A sixth dead North Atlantic right whale has been discovered in the Gulf of St. Lawrence this year, Fisheries and Oceans Canada said Thursday evening, hours after announcing heightened protective measures for the endangered species.

It's the fourth whale carcass discovered in the past 48 hours. The sixth whale, which has yet to be identified, was found drifting off Quebec's Gaspé Peninsula during an aerial surveillance flight.

"We are currently assessing the recovery and necropsy options," the federal agency said in a statement.

The latest discovery came less than a day after the fifth whale was discovered along Anticosti Island in Quebec.

"It feels a little déjà vu. We have another scenario where we're getting … calls about a whale after a whale, after a whale," said Tonya Wimmer, executive director of the Marine Animal Response Society in Halifax.

"It's heartbreaking."

She said the fifth whale was found by scientists with DFO in a remote area on the island. While a necropsy could be "extremely complicated," she's hopeful one will be able to take place.

"The information that we can learn from them is too invaluable to be lost."

The fifth confirmed dead North Atlantic right whale this year was identified as #3329, a 16-year-old female. (Jolinne Surette/Quoddy Link Marine)

The fifth dead whale was identified as #3329, a 16-year-old female who had yet to calve, according to the Anderson Cabot Center for Ocean Life at the New England Aquarium. The organization said in a release Thursday afternoon she had become entangled in fishing gear at least four times.

Earlier on Thursday, Transport Canada announced it had implemented an interim, precautionary speed restriction of 10 knots, for vessels of 20 metres or more in length travelling in the western Gulf of St. Lawrence, in two designated shipping lanes north and south of Anticosti Island.

Unfortunately, we confirmed another <a href="https://twitter.com/hashtag/rightwhale?src=hash&ref_src=twsrc%5Etfw">#rightwhale</a> death today. It was found washed up on the shore of Anticosti Island, bringing the total deaths in Canadian waters for 2019 to 5. <a href="https://t.co/XVvn2WgYrq">pic.twitter.com/XVvn2WgYrq</a> —@FishOceansCAN

The department said the new measure is effective immediately.

"Protecting our endangered North Atlantic right whales is an important task, one that our government takes seriously," said Transport Minister Marc Garneau in a statement.

At the moment we just have too many animals in too many different locations. -Tonya Wimmer, Marine Animal Response Society

"We will continue to work with our partners to ensure the safety of these marine mammals, as well as vessels, and crew."

This measure is in addition to the fixed speed restriction introduced in April in a large area in the Gulf of St. Lawrence, where vessels 20 metres or longer are restricted to a maximum of 10 knots until Nov. 15.

Michelle Saunders, a Transport Canada official, said a 10-knot maximum reduces the chances of a fatality by 70 per cent.

Inspectors with Transport Canada and the Canadian Coast Guard's Marine Communications and Traffic Services will enforce the precautionary measure. Failure to comply will result in an administrative monetary penalty of up to $25,000.

Tonya Wimmer, director for the Marine Animal Response Society, said the recent right whale death is heartbreaking for researchers, scientists and government officials trying to protect the species. (Nicole Williams/CBC)

Transport Canada will also continue to monitor the whales in Canadian waters through its National Aerial Surveillance program as well as vessel-based surveys and acoustic technology. Officials are still trying to determine the distribution of the growing number of right whales in the gulf.

More whales found dead

On June 25, two dead right whales were found floating in the Gulf of St. Lawrence.

The female, #3815, was on the cusp of sexual maturity and had yet to give birth, according to the New England Aquarium.

The aquarium said the whale was born in 2008 and sighted every year since, usually in Cape Cod Bay off the Massachusetts coast. She was first spotted in the Gulf of St. Lawrence in 2017 and returned the following the two years.

She had been entangled in fishing gear on four separate occasions.

The fourth dead North Atlantic right whale discovered in Canadian waters this year was identified as an 11-year-old female on the cusp of sexual maturity. (Candace Borutskie/Anderson Cabot Center at the New England Aquarium.)

The dead male, believed to be at least 33 years old, was named Comet for a long scar on his right side. He was an "old favourite" of researchers, and fathered a daughter in 1990. Comet became a grandfather in 2013.

The aquarium said visible scarring indicated he had been involved in three minor entanglements.

Comet was found off the Acadian Peninsula in northeastern New Brunswick and No. 3815 is still floating west of the Magdalen Islands

"We will have to see with the animal that is floating," Wimmer said. "At the moment we just have too many animals in too many different locations."

Officials prepare for another necropsy

Right now a team of experts is getting ready to conduct a necropsy on Comet. The necropsy will take place on Prince Edward Island on Friday morning.

Helping to keep <a href="https://twitter.com/hashtag/rightwhales?src=hash&ref_src=twsrc%5Etfw">#rightwhales</a> safe: important announcement by <a href="https://twitter.com/Transport_gc?ref_src=twsrc%5Etfw">@Transport_gc</a>. <a href="https://t.co/ovAlNlCPQQ">https://t.co/ovAlNlCPQQ</a> —@FishOceansCAN

Meanwhile, on June 19, there was also a discovery of a dead 38-year-old female, known as Punctuation. Preliminary necropsy results are compatible to sharp trauma, consistent with vessel strike, said Fisheries and Oceans Canada. The final detailed results of the necropsy will be available in the coming months.

Researchers have also said Punctuation had been entangled in fishing nets five times and struck by ships twice in her lifetime.

Punctuation the right whale, seen from the rear, was towed to Cape Breton for examination on Tuesday. (Gary Mansfield/CBC)

A nine-year-old male, known as Wolverine, was also found dead on June 4.

An assessment came back inconclusive, but fisheries officials said the death did not appear to be caused by a vessel strike or entanglement in fishing gear.

Wolverine, a nine-year-old north Atlantic right whale, was the first whale death reported in 2019. (Gabrielle Fahmy/CBC)

Kim Davies, an oceanographer and assistant professor at the University of New Brunswick in Saint John, wasn't surprised a fifth whale was found dead.

"Once you get up to three or four … I wouldn't be surprised if there are more than five," she said.

Next week, Davies will lead a team of scientists in the Gulf of St. Lawrence over the summer to study right whales, and try to understand more about their distribution and where the animals will travel from year to year.

"One of the things that caught us off guard this year is that the right whales are in a really different location than in previous years," she said.

Davies said the animals are aggregating further north and further east in the Gulf of St. Lawrence, closer to shipping lanes.

"The whales are present over a really, really large area of the Gulf and individual right whales move around constantly," she said.

Saving a species

There are believed to be 413 North Atlantic right whales left in the world.

No right whales were recorded dying in Canadian waters last year, but 12 were found dead in the Gulf of St. Lawrence in 2017.

Necropsies on seven of them found four died from trauma consistent with vessel collisions, while two deaths were the result of entanglement in fishing gear.

Wimmer said biologists, researchers, conservation officers, and government officials in Canada and the United States are working hard to save the species.

"We don't want any further deaths of this species or any others."