The Spokesman-Review —
A controversial new study is challenging long-standing science that pins salmon declines in the Snake River Basin on dams and is roiling the already rough waters of fish recovery.
The work by British Columbia scientist David Welch puts the blame for poor returns of adult Snake River spring and fall chinook salmon on conditions in the Pacific Ocean instead of the dams and argues chinook runs from California to Alaska have suffered similar declines. Some salmon researchers are skeptical of that conclusion and say the effects of dams can’t be dismissed.
Welch’s work, funded by the Bonneville Power Administration and published in the journal “Fish and Fisheries,” argues since chinook runs in rivers with pristine freshwater habitat and those with highly degraded habitat have suffered similar declines, the problem must be in the ocean.
Welch and his colleagues looked at data from chinook runs up and down the west coast of North America and worked to establish and compare smolt-to-adult return rates for each of the runs. The rate is the measure of the number of juvenile chinook that leave a river system to spend two to three years in the ocean and ultimately survive and return to freshwater. In the Columbia River Basin, salmon managers believe a rate of 2 percent is required for chinook runs to hold steady and 4% to 6% is needed for runs to grow. However, rates are often 1% or less.