Estimating the impact of bay scallop restoration efforts using genetic data

Shellfish populations in many areas are being augmented with hatchery-produced animals in an effort to counteract the effects of overfishing, habitat degradation and disease. While such efforts have the immediate effect of increasing local abundance, it is the expectation that the restorations will have a more dramatic effect on subsequent generations. Until recently, it has been difficult to evaluate the contribution made by such restorations because the offpsring of hatchery-produced animals are not readily distinguishable from wild conspecifics. The constraints of hatchery methodologies, however, prevent the production of stocks that mimic natural populations with respect to genetic variation. These inevitable genetic differences between hatchery-produced and wild stocks can be used to differentiate individuals in the cohort following restoration. Recent efforts to assess the contribution of hatchery-produced bay scallops based on sequence analysis of mitochondrial DNA markers serve as a field test of this approach. Assessment of restoration efforts in Florida provided no genetic evidence of a contribution from the hatchery stock despite substantial increases in abundance following the restoration. In contrast, a substantial contribution from hatchery-produced scallops deployed in Chincoteague Bay was suggested by mtDNA analysis, indicating that the restoration effort was in part responsible for the increase in abundance.