Reproductive Behavior and Breeding Success of Captively Reared Chinook Salmon

Abstract

Release of captively reared adults is one of several strategies currently being used to maintain imperiled populations of chinook salmon Oncorhynchus tshawytscha in the Pacific Northwest. This study evaluated the breeding behavior and success of captively reared chinook salmon released at maturity into a controlled-flow stream channel. Female egg deposition was 49.5%, which is much lower than that reported for wild populations, but egg-to-fry survival was 62.5%. Females abandoned 40% of the nests they constructed, and males were often absent during the female's nest construction. The underlying causes of these presumed behavioral deficiencies might have limited the breeding success of the population. The efficacy of adult release strategies should be assessed within the context of other potential release options, keeping in mind the objectives of the individual program. Under current culture practices, the reproductive success of captively reared chinook salmon that are released as adults may be less than that of wild salmon.