Estimates of heritabilities and genetic correlations of growth and external skeletal deformities at different ages in a reared gilthead sea bream (Sparus aurata L.) population sourced from three broodstocks along the Spanish coasts

Growth rates and the presence of deformities can be affected by the use of different rearing systems as well as by the different genetic origins of the stocks. At the same time, strategies that involve the development of selection schemes for these traits of economic interest are scarce. In this study the effect of the origin of the broodstock on growth traits and external deformities as well as genetic parameters (heritabilities and genetic correlations) for these traits were estimated at different ages (days post-hatching; dph). For this purpose, a population of farmed gilthead sea bream was obtained from three broodstock of different origins along the Spanish coasts [Cantabrian Sea (CAN), the Atlantic Ocean (ATL) and Mediterranean Sea (MED)] and reared under the same intensive conditions. Parental assignments between breeders and their offspring were carried out a posteriori using a microsatellite multiplex (SMsa1). Juveniles from MED showed the fastest growth while those from ATL showed the slowest growth and the highest incidence of vertebral column deformities. Differences among origins could be explained not only through their different genetic backgrounds but also by environmental conditions in the initial facilities, where different origins were reared separately, and by genotype×environment interactions. Growth traits showed low heritabilities at 163dph (0.11±0.03) and medium at 690dph (0.25±0.06 for weight; 0.22±0.07 for length) suggesting that selection at the later age would be more appropriate. Both traits were highly and positively correlated at both ages at the genetic and phenotypic levels. External deformities in the vertebral column as well as in the operculum showed medium–high heritability at both studied ages with higher values at 690dph (0.56 [0.17–0.69] and 0.46 [0.20–0.90], respectively). These results revealed that the ontogenesis of deformities exhibits a partial genetic basis. Nevertheless, for those in the rest of the head the heritability was close to zero. Initially, positive genetic correlations between growth and deformities in the vertebral column were observed (83% probability of being positive for weight-vertebral column deformity; 81% for length-vertebral column deformity). However, these correlations seem to be negative at 690dph (94.2% probability of being negative for weight-vertebral column; 80.6% for length-vertebral column). Results confirm that it could be recommended to eliminate deformed fish from a breeding nu