News of the extinction of the Yangtze river dolphin, or baiji, sent shockwaves around the world last year. The revelation had all the more impact because the beautiful baiji was at the heart of many Chinese legends. The Goddess of the Yangtze, as it was known, was also the lone representative of an entire, ancient branch of the tree of life.

Samuel Turvey, a research fellow at the Zoological Society of London, here documents the plight of the Yangtze river dolphin. This chronicle of his subject's demise makes bleak reading.

Turvey's elegiac twilight trawl between the Yangtze's soggy mud banks heavy with wet grass and tree skeletons consumes six sorry weeks of 2006.

After covering the middle section of the great river twice, he and his peers become increasingly despondent, resentful, almost mutinous, irked by funding problems and failure.

Most days, only finless porpoises materialise. 'Paradoxically,' Turvey writes, 'after so many months and years of trying desperately to muster support for its conservation, now that we were actually out on the Yangtze the animal's reality seemed to be receding further...'

The list of suspects for the crime whose shadow hangs heavily over the book is long. As always, of course, essentially all of the evidence points to that singularly accomplished destroyer of species: man.

But poachers and people who defecate into the river appear worthy of particular blame. Ditto the shadowy figures staffing the freighters, oil refineries, factories and chemical plants that pour pollutants into the waters.

Turvey's expose strengthens the argument propounded by philosopher John Gray and others that Homo sapiens is an unpleasant, invasive species unworthy of control of the planet. This view is bolstered when Turvey branches out and takes a look at the next cetacean species in extinction's crosshairs: the vaquita of the Gulf of California.

Then a wave of optimism stems from a report that a baiji may have been seen and filmed in a Yangtze offshoot near the port city of Tongling in August 2007. Local man Zeng Yujiang spotted a 'big white animal' and filmed it from the bank with a digital camera for several minutes, he told Xinhua.

Alas, Yangtze locals who claim to spot baiji have a strong motive: institutional funding for nominally protecting them. Worse, the footage is unconvincing. 'All that it seemed to consist of was a pale dot that broke the surface to the far left of the frame a couple of times - that was it,' Turvey writes.

The last confirmed sighting of a baiji in the wild was in September 2004. Perhaps the most famous of the species was QiQi, a male, shown below during a check-up at the Institute of Hydrobiology in Wuhan, where he lived.

He was rescued, injured, from the Yangtze in 1980 and died in July 2002.