Principles of Genetics and Breeding

13.1.1 Selective breeding programmes in aquaculture

Selection methods and breeding plans, mating designs

Adaptation to the captive environment, as described under domestication, may be termed “automatic selection”. Further genetic improvement requires active intervention of the breeder.

Falconer described two ways in which the action of the breeder can change the genetic properties of the population;

i) by the choice of the individuals to be used as parents, which constitutes selection, and

ii) by control of the way in which the parents are mated, which embraces inbreeding and crossbreeding.

• Selection is intentionally applied by the manager to improve performance, by selecting broodfish or offspring because of certain heritable phenotypic traits or characters.
• Selection is a microevolutionary process resulting in genetic change.
• Selection occurs from the interaction of a gene pool or population genotype with its environment resulting in adaptation and genetic loss.
• Generally, selection results in a relative increase in frequency of those genotypes influencing fitness, such as mating choice, fecundity, viability, longevity, and emigration.
• Selection of some genotypes is at the expense of less favourable genotypes with the net result being a fitter individual or population within its environment.
• The fish hatchery manager’s goal is to intentionally change the population’s identity and character in desirable ways through artificial selection.