Cable research could lead to shark repellent

By Beverly Creamer
Advertiser Education Writer

Both deep-sea oil exploration rigs and Navy subs skulking the Pacific listening for bad guys have turned to University of Hawai'i shark researchers at Coconut Island to save them from a persistent and expensive problem — sharks attacking cables that stretch a mile or two behind them carrying sensitive equipment.

"They're both dragging extremely expensive cables carrying hydrophones through the water to pick up underwater noise," said Kim Holland, an aquatic biologist and shark researcher at the Hawai'i Institute of Marine Biology at Coconut Island. "And they're both suffering millions of dollars in damage every year because sharks are biting the cables and rendering them inoperable."

Because the sharks are mistaking the cables for food, it follows that they can detect anything producing an electric field, including humans.

"Prior to this work, sharks were not thought to be able to identify high-frequency current, and these seem to be able to do so," Holland said.

If scientists can figure out how to stop sharks from biting the cables, it could lead to safety measures to protect people, said Holland and zoology graduate student Tim Fitzgerald, who is working on the project.

Holland questions the effectiveness of devices on the market that give an electric charge to repel sharks. He said there are no fool-proof methods — but he hopes to find one.

Holland and Fitzgerald have been testing which levels of electric current appear to attract the animals, and which they ignore.

With the discovery of sharks' ability to recognize electrical currents — their electroreception — the scientists also have recognized the animal uses the ability as a fine-tuning locator for prey, Fitzgerald said. Once the shark has found its potential prey through smell, being able to pick up the electrical field around it makes the strike precise.

The cable attacks are a "significant problem for the Navy and oil exploration companies, especially when they're working in warmer oceans" where sharks generally live, Holland said. When cables are bitten, salt water leaks in and destroys their ability to transmit data.

The $90,000 UH research grant was provided by the Schlumberger Foundation, one of the world's leading international offshore oil exploration companies.

The researchers should hear within two weeks whether another year's worth of money will be approved through the Defense Department's Office of Naval Research.