Optimizing hatchery practices for genetic improvement of marine bivalves

Aquaculture currently accounts for approximately half of all seafood producedand is the fastest growing farmed food sector globally. Marine bivalve aquacul-ture, the farming of oysters, mussels and clams, represents a highly sustainablecomponent of this industry and has major potential for global expansion viaincreased efficiency, and numbers of, production systems. Artificial spat propaga-tion (i.e. settled juveniles) in hatcheries and selective breeding have the potentialto offer rapid and widespread gains for molluscan aquaculture industry. However,bivalves have unique life-histories, genetic and genomic characteristics, whichpresent significant challenges to achieving such genetic improvement. Selectionpressures experienced by bivalve larvae and spat in the wild contribute to drivepopulation structure and animal fitness. Similarly, domestication selection islikely to act on hatchery-produced spat, the full implications of which have not been fully explored. In this review, we outline the key features of these taxa and production practices applied in bivalve aquaculture, which have the potential to affect the genetic and phenotypic variability of hatchery-propagated stock. Along-side, we compare artificial and natural processes experienced by bivalves to investigate the possible consequences of hatchery propagation on stock production. In addition, we identify key areas of investigation that need to be prioritized to continue to the advancement of bivalve genetic improvement via selective breeding. The growing accessibility of next-generation sequencing technology and high-powered computational capabilities facilitate the implementation of novel genomic tools in breeding programmes of aquatic species. These emerging techniques represent an exciting opportunity for sustainably expanding the bivalve aquacul-ture sector