A 1,500 pound, eight-foot long male leatherback turtle that had become entangled in fishing gear was rescued in Nantucket Sound on Friday by a group that included the Oak Bluffs harbor master and shellfish constable.

“I couldn’t believe the size of that thing. That is a first for me,” said harbor master Todd Alexander.

The call for help first came to town shellfish constable David Grunden, who is a member of the region’s sea turtle disentanglement group. Mr. Grunden said the call came in at noon via the Coast Guard that the sailboat Way to Go had spotted the troubled turtle in the Sound, swimming with what looked like a lobster pot or conch buoy attached. The sighting was about nine miles east of the Oak Bluffs harbor, a few miles west of the Cape Pogue lighthouse.

Mr. Grunden, his wife Sharry and Roger Williams, a veterinarian, were taken to the scene by the harbor master in his 25-foot powerboat.

The trip took about 30 minutes, Mr. Grunden said. He said locating the turtle was made easier by the fact that the sailboat remained on scene, its sails luffing.

When they pulled alongside the ailing turtle, Mr. Grunden said a fishing boat from Woods Hole named the Rolling Stone arrived.

Onboard was Kara Dodge, a researcher with the Large Pelagics Research Center at the University of New Hampshire. She was hoping not only to release the animal but also to attach a transmitter to it.

Mr. Grunden said the turtle seemed feisty, strong and free enough to tow what was apparently a fish pot attached to the buoy. “The line was wrapped around its left flipper. He had no problem dragging what was on the bottom,” Mr. Grunden said.

The Vineyard team watched as the Rolling Stone came alongside the turtle and disentangled it from the gear.

Brian Sharp of the Provincetown Center for Coastal Studies said that while Ms. Dodge had hoped to attach a satellite transmitter to the turtle before it was released, the turtle freed itself too quickly.

Mr. Alexander, who watched the rescue operation, said at one point it looked like the big turtle was going to pull the two people out of the boat into the water. “At one point we were calling it an Oak Bluffs sleigh ride,” he said.

He speculated that the sea turtle had not been entangled long. They observed other fish pots floating in the area.

Mr. Sharp, who coordinates all sea turtle entanglements in this region, said the incident is common for this time of year. He praised the sailboat owners for not only making the call but staying nearby in case they were needed for assistance.

“We encourage boat owners to call us directly at the Marine Animal Entanglement Hotline 1-800-900-3622 or to contact the Coast Guard,” Mr. Sharp said. “We have a trained network of local, state and federal responders throughout Massachusetts. We have trained 85 to 90 people in this.”

He said Ms. Dodge has been tagging a number of free swimming sea turtles in area waters this summer. Had she tagged this turtle, it would have been the first this summer of an entangled sea turtle.

“In a typical year we get from 22 to 25 reports of animal entanglements [in state waters],” Mr. Sharp said, adding: “Sea turtles cover the entire Atlantic Ocean. They predominantly feed on jellyfish. When you see jellyfish, you usually see turtles. The leatherback sea turtle is the largest turtle and it almost exclusively feeds on jellyfish.”

Mr. Sharp said his group has no data on the number of leatherback sea turtles that swim in Nantucket Sound or in waters around the Cape and Islands. He said there are estimates about how many turtles return to the Caribbean to lay eggs, but once the animals and the babies are at sea, populations are difficult to estimate.

Entanglement sightings are a critical part of sea turtle studies.

Mr. Sharp urged anyone who sees an entangled sea turtle to contact his group. And he cautioned against attempting a rescue and said anyone who sees an entangled turtle should stay 150 to 200 feet away. “Staying clear is not only safe for the sea turtle it is safe for the boat owner,” he said.