Effects of hook and bait in a tropical northeast Atlantic pelagic longline fishery: Part I-Incidental sea turtle bycatch

Published source details Coelho R., Santos M.N., Fernandez-Carvalho J. & Amorim S. (2015) Effects of hook and bait in a tropical northeast Atlantic pelagic longline fishery: Part I-Incidental sea turtle bycatch. Fisheries Research, 164, 302-311.
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This study is summarised as evidence for the following.

	Action	Category
	Use non-offset hooks Action Link
	Use a different bait type: Sea turtles Action Link
	Use circle hooks instead of J-hooks Action Link

Use non-offset hooks

A replicated, controlled, paired study in 2008–2011 in pelagic waters in the north-east Atlantic Ocean (Coelho et al. 2015) found that using non-offset circle hooks instead of offset J-hooks in a longline swordfish Xiphias gladius fishery reduced unwanted catch of sea turtles. Unwanted sea turtle catch was reduced with non-offset G-style circle hooks (leatherback turtles Dermochelys coriacea: 0.3–0.5 turtles/1,000 hooks; hard-shell sea turtles [Cheloniidae spp.]: 0.1), but not offset Gt-style circle hooks (leatherback turtles: 0.7–0.8 turtles/1,000 hooks; hard-shell turtles: 0.1–0.2), compared to traditional offset J-hooks (leatherback turtles: 0.9–1.0 turtles/1,000 hooks; hard-shell turtles: 0.2–0.4). Mortality and hooking location of leatherback turtles was similar between hook types (see paper for details). In August 2008–December 2011, a commercial vessel carried out 202 overnight longline fishing deployments (lines: 55 nm long with 5 branchlines, deployed 20–50 m deep, lit by green lights). Whole squid (Illex spp.) or mackerel (Scomber spp.) were used as bait (one type of bait/line deployment). Three hook styles: 10° offset J-hooks traditionally used in the fishery; non-offset G-style circle hooks; and 10° offset Gt-style circle hooks were alternated every 70–80 hooks along the line in a randomized start order (254,520 total hooks deployed with 42,420 of each hook/bait combination). Unwanted catch was counted and released.

(Summarised by: Katie Sainsbury)
Use a different bait type: Sea turtles

A replicated, paired, controlled study in 2008–2011 in pelagic waters in the north-east Atlantic Ocean (Coelho et al. 2015) found that changing from squid Illex spp. bait to mackerel Scomber spp. bait reduced unwanted catch of hard-shell sea turtles (Cheloniidae spp.), but not leatherback turtles Dermochelys coriacea in a pelagic longline swordfish Xiphias gladius fishery. Unwanted catch of hard-shell sea turtles (loggerhead Caretta caretta, olive ridley Lepidochelys olivacea and Kemp’s ridley Lepidochelys kempii turtles) was reduced when mackerel bait was used (0.07–0.16 turtles/1,000 hooks) compared to squid (0.14–0.35 turtles/1,000 hooks). Unwanted catch of leatherback turtles was similar when mackerel (0.39–0.95 turtles/1,000 hooks) or squid (0.50–0.10 turtles/1,000 hooks) bait was used. In August 2008–December 2011, a commercial vessel carried out 202 overnight longline fishing deployments (lines: 55 nm long with 5 branchlines, deployed 20–50 m deep, lit by green lights). Whole squid or mackerel were used as bait (one type of bait/line deployment). Hook styles (10° offset J-hooks traditionally used in the fishery; non-offset G-style circle hooks; and 10° offset Gt-style circle hooks) were alternated every 70–80 hooks along the line in a randomized start order (254,520 total hooks deployed with 42,420 of each hook/bait combination). Unwanted catch was counted and released.

(Summarised by: Katie Sainsbury)
Use circle hooks instead of J-hooks

A replicated, controlled paired study in 2008–2011 in pelagic waters in the north-east Atlantic Ocean (Coelho et al. 2015) found that changing to non-offset circle hooks from offset J-hooks in a longline swordfish Xiphias gladius fishery reduced unwanted catch of sea turtles. Unwanted sea turtle catch was reduced with non-offset G-style circle hooks (leatherback turtles Dermochelys coriacea: 0.34–0.50 turtles/1,000 hooks; hard-shell turtles (Cheloniidae spp.): 0.07–0.14), but not offset Gt-style circle hooks (leatherback turtles: 0.73–0.78 turtles/1,000 hooks; hard-shell turtles: 0.07–0.19), compared to traditional offset J-hooks (leatherback turtles: 0.94–0.99 turtles/1,000 hooks; hard-shell turtles: 0.16–0.35). Mortality and hooking location of leatherback turtles was similar between hook types (see paper for details). In August 2008–December 2011, a commercial vessel carried out 202 overnight longline fishing deployments (lines: 55 nm long with 5 branchlines, deployed 20–50 m deep, lit by green lights). Whole squid (Illex spp.) or mackerel (Scomber spp.) were used as bait (one type of bait/line deployment). Three hook styles: 10° offset J-hooks traditionally used in the fishery; non-offset G-style circle hooks; and 10° offset Gt-style circle hooks were alternated every 70–80 hooks along the line in a randomized start order (254,520 total hooks deployed with 42,420 of each hook/bait combination). Unwanted catch was counted and released.

(Summarised by: Katie Sainsbury)