Shark Attack Research – Repellent Technology
Anti-Shark Shields – Magnetic, Electric and Semiochemical Deterrents
Mar 28, 2009
According to the International Shark Attack File, it is statistically more likely that a person will die from a lightning strike than a shark attack. However, this offers little comfort to the swimmer who encounters an aggressive shark.
Using non-fatal anti-shark compounds to protect against shark attack was first trialled by the US Navy during World War 2, due to the alarming number of encounters with sharks experienced by sailors and pilots who found themselves in the open ocean as a consequence of combat. The result was Shark Chaser, the first synthetic chemical shark repellent.
Encounters with Shark Chaser
Unfortunately, as explained by H. David Baldridge in his book Shark Attack, Shark Chaser was largely ineffective. The compound was mixed with a yellow dye designed to cloud the vision of any approaching shark, while the active chemical, copper acetate, would drive a shark away by mimicking the odour of a dead shark. However, in open water, Shark Chaser became rapidly dilute and dispersed too quickly to offer any real protection from shark attack.
Research into Shark Chaser was eventually abandoned, and it is only in recent years that new technologies have emerged that potentially offer a non-fatal solution to the problem of shark attack. These technologies include magnetic repellents, electropositive repellents and semiochemical repellents.
Magnetic Repellents
Anti-shark magnetic deterrents work by affecting the Ampullae of Lorenzini which provides a shark's electrosense in certain shark species. By overstimulating the shark's electrosense, barium ferrite, neodymium iron boride and other rare earth magnets have been demonstrated by SharkDefense to repulse feeding sharks of the nurse, hammerhead, Atlantic sharpnose, lemon, and blacktip varieties.
Electropositive Repellents
Like magnetic repellents, electropositive shark deterrents work by overwhelming the shark's ampullae apparatus by immersing an electropositive metal into sea water, which acts as an electrolyte. SharkDefense found that even small quantities of electropositive metal, when in contact with sea water, produces sufficient voltage to disturb a shark's electrosense, and repel the shark.
Semiochemical Repellents
Semiochemical shark deterrents offer a different avenue of defense against shark attack by utilizing the natural chemical triggers that govern shark behaviour. Semiochemicals are chemical messengers produced by animal species that communicate information through scent. Such semiochemicals pheromones include sexual stimulants to attract sharks, predatory repellents and warnings to other members of the same species to flee danger.
The University of Miami has reported encouraging test results in isolating the semiochemical that causes shark species to respond to its presence by reflexively displaying flight behaviour.
Shark Protection and Conservation
These emerging technologies do more than reassure recreational swimmers who may encounter sharks. Foremost, shark deterrent technology will save these predators in danger of extinction caused by overfishing.
Each year in commercial fishing, thousands of sharks are harmed by long-line fishing and destroyed as part of the by-catch of deep-sea trawling. Using shark repellents, fishing fleets could avoid further depletion of dwindling shark populations by preparing their lines and nets with such anti-shark devices as magnetic, electropositive and semiochemical deterrents.
Sources
Baldridge, H. David. Shark Attack. Chaucer Press, 1976.
Handwerk, Brian. “New Shark Repellent Uses Chemical Signals” in National Geographic News, July 29, 2004.
Kalmijn, A.J. “The Electric Sense of Sharks and Rays” in Journal of Experimental Biology 55. 1971.
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