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NUNAVUT - Whales and seals in Hudson Bay may have a new predator.

Steve Ferguson, a biologist working for the federal Department of Fisheries and Oceans, said the Inuit traditional knowledge of people he's consulted suggests an increase in the number of orcas, or killer whales, in the region.

Orcas like this one are competing with Inuit hunters for game in Hudson Bay. - photo courtesy of NOAA

Commercial whaling records from the 1940s do not mention orcas in Hudson Bay.

"It's pretty clear to us," he said.

Ferguson's research group out of the University of Manitoba conducted a traditional knowledge survey in Arviat, Repulse Bay, Hall Beach, Iglulik and Rankin Inlet and received two dozen reported sightings, mostly of six to 12 orcas together. The orcas especially seem to favour the areas near Repulse Bay, judging by the number of reports received from that community. Ferguson wants Nunavummiut to report any such sightings to his group so they can add it to their data.

Ferguson said the orcas are likely taking advantage of thinning sea ice in Hudson Strait to get to Hudson Bay. He said orcas instinctively avoid ice because the big dorsal fins on their backs get in the way as they look for a place to breathe.

The presence of orcas in Hudson Bay could have a serious impact on the local wildlife. Orcas are efficient predators and marine mammals are one of their specialties. Other populations of orcas have been known to eat belugas, narwhals, seals and bowhead whales – especially calves.

Worse, belugas and narwhales rely on their greater skill in navigating sea ice to avoid orca predation. As sea ice declines, their cover disappears.

Ferguson's research group has started a catalogue of individual orcas based off identifying characteristics such as their back and white markings and scars. The group has identified 67 different orcas in Nunavut's waters including Hudson Bay. Ferguson would also like to consult the traditional knowledge of the communities of Pangnirtung, Pond Inlet and Arctic Bay, where orcas have also been spotted.

He's also trying to get his hands on some of the orcas' teeth, which can be analysed to find out what the whales eat in winter. There's too much winter ice in Hudson Bay for the orcas, so they must leave in the autumn.

"The real mystery is where they go in the winter," Ferguson said. "We have no idea."

Determining their winter diet could reveal where the orcas go. Ferguson said it's possible the orcas don't eat at all over the winter. They are big enough that they could live off their fat deposits and replenish them with an annual summer feast in Hudson Bay.