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Salmon Dying at Sawtooth Hatchery

by Steve Benson
Idaho Mountain Express, August 25, 2006

Parasite kills more than half of spawning fish

Half of the 320 adult chinook salmon being held for spawning purposes at the Sawtooth Fish Hatchery near Stanley have died from a parasitic disease.

The parasite, known as ICH or "white spot," creates a white spot on the fish and can create severe infections on the gills. Common in fresh water, the parasite becomes more prevalent when water temperature approaches 72 degrees. By mid-August, the temperature of the hatchery's ponds, which hold salmon prior to spawning, had climbed to the low 70s. In an average year, about 10 percent of the hatchery's adult salmon die before spawning.

Brent Snider, manager of the Sawtooth Fish Hatchery, said while ICH is natural and difficult to control, he's never seen it on this scale.

"We had some warm water last year and we had a mild outbreak," Snider said. "But all of the treatments worked, and they did not work as effectively this year."

Chemicals and cooler water pumped in from the hatchery's wells helped curb the outbreak, but Snider said it has taken its toll.

The hatchery has a target of producing 1.3 million smolt, or juvenile salmon, every year. Snider said ICH will likely reduce that number by more than half.

"It's reduced our egg take by a significant amount," he said. "It could be half or more, depending on how many females have been affected. We don't know that yet."

Spawning chinook salmon historically flourished in the Stanley basin, with hundreds of thousands completing the 900-mile journey from the Pacific Ocean every year.

But dams, particularly the four on the Lower Snake River in southeastern Washington, have put the fish on the brink of extinction. Sockeye and chinook were listed as endangered species in 1991. Coho salmon were declared extinct on the Snake River in 1985.

This year, only about 700 chinook returned to spawn in the Salmon River and its tributaries in the Sawtooth Valley. "That's a little lower than the 20-year average," Snider said.

Other hatchery and wild salmon passed through the Sawtooth Fish Hatchery and moved upstream to spawn. Snider said many spread the disease or contracted it at that time.

"Those fish are likely carrying it, but they have the advantage of not being in a confined space," Snider said. "When warm water hits they can go seek cooler refuge in tributaries and spring-fed creeks. We don't know for sure if (ICH has) actually had an impact out there or not."

Snider said biologists will begin observing salmon in their spawning beds, known as redds, in the next week.

Steve Benson
Salmon Dying at Sawtooth Hatchery
Idaho Mountain Express, August 25, 2006

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