Two scientific survey ships leave for the upper reaches of the Yangtze River from Wuhan in central China's Hubei Province on Nov. 10, 2017. China on Friday launched its first survey of endangered finless porpoises in five years, to monitor their living conditions in moves to better rehabilitate their habitat in the Yangtze River. (Xinhua/Xiong Qi)  

WUHAN, Nov. 10 (Xinhua) -- China on Friday launched its first survey of endangered finless porpoises in five years, to monitor their living conditions in moves to better rehabilitate their habitat in the Yangtze River.

Two scientific survey ships left for the upper reaches of the river on Friday morning from Wuhan, a central Chinese city on the river, marking the beginning of the 40-day survey.

Consisting of researchers from the Ministry of Agriculture and the Chinese Academy of Sciences, the survey covers water areas and major lakes along the river from the city of Yichang in central China's Hubei Province to the eastern city of Shanghai, the estuary of the river.

The survey will use sonar, and remote control drones to collect data on the porpoise population, according to Wang Ding, chief commander of the survey.

The previous survey in 2012 found the population of finless porpoises had fallen below a thousand. A similar survey in 2006 found the population of finless porpoises down to 1,800 from 3,000 at the turn of the 21st century.

"As the flagship species in the Yangtze, finless porpoises are the barometer of the river's ecological conditions," said Cao Wenxuan, an academician at the Chinese Academy of Sciences.

The Ministry of Agriculture announced a Yangtze River Finless Porpoises Rescue Action Plan (2016-2025) at the end of 2016, calling for on-site protection, relocation protection and genetic protection of the porpoises.

"The declining trend of wild finless porpoises has not changed," said Cao. "Busy navigation and illegal fishing are to blame for the decrease."

Researchers install a sonar on a scientific survey ship in Wuhan, central China's Hubei Province, on Nov. 10, 2017.  (Xinhua/Xiong Qi)  

Researchers observe finless porpoises on a scientific survey ship in Wuhan, central China's Hubei Province, on Nov. 10, 2017. (Xinhua/Xiong Qi)  

Two scientific survey ships leave for the upper reaches of the Yangtze River from Wuhan in central China's Hubei Province on Nov. 10, 2017. (Xinhua/Xiong Qi)