Finless porpoises, a highly endangered species of freshwater dolphin that only lives in the Yangtze River are facing an 80% decrease over the next 30 years, an expert warned.

Wang Ding, a dolphin expert at the Hydrobiology Institute under the Chinese Academy of Sciences, was quoted by Xinhua as saying that the rare species will edge closer to extinction if no action is taken.

Wang's team conducted a survey on Poyang Lake, Dongting Lake and other locations along the Yangtze from Sunday to Wednesday this week.

The dolphin population is only 1,000, even fewer than that of the giant panda, and is decreasing at a rate of 6.4 percent annually, Wang said.

He said the water level has dropped to 27.38 meters in the Swan Island National Nature Reserve in Shishou, Hubei Province, and finless porpoises will die if this trend continues.

"The next ten years will be a critical period for the conservation of this species," Wang said.

A long-lasting drought in central China has lowered water levels in many of the region's lakes and rivers, doing great harm to the dolphins' habitat and leading to a decrease in population, Wang said.

The dolphins mainly feed on fish. Even if they can survive the drought, the drop in fish numbers in the river and lakes would cause serious food shortages for the dolphins in the future, according to Xinhua.

The local government in Hubei Province has banned water pumping from the nature reserves where the freshwater dolphins live to protect the rare species.