Preliminary results on rearing of Sparus aurata x Pagrus pagrus hybrids. Performance comparison with the parental species

Hybridization between gilthead sea bream, Sparus aurata, and red porgy, Pag rus pagrus, was undertaken and viable hybrids were produced by an artificia l hormonal-induced cross. The hybrids, from the cross of female red porgy a nd male gilthead sea bream (Pp x Sa), survived through the yolk-sac larval stage. The hybrids produced from the cross of female gilthead sea bream and male red porgy (Sa x Pp) presented higher mortality in the larval stage (9 8.4%) compared to gilthead sea bream (80.0%) and red porgy (92.5%). Afterwa rds, the Sa x Pp hybrid was compared to the offspring of its parental speci es under the same rearing conditions (tanks of 500 l capacity, natural ligh t, ambient temperature, self-feeding with commercial feed) in a 40-week exp eriment. In this comparative study, the Sa x Pp hybrid had intermediate mor tality rate (6%), compared to gilthead sea bream (0%) and red porgy (21%). The growth profile of this hybrid resembled the slow growing phases of its parents (red porgy in warm period and gilthead sea bream in cold period). T he feed conversion ratio between fish forms was not significantly different (1.54-1.84 in the Sa x Pp hybrid, 1.53-1.56 in the maternal species and 1. 33-1.40 in the paternal one). The body weight variation in the Sa x Pp hybr id was quite high (31.7-37.9%), compared to that in gilthead sea bream (19. 7-24.7%) and red porgy (18.0-31.3%). With respect to body coloration, the S a x Pp hybrid was distinguishable and classified into groups of red porgy-l ike (55.1%), gilthead sea bream-like (40.6%), and intermediate forms (4.3%) . The preliminary results of this study proved that the produced Sa x Pp hy brid had too low a performance for aquaculture use, but the interesting con sequent hereditary potential could be a useful tool in fish hybridization p ractice.