North Atlantic right whales nearly went extinct a century ago, and after a recovery, the population is falling again. (Michael Dwyer/AP)

Regina Asmutis-Silvia, a biologist who has dedicated her career to saving a type of whale called right whales, is cleaning out a file cabinet from the early 1990s, and the documents inside tell a familiar story: The whales are dying by colliding with ships and getting tangled up in fishing gear. The species might not survive.

Fast-forward 25 years, and it’s happening again.

“It’s a little scary to think if we hadn’t been working on this all these years, would they have been relegated to history instead of Cape Cod Bay?” said Asmutis-Silvia, who works for Whale and Dolphin Conservation in Plymouth, Massachusetts. “We’re standing on the cliff and going: ‘It matters. They’re still here. They’re still something to fight for.’ ”

Despite eight decades of conservation efforts, North Atlantic right whales are facing a new crisis. The threat of extinction within a generation looms, and conservationists are trying to come up with new solutions.

The whales are one of the rarest marine mammals in the world, numbering about 450. The 100,000-pound animals have been even closer to extinction before, and the effort to save them was one of the most visible wildlife conservation movements in U.S. history.

But the population is falling again because not many babies are being born and many whales are dying from ship strikes and entanglement. Scientists and environmentalists say they worry that the species could disappear as soon as 2041.

“There’s a fair amount of sadness, dealing with these creatures,” said Charles “Stormy” Mayo, director of the right whale ecology program at the Center for Coastal Studies in Provincetown, Massachusetts. “They are on the brink of extinction now, and their future is truly in doubt,” he said. “I don’t think any of us are discouraged, but many of us are fearful. I certainly am.”

Scientists Charles “Stormy” Mayo, center, and Lauri Leach spot North Atlantic right whales off the coast of Plymouth, Massachusetts, as Lauren Goodwin records data. (Michael Dwyer/AP)

The decline of right whales started centuries ago, when they were targeted as the “right” whale to hunt because they were slow and floated when killed. They were harvested for their oil and meat. Their numbers dropped to double digits until international protections took hold in 1935. Their population grew to about 275 in 1990 and 500 around 2010. But then things changed.

Scientists are still trying to figure out why the whales have lost about 10 percent of their population in just eight years, but one theory blames the warming of the Atlantic Ocean. The whales migrate from Georgia and Florida to New England and Canada every year, seeking food. There are laws to protect them on that path as they eat copepods, which are crustaceans the size of a flea.

But as waters have warmed, the tiny organisms appear to be moving, and the whales are following, sometimes putting themselves in harm’s way, said Mark Baumgartner, a scientist with Woods Hole Oceanographic Institution.

“The whales are moving around a lot more, and they are not finding food,” he told a gathering of Maine fishermen in March.

Last year, there were 17 confirmed deaths of right whales in Canada and the United States. Scientists haven’t observed any new right whale calves this year.

Those fighting for the whales are asking for new safeguards in the United States and Canada. They are also looking at technology to lower the number of fishing lines that entangle whales. Fishermen have doubts about the technology.

Still, advocates see reasons to be optimistic. Canada recently changed the dates of the snow crab season to get those fishing lines out of the water before the whales arrive. The country also established a permanent speed limit in the Gulf of St. Lawrence.

And this winter, scientists observed a “surface active group” for the first time in a year. The whales gather at the surface for males to compete to mate with a female. Scientists hope that means they may see a baby whale in the future.

“They can recover. They’re not a hopeless species,” Asmutis-Silvia said. “We just have to stop killing them.”

Scientists haven’t given up hope that the species can be saved. (Michael Dwyer/AP)