Patent Abstract:
a fishing hook with elasmobranch - repelling qualities is disclosed . the fishing hook , comprised of a ferromagnetic material , is rendered repellent to elasmobranchs through the incorporation of an exterior coating of an electropositive metal , and contact or impulse magnetization .

Detailed Description:
“ by - catch ” is any kind of fish that is caught in a fishing operation wherein the catching of 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 . “ 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 orectolobiformes ( carpet sharks ). “ electropositive ” in this specification means possessing a revised pauling electronegativity of less than 1 . 3 . examples of an electropositive metal suitable for use in the present invention are a lanthanide ( also referred to as lanthanoid ) metal , a group 1 metal , a group ii metal , a group iii metal , magnesium metal , or an alloy of electropositive metals . “ ferromagnetic ” in this specification means capable of retaining a magnetic characteristic after exposure to another magnetic field . alloys of iron , cobalt , and many steels possess this property . within ferromagnetic materials , the spin of unpaired electrons are aligned in the same direction . also , a greater - than - average number of magnetic domains containing these aligned electrons are also aligned in the same direction , creating a net moment . this moment creates the familiar “ north ” and “ south ” poles of a permanent magnet or a ferromagnetic material . “ gauss ” is a measure of magnetic field strength . gauss is a unit of the density of a magnet &# 39 ; 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 . “ 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 &# 39 ; 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 . “ hook ” in this specification refers to a metal fishing hook for marine use . fishing hooks are further divided into specialized shapes depending on the type of prey sought , such as circle hooks , j - hooks , and treble hooks . the metals used in the manufacture a fishing hook typically include steel or stainless steel , and optionally include cadium , tin , zinc , gold , or nickel platings . “ 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 . “ 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 . “ 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 . while not wishing to be bound to a specific physiological mechanism , the inventor hypothesizes that weakly magnetized materials are capable of repelling elasmobranchs more efficiently than high pull force magnets . in recent experimentation with captive juvenile lemon sharks ( n . brevirostris ) and free - swimming blacktip sharks ( c . limbatus ) magnetic fluxes of 0 . 6 gauss to 100 gauss measured at the hook were effective in reducing shark captures when compared to nonmagnetized control hooks . the inventors hypothesize that very high pull force magnets , particularly grade n38 and higher neodymium - iron - boride magnets , may be too strong to achieve consistent repellency with elasmobranchs . for example , rare earth magnets are capable of producing thousands of gauss near their surfaces . this is thousands of times greater than the earth &# 39 ; s geomagnetic signature that is observed around 500 milligauss . the presence of an overly powerful permanent magnetic flux may be so “ unnatural ” to an elasmobranch &# 39 ; s ampullary organ that the organ does not register the effect at all , or nullifies it rather than produce an aversion signal . in contrast , a weakly magnetized steel fishing hook may only produce 100 gauss at its surface , and this is only 200 times stronger than the earth &# 39 ; s geomagnetic signature . this effect was observed using the tonic immobility bioassay with juvenile lemon sharks ( n . brevirostris ). the sharks terminated tonic immobility more often when weakly magnetized hooks were presented versus powerful rare earth magnets . the strength of the magnetic flux decreases with the inverse cube of the distance from the magnetized hooks surface . a shark would experience less than 10 gauss only a few inches from the magnetized hook . cobalt and iron are examples of ferromagnetic elements at room temperature . steel , low - austenitic stainless steels , samarium - cobalt , sendust , neodymium - iron - boride , permalloy , supermalloy , alnico , bismanol , cunife , heusler alloy , and fernico are examples of room - temperature ferromagnetic alloys . some ferromagnetic materials , are strong enough to be used directly as a fishing hook . steel and 400 - series stainless steels are examples of materials suitable for use as the entire fishing hook . soft alloys , such as bismanol , do not possess this structural integrity and therefore are more useful as