Principles of Genetics and Breeding

13.1.2. Prospects for genetic improvement

Genetic improvements in farm animals accelerated dramatically after II World War, mainly because of new technologies and knowledge, and this resulted in manifold increased production. However, aquaculture did not participate in these advances during that period (Fig.1) and selective breeding in Atlantic salmon started only in mid 1970s.

When compared to farmed animals the high fecundity in fishes gives possibilities for high selection intensities and thereby high genetic gains.

A prerequisite for genetic gain is the determination of genetic variation in important economic traits, but only a small number of fish and shellfish species have been evaluated for this.

In domesticated populations of fish it is desirable to maintain high levels of genetic variation for the following reasons:

i) Genetic variation provides the raw material for selection. Without additive genetic variance there can be no response to selection.

ii) Rare alleles in a population may not be of value to aquaculture today but may be tomorrow. For e.g. in conferring resistance to an outbreak of new disease.

iii) Once alleles are lost from a population, they cannot be recovered without addition of new material.

iv) Genetically variable populations are thought to have higher levels of developmental stability and fitness.

v) Inbreeding depression is prevented.