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Tagging along with great whites

Sharks are likely to return to Cape, research suggests

By Beth Daley
Globe Staff / March 4, 2010

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Remember those great white sharks that swam so close to shore last summer officials closed some Cape Cod beaches?

At least three - and probably a lot more - are enjoying the warm water off Florida this winter, according to new state Division of Marine Fisheries research. And they’ll probably be back.

The sharks’ whereabouts are being transmitted to state marine biologists from electronic tags they managed to affix on five of the mysterious, fierce predators in September, providing some of the first-ever insights into the Atlantic Ocean travels and behavior of great whites.

The preliminary results suggest that the sharks are following a migratory path along the Eastern Seaboard used by other marine species, from whales to fish - and like them, will return when the water warms in the summer.

New England waters have long been known to host the great white - the iconic species made famous in the movie “Jaws’’ - but they were considered rare visitors. The new findings, however, are being released as an increasing number of the sharks have been spotted closer to shore in recent years, perhaps to feed on growing populations of gray seals.

“These . . . sharks have turned out to be snowbirds,’’ said Ian Bowles, state secretary of energy and environmental affairs. “This research reveals new insights into shark behavior . . . and informs biologists about the habits and preferences of this amazing species.’’

Greg Skomal, a state shark expert who spoke at a New England Aquarium news conference, said he had expected one or more of the sharks to travel far out to sea, as better-studied Pacific sharks do. But all three sharks hugged the coast along the continental shelf and in two months traveled 1,000 miles south to waters off Florida.

At least one shark deep-dived to 1,500 feet during its travels. Such behavior has been seen in great whites off the Pacific Coast. But Skomal warned not to read too much into “first insights and glimpses.’’

“We are just beginning to understand them,’’ he said. “What is their size and population? That is a big blank.’’

Skomal was ecstatic last fall when he and a harpoon fishing captain began chasing great whites off Chatham to place satellite tags on them. They tagged five, but the $3,500 electronic devices can malfunction, so he was unsure whether they would get any useful data. Skomal had successfully tagged a great white trapped in a lagoon off Cape Cod in 2004, but the device detached prematurely.

He said he was on “pins and needles’’ until Jan. 15, when the first satellite tag surfaced about 50 miles east of Jacksonville, Fla. It was attached to a 12-foot-long shark. The tags are programmed to pop to the water’s surface after a certain amount of time and begin transmitting data about the shark’s movements over the previous months. A second tag, which had been placed on a 10-foot-long shark, surfaced Feb. 4 about 30 miles north of where the first tag had. A third tag appeared 80 miles south Monday. One more is supposed to pop up in May.

Why are the sharks off Florida? Skomal suspects it is for food.

At least a dozen shark species migrate in and out of New England waters every year, although it is the great whites that, deservingly or not, capture the most attention. The animals can reach 20 feet long and weigh more than 4,000 pounds, but unlike their reputation, they are not usually man-hunters. Rather, the animals tend to go after seals and porpoises and feed on whale carcasses - although there are occasions when the fish attack humans. The last New England death blamed on a great white occurred off Mattapoisett in 1936.

Skomal is hoping to tag more sharks this summer - yesterday, the Division of Marine Fisheries said it received a private donation of $25,000 and was looking for more funding.

Skomal is fascinated with the basic biology of the creatures, but understanding their behavior may be just as critical if more great whites visit Cape Cod beaches in the summer.

Beth Daley can be reached at bdaley@globe.com.