Genotype - Environment interaction

Abstract

Aquaculture takes place under very different environmental conditions. There may be differences in water temperature, salinity, technology or feed for example. No species of fish or shellfish are adapted to all kinds of environments. Outside the environment to which it is adapted, a particular species may not thrive or may not be able to survive at all. For example, salmon cannot compete with tilapia at high water temperatures while tilapia are not able to grow and survive in cold waters. We therefore talk about warm water species, coldwater species and species suitable for temperate climate. Similarly some species are adapted to freshwater, brackish water or salt water. Genotype-environment interaction may partly be ascribed to sensitivity of animals to variation in environmental conditions. Departures in environmental condition from those to which a species is adapted can cause the animal to become stressed. The main factors causing stress-situations for the animals are temperature, salinity, handling and water quality both in running and stagnant waters. Type and availability of feed may also cause interaction. We want robust animals, which will tolerate fluctuations in environmental conditions. In order to avoid developing strains sensitive to different environmental conditions, breeding values should be estimated on data from animals tested under varying farming conditions representative to the industry. The simple model where phenotype equals genotype plus environment (P = G + E) will only be a rough approximation. The model can be extended to include genotypeenvironment interaction (P = G + E + COVGE). Methods for estimation of the genotype - environment interaction component is shown in chapter 9.