But Dr Sam Turvey, of the Zoological Society of London, is spearheading a plan to set up a sanctuary on a lake next to the river. The society plans to capture the survivors and put them in a 13-mile-long lake at the Tian-e-Zhou National Baiji Reserve. There they will be able to breed in safety.

Dr Turvey, writing in the journal Oryx, said: "This really is the last chance we have to save one of the world's most evolutionarily distinct animals, which the Chinese government describes as a national treasure. It is essential we now raise the funding necessary."

The Yangtse dolphin is the only living member of the Lipotidae, an ancient mammal family which separated from other whales, dolphins and porpoises up to 40million years ago.

It is a white freshwater species with a long, narrow beak and low dorsal fin. It tends to live in groups of three or four and feeds on freshwater fish.