Adverse Impact of Hatchery Fish on the Natural Reproductive Resilience of Salmon and Steelhead Populations

We found a negative relationship between the natural reproductive resilience in 93 natural populations of steelhead, coho, and Chinook salmon and the proportion of hatchery fish in these populations.  We used intrinsic productivity as estimated from fitting a variety of recruitment models to abundance data for each population as our indicator of reproductive resilience.  The strength of this relationship was such that a hypothetical population comprised entirely of hatchery spawners would have an intrinsic productivity only 0.128 of that for a population composed entirely of wild fish. There was no difference in this effect among the three species examined. Further, the impact of hatchery fish from ‘wild type’ hatchery broodstocks was no less adverse than hatchery fish from traditional, domesticated broodstocks.  We conclude, based on that the mixing of hatchery fish into natural populations is a management strategy that is an ineffective long-term means to conserve and recover at risk species.