U.S. patent application number 11/886109 was filed with the patent office on 2009-02-12 for elasmobranch-repelling magnets and methods of use.
Invention is credited to Eric Matthew Stroud.
Application Number | 20090038205 11/886109 |
Document ID | / |
Family ID | 36992265 |
Filed Date | 2009-02-12 |
United States Patent
Application |
20090038205 |
Kind Code |
A1 |
Stroud; Eric Matthew |
February 12, 2009 |
Elasmobranch-Repelling Magnets and Methods of Use
Abstract
Devices and methods are disclosed for repelling elasmobranchs
with high-pull-force magnets, including devices and methods for
reducing by-catch in commercial fisheries and protecting humans
from attacks by elasmobranchs.
Inventors: |
Stroud; Eric Matthew; (Oak
Ridge, NJ) |
Correspondence
Address: |
KENYON & KENYON LLP
ONE BROADWAY
NEW YORK
NY
10004
US
|
Family ID: |
36992265 |
Appl. No.: |
11/886109 |
Filed: |
March 10, 2006 |
PCT Filed: |
March 10, 2006 |
PCT NO: |
PCT/US06/08587 |
371 Date: |
October 7, 2008 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60660193 |
Mar 10, 2005 |
|
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60699591 |
Jul 15, 2005 |
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Current U.S.
Class: |
43/4.5 ; 2/67;
335/302; 405/185; 43/4; 43/43.16; 441/1; 441/74; 63/3 |
Current CPC
Class: |
A01K 91/18 20130101;
A01K 95/00 20130101; H01F 7/0231 20130101; A01K 75/00 20130101;
A01K 83/00 20130101; A01M 29/24 20130101; B63B 32/70 20200201; A01K
99/00 20130101; E02B 1/006 20130101; A01K 79/02 20130101 |
Class at
Publication: |
43/4.5 ; 43/4;
335/302; 43/43.16; 441/74; 441/1; 2/67; 63/3; 405/185 |
International
Class: |
A01K 99/00 20060101
A01K099/00; A01K 83/00 20060101 A01K083/00; A01K 91/00 20060101
A01K091/00; B63B 35/79 20060101 B63B035/79; B63B 22/00 20060101
B63B022/00; A41D 7/00 20060101 A41D007/00; A44C 5/00 20060101
A44C005/00; B63C 11/02 20060101 B63C011/02 |
Claims
1. An apparatus for repelling an elasmobranch comprising a
high-pull-force magnet.
2. The apparatus of claim 1 wherein the high-pull-force magnet is a
permanent magnet.
3. The apparatus of claim 2 wherein the permanent magnet is a
neodymium-iron-boride magnet.
4. The apparatus of claim 3 wherein the neodymium-iron-boride
magnet is coated with nickel.
5. The apparatus of claim 1 wherein the high-pull-force magnet has
a shape of a cylinder, a cone, a circle, a cube, a disk, a bar, a
sphere, a plate, a rod, a ring, a tube, a stick, a block, or a
tapered cone.
6. The apparatus of claim 1 wherein the high-pull-force magnet
comprises a hollow portion.
7. The apparatus of claim 1 wherein a plurality of high-pull-force
magnets are arranged together in a ring.
8. The apparatus of claim 1 wherein the high-pull-force magnet is
capable of spinning.
9. The apparatus of claim 1 wherein the high-pull-force magnet has
a pull force of greater than about 50 pounds.
10. The apparatus of claim 9 wherein the high-pull-force magnet has
a pull force of greater than about 100 pounds.
11. The apparatus of claim 10 wherein the high-pull-force magnet
has a pull force of greater than about 200 pounds.
12. The apparatus of claim 1 wherein the high-pull-force magnet has
a nominal strength of greater than about 5000 gauss alone or in
combination with one or more other magnets.
13. The apparatus of claim 1 wherein the high-pull-force magnet has
a nominal strength of greater than about 10,000 gauss alone or in
combination with one or more other magnets.
14. The apparatus of claim 1 wherein the high-pull-force magnet has
a nominal strength of greater than about 20,000 gauss alone or in
combination with one or more other magnets.
15. The apparatus of claim 1 wherein the high-pull-force magnet has
greater than about 5 gauss of magnetic strength at a distance of
about 0.01 m to about 1.0 m.
16. The apparatus of claim 1 wherein the high-pull-force magnet has
up to about 14,000 gauss of magnetic strength at a distance of
about 0.01 m to about 0.5 m.
17. The apparatus of claim 1 wherein the high-pull-force magnet has
up to about 320 gauss of magnetic strength at a distance of about
0.1 m to about 0.4 m.
18. The apparatus of claim 1 further comprising a buoy, a barge, a
net, fishing tackle or any combination thereof.
19. An apparatus comprising a high-pull-force magnet and a fish
hook.
20. The apparatus of claim 19 further comprising fishing
tackle.
21. The apparatus of claim 20 wherein the fishing tackle is
selected from the group consisting of a longline, a mainline, a
gangion, a lead, a weight, a buoy, a net, or any combination
thereof.
22. The apparatus of claim 19 wherein the high-pull-force magnet
has a shape of a cylinder, a cone, a circle, a cube, a disk, a bar,
a sphere, a plate, a rod, a ring, a tube, a stick, a block or a
tapered cone and is located in close proximity to the fish
hook.
23. A longline comprising a high-pull-force magnet.
24. A surfboard comprising a high-pull-force magnet.
25. The surfboard of claim 24 wherein the high-pull-force magnet is
integrated into the surfboard.
26. The surfboard of claim 24 wherein the high-pull-force magnet is
connected to the surfboard such that it trails behind the
surfboard.
27. A buoy comprising a high-pull-force magnet.
28. A swim suit comprising a high-pull-force magnet.
29. A bracelet comprising a high-pull-force magnet.
30. Dive equipment comprising a high-pull-force magnet.
31. A method of using a magnetic field to repel an elasmobranch
comprising attaching a high-pull-force magnet to fishing
tackle.
32. The method of claim 31 wherein the fishing tackle is selected
from the group consisting of a hook, a longline, a mainline, a
gangion, a lead, a weight, a buoy, a net or any combination
thereof.
33. A method of using a magnetic field to repel an elasmobranch
comprising attaching a high-pull-force magnet to a human body or to
clothing or accessory associated with a human body.
34. The method of claim 33 wherein the high-pull-force magnet is a
bracelet attached to a human ankle or wrist.
Description
[0001] This invention relates generally to high-pull-force magnets
for repelling elasmobranchs and methods of using high-pull-force
magnets to repel elasmobranchs.
BACKGROUND OF THE INVENTION
[0002] Elasmobranchs represent a significant problem in the
commercial fishing industry. Elasmobranchs are often inadvertently
caught on fishing hooks and tackle directed at other more
commercially valuable kinds of fish. This inadvertent catching of
elasmobranchs (or other non-valued fish) is called "by-catch." As
many as 100 million elasmobranchs are killed each year as by-catch.
This loss of life has resulted in a real threat to several shark
species. Currently, as many as 80 species of shark are considered
threatened with extinction.
[0003] Further, when elasmobranchs are caught as by-catch, fishing
operations receive no return on their investment since the shark is
caught on a hook that might have otherwise brought in a marketable
fish. Additionally, the fishing tackle on which a shark is caught
often must be cut loose for the safety of those working on the
fishing vessel causing a loss of both equipment and time.
[0004] Longlining is a commercial fishing method that suffers
significant losses from shark by-catch. Longlining uses multiple
baited individual fish hooks with leaders strung at intervals along
an often very long (2-3 miles) main fishing line. Longline fishing
operations routinely target swordfish and tuna. The longline hooks,
however, are not selective and elasmobranchs are sometimes caught
in greater numbers than the intended catch. The result is great
loss of life in elasmobranchs and significant financial losses in
the longline industry. Elasmobranchs cause additional losses in the
longline fishing industry by scavenging marketable fish caught on
longlines before the fish may be retrieved for processing.
[0005] Elasmobranchs also represent a problem in the commercial
trawling industry. Trawling is a commercial fishing method that
catches fish in nets. Elasmobranchs cause significant losses for
trawlers because they scavenge fish caught in trawl nets before
they are retrieved for processing. As such, valuable fish are often
lost to shark predation. Also, sharks often tear holes in the nets,
resulting in partial or complete loss of catch and significant
repair costs.
[0006] There has been a long-felt need for methods and devices to
deter elasmobranchs from commercial fishing lines and nets.
Attempts in the middle of the twentieth century were made to
protect trawl nets with electric discharge devices. (Nelson, "Shark
Attack and Repellency Research: An Overview," Shark Repellents from
the Sea ed. Bernhard Zahuranec (1983) at p. 20). Nevertheless, no
commercially effective repellent has yet to be made available for
reducing shark by-catch in the commercial fishing industry or for
reducing loss of valuable fish or fishing tackle to shark
predation. Further, Applicant is unaware of any consideration in
the art of the use of magnets to repel elasmobranchs to limit
by-catch and other losses from elasmobranchs.
