Evaluation of Hook and Bait Type on the Catch Rates in the Western North Atlantic Ocean Pelagic Longline Fishery

Research was conducted in 2002 and 2003 by noaa's national Marine fisheries service, southeast fisheries science center, to investigate changes in hook design and bait type to reduce the bycatch of sea turtles on pelagic longlines in the western north atlantic ocean. The effectiveness of 18/0-20/0 circle hooks and 10/0 Japanese tuna hooks with squid (Illex spp.) and mackerel bait (Scomber scombrus linnaeus, 1758) was evaluated against the industry standard 9/0 J-hooks with squid bait with respect to reducing sea turtle and shark interactions while maintaining swordfish (Xiphias gladius linnaeus, 1758) and tuna (Thunnus spp.) catch rates. In total, 973,734 hooks were deployed during the study. Individually, circle hooks and mackerel bait significantly reduced both loggerhead [Caretta caretta (linnaeus, 1758)] and leatherback [Dermochelys coriacea (vandelli, 1761)] sea turtle bycatch. The combination of 18/0 circle hooks with mackerel bait was even more effective for loggerhead sea turtles and had a significant increase in swordfish catch by weight. The combination 18/0 circle hooks with squid bait resulted in a significant decrease in the swordfish catch and a significant increase in the catch rate of blue shark [Prionace glauca (linnaeus, 1758)] , bluefin tuna [Thunnus thynnus (linnaeus, 1758)], and albacore tuna [Thunnus alalunga (bonnaterre, 1788)]. With all hook types, mackerel bait resulted in a significant decrease in blue shark, bigeye tuna [Thunnus obesus (lowe, 1839)], and albacore tuna, but significantly increased the catch of porbeagle [Lamna nasus (bonnaterre, 1788)] and shortfin mako (Isurus oxyrinchus rafinesque, 1810).