Does hydrologic regime affect fish diversity? -A case study of the Yangtze Basin (China)

The Yangtze Basin is taken as a case study to investigate statistically whether the hydrologic regime affects fish diversity. Jaccard's similarity index (I (JS)) is used to characterize the fish species similarity of any pair of sample rivers. On the basis of the IHA (Indicators of Hydrologic Alteration) method, a series of hydrologic indicators, some of which are modified according to the practical hydrologic characters of the Yangtze Basin, are used to characterize the hydrologic regime. A new index, named the degree of the hydrologic regime difference (I (DHRD)) is constructed to measure the difference between hydrologic regimes of any pair of sample rivers. An exponential model is used to estimate the correlation curve of I (JS) and I (DHRD). We observed a negative relationship between I (JS) and I (DHRD), which suggests that hydrologic regime affects fish diversity.