Scientists figure out beluga's Beaufort Sea menu

The first fish survey of the Beaufort Sea found Arctic cod in "huge concentrations," which may be the main source of food for beluga whales and seals in the region.
Aurora, a 20-year-old Beluga whale, swims with her calf at the Vancouver Aquarium in 2009. The first fish survey of the Beaufort Sea has found what scientists think may be the main source of food for belugas in the region. (Darryl Dyck/Canadian Press)

What do you serve 25,000 beluga whales who drop in for a summer picnic?

The first fish survey of the Beaufort Sea has finally figured it out.

"Those whales have to eat something," said Jim Reist, a Department of Fisheries and Oceans biologist who presented some early findings from the survey at a conference of Arctic scientists in Vancouver this week.

Every summer, the whales converge in the Canadian part of the Beaufort Sea. They come to calve and shed their old skin in the shallow coastline waters and river estuaries of the Northwest Territories. They also make up an important food source for the Inuvialuit.

Science has never fully understood what made up the food source for the whales. Until now.

Reist and his fellow scientists cruised the seat last summer on board the fisheries vessel Frosti as part of the Beaufort Regional Environmental Assessment. Initiated to help develop regulations for any future offshore resource development, the assessment was the first time scientists took a look at what was in the water beyond the first couple hundred of metres from shore.

The scientists realized that the Beaufort is actually a layer-cake of sea water with various temperatures and salinity. At about 200 metres down, water originating in the Pacific Ocean begins to give way to colder, saltier water coming from the Atlantic.

"It's a mixing zone," said Reist. 

"Mixing areas tend to be very species-rich and they also tend to be very productive. It concentrates the food and productivity in the area."

This zone was true to form.

"It provides the larder for one of the key species in the area — the Arctic cod, a small fish but a very pivotal one," Reist said.

Team members found the cod in "huge concentrations." They also found the answer to what the beluga have been eating.

Although data about the size of the fish population is still being analyzed, Reist said calculations suggest it would take millions and millions of the 12-centimetre-long fish to support the area's beluga and seal numbers.

"The findings are pretty impressive," he said. "We suspected that this concentration of Arctic cod had to be there, but we haven't had that confirmation.

"I was pleasantly surprised."

Such a basic link in the Arctic food web being a mystery until now shows how much remains to be understood about the Beaufort. Reist said the cruise also found at least six species of fish that nobody knew were there.

That kind of basic environmental understanding will be crucial to the development of any offshore energy resources, suggested Reist.

"It allows us to better define what the fish species biodiversity is (and) associate that biodiversity with particular habitats. It also allows us to identify key habitat.

"That in turn will hopefully allow the regulatory process to proceed from a much better information base."

There are currently 10 energy companies with exploration leases in the Beaufort. Although there are currently no applications to drill, a report prepared for the federal government last spring suggested that activity in shallow waters would begin in 2016, to be followed by deep-water drilling two years later.

Reist expects to return on the Frosti to the Beaufort next summer as part of an $11-million, five-year study.