The mature 0⁺ crabs, Eriocheir sinensis, hold the spawning migration and some of them have the mating behavor in freshwater lakes, and the sperm in the female spermathecum is observed in next March. The peak of mature 0⁺ crabs, activity arrives at October and next March. 79 mature 0⁺crabs (27 ♀, 52♂) were caputured from the 272 crab-holes in earth-ponds in March 1995. The new soft shells with distinctive spines and ridges were peeled from the dead female crabs in early July 1995. But the authors don't find the old shells taken off by crabs themselves.