Evaluating Supplementation of Spring Chinook Salmon In the Yakima Basin, WA

The Cle Elum Supplementation and Research Facility (CESRF) was designed to address uncertainties regarding the use of hatcheries to rebuild natural populations of salmon in the upper Yakima River in central Washington State. CESRF is a conservation hatchery that began operating in 1997 utilizing naturally produced adult spring Chinook salmon collected throughout the adults spawning run as broodstock.  Spawning consists of factorial mating of each female with multiple males.  Each female’s eggs are divided into two equal components that are used as control and treatment for research groups.  Approximately 800,000 juveniles are produced annually with half of the juveniles reared in nine treatment raceways and the other half in nine control raceways to allow statistical evaluation of each experiment.  The fish are transported in late winter to three acclimation sites with six raceways (3 treatment groups and 3 controls) to increase statistical power and evaluate homing fidelity of returning adults to acclimation areas. Supplementation adults are not taken back into hatchery as broodstock, but allowed to spawn in the natural environment.

All experiments evaluate the survival of out-migrating smolts at various mainstem Columbia River dams and also the survival to adults returning back to the Yakima. Experiments conducted to date include comparison of juveniles reared under semi-natural treatment (SNT) conditions with underwater feeders, overhead cover, and camouflage painted raceway walls against those reared under optimum conventional technologies (OCT) with standard hand feeding, concrete walls and no cover.  Another experiment varied the growth regimes in the hatchery rearing environment to create a treatment group of smaller size compared to larger smolts to evaluate production of precocial males that spawn as juveniles against smolt survival (larger smolts survive outmigration better than smaller ones).

An artificial spawning channel was also constructed to conduct controlled RRS experiments. Variables include changing the density of adults in the channel, and varying the percentage of wild and supplementation fish in each experiment.  All adults are genotyped and Peterson disk tags are inserted in the dorsal fin to allow visual observations.  Subsamples of fry produced are genotyped to evaluate RSS. Genetic samples are also collected from each adult in the population as they return to the upper Yakima for Relative Reproductive Success (RRS) evaluations of the entire population.