Population genetic diversity and structure of wild and hatchery-raised populations of European abalone <i>Haliotis tuberculata tuberculata</i>: guidelines for future restocking and stock-enhancement programs

Populations of Haliotis tuberculata tuberculata declined sharply over the last two decades, mainly due to pathogenic bacteria, Vibrio Harveyi. In this context, restocking or stock-enhancement operations based on hatchery juveniles might be relevant to restore populations and ensure sustainable fisheries. Maintaining the genetic diversity of wild populations and hatchery individuals is a primary concern in supplementation programs. Here, the genetic diversity of 14 hatchery samples and 10 wild populations was assessed using 158 nuclear SNPs. Genetic diversity was comparable between wild and hatchery samples, and even slightly higher in the hatchery. However, high genetic differentiation and small effective population sizes suggested strong genetic drift in the hatchery. Pooling hatchery samples decreased differentiation levels with wild samples, suggesting that released juveniles should be composed of several cohorts and/or generations to limit the genetic heterogeneity between seed and wild populations. Moreover, reduced connectivity was detected between northwestern and southeastern populations, suggesting that restocking broodstock should be chosen depending on the locality where it would be released. Overall, this study provides useful guidelines for future restocking programs.