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For Immediate Release Thursday, August 7, 2003

Anglers and Other River Users May Notice Dead Fish
as Temperatures Soar

CLACKAMAS - Hot, dry summer weather can hinder Oregon's migrating fish by raising water temperatures and causing die-offs of salmon and steelhead in local rivers. The cycle is normal and this year is no exception, say Oregon Department of Fish and Wildlife biologists.

"We're seeing dead salmon along several portions of the Willamette River, but mostly near Oregon City," said Rick Boatner, ODFW fisheries biologist. "It's not unusual that we would have some natural mortality this time of year. Migrating adult salmon need cooler water temperatures. Water temperatures in the upper 60s and 70s will cause stress to salmon and steelhead."

Boatner noted that the Willamette River is now 76 degrees Fahrenheit, two degrees above the average high temperature for this time of year.

"Although this is a high temperature, it's a normal cycle," he said. "We've been studying pre-spawning mortality rates below Willamette Falls since 1972 and this is about the typical number of salmon that would die off from a record run of spring chinook. This year, we have passed about 87,000 spring chinook adults over Willamette Falls."

In southern Oregon, the Rogue River has seen fish die-offs in the past when summer temperatures flared and triggered outbreaks of columnaris disease in spring chinook salmon that were migrating upstream to spawn. Last year, for example, several hundred chinook died when the river reached 76 degrees Fahrenheit for more than a week.

Fortunately nothing on that scale has occurred this year on the Rogue, according to acting district fish biologist David Haight. Anglers reported only a small number of dead fish during the extremely hot weather at the end of July, he noted.

"The problem typically ends on the Rogue with mid-August water releases from Lost Creek Reservoir that help fall chinook migrating up the canyon," Haight said. "Fall rains and cooler temperatures also increase river flows and lower the water temperatures. Overall fish populations should not be adversely affected by what is a normal summer phenomenon."

Anglers and other water recreationists who spot dead fish should not be alarmed, but should call the nearest ODFW field office if they see large numbers of dead fish so that agency biologists can keep track of fish mortality levels.

Information and Education Division
Oregon Department of Fish and Wildlife
(503) 872-5264 ext 5528
 
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