Strong early numbers at Bonneville Dam haven’t led to a lot of fish making it to Lower Granite Dam
By Eric Barker
Aug 4, 2023
The promising start to the Snake River sockeye run appears to have melted away as the adult fish progressed upstream.
Sockeye that return to Redfish, Pettit and Alturas lakes in the shadow of Idaho’s Sawtooth Mountains are the most imperiled salmon run in the Columbia River basin and listed as endangered by the federal government. But in mid-July, fisheries managers at the Idaho Department of Fish and Game were hopeful at the number of Idaho-bound sockeye detected at Bonneville Dam, the first in a series of dams salmon and steelhead from the Columbia and Snake rivers must pass on their way home. They estimated 4,351 had navigated past the dam, a number that would be the most since 2012.
Even so, there already were signs that those fish faced tough conditions. Flows in the Columbia and Snake were dropping and water temperatures were already above seasonal norms at federal dams on the two rivers.
On average, 40% to 70% of adult Snake River sockeye counted at Bonneville Dam make it to Lower Granite Dam on the Snake River. Known as conversion, the rate varies based on river conditions.
In mid-July, Eric Johnson, a sockeye specialist with the Idaho Department of Fish and Game, predicted survival would be in the 40% range this year. Fast forward two weeks and the Bonneville-to-Granite conversion rate is only at 20%. That compares to a conversion rate of 66% in 2022.
“It’s definitely lower than average and lower than we would have hoped for,” Johnson said. “We are not completely through the run. I expect that it will probably improve a little bit but I’m not expecting it’s going to improve too much.”
He said a climb as much as 25% is possible but would be surprised to see it go any higher. Lower Granite Dam marks about the halfway point for sockeye. They still have to swim up the Snake River to the mouth of the Salmon and then follow it nearly to its headwaters in the Sawtooth Basin.
Johnson said while the Snake River above Lower Granite and the lower Salmon River can see high temperatures, conditions are looking OK for now.
“I think fish are going to have it a little easier once they get above Granite; it’s looking a bit more average."
The Snake River was 73.9 degrees this week at the U.S. Geological Survey gauge at Anatone. That is above the 70-degree threshold where salmon begin to suffer. Johnson said there are places fish can find cooler water.
“The Snake in that stretch is really big and there are some 100-feet-deep pockets that people sturgeon fish. The upper Salmon still seems to have a lot of water. The water is still high up there, higher than normal for this time of year. It tends not to heat up as fast when you have some decent flows.”
Last week, four conservation groups announced they intend to sue the Army Corps of Engineers and ask a judge to order dams on the lower Snake River to As of Tuesday, eight adult sockeye had been trapped in the Sawtooth Basin. Johnson said about 15% of the sockeye counted at Bonneville Dam missed the turn into the Snake River and continued up the Columbia. He said those fish may have opted to stay in the Columbia where the water is two to three degrees cooler, or they may have simply followed the more than 200,000 sockeye bound for the mid-Columbia River be breached as a necessary step to prevent the extinction of sockeye. The salmon advocates claim the four dams, by impounding the river, cause it to overheat just as adult sockeye salmon are migrating upstream.
Tom Conning, a spokesperson for the Corps at Portland, Ore., said the agency is reviewing a 60-day notice of intent to sue issued by Columbia River Keeper, Idaho Rivers United, Idaho Conservation League and the Northwest Sport Fishing Alliance. He said in an emailed statement the Corps and other federal agencies are committed to developing “a durable long-term strategy to restore salmon and other native fish populations to healthy and abundant levels, while honoring Federal commitments to Tribal Nations, delivering affordable and reliable clean power, and meeting the many resilience needs of stakeholders across the region through a whole-of-government approach.”
The Corps, Bonneville Power Administration, Bureau of Reclamation and other federal agencies are in mediated talks with litigants that include a coalition of environmental and fishing groups, Oregon and the Nez Perce Tribe. Those talks are related to a long-running lawsuit over harm to salmon and steelhead caused by federal dams on the Snake and Columbia rivers and are set to conclude at the end of this month.