Looking for Half-Siblings and Beyond: Application to the Management of Threatened Species

Reliable and cost-effective assessment and monitoring tools are urgently required for the conservation and management of data-poor, low abundance, threatened species in Australia, including the Largetooth Sawfish and the Speartooth Shark. In these two species, adults are marine and/or estuarine and too rare for any population assessment based on catch records. Juveniles, however, are easier to access in rivers. We present here a new method that combines close kin genetics and acoustic tagging of juveniles to provide the basic information required for population assessment and management. Juveniles from multiple cohorts are sampled over several years, acoustically tagged, and a genetic samples collected. Acoustic telemetry receivers provide estimates of survivorship and genetic samples are used to identify half-siblings (HS). We will discuss how these data can be used to infer spatial demographic structure, abundance trends, and absolute abundance in adults. We will also discuss preliminary results as well as the methodological challenges we faced and are still facing. This includes ddRAD genotyping and whole genome assembly using NGS and the development of a new statistical method for accurate identification of HS in non-model species. Finally we will discuss how the inference of more distant relationships could help to refine this approach.