Evaluating the relationship between basin-scale fish species richness and ecologically relevant flow characteristics in rivers worldwide

1. River flow alterations due to climate change and increasing water usage affect freshwater biodiversity including fish species richness. Here, we statistically explored the relationships of fish species richness to 14 ecologically relevant flow metrics as well as basin area and latitude in 72 rivers worldwide. 2. The statistical models best supported by the data included three variables with positive coefficients (mean river discharge, basin area and the maximum proportion of no-flooding period) and three variables with negative coefficients (latitude, coefficients of variation in the frequency of low flow and the Julian date of annual minimum flow). 3. The model outputs have provided the first empirical indication that specific low- and high-flow characteristics may be important in explaining variations in basin-scale fish species richness. Our findings can be useful in identifying high-risk basins for conservation of fish species diversity. 4. The results not only support the adoption of mean discharge as a predictor, but also suggest the importance of basin area in predicting basin-scale fish species richness around the world.