Walrus areas of use in the Chukchi Sea during sparse sea ice cover
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Full Publication: https://doi.org/10.3354/meps10057Product Type: Journal Article
Year: 2012
Authors: Jay, C. V., A. S. Fischbach, and A. A. Kochnev
Suggested Citation:
Jay, C. V., A. S. Fischbach, and A. A. Kochnev. 2012. Walrus areas of use in the Chukchi Sea during sparse sea ice cover. Marine Ecology Progress Series 468:1-13. doi:10.3354/meps10057
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 nearshore area of northwestern Alaska that is apparently depauperate in walrus prey. With increasing sea ice loss, it is likely that walruses will increase their use of coastal haul-outs and nearshore foraging areas, with consequences to the population that are yet to be understood.
Keywords: Climate warming, sea ice decline, marine mammal distribution
Annotation
With climate warming, ice-free periods in the Chukchi Sea have increased and are projected to increase further in frequency and duration. 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. With increasing sea ice loss, it is likely that young and adult female walruses will occupy the Chukchi Sea for longer periods during the year and increase their use of coastal haul-outs and associated nearshore foraging areas. The energetic consequences of altered habitat use and activity patterns of walruses from decreased sea ice habitat in the Chukchi Sea are not fully understood, but lactating females and the young are likely to be the most vulnerable. On-shore development activities that disturb walrus haulouts could negatively impact these populations, especially as declining sea ice drives them to increasingly utilize terrestrial habitats.