Marine Biologist Warns of Sharks’ Peril : Ecology: He hopes to save them from extinction by studying their lifestyle, and by changing their fearsome image. His version of ecotourism includes diving with the creatures.

BIMINI, Bahamas —  Sonny Gruber warns the snorkelers to stay close to the boat. A few feet below, a dozen sharks cruise around, attracted by the chunks of fish Gruber tosses into the turquoise water.

“I’m not too worried about them getting bitten, but they’re scaring the sharks away,” says Gruber, a marine biologist with the University of Miami’s Rosenstiel School of Marine and Atmospheric Science.

Gruber has brought the snorkelers to a coral reef just south of this Bahamian island as part of his public relations campaign to improve the sharks’ terrible image and help save them from extinction.

“They’re highly intelligent, very elegant and beautiful creatures,” he says. “And they are in terrible danger. While sharks have a reputation of being indestructible, in reality they’re extremely delicate.”

After more than 400 million years of evolution, the world’s 350 species of sharks are threatened by overfishing. Those that remain are sought for their meat and fins, prized for shark-fin soup.

From his field research station in Bimini, Gruber and a team of graduate students study lemon sharks. By learning more about how they live, they hope to lay the scientific foundation for a shark-farming industry.

“Our goal is learning what it takes to make these little lemon sharks grow to become big lemon sharks,” Gruber says. “This way people can have sharks, sharks can have sharks, and the fishermen won’t go broke.”

As an offshoot of his research, Gruber feels compelled to try to change the fearsome image of sharks inspired by the movie “Jaws.” In the process, he’s giving ecotourism a new twist: shark diving.

Gruber brings students and tourists interested in learning about sharks to his research station and allows them to snorkel among Caribbean reef and lemon sharks ranging from three feet to seven feet long.

“You will be frightened at first, but it will give way to fascination,” Gruber tells a group from the Boston-based environmental organization Earthwatch.

Some Earthwatch snorkelers are nervous as they enter the water while Gruber creates a shark feeding-frenzy by tossing chunks of fish off the boat.

Jeff Borland, 17, a senior at Stuyvesant High School in New York City, jumps back in the boat at the first sight of a lemon shark.

“You can’t really express how it feels,” he says later. “They were only a yard away. The closest thing to this in New York is riding in the subway with a couple of hoods. But that’s a little different.

“This is the opportunity of a lifetime. Sharks are stereotyped as mean,” Borland adds. “But they were close enough that they could have attacked. This is kind of the ultimate.”

That measured combination of respect and fear for sharks is what’s needed to save them, Gruber says. The 57-year-old “shark doctor” has been studying sharks since 1961, when he was a graduate student at the University of Miami.

“He is one of the foremost experts on sharks,” says George Burgess, director of the International Shark Attack File at the University of Florida in Gainesville. “Sharks have historically been the stepchild of fish-related research. Most people didn’t care if they were killed.”

Gruber says his love of sharks grew from his childhood fascination with the sea. “While other kids were playing ball, I combed the beach for shells.”

At 20, while diving a reef off the Florida coast, Gruber had his first close encounter with a shark.

“I was menaced by what seemed like a 2,000-foot hammerhead,” he says. “I was certain I was dead. But he left me alone. It probably never even looked at me.”

Gruber says he returned to Miami and told his father he was dropping his zoology studies at Emory University in Atlanta and transferring to the University of Miami to study sharks.

Gruber’s shark lab, formally known as the Bimini Biological Field Station, is part research center, part public relations battlefront in the campaign to save sharks.

The lab is in a small waterfront clearing on sparsely populated South Bimini, about 50 miles east of Miami. Its location gives Gruber and the graduate students access to a healthy population of sharks that use the area as a spawning ground.

The no-frills field station consists of two trailers combined to make room for dormitories, a kitchen and dining room, two bathrooms and a lab.

The researchers are focusing on the local population of lemon sharks to learn how their habits are affected by the tides and other climatic conditions.

They hope their findings will make it easier to raise sharks in captivity, eventually making it possible to start a shark-farming branch of aquaculture that would reduce the fishing pressure on wild sharks.

“We know sharks can’t be taken into captivity very easily,” Gruber says. “But very little is known about them. How they fish, what influences their behavior--these kinds of studies have never been done. Before you can manage a species, you have to know them.”

The researchers implanted transmitters in sharks to track their movements. They have begun to see patterns possibly related to the tides and times of day.

Federal regulations passed in 1993 are aimed at protecting 39 species of sharks from overfishing in the Atlantic Ocean and the Gulf of Mexico. But Gruber says more must be done to protect sharks in the Pacific and other oceans.

The sharks’ life cycle mirrors that of their human predators. Sharks take from 12 to 15 years to become sexually mature. When they reproduce, they have few offspring, usually two. Gruber says that means it could take sharks a generation to recover from overfishing--if at all.

Gruber grows animated when he talks about the myth and reality of sharks. As long as people mistakenly see them as mean, mindless, eating machines, they won’t think much about saving them.

“The reality is so far from the myths that I can’t really understand how they started,” he says. But he acknowledges that sharks do bite people.

According to the International Shark Attack File at the University of Florida, there are an average of 50 to 75 shark attacks on humans worldwide each year, resulting in from five to 10 deaths.

By taking students and tourists snorkeling, Gruber hopes to show that sharks deserve respect, but don’t need to be feared. Every novice who enters the water with the sharks seems to leave with a new appreciation.

“It works,” he says. “It’s a great motivator.”

As Gruber keeps a close eye on the snorkelers, one Earthwatcher screams when a shark comes close to her. “I’m not a water person,” says Gale Brownson, a third-grade teacher from Los Angeles. “When I saw the sharks I thought, I gotta remember to keep breathing.”

Brownson and another Los Angeles teacher, Craig Honda, say they will incorporate what they learn at the shark lab into their lessons.

“There is no empathy for sharks,” Honda says. “I want to teach empathy. At least I want [students] to think about it.”

Almost on cue, one shark reinforces Gruber’s warning that sharks can be dangerous as well as beautiful.

A 6-foot Caribbean reef shark mistakes Andrew Johnson, an electronics engineer from Cambridge, England, for a chunk of fish. The shark comes within inches of taking a bite, but darts off when Gruber’s daughter, Aya, pushes Johnson and flutters in the water.

Back on shore, Johnson remains unscarred, but says he’s been bitten by the shark bug.

“They’re fascinating,” he says. “I don’t think it was particularly dangerous. There are other guys watching your back. I have no qualms about getting back in the water. But I certainly wouldn’t do this by myself.”