The survey on the Yangtze River, the first in six years, comes after more than 20 finless porpoises were found dead on the river and in two nearby lakes earlier this year, China's state-run Xinhua news agency reported.
With fears the deaths may have been caused by pollution and human activity, there are concerns the porpoises could go extinct within decades if efforts are not made to preserve them, conservationists said.
"We just hope that the survey results won't be too pessimistic. We hope they will help to beef up protection efforts," Wang Kexiong, deputy commander of the survey team, said.
In a 40-day survey to begin in November the WWF, working with the Ministry of Agriculture and Institute of Hydrobiology under the Chinese Academy of Sciences, will analyze the porpoise population and distribution and evaluate the threats the animals face.
The survey data will allow the agencies involved to offer suggestions regarding further protection efforts, including setting up new nature reserves, said Peter Beaudoin, head of WWF's China office.
A 2006 survey found around 1,200 finless porpoises living in the river with 600 porpoises in the nearby lakes of Poyang and Dongting.