On June 4, a nine-year-old North Atlantic right whale named Wolverine was found dead in the Gulf of St. Lawrence. Scientists had given him the moniker because of three scars on his back from a propeller strike that resembled the iconic superhero’s claws.

Two weeks later, on June 20, another right whale was found dead in a similar location. Aerial surveyors then located another dead whale on June 25. They found two more dead on June 26. By June 27, they’d found another.

One month, six dead right whales, four of them females. That doesn’t augur well for a species with barely 400 whales left, its population still fluttering on the point of extinction despite a now trans-national conservation effort.

“Six deaths is devastating, and having four of them being females is . . . whatever the word is beyond devastating,” said Philip Hamilton, research scientist and member of the right whale team at the New England Aquarium’s Cabot Center for Ocean Life. “You don’t have to be a mathematician to know what that portends.”

After a particularly bad 2017, in which no right whale calves were born and scientists declared an “unusual mortality event” in the aftermath of 17 whale deaths, experts hoped to see better numbers during the recent calving season. This winter, most conservationists were cautiously optimistic when surveys showed the birth of seven right whale calves off the coasts of Florida and Georgia. But the five deaths in the past week, and six deaths overall, have them once again seriously concerned about a species that remains nearly impossible to track and even more difficult to protect.

“Seven births was an improvement over no births,” Mr. Hamilton said. “But we would have hoped for 20 to 30 calves this year. Seven is not enough, especially with the high mortality.”

Of the six right whales that died recently, scientists have performed necropsies on four of them, with post-mortem analyses showing that three of the four whales died from vessel strikes in the Gulf of St. Lawrence, according to Mr. Hamilton. Punctuation, a 38-year-old female that had given birth to eight calves during her lifetime, was one of those whales. Comet, a 34-year-old male, and Clipper, a calving female as well, were the others hit by boats.

“We knew all six of the whales,” Mr. Hamilton said. “It is in no way common,” he said referring to the number of deaths in a somewhat concentrated location.

Mr. Hamilton added that Wolverine, the first whale found, still had flesh samples being tested in the lab. Neither of the other two found dead had previously calved. The final two were still undergoing necropsies at press time.

At the New England Aquarium, one of the core responsibilities of the right whale team is to maintain the immense photo identification catalogue of all the right whales still in existence. The team then monitors the right whale population, identifying individual whales by their natural markings. When whales die, however, they float on their backs, making it difficult to identify the carcasses. That’s why Mr. Hamilton helps maintain an entire database that is exclusively devoted to listing right whale scars.

“Thanks to the hundreds of thousands of images that we have, we are able to search for a black-bellied female and identify marks on the chin to ID the whale,” the scientist said.

The aquarium’s knowledge of the whales also allows scientists to study the more broadscale effects of the fishing industry on the species. Studies have shown that most right whales experience entanglements at some point in their lifetime, including those that died in the past month.

“All the whales that have died this summer have been entangled two to five times before they have been killed,” Mr. Hamilton said.

According to a paper published by scientists from NOAA this past winter, the energy expended from fishing gear entanglements can cause female right whales to put off calving in favor of staying north for the winter. While scientists are still unsure about the exact migratory patterns of the whales — or whether they migrate at all — aerial surveys have shown that most potential mothers calf along the coasts of Florida and Georgia.

Mr. Hamilton said all six of the whales that died this past month were found in the St. Lawrence, a somewhat unusual locale for the whales in late June.

“Their presence in the St. Lawrence is probably due to climate change,” he said. He added that because of changing ocean temperatures and the location of their food — plankton — the whales have abandoned three of their four main feeding grounds in the Bay of Fundi and around Nova Scotia, with their movements becoming less predictable even though aerial monitoring has remained intense.

“When NOAA did surveys in June, whales were found further to the north and east than in the last few years,” Mr. Hamilton said. “So the plankton just ended up closer to shipping lanes than they had been in the past.”

Peter Corkeron, a scientist at NOAA who heads the large whale research team, said approximately one third of the remaining whales have been spotted in the St. Lawrence, and that the Canadian government has protections in place to prevent vessel strikes similar to those in the United States. But he maintained that it was very difficult to monitor the locations of the whales, especially because there are so few left.

“We don’t really know where the other ones are,” Mr. Corkeron said. “About half of them are missing right now.”

Mr. Corkeron said that while the whales are traditionally in and around the Gulf of Maine at this time of year, fattening up on copepods, their movements are unpredictable and they could be spotted any time east of Cape Cod or south of Nantucket and the Vineyard. Three weeks ago, he said one was seen off the coast of France.

Mr. Hamilton said one of the primary steps in the conservation effort was gaining a better understanding of the whale’s movements. Both the Canadian and American governments have worked together to protect the whales in their known locations, but it’s difficult to institute vessel speed restrictions to protect the whales if scientists don’t know where they are.

“There needs to be a broader way to manage the population and less of a patchwork approach,” Mr. Hamilton said.

Mr. Hamilton has worked to protect right whales for the last 33 years, watching many of them grow from infancy. Their deaths made him emotional.

“Many of these whales, I remember seeing them in mating groups. And seeing them as calves. And watched them as they moved up and down the coast. They all have great stories attached to them. It’s not just numbers.” Mr. Hamilton said. “I have a heavy heart these days.”