Abstract: Impoundment in the Three Gorges Reservoir has remarkably changed the hydrodynamic conditions and sediment movement in the fluctuating backwater zone and has affected the fish habitat to varying degrees. The habitat characteristics and distribution of fish swarm in the fluctuating backwater zone of the Three Gorges Reservoir from Chongqing to Fuling was obtained by using the scientific echo sounder Bisonics DT-X). Results revealed no significant spatial distribution of water environmental factors in the study reach, implying that water environmental factors were not the major factors that affect the distribution of fish. Water depth and flow velocity, which varied notably, were key factors affecting fish habitat distribution. The average density of the eight fish swarm was (64.6±13.5) ind/(10³ m³), and the fish swarm was dominated by small and medium-sized fish whose average body length was (16.8±4.6)cm. The backwater pool, deep pool and branching channel are fish’s favorite habitat sections. The results provided scientific basis for fish protection and habitat restoration in the fluctuating backwater zone of the Three Gorges Reservoir.

Key words: fish distribution, habitat characteristics, Three Gorges Reservoir, fluctuating backwater area, impoundment period, hydroacoustic