In this March 28, 2018, file photo, a North Atlantic right whale feeds on the surface of Cape Cod bay off the coast of Plymouth, Massachusetts. Credit: Michael Dwyer / AP

NANTUCKET, Massaschusetts — The federal government said it’s extending a voluntary protective zone designed to help rare whales into September.

The National Oceanic and Atmospheric Administration said the protective zone is located south of Nantucket and it’s designed to help North Atlantic right whales. The whales number only about 360 and are vulnerable to ship collisions, so NOAA has asked mariners to slow down when near them.

An aerial survey team sighted the whales in the area on Aug. 25. NOAA said the slow zone has been extended through Sept. 9.

There is also another slow zone southeast of Nantucket until Aug. 31. The agency has asked that mariners avoid the areas or transit through them at 10 knots or less.