Anyone familiar with the Columbia River’s massive salmon die-off a few summers ago might also be concerned about how climate change will affect fish habitats. The 2015 die-off killed more than 250,000 fish and was blamed on record low streamflows and high water temperatures. While coldwater fish such as salmon and trout can adjust to slightly warmer-than-normal temperatures for short periods, abnormally high temperatures for prolonged periods lower oxygen levels, increase the likelihood of deadly diseases, and cause life-threatening physiological stress.
To understand whether the 2015 die-off was an anomaly or part of a longer-term trend, scientists at the Rocky Mountain Research Station’s Aquatic Sciences Lab in Boise, Idaho, compiled temperature records from more than a dozen natural resource agencies monitoring nearly 400 sites along large rivers in the northwestern United States. Results of the study, entitled “Global warming of salmon and trout in the northwestern U.S.: Road to ruin or path through purgatory?” were recently published in Transactions of the American Fisheries Society.