He demonstrated that effect in a seaside pen in the Bahamas. His field assistant, T. J. Ostendorf, captured a small lemon shark and slowly rotated it onto its back, underwater. That put the shark into a sleep-like state. Then Stroud took a magnet and spun it as he moved it toward the shark. The shark immediately bent away from the magnet — “like it’s another magnet,” Stroud said...It appears that the magnet needs to be spinning or rotating. So it's not enough to keep one in your pocket while swimming.
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 suspects the spinning magnet overwhelms those electrical sensors.
“It’s probably something like a bright flashlight across your eyes,” he said. “It’s just temporarily blinding, and you’re startled. And it’s not pleasant.”..
Many shark species are being overfished, and some are endangered. One reason is that fishermen trying to catch other fish often catch sharks by accident. Stroud wondered – what if he could produce fishhooks that catch fish like tuna and halibut as usual, but that sharks avoid?
More at Public Radio International.
"It appears that the magnet needs to be spinning or rotating. So it's not enough to keep one in your pocket while swimming."
ReplyDeleteWhat if you only swam in circles? ;-)
They demonstrated this on the Nova show "Hunting the Elements" the other night...that magnet wasn't spinning and still worked. But they found that the magnets kept fouling the fishhooks, so they tried non-magnetic rare earth elements and found that one of them worked just as well!
ReplyDeleteThis is amazing demonstration though I'm not familiar with these magnets that can be used in water.
ReplyDelete??? what kind of magnet can't be used in water?
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