Evaluating The Biotic Integrity Of Up And Middle Reaches Of Nujiang River Based On Fish Assemblages

Nu-jiang River is an international open running river. Its up and middle reaches are 620 km long, which from Gongshan to Baoshan. It contained two world-class fauna, Qinghai-Tibetan Plateau fauna and Oriental fauna. In July of 2004, we investigated 65 sites of this area. Based on these information and historical data, we evaluated the IBI of up and middle reaches of Nujiang River. The main results were as follows:1. According to the fish assemblages of Nujiang River, we selected 10 metrics from 18 candidate metrics, these metrics are species composition and richness, tolerance, trophic composition, reproduction guild, fish condition and abundance. Metrics scored into three levels (1, 3, 5). The formula of IBI scores is (total of metrics scores)/number of metrics ×12.2. field work divided into 4 group, that is, Gongshan, Fugong, Liuku and Baoshan. The result of IBI showed that Fugong is excellent, Liuku is the second, Gongshan and Baoshan are fair. This suggested that the whole condition of Nujiang River is in shape, these area were with low human disturbance.3. With the assessment of IBI, we found the main impacts in Nujiang River are habitat types and low trophic condition. Human disturbances are distinct in Baoshan reach.