Performance of Non-Offset and 10° Offset 18/0 Circle Hooks in the United States Pelagic Longline Fishery

Industry standard fishing hooks used prior to 2004 during US commercial pelagic longline (PLL) fishing were the 8/0-10/0 J-hooks with a 20 degree to 25 degree offset; a lateral deviation of the hook point relative to the hook shaft. However, federal regulations enacted in 2004 require the US PLL industry to employ circle hooks allowing up to 10 degree offset during fishing operations. Until recently, there have been no studies directly comparing the performance of non-offset and 10 degree offset circle hooks in commercial PLL applications. Our study alternated non-offset and 10 degree offset circle hooks along the gear length on individual PLL deployments in the western north Atlantic, gulf of Mexico, and Windward Passage in the Caribbean sea. The study compared the relative performance of both hook types in terms of: (1) catch rates, (2) percent mortality, and (3) the percentage of deep-hooked target and bycatch species. For swordfish, Xiphias gladius (Linnaeus, 1758), several experiments indicate: (1) marginally higher catch rates, (2) significantly lower mortality, and (3) significantly less deep hooking on non-offset than 10 degree offset circle hooks. Most of the performance differences for blue marlin, Makaira nigricans Lacepede, 1802, were insignificant; however, one study produced significantly higher mortality on 10 degree offset than non-offset circle hooks. The present study suggests that, relative to non-offset circle hooks, 10 degree offset circle hooks may reduce fishing efficiency and can counteract the conservation benefits commonly associated with circle hooks (e.g., lower mortality). However, additional research is required to assess the effects of offset hooks on tunas, billfishes, and elasmobranchs.