The effect of dams on the larval abundance and composition of four carp species in key river systems in China

The four species of carp present in China (grass carp, black carp, silver carp and bighead carp) are all commercially important freshwater fish species. However, the construction of large-scale hydraulic projects, such as dams, along with other anthropogenic changes to river systems has resulted in the rapid decline in abundance of all four carp species. Indeed, the effect of dams on the reproduction of the four species has become a highly sensitive issue in China. Historically, the Ganjiang River contained 12 spawning grounds for the four species. After the construction of the Wan'an Dam, however, four of these spawning areas were flooded. Three additional dams are currently under construction below the Wan'an Dam. While it is clear that these dams will further alter the hydrological regime in the river, there is currently little information available for the management and protection of carp in this river. In this study, we review published studies to characterize the patterns of larval abundance of the four species of carp in relation to environmental correlates in the Ganjiang River to provide baseline information that can be used to conserve these species.