• citocromo ossidasi
• diversità genetica
• DNA mitocondriale
• genetica della pesca
• genetica di popolazione

Genetic structure of the Bluefish, Pomatomus saltatrix (Acanthopterygii: Pomatomidae), through mitocondrial DNA sequences.
The bluefish, Pomatomus saltatrix (Linnaeus, 1766), is a migratory marine costal pelagic species. It’s a very active predator which lies at the top of the coastal marine ecosystem trophic network. It has a wide area of distribution, and can be found in all seas and oceans in tropical and temperate latitudes, with the only exception of eastern Pacific Ocean. In recent years this species seems to have become more common in northern Mediterranean Sea, probably as a result of climate changes that are leading to an expansion in the distribution of termophilic species. This species has a commercial value in some countries and is therefore subject to professional fishing. In the present work we have carried out an analysis of the genetic diversity of P. saltatrix on a global scale. Analysis of historical demography were also carried out, in order to evaluate the possible expansions in the size of populations. The aims of this thesis were: i) to investigate the genetic structure of P. saltatrix on a global scale; ii) to contribute to the identification of stocks for management purposes; iii) to test the hypothesis of a recent demographic expansion of this species, especially in the Mediterranean Sea. In total, 177individuals were sampled (about 30 for each sampling location) in the following geographic areas: Mediterranean Sea (2 locations), south-western Pacific Ocean (2 locations), south-western Atlantic Ocean and south-western Indian Ocean. As genetic marker we have used sequences of a fragment of the cytochrome oxidase subunit I (COI), 509 bp. A total of 33 haplotypes were identified, of which only one resulted to be shared between two regions: Mediterranean Sea and South Africa. The haplotype median-joining networks showed the presence of three haplogroups, the first comprising the Mediterranean and South African individuals, the second comprising all the Australian individuals and the third all the individuals sampled in Argentina. The same partitioning scheme was confirmed by the Bayesian assignment test. The AMOVA detected a significant genetic structuring for the species, with 90% of molecular variance assigned to the "between geographical areas" level. The historical demography, as inferred by mismatch distribution, suggested a demographic expansion event occurred in all of the regions with the exception of the Mediterranean Sea. This result was also confirmed by R2 and FS tests. The haplotype network and the phylogenetic tree obtained with the 177 sequences in our dataset along with 36 available in GenBank and 79 available in Bold, outlined the presence of six major haplogroups: Mediterranean + South Africa, North America, Brazil, Brazil + Argentina, Australia and a sixth haplogroup close to the latter, comprising haplotypes deposited in Bold by Turkish researchers. This work has highlighted a significant genetic structure in P. saltatrix at the considered geographical scale. This suggests that wide tracts of ocean are the main factors determining the observed genetic divergence. The lower level of genetic divergence observed between the Mediterranean and South African population could be due to the fact that between these two geographically distant areas there is a coastline’s continuity, a factor that could encourage migration in a coastal species, such as the bluefish. The results of this study may also have practical implications, since the partitioning of the species in genetic stocks (sensu Carvalho & Hauser) requires a separate management of the resource. These findings may also offer the opportunity to identify the area of origin of individuals (whole or fillets) on a large scale, in a seafood traceability perspective.