Identification and adaptability of hatchery-origin Japanese flounder released into the Bohai Sea after the summer fishing moratorium

Because the artificial cultivation environment differs from the natural habitat of the Bohai Sea, it is essential to study the adaptability of hatchery-reared juveniles released into this area. Hatchery-origin Paralichthys olivaceus stocks were identified via morphological observation and genetic tags (i.e., mitochondrial DNA and microsatellites). Seven genomic microsatellite loci with a high PIC (polymorphic information content, 0.885–0.945) and a high exclusion probability (0.930–0.981) were selected and arranged into two multiplex PCRs. In total, 46.75% of the captures were assigned to our broodstocks. There were no significant differences in genetic diversity, such as Ar (allelic richness, P = .754) and He (expected heterozygosity, P = 0. 658), among the hatchery-origin stock (HS), their parents (P), the wild stock (WS) and the captured broodstocks (CB) in 2016. However, losses of Ar in the HS indicated that more attention should be given to the number of broodstocks in a reared population. The overall genetic divergence among these four groups was low (FST = 0.005), and the results of AMOVA also showed no genetic differences among them (P = .500), indicating that no pronounced genetic differentiation was found following the stock enhancement program in the Bohai Sea. There was no significant difference between HS and WS in terms of growth parameters (P > .05) and feeding ecology (P > .05). Furthermore, the stomach contents of the two groups were basically identical and consisted mainly of fish. Therefore, overall, the hatchery-origin juveniles had already adapted to the natural area after the summer fishing moratorium.