Codeveloping on deck conservation technology with tropical tuna purse seine fishers to mitigate elasmobranch bycatch

Abstract

Current efforts to mitigate impacts on threatened elasmobranch species in tuna fisheries focus primarily on best handling and release practices for individuals caught in the gear or arriving on deck. Releasing elasmobranchs fast is key as prolonged ventilatory restriction results in reduced survival. Yet, because handling large sharks and mobulid rays can be very demanding and dangerous for crew, release times can be significantly delayed. To address these challenges, we developed and improved a series of novel bycatch release devices (BRDs) such as release ramps, stretchers, shark velcros, hoppers, lower deck gutters, mobulid sorting grids, and straps in close collaboration with Spanish tropical tuna purse seiner fishers. Our BRDs minimize contact between fishers and elasmobranchs for increased crew safety and release time acceleration to improve postrelease survival thus resulting in a win-win formula. Long-term cooperation between Spanish fleet fishers and our scientific group has been key to fine-tuning BRD performance, and more importantly, generating trust and promoting readiness for their voluntary uptake. Increasing sustainable fishing requirements by markets have also favoured adoption willingness. Several tuna Regional Fisheries Management Organizations have begun endorsing the new BRDs, potentially leading to greater implementation across purse seine fleets globally. The success of our case study offers insights for researchers and managers seeking to achieve effective conservation outcomes through fisher involvement.