QUINCY, Mass. — A canoe outing on a Massachusetts river this week turned into a natural history lesson for four young women.

The canoeists were padding the North River south of Boston on Wednesday when they came across a six-foot long carcass of a rare Atlantic sturgeon.

They pulled the prehistoric fish on board and notified state wildlife authorities.

A New England Aquarium veterinarian performed a necropsy on the 75-pound fish and confirmed it was a sexually mature female, although it did not have any eggs.

An aquarium spokesman says Atlantic sturgeon as long as 14 feet were once commonplace in Massachusetts coastal waters, but industrialization and pollution decimated their numbers.

The presence of the endangered fish in the river in Pembroke may be a sign that water quality is improving.