Genetic divergence among broodstocks of Arctic charr Salvelinus alpinus in eastern Canada derived from the same founding populations

We examined the amount and distribution of molecular variation at microsatellite loci in 21 broodstocks of Arctic charr Salvelinus alpinus derived from the Fraser River, Labrador and the Nauyuk Lake, Nunavut, Canada. Our goal was to assess the amount of genetic diversity and differentiation as broodstocks are subdivided and propagated in different hatcheries and grow-out facilities. We observed significant heterogeneity across pairs of ancestral and descendant broodstocks in the mean numbers of alleles at microsatellite loci. We detected a significant decrease in the observed heterozygosity between ancestors and descendants but the amount of decrease did not depend on either the degree of removal from the wild (number of sequential transfers) or the strain (Fraser vs. Nauyuk). Based on allele frequency distributions, there was little genetic evidence of bottlenecks during the creation of subsequent broodstock populations after the initial founding events. All broodstock samples were significantly differentiated from each other but those within the same strain were more similar to each other than to broodstocks from different strains. Broodstocks from the Nauyuk Lake broodstocks showed greater differentiation from each other than did Fraser River broodstocks, which could be attributed to differences in the number of founders.