Evaluation of Neodymium-Iron-Boride Magnets as Selective Shark Repellents on Demersal Longlines
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Transcript of Evaluation of Neodymium-Iron-Boride Magnets as Selective Shark Repellents on Demersal Longlines
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Evaluation of Neodymium-Iron-Boride Magnets as Selective Shark Repellents on Demersal Longlines
Michael M. Herrmann, July 17, 2006
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Introduction
What we know to date:MaterialsGeometriesTonic Immobility responsesEffects on Fish
RiggingPreliminary results on demersal lines
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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)
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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)
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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)
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Tonic Immobility Assay
Fields greater than 50G will terminate TI at a distance of 0.0 – 0.3m
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Responses to Magnets - Sharks
Free-swimming sharks will turn off of a buried magnet
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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
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Responses to Magnets - Sharks
Diminishing response with continuing exposure
Magnetosense appears to be “switchable”
High olfactory stimulation overrides magnetosense
Diminishing response
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Responses to Magnets - Sharks
Diminishing response with continuing exposure
Magnetosense appears to be “switchable”
High olfactory stimulation overrides magnetosense
Essentially no response
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Responses to Magnets - Sharks
Spotted wobbegongs (O. maculatus) do not appear
to respond to NIB and BaFerrite magnets
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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
Feeding behavior is not affected by the presence of
NIB magnets
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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
Feeding behavior is not affected by the presence of
NIB magnets
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Selecting a Geometry
•Optimum geometry is pyramidal stacking
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Selecting a Geometry
•Optimum geometry is pyramidal stacking
•Highest measurable flux at tips
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Selecting a Geometry
•Optimum geometry is pyramidal stacking
•Highest measurable flux at tips
9,000G - 9,300G
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Practical Rigging
1”x1” cylinder with 3/16” center bore is preferred
Shape the magnetic flux to encompass the bait
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Shaping the Flux
1”x1” cylinder with 3/16” center bore is preferred
Shape the magnetic flux to encompass the bait
Steel tophat
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Shaping the Flux
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Rigging
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Rigging
2” Steel tophat
1” NIB
Sleeve
16/0 hook
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Possible Galvanic Cell
Steel with cold galvanizing compound
Copper sleeve
Passive Ni-plate NIB
Mild steel tophat+ + +
+ + + +
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Rigging
NIB
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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
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Setting the Demersal Line
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Setting the Demersal Line
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Preliminary Results
N48 square blocks, 67 hour total soak time
NOVEMBER 2005
2”x2”x1/8” square N48
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Preliminary Results
N48 square blocks, 67 hour total soak time
NOVEMBER 2005
1”x1”x1/8” square N48
High flux, clumsy shape
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Preliminary Results
0
1
2
3
Controls Treatments
Sh
arks
Cap
ture
d
N48 square blocks, 67 hour total soak time
No sharks captured on treatment hooks
NOVEMBER 2005
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Preliminary Results
N48 mini-cylinders, 24 hour total soak time
FEBRUARY 2006 – UNDERSIZED MAGNETS
0.4” x 1” minicylinders
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Preliminary Results
N48 mini-cylinders, 24 hour total soak time
FEBRUARY 2006 – UNDERSIZED MAGNETS
0.4” x 1” minicylinders
Polarized along length, weak flux
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Preliminary Results
N48 mini-cylinders, 24 hour total soak time
FEBRUARY 2006 – UNDERSIZED MAGNETS
0
1
2
3
Controls Treatments
Sh
ark
s c
ap
ture
d
3 tigers (TL>2m) in same 4hr period
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Preliminary Results
N48 1” cylinders, 24 hour total soak time
FEBRUARY 2006 CONTINUED
1”x1” N48 cylinders
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Preliminary Results
N48 1” cylinders, 24 hour total soak time
FEBRUARY 2006 CONTINUED
0
1
2
3
Controls Treatments
Sh
arks
Cap
ture
d
Sharpnose
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Preliminary Results
N50 1”x1” cylinder with 2” tophat
N50 1” cylinders with tophats, 48 hour total soak time
JUNE 2006
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Preliminary Results
N50 1” cylinders with tophats, 48 hour total soak time
0
1
2
3
4
Controls Treatments
Sh
arks
Cap
ture
d
No sharks captured on treatments
JUNE 2006
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Next Steps
Many more tests CPUE is too lowNovember 2006 NOAA cruiseAlaskan and Chilean fisheries
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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