WUHAN, Nov. 25 (Xinhua) -- A total of 165 Yangtze finless porpoises have been visually identified during a survey expedition along the Yangtze River, a significant increase from previous research in 2012.

Acoustic equipment identified 102 finless porpoises during the expedition.

"There is a notable increase in the population size of the finless porpoise based on our observation," said Hao Yujiang, head of the research expedition.

Two scientific research vessels docked at a wharf in Wuhan, capital of central China's Hubei Province, Wednesday, concluding a 1,300 kilometers round-trip between Wuhan and Yichang in Hubei.

On November 10, a scientific expedition to the Yangtze River to study wild finless porpoise and their habits was launched.

The 40-day expedition, organized by the Ministry of Agriculture, will be conducted in the main stream of the middle and lower reaches of the Yangtze spanning from Yichang to Shanghai, as well as the river's largest tributaries and the lakes of Dongting and Boyang.

"Results of the expeditions, including the population of the finless porpoise, are to be made available after sufficient analysis," Hao said.

A separate expedition in 2012 found the population of finless porpoises had shrank to about 1,040, about 14 percent less than six years previously.

Scientists say insufficient food, illegal fishing tools, water pollution and habitat destruction are the major reasons for the decline.