Microsatellite DNA variation reveals high gene flow and panmictic populations in the Adriatic shared stocks of the European squid and cuttlefish (Cephalopoda)

In the semienclosed Adriatic Sea, the shared stocks of the cephalopods Loligo vulgaris and Sepia officinalis represent important marine fisheries resources exploited by all coastal countries. The improving of knowledge on the demographic features of these shared stocks is internationally relevant for adopting responsible management and conservation of these marine resources. Analyses of microsatellite variation in geographical samples collected from all parts of the Adriatic Sea were performed using arrays of species-specific di-nucleotide and tri-nucleotide loci. In L. vulgaris the level of genetic variability was consistent with that observed in other loliginid species, whereas the S. officinalis stock showed a microsatellite variation markedly lower than that estimated for the Atlantic and Mediterranean populations collected around the Iberian peninsula. The weak spatial genetic differentiation, the discordant results of the genetic divergence estimators and the lack of any geographical cline in the spatial genetic differences suggest the occurrence of single genetically homogeneous populations within the Adriatic stocks of both species, recommending a coordinated management of the squid and cuttlefish by the Adriatic fishing countries. On the contrary, significant differences detected in temporal replicates of S. officinalis might suggest that allelic frequency can change relating to reproductive behaviour.