Assessing fish habitat quality and stability in alluvial rivers: Eco-hydraulic insights into designed riffle-pool sequences and sandbar rivers

Abstract

Riffle-pool sequences and sandbar rivers, as the subsystems of alluvial rivers, have the potential to enhance fish conservation in river management. Research gaps remain in the significance of riffle-pool sequences and sandbar rivers for fish habitats. In this study, three types of riffle-pools and three types of sandbar rivers were designed, and bighead carp (Aristichthy nobilis) and Schizothorax prenanti possessing high economic value in China were selected as two target species. Influences of hydrodynamics and riverbed deformation on the habitat quality of six river channels were evaluated by an eco-hydraulic model with normal discharge and flood flush. WUA and OSI were employed to analyze the habitat sensitivity. Habitat quality and stability under long time impacts of hydrodynamics were also analyzed. The results showed that substantial differences existed among different river channels. Compact riffle-pool structure was advantageous for enhancing habitat quality and high habitat suitability was found near sandbars with the increasing of discharge. Flood flush fragmented the habitat quality of bighead carp while improved that of Schizothorax prenanti in generally. Overall, long time influence of hydrodynamics decreased the habitat quality of six river channels for two species. These results illustrated valuable information for evaluating habitat quality of riffle-pool sequences and sandbar rivers in fish conservation.