Genetic improvement of fish: Achievements and challenges for tomorrow

Genetic improvement is a major contributing factor in developing efficient aquaculture, as it is in other forms of animal production. Moreover, as most fish species are only slightly domesticated, the potential gains are very large. Many of the current methods, developed during the XXth century, are classically used in livestock rearing (choice of breeds, crossbreeding, selective breeding). Others are much more specific to aquatic organisms (genetic control of sex, sterilization through triploidization). The spread of selected lines in aquaculture has been effective only since the 1990s, with lines selected essentially on growth and producing some impressive results. Transgenesis, although technically feasible on growth rate, is not used in practice and will become of use only through the definition of new phenotypes, beneficial for all and out of reach of classical selection. In order to allow a sustainable development of aquaculture, selection criteria should evolve towards an improvement of production efficiency (feed efficiency, slaughtering yields, disease resistance) and adaptation to new contexts (fluctuating environment, vegetal-based feeds). An improvement of selection in such a direction, in addition to the high potential of "classical" methods, should take advantage of the development of genomic technologies, first to make the best use of molecular pedigrees and in the longer term to improve the knowledge in the genetic and biological bases of traits and to select directly on the genotype (genomic selection).