Fishermen are usually trying to find ways to get fish to take the bait. When it comes to sharks, though, they’re trying to find ways to get them to leave the bait alone. And one strategy seems to have the potential to keep the sharks away: using metals with special magnetic properties.
An illustration depicting how a SMART Hook is deployed and how it can selectively repel a shark without affecting target fish catch. Credit: Conrad Eskelinen / SharkDefenseMany species of sharks are endangered. In part, that’s because they’re common “bycatch.” They’re not the intended catch, but they’ll take just about any bait that’s put in front of them, so they get caught anyway. Millions of sharks are taken as bycatch each year.
But a few years back, researchers discovered that sharks stay away from certain types of metals that have magnetic properties. Since then, several studies have supported that finding. Sharks don’t always stay away, but they’re more likely to avoid those types of metals than others.
The most likely explanation is that the metals interfere with the shark’s ability to navigate and find prey. A shark’s head is covered with a network of sensors known as the ampullae of Lorenzini. The sensors detect electric fields generated by other fish, as well as Earth’s magnetic field. So interfering with the shark’s sensors is like partially blinding it.
More tests are needed to confirm the effect and put it to use. Researchers say the metals probably wouldn’t repel sharks from individual swimmers — you’d need a lot of magnets, and the sharks have to get really close to sense them. But the tests could lead to a better fishhook — one that keeps the fish away.
This episode of Science and the Sea was made possible by Chuck Nash Chevrolet.
