Beginning on Tuesday, ships that are 65 feet long or longer will have to slow down along the east coast to reduce collisions with endangered North Atlantic Right Whales.
Under the new federal regulation, the ships must travel no faster than 10 Knots in southeastern and mid-Atlantic waters, where the whales usually gather.
The speed restriction will extend 20 nautical miles around all major ports.
Similar speed restrictions will take effect in waters off New England starting in January, as the whales begin to migrate north to the Gulf of Maine.
NOAA says only 300 to 400 North Atlantic Right Whales remain in existence.