Optimal fishing time window: an approach to mitigate bycatch in longline fisheries (IOTC WPEB11-15)

One of the main concerns of the ecosystem approach to fisheries is the mitigation of bycatch, especially in pelagic longline fisheries. Bycatch represent unmarketable species and protected species for some of them. Various mitigation measures already exist to reduce bycatch in longline fisheries, notably concerning the equipment used and the strategy of fishing gear deployment. However, measures that concern the hours of gear deployment remain poorly studied. Using hook-timer data collected during scientific longline fishing campaigns between 2004 and 2014 in the South West Indian Ocean, we developed a method to identify optimal fishing practice that maximizes bycatch reduction and swordfish yield (in number). Here we found that hourly capture patterns of swordfish and bycatch (sharks, turtles) are different and allow to identify an optimal fishing practice that consists in fishing between 18pm and 9am. This methodology certainly provides a relevant bycatch mitigation approach that benefits to fishermen but also allow to mitigate the impact of longline fisheries on the ecosystem