Effects of hook and bait in a tropical northeast Atlantic pelagic longline fishery: Part I - Incidental sea turtle bycatch

Experimental studies were conducted over a three year period (August 2008-December 2011) to determine the effects of changing traditional J-hooks baited with squid bait to circle hooks (offset and non offset) with mackerel bait on sea turtle interactions. Studies were carried out aboard pelagic longline vessels targeting swordfish (Xiphias gladius) in the tropical northeast Atlantic Ocean. Overall, sea turtle interactions were reduced when circle, compared to J-hooks, were used. However species specific differences did occur. Leatherback (Dermochelys coriacea) interactions were only reduced when circle hooks with an offset were used. Leatherback interactions can be reduced by 55% in this fishery by switching from J-style to circle hooks. Hardshell turtle interactions (loggerhead Caretta caretta, olive ridley Lepidochelys olivacea, Kemp ridley Lepidochelys kempii) were reduced when both circle hook styles and mackerel bait were used. Interactions with hardshelled turtles can be reduced by 50-55% in this fishery by switching from J-style to circle hooks.  A 55% reduction in hardshell turtle bycatch is expected to occur in this fishery by switching from squid to mackerel bait.