Effects of 17/0 circle hooks and bait on fish catches in a Southern Atlantic swordfish longline fishery

Published source details Amorim S., Santos M.N., Coelho R. & Fernandez-Carvalho J. (2015) Effects of 17/0 circle hooks and bait on fish catches in a Southern Atlantic swordfish longline fishery. Aquatic Conservation: Marine and Freshwater Ecosystems, 25, 518-533.
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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 2008–2012 in a wide area of pelagic water spanning the Southern Atlantic Ocean (Amorim et al. 2015) found that using two circle hook types instead of a traditional J hook in a commercial longline fishery targeting swordfish Xiphias gladius, reduced the overall discarded catch of bony fish, but not sharks and rays (Elasmobranchii), and the effects varied between species. Average catch rates of total discarded bony fish (five species/groups) were lower on circle hooks than J hooks (circle: 0.8–0.9, J hook: 1.8 ind/1,000 hooks), but this varied between individual species. Catch rates of all shark and ray discards (nine species/groups) did not differ between hook types (circle: 2.3–2.6, J hook: 2.3 ind/1,000 hooks), but there were also differences for individual species (see original paper for species individual data). Data were collected from 310 experimental longline sets, deployed from October 2008 to February 2012. Three different hook types were tested: two circle hooks of identical dimensions, but one with no offset angle and one offset by 10°, and one existing J-style hook used by the Portuguese swordfish pelagic longline fleet (see original paper for gear specifications). A total of 446,400 hooks were fished, baited with mackerel Scomber spp. and squid Illex spp., with hook types alternated in groups of 80 hooks.

(Summarised by: Chris Barrett/Natasha Taylor)