Haida Gwai Shark Schooling

Surprisingly, no one has reallyunderstood the extent of the shark interception of the salmon migration pathand this is a major revelation.  We donot know the details but it could well be a major cause of salmon population volatilityover the decades.

This past year we had a majorreturn of sockeye following years of devastated returns.  The interception can best explain the sharpswings were every other explanation is clearly wanting and unconvincing.  Here we are seeing enough sharks to beconvincing.

The shark population may wellalso need strong harvesting pressure to relieve pressure on the salmon.

Shark week: Marine biologists hit ‘hot spot’ off B.C. coast

MARK HUME  

VANCOUVER— From Monday's Globe and Mail

Published Sunday, May. 08, 2011 10:07PM EDT

When the group of volunteers set out, following a zigzag course alongthe coast of British Columbia,they never expected to sail into shark-infested waters.

But midway through their cetacean survey between Washingtonand Alaska,there was no doubt about what they were seeing. All around the boat, which hadsteadily been working its way north at about nine knots, the dorsal fins ofsharks could be seen slicing the surface.

“All of a sudden, it was shark, shark, shark every few seconds,” Dr.Rob Williams said. “It was obvious we’d hit a huge hot spot.”

It has long been known that salmon sharks and blue sharks visit B.C.waters. Dead ones wash ashore now and then and fishermen sometimes bringthem up thrashing in trawl nets.

But it wasn’t until Dr. Williams and his associates surveyed thecoast a few years ago that anyone realized a huge population of sharks gathersin the late summer, just south of Haida Gwaii, in Queen Charlotte Sound.

It makes you wonder what else might be out there.

Dr. Williams, a research fellow at the University of St. Andrews inScotland, made the shark discovery while conducting a marine mammal survey withthe Raincoast Conservation Foundation, which is concerned about the potentialimpact of oil and gas development on the West Coast.

Using a 21-metre Raincoast research vessel, they set off to survey thenear shore waters to get abundance estimates for seven key species: harbourporpoise, Dall’s porpoise, Pacific white-sided dolphin, humpback whale, finwhale, common minke whale and northern resident killer whale.

Then they ran into the sharks – and made one of the most remarkablemarine findings in many years. In a paper published last year, and tabled lastweek with the Cohen Commission in Vancouver,Dr. Williams states an estimated 20,000 blue and salmon sharks gather in a relativelysmall area each summer. How long they are there and why isn’t known, but sharksare driven by hunger, so it’s a good guess they are there to feed.

“Explanations for this concentration of sharks include foraging,resting and reproduction,” Dr. Williams states in his paper. “These sharks mayconcentrate in this area during July and August to intercept adult salmon ontheir return migration from the North Pacific Oceanto natal streams in the region. For instance, salmon returning to the Fraser River– the largest of Canadian salmon runs – use this more northerly route through Queen CharlotteSound and Johnstone Straitduring times of higher-than-normal sea temperatures.”

Dr. Williams said because they were doing an abundance survey, the teamdidn’t stop to catch sharks to look at stomach contents. That would have toldthem if the sharks were indeed feeding on salmon, or on the northern elephantseals, Pacific white sided dolphins and ocean sunfish that also concentrate inthe area.

“I would love to go back there and tag some sharks, take some stomachsamples, and even put critter cameras on some to see what they are up to,” hesaid in an interview from Scotland.

“And who knows what else we might find out there.”

Indeed. One has to ask, if 20,000 sharks were overlooked until now,what else is going on out there that we don’t know about?

Dr. Williams said his research was restricted to the sheltered inshorewaters east of Haida Gwaii and Vancouver Islandbecause the vessel he had wasn’t built to go far offshore. Funding was alsolimited, and it all came from private sources.

He wants to return to the West Coast, to spend more time in the sharkhot spot and to venture farther out, where he’s convinced there are moresurprising discoveries just waiting to be made.

“The seaward extent [of the aggregation zone] is completely unknown,”he said. “I would love to go out there, but you can’t rely on the kindness ofnon-profits to go out 50 to 60 kilometres offshore.”

In other words, he needs a bigger boat and more funding.

There are two reasons the government should support him. First, if youdon’t know what you’ve got, you can’t protect it. And second, the idea of aB.C. shark cam is just too cool to pass up.