INTER-ISLAND VARIATION IN THE DIET OF FEMALE NORTHERN FUR SEALS (CALLORHINUS-URSINUS) IN THE BERING SEA

The diet of adult female northern fur seals (Callorhinus ursinus) is e xamined through the analysis of faecal material collected during the s ummer breeding season at three breeding locations in the Bering Sea: S t. Paul Island (1988, 1990) and St. George Island (1988, 1990) of the Pribilof Islands Group (USA), and Medny Island (1990) of the Commander Islands Group (Russia). Prey consumption varies annually and accordin gly with the physical and biological environment surrounding each isla nd. Juvenile walleye pollock (Theragra chalcogramma) is the most commo n prey of northern fur seals from St. Paul Island; the island is surro unded by a broad neritic environment with widely separated frontal zon es and is the greatest distance from the continental shelf-edge. Gonat id squid (Gonatopsis borealis/Berryteuthis magister and Gonatus madoka i/Gonatus middendorffi) were the most common prey of northern fur seal s from Medny Island; the island is surrounded by a compressed neritic environment and is adjacent to the continental shelf-edge and the ocea nic marine environment. A combination of walleye pollock and gonatid s quid is consumed by northern fur seals from St. George Island; the isl and has a surrounding oceanographic environment intermediate between t he other two islands. Variability in predation on walleye pollock is c onsistent with fishery information concerning the relative abundance a nd availability of walleye pollock around St. George and St. Paul Isla nds. The abundance and availability of these prey resources during the summer breeding season are key factors which influence the health and growth of the northern fur seal populations in the Bering Sea.