Relatedness inferred from microsatellite genotypes as a tool for broodstock management of Japanese flounder Paralichthys olivaceus

We propose here a possible way to retard the loss of genetic variation in closed and non-pedigreed captive populations of Japanese flounder Paralichthys olivaceus by using a microsatellite-based kinship estimator (r_xy). We explored the utility of the estimator by applying the statistic to kinship discrimination in a Japanese flounder hatchery strain (83 offspring). We also investigated the effectiveness of minimal kinship selection (mk selection), which conceptually gives a high priority to individuals with rarer genotypes as broodstock parents, to minimize the loss of genetic variations in the next generation. A nonparametric analysis revealed that the difference of the pairwise r_xy values estimated for the offspring was highly significant between full-sib, half-sib, and unrelated categories, although this statistic showed a wide range of variations even within a kinship category. The mk selection based on the kinship estimator gave a benefit in the retention of both allelic diversity (number of alleles per locus) and gene diversity (unbiased expected heterozygosity) in the fish selected from the offspring pool: this approach, however, did not necessarily select unrelated fish, possibly resulting in sib mating, it should thus be necessary to preclude the mating between highly related individuals in the selected fish to minimize risk of inbreeding.