Marine-mammal experts began carving up the remains of another endangered North Atlantic right whale on Friday in a bid to determine what caused the death of the latest whale to be found floating in the Gulf of St. Lawrence.

Matthew Hardy of the Fisheries Department said around 30 people were assisting in the necropsy – or animal autopsy – being conducted near a lighthouse on the northern tip of Miscou Island, N.B. The animal is the eighth North Atlantic right whale to have died in the Gulf over the last six weeks.

Mr. Hardy said the whale was first spotted Wednesday afternoon east of Shippigan, N.B., while another right whale was found entangled in fishing gear in the in the Gulf.

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"We're responding to this in a very … pro-active manner to try to get to the bottom of this," Mr. Hardy said in an interview Friday. "This opens more questions than we've answered."

A full-sized excavator was on site, peeling back layers of blubber so scientists can look at the animal's internal organs, Mr. Hardy said. He described the smell as "unforgettable," but said the 14-metre carcass is in fresher condition than the rotting remains that were examined in the previous five necropsies.

The Fisheries Department closed a snow-crab fishing area encompassing most of the southern Gulf to protect right whales from the dangers posed by fishing gear.

"This is sort of a first for the department, to make an emergency closure like this," Mr. Hardy said. "It's that serious when we have eight confirmed mortalities of a population of about 500 [right whales]."

In a statement Thursday, the Fisheries Department acknowledged that the closure could have an impact on fishermen, but said the measure was warranted by the "unprecedented" string of North Atlantic right whale deaths in the Gulf. Officials added that 98 per cent of the allowable snow-crab catch in the area has already been harvested.

Prime Minister Justin Trudeau said he has asked Fisheries to keep a close watch on the issue.

"This is something that is extremely concerning to me," he said in Shelburne, N.S., when asked about the situation. "We know we need to take very seriously threats to marine mammals and that is why we're doing our due diligence on that and trying to understand what happened and how we can make sure it doesn't happen any more."

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Sean Brilliant of the Canadian Wildlife Federation applauded the effort, but said the government will have to go further to protect the critically endangered species.

"It's never too little, too late," Mr. Brilliant said in an interview Friday. "We need to look after this whale. It is a part of who we are [as] Canadians."

Mr. Brilliant said the North Atlantic right whale was hunted to near extinction before the practice was banned in the 1930s. Today, he said, other kinds of human activity in the ocean threaten the species' survival.

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 an entanglement in fishing line.

"We have a responsibility to the world to make sure we're being responsible in how we're using the ocean," Mr. Brilliant said. "We have to start paying more attention to these things, because it's the right thing to do."

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Scott Kraus, vice-president and senior science adviser at the Anderson Cabot Center for Ocean Life at the New England Aquarium in Boston, said another death may be imminent after an entangled right whale was spotted in the Gulf.

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.

Mr. Kraus said Canadian fisheries officials are trying to tag the entangled animal with a satellite tracker so they can monitor its movements, but absent human intervention, the whale may not be able to free itself.

"[Its] prospects are probably not that good," Mr. Kraus said. "The photographs that I've seen make it look like pretty heavy fishing gear ... The stronger the rope, the harder it is for whales to get out of it."

Researchers at the New England Aquarium tweeted Thursday that the animal is "severely wounded."

Mr. Kraus said the vast majority of North Atlantic right whales have at some point experienced an entanglement.

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"Disentanglement is a bit of a band-aid to really addressing the issue of entanglement in fishing gear," he said. "It does save whales lives, but it is not the solution to long-term sustainability of either the fisheries or this population of whales."

The Gulf is a relatively new environment for right whales, said Mr. Kraus, and more research is needed in order to find long-term solutions.

"We're not helpless here. It's just that we don't have enough information to really do too much at the moment," said Mr. Kraus. "I think it's going to be a bit of a crash learning course for us all trying to figure out what the best strategy is going forward."