Hatchery spring Chinook salmon (Oncorhynchus tshawytscha) eggs from Round Butte State Fish Hatchery (RBH) and Parkdale Fish Hatchery (PFH) were reared and released at Warm Springs National Fish Hatchery (WSNFH). To assess stock performance, stocks were monitored for size, condition factor, on-station survival, pre-release precocial rate, juvenile survival, migration timing, release to adult return survival rates, size, age structure, and external mark identification accuracy. Although on-station survival and growth did not show significant differences, return timing and survival was earlier and higher for WSNFH stock fish. While RBH and PFH stock fish contributed to harvest benefits, there is some level of genetic risk to the Warm Springs population if fish from RBH or PFH stock are incorporated into the WSNFH population during spawning. Segregating RBH and PFH stock adult returns based on external marks had an overall 11% error rate. This evaluation provides managers with a better understanding of the short and long-term benefits and risks of supplementing the Warm Springs NFH program with non-Warm Springs stock fish during years of production shortfalls.
