Background/Aims
Set net fisheries in northern Australia face significant challenges in mitigating the bycatch of threatened species, including sawfishes, river sharks, and devil rays. These species are vulnerable to capture due to overlap of key habitats and migratory pathways with fishing grounds and their biological characteristics, which make them slow to recover from population declines. This project aimed to test bycatch mitigation technologies, static green LED lights and electric deterrents, in Australian set net fisheries for the first time to improve conservation outcomes while maintaining the sustainability of fisheries.
Methods
The project tested the effectiveness of green LED lights and electric deterrents in reducing bycatch through three components: aquarium trials to evaluate the response of elasmobranchs to the devices, fishery-independent trials to assess catch rates of bycatch and target species, and fishery-dependent trials within commercial fishing operations in northern Australian set net fisheries.
Results
Green LEDs showed potential for deterring sawfish in inshore fishery-independent trials but attracted hammerhead sharks in offshore fishery-dependent trials. Electric deterrents showed promising trends for deterring sawfish and hammerhead sharks, though results were inconclusive due to low sample sizes. Neither device appeared to negatively impact target species, such as grey mackerel or blacktip sharks, in offshore fishery-dependent trials, although some unintended effects, such as increased catches of blue threadfin and barramundi in inshore fishery-independent trials, were observed.
Conclusion
Green LEDs and electric deterrents showed some promise for threatened species bycatch reduction, particularly for sawfish in inshore fisheries. However, further research with larger sample sizes is needed to refine their effectiveness and mitigate unintended impacts before widespread adoption in commercial fisheries can be recommended. This project provides important foundational data for threatened species bycatch reduction technologies while ensuring the sustainability of northern Australian set net fisheries, and highlights the importance of partnerships between researchers, managers and industry for developing and implementing effective, science-based solutions to conservation challenges in commercial fisheries.