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Biting back

A USF scientist measures the bite marks of sharks in an attempt to help the U.S. Navy protect valuable equipment. And he needs your help.

By TERRY TOMALIN, Times Outdoors Editor

© St. Petersburg Times, published January 4, 2002


A USF scientist measures the bite marks of sharks in an attempt to help the U.S. Navy protect valuable equipment. And he needs your help.

The U.S. Navy is looking for a few good fishermen.

"It is a matter of national security," Dr. Philip J. Motta of the University of South Florida said. "We need their help."

Open ocean predators, including several species of sharks, have a habit of attacking the acoustic array cables towed by submarines.

"When a fish hits one of these cables, it does more than just destroy a valuable piece of government equipment," he said. "It leaves the ship without the ability to listen. It loses its underwater ears."

Motta, along with fellow scientists at the University of Hawaii, is looking for ways to modify these array cables to reduce the attacks.

Working in the Bahamas with a team of graduate students, Motta has succeeded in getting a wide variety of sharks to bite pieces of hose so they can compare them to damaged hose sent by the Navy. In the process, he has learned interesting things about one of nature's most fearsome predators.

"Believe it or not, the bite force of a shark is not as great as people would think," Motta said. "A 4- to 6-foot shark would bite with the same force as an adult human."

But bite pressure (which equals force per unit area) of a shark is much greater.

"It is just like a woman wearing high heels," he said. "The amount of pressure exerted by the foot isn't that great, but the pressure at the tip of the heel is tremendous. So just imagine how great the pressure is at the tip of a sharp shark's tooth."

Over the years, Motta has learned a great deal about the feeding habits and bite strength of numerous species of sharks.

"A tiger shark, for example, can exert enormous pressure," he said. "A 14- or 15-foot tiger shark can bite clean through a large sea turtle's shell."

Much of Motta's work, however, has been with smaller species, such as the Caribbean reef shark.

"They are all different," he said. "Some you treat with more respect. With a species like the lemon shark, you have to be careful. They will turn around and bite you."

But there is one shark that Motta won't even mess with.

"If there is a bull shark in the water, I am out of the water," he said. "It is as simple as that."

One thing that Motta hasn't been able to do is get fish other than sharks to bite the test tubing.

"We have not been very successful in getting bites on this tubing by fish such as barracuda, wahoo, king mackerel or tuna," Motta said. "We need large "toothy' predators to bite some hose samples. This is where some good fishermen and fisherwomen come in."

Motta said he will provide pieces of array hose, approximately 1 inch in diameter, pliable, thin-walled and black in color.

He wants fishermen to fashion any type of lure, fit it over existing trolling skirts, paint it and do whatever it takes to get some good bites with lots of tooth marks.

Motta recommends fitting a hook to the lure so the type and size of predator can be recorded along with the hose when it's mailed back to be analyzed.

"Then we can compare the bites we see on Navy arrays to this reference collection to help us discern what type of predator is doing the damage," he said.

Armed with this knowledge, the Navy can begin to work on countermeasures.

"So this is your opportunity to help your Navy and go fishing at the same time," Motta said. "We are looking for serious anglers, people who go offshore."

This project is ongoing, so fishermen can get ready for the spring season and help out throughout the rest of 2002.

If you think you can make fish bite, contact Motta after Tuesday at the Biology Department, University of South Florida, 4202 E Fowler Ave., Tampa, FL 33620. Or call and leave a message at (813) 974-2878. Motta will make arrangements send a piece of hose to you along with instructions.

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