Law enforcement officers from the fishery and public security sectors patrol a porpoise conservation area on the Yangtze River in Anqing, east China's Anhui Province, March 1, 2019. China has imposed a four-month fishing ban in the Yangtze River, the Pearl River, the Huai River, the Qiantang River, the Min River as well as inland waters on the Hainan island, starting on Friday. (Xinhua/Huang Youan)