Genetic evaluation for releasing hatchery population of ayu Plecoglossus altivelis altivelis by microsatellite DNA analysis

We assayed the genetic characteristics of hatchery-reared and wild Ayu Plecoglossus altivelis altivelis populations in Aichi Prefecture using microsatellite DNA analysis. No statistical differences were detected in pairwise Fst values among different populations and life stages of wild fish. Wild fish populations from the rivers flowing into Ise and Mikawa bays were thought to constitute the same genetic population. Genetic characteristics of a hatchery stock Fl from wild population, medium in size selection was similar to that of wild populations in terms of both allele number and heterozygosity, and pairwise Fst values. A marked reduction in genetic variability and/or considerable genetic drift was observed in some of hatchery stocks, domesticated stock and artificially selected stock. However, an increase in genetic variability was observed in a cross-breeding stock that had wild fish and domesticated stock as parents. We propose that F1 hatchery stocks originating from wild, amphidromous parents that are not under any strong selection are well suited for release and stock enhancement. In conclusion, in order to reduce the risk of genetic disturbance to wild ayu population, production management initiatives related to managing the genetic aspects of ayu hatchery stocks need to be implemented.