Principles of Genetics and Breeding

13.1.3. Breeding goals

The ultimate goal for a commercial breeding programme is to increase the biological efficiency of the production, by utilizing the genetic variation among individuals present in the population.

Some of the most important traits for genetic improvement are: growth rate, feed conversion efficiency, age at sexual maturation, disease resistance and quality.

• Large genetic variation for growth rate has been found in Atlantic salmon, rainbow trout, tilapia, catfish, carp, shrimp and oysters.
• Disease resistance, which is a very important economic trait, shows varying estimates of genetic variation. Some selection experiments have shown genetic improvement for disease resistance. E.g., dropsy disease in common carp and furunculosis in brown trout and brook trout.
• In general, rate of survival shows low genetic variation. However, when genetic groups are challenged with specific pathogens, relatively large heritabilities and genetic variation have been found.
• Flesh quality traits in Atlantic salmon and rainbow trout also show considerable genetic variation.
• The advantage of fish as breeding stock is their high fecundity and relatively large genetic variation.

There are different options for the overall structure of breeding programmes.

For e.g., a large breeding programme might involve a single nucleus breeding centre where the selective breeding would be carried out with multiplier stations which would concentrate on large scale fry production without having to be concerned about broodstock management or selective breeding.