Effects of circle versus J-style hooks on target and non-target species in a pelagic longline fishery

The U.S. Atlantic coastal pelagic longline fishery that targets tunas and swordfish also interacts with a wide range of non-target species ncluding billfishes and sea turtles. Preliminary studies indicate that a change in terminal gear from J-style hooks to circle hooks may reduce ycatch mortality, but the effects of this change on catch rates of target species are unclear. To evaluate this, we monitored catch composition, atch rates, hooking location, and number of fish alive at haulback during 85 sets in the fall and spring seasonal fisheries from a commercial essel operating in the western North Atlantic. Circle (size 16/0, 0◦ offset) and J-style (size 9/0, 10◦ offset) hooks were deployed in an lternating fashion. Hook–time recorders were used to assess time at hooking and temperature–depth recorders to measure gear behavior. atch rates for most species categories were not significantly different between hook types (P< 0.05), although circle hooks generally had igher tuna catch rates in the fall and lower swordfish catch rates in the spring. In the fall, both total catches and catches of pelagic rays were ignificantly higher on J-style hooks. Yellowfin tuna in the fall and dolphinfish in the spring caught on circle hooks were significantly larger han those caught on J-style hooks. In both seasonal fisheries, circle hooks caught fishes in the mouth more frequently than J-style hooks, hich hooked more often in the throat or gut, although these differences between hook types were not statistically significant. Yellowfin una in the fall fishery were over four times more likely to be hooked in the mouth with circle hooks than with J-style hooks. Several target nd bycatch species showed higher rates of survival at haulback with circle hooks, although only for dolphinfish in the fall fishery was this ifference statistically significant. Our results suggest that the use of 0◦ offset circle hooks in the coastal pelagic longline fishery will increase he survival of bycatch species at haulback with minimal effects on the catches of target species. 2006 Elsevier B.V. All rights reserved.