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Endangered Adult Sockeye Passing Little Goose Dam Then Hitting Lower Granite’s ‘Thermal Barrier’
Posted on Friday, August 02, 2013 (PST)

Sockeye salmon returns this year have been slightly stronger than expected overall for the Columbia River basin, though the endangered Snake River fish have passed upstream with fits and starts because of low flows and warmer than normal water temperatures.

Salmon managers from federal agencies and Northwest states and tribes have been working with Columbia/Snake river hydro system managers in recent days to devise operational strategies that might unplug an apparent “thermal barrier” to fish passage at Lower Granite Dam on the lower Snake River in southeast Washington.

Fish ladder counts had through July 18 been proceeding as expected at Lower Granite with 558 sockeye having been accounted for as they passed the eighth and final hydro project on their way up the Columbia, Snake and Salmon rivers to their home base in central Idaho’s Stanley Basin.

That overall count was already the fifth highest recorded since counts began in 1975 at the newly construction Lower Granite hydro facility.

But, after a series of daily counts in the 30s and 40s, the next week’s total was only 16.

Last week a variety of operational changes were implemented – including the firing up of “emergency pumps” installed in 1992 to feed water into fish ladders during an experimental drawdown of Lower Granite’s reservoir -- to test effects on juvenile salmon migration.

Turbine operations were also switched back and forth in the hope that cooler water could be channeled toward the fish ladders, where temperatures had risen into the 70s. Fish, including chinook, seemed reluctant to enter the fish ladders, and also reluctant to exit fish ladders into a reservoir with higher than desirable surface water temperatures.

This week, the U.S. Army Corps of Engineers, which operates Lower Granite, agreed to implement operations that prioritized operation of power unit 1, which can pass more water than the other five generating units but, at a time of relatively flows, limits the amount of water that can be sent downstream via spill, a preferred mode for passing salmon juveniles downstream.

The hope is to pass as many adult sockeye, listed under the Endangered Species Act as endangered in 1991, as possible so that they can swim an additional 400 miles up the lower Snake and Salmon rivers to their spawning grounds. Most of the returning fish will ultimately be trapped either at Sawtooth Hatchery near Stanley, Idaho, or in nearby Redfish Lake Creek.

The fish provide materials for genetic analysis, and as a result are either spawned at Eagle Hatchery near Boise so their progeny can boost an ongoing captive broodstock program, or are released into Redfish Lake to spawn naturally.

Annual counts of naturally produced sockeye spawners fell into the single digits in the 1980s and 1990s. Efforts to revive the stock, beset by degraded habitat conditions, hydro passage issues and other factors, began to build in 1991 with the beginning of the Snake River Sockeye Salmon Captive Broodstock Program led by the Idaho Department of Fish and Game and funded, for the most part, by the Bonneville Power Administration. BPA markets power generated in the federal Columbia/Snake hydro system and funds mitigation for impacts to fish and wildlife.

Timing is everything.

“Usually sockeye are past the project” by the time flows drop and water temperatures rise to levels now being experienced, said Russ Kiefer, a representative of the state of Idaho.

The state had proposed activating an adult fish trap in the fish ladder to corral sockeye that could be transported via tanker truck past those warm river miles to central Idaho’s high country. It is believed that temperature-stressed fish might benefit from a free ride upstream.

But as of late this week water flows and temperatures through the ladder and trap have not been conducive to fish trapping.

Dam operations early this week did seem to trigger a response. The daily count rose to 30 on Saturday and 41 on Sunday before falling off again. Counts Monday through Wednesday were two sockeye each day.

The Unit 1 operations were launched Wednesday, with the hope the changed water flows, along with cooler water pumped into the ladder system, would trigger fish movement. The count climbed to 22 Thursday.

“We’ve had good counts all the way through Goose,” Kiefer said of fish ladder passage up through the Columbia and lower Snake to Little Goose, the next dam downstream of Lower Granite. As of Thursday nearly 300 more sockeye had been counted passing Little Goose than Lower Granite.

Overall, a total of 184,946 sockeye salmon had been counted through Wednesday of this year at Bonneville Dam, the first hydro project the fish encounter on their way upriver. That’s slightly higher than the 2013 preseason forecast of a Columbia River sockeye run return of 180,500 adults to the Columbia River mouth. That preseason forecast includes a forecast return of 44,600 fish to central Washington’s Wenatchee River basin, 134,500 fish to the Okanogan, and 1,250 to the Snake River. The sockeye breadbasket, the Okanogan, flows south out of British Columbia and across north-central Washington into the Columbia.

That preseason forecast is nearly equal to the 2003-2012 average return of 179,900 fish.

A return of 1,250 Snake River sockeye to the mouth of the Columbia would be 158 percent of the recent 10-year average return.

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