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

Evaluation of Neodymium-Iron-Boride Magnets as Selective Shark Repellents on Demersal Longlines. Michael M. Herrmann, July 17, 2006. Introduction. What we know to date: Materials Geometries Tonic Immobility responses Effects on Fish Rigging Preliminary results on demersal lines.

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

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  1. Evaluation of Neodymium-Iron-Boride Magnets as Selective Shark Repellents on Demersal Longlines Michael M. Herrmann, July 17, 2006

  2. Introduction • What we know to date: • Materials • Geometries • Tonic Immobility responses • Effects on Fish • Rigging • Preliminary results on demersal lines

  3. 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)

  4. 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)

  5. 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)

  6. Tonic Immobility Assay Fields greater than 50G will terminate TI at a distance of 0.0 – 0.3m

  7. Responses to Magnets - Sharks Free-swimming sharks will turn off of a buried magnet

  8. Responses to Magnets - Sharks • Diminishing response with continuing exposure • Magnetosense appears to be “switchable” • High olfactory stimulation overrides magnetosense Magnet at d=0.0m to shark, no response

  9. Responses to Magnets - Sharks • Diminishing response with continuing exposure • Magnetosense appears to be “switchable” • High olfactory stimulation overrides magnetosense Diminishing response

  10. Responses to Magnets - Sharks • Diminishing response with continuing exposure • Magnetosense appears to be “switchable” • High olfactory stimulation overrides magnetosense Essentially no response

  11. Responses to Magnets - Sharks Spotted wobbegongs (O. maculatus) do not appear to respond to NIB and BaFerrite magnets

  12. Responses to Magnets - Teleosts Feeding behavior is not affected by the presence of NIB magnets • IATTC Achotines, Panama, July 2005 • Feeding preference trials in Thunnus albacares (magnetoreceptive) • University of Miami, RSMAS, August 2005 • Feeding preference trials in Rachycentron canadum

  13. Responses to Magnets - Teleosts Feeding behavior is not affected by the presence of NIB magnets • IATTC Achotines, Panama, July 2005 • Feeding preference trials in Thunnus albacares (magnetoreceptive) • University of Miami, RSMAS, August 2005 • Feeding preference trials in Rachycentron canadum

  14. Selecting a Geometry • Optimum geometry is pyramidal stacking

  15. Selecting a Geometry • Optimum geometry is pyramidal stacking • Highest measurable flux at tips

  16. Selecting a Geometry • Optimum geometry is pyramidal stacking • Highest measurable flux at tips 9,000G - 9,300G

  17. Practical Rigging • 1”x1” cylinder with 3/16” center bore is preferred • Shape the magnetic flux to encompass the bait

  18. Shaping the Flux • 1”x1” cylinder with 3/16” center bore is preferred • Shape the magnetic flux to encompass the bait Steel tophat

  19. Shaping the Flux

  20. Rigging

  21. Rigging 2” Steel tophat 1” NIB Sleeve 16/0 hook

  22. Possible Galvanic Cell + + + Mild steel tophat Passive Ni-plate NIB Copper sleeve Steel with cold galvanizing compound + + + +

  23. Rigging NIB

  24. 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

  25. Setting the Demersal Line

  26. Setting the Demersal Line

  27. Preliminary Results NOVEMBER 2005 2”x2”x1/8” square N48 N48 square blocks, 67 hour total soak time

  28. Preliminary Results NOVEMBER 2005 1”x1”x1/8” square N48 High flux, clumsy shape N48 square blocks, 67 hour total soak time

  29. Preliminary Results NOVEMBER 2005 No sharks captured on treatment hooks N48 square blocks, 67 hour total soak time

  30. Preliminary Results FEBRUARY 2006 – UNDERSIZED MAGNETS 0.4” x 1” minicylinders N48 mini-cylinders, 24 hour total soak time

  31. Preliminary Results FEBRUARY 2006 – UNDERSIZED MAGNETS 0.4” x 1” minicylinders Polarized along length, weak flux N48 mini-cylinders, 24 hour total soak time

  32. 3 2 Sharks captured 1 0 Controls Treatments Preliminary Results FEBRUARY 2006 – UNDERSIZED MAGNETS 3 tigers (TL>2m) in same 4hr period N48 mini-cylinders, 24 hour total soak time

  33. Preliminary Results FEBRUARY 2006 CONTINUED 1”x1” N48 cylinders N48 1” cylinders, 24 hour total soak time

  34. Preliminary Results FEBRUARY 2006 CONTINUED Sharpnose N48 1” cylinders, 24 hour total soak time

  35. Preliminary Results JUNE 2006 N50 1”x1” cylinder with 2” tophat N50 1” cylinders with tophats, 48 hour total soak time

  36. Preliminary Results JUNE 2006 No sharks captured on treatments N50 1” cylinders with tophats, 48 hour total soak time

  37. Next Steps • Many more tests • CPUE is too low • November 2006 NOAA cruise • Alaskan and Chilean fisheries

  38. 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 Acknowledgements

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