Mitigating shark bycatch
This presentation is a short version of the synthesis presented at the FAO in Rome in march 2019 during the workshop on mitigating environmental impacts of FADs, organized by ISSF and the GEF/FAO ABNJ project. The silky shark and the oceanic white tip shark commonly associate with FOBs: 77% of FOBs in the Indian Ocean have sharks, against 40% in the Atlantic Ocean, which explains why they are incidentally caught by purse seiners. The vulnerability of these species explains why mitigating their catches is a priority for the sustainability of the tropical tuna purse seine fishery.
There is not a unique and simple method to eliminate the impacts of FADs on sharks, but 4 methods have been found to partially reduce these impacts. The first one is not related to fishing. Using FADs without any netting eliminates the risk of entanglement of sharks in the underwater structure of FADs, a major threat for sharks. Three methods would reduce the fishery induced shark mortality: avoiding setting on small tuna schools, fishing sharks in the net with handlines and releasing them outside the net, releasing sharks from the purse seiner deck following good practices. In total, 62% of sharks could be saved by following these last three methods, along with a shift of 20% of the effort to free school sets. Future research options are also discussed.