Genetic effects on carcass-quality traits in hybrid striped bass (Morone chrysops ♀ x Morone saxatilis ♂)

A 10 x 10 factorial mating design was used to examine the genetic effects on various carcass-quality traits in hybrid striped bass (Morone chrysops female x Morone saxatilis male). A total of 448 offspring were raised in a 'common-garden' environment and carcass-quality traits were assessed at 389 days post fertilization; parentage of each fish was inferred from genotypes at 5-10 nuclear-encoded microsatellites. There was a significant effect of dam and sire on body weight and fillet weight and a significant effect of dam on viscera weight and condition factor. When carcass-quality traits were standardized to body weight, there was a significant effect of dam, sire and dam x sire interaction on viscera percentage (proportion of viscera weight to body weight). Phenotypic correlations between body weight and non-standardized carcass-quality traits were high (r(p)=0.80-0.92), whereas phenotypic correlations between body weight and standardized carcass-quality traits were low (r(p)=0.13-0.19). Genetic correlations between body weight and fillet weight (dams and sires), and body weight and viscera weight (dams only) were significant and positive, while the genetic correlations between body weight and viscera percentage (dams and sires) were significant and negative. Significant general combining ability values for favourable carcass-quality traits in the same breeder (dam or sire) occurred only in one or two of 20 (dams and sires) used in this study, suggesting that simultaneous improvement in multiple traits in hybrid striped bass may require evaluation of large numbers of candidate breeders. The effect of sex on body weight and all non-standardized carcass-quality traits was significant and appeared to be due to faster growth in females. These results indicate that selection for faster growth of hybrid striped bass would lead to a correlated increase in fillet weight and viscera weight but not necessarily to an increase in the proportion of fillet and waste product generated. The significant dam, sire and dam x sire interaction effects on viscera percentage and the negative genetic correlations between body weight and viscera percentage indicate that selection for reduced proportion of viscera relative to body weight might be feasible.