Multi-index evaluation of fish habitat in a cascaded hydropower reservoir of the Yangtze River, China

Abstract

Cascaded hydropower development in rivers has a greater negative impact on native fish than a single hydropower station. The effectiveness of commonly used measures to restore fish resources, such as ecological discharges, depends largely on reliable assessments of habitat quality. In this study, we developed a synthesized habitat quality index (SHQI) by combining the habitat suitability index (HSI) and habitat fragmentation indices to evaluate the fish habitat in the Longkaikou (LKK) reservoir between the Jinanqiao (JAQ) and LKK dams in the upper Yangtze River. We coupled a 2-dimensional physical habitat model and a fuzzy-logic habitat suitability model for spawning and juvenile Coreius guichenoti, an Endangered fish endemic to the Jinsha River basin. The impact of the JAQ reservoir flow and the impoundment level of the LKK reservoir were considered to analyze variation in habitat quality. The results revealed that habitat suitability and fragment conditions were, to some extent, spatially inconsistent. The SHQI suggested lentic areas could benefit juvenile fish more than lotic zones with higher quality but less connectivity. A higher impounded level of the LKK reservoir may be more favorable for juvenile fish in the lentic area. Only the lotic area was suitable for fish spawning, and a lower discharge from the JAQ reservoir and lower impounded level of the LKK reservoir could be more beneficial, with optimal values of 560 m3 s-1 and 1294 m, respectively. This study proposes a comprehensive assessment method for habitat quality that could provide scientific support for the conservation of fish resources and populations in cascaded hydropower developments.