Population genetic structure of reared and wild gilthead sea bream (Sparus aurata) in the Adriatic Sea inferred with microsatellite loci

Gilthead sea bream (Sparus aurata) is considered the most important finfish aquaculture product in the Mediterranean Sea, but inadequate number of domestic hatcheries has reflected in fact that 70% of fingerlings are imported, mainly from Italy and France. In order to assess potential genetic differentiation between wild and cultured sea breams, we screened eight microsatellite loci. Analyses evidenced heterogeneous genotypic distributions for each population, with extensive polymorphism and overall expected heterozygosity levels > 71%. Such a high admixture and weak population structuring has previously been reported in the rest of the Mediterranean Sea. Results imply that farmed escapees are involved in genetic pollution of adjacent wild populations showing lower differentiation among themselves. Inference of such a situation strongly encourages strengthening of routine aquaculture practice in the Adriatic through development of genetic-based management for broodstock, fingerlings and farmed fish, as well as better zootechnological protocol related to maintenance of nets and cages.