Critically endangered Yangtze finless porpoise shows signs of recovery Over 50 billion tons of sand is mined every year—and it's pushing species to the brink of extinction.Overfishing, increased shipping traffic and noise pollution have all been linked with the decline of the porpoise, which only breeds once every 18 months or so.While the practice has been taking place for many years, the number of sand mining vessels on Dongting lake grew substantially after 2006, reaching a peak of 80 in 2013 when almost 70% of the lake was being mined for sand.The researchers behind the current study of the porpoises conducted a number of surveys between 2006 and 2019 in Dongting lake, which is connected to the Yangtze River by a channel, using counts, acoustic surveys and the study of satellite images.Sand mining on the lake was banned in 2017, and access to the Yangtze River restored, which has seen the porpoise return to areas of the lake it had previously avoided."