Genetic structure and diversity of two highly vulnerable carcharhinids in Australian waters

Abstract

Molecular techniques were employed to investigate genetic structure and diversity in dusky Carcharhinus obscurus and sandbar C. plumbeus sharks in the Indo-Australian region. Tissue samples of 423 C. obscurus and 442 C. plumbeus defined 18 and 11 mtDNA ND4 haplotypes, respectively. For C. obscurus, weak genetic differentiation was detected between eastern and western Australian waters (pairwise ΦST = 0.04437, p < 0.008; pairwise FST = 0.02403, p < 0.035), suggesting the delineation of 2 independent populations, while patterns of gene flow between Australia and Indonesia were inconclusive. Rarefaction analysis, however, indicated that robust population comparisons in these species were reliant on sample numbers >100 at any particular location. Off Australia’s temperate east coast, C. obscurus and C. plumbeus exhibited strong similarities in genetic structure, suggestive of similar evolutionary histories in the region. In addition, genetic validation revealed observers to be highly accurate in the identification of both target species in an eastern Australian shark fishery. Our findings contribute valuable information for the management and conservation of both species.