Selective breeding and shift to plant-based diets in fish farming

Abstract

World fish farm production is growing rapidly. However, the supply of fishmeal and fish oil, the major ingredients of fish diets, has reached a limit because of the limits in the exploitation of wild fish stocks that cannot be increased to meet a growing demand. The main response, especially in Europe, has been the progressive replacement of fishmeal and fish oil by plant products. However, the strong reduction of growth and sometimes survival of fish fed highly substituted diets has urged research on the genetic potential for adaptation to plant-based diets. Recent results clearly demonstrate that fish can be selected for their capacity to grow when fed plantbased diets, even though the underlying mechanisms remain unknown. Genotype-diet interactions have been shown, indicating that the best performers differ according to the diet. Such interactions may make the management of breeding programmes difficult, as progeny may be reared with a diet differing from the one used to select the breeders. Simulations of the expected genetic gain according to different scenarios can help manage selection programmes for sea bass and rainbow trout, the main farmed species in France. Using both selective breeding and optimized diets provide the opportunity to increase sustainability of fish farming, whilst maintaining product quality.