Study

Effects of barium-ferrite permanent magnets on great hammerhead shark Sphyrna mokarran behavior and implications for future conservation technologies

  • Published source details O'Connell C.P., Hyun S., Gruber S. & He P. (2015) Effects of barium-ferrite permanent magnets on great hammerhead shark Sphyrna mokarran behavior and implications for future conservation technologies. Endangered Species Research, 26, 243-256.

Actions

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, randomized, controlled study in 2010–2013 in one area of sandy seabed in the Atlantic Ocean off South Bimini, Bahamas (O'Connell et al. 2015) found that great hammerhead sharks Sphyrna mokarran avoided bait bags with permanent magnet deterrents attached and fed less frequently compared to bait with no deterrents or bait set with non-magnetic deterrents. All data were reported on a log scale. In two of two experiments, sharks demonstrated greater avoidance behaviour to bait bags with magnet deterrents attached compared to bait bags with no deterrents or nets with non-magnetic deterrents attached. Feeding rates were lower on bait bags with magnet deterrents than bait with no deterrents or non-magnetic deterrents, between which feeding rates were similar. Sharks also exhibited higher rates of avoidance behaviour around ropes set with magnets and non-magnetic deterrents than ropes with no deterrents, around which avoidance behaviour was similar. Two experiments were undertaken between January 2010-March 2013 at depths of 3–8 m. In the first, mesh bags baited with great barracuda Sphyraena barracuda were set on 1 m2 plastic apparatus with either a magnetic deterrent, a visually identical non-magnetic deterrent, or no deterrent (90 trials of 30 min). The deterrents were randomly ordered. In the second experiment, three 6 m surface ropes were set with either no vertical ropes, vertical ropes (1.5 m apart) mounted with the magnetic deterrent or ropes mounted with the non-magnetic deterrent (42 × 30 min trials). Shark behaviour was monitored from a vessel observation platform.

    (Summarised by: Leo Clarke)

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