A Northern Right Whale was spotted in Greenport Harbor Thursday, exciting spectators and prompting the U.S. Coast Guard to advise boaters to stay at least 500 yards away.

"It is a rare occurrence, even though this is their normal migratory route . . . along the shore of Long Island," said Robert DiGiovanni, executive director and senior biologist for the Riverhead Foundation for Marine Research and Preservation. "Whenever we have a whale in the area, there's always a heightened level of excitement."

Foundation members in a boat snapped pictures of the endangered whale, which was also seen in waters north of Shelter Island. They're hoping Friday to get a better look from the air, DiGiovanni said. "We're going to try to monitor the animal and see if it's in the area tomorrow," he said Thursday night.

While the whale appeared healthy, the foundation is hoping the marine mammal can find its way out of the Orient Harbor area and return to its normal migratory path.

There are only about 350 to 450 North Atlantic right whales alive today, according to the National Oceanic and Atmospheric Administration. The stocky black whales are usually about 50 feet long, weigh 70 tons and travel alone or in small groups, NOAA says.

Most right whale fatalities happen when the animals are struck by boats or ensnared in fishing lines.

"Hopefully, people will stay away from the animal and not change its behavior. We hope it will move on," DiGiovanni said. "Altering the animal's behavior could make the situation worse, so it's really important that the public knows to stay away."A spokesman for the Coast Guard's Long Island Sound sector said the agency broadcast a message Thursday warning boaters to keep a safe distance from the whale. Anyone who spots the whale is asked to call the foundation hotline at 631-369-9829.

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