Queensland Shark Control Program: Catch alert drumline trial 2022–2023

Abstract

The Queensland shark management plan 2021–2025 describes how the Queensland Government is continuing work to reduce the risk of shark bites through the traditional Shark Control Program, while researching and trialling new shark mitigation technologies and increasing community education on SharkSmart behaviours.

The catch alert drumline trial is a key initiative in the plan and part of the Queensland Government’s commitment to trialling non-lethal shark bite mitigation technologies to determine their suitability for Queensland conditions.

Catch alert drumlines (CADs) are fishing apparatus used to catch dangerous sharks using baited hooks suspended from surface floats that are anchored to the seabed. The devices have been successfully used in New South Wales and at Reunion Island to reduce the mortality of non-target species. CADs differ from traditional drumlines as they include a satellite buoy that alerts relevant personnel when a shark or other marine animal is caught, allowing a timely response to the captured animal. CADs are deployed during daylight hours only, while traditional drumlines are set 24 hours a day and serviced daily.

Between 24 January 2022 and 23 January 2023, 11 CADs were alternated with 11 modified traditional drumlines (MTDs) using standardised hook and trace configurations across 4 beaches on the Capricorn Coast in central Queensland, enabling a comparison of catches and survival of marine fauna caught on the two drumline types. The MTDs caught more target sharks than CADs; however, a significant number of these were caught at night and dawn and dusk when CADs were not deployed. Catches of target shark species were more likely during the summer months, when sea surface temperatures were highest (>25°C), irrespective of drumline type.

The two most common species caught on both drumline types – bull whalers and pigeye whalers – were mostly small (mean = 1.24 m and 1.09 m total length, respectively) and likely use the turbid waters adjacent to the Fitzroy River to forage and avoid predators. Survival of bull and pigeye whalers was higher on CADs (93.8% when satellite buoys were activated) than MTDs (27.3%), due to the reduced time the animals spent hooked. Survival also increased with size. Tiger shark survival was high on both drumline types. Overall, CADs increased the survival of target and non-target species at the point of release.