Mitigating the bycatch of threatened species in Australian gillnet fisheries is a major management challenge. Australian prawn trawl gear is a well-documented example of how the testing and implementation of bycatch reduction devices has resulted in the significant reduction in the bycatch of non-target species including threatened species. However, devices or modifications to reduce bycatch in gillnets are far less well studied. Where the deployment of gillnets overlaps with the habitat of threatened species, bycatch of these species can occur, creating a significant management issue. Within northern Australian gillnet fisheries, bycatch of threatened/migratory sawfishes, river sharks, and devil rays listed under the EPBC Act is an on-going issue requiring evidence-based interventions. Northern Australia holds the most significant remaining populations of sawfishes and river sharks globally, but these important species form the most numerous threatened species bycatch in local gillnet fisheries. Within these fisheries, the target bony fish are harvested at sustainable levels with high-quality seafood product providing important economic contributions locally and nationally. Mitigating the on-going bycatch of non-target threatened species is arguably the most significant challenge facing these fisheries.

This project will test novel mitigation devices (static green LED lights and an electric deterrent (SharkGuard)) and assess alternative gears to gillnets to reduce bycatch of EPBC Act listed sharks and rays. In partnership with industry, trials will assess the effectiveness of devices to elicit a response in bycatch species, their ability to reduce bycatch levels, and their impact on target species. An assessment of alternative gear types will consider the feasibility of transitioning the commercial sector of the NT Barramundi Fishery to fishing gear with lower bycatch levels in the future. Trial outcomes will provide industry and managers with proven options to assist implementation of threatened species mitigation strategies in northern gillnet fisheries.

This project will give industry and managers confidence in tested bycatch mitigation technologies. Only by comprehensively testing static green LED lights and the SharkGuard electric deterrent through aquarium and field trials under varied local conditions can a scientifically robust evaluation of bycatch reduction be undertaken. Successful demonstration overseas of the devices to be trialled provides the starting knowledge that they can deter sharks and rays and reduce their bycatch levels by up to 95%. To our knowledge, these bycatch mitigation devices have not been tested in Australian gillnet fisheries. If demonstrated and applied in northern Australian gillnet fisheries, these devices may have the ability to significantly reduce the bycatch of eight EPBC Act listed threatened and/or migratory sharks and rays, as well as other sharks of conservation concern (notably, hammerhead sharks). Furthermore, there may be flow-on benefits to other EPBC Act listed species groups, particularly marine turtles. LED lights were initially applied as a bycatch reduction measure for turtles, and they have been demonstrated to reduce turtle bycatch (turtle bycatch is at a low level in NT and WA gillnet fisheries making direct experimental/field evaluation of bycatch reduction difficult in the NT/WA).