Fish Community Changes And The Evaluating The Biotic Integrity In Dongjiang River Mainstream

Eleven surveys were carried on in Dongjiang Rriver mainstream from September 2009 to March 2010.27138 fish were collected and measured.85 freshwater fish species belong to 8 orders,22 families and 66 genura were identified. Cyorinidae (46 species), Bagridae (7 species) and Cobitidae (5 species) are preponderant. Besides Gambusia affinis, six exotic species including Labeo rohita, Cirrhina mrigala, Clarias lazera, Hypostomus plecostomus, Tilapia nilotica, and Tilapia zillii were newly recorded.Compared with the research data in 1980s', the proportion of sedentary and omnivore species increased, but the proportion of migratory and carnivore species declined. The result by using autecology matrix analysis showed that carnivore small size fish species living at gravel Sub-stratum decreased greatly, however, sedentary and omnivore fish living at Substrate mud and in Slow current became dominated species in Dongjiang Rriver mainstream. According to Simpson index, Shannon-Wiener index, Pielou's index, Margalef index and G-F index, the differences of the fish community diversity in the up and down of Dam had appeared. The important factors influencing the change of fish community in the lower reaches of the Dongjiang River might be the dam construction, water pollution, and excessive catching.According to Karr's IBI index system and the condition of Dongjiang Rriver mainstream, eleven metrics, which best represented the fish assemblages's chara cteristics and the patterns of degradation in Dongjiang Rriver were selected.These metrics were total number of native fish species,%number of species in the family Cyprinidae,%number of species in the family Cobitidae, number of families in fishery catches, percent of tolerance individuals, percent of carnivore individuals, percent of top carnivores individuals, percent of omnivores individuals, catch per unit effort and percent individuals with DELT. The IBI classes of each reach were calculated according the value of metrics and expectation value. The result of IBI showed that Guzhu was good, Laolong and Luoyang were fair, Dongshui and Ruhu were poor and Linjiang was very poor. With the assessment of IBI, it was demonstrated that the space characteristic of The Biotic Integrity of Dongjiang Rriver mainstream wasn't continuous and each reach contained relative independence.This result and the habitat fragmentation that caused by cascade hydropower stations are closely.