China surveys endangered porpoises amid extinction fears (3)

"NOT OPTIMISTIC"

Scientists said the survey may not produce optimistic results, as human activities including illegal fishing, sand dredging and pollution have pushed the species to the brink of extinction.

In 2006, a similar survey found no white-flag dolphins along the Yangtze River, suggesting them as being "functionally extinct," which means the population is too small for the species' reproduction.

Both mammals were regarded as the symbol of the river, with groups of them seen swimming around ships, a demonstration of better river ecology back then.

A 2010 WWF report said illegal fishing, inadequate water conservancy facilities and pollution in the Yangtze, China's busiest waterway, is to blame for the declining number of porpoises.

Since the beginning of the year, more than 20 porpoises have been found dead in the Yangtze River and the lakes of Dongting and Poyang.