Effects of a hook ring on catch and bycatch in a Mediterranean swordfish longline fishery: small addition with potentially large consequences

  • Published source details Piovano S. & Swimmer Y. (2017) Effects of a hook ring on catch and bycatch in a Mediterranean swordfish longline fishery: small addition with potentially large consequences. Aquatic Conservation: Marine and Freshwater Ecosystems, 27, 372-380.


This study is summarised as evidence for the following.

Action Category

Use non-ringed hooks

Action Link
Reptile Conservation

Use a different hook type

Action Link
Marine Fish Conservation
  1. Use non-ringed hooks

    A replicated, paired study in 2009–2013 in pelagic waters in the Strait of Sicily and South Tyrrhenian Sea, central Mediterranean Sea (Piovano & Swimmer 2017) found that fewer loggerhead turtles Caretta caretta were incidentally caught on non-ringed circle hooks than ringed circle hooks in a longline fishery targeting swordfish Xiphias gladius. No loggerhead turtles were caught on non-ringed hooks, compared to six turtles caught on ringed hooks (statistical analyses not carried out due to small sample size). Catch rates of target swordfish were lower on non-ringed hooks (7 fish/1,000 hooks) compared to ringed hooks (9 fish/1,000 hooks). Ringed and non-ringed circle hooks (size: 16/0) with a 10° offset were alternately set along a mainline in an even ratio from six longline vessels (600–1,100 hooks/vessel). Data were collected during 65 longline deployments (using 25,400 of each hook type) in July-September in 2009–2010 and 2012–2013.

    (Summarised by: Katie Sainsbury)

  2. Use a different hook type

    A replicated, controlled study in 2009–2013 in an area of pelagic water in the Mediterranean Sea, off Sicily, Italy (Piovano & Swimmer 2017) found that hooks attached to the fishing line with rings (‘ringed’ hooks) caught fewer of two of three unwanted species in a longline swordfish Xiphias gladius fishery, compared to hooks attached directly to the line. Ringed hooks caught fewer unwanted sunfish Mola mola (0.04 ind/1,000 hooks) and blue shark Prionace glauca (0.04 ind/1,000 hooks) compared to non-ringed hooks (sunfish: 0.08, blue shark: 0.19 ind/1,000 hooks). However, numbers of unwanted pelagic stingray Pteroplatytrygon violacea were higher on ringed hooks than non-ringed hook (ringed: 0.71, non-ringed: 0.63 ind/1,000 hooks). Target swordfish and bluefin tuna Thunnus thynnus catches were higher on ringed hooks than non-ringed hooks (swordfish: 8.47 vs 6.65, tuna: 0.71 vs 0.47 ind/1,000 hooks). Catches of targeted little tunny Euthynnus alletteratus were similar between hook types (both 0.04 ind/1,000 hooks) but target dolphinfish Coryphaena hippurus catches were lower on ringed hooks (ringed: 0.00, non-ringed: 0.04 ind/1,000 hooks). Fishing trials took place in July–September in 2009–2013 using ringed or non-ringed circle hooks (size 16/0). Hooks were 5 cm long and either attached to the branchline with a ring or directly to the line, with each type set alternately along the mainline. Sixty-five sets of gear were fished from six vessels, totalling 50,800 hooks.

    (Summarised by: Chris Barrett)

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