Estimates of heritabilities and genetic correlations for body composition traits and G×E interactions, in gilthead seabream (Sparus auratus L.)

In this study, heritabilities for body composition traits, their genetic correlations with growth traits and the genotype–environment interaction (G×E) were estimated at 509days (harvest size) for the first time in gilthead seabream (Sparus auratus L.), from the offspring in two different production systems (cages and tanks) in the Canary Islands. A total of 867 offspring from an industrial mass-spawning of 66 broodstocks were analysed. Parental assignment showed a total of 89 full-sib families (between 1 and 53 descendents per family) and was inferred using the RimA multiplex PCR designed by Navarro et al. (2008) [Navarro, A., Badilla, R., Zamorano, M.J., Pasamontes, V., Hildebrandt, S., Sánchez, J.J., Afonso, J.M., 2008. Development of two new microsatellite multiplex PCRs for three sparid species: gilthead seabream (Sparus auratus L.), red porgy (Pagrus pagrus L.) and redbanded seabream (P. auriga, Valenciennes, 1843) and their application to paternity studies. Aquaculture 285, 30–37.] with 100% success. The G×E interaction was analysed in 61 families present in the two environments and was null for visceral fat and it cannot be excluded for flesh composition traits. The heritability for visceral fat, expressed as a percentage of body weight, was 0.50±0.07. The heritabilities for flesh composition traits, expressed as a percentage of fresh muscle weight, were 0.05±0.03 for fat, 0.09±0.03 for moisture, 0.08±0.03 for ash and 0.02±0.01 for collagen. Genetic and phenotypic correlations among body composition traits were mainly low–medium, except for moisture vs. muscular fat (−0.98 and −0.61, respectively), moisture vs. collagen (0.85 and 0.45, respectively), collagen vs. muscular fat (−0.80 and −0.35, respectively), and dressing percentage vs. visceral fat (−0.92 and −0.51 respectively). Genetic correlations between body composition traits and growth traits were low for weight and length except with collagen for which they were high, and, in general, they were medium–high for condition factor. All these phenotypic correlations were low. These data suggest that selection through growth would improve flesh texture, but could decrease muscular fat in the long term. The latter trait could be improved by selection through moisture which is the flesh composition trait with the highest heritability and is the easiest to measure. The data also suggest that the inclusion of visceral fat percentage in a selection programme would thwart the negative effect of fat concentrated in the visceral cavity and increase the dressing percentage.