Photo: The Canadian Press

After years of increasingly bad news, there's a glimmer of hope for the beleaguered North Atlantic right whale.

There are estimated to be fewer than 420 of the endangered mammals left, and their ranks have been decimated as deaths far outpaced live births — there were no births at all during last winter's calving season.

But researchers have reported seeing seven right whale calves so far this winter off the southern U.S. coast, where the mammals spend their winters before coming north to Canada as temperatures warm.

"Seven is definitely better than last year," said Barb Zoodsma, a fisheries biologist with the U.S. National Oceanic and Atmospheric Administration.

"Last year was dismal with zero, and the year before that, there were five. However when you look at the average number of calves produced in any given year for the last 10 years it has been just under 17 mom-calf pairs. Although we're at seven, we're not at the average level yet," she said.

The right whale is one of the largest mammals in the sea, and among the most imperilled.

Populations have only slightly rebounded from the whaling era, when the blubber-rich baleen whale nearly became extinct.

Zoodsma said the seventh calf was confirmed last week.

She said they hope to see more calves between now and the end of the calving season, around mid-April.

"Keep in mind we're on the tail end of an unusual mortality event where we had 18 right whales that died in just a few short years. Seven doesn't make up that number, so we have a ways to go yet," she said in an interview from Fernandina Beach, Fla.

Zoodsma said healthy females have a calf every three or four years, but recently that has dropped to an average of every 10 years.

She said it's believed a number of factors are to blame, including the shifting location of food sources, and stresses imposed by fishing gear and large vessels.

Laurie Murison, executive director of the Grand Manan Whale and Seabird Research Station, said food supply is a huge factor.

"If the females are not getting enough to eat they will not be reproducing," she said.