Molecular genetic assessments of the ongoing restocking activities on Salmo caspius Kessler, 1877

Maintenance of genetic diversity in broodstocks is highly important for restocking and aquaculture activities. Salmo caspius, a native species in the southern basin of the Caspian Sea, is a commercially important species, yet wild populations of S. caspius are experiencing severe reduction in size. Restocking has been the main conservation approach for S. caspius; however, there are no data describing whether stocking activities are having a positive or negative impact on the wild populations. In this study, we employed 28 polymorphic simple sequence repeats (SSRs) to assess the genetic population structure of S. caspius (n = 67) in the restocking centre of southern Caspian basin. Results showed a high level of genetic diversity (mean H_o = 0.88) with no signatures of inbreeding. Structural analyses recognized the wild individuals (CP); however, a severe admixture structure for the hatchery-originated populations was observed, which can be due to the interbreeding events during restocking activity. Inter-population crosses would have diminished the level of differentiation among different populations (overall F_st = 0.01), resulting in a population collapse in the future. Therefore, pre-use of kinship information obtained through genetic data accompanied by rehabilitation of natural habitats is highly suggested to amend the genetic health of S. caspius in the southern Caspian Sea.