A first demonstration of realized selection response for fillet yield in fish, in rainbow trout oncorhynchus mykiss

A first demonstration of realized selection response for fillet yield in fish, in rainbow trout oncorhynchus mykiss. 13. International Symposium for Genetics in Aquaculture (ISGA XIII

First Evidence of Realized Selection Response on Fillet Yield in Rainbow Trout Oncorhynchus mykiss, Using Sib Selection or Based on Correlated Ultrasound Measurements

Fillet yield, the proportion of edible fillet relative to body weight, is a major trait to improve in fish sold processed, as it has a direct impact on profitability and can simultaneously decrease the environmental impact of producing a given amount of fillet. However, it is difficult to improve by selective breeding, because it cannot be measured on live breeding candidates, its phenotypic variation is low, and, as a ratio, it is not normally distributed and a same change in fillet yield can be the result of different changes in fillet weight and body weight. Residual headless gutted carcass weight (rHGCW) is heritable and highly genetically correlated to Fillet% in rainbow trout, and can be predicted by the ratio of abdominal wall thickness to depth of the peritoneal cavity (E8/E23), measured on live fish by ultrasound tomography. We selected broodstock based on rHGCW, measured on sibs of the selection candidates, on ultrasound measurements (E8/E23) measured on the selection candidates, or a combination of both. Seven broodstock groups were selected: fish with 15% highest (rHGCW+) or lowest (rHGCW−) EBV for rHGCW, with 15% highest (E8/E23+) or lowest (E8/E23−) EBV for E8/E23, with both rHGCW+ and E8/E23+ (Both+) or rHGCW− and E8/E23− (Both−), or with close to zero EBVs for both traits (Mid). Seven corresponding groups of offspring were produced and reared communally. At harvest size (1.5 kg mean weight), 1,561 trout were slaughtered, measured for the traits of interest, and pedigreed with DNA fingerprinting. Offspring from groups Both+, rHGCW+ and E8/E23+ had a higher EBV for rHGCW than the control group, while down-selected groups had a lower EBV. Looking at the phenotypic mean for Fillet% (correlated response), up-selected fish had more fillet than down-selected fish. The highest difference was between Both+ (69.36%) and Both− (68.20%), a 1.16% units difference in fillet percentage. The change in Fillet% was explained by an opposite change in Viscera%, while Head% remained stable. Selection using sib information on rHGCW was on average more efficient than selection using the candidates’ own E8/E23 phenotypes, and downward selection (decreasing Fillet%) was more efficient than upward selection

Successful realized selection response for fillet yield in rainbow trout Oncorhynchus mykiss

Successful realized selection response for fillet yield in rainbow trout Oncorhynchus mykiss. World Aquaculture 201

Investigation of morphological predictors of fillet and carcass yield in European sea bass (Dicentrarchus labrax) for application in selective breeding

Genetic parameters for carcass and fillet percentage were estimated in 760 European sea bass reared under commercial conditions and slaughtered at 573 days post fertilization (395 g mean body weight). Phenotyped fish were the offspring of 45 sires and 20 dams crossed in a factorial mating design. Pedigrees were re-constructed with 90.7% success using 12 microsatellites. The heritability of fillet yield was moderately low (0.21), while it was high for carcass yield (0.57). Both traits were poorly correlated (− 0.01 to 0.28) making space for their combined improvement. We investigated different predictors derived from measurement of surfaces on digital pictures and ultrasound measurements at several points of the body. The accuracy of the phenotypic prediction was rather low for fillet yield (r2 = 0.02–0.18), but higher for carcass yield (r2 = 0.27–0.41). However, genetic correlations of predictors with the traits to predict were reasonably high (up to 0.67 for fillet yield and 0.95 for carcass yield), thus allowing to consider them for performing indirect individual selection instead of sib selection. However, it was difficult to design a predictor that would simultaneously increase fillet yield and carcass yield because of contradicting effects of relative head size, an important component of the predictors which was positively correlated to carcass yield but not to fillet yield. Statement of relevance We estimated phenotypic predictors for processing yields in the European sea basslane estimated their genetic variation and correlations with the traits to predict. This is important to be able to apply indirect selection for processing yields in this species. This showed that although the traits of interest were hardly correlated, it was not possible to find external predictors having a significant positive impacts on both traits (carcass and fillet yield) simultaneously. This highlights the need to study specifically these issues in different species and conditions, as the picture here is very different to the well studied case of rainbow trout for example