A near-catastrophic plunge in the population of ringed seals in Hudson Bay is being blamed on melting sea ice caused by global warming, says a study led by a Manitoba researcher.

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A near-catastrophic plunge in the population of ringed seals in Hudson Bay is being blamed on melting sea ice caused by global warming, says a study led by a Manitoba researcher.

The population has been diminished by 75 per cent since aerial surveys started 20 years ago, according to data that will be presented to the ArcticNet conference of scientists in Winnipeg this week.

Lead researcher Steve Ferguson, a scientist with Fisheries and Oceans Canada and the University of Manitoba, said global warming is causing sea ice to disappear earlier in spring and form later in the fall, and there is less of it in Hudson Bay.

Ringed seals feast on smaller fish beneath the ice. The food around ice has lots of fat, important in the Arctic where animals need to build up body mass to survive the extreme conditions. Seals also depend on sea ice for molting in late spring when they change their coats.

Bearded seals, which forage under ice for food such as clams, are also likely to be negatively affected, he said.

And in turn, the polar bear population will suffer because seals are the main component of their winter diet. The problem is compounded, as less sea ice means the bears have less area to hunt.

Hudson Bay could experience its first ice-free winter within five to 10 years, Ferguson said

"I don't think polar bears and seals will be able to adapt. I think they'll just die out in places like Hudson Bay. There's little to stop the trend in loss of sea ice, even if we stop producing greenhouse gasses," he said.

In addition, killer whales are beginning to migrate deeper into Hudson Bay and are staying longer. The predators feast on both seals and beluga whales. Killer whales have been spotted as far south as Churchill during the past decade.

An estimated 60,000 belugas — about 35 per cent of the world's number — migrate from Hudson Strait into western Hudson Bay each summer. The eastern Beaufort Sea has a similar population.

The study's findings portend disaster for the Arctic generally.

"Hudson Bay is the early warning area of climate change because it is so far south," Ferguson said. "We're seeing the changes more dramatic in Hudson Bay, and it's showing us how the rest of the Circumpolar Arctic will be impacted."

Ferguson said while many people believe climate change is gradual, aerial surveys reveal mammals can disappear in huge numbers in a short period of time.

After a particularly warm 2010, the seal population plunged almost 80 per cent. Seal immune systems seemed to weaken, making them more susceptible to pathogens. Some of that loss has been recovered, he said.

Aerial surveys are not really "population surveys," but are the most accurate available indicator, and they show a definite trend. They're done each spring by counting seals on the ice.

About 800 research scientists are expected at the ArcticNet conference, which continues at the RBC Convention Centre until Friday. It's the largest single gathering of scientists focused on the North in Canada.

 

bill.redekop@freepress.mb.ca