Purse Seine Fishing

A purse seine is a wall of netting, often 500 m to over 2 km long and 100-250 m deep, set in a circle around a school of fish and then closed at the bottom by pursing a line through rings along the footrope, trapping the entire school before it can dive out. The method is the dominant gear for tuna, sardine, anchovy, and other schooling pelagics because it captures large biomass in a single set with little seabed contact, but it carries a bycatch risk specific to its targeting method: tuna sets made around floating objects or fish aggregating devices catch far more juvenile tuna, sharks, and other species than sets made on free-swimming schools spotted visually or by sonar. Net design increasingly includes non-entangling mesh and biodegradable panels on FAD-associated sets to reduce ghost-gear mortality when devices are lost at sea. For the seafood supply chain, purse-seine origin and set type (FAD-associated versus free-school, often disclosed on can labels) has become a consumer-facing sustainability marker alongside dolphin-safe certification in the Eastern Pacific tuna fishery.