Federal fisheries managers and conservation groups raised concerns Tuesday about threats to endangered right whales after two were found dead off the Maine coast and a third was disentangled from fishing gear near Cape Cod.

The spate of three incidents reported in a three-day span is renewing the focus on a whale population that has been growing but remains in a precarious position. Fisheries managers will also be studying the two entanglements, one of which is being now blamed for the death of a female whale just entering its reproductive years.

Last Friday, a whale-watching boat spotted what turned out to be an 11-year-old female North Atlantic right whale floating dead off Boothbay Harbor. On Saturday, the same day that Maine Marine Patrol and Coast Guard crews were towing the 43-foot-long whale into Portland Harbor, a second, badly decomposed right whale was reported about 8 miles off Mount Desert Rock south of Mount Desert Island. And just two days earlier, whale disentanglement specialists freed a third right whale from hundreds of feed of fishing line and buoys near Provincetown, Massachusetts. That whale survived and swam away.

So on Tuesday, representatives with the National Oceanic and Atmospheric Administration and several conservation organizations took the unusual step of highlighting the cases to raise awareness.

“I think we have done a pretty good job working hard to recover the species and have seen the fruits of our labor in terms of progress being made on our recovery efforts for right whales,” said David Gouveia, marine mammal and sea turtle program coordinator for NOAA’s Greater Atlantic region. “However, in recent years we have not seen the strides that we had once seen perhaps and I think we want to assure ourselves that we are not complacent and that we are continuing our drive to recover this species.”

Marine biologists estimate that there are roughly 500 North Atlantic right whales, a type of large baleen whale found seasonally off the coasts of New England and the Canadian Maritimes. That is up from estimates of just 300 to 350 individual whales about a decade ago but still places the right whale among the most critically endangered whale species in the world.

Among the top threats to right whales are ship collisions – due to their tendency to lumber near the water’s surface – and entanglement in fishing gear. In response to the latter threat, fisheries regulators have imposed new – and costly – regulations on lobstermen and other so-called “fixed-gear” fishermen aimed at reducing the likelihood that whales will become entangled in lines.

But biologists warn that entanglements in fishing gear continue to take a toll on the species.

The dead whale spotted off of Mount Desert Rock was so badly decomposed – and at-sea weather conditions so rough – that crews were not able to retrieve the animal in order to determine a cause of death. The two other whales are providing useful information to biologists, however.

A team of researchers and biologists conducted a necropsy of the Boothbay Harbor whale – officially dubbed “3694” by researchers who track individual whales – after the 43-foot-long behemoth was driven by tractor-trailer through downtown Portland to a composting facility in Gorham. The 11-year-old whale was found with rope entangled around its head, in its mouth and around both flippers.

“The female whale presented with a thin blubber layer and other findings consistent with prolonged, chronic stress,” said Kim Durham, rescue program director for the Riverhead Foundation for Marine Research and Preservation in New York, who led the necropsy. “The cause of death of this animal was determined to be from chronic entanglement.”

Compounding the loss, whale 3694 was just entering reproductive age and would have been expected to produce five or six calves over the next 25 to 30 years, biologists said.

Patrice McCarron, executive director of the Maine Lobstermen’s Association, said Monday that the size of rope that fatally entangled the Boothbay Harbor whale appeared to be larger than that typically used by lobstermen. Whales have been known to carry fishing gear for extended periods of time – and thousands of miles – making it difficult to determine where an entanglement occurred. But NOAA officials continue to investigate the case.

NOAA representatives said there were no identification markers, buoys or other ways for the team to pinpoint the origins of the rope or even immediately confirm it was fishing gear. The rope was described as relatively “clean,” meaning it had not been submerged long.

“That makes our job a little bit more difficult as managers to try and trace back what may have caused that particular entanglement,” Gouveia said. “So we are going to continue to do our research and look at the rope in more detail to see if there are any markings on it that are required under our management to give us a clue as to what fishery it might have come from.”

The Massachusetts whale, meanwhile, could provide a wealth of useful information.

A marine mammal entanglement response team from the Center for Coastal Studies in Massachusetts was able to remove more than 200 feet of rope as well as buoys and other gear from the whale. The gear and rope still contained permit information and other data that NOAA can use to determine who owned the gear and the type of fisheries they were targeting.

NOAA officials declined to provide specifics on Tuesday beyond confirming it was a U.S. permit likely for fixed gear, but said the review is ongoing. Gouveia said those findings could determine if the owner of the gear did anything wrong, such as using the wrong type of line or setting gear in the wrong place. But even if no violations occurred, it could influence future discussions about changing fisheries regulations or management practices.

Scott Landry, director of the Center for Coastal Studies’ entanglement response group, described the case as potentially setting the “gold standard” for information because it is so rare to retrieve gear with identifying information.

“Besides looking at compliance, the gear recovered from both of these cases can give us a better understanding of how entanglements happen,” Landry said. “So it’s not necessarily just about law enforcement. It is also a way for us to look at how entanglements happen so we can prevent them in the future.”

It is too early to say whether the recent incidents are part of a larger trend or if the entanglements will lead to a push for additional changes on fisheries regulations. But biologists said the spate was troublesome enough that they want the public to be aware of it.

“The population (of right whales) is around 500 animals,” said Sean Hayes, chief of protected species at NOAA’s Northeast Fisheries Science Center. “It’s a small population at this point, so we are concerned.”