A Yangtze finless porpoise swims at the Yangtze River Dolphin aquarium in the Institute of Hydrobiology of the Chinese Academy of Sciences in Wuhan, capital of central China's Hubei Province, on Nov. 10, 2018. With a slightly curved mouth, the Yangtze finless porpoise is often called the "smiling angel" of the Yangtze by Chinese. However, the population has been rapidly decreasing over the last three decades due to environmental deterioration. The species now teeters on the brink of extinction with a population of around 1,000 in the main waterway of the Yangtze, according to research conducted in 2012. (Xinhua/Xiao Yijiu)