Blue shark numbers can handle bycatch mortality, says DFO

The Department of Fisheries and Oceans has released new research on the large numbers of blue sharks killed as bycatch in other fisheries.

Federal authorities will soon review whether blue sharks need protection. According to the Committee on the Status of Endangered Wildlife in Canada, blue sharks are currently listed as a species of "special concern."

This week, DFO scientist Steve Campana​ delivered a report on the status and threats to blue sharks.

"Some of it confirmed what we already knew and some was kind of exciting," he says.

As it turns out, blue sharks are travellers. Sharks tagged off Nova Scotia are being caught far from Canadian waters.

"A lot of these tags are being recaptured way off in the middle of the Atlantic Ocean, often by Spanish fishermen of all things," he says.

About 8,000 blue sharks are caught accidentally in Canadian waters annually — mostly off Nova Scotia by vessels trailing long lines of baited hooks — fishing for swordfish or tuna.

Campana says the blue shark bycatch is quite large. But he says the stock can handle it.

"It doesn't look like the number that are being caught are seriously impacting the population. But, basically, it’s turning out to be a big waste," he says.

Nova Scotia's swordfish and tuna fishery have received Marine Stewardship Council certification as sustainable.

Heather Grant, with the Ecology Action Centre in Halifax, says the bycatch raises doubts about MSC certification.

"When somebody goes to the grocery store, they’re trying to make a quick decision, they’re going to pick the sustainable option but of course they don't know that, that is coming with a great deal of shark mortality," she says.

Troy Atkinson of the Nova Scotia Swordfishermen's Association says his fishery poses no threat.

"The levels are relatively low. Canada makes up, in total, about four per cent of the entire take in the North Atlantic," he says.

This week's DFO research also debunks the idea that shark derbies threaten the species.

Campana says the number killed is "a drop in the ocean," perhaps 200 per year out of a summertime population of one million.

In fact, he says tags fixed on the smaller sharks that are automatically released by fishermen during the derby provide valuable information to scientists.