Genetic Considerations in the Ethics of Aquaculture

Our ethical responsibility in aquaculture includes maintaining the genetic diversity of both cultured fish species and wild native populations.  In order to maintain this genetic diversity, several factors need to be considered, such as the role of selection, hybridization, and effective population size.  Stabilizing selection can maintain genetic diversity in populations and mate selection often contributes to maintaining heterozygotes.  If aquaculture eliminates natural mate selection, this variation may not be maintained.  Additionally, selective pressures in the hatchery setting likely differ from the pressures faced in the wild.  Escape of aquaculture fish could therefore alter that dynamic in the wild.  Hybridization and subsequent introgression can threaten native populations.  Introgression can have varying effects on fitness (hybrid vigor or outbreeding depression); both consequences will be discussed.  Finally, aquaculture can reduce the effective population size primarily through high variance in family size and fluctuating population sizes.  Approaches in aquaculture that increase the ratio of effective population size to census population size will be discussed.  As new genetic technologies are quickly being developed, there will be additional genetic considerations.