THE Yangtze River dolphin, until recently one of the most endangered species on the planet, has been declared officially extinct after an intensive survey of its natural habitat.
The freshwater marine mammal, which could weigh up to a quarter of a tonne, is the first large vertebrate forced to extinction by human activity in 50 years, and only the fourth time an entire evolutionary line of mammals has vanished from the face of the earth since 1500.
Conservationists described the extinction as a "shocking tragedy", caused not by active persecution but accidentally and carelessly through a combination of factors including unsustainable fishing and mass shipping.
In the 1950s the Yangtze had a population of thousands of freshwater dolphins, but their numbers declined dramatically when China industrialised and transformed the Yangtze into a crowded artery of mass shipping, fishing and power generation. A survey in 1999 estimated the population was just 13.
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Historically, the species achieved nearly demi-god status among fishermen who recounted tales of dolphins being reincarnations of drowned princesses.
Sam Turvey, a biologist at London Zoo, worked with Chinese government scientists to survey the Yangtze downstream of the giant Three Gorges Dam. The researchers hoped that if any dolphins were spotted, they could be taken to a reserve.
But at the end of the survey, they had neither seen nor heard any sign of the dolphins, according to their report in the journal, Biology Letters.
"The hopes of each person on the survey died at different points; everyone had a moment of realisation that we weren't going to find anything," Dr Turvey said.
Copyright © 2007. The Sydney Morning Herald.