Enhanced individual selection for selecting fast growing fish: the ?PROSPER? method, with application on brown trout (Salmo trutta fario)

Abstract

-Growth rate is the main breeding goal of fish breeders, but individual selection has often shown poor responses in fish species. The PROSPER method was developed to overcome possible factors that may contribute to this low success, using (1) a variable base population and high number of breeders (Ne > 100), (2) selection within groups with low non-genetic effects and (3) repeated growth challenges. Using calculations, we show that individual selection within groups, with appropriate management of maternal effects, can be superior to mass selection as soon as the maternal effect ratio exceeds 0.15, when heritability is 0.25. Practically, brown trout were selected on length at the age of one year with the PROSPER method. The genetic gain was evaluated against an unselected control line. After four generations, the mean response per generation in length at one year was 6.2% of the control mean, while the mean correlated response in weight was 21.5% of the control mean per generation. At the 4th generation, selected fish also appeared to be leaner than control fish when compared at the same size, and the response on weight was maximal (≈130% of the control mean) between 386 and 470 days post fertilisation. This high response is promising, however, the key points of the method have to be investigated in more detail.Salmo trutta / selective breeding / aquaculture / genetics / individual selection

Amélioration génétique et utilisation des aliments à base de végétaux en pisciculture

“…Dans le cas simple d'une sélection individuelle (sélection dans laquelle les individus sont choisis à partir de leur performance propre), si P est la moyenne du caractère dans la population initiale et σP est l'écart-type phénotypique de ce caractère dans la population, le progrès génétique ΔP (écart entre la performance moyenne des parents et la performance moyenne des descendants) attendu à chaque génération sera : élevée, il est possible d'appliquer de fortes pressions de sélection, la combinaison de ces deux facteurs permettant au final d'obtenir des progrès génétiques rapides, de l'ordre de 4 à 20% par génération pour la croissance (Olesen et al 2003, Chevassus et al 2004.…”

Perspectives pour la recherche biotechnique en pisciculture

“…La question de l'amélioration des performances d'un peuplement multispécifique sous contrainte trophique globale (la productivité totale potentielle du milieu) est donc beaucoup plus complexe que celle de l'amélioration d'une production monospécifique non limitée par l'apport d'intrants. En effet, dans ce dernier cas, l'amélioration de la croissance par sélection semble résulter essentiellement d'une augmentation de la consommation journalière spontanée, sans amélioration de l'efficacité des aliments, comme cela a été montré chez les salmonidés (Chevassus et al, 2004 ;Mambrini et al, 2004aMambrini et al, et 2004b.…”

Animal welfare aspects of husbandry systems for farmed trout ‐ Scientific Opinion of the Panel on Animal Health and Welfare

“…Selection based on individual and related performances (family selection) was more widely used in North of Europe but require large rearing facilities. A new selection procedure more adapted to a SME's (Small and Medium Enterprises) has been developed in France (Chevassus et al, 2004). This procedure of selection uses external indirect quality traits or technologies (morphology, fat in the muscle with micro-waves, body thickness and processing yields using ultrasound) and genealogical management of the genetic resources using genetic fingerprinting (Haffray et al, 2004).…”

“…Main traits selected today are growth, body morphology to improve gutted yield and lipid muscle content. These traits have moderate heritability (Gjedrem, 2000;Chevassus et al, 2004;Quillet et al, 2004) and should produce significant genetic gain. More that 70 % of the EU production benefits from juveniles genetically improved according to selection programmes based on scientific basis.…”