Chilmark, Mass. (AP) — The federal government is implementing a new “slow zone” for boaters south of Martha's Vineyard to try to protect rare whales.

The National Oceanic and Atmospheric Administration said Tuesday that the new slow zone will be in effect until July 18. It's designed to protect North Atlantic right whales, which number only about 360.

The agency is asking mariners to route around the area altogether or travel through it at 10 knots (11.5 mph) or less. The zone went into effect on July 2.

The whales are often located off New England at this time of year. Acoustic buoys detected the right whales southwest of Martha's Vineyard, prompting NOAA to create the zone.

The whales are vulnerable to ship strikes and entanglement in fishing gear.