a coating or external treatment on an existing fishing hook . a nonmagnetized ferromagnetic hook is made magnetic by exposing the hook to another permanent magnet or an energized electromagnet . preferably , the nonmagnetized hook is placed in physical contact with a permanent magnet , such as a barium - ferrite ceramic magnet . a nonmagnetized ferromagnetic hook may also be magnetized by placing it in close proximity to an electrified coil , commonly found on electromagnets . the magnetization process is nearly instantaneous and is reversible by heating above the curie temperature , repeated mechanical shock , or degaussing equipment . weakly magnetized hooks are also desirable to fishermen for four reasons . first , in many commercial fisheries , sharks comprise a significant portion of by - catch . more by - catch equates to less target fish and potential loss of income and tackle . for this reason , it is very desirable for fishermen to have a shark by - catch reduction device which does not affect the target fish . permanent magnets fulfill this requirement . secondly , there is no additional tackle in the form of permanent magnets to store and rig onboard a moving metallic vessel . the present invention saves storage space and reduces vessel weight . third , since the hook is only weakly magnetized , the tendency for the hooks to entangle and attach to other metal surfaces is greatly reduced . this makes handling magnetized metals on a metal vessel much easier than having a plurality of permanent magnets to contend with . finally , if a ferromagnetic fishing hook , such as a steel circle hook , is used , there is no significant additional expense to the fishermen to magnetize the hook other than their time . this eliminates the expense of purchasing permanent magnets to achieve the same effect . the second component of the magnetoelectropositive hook incorporates the use of an electropositive metal on or within the hook material . the pure metal ( ground state ) form of praseodymium , neodymium , cerium , samarium , ytterbium , or magnesium metal is particularly effective at inducing aversive behavioral responses in juvenile sharks . for reasons not yet fully understood , elasmobranchs , particularly those of the order carcharhiniformes , exhibit aversive behavior within a 0 . 2 meter range of these electropositive metals . we first observed the unusual repellent effects of lanthanide metals on sharks when tonically - immobilized juvenile lemon sharks ( n . brevirostris ) exhibited violent rousing behavior in the presence of a 153 gram 99 . 95 % samarium metal ingot . as the samarium metal was moved towards the immobilized shark , the shark terminated tonic immobility , in the direction away from the approaching metal . for experimental controls , pure chromium , an antiferromagnetic metal , and pyrolytic graphite , a highly diamagnetic substance , failed to produce any behavioral responses in juvenile lemon sharks . next , a polystyrene white plastic blinder was used to remove any visual and motion cues from an approaching metal . this blinder was placed close to the shark &# 39 ; s eye , sufficiently shielding its nares , eyes , gills , and head up to its pectoral fin . again , samarium metal terminated tonic immobility in all test subjects at a range of 2 to 50 cm from the blinder . chromium metal and pyrolytic graphite did not produce any notable behavioral shifts . in order to confirm that pressure waves were not affecting the test subjects , the tester &# 39 ; s hand was moved underwater towards the shark &# 39 ; s head both with and without blinders at varying speeds . this motion also did not disrupt the immobilized state . the same series of experiments were repeated with juvenile nurse sharks ( g . cirratum ) and yielded the same behavioral results . the same experimental protocol was repeated with a 73 gram ingot of 99 . 5 % gadolinium metal and yielded the same behavioral results in both juvenile lemon sharks and nurse sharks . it is noted that the rousing behavior was most violent when samarium metal was used . additionally , the gadolinium metal corroded quickly after seawater exposure , and therefore would be appropriate for a one - time use application . next , in order to eliminate the possibility of galvanic cell effects , juvenile sharks were removed from their pens and brought at least 15 meters away from any submerged metal objects . all testers and witnesses removed watches , rings , and jewelry so that only the lanthanide metal was exposed to seawater . the same experimental method was repeated in lemon sharks and we report that tonic immobility was terminated with samarium metal in all tests . we report that waving samarium or gadolinium in air above immobilized or resting sharks