BOISE — Salmon in the Columbia, Snake and even Salmon rivers are swimming into lethally hot waters that are at even higher temperatures than when nearly all of the Columbia and Snake sockeye died in 2015.
“This is worse,” said Lisa Crozier, a research biologist for NOAA Fisheries in Seattle.
That’s because the water temperatures in 2015 of 68 degrees and hotter came a little later in the summer. The unprecedented extreme heat in the Pacific Northwest, combined with low river flows, drove the river temperatures into the 70s earlier this week, threatening not only sockeye, but other migrating salmon and steelhead in the rivers.
Temperatures in the Snake River reached 74 degrees, and even the upper Salmon River warmed to 75, said Eric Johnson, a research biologist for the Idaho Department of Fish and Game. Salmon begin to die when water temperatures reach 68.
Fish and Game biologists are preparing to collect sockeye from below Lower Granite Dam — the final dam on the Snake River near Lewiston — and truck them to the Eagle Hatchery, the headquarters of the successful captive rearing program, which prevented endangered sockeye from going extinct in the 1990s and 2000s.
The agency was able to save 35 Snake River sockeye by trucking in 2015. Another 56 sockeye made the perilous trip to Redfish Lake on their own. Biologists had counted 4,000 sockeye that year at the Columbia River’s Bonneville Dam. Hundreds of thousands of sockeye headed for the upper Columbia also died in 2015.