Anthropogenic factors affecting the status of salmon stocks in Pacific Northwest watersheds

Anthropogenic effects on watersheds are important in explaining the decline of Pacific Northwest salmon stocks. Associations were tested between thirteen anthropogenic variables in 202 watersheds in Washington, Oregon, Idaho and California and the stock status of summer, spring and fall Chinook Onchorhynchus tshawytsha, coho O. kisutch, and winter steelhead O. mykiss. Summer Chinook had the highest risk status, followed by spring Chinook, coho, fall Chinook and winter steelhead. Difference in life history characteristics helped explain some of the results. Significant associations (P < 0.001) were found between the status of salmon and all anthropogenic variables, but dams were the only variable associated with higher risk stocks for all species and races. The combination of dams, subdvision development, USFS land, and watershed groups, correctly classified 95% of summer Chinook stocks. Number of dams and absence of wild and scenic rivers correctly classified 86% of spring Chinook stocks. Watershed groups, human population, and number of dams correctly classified 77% of coho stocks. Number of dams, USFS land and lack of forest area correctly classified 71% of fall Chinook stocks. Indian tribal land, human population and number of dams correctly classified 86 % of winter steelhead stocks. Coastal stocks presented an average status of “special concern” and were associated with land use variables. Columbia Basin stocks averaged a “moderate to high risk of extinction” status and were associated with dams, wild and scenic rivers, and land use variables. Results between status of salmon and anthropogenic variables can be used to prioritize action towards salmon recovery. INTRODUCTION Anthropogenic factors affecting the status of salmon stocks in Pacific Northwest watersheds Karina Lorenz Mrakovcich, US Coast Guard Academy