PREY SELECTION BY NORTHERN FUR SEALS (CALLORHINUS-URSINUS) IN THE EASTERN BERING SEA

Gastrointestinal tract contents were evaluated from 73 female and juve nile male northern fur seals (Callorhinus ursinus) for analysis of the ir diet in the Bering Sea. Fur seals were collected from August to Oct ober of 1981, 1982, and 1985. Juvenile walleye pollock (Theragra chalc ogramma) and gonatid squid were the primary prey. Pacific herring (Clu pea pallasi) and capelin (Mallotus villosus), considered important fur seal prey in previous reports, were absent from the diet. Prey specie s and size varied among years and between near-shore and pelagic sampl e locations. Interannual variation in the importance of pollock in the diet of fur seals was positively related to year-class strength of po llock. Midwater (n=23) and bottom (n=116) trawls were conducted at the location of fur seal collections to determine availability of fish an d squid relative to prey species eaten by fur seals. The species and s ize composition of prey taken by fur seals was similar to midwater tra wl collections, but differed from bottom trawl catches. Contrary to ea rlier conclusions that northern fur seals are opportunistic in their f eeding habits, we conclude that fur seals are size-selective midwater feeders during the summer and fall in the eastern Bering Sea.