[0007] U.S. Pat. No. 4,667,431 discloses an electric prod for
repelling fish. Within the electric prod, the switch for providing
electric current to the prod is a reed switch, which contains a
magnet. However, the magnet is not a part of the repelling portion
of the electric prod.
[0008] An effective shark repellent would not only be valuable to
the fishing industry but also would be valuable for protecting
humans from shark attacks. No effective repellent has yet to be
marketed for limiting the risk of shark attacks faced by humans
exposed to elasmobranchs. Over the last 50 years antishark measures
employed to protect humans from shark have included electrical
repellent devices (Gilbert & Springer 1963, Gilbert &
Gilbert 1973), acoustical playbacks (Myrberg et al. 1978, Klimley
& Myrberg 1979), visual devices (Doak 1974) and chemical
repellents (Tuve 1963, Clark 1974, Gruber & Zlotkin 1982). None
of these procedures proved satisfactory in preventing shark
attacks. (Sisneros (2001)). As such, the long felt need for an
effective repellent has not been satisfied.
[0009] Researchers have historically used several bio-assays to
determine if a repellent evokes a flight response in shark. One
such bio-assay measures the effect of a repellent on a shark that
is immobilized in "tonic immobility." Tonic immobility is a state
of paralysis that typically occurs when a shark is subject to
inversion of its body along the longitudinal axis. This state is
called "tonic," and the shark can remain in this state for up to 15
minutes thereby allowing researchers to observe effects of
repellents. After behavioral controls are established, an object or
substance that has a repelling effect will awaken a shark from a
tonic state. Researches can quantify the strength of a repellent
effect from these studies.
[0010] Another bio-assay employs a Y-shaped maze wherein a shark is
exposed to a choice between two paths containing the same olfactory
stimulus. One path exits the maze without a repellent while the
other contains a repellent. If the sharks consistently choose the
path without the repellent or consistently become agitated in the
path having the repellent, researchers may conclude the repellent
is effective.
BRIEF SUMMARY OF THE INVENTION
[0011] Applicant has discovered that a high-pull-force magnet is an
effective elasmobranch repellent useful in limiting by-catch as
well as protecting humans. High-pull-force magnets, known or
hereinafter developed, that are of sufficient strength to repel
elasmobranchs are acceptable in aspects of the present
invention.
[0012] According to a non-limiting embodiment of the present
invention, an apparatus for repelling elasmobranchs is provided
comprising a high-pull-force magnet. Preferably, the
high-pull-force magnet is a permanent magnet. More preferably, the
high-pull-force magnet is a neodymium-iron-boride magnet. According
to a non-limiting embodiment of the invention, the high-pull-force
magnet may have a nickel coating to protect the magnet from
corrosion. High-pull-force magnets in accordance with the present
invention may have a shape of a cylinder, a cone, a circle, a cube,
a disk, a bar, a sphere, a plate, a rod, a ring, a tube, a stick, a
block or other shape. In a non-limiting embodiment of the
invention, a high-pull-force magnet may have a hollow portion. In a
non-limiting embodiment of the invention, a plurality of
high-pull-force magnets may be arranged together in a ring. In
another non-limiting embodiment of the invention, an apparatus is
provided with a high-pull-force magnet that is capable of
spinning.
[0013] High-pull-force magnets of the present invention have a pull
force preferably of greater than about 50 pounds, more preferably
greater than about 100 pounds, and most preferably greater than
about 200 pounds. In a non-limiting embodiment, a high-pull-force
magnet has a nominal strength of preferably greater than about 5000
gauss, more preferably greater than about 10,000 gauss, and most
preferably greater than about 20,000 gauss. In a non-limiting
embodiment, a high-pull-force magnet produces a magnetic strength
preferably of about 5 gauss at a distance of about 0.01 m to about
1 m, more preferably of about 5 gauss to about 14,000 gauss at a
distance of about 0.01 to about 0.5 m, and most preferably of about
10 gauss to about 320 gauss or greater at a distance of about 0.1 m
to about 0.4 m.
[0014] According to a first non-limiting aspect of the present
invention, an apparatus is provided comprising a high-pull-force
magnet and a buoy, a barge, a net, fishing tackle or any
combination thereof. Fishing tackle may comprise a longline, a main
line, a gangion, a lead, a weight, a buoy, a net, or any
combination thereof.
[0015] According to a second non-limiting aspect of the present
invention, an apparatus is provided comprising a high-pull-force
magnet and a fish hook. Such fish hook may be individual or
attached to longline or mainline and such fish hook may have a
single hook or multiple hooks.
[0016] According to a third non-limiting aspect of the present
invention, a method is provided for repelling elasmobranchs
comprising attaching a high-pull-force magnet to a hook, longline,
mainline, fishing tackle, gangion, lead, weight, buoy, net, boat or
any combination thereof.
[0017] According to a fourth non-limiting aspect of the present
invention, an apparatus is provided comprising a surfboard and a
high-pull-force magnet. A high-pull-force magnet may be housed
within the surfboard, be attached to the surfboard, or be trailed
behind the surfboard in the water.
[0018] In fifth non-limiting aspect of the present invention, a
method is provided for repelling elasmobranchs comprising attaching
a high-pull-force magnet to a human body or to clothing or
accessories associated with a human body. In a preferred technique,
a high-pull-force magnet may be attached to a human ankle or wrist
or may be attached to a bracelet. A high-pull-force magnet may also
be attached to a belt, a weight belt for diving, or flippers for
diving and snorkeling.
[0019] In a sixth non-limiting aspect of the present invention, a
kit is provided comprising a high-pull-force magnet.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020] The invention will now be described by way of example with
reference to the accompanying drawings wherein:
[0021] FIG. 1 illustrates a traditional circle hook attached to a
line and a non-limiting preferred zone (I) for locating a
high-pull-force magnet in accordance with the present
invention.
[0022] FIGS. 2A-C illustrate non-limiting positions within the zone
(I) for locating a high-pull-force magnet in accordance with the
present invention. FIG. 2A illustrates a high-pull-force magnet
attached to the line above the hook. FIG. 2B illustrates a
high-pull-force magnet attached to the hook. FIG. 2C illustrates a
high-pull-force magnet attached to the hook shank and clear of the
hook eye.
[0023] FIGS. 3A-C illustrate non-limiting positions within the zone
(I) for locating a high-pull-force magnet on a J-hook in accordance
with the present invention. FIG. 3A illustrates a high-pull-force
magnet attached to the line above the hook. FIG. 3B illustrates a
high-pull-force magnet attached to the hook. FIG. 3C illustrates a
high-pull-force magnet attached to the hook shank and clear of the
hook eye.
[0024] FIGS. 4A-B illustrate non-limiting positions within the zone
(I) for locating a high-pull-force magnet on a treble hook in
accordance with the present invention. FIG. 4A illustrates a
high-pull-force magnet attached to the line above the hook. FIG. 4B
illustrates a high-pull-force magnet attached to the hook.
[0025] FIG. 5 illustrates an exemplary demersal longline with a
high-pull-force magnet in accordance with the present
invention.
[0026] FIGS. 6A-B illustrate non-limiting devices for repelling
elasmobranchs in accordance with the present invention. FIG. 6A
illustrates a buoy and high-pull-force magnet and a net with a
plurality of high-pull-force magnets in accordance with the
invention. FIG. 6B illustrates a barge and a high-pull-force magnet
in accordance with the present invention.
[0027] FIGS. 7A-B illustrate non-limiting exemplary surfboards with
a high-pull-force magnet in accordance with the invention. FIG. 7A
illustrates a surfboard with a high-pull-force magnet embedded in
or attached to the surfboard in accordance with the invention. FIG.
7B illustrates a surfboard with a high-pull-force magnet that is
capable of spinning in accordance with the invention.
[0028] FIGS. 8A-C illustrate exemplary accessories for attaching a
high-pull-force magnet to a human or other subject or object. FIG.
8A illustrates a belt or weight belt with a high-pull-force magnet
in accordance with the invention. FIG. 8B illustrates a bracelet or
wristband with a high-pull-force magnet in accordance with the
invention. FIG. 8C illustrates flippers for snorkeling or diving
with a high-pull-force magnet in accordance with the present
invention.
[0029] FIG. 9 illustrates a plurality of high-pull-force magnets
arranged into exemplary bracelets, belts or attachable rings in
accordance with the invention.
DETAILED DESCRIPTION OF THE INVENTION
[0030] "By-catch" is any kind of fish that is caught in a fishing
operation wherein the fish is not the object of the fishing
operation. For example, if the target fish of a longline fishing
operation is tuna, an elasmobranch caught on a hook of the longline
is by-catch.
