Abstract: Most of lakes along the Yangzte River were disconnected from the river because of hydrautic projects, which caused many ecological problems. Here, we took demonstration study of the ecological impacts of disconnection from the river on fish recources in Zhangdu Lake. Our results showed that: (1) Fishery mode changed and the rate of wild fishery production changed from 95% in 1949 to less than 5% in 2002. (2) Fish species have decreased from 80 in 1950s to 52 at present, and the rate of migrant and potamic species decreased from 50% in 1950s to 30% at present. (3) Comparing with the linking lake, Zhangdu Lake had higher fishing production, larger individual size, fewer species number and lower diversity index of “mihunzheng” fishery, a universal fishing tool in Yangtze. Therefore, disconnecting lake from Yangtze had significant negative impacts on lake fish resources, which resulted in the decrease of the wild fish diversity in the lake. 〖

Key words: linking lakes, disconnection between lake and river, ecological impacts, fish diversity