Aggregating Device

An aggregating device is any floating or anchored object deployed to draw pelagic fish into a concentrated school for capture, the best known being the fish aggregating device (FAD) used in tropical tuna purse-seine fisheries. Tunas, dolphinfish, and triggerfish associate with drifting flotsam, so fishers attach satellite buoys to drifting FADs (dFADs) and set the purse seiner once the echosounder shows enough biomass. The tuna RFMOs (IATTC, ICCAT, IOTC, WCPFC) cap dFAD numbers and set per-vessel limits because dFAD sets take a higher proportion of juvenile bigeye and yellowfin and more silky-shark bycatch than free-school sets.