Tag Archives: Phoca hispida

Snow depth over spring sea ice affects polar bear feeding success and ringed seal survival

Snow depth over sea ice in spring affects the hunting success of polar bears on ringed seal (Phoca hispida) pups, but the relationship is more complicated than you might think and there is less data on this phenomenon than you would believe.

Ringed seal lair_snow and ice thickness_PolarBearScience_sm

Regional snow depth in spring (April-May) varies naturally from year to year due to weather patterns driven in part by long-term climate cycles (like the Atlantic Multidecadal Oscillation, Pacific Decadal Oscillation, and the Arctic Oscillation).

This year, it was very cold in Eastern North America, with record-breaking snow fall in some areas. Snow depth was apparently greater than average over Hudson Bay sea ice this spring but was it deep enough to have impaired polar bear hunting success?

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Chukchi/Bering Sea ringed seals doing better despite declines in ice and snow: new study

Ringed seal pup in snow cave

Previously, I highlighted new research results that showed, contrary to expectations, polar bears in the Chukchi Sea subpopulation are doing better – despite declines in extent of September sea ice – since the 1970s. So it might not come as much of a surprise to find that the same is true for the primary prey of polar bears in the Chukchi and Bering Seas, Arctic ringed seals (Phoca hispida hispida).

Surprisingly, less than 6 months after Arctic ringed seals were placed on the American list of “threatened” species (under the ESA, see previous post here), actual research in Alaska has shown that declines in sea ice have proven better for ringed seals, not worse.

At a presentation given at the Lowell Wakefield Fisheries Symposium in March (Anchorage, Alaska) [program and links to pdfs here] Justin Crawford, a biologist with the Alaska Department of Fish and Game (ADF&G) presented the results of ringed seal research conducted by himself and fellow ADF&G biologist Lori Quakenbush in the Chukchi and Bering Seas (posted online by the event organizers, see references below).

As for polar bears, the Crawford and Quakenbush presentation provides some very interesting details on the status of Chukchi and Bering Sea ringed seals over the last 40 years, and contains some mighty “inconvenient” conclusions that should raise some eyebrows.

I’ve summarized these details and conclusions below in point form, with a map.
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Bearded and ringed seals join the polar bear as “threatened” by a computer-modeled future

As I pointed out in Featured Quote #22 (posted on Dec. 23, 2012), bearded and ringed seals have recently joined the polar bear on the American ESA’s list of animals that are “threatened” by computer-modeled predictions of Arctic sea ice declines projected 50-100 years into the future (USFWS 2008, 2012a, 2012b).

NOAA photos of bearded seal (top) and ringed seal (bottom)

NOAA photos of bearded seal (top) and ringed seal (bottom). The bearded seal is one of the largest Arctic ice seal while the ringed seal is the smallest. Both are eaten by polar bears, although ringed seals are consumed most often.

The decision by NOAA (National Oceanographic and Atmospheric Administration) affects the Arctic subspecies of ringed seal (Phoca hispida hispida) as well as the Okhotsk subspecies (Phoca hispida ochotensis) (in addition to several others) and thus includes all ringed seals off Alaska’s coast in the Beaufort, Chukchi and Bering Seas. The decision also affects two particular subpopulations of bearded seal (Erignatha barbatus): the “Beringia” [Bering Sea/Chukchi] subpopulation (about half of which reside in Alaskan waters), and the subpopulation that lives in the Sea of Okhotsk. (Alaska Fisheries (NOAA) Final Decision). Continue reading