Fish Temporal And Spatial Distribution Of The Three Gorges Reservoir And Related Factors And Analysis

The Three Gorges Reservoir is the best habitat, foraging and spawning grounds for many rare, unique and economic fishes, fishery resource in which is very ample. Hence, the scientific, ecological, social and economic value of the reservoir is important and the protection and utilization of fishery resource in the Three Gorges Reservoir is a hot point.The ecology environment of the Three Gorges Reservoir was inevitably changed as the huge storage and discharge. Therefore, the distribution of fish in the reservoir would change correspondingly. To study the fishery resource and its distribution characteristic under different water level and analysis the relationship between fish density and relative environmental and hydrologic factors is significant to fish protection and utilization of the Three Gorges Reservoir.In this study, the studied area was from Zigui to Chongqing. First, we detected the fish distribution in this area using hydroacoustic equipment. Second, we investigated fish catch at Wushan, Wanzhou, Zhongxian and Changshou sections and compared the fish catch data with the hydroacoustic data. Third, we monitored some environmental factors and analysis the dependency of these factors and fish density. Finally, we imitated the water depth, water velocity and water volume of the Three Gorges Reservoir using the model MIKE11and analysis the influence of these factors to the fish distribution.The conclusions are as following.The fish density in the main stream of the Three Gorges Reservoir was increasing year by year when we compared the data in same season and the fish density in winter was always higher than the value in spring of the same year. Furthermore, the fish density in the upper reach was almost higher than that in the lower reach of the reservoir. In winter, fishes like to live at the section around Zhongxian and in spring, fishes apt to live at the section from Changshou to Chongqing. To the branches of the reservoir, we found the fish density of every branch in winter was almost higher than that in spring and also higher than that in the main stream. In winter, the highest fish density was detected in the Daning River and in spring, the highest density was found in the Meixi River, Zhuyi River and Modao River.Fish catch investigations were conducted in Wushan, Wanzhou, Zhongxian and Changshou section from2006to2010, the results showed that different section had different dominant species and silver carp, southern catfish, crucian, common carp, copper fish, rhinogobio ventralis and coreius guichenoti were dominant species of the whole reservoir. The habits of the dominant species were coincided with the fish distribution characteristics in the hydroacoustic detection. The fish catch and average daily output at the Wanzhou section were increasing year by year, which was similar to the hydroacoustic data.The detected environmental factors included water temperature, dissolved oxygen, salinity, conductivity, resistance, total dissolved solid and pH. During the seven factors, water temperature was significant correlated with the fish distribution in spring, but all of the environmental factors has no correlation with the fish distribution in winter. In spring, the water temperature was increasing from lower to upper reach of the reservoir which resulted in the fish density in the upper reach was the highest. In winter, the tested environmental factors were not limiting factor for fish distribution in the Three Gorges Reservoir.The imitated hydrologic factors included water depth, discharge, water velocity, flow area and flow width. The relationship between hydrologic factors and fish density of different section was analyzed, the results showed that water velocity, water depth and flow area were highly siginificant correlated with fish density in spring and flow width was significant correlated with fish density in winter. The demand of water velocity was another important reason for fish distribution in spring. In winter, the imitated hydrologic factors were not limiting factor for fish distribution.Finally, we summaried the reasons for fish amount increasing and distribution characteristics in the Three Gorges Reservoir and considered water temperature, water velocity, water depth, flow state, living habit of fish and protection policy were the main factors.