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Dolphin feared extinct in polluted Yangtze

December 14, 2006 By Michael Hopkin This article courtesy of Nature News.

Overfishing and boat noise are killing aquatic mammals in Chinese river.

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Human activity in China's Yangtze river is causing the region's dolphins to go extinct and more species will follow if fishing is not regulated, conservationists have warned.

Scientists on an expedition in China claimed this week that the freshwater baiji (Lipotes vexillifer), also called the river dolphin, should be declared 'functionally extinct' in the river. This means that even if a tiny handful of individuals still remains, their numbers will not be enough for them to bounce back. The creature does not live anywhere else making it the first cetacean to be driven to extinction by humans.

"There's no hope to save them," says August Pfluger, chief executive of the foundation, which has just completed a six-week survey of the Yangtze during which they found no baijis. The news is a blow to the team although a shorter survey in March also found no evidence of the dolphins, they had still hoped that around 100 dolphins might remain in the river (see ' Last hope for river dolphins').

Only the International Conservation Union can officially declare a species extinct, and only after it has not been sighted after several years of searching. "There's not enough data," says Rob Shore, freshwater programmes officer for the WWF in Godalming, UK. "But what we do know is that there are very, very few individuals left."

Thousands no more

What's more, another Yangtze mammal, the finless porpoise (Neophocaena phocaenoides), is also heading the same way, Pfluger says. "In the 1980s there were thousands and thousands," he says. "In the 1990s there were around 6,000, according to surveys. Now there are around 400. The population is declining at an alarming speed."

Wang Ding, head of freshwater cetacean research at the Institute of Hydrobiology in Wuhan, China, agrees. "If we do not act soon they will become a second baiji," he says.

Pfluger adds that other large species living in the river, such as the sturgeon and the giant salamander, are also being harmed by human activity. "There is no area in the river where the sturgeon can breed," he says.

Conservationists blame overfishing for the decline in the Yangtze's species. For the baijis, which are almost blind and rely on sonar to find food, the presence of so many fishing boats causes noise pollution and the danger of collisions. "The river is no longer natural, it's just a channel with thousands of ships," Pfluger says.

He is planning to meet with Chinese fishing organizations next year to ask them to report any baiji sightings, and to emphasize the importance of enforcing fishing licences. The Yangtze currently hosts thousands of unlicensed fishing boats, which damages fish stocks as well as rare species.


The Yangtze basin, which winds for 1,750 kilometres and ends at Shanghai, is the most densely populated place on the planet around 400 million people live along its banks. "The habitat is so degraded that it's very difficult for large animals to survive," says Shore.

In the short term, he suggests that remaining dolphin species and other mammals should be taken from the river and put into lakes to safeguard them until the river can be restored. "It's not an ultimate solution but it might have to be the way forward," he says.

Pfluger says there is no hard evidence that the construction of the controversial Three Gorges Dam on the river has contributed to the baijis' decline. But he adds that the project has lowered the water level downstream by around 2 metres, and reduced the amount of plankton, which supports the river's ecosystems.

Overall, he is more pessimistic than Shore. "I've had the amazing privilege to observe a living baiji in the Yangtze," he says, referring to a 1997 expedition when 13 of the dolphins were spotted. "Now the problems are so huge, so endless, I feel a little hopeless about this."

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