06/30/2017 15:34 EDT | Updated 07/03/2017 09:43 EDT

Gulf of St. Lawrence whale deaths a 'mortality disaster,' American expert says

NORWAY, P.E.I. — The deaths of six right whales in the Gulf of St. Lawrence are a "mortality disaster" on a scale likely not seen since whaling decimated their population in the 19th century, an American scientist says.

Mark Baumgartner of the Woods Hole Oceanographic Institute on Cape Cod said the June deaths should be a call for humans to do more to protect the animals when possible.

"With such a small and declining population, right whales have little capacity to deal with both natural and human-caused mortality simultaneously," he said.

North Atlantic right whales are among the most endangered large mammals on Earth, with only about 500 still alive.

Six were found dead in the Gulf of St. Lawrence near Quebec's Magdalen Islands in June.

"For a small population like right whales, the difference between population growth and a path toward extinction can be the matter of a handful of animals," said Scott Kraus, vice-president and senior science adviser at the Anderson Cabot Center for Ocean Life at the New England Aquarium in Boston.

A necropsy was conducted Thursday on a male whale that was first spotted on June 18, and marine mammal experts carved up a second carcass Friday on a Prince Edward Island beach.

Officials want to determine if boat strikes, fishing gear or a possible toxic algal bloom could be to blame for the whales' deaths.

The autopsies are being done in Norway, a tiny hamlet near P.E.I.'s northwestern tip.

Federal fisheries officials said late Friday that the remains of another species of whale, a dead fin whale, was discovered near Prince Edward Island by a recent aerial patrol.  The cause of death is not known and officials were trying to determine the next step.

— With files from The Associated Press