Longline fishing for tuna accounts for roughly 13% of the world’s tuna.
The method consists of a main line, kept afloat with buoys, from which lines are suspended. Longline fisheries supply the fresh and frozen tuna markets, with many vessels targeting other non-tuna species. Longline is considered the ideal way to catch fish that inhabit deeper waters, like albacore, bigeye and yellowfin. Fish are caught one by one and frozen in blast freezing systems, the same freezing method used for sashimi.
The average bycatch rate for longline fishing is 28% of the total catch. Mitigation methods, such as circle hooks and torey lines, have been developed to prevent the catch of marine life, such as turtles and birds.
The longline method burns roughly 1070 liters of fuel to land a ton of tuna.