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July 8, 2015
THE DALLES, Ore. -- Dead and distressed sockeye salmon found this past weekend in the Deschutes River appear to have been fish from the Columbia River bound for other upriver locations who likely swam into the Deschutes in search of cooler water.
Early pathology results suggest the sockeye salmon died from columnaris, a bacterial infection typically associated with high water temperatures and/or low levels of dissolved oxygen.
Fish biologists with the Oregon Department of Fish and Wildlife found approximately 45 dead and distressed sockeye salmon in a four-mile stretch of the lower Deschutes River between the Colorado Rapids and the mouth. Biologists also collected several dead sockeye from the banks of the Columbia River just upriver of the mouth of the Deschutes.
According to Rod French, ODFW fish biologist, none of the fish found were migrating to waters above the Pelton-Round Butte Dam complex, where efforts are underway to re-introduce sockeye, other salmon and steelhead. These fish are fin clipped as smolts, French said, and can be distinguished from Columbia upriver stocks that are not.
French said there could be additional fish die-offs if this year’s drought conditions continue.
“These low water levels and high temperatures can be lethal to some fish,” he said. “If there is any good news, it’s that the native Deschutes redband trout and steelhead are genetically adapted to withstand periods of warmer water.”
In recent days, water temperatures Columbia River has been hovering around 73 degrees F. Unlike the Columbia, Deschutes temperatures fluctuate on a daily basis, where they have been ranging from 68 to 74 degrees. Sockeye can be more affected by warm water than other cold water fish like trout, steelhead, and even Chinook salmon.
Biologists will continue to monitor water conditions on the lower Deschutes and any effects on native fish. French said ODFW also could consider some fishing restrictions if conditions warrant.
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