Tuesday, July 31, 2012

Hatchery Supplementation Decreases Genetic Diversity in Salmon Populations

Over the last several years, a string of science papers have come out of more than a decade of research that was done on the Hood River prior to the removal of Powerdale Dam. By sampling every fish passed through the fish ladder to spawning areas above the dam for multiple generations researchers were able to track the reproductive success of individual fish, comparing the number of adult offspring produced by both wild and hatchery fish. 

The work has served to strengthen the argument against the use of hatcheries in restoring wild populations and provided compelling evidence that wild broodstock hatcheries are not a viable solution to the problems associated with hatchery programs. Among the papers that have come out of the research on the Hood are several publications that have demonstrated the rapid decline in fitness that results from domestication of steelhead in a hatchery environment. Now Mark Christie, a researcher at Oregon State University and a group of colleagues have published another piece of their work which examines the impact of the wild broodstock hatchery program on effective population size, a metric that reflects the effective number of fish that contribute to the next generation. Effective population size is a good predictor of the ability of a population to maintain crucial genetic diversity. 

They found that despite the fact that the total number of spawners was enhanced by the presence of hatchery fish, hatchery supplementation actually served to decrease the genetic diversity of the wild population. This is critical information for managers who may be temped to resort to using hatcheries as a means of increasing the size of spawning populations over the short term. 

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