What began as a concern for people who get bitten by sharks has now become a way to prevent sharks from getting caught in fish hooks. One man’s discovery might help protect sharks and also humans from these predators by simply using magnets.
Eric Stroud was a chemist by profession but one summer of 2001 as he went on a vacation to Bahamas with his wife, he heard disturbing news.
“We hit bad weather, and we were trapped in a cabin, and on the news was shark bite after shark bite,” he says. “It seemed like everyone that stepped in the ocean in Florida was getting attacked by a shark that summer.”
That is when Eric’s wife suggested him to develop a mechanism that could deter sharks from attacking humans.
Eric set up several small pools in his New Jersey home and filled them with small sharks. He observed their behavior, feeding pattern etc. One night he accidently dropped a magnet into the pool and immediately saw small sharks dart away from that area. Eric knew that he had found his repellant.
“That night, we put magnets into the water and couldn’t believe the nurse sharks were extremely distressed and stayed away from them,” he says.
Recently Eric demonstrated his theory at the Bimini Biological Field Station in the Bahamas. He stood in waist deep water in a fenced-in pen in the sea. Several young Lemon sharks glided around the perimeter as his assistant captured one and slowly roated it on its back to put the shark into a sleep like state. Stroud then took a magnet and spun it towards the shark. The predator immediately darted away.
“There you go,” said Eric after the experiment. “Look at that beautiful bend away from the magnet like he’s repelled by it”.
Sharks possess electrical sensors, called the ampullae of Lorenzini, that look like tiny freckles on their snouts. Biologists believe sharks use these sensors to detect the heartbeats of their prey and to navigate using the Earth’s magnetic field.
Eric has also created a special fish hook which is magnetized and wrapped in magnesium alloy foil. He calls it the smart hook. When the hook or the magnet is spun, Eric believes the shark get confused and their electric censors are disturbed.
“It’s probably something like a bright flashlight across your eyes,” he says. “It’s just temporarily blinding, and you’re startled. And it’s not pleasant.”
Other shark experts however say it is too early to rely or magnets.
Rob Lawrence, who has been working with great white sharks for more than 20 years and takes tourists in Cape Town cage diving, says, “It could work if a lot more research was done on this. Sharks have a lot of sensory organs in their snout so potentially the magnetic field could affect it. But people here in South Africa have looked into this and there hasn’t been much success with it.”
According to Geremy Cliff, head of research at KwaZulu-Natal Sharks Board, and Australian study conducted in 2009 suggested that magnets could repel five shark species, but had little effect on one teleost species in a test tank environment.
“But the authors had raised concerns that the size and weight of the magnets was considerable and that many would be needed to keep sharks out of nets,” he adds.
Eric adds that while sharks dart away from magnets, other fish species are not affected.
“Bony fish, like tuna or swordfish, do not have this special organ. Therefore, they are not affected at all in the presence of magnets or metals.”
“We have not tested this on sea turtles – which, like sharks, use the Earth’s magnetic field as a compass – but some early work by other researchers indicates they have no effect.”
He adds that eels, invertebrates and crabs too are not affected by the magnets.
After his discovery in 2004 Eric started a company called SharkDefense to develop and make shark repellants commercially available.
He and his team also found that some other metals worked as repellants too, like rare-earth metals samarium, neodymium, and praseodymium.
“Certain metals didn’t work, others did”, says Stroud. “You begin to hone down the periodic table”.
He is now also testing some chemical shark repellants. Other deterrants like electronic waves are already in use.
As Eric’s original idea was to stop shark attacks, he and his partner are in the process of developing a magnetic underwater fence that could save swimmers. But he is increasingly working on using the same technique to protect sharks from becoming accidental catch.
Many shark species around the world are on a decline due to habitat destruction and overfishing. But by catch is also a major reason for the decreasing number of sharks. Eric’s idea is to have fish hooks that catch the tunas and halibuts as usual but spare the sharks.
“We realised we could magnetise the fishing hook, and coat it with a rare earth metal,” he says. “It looks just like a regular hook.”
People of several countries who have already used his product say they have observed a 60 to 70 percent reduction in the number of sharks accidentally caught.
For his innovative idea, Stroud received an award from World Wildlife Fund. Hopefully, his design would be commercially viable and help save the sharks as well humans from being attacked by each other.