does not effect behavior , even when the metal is very close to the water &# 39 ; s surface . the metal must be in contact with seawater in order to produce the repellent effect . this is notably different from the effects of a rare - earth magnet , which will often terminate tonic immobility at close range in air . it is thus proposed that any electropositive metal or alloy must be in contact with the seawater to produce the desired repellency effect . the effects of lanthanide metal on free - swimming sharks were also evaluated . two juvenile nurse sharks ( less than 150 cm total length ) were allowed to rest in an open - water captive pen . the tester approached the nurse sharks and moved his hand near the pen wall . his hand contained no metal . both nurse sharks remained at rest . next , the tester presented the 153 gram ingot of samarium metal underwater to the pen wall and we note that both nurse sharks awakened and rapidly swam away from the tester &# 39 ; s locale . next , a highly - stimulated competitively - feeding population of six blacknose sharks ( c . acronotus ) ( total length up to 120 cm ) and six carribean reef sharks ( c . perezii ) ( total length up to 210 cm ) was established using chum and fish meat . a diver entered the water near the population of sharks with the 153 gram of samarium metal secured to one end of a 1 . 5 meter - long polyvinyl chloride pole . as free - swimming sharks swam close to the diver , the control end of the pole ( without metal ) was presented in a left - right waving motion . approaching sharks would swim past , bump , or briefly bite the pole . the diver then turned the samarium metal - end of the pole towards the approaching sharks . all blacknose sharks exhibited a “ twitching ” or “ jerking ” behavior as they came near the metal ingot and quickly swam away . caribbean reef sharks generally avoided the metal , but did not exhibit the twitching behavior . some pure lanthanide metals are extremely reactive to air and water , and therefore are not particularly well - suited for long time use in the marine environment . for example , pure europium metal has been observed to appreciably oxidize in air in a matter of hours and degrades quickly in moist air . other metals , such as erbium and samarium have a much higher resistance to oxidation in air and slowly react with cold seawater . other reactive pure lanthanide metals are acceptable for one - time use as long as they are kept protected prior to use . mixtures and alloys containing lanthanide metals may serve as an economical alternative to pure lanthanide metals . in particular , cerium misch metal , lanthanum misch metal , neodymium - praseodymium misch metal and samarium - cobalt ( smco ) mixtures and alloys may be used in shark - repelling devices . it is not yet fully understood why sharks are responding to lanthanide metals . it would seem that some type of detection is occurring in the ampullae of lorenzini organ , but how electrical currents are being generated and detected with a solitary rare earth metal in seawater is not known at this time . we hypothesized that a magnetic or electrical field was being induced by the metal &# 39 ; s movement through seawater . we attempted to measure minute magnetic fields being produced by the movement of samarium metal through seawater in a closed system . a submersible calibrated milligauss meter probe was secured in a plastic tank containing seawater with the same salinity , ph , and temperature of the water used in previous shark testing . after zeroing out the earth &# 39 ; s magnetic field , we did not detect any magnetic fields being produced by the movement of samarium metal through the tank , within tenths of a milligauss . because there appears to be a lack of a magnetic field component , there cannot be an electrical field component . this is a difficult concept because the sharks are responding , at most times violently , only when the metal is in contact with seawater . the same phenomenon occurs when the sharks are far - removed from any other pure metals or alloys in seawater . the effect is not limiting to the order of the shark , as both nurse sharks ( orectolobiformes ) and lemon sharks ( carcarhiniformes ) responded in a similar manner . another hypothesis is that water - soluble salts are being formed and driven towards the shark as the metal is moved through seawater . the shark , in turn , may be hypersensitive to the presence of rare - earth compounds or ions . the use of our blinder during the experiments should have steered any water containing rare earth salts around the shark &# 39 ; s nose and mouth , limiting exposure , but the response was equal with or without blinders . in one test , an immobilized shark was moved towards a