Idaho’s salmon face many obstacles and dangers as they live their amazing lives starting at 6,500 feet above sea level and almost 900 miles from the Pacific.
They leave the Salmon, Clearwater and Snake rivers, are swept by the current out to the ocean, and then travel thousand of miles through the habitat and ecosystems of many species including us. Beginning in the 1860s we began altering many of those ecosystems to mine, farm, fish, log and manufacture what we needed and wanted.
But despite all of these changes, including a series of dams that block off many spawning grounds and make migration even harder, they survive even though most stocks in the Columbia Basin are threatened or endangered. But since the 1950s the high maximum temperatures in the Columbia River have risen 2.7 degrees Fahrenheit.
Add the rise in acidification measured in the ocean and the salmon, like other creatures will face existential threats over the next century. But for some salmon the warming is already killing them.
Oregon officials reported more than 180 wild Chinook salmon died in a remote section of the Middle Fork of the John Day River, a tributary of the Columbia. River temperatures were measurd at 74 degrees far higher than salmon can stand for long.
Since July 22 water temperatures reached 70 degrees or higher 35 times at four federal dams on the Columbia and Snake Rivers passable to salmon. All readings at Ice Harbor Dam on the Snake River surpassed 70 degrees during this week, and readings at The Dalles Dam surpassed 70 degrees.
Salmon can survive this, research shows, because they can seek out areas of cooler waters to hang out until temperatures drop again. Biologists have found that when temperatures exceeded 68 degrees the salmon and steelhead delay their migration and stay where the water is cooler.
This is becoming a larger part of the steelhead run in particular and the delays appear to be getting longer. The good news for Idaho is the critical spawning and rearing streams are at higher elevations where temperatures are lower.
But getting these fish through an increasingly hot migration corridor is going to be a major challenge for the next century. For the salmon that spawn in the lower elevations, the threat is far worse.