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Hatchery stocking for restoring wild populations: a genetic evaluation of the reproductive success of hatchery fish vs. wild fish

01/2008;

ABSTRACT Potential impacts of hatchery programs on wild populations have long been discussed, and of particular interest is the reproductive success of hatchery-born fish in natural environments. Here I summarize our recent studies, in which DNA fingerprinting and genetic parentage analyses were used to esti-mate adult-to-adult reproductive fitness of steelhead trout (Oncorhynchus mykiss) in the Hood River, Oregon (USA). We found: (1) Hatchery fish left fewer adult offspring per parent than wild fish, but supplementation hatchery fish (from local, wild broodstock; H supp) left larger numbers of offspring than traditional hatchery fish (from nonlocal, multi-generation hatchery broodstock; H trad); (2) The reproductive fitness of H supp declined unexpectedly fast (~40% per generation) when H supp were reused as broodstock in a hatchery, suggest-ing that the negative effects of hatchery rearing are cumulative and heritable; (3) Effective population size was mainly restricted by variance in reproductive success among individuals, rather than by biased sex ratio and temporal fluc-tuation of population sizes; (4) H trad showed particularly large variance in re-productive success, indicating another negative effect of traditional programs. Our case studies suggest that using local, wild broodstock reduces negative effects of hatchery rearing, but the repeated use of H supp as broodstock should be minimized for efficient supplementation.

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