraham, Jr., K. D. Waldron, E. A. Best, 

 V. G. Wespestad, L. H. Barton, G. B. Smith, R. G. Bakkala, 

 R. R. Straty, and T. Laevastu. 1979. Fisheries oceanog- 

 raphy — eastern Bering Sea Shelf. Proc. Rep. 79-20, 481 p. 

 Northwest and Alaska Fisheries Center Seattle Laboratory, 

 National Marine Fisheries Service, NOAA, 2725 Montlake 

 Blvd. E., Seattle, WA 98112. 



7 Bakkala, R., L. Low, and V. Wespestad. 1979. Condition 

 of groundfish resources in the Bering Sea and Aleutian area. 

 NMFS Northwest and Alaska Fisheries Center report sub- 

 mitted to the International North Pacific Fisheries Commis- 

 sion, 106 p. 



pelagic survey data (Lander 1981). Stomach con- 

 tent data were pooled over years by region and by 

 month, and were presented as the frequency of 

 occurrence (proportion of stomachs containing a 

 particular food item), the volume and the percent 

 of total food volume comprised by each prey type, 

 and the number of specimens of each prey type 

 and their percent of the total diet. Diet compo- 

 sition of fur seal stomachs by percent volume 

 (which we consider to be the most reliable mea- 

 sure of prey abundance in predator stomachs) in 

 the eastern Bering Sea is given in Table 1 (modi- 

 fied from Kajimura et al. footnote 3) pooled by 

 month over all years of data collection. 



Table 1.— Major species in fur seal diets in the east- 

 ern Bering Sea (percent volume), June-September. 

 (Kajimura et al. footnote 3). 



Fur seals are pelagic feeders and are highly 

 opportunistic (Kajimura 1981 8 ), feeding on a 

 wide variety of species. Of their major prey only 

 pollock and herring are target species for a fish- 

 ery. Data on fur seal diets outside the eastern 

 Bering Sea corroborate the pattern of fur seals 

 feeding primarily on schooling fish. South of 

 British Columbia, hake replaces pollock in seal 

 stomachs and herring and sand lance are increas- 

 ingly important, while capelin decreases in im- 

 portance. Anchovy is the most important fur seal 

 food off California. Since fur seals and fisheries 

 both tend to exploit schooling species, a possible 

 competitive relationship may exist between fur 

 seals and fisheries. Most fur seal feeding in the 

 Bering Sea is done by lactating females during 

 the summer pupping period, so the importance 

 of food during this period cannot be overempha- 

 sized. Since this is the period of rapid pup growth 

 and is also the period of maximum growth for 

 nonpregnant females and subadult males (Fig. 

 1), food limitation during this period could have 

 drastic consequences to pup survival, especially 

 after they leave the rookeries. 



8 Kajimura, H. 1981. The opportunistic feeding of north- 

 ern fur seals off California. Unpubl. manuscr., 46 p. North- 

 west and Alaska Fisheries Center National Marine Mammal 

 Laboratory, National Marine Fisheries Service, NOAA, 7600 

 Sand Point Way NE., Seattle, WA 98115. 



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