Casual news readers this summer were greeted with cheerful headlines referring to a “record sockeye run” in the Columbia River. According to dam operators, more than 750,000 sockeye salmon (Onchorhynchus nerka) passed through Bonneville Dam near Portland this year, bound for their natal habitat upstream, including in the Snake River. But, Idaho’s sockeye salmon remain on the very edge of extinction—the most endangered fish in the state. So, what gives?
Running the Gauntlet
Sockeye salmon endure some of the longest migrations of any fish in the Columbia River Basin. Each year, they swim hundreds of miles upstream to lakes in northern Washington and central Idaho to spawn. Unfortunately, this migration occurs at the height of summer in July and August, when the weather and the water are at their hottest. Like all salmon species, sockeye struggle when water gets too warm—anything above 68°F will force the fish to slow down. If the water stays too hot for too long, it can delay migration and eventually lead to injury and death.
Northwest rivers have always been hot in summer, but two factors make this migration a gauntlet for salmon today: hydroelectric dams and climate change. Dams built on the river impound water into stagnant reservoirs that take longer to cool down than a free-flowing river would. Climate change creates more frequent, longer lasting, more intense heat waves. These two factors, taken together, make the journey upstream for sockeye a harrowing one.
Hot reservoirs have doomed sockeye runs in the past. Just last year, only 10% of the Snake River sockeye that arrived at Bonneville Dam made it all the way to Idaho. In 2015, fish managers expected a record run of sockeye to return to the region. This came as welcome news after Tribes and states had invested hundreds of millions of dollars in recovering sockeye from functional extinction in the 1990s. Even though 500,000 adult sockeye reached Bonneville that year, 99% of them died in the Columbia and Snake River reservoirs in the middle of one of the worst heat waves on record.
Weathering the Storm on the Columbia
2024 brought another strong run of sockeye to Bonneville Dam. Of the 750,000 fish that arrived at the dam, the vast majority were bound for Columbia River tributaries in Washington state such as the Wenatchee River and the Okanogan River, which stretches across the border into Canada. However, in the course of this year’s journey, these fish faced the sudden onset of a heat wave. The Columbia’s reservoirs got hot, but then relief came. The weather broke as the bulk of the sockeye run was approaching their home territory, allowing more than 350,000 of the fish to make it home to the Okanogan.
Columbia River sockeye runs are improving thanks to more hospitable conditions in Canada, but also because of serious efforts by federal agencies and other dam owners to operate the river to deliver maximum benefits to juvenile sockeye as they migrate downstream. Those efforts have been successful, so far. Sockeye in any part of the Northwest remain susceptible to harsh summer heat waves in their adult migration upstream. Still, the good run this year is something to be celebrated.
Sparse Sockeye on the Snake
For years, wild sockeye returns to central Idaho’s Sawtooth Valley have been sparse. Over the past five years, an average 44 natural-origin fish returned to this area, a tiny slice of the state’s recovery goal of 8,000 adults returning each year. 2024 was more of the same. The heat wave affected these fish more than the Columbia River run. According to preliminary estimates, about half of the Snake River sockeye that passed Bonneville Dam didn’t make it to Lower Granite Dam, the last dam they pass on their way to Idaho.
Once they reached Lower Granite, state fish managers took extraordinary measures to ensure at least some fish made it back to Idaho. They trapped many of the sockeye as they passed through Lower Granite and transported them, via truck, to Eagle Fish Hatchery in the Boise area. Here, staff took genetic samples to determine the heritage of each fish and release all the Snake River sockeye into Redfish Lake.
Some sockeye were left in the river to complete their journey past Lower Granite and up another 450 miles to the Sawtooth Valley as they always had. The end result was similar to previous years: 31 natural-origin fish, according to a preliminary count.
So, while the Columbia River got a promising return of sockeye this year, Idaho’s iconic red fish remain in danger. Dams on the lower Snake River are the difference between these two runs: they make the river and its reservoirs dangerously hot for salmon. Operational schemes like those implemented on the Columbia are not as effective on the Snake because of the disparity in river flows. However, analysis shows that without the dams in place, the Snake River would be cool enough for sockeye to migrate safely, even with the effects of climate change.
Let’s bring healthy runs of sockeye back to all corners of the Columbia and Snake Rivers. By removing the four lower Snake River dams and restoring a free-flowing river, we can make sure Redfish Lake continues to be a home to the sockeye for which it is named.