Flatfishes of the Genus Paralichthys in the Southwestern Atlantic: Integrating molecular taxonomy and morphometric data.

Flatfish fisheries represent an important resource at the artisanal and industrial levels, with the largest catches in the Southwestern Atlantic belonging to the species of the genus Paralichthys. The lack of tools and consensus in the identification of flatfish species is a problem to achieve correct resource management. Currently, several Paralichthys species are classified as overexploited or vulnerable. The present study was based on the analysis of 147 specimens belonging to six Paralichthys species: P. brasiliensis, P. isosceles, P. patagonicus, P. orbignyanus, P. triocellatus and P. tropicus. The flatfishes were obtained in research cruises, artisanal and commercial fishing on the Southwestern Atlantic coast, 11°S and 40.5°S. Meristic data were collected and the similarity of the variables between the species was analysed by means of a non-parametric multivariate analysis (ANOSIM) and also carried out a multidimensional scaling analysis (MDS). Two geometric morphometric protocols were performed on the ocular side of the fishes employing different "Box Truss" networks. Principal Component Analysis was conducted, and the principal component scores were subjected to cross-validation Discriminant Analysis. It was possible to identify four flatfish species (P. brasiliensis, P. isosceles, P. patagonicus and P. orbignyanus) using the 5' region of the COI gene (barcode region). A Maximum Likelihood phylogenetic tree was constructed, which resulted in a topology that clearly separated the species. Four of the six species studied were discriminated by meristic, morphometric and genetic analyses. Meristic and morphometric analyses were carried out for P. triocellatus, whereas only a meristic analysis was performed for P. tropicus. Of these species, P. brasiliensis-P. orbignyanus and P. isosceles-P. triocellatus showed some degree of overlap between them in meristic and morphometric characters. This overlap could be due to their shared distribution and habitat, as well as their genetic proximity. The results obtained are important not only for the development of correct fishery management but also for providing general information on the taxonomy, morphometry, and genetics of this genus. [ABSTRACT FROM AUTHOR]