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

Published source details Curran D. & Bigelow K. (2011) Effects of circle hooks on pelagic catches in the Hawaii-based tuna longline fishery. Fisheries Research, 109, 265-275.
Share Tweet Email

Actions

This study is summarised as evidence for the following.

	Action	Category
	Use a different hook type Action Link

Use a different hook type

A replicated, controlled study in 2005–2006 in an area of pelagic water in the Pacific Ocean around Hawaii, USA (Curran & Bigelow 2011) found that circle hooks typically caught fewer and larger unwanted non-target fish species compared to two conventional hook types used in the longline fishery for bigeye tuna Thunnus obesus, and that fish condition (as a proxy for post-release survival) was higher for some unwanted species. Circle hooks reduced catch rates of 14 of 14 and eight of 14 unwanted species, compared to conventional tuna and J hooks respectively, as well as two of three and three of three non-target but commercially valuable (incidental) species. Circle hooks caught similar numbers of bigeye and incidental yellowfin tuna Thunnus albacares as tuna hooks and similar numbers of bigeye tuna as J hooks (data reported as statistical model results). Fish length varied between hook types for four of seven unwanted species, and two incidental species. Of the unwanted species that showed differences, two species were largest with circle hooks and two with J hooks. Length of target bigeye tuna and incidental yellowfin tuna were similar across hook types (data reported as statistical model results). The condition (as a proxy for survival) of fish captured using circle hooks was higher for three and five unwanted species compared to tuna and J hooks respectively (data reported as statistical model results). Data were collected between June 2005–February 2006 on 16 tuna longline vessels. Vessels alternated a circle hook type (size 18/0) with one of two existing hook types (Japanese tuna hook or J hook, size 9/0) throughout the longline gear. Observers monitored 1,393 sets (1,182 circle vs tuna hooks, 211 circle hooks vs J hooks). See original paper for gear specifications. All fish caught were identified, and fish length and condition recorded.

(Summarised by: Leo Clarke)