title: Little impact of hatchery supplementation that uses native broodstock on the genetic structure and diversity of steelhead trout revealed by a large-scale spatio-temporal microsatellite survey.
abstract: Artificial breeding programs initiated to enhance the size of animal populations are often motivated by the desire to increase harvest opportunities. The introduction of non-native genotypes, however, can have negative evolutionary impacts. These may be direct, such as introgressive hybridization, or indirect via competition. Less is known about the effects of stocking with native genotypes. We assayed variation at nine microsatellite loci in 902 steelhead trout (Oncorhynchus mykiss) from five rivers in British Columbia, Canada. These samples were collected over 58 years, a time period that spanned the initiation of native steelhead trout broodstock hatchery supplementation in these rivers. We detected no changes in estimates of effective population size, genetic variation or temporal genetic structure within any population, nor of altered genetic structure among them. Genetic interactions with nonmigratory O. mykiss, the use of substantial numbers of primarily native broodstock with an approximate 1:1 male-to-female ratio, and/or poor survival and reproductive success of hatchery fish may have minimized potential genetic changes. Although no genetic changes were detected, ecological effects of hatchery programs still may influence wild population productivity and abundance. Their effects await the design and implementation of a more comprehensive evaluation program.
authors.affiliation: Department of Zoology, Biodiversity Research Centre and Native Fishes Research Group, University of British Columbia Vancouver, BC, Canada.
authors.forename: Jennifer L
authors.initials: JL
authors.lastname: Gow
authors.affiliation: Department of Zoology, Biodiversity Research Centre and Native Fishes Research Group, University of British Columbia Vancouver, BC, Canada.
authors.forename: Patrick
authors.initials: P
authors.lastname: Tamkee
authors.affiliation: Department of Zoology, Biodiversity Research Centre and Native Fishes Research Group, University of British Columbia Vancouver, BC, Canada ; Laboratory of Freshwater Ecology, University of Oslo Oslo, Norway.
authors.forename: Jan
authors.initials: J
authors.lastname: Heggenes
authors.affiliation: British Columbia Ministry of Environment Surrey, BC, Canada.
authors.forename: Greg A
authors.initials: GA
authors.lastname: Wilson
authors.affiliation: Department of Zoology, Biodiversity Research Centre and Native Fishes Research Group, University of British Columbia Vancouver, BC, Canada.
authors.forename: Eric B
authors.initials: EB
authors.lastname: Taylor
keywords: effective population size; gene flow; genetic drift; historical DNA samples; microsatellite DNA; native broodstock; salmonid; temporal analysis