Gillnet illumination as an effective measure to reduce sea turtle bycatch

Net illumination reduces fisheries bycatch, maintains catch value, and increases operational efficiency

Small-scale fisheries are vital for food security, nutrition, and livelihoods in coastal areas throughout the world's oceans.^1-9 As intricately linked social-ecological systems, small-scale fisheries require management approaches that help ensure both ecological and socioeconomic sustainability.^7,10-14 Given their ease of use and lucrative nature, coastal gillnet fisheries are globally ubiquitous.^10,15 However, these fisheries often result in high discarded capture of non-target organisms (bycatch) that can lead to significant cascading effects throughout trophic chains^16-18 and costly fisheries restrictions that result in important revenue losses in coastal communities with scarce economic alternatives.^19,20 Despite these challenges, few solutions have been developed and broadly adopted to decrease bycatch in coastal gillnet fisheries, particularly in developing nations.^5,21 Here we used controlled experiments along Mexico's Baja California peninsula to show that illuminating gillnets with green LED lights-an emerging technology originally developed to mitigate sea turtle bycatch-significantly reduced mean rates of total discarded bycatch biomass by 63%, which included significant decreases in elasmobranch (95%), Humboldt squid (81%), and unwanted finfish (48%). Moreover, illuminated nets significantly reduced the mean time required to retrieve and disentangle nets by 57%. In contrast, there were no significant differences in target fish catch or value. These findings advance our understanding of how artificial illumination affects operational efficiency and changes in catch rates in coastal gillnet fisheries, while illustrating the value of assessing broad-scale ecological and socioeconomic effects of species-specific conservation strategies.