All along the West Coast, chinook salmon returns are highly variable and extremely difficult to predict from year to year. The goal of this project is to identify primary oceanographic drivers of salmon survival and their spatial extent. This is being done through a retrospective study of more than three-decades worth of coded wire-tag data (available from the Regional Mark Processing Center), analyzed in relation to physical oceanographic data over the same period (i.e., sea-surface temperature, upwelling intensity, the Pacific Decadal Oscillation [PDO] and North Pacific Gyre Oscillation [NPGO]). The fellow reports that salmon survival is most strongly correlated with the NPGO (positively) and PDO (negatively) for runs between Southern Oregon and West Vancouver Island in British Columbia. Such a correlation was absent for salmon in the Central Valley. In the coming months, the fellow will refine his analysis to better quantify the general patterns he has found. Findings should help managers better understand the role of oceanic conditions on regional variations in salmon survival.
Understanding the Influence of a Variable Ocean Environment on Chinook Salmon (Oncorhyncus tshawytscha)