Found in the coastal waters of all continents, gillnets are the largest component of small-scale fisheries for many countries. Numerous studies show that these fisheries often have high bycatch rates ...of threatened marine species such as sea turtles, small cetaceans and seabirds, resulting in possible population declines of these non-target groups. However, few solutions to reduce gillnet bycatch have been developed. Recent bycatch reduction technologies (BRTs) use sensory cues to alert non-target species to the presence of fishing gear. In this study we deployed light emitting diodes (LEDs) - a visual cue - on the floatlines of paired gillnets (control vs illuminated net) during 864 fishing sets on small-scale vessels departing from three Peruvian ports between 2015 and 2018. Bycatch probability per set for sea turtles, cetaceans and seabirds as well as catch per unit effort (CPUE) of target species were analysed for illuminated and control nets using a generalised linear mixed-effects model (GLMM). For illuminated nets, bycatch probability per set was reduced by up to 74.4 % for sea turtles and 70.8 % for small cetaceans in comparison to non-illuminated, control nets. For seabirds, nominal BPUEs decreased by 84.0 % in the presence of LEDs. Target species CPUE was not negatively affected by the presence of LEDs. This study highlights the efficacy of net illumination as a multi-taxa BRT for small-scale gillnet fisheries in Peru. These results are promising given the global ubiquity of small-scale net fisheries, the relatively low cost of LEDs and the current lack of alternate solutions to bycatch.
Small-scale fisheries are economically and culturally important throughout the world’s coastal waters. These fisheries, however, often have high bycatch rates of protected marine species. Bycatch in ...small scale gillnet fisheries is thought to be a major driver behind the declines of several sea turtle populations. Recent studies addressing this issue have identified net illumination as a potentially effective bycatch reduction technology (BRT) to reduce sea turtle interactions with gillnet fisheries. In Southeast Asia, small-scale gillnet fisheries make up a large components of fishing effort often in areas that overlap with important sea turtle habitat. We conducted controlled experiments of net illumination as a potential BRT to reduce sea turtle bycatch in a coastal gillnet fishery based in Paloh, West Kalimantan, Indonesia. Results indicated that net illumination significantly reduced multi-species sea turtle bycatch by 61.4% and specifically green sea turtles (
Chelonia mydas
) by 59.5%, while the CPUE of total catch and target species remained similar. Moreover, this study suggests that Indonesian fishers can increase their overall market value when using net illumination as the market value per unit effort (MVPUE) of both the total catch and target catch showed significant increases. These results suggest that net illumination could be an effective sea turtle conservation tool for small-scale coastal gillnet fisheries in Indonesia and potentially throughout Southeast Asia. In addition, data from the control treatments of this study also provided the first observer based sea turtle bycatch estimate for a small-scale gillnet fishery in Southeast Asia. Challenges to the broad scale implementation of net illumination to reduce this bycatch of sea turtles include the cost, availability of the technology, socialization of the BRT to fishers, and government interest and support for net illumination as a tool for bycatch reduction.
