Genetic and morphological impact of the cultured gilthead sea bream (Sparus aurata Linnaeus, 1758) populations on wild stocks

Sparus aurata is a very important fish, in fisheries and aquaculture. In this study, the genetic impact of cultured gilthead sea bream S. aurata was examined on wild stocks in the Iskenderun Bay (Northeastern Mediterranean) by genetic and morphological analyzes. Morphometric traits of gilthead sea bream were investigated using a traditional set of measurements and network system. In total, 91 morphometric characters were measured for the Biomorph v3 of measurements and 14 for the truss network system. Results of discriminant function analysis (DF), three functions were produced, and the first two discriminant functions (DFs) explained 90.1% of between-group variability and plotting DF1 (55.2%) and DF2 (34.8%). Mitochondrial DNA sequencing of 16S rRNA region was found to be 830 base pair and 21 bp variable and 3 bp parsimony informative sites between populations. The nucleotide composition was found to be 21.1%, 24.1%, 32.9% and 21.1% for T, C, A and G, respectively. The average value of genetic diversity and genetic distance within populations was found to be 0.00316 and -0.00088, respectively. Haplotype diversity of the cultured population was found to be 0.6710 while the wild population was found to be 0.8333. In the present study, the morphological and molecular analysis identified cultured fish escapees in the wild data set sampled in the aquaculture sites. Despite a mixed gene pool in the wild population, as a result of a long-term culture period of fish originating from Mediterranean broodstocks, the molecular genetics tools identified potential cultured escapees.