stationary samarium ingot . the shark exhibited bending away from the ingot prior to terminating immobility . this movement would have pushed metal salts away from the shark . further experiments using solutions of the nitrates and chlorides of the early - lanthanide metals showed no behavioral shifts ( using seawater controls ) when presented to immobilized sharks at doses up to 25 ml to the nares . captive cobia , which are commercially valuable marine fish , were exposed to lanthanide metals during feeding trials . we report that exposure to holmium , gadolinium , dysprosium , and samarium ingots did not disrupt normal feeding behavior . cobia do not possess the ampullae of lorenzini organ found in sharks . a close correlation was found between the revised pauling electronegativity values for these metals , and behavioral response . as the revised pauling electronegativity decreased , the violence of the response seemed to increase . a repellency threshold was found at an electronegativity of 1 . 3 or less — metals with electronegativities greater than 1 . 3 did not produce the response . highly reactive metals , such as strontium and calcium ( electronegativities of 0 . 89 and 1 . 00 respectively ) produced a rousing reaction as expected . the present invention combines the repellent effects of ferromagnetism along with electropositivity to offer two shark repellents within a standard metal fishing hook . in one embodiment of the invention , an electropositive metal is incorporated onto the hook by wrapping a ribbon , foil , or sheet of the metal around a portion , portions , or the entire magnetized hook . in another embodiment of the invention , a coating of electropositive metal is deposited onto a portion , portions , or the entire magnetized exterior hook surface through sputtering , thermal evaporation , thick - film deposition , or chemical vapor deposition techniques . in a third non - limiting embodiment of the invention , an electropositive metal or an alloy of electropositive metals is combined with gallium metal to produce a low - melting point alloy . the gallium - electropositive metal alloy is warmed to its melting point and applied to a portion , portions , or the entire surface of a cleaned and magnetized hook . upon cooling , an electropositive coating remains at the application site of the magnetized hook . in yet another non - limiting embodiment of the invention , a hook is made directly from a ferromagnetic alloy that also contains one or more electropositive metals . this alloy would ideally have a mechanical strength and machinability comparable to standard fishing hooks . the present invention finds use in commercial fisheries where unintentional shark by - catch is a problem . the use of magneto - electropositive fishing hooks reduces the number of sharks captured on hook and therefore makes these hooks available for target fish . the magneto - electropositive hook is particularly useful in tuna and swordfish fisheries . noaa fisheries , national marine fisheries service , 2004 . profile : the atlantic pelagic longline fleet . northeast distant fishery sea turtle bycatch reduction fact sheet . available online : www . nmfs . noaa . gov / mediacenter / turtles / docs / pelagic_longlining . pdf gilman , e ., clarke , s ., brothers , n ., alfaro - shigueto - j ., mandelman , j ., mangel , j ., petersen , s ., piovano , s ., thomson , n ., dalzell , p ., donoso , m ., goren , m ., werner , t . 2007 . shark depredation and unwanted bycatch in pelagic longline fisheries : industry practices and attitudes , and shark avoidance strategies . western pacific regional fishery management council . kalmijn a . 1973 . electro - orientation in sharks and rays : theory and experimental evidence . scripps institute of oceanography , manuscript . 73 - 39 . kalmijn , a . j . 1974 . the detection of electric fields from inanimate and animate sources other than electric organs . handbook of sensory physiology ( ed . a . e . fessard ), 147 - 200 . kalmijn a . 1982 . electric and magnetic field detection in elasmobranch fishes . science . 218 : 916 - 918 . kalmijn a . 1984 . theory of electromagnetic orientation : a further analysis . in : bolis l , keynes r d , maddrell s h p , editors . comparative physiology of sensory systems . cambridge , uk : cambridge univ press . p 525 - 560 . carey , f . g ., scharold , j . v . 1990 . movements of blue sharks ( prionace glauca ) in depth and course . mar . biol . 106 : 329 - 342 . klimley , a . p . 1993 . highly directional swimming by the scalloped hammerhead sharks , sphyrna lewini , and subsurface irradiance , temperature , bathymetry , and geomagnetic field . mar . biol . 117 : 1 - 22 . holland , k . n ; 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