Reproductive success of released hatchery stocks in the Pacific abalone Haliotis discus hannai

Abstract There has been grave concern in stock enhancement programs regarding the effects of stocking practices on resource augmentation of ensuing generations through reproduction of released hatchery stocks. Evaluation of whether released seedlings successfully produce offspring in the natural environment is a first step toward a better understanding of such inter-generation stocking effects. Against this background, we examined the reproductive success of released hatchery stocks of a Pacific abalone species, Haliotis discus hannai , on the basis of microsatellite-based parentage analysis. Adults of hatchery-raised abalone were released from 2014 to 2016 into the Toyoura area of Funka Bay (Hokkaido Island, Japan), where natural gene flow from other habitats was expected to rarely occur. After the reproductive season of H. discus hannai in Funka Bay in 2016, we collected 2016-year-class wild-born juveniles from Toyoura and determined parentages between the juveniles and released individuals. The results of this analysis revealed that approximately 10% of the juveniles were descended from the released hatchery stocks.