In a series called Deep Trouble, CBC News explores the perils facing the endangered North Atlantic right whale.

For the first time in more than a year, a North Atlantic right whale calf has been spotted.

The finding is significant, as there are only an estimated 411 members of the endangered species left, and until now there have been no sightings of calves in 2018.

Chad Leedy was working aboard a dredge as an endangered species monitor when he spotted an adult whale Friday near the entrance of the St. Johns River by the border of Florida and Georgia.

"A little bit later, I started noticing when the adult would kind of drop just under the surface, I kept seeing something. At first I thought it was a fin and I was like, 'That doesn't look right. That's not a fin.' The more I started looking, I was like, 'That's a calf.'

"It was really exciting," Leedy said.

Chris Slay, who runs Coastwise Consulting, the company doing the monitoring on the vessel, said the sighting is wonderful news.

"I don't want to overstate it or be overly sentimental, but I think it made a lot of people feel good yesterday and gave us all a little bit of hope after such dismal news over the past couple of years," he said.

Declining numbers

The dismal news is that the number of North Atlantic right whale calves has dropped in recent years, and several adults were found dead in 2017.

Only five calves were observed in 2017 and at least two, possibly three, of those animals have died, said Tony LaCasse, spokesperson for the New England Aquarium in Boston.

Even the birth of five whales that year was considered a notable drop compared with previous years, when the number of new calves spotted annually was in the high teens or low 20s.

"As anybody can see who can do the arithmetic, that is not a formula for a species to survive," LaCasse said.

In this 2009 file photo, a female right whale swims at the surface of the water with her calf a few miles off the Georgia coast. (John Carrington/Savannah Morning News/AP)

Calving season usually starts in December and lasts until March, with the bulk of the births happening in January and February.

North Atlantic right whales use the warm waters off Florida and Georgia as a nursery for their young so the calves don't have to burn unnecessary energy trying to stay warm in cold waters. Traditionally, the whales then move up the East Coast to their "summer nursery" in the Bay of Fundy, LaCasse said.

Change in migration pattern

But due to a lack of sufficient plankton in the Bay of Fundy, in recent years the whales have moved to other areas, including the Gulf of St. Lawrence.

LaCasse said that unexpected migration led to the "calamity" of many whales becoming entangled in fishing gear or being killed by vessel strikes.

Canada implemented new measures to try to protect right whales after 12 were reported dead in Canadian waters in 2017, along with another five in U.S. waters.

In addition to stressors such as vessel strikes, rope entanglements and food disruption due to climate change, LaCasse said North Atlantic right whales will soon face another significant hurdle to their survival. The U.S. government has approved permitting for seismic blasting along the southeast coast for offshore oil and gas exploration.

"This level of noise that's in the ocean with this would be the equivalent of somebody being at the edge of a tarmac in Halifax as the jets are taking off and being there for weeks at a time," LaCasse said.

While the birth of the calf is an encouraging sign, LaCasse said, "we're a long way from declaring victory."

"We're excited.… It's an optimistic sign. It's something we can be hopeful for."