Contribution of Maturing, Captive-Reared Adult Salmon to Aid Recovery of At-Risk Populations

Precipitous declines of Pacific salmon (Oncorhynchus spp.) have led to population levels that require prompt reactions to avoid extinction of some stocks. One rarely attempted strategy for reducing short term extinction risk and providing a demographic boost to natural populations is to initiate conservation hatchery propagation programs that release captive adults to volitionally spawn in the natural environment. For these restoration efforts to succeed, captive adults must be able to successfully survive and reproduce in the wild.  These programs require monitoring and evaluation components to describe reproductive success, determine the relative contribution of multiple release strategies and estimate subsequent abundance and productivity. We provide examples from two conservation hatchery programs in Idaho: Snake River sockeye salmon captive broodstock program and Snake River Spring Chinook salmon captive rearing program, which highlight some of the current evaluations. In both of these programs, we documented that captive- reared adults released into natural habitats successfully constructed redds, spawned, produced progeny that migrated to the ocean, and returned successfully as adults. We thus confirmed that captive-reared adults released into the freshwater environment contributed to the next generation of the natural population. These findings provide insight into the utility of using the captive propagation approach as a tool towards recovering severely depressed populations of salmon.