PORTLAND, Maine (AP) — Marine scientists are alarmed by the deaths of six endangered North Atlantic right whales in Canadian waters during the past three weeks and say humans must help protect them.

North Atlantic right whales are among the most endangered large mammals on Earth, with only about 500 still alive. Mark Baumgartner, an associate scientist with the Woods Hole Oceanographic Institute on Cape Cod, said Friday the deaths are a "mortality disaster."

The loss of so many right whales so quickly was probably last seen when whaling decimated their population in the 19th century, Baumgartn...