A volunteer is distraught after seeing the Yangtze River finless porpoise rescued in Shishou, Hubei province, in May. Gao Baoyan / For China Daily

Increasing pollution of the Yangtze River and the threat this poses to the finless porpoise is also a warning for a third of the nation's population that depends on these waters. Wang Ru reports.

Growing up in Huanggang, a city by the Yangtze River in Central China's Hubei province, He Dan had heard from elderly fishermen about a rare fish, dubbed the "river pig" by locals.

The fishermen described them as shy animals that often chased their boats, making a whistling sound. However, the term "river pig" was not really appropriate for the clever animal, that fishermen recall leaping out of the water in pairs or as a group.

He says she never spotted a "river pig" in her childhood, but did witness the increasing dredging of the river to feed the construction sites on its banks, and the resulting muddying of its waters.

He, a junior student of Chinese literature at Central South University in Hunan province, recalls how shocked she was to see a photograph that stirred much online discussion. It was of a rescued dolphin-like animal seemingly shedding tears. She learnt it was the "river pig" - the Yangtze finless porpoise - of her childhood.

"I didn't know dolphins could really cry until I joined the volunteer program funded by the World Wildlife Fund (WWF) to protect the lovely but highly-endangered animal, but I now believe they do," He says.

Even as World Freshwater Dolphin Day was marked on Oct 24, the finless porpoise in the Yangtze River is likely to meet the same fate as the baiji, the Yangtze River dolphin known as "the Yangtze goddess", and declared "functionally extinct" in 2006.

According to WWF, after years of efforts by scientists and environment protection organizations, China's Ministry of Agriculture upgraded the conservation level of the finless porpoise from grade 2 to grade 1 in June. The move is awaiting final approval from the State Council.

Scientists estimate that the finless porpoise, a freshwater dolphin which has lived in the Yangtze River and adjacent lakes for over 20 millions years, will become extinct within 15 years.

According to surveys done by the Hydrobiology Institute of the Chinese Academy of Sciences, the population of the Yangtze finless porpoise was about 2,700 in 1991.

By 2006, however, the numbers had dropped to between 1,200 and 1,400, with between 700 and 900 in the Yangtze River and 500 in Poyang and Dongting lakes.

Now, scientists estimate the number of Yangtze finless porpoises is around 1,000 (there are more giant pandas), and the number is decreasing at the rate of 5 percent every year.