Background/Aims
Northern Australia is described as a “lifeboat” for 45 globally threatened elasmobranchs (sharks and rays). However, commercial fisheries operating in the region continue to interact with a range of threatened, endangered, and protected species (TEPs). These interactions pose risks to conservation outcomes and the longevity of fisheries. While traditional bycatch mitigation methods, such as limited entry, fishery closures, and gear restrictions have been effective, there is a growing interest in the use of bycatch deterrents to help mitigate TEPs interactions. Overseas studies have shown promising results for elasmobranchs using pulsed electric deterrents (EDs), designed to overstimulate the electrosensory system, and green LED lights, designed to illuminate fishing gear. In collaboration with industry partners, this study aims to test the effectiveness of these deterrents in reducing TEPs bycatch in commercial pelagic gillnet fisheries in northern Australia while evaluating their operational feasibility.
Methods
Fishery-dependent trials were conducted across two fisheries using commercial gillnets with and without deterrents to evaluate whether either device could significantly reduce TEPs bycatch rates while maintaining target species. The first phase of trials is complete, with the second currently underway.
Results
Preliminary findings indicated species- and context-specific effects. While no sawfish were recorded, Hammerhead Sharks, a group of conservation concern, showed a potential attractant response for LEDs and a potential deterrent response for EDs in twine gillnets, but not in monofilament nets. Neither deterrent significantly affected the catch rates of target species (Grey Mackerel or Blacktip Sharks). Spot-tail Shark catch was reduced with LEDs in twine nets but increased with EDs in monofilament nets. Between-set variability was high, suggesting environmental and operational factors influenced outcomes.
Conclusion
This research provides the first evaluation of elasmobranch bycatch deterrents in northern Australian gillnet fisheries. Preliminary results show limited, context-dependent effectiveness for TEPS deterrence with no impact on target catches. Full results from both phases will be presented, offering a comprehensive assessment of the potential of bycatch deterrents as a conservation tool in northern Australian gillnet fisheries. The outcomes will inform future management strategies to reduce TEPs interactions and support the sustainability of gillnet fisheries in northern Australia.