ODFW: Dead fish in the Deschutes were not headed upstream

July 11, 2015
ODFW: Dead fish in the Deschutes were not headed upstream

Deschutes’ cooler water likely lured sockeye from the Columbia

By Dylan J. Darling / The Bulletin / @DylanJDarling

Sockeye salmon found dying and dead recently in the Lower Deschutes River, near the Columbia River, were not headed up the Deschutes, said a state biologist.

“These are not Deschutes origin fish,” said Rod French, fish biologist with the Oregon Department of Fish and Wildlife in The Dalles. The fish likely were from runs on the Columbia and Snake rivers, lured into the Deschutes by its cooler temperatures.

Low water flows and high temperatures have combined to make the Columbia and rivers flowing into it warmer than normal for this time of year, French said. Being smaller than the Columbia, the Deschutes River cools down more at night. The cool waters likely drew the salmon out of the Columbia and into the first few miles of the Deschutes.

Daytime temperatures of both rivers have recently been warmer than normal, French said, with water temperatures over 70 degrees. The Deschutes drops as much as 6 degrees each night while the Columbia’s temperature stays steady.

The warm rivers have created an incubator for bacteria that can be harmful to fish. French said columnaris, a bacteria often associated with high water temperatures, infected the fish found severely distressed or dead along the first 3 miles of the Deschutes upstream from the Columbia.

The first reports of the fish die-off along the lower Deschutes came in over the weekend, and French went out this week to check on the situation. He found 10 dead fish and 40 to 50 fish close to death.

“They are essentially swimming dead fish,” he said Friday. “They just haven’t died yet.” Even more fish likely succumbed to the bacteria and were eaten by scavengers, such as birds and raccoons.

Sockeye salmon are more susceptible to illness brought on by warm water than redband trout and steelhead, French said in an ODFW news release. He warned that drought conditions could lead to more fish die-offs, although cooler weather has brought some relief.

Portland General Electric and the Confederated Tribes of Warm Springs, who jointly own the Pelton-Round Butte dam complex, have been trying to establish a sockeye salmon run to the Deschutes River over the past five years.

Steve Corson, PGE spokesman, said the bulk of the sockeye return in August.

While the Deschutes sockeye run has not seen a fish die-off, he said the returns have been lower than hoped. In 2012, a little more than 100 fish returned to the dams; in 2013, a little over 30 fish made it, and last year it was 26.

The fish die-off on the Deschutes led the Deschutes River Alliance, a nonprofit conservation group based in Maupin, to call this week for PGE and the tribes to release more cold water down the river from Lake Billy Chinook.

More cool water, pulled from the bottom of the lake, has been flowing down this week, Corson said, but not because of the Deschutes River Alliance request.

“We release water at the temperature that we would expect it to be if the dams were not there,” he said, which varies depending on the weather.

Greg McMillan, president of the Deschutes River Alliance, said his group believes that if the power company and tribes continue to manage releases from Lake Billy Chinook as they have there could be more fish deaths in the Deschutes.

“Conditions in the Columbia are bad, and conditions in the Deschutes are not helping the problem,” he said.

— Reporter: 541-617-7812, ddarling@bendbulletin.com

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