MEPS 544:183-196 (2016)  -  DOI: https://doi.org/10.3354/meps11596

ABSTRACT: The population genetic structure and demographics of the common smoothhound shark Mustelus mustelus were investigated across 2 major oceanographic barriers along the southern African coastline: the Angola-Benguela Front and the Indian/Atlantic boundary. Population genetic structure was inferred using multilocus data generated from 8 microsatellite loci and the sequence polymorphism of a 793 bp fragment of the mitochondrial (mtDNA) ND4 gene region. Microsatellites revealed significant interoceanic genetic structure (F_ST = 0.007–0.296) between the South-East Atlantic and South-West Indian Ocean, while mtDNA suggested interoceanic gene flow (pairwise φ_ST = 0–0.288). A coalescent analysis in MIGRATE-N suggested asymmetrical gene flow that predominantly occurs from the South-West Indian to South-East Atlantic Oceans, with relatively small (<50) estimates of effective population size. Tests of selective neutrality and mismatch distribution indicated a population history consistent with a population expansion event. Contemporary restriction to gene flow is proposed to account for the present-day genetic structuring observed for M. mustelus in South Africa. Due to the vulnerable status of the species, these results should be considered in future management and conservation strategies addressing the sustainable exploitation of this fisheries resource.

KEY WORDS: Gene flow · Indian/Atlantic boundary · Interoceanic genetic structure · Mustelus mustelus · Oceanographic barrier