Genetic improvement through selection for growth performance in Atlantic salmon. The graph shows relative growth performance during the fresh-water phase and grow-out phase in seawater of wild and selected stocks. The selected stock had been under selection for four generations. The growth superiority of the selected stock was +175% and +75% in freshwater and during the grow-out phase, respectively.

The first and foremost task for any aquacultural industry is to develop the founder stock of the economically important aquaculture species that will have the genetic ability to use feed and land resources efficiently. The science of quantitative genetics and applied selective breeding theory has been the key to the impressive increase in production efficiency in livestock and plants over the last decades. Today, the high yields obtained from agriculture are almost entirely based on genetically improved breeds. In spite of its long history, the current aquacultural production is mainly based on the use of undomesticated fish from wild populations to regularly refresh the cultivated stocks. Such protocols cannot possibly generate any significant genetic improvement over time. Selective breeding capitalizing on additive genetic variation has been the single most effective method for genetic improvement in any aquatic or livestock species, as well as in a variety of plant species. This is not likely to change in the foreseeable future, although the significant non-additive genetic effect recently discovered and the emerging DNA sequencing and marker technologies derived in the field of molecular genetics may provide supplementary tools allowing further sophistication of genetic improvement programmes based on selective breeding. Significant and sustained genetic improvement through a selective breeding programme does not require gene transfer, manipulation of single gene expression or the number of chromosomes in the target species. Therefore, it does not involve controversial issues such as animal welfare, food safety, and the possible impact of gene-modified animals may have on natural ecosystems. The method is solely capitalizing on the natural genetic variation present in any population of living organisms. Genetic gain is obtained by increasing the proportion of desirable genes for desirable traits in the target populations, under close monitoring of possible side effects.