10 Endangered Right Whales Spotted in Cape Cod Bay

Ten endangered right whales were spotted in Cape Cod Bay Thursday as officials warned boaters to stay alert and avoid collisions.

The five mother/calf North Atlantic right whale pairs were seen between Plymouth and Sandwich. The whales are highly endangered; their population has dwindled down to about 550.

One of their biggest threats is boat collisions.

"Right whales are the most endangered large whale in the North Atlantic," the state Division of Marine Fisheries said in a statement. "Vessel operators in this area are strongly urged to proceed with caution, reduce speed (less than 10 knots), and post lookouts to avoid (collisions)."

The mothers observed Thursday were seen feeding on zooplankton near the surface. More right whales were spotted earlier this week.

"Given their behavior and the proximity to vessel traffic, the situation presents a high risk of vessel collision to a sensitive and important segment of the right whale population," the fisheries division said.

Federal law prohibit vessels from coming within 500 yards of right whales.

"Vessel traffic is expected to increase in this area over the next few weeks with seasonal increases in recreational and commercial fishing, as well as whale watching, and passenger ship activity," the fisheries division said. "Massachusetts Environmental Police and U.S. Coast Guard are authorized to enforce the 500-yard rule."

The fisheries division shared this graphic of the most high-risk area for right whale vs. boat collisions:

Top photo: A right whale mother and calf. (Credit: Gill Braulik)