Empirical Results of Salmon Supplementation in the Northeast Pacific: A Preliminary Assessment

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For over a century, aquaculture of Pacific salmon has been used to provide increased harvest opportunities and to mitigate reductions in natural populations due to factors such as habitat destruction, overharvest, and blockage of migratory routes. More recently, attention has focused on the potential of hatchery propagation to reduce risks to and speed recovery of depleted natural populations. A large number of these “supplementation” programs have already been initiated and many more are planned, in spite of the fact that there is almost no empirical information on their long-term effects. Here we present preliminary results of a survey of 22 salmon supplementation programs in northwestern North America. Rather than using a single measure of “success,” we evaluated programs according to how well they have accomplished a series of specific objectives. Some major conclusions emerge from the review: (1) many supplementation programs have achieved a measure of success in the aspects of fish culture traditionally associated with salmon hatcheries (e.g., high egg-to-smolt survival; adult-to-adult replacement rates in excess of 1.0); (2) to date, however, little information is available about the performance of hatchery fish and their progeny in the natural environment. Therefore, the premise that hatchery supplementation can provide a net long-term benefit to a natural population is a hypothesis that has not yet been tested. This fact should be kept in mind in evaluating the appropriate use of supplementation programs.