James Pilkington, with Fisheries and Oceans Canada, first spotted the whale off the west coast of Haida Gwaii on June 9.
He says he initially thought it was a humpback, which is fairly common in the area. But once he got out his binoculars, he realized it was a North Pacific right whale.
"When we realized what we were looking at, we were in a state of disbelief," Pilkington said in a written statement.
"I never thought I’d see a North Pacific right whale in my lifetime, let alone have the opportunity to study it over several days. I was ecstatic!"
Fisheries and Oceans Canada whale biologist John Ford, based nearby at Langara Island, also observed the whale, accompanied by a third biologist, about 20 nautical miles south.
Ford told CBC Radio Daybreak North it was the "thrill of a lifetime."
"It was a species that none of us ever thought we'd get to see," he said.
"They're so rare that there's believed to be fewer than 50 of them alive in the entire eastern half of the North Pacific Ocean."
"They've never recovered from severe whaling that went right through into the 1960s," he said.
Brink of extinction
The North Pacific right whale was a favourite target of whalers and was hunted to near-extinction in the 19th century. It is believed there are only a few hundred of the whales alive worldwide today.
Canada has been working on recovery strategies for the right whale for decades, in case it is confirmed the whales are still off the B.C. coast.
Ford said the sighting in June -- during which the whale was observed eating zooplankton over the course of three days -- could help promote the recovery of the remaining population.
"This is a positive sign," Ford said. "It was a sign that this species still exists in Canadian waters."
A North Pacific right whale was last seen in Canadian waters off B.C. in 1951. Unfortunately, that whale was accidentally killed.
Ford said the whale spotted in June was photographed for identification, but didn't match any of the 19 right whales already photographed and catalogued in the Bering Sea.
The scientists also collected samples of the whale's waste, which will allow them to determine a number of features of the whale, including its diet, gender and possibly age.
According to Ford, Fisheries and Oceans Canada placed underwater acoustic recording devices to listen for right whales around Haida Gwaii about two years ago.
He's hopeful that more evidence of right whales will surface in the recordings picked up next month.
"Their sounds travel a long way underwater. We're more likely to hear them, if they're out there, than actually to find one," he said.
Listen to an in-depth interview with Fisheries and Oceans Canada whale biologist John Ford by clicking on the audio player in the top-left corner.