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Welch Paper says Salmon Delayed Mortality
Happens Farther Out in Ocean

by Rocky Barker
Idaho Statesman, June 30, 2009

Canadian scientist David Welch has moderated his conclusions about the effects of eight dams on the Columbia and Snake rivers on migrating Idaho salmon.

But he still thinks the evidence shows the problems for Idaho's fish lie in the ocean, not the rivers. Welch has a new peer reviewed study in the Canadian Journal of Fisheries and Aquatic Sciences that shows salmon in the Snake and Salmon in the Yakima, which only have to go through four dams, survive the trip to his first acoustic monitor in the ocean at about the same rate.

That suggests, he said, the delayed mortality clearly documented in the Snake River fish, must be happening further out in the ocean. This challenges the prevailing idea that the delayed mortality happens in the estuary and as the fish leave the Columbia because of stress and timing issues from negotiating the dams.

What Welch says the new study demonstrates is that his Pacific Ocean Shelf Tracking System, is a reliable tool for studying salmon in the ocean.

Two years ago he said the Idaho fish that have to swim through eight dams survive the first part of the ocean trip as well as Washington salmon that only must negotiate four dams. But scientists questioned whether he had enough sample and also raised questions about how the transmitters placed in larger fish leave smaller, more vulnerable salmon out of the sample.

Welch's paper in 2008 said survival of salmon migrating from Idaho to the Pacific through the Snake and the Columbia was the same for spring chinook and actually higher for steelhead than salmon migrating out of the Fraser River in British Columbia.

Welch's research is highly controversial, especially in Canada, but the Bonneville Power Administration has been a major funder of his work.

His latest results are certain to keep his work controversial. His first issue amongst scientists is the small size of his samples.

This time Welch addresses the delayed mortality issue he has not tackled in the past. It gives his work more credibility but still doesn't overcome the sample issues that are huge. The fish transmitters were installed at the Kooskia hatchery in North Idaho.

"It remains unclear whether the entire size range of these two populations, as well as wild smolts, have similar survival and behavior as the smolts reported here," Welch and his coauthors wrote.

Overall Welch hypothesizes that since salmon return to their same rivers to spawn there is at least some logic in the idea they may return to the same places in the ocean. His latest study adds to his evidence but still falls short of the proof he continues to seek.

Rocky Barker
Welch Paper says Salmon Delayed Mortality Happens Farther Out in Ocean
Idaho Statesman, June 30, 2009

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