Shark attack: menace or myth?

POSTED 12 AUG 2004

1. Shark repellent

2. How dangerous?

3. Shark lovers

4. A social killer?

5.Hammerhead's head
Painting by John Singleton Copley, Watson and the Shark, 1778. From National Gallery of Art

Want to guess last year's global death toll from unprovoked shark attacks? Four people

For a shallow-water ocean test, Eric Stroud and colleagues sprayed repellent from this tripod.
Photo: Shark Defense

With bait like this, you need a real shark repellent. Tests to date show the new formulation works with four species. Photo: Shark Defense

Shark repellent found?
Picking up a research quest that dates to World War II, when some fliers and sailors got shredded by sharks, two New Jersey entrepreneurs say they have found a shark repellent that works. Stir a tiny dollop of this stuff into the water, and sharks leave faster than disappointed fans at a J-Lo Ben-Affleck box-office disaster.

Boat of men try to save boy as menacing shark lunges.

You don't have to see "Open Water," the latest update of "Jaws," to know sharks are scary. Hasn't anybody who's ever splashed in salt water wondered what lurks beneath the waves? Was that a dorsal fin? What just brushed my leg?

Sharks don't just arouse fear in swimmers and divers. The depths of their "public-relation issue" is embedded in our language. "To shark" once meant "to obtain by deceit or trickery," thus the basis for "pool shark." "Loan sharks" lend money at inflated rates, then rely on thugs to collect. When corporados speak of a "shark attack," they mean a hostile takeover, which can be fended off with "shark repellent."

But let's return to the fish. Sharks are fish with skeletons made of cartilage instead of bone. Nearly 500 species -- all predators or scavengers -- occur in oceans from the tropics to the Arctic. Sharks, rays and skates reside in the biological sub-class Elasmobranchii.

A repulsive repellant?
Three scientists wading in ocean during an experiment.The new repellent, from a New Jersey company called Shark Defense, was based on chemicals found in dead sharks. In searching for something that would send sharks packing, chemical engineer Eric Stroud focused on naturally occurring signaling chemicals. These molecules include the pheromones that animals use to communicate. Moths, for example, release pheromones to announce mating season.

Starting from the observation that sharks dislike dead sharks, Stroud apparently worked through a process of elimination (associate Mike Herrmann was mum on the details) to come up with "complex water-soluble molecules" which don't seem toxic to sharks or other fish.

For more than a year, said Herrmann, the repellent has been entirely made in the laboratory. "We don't need any dead sharks."

Two men on boat baiting shark with fish head.

In tests, the repellent repelled four species of sharks. It has yet to square off against the white shark, which causes 87 percent of human attacks on the Pacific coast of North America.

The repellent even seems to work on sharks that are feeding. It also works during the state of "tonic immobility." When a shark is held upside down, you can perform surgery without anesthetic. The new repellent causes immobile sharks to wake up and fly right -- away.

But how dangerous are sharks?

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Megan Anderson, project assistant; Terry Devitt, editor; S.V. Medaris, designer/illustrator; David Tenenbaum, feature writer; Amy Toburen, content development executive

©2004, University of Wisconsin, Board of Regents.