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

BOSTON — Several protected zones off the East Coast that are designed to aid rare whales are set to expire in the coming days.

The zones are voluntary slow zones meant to prevent North Atlantic right whales from colliding with ships. The whales number less than 340 and they have suffered high mortality in recent years.

Mariners are asked to avoid the areas altogether or transit through them slowly. The first of the zones, located east of Boston, expired Tuesday.

A zone located east of Virginia Beach, Virginia, expires Thursday. Another east of Ocean City, Maryland, ends Friday. Two more located east of Boston expire April 2 and April 10, respectively.

A slow zone located southwest of Martha’s Vineyard, Massachusetts, ends April 7, and another west of Martha’s Vineyard ends April 8. A zone southeast of Atlantic City, New Jersey, expires April 8. Zones located southwest of Nantucket, Massachusetts, and southeast of New York City end April 10 and April 12, respectively.

The National Oceanic and Atmospheric Administration uses the slow zones and other tools to try to protect the whales from threats such as ship collisions and entanglement in fishing gear.