Rare metal generates electric field, repels sharks

BEIJING, May 7 (Xinhuanet) -- Researchers have discovered a rare metal alloy can be used to produce electric fields that repel sharks, limiting bycatch by commercial fisherman harvesting other species.

Sharks have an innate ability to detect electric fields, useful for sensing the bioelectric activity of their prey. Researchers discovered that strong electric fields could repel these predators, most likely by overwhelming their electricity sensors.

"It's a sense we don't have," said Richard Brill, a biologist at the National Oceanographic and Atmospheric Association's Northeast Fisheries Science Center and head of the Cooperative Marine Education and Research Program at the Virginia Institute of Marine Science. "The closest [analogy] I can come up with is if you get exposed to a bright light, you squint and look away."

A recent test showed small disks of palladium neodymium interact with the salt in seawater to produce electric fields strong enough to ward off sharks. These disks could be attached to fishing lines to deter sharks from fishers aiming for other animals, thereby reducing bycatch of endangered shark species.

"We were just slack-jawed when we saw how well it worked," Brill told LiveScience. "I was stunned, I thought this was the stupidest idea I'd ever heard. I saw the evidence and thought, 'This can't be right.'"

To test the idea, the scientists placed the small metal disks in a tank with captive juvenile sandbar sharks. They were surprised to find the metal had such a strong effect: The sharks generally wouldn't swim within 24 inches (61 centimeters) of the disks, or bite at bait hung within 12 inches of the disks.

Most fish cannot detect electric fields, so the metal disks could be perfect for deterring sharks without affecting the animals fishers hope to catch.

About 11 million to 13 million sharks worldwide are caught as bycatch every year, sometimes more than the targeted fish species, according to NOAA. In addition, sharks are hunted for food, especially for their fins, considered a delicacy in some Asian diets. Hunters sometimes simply cut off a shark's fin and leave the animal to die in the ocean (a finless shark can no longer swim or feed).

(Agencies)