Effects of circle hooks on pelagic catches in the Hawaii-based tuna longline fishery

Tests were conducted aboard deep-set Hawaii tuna longline vessels to determine differences in catches, fish size selectivity and survival on 18/0 circle hooks vs. Japanese style tuna hooks size 3.6 sun and vs. 9/0 "J" hooks.  There were no significant differences in catch, catch rate or mean length between hook types for bigeye tuna (the primary target) but catch rates on circle hooks were lower for 16 other species than on the Japanese style tuna hook and for 8 species on the "J" hook.  Fish length was significantly shorter on Japanese style tuna hooks for four species compared to circle hooks and four 3 species on "J" hooks.  Survival was significantly higher for 6 species, including bigeye tuna, on circle hooks compared to Japanese style hooks and for five species on "J" hooks.