UC Marine Council

Pacific coast salmonids, including California stocks, have declined in numbers with all populations of California Central Valley Chinook salmon (Oncorhynchus tshawytscha) listed or proposed for listing as endangered or threatened under the U.S. Endangered Species Act. Although California's natural stocks are declining, mass production of Central Valley fall-run Chinook salmon through hatchery production has supplemented the commercial and recreational fisheries. One challenge in understanding population dynamics of the California Central Valley Chinook salmon, is understanding the mechanisms that contribute to persistence of the populations. Key to understanding how spatial structure influences population dynamics is identification of habitats or distinct populations that may contribute differentially to juvenile recruitment into the adult population. Currently, the only method for understanding these mechanisms is based on recoveries of hatchery fish with coded wire tags in commercial and recreational landings. The small proportion of tagged hatchery fish and few coded wire tag returns limits information derived for hatchery populations and provides no method to explicitly monitor population trends of wild populations. Restoring exploited fisheries stocks relies on understanding the links between larval supply and adult recruitment, as well as determining temporal and spatial population structure.

My research will use natural population markers to determine the relative contribution of production sources, both natural and supplemental, as well as the role of stock structure to the persistence of California Central Valley Chinook salmon. I will use a newly developed technique to analyze the microstructure and geochemical composition of otoliths, fish ear bones, to determine the production source and stream-of-origin for adult Chinook salmon. Understanding the ecology of Chinook salmon along the central California coast and the relative contributions of production sources and individual tributaries to the adult population are data critically important to the management and conservation of Chinook salmon in California.