A Yangtze finless porpoise plays with a worker in a pool at the Baiji dolphinarium in Wuhan on November 10, 2018. (Photos: VCG)

One of the world's few freshwater porpoise sub-species and the only aquatic mammal left in China's longest river, the Yangtze finless porpoise is critically endangered due to pollution, overfishing, hydroelectric dams and shipping traffic.

The number of finless porpoises is getting lower, reading less than 1,000. The finless porpoise was one of the few subspecies of freshwater dolphins in the world.

A Yangtze finless porpoise is being fed at the Tianezhou national nature reserve in Shishou on November 9, 2018.

A Yangtze finless porpoise is being fed at the Tianezhou national nature reserve in Shishou on November 9, 2018. (Compiled by Dong Feng)