Community characteristics of aquatic organisms and management implications after construction of Shihutang Dam in the Gangjiang River, China

The Ganjiang River is the largest river in Jiangxi Province, China, and plays a significant role in maintaining and replenishing the aquatic biodiversity for Poyang Lake and the Yangtze River. Understanding the effects of dam construction on aquatic biodiversity is critical because of the increasing number of dams and their adverse environmental impacts on the Ganjiang River. In this study, community structure of aquatic organisms and physicochemical parameters in the Shihutang Dam were investigated during March, July, and December 2015. We found that species number, density, and biomass of phytoplankton upstream of the dam were greater than downstream of the dam. Moreover, analysis of aquatic biodiversity showed that phytoplankton, zooplankton, and macrozooben-thos upstream of the dam were more abundant and richer than downstream of the dam, and fish downstream of the dam were more abundant and the fish community richer than upstream of dam. Fish life habits revealed that resident fish were the dominant species, but the proportion of migratory fish was low. Additionally, species composition of aquatic organisms was related to dissolved oxygen, turbidity, water depth, some nutrients, and velocity, based on redundancy analysis. The study showed that aquatic organism community structure was influenced by the Ganjiang River dam. We therefore proposed a series of dam management strategies, such as establishing artificial fish spawning substrate and implementing eco-hydraulic regulations. These dam management strategies can play an important role in protecting aquatic biodiversity and sustaining the resources in the Ganjiang River.