An Overview on Dams in the Yangtze River Basin: Fishery Resources, Biodiversity, and Water Quality

Dams and other hydrological modifications are the biggest anthropogenic stressors for fishery resources in the Yangtze River Basin. There were over 50,000 dams built from the Yangtze main stem, tributaries, and associated lakes in the basin. The largest dams in the main stem include the Gezhouba Dam and the Three Gorges Dam, which have been built for full operations since late 1980s and late 2000s, respectively. Major aquatic impacts from these dams include: (1) habitat fragmentation, shifts of flow regimes, water levels, and water temperature, and loss of spawning grounds for fish; (2) shifts of fish communities, reduced fish biodiversity and total abundance, especially the extinction of ancient and migrating fishes; (3) shifts of benthic macroinvertebrates and phytoplankton dominant species; and (4) changes of sediment discharge load and nutrients patterns, and increased occurrence of algal blooms. Research and conservation priority efforts need to be put on the current dam related issues: (1) expansion of building small cascade dams in headwaters and upper tributaries; (2) potential damming between the Yangtze main stem and connected lakes, which are the last reserves for maintaining aquatic biodiversity in the Yangtze River Basin. Related strategies were also discussed in the current study.