[0031] "Elasmobranchs" in this specification means one or more
elasmobranchii in the super-orders Galeomorphii and Squalomorphii
and orders Squaliforms (dogfish), Carcharhiniformes (requiem
sharks), Lamniformes (mackerel sharks), and certain
Orectolobiformes (carpet sharks). Elasmobranchs in this
specification includes nurse sharks, an Orectolobiforme, but this
specification does not include the other carpet sharks, such as
wobbegongs.
[0032] "Gauss" is a measure of magnetic field strength. Gauss is a
unit of the density of a magnet's flux (or flux density) measured
in centimeter-gram-second. A tesla is equal to 10,000 gauss. Gauss
and tesla are common units for referring to the power of a magnet
to attract (or repel) other magnets or magnetic materials. The
Gauss unit describes both the coercivity of a magnet and its
saturation magnetization. Gauss describes how strong the magnetic
fields are extending from the magnet and how strong of a magnetic
field it would take to de-magnetize the magnet.
[0033] "Grade" of a neodymium-iron-boride magnet specifies the
quality of material used to construct the magnet. All else being
equal, the higher the quality of materials used to construct the
magnet, the greater the magnet's strength. In grading
neodymium-iron-boride magnets, a lower grade, e.g., N35, does not
have as much magnetic strength as a higher grade, e.g. N45.
[0034] "Longline" refers to a fishing line that may extend up to
many miles wherein a mainline extends the full length of the
longline and individual shorter gangion lines attached to the
mainline are spaced at set intervals (perhaps several feet or
meters or perhaps 1000 feet or greater apart). Hooks are attached
to the individual gangion lines. Hooks may be baited and used to
catch target fish. The addition of a magnet of sufficient strength
repels elasmobranchs from the baited hooks as well as from the
region of the longline generally.
[0035] "Nominal strength" of a magnet is measured in gauss or tesla
and reflects the theoretical strength of a magnet at its core.
Nominal strength is a function of the grade of a magnet. The higher
the grade, the higher the nominal strength. Nominal strength is the
strength necessary to demagnetize the magnet.
[0036] "Pull force" is the attractiveness of a magnet to a mild
steel flat surface in pounds. The formula for calculating pull
force is provided in detail herein.
[0037] "Target fish" is any kind of fish, the catching of which is
the object of a fishing operation. For example, the target fish of
a longline fishing operation may be tuna. A fish that is caught on
the longline that is not tuna would not be a target fish.
[0038] "Tonic immobility" is the state of paralysis that typically
occurs when an elasmobranch is subject to inversion of its body
along the longitudinal axis of the body, i.e., is belly up. An
elasmobranch can remain in this state for up to 15 minutes.
I. HIGH-PULL-FORCE MAGNETS AS REPELLENTS OF ELASMOBRANCHS
[0039] It has been discovered that high-pull-force magnets repel
elasmobranchs. High-pull-force magnets comprising a pull force of
about 50 pounds or greater introduced into the environment of an
elasmobranch have demonstrated repelling action on elasmobranchs.
Likewise, magnets comprising a nominal strength of greater than
about 0.5 teslas (5000 gauss) have demonstrated repelling action on
elasmobranch. Further, magnets producing about 5,000 mG to about
500,000 mG of magnetic strength at a distance of about 0.01 m to
about 1 m from the magnet or about 10,000 mG to about 320,000 mG of
magnetic strength at a distance of about 0.1 m to about 0.4 m from
the magnet have demonstrated repelling action on elasmobranchs.
[0040] High-pull-force magnets may be employed near fishing lines,
fish hooks or fishing nets to repel sharks from bait, hooks or nets
that have been set for target fish (not sharks). High-pull-force
magnets may also be employed near people, animals or objects in the
water to repel elasmobranchs from frightening or injuring the
people, animals or objects in a particular area.
[0041] Sufficient magnetic force to repel elasmobranchs may be
measured in a number of ways. Magnetic force may be measured as
pull force, as nominal magnetic strength at the core of the magnet
(in gauss) or at a distance of interest from the magnet (in gauss).
Any measurement known to an artisan practicing the invention may be
useful.
[0042] The high-pull-force magnet may be a permanent magnet or an
electromagnet. Magnets made of neodymium-iron-boride (NdFeB) are
preferred, given present magnet technology, since these magnets
have high pull force relative to their physical size. A coating,
such as nickel, may protect permanent high-pull-force magnets from
corrosion in water. A preferred NdFeB magnet, in accordance with
the present invention, may have a grade of about N38 through about
N50 or greater.
[0043] A high-pull-force magnet for repelling elasmobranchs may
comprise the shape of a cylinder, a cone, a circle, a cube, a disk,
a bar, a sphere, a plate, a rod, a ring, a tube, a stick, a block,
a tapered cone, or any other shape. The high-pull-force magnet may
further comprise a hollow portion for stringing, like beads, on a
fishing hook, line, belt, bracelet or rings. A high-pull-force
magnet comprising a cylinder with a diameter of about 4 inches to
about 8 inches and a thickness of about 1 inch to about 4 inches is
preferred. A magnet with a diameter of about 4 inches and a
thickness of about 1.5 inches is most preferred.
[0044] High-pull-force magnets having a pull force of about 50
pounds or greater have demonstrated repelling activity on
elasmobranch species at distances as great or greater than 0.3 m
from the elasmobranches. Further, a longline fitted with a series
of seven magnets set more than 100 feet apart has shown repelling
activity across an entire longline of about 2000 feet. As such,
high-pull-force magnets in accordance with the invention may be
used to repel elasmobranches. The repelling activity of
high-pull-force magnets may be useful in the commercial fishing
industry to reduce elasmobranch by-catch and predation, and useful
to repel elasmobranchs from humans in the environment of an
elasmobranch or repel elasmobranchs from an area of interest.
[0045] The mode of action of high-pull-force magnets on
elasmobranchs is not fully understood. While not wishing to be
bound by any particular theory, one plausible theoretical
explanation for this surprising finding of repellent activity of
high-pull-force magnets is the possibility that electrical eddy
currents are generated by an elasmobranch moving through the strong
magnetic field created by the high-pull-force magnet. The resulting
eddy currents may over stimulate ampullae of Lorenzini (known to be
used by elasmobranchs for navigation and orientation) causing the
ampullae of Lorenzini to disorient the elasmobranch or otherwise
signal danger to the elasmobranch causing aversive behavior.
[0046] Several species of sharks have demonstrated the ability to
sense magnetic fields (Kalmijn, 1978; Ryan, 1980; Klimley, 1993;
2002) but were not repelled by the use of such magnets. The
ampullae of Lorenzini organ within sharks is used to detect weak
electrical fields at short ranges, which functions in the final
stages of prey capture: usually when a shark is inches from its
prey. A shark's prey emits weak electric fields that are detectable
to the shark. As a shark approaches prey, the shark can sense the
weak electric field emitted therefrom. In the natural environment,
the detection range of the shark's ampullae of Lorenzini is
effective only within inches of an object. As magnetic field
strength is increased elasmobranchs sense the magnetic field at
much greater distances, such as 0.3 m or greater. When a plurality
of magnets are introduced across a large area or region (such as
along a fishing longline) sharks may sense a powerful magnetic
field at close range spanning an area/length of 1000 feet.
[0047] Magnetic fields generated by high-pull-force magnets such as
permanent magnets are effective repellents for elasmobranchs,
excluding certain carpet sharks in the Orectolobidae family. It is
believed that high-pull-force magnets are not effective repellents
against certain carpet sharks, particularly spotted wobbegongs
(Orectolobus maculatus), because they ambush predators and rely
more on visual, olfaction, and lateral line clues than this
magnetic sense. This species of shark is found chiefly in Australia
and Indonesia, and does not represent significant by-catch species
or species that are known to be aggressive against humans. Magnets,
however, are effective against nurse sharks in the Orectolobiform
family.
[0048] While not wishing to be bound by a particular theory, the
flux of a permanent magnet, such as an NdFeB magnet, may correlate
with the detection range of the ampullae of Lorenzini. Since, the
magnetic flux from a magnet decreases at the inverse cube of the
distance from the magnet, at only a few meters distance the
magnetic field exerted by the magnet is less than the Earth's
magnetic field. As such, repelling of elasmobranchs with magnets
appears to occur within several meters of a high-pull-force magnet.
Additionally, if a series of high-pull-force magnets is spaced in a
region, a measurable level of repelling appears to occur over the
entire region.
[0049] High-pull-force magnets have been demonstrated by Applicant
to act as acceptable repellents of elasmobranchs. The repellent
activity of high-pull-force magnets has been shown to be better
than existing shark-repellent technology with the exception of
certain chemical repellents being developed by SHARK DEFENSE LLC
that have a greater range of action.
[0050] A. Magnetic Forces
[0051] The force of a magnet may be measured in a variety of ways.
