Assessing the impact of releasing exogenous hatchery-reared juveniles of Pacific abalone, Haliotis discus

We studied the impact of releasing exogenous hatchery-reared juveniles on populations in Pacific abalone based on 10 microsatellite loci at the population and individual level. Standard measures of genetic variation (RS and HE) for collections from Ezo-and Kuro-abalone habitats did not differ. However, samples from Ezo-and Kuro-abalone habitats, respectively, were clearly divided into genetically distinct clusters; a result that was consistent with the FST analysis. In population-assignment testing, most individuals collected from Kuro-abalone habitats, where intensive release of hatchery-reared Ezo-abalone juveniles have been carried out, were assigned to a genetically defined Kuro-abalone group, suggesting that most of exogenous hatchery-reared Ezo-abalone had difficulty reproducing successfully in Kuro-abalone habitats. However, in the warm-water sampling area stocked with the greatest number of exogenous Ezo-abalone hatchery-reared juveniles, the numbers of misassigned individuals were highest. This suggests that the reproductive contribution of stocked hatchery-reared Ezo-abalone cannot be ruled out completely. Therefore, hatchery-mediated introgression of exogenous Ezo-abalone genes into the Kuro-abalone subspecies remains a possibility. To support the goal of a genetically fit and sustainable abalone fishery, further detailed studies and evaluation of the potential impact of introgression are needed.