Introduction What we know to date



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tarix05.03.2018
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Evaluation of Neodymium-Iron-Boride Magnets as Selective Shark Repellents on Demersal Longlines


Introduction

  • What we know to date:

  • Rigging

  • Preliminary results on demersal lines



Materials

  • NIB

    • Neodymium-iron-boride sinter with Ni or Zn plate
    • Nd2Fe4B (Empirical)
    • Highest flux per size (BHmax is > 50 MGOe) “N50”
    • Poor corrosion resistance
  • Ceramics

    • Barium-ferrite material
    • BaFe12O19 (Empirical)
    • Cheap and heavy, largest flux area
  • SmCo

    • Samarium-cobalt sinter
    • SmCo5, Sm2Co17(Empirical)
    • Corrosion-resistance and expensive (BHmax ~43 MGOe)


Materials

  • NIB

    • Neodymium-iron-boride sinter with Ni or Zn plate
    • Nd2Fe4B (Empirical)
    • Highest flux per size (BHmax is > 50 MGOe) “N50”
    • Poor corrosion resistance
  • Ceramics

    • Barium-ferrite material
    • BaFe12O19 (Empirical)
    • Cheap and heavy, largest flux area
  • SmCo

    • Samarium-cobalt sinter
    • SmCo5, Sm2Co17(Empirical)
    • Corrosion-resistance and expensive (BHmax ~43 MGOe)


Materials

  • NIB

    • Neodymium-iron-boride sinter with Ni or Zn plate
    • Nd2Fe4B (Empirical)
    • Highest flux per size (BHmax is > 50 MGOe) “N50”
    • Poor corrosion resistance
  • Ceramics

    • Barium-ferrite material
    • BaFe12O19 (Empirical)
    • Cheap and heavy, largest flux area
  • SmCo

    • Samarium-cobalt sinter
    • SmCo5, Sm2Co17 (Empirical)
    • Corrosion-resistance and expensive (BHmax ~43 MGOe)


Tonic Immobility Assay

  • Fields greater than 50G will terminate TI at a distance of 0.0 – 0.3m



Responses to Magnets - Sharks

  • Free-swimming sharks will turn off of a buried magnet



Responses to Magnets - Sharks

  • Diminishing response with continuing exposure

  • Magnetosense appears to be “switchable”

  • High olfactory stimulation overrides magnetosense



Responses to Magnets - Sharks

  • Diminishing response with continuing exposure

  • Magnetosense appears to be “switchable”

  • High olfactory stimulation overrides magnetosense



Responses to Magnets - Sharks

  • Diminishing response with continuing exposure

  • Magnetosense appears to be “switchable”

  • High olfactory stimulation overrides magnetosense



Responses to Magnets - Sharks

  • Spotted wobbegongs (O. maculatus) do not appear

  • to respond to NIB and BaFerrite magnets



Responses to Magnets - Teleosts

  • IATTC Achotines, Panama, July 2005

    • Feeding preference trials in Thunnus albacares (magnetoreceptive)
  • University of Miami, RSMAS, August 2005

    • Feeding preference trials in Rachycentron canadum


Responses to Magnets - Teleosts

  • IATTC Achotines, Panama, July 2005

    • Feeding preference trials in Thunnus albacares (magnetoreceptive)
  • University of Miami, RSMAS, August 2005

    • Feeding preference trials in Rachycentron canadum


Selecting a Geometry



Selecting a Geometry



Selecting a Geometry



Practical Rigging

  • 1”x1” cylinder with 3/16” center bore is preferred

  • Shape the magnetic flux to encompass the bait



Shaping the Flux

  • 1”x1” cylinder with 3/16” center bore is preferred

  • Shape the magnetic flux to encompass the bait



Shaping the Flux



Rigging



Rigging



Possible Galvanic Cell



Rigging



Setting the Demersal Line

  • 1 demersal line with 15 16/0 circle hooks

  • Same type of bait

  • L-P Hook Event Timers

  • 24 hour rebait periods

  • Lines checked every 4 hours

  • Alternating magnets and controls



Setting the Demersal Line



Setting the Demersal Line



Preliminary Results



Preliminary Results



Preliminary Results



Preliminary Results



Preliminary Results



Preliminary Results



Preliminary Results



Preliminary Results



Preliminary Results



Preliminary Results



Next Steps

  • Many more tests

  • CPUE is too low

  • November 2006 NOAA cruise

  • Alaskan and Chilean fisheries



Acknowledgements

  • Bimini Biological Field Station

    • Dr. Samuel Gruber
    • Steve Kessel, Tristan Guttridge, Grant Johnson, Katie Grudecki, Jo Imhoff, and the crew
  • Vernon Scholey, IATTC

  • NOAA – Pascagoula

    • Mark A. Grace
    • Charles Bergmann RSMAS
    • Dr. Dan Benetti
    • Patrick H. Rice
  • WWF SmartGear 2006 Committee

    • Kim Davis
    • Rodrigo Donadi
  • George Mizzell, ENG Concepts



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