Gauss is a unit of the density of a magnet's flux (or flux density)
measured in centimeter-gram-second. A tesla is equal to 10,000
gauss. Gauss and tesla are known common units for referring to the
power of a magnet to attract (or repel) other magnets or magnetic
materials. The Gauss unit describes both the coercivity of a magnet
and its saturation magnetization. Basically, it describes how
strong the magnetic fields are extending from the magnet and how
strong of a magnetic field it would take to de-magnetize the
magnet.
[0052] The pull force of a magnet is related to the magnet's
nominal strength in gauss or teslas but uses the nominal strength
to create a practical measure of a magnets ability to apply a
pulling force on materials that are attracted to a magnetic field,
such as ampullae of Lorenzini in elasmobranch. Pull force is
related to the flux density of the magnet's magnetic field (in
gauss or tesla) and the shape of the magnet. Pull force is
calculated using the following equation: Pull
Force=0.576.times.Br.sup.2.times.(Th).times.A.sup.1/2 where Br=Flux
Density in KiloGauss, Th=Thickness of Magnetized Surfaces in inches
and A=Surface Area of the magnet in inches. Using this equation, a
magnet's pull force may be determined. A high pull force value for
magnets is greater than about 50 pounds.
[0053] The strength of a magnet's magnetic field is inversely
related to the distance an object is from the magnet. As such,
magnets of very low strength (or gauss) may repel elasmobranchs if
the elasmobranch moves close enough to sense the magnetic field of
the magnet. A high-pull-force magnet having sufficient strength to
repel an elasmobranch at sufficient distance such that the
elasmobranch is deterred from striking a baited hook or coming near
a person or other subject is preferred. It is more preferred that a
high-pull-force magnet have a pull force of at least 100 pounds to
provide sufficient magnetic force to repel an elasmobranch away
from a baited hook or a person before the elasmobranch may bight
the hook or harm the person. Because an elasmobranch may act to
strike a hook or person at a distance from the target, the stronger
the high-pull-force magnet, the more effective it will be. It has
been reported that magnets have a beneficial health effect in
humans and a negative health effect in humans at high power.
Applicant makes no representation herein of the safety of use of
high-pull-force magnets by humans during short- or long-term
use.
II. METHODS AND DEVICES FOR MAGNETIC REPELLENTS
[0054] A. Magnets
[0055] Exemplary and non-limiting high-pull-force magnets in
accordance with the invention may be constructed of any material
that is capable of generating a magnetic field without requiring an
outside energy source (such a permanent ferrous magnet). Magnetism
may be generated in any manner known to the skilled artisan who is
practicing aspects of the invention.
[0056] There are many varieties of permanent magnet materials
including neodymium magnets (which are some of the most powerful
permanent magnets known at this time), samarium-cobalt magnets,
ceramic magnets, plastic magnets, Alnico magnets as well as
traditional ferrous magnets. Any magnetic material having
sufficient pull force may be used as a repellent of
elasmobranchs.
[0057] Exemplary permanent magnets include neodymium-iron-boride
(NdFeB) magnets, ferrous metal magnets, samarium-cobalt magnets, or
any other magnetic material. High-pull-force magnets may be
flexible or inflexible. High-pull-force magnets may be made of
sintered metal powder or of metal or any other magnetizable
material.
[0058] A preferred magnetic material for high-pull-force magnets
contemplated within an aspect of the invention is NdFeB. NdFeB is a
more preferred material than ferrous magnets, flexible magnets or
samarium-cobalt magnets. Flexible magnetic strips may be
constructed from magnetic powder such as ferrous or other powder
mixed with polymer bonding material such as rubber-like material.
Samarium-cobalt magnets are less preferred in that they may be more
brittle than other magnets.
[0059] In selecting a high-pull-force magnet, a pull force of about
50 pounds or greater is preferred. A pull force of about 100 pounds
or greater is more preferred since the impact of the magnetic field
will felt at a greater distance from the magnet.
[0060] Neodymium-iron-boride magnets, commonly called "rare earth,"
"NdFeB," or "NIB" magnets, typically meet or exceed residual
inductances greater than about 5,000 gauss, which is preferred.
Residual inductance defines how changing magnetic fields generate
electric currents and is also measured in gauss.
[0061] In order to maximize high pull force, the surface area of a
magnet may be maximized. For example, a 6'' diameter by 2'' thick
cylindrical N38 NdFeB magnet (nominal strength 13000 gauss; pull
force 1042 pounds) may be effective in repelling elasmobranchs at a
range of 6''.
[0062] A plurality of magnets may be employed to repel
elasmobranchs. For example, 1'' cube magnets may be arranged in a
12'' long bar and used to repel elasmobranchs. The cube magnets may
be of any magnetic material capable of producing sufficient
magnetic strength at any distance of interest from the magnet to
repel elasmobranchs.
[0063] Alternatively, a plurality of 1'' cube magnets may be
arranged linearly with a distance between each magnet. The magnets
may be arranged linearly with positive poles facing one another or
may be arranged with positive poles facing negative poles. Smaller
magnets are also effective in repelling elasmobranchs and may
preferably be arranged to maximize surface area presented to an
oncoming elasmobranch.
[0064] Metals with special magnetic properties may be used in
conjunction with permanent magnets in order to maximize or shape
the magnetic flux profile of the magnet and thereby increase the
pull force by directing the magnetic force more powerfully at an
elasmobranch of choice. For example, holmium metal, which possesses
the highest magnetic moment of the known elements, may be used to
optimize the magnetic flux profile. A 1.5'' holmium ring with a
drilled 0.5'' diameter center, coupled to an NdFeB 1.5'' diameter
cylindrical magnet, produced aversive reactions in immobilized
sharks when the holmium end was oriented to the shark's nares.
Other materials that may also be used, among others, for
controlling the shape of the magnetic flux of a magnet may be
gadolinium; pyrolytic graphite; mu-metal (a nickel-iron alloy
comprising copper and molybdenum that has a very high magnetic
permeability and is, therefore, very effective at screening
magnetic fields); and bismuth.
[0065] To protect permanent magnets from corrosion when placed in
water, permanent magnets may be coated with any coating that will
reduce corrosion and preserve the magnetic force of the magnet. For
example, magnets may be coated with nickel, rubber, plastic,
acrylic, enamel, paint or other coating. Nickel-plated NdFeB
magnets are an example of preferred high-pull-force magnets so long
as the coating remains intact.
[0066] It may be desirable to encase a magnet in paint. Black paint
is a preferred paint color to avoid underwater reflections and
flashes of sunlight from the magnet's surface that can act as an
attractant. A magnet may also be enclosed in any waterproof
housing, such as a polymer coating.
[0067] B. High-Pull-Force Magnets in Combination with Hooks
[0068] A non-limiting aspect of the present invention is the use of
high-pull-force magnets to repel elasmobranchs from baited hooks.
Exemplary and non-limiting combinations of a high-pull-force magnet
and a hook are illustrated in FIGS. 1-4. For example, in FIG. 1, an
exemplary and non-limiting circle hook and line (100) are
illustrated wherein a circle hook (140) is attached to a line (150)
along with an exemplary and non-limiting Zone I in the circle hook
and line where a high-pull-force magnet may be placed or affixed.
The preferred region (Zone I) for magnet placement along the line
(150) or shank (142) of the hook is any region wherein the affixed
or placed magnet does not obstruct the hook gap distance (Zone II).
Not more than 20% of the hook gap distance (Zone II) is preferably
obstructed by the magnet such that the hook is not prevented from
being baited or setting in the corner of the mouth of a target
fish. Nevertheless, any arrangement wherein the hook is not
prevented from catching target fish is acceptable. Tapered conical
designs (not illustrated) are contemplated such that the diameter
of the high-pull-force magnet at the hook end is smaller than the
diameter of the high-pull-force magnet at the line end of Zone
I.
[0069] Exemplary and non-limiting combinations of a high-pull force
magnet on a hook and line are illustrated in FIGS. 2A-C. As in FIG.
2A, a high-pull-force magnet (210) may be placed in proximity to a
circle or offset circle hook (240) attached to a line (250) so that
it rests on the hook eye (241) providing an exemplary embodiment
such as the hook-magnet combination embodied at 260. As in FIG. 2B,
a high-pull-force magnet (210) may be placed in proximity to a
circle or off-set circle hook (240) so that it rests on the shank
(242) of the hook providing an exemplary embodiment such as the
hook-magnet combination embodied at 270. As in FIG. 2C, a
high-pull-force magnet (210) may be placed on a circle or offset
circle hook (240) so that it is secured to the outside of the shank
(242) and the hook eye (241) providing an exemplary embodiment such
as the hook-magnet combination embodied at 280. A high-pull-force
magnet may be affixed outside the shank (241) of a hook simply by
the magnetic force of the high-pull-force magnet. Vinyl electric
tape (not illustrated) may be used to secure the high-pull-force
magnet. Black vinyl tape is preferred to reduce reflections of
light.
