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

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 fifty eight years, a time period that spanned the initiation of native steelhead trout broodstock hatchery supplementation in these rivers. We detected no hanges 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 non-migratory O. mykiss, the use of substantial numbers of primarily native broodstoc...