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

PORTLAND, Maine — Federal ocean managers say a rare species of whale has been detected east of Portland, Maine, and they are using a special protected zone to try to keep them safe.

The right whales are believed to number less than 350 and they are vulnerable to ship collisions and entanglement in fishing gear. The National Oceanic and Atmospheric Administration said it’s asking mariners to avoid the area where the whales were spotted or transit through it slowly.

The area is about 80 nautical miles east of Portland in the Gulf of Maine.

The protected zone will be in effect until at least Nov. 19. NOAA has also used another protected zone recently south of Nantucket, Massachusetts.