[0070] High-pull-force magnets may be provided in any shape. It is
preferred that a magnet's shape not significantly obstruct the hook
gap distance (zone II). The magnet may comprise a hole through
which a lead, or gangion, or mainline or other filamentous object
may pass. Exemplary non-limiting shapes may include a cube or block
of any size or other object having at least one plane comprising
four right angles and a hole passing through the object such that
fishing line or other filament may be passed through to affix the
magnet in place on fishing tackle or other object. Alternative,
non-limiting shapes may also include cylindrical or other circular,
oval or oblong three-dimensional shapes having a hole passing
through some portion of the shape. Alternative, non-limiting shapes
may also include a hollow pyramid or a hollow trapezoid.
[0071] Alternative, non-limiting shapes may also include a solid
cube or similar shape, a solid rectangle or similar shape, a solid
bar or similar shape, a solid pyramid or similar shape, a solid
trapezoid or similar shape or any other shape. Magnets may be
shaped as a ring, a trapezoid, a series of trapezoids, a series of
trapezoids arranged in a larger ring pattern, a cone, a tapered
cone, a narrow or wide cylinder or in the shape of a Billy club.
Preferably, the shape when combined with a hook provides a hook in
proximity to a magnet comprising sufficient magnetic field strength
to repel elasmobranchs.
[0072] Exemplary and non-limiting combinations of a high-pull-force
magnet and a hook are also illustrated in FIGS. 3A-C. As in FIG.
3A, a high-pull-force magnet (310) may be placed in proximity to a
j-hook (340) on a line (350) such that it rests on the hook eye
(341) providing an exemplary embodiment such as the hook-magnet
combination embodied at 360. As in FIG. 3B, a high-pull-force
magnet (310) may be placed in proximity to a j-hook (340) such that
it rests on the shank (342) of the hook providing an exemplary
embodiment such as the hook-magnet combination embodied at 370. As
in FIG. 3C, a high-pull-force magnet (310) may be placed on a
j-hook (340) such that it is secured to the outside of the shank
(342) and the hook eye (341) providing an exemplary embodiment such
as the hook-magnet combination embodied at 380. As described above
in the illustration of FIG. 2, magnets may be provided in any
shape.
[0073] Exemplary and non-limiting combinations of magnet and hook
are also illustrated in FIGS. 4A-B. In FIG. 4A, a high-pull-force
magnet (410) may be placed in proximity to a treble hook (440) on a
line (450) such that it rests on the hook eye (441) providing an
exemplary embodiment such as the hook-magnet combination embodied
at 460. As in FIG. 4B, a magnet (410) may be placed in proximity to
a treble hook (440) such that it contacts the shank (442) of the
hook providing an exemplary embodiment such as the hook-magnet
combination embodied at 470.
[0074] A hook in accordance with the invention may be any hook that
is capable of catching target fish. The hook may comprise stainless
steel, steel, galvanized metals, ferromagnetic metals or any other
material, metallic or plastic or any other composite.
[0075] A high-pull-force magnet in accordance with an aspect of the
invention may comprise any magnetic material.
[0076] C. High-Pull-Force Magnets on Longlines
[0077] An exemplary and non-limiting method of repelling
elasmobranchs involving repelling elasmobranchs from longlines in
accordance with the invention is illustrated in FIG. 5. A longline
(500) may be deployed from a boat (561) to fish for a target fish
of interest. The main line (550) of the longline may be attached to
a buoy (520) and at a set distance from the buoy may be attached to
an anchor (562). A set of gangions (530) with hooks (540) may be
attached to the mainline beginning at the anchor (562) and may be
spaced sufficiently to limit interaction between individual gangion
lines (530). Each hook may have a magnet (510) mounted resting on
the hook eye (541). Alternatively, the magnet may be mounted on a
hook shank (542) or may be secured to the outside of the hook
(540). The hooks may be baited. The longline may be a demersal
longline such that the main line is proximal to the ocean or
otherwise water's floor. The longline may be a pelagic long line,
such that the main line is nearer to the surface of the water,
suspending in the water column, typically at about 100 to about 500
feet below the surface. In the aspect of the invention where the
longline is a pelagic longline, anchors (562) may have less weight
or may be absent from the longline apparatus. The longline may also
be a semipelagic longline wherein the mainline is further down the
water column from the surface as compared to a pelagic line but is
not proximal to the water's floor or is not proximal to the water's
floor on at least one end of the longline. Use of magnets with
longlines reduces by-catch of elasmobranchs.
[0078] Longlines comprising magnets may be handled in the
commercial environment in a manner similar to those practices known
in the art of longline commercial fishing. Because hooks must be
carefully managed to control tangling and hooking of objects on a
longlining boat, including other portions of the tackle of the
longline, commercial fishing operations and those of skill in the
art will recognize how to handle longlines with hooks.
High-pull-force magnets on longlines likewise may be handled in the
same manners as one would consider appropriate in the art to avoid
entanglements of magnets or magnets sticking together. The
long-distances between gangions (often more than 100 feet) allow
for commercial fishing operators to provide sufficient distance
between magnets to avoid the magnets sticking together during
fishing or during handling of tackle. Further, high-pull-force
magnets used for longlines are of sufficiently small size and
magnetic force that the magnets may be separated from one another
by hand if they do become stuck together.
[0079] As described above, high-pull-force magnets of any size may
be used in combination with a longline hook so long as the target
fish may be caught on the hook. An exemplary high-pull-force magnet
on a longline hook may be 2''.times.25''.times.2''. Smaller
high-pull-force magnets are also acceptable. High-pull-force
magnets of less than 0.5'' cubed may be appropriate for smaller
hook settings. Smaller high-pull-force magnets having sufficiently
powerful magnetic fields such as N48 grade NdFeB are more
preferred.
[0080] D. High-Pull-Force Magnet Repellents on Buoys, Nets and
Barges
[0081] An exemplary and non-limiting method of repelling
elasmobranchs with a high-pull-force magnet or a plurality of
high-pull-force magnets placed on a buoy or barge or net is
illustrated in FIGS. 6A-B. Buoys with high-pull-force magnets as
their weighted bases are shown as element 660 and 661 in FIG. 6A.
The floating portion of the buoy (620) allows the buoy to float
while the high-pull-force magnet portion of the buoy (610) remains
in the water because of its weight. A series of buoys comprising
high-pull-force magnets may be placed in a region to repel
elasmobranchs or may be placed around a swimming area or rescue
area to repel elasmobranchs. A series of buoys with high-pull-force
magnets may be accompanied by a series of high-pull-force magnets
submerged (611) in an area of interest, such as a swimming area. As
illustrated in FIG. 6B, very large high-pull-force magnets may be
placed on a large floating barge (670) comprising a high-pull-force
magnet (610).
[0082] An exemplary and non-limiting device for repelling
elasmobranchs with a plurality of magnets is illustrated in FIG. 6A
as element 600, an elasmobranch repelling net apparatus. Buoys (660
and 661) may be employed to float a net (650) comprising a series
of magnets (640) held within the net and magnetic rings (630)
holding the ropes of the net together. The net may be strung to the
bottom of the water column using weighted magnets (611). The net
may be anchored to a specific location to provide a physical
barrier. The net may provide a curtain of magnetic field to repel
elasmobranchs from an area or to keep elasmobranchs from entering
an area of interest, such as a swimming or working area. A net
(650) comprising magnets such as those illustrated as elements 610,
611, 630 and 640 may also be used to trawl for fish, shrimp or
other aquatic species. In another non-limiting aspect of the
invention, high-pull-force magnets may be placed in aquaculture
cages to repel sharks from predation or scavenging of cultured
stock. High-pull-force magnets are useful to prevent damage by
elasmobranchs to aquaculture cages, nets or other equipment.
[0083] E. Surfboard Fitted with High-Pull-Force Magnet
[0084] A non-limiting repelling device in accordance with the
invention may comprise a surfboard comprising a high-pull-force
magnetic device. FIG. 7A illustrates exemplary surfboards in
accordance with an aspect of the invention. A surfboard (720) may
comprise a high-pull-force magnetic device such as a permanent
high-pull-force magnet (710) imbedded, affixed, attached or
otherwise associated in any manner contemplated by one of skill in
the art with the surfboard. A permanent high-pull-force magnet may
be pressed into a space drilled into the surfboard (730). It may
also be affixed with glue, waterproof tape, Velcro or any other
mechanism known in the art now and hereafter.
[0085] In an alternative non-limiting example in FIG. 7B, a
surfboard (750) may comprise a high-pull-force magnet or plurality
of high-pull-force magnets in association with one another wherein
the high-pull-force magnet or magnets are capable of spinning when
placed in water (740). Such a spinning high-pull-force magnet (740)
may comprise individual magnets attached to a hub (770) that is
attached to an axle (760) to allow free spinning of the
high-pull-force magnet or magnets attached to the surfboard (750)
when water current is present.
