Improving white shark detection capabilities in an Australian bather protection programme using environmental DNA

Abstract

Bather protection programmes rely heavily on surveillance tools capable of detecting the presence of shark species that are known to physically interact with humans. This study investigates the potential for environmental DNA (eDNA) technologies to improve shark detection capabilities and complement current survey methods. We conducted a 14-month monitoring programme at two white shark (Carcharodon carcharias) visitation hotspots in eastern Australia and assessed spatio-temporal patterns of near-shore visitation using a species-specific eDNA assay, SMART (Shark-Management-Alert-in-Real-Time) drumline captures, and acoustic telemetry data from tagged white sharks. We observed higher shark detection frequencies across both survey locations using eDNA compared to the SMART drumline and telemetry survey methods. Specifically, eDNA surveys provided relatively constant rates of detection across the survey period, whereas SMART drumline and telemetry detections were highly seasonal and largely restricted to the austral winter-spring period. Findings from the eDNA surveys are consistent with current assumptions about white shark spatial ecology with year-long presence of white sharks in near-shore subtropical habitats in eastern Australia but suggest that shark presence during the summer-autumn months is possibly more prevalent than currently assumed. Overall, this study highlights the value of eDNA as a tool for enhancing shark detection capabilities, and the importance of adopting multiple complementary survey methods when assessing shark visitation rates. We discuss the implications of these findings for bather protection and white shark mitigation programmes in Australia and overseas.