Researchers make promising shark repellent

Researchers hope to protect sharks from fishing operations.
SAN JUAN, Puerto Rico (AP) -- Excited by the scent of blood, a dozen sharks dart about in a frenzy as a researcher dips a pole in the sea and squirts out a clear, yellowish substance. Within seconds, the sharks jerk their snouts away and vanish.
Researchers say they finally have found a potent repellent to drive away sharks, after testing off Bimini island in the Bahamas. It's a goal that's eluded scientists for decades.
If proved effective, the repellent one day might protect divers, surfers and swimmers. But researchers say that would require much more study. First they hope it can protect sharks -- in decline worldwide because of overfishing -- by reducing the numbers caught needlessly by long-line commercial fishermen.
"You introduce this chemical, and they all leave," said lead researcher Eric Stroud, a 30-year-old chemical engineer from Oak Ridge, N.J. "It works very, very well."
Derived from dead sharks
The repellent, called A-2 because it was the second recipe tried, is derived from extracts of dead sharks that Stroud gathered at New Jersey fish markets and piers. Fishermen and scientists have long noted sharks stay away if they smell a dead shark.
"We have something that really works, but research remains," said Samuel Gruber, a University of Miami marine biologist and shark expert who is helping conduct tests at the Bimini Biological Field Station.
Tests have found the repellent effective on three species: the Caribbean reef, blacknose and lemon sharks. Studies are needed on other species such as the great white, mako and oceanic whitetip.
Gruber said the repellent seems to carry a chemical messenger that triggers a flight reaction. He said more studies are needed to pinpoint the active molecule.
A dose of 4 fluid ounces is enough to scare away feeding sharks, Stroud said, keeping them away from a fish head for two hours with just a few drops per minute. In contrast, sharks didn't respond to a red dye in control tests.
Presented work
The researchers presented their work in May during a meeting of the American Society of Ichthyologists and Herpetologists in Norman, Okla. Films of their tests captured images of sharks splashing the surface as they turn to flee.
They hope to make a slow-dissolving repellent for use in baits and fishing nets, and to guard equipment on submarines and oil exploration vessels that sharks have damaged in the past.
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