[0086] A high-pull-force magnet may be enclosed in the body of a
surfboard or other watercraft or may be trailed behind a surfboard,
other watercraft or swimmer.
[0087] F. High-Pull-Force Magnet Repellents on Swimming and Diving
Clothing and Accessories
[0088] One exemplary non-limiting aspect of the present invention
comprises a magnetic material for producing a magnetic field near a
swimmer or diver or other person or object in an elasmobranch
environment.
[0089] High-pull-force magnets, such as, for example,
high-pull-force NdFeB magnets or other high-pull-force permanent
magnets may be worn as a bracelet or a band or otherwise placed in
proximity of a person or object. An increase in the number of
high-pull-force magnets and an increase in the grade of
high-pull-force magnets that may be worn increases the magnetic
field around the wearer and increases the repelling activity of the
bracelet, band or other magnet article. Research on captive nurse
sharks suggests that such a bracelet is effective in repelling
sharks. Using a vinyl-walled tank, high-pull-force magnets were
waved outside the tank wall near a resting nurse shark inside the
tank. The shark had no olfactory, motion, sound, or visual clues.
In seven separate observations, the nurse shark always rapidly fled
from its resting site once the high-pull-force magnet was waved on
the tank wall near the subject.
[0090] In a non-limiting example, an omnidirectional permanent
magnetic field may be affixed or arranged near a subject or object
exposed to an elasmobranch environment. The permanent magnetic
field may be generated from, for example, a permanent magnet or an
electromagnet. A permanent magnet may be affixed, for example, to
any portion of a swimmer's or diver's body such as the head, the
leg, the arm, the torso, the ankle, the wrist, or any other
portions of the body.
[0091] FIGS. 8A-C illustrate non-limiting examples of permanent
high-pull-force magnets (810) attached to a belt (801) (FIG. 8A) or
bracelet (802) (FIG. 8B) or flippers (803) (FIG. 8C).
[0092] FIG. 9 illustrates a variety of non-limiting alternative
designs for bracelets, belts or rings constructed solely from
high-pull-force magnets. A plurality of bar magnets (981) (982)
(983), larger spherical magnets of varying sizes (984) or smaller
spherical magnets (985) may be shaped into a bracelet or belt. A
plurality of discs (986) may be shaped into a bracelet or a belt or
any shape that keeps the magnets in proximity to the body. Two
concave bar magnets (987) may be placed on the ankle or wrist
opposite each other such that they are held in place on the ankle
or wrist by attractive magnetic forces.
[0093] The bracelets in FIG. 9 may be flexible and may be modulated
to fit a portion of the body. Individual magnets of the bracelet
may be easily separated and placed on the ankle or wrist.
[0094] The disks (986) may be magnetized on their edges and not
magnetized on their faces. As such, the disks may be assembled as a
ring using magnetic connections on their edges. The disks may be
manipulated and may be returned to a circle. As such, they may
conform to a ring to attach to any type of clothing, equipment or
body part to which a ring may be attached.
[0095] High-pull-force magnets may likewise be attached to clothing
or water accessories such as swim trunks, wet suits, headbands,
flippers, goggles or other piece of clothing or accessory.
High-pull-force magnets may be sewn into such clothing or may be
affixed with tape, glue, Velcro or any other mechanism for affixing
to clothing or accessories for swimming, diving or otherwise
working or playing in water.
[0096] Many human-shark interactions in shallow water, especially
around the State of Florida in the United States, are hypothesized
to be "mistaken identity" by the shark in water with poor
visibility. The blacktip shark (C. limbatus) and nurse shark (G.
cirratum) are often implicated in these encounters. The sharks do
not have an olfactory clue in most of these "mistaken identity"
cases. A series of high-pull-force magnets, such as NdFeB
high-pull-force magnets or other strong permanent high-pull-force
magnets, may be used as means to repel the shark as it approaches
within a few inches of the magnets. With a strong high-pull-force
magnet, such as NdFeB, or an increased number of high-pull-force
magnets, to increase magnetic field strength, repellent activity
increases and the chance that a shark will be repelled prior to an
investigatory bump or bite is greatly increased.
[0097] The invention is further described with the following
non-limiting examples, which are provided to further illuminate
aspects of the invention.
EXAMPLES
Example 1
Pull Force of High-Pull-Force Magnets
[0098] Some of the high-pull-force magnets that have been used in
examples in this application are listed below in Table 1 with
calculation of the pull force of the respective high-pull-force
magnets based on the geometry, size, grade and nominal strength
(conservative BR) of the high-pull-force magnet.
TABLE-US-00001 TABLE 1 Conservative Pull Force Geometry Size Grade
Br (Gauss) (pounds) Puck 4'' .times. 1.5'' N38 13000 521 magnet Bar
6'' .times. 2'' .times. 0.5'' N48 13800 191.31 Hollow 1'' .times.
1'' with 3/16'' N42 13200 72.75 cylinder hollow center 2 stacked
0.472'' .times. 1.97'' .times. N50 14100 46.7 hollow 0.24'' hollow
cylinders center Cube 1'' .times. 1'' .times. 1'' N48 13800 110.5
longlines
[0099] Pull force is descriptive of the attractiveness of a magnet
to a steel flat surface. A shark is not a magnetic steel surface,
but it does have a surface (likely the ampullae of Lorenzini) that
interacts with the magnetic field of the magnet. As such, pull
force is an appropriate method for measuring interaction of an
elasmobranch with a magnetic field.
Example 2
High-Pull-Force Magnets as Repellents on Longlines
[0100] The following example demonstrates the elasmobranch
repellent activity of high-pull-force magnets of greater than about
150 pounds of pull force on long lines. High-pull-force magnet
treatments were evaluated on one demersal longline located in the
middle of a large lagoon. Adjacent longlines in the same lagoon
produced large shark catch (generally greater than two sharks over
the 15 hooks on a line).
[0101] Seven hooks on a demersal longline of about 1000 feet were
treated with 2''.times.0.25''.times.2'' NdFeB N48 magnets (nominal
force 14,000 gauss; pull force about 161 pounds). The
high-pull-force magnets were secured at even-numbered hooks on the
longline, directly above the eye of the hook and strapped to the
gangion leader with black vinyl electrical tape. All hooks received
bait. If the bait was lost during the experiment, the hook was
re-baited while the high-pull-force magnets were not removed or
replaced; only the bait was exchanged.
[0102] A large nurse shark of about 250 cm was captured on a
control hook (hook with no magnet affixed) after a second re-bait.
From earlier longline trials at this spot, a much higher nurse
catch was expected on this line, especially since the
high-pull-force magnets acted as weights and held the baits closer
to the sea floor. However, only one nurse shark was caught. As
such, it is believed sharks were repelled from the entire longline
by the series of high-pull-force magnets affixed thereto.
TABLE-US-00002 TABLE 2 1.sup.st Set 2nd Re- Hook Treatment Bait
Bait bait Bait Species Caught 1 None Barracuda Barracuda Tuna 2
Magnet Barracuda Barracuda Barracuda 3 None Barracuda Barracuda
Barracuda 4 Magnet Barracuda Barracuda Tuna 5 None Barracuda
Barracuda Tuna 6 Magnet Barracuda Barracuda Tuna 7 None Barracuda
Barracuda Tuna 8 Magnet Barracuda Barracuda Tuna 9 None Barracuda
Barracuda Tuna 10 Magnet Barracuda Barracuda Tuna 11 None Barracuda
Barracuda Tuna 12 Magnet Barracuda Barracuda Tuna 13 None Barracuda
Barracuda Tuna Nurse, 250 cm 14 Magnet Barracuda Barracuda
Barracuda 15 None Barracuda Barracuda Tuna
Example 3
High-Pull-Force Magnets as Repellents on Longlines
[0103] The following example demonstrates the elasmobranch
repellent activity of high-pull-force magnets of greater than 50
pounds of pull force on long lines. A first demersal longline with
eight hook sets was baited with barracuda flesh and placed in open
water. No high-pull-force magnets were placed on the hooks. Five
sharks were captured on the longline over 24 hours representing 5
separate shark species ranging in size from 97 cm to 240 cm. See
Table 3.
TABLE-US-00003 TABLE 3 Hook Species 1 1. Tiger (F), 235 cm 2. Nurse
(F) 231 cm 3. Sharpnose (F), 97 cm 2 3 4 Nurse 240 cm 5 6 7 8 9 10
11 12 13 14 Blacknose 115 cm 15
[0104] A second demersal longline with fifteen hook sets was baited
with squid and placed in the same position in open water as the
first demersal longline discussed above for 67 hours. The trial
with the second demersal longline was run three months after the
trial with the first demersal longline. Seven of the fifteen hooks
were treated with 1''.times.1''.times.1'' neodymium-iron-boride
grade N48 cube magnets (pull force of about 110 pounds; nominal
force around 14,000 gauss) with the high-pull-force magnet secured
to the outside of the hook shank using the magnetic force of the
hook and black vinyl electric tape. All hooks received bait. During
re-baits, the high-pull-force magnets were not removed or replaced;
only the bait was exchanged.
