Mariners are being urged to proceed with caution through the waters of Martha’s Vineyard and Nantucket following the probable sighting Sunday of three right whales north of Oak Bluffs.

The whales were spotted two and three miles offshore, said Tim Cole, a fisheries biologist with the National Fisheries Science Center in Woods Hole.

Less than 450 Atlantic right whales are known to be in existence, making them one of the most endangered marine mammals in this area.

The whales were spotted by a recreational boater who then made contact with state experts, said Mr. Cole. The mariner did not take photographs, which would allow experts to confirm the sighting.

“Staff of the state Division of Marine Fisheries interviewed the guy, sent him pictures of whales. They felt pretty strongly and were confident to list the report as ‘probable,’” Mr. Cole said. “We just wish we had photographs.”

This is not the first time endangered right whales have been spotted near the Island. Though more often seen in the waters of Cape Cod Bay and Great South Channel, they have also been seen closer to Martha’s Vineyard, Mr. Cole said.

Two whales were spotted north of Menemsha in March. In February several whales were spotted southeast of Wasque. They also have been spotted in the vicinity of Nantucket.

In response to the sighting, the National Oceanic and Atmospheric Administration’s Fisheries Service established a voluntary vessel speed restriction area comprising all of Nantucket Sound and the waters around the Vineyard and part of Nantucket. “Mariners are requested to route around this area or transit through it at 10 knots or less,” the notice says.

The restriction will remain in effect until July 21.

NOAA maintains a right whale monitoring website at Anyone who thinks they see a right whale should call 866-755-6622.