UNDERSTANDING LANDSCAPE DRIVERS OF ENDANGERED COHO SALMON OUTMIGRATION TIMING TO MAXIMIZE RETURNS TO THE RUSSIAN RIVER, CALIFORNIA
California’s Pacific salmon are in widespread decline and population recovery requires suitable habitat in both marine and freshwater environments. Adult return rates to natal streams for breeding are higher when outmigrating juvenile salmon reach the ocean during periods of high food productivity. However, marine food availability is variable over time because biological productivity is driven by temporally variable coastal upwelling. Therefore, diversity in salmon outmigration timing among populations within a complex is expected to stabilize returns as a whole. This asynchrony in subpopulation dynamics that contributes to population stability has been coined the “portfolio effect”. Still, the mechanisms that control salmon outmigration timing and contribute to the portfolio effect remain unclear. This study investigates how variation in landscape characteristics, including channel form and streamflow dynamics, influence outmigration timing of endangered coho salmon (Oncorhynchus kisutch) in California’s Russian River tributaries. We are developing statistical models to identify factors that explain outmigration timing variation among tributaries and years, focusing on stream geomorphology, hydrology, hydraulics, and their interactions. Results will inform the prioritization of streams for protection and enhancement with the goal of optimizing variation in outmigration timing to stabilize anadromous fish populations.
Ted Grantham (Co-Presenter/Co-Author), University of California, Berkeley, firstname.lastname@example.org;
Stephanie Carlson (Co-Presenter/Co-Author), Department of Environmental Science, Policy, and Management, University of California, Berkeley, California, U.S., email@example.com;
Mariska Obedzinski (Co-Presenter/Co-Author), California Sea Grant, firstname.lastname@example.org;
Sarah Nossaman Pierce (Co-Presenter/Co-Author), California Sea Grant, email@example.com;
Brian Kastl (Primary Presenter/Author), University of California, Berkeley, firstname.lastname@example.org;