An improved habitat model to evaluate the impact of water conservancy projects on Chinese sturgeon (Acipenser sinensis) spawning sites in the Yangtze River, China

Construction of water conservation projects may change the transport of water and sediment, and nutrient and food web dynamics in river systems, thus impacting the ecological systems downstream, especially fish habitats. This study proposed an improved habitat model that consider both habitat quality and quantity and applied it to evaluate the impact of water conservancy projects on fish habitats. The indices of fragmentation, which emphasize the core habitat patch, and connectivity, based on the minimum spanning tree, appeared to be the most suitable indicators of fish habitat quality. Chinese Sturgeon (Acipenser sinensis) was used as an indicator species and spawning sites between the Gezhouba Dam and Yichang Station were selected as study areas. The relationships between habitat quality and water temperature and discharge were established in these areas. The results indicated that discharges from 13,100 m3/s to 24,200 m3/s and water temperatures from 17.1 °C to 20.0 °C are recommended for Chinese sturgeon spawning and hatching. The improved habitat model showed that the impoundment and operation of the Three Gorges Dam and the construction of the separation levee project both caused a decrease in the habitat quality of Chinese sturgeon spawning sites. Compared to previous studies, the improved habitat model provides a promising intermediate step to reduce the uncertainty in evaluating and quantifying the impact of water conservation projects on fish habitats.