Large fall chinook run stalled on Snake River

Returning fish hit high water temperatures at Lower Granite Dam.

LEWISTON TRIBUNESeptember 19, 2013 

Managers can’t seem to cool the water at Lower Granite Dam.

JOE JASZEWSKI — Idaho Statesman file

As measured at Bonneville Dam, the Columbia River fall chinook run is booming, but Idaho isn't sharing the wealth yet.

Nearly 64,000 fall chinook stormed past Bonneville on Sept. 9 to set a new daily record, and the previous record - 45,884, set in 2003 - was topped two other times that week.

So far this year, a record 700,000 fall chinook have been counted at Bonneville. The run likely will double the preseason forecast of 434,000 fish, and forecasters say it could top 1 million.

Most of those fish will stay in the Columbia and head up the Hanford Reach, but a growing number are bound for the Snake River.

Information gleaned from pit tags implanted in hatchery fall chinook indicates that 58,000 of the fish counted at Bonneville are headed for the Snake River, and that number could grow to 75,000.

With a typical conversion rate of 65 percent, as many as 49,000 hatchery fall chinook could return above Lower Granite this fall, plus another 30,000 wild fish. The preseason forecast called for 24,000 hatchery fish and 16,000 wild fish.

But fish have been slow to reach Idaho.

Through Monday, about 16,000 of those fish have crossed Granite, and water temperatures there were about 70 degrees.

Passage of fall chinook, sockeye salmon and steelhead has been delayed at the dam because of high temperatures in the fish ladder there. There are more than 10,000 fall chinook stalled between Little Goose and Lower Granite dams.

Fish typically continue upstream when water temperatures drop to the mid-60s.

Fisheries officials have been attempting to prompt fish movement by pumping cold water into the ladder. The strategy has met with only limited success and has been confounded by other issues there.

Biologists Becky Johnson of the Nez Perce Tribe and Russ Kiefer of the Idaho Department of Fish and Game said the hydroelectric turbine closest to the fish ladder is down for repairs.

Typically, that turbine is used this time of year so the current it generates also helps to attract fish near the entrance of the fish ladder. To make matters worse, the roof of the powerhouse is being repaired, and that has led to changing flow regimes.

"It feels like you are kind of watching a train wreck coming, where 50,000 fish are heading for the Snake but the water is warm and we can't cool it," Johnson said. "It's very frustrating."

"It's encouraging they are coming, it's a little discouraging they are momentarily delayed below Granite," Kiefer said.

The tribe and others normally trap some of the fall chinook in the Granite fish ladder for hatchery spawning, but they haven't been able to start because the trap and pumps can't be operated at the same time.

Kiefer said the fish, fisheries officials and fishermen may have to wait for Mother Nature to correct the problem.

"It is looking likely that we are going to have to wait for the weather to change conditions down there to allow adults better passage," he said.

Fall chinook fishing season is open on the Snake River in Idaho and Washington and on short sections of the Clearwater and Salmon rivers in Idaho.

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