Mariners are asked to take caution in waters around Martha’s Vineyard, with more than a dozen critically-endangered North Atlantic right whales seen feeding in waters south of the Island.

In late February NOAA fisheries announced a voluntary vessel speed restriction zone 16 nautical miles south of the Vineyard. Mariners are asked to either avoid the area or travel through at 10 knots or less.

Coordinates are available at the fisheries website.

According to NOAA an aggregation of 10 right whales was spotted in the area on Feb. 21, including one whale south of Gay Head and Noman’s Land and several other whales directly south of the middle of the Island.

The speed restriction zone was scheduled to be in effect through March 8, but NOAA later extended the precautionary zone after 14 North Atlantic right whales were seen in the area on March 6. The restrictions are now in effect until Tuesday, March 21.

North Atlantic right whales weigh up to 79 tons and can grow to be 50 feet long. They give birth to calves from December through March in coastal waters off Georgia and Florida, and travel north to New England waters to feed on plankton. The first reports of North Atlantic right whales this season in Cape Cod Bay came in late December, and aerial surveys have shown aggregations of 25 to 30 whales in the bay since then, according to the Center for Coastal Studies, a larger than average number. Right whale sightings usually increase beginning in mid-March.

According to a whale season update by Charles (Stormy) Mayo, director of the right whale ecology program at the Center for Coastal Studies, the whale behavior follows recent patterns. Centropages, a winter copepod genus, is dominating the zooplankton in the Cape Cod Bay and in the areas where the whales had been feeding, he said in an update.

North Atlantic right whales are federally listed as an endangered species, with an estimated population of around 500. Collisions with ships and entanglement in fishing gear are some of the main threats to the whales, and NOAA has instituted seasonal mandatory speed restrictions for vessels larger than 65 feet long in some areas the right whales frequent. Voluntary speed restrictions are issued for other areas for when the endangered whales have been seen. A whale alert phone app has also been design to inform mariners about where whales have been seen and for whale reports.

Approaching a right whale closer than 500 yards violates state and federal law. All right whale sightings should be reported to 866-755-6622.