Analysis of the genetic stock structure and phylogenetic relationship of narrow-barred Spanish mackerel Scomberomorus commerson (Lacépède, 1800) along the northern Tanzanian coastal waters using mitochondrial DNA

The present study used mitochondrial DNA control region to investigate the genetic stock structure and phylogenetic relationship of 38 samples of Narrow-barred Spanish mackerel Scomberomorus commerson (Lacépède, 1800) from two sites (Dar es Salaam and Pangani) located along the northern Tanzanian coastal waters. The study revealed that the Narrow-barred Spanish mackerel were characterized by high levels of mitochondrial DNA genetic diversity, at both haplotypes and nucleotide levels which is indicative of a large population size. The Analysis of Molecular Variance (AMOVA) test gave a significantly low FST value (FST=0.0011), suggestive of a lack of genetic differentiation between the fish populations of the two investigated sites (p=0.925). Furthermore, AMOVA analysis showed that 99.50% of the total molecular variance was distributed within the populations, while only 0.5% was distributed between the populations. The Median-Joining network revealed a star-like median network, suggesting that the collected samples had similar evolutionary history and characterized by a recent historical population expansion. The present study recommends a single stock model for management of Narrow-barred Spanish mackerel in the northern coastal waters of Tanzania. However, due to the migratory nature of the species, a co-management initiative between coastal states within the Western Indian Ocean (WIO) region along with further studies focused on acquiring detailed information on the genetic stock structure covering the entire area is being recommended.