WUHAN - Chinese scientists on Sunday launched a survey of endangered finless porpoises in the country's largest river Yangtze, as they worried the freshwater mammal is on the verge of extinction.

Consisting of researchers from the Ministry of Agriculture, the Chinese Academy of Sciences (CAS) and the World Wide Fund for Nature (WWF), the survey team set off in Wuhan, a central Chinese city along the Yangtze River.

The 40-day survey is the most comprehensive since 2006, when a survey found the population of finless porpoises down to 1,800 and pronounced the white-flag dolphin, a larger mammal native to the river, close to extinction.

There are probably only 1,000 finless porpoises in the Yangtze and two lakes linked to the waterway after continuous drops in the number, said Wang Ding, researcher from the Institute of Hydrobiology under the CAS.

"Finless porpoises may die out within 10 to 15 years, if strong measures are not taken," Wang warned.

The survey team will trace the porpoises using sonar system along the middle and lower reaches of the river, collecting data on the species' population, which will assist in the making of future protection policies.

The initial results of the survey will be published in December.

"As the flagship species in the Yangtze, finless porpoises are the barometer of the river's ecological conditions," said Wang Kexiong, deputy commander of the survey team.

Scientists say the survey may not produce optimistic results, as human activities and water pollution have pushed the species to the brink of extinction.

A 2010 WWF report blamed illegal fishing, inadequate water conservancy facilities and pollution in the Yangtze, China's busiest waterway, for the declining number of porpoises.