Characterisation of common skate species Dipturus spp. through molecular and morphological identification

Elasmobranchs are marine vertebrates with a global decline in catches due to overfishing (2). Skates and rays have particular biological characteristics including large sizes, slow growth, late reproduction and low fecundity, which increase vulnerability to fisheries (4). They present a high morphological variability during their growth, which makes a correct identification difficult; there is scientific evidence of misidentifications and mixtures of species, which prevents a proper fisheries management. In fisheries management it is very useful to combine morphological and molecular techniques for the unequivocal identification of species. The EU has established a landing ban on the common skate, Dipturus batis, which inhabits the Northeast Atlantic, and it is currently listed as "critically endangered" by the IUCN (1) due to overfishing (6). In addition, there is currently a great controversy surrounding the taxonomic confusion of this skate, since this species was considered in the literature as a single species, being in fact a complex of species formed by the provisionally named Dipturus batis and Dipturus intermedia (3, 5, 6). The aim of this study is to combine morphometric and molecular analyses for the correct identification. For the analyses, samples of Dipturus batis, Dipturus oxyrinchus and Dipturus nidarosiensis were taken. Type entire specimens were storage for morphometric analysis, and muscle samples preserved in absolute alcohol for genetic analysis. Twenty-nine morphometric measurements were taken from each type specimen and DNA extraction on muscle and amplification of two mitochondrial, genes were performed, a Cytochrome Oxidase I (COI) fragment (aprox. 600pb) and a 16S fragment (aprox. 500pb). Identification was made through the Basic Local Alignment Search Tool of GenBank. According to the preliminary results obtained from the analysis of the sequences, this would correspond mainly to D. batis