BOSTON -- A state biologist and a team of Cape Cod fishermen became the first group to successfully tag a great white shark in the Atlantic Ocean on Saturday, placing tracking devices on two sharks off the coast of Chatham, according to the Department of Marine Fisheries.

Beaches in Chatham were closed in the afternoon after the sharks came within 75 yards of the coastline, and they'll remain off-limits to swimmers till the middle of the week, safety officials said.

Biologists from the Massachusetts Shark Research Program have been closely monitoring the waters near Monomy Island to locate and identify sharks after five were spotted in the waters off Cape Cod on Thursday.

At about 10 a.m. Saturday, senior biologist Greg Skomal and the crew of the fishing vessel Ezduzit found a great white off the coast of Chatham and harpooner Bill Chaprales landed the satellite tracking device on a fin. The crew then spotted a second great white at 3:30 p.m. and placed a second satellite tracker.

Researchers use the tags to record where sharks travel, allowing scientists to better understand their migratory patterns. Great whites that have been tagged off the coasts of South Africa and Australia have provided researchers with valuable data about the vulnerability of sharks to human fishing patterns.

No fewer than a dozen shark species, including makos, blue sharks and thresher sharks, swim in and out of New England waters each year, according to the Division of Marine Fisheries. The sharks are common in the area because of the thousands of seals that call Chatham home.

In 2004, Skomal helped tag another great white in Massachusetts waters, but the tracking device malfunctioned and researchers weren't able to gather any data about the shark's movements.