An amateur conservationist claims he's spotted a Chinese river dolphin swimming in the Yangtze river, 10 years after scientists declared the species functionally extinct.

The baiji, or 'goddess of the Yangtze', was a species of white river dolphin that was abundant in the Yangtze for around 20 million years before it was wiped out by hunting and pollution. 

But now a group of amateur conservationists claim they spotted the dolphin (Lipotes vexillifer) during an expedition last week, and say it's evidence that the species is still around. The image above shows a baiji before it was classified as extinct.

The sighting occurred near the city of Wuhu in Anhui province, during a seven-day expedition that aimed to look for any remaining trace of the river dolphin.

"No other creature could jump out of the Yangtze like that," Song Qi, the leader of that expedition told government news site Sixth Tone. "All the eyewitnesses - which include fishermen - felt certain that it was a baiji."

To be clear, this sighting hasn't been confirmed by scientists, and the whole thing happened so quickly, the team didn't take photos that could be studied in more detail.

In the past, there have been plenty of false sightings of baijis, which often turned out to be a finless porpoise (Neophocaena phocaenoides) - a critically endangered marine mammal in the Yangtze. So a lot more research needs to be done before we can officially say that a baiji has been spotted.

But the claim has reignited interest in the possibility that the white river dolphin could still be around in the murky waters of the Yangtze.

Back in the 1950s, there were estimated to be thousands of baijis living in the Yangtze, Asia's longest river. But there are reports that during the Great Famine of the late 1950s, the millions of starving Chinese people under Mao Zedong's rule resorted to eating the species in order to survive. 

"It was the dolphins or it was our children," one Yangtze fisherman is quoted as telling a journalist in zoologist Samuel Turvey's book on the baiji, Witness to Extinction. "Which would you choose?"

By the end of the 1980s, the population had fallen to just 200, thanks to a mix of over-fishing, boat traffic, pollution, and dam-building on the river - more than 400,000 chemical enterprises are now reported as operating on the banks of the Yangtze.

By the turn of the century, one survey concluded there were only 13 baijis left.

In 2006, a six-week scientific expedition set out to study the population of baijis left in the river, and couldn't find a single one, causing scientists to declare the species functionally extinct - which means that even if there were individuals left, they were so few in number that the species couldn't possibly survive. 

Which is why, 10 years later, the possible sighting on the baiji is so exciting.

The group of amateur conservationists, who don't have scientific training, set out on September 30 from Anqing to travel down the Yangtze and look for signs of the baiji.

On the morning of October 4, Qi told Tom Phillips from The Guardian that he spotted a "white dot" emerge from the river.

He then saw the creature jump up a second and third time, before it swam towards the river's bank.

Immediately after the sighting, Qi contacted specialists at the Chinese Academy of Sciences in Wuhan, who joined them for the rest of their expedition, but they didn't make any more sightings of the mysterious animal. 

Qi now plans to run another expedition along the Yangtze early next year to search for more evidence of the baiji's existence - he hopes the potential sighting will invigorate the search for the dolphin, and renew efforts to protect the species. "I want society to realise that the baiji is not extinct," he told The Guardian.

Turvey, who works at the Zoological Society of London and who took part in the 2006 expedition, is doubtful that the sighting was really a baiji - more likely it was a finless propose, he says.

"Extreme claims for the possible survival of probably extinct species require robust proof, and while I would deeply love there to be strong evidence that the baiji is not extinct, this isn't it," Turvey told Phillips. 

"Ecologically, the question is: if this is a baiji, where has the species been hiding for the past decade?"

He also said these reports detract attention from more practical conservation efforts, such as focussing on the plight of the Yangtze finless propose which is critically endangered.

"This animal needs urgent media interest and conservation attention in order to combat its total population collapse, while there is still time to do something about it," added Turvey.

Let's hope that, if nothing else, Qi's possible sighting increases awareness about the ecological challenges facing the Yangtze, and inspires local government to protect whatever species are left living in there. Because you never know when it's too late.