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

摘要

Hatchery managers seek to maximize production and survival in a cost-effective manner while adapting to hatchery reform recommendations. Evaluation of changing hatchery rearing practices is necessary under an adaptive management paradigm. 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 basin from brood years 2003-2005. In all study years, smolt-to-adult survival rates were higher for forced releases, and significant differences were observed in brood years 2004 and 2005. To optimize hatchery fish performance, hatchery managers should evaluate their smolt release methodology. However, any proposed changes in hatchery release methodology should also take into account variability in survival within the migration corridor and a risk assessment such that any realized increase in survival is not offset by increased risk to natural populations.