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4 Octobre 2014 , Rédigé par Bioécologie Publié dans #Biodiversité, #Faune et Flore, #Océanographie

A walrus hits the ice with its tusks near Baffin Island, Canada by Paul Nicklen
A walrus hits the ice with its tusks near Baffin Island, Canada by Paul Nicklen

Author: Julie Speegle, NOAA Fisheries, September 30, 2013 (Image ©Paul Nicklen)

NOAA scientists participating in this year's annual Aerial Surveys of Arctic Marine Mammals project in Alaska say they have photographed an area where thousands of Pacific walruses haul out of the ocean on a remote barrier island in the Chukchi Sea, near Pt. Lay.

This study is being funded and co-managed by the Bureau of Ocean Energy Management (BOEM)'s environmental studies program.

Scientists say it is difficult to provide an accurate count of the number of walruses densely packed together on coastal haulouts. Using aerial photographs, scientists estimated that this year's haulout at Pt. Lay initially contained 1,500 to 4,000 animals on Sept. 12. The number of walruses had increased to 5,500 to 8,000 when sighted on Sept. 22, and on Sept. 27, biologists estimated that there were approximately 10,000 walruses.

In 2011, scientists estimated that 30,000 walruses were hauled out along one kilometer of beach near Pt. Lay.

"Large walrus haulouts along the Alaskan coasts in the northeastern Chukchi Sea are a relatively new phenomenon," said Megan Ferguson, marine mammal scientist with NOAA Fisheries. "NOAA's research doesn't typically extend to studying walruses, since this is a species managed by the U.S. Fish and Wildlife Service (USFWS), so you can imagine how exciting it was for us to be able to collect such valuable data for our partner agencies."

Conserving and restoring protected species such as whales is one of NOAA Fisheries' core missions. The goal of the surveys is to document the distribution and relative abundance of bowhead, gray, minke, fin whales, beluga whales and other marine mammals in areas of potential oil and natural gas exploration, development and production activities in the Alaskan Arctic.

"In addition to photographing the walrus haulout area, NOAA scientists documented more bowhead whales, including calves and feeding adults in the Beaufort Sea this summer compared to 2012," said Ferguson. "We are also seeing more gray whale calves in the Chukchi Sea than we have in recent years."

Documenting the walrus haulout near Pt. Lay was a bonus for the scientists, since this information provides useful data for partners studying walruses in the Arctic. One of the reasons photograph documentation of the walrus haulout areas is so important is because seeing so many along the beaches is a relatively new phenomenon.

In the past, walruses used sea ice habitat offshore in the northern Chukchi Sea as resting platforms in between dives to the bottom of the shallow Chukchi Sea where they feed on their preferred prey, including clams, snails and worms, during the summer and autumn. Due to loss of ice in offshore areas, walruses are foraging in more coastal areas and using beaches for resting (hauling out).

The first large beach haulout in this region formed in 2007 near Pt. Lay, coinciding with an unprecedented loss of sea ice across the Chukchi Sea. Subsequent haulouts formed in northwestern Alaska near Icy Cape and Cape Lisburne in 2009, and near Pt. Lay in 2010, 2011 and 2013. During 2008 and 2012, remnants of sea ice offshore in the Chukchi Sea were sufficient for walruses to rest on between foraging bouts.

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