MEPS 281:193-205 (2004)  -  doi:10.3354/meps281193

ABSTRACT: Pelagic marine fishes generally show little geographical population differentiation. Of special interest are marine species with Atlantic-Mediterranean distribution because of the possible effect of past and present day restrictions to gene flow between the 2 seas. Thus, restriction analysis of the whole control region (D-loop) of mitochondrial DNA (mtDNA) was used to extensively investigate the genetic structure of the 3 Trachurus species present both in Atlantic and Mediterranean waters: T. trachurus, T. mediterraneus and T. picturatus. In total, 666 individuals were screened from 5 Mediterranean and 6 Atlantic areas. Two African areas were also sampled for T. trachurus. No differentiation was revealed among European populations within the 3 studied species. Additionally, no sign of Atlantic-Mediterranean division was found, probably due to the fact that specific life history traits provide the Trachurus species with flexibility to oceanographical constraints and give them the ability to migrate long distances. Differentiation was only revealed between European and African populations of T. trachurus, reinforcing the existence of the T. trachurus capensis subspecies in African waters. Populations are probably under long and stable demographic equilibrium conditions as indicated by high haplotypic and nucleotide diversity values for all 3 species. Thus, mtDNA could be a powerful tool in determining the taxonomic distinctiveness of individual populations and species, and therefore, aid in setting priorities for future management policies. The present results are also discussed in comparison with the results of previous cytochrome b sequence analysis of the 3 Trachurus species.

KEY WORDS: Trachurus spp. · Mitochondrial DNA · D-loop · RFLP · Marine species · Mediterranean