A North Atlantic right whale feeds on the surface of Cape Cod bay off the coast of Plymouth, Massachusetts, March 28, 2018. Credit: Michael Dwyer | AP

The federal government is expanding a protected zone off New England to attempt to protect endangered right whales.

The National Oceanic and Atmospheric Administration said a voluntary speed restriction zone it established off of Nantucket has been extended through March 17. The zone is designed to protect a group of 10 of the whales that was seen in the area March 1.

There are only a little more than 400 of the whales left. NOAA is asking mariners to route around the area south of Nantucket altogether or transit through it at 10 knots or less.

NOAA also uses mandatory speed restriction areas to protect the whales in Cape Cod Bay, the mid-Atlantic and off the southeastern states.