Population genetics of two tropical sharks, Carcharhinus tilstoni and C. sorrah, in Northern Australia

Abstract

The genetic structure of the Australian populations of Carcharhinus tilstoni and C. sorrah was investigated by starch gel electrophoresis. Tissue samples were taken from 1580 sharks from throughout the fishery, which extends from the North-West Shelf (off Western Australia) to the north-eastern coast of Queensland. From a total of 47 enzyme loci screened in each species, 13 proved to be polymorphic (P_0.99) for at least one species, with only 5 loci for each species showing sufficient variation (P_0.95) to be of use in the analysis of population structure. Mean heterozygosity values were relatively low: 0.037 for C. tilstoni and 0.035 for C. sorrah. A low level of population subdivision was found within each species, with F_ST values of 0.0094 for C. tilstoni and 0.0076 for C. sorrah. There was insufficient evidence to suggest that there is more than one population of either species of shark in Australian waters.