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Repellent Could Save Humans and Sharks, Too

"We're talking about a small number of people who are dying," Burgess said. "Shark attacks are largely a human phenomenon, not a shark phenomenon, simply because the number of attacks are a product of the number of people in the water."

Experts say swimmers and surfers can take several steps to avoid shark attacks, including remaining close to shore, staying out of the water at dusk and dawn and while bleeding, and avoiding steep drop-offs in the water and areas where bait fish congregate.

It takes less than a pint of Stroud's repellent, which smells slightly sweet, to scare off a group of sharks. "They just have to get a whiff of it, that's all," said Michael Herrmann, Stroud's business partner and an electrical engineer by training.

Stroud has successfully tested the substance on tuna in Panama to make sure they will approach fishing lines despite the repellent, because fishermen will not use it if it scares off commercially targeted species.

Ellen Peel, president of the Billfish Foundation, a sport fishing conservation group, said the fishing industry has an incentive to use such a repellent because sharks can eat commercially desirable fish near longlines as well as occupy needed hooks.

Christofer Boggs, a biologist at the National Oceanic and Atmospheric Administration's Pacific Islands Fisheries Science Center in Honolulu, has been working with Shark Defense. He said that although Stroud deserves credit for developing a chemical shark repellent that works, "getting it to work on longline gear is a challenge." Longlines can stretch across 60 miles of ocean, and the repellent must be released around every hook: 800 to 2,500 sites for a single longline.

As Boggs put it, "It's not time to crow."

Gruber, who has studied sharks for about three decades, estimates the repellent could save as many as 50,000 a night worldwide. According to NOAA officials, nearly 124,000 sharks were caught accidentally off U.S. coasts in 2003, although some were released alive.

"Do I think it will save a lot of people? No," Gruber said of Stroud's repellent. "What I believe this could be beneficial in is protecting sharks. You cannot protect yourselves against a shark attack, short of staying out of the water."

Still, Stroud and Herrmann are hoping to minimize the public safety threat that sharks can pose. They are developing a prototype that beach lifeguards could throw in the water just after a shark attack, as a rescue cannot be attempted when a shark is still in the area.

"The first thing a rescuer has to determine is: Is it safe to approach the water? In a shark attack, it is not safe for a rescuer to approach unless they have a boat," said B.J. Fisher, director of health and safety for the American Lifeguard Association.

Fisher's association has endorsed Shark Defense's repellent, and other groups are urging the company to develop different applications. Surfers have suggested they incorporate it into surfboard wax, and swimmers are seeking a suntan lotion that provides shark protection, as well.

Herrmann cautioned, however, that Shark Defense may not be able to sell such a product, which could take years to gain approval by several government agencies. "It's going to take significantly more research to determine if you could incorporate this substance into suntan lotion, or in a sponge within a child's bathing suit. That's in the future."

Researcher Karl Evanzz contributed to this report.

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