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.
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[Show abstract][Hide abstract]ABSTRACT: The evaluation of the reproductive success (RS) of hatchery fish in the wild is one of the most important issues in hatchery supplementation, aquaculture, and conservation. Estimates of the relative reproductive success (RRS) have been used to evaluate RS. Because RRS may vary greatly depending on cross, years of release, and environmental conditions, we introduced a log-normal distribution to quantify the variation. The classical estimator of RRS based on multiple measurements is contrasted with the mean of this distribution. We derived the mean, variance, and relative bias and applied our Bayesian hierarchical model to 42 empirical RRS estimates of steelhead trout (Oncorhynchus mykiss) in the Hood River, Oregon, USA. The RRS estimate generally had an upward bias. Although the average level of RRS implied the reproductive decline of hatchery fish and wild-born hatchery descendants, we could not reject the null hypothesis that hatchery fish and their descendants have the same chance of having smaller RS than wild fish as they do of having larger RS than wild fish.
Preview · Article · Oct 2011 · Canadian Journal of Fisheries and Aquatic Sciences
[Show abstract][Hide abstract]ABSTRACT: In 1997 the Cle Elum Supplementation Research Facility was established to enhance spring Chinook salmon returning to the upper
Yakima River, Washington State. This effort increased spring Chinook abundance, yet conditions at the hatchery also significantly
elevated the occurrence of jacks and yearling precocious males. The potential genetic effect that a large influx of early
maturing males might have on the upper Yakima River spring Chinook population was examined in an artificial stream. Seven
independent groups of fish were placed into the stream from 2001 through 2005. Males with four different life history strategies,
large anadromous, jacks, yearling precocious, and sub-yearling precocious were used. Their breeding success or ability to
produce offspring was estimated by performing DNA-based pedigree assessments. Large anadromous males spawned with the most
females and produced the greatest number of offspring per mate. Jacks and yearling precocious males spawned with more females
than sub-yearling precocious males. However, jacks, yearling and sub-yearling precocious males obtained similar numbers of
fry per mate. In the test groups, large anadromous males produced 89%, jacks 3%, yearling precocious 7%, and sub-yearling
precocious 1% of the fry. These percentages remained stable even though the proportion of large anadromous males in the test
groups ranged from 48% to 88% and tertiary sex ratios varied from 1.4 to 2.4 males per female. Our data suggest that large
anadromous males generate most of the fry in natural settings when half or more of the males present on a spawning ground
use this life history strategy.
KeywordsSpring Chinook salmon–Jacks–Precocious males–Breeding success–Relative breeding success
Full-text · Article · May 2012 · Environmental Biology of Fishes
[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
Full-text · Article · Feb 2012 · North American Journal of Fisheries Management