No Evidence of Increased Survival or Decreased Straying from Acclimating Subyearling Fall Chinook Salmon to Release Locations in the Umatilla River of Oregon

Smolt-to-adult survival (SAS) and straying of subyearling fall Chinook Salmon Oncorhynchus tshawytscha that were acclimated in waters of their release site before river release was compared with those of fish that were transported to the river and released directly into the river. Results showed that there were no differences in average SAS, which was 0.08% for both acclimated and direct-release groups, or straying, which averaged 33.8% and 35.3% for direct and acclimated release groups, respectively. We conclude that an acclimation period may not improve these metrics in subyearling-released salmon. Received June 19, 2015; accepted October 31, 2015