Knowledge of the Atlantic great white shark has been relegated for too long to the fevered imaginations of nervous beachgoers and boaters. With the animals returning to the New England coastline in larger numbers, one state scientist with Vineyard roots is bringing that understanding out of the realm of the mythical and uncovering fascinating insights into this elusive two-ton, apex predator’s behavior.

Although news reports about shark sightings can tend toward the hysterical, senior state shark biologist Greg Skomal doesn’t deny that the animals are rebounding in the Northeast.

“What we’re seeing here is what may be either a shift in the distribution of the white shark and most likely a shift in the distribution in response to the gray seals,” Mr. Skomal said, referring to the population explosion of the sharks’ favorite prey following the passage of the 1972 Marine Mammal Protection Act.

“But it could also be an increase in abundance of sharks. We don’t know which it is, but needless to say we know we’re seeing more white sharks off the Cape Cod coastline.”

Mr. Skomal will speak on the subject of sharks at the Tabernacle on Thursday night this week. And Thursday marks the start of the 25th annual monster shark tournament in Oak Bluffs.

In 2009 Mr. Skomal and his team began tagging the animals as they patrolled the seal breeding grounds of Monomoy Island south of Chatham. Last summer Mr. Skomal’s team of spotters and taggers nabbed six sharks, fitting five with Pop-up Satellite Archival Transmitting (PSAT) tags and one with a more precise acoustic transmitter to monitor fine-scale movements. Information from some of those tags continued to pour in throughout the spring.

Much is already known about sharks to stir the popular imagination, from their remarkable efficiency (they can survive for up to a month and a half on a single bite) or their venerable lineage (they predate dinosaurs by almost 200 million years), but what Mr. Skomal and his team uncovered is the remarkable lengths and depths the animals will go to feed and reproduce in the Atlantic.

While many of the animals tagged by Mr. Skomal in the past three years have tended to stay near coastal feeding grounds between New England and northern Florida, this winter Mr. Skomal’s data revealed a more eclectic group, including one 18-foot female that left the continental shelf altogether to plummet some 2,700 feet into the darkness hundreds of miles off the coast of Georgia. Why the animal took that plunge Mr. Skomal can’t say.

“I have no idea,” he said. “The deep-diving behavior is exhibited in the Pacific Ocean and it’s thought that these sharks are going down there to feed. Whatever they are feeding on is obviously energetically profitable. It makes it worth their while to do it. It’s been put forth that they may be feeding on giant squid.”

If the ineffable prospect of a great white diving into the abyss to do battle with giant squid fails to impress, the sharks can also cover remarkable distances horizontally. One of the sharks Mr. Skomal tagged off Monomoy was found wandering the Gulf of Mexico in January.

“Our results in 2010 showed us that the sharks went in a very simple migration north to south,” he said. “What’s kind of interesting is that the results we got in 2011 indicate that not all the sharks do that. We’re starting to see exceptions to a pattern we thought was emerging and that’s somewhat surprising.”

Perhaps no animal has done more to instill in the general public what David Foster Wallace once described as an intuition that the ocean is a “primordial nada, bottomless depths inhabited by tooth-studded things rising angelically toward you.” And with several reported sightings already this year curiosity about the animals is on the rise.

Earlier this month the Division of Marine Fisheries confirmed three great white sightings off Truro, Chatham and Monomoy Island. In West Hampton, N.Y., police were forced to close one beach Memorial Day weekend after two 18-foot sharks and one mangled seal were spotted close to shore. On Saturday WCVB posted a video online reportedly filmed off of the Vineyard of a massive shark circling a fishing boat.

“Oh my God!” screams an incredulous fisherman in the video. “Dude, did you see the size of that thing?!”

If it was a great white, it wasn’t the first sighting off the Vineyard this year. In May Jeff Lynch of Chilmark and his friends Will Farrissey and Mike Capin, both of Oak Bluffs, had the unsettling experience of being followed around for almost two hours in their 23-foot boat Scup Bucket by a 20-foot great white. The shark was investigating a minke whale carcass floating near Devil’s Bridge off Aquinnah.

“It was so big,” Mr. Lynch told the Gazette. “It was incredible, the size of its girth, not like any other big fish.”

And last summer the Coast Guard issued a first-of-its-kind shark advisory for the entire Northeast to recreational boaters and swimmers.

Although Mr. Skomal acknowledges a marked rise in the number of sharks, he says it is safe to go in the water.

“Over eons people have an inherent fear of sharks because they occasionally attack,” he said. “But it’s important to know that shark attacks are extremely rare and perhaps some of the bad reputation they get is not warranted. They’re maligned in many ways.”

The last fatal shark attack in Massachusetts was in 1936 off Mattapoisett in Buzzards Bay. A morbid fascination with these grizzly encounters is not what drives Mr. Skomal’s interest in these animals. Instead, he says, the state of great white shark knowledge is surprisingly incomplete.

“We don’t know a lot about their basic life history and biology,” he said. “Good examples of this are longevity rates, growth rates, reproductive biology and nursery habitats. These are real simple questions we have yet to answer here in the Atlantic.”

As soon as a window of optimal weather and predictable shark sightings opens Mr. Skomal is eager to get out and tag again this year.

“Even though they’ve tagged dozens if not hundreds of animals in the Pacific, each year of tagging reveals a new secret and solves another riddle,” he said. “We’re just getting off the ground here in the Atlantic and there’s so much we don’t know.”


On Thursday Mr. Skomal will present his lecture Jaws Revisited: The White Shark in New England, at 8 p.m. in the Tabernacle in Oak Bluffs. Admission is free.