Habitat Use of Indo-Pacific Leopard Sharks (Stegostoma tigrinum) in Southeast Queensland: Insights from Drone and Acoustic Telemetry Data

Abstract

Background/Aims
Seasonal aggregations play an essential role in the ecology of many elasmobranchs, offering opportunities for mating, thermoregulation, or foraging. The Indo-Pacific leopard shark (Stegostoma tigrinum) forms the world’s largest known aggregation off North Stradbroke Island, Queensland, yet its broader habitat use across adjacent coastal areas remains poorly understood. This study aims to identify spatial and temporal patterns of habitat use and behaviour across Southeast Queensland beaches, examine sex-specific space use, and assess the complementarity of drone and telemetry-based monitoring.

Methods
This study integrates drone footage from the SharkSmart program (2019–2024) with acoustic telemetry detections from the Integrated Marine Observing System (IMOS) network. Drone data are used to calculate sightings per unit effort (SPUE) and categorise behaviour (e.g., milling, resting, transiting). Acoustic data provide information on individual residency, diel and seasonal patterns, and sex-based spatial differences. Residency Index (RI), circular statistics, and niche overlap analyses (Pianka’s Index) are applied across seven beach sites to compare patterns in habitat use and temporal presence between males and females.

Results
Drone-based sighting data have been collated, and preliminary visual scans indicate spatial variation in leopard shark presence across the seven beaches. Behavioural observations suggest repeated milling and resting events in shallow surf zones, though formal behavioural classification is ongoing. Acoustic telemetry data are currently being processed, with analysis focusing on identifying periods of spatial and temporal overlap with drone detections and evaluating site use by sex. Sex-specific differences in spatial use and diel activity patterns are expected, based on previous studies from The Group aggregation site (Dudgeon et al., 2008, 2013). While formal results are forthcoming, the dataset is expected to clarify the ecological roles of these coastal areas.

Conclusion
This study demonstrates the value of combining drone and acoustic telemetry methods to investigate elasmobranch habitat use in dynamic nearshore environments. The results will improve our understanding of spatial ecology and contribute to identifying essential habitats for leopard sharks in Southeast Queensland, supporting future conservation and spatial management strategies.