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

Published source details Kerstetter D.W. & Graves J.E. (2006) Effects of circle versus J-style hooks on target and non-target species in a pelagic longline fishery. Fisheries Research, 80, 239-250.
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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 2003–2004 in an area of pelagic water in the Atlantic Ocean and the Gulf of Mexico (Kerstetter & Graves 2006) found that changing conventional J-shaped hooks to circle hooks did not typically reduce the catches or mortality of non-target fish species in a longline fishery, but deep-hooking (associated with post-release mortality) was reduced. Across both surveys, catch rates of one of seven non-target fish species were lower on circle hooks than J hooks (see original paper for species individual data). The percentage mortality was lower on circle hooks than J hooks for only one of the 10 most commonly caught non-target species in both 2003 (circle: 7%, J hook: 30%) and 2004 (circle: 26%, J hook: 58%). However, the occurrence of deep-hooking was lower on circle hooks than J hooks for four of five species (data reported as statistical model results). Data were collected on a commercial pelagic longline vessel in the tuna Thunnus spp. and/or swordfish Xiphias gladius fisheries during two surveys: July-September 2003 (39 longline sets, using squid Ilex sp. as bait) and January-April 2004 (46 sets, mixed squid/mackerel Scomber scombrus bait). One circle hook type (size 16/0) and one J-shaped hook type (size 9/0) were set alternately on longline sections (30,600 hooks). See original paper for gear specifications.

(Summarised by: Leo Clarke)