Somewhere north of Vancouver Island, something is killing lots of chinook salmon.
So says a new report by Nanaimo-based Kintama Research that examines salmon mortality in the Snake River, a tributary of the Columbia.
And whatever’s killing the Snake River salmon, could also be behind the Yukon River’s own catastrophic salmon declines.
The Snake River, located in the US states of Wyoming, Idaho, Oregon and Washington, saw catastrophic population declines in the 1990s.
For years, salmon deaths had been blamed on the river’s hydroelectric dams.
Researchers had theorized that mounting stress from so many dam passages was causing salmon to drop dead before hitting the ocean.
Kintama fitted a sample group of salmon with tiny sensors—and a low-cost array of marine sensors was laid along the entire length of the river.
Researchers were then able to track the precise movements of the fish.
Contrary to the dam-stress theory, researchers found that almost all the Snake River salmon were making it safely to the sea.
They were even making it safely past the tip of Vancouver Island.
Salmon deaths were taking place somewhere north—outside the range of Kintama transponders.
Until a more comprehensive array can be extended up the Pacific Coast—and into the Bering Sea—the exact cause remains a mystery.
A Yukon River study similar to the Snake River study could lay to rest similar theories about in-river salmon deaths.
“After the fish spawn we have relatively little information until we start to see them come back as adults,” said Sandy Johnston, head of stock assessment and fisheries management for the department of fisheries and oceans.
“That’s a big gap in terms of the knowledge,” he said.
Higher river temperatures are suspected of slowing down returning salmon.
Midway down the Yukon River, water temperatures are already as high as 19 degrees Celsius.
“For this early in the season, it’s approaching a pretty high level, which could cause problems for the fish coming back,” said Johnston.
Ichthyophonus, a salmon heart disease that has broken out among Yukon River chinook, is also a potential limit to their ability
Even Dawson City’s Yukon Queen II catamaran has been blamed for taking a chunk out of salmon stocks.
And of course, there’s the Alaskan pollock industry.
An average of 80,000 chinook are killed every year in the nets of Bering Sea pollock fishers.
While bycatch is definitely wiping out thousands of salmon per year, it’s hard to determine how many Yukon River salmon are getting snagged in pollock nets.
“Nobody has any idea of what the contribution of Canadian stock is in the bycatch,” said Quinn.
Research from the late 1990s showed that bycatch of Yukon salmon was as high as 20 per cent.
A report from last year put it as low as 0.7 per cent.
A Yukon River Kintama study would “take some things off the table,” said David Welch, president of Kintama Research.
As with last year, the Yukon salmon run is expected to be dismal.
Under the Yukon River Salmon Treaty, Alaska is obligated to allow a certain quantity of salmon to cross into the Yukon—usually between 40,000 and 50,000 fish.
For the past three years, Alaska has fallen short of treaty provisions.
For 2009, Alaska has cancelled its commercial fishery and halved its subsistence fishery.
It remains to be seen if the restrictions will be enough to allow enough fish over the border.
“It’s early in the season to say if Alaska isn’t going to meet its obligations,” said Frank Quinn, area director for the Department of Fisheries and Oceans.
Contact Tristin Hopper at