Decadal Scale Climate Pattern and Salmon Survival: Indicators, Interactions and Implications

The influence of decadal scale climatic variations on the decline of Columbia River salmon was not realized until recently. I evaluate the implications of this omission using a stock recruitment model with climatic and anthropogenic factors. I conclude that fisheries managers over the past century have misinterpreted the anthropogenic impacts on Columbia River salmon. In particular, I suggest three major events have been misinterpreted: 1) managers overestimated the significance of harvest on the catch decline after 1920 by not accounting for climatic changes that lowered ocean survival at this time, 2) managers under -represented the detrimental effects of the hydrosystem by not accounting for the contribution of good ocean survival during the years of hydrosystem development and, 3) managers underestimated the success of stock rebuilding measures in the last two decades because the concomitant poor ocean survival was not accounted for. I also suggest that the fisheries community is now evolving an ecosystem approach that considers both environmental and anthropogenic impacts on salmon.