Modeling and analysis of eco-hydrological factors influencing fish distribution

The change of flow regime under the disturbance of human activity leads to alteration in fish distribution.To accurately analyze key eco-hydrological characteristics, Arkansas River federally endangered small-bodied fish: pelagic broadcast-spawning cyprinids reproductive guild(Arkansas River Shiner, Notropis girardi, “ARS” for short) was studied.According to the hydrological requirements for the spawning, daily flow data from 40 flow gages in the historic period(1950-1962) and the current period(1989-2010) were downloaded for the calculation of three important ecological hydrological fators: high flow, high flow duration and zero flow days.In combination with 25 other environmental factors, three species distribution model based on the theory of maximum entropy(MaxEnt) were established to analyze the contribution and influence of three flow metrics to the predicted distribution.The classical method(Receiver Operating Characteristic, ROC) and Parolo’s calculation of the Spearman's rho correlation coefficient before and after the transfer of the models were used to evaluate the model fit and transferability of the models.The area under the ROC curve(AUC) greater than 0.95 and the Spearman’s rho value greater than 0.6 for all the three models showed the good model fit and transferability of the models.Of the three flow metrics, high flow made the highest contribution to the model fit and had the most significant effect on the potential distribution of the fish.In different period, the species occurrence probability changed differently as the flow metric varied.Our study could provide valuable references for the protection of endangered fish in China.