Fish Stocks Around the Gezhouba and Their Response During Fishing Moratorium in the Yangtze River, China

To explore the impact of the fishing moratorium on fish stocks, some parameters and environmental factors were monitored downstream of Gezhouba Dam in April, June and August of 2013. Fish density and target length were get using hydro-acoustics (DIDSON). The results indicated that the fish density distributions in April, June and August were significantly different. The fish density decreased with time but kept a level that was close and steady in April and June. The average fish density of April was significantly greater than that in August (P<0.05). The percentage of fish target length distribution was consistent in time and space. In the study, the hydraulic and environmental factors were not the main reasons for the decrease of fish density and target body length in the spatial and temporal scale. Overfishing was the main cause and the fishing moratorium was substantially effective for keeping the sustainability of the fish resources in the adjacent areas of Gezhouba Dam.