Effects of water temperature and discharge on natural reproduction time of the Chinese sturgeon, Acipenser sinensis, in the Yangtze River, China and impacts of the impoundment of the Three Gorges Reservoir.

Chinese sturgeon, Acipenser sinensis, is a critically endangered anadromous fish species spawning in the Yangtze River of China during October and November. In this study, we analyzed the effects of hydrological factors, such as water temperature and discharge, on the natural reproduction time of the Chinese sturgeon and evaluated the impact of the impoundment of the Three Gorges Reservoir (TGR) based on our survey data from 1998 to 2011. The results showed that the first spawning dates were significantly (P < 0.05) correlated with the date of water temperature reaching 20°C (20°C WT dates), October mean discharge (Oct. discharge), and the discharge change from October to November (Oct-Nov Δdischarge). Regression analysis suggested that one day delay of 20°C WT dates could postpone the first spawning date by 0.673 days. A discharge increase of 1000 m(3)s(-1) in October could bring forward the first spawning date by two days. Our results also indicated that the impoundment of the TGR had delayed the first spawning time due to water temperature lag and flow regulation. We suggest the following ecological regulations in order to facilitate conservation of the Chinese sturgeon: to eliminate water temperature lag by regulating water temperature downstream of the Three Gorges Dam (TGD), to enhance water discharge downstream in October, and to complete impoundment before October.