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: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