Investigating the genetic structure of wild and hatchery populations of Kutum Rutilus kutum Kamensky, 1901 using ten microsatellite markers

Kutum (R. kutum) is regarded as the most important commercial bony fish in the southern Caspian Sea. Restocking of this fish is done by releasing the larva produced by artificial propagation. In the present study, genetic diversity and structure of wild populations (caught in Gorgan bay and Gomishan wetland) and hatchery population used for restocking were investigated and compared using ten microsatellite loci. The microsatellite loci showed high polymorphism. The mean number of alleles was 9.4, 8.9 and 8 for Gomishan wetland, Gorgan bay and hatchery samples, respectively. The mean observed heterozygosity was 0.80 for Gomishan wetland samples, 0.798 for Gorgan bay samples and 0.728 for hatchery samples. Despite the lower levels of allelic diversity and heterozygosity of hatchery samples, no significant difference was observed in this respect. Twenty six cases out of 30 tests showed significant deviation from Hardy-Weinberg equilibrium. Moreover, high deficiency of heterozygosity was observed in some of loci. The mean values of Fst and Rst as the indices of genetic differentiation were obtained 0.018 and 0.044 respectively indicating low differentiation between the samples. The highest value of genetic distance was observed between Gorgan bay and hatchery samples. According to UPGMA dendrogram, the wild samples were separated from the hatchery ones. According to the obtained results, wild populations of Kutum had proper allelic and gene diversity in the investigated regions. However, considering the persistence of restocking programs by artificial reproduction, it is necessary to establish appropriate strategies to maintain and improve the observed diversity in wild populations.