NANTUCKET, Mass. — The National Oceanic and Atmospheric Administration is announcing a voluntary speed restriction zone south of Nantucket to protect a group of rare whales.

The federal agency said Tuesday that the restriction for mariners will be in effect through Feb. 5 to protect a group of 22 North Atlantic right whales seen south of Nantucket on Tuesday.

Right whales are among the most endangered marine mammals, and are coming off of a year of high mortality and low reproduction.

NOAA Fisheries says it’s asking mariners to either travel around an area 30 nautical miles south of Nantucket or transit through the area at 10 knots or less.

Right whales were decimated during the whaling era and are the source of longstanding conservation efforts.