Research Reveals the Effects of Climate Extremes on Pacific Salmon

Extreme weather and hydrologic events are becoming more frequent across the globe, affecting ecosystems, plant and animal species, and people. In southeast and south-central Alaska, watersheds that support productive salmon populations are experiencing more frequent and severe floods and droughts.

J. Ryan Bellmore, a research fish biologist with the Pacific Northwest Research Station, worked with colleagues at the U.S. Geological Survey, the University of Washington, the University of Alaska Southeast, the University of Alaska Fairbanks, and the Southeast Alaska Watershed Coalition to conduct research that investigated the effects of extreme events on salmon populations. Their studies found that both floods and droughts can negatively impact salmon populations in several ways. For instance, large floods can crush and destroy salmon embryos that incubate just under the surface of the stream bed, and drought conditions that result in low flows and high water temperatures can result in low-oxygen events that can kill large numbers of adult salmon. The team’s research resulted in new models that can be used to explore climate impacts on salmon populations. So far, model analyses have suggested that salmon populations living in rivers that are primarily fed by rainfall will be the most susceptible to climate extremes.

The Southeast Alaska Watershed Coalition and local tribal and community partners are currently using these models to predict how salmon populations may respond to shifting patterns of streamflow and water temperature.