American chemist Eric Stroud says he’s found several substances that can repel sharks, and he wants to use his discovery to protect them.

Stroud, 38, used to work fulltime as a chemist in the pharmaceutical industry. Then, in the summer of 2001, after he and his wife noticed that the news was filled with stories of shark bite after shark bite in the Florida oceans, he turned his talents to developing shark repellents. Stroud has now been doing this for more than a decade, founding a company, SharkDefense, which aims to develop and commercialize shark repellents.

When Stroud started, he set up several kiddie pools in his basement, filled them with small sharks, and observed how the sharks fed, swam, and behaved. Then, one day in 2004, he accidentally dropped a large magnet from his workbench. He noticed some small nurse sharks dart away.

“That night, we put magnets into the tank and couldn’t believe [that] the nurse sharks were just extremely distressed and stayed away from them,” he says. It led to an AHA discovery: Magnets repel sharks.

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. Stroud believes the spinning magnet overwhelms and interferes with those electrical sensors. “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.”

They’ve tested other substances, too, and have found that some non-magnetic metals also interfere with a shark’s electrical sensors, including rare-earth metals like samarium, neodymium, and praseodymium.

Since many shark species are being over-fished (fishermen trying to catch other fish often catch sharks by accident), and some are endangered, Shark Defense’s main focus has switched to using repellents to protect sharks, and has created a magnetized fishing hook.

“We realized we could magnetize the fishing hook, and we can coat it with a rare earth metal,” he says. “It looks just like a regular hook, and we get the benefit of two repellents at the hook.” Some tests show a 60 to 70 percent reduction in the number of sharks caught.

Stroud received an award from the World Wildlife Fund for his invention, and he’s hoping to soon sell it commercially. In the meantime, he continues to refine the design, trying new combinations of metals and magnets, and observing how they affect different types of sharks.

Holy mackerel! Looks like we won’t need the bat-shark repellant!