Abstract
A number of elasmobranchs across different families exhibit sex-biased dispersal. However, the selective pressures that favor the evolution of sex-biased dispersal in elasmobranchs are not well understood and sex-biased dispersal has been assessed in too few species for a clear pattern(s) to emerge. This study provides the first evidence of sex-biased dispersal in sawfishes and demonstrates how such dispersal may vary with habitat usage in Indo-West Pacific species. The Freshwater Sawfish, Pristis microdon, which utilizes freshwater rivers as juveniles and marine/estuarine waters as adults, was found to have male-biased dispersal in Australian waters. In contrast, P. clavata and P. zijsron, which spend their entire lives in marine and/or estuarine waters, are genetically structured in northern Australian waters. The use of freshwater rivers as juveniles by P. microdon suggests that the evolutionary history of this species in Australian waters was potentially very different to those for P. clavata and P. zijsron and may have influenced the evolution of sex-biased dispersal in the former, but not the latter, species.