June’s heat wave led to some unhealthy hot water for salmon. But, fish managers said it hasn’t been as devastating for salmon runs as the warm water temperatures were in 2015.
Underwater video from a Columbia River tributary in south-central Washington shows sockeye salmon infected with fungus caused by heat stress. They’re hiding out in the cooler waters of the Little White Salmon River, far from their spawning grounds.
After the heatwave, water temperatures in many parts of the Columbia River rose beyond the 68-degree high that salmon can stand. Above that, the fish can potentially die.
In 2015, the heat and low river flows caused nearly 99% of the sockeye salmon to die before they reached spawning grounds. The heat wave timing was fortunate for sockeye runs, said Ritchie Graves, Columbia Hydropower Branch chief with NOAA Fisheries.
“A big chunk of sockeye had already migrated past Bonneville Dam” when the heatwave hit, Graves said.
So far, more than 580 salmon have made it past the Snake River dams. As of last week, Idaho Fish and Game has collected about 179 fish to transport around the Lower Granite Dam.
Those numbers surpassed fish managers’ fears, Graves said, when they learned of the impending heat wave.
“It could have been a lot worse,” Graves said. “We’re fairly pleased with how this has turned out. Is it as good as a kind of normal temperature year? No, clearly not.”
Rivers throughout the Northwest experienced exceptionally high temperatures during the heatwave, he said, which can harm salmon runs across the region from the Salmon to the Okanogan rivers.
Environmental groups say the sick fish in this recent underwater video could be a glimpse into the future as the climate warms.
“We’re seeing sockeye salmon dying because the Columbia River is too hot,” said Brett VandenHeuvel, executive director with Columbia Riverkeeper. “The sockeye dying this way is heartbreaking.”