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
Free-swimming sharks will turn off of a buried magnet
Responses to Magnets - Sharks 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
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
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 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 George Mizzell, ENG Concepts
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