evaluation of neodymium-iron-boride magnets as selective shark repellents on demersal longlines...
TRANSCRIPT
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:MaterialsGeometriesTonic Immobility responsesEffects on Fish
RiggingPreliminary 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
Magnet at d=0.0m to shark, no response
Responses to Magnets - Sharks
Diminishing response with continuing exposure
Magnetosense appears to be “switchable”
High olfactory stimulation overrides magnetosense
Diminishing response
Responses to Magnets - Sharks
Diminishing response with continuing exposure
Magnetosense appears to be “switchable”
High olfactory stimulation overrides magnetosense
Essentially no response
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
Feeding behavior is not affected by the presence of
NIB 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
Feeding behavior is not affected by the presence of
NIB magnets
Selecting a Geometry
•Optimum geometry is pyramidal stacking
Selecting a Geometry
•Optimum geometry is pyramidal stacking
•Highest measurable flux at tips
Selecting a Geometry
•Optimum geometry is pyramidal stacking
•Highest measurable flux at tips
9,000G - 9,300G
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
Steel tophat
Shaping the Flux
Rigging
Rigging
2” Steel tophat
1” NIB
Sleeve
16/0 hook
Possible Galvanic Cell
Steel with cold galvanizing compound
Copper sleeve
Passive Ni-plate NIB
Mild steel tophat+ + +
+ + + +
Rigging
NIB
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
N48 square blocks, 67 hour total soak time
NOVEMBER 2005
2”x2”x1/8” square N48
Preliminary Results
N48 square blocks, 67 hour total soak time
NOVEMBER 2005
1”x1”x1/8” square N48
High flux, clumsy shape
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
Preliminary Results
N48 mini-cylinders, 24 hour total soak time
FEBRUARY 2006 – UNDERSIZED MAGNETS
0.4” x 1” minicylinders
Preliminary Results
N48 mini-cylinders, 24 hour total soak time
FEBRUARY 2006 – UNDERSIZED MAGNETS
0.4” x 1” minicylinders
Polarized along length, weak flux
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
Preliminary Results
N48 1” cylinders, 24 hour total soak time
FEBRUARY 2006 CONTINUED
1”x1” N48 cylinders
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
Preliminary Results
N50 1”x1” cylinder with 2” tophat
N50 1” cylinders with tophats, 48 hour total soak time
JUNE 2006
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
Next Steps
Many more tests CPUE is too lowNovember 2006 NOAA cruiseAlaskan 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