HALIFAX -- Another endangered North Atlantic right whale that was found lifeless in the Gulf of St. Lawrence is being towed to a New Brunswick island for a post-mortem examination, an animal rescue group said Thursday.

Tonya Wimmer, director of the Marine Animal Response Society, said that marine mammal experts will carve up a fourth right whale carcass on a beach on Miscou Island, N.B., on Friday. The animal is the latest of eight North Atlantic right whales found dead in the Gulf of St. Lawrence over about six weeks.

The society said an aerial survey conducted by the National Oceanic and Atmospheric Administration in the U.S. spotted the whale carcass late Wednesday afternoon east of Shippagan, N.B. The group said the survey also revealed another entangled right whale in the Gulf of St. Lawrence.

Wimmer said there was a sense of urgency to haul the whale carcass ashore for a necropsy, or animal autopsy, as the mid-summer sun threatened to broil the animal's remains.

"As soon as you hit the height of summer ... you want to do these necropsies as quickly as possible," Wimmer said in an interview. "Anything with the animal itself will deteriorate really quickly."

The society's response co-ordinator Andrew Reid said they are working with the federal Fisheries Department and the Canadian Wildlife Health Co-operative to determine what killed the whale.

Reid called the whale deaths "unprecedented."

"Where we're dealing with such an endangered species, it's very concerning. For any species it would be concerning to have this many animals die in such a short period," he said.

"For a species like the North Atlantic right whale, where there are so few animals left, it's a heightened concern."

North Atlantic right whales are critically endangered, with only about 525 estimated alive.

Last week, the wildlife co-operative said a necropsy performed in the Magdalen Islands on one of the dead right whales found floating in the Gulf of St. Lawrence showed it had marks of blunt trauma, suggesting it may have collided with a vessel.

Tests performed earlier on two other North Atlantic right whales in Prince Edward Island also showed signs of blunt trauma. Another died as a result of what the group called a chronic entanglement in fishing line.

Federal Green Party Leader Elizabeth May released a statement calling on the Fisheries Department to order a complete review of fishing gear and shipping lanes in the areas of Gulf where the right whale carcasses have been found.

Disentanglements of right whales were recently put on hold by Ottawa following the death of a whale rescuer in New Brunswick. Joe Howlett, who was also a lobster fishermen, died after freeing a North Atlantic right whale that had been entangled in fishing gear near Shippagan.

The United States had implemented similar protocols, but announced earlier this week that it was allowing its whale-disentanglement teams to resume most rescue operations, except for the disentangling of right whales.

Chris Oliver, assistant administrator with the National Oceanic and Atmospheric Administration, cited right whales' unpredictable behaviour as a challenge during rescue attempts.

Jerry Conway of the Canadian Whale Institute in Campobello, N.B., agreed.

"The North Atlantic right whale has a violent reaction when certainly the weight that has been restricting it is released, and it's an escape mechanism," Conway said. "Some of the other whales are far more docile and just swim away. The North Atlantic right whale reacts violently and this is why they have to be treated entirely differently."

Conway said the Fisheries Department has sent an aircraft to locate the entangled whale so it can be tagged with a tracking device to monitor its movements. He said officials will then consult with experts on the safest course of action.

The Gulf is a relatively new environment for right whales, said Conway, whose primary feeding grounds have traditionally been in the Bay of Fundy and Roseway Basin.

With initial findings suggesting that human activity may have played a role in the string of right whale deaths, Conway said that fishermen in the Gulf will have to be a part of any effort to save the lumbering giants.

"The fishing industry itself is the answer and will possibly help solve this problem," said Conway. "Fishermen are very innovative. They can develop strategies, with the right information and given the time and resources, that could mitigate this a great deal."

Conway said if the current rate of right whale deaths persists over the next few years, the demise of the endangered animals will become "inevitable."

- With files from Aly Thomson in Halifax