Adaptive Management and the Nez Perce Tribal Hatchery Spring Chinook Salmon Supplementation Program

Beginning in 2003, the Nez Perce Tribe implemented a supplementation program in the Clearwater River basin with the goal of restoring spring Chinook salmon populations to self-sustaining levels and provide harvest opportunities for Tribal and non-Tribal anglers.  This program utilizes fall releases of pre-smolt life stages, low density rearing and acclimation to best mimic natural production and minimize ecological impacts.  Hatchery and natural juveniles and adults were evaluated using abundance, survival and productivity performance measures.  Although overwinter survival of hatchery origin presmolts was low, surviving smolts demonstrated similar survival to Lower Granite Dam (LGR) and similar smolt-to-adult survival from LGR to LGR compared to natural origin smolts.  Finally, adult age structure (including jack proportions) of returning hatchery origin adults was similar to that of natural production.  Overall, the results suggest that a pre-smolt release strategy may minimize impacts by producing fish similar to that of the natural population.  However, survival from release to the smolt stage was very low and resulted in hatchery abundance levels well below the goals of the program.  An adaptive management framework was developed to evaluate alternative hatchery management approaches that can meet the program goals and limit impacts to natural populations.