Chemist Eric Stroud is the proprietor of SharkDefense, a company that develops new shark repellents. His aim is to protect sharks from people, keeping them away from trawling nets and fishing lines. Apparently, approximately 12 million sharks are accidentally ensnared each year. Some of Stroud's experimental repellents are extracted dead sharks themselves. The odor, which smells like stinky feet, is quite abhorrent to the sharks. From Smithsonian:
Magnets made from iron, boron and neodymium are another promising repellent being developed by SharkDefense. Eric Stroud discovered their repellent potential by accident. According to Stroud, he and colleague Michael Hermann were playing with magnets near a research tank containing lemon and nurse sharks. After spotting a broken pump, Stroud set a magnet down on the tank's side, and the sharks took off. He thinks that the magnets may overload the sharks' Ampullae of Lorenzini. These tiny pits found along a shark's head are used to detect faint electrical signals emitted by prey, in the same way a doctor uses an EKG to detect the electricity generated by your pumping heart. The magnets are unlikely to cause pain, says Richard Brill, a SharkDefense collaborator at the Virginia Institute of Marine Science. He and others hypothesize that it's equivalent to a bright flash of light. You wince because it's overloading the visual receptors in your eyes. "It's the same idea with the sharks, except it's overloading these electrical receptors, " Brill says. Stroud has been using stationary magnets so far, but he also sees potential in spinning magnets, which generate a greater magnetic field.
Stroud and his team are also working with electropositive metals, which produce a current when placed in seawater and also possibly affect sharks' electromagnetic sense organs. Scientists are testing the metal repellents as a solution for the dogfish bycatch problem. Researchers found that the metals, when attached to fishing lines, reduced shark bycatch by 17 percent in Alaskan fisheries. But when the experiment was repeated in the Gulf of Maine, the results were negligible. "We think the dogfish are just going after two different preys," says Stroud, who is completing a Ph.D. in chemistry at Seton Hall University. Rice speculates that the metals may not affect Northeast dogfish because the sharks are using smell more than their Ampullae of Lorenzini to detect prey.