Adult Survival of Hatchery Spring Chinook Salmon Volitionally or Forced-Released as Juveniles

Hatchery managers seeking to maximize production must do so in the evolving framework of hatchery reform recommendations. Evaluation of changing practices is necessary for effective adaptive management and attainment of escapement goals. In this study, we compared the adult survival of hatchery reared spring Chinook Salmon Oncorhynchus tshawytscha released volitionally or forcibly from an acclimation facility in the upper Wenatchee River watershed from 2005-2007. In all study years, smolt-to-adult survival rates were higher for forced releases, with significant differences observed in 2006 and 2007. For hatchery programs that experience low smolt-to-adult survival rates, managers should evaluate the smolt release methodology. However, proposed changes to release method should be paired with a study design that accounts for other mechanisms that influence survival (e.g. mainstem riverine conditions during emigration) and ensure that any increase in survival is not offset by increased risk to natural populations.