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

Fisheries for global welfare and environment: 5th world fisheries congress 2008 01/2008;


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.


Available from: Hitoshi Araki, Jan 14, 2014
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    [Show abstract] [Hide abstract] ABSTRACT: Understanding the impact of hatchery supplementation on the genetics of wild fish populations is important for designing and evaluating ecologically sound stocking practices. For species such as brook trout Salvelinus fontinalis, which are a high priority for conservation and restoration in their native range, understanding the potential impacts of stocking on the functional diversity of wild populations is critical. We sought to determine whether brook trout stocked in low-order reservoirs colonize impoundment feeder streams and if they naturally reproduce and interbreed with established native populations in these tributaries. Analysis of microsatellite DNA allowed us to distinguish hatchery-origin brook trout and putative native strains among tributaries of three stocked reservoirs and one unstocked stream. Hatchery-origin fish were found in tributaries of all stocked reservoirs, mixed with native populations; none were found in an unstocked reference stream that supported wild brook trout. Age-1 brook trout genetically matching a known hatchery strain were found in tributaries of stocked reservoirs, although none of this age were stocked, suggesting that stocked trout have successfully reproduced in these streams. Assignment tests indicated that 4 of the 98 brook trout collected from mixed stocked–native streams were probably hybrids (∼4.1%; 95% confidence interval = 1.3–10.0%). These results suggest that to date the direct impacts of stocking on the genetics of these native populations have been limited but that indirect impacts through competition or similar interactions may still be occurring.Received January 24, 2011; accepted October 13, 2011
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