Genetic characterization of hatchery populations of Korean spotted sea bass (Lateolabrax maculatus) using multiplex polymerase chain reaction assays.

The spotted sea bass, Lateolabrax maculatus, is an important commercial and recreational fishery resource in Korea. Aquacultural production of this species has increased because of recent resource declines, growing consumption, and ongoing government-operated stock release programs. Therefore, the genetic characterization of hatchery populations is necessary to maintain the genetic diversity of this species and to develop more effective aquaculture practices. In this study, the genetic diversity and structure of three cultured populations in Korea were assessed using multiplex assays with 12 highly polymorphic microsatellite loci; 144 alleles were identified. The number of alleles per locus ranged from 6 to 28, with an average of 13.1. The mean observed and expected heterozygosities were 0.724 and 0.753, respectively. Low levels of inbreeding were detected according to the inbreeding coefficient (mean FIS = 0.003-0.073). All hatchery populations were significantly differentiated from each other (overall fixation index (FST) = 0.027, P < 0.01), and no population formed a separate cluster. Pairwise multilocus FST tests, estimates of genetic distance, mantel test, and principal component analyses did not show a consistent relationship between geographic and genetic distances. These results could reflect the exchange of breeds and eggs between hatcheries and/or genetic drift due to intensive breeding practices. For optimal resource management, the genetic variation of hatchery stocks should be monitored and inbreeding controlled within the spotted sea bass stocks that are being released every year. This genetic information will be useful for the management of both L. maculatus fisheries and the aquaculture industry.

Population genetic structure of wild and hatchery black rockfish Sebastes inermis in Korea, assessed using cross-species microsatellite markers.

The population structure of the black rockfish, Sebastes inermis (Sebastidae), was estimated using 10 microsatellite loci developed for S. schlegeli on samples of 174 individuals collected from three wild and three hatchery populations in Korea. Reduced genetic variation was detected in hatchery strains [overall number of alleles (N(A)) = 8.07; allelic richness (A(R)) = 7.37; observed heterozygosity (H(O)) = 0.641] compared with the wild samples (overall N(A) = 8.43; A(R) = 7.83; H(O) = 0.670), but the difference was not significant. Genetic differentiation among the populations was significant (overall F(ST) = 0.0237, P < 0.05). Pairwise F(ST) tests, neighbor-joining tree, and principal component analyses showed significant genetic heterogeneity among the hatchery strains and between wild and hatchery strains, but not among the wild populations, indicating high levels of gene flow along the southern coast of Korea, even though the black rockfish is a benthic, non-migratory marine species. Genetic differentiation among the hatchery strains could reflect genetic drift due to intensive breeding practices. Thus, in the interests of optimal resource management, genetic variation should be monitored and inbreeding controlled within stocks in commercial breeding programs. Information on genetic population structure based on cross-species microsatellite markers can aid in the proper management of S. inermis populations.