Reliable, cost-effective assessment tools are vital for managing rare and threatened species. Northern Australia has some of the last remaining populations of sawfish, sharks and rays that live in both freshwater and seawater environments. The population status of these species and the effectiveness of conservation management – a key requirement of recovery plans – are unknown.  The NERP Marine Biodiversity Hub will provide the first estimate of population status for these species using electronic tagging (acoustic telemetry) and advanced genetic techniques (close-kin genetics) designed for this project.