Whirling disease confirmed in Oregon's Clackamas drainage

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Whirling disease found in Clackamas River.

PORTLAND, Ore. (AP) - Whirling disease has been detected in Oregon's Clackamas River drainage, the first time the parasitic disease has been found in the lower Columbia River since 1987.
The Oregon Department of Fish and Wildlife, which routinely monitors private and public hatcheries for whirling disease, discovered its spores in trout from the Clear Creek Rainbow Ranch. Clear Creek is a tributary of the Clackamas River and supplies water to the commercial trout farm.

Fish biologist Bob Hooton told the state Fish and Wildlife Commission that no one knows how whirling disease spores got into the ranch's trout, but they are suspected to have come from steelhead bound for the Snake River.

All public hatcheries and some private trout operations on the Clackamas are clear of the disease, he said. The department is testing for whirling disease in all 40 of Oregon's privately operated trout hatcheries.

The disease has decimated trout populations in Montana and Colorado and has been found in Idaho and many other western states. It is caused by a parasite that can live for years in its spore form.

For reasons still unclear, but probably related to stress, the spore erupts into an adult stage that can attack cartilage and cause spinal deformities that make fish spin and whirl while swimming.

Hooton said the Clear Creek fish had only spores, not behavioral symptoms.

In 1987, whirling disease was discovered in steelhead, spring chinook and a single sockeye salmon in the Deschutes River. However, whirling disease has never been found in native trout in the Deschutes, Hooton said.

Salmon and steelhead from the Snake River carry the disease but are not affected by it, Hooton said.
 

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