Yangchen lake is located between Lake Tai and the Yangtze River. It crosses the boundary of the cities Suzhou, Changshu and Kunshan and has a surface area of about 20 square kilometres (7.7 sq mi).
The Chinese mitten crabs migrate from Yangcheng Lake towards the Yangtze delta for mating in September and October. The local fishermen harvest the animals during this migration. In 2002, the total production of Chinese mitten crabs in Yangcheng Lake was estimated to be about 1,500 tonnes (1,500 long tons; 1,700 short tons).