Hydrologic regimes play a major role in determining aquatic ecosystems. However, most research has not focused on the effects of flow characteristics on fish species richness in freshwater at the global scale. In this paper, we evaluated flow characteristics in world rivers and showed general trends of rivers and distinctive features of Japanese rivers. The results showed that daily mean discharge and duration and frequency of floods significantly correlated with fish species richness. The present study suggests that it is important for the prediction of fish species richness in freshwater to consider not only average flow volume but also other flow characteristics such as variability and seasonality.
