"Unfortunately the baiji is functionally extinct. We did not see any animals in the river," August Pfluger, chief executive of the baiji.org Foundation, told Reuters in an interview this week.

"If there are maybe one or two or three left in the river, we don't believe that they have any chance to survive. We were obviously too late. For me, it's a tragedy in terms of conservation. We lost the race."

The long-beaked, nearly blind baiji is related to other freshwater species found in the Mekong, Indus, Ganges and Amazon rivers.

In the late 1970s, scientists believed several hundred baiji were still alive, but by 1997 a survey listed just 13 sightings.

The last confirmed sighting was in 2004 and the last captive baiji, Qi Qi, died in 2002.

The Chinese government had set up a reserve in a lake in central Hubei province to look after captured baiji, but failed to find any.

"The strategy of the Chinese government was a good one, but we didn't have time to put it into action," added Pfluger, who has only once seen a baiji in the wild, in 1997.

Chinese view the baiji as the reincarnation of a princess who refused to marry a man she did not love and was drowned by her father for shaming the family.

"The baiji was considered a goddess of the Yangtze River. This goddess obviously is not here anymore," said Pfluger. "I think in the last few years the government has put more attention on the issue, but we have all been too late."

The six-week expedition, made up of two ships and 30 scientists from Japan, China, the United States and Switzerland, did spot some 300 of another threatened species, the Yangtze finless porpoise, far less than they had thought they would see.

Though the baiji reserve could not offer the dolphin sanctuary, Pfluger said 28 finless porpoises are "doing well" there and even breeding.

"We must redouble our efforts to save the Yangtze finless porpoise too," he said.