[0105] Two small sharks were caught on the second demersal
longline. A blacknose shark of 110 cm was caught on a control line
with no magnets. A sharpnose shark of 80 cm was caught on
high-pull-force magnet line. The large decrease in shark catch
between the first demersal longline trial (five relatively large
sharks for their species) and the second demersal longline trial
(two relatively small sharks) was ascribed to the presence of
magnets along the longline. See Table 4.
TABLE-US-00004 TABLE 4 Hook # Trtmt Bait Species Caught 1 control
squid 2 magnet squid 3 control squid 4 magnet squid 5 control squid
6 magnet squid sharpnose 80 cm 7 control squid blacknose 110 cm 8
magnet squid 9 control squid 10 magnet squid 11 control squid 12
magnet squid 13 control squid 14 magnet squid 15 control squid
[0106] A third demersal longline was set with 15 hooks in the same
position as the first and second demersal longlines discussed
above. The third demersal longline was set within a day of the
second demersal longline. Seven of the eight hooks were fixed with
magnets at the same position. Magnets were small NdFeB grade N50
hollow cylinders (12 mm outer diameter.times.6.1 mm inner
diameter). Two magnets were placed on each hook creating a total
magnet length of 50 mm. Together the magnets have a pull force of
about 47 pounds and a nominal force of 14,100 gauss. The demersal
line was placed in the same open water position as both demersal
lines in Example 3. Within a 24-hour period, 3 large (>200 cm)
tiger sharks were captured, 2 on magnet treatments. The smaller
(less powerful) magnets did not repel tiger sharks.
[0107] Since a larger number of sharks (and of larger size) were
caught on the first and third longlines, the three trials presented
in this example demonstrate that sharks were repelled from the
second longline comprising magnets of sufficient magnetic strength
to repel sharks. Together, the three longline trials contained in
this example demonstrate repelling of sharks by magnets of
sufficient magnetic strength to repel sharks across a longline.
Example 4
High-Pull-Force Magnet Terminates Tonic Immobility at Greater Than
30 cm Distance
[0108] Preliminary research conducted on the effects of specific
magnetic fields on shark behavior suggests that weak magnetic
fields (0.3-0.5 Gauss) produced by electromagnets had no
significant repelling effect on juvenile nurse sharks,
Ginglymostomata cirratum, and juvenile lemon sharks (Negaprion
brevirostris) under tonic immobility, however, very strong magnetic
fields (i.e. about 14,000 Gauss or 1.4 Tesla) produced by large
(4'' diameter.times.1.5'' height) "rare earth" magnets
(neodymium-iron-boride; NdFeB) (13000 gauss, pull force of 521
pounds) had a significant repelling effect on both shark species at
distances of 0.3 m or less. Additional experiments on captive
sharks in an offshore, sandy bottom, fenced-in enclosure were done
with NdFeB high-pull-force magnets buried under the sand. Exposure
of the sharks to the buried magnets resulted in "violent
reorientation" as the captive sharks came into proximity of the
buried high-pull-force magnets.
Example 5
Y-Maze Preference Bioassays
[0109] A Y-maze was constructed to establish a preference test to
determine the repellent activity of magnets on elasmobranchs. The
maze was constructed of three sections of clear acrylic 8 inch
diameter tubing, connected at 33.degree. angles to form a Y-shape.
Slotted guides were secured to the entrances of each tube, to allow
the insertion of a moveable door, which obstructs one exit. The
entire maze was submerged in a test tank. Sharks were allowed to
freely enter the maze and exit the maze. A high-pull-force magnet
was placed, south pole facing the maze junction, in an obstructed
leg of the maze, preventing an exit from the maze in that direction
if that obstructed leg is chosen. The diameter of the tubing was
sufficient to allow juvenile nurse sharks, juvenile lemon sharks,
and juvenile wobbegong sharks to enter and pass through, but it was
small enough to prevent the specimen from turning around within the
tube.
[0110] For each trial, uncooked shrimp were used as a reward, and
the south pole of a 4'' diameter NdFeB nickel-coated cylindrical
high-pull-force magnet (pull force 521 pounds; nominal force about
13000 gauss) was placed in the obstructed leg. One shrimp was
positioned midway into the entrance tube to entice the shark to
enter the maze. Two shrimp were placed midway into the exit tube,
and two shrimp were placed midway into the tube containing the
magnet. When the shark entered the maze and reached the Y-junction,
the shark was presented with approximately the equal odor gradient
from the shrimp in the exit tube and the tube containing the
magnet. If the shark chose the maze without the high-pull-force
magnet, it was rewarded with two additional shrimp as it exited. If
the shark chose the maze with the high-pull-force magnet, it was
subjected to an exponentially-increasing magnetic field as it moved
down the tube. The shark could only physically back out of the
high-pull-force magnet tube and into the junction. Sharks that
moved into the magnet and attempted to back out were visible
traumatized. Feeding observations regarding the two shrimp in the
high-pull-force magnet tube were made.
[0111] Each trial was scored as follows:
TABLE-US-00005 +1 Subject enters the maze +1 Subject exits the maze
+1 Subject takes the first reward shrimp just after entry (teaser)
+2 The unobstructed path is chosen at the junction +3 At least one
reward shrimp in the unobstructed path is taken -2 The obstructed
path is chosen (magnet) at the junction -3 The specimen enters more
than 6'' into the obstructed path and is visibly struggling.
[0112] A perfect score=7 for each trial. If a shark became
traumatized and requires removal from the maze for its own safety,
a score is calculated up to the point of the rescue. A rescue is
made whenever a subject appears to be highly distressed, and a
physical injury is likely.
[0113] For example, a nurse shark entered the maze, took its first
reward shrimp, and immediately chose the unobstructed path. As it
exited, it took its two reward shrimp, and exited the maze without
a change in behavior.
Score=1+1+2+3=7
[0114] In another example, a nurse shark entered the maze and took
its first reward shrimp. It chose the obstructed path but was
repelled by the magnet. The shark backed up into the Y-junction;
reoriented itself; and exited the unobstructed path without taking
the two shrimp available in the unobstructed path.
Score=1+1-2+1=1
[0115] In yet another example, a lemon shark entered the maze and
took its first reward shrimp. It chose the obstructed path, and
then continued down the magnet to within 6'' of the magnet. It
became extremely distressed and a rescue was made.
Score=1+1-2-3=-3
[0116] In an investigation, three nurse sharks were subjected to
the maze. Shark 1 was subjected to the maze five times. Shark 2 was
subjected to the maze 5 times but only entered the maze 4 times.
Shark 3 was subjected to the maze once but required rescue when it
encountered the magnet and subsequently died, apparently from
stress related to exposure to the magnet. The magnet in the
obstructed maze was a 4''.times.1.5'' cylindrical NdFeB magnet of
grade N48 (13000 gauss, 521 pounds pull force). The results are
contained in Table 5.
TABLE-US-00006 TABLE 5 Obstruction Nurse 2 Exit Nurse 1 (Lg.)
(Med.) Nurse 3 Trial 1 L 1 1 -4 Trial 2* L 5 1 (rescue Trial 3 R 4
3 performed) Trial 4 L 4 4 Shark would Trial 5 R 5 Did not enter
not re-enter maze in subsequent trials
[0117] The data suggest that Nurse 1 has learned to navigate the
maze, retrieve a reward, and exit without distress. Nurse 2 appears
to be learning, but did not re-enter on the fifth trial. Nurse 3
had to be rescued. It was notably distressed by the magnet.
Unfortunately, Nurse 3 did not eat after this experience, and
subsequently died at about 30 days after the experiment. We did not
observe any external injuries on Nurse 3. We attribute this to
stress and possibly shock from encounter with the high-pull-force
magnet in the maze.
Example 6
N48 Neodymium-Iron-Boride (NdFeB) Nickel-Coated Permanent Magnet
Terminate Tonic Immobility
[0118] Juvenile lemon sharks (Negaprion brevirostris) and juvenile
nurse sharks (Ginglymostoma cirratum) that had been placed in tonic
immobility were subjected to the magnetic field of an N48
neodymium-iron-boride (NdFeB) nickel-coated 4''.times.1.5''
cylinder permanent high-pull-force magnet and were observed. The
high-pull-force magnet had the following characteristics:
TABLE-US-00007 Calculated Pull Force 521 pounds Residual Induction:
14 KGs Coercive Force: 11.0 KOe Intrinsic Coercive Force:
.gtoreq.12.0 KOe Maximum Energy Produce: 48 MGOe Curie Temperature:
320.degree. C.-330.degree. C. Vickers Hardness: 500-600 Working
Temperature: <-80.degree. C. Temperature Coefficient -0.11% per
.degree. C.
[0119] A DC milligauss magnetometer (Alpha Labs, Inc.) was used to
record magnetic field strength during the study. The magnetometer
sensor was secured to the top of a nonmagnetic 1/2'' polyvinyl
chloride stake, which was driven vertically into the sand at the
test site. The magnetometer sensor was submerged for the study.
Water depth did not exceed 36'' at the test site. A meter-long rule
was secured to the magnetometer sensor.
[0120] A control test was preformed in order to determine if the
activated magnetometer sensor would terminate tonic immobility. The
magnetometer was set to zero to compensate for the background
magnetic field of the earth, which allowed fluctuations from the
permanent magnet to be measured. A juvenile female lemon shark in
tonic immobility was held directly at the magnetometer sensor.
Tonic immobility did not terminate. The magnetometer readings did
not fluctuate when the lemon shark was in proximity to the sensor
demonstrating no change in magnetic field strength.
[0121] Two 4'' cylindrical N48 grade NdFeB nickel-coated permanent
high-pull-force magnets (nominal strength 14000 gauss, pull force
about 521 pounds) were calibrated by observing the magnetic field
strength versus distance from the magnet under water. The following
data were recorded:
TABLE-US-00008 TABLE 6 Distance milliGauss (mG) 1.5 m +191 1.0 m
+524 0.9 m +700 0.8 m +920 0.7 m +1310 0.6 m >+2000
Because the maximum reading of the magnetometer used in the
experiments was 2000 mG, magnetic fields at distances less than 0.6
m from the magnet were calculated using a standard gauss
calculation for a cylindrical magnet. In this case, we used the
calculator provided at
www.arnoldmagnetics.com/mtc/calc_gauss_cyl.htm. The following
parameters were in-put into the magnetic field calculator: L=4 in.;
D=1.5 in; Br=13,000 G; Z=distance from magnet.
[0122] With a juvenile shark subject to tonic immobility at the
magnetometer sensor, the permanent magnet was moved along a
stationary rule, level with the shark and the sensor, towards the
shark. The high-pull-force magnet was not moved faster than 0.1 m/s
toward the shark. The following results were obtained for
termination of tonic immobility. (Note: +denotes the north pole,
electrically on the gaussmeter.)
TABLE-US-00009 TABLE 7 Magnetic Distance (m) Pole to terminate
Facing tonic Specimen Shark immobility Calculated mG Juvenile lemon
shark, + 0.1 246971 Juvenile lemon shark, - flipped + 0.0 3130415
Juvenile nurse shark, - 0.3 14477 Juvenile nurse shark, + 0.3 14477
Juvenile nurse shark, + 0.2 44154 Juvenile nurse shark, - 0.2 44154
Juvenile nurse shark, + 0.2 44154 Juvenile nurse shark, + 0.2
44154
[0123] Since the movement of the permanent high-pull-force magnet
underwater induces an electrical current, the next study moved the
tonic shark toward two stationary high-pull-force magnets, each
fixed at 1.5 m from the sensor. Tonic immobility was terminated
when the sharks were brought within 0.2 m of the high-pull-force
magnet faces.
[0124] It was consistently observed that tonic sharks awoke by
turning away from the magnet's face. This was independent of the
pole of the high-pull-force magnet, and the orientation of the
shark's head toward the magnet. More violent responses occurred
when the shark's head was oriented 90 degrees to the
high-pull-force magnet face, rather than 0 degrees (nose-to-magnet
face).
[0125] The movement of the shark toward the high-pull-force magnet,
as well as the movement of the high-pull-force magnet toward the
shark might create electric current and awaken the shark. To
eliminate this possibility, care was taken not to move the
high-pull-force magnets in a rapid manner.
Example 7
Electromagnetic Device with Lower Magnetic Strength Did Not
Terminate Tonic Immobility
[0126] In a first experiment using an electromagnetic device, an
iron-core electromagnet was secured to the end of a PVC pole, and
energized with 12VDC using a marine wet-cell battery. Current was
monitored using a digital multimeter. A tonic juvenile female lemon
shark was held at the magnetometersensor, while the tip of the
electromagnet was moved. The following results were obtained:
TABLE-US-00010 TABLE 8 Distance between AMPS to shark and
electromagnet @ Measured Shark's electromagnet 12 VDC mG Response
1.0 m 6.27 A -10 Did not awaken 0.5 m 6.28 A -139 Did not awaken
0.0 m 6.24 A -1700 Did not awaken 0.0 m 6.16 A (reversed polarity)
>2000 Did not awaken
[0127] In a second experiment using an electromagnetic device, a
commercial 1000 lb.-strength waterproof electromagnet, produced by
LOCKNETICS, INC., was energized with 12V DC using a marine wet-cell
battery. According to the product specifications, this magnet draws
a consistent 30 A at 12VDC, which exceeded the capability of the
digital multimeter. A tonic juvenile female lemon shark was held at
the magnetometersensor, while the face of the electromagnet was
moved. The following results were obtained:
TABLE-US-00011 TABLE 9 Distance between AMPS to lemon shark and
electromagnet @ Measured Lemon shark's electromagnet 12 VDC mG
Response 1.5 m 30 A -20 Did not awaken 1.0 m 30 A -40 Did not
awaken 0.5 m 30 A -280 Did not awaken 0.5 m 30 A, but flickered
-280 Did not awaken powered randomly instead of a constant supply
0.0 m 30 A >2000 Did not awaken 0.0 m 30 A reversed polarity
>2000 Did not awaken randomly
[0128] These two experiments demonstrate that despite strong
electromagnetic fields in close proximity, such fields were not
sufficient to terminate tonic immobility in juvenile nurse sharks
and lemon sharks. The magnetic field strength was not sufficient to
terminate tonic immobility.
[0129] However, as seen above, a powerful field from an NdFeB
permanent high-pull-force magnet is sufficient to terminate tonic
immobility in juvenile nurse sharks and lemon sharks. It is
believed that a field strength of approximately 50 G at least 0.1 m
distance from am elasmobranch reliably terminates tonic immobility.
50 gauss is about 100 times the Earth's magnetic field.
Example 8
Bracelet, Belt or Other High-Pull-Force Magnet as Repellent of
Shark
[0130] Two lemon sharks in an outdoor pen were placed in tonic
immobility. A blinder was placed between the sharks and a magnet
having about 191 pounds of pull force and a nominal strength of
about 14000 gauss. Upon introducing the magnetic bar up to about
0.2 meters behind the blind, tonic immobility was terminated and
the sharks violently moved in orientation away from the
high-pull-force magnet.
Example 9
Bracelet as Repellent of Shark
[0131] Research on captive nurse sharks suggests that a
high-pull-force bracelet is effective in repelling sharks. Using a
vinyl-walled tank, high-pull-force magnets were waved outside the
tank wall near a resting nurse shark inside the tank. The shark had
no olfactory, motion, sound, or visual clues. In seven separate
observations, the nurse shark always rapidly fled from its resting
site once the high-pull-force magnet was waved on the tank wall
near the subject. When non-magnetic objects were waived at the same
position outside the tank, no change in behavior was observed.
Example 10
Target Fish not Repelled by High-Pull-Force Magnets
[0132] Preliminary research conducted on the effects permanent
magnetic fields on adult cobia, Rachycentron canadum, suggests that
very strong magnetic fields (i.e. >14,000 Gauss or 14 Tesla)
produced by "rare earth" magnets (NdFeB) (13,800 gauss, 110 pounds
pull force) had little effect on cobia during feeding. Digital
video of cobia feeding within 5 cm of the "rare earth"
high-pull-force magnet was recorded. In three trials sardines were
offered to the cobia on PVC tubes with no magnets inside. In three
subsequent trials sardines were offered on PVC tubes with a
high-pull-force magnet inside. The high-pull-force magnet was
composed of 4 discs (1'' diameter.times.1/441 height) stacked on
top of each other with Teflon.TM. rings between each magnet.
[0133] In another control test, squid was presented to yellowfin
tuna in the presence of an NdFeB high-pull-force magnet of grade
N48. A horizontal pole with six squid (and a corresponding
high-pull-force magnet) hung equally spaced along the pole was
presented to the tuna. The pole was lowered into the tank. The tuna
took the bait in the presence of the high-pull-force magnets. The
tuna were not repelled.
[0134] The ability to selectively repel elasmobranch is useful both
for longline fishing applications (to catch target fish and avoid
killing elasmobranch) and for human applications, particularly for
divers and snorkelers (to repel elasmobranchs and not repel
fish).
* * * * *
References