Yangtze dolphin 'functionally extinct'-英语点津

Yangtze dolphin 'functionally extinct' [ 2007-08-10 14:36 ] Download

The long-threatened Yangtze River dolphin has been declared "functionally extinct" after an expedition late last year failed to find any, international researchers have said.

Samuel Turvey, a conservation biologist with the Zoological Society of London who took part in the intensive six-week search, said no evidence was found of the freshwater dolphin, also known as the baiji, which was last spotted several years ago.

He said the dolphin's demise - a result of over-fishing, pollution and lack of intervention - was a cautionary tale and should spur governments and scientists to act to save other species on the verge of extinction.

"Ours is the first scientific study to have failed to find any," Turvey said in a telephone interview.

"Even if there are a few left, we couldn't find them and therefore can't do anything to stop their extinction."

The team, which published its findings in the Journal of the Royal Society's Biology Letters on Wednesday, included researchers from the United States, Britain, Japan and China.

The research was authorized by the Chinese government, Turvey said.

The last confirmed baiji sighting was in 2002, although there have been a handful of unconfirmed sightings since then, he said.

The last baiji in captivity died in 2002, Turvey said.

During the search, the team carried out both visual and acoustic surveys and used two boats to twice cover a 1,669-km stretch of the river from the city of Yichang, just downstream from the Three Gorges dam, to Shanghai.

The last survey, conducted between 1997 and 1999, turned up 13 of the mammals, but Turvey said fishing, pollution and boat traffic in the busy river, which was home to about 10 percent of the world population, had likely led to the baiji's demise.

"We twice covered the dolphin's range," Turvey said. "It is difficult to see how we could have missed them."

The dolphins will now be classified as critically endangered and possibly extinct, but Turvey said there is little chance there are any baiji still alive.

Wang Ding, a co-author of the report and deputy director of the Institute of Hydrobiology under the Academy of Sciences, said the dolphins faced "functional extinction".

This means that even if there remains a small population of breeding individuals, it will not be sufficient to sustain the species.

According to the World Conservation Union, an animal can be declared extinct only if it has not been seen for more than 50 years.

"At present, we cannot make the judgment that the dolphins are already extinct because it is only nine years since 13 of them were seen in wild," Wang said.

Researchers have known for years about the dolphin's precarious situation but indecision about how best to save them meant little was actually done, he said.

This underscores the need to act quickly to prevent the extinction of other similar shallow-water aquatic mammals, such as the vaquita found in the Sea of Cortez and the Yangtze finless porpoise, Turvey said.

"We really need to learn from this to make sure future conservation efforts are more dynamic," he said.

"There has always been a lot of focus on saving the whale, but that has led to these range-restricted shallow-water cetaceans slipping through the net.