Ecological influence of dam construction and river-lake connectivity on migration fish habitat in the Yangtze River basin, China

Habitat fragment owning to obstruct of dams and barriers badly affect the aquatic faunas. Many spawning sites of migration fishes are lost, and their growth and reproduction are affected. The Yangtze River with connected lakes is the most important fresh water fishery area in China. The Yangtze's four major carp species (YFMCS) are the most typical migration fish lived in this area. They reproduce in river and grow in lake. Distributaries lies between the Yangtze River and Dongting Lake are the passages for these migration fishes. Due to the construction of dams and barriers, some original passages were out of use. Up to now, only four channels exist between the river and lake, there are Songcikou, Taipingkou and Ouchikou normally called “three outlets”, and Chenglingji inlet. Diverted Water Volume (DWV) and the Percentage of Diverted Water (PDW) through the three outlets reflect the relationship between the Yangtze River and the Dongting Lake.The variation of river-lake relation caused by dam construction, and the effect on migration fishes are discussed in this paper. The relationship of DWV and fry output in middle reach of the Yangtze river and the Dongting Lake, PDW and the percentage of the YFMCS in a total catch of fish, DWV and flux of carp fry at the Jianli station, DWV and yield of the YFMCS were analyzed. The results show that dams and barriers constructed on the Yangtze River threaten some fish species in this area, especially the migration fishes. The connectivity degree of river and lake decide the growth and reproduction of emigration fishes, the yield of the YFMCS increase by the DWV increase, and hydraulic project have important influence on reproduction of fishes. In order to reduce the ecological influence of hydropower projects, reservoir management especially in spawning season should integrate ecological demand.