No effect from rare-earth metal deterrent on shark bycatch in a commercial pelagic longline trial

  • Published source details Godin A.C., Wimmer T., Wang J.H. & Worm B. (2013) No effect from rare-earth metal deterrent on shark bycatch in a commercial pelagic longline trial. Fisheries Research, 143, 131-135.


This study is summarised as evidence for the following.

Action Category

Attach an electropositive deterrent to fishing gear

Action Link
Marine Fish Conservation
  1. Attach an electropositive deterrent to fishing gear

    A replicated, controlled study in 2011 in an area of pelagic water in the northwest Atlantic Ocean off Nova Scotia, Canada (Godin et al. 2013) found that longline hooks with electropositive metal attached did not reduce the unwanted catches of sharks (Selachii) overall or of blue shark Prionace glauca compared to standard hooks. Total shark catches (all species) were not statistically different between hooks with electropositive weights (33 ind./1,000 hooks), standard hooks (36 ind./1,000 hooks), or hooks with inert lead weights (44 ind./1,000 hooks). Blue shark catches were also similar across hook types (electropositive: 31, standard: 33, inert: 40 ind./1,000 hooks). Catches of other unwanted sharks (mako Isurus oxyrinchus, porbeagle Lamna nasus) and other, commercially valuable species (bluefin tuna Thunnus thynnus, albacore Thunnus alalunga, anglerfish Lophiiformes spp.) were generally low across all hook types (data not tested statistically). Target catches of swordfish Xiphias gladius were lower on hooks with electropositive weights (12 fish/1,000 hooks) and lead weighted hooks (10 fish/1,000 hooks) compared to standard hooks (23 fish/1,000 hooks). In September and October 2011, a total of 6,300 hooks were set during 70 experimental gear sets (900 hooks/set) in a longline swordfish Xiphias gladius fishery. Each set used three hook types: standard hooks, hooks with electropositive metal weights (neodymium and praseodymium), and hooks with inert lead weights, with 300 hooks/hook type.

    (Summarised by: Leo Clarke)

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