In this April 10, 2008, file photo, three right whale tails surface in Cape Cod Bay near Provincetown, Mass. Credit: Stephan Savoia / AP

BOURNE, Mass. — Dozens of rare whales have returned to the waters off Massachusetts for the spring.

The whales are North Atlantic right whales and they have been sighted in Cape Cod Bay this month. The National Oceanic and Atmospheric Administration said there were 89 right whales spotted in the bay on March 21, including three pairs of mothers and babies.

The whales number only about 360 and they are vulnerable to ship strikes and entanglement in fishing gear. NOAA said it is asking vessel operators to slow down to 10 knots or less and respect other speed restriction methods that are in place in state and federal waters off New England.

Cape Cod Bay is subject to a mandatory speed restriction of 10 knots or less until May 15.