Shark Repellent is a Matter of Life and Death – for Sharks
By Joanne Kimberlin, The Virginian-Pilot, Norfolk, Va.
Aug. 2–WACHAPREAGUE — Out here on the Eastern Shore, where voracious greenhead flies rule the marsh and waves of grass roll to the sunrise, scientists are fishing for sharks so they can learn how not to catch them.
More than 11 million sharks die every year on fishing hooks that aren’t intended for them. Up until recently, few people really cared — at least no one who remembers “Jaws.”
Now, it’s becoming clear that these wolves of the sea are vital for balancing the ocean’s complex cascade of life. But sharks mature slowly and bear few young, which makes them easy to wipe out with overfishing.
One main culprit: longlining, in which commercial outfits targeting tuna or swordfish deploy thousands of hooks hung from a main line that can stretch for 40 miles or more. Sharks are an unwanted by-catch, often tossed overboard, dead or dying.
The solution could lie in fitting longlines with ingots made of a metal that few have ever heard of, much less know how to pronounce: Neodymium-praseodymium.
“Even I have a hard time saying it,” said Rich Brill, the NOAA fisheries biologist heading up the shark project.
Neodymium-praseodymium (neo-DIM-eum prais-eo-DIM-eum) is a byproduct of steel mining in Mongolia. Commonly referred to as “misch metal” — an all-purpose term for a particular family of blended metals — neodymium-praseodymium is used in electronics manufacturing.
But warding off sharks?
“They start coming at it and then it’s like someone whacked them on the head with an invisible stick,” said Peter Bushnell, one of the biologists studying the phenomenon. “They don’t just turn away. They jerk away.”
Bushnell and Brill are now believers. “We went into this thinking, ‘No way,’ ” Brill said.
After all, the quest for an effective shark repellent has been under way for decades. Chemicals, dyes, compounds and assorted gizmos have all been hawked — most with human protection in mind — but few have been shown to really work.
In recent years, with concern mounting for the sharks themselves, a chemist in New Jersey came up with the neodymium-praseodymium idea. When submerged in seawater, the metal produces a tiny electrical field that seems to offend certain types of sharks.
Brill thinks it overwhelms their ultrasensitive receptors. A shark’s snout is peppered with sensors that can detect minuscule electrical currents, generated by contracting muscles and firing nerves, much the way an EKG works in the doctor’s office. That ability allows sharks to feed in murky water or find prey burrowed into the bottom.
“If you were in the pitch-dark and a shark was swimming by,” Brill said, “he could sense your heartbeat.”
A run-in with an electropositive metal such as neodymium-praseodymium is the equivalent of “a bright flash of light or a loud sound to humans,” Brill said. “You tend to veer away.”
The study is in its second summer at Wachapreague’s seaside lab, operated by the Virginia Institute of Marine Science. The lab is near the northern end of the village’s weathered docks, perched on the edge of one of the Atlantic coast’s top breeding spots for sandbar sharks, the guinea pigs for this study.
“There’s an endless supply right there,” Bushnell said, waving a hand toward the vast marsh and its maze of flats and fingers. “Few facilities in the world have that.”
Availability was just one plus for the sandbar sharks. They also do well in captivity and are closely related to the types of sharks hit hardest by the longlines — blues, silkies and oceanic whitetips. Another useful trait: Sandbars are nearly constant swimmers, moving forward relentlessly, which makes it easier to measure changes in their patterns.
The misch metal doesn’t work all the time. Some shark species, such as the dogfish that overwhelm halibut and haddock fishing gear, don’t seem to notice it at all. Not even the sandbars are turned off all the time.
During last year’s studies, young sandbar sharks 2 to 3 feet long were caught offshore and placed in round tanks. Two types of ingots — one made of misch metal, one of lead — were alternately dangled into the water. Cameras recording swimming motion showed the sharks circling close to the lead but steering clear of the misch.
“There seems to be a no-go zone of about 15 inches,” Bushnell said.
Food and time, however, can overcome a shark’s reluctance. Baitfish were offered, some tied near a disc of plastic, some near a disc of misch. Initially, the sharks gulped the first while avoiding the second.
But then, with enough exposure, some began to, as Brill put it, “hold their noses and go for it.”
This summer’s task was to find out how well misch metal works in the wild. Small longlines — each about eight football fields long — were baited with menhaden and spooled out off Wachapreague. A small disc of misch was hung above every other hook. The hooks in between had discs of plastic. The idea was to see which ones caught more sharks.
The final line was deployed last week. Two hours later, stalked by a horde of the seaside’s ruthless biting flies, the researchers set out in skiffs to record and release their last catch.
“We don’t fear the sharks,” Bushnell confided. “We fear the greenheads.”
That’s saying a lot, given the bad temper and sharp teeth of what was hauled from the water. As the boat’s motorized spool whined in the line, seven sharks were boated, measured and checked for gender.
None was pleased to take part in the experiment.
“Come on now… just relax,” Brill coaxed a 4-foot, torpedo-shaped mass of writhing muscle. “It’ll go easier for you.”
Hooks were clipped away with bolt cutters to preserve fingers, and the fish were flipped quickly back over the side, where it’s expected they’ll recover from the experience.
Bottom line for the summer: 42 sharks caught on lines with plastic discs, 15 caught on lines with misch.
Back at the lab, Bushnell ran the math and concluded that there’s a 3 in 10,000 chance that such results could be random.
“That tells me that the misch metal works,” he said. “Not 100 percent, but if it reduces the by-catch by two-thirds, or even just a third, that’s millions of sharks saved every year.”
Misch won’t rescue the species. It’s estimated that 100 million sharks are killed worldwide every year. Their meat is prized in some countries, as is a soup made from their fins.
But that’s another story. Misch is aimed at reducing the unintentional waste. Brill hopes commercial longliners can be convinced that the relatively inexpensive metal is a smart alternative to torn-up gear and wasted bait. If not, regulations could eventually come into play, but getting global cooperation will be a challenge, to say the least.
For now, the researchers plan to publish their findings and hope funding comes their way for more studies. There are plenty of details to be worked out — such as environmental impact, manufacturing and marketing.
On our part of the coast, where fishing is big but longlining isn’t, neodymium-praseodymium might someday be used by sportfishermen to keep sharks from swooping in on a hooked catch.
Worn as an anklet or bracelet, it might even be the tongue-twisting antidote to man’s ancient fear of things that lurk in the deep.
Or not. Cue that ominous theme song from “Jaws.”
“Remember, it only works within about 15 inches,” Bushnell said. “Do you really want a shark to get even that close?”
Joanne Kimberlin, (757) 446-2338, firstname.lastname@example.org
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Copyright (c) 2008, The Virginian-Pilot, Norfolk, Va.
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