Drone monitoring of endangered scalloped hammerhead shark Sphyrna lewini movements and habitat use on a dynamic urbanised coastline in Australia

Abstract

Many elasmobranch species face increasing pressures from overfishing, habitat degradation, and coastal development, highlighting the need to identify and protect habitats used during critical life stages. Unmanned Aerial Vehicles or drones offer a non-invasive method to study the distribution and habitat use of species frequenting inshore areas. Scalloped hammerhead sharks ( Sphyrna lewini ), listed as Critically Endangered on the International Union for the Conservation of Nature (IUCN) Red List, have experienced global population declines prompting the need for research that identifies key habitats, including nursery and aggregation sites. This study analysed archived footage from the Queensland SharkSmart drone program at nine beaches in southeast Queensland between September 2020 and December 2024. The frequency of scalloped hammerhead sightings was quantified, along with the influence of environmental, biotic, and operational variables on detectability. Eighty-four sightings were recorded, primarily between April and June. Sightings were significantly influenced by turbidity, presence of other fauna, time of day, month, and location. Aggregations of up to 80 juvenile sharks (mean ± SD: 109 ± 25 cm) were observed at Burleigh Beach, with additional sightings at Noosa Main Beach. These findings provide the first detailed description of seasonal juvenile scalloped hammerhead aggregations in southeast Queensland, Australia, and highlight the value of drone monitoring for identifying habitats of conservation importance and informing targeted spatial management.