Comparative morphology of wild, farmed and hatchery-released gilthead sea bream (Sparus aurata) in western Greece

Abstract

In May 2001, 60,000 individuals of gilthead sea bream (Sparus aurata) fry, originating from a common bloodstock of the Ionian coastal region, were allocated between Papas lagoon and cages of mariculture enterprises located at Western Greece. During the period of November to December 2001, a sample of 531 gilthead sea bream individuals was collected from the lagoon and the cages. The variations in 24 morphomertic characters and in two indices (condition factor and gonadosomatic index) were examined using multivariate analysis, in order to evaluate the morphological similarity/dissimilarity between hatchery-released (EN), wild (WL) and farmed (RR) individuals. Statistically significant differences were observed among the groups in mean and standard deviation values for most of the morphometric characters, a fact that can be possibly attributed to the life-history of the fish. Principal component analysis along with discriminant analysis identified that the characters of primary importance in distinguishing the three groups were those related to head, fin and lengthwise dimensions. Discriminant analysis also revealed that about 86.1% of the examined specimens could be correctly classified in the three groups. The above findings can be useful for scientific but also for commercial reasons, since the market value of the fish is highly dependant on its origin. Key words: Sparus aurata, gilthead sea bream, hatchery-release, multivariate analysis, morphometrics, lagoon