MEPS 468:1-13 (2012)  -  doi:10.3354/meps10057

Walrus areas of use in the Chukchi Sea during sparse sea ice cover

Chadwick V. Jay1,*, Anthony S. Fischbach1, Anatoly A. Kochnev2

1US Geological Survey, Alaska Science Center, 4210 University Drive, Anchorage, Alaska 99508, USA
2Pacific Research Fisheries Center, Chukotka Branch, Otke 56 Box 29, Anadyr, Chukotka 689000, Russia

ABSTRACT: The Pacific walrus Odobenus rosmarus divergens feeds on benthic invertebrates on the continental shelf of the Chukchi and Bering Seas and rests on sea ice between foraging trips. With climate warming, ice-free periods in the Chukchi Sea have increased and are projected to increase further in frequency and duration. We radio-tracked walruses to estimate areas of walrus foraging and occupancy in the Chukchi Sea from June to November of 2008 to 2011, years when sea ice was sparse over the continental shelf in comparison to historical records. The earlier and more extensive sea ice retreat in June to September, and delayed freeze-up of sea ice in October to November, created conditions for walruses to arrive earlier and stay later in the Chukchi Sea than in the past. The lack of sea ice over the continental shelf from September to October caused walruses to forage in nearshore areas instead of offshore areas as in the past. Walruses did not frequent the deep waters of the Arctic Basin when sea ice retreated off the shelf. Walruses foraged in most areas they occupied, and areas of concentrated foraging generally corresponded to regions of high benthic biomass, such as in the northeastern (Hanna Shoal) and southwestern Chukchi Sea. A notable exception was the occurrence of concentrated foraging in a nearshor