The Mediterranean Sea hosts endemic haplotypes and a distinct population of the dolphinfish Coryphaena hippurus Linnaeus, 1758 (Perciformes, Coryphaenidae)

The dolphinfish, Coryphaena hippurus Linnaeus, 1758, is an important target species for Mediterranean artisanal, recreational and commercial fisheries but to date only scarce genetic data are available for its Mediterranean population(s). The genetic variation of Mediterranean dolphinfishes was thus investigated through the sequencing of fragments of the cytochrome c oxidase subunit 1 (COI) gene and the NADH dehydrogenase subunit 1 (ND1) mitochondrial DNA markers with the explicit aims of (i) testing for significant genetic differentiation of the Mediterranean vs. non-Mediterranean populations of the species, and (ii) investigating the possible presence of molecular structuring within the Mediterranean basin. Performed analyses revealed significant genetic differentiation between Mediterranean and Atlantic dolphinfish population, while no significant geographically-based genetic differentiation was detected within the Mediterranean basin. The apparent lack of genetic structuring at the Mediterranean level is likely due to the highly mobile behaviour of the species, which is typical of large pelagic fishes and in agreement with the few tag data currently available. Based on presented results, the Mediterranean dolphinfishes are thus suggested to be considered a distinct management unit from those outside the Mediterranean. Conversely, in order to test for the presence of a single vs. multiple Mediterranean stock units, the fulfillment of further analyses implementing fast-evolving nuclear markers is advisable.