Abstract: Altogether there are 15 kindo of indigenous fishes in it.The fish fauna is radically different from that of other lakes but shares characteristics with fish fauna of the China Plain,showing that the fish fauna of Chenhai had derived from a common origin with Yangtze River.Having isolated from Chinsha River,Chenhai provided unoccupied niches for fishes.It is an important factor leading to species differentiation.Cyprinus carpio L.sets an excellent example in this respect showing a series of adaptative morhphological modifications.These modifications occurred within recent 300 years.Such a span of time is much shorter than the formation of Gymnocypris przewalskii ganzihoensis Zhu et Wu from its ancestral stock but is longer than the formation of the domastic golden crucian carp from its wild ancestor Carassius auratus (L.).It is clear,therefore,that the process of differentiation varies depending on different kinds of animals as